Title of Invention	A PROCESS FOR PRODUCING ISOCYANATES
Abstract	An object of the present invention is to provide a process that enables isocyanates to be stably produced over a long period of time at high yield without encountering various problems as found in the prior art when producing isocyanates without using phosgene. The present invention discloses a process for producing an isocyanate, comprising the steps of: reacting a carbamic acid ester and an aromatic hydroxy compound to obtain an aryi carbamate having a group derived from the aromatic hydroxy compound; and subjecting the aryl carbamate to a decomposition reaction, wherein the aromatic hydroxy compound is an aromatic hydroxy compound which is represented by the following formula (1) and which has a substituent R1 at at least one ortho position of a hydroxyl group: (wherein ring A represents an aromatic hydrocarbon ring in a form of a single or multiple rings which may have a substitute and which have 6 to 20 carbon atoms; R1 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom; and R1 may bond with A to form a ring structure).

Title of Invention

A PROCESS FOR PRODUCING ISOCYANATES

Abstract

An object of the present invention is to provide a process that enables isocyanates to be stably produced over a long period of time at high yield without encountering various problems as found in the prior art when producing isocyanates without using phosgene. The present invention discloses a process for producing an isocyanate, comprising the steps of: reacting a carbamic acid ester and an aromatic hydroxy compound to obtain an aryi carbamate having a group derived from the aromatic hydroxy compound; and subjecting the aryl carbamate to a decomposition reaction, wherein the aromatic hydroxy compound is an aromatic hydroxy compound which is represented by the following formula (1) and which has a substituent R1 at at least one ortho position of a hydroxyl group: (wherein ring A represents an aromatic hydrocarbon ring in a form of a single or multiple rings which may have a substitute and which have 6 to 20 carbon atoms; R1 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom; and R1 may bond with A to form a ring structure).

Full Text	A PROCESS FOR PRODUCING ISOCYANATES Technical Field The present invention relates to a process for producing isocyanate. Background Art Isocyanates are widely used as production raw materials of such products as polyurethane foam, paints and adhesives. The main industrial production process of isocyanates involves reacting amines with phosgene (phosgene method), and nearly the entire amount of isocyanates produced throughout the world are produced according to the phosgene method. However, the phosgene method has numerous problems. Firstly, this method requires the use of a large amount of phosgene as raw material. Phosgene is extremely toxic and requires special handling precautions to prevent exposure of handlers thereof, and also requires special apparatuses to detoxify waste. Secondly, since highly corrosive hydrogen chloride is produced in large amounts as a by-product of the phosgene method, in addition to requiring a process for detoxifying the hydrogen chloride, in many cases hydrolytic chlorine is contained in the isocyanates produced, which may have a detrimental effect on the weather resistance and heat resistance of polyurethane products in the case of using isocyanates produced using the phosgene method. On the basis of this background, a process for producing isocyanates has been sought that does not use phosgene. One example of a method for producing isocyanate compounds without using phosgene that has been proposed involves thermal decomposition, of carbamic acid esters. Isocyanates and hydroxy compounds have long been known to be obtained by thermal decomposition of carbamic acid esters (see, for example, Berchte der Deutechen Chemischen Geselischaft, Vol. 3, p. 653, 1870). The basic reaction is illustrated by the following formula: R(NHCOOR')a ----------> R(NCO)a + a R'OH (1) (wherein R represents an organic residue having a valence of a, R' represents a monovalent organic residue, and a represents an integer of 1 or more). The thermal decomposition reaction represented by the above-mentioned formula is reversible, and in contrast to the equilibrium thereof being towards the carbamic acid ester on the left side at low temperatures, the isocyanate and hydroxy compound side becomes predominant at high temperatures. Thus, it is necessary to carry out the carbamic acid ester thermal decomposition reaction at high temperatures. In addition, in the case of alkyl carbamates in particular, since the reaction rate is faster for the reverse reaction of thermal decomposition, namely the reaction by which alkyl carbamate is formed from isocyanate and alcohol, the carbamic acid ester ends up being formed before the isocyanate and alcohol formed by thermal decomposition are separated, thereby frequently leading to an apparent difficulty in the progression of the thermal decomposition reaction. On the other hand, thermal decomposition of alkyl carbamates is susceptible to the simultaneous occurrence of various irreversible side reactions such as thermal denaturation reactions undesirable for alkyl carbamates or condensation of isocyanates formed by the thermal decomposition. Examples of these side reactions include a reaction in which urea bonds are formed as represented by the following formula (2), a reaction in which carbodiimides are formed as represented by the following formula (3), and a reaction in which isocyanurates are formed as represented by the following formula (4) (see, Berchte der Deutechen Chemischen Gesellschaft, Vol. 3, p. 653, 1870 and Journal of American Chemical Society, Vol. 81, p. 2138, 1959): In addition to these side reactions leading to a decrease in yield and selectivity of the target isocyanate, in the production of polyisocyanates in particular, these reactions may make long-term operation difficult as a result of, for example, causing the precipitation of polymeric solids that clog the reaction vessel. Various methods have been proposed to solve such problems. For example, a method for producing polyisocyanate has been proposed in which an alkyl polycarbamate, in which ester groups are composed of alkoxy groups corresponding to a primary alcohol, is subjected to a transesterification reaction with a secondary alcohol to produce an alkyl polycarbamate in which the ester groups are composed of alkoxy groups corresponding to the secondary alcohol, followed by thermal decomposition of the alkyl polycarbamate (see, for example, International Publication No. WO 95/23484). It is described in this method that the thermal decomposition temperature of the alkyl polycarbamate can be set to a lower temperature by going through an alkyl polycarbamate in which the ester groups are composed of alkoxy groups corresponding to the secondary alcohol, thereby resulting in the effect of being able to inhibit precipitation of polymeric solid. However, the reverse reaction rate between the polyisocyanate formed by the thermal decomposition reaction of the alkyl polycarbamate and the secondary alcohol is still fast, thereby leaving the problem of inhibiting the formation of alkyl polycarbamate by the reverse reaction unsolved. An alternative method has been disclosed whereby, in the production of aromatic isocyanates, for example, an aromatic alkyl polycarbamate and an aromatic hydroxy compound are subjected to a transesterification reaction to produce an aromatic aryl polycarbamate followed by thermal decomposition of the aromatic aryl polycarbamate to product an aromatic isocyanate (see, for example, US Patent No. 3,992,430). This method describes the effect of being able to set the thermal decomposition temperature to a lower temperature by going through an aromatic aryl polycarbamate. However, in the case of this aromatic aryl polycarbamate as well, under temperatures like those at which the transesterification reaction or thermal decomposition reaction is carried out, there are many cases in which side reactions like those described above still occur, there leaving the problem of improving isocyanate yield unsolved. Moreover, thermal decomposition of N-substituted aromatic urethanes in the gaseous phase or liquid phase is known to frequently result in the occurrence of various undesirable side reactions (see, for example, US Disclosure of Invention Problems to be Solved by the Invention As has been described above, there are currently hardly any methods for industrially producing polyisocyanates at favorable yield without using extremely toxic phosgene. An object of the present invention is to provide a process that enables isocyanates to be stably produced over a long period of time at high yield without encountering various problems as found in the prior art when producing isocyanates without using phosgene. Means for Solving the Problems In view of the above, as a result of conductive extensive studies on the above-mentioned problems, the inventors of the present invention found that a production process in which a carbamic acid ester and a specific aromatic hydroxy compound are subjected to a transesterification reaction to produce an aryl carbamate followed by subjecting the aryl carbamate to a thermal decomposition reaction to produce isocyanate enables the above-mentioned problems to be solved, thereby leading to completion of the present invention. Namely, the present invention provides the followings: [1] a process for producing an isocyanate, comprising the steps of: reacting a carbamic acid ester and an aromatic hydroxy compound to obtain an aryl carbamate having a group derived from the aromatic hydroxy compound; and subjecting the aryl carbamate to a decomposition reaction, wherein the aromatic hydroxy compound is an aromatic hydroxy compound which is represented by the following formula (5) and which has a substituent R1 at at least one ortho position of a hydroxyl group: (5) (wherein ring A represents an aromatic hydrocarbon ring in a form of a single or multiple rings which may have a substituent and which have 6 to 20 carbon atoms; R1 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom; and R1 may bond with A to form a ring structure), [2] the process according to item [1], wherein the aromatic hydroxy compound is a compound represented by the following formula (6): (6) (wherein ring A and R1 are the same as defined above, R2 represents a hydrogen atom or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or aralkyloxy group having 7 to 20 atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl and the aralkyloxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom, and R2 may bond with A to form a ring structure), [3] the process according to item [2], wherein in the formula (6), a total number of the carbon atoms constituting R1 and R2 is 2 to 20, [4] the process according to any one of items [1] to [3], wherein the ring A of the aromatic hydroxy compound comprises a structure containing at least one structure selected from the group consisting of a benzene ring, a naphthalene ring and an anthracene ring, [5] the process according to item [4], wherein the aromatic hydroxy compound is a compound represented by the following formula (7): (wherein R1 and R2 are the same as defined above, and each of R3, R4 and R5 independently represents a hydrogen atom or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl and the aralkyloxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom), [6] the process according to item [5], wherein the aromatic hydroxy compound is such that in the formula (7), each of R1 and R4 independently represents a group represented by the following formula (8), and R2, R3 and R5 represent a hydrogen atom: (wherein X represents a branched structure selected from the structures represented by the following formulas (9) and (10): (wherein R6 represents a linear or branched alkyl group having 1 to 3 carbon atoms), [7] the process according to item [5], wherein the aromatic hydroxy compound is such that in the formula (3), R1 represents a linear or branched alkyl group having 1 to 8 carbon atoms, and each of R2 and R4 independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, [8] the process according to any one of items [1] to [7], wherein the carbamic acid ester is an aliphatic carbamic acid ester, and a low boiling point component formed with the aryl carbamate is an aliphatic alcohol, [9] the process according to item [8], wherein the aliphatic carbamic acid ester is an aliphatic polycarbamic acid ester. [10] the process according to item [8], further comprising the steps of: continuously supplying the aliphatic carbamic acid ester and the aromatic hydroxy compound to a reaction vessel so as to react the aliphatic carbamic acid ester and the aromatic hydroxy compound inside the reaction vessel; recovering a formed low boiling point component in a form of a gaseous component; and continuously extracting a reaction liquid containing the aryl carbamate and the aromatic hydroxy compound from a bottom of the reaction vessel, [11] the process according to any one of items [1] to [10], wherein the decomposition reaction is a thermal decomposition reaction, and is a reaction in which a corresponding isocyanate and aromatic hydroxy compound are formed from the aryl carbamate, [12] the process according to item [11], wherein at least one compound of the isocyanate and aromatic hydroxy compound formed by the thermal decomposition reaction of the aryl carbamate is recovered in a form of a gaseous component, [13] the process according to item [8], wherein the aliphatic carbamic acid ester is a compound represented by the following formula (11): (wherein R7 represents a group selected from the group consisting of an aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atoms, and having a valence of n, R8 represents an aliphatic group which has 1 to 8 carbon atoms and which contains an atom selected from a carbon atom, an oxygen atom and a nitrogen atom, and n represents an integer of 1 to 10), [14] the process according to item [13], wherein the aliphatic carbamic acid ester is such that R8 in the compound represented by the formula (11) is a group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms and a cycloalkyl group having 5 to 20 carbon atoms, [15] the process according to item [14], wherein the aliphatic carbamic acid ester is at least one compound selected from the group consisting of compounds represented by the following formulas (12), (13) and (14): (wherein R8 is the same as defined above), [16] an aryl polycarbamate represented by the following formula (15), (16) or (17): (wherein a ring B represents a structure which may have a substituent and which contains at least one structure selected from the group consisting of a benzene ring, a naphthalene ring and an anthracene ring, R9 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom, and R10 represents an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl and aralkyloxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom), [17] the aryl polycarbamate according to item [16], which is represented by the following formula (18), (19) or (20): (wherein R9 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom, and each of R10, R11 R12 and R13 independently represents a hydrogen atom or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl, and the aralkyloxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atoms). Advantageous Effect of the Invention According to the present invention, an isocyanate can be produced efficiently without using phosgene. Brief Description of Drawings Fig. 1 shows a conceptual drawing showing a continuous production apparatus for producing carbonic acid ester according to an embodiment of the present invention; Fig. 2 shows a conceptual drawing showing a transesterification reaction apparatus according to an embodiment of the present invention; Fig. 3 shows a conceptual drawing showing a thermal decomposition reaction apparatus according to an embodiment of the present invention; Fig. 4 shows a conceptual drawing showing a thermal decomposition reaction apparatus according to an embodiment of the present invention; Fig. 5 shows a conceptual drawing showing an isocyanate production apparatus according to an embodiment of the present invention; Fig. 6 shows the 1H-NMR spectrum of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-butylphenyl) ester obtained in step (3-4) of Example 3 of the present invention; and, Fig. 7 shows the 13C-NMR spectrum of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-butylphenyl) ester obtained in step (3-4) of Example 3 of the present invention. Description of Reference Numericals: (Fig. 1) 101, 107 : distillation column, 102 : column-type reaction vessel, 103, 106 : thin film evaporator, 104 : autoclave, 105 : decarbonization tank, 111, 112, 117 : reboiler, 121, 123, 126, 127 : condenser, 1,9: supply line, 2, 4, 5, 6, 7, 8, 10, 11, 12, 13, 14 : transfer line, 3, 15 : recovery line, 16 : extraction line, 17 : feed line. (Fig. 2) 201 : feed tank, 202 : thin film evaporator, 203 : distillation column, 204 : condenser, 21, 22, 23, 24, 25, 26, 27, 28, 29 : transfer line (Fig.3) 301 : feed tank, 302 : thin film evaporator, 303 : distillation column, 304 : reboiler, 305 : condenser, 31, 32, 33, 34, 35, 36, 37, 38, 39, transfer line (Fig. 4) 401 : feed tank, 402 : thin film evaporator, 403, 404 : distillation column, 405, 407, condenser, 406, 408 : reboiler, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53 : transfer line (Fig. 5) 601, 604 : stirring tank, 602, 605, 608 : tank, 603, 606, 609 : thin film evaporator, 607, 610 : distillation column, 611, 613 : condenser, 612 : reboiler, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81 : transfer line Best Mode for Carrying Out the Invention The following provides a detailed explanation of the best mode for carrying out the present invention (to be referred to as the present embodiment). Furthermore, the present invention is not limited to the following present embodiment, but rather can be modified in various ways within the scope of the gist thereof. The isocyanate production process of the present embodiment is a process for producing isocyanates which comprises the steps of: reacting a carbamic acid ester and an aromatic hydroxy compound to obtain an aryl carbamate having a group derived from the aromatic hydroxy compound; and subjecting the aryl carbamate to a decomposition reaction; wherein the aromatic hydroxy compound uses an aromatic compound having a specific composition. The following indicates an example of the detailed reaction scheme of the present embodiment. However, the isocyanate production process as claimed in the present invention is not limited to the following reaction scheme. isocyanate production process of the present embodiment. The aromatic hydroxy compounds used in the isocyanate production process of the present embodiment are aromatic hydroxy compounds which are represented by the following formula (5) and which have a substituent at at least one site ortho to a hydroxyl group: (wherein ring A represents an aromatic hydrocarbon ring in a form of a single or multiple rings and which have a substitute and which have 6 to 20 carbon atoms; R1 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom, and R1 may bond with A to form a ring structure). Examples of R1 in formula (1) above include aliphatic alkyl groups in which the number of carbon atoms constituting the group is a number selected from integers of 1 to 20, such as a methyl group, an ethyl group, a propyl group (isomers), a butyl group (isomers), a pentyl group (isomers), a hexyl group (isomers), a heptyl group (isomers), an octyl group (isomers), a nonyl group (isomers), a decyl group (isomers), a dodecyl group (isomers), an octadecyl group (isomers) or the like; aliphatic alkoxy groups in which the number of carbon atoms constituting the group is a number selected from integers of 1 to 20, such as a methoxy group, an ethoxy group, a propoxy group (isomers), a butyloxy group (isomers), a pentyloxy group (isomers), a hexyloxy group (isomers), a heptyloxy group (isomers), an octyloxy group (isomers), a nonyloxy group (isomers), a decyloxy group (isomers), a dodecyloxy group (isomers), an octadecyloxy group (including isomers) or the like; aryl groups in which the number of carbon atoms constituting the group is 6 to 20, such as a phenyl group, a methylphenyl group (isomers), an ethylphenyl group (isomers), a propylphenyl group (isomers), a butylphenyl group (isomers), a pentylphenyl group (isomers), a hexylphenyl group (isomers), a heptylphenyl group (isomers), an octylphenyl group (isomers), a nonylphenyl group (isomers), a decylphenyl group (isomers), a biphenyl group (isomers), a dimethylphenyl group (isomers), a diethylphenyl group (isomers), a dipropylphenyl group (isomers), a dibutylphenyl group (isomers), a dipentylphenyl group (isomers), a dihexylphenyl group (isomers), a diheptylphenyl group (isomers), a terphenyl group (isomers), a trimethylphenyl group (isomers), a triethylphenyl group (isomers), a tripropylphenyl group (isomers), a tributylphenyl group (isomers)or the like; aryloxy groups in which the number of carbon atoms constituting the group is 6 to 20, such as a phenoxy group, a methylphenoxy group (isomers), an ethylphenoxy group (isomers), a propylphenoxy group (isomers), a butylphenoxy group (isomers), a pentylphenoxy group (isomers), a hexylphenoxy group (isomers), a heptylphenoxy group (isomers), an octylphenoxy group (isomers), a nonylphenoxy group (isomers), a decylphenoxy group (isomers), a plnenylphenoxy group (isomers), a dimethylphenoxy group (isomers), a diethylphenoxy group (isomers), a dipropylphenoxy group (isomers), a dibutylphenoxy group (isomers), a dipentylphenoxy group (isomers), a dihexylphenoxy group (isomers), a diheptylphenoxy group (isomers), a diphenylphenoxy group (isomers), a trimethylphenoxy group (isomers), a triethylphenoxy group (isomers), a tripropylphenoxy group (isomers), a tributylphenoxy group (isomers) or the like; aralkyl groups in which the number of carbon atoms constituting the group is 7 to 20, such as a phenylmethyl group, a phenylethyl group (isomers), a phenylpropyl group (isomers), a phenylbutyl group (isomers), a phenylpentyl group (isomers), a phenylhexyl group (isomers), a phenylheptyl group (isomers), a phenyloctyl group (isomers), phenylnonyl group (isomers) or the like; and aralkyloxy groups in which the number of carbon atoms constituting the group is 7 to 20, such as a phenylmethoxy group, a phenylethoxy group (isomers), a phenylpropyloxy group (isomers), a phenylbutyloxy group (isomers), a phenylpentyloxy group (isomers), a phenylhexyloxy group (isomers), a phenylheptyloxy group (isomers), a phenyloctyloxy group (isomers), a phenylnonyloxy group (isomers) or the like. Examples of ring A in formula (1) above include a benzene ring, a naphthalene ring, an anthracene ring, a phenanthrene ring, a naphthacene ring, a chrysene ring, a pyrene ring, a triphenylene ring, a pentalene ring, an azulene ring, a heptalene ring, an indacene ring, a biphenylene ring, an acenaphthylene ring, an aceanthrylene ring, an acephenanthrylene ring or the like, preferable examples include rings selected from the group consisting of a benzene ring, a naphthalene ring and an anthracene ring. In addition, these rings may have a substituent other than the above-mentioned R1 examples of which include aliphatic alkyl groups in which the number of carbon atoms constituting the group is a number selected from integers of 1 to 20, such as a methyl group, an ethyl group, a propyl group (isomers), a butyl group (isomers), a pentyl group (isomers), a hexyl group (isomers), a heptyl group (isomers), an octyl group (isomers), a nonyl group (isomers), a decyl group (isomers), a dodecyl group (isomers), an octadecyl group (isomers) or the like; aliphatic alkoxy groups in which the number of carbon atoms constituting the group is a number selected from integers of 1 to 20, such as a methoxy group, an ethoxy group, a propoxy group (isomers), a butyloxy group (isomers), a pentyloxy group (isomers), a hexyloxy group (isomers), a heptyloxy group (isomers), an octyloxy group (isomers), a nonyloxy group (isomers), a decyloxy group (isomers), a dodecyloxy group (isomers), an octadecyloxy group (isomers) or the like; aryl groups in which the number of carbon atoms constituting the group is 6 to 20, such as a phenyl group, a methylphenyl group (isomers), an ethylphenyl group (isomers), a propylphenyl group (isomers), a butylphenyl group (isomers), a pentylphenyl group (isomers), a hexylphenyl group (isomers), a heptylphenyl group (isomers), an octylphenyl group (isomers), a nonylphenyl group (isomers), a decylphenyl group (isomers), a biphenyl group (isomers), a dimethylphenyl group (isomers), a diethylphenyl group (isomers), a dipropylphenyl group (isomers), a dibutylphenyl group (isomers), a dipentylphenyl group (isomers), a dihexylphenyl group (isomers), a diheptylphenyl group (isomers), a terphenyl group (isomers), a trimethylphenyl group (isomers), a triethylphenyl group (isomers), a tripropylphenyl group (isomers), a tributylphenyl group (isomers) or the like; aryloxy groups in which the number of carbon atoms constituting the group is 6 to 20, such as a phenoxy group, a methylphenoxy group (isomers), an ethylphenoxy group (isomers), a propylphenoxy group (isomers), a butylphenoxy group (isomers), a pentylphenoxy group (isomers), a hexylphenoxy group (isomers), a heptylphenoxy group (isomers), an octylphenoxy group (isomers), a nonylphenoxy group (isomers), a decylphenoxy group (isomers), a phenylphenoxy group (isomers), a dimethylphenoxy group (isomers), a diethylphenoxy group (isomers), a dipropylphenoxy group (isomers), a dibutylphenoxy group (isomers), a dipentylphenoxy group (isomers), a dihexylphenoxy group isomers), a diheptylphenoxy group (isomers), a diphenylphenoxy group (isomers), a trimethylphenoxy group (isomers), a triethylphenoxy group (isomers), a tripropylphenoxy group (isomers), a tributylphenoxy group (isomers) or the like; aralkyl groups in which the number of carbon atoms constituting the group is 7 to 20, such as a phenylmethyl group, a phenylethyl group (isomers), a phenylpropyl group (isomers), a phenylbutyl group (isomers), a phenylpentyl group (isomers), a phenylhexyl group (isomers), a phenylheptyl group (isomers), a phenyloctyl group (isomers), a phenylnonyl group (isomers) or the like; and aralkyloxy groups in which the number of carbon atoms constituting the group is 7 to 20, such as a phenylmethoxy group, a phenylethoxy group (isomers), a phenylpropyloxy group (isomers), a phenylbutyloxy group (isomers), a phenylpentyloxy group (isomers), a phenylhexyloxy group (isomers), a phenylheptyloxy group (isomers), a phenyloctyloxy group (isomers), a phenylnonyloxy group (isomers). In addition, the aromatic hydroxy compounds can be used preferably whether it is an aromatic hydroxy compound having a substituent at one ortho position to a hydroxyl group or an aromatic hydroxy compound having substituents at two ortho positions to a hydroxyl group as in compounds represented by the following formula (6): (wherein ring A and R1 are the same as defined above, R2 represents an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl, and the aralkyloxy groups containing atoms selected from a carbon atom, an oxygen atom and a nitrogen atom, and R2 may bond with A to form a ring structure). Examples of R2 in the above-mentioned formula (6) include a hydrogen atom; aliphatic alkyl groups in which the number of carbon atoms constituting the group is a number selected from integers of 1 to 20, such as a methyl group, an ethyl group, a propyl group (isomers), a butyl group (isomers), a pentyl group (isomers), a hexyl group (isomers), a heptyl group (isomers), an octyl group (isomers), a nonyl group (isomers), a decyl group (isomers), a dodecyl group (isomers), an octadecyl group (isomers) or the like; aliphatic alkoxy groups in which the number of carbon atoms constituting the group is a number selected from integers of 1 to 20, such as a methoxy group, an ethoxy group, a propoxy group (isomers), a butyloxy group (isomers), a pentyloxy group (isomers), a hexyloxy group (isomers), a heptyloxy group (isomers), an octyloxy group (isomers), a nonyloxy group (isomers), a decyloxy group (isomers), a dodecyloxy group (isomers), an octadecyloxy group (isomers) or tine like; aryl groups in which the number of carbon atoms constituting the group is 6 to 20, such as a phenyl group, a methylphenyl group (isomers), an ethylphenyl group (isomers), a propylphenyl group (isomers), a butylphenyl group (isomers), a pentylphenyl group (isomers), a hexylphenyl group (isomers), a heptylphenyl group (isomers), an octylphenyl group (isomers), a nonylphenyl group (isomers), a decylphenyl group (isomers), a biphenyl group (isomers), a dimethylphenyl group (isomers), a diethylphenyl group (isomers), a dipropylphenyl group (isomers), a dibutylphenyl group (isomers), a dipentylphenyl group (isomers), a dihexylphenyl group (isomers), a diheptylphenyl group (isomers), a terphenyl group (isomers), a trimethylphenyl group (isomers), a triethylphenyl group (isomers), a tripropylphenyl group (isomers), a tributylphenyl group (isomers) or the like; aryloxy groups in which the number of carbon atoms constituting the group is 6 to 20, such as a phenoxy group, a methylphenoxy group (isomers), an ethylphenoxy group (isomers), a propylphenoxy group (isomers), a butylphenoxy group (isomers), a pentylphenoxy group (isomers), a hexylphenoxy group (isomers), a heptylphenoxy group (isomers), an octylphenoxy group (isomers), a nonylphenoxy group (isomers), a decylphenoxy group (isomers), a phenylphenoxy group (isomers), a dimethylphenoxy group (isomers), a diethylphenoxy group (isomers), a dipropylphenoxy group (isomers), a dibutylphenoxy group (isomers), a dipentylphenoxy group (isomers), a dihexylphenoxy group (isomers), a diheptylphenoxy group (isomers), a diphenylphenoxy group (isomers), a trimethylphenoxy group (isomers), a triethylphenoxy group (isomers), a tripropylphenoxy group (isomers), a tributylphenoxy group (isomers) or the like; aralkyl groups in which the number of carbon atoms constituting the group is 7 to 20, such as a phenylmethyl group, a phenylethyl group (isomers), a phenylpropyl group (isomers), a phenylbutyl group (isomers), a phenylpentyl group (isomers), a phenylhexyl group (isomers), a phenylheptyl group (isomers), a phenyloctyl group (isomers), a phenylnonyl group (isomers) or the like; and aralkyloxy groups in which the number of carbon atoms constituting the group is 7 to 20, such as a phenylmethoxy group, a phenylethoxy group (isomers), a phenylpropyloxy group (isomers), a phenylbutyloxy group (isomers), a phenylpentyloxy group (isomers), a phenylhexyloxy group (isomers), a phenylheptyloxy group (isomers), a phenyloctyloxy group (isomers), a phenylnonyloxy group (isomers) or the like. In the case the aromatic hydroxy compound used in the isocyanate production process of the present embodiment are aromatic hydroxy compounds having substituents at two ortho positions to a hydroxyl group, aromatic hydroxy compounds in which the total number of carbon atoms constituting R1 and R2 is 2 to 20 are used preferably among the compounds represented by the above-mentioned formula (6). There are no particular limitations on the combinations of R1 and R2 provided the total number of carbon atoms constituting R1 and R2 is 2 to 20. Examples of such aromatic hydroxy compounds include compounds represented by the following formula (7): (wherein R1 and R2 are the same as defined above, and each of R3, R4 and R5 independently represents a hydrogen atom or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl, and the aralkyloxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atoms). In particular, aromatic hydroxy compounds in which each of R1 and R4 in the above-mentioned formula (7) independently represents a group represented by the following formula (8) and R2, R3 and R5 represent hydrogen atoms, or aromatic hydroxy compounds in which R1 in the above-mentioned formula (7) is a linear or branched alkyl group having 1 to 8 carbon atoms and each of R2 and R4 independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms, are used preferably: (wherein X represents a branched structure selected from the structures represented by the following formulas (9) and (10): (wherein R6 represents a linear or branched alkyl group having 1 to 3 carbon atoms). Examples of such aromatic hydroxy compounds include 2-ethylphenol, 2-propylphenol (isomers), 2-butylphenol (isomers), 2-pentylphenol (isomers), 2-hexylphenol (isomers), 2-heptylphenol (isomers), 2,6-dimethylphenol, 2,4-diethylphenol, 2,6-diethylphenol, 2,4-dipropylphenol (isomers), 2,6-dipropylphenol (isomers), 2,4-dibutylphenol (isomers), 2,4-dipentylphenol (isomers), 2,4-dihexylphenol (isomers), 2,4-diheptylphenol (isomers), 2-methyl-6-ethylphenol, 2-methyl-6-propylphenol (isomers), 2-methyl-6-butylphenol (isomers), 2-methyl-6-pentylphenol (isomers), 2-ethyl-6-propylphenol (isomers), 2-ethyl-6-butylphenol (isomers), 2-ethyl-6-pentylphenol (isomers), 2-propyl-6-butyl phenol (isomers), 2-ethyl-4-methylphenol (isomers), 2-ethyl-4-propyl phenol (isomers), 2-ethyl-butylphenol (isomers), 2-ethyl-4-pentyl phenol (isomers), 2-ethyl-4-hexylphenol (isomers), 2-ethyl-4-heptylphenol (isomers), 2-ethyl-4-octylphenol (isomers), 2-ethyl-4-phenylphenol (isomers), 2-ethyl-4-cumylphenol (isomers), 2-propyl-4-methylphenol (isomers), 2-propyl-4-ethylphenol (isomers), 2-propyl-4-butylphenol (isomers), 2-propyl-4-pentylphenol (isomers), 2-propyl-4-hexylphenol (isomers), 2-propyl-4-hetpylphenol (isomers), 2-propyl-4-octylphenol (isomers), The aromatic hydroxy compounds are preferably aromatic hydroxy compounds having a standard boiling point higher than the standard boiling point of a hydroxy compound corresponding to an aliphatic alkoxy group, aryloxy group or aralkyloxy group that composes the ester group of the carbamic acid ester described below. The term "standard boiling point" as referred to in the present invention indicates the boiling point at 1 atmosphere. There are no particular limitations on the carbamic acid ester used in the isocyanate production process of the present embodiment, and an aliphatic carbamic acid ester is used preferably. Examples of aliphatic carbamic acid esters include compounds represented by the following formula (11): (wherein R7 represents a group selected from the group consisting of an aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to 20 carbon atoms, the group containing an atom selected from a carbon atom and an oxygen atom, and having a number of atoms equal to n, R8 represents an aliphatic group having 1 to 8 carbon atoms containing an atom selected from a carbon atom and an oxygen atom, and n represents an integer of 1 to 10). In formula (11) above, n is preferably a number selected from integers of 2 or more, and more preferably an aliphatic polycarbamic acid ester in which n is 2. Examples of R7 in formula (11) include linear hydrocarbon groups such as methylene, dimethylene, trimethylene, tetramethylene, pentamethylene, hexamethylene, octamethylene or the like; unsubstituted acyclic hydrocarbon groups such as cyclopentane, cyclohexane, cycloheptane, cyclooctane, bis(cyclohexyl)alkane or the like; alkyl-substituted cydohexanes such as methylcyclopentane, ethylcydopentane, methylcyclohexane (isomers), ethylcyclohexane (isomers), propylcyclohexane (isomers), butylcyclohexane (isomers), pentylcydohexane (isomers), hexylcyclohexane (isomers) or the like; dialkyl-substituted cydohexanes such as dimethylcyclohexane (isomers), diethylcyclohexane (isomers), dibutylcydohexane (isomers) or the like; trialkyl-substituted cydohexanes such as 1,5,5-trimethylcyclohexane, 1,5,5-triethylcyclohexane, 1,5,5-tripropylcyclohexane (isomers), 1,5,5-tributylcyclohexane (isomers) or the like; monoalkyl-substituted benzenes such as toluene, ethylbenzene, propylbenzene or the like; dialkyl-substituted benzenes such as xylene, diethylbenzene, dipropylbenzene or the like; and aromatic hydrocarbons such as diphenylalkane, benzene or the like. In particular, hexamethylene, phenylene, diphenylmethane, toluene, cyclohexane, xylene, methylcyclohexane, isophorone and dicyclohexylmethane are used preferably. Examples of R8 include alkyl groups in which the number of carbon atoms constituting the group is selected from an integer of 1 to 8, such as a methyl group, an ethyl group, a propyl group (isomers), a butyl group (isomers), a pentyl group (isomers), a hexyl group (isomers), a heptyl group (isomers), an octyl group (isomers) or the like; and cydoalkyl groups in which the number of carbon atoms constituting the group is selected from an integer of 5 to 14, such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, a dicyclopentyl group (isomers), a dicyclohexyl group (isomers), a cyclohexyl-cydopentyl group or the like. Examples of alkyl polycarbamates represented by the above-mentioned formula (11) include alkyl carbamates such as N,N'-hexanediyl-bis-carbamic acid dimethyl ester, N,N'-hexanediyl-bis-carbamic acid diethyl ester, 3-(methoxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid methyl ester, 3-(ethoxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid ethyl ester, 3-(propyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid propyl ester (isomers), 3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid butyl ester (isomers). 3-(pentyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid pentyl ester (isomers), 3-(hexyloxycarbonylannino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid hexyl ester (isomers), 3-(heptyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid heptyl ester (isomers), 3-(octyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid octyl ester (isomers), toluene-dicarbamic acid dimethyl ester (isomers), toluene-dicarbamic acid diethyl ester (isomers), toluene-dicarbamic acid dipropyl ester (isomers), toluene-dicarbamic acid dibutyl ester (isomers), toluene-dicarbamic acid dipentyl ester (isomers), toluene-dicarbamic acid dihexyl ester (isomers), toluene-dicarbamic acid diheptyl ester (isomers), toluene-dicarbamic acid dioctyl ester (isomers), N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dimethyl ester, N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid diethyl ester, N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dipropyl ester, N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester, N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dipentyl ester, N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dihexyl ester, N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid diheptyl ester, N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dioctyl ester or the like. Among these, alkyl carbamates in which R7 in formula (11) above is a group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms and a cydoalkyl group having 5 to 20 carbon atoms are used preferably, while alkyl carbamates represented by any of the following formulas (12) to (14) are used particularly preferably: (wherein R8 is the same as defined above). Examples of alkyl polycarbamates represented by formula (12) include N,N'-hexanediyl-bis-carbamic acid dimethyl ester, N,N'-hexanediyl-bis-carbamic acid diethyl ester, N,N'-hexanediyl-bis-carbamic acid dibutyl ester (isomers), N,N'-hexanediyl-bis-carbamic acid dipentyl ester (isomers), N,N'-hexanediyl-bis-carbamic acid dihexyl ester (isomers) and N,N'-hexanediyl-bis-carbamic acid dioctyl ester (including isomers). In addition, examples of alkyl polycarbamates represented by formula (13) include dimethyl-4,4'-methylene-dicyclohexyl carbamate, diethyl-4,4'-methylene-dicyclohexyl carbamate, dipropyl-4,4'-methylene-dicyclohexyl carbamate (isomers), dibutyl-4,4'-methylene-dicyclohexyl carbamate (isomers), dipentyl-4,4'-methylene-dicyclohexyl carbamate (isomers), dihexyl-4,4'-methylene-dicyclohexyl carbamate (isomers), diheptyl-4,4'-methylene-dicyclohexyl carbamate (isomers) and dioctyl-4,4'-methylene-dicyclohexyl carbamate (isomers). Moreover, examples of alkyl polycarbamates represented by formula (14) Include alkyl polycarbamates such as 3-(methoxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid methyl ester, 3-(ethoxycarbonylamlno-methyl)-3,5,5-trimethylcyclohexyl carbamic add ethyl ester, 3-(propyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid propyl ester (isomers), 3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid butyl ester (isomers), 3-(pentyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid pentyl ester (isomers), 3-(hexyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid hexyl ester (isomers), 3-(heptyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid heptyl ester (isomers), 3-(octyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid octyl ester (isomers) or the like. A known method can be used to produce the carbamic acid esters. For example, carbamic esters may be produced by reacting amine compounds with carbon monoxide, oxygen and aliphatic alcohols or aromatic hydroxy compounds, or reacting amine compounds with urea and aliphatic alcohols or aromatic hydroxy compounds. In the present embodiment, the carbamic acid esters are preferably produced by reacting carbonic acid esters and amine compounds. The following provides an explanation of the production of alkyl carbamates by reacting dialkyl carbonates and amine compounds. Dialkyl carbonates represented by the following formula (21) can be used for the dialkyl carbonates: (wherein R17 represents a linear or branched alkyl group having 1 to 8 carbon atoms). Examples of R17 include alkyl groups in a form of aliphatic hydrocarbon groups in which the number of carbon atoms constituting the group is a number selected from an integer of 1 to 8, such as a methyl group, an ethyl group, a propyl group (isomers), a butyl group (isomers), a pentyl group (isomers), a hexyl group (isomers), a heptyl group (isomers), an octyl group (isomers) or the like. Examples of such dialkyl carbonates include dimethyl carbonate, diethyl carbonate, dipropyl carbonate (isomers), dibutyl carbonate (isomers), dipentyl carbonate (isomers), dihexyl carbonate (isomers), diheptyl carbonate (isomers) and dioctyl carbonate (isomers). Among these, a dialkyl carbonate in which the number of carbon atoms constituting the alkyl groups is a number selected from an integer of 4 to 6 is used particularly preferably. Amine compounds represented by the following formula (22) are preferably used for the amine compounds: (wherein R7 represents a group selected from the group consisting of an aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to 20 carbon atoms, the group containing an atom selected from a carbon atom and an oxygen atom, and having a valence of n, and n represents an integer of 1 to 10). In formula (22) above, a polyamine compound is used in which n is preferably 1 to 3 and more preferably n is 2. Examples of such polyamine compounds include aliphatic diamines such as hexamethylene diamine, 4,4'-methylenebis(cyclohexylamine) (isomers), cydohexane diamine (isomers), 3-aminomethyl-3,5,5-trimethylcyclohexyl amine (isomers) or the like; and aromatic diamines such as phenylene diamine (isomers), toluene diamine (isomers), 4,4'-methylene dianiline (isomers) or the like. Among these, aliphatic diamines such as hexamethylene diamine, 4,4'-methylenebis(cyclohexylamine) (isomers), cydohexane diamine (isomers), 3-aminomethyl-3,5,5-trimethylcyclohexyl amine (isomers) or the like are used preferably, while hexamethylene diamine, 4,4'-methylenebis(cyclohexylamine) and 3-aminomethyl-3,5,5-trimethylcyclohexyl amine are used more preferably. Reaction conditions vary according to the reacted compounds, and although the dialkyl carbonate is preferably in excess based on the amino groups of the amine compound to accelerate the reaction rate and complete the reaction quickly at a stoichiometric ratio of the dialkyl carbonate to amino groups of the amine compound within a range of from 2 to 1000 times, the range is preferably from 2 to 100 times and more preferably from 2.5 to 30 times in consideration of the size of the reaction vessel. The reaction temperature is generally within the range of from normal temperature (20°C) to 300°C, and although higher temperatures are preferable in order to accelerate the reaction rate, since undesirable reactions may conversely occur at high temperatures, the reaction temperature is preferably within the range of from 50 to 150°C. A known cooling apparatus or heating apparatus may be installed in the reaction vessel to maintain a constant reaction temperature. In addition, although varying according to the types of compounds used and reaction temperature, the reaction pressure may be decreased pressure, normal pressure or increased pressure, and the reaction is generally carried out at a pressure within the range of from 20 to 1 x 106 Pa. There are no particular limitations on the reaction time (residence time in the case of a continuous method), and is generally from 0.001 to 50 hours, preferably from 0.01 to 10 hours and more preferably from 0.1 to 5 hours. In addition, the reaction can also be completed by confirming that a desired amount of alkyl carbamate has been formed by, for example, liquid chromatography after sampling the reaction liquid. In the present embodiment, a catalyst can be used as necessary, and examples of catalysts that can be used include organic metal compounds and inorganic metal compounds of tin, lead, copper or titanium, and basic catalysts such as alkylates of alkaline metals or alkaline earth metals in the form of methylates, ethylates and butyrates (isomers) of lithium, sodium, potassium, calcium, or barium. Although the use of a reaction solvent is not necessarily required in the present embodiment, a suitable inert solvent is preferably used as a reaction solvent for the purpose of facilitating the reaction procedure, examples of which include alkanes such as hexane (isomers), heptane (isomers), octane (isomers), nonane (isomers), decane (isomers) or the like; aromatic hydrocarbons and alkyl-substituted aromatic hydrocarbons such as benzene, toluene, xylene (isomers), ethyl benzene, diisopropyl benzene (isomers), dibutyl benzene (isomers), naphthalene or the like; aromatic compounds substituted with a halogen or nitro group such as chlorobenzene, dichlorobenzene (isomers), bromobenzene. dibromobenzene (isomers), chloronaphthalene, bromonaphthalene, nitrobenzene, nitronaphthalene or the like; polycyclic hydrocarbon compounds such as diphenyl, substituted diphenyl, diphenyl methane, terphenyl, anthracene, dibenzyl toluene or the like; aliphatic hydrocarbons such as cyclohexane, cyclopentane, cyclooctane, ethylcyclohexane or the like; ketones such as methyl ethyl ketone, acetophenone or the like; esters such as dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, benzylbutyl phthalate or the like; ethers and thioethers such as diphenyl ether, diphenyl sulfide or the like; and sulfoxides such as dimethylsulfoxide, diphenylsulfoxide or the like. These solvents can be used alone or two or more types can be used as a mixture. In addition, the dialkyl carbonate used in excess based on amino groups of the amine compound is also preferably used as a solvent in the reaction. A known tank reactor, column reactor or distillation column can be used for the reaction vessel, and although known materials may be used for the reaction vessel and lines provided they do not have a detrimental effect on the starting substances or reactants, SUS304, SUS316 or SUS316L and the like can be used preferably since they are inexpensive. In the isocyanate production process of the present embodiment, carbamic acid esters and aromatic hydroxy compounds are first reacted to obtain aryl carbamates having a group derived from the aromatic hydroxy compounds. This reaction involves an exchange between an aliphatic alkoxy group or aralkyloxy group constituting the ester group of the carbamic acid ester and an aryloxy group derived from the aromatic hydroxy compounds resulting in the formation of the corresponding aryl carbamate and a hydroxy compound derived from the carbamic acid ester (and is referred to as a transesterification reaction in the present description). Although varying according to the reacted compounds, the reaction conditions of this transesterification reaction are such that the aromatic hydroxy compound is used within the range of from 2 to 1000 times the ester group of the carbamic acid ester when expressed as the stoichiometric ratio. As a result of conducting extensive studies, the inventors of the present invention surprisingly found that by using the aromatic hydroxy compounds having a substituent at at least one ortho position with respect to the hydroxyl group in this transesterification reaction as described above, side reactions as previously-described attributable to the carbamic acid ester and / or product in the form of the aryl carbamate can be inhibited in the transesterification reaction. In the transesterification reaction, although the aromatic hydroxy compound is preferably used in excess based on the ester group of the carbamic acid ester in order to inhibit side reactions attributable to the carbamic acid ester and / or product in the form of the aryl carbamate as well as allow the reaction to be completed quickly, the aromatic hydroxy compound is preferably used within the range of from 2 to 100 times and preferably within the range of from 5 to 50 times in consideration of the size of the reaction vessel. The reaction temperature is generally within the range of from 100 to 300°C, and although high temperatures are preferable in order to increase the reaction rate, since there conversely may be greater susceptibility to the occurrence of side reactions at high temperatures, the reaction temperature is preferably within the range of from 150 to 250°C. A known cooling apparatus or heating apparatus may be installed in the reaction vessel to maintain a constant reaction temperature. In addition, although varying according to the types of compounds used and reaction temperature, the reaction pressure may be decreased pressure, normal pressure or increased pressure, and the reaction is generally carried out at a pressure within the range of from 20 to 1 x 106 Pa. There are no particular limitations on the reaction time (residence time in the case of a continuous method) and is generally from 0.001 to 100 hours, preferably from 0.01 to 50 hours and more preferably from 0.1 to 30 hours. In addition, the reaction can also be completed by confirming that a desired amount of aryl carbamate has been formed by, for example, liquid chromatography after sampling the reaction liquid. In the present embodiment, the catalyst is used at from 0.01 to 30% by weight and preferably at from 0.5 to 20% by weight based on the weight of the carbamic acid ester. For example, organic metal catalysts such as dibutyl tin dilaurate, ferrous octoate or stannous octoate, or amines such as 1,4-diazabicyclo[2,2,2]octane, triethylenediamine or triethylamine are suitable for use, while organic metal catalysts such as dibutyl tin dilaurate, ferrous octoate or stannous octoate are particularly preferable. These compounds may be used alone or two or more types may be used as a mixture. Although the use of a reaction solvent is not necessarily required in the present embodiment, a suitable inert solvent is preferably used as a reaction solvent for the purpose of facilitating the reaction procedure, examples of which include alkanes such as hexane (isomers), heptane (isomers), octane (isomers), nonane (isomers), decane (isomers)or the like; aromatic hydrocarbons and alkyl-substituted aromatic hydrocarbons such as benzene, toluene, xylene (isomers), ethylbenzene, diisopropyl- benzene (isomers), dibutylbenzene (isomers), naphthalene or the like; aromatic compounds substituted with a halogen or nitro group such as chlorobenzene, dichlorobenzene (isomers), bromobenzene, dibromobenzene (isomers), chloronaphthalene, bromonaphthalene, nitrobenzene, nitronaphthalene or the like; polycyclic hydrocarbon compounds such as diphenyl, substituted diphenyl, diphenyl methane, terphenyl, anthracene, dibenzyltoluene (isomers) or the like; aliphatic hydrocarbons such as cyclohexane, cyclopentane, cyclooctane, ethylcydohexane or the like; ketones such as methyl ethyl ketone, acetophenone or the like; esters such as dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, benzylbutyl phthalate or the like; ethers and thioethers such as diphenyl ether, diphenyl sulfide or the like; and sulfoxides such as dimethylsulfoxide, diphenylsulfoxide or the like; and, silicone oil. These solvents can be used alone or two or more types can be used as a mixture. As has been described above, although the transesterification reaction in the present embodiment involves the exchange between the aliphatic alkoxy group constituting the ester group of the carbamic acid ester and the aryloxy group derived from the aromatic hydroxy compound resulting in the formation of the corresponding aryl carbamates and the alcohols, the transesterification reaction is an equilibrium reaction. Thus, in order to efficiently produce the aryl carbamates by this transesterification reaction, it is preferable to remove the products from the reaction system. Since the compounds having the lowest standard boiling point in the reaction system are the alcohols formed by the transesterification reaction, the alcohols are preferably removed from the reaction system by a method such as distillative separation. In addition, the transesterification reaction is preferably carried out with a continuous method to allow the transesterification reaction to proceed efficiently. Namely, a method is preferably used in which the carbamic acid esters and the aromatic hydroxy compounds are supplied continuously to the reaction vessel to carry out the transesterification reaction, the alcohols formed are removed from the reaction vessel in the form of the gaseous components, and reaction liquids containing the formed aryl carbamates and the aromatic hydroxy compounds are continuously removed from the bottom of the reaction vessel. In the case of carrying out the transesterification reaction according to this method, in addition to promoting the transesterification reaction, there is also the surprisingly effect of being able to improve the final yield of isocyanates by inhibiting side reactions as previously described. Although known materials may be used for the reaction vessel and lines used to carry out the transesterification reaction provided they do not have a detrimental effect on the starting substances or reactants, SUS304, SUS316 or SUS316L and the like can be used preferably since they are inexpensive. There are no particular limitations on the type of reaction vessel, and a known tank reactor or column reactor can be used. A reaction vessel is preferably used that is provided with lines for extracting a low boiling point reaction mixture containing alcohol formed in the transesterification reaction from the reaction vessel in the form of the gaseous components, and for removing mixed liquids containing the produced aryl carbamates and aromatic hydroxy compounds from the lower portion of the reaction vessel in the form of a liquid. Various known methods are used for such a reaction vessel, examples of which include types using reaction vessels containing a stirring tank, a multistage stirring tank, a distillation column, a multistage distillation column, a multitubular reactor, a continuous multistage distillation column, a packed column, a thin film evaporator, a reactor provided with a support inside, a forced circulation reactor, a falling film evaporator, a falling drop evaporator, a trickle flow reactor, a bubble column, and types using combinations thereof. Methods using the thin film evaporator or columnar reactor are preferable from the viewpoint of efficiently shifting the equilibrium to the products side, while a structure having a large gas-liquid contact area is preferable for being able to rapidly transfer the alcohol formed to the gaseous phase. The multistage distillation column refers to a distillation column having multiple stages in which the number of theoretical plates of distillation is 2 or more, and any multistage distillation column may be used provided it allows continuous distillation. Any multistage distillation column can be used for the multistage distillation column provided it is ordinarily used as a multistage distillation column, examples of which include tray column types using a bubble tray, a porous plate tray, a valve tray, a counter-current tray or the like, and packed column types packed with various types of packing materials such as a raschig ring, a lessing ring, a pole ring, a Berl saddle, an Interlock saddle, a Dixon packing, a McMahon packing, Helipack, a Sulzer packing, Mellapak or the like. Any packed column can be used provided the column is packed with known packing materials as described above. Moreover, a combination tray-packed column type is also used preferably that combines a tray portion with the portion packed with the packing materials. The reaction vessel is preferably provided with a line for supplying a mixture containing the carbamic acid esters and the aromatic hydroxy compounds, a line for removing the gaseous phase components containing alcohols formed by the transestehfication reaction, and a line for extracting mixed liquids containing the carbamic acid esters and aromatic hydroxy compounds, and the line for removing the gaseous phase components containing the alcohols is preferably at a location that allows the gaseous phase components in the reaction vessel to be removed, and the line for extracting the mixed liquids containing the aryl carbamates and the aromatic hydroxy compounds is particularly preferably located there below. A line for supplying inert gas and / or liquid inert solvent from the lower portion of the reaction vessel may be separately attached, and in the case the mixed liquids containing the formed aryl carbamates and the aromatic hydroxy compounds contain unreacted carbamic acid esters, a line may be attached for recirculating all or a portion of the mixed liquids to the reaction vessel. Note that in the case of using the above-mentioned inert solvent, the inert solvent may be in the form of a gas and / or a liquid. The gaseous components containing alcohols extracted from the reaction vessel may be purified using a known method such as a distillation column, and the azeotropic and / or accompanying aromatic hydroxy compound and the like may be recycled. Equipment for warming, cooling or heating may be added to each line in consideration of clogging and the like. The aryl carbamates preferably produced by the transesterification reaction are aryl carbamates represented by any of the following formulas (15) to (17): (wherein ring B represents a structure which may have a substituent and which contains at least one structure selected from the group consisting of a benzene ring, a naphthalene ring and an anthracene ring, R9 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom, and R10 represents an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl and aralkyoxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atoms). Among these, more preferably produced aryl carbamates are aryl carbamates represented by any of the following formulas (18) to (20); (wherein R9 represents a group other than a hydrogen atom in a form of an alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atoms, and each of R10, R11, R12 and R13 independently represents a hydrogen atom or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl, and the aralkyoxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom). include 3-((2-ethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2-ethylphenyl)ester, 3-((2-propylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2-propylphenyl)ester (isomers), 3-((2-butylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2-butylphenyl)ester (isomers), 3-((2-pentylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2-pentylphenyl)ester (isomers), 3-((2-hexylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2-hexylphenyl)ester (isomers), 3-((2-heptylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2-heptylphenyl)ester (isomers), 3-((2-octylphenoxy)carbonyiamino-methyl)-3,5,5-trimethyicyclohexyl carbamic acid (2-octylphenyl)ester (isomers), 3-((2-cumyiphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2-cumyiphenyi)ester (isomers), 3-((2,4-diethylphenoxy)carbonylamino-methyi)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-diethylphenyl)ester, 3-((2,4-dipropylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-dipropylphenyl)ester (isomers), 3-((2,4-dibutylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-dibutylphenyl)ester (isomers), 3-((2,4-dipentylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-dipentylplnenyl)ester (isomers), 3-((2,4-dihexylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-dihexylphenyl)ester (isomers), 3-((2,4-diheptylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-diheptylphenyl)ester (isomers), 3-((2,4-dioctylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-dioctylphenyl)ester (isomers), 3-((2,4-dicumylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-dicumylphenyl)ester, 3-((2,6-dimethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,6-dimethylphenyi)ester, 3-((2,6-diethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,6-diethylphenyl)ester, 3-((2,6-dipropylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,6-dipropylphenyl)ester (isomers), 3-((2,4,6-trimethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4,6-trimethylphenyl)ester, 3-((2,4,6-triethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4,6-triethylphenyl)ester, and 3-((2,4,6-tripropylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4,6-tripropylphenyl)ester (isomers). The aryl carbamates produced in the transesterification reaction may be subjected to the subsequent thermal decomposition reaction while still as a mixed liquid containing aryl carbamates and aromatic hydroxy compounds which are removed from the reactor, or the aryl carbamates may be subjected to the thermal decomposition reaction after purifying from the mixed liquid. A known method can be used to purify the aryl carbamate from the reaction liquid, examples of which include removal of the aromatic hydroxy compounds by distillation, washing with solvents and purification of the aryl carbamates by crystallization. Since the aryl carbamates of the present embodiment are carbamic acid esters composed of aromatic hydroxy compounds and isocyanates, the thermal decomposition temperature is low as is generally known. In addition, the aryl carbamates of the present embodiment are surprisingly extremely resistant to the occurrence of side reactions (such as a reaction resulting in the formation of a urea bond as previously described) at high temperatures (such as 180°C) at which thermal decomposition is carried out. Although the mechanism by which side reactions are inhibited is unclear, as was previously described, it is presumed that a substituent at the ortho position relative to the hydroxyl group sterically protects a urethane bond, thereby hindering the reaction between a different carbamic acid ester and the urethane bond. Moreover, although the aromatic hydroxy compounds formed by the thermal decomposition reaction of the aryl carbamates of the present embodiment are aromatic hydroxy compounds having a substituent at the ortho position relative to a hydroxyl group, since the reaction rate between the aromatic hydroxy compounds and isocyanates are surprisingly late, namely the reverse reaction rate in the thermal decomposition reaction is slow, when carrying out the thermal decomposition reaction on the aryl carbamates, there is the advantage of being able to easily separate the aromatic hydroxy compounds and the isocyanates. The following provides an explanation of the aryl carbamate decomposition reaction of the present embodiment. The decomposition reaction of the present embodiment is a thermal decomposition reaction by which corresponding isocyanates and aromatic hydroxy compounds are formed from the aryl carbamates. The reaction temperature is generally within the range of from 100 to 300°C, and although a high temperature is preferable for increasing the reaction rate, since side reactions as described above may be conversely caused by the aryl carbamates and / or the reaction products in the form of the isocyanates, the reaction temperature is preferably within the range of from 150 to 250°C. A known cooling apparatus or heating apparatus may be installed in the reaction vessel to maintain a constant reaction temperature. In addition, although varying according to the types of compounds used and reaction temperature, the reaction pressure may be decreased pressure, normal pressure or increased pressure, and the reaction is normally carried out at a pressure within the range of from 20 to 1 x 106 Pa. There are no particular limitations on the reaction time (residence time in the case of a continuous method) and is generally from 0.001 to 100 hours, preferably from 0.01 to 50 hours and more preferably from 0.1 to 30 hours. A catalyst can be used in the present embodiment, and the catalyst is used at from 0.01 to 30% by weight and preferably at from 0.5 to 20% by weight based on the weight of the aryl carbamates. For example, organic metal catalysts such as dibutyl tin dilaurate, ferrous octoate, stannous octoate or the like, or amines such as 1,4-diazabicyclo[2,2,2]octane, triethylenediamine, triethylamine or the like are suitable for use as catalysts, while organic metal catalysts such as dibutyl tin dilaurate, ferrous octoate, stannous octoate or the like are particularly preferable. These compounds may be used alone or two or more types may be used as a mixture. In the case of using the catalysts in the above-mentioned transesterification reaction, the catalysts contained in the mixed liquid following the transesterification reaction may be used as a catalyst in the thermal decomposition reaction or catalysts may be freshly added to the aryl carbamates when the thermal decomposition reaction is carried out. Although the use of a reaction solvent is not necessarily required in the present embodiment, a suitable inert solvent can be used as a reaction solvent for the purpose of facilitating the reaction procedure, examples of which include alkanes such as hexane (isomers), heptane (isomers), octane (isomers), nonane (isomers), decane (isomers) or the like; aromatic hydrocarbons and alkyl-substituted aromatic hydrocarbons such as benzene, toluene, xylene (isomers), ethyl benzene, diisopropyl benzene (isomers), dibutyl benzene (isomers), naphthalene or the like; aromatic compounds substituted with a halogen or nitro group such as chlorobenzene, dichlorobenzene (isomers), bromobenzene, dibromobenzene (isomers), chloronaphthalene, bromonaphthalene, nitrobenzene, nitronaphthalene or the like; polycyclic hydrocarbon compounds such as diphenyl, substituted diphenyl, diphenyl methane, terphenyl, anthracene, dibenzyl toluene (isomers) or the like; aliphatic hydrocarbons such as cydohexane, cyclopentane, cyclooctane, ethylcyclohexane or the like; ketones such as methyl ethyl ketone, acetophenone or the like; esters such as dibutyl phthalate, dihexyl phthalate, dioctyl phthalate, benzylbutyl phthalate or the like; ethers and thioethers such as diphenyl ether, diphenyl sulfide or the like; and sulfoxides such as dimethylsulfoxide, diphenylsulfoxide or the like; and, silicone oil. These solvents can be used alone or two or more types can be used as a mixture. As was previously described, although the thermal decomposition reaction of the present embodiment is a reaction by which the corresponding isocyanates and the aromatic hydroxy compounds are formed from the aryl carbamates, the thermal decomposition reaction is an equilibrium reaction. Thus, in order to efficiently obtain isocyanates in this thermal decomposition reaction, it is preferable to remove at least one of the products of this thermal decomposition reaction in the form of the isocyanates and the aromatic hydroxy compounds from the thermal decomposition reaction system in the form of a gaseous component by a method such as distillation. Whether the isocyanates or aromatic hydroxy compounds are removed as the gaseous components can be arbitrarily determined according to the compounds used, and for example, the respective standard boiling points of the isocyanates and the aromatic hydroxy compounds are compared followed by removing the compounds having the lower standard boiling point in the form of the gaseous components. The aryl carbamates are also susceptible to the occurrence of side reactions as described above in the case of being held at a high temperature for a long period of time, although to a much lower degree than carbamic acid esters. In addition, the above-mentioned side reactions may also be induced by the isocyanates formed by the thermal decomposition reaction. Thus, the time during which the aryl carbamates and the isocyanates are held at a high temperature is preferably as short as possible, and the thermal decomposition reaction is preferably carried out by the continuous method. The continuous method refers to a method in which the aryl carbamates are continuously supplied to a reaction vessel where it is subjected to a thermal decomposition reaction, and at least either the formed isocyanates or aromatic hydroxy compounds are removed from the reaction vessel in the form of a gaseous component. Although known materials may be used for the reaction vessel and lines used to carry out the thermal decomposition reaction provided they do not have a detrimental effect on the aryl carbamate or the products in the form of the aromatic hydroxy compounds and isocyanates, SUS304, SUS316 or SUS316L and the like can be used preferably since they are inexpensive. There are no particular limitations on the type of reaction vessel, and a known tank reactor or column reactor can be used. A reaction vessel is preferably used that is provided with lines for extracting a low boiling point mixture containing at least either the isocyanates or aromatic hydroxy compounds formed in the thermal decomposition reaction from the reaction vessel in the form of the gaseous components, and for removing mixed liquids containing unreacted aryl carbamates and the compounds not extracted in the form of the gaseous components from the lower portion of the reaction vessel. Various known methods are used for such reaction vessels, examples of which include types using reaction vessels containing a stirring tank, a multistage stirring tank, a distillation column, a multistage distillation column, a multitubular reactor, a continuous multistage distillation column, a packed column, a thin film evaporator, a reactor provided with a support inside, a forced circulation reactor, a falling film evaporator, a falling drop evaporator, a trickle flow reactor or a bubble column, and types using combinations thereof. Methods using the thin film evaporator or columnar reactor are preferable from the viewpoint of rapidly removing low boiling point components from the reaction system, while a structure having a large gas-liquid contact area is preferable for rapidly transferring the low boiling point components formed to the gaseous phase. The reaction vessel is preferably provided with a line for supplying the aryl carbamates, a line for removing a gaseous component containing at least either the isocyanates or aromatic hydroxy compounds formed by the thermal decomposition reaction, and a line for removing a mixed liquid containing the compounds not removed as a gaseous component and unreacted aryl carbamates, the line for removing the gaseous components containing at least either the isocyanates or aromatic hydroxy compounds is preferably located at a location that allows the gaseous components in the reaction vessel to be removed, and the line for extracting the mixed liquids containing the compounds not removed as the gaseous components and the unreacted aryl carbamates is particularly preferably located there below. In addition, a line for supplying inert gas and / or liquid inert solvent from the lower portion of the reaction vessel may be separately attached, and a line may also be attached for recirculating all or a portion of the mixed liquid containing the unreacted aryl carbamates and the compounds not removed as the gaseous components to the reaction vessel. Equipment for warming, cooling or heating may be added to each line in consideration of clogging and the like. Furthermore, in the case of using the above-mentioned inert solvent, the inert solvent may be in the form of a gas and / or a liquid. The isocyanate obtained by the above-mentioned production process can be preferably used as a production raw material of polyurethane foam, paints, adhesives and the like. Since this process enables isocyanates to be efficiently produced without using extremely toxic phosgene, the present invention is industrially extremely significant. EXAMPLES Although the following provides a detailed explanation of the present invention based on examples thereof, the scope of the present invention is not limited by these examples. 1) NMR Analysis Apparatus: JNM-A400 FT-NMR system, JEOL Ltd., Japan (1) Preparation of 1H and 13C-NMR Analysis Samples About 0.3 g of sample solution were weighed followed by the addition of about 0.7 g of heavy chloroform (99.8%, Aldrich Corp., USA) and about 0.05 g of internal standard in the form of tetramethyl tin (guaranteed reagent, Wako Pure Chemical Industries, Ltd., Japan) and mixing to uniformity to obtain solutions used as NMR analysis samples. (2) Quantitative Analysis Analyses were performed for each standard and quantitative analyses were performed on the analysis sample solutions based on the resulting calibration curve. 2) Liquid Chromatography Apparatus: LC-1 OAT system, Shimadzu Corp., Japan Column: Silica-60 column, Tosoh Corp., Japan, two columns connected in series Developing solvent: Mixed liquid of hexane / tetrahydrofuran (80/20) (v/v) Solvent flow rate: 2 mL / min Column temperature: 35°C Detector: R.I. (refractometer) (1) Liquid Chromatography Analysis Samples About 0.1 g of sample were weighed followed by the addition of about 1 g of tetrahydrofuran (dehydrated, Wako Pure Chemical Industries, Ltd., Japan) and about 0.02 g of internal standard in the form of bisphenol A (guaranteed reagent, Wako Pure Chemical Industries, Ltd., Japan) and mixing to uniformity to obtain solutions used as liquid chromatography analysis samples. (2) Quantitative Analysis Analyses were performed for each standard and quantitative analyses were performed on the analysis sample solutions based on the resulting calibration curve. 3) Gas Chromatography Apparatus: GC-2010, Shimadzu Corp., Japan Column: DB-1 column, Agilent Technologies Corp., USA, length: 30 m, inner diameter: 0.250 mm, film thickness: 1.00 μm Column temperature: Held at 50°C for 5 minutes followed by increasing at the rate of 10°C / min to 200°C; held at 200°C for 5 minutes followed by increasing at the rate of 10°C / min to 300°C Detector: FID (1) Gas Chromatography Analysis Samples About 0.05 g of sample were weighed followed by the addition of about 1 g of acetone (dehydrated, Wako Pure Chemical Industries, Ltd., Japan) and about 0.02 g of internal standard in the form of toluene (dehydrated, Wako Pure Chemical industries, Ltd., Japan) and mixing to uniformity to obtain solutions used as gas chromatography analysis samples. (2) Quantitative Analysis Analyses were performed for each standard and quantitative analyses were performed on the analysis sample solutions based on the resulting calibration curve. [Reference Example 1] Production of Bis(3-methylbutyl) Carbonate Step (1-1): Production of Dialkyl Tin Catalyst 625 g (2.7 mol) of di-n-butyl tin oxide (Sankyo Organic Chemicals Co., Ltd., Japan) and 2020 g (22.7 mol) of 3-methyl-1-butanol (Kuraray Co., Ltd., Japan) were placed in a 5000 mL volumetric pear-shaped flask. The flask was connected to an evaporator (R-144, Shibata Co., Ltd., Japan) to which was connected an oil bath (OBH-24, Masuda Corp., Japan) equipped with a temperature controller, a vacuum pump (G-50A, Ulvac Inc., Japan) and a vacuum controller (VC-10S, Okano Seisakusho Co., Ltd., Japan). The purge valve outlet of this evaporator was connected to a line containing nitrogen gas flowing at a normal pressure. After closing the purge valve of the evaporator to reduce pressure inside the system, the purge valve was opened gradually to allow nitrogen to flow into the system and return to normal pressure. The oil bath temperature was set to about 145°C, the flask was immersed in the oil bath and rotation of the evaporator was started. After heating for about 40 minutes in the presence of atmospheric pressure nitrogen with the purge valve of the evaporator left open, distillation of 3-methyl-1-butanol containing water began. After maintaining in this state for 7 hours, the purge valve was closed, pressure inside the system was gradually reduced, and excess 3-methyl-1-butanol was distilled with the pressure inside the system at 74 to 35 kPa. After the fraction no longer appeared, the flask was taken out of the oil bath. After allowing the flask to cool to the vicinity of room temperature (25°C), the flask was taken out of the oil bath, the purge valve was opened gradually and the pressure inside the system was returned to atmospheric pressure. 1173 g of reaction liquid were obtained in the flask. Based on the results of 119Sn-, 1H- and 13C-NMR analyses, 1,1,3,3-tetra-n-butyl- 1,3-bis(3-methylbutyloxy) distannoxane was confirmed to have been obtained at a yield of 99% based on di-n-butyl tin oxide. The same procedure was then repeated 12 times to obtain a total of 10335 g of 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane. Step (1-2): Production of Bis(3-methylbutyl) Carbonate Bis(3-methylbutyl) carbonate was produced in a continuous production apparatus like that shown in FIG. 1. 1,1,3,3-tetrabutyl-1,3-bis(3-methylbutyloxy) distannoxane produced in the manner described above was supplied at the rate of 4388 g / hr from a transfer line 4 into a column-type reaction vessel 102 packed with Metal Gauze CY Packing (Sulzer Chemtech Ltd., Switzerland) and having an inner diameter of 151 mm and effective length of 5040 mm, and 3-methyl-1-butanol purified with a distillation column 101 was supplied at the rate of 14953 g / hr from a transfer line 2. The liquid temperature inside reaction vessel 102 was controlled to 160°C by a heater and a reboiler 112, and the pressure was adjusted to about 120 kPa-G with a pressure control valve. The residence time in the reaction vessel was about 17 minutes. 3-Methyl-1-butanol containing water at the rate of 15037 g / hr from tine top of tine reaction vessel via a transfer line 6, and 3-methyl-1-butanol at the rate of 825 g / hr via feed line 1, were pumped to distillation column 101 packed with Metal Gauze CY Packing and provided with a reboiler 111 and a condenser 121 to carry out distillative purification. In the top of distillation column 101, a fraction containing a high concentration of water was condensed by condenser 121 and recovered from a recovery line 3. Purified 3-methyl-1-butanol was pumped to column-type reaction vessel 102 via transfer line 2 located in the bottom of distillation column 101. An alkyl tin alkoxide catalyst composition containing di-n-butyl-bis(3-methylbutyloxy) tin and 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane was obtained from the bottom of column-type reaction vessel 102, and supplied to a thin film evaporator 103 (Kobeico Eco-Solutions Co., Ltd., Japan) via a transfer line 5. The 3-methyl-1-butanol was distilled off in thin film evaporator 103 and returned to column-type reaction vessel 102 via a condenser 123, a transfer line 8 and transfer line 4. The alkyl tin alkoxide catalyst composition was pumped from the bottom of thin film evaporator 103 via a transfer line 7 and supplied to an autoclave 104 while adjusting the flow rate of di-n-butyl-bis(3-methylbutyloxy) tin and 1,1,3,3-tetra-n- butyl-1,3-bis(3-methylbutyloxy) distannoxane to about 5130 g / hr. Carbon dioxide was supplied to the autoclave by a transfer line 9 at the rate of 973 g / hr, and the pressure inside the autoclave was maintained at 4 MPa-G. The temperature inside the autoclave was set to 120°C, the residence time was adjusted to about 4 hours, and a reaction between the carbon dioxide and the alkyl tin alkoxide catalyst composition was carried out to obtain a reaction liquid containing bis(3-methylbutyl) carbonate. This reaction liquid was transferred to a decarbonization tank 105 via a transfer line 10 and a control valve to remove residual carbon dioxide, and the carbon dioxide was recovered from a transfer line 11. Subsequently, the reaction liquid was transferred to a thin film evaporator (Kobelco Eco-Solutions Co., Ltd., Japan) 106 set to about 142°C and about 0.5 kPa via a transfer line 12 and supplied while adjusting the flow rate of 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane to about 4388 g / hr to obtain a fraction containing bis(3-methylbutyl) carbonate. On the other hand, the evaporation residue was circulated to column-type reaction vessel 102 via transfer line 13 and transfer line 4 while adjusting the flow rate of 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane to about 4388 g / hr. The fraction containing bis(3-methylbutyl) carbonate was supplied to a distillation column 107 packed with Metal Gauze CY packing and equipped with a reboiler 117 and a condenser 127 via a condenser 126 and a transfer line 14 at the rate of 959 g / hr followed by distillative purification to obtain 99 wt% bis(3-methylbutyl) carbonate from a recovery line 16 at the rate of 944 g / hr When the alkyl tin alkoxide catalyst composition of a transfer line 13 was analyzed by 119Sn-, 1H- and 13C-NMR analysis, it was found to contain 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane but not contain di-n-butyl-bis(3-methylbutyloxy) tin. After carrying out the above-mentioned continuous operation for about 240 hours, alkyl tin alkoxide catalyst composition was extracted from an extraction line 16 at the rate of 18 g / hr, while 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane produced according to the above process was supplied from a feed line 17 at the rate of 18 g / hr. [Reference Example 2] Production of Dibutyl Carbonate Step (11-1): Production of Dialkyl Tin Catalyst 692 g (2.78 mol) of di-n-butyl tin oxide and 2000 g (27 mol) of 1-butanol (Wako Pure Chemical Industries, Ltd., Japan) were placed in a 3000 mL volumetric pear-shaped flask. The flask containing the white, slurry-like mixture was attached to an evaporator to which was connected an oil bath equipped with a temperature controller, a vacuum pump and a vacuum controller. The purge valve outlet of this evaporator was connected to a line containing nitrogen gas flowing at normal pressure. After closing the purge valve of the evaporator to reduce pressure inside the system, the purge valve was opened gradually to allow nitrogen to flow into the system and return to normal pressure. The oil bath temperature was set to about 126°C, the flask was immersed in the oil bath and rotation of the evaporator was started. After rotating and heating for about 30 minutes at normal pressure with the purge valve of the evaporator left open, the mixture boiled and distillation of the low boiling point component began. After maintaining in this state for 8 hours, the purge valve was closed, pressure inside the system was gradually reduced, and residual low boiling point component was distilled off with the pressure inside the system at 76 to 54 kPa. After the low boiling point component no longer appeared, the flask was taken out of the oil bath. The reaction liquid was in the form of a clear liquid. The flask was subsequently taken out of the oil bath, the purge valve was opened gradually and the pressure inside the system was returned to normal pressure. 952 g of reaction liquid were obtained in the flask. Based on the results of 119Sn-, 1H- and 13C-NMR analyses, a product in the form of 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane was obtained at a yield of 99% based on di-n-butyl tin oxide. The same procedure was then repeated 12 times to obtain a total of 11480 g of 1,1,3,3-tetra-n-butyl-1,3-di(butyloxy) distannoxane. Step (11-2): Production of Dibutyl Carbonate Carbonic acid ester was produced in a continuous production apparatus like that shown in FIG. 1. 1,1,3,3-Tetra-n-butyl-1,3-di(n-butyloxy) distannoxane produced in step (11-1) was supplied at the rate of 4201 g / hr from transfer line 4 into a column-type reaction vessel packed with Mellapak 750Y packing (Sulzer Chemtech Ltd., Switzerland) and having an inner diameter of 151 mm and effective length of 5040 mm, and 1-butanol purified with distillation column 101 was supplied to column-type reaction vessel 102 at the rate of 24717 g / hr from feed line 2. The liquid temperature inside the reaction vessel was controlled to 160°C by a heater and reboiler 112, and the pressure was adjusted to about 250 kPa-G with a pressure control valve. The residence time in the reaction vessel was about 10 minutes. 1-Butanol containing water at the rate of 24715 g / hr from the top of the reaction vessel via transfer line 6, and 1-butanol at the rate of 824 g / hr via feed line 1, were pumped to distillation column 101 packed with Metal Gauze CY packing (Sulzer Chemtech Ltd., Switzerland) and provided with reboiler 111 and condenser 121 to carry out distillative purification. In the top of distillation column 101, a fraction containing a high concentration of water was condensed by condenser 121 and recovered from transfer line 3. Purified 1-butanol was pumped via transfer line 2 located in the bottom of distillation column 101. An alkyl tin alkoxide catalyst composition containing di-n-butyl tin di-n-butoxide and 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane was obtained from the bottom of column-type reaction vessel 102, and supplied to thin film evaporator 103 (Kobelco Eco-Solutions Co., Ltd., Japan) via a transfer line 5. The 1-butanol was distilled off in thin film evaporator 103 and returned to column-type reaction vessel 102 via condenser 123, transfer line 8 and transfer line 4. The alkyl tin alkoxide catalyst composition was pumped from the bottom of thin film evaporator 103 via transfer line 7 and supplied to autoclave 104 while adjusting the flow rate of the active components in the form of dibutyl tin dibutoxide and 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane to about 4812 g / hr Carbon dioxide was supplied to the autoclave by feed line 9 at the rate of 973 g / hr, and the pressure inside the autoclave was maintained at 4 MPa-G. The temperature inside the autoclave was set to 120°C, the residence time was adjusted to about 4 hours, and a reaction between the carbon dioxide and the alkyl tin alkoxide catalyst composition was carried out to obtain a reaction liquid containing dibutyl carbonate. This reaction liquid was transferred to decarbonization tank 105 via transfer line 10 and a control valve to remove residual carbon dioxide, and the carbon dioxide was recovered from transfer line 11. Subsequently, the reaction liquid was pumped to thin film evaporator 106 (Kobeico Eco-Solutions Co., Ltd., Japan) set to about 140°C and about 1.4 kPa via transfer line 12 and supplied while adjusting the flow rate of the 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane to about 4201 g / hr to obtain a fraction containing dibutyl carbonate. On the other hand, the evaporation residue was circulated to column-type reaction vessel 102 via transfer line 13 and transfer line 4 while adjusting the flow rate of 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane to about 4201 g / hr. The fraction containing dibutyl carbonate was supplied to distillation column 107 packed with Metal Gauze CY packing (Sulzer Chemtech Ltd., Switzerland) and equipped with reboiler 117 and condenser 127 via condenser 126 and a transfer line 14 at the rate of 830 g / hr followed by distillative purification to obtain 99 wt% bis(3-methylbutyl) carbonate from recovery line 16 at the rate of 814 g / hr. When the alkyl tin alkoxide catalyst composition of transfer line 13 was analyzed by 119Sn-, 1H- and 13C-NMR analysis, it was found to contain 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane but not contain di-n-butyl tin di-n-butoxide. After carrying out the above-mentioned continuous operation for about 600 hours, alkyl tin alkoxide catalyst composition was extracted from extraction line 16 at the rate of 16 g / hr, while 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane produced in step (11-1) was supplied from feed line 17 at the rate of 16 g / hr. [Example 1] Step (1-1): Production of N,N'-hexanediyl-bis-carbamic Acid Di(3-methylbutyl) Ester 1818 g (9.0 mol) of bis(3-methylbutyl) carbonate and 208.8 g (1.8 mol) of hexamethylene diamine (Aldrich Corp., USA) were placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser and three-way valve were attached to the flask. After replacing the inside of the system with nitrogen, the four-mouth flask was immersed in an oil bath (OBH-24, Masuda Corp., Japan) heated to 80°C followed by the addition of 3.5 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd., Japan) to start the reaction. Samples of the reaction liquid were suitably collected and subjected to NMR analysis, and the reaction was terminated at the point hexamethylene diamine was no longer detected. As a result of analyzing the resulting solution by liquid chromatography, the solution was found to contain 29.9% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester. Step (1-2): Distillation of Low Boiling Point Component The solution obtained in step (1-1) was placed in a 5 L volumetric flask equipped with a three-way valve, condenser, distillate collector and thermometer, and the inside of the flask was replaced with nitrogen in a vacuum. The flask was immersed in an oil bath heated to about 130°C. Distillation was carried out while gradually reducing the pressure in the flask to a final pressure of 0.02 kPa. 1410 g of distillate were obtained. As a result of analyzing by gas chromatography, the distillate was found to be a solution containing 78.3% by weight of bis(3-methylbutyl) carbonate and 21.4% by weight of isoamyl alcohol. In addition, as a result of analyzing the resulting distillation residue in the flask by liquid chromatography, the distillation residue was found contain 98.0% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester. Step (1-3): Production of N,N'-h6xanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester by Transesterification A transesterification reaction was carried out in a reaction apparatus like that shown in FIG. 2. 111 g of dibutyl tin dilaurate (chemical grade, Wako Pure Chemical Industries, Ltd., Japan) and 4119 g of 2,4-di-tert-amylphenol (Tokyo Chemical Industry Co., Ltd., Japan) were added to 618 g of the distillation residue obtained in step (1-2) and stirred to obtain a homogeneous solution which was then placed in a feed tank 201. A thin film distillation apparatus 202 (Kobelco Eco-Solutions Co., Ltd., Japan) having heat-conducting surface area of 0.2 m2 was heated to 240°C, and the inside of the thin film distillation apparatus was replaced with a nitrogen atmosphere at atmospheric pressure. The solution was supplied to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr. A mixed gas containing 3-methyl-1-butanol and 2,4-di-tert-amylphenol was extracted from a line 25 provided in the upper portion of the thin film distillation apparatus 202, and supplied to a distillation column 203 packed with Metal Gauze CY Packing (Sulzer Chemtech Ltd., Switzerland). The 3-methyl-1-butanol and 2,4-di-tert-amylphenol were separated in the distillation column 203, and the 2,4-di-tert-amylphenol was returned to the upper portion of thin film distillation apparatus 202 by a line 26 provided in the bottom of distillation column 203. The reaction liquid was extracted from a line 22 provided in the bottom of thin film distillation apparatus 202 and returned to feed tank 201 via a line 23. After carrying out this step for 62 hours, the reaction liquid was extracted from a line 24. 4532 g of extracted liquid were extracted, and 304 g of solution were recovered from a line 27 provided in the upper portion of distillation column 203. As a result of analyzing the extracted reaction liquid by liquid chromatography, the reaction liquid was found to contain 24.2% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester. In addition, as a result of analyzing the solution recovered from line 27 by 1H- and 13C-NMR analysis, the solution was found to contain 98% by weight of 3-nnethyl-1-butanol. Step (1-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester A thermal decomposition reaction was carried out in a reaction apparatus like that shown in FIG. 2. A thin film distillation apparatus 302 (Kobelco Eco-Solutions Co., Ltd., Japan) having a heat-conducting surface area of 0.2 m2 was heated to 200°C and the pressure within the thin film distillation apparatus was set to about 1.3 kPa. The solution obtained in step (1-3) was placed in a feed tank 301 and supplied to the thin film distillation apparatus at the rate of about 980 g / hr via a line 31. A liquid component was extracted from a line 33 provided in the bottom of thin film distillation apparatus 302 and returned to feed tank 301 via a line 34. A gaseous component containing hexamethylene diisocyanate and 2,4-di-tert-amylphenol was extracted from a line 32 provided in the upper portion of a thin film distillation apparatus 302. The gaseous component was introduced into a distillation column 303 followed by separation into hexamethylene diisocyanate and 2,4-di-tert-amylphenol, and a portion of the 2,4-di-tert-amylphenol was returned to feed tank 301 through line 34 via a line 36 provided in the bottom of distillation column 303. When this reaction was carried out for 13 hours, 266 g of a solution were recovered from a line 35, and as a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 88%. [Example 2] Step (2-1): Production of N,N'-hexanecliyl-bis-carbamic Acid Di(3-methylbutyl) Ester A solution containing 12.8% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of adding 2230 g of 3-methyl-1-butanol to a 5 L volumetric four-mouth flask and then adding 1515 g (7.5 mol) of bis(3-methylbutyl) carbonate and 174 g (1.5 mol) of hexamethylene diamine thereto and using 28.9 g of sodium methoxide. The solution was passed through a column packed with an ion exchange resin (Amberlyst 15 Dry, Rohm and Haas Co., USA) and 3919 g of solution were recovered. Step (2-2): Distillation of Low Boiling Point Component 3373 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (2-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 27.0% by weight of bis(3-methylbutyl) carbonate and 72.9% by weight of 3-methy 1-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 92.1% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester. Step (2-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-butylphenyl) Ester by Transesterification 3351 g of a reaction liquid were extracted from line 24 by carrying out the same method as step (1-3) of Example 1 with the exception of using 544 g of the distillation residue obtained in step (2-2) instead of the distillation residue obtained in step (1-2), using 92 g of dibutyl tin diiaurate, using 2999 g of 2,4-di-tert-butylphenol (Wako Pure Chemical Industries, Ltd., Japan) instead of 2,4-di-tert-amylphenol, and carrying out the reaction for 70 hours. In addition, 246 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203. The extracted reaction liquid contained 24.2% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-butylphenyl) ester. Step (2-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-butylphenyl) Ester 225 g of a solution were recovered from line 35 by carrying out the same method as step (1-4) of Example 1 in a reaction apparatus like that shown in FIG. 2 with the exception of heating thin film distillation apparatus 302 to 200°C, setting the pressure within the thin film distillation apparatus to about 1.3 kPa, supplying the solution obtained in step (2-3) to the thin film distillation apparatus at the rate of about 980 g / hr via line 31, and carrying out the reaction for 11 hours. As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 89%. [Example 3] Step (3-1): Production of N,N'-hexanediyl-bis-carbamic Acid Di(3-methylbutyl) Ester 2754 g of a solution containing 21.6% by weight of N,N'-hexanediyl-bis- carbamic acid di(3-methylbutyl) ester were obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 2545 g (12.6 mol) of bis(3-methylbutyl) carbonate and 209 g (1.8 mol) of hexamethylene diamine along with the stirrer, and using 3.5 g of sodium methoxide. Step (3-2): Distillation of Low Boiling Point Component 2150 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (3-1) instead of the solution obtained in step (1-1). As a result of analyzing the distillate by gas chromatography, the distillate was found to contain 85.6% by weight of bis(3-methylbutyl) carbonate and 14.0% by weight of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.4% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester. Step (3-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester by Transesterification 4834 g of a reaction liquid were extracted from line 24 by carrying out the same method as step (1-3) of Example 1 with the exception of using 602 g of the distillation residue obtained in step (3-2) instead of the distillation residue obtained in step (1-2), using 109 g of dibutyl tin dilaurate, using 4431 g of 2,4-di-tert-amylphenol and carrying out the reaction for 70 hours. In addition, 297 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203. The extracted reaction liquid contained 22.2% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester. Step (3-4): Distillation of 2,4-di-tert-amylphenol A vacuum pump and a vacuum controller were attached to a molecular distillation apparatus having a jacketed heating unit operated by oil circulation (80 molecular distillation apparatus, Asahi Seisakusho Co., Ltd., Japan), and the purge line of the vacuum controller was connected to a nitrogen gas line. The air inside the molecular distillation apparatus was replaced with nitrogen and the heating unit was heated to 150°C with an oil circulator. The pressure in the molecular distillation apparatus was reduced to 0.3 kPa, and the solution obtained in step (3-3) was fed to the molecular distillation apparatus at the rate of about 5 g / min while rotating the wiper of the molecular distillation apparatus at about 300 rpm to distill off the 2,4-di- tert-amylphenol. 1291 g of a high boiling point substance were recovered in a high boiling point sample collector held at 120°C and as a result of analyzing by liquid chromatography, was found to contain 83.1% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester. Step (3-5): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester A thermal decomposition reaction was carried out in a reaction apparatus like that shown in FIG. 2. 290 g of a solution were recovered from line 35 by carrying out the same method as step (1-4) of Example 1 with the exception of feeding a mixed liquid in the form of a slurry comprising a mixture of 1289 g of the carbamic acid ester-containing substance obtained in step (3-4) and 3422 g of benzylbutyl phthalate (guaranteed reagent, Wako Pure Chemical Industries, Ltd., Japan) to feed tank 301, supplying to the thin film distillation apparatus at the rate of about 980 g / hr and reacting for 14 hours. As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 83%. [Example 4] Step (4-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl Ester A solution containing 30.8% by weight of N,N'-hexanediyl-bis-carbamic acid dibutyl ester was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 1479 g (8.5 mol) of dibutyl carbonate produced according to the method of Reference Example 2 and 197 g (1.7 mol) of hexamethylene diamine (Aldrich Corp., USA), and using 3.3 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd., Japan) in a 5 L volumetric four-mouth flask. Step (4-2): Distillation of Low Boiling Point Component 1156 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (4-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 78.5% by weight of dibutyl carbonate and 20.8% by weight of n-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.8% by weight of N,N'-hexanediyl-bis-carbamic acid dibutyl ester. Step (4-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester by Transesterification 4929 g of a reaction liquid were extracted from line 24 by carrying out the same method as step (1-3) of Example 1 with the exception of using the distillation residue obtained in step (4-2) instead of the distillation residue obtained in step (1-2), using 82 g of dibutyl tin diiaurate, adding 4566 g of 2,4-di-tert-amyiphenol followed by stirring to obtain a homogeneous solution that was then fed to feed tank 201, heating thin film distillation apparatus 202 having a heat-conducting surface area of 0.2 m2 to 240°C and reacting for 86 hours. 233 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203. When the extracted reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 20.4% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99.9% by weight 1-butanol. Step (4-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester A thermal decomposition reaction was carried out in a reaction apparatus like that shown in FIG. 2. 248 g of a solution were recovered from line 35 by carrying out the same method as step (1-4) of Example 1 with the exception of using the solution extracted from line 24 in step (4-3) instead of the solution extracted from line 24 in step (1-3) and reacting for 14 hours. As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 87%. [Example 5] Step (5-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl Ester 2091 g of a solution containing 26.2% by weight of N,N'-hexanediyl-bis- carbamic acid dibutyl ester was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 1879 g (10.8 mol) of dibutyl carbonate and 209 g (1.8 mol) of hexamethylene diamine, adding a stirrer and adding 3.5 g of sodium methoxide. Step (5-2): Distillation of Low Boiling Point Component 1537 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (5-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 82.9% by weight of dibutyl carbonate and 16.6% by weight of n-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 99.0% by weight of N,N'-hexanediyl-bis-carbamic acid dibutyl ester. Step (5-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-dimethylphenyl) Ester by Transesterification 3554 g of a reaction liquid were extracted from line 24 by carrying out the same method as step (1-3) of Example 1 with the exception of using 548 g of the distillation residue obtained in step (5-2) instead of the distillation residue obtained in step (1-2), using 3142 g of 2,6-dimethylphenol (Aldrich Corp., USA) instead of 2,4-di-tert-amylphenol, using 109 g of dibutyl tin dilaurate, making the temperature of thin film distillation apparatus 202 200°C and carrying out the reaction for 225 hours. In addition, 239 g of a solution was recovered from line 27 provided in the upper portion of distillation column 203. The extracted reaction liquid contained 18.7% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,6-dimethylphenyl) ester. Step (5-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-dimethylphenyl) Ester A thermal decomposition reaction was carried out in a reaction apparatus like that shown in FIG. 4. A thin film distillation apparatus 402 (Kobelco Eco-Solutions Co., Ltd., Japan) having a heat-conducting surface area of 0.2 m2 was heated to 200°C and the pressure within the thin film distillation apparatus was set to about 1.3 kPa. The solution obtained in step (5-3) was placed in a feed tank 401 and supplied to the thin film distillation apparatus at the rate of about 680 g / hr via a line 41. A liquid component was extracted from a line 43 provided in the bottom of thin film distillation apparatus 402 and returned to feed tank 401 via a line 44. A gaseous component containing hexamethylene diisocyanate and 2,6-dimethylphenol was extracted from a line 42 provided in the upper portion of thin film distillation apparatus 402. The gaseous component was introduced into a distillation column 403 followed by separation into hexamethylene diisocyanate and 2,6-dimethylphenol, the 2,6-dimethylphenol was extracted from a line 45 via the top of the distillation column 403, and a gaseous component containing hexamethylene diisocyanate was extracted from a line 47 provided in the distillation column 403. On the other hand, a high boiling point substance was extracted from a line 46 provided in the bottom of the distillation column, and a portion was returned feed tank 401 through line 44. The gaseous component containing hexamethylene diisocyanate extracted from line 47 was pumped to a distillation column 404, and the hexamethylene diisocyanate was distilled off and separated in the distillation column 404. A high boiling point substance was extracted from a line 48 provided in the distillation column 404, and a portion was returned to feed tank 401 through line 44. On the other hand, a gaseous component was extracted from a line 49, and hexamethylene diisocyanate was extracted from a line 52 via a condenser. After reacting for 11 hours, 249 g of a solution containing 99% by weight of hexamethylene diisocyanate was recovered from line 47. The yield based on hexamethylene diamine was 82%. [Example 6] Step (6-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dimethyl Ester A solution containing 39.0% by weight of N,N'-hexanediyl-bis-carbamic acid dimethyl ester therein was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 765 g (8.5 mol) of dimethyl carbonate (Aldrich Corp., USA) and 197 g (1.7 mol) of hexamethylene diamine, and using 3.3 g of sodium methoxide in a 2 L volumetric four-mouth flask. Step (6-2): Distillation of Low Boiling Point Component 582 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (6-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 80.8% by weight of dimethyl carbonate and 17.9% by weight of methanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.9% by weight of N,N'-hexanediyl-bis-carbamic acid dimethyl ester. Step (6-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester by Transesterification 4517 g of a reaction liquid were extracted from line 24 by carrying out the same method as step (1-3) of Example 1 with the exception of using 376 g of the distillation residue in the flask obtained in step (6-2) instead of the distillation residue in the flask obtained in step (1-2), using 82 g of dibutyl tin dilaurate, using 4161 g of 2,4-di-tert-amylphenol and carrying out the reaction for 86 hours. 100 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203. When the extracted reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 22.1% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99.4% by weight methanol. Step (6-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert~amylphenyl) Ester 242 g of a solution were recovered from line 35 by carrying out the same method as step (1-4) of Example 1 with the exception of using the solution extracted from line 24 in step (6-3) instead of the solution extracted from line 24 in step (1-3), and carrying out the reaction for 13 hours. As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 85%. [Example 7] Step (7-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dimethyl Ester 934 g of a solution containing 42.4% by weight of N,N'-hexanediyl-bis-carbamic acid dimethyl ester was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 729 g (8.1 mol) of dimethyl carbonate and 209 g (1.8 mol) of hexamethylene diamine, and using 0.35 g of sodium methoxide. Step (7-2): Distillation of Low Boiling Point Component 533 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (7-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 77.8% by weight of dimethyl carbonate and 20.6% by weight of methanol, in addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 99.7% by weight of N,N'-hexanediyl-bis-carbamic acid dimethyl ester. Step (7-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-di-methylphenyl) Ester by Transesterification 3537 g of a reaction liquid were extracted from line 24 by carrying out the same method as step (1-3) of Example 1 with the exception of using 395 g of the distillation residue obtained in step (7-2) instead of the distillation residue obtained in step (1-2), using 108 g of dibutyl tin dilaurate, using 3133 g of 2,6-dimethylphenol instead of 2,4-di-tert-amylphenol, heating the thin film distillation apparatus 202 to 200°C and carrying out the reaction for 250 hours. In addition, 100 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203. The extracted reaction liquid contained 18.3% by weight of N,N'-hexanediyi-bis-carbamic acid di(2,6-di-methylphenyl) ester. Step (7-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-di-methylphenyl) Ester 243 g of a solution containing 99% by weight of hexamethylene diisocyanate were recovered from line 52 by carrying out the same method as step (5-4) of Example 5 with the exception of using the reaction liquid obtained from line 24 in step (7-3) instead of the solution obtained in step (5-3), and carrying out the reaction for 16 hours. The yield with respect to hexamethylene diamine was 81 %. [Example 8] Step (8-1): Production of 3-((3-methylbutyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic Acid (3-methylbutyl) Ester 1980 g (9.8 mol) of bis(3-methylbutyl) carbonate and 239 g (1.8 mol) of 3-aminomethyl-3,5,5-trimethylcyclohexylamine (Aldrich Corp., USA) were placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser and three-way valve were attached to the flask. After replacing the inside of the system with nitrogen, the four-mouth flask was immersed in an oil bath (OBH-24, Masuda Corp., Japan) heated to 100°C followed by the addition of 2.7 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd., Japan) to start the reaction. Samples of the reaction liquid were suitably collected and subjected to NMR analysis, and the reaction was terminated at the point 3-aminomethyl-3,5,5-trimethylcyclohexylamine was no longer detected. As a result of analyzing the resulting solution by liquid chromatography, the solution was found to contain 23.9% by weight of 3-((3-methylbutyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (3-methylbutyl) ester. Step (8-2): Distillation of Low Boiling Point Component 1683 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (8-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 85.4% by weight of bis(3-methylbutyl) carbonate and 13.8% by weight of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 99.4% by weight of 3-((3-methylbutyl)oxycarbonylamino- methyl)-3,5,5-trimethylcyclohexylcarbamic acid (3-methylbutyl) ester. Step (8-3): Production of 3-((2,4-di-tert-amylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic Acid (2,4-di-tert-amylphenyl) Ester by Transesterification 5034 g of a reaction liquid were extracted from line 24 and 221 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of using 530 g of the distillation residue obtained in step (8-2) instead of the distillation residue obtained in step (1-2), using 84 g of dibutyl tin dilaurate, using 4645 g of 2,4-di-tert-amylphenol, heating the thin film distillation apparatus 202 to 240°C, supplying the solution to the thin film distillation apparatus via feed line 21 at the rate of about 1200 g / hr, and carrying out the reaction for 75 hours. When the extracted reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 17.2% by weight of 3-((2,4-di-tert-amylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-di-tert- amylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 3-methyl-1-butanol. Step (8-4): Production of Isophorone Diisocyanate by Thermal Decomposition of 3-((2,4-di-tert-amylphenyl)oxycarbonylamino-methyl)-3,5,5- trimethylcyclohexylcarbamic Acid (2,4-di-tert-amylphenyl) Pentyl Ester 257 g of a solution containing 99% by weight of isophorone diisocyanate were recovered from line 52 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 200°C, making the pressure in the thin film distillation apparatus about 1.3 kPa, feeding the solution obtained in step (8-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out the reaction for 11 hours. The yield based on 3-aminomethyl-3,5,5-trimethylcyclohexylamine was 83%. [Example 9] Step (9-1): Production of 3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic Acid Butyl Ester The same method as step (8-1) of Example 8 was carried out with the exception of using 2349 g (13.5 mol) of dibutyl carbonate, 255 g (1.5 mol) of 3-aminomethyl- 3,5,5-trimethylcyclohexyiamine and 2.9 g of sodium methoxide. As a result of analyzing the resulting solution by liquid chromatography, the solution was found to contain 20.0% by weight of 3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid butyl ester therein. Step (9-2): Distillation of Low Boiling Point Component 2075 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (9-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 89.2% by weight of dibutyl carbonate and 10.0% by weight of n-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.7% by weight of 3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid butyl ester. Step (9-3): Production of 3-((2,4-di-tert-butylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic Acid (2,4-di-tert-butylphenyl) Ester by Transesterification 4077 g of a reaction liquid were extracted from line 24 and 197 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of using 525 g of the distillation residue obtained in step (9-2), using 89 g of dibutyl tin dilaurate, using 3751 g of 2,4-di-tert~butylphenol to obtain a homogeneous solution, heating the thin film distillation apparatus 202 to 240°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 84 hours. When the recovered reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 20.7% by weight of 3-((2,4-di-tert-butylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid (2,4-di-tert-butylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 13H- and 13C-NMR analysis, the solution was found to contain 98% by weight of 1-butanol. Step (9-4): Production of Isophorone Diisocyanate by Thermal Decomposition of 3-((2,4-di-tert-butylphenyl)oxycarbonylamino-methyl)-3,5,5- trimethylcyclohexylcarbamic Acid (2,4-di-tert-butylphenyl) Ester 271 g of a solution containing 99% by weight of isophorone diisocyanate were recovered from line 52 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 200°C, making the pressure in the thin film distillation apparatus about 1.3 kPa, feeding the solution obtained in step (9-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out the reaction for 11 hours. The yield based on 3-aminomethyl-3,5,5-trimethylcyclohexylamine was 82%. [Example 10] Step (10-1): Production of 3-(butyloxycarbonylamino-methyl)-3,5,5- trimethylcyclohexylcarbamic acid Butyl Ester A solution containing 25.1% by weight of 3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbannic acid butyl ester was obtained by carrying out the same method as step (8-1) of Example 8 with the exception of using 1949 g (11.2 mol) of dibutyl carbonate, 272 g (1.6 mol) of 3-aminomethyl-3,5,5-trimethylcyclohexylamine and 3.1 g of sodium methoxide. Step (10-2): Distillation of Low Boiling Point Component 1657 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (10-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 85.7% by weight of dibutyl carbonate and 13.4% by weight of n-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.9% by weight of 3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid butyl ester. Step (10-3): Production of 3-((2,4,6-tri-methylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylc arbamic Acid (2,4,6-tri-methylphenyl) Ester by Transesterification 3067 g of a reaction liquid were extracted from line 24 and 208 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 76 g of dibutyl tin dilaurate to 560 g of the distillation residue obtained in step (10-2), adding 2645 g of 2,4,6-trimethylphenol (Aldrich Corp., USA) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 220°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 120 g/hr and carrying out the reaction for 180 hours. When the extracted reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 22.7% by weight of 3-((2,4,6-tri-methylphenyl)oxycarbonylamino-methyl)-3,5,5- trimethylcyclohexylcarbamic acid (2,4,6-trimethylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 1-butanol. Step (10-4): Production of Isophorone Diisocyanate by Thermal Decomposition of 3-((2,4,6-trimethylphenyl)oxycarbonylamino-methyl)-3,5,5- trimethylcyclohexylcarbamicAcid (2,4,6-trimethylphenyl) Ester 286 g of a solution containing 99% by weight of isophorone diisocyanate were recovered from line 52 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 200°C, making the pressure in the thin film distillation apparatus about 1.3 kPa, feeding the solution obtained in step (10-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out the reaction for 14 hours. The yield based on 3-aminomethyl-3,5,5-trimethylcyclohexylamine was 81%. [Example 11] Step (11-1): Production of 3-(methyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid Methyl Ester A solution containing 33.6% by weight of 3-(methyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbannic acid methyl ester was obtained by carrying out the same method as step (8-1) of Example 8 with the exception of using 1323 g (14.7 mo!) of dimethyl carbonate, 357 g (2.1 mol) of 3-aminomethyl-3,5,5-trimethylcyclohexylamine and 4.1 g of sodium methoxide. Step (11-2): Distillation of Low Boiling Point Component 1111 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (11-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 86.7% by weight of dimethyl carbonate and 11.3% by weight of methanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 99.1% by weight of 3-(methyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid methyl ester. Step (11-3): Production of 3-((2,4,6-tri-methylphenyl)oxycarbonylamino- methyl)-3,5,5-trimethylcyclohexylcarbamic Acid (2,4,6-tri-methylphenyl) Ester by Transesterification A transesterification reaction was carried out in a reaction apparatus like that shown in FIG. 2. 4457 g of a reaction liquid were extracted from line 24 and 118 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 99 g of dibutyl tin dilaurate and 4006 g of 2,4,6-trimethylphenol to 567 g of the distillation residue obtained in step (11-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 220°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 90 hours. When the reaction liquid was analyzed by liquid chromatography the reaction liquid was found to contain 20.5% by weight of 3-((2,4,6-tri-methylphenyl)oxycarbonylamino-methyl)-3,5,5- trimethylcyclohexylcarbamic acid (2,4,6-trimethylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of methanol. Step (11-4): Production of Isophorone Diisocyanate by Thermal Decomposition of 3-((2,4,6-trimethylphenyl)oxycarbonylamino-methyl)-3,5,5- trimethylcyclohexylcarbamicAcid (2,4,6-trimethylphenyl) Ester 368 g of a solution containing 99% by weight of isophorone diisocyanate were recovered from line 47 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 200°C, making the pressure in the thin film distillation apparatus about 1.3 kPa, feeding the solution obtained in step (11-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 900 g / hr, and carrying out the reaction for 13 hours. The yield based on 3-aminomethyl-3,5,5-trimethylcyclohexylamine was 79%. [Example 12] Step (12-1): Production of Bis(3-methylbutyl)-4,4'-methylene-dicyclohexyl Carbamate 1313 g (6.5 mol) of bis(3-methylbutyl) carbonate and 273 g (1.3 mol) of 4,4'- methylenebis(cyclohexylamine) (Aldrich Corp., USA) were placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser and three-way valve were attached to the flask. After replacing the inside of the system with nitrogen, the four-mouth flask was immersed in an oil bath (OBH-24, Masuda Corp., Japan) heated to 100°C followed by the addition of 2.5 g of sodium methoxide to start the reaction. Samples of the reaction liquid were suitably collected and subjected to NMR analysis, and the reaction was terminated at the point 4,4'-methylenebis(cyclohexylamine) was no longer detected. As a result of analyzing the resulting solution by liquid chromatography, the solution was found to contain 34.3% by weight of bis(3-methylbutyl)-4,4'-methylene-dicyclohexyl carbamate. Step (12-2): Distillation of Low Boiling Point Component 1034 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (12-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 77.8% by weight of bis(3-methylbutyl) carbonate and 21.2% by weight of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 99.0% by weight of bis(3-methylbutyl)-4,4'-methylene- dicyclohexyl carbamate. Step (12-3): Production of Bis(2,4-di-tert-amylphenyl)-4,4'-methylene- dicydohexyl Carbamate by Transesterification 4702 g of a reaction liquid were extracted from line 24 and 210 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 79 g of dibutyl tin dilaurate and 4358 g of 2,4-di-tert-amylphenol to 547 g of the distillation residue obtained in step (12-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 260°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 58 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 18.2% by weight of bis(2,4-di-tert-amylphenyl)-4,4'-methylene-dicyclohexyl carbamate. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 3-methyl-1-butanol. Step (12-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of Bis(2,4-di-tert-amylphenyl)-4,4'-methylene-dicyclohexyl Carbamate 287 g of a substance containing 99% by weight of 4,4'-methylene- di(cyclohexylisocyanate) were recovered from line 47 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 210°C, making the pressure in the thin film distillation apparatus about 0.13 kPa, feeding the solution obtained in step (12-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out the reaction for 11 hours. The yield based on 4,4'-methylenebis(cyclohexylamine) was 84%. [Example 13] Step (13-1): Production of Bis(3-methylbutyl)-4,4'-methylene-dicyclohexyl Carbamate A solution containing 29.4% by weight of bis(3-methylbutyl)-4,4'-methylene-dicyclohexyl carbamate was obtained by carrying out the same method as step (12-1) of Example 12 with the exception of using 1818 g (9.0 moi) of bis(3-methylbutyl) carbonate, 315 g (1.5 mol) of 4,4'-methylenebis(cyclohexylamine) and 2.9 g of sodium methoxide. Step (13-2): Distillation of Low Boiling Point Component 1490 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (13-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 82.6% by weight of bis(3-methylbutyl) carbonate and 16.8% by weight of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.0% by weight of bis(3-methylbutyl)-4,4'-methylene- dicyclohexyl carbamate. Step (13-3): Production of Bis(2,4-di-tert-butylphenyl)-4,4'-methylene- dicyclohexyl Carbamate by Transesterification 4987 g of a reaction liquid were extracted from line 24 and 238 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 90 g of dibutyl tin dilaurate and 4511 g of 2,4-di-tert-butylphenol to 633 g of the distillation residue obtained in step (13-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 240°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g/hr and carrying out the reaction for 78 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 18.3% by weight of bis(2,4-di-tert-butylphenyl)-4,4'-methylene-dicyclohexyl carbamate. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 3-methyl-1-butanol. Step (13-4): Production of 4,4'-methylene-di(cyclohexylisocyanate) by Thermal Decomposition of Bis(2,4-di-tert-butylphenyl)-4,4'-methylene-dicyclohexyl Carbamate 325 g of a substance containing 99% by weight of 4,4'-methylene- di(cyclohexylisocyanate) were recovered from line 52 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 210°C, making the pressure in the thin film distillation apparatus about 0.13 kPa, feeding the solution obtained in step (13-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out the reaction for 14 hours. The yield based on 4,4'-methylenebis(cyclohexylamine) was 83%. [Example 14] Step (14-1): Production of Dibutyl-4,4'-methylene-dicyclohexyl Carbamate A solution containing 29.0% by weight of dibutyl-4,4'-methylene-dicyclohexyl carbamate was obtained by carrying out the same method as step (12-1) of Example 12 with the exception of using 1696 g (9.8 mol) of dibutyl carbonate, 315 g (1.5 mol) of 4,4'-methylenebis(cyclohexy!amine) and 2.9 g of sodium methoxide. Step (14-2): Distillation of Low Boiling Point Component 1409 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (14-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 84.0% by weight of dibutyl carbonate and 14.9% by weight of n-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 97.3% by weight of dibutyl-4,4'-methylene-dicyclohexyl carbamate. Step (14-3): Production of Bis(2,6-dimethylphenyl)-4,4'-methylene- dicyclohexyl Carbamate by Transesterification 3923 g of a reaction liquid were extracted from line 24 and 194 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 89 g of dibutyl tin dilaurate and 3447 g of 2,6-dimethylphenol to 595 g of the distillation residue obtained in step (14-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 200°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 350 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 16.8% by weight of bis(2,6-dimethylphenyl)-4,4'- methylene-dicyclohexyl carbamate. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 97% by weight of 1-butanol. Step (14-4): Production of 4,4'-methylene-di(cyclohexylisocyanate) by Thermal Decomposition of Bis(2,6-dimethylphenyl)-4,4'-methylene-dicyclohexyl Carbamate 313 g of a solution containing 99% by weight of 4,4'-methylene- di(cyclohexylisocyanate) were recovered from line 52 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 210°C, making the pressure in the thin film distillation apparatus about 0.13 kPa, feeding the solution obtained in step (14-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 700 g/hr, and carrying out the reaction for 15 hours. The yield based on 4,4'-methylenebis(cyclohexylamine) was 80%. [Example 15] Step (15-1): Production of Dibutyl-4,4'-methylene-dicyclohexyl Carbamate A solution containing 27.0% by weight of dibutyl-4,4'-methylene-dicyclohexyl carbamate was obtained by carrying out the same method as step (12-1) of Example 12 with the exception of using 1705 g (9.8 mol) of dibutyl carbonate, 294 g (1.4 mol) of 4,4'-methylenebis(cyclohexylamine) and 0.27 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.). Step (15-2): Distillation of Low Boiling Point Component 1643 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (15-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 87.7% by weight of dibutyl carbonate and 11.7% by weight of n-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 99% by weight of dibutyl-4,4'-methylene-dicyclohexyl carbamate. Step (15-3): Production of Bis(2-tert-butylphenyl)-4,4'-methylene- dicydohexyl Carbamate by Transesterification 4256 g of a reaction liquid were extracted from line 24 and 181 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 84 g of dibutyl tin dilaurate and 3980 g of 2-tert-butylphenol to 562 g of the distillation residue obtained in step (15-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 220°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 180 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 15.5% by weight of bis(2-tert-butylphenyl)-4,4'-methylene-dicyclohexyl carbamate. In addition. when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 1-butanol. Step (15-4): Production of 4,4'-methylene-di(cyclohexylisocyanate) by Thermal Decomposition of Bis(2-tert-butylphenyl)-4,4'-methylene-dicyclohexyl Carbamate 287 g of a solution containing 99% by weight of 4,4'-methylene- di(cyclohexylisocyanate) were recovered from line 52 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 210°C, making the pressure in the thin film distillation apparatus about 0.13 kPa, feeding the solution obtained in step (15-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 710 g / hr, and carrying out the reaction for 14 hours. The yield based on 4,4'-methylenebis(cyclohexylamine) was 78%. [Example 16] Step (16-1): Production of Dimethyl-4,4'-methylene-dicyclohexyl Carbamate A solution containing 28.2% by weight of dimethyl-4,4'-methylene-dicyclohexyl carbamate was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 1440 g (16.0 mol) of dimethyl carbonate, 336 g (1.6 mol) of 4,4'-methylenebis(cyclohexylamine) and 1.5 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.). Step (16-2): Distillation of Low Boiling Point Component 1271 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (16-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 91.3% by weight of dimethyl carbonate and 7.7% by weight of methanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 99.4% by weight of dibutyl-4,4'-methylene-dicyclohexyl carbamate. Step (16-3): Production of Bis(2,4-di-tert-amylphenyl)-4,4'-methylene- dicyclohexyl Carbamate by Transesterification 5151 g of a reaction liquid were extracted from line 24 and 88 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 97 g of dibutyl tin dilaurate and 4645 g of 2,4-di-tert-amylphenol to 501 g of the distillation residue obtained in step (16-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 240°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 80 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 19.5% by weight of bis(2,4-di-tert-amylphenyl)-4,4'-methylene-dicyclohexyl carbamate. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of methanol. Step (16-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of Bis(2,4-di-tert-amylphenyl)-4,4'-methylene-dicyc!ohexyl Carbamate The same method as step (5-4) of Example 5 was carried out with the exception of heating the thin film distillation apparatus 402 to 210°C, making the pressure in the thin film distillation apparatus about 0.13 kPa, feeding the solution obtained in step (16-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out the reaction for 16 hours. 323 g of a solution containing 99% by weight of 4,4'-methylene-di(cyclohexylisocyanate) were recovered from line 52. The yield based on 4,4'-methylenebis(cyclohexylamine) was 77%. [Example 17] Step (17-1): Production of Toluene-2,4-dicarbamic Acid Bis(3-methylbutyl) Ester 1818 g (9.0 mol) of bis(3-methylbutyl) carbonate and 220 g (1.8 mol) of 2,4-toluene diamine (Aldrich Corp., USA) were placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser and three-way valve were attached to the flask. After replacing the inside of the system with nitrogen, the four-mouth flask was immersed in an oil bath (OBH-24, Masuda Corp., Japan) heated to 80°C followed by the addition of 0.35 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.) to start the reaction. Samples of the reaction liquid were suitably collected and subjected to NMR analysis, and the reaction was terminated at the point 2,4-toluenediamine was no longer detected. As a result of analyzing the resulting solution by liquid chromatography, the solution was found to contain 29.7% by weight of toluene-2,4-dicarbamic acid bis(3-methylbutyl) ester. Step (17-2): Distillation of Low Boiling Point Component 1422 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (17-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 78.2% by weight of bis(3-methylbutyl) carbonate and 21.2% by weight of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.0% by weight of toluene-2,4-dicarbamic acid bis(3-methylbutyl) ester. Step (17-3): Production of Toluene-2,4-dicarbamic acid bis(2,4-di-tert-amylphenyl) Ester by Transesterification 5258 g of a reaction liquid were extracted from line 24 and 289 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 109 g of dibutyl tin dilaurate and 4835 g of 2,4-di-tert-amylphenol to 615 g of the distillation residue obtained in step (17-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 240°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 70 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 20.0% by weight of toluene-2,4-dicarbamic acid bis(2,4-di-tert-amylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 98% by weight of 3-methyl-1-butanol. Step (17-4): Production of Toluene-2,4-diisocyanate by Thermal Decomposition of Toluene-2,4-dicarbamic Acid Bis(2,4-di-tert-amylphenyl) Ester The same method as step (1-4) of Example 1 was carried out with the exception of heating the thin film distillation apparatus 302 to 200°C, making the pressure in the thin film distillation apparatus about 1.3 kPa, feeding the solution obtained in step (17-3) to feed tank 301, supplying to the thin film distillation apparatus via line 31 at the rate of about 1000 g / hr, and carrying out the reaction for 15 hours. 267 g of a solution were recovered from line 35, and as a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of toluene-2,4-diisocyanate. The yield based on 2,4-toluene diamine was 85%. [Example 18] Step (18-1): Production of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Dibutyl Ester 1774 g (10.2 mol) of dibutyl carbonate and 336 g (1.7 mol) of 4,4'-methylene dianiline (Aldrich Corp., USA) were placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser and three-way valve were attached to the flask. After replacing the inside of the system with nitrogen, the four-mouth flask was immersed in an oil bath (OBH-24, Masuda Corp., Japan) heated to 80°C followed by the addition of 3.3 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.) to start the reaction. Samples of the reaction liquid were suitably collected and subjected to NMR analysis, and the reaction was terminated at the point 4,4'-methylene dianiline was no longer detected. As a result of analyzing the resulting solution by liquid chromatography, the solution was found to contain 30.8% by weight of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester. Step (18-2): Distillation of Low Boiling Point Component 1452 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (18-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 82.7% by weight of dibutyl carbonate and 16.6% by weight of 1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.5% by weight of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester. Step (18-3): Production of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Bis(2,4-di-tert-amylphenyl) Ester by Transesterification 4322 g of a reaction liquid were extracted from line 24 and 226 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 103 g of dibutyl tin dilaurate and 3799 g of 2,4-di-tert-amylphenol to 656 g of the distillation residue obtained in step (18-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 240°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 62 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 25.3% by weight of N,N'-(4,4'-methanediyl-diphenyl)- biscarbamic acid bis(2,4-di-tert-amylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 1-butanol. Step (18-4): Production of 4,4'-diphenylmethane Diisocyanate by Thermal Decomposition of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Bis(2,4-di-tert-amylphenyl) Ester When the thin film distillation apparatus 402 was heated to 210°C, the pressure in the thin film distillation apparatus was made to be about 0.1 kPa, the solution obtained in step (18-3) was fed to feed tank 401, supplied to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and the reaction was carried out for 11 hours, 351 g of a solution containing 99% by weight of 4,4'-diphenylmethane diisocyanate were recovered from line 52. The yield based on 4,4'-methylene dianiline was 83%. [Example 19] Step (19-1): Production of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Dibutyl Ester A solution containing 26.7% by weight of N,N'-(4,4'-methanediyl-diphenyl)- biscarbamic acid dibutyl ester was obtained by carrying out the same method as step (18-1) of Example 18 with the exception of using 1583 g (9.1 mol) of dibutyl carbonate, 257 g (1.3 mol) of 4,4'-methylene dianiline and 2.5 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.). Step (19-2): Distillation of Low Boiling Point Component 1342 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (19-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography the distillate was found to contain 85.5% by weight of dibutyl carbonate and 13.6% by weight of 1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.6% by weight of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester. Step (19-3): Production of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Bis(2,6-dimethylphenyl) Ester by Transesterification 2824 g of a reaction liquid were extracted from line 24 and 160 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 74 g of dibutyl tin dilaurate and 2441 g of 2,6-dimethylphenol to 475 g of the distillation residue obtained in step (19-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 200°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 662 hours. When the reaction liquid was analyzed by liquid chromatography the reaction liquid was found to contain 18.9% by weight of toluene-2,4-dicarbamic acid bis(2,6-dimethylphenyl) ester. In addition, when tine solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 1-butanol. Step (19-4): Production of 4,4'-diphenylmethane Diisocyanate by Thermal Decomposition of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Bis(2,6-dimethylphenyl) Ester 244 g of a solution containing 99% by weight of 4,4'-diphenylmethane diisocyanate was recovered from line 52 by carrying out the same method as step (5-4) of Example 5 with the exception of heating the thin film distillation apparatus 402 to 210°C, making the pressure in the thin film distillation apparatus to be about 0.1 kPa, feeding the solution obtained in step (19-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 700 g / hr, and carrying out the reaction for 13 hours. The yield based on 4,4'-methylene dianiline was 75%. [Example 20] Step (20-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl Ester A solution containing 22.7% by weight of N,N'-hexanediyl-bis-carbamic acid dibutyl ester was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 2192 g (12.6 mol) of dibutyl carbonate, 209 g (1.8 mol) of hexamethylene diamine and 3.5 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.). Step (20-2): Distillation of Low Boiling Point Component 1845 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (20-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 85.9% by weight of dibutyl carbonate and 13.6% by weight of 1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.6% by weight of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester. Step (20-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-di-tert-butylphenyl) Ester by Transesterification 5395 g of a reaction liquid were extracted from line 24 and 206 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of obtaining a homogeneous solution of 550 g of the distillation residue obtained in step (20-3), 109 g of dibutyl tin dilaurate and 4950 g of 2,6-di-tert-butylphenol, heating the thin film distillation apparatus 202 to 240°C, and carrying out the reaction for 86 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 14.9% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,6-di-tert-butylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 1-butanol. Step (20-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-di-tert-butylphenyl) Ester The same method as step (1-4) of Example 1 was carried out with the exception of heating the thin film distillation apparatus 302 was heated to 200°C, making the pressure in the thin film distillation apparatus to be about 1.3 kPa, feeding the solution obtained in step (20-3) was fed to feed tank 301, supplying to the thin film distillation apparatus via line 31 at the rate of about 980 g / hr, and carrying out the reaction for 13 hours. 210 g of a solution were recovered from line 35. As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 70%. [Example 21] Step (21-1): Production of N,N'-hexanediyl-bis-carbamic Acid Di(3-methylbutyl) Ester A solution containing 24.0% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 2290 g (11.3 mol) of bis(3-methylbutyl) carbonate, 208.8 g (1.8 mol) of hexamethylene diamine and 3.5 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.). Step (21-2): Distillation of Low Boiling Point Component 1891 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (21-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 83.6% by weight of bis(3-methylbutyl) carbonate and 16.1% by weight of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.6% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester. Step (21-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2-phenylphenyl) Ester by Transesterification 3977 g of a reaction liquid were extracted from line 24 and 276 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 110 g of dibutyl tin dilaurate and 3545 g of 2-phenylphenol to 606 g of the distillation residue obtained in step (21 -2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 240°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out the reaction for 80 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 20.0% by weight of N,N'-hexanediyl-bis-carbamic acid di(2-phenylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 3-methyl-1-butanol. Step (21-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2-phenylphenyl) Ester 241 g of a solution were recovered from line 35 by carrying out the same method as step (1-4) of Example 1 with the exception of heating the thin film distillation apparatus 302 to 200°C, making the pressure in the thin film distillation apparatus to be about 1.3 kPa, feeding the solution obtained In step (21-3) to feed tank 301, supplying to the thin film distillation apparatus via line 31 at the rate of about 980 g / hr, and carrying out the reaction for 13 hours. As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 80%. [Example 22] Step (22-1): Production of N,N'-hexanediyl-bis-carbamic Acid Di(3-methylbutyl) Ester A solution containing 23.8% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester was obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 2163 g (10.7 mol) of bis(3-methylbutyl) carbonate, 197 g (1.7 mol) of hexamethylene diamine and 3.3 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.). Step (22-2): Distillation of Low Boiling Point Component 1783 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (22-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 83.5% by weight of bis(3-methylbutyl) carbonate and 16.0% by weight of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 97.1 % by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester. Step (22-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-bis(a,a-dimethylbenzyl)phenyl) Ester by Transesterification 4689 g of a reaction liquid were extracted from line 24 and 259 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of adding 103 g of dibutyl tin dilaurate and 4385 g of 2,4-bis(a,a-dimethylbenzyl)phenol (Aldrich Corp., USA) to 575 g of the distillation residue obtained in step (22-2) and using in the form of a homogeneous solution, heating the thin film distillation apparatus 202 to 240°C, replacing the inside of the thin film distillation apparatus with nitrogen at atmospheric pressure, supplying the solution to the thin film distillation apparatus via supply line 21 at the rate of about 1200 g/hr and carrying out the reaction for 80 hours. When the reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 25.8% by weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-bis(α,α-dimethylbenzyl)phenyl ester In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of 3-methyl-1-butanol. Step (22-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-bis(aa-dimethylbenzyl)phenyl) Ester 220 g of a solution were recovered from line 35 by carrying out the same method as step (1-4) of Example 1 with the exception of heating the thin film distillation apparatus 302 to 200°C, making the pressure in the thin film distillation apparatus to be about 1.3 kPa, feeding the solution obtained in step (22-3) to feed tank 301, supplying to the thin film distillation apparatus via line 31 at the rate of about 980 g / hr, and carrying out the reaction for 18 hours. As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 77%. [Example 23] Hexamethylene diisocyanate was produced in a reaction apparatus like that shown in FIG. 5. Step (23-1): Production Process of N,N'-hexanediyl-bis-carbamic Acid Di(3-methylbutyl) Ester A stirring tank 601 (internal volume: 5 L) was heated to 80°C. Bis(3-methylbutyl) carbonate was transferred to the stirring tank 601 from a line 60 at the rate of 678 g / hr with a line 62 closed, and a mixed solution of hexamethylene diamine, 3-methyl-1-butanol and sodium methoxide (28% methanol solution) (mixing ratio: hexamethylene diamine 50 parts/3-methyl-1-butanol 50 parts / sodium methoxide 0.42 parts) was simultaneously transferred from a line 61 at the rate of 112 g / hr. After 4 hours, line 62 was opened with a line 63 closed, and transfer of the reaction liquid to a tank 602 was started at the rate of 790 g / hr. Line 62 was maintained at 80°C to prevent precipitation of solids from the reaction liquid. When the reaction liquid transferred to a line 602 was analyzed by liquid chromatography, the reaction liquid was found to contain 20.3% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester. Step (23-2): Low Boiling Point Component Distillation Process A thin film distillation apparatus 603 (heat-conducting surface area of 0.2 m2, Kobelco Eco-Solutions Co., Ltd., Japan) was heated to 150°C and the pressure inside the apparatus was made to be about 0.02 kPa. The solution stored in tank 602 was transferred to thin film distillation apparatus 603 from line 63 at the rate of 790 g / hr where a low boiling point component contained in the solution were distilled off. The low boiling point component that had been distilled off was extracted from the thin film distillation apparatus 603 via a line 64. On the other hand, a high boiling point component was extracted from the thin film distillation apparatus 603 via a line 65 maintained at 150°C, and transferred to a stirring tank 604 maintained at 120°C. At the same time, 2,4-di-tert-amylphenol was transferred via a line 66 to stirring tank 604 at the rate of 1306 g / hr, and dibutyl tin dilaurate was transferred to stirring tank 604 via a line 67 at the rate of 29 g / hr. The mixed liquid prepared in stirring tank 604 was transferred to a tank 605 via a line 68 with a line 69 closed, and stored in the tank 605. When the solution stored in the tank 605 was analyzed by liquid chromatography, the solution was found to contain 10.7% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester. Step (23-3): Production Process of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester by Transesterification A thin film distillation apparatus 606 (heat-conducting surface area of 0.2 m2, Kobelco Eco-Solutions Co., Ltd., Japan) was heated to 240°C. A transesterification reaction was carried out by transferring a mixed liquid of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester, 2,4-di-tert-amylphenol and dibutyl tin dilaurate stored in tank 605 to thin film distillation apparatus 606 via a line 69 at the rate of 1496 g / hr with a line 72 closed. A mixed gas containing 3-methyl-1 -butanol and 2,4-di-tert-amylphenol was extracted from a line 73 provided in the upper portion of the thin film distillation apparatus 606, and supplied to a distillation column 607. The 3-methyl-1-butanol and 2,4-di-tert-amylphenol were separated in the distillation column 607, and the 2,4-di-tert-amylphenol was returned to the upper portion of thin film distillation apparatus 606 via a line 74 provided in the bottom of distillation column 607. A reaction liquid was extracted from a line 70 provided in the bottom of the thin film distillation apparatus 606, and supplied to thin film distillation apparatus 606 via a line 71. When the N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester in the reaction liquid extracted from line 70 reached 20.3% by weight, line 72 was opened with line 75 closed and the reaction liquid was transferred to a tank 608. Step (23-4): Production Process of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl) Ester The solution stored in tank 608 was supplied to a thin film distillation apparatus 609 (heat-conducting surface area of 0.2 m2, Kobelco Eco-Solutions Co., Ltd., Japan) heated to 200°C and set to an internal pressure of about 1.3 kPa via line 75 at the rate of 1395 g / hr. A gaseous component containing hexamethylene diisocyanate was extracted from a line 77 provided in the upper portion of the thin film distillation apparatus 609 and supplied to a distillation column 610. Distillative separation was carried out in distillation column 610, and hexamethylene diisocyanate was recovered from a line 79 at the rate of 72 g / hr. [Comparative Example 1] Step (A-1): Production of N,N'-hexanedlyl-bis-carbamic Acid Dimethyl Ester 1044 g of a solution containing 29.6% by weight of N,N-hexanediyl-bis- carbamic acid methyl ester were obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 882 g (9.8 mol) of dimethyl carbonate and 162 g (1.4 mol) of hexamethylene diamine, adding a stirrer, and using 2.7 g of sodium methoxide. Step (A-2): Distillation of Low Boiling Point Component 729 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (A-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 87.5% by weight of dimethyl carbonate and 11.7% by weight of methanol. As a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.2% by weight of N,N'-hexanediyl-bis-carbamic acid dimethyl ester. Step (A-3): Production of N,N'-hexanediyl-bis-carbamic Acid Diphenyl Ester by Transesterification 4101 g of a reaction liquid were extracted from line 24 and 65 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of using 316 g of the distillation residue obtained in step (A-2) instead of the distillation residue obtained in step (1-2), using 85 g of dibutyl tin dilaurate and 3770 g of phenol (for nucleic acid extraction, Wako Pure Chemical Industries, Ltd., Japan), setting the heating unit of the thin film distillation apparatus to 180°C and carrying out the reaction for 430 hours. The extracted reaction liquid contained 8.7% by weight of N,N'-hexanediyl-bis-carbamic acid diphenyl ester. Step (A-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Diphenyl Ester The same method as step (5-4) of Example 5 was carried out with the exception of heating thin film distillation apparatus 402 to 200°C, making the pressure inside the thin film distillation apparatus about 1.3 kPa, feeding the solution obtained in step (A-3) to feed tank 401, supplying to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out the reaction for 11 hours. 134 g of a solution containing 99% by weight of hexamethylene diisocyanate was recovered from line 47. The yield based on hexamethylene diamine was 57%. In addition, a black solid was adhered to the sidewalls of the thin film distillation apparatus 402 following completion of step (A-4). [Comparative Example 2] Step (B-1): Production of N.N'-hexanediyl-bis-carbamic Acid Di(3-methylbutyl) Ester 2146 g of a solution containing 23.1% by weight of N,N-hexanediyl-bis- carbamic acid di(3-methylbutyl) ester were obtained by carrying out the same method as step (1-1) of Example 1 with the exception of using 1970 g (9.8 mol) of bis(3-methylbutyl) carbonate and 174 g (1.5 mol) of hexamethylene diamine, adding a stirrer, and using 2.9 g of sodium methoxide. Step (B-2): Distillation of Low Boiling Point Component 1631 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (B-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 84.2% by weight of bis(3-methylbutyl) carbonate and 15.4% by weight of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 96.7% by weight of N,N'-hexanediyl-bis-carbamic acid bis(3-methylbutyl) ester. Step (B-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(4-methylphenyl) Ester by Transesterification 4978 g of a reaction liquid were extracted from line 24 and 185 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of using 510 g of the distillation residue obtained in step (B-2) instead of the distillation residue obtained in step (1-2), using 91 g of dibutyl tin dilaurate and 4645 g of 4-methylphenol (Aldrich Corp., USA), and carrying out the reaction for 58 hours. The extracted reaction liquid contained 8.1% by weight of N,N'-hexanediyl-bis-carbamic acid di(4-methylphenyl) ester. Step (B-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(4-methylphenyl) Ester A thermal decomposition reaction was carried out in a reaction apparatus like that shown in FIG. 4. Thin film distillation apparatus 402 (Kobelco Eco-Solutions Co., Ltd., Japan) having a heat-conducting surface area of 0.2 m2 was heated to 200°C and the pressure inside the thin film distillation apparatus was made to be about 1.3 kPa. The solution obtained in step (B-3) was fed to feed tank 401 and supplied to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr. A liquid component was extracted from line 43 provided in the bottom of the thin film distillation apparatus 402, and returned to feed tank 401 via line 44. A gaseous component containing hexamethylene diisocyanate and 4-methylphenol was extracted from line 42 provided in the upper portion of thin film distillation apparatus 402. The gaseous component was fed to distillation column 403 where the hexamethylene diisocyanate and 4-methylphenol were separated, the 4-methylphenol was extracted from line 45 connected to the top of distillation column 403, the hexamethylene diisocyanate was extracted from line 47 provided at an intermediate stage of distillation column 403, a high boiling point substance was extracted from line 46 provided in the bottom of distillation column 403, and a portion was returned to feed tank 401 via line 44. When the reaction was carried out for 11 hours, 114 g of a solution containing 99% by weight of hexamethylene diisocyanate was recovered from line 47. The yield based on hexamethylene diamine was 57%. In addition, a black solid was adhered to the sidewalls of the thin film distillation apparatus 402 following completion of step (B-4). [Comparative Example 3] Step (C-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl Ester 1818 g (10.5 mol) of dibutyl carbonate produced using the method of Reference Example 2 and 220 g (1.9 mol) of hexamethylene diamine were placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser and three-way valve were attached to the flask. After replacing the inside of the system with nitrogen, the four-mouth flask was immersed in an oil bath (OBH-24, Masuda Corp.) heated to 80°C followed by the addition of 3.7 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.) to start the reaction. Samples of the reaction liquid were suitably collected and subjected to NMR analysis, and the reaction was terminated at the point hexamethylene diamine was no longer detected. As a result of analyzing the resulting solution by liquid chromatography, the solution was found to contain 28.3% by weight of N,N'- hexanediyl-bis-carbamic acid di butyl ester. Step (C-2): Distillation of Low Boiling Point Component 1444 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (C-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 80.9% by weight of dibutyl carbonate and 18.6% by weight of 1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 98.0% by weight of N,N'-hexanediyl-bis-carbamic acid dibutyl ester. Step (C-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(4-octyl phenyl) Ester by Transesterification 6122 g of a reaction liquid were extracted from line 24 and 182 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of using 594 g of the distillation residue obtained in step (6-3) instead of the distillation residue obtained in step (1-2), adding 114 g of dibutyl tin dilaurate and 5611 g of 4-octylphenol and using in the form of a homogeneous solution, feeding to feed tank 201, heating the thin film distillation apparatus 202 having a heat-conducting surface area of 0.2 m2 to 240°C, and carrying out the reaction for 86 hours. When the extracted reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 11.5% by weight of N,N'-hexanediyl-bis-carbamic acid di(4-octylphenyl) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99.0% by weight of 1-butanol. Step (C-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(4-octylphenyl) Ester A thermal decomposition reaction was carried out in a reaction apparatus like that shown in FIG. 3. Thin film distillation apparatus 302 having a heat-conducting surface area of 0.2 m2 was heated to 200°C and the pressure inside the thin film distillation apparatus was made to be about 1.3 kPa. The solution obtained in step (C-3) was fed to feed tank 301 and supplied to the thin film distillation apparatus via line 31 at the rate of about 980 g / hr. A liquid component was extracted from line 33 provided in the bottom of the thin film distillation apparatus 302, and returned to feed tank 301 via line 34. A gaseous component containing hexamethylene diisocyanate and 4-octylphenol was extracted from line 32 provided in the upper portion of thin film distillation apparatus 302. The gaseous component was fed to distillation column 303 where the hexamethylene diisocyanate and 4-octylphenol were separated, and a portion of 4-octylphenol was returned to feed tank 301 through line 34 via line 36 provided in the bottom of distillation column 303. When the reaction was carried out for 13 hours, 167 g of a solution were recovered from line 35, and as a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of hexamethylene diisocyanate. The yield based on hexamethylene diamine was 53%. In addition, a black solid was adhered to the sidewalls of the thin film distillation apparatus 302 following completion of step (C-4). [Comparative Example 4] Step (D-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl Ester 1914 g (11.0 mol) of dibutyl carbonate produced using the method of Reference Example 2 and 232 g (2.0 mol) of hexamethylene diamine were placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser and three-way valve were attached to the flask. After replacing the inside of the system with nitrogen, the four-mouth flask was immersed in an oil bath heated to 80°C followed by the addition of 0.37 g of sodium methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.) to start the reaction. Samples of the reaction liquid were suitably collected and subjected to NMR analysis, and the reaction was terminated at the point hexamethylene diamine was no longer detected. As a result of analyzing the resulting solution by liquid chromatography, the solution was found to contain 28.3% by weight of N,N'- hexanediyl-bis-carbamic acid dibutyl ester. Step (D-2): Distillation of Low Boiling Point Component 1532 g of a distillate were obtained by carrying out the same method as step (1-2) of Example 1 with the exception of using the solution obtained in step (D-1) instead of the solution obtained in step (1-1). As a result of analyzing by gas chromatography, the distillate was found to contain 80.9% by weight of dibutyl carbonate and 18.5% by weight of 1-butanol. In addition, as a result of analyzing by liquid chromatography, the distillation residue in the flask was found to contain 99.5% by weight of N,N'-hexanediyl-bis-carbamlc acid dibutyl ester. Step (D-3): Production of N,N'-hexanediyl-bis-carbamic Acid Di(3-octyloxy) Ester by Transesterification 4203 g of a reaction liquid were extracted from line 24 and 250 g of a solution were recovered from line 27 provided in the upper portion of distillation column 203 by carrying out the same method as step (1-3) of Example 1 with the exception of using 605 g of the distillation residue obtained in step (6-3) instead of the distillation residue obtained in step (1-2), adding 120 g of dibutyl tin dilaurate and 3727 g of 3-octanol (Aldrich Corp., USA) and using in the form of a homogeneous solution, feeding to feed tank 201, heating the thin film distillation apparatus 202 having a heat-conducting surface area of 0.2 m2 to 175°C, and carrying out the reaction for 180 hours. When the extracted reaction liquid was analyzed by liquid chromatography, the reaction liquid was found to contain 17.1% by weight of N,N'-hexanediyl-bis-carbamic acid di(3-octyloxy) ester. In addition, when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was found to contain 99.0% by weight of 1-butanol. Step (D-4): Production of Hexamethylene Diisocyanate by Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(3-octyloxy) Ester A thermal decomposition reaction was carried out in a reaction apparatus like that shown in FIG. 4. Thin film distillation apparatus 402 (Kobelco Eco-Solutions Co., Ltd., Japan) having a heat-conducting surface area of 0.2 m2 was heated to 200°C and the pressure inside the thin film distillation apparatus was made to be about 1.3 kPa. The solution obtained in step (D-3) was fed to feed tank 401 and supplied to the thin film distillation apparatus via line 41 at the rate of about 680 g / hr. A liquid component was extracted from line 43 provided in the bottom of the thin film distillation apparatus 402, and returned to feed tank 401 via line 44. A gaseous component containing hexamethylene diisocyanate and 3-octanol was extracted from line 42 provided in the upper portion of thin film distillation apparatus 402. The gaseous component was fed to distillation column 403 where the hexamethylene diisocyanate and 3-octanol were separated, the 3-octanol was extracted from line 45 connected to the top of distillation column 403, hexamethylene diisocyanate was extracted from line 47 provided in an intermediate stage of distillation column 403, a high boiling point substance was extracted from line 46 provided in the bottom of distillation column 403, and a portion was returned to feed tank 401 via line 44. When the reaction was carried out for 11 hours, 149 g of a solution containing 99% by weight of hexamethylene diisocyanate were recovered from line 47. The yield based on hexamethylene diamine was 45%. In addition, a black solid was adhered to the sidewalls of the thin film distillation apparatus 402 following completion of step (D-4). Industrial Applicability Since the isocyanate production process according to the present invention enables isocyanates to be efficiently produced without using extremely toxic phosgene, the production process of the present invention is extremely useful industrially and has high commercial value. CLAIMS 1. A process for producing an isocyanate, comprising the steps of: reacting a carbamic acid ester and an aromatic hydroxy compound to obtain an aryl carbamate having a group derived from the aromatic hydroxy compound; and subjecting the aryl carbamate to a decomposition reaction, wherein the aromatic hydroxy compound is an aromatic hydroxy compound which is represented by the following formula (1) and which has a substituent R1 at at least one ortho position of a hydroxyl group: (wherein ring A represents an aromatic hydrocarbon ring in a form of a single or multiple rings which may have a substituent and which have 6 to 20 carbon atoms; R1 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom; and R1 may bond with A to form a ring structure). 2. The process according to Claim 1, wherein the aromatic hydroxy compound is a compound represented by the following formula (2): (wherein ring A and R1 are the same as defined above, R2 represents a hydrogen atom or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or aralkyloxy group having 7 to 20 atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl and the aralkyloxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom, and R2 may bond with A to form a ring structure). 3. The process according to Claim 2, wherein in the formula (2), a total number of the carbon atoms constituting R1 and R2 is 2 to 20. 4. The process according to any one of Claims 1 to 3, wherein the ring A of the aromatic hydroxy compound comprises a structure containing at least one structure selected from the group consisting of a benzene ring, a naphthalene ring and an anthracene ring. 5. The process according to Claim 4, wherein the aromatic hydroxy compound is a compound represented by the following formula (3): (wherein R1 and R2 are the same as defined above, and each of R3, R4 and R5 independently represents a hydrogen atom or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl and the aralkyloxy groups containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom). 6. The process according to Claim 5, wherein the aromatic hydroxy compound is such that in the formula (3), each of R1 and R4 independently represents a group represented by the following formula (4), and R2, R3 and R5 represent a hydrogen atom: (wherein X represents a branched structure selected from the structures represented by the following formulas (5) and (6): (wherein R6 represents a linear or branched alkyl group having 1 to 3 carbon atoms). 7. The process according to Claim 5, wherein the aromatic hydroxy • compound is such that in the formula (3), R1 represents a linear or branched alkyl group having 1 to 8 carbon atoms, and each of R2 and R4 independently represents a hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms. 8. The process according to any one of Claims 1 to 7, wherein the carbamic acid ester is an aliphatic carbamic acid ester, and a low boiling point component formed with the aryl carbamate is an aliphatic alcohol. 9. The process according to Claim 8, wherein the aliphatic carbamic acid ester is an aliphatic polycarbamic acid ester. 10. The process according to Claim 8, further comprising the steps of: continuously supplying the aliphatic carbamic acid ester and the aromatic hydroxy compound to a reaction vessel so as to react the aliphatic carbamic acid ester and the aromatic hydroxy compound inside the reaction vessel; recovering a formed low boiling point component in a form of a gaseous component; and continuously extracting a reaction liquid containing the aryl carbamate and the aromatic hydroxy compound from a bottom of the reaction vessel. 11. The process according to any one of Claims 1 to 10, wherein the decomposition reaction is a thermal decomposition reaction, and is a reaction in which a corresponding isocyanate and aromatic hydroxy compound are formed from the aryl carbamate. 12. The process according to Claim 11, wherein at least one compound of the isocyanate and aromatic hydroxy compound formed by the thermal decomposition reaction of the aryl carbamate is recovered in a form of a gaseous component. 13. The process according to Claim 8, wherein the aliphatic carbamic acid ester is a compound represented by the following formula (7): (wherein R7 represents a group selected from the group consisting of an aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atoms, and having a valence of n, R8 represents an aliphatic group which has 1 to 8 carbon atoms and which contains an atom selected from a carbon atom, an oxygen atom and a nitrogen atom, and 14. The process according to Claim 13, wherein the aliphatic carbamic acid ester is such that R8 in the compound represented by the formula (7) is a group selected from the group consisting of an alkyl group having 1 to 20 carbon atoms and a cycloalkyl group having 5 to 20 carbon atoms. 15. The process according to Claim 14, wherein the aliphatic carbamic acid ester is at least one compound selected from the group consisting of compounds represented by the following formulas (8), (9) and (10): (wherein R8 is the same as defined above). An object of the present invention is to provide a process that enables isocyanates to be stably produced over a long period of time at high yield without encountering various problems as found in the prior art when producing isocyanates without using phosgene. The present invention discloses a process for producing an isocyanate, comprising the steps of: reacting a carbamic acid ester and an aromatic hydroxy compound to obtain an aryi carbamate having a group derived from the aromatic hydroxy compound; and subjecting the aryl carbamate to a decomposition reaction, wherein the aromatic hydroxy compound is an aromatic hydroxy compound which is represented by the following formula (1) and which has a substituent R1 at at least one ortho position of a hydroxyl group: (wherein ring A represents an aromatic hydrocarbon ring in a form of a single or multiple rings which may have a substitute and which have 6 to 20 carbon atoms; R1 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom; and R1 may bond with A to form a ring structure).

Full Text

A PROCESS FOR PRODUCING ISOCYANATES
Technical Field
The present invention relates to a process for producing isocyanate.
Background Art
Isocyanates are widely used as production raw materials of such
products as polyurethane foam, paints and adhesives. The main industrial
production process of isocyanates involves reacting amines with phosgene
(phosgene method), and nearly the entire amount of isocyanates produced
throughout the world are produced according to the phosgene method.
However, the phosgene method has numerous problems.
Firstly, this method requires the use of a large amount of phosgene as
raw material. Phosgene is extremely toxic and requires special handling
precautions to prevent exposure of handlers thereof, and also requires special
apparatuses to detoxify waste.
Secondly, since highly corrosive hydrogen chloride is produced in large
amounts as a by-product of the phosgene method, in addition to requiring a
process for detoxifying the hydrogen chloride, in many cases hydrolytic
chlorine is contained in the isocyanates produced, which may have a
detrimental effect on the weather resistance and heat resistance of
polyurethane products in the case of using isocyanates produced using the
phosgene method.
On the basis of this background, a process for producing isocyanates

has been sought that does not use phosgene. One example of a method for
producing isocyanate compounds without using phosgene that has been
proposed involves thermal decomposition, of carbamic acid esters.
Isocyanates and hydroxy compounds have long been known to be obtained by
thermal decomposition of carbamic acid esters (see, for example, Berchte der
Deutechen Chemischen Geselischaft, Vol. 3, p. 653, 1870). The basic
reaction is illustrated by the following formula:
R(NHCOOR')a ----------> R(NCO)a + a R'OH (1)
(wherein R represents an organic residue having a valence of a, R' represents
a monovalent organic residue, and a represents an integer of 1 or more).
The thermal decomposition reaction represented by the
above-mentioned formula is reversible, and in contrast to the equilibrium
thereof being towards the carbamic acid ester on the left side at low
temperatures, the isocyanate and hydroxy compound side becomes
predominant at high temperatures. Thus, it is necessary to carry out the
carbamic acid ester thermal decomposition reaction at high temperatures. In
addition, in the case of alkyl carbamates in particular, since the reaction rate is
faster for the reverse reaction of thermal decomposition, namely the reaction
by which alkyl carbamate is formed from isocyanate and alcohol, the carbamic
acid ester ends up being formed before the isocyanate and alcohol formed by
thermal decomposition are separated, thereby frequently leading to an
apparent difficulty in the progression of the thermal decomposition reaction.
On the other hand, thermal decomposition of alkyl carbamates is
susceptible to the simultaneous occurrence of various irreversible side
reactions such as thermal denaturation reactions undesirable for alkyl

carbamates or condensation of isocyanates formed by the thermal
decomposition. Examples of these side reactions include a reaction in which
urea bonds are formed as represented by the following formula (2), a reaction
in which carbodiimides are formed as represented by the following formula (3),
and a reaction in which isocyanurates are formed as represented by the
following formula (4) (see, Berchte der Deutechen Chemischen Gesellschaft,
Vol. 3, p. 653, 1870 and Journal of American Chemical Society, Vol. 81, p.
2138, 1959):

In addition to these side reactions leading to a decrease in yield and
selectivity of the target isocyanate, in the production of polyisocyanates in
particular, these reactions may make long-term operation difficult as a result of,
for example, causing the precipitation of polymeric solids that clog the reaction
vessel.
Various methods have been proposed to solve such problems. For
example, a method for producing polyisocyanate has been proposed in which
an alkyl polycarbamate, in which ester groups are composed of alkoxy groups
corresponding to a primary alcohol, is subjected to a transesterification
reaction with a secondary alcohol to produce an alkyl polycarbamate in which
the ester groups are composed of alkoxy groups corresponding to the
secondary alcohol, followed by thermal decomposition of the alkyl

polycarbamate (see, for example, International Publication No. WO 95/23484).
It is described in this method that the thermal decomposition temperature of
the alkyl polycarbamate can be set to a lower temperature by going through an
alkyl polycarbamate in which the ester groups are composed of alkoxy groups
corresponding to the secondary alcohol, thereby resulting in the effect of being
able to inhibit precipitation of polymeric solid. However, the reverse reaction
rate between the polyisocyanate formed by the thermal decomposition reaction
of the alkyl polycarbamate and the secondary alcohol is still fast, thereby
leaving the problem of inhibiting the formation of alkyl polycarbamate by the
reverse reaction unsolved.
An alternative method has been disclosed whereby, in the production of
aromatic isocyanates, for example, an aromatic alkyl polycarbamate and an
aromatic hydroxy compound are subjected to a transesterification reaction to
produce an aromatic aryl polycarbamate followed by thermal decomposition of
the aromatic aryl polycarbamate to product an aromatic isocyanate (see, for
example, US Patent No. 3,992,430). This method describes the effect of
being able to set the thermal decomposition temperature to a lower
temperature by going through an aromatic aryl polycarbamate. However, in
the case of this aromatic aryl polycarbamate as well, under temperatures like
those at which the transesterification reaction or thermal decomposition
reaction is carried out, there are many cases in which side reactions like those
described above still occur, there leaving the problem of improving isocyanate
yield unsolved. Moreover, thermal decomposition of N-substituted aromatic
urethanes in the gaseous phase or liquid phase is known to frequently result in
the occurrence of various undesirable side reactions (see, for example, US

Disclosure of Invention
Problems to be Solved by the Invention
As has been described above, there are currently hardly any methods for
industrially producing polyisocyanates at favorable yield without using
extremely toxic phosgene.
An object of the present invention is to provide a process that enables
isocyanates to be stably produced over a long period of time at high yield
without encountering various problems as found in the prior art when
producing isocyanates without using phosgene.
Means for Solving the Problems
In view of the above, as a result of conductive extensive studies on the
above-mentioned problems, the inventors of the present invention found that a
production process in which a carbamic acid ester and a specific aromatic
hydroxy compound are subjected to a transesterification reaction to produce
an aryl carbamate followed by subjecting the aryl carbamate to a thermal
decomposition reaction to produce isocyanate enables the above-mentioned
problems to be solved, thereby leading to completion of the present invention.
Namely, the present invention provides the followings:
[1] a process for producing an isocyanate, comprising the steps of:
reacting a carbamic acid ester and an aromatic hydroxy compound to
obtain an aryl carbamate having a group derived from the aromatic hydroxy
compound; and

subjecting the aryl carbamate to a decomposition reaction,
wherein the aromatic hydroxy compound is an aromatic hydroxy
compound which is represented by the following formula (5) and which has a
substituent R1 at at least one ortho position of a hydroxyl group:
(5)
(wherein ring A represents an aromatic hydrocarbon ring in a form of a single
or multiple rings which may have a substituent and which have 6 to 20 carbon
atoms;
R1 represents a group other than a hydrogen atom in a form of an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group
containing an atom selected from a carbon atom, an oxygen atom and a
nitrogen atom; and R1 may bond with A to form a ring structure),
[2] the process according to item [1], wherein the aromatic hydroxy compound
is a compound represented by the following formula (6):
(6)
(wherein ring A and R1 are the same as defined above,
R2 represents a hydrogen atom or an aliphatic alkyl group having 1 to 20
carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl

group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon
atoms, an aralkyl group having 7 to 20 carbon atoms or aralkyloxy group
having 7 to 20 atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the
aryloxy, the aralkyl and the aralkyloxy groups containing an atom selected from
a carbon atom, an oxygen atom and a nitrogen atom, and R2 may bond with A
to form a ring structure),
[3] the process according to item [2], wherein in the formula (6), a total number
of the carbon atoms constituting R1 and R2 is 2 to 20,
[4] the process according to any one of items [1] to [3], wherein the ring A of
the aromatic hydroxy compound comprises a structure containing at least one
structure selected from the group consisting of a benzene ring, a naphthalene
ring and an anthracene ring,
[5] the process according to item [4], wherein the aromatic hydroxy compound
is a compound represented by the following formula (7):

(wherein R1 and R2 are the same as defined above, and
each of R3, R4 and R5 independently represents a hydrogen atom or an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic
alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl and the aralkyloxy

groups containing an atom selected from a carbon atom, an oxygen atom and
a nitrogen atom),
[6] the process according to item [5], wherein the aromatic hydroxy compound
is such that in the formula (7), each of R1 and R4 independently represents a
group represented by the following formula (8), and R2, R3 and R5 represent a
hydrogen atom:

(wherein X represents a branched structure selected from the structures
represented by the following formulas (9) and (10):

(wherein R6 represents a linear or branched alkyl group having 1 to 3 carbon
atoms),
[7] the process according to item [5], wherein the aromatic hydroxy compound
is such that in the formula (3), R1 represents a linear or branched alkyl group
having 1 to 8 carbon atoms, and each of R2 and R4 independently represents a
hydrogen atom or a linear or branched alkyl group having 1 to 8 carbon atoms,
[8] the process according to any one of items [1] to [7], wherein the carbamic
acid ester is an aliphatic carbamic acid ester, and a low boiling point
component formed with the aryl carbamate is an aliphatic alcohol,
[9] the process according to item [8], wherein the aliphatic carbamic acid ester
is an aliphatic polycarbamic acid ester.

[10] the process according to item [8], further comprising the steps of:
continuously supplying the aliphatic carbamic acid ester and the aromatic
hydroxy compound to a reaction vessel so as to react the aliphatic carbamic
acid ester and the aromatic hydroxy compound inside the reaction vessel;
recovering a formed low boiling point component in a form of a gaseous
component; and
continuously extracting a reaction liquid containing the aryl carbamate
and the aromatic hydroxy compound from a bottom of the reaction vessel,
[11] the process according to any one of items [1] to [10], wherein the
decomposition reaction is a thermal decomposition reaction, and is a reaction
in which a corresponding isocyanate and aromatic hydroxy compound are
formed from the aryl carbamate,
[12] the process according to item [11], wherein at least one compound of the
isocyanate and aromatic hydroxy compound formed by the thermal
decomposition reaction of the aryl carbamate is recovered in a form of a
gaseous component,
[13] the process according to item [8], wherein the aliphatic carbamic acid
ester is a compound represented by the following formula (11):

(wherein R7 represents a group selected from the group consisting of an
aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to
20 carbon atoms, the group containing an atom selected from a carbon atom,
an oxygen atom and a nitrogen atoms, and having a valence of n,

R8 represents an aliphatic group which has 1 to 8 carbon atoms and
which contains an atom selected from a carbon atom, an oxygen atom and a
nitrogen atom, and
n represents an integer of 1 to 10),
[14] the process according to item [13], wherein the aliphatic carbamic acid
ester is such that R8 in the compound represented by the formula (11) is a
group selected from the group consisting of an alkyl group having 1 to 20
carbon atoms and a cycloalkyl group having 5 to 20 carbon atoms,
[15] the process according to item [14], wherein the aliphatic carbamic acid
ester is at least one compound selected from the group consisting of
compounds represented by the following formulas (12), (13) and (14):

(wherein R8 is the same as defined above),
[16] an aryl polycarbamate represented by the following formula (15), (16) or
(17):

(wherein a ring B represents a structure which may have a substituent and
which contains at least one structure selected from the group consisting of a
benzene ring, a naphthalene ring and an anthracene ring,
R9 represents a group other than a hydrogen atom in a form of an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group
containing an atom selected from a carbon atom, an oxygen atom and a
nitrogen atom, and
R10 represents an aliphatic alkyl group having 1 to 20 carbon atoms, an
aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to
20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl
group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20
carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the

aralkyl and aralkyloxy groups containing an atom selected from a carbon atom,
an oxygen atom and a nitrogen atom),
[17] the aryl polycarbamate according to item [16], which is represented by the
following formula (18), (19) or (20):

(wherein R9 represents a group other than a hydrogen atom in a form of an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group
containing an atom selected from a carbon atom, an oxygen atom and a
nitrogen atom, and
each of R10, R11 R12 and R13 independently represents a hydrogen atom
or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy
group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms,
an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20

carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic
alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl, and the aralkyloxy
groups containing an atom selected from a carbon atom, an oxygen atom and
a nitrogen atoms).
Advantageous Effect of the Invention
According to the present invention, an isocyanate can be produced
efficiently without using phosgene.
Brief Description of Drawings
Fig. 1 shows a conceptual drawing showing a continuous production
apparatus for producing carbonic acid ester according to an embodiment of the
present invention;
Fig. 2 shows a conceptual drawing showing a transesterification reaction
apparatus according to an embodiment of the present invention;
Fig. 3 shows a conceptual drawing showing a thermal decomposition
reaction apparatus according to an embodiment of the present invention;
Fig. 4 shows a conceptual drawing showing a thermal decomposition
reaction apparatus according to an embodiment of the present invention;
Fig. 5 shows a conceptual drawing showing an isocyanate production
apparatus according to an embodiment of the present invention;
Fig. 6 shows the 1H-NMR spectrum of N,N'-hexanediyl-bis-carbamic acid
di(2,4-di-tert-butylphenyl) ester obtained in step (3-4) of Example 3 of the
present invention; and,
Fig. 7 shows the 13C-NMR spectrum of N,N'-hexanediyl-bis-carbamic

acid di(2,4-di-tert-butylphenyl) ester obtained in step (3-4) of Example 3 of the
present invention.
Description of Reference Numericals:
(Fig. 1)
101, 107 : distillation column, 102 : column-type reaction vessel, 103, 106 : thin
film evaporator, 104 : autoclave, 105 : decarbonization tank, 111, 112, 117 :
reboiler, 121, 123, 126, 127 : condenser, 1,9: supply line, 2, 4, 5, 6, 7, 8, 10,
11, 12, 13, 14 : transfer line, 3, 15 : recovery line, 16 : extraction line, 17 : feed
line.
(Fig. 2)
201 : feed tank, 202 : thin film evaporator, 203 : distillation column, 204 :
condenser, 21, 22, 23, 24, 25, 26, 27, 28, 29 : transfer line
(Fig.3)
301 : feed tank, 302 : thin film evaporator, 303 : distillation column, 304 :
reboiler, 305 : condenser, 31, 32, 33, 34, 35, 36, 37, 38, 39, transfer line
(Fig. 4)
401 : feed tank, 402 : thin film evaporator, 403, 404 : distillation column, 405,
407, condenser, 406, 408 : reboiler, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,
52, 53 : transfer line
(Fig. 5)
601, 604 : stirring tank, 602, 605, 608 : tank, 603, 606, 609 : thin film
evaporator, 607, 610 : distillation column, 611, 613 : condenser, 612 : reboiler,
61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80,
81 : transfer line

Best Mode for Carrying Out the Invention
The following provides a detailed explanation of the best mode for
carrying out the present invention (to be referred to as the present
embodiment). Furthermore, the present invention is not limited to the
following present embodiment, but rather can be modified in various ways
within the scope of the gist thereof.
The isocyanate production process of the present embodiment is a
process for producing isocyanates which comprises the steps of: reacting a
carbamic acid ester and an aromatic hydroxy compound to obtain an aryl
carbamate having a group derived from the aromatic hydroxy compound; and
subjecting the aryl carbamate to a decomposition reaction; wherein the
aromatic hydroxy compound uses an aromatic compound having a specific
composition.
The following indicates an example of the detailed reaction scheme of the
present embodiment. However, the isocyanate production process as
claimed in the present invention is not limited to the following reaction scheme.

isocyanate production process of the present embodiment.

The aromatic hydroxy compounds used in the isocyanate production
process of the present embodiment are aromatic hydroxy compounds which
are represented by the following formula (5) and which have a substituent at at
least one site ortho to a hydroxyl group:

(wherein ring A represents an aromatic hydrocarbon ring in a form of a single
or multiple rings and which have a substitute and which have 6 to 20 carbon
atoms;
R1 represents a group other than a hydrogen atom in a form of an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group
containing an atom selected from a carbon atom, an oxygen atom and a
nitrogen atom, and R1 may bond with A to form a ring structure).
Examples of R1 in formula (1) above include aliphatic alkyl groups in
which the number of carbon atoms constituting the group is a number selected
from integers of 1 to 20, such as a methyl group, an ethyl group, a propyl
group (isomers), a butyl group (isomers), a pentyl group (isomers), a hexyl
group (isomers), a heptyl group (isomers), an octyl group (isomers), a nonyl

group (isomers), a decyl group (isomers), a dodecyl group (isomers), an
octadecyl group (isomers) or the like; aliphatic alkoxy groups in which the
number of carbon atoms constituting the group is a number selected from
integers of 1 to 20, such as a methoxy group, an ethoxy group, a propoxy
group (isomers), a butyloxy group (isomers), a pentyloxy group (isomers), a
hexyloxy group (isomers), a heptyloxy group (isomers), an octyloxy group
(isomers), a nonyloxy group (isomers), a decyloxy group (isomers), a
dodecyloxy group (isomers), an octadecyloxy group (including isomers) or the
like; aryl groups in which the number of carbon atoms constituting the group is
6 to 20, such as a phenyl group, a methylphenyl group (isomers), an
ethylphenyl group (isomers), a propylphenyl group (isomers), a butylphenyl
group (isomers), a pentylphenyl group (isomers), a hexylphenyl group
(isomers), a heptylphenyl group (isomers), an octylphenyl group (isomers), a
nonylphenyl group (isomers), a decylphenyl group (isomers), a biphenyl group
(isomers), a dimethylphenyl group (isomers), a diethylphenyl group (isomers),
a dipropylphenyl group (isomers), a dibutylphenyl group (isomers), a
dipentylphenyl group (isomers), a dihexylphenyl group (isomers), a
diheptylphenyl group (isomers), a terphenyl group (isomers), a trimethylphenyl
group (isomers), a triethylphenyl group (isomers), a tripropylphenyl group
(isomers), a tributylphenyl group (isomers)or the like; aryloxy groups in which
the number of carbon atoms constituting the group is 6 to 20, such as a
phenoxy group, a methylphenoxy group (isomers), an ethylphenoxy group
(isomers), a propylphenoxy group (isomers), a butylphenoxy group (isomers),
a pentylphenoxy group (isomers), a hexylphenoxy group (isomers), a
heptylphenoxy group (isomers), an octylphenoxy group (isomers), a

nonylphenoxy group (isomers), a decylphenoxy group (isomers), a
plnenylphenoxy group (isomers), a dimethylphenoxy group (isomers), a
diethylphenoxy group (isomers), a dipropylphenoxy group (isomers), a
dibutylphenoxy group (isomers), a dipentylphenoxy group (isomers), a
dihexylphenoxy group (isomers), a diheptylphenoxy group (isomers), a
diphenylphenoxy group (isomers), a trimethylphenoxy group (isomers), a
triethylphenoxy group (isomers), a tripropylphenoxy group (isomers), a
tributylphenoxy group (isomers) or the like; aralkyl groups in which the number
of carbon atoms constituting the group is 7 to 20, such as a phenylmethyl
group, a phenylethyl group (isomers), a phenylpropyl group (isomers), a
phenylbutyl group (isomers), a phenylpentyl group (isomers), a phenylhexyl
group (isomers), a phenylheptyl group (isomers), a phenyloctyl group (isomers),
phenylnonyl group (isomers) or the like; and aralkyloxy groups in which the
number of carbon atoms constituting the group is 7 to 20, such as a
phenylmethoxy group, a phenylethoxy group (isomers), a phenylpropyloxy
group (isomers), a phenylbutyloxy group (isomers), a phenylpentyloxy group
(isomers), a phenylhexyloxy group (isomers), a phenylheptyloxy group
(isomers), a phenyloctyloxy group (isomers), a phenylnonyloxy group (isomers)
or the like.
Examples of ring A in formula (1) above include a benzene ring, a
naphthalene ring, an anthracene ring, a phenanthrene ring, a naphthacene ring,
a chrysene ring, a pyrene ring, a triphenylene ring, a pentalene ring, an
azulene ring, a heptalene ring, an indacene ring, a biphenylene ring, an
acenaphthylene ring, an aceanthrylene ring, an acephenanthrylene ring or the
like, preferable examples include rings selected from the group consisting of a

benzene ring, a naphthalene ring and an anthracene ring. In addition, these
rings may have a substituent other than the above-mentioned R1 examples of
which include aliphatic alkyl groups in which the number of carbon atoms
constituting the group is a number selected from integers of 1 to 20, such as a
methyl group, an ethyl group, a propyl group (isomers), a butyl group (isomers),
a pentyl group (isomers), a hexyl group (isomers), a heptyl group (isomers), an
octyl group (isomers), a nonyl group (isomers), a decyl group (isomers), a
dodecyl group (isomers), an octadecyl group (isomers) or the like; aliphatic
alkoxy groups in which the number of carbon atoms constituting the group is a
number selected from integers of 1 to 20, such as a methoxy group, an ethoxy
group, a propoxy group (isomers), a butyloxy group (isomers), a pentyloxy
group (isomers), a hexyloxy group (isomers), a heptyloxy group (isomers), an
octyloxy group (isomers), a nonyloxy group (isomers), a decyloxy group
(isomers), a dodecyloxy group (isomers), an octadecyloxy group (isomers) or
the like; aryl groups in which the number of carbon atoms constituting the
group is 6 to 20, such as a phenyl group, a methylphenyl group (isomers), an
ethylphenyl group (isomers), a propylphenyl group (isomers), a butylphenyl
group (isomers), a pentylphenyl group (isomers), a hexylphenyl group
(isomers), a heptylphenyl group (isomers), an octylphenyl group (isomers), a
nonylphenyl group (isomers), a decylphenyl group (isomers), a biphenyl group
(isomers), a dimethylphenyl group (isomers), a diethylphenyl group (isomers),
a dipropylphenyl group (isomers), a dibutylphenyl group (isomers), a
dipentylphenyl group (isomers), a dihexylphenyl group (isomers), a
diheptylphenyl group (isomers), a terphenyl group (isomers), a trimethylphenyl
group (isomers), a triethylphenyl group (isomers), a tripropylphenyl group

(isomers), a tributylphenyl group (isomers) or the like; aryloxy groups in which
the number of carbon atoms constituting the group is 6 to 20, such as a
phenoxy group, a methylphenoxy group (isomers), an ethylphenoxy group
(isomers), a propylphenoxy group (isomers), a butylphenoxy group (isomers),
a pentylphenoxy group (isomers), a hexylphenoxy group (isomers), a
heptylphenoxy group (isomers), an octylphenoxy group (isomers), a
nonylphenoxy group (isomers), a decylphenoxy group (isomers), a
phenylphenoxy group (isomers), a dimethylphenoxy group (isomers), a
diethylphenoxy group (isomers), a dipropylphenoxy group (isomers), a
dibutylphenoxy group (isomers), a dipentylphenoxy group (isomers), a
dihexylphenoxy group isomers), a diheptylphenoxy group (isomers), a
diphenylphenoxy group (isomers), a trimethylphenoxy group (isomers), a
triethylphenoxy group (isomers), a tripropylphenoxy group (isomers), a
tributylphenoxy group (isomers) or the like; aralkyl groups in which the number
of carbon atoms constituting the group is 7 to 20, such as a phenylmethyl
group, a phenylethyl group (isomers), a phenylpropyl group (isomers), a
phenylbutyl group (isomers), a phenylpentyl group (isomers), a phenylhexyl
group (isomers), a phenylheptyl group (isomers), a phenyloctyl group (isomers),
a phenylnonyl group (isomers) or the like; and aralkyloxy groups in which the
number of carbon atoms constituting the group is 7 to 20, such as a
phenylmethoxy group, a phenylethoxy group (isomers), a phenylpropyloxy
group (isomers), a phenylbutyloxy group (isomers), a phenylpentyloxy group
(isomers), a phenylhexyloxy group (isomers), a phenylheptyloxy group
(isomers), a phenyloctyloxy group (isomers), a phenylnonyloxy group
(isomers).

In addition, the aromatic hydroxy compounds can be used preferably
whether it is an aromatic hydroxy compound having a substituent at one ortho
position to a hydroxyl group or an aromatic hydroxy compound having
substituents at two ortho positions to a hydroxyl group as in compounds
represented by the following formula (6):

(wherein ring A and R1 are the same as defined above,
R2 represents an aliphatic alkyl group having 1 to 20 carbon atoms, an
aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to
20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl
group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20
atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl,
and the aralkyloxy groups containing atoms selected from a carbon atom, an
oxygen atom and a nitrogen atom, and R2 may bond with A to form a ring
structure).
Examples of R2 in the above-mentioned formula (6) include a hydrogen
atom; aliphatic alkyl groups in which the number of carbon atoms constituting
the group is a number selected from integers of 1 to 20, such as a methyl
group, an ethyl group, a propyl group (isomers), a butyl group (isomers), a
pentyl group (isomers), a hexyl group (isomers), a heptyl group (isomers), an
octyl group (isomers), a nonyl group (isomers), a decyl group (isomers), a
dodecyl group (isomers), an octadecyl group (isomers) or the like; aliphatic
alkoxy groups in which the number of carbon atoms constituting the group is a

number selected from integers of 1 to 20, such as a methoxy group, an ethoxy
group, a propoxy group (isomers), a butyloxy group (isomers), a pentyloxy
group (isomers), a hexyloxy group (isomers), a heptyloxy group (isomers), an
octyloxy group (isomers), a nonyloxy group (isomers), a decyloxy group
(isomers), a dodecyloxy group (isomers), an octadecyloxy group (isomers) or
tine like; aryl groups in which the number of carbon atoms constituting the
group is 6 to 20, such as a phenyl group, a methylphenyl group (isomers), an
ethylphenyl group (isomers), a propylphenyl group (isomers), a butylphenyl
group (isomers), a pentylphenyl group (isomers), a hexylphenyl group
(isomers), a heptylphenyl group (isomers), an octylphenyl group (isomers), a
nonylphenyl group (isomers), a decylphenyl group (isomers), a biphenyl group
(isomers), a dimethylphenyl group (isomers), a diethylphenyl group (isomers),
a dipropylphenyl group (isomers), a dibutylphenyl group (isomers), a
dipentylphenyl group (isomers), a dihexylphenyl group (isomers), a
diheptylphenyl group (isomers), a terphenyl group (isomers), a trimethylphenyl
group (isomers), a triethylphenyl group (isomers), a tripropylphenyl group
(isomers), a tributylphenyl group (isomers) or the like; aryloxy groups in which
the number of carbon atoms constituting the group is 6 to 20, such as a
phenoxy group, a methylphenoxy group (isomers), an ethylphenoxy group
(isomers), a propylphenoxy group (isomers), a butylphenoxy group (isomers),
a pentylphenoxy group (isomers), a hexylphenoxy group (isomers), a
heptylphenoxy group (isomers), an octylphenoxy group (isomers), a
nonylphenoxy group (isomers), a decylphenoxy group (isomers), a
phenylphenoxy group (isomers), a dimethylphenoxy group (isomers), a
diethylphenoxy group (isomers), a dipropylphenoxy group (isomers), a

dibutylphenoxy group (isomers), a dipentylphenoxy group (isomers), a
dihexylphenoxy group (isomers), a diheptylphenoxy group (isomers), a
diphenylphenoxy group (isomers), a trimethylphenoxy group (isomers), a
triethylphenoxy group (isomers), a tripropylphenoxy group (isomers), a
tributylphenoxy group (isomers) or the like; aralkyl groups in which the number
of carbon atoms constituting the group is 7 to 20, such as a phenylmethyl
group, a phenylethyl group (isomers), a phenylpropyl group (isomers), a
phenylbutyl group (isomers), a phenylpentyl group (isomers), a phenylhexyl
group (isomers), a phenylheptyl group (isomers), a phenyloctyl group (isomers),
a phenylnonyl group (isomers) or the like; and aralkyloxy groups in which the
number of carbon atoms constituting the group is 7 to 20, such as a
phenylmethoxy group, a phenylethoxy group (isomers), a phenylpropyloxy
group (isomers), a phenylbutyloxy group (isomers), a phenylpentyloxy group
(isomers), a phenylhexyloxy group (isomers), a phenylheptyloxy group
(isomers), a phenyloctyloxy group (isomers), a phenylnonyloxy group (isomers)
or the like.
In the case the aromatic hydroxy compound used in the isocyanate
production process of the present embodiment are aromatic hydroxy
compounds having substituents at two ortho positions to a hydroxyl group,
aromatic hydroxy compounds in which the total number of carbon atoms
constituting R1 and R2 is 2 to 20 are used preferably among the compounds
represented by the above-mentioned formula (6). There are no particular
limitations on the combinations of R1 and R2 provided the total number of
carbon atoms constituting R1 and R2 is 2 to 20.
Examples of such aromatic hydroxy compounds include compounds

represented by the following formula (7):

(wherein R1 and R2 are the same as defined above, and
each of R3, R4 and R5 independently represents a hydrogen atom or an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic
alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl, and the aralkyloxy
groups containing an atom selected from a carbon atom, an oxygen atom and
a nitrogen atoms).
In particular, aromatic hydroxy compounds in which each of R1 and R4 in
the above-mentioned formula (7) independently represents a group
represented by the following formula (8) and R2, R3 and R5 represent hydrogen
atoms, or aromatic hydroxy compounds in which R1 in the above-mentioned
formula (7) is a linear or branched alkyl group having 1 to 8 carbon atoms and
each of R2 and R4 independently represents a hydrogen atom or a linear or
branched alkyl group having 1 to 8 carbon atoms, are used preferably:

(wherein X represents a branched structure selected from the structures
represented by the following formulas (9) and (10):

(wherein R6 represents a linear or branched alkyl group having 1 to 3 carbon
atoms).
Examples of such aromatic hydroxy compounds include 2-ethylphenol,
2-propylphenol (isomers), 2-butylphenol (isomers), 2-pentylphenol (isomers),
2-hexylphenol (isomers), 2-heptylphenol (isomers), 2,6-dimethylphenol,
2,4-diethylphenol, 2,6-diethylphenol, 2,4-dipropylphenol (isomers),
2,6-dipropylphenol (isomers), 2,4-dibutylphenol (isomers), 2,4-dipentylphenol
(isomers), 2,4-dihexylphenol (isomers), 2,4-diheptylphenol (isomers),
2-methyl-6-ethylphenol, 2-methyl-6-propylphenol (isomers),
2-methyl-6-butylphenol (isomers), 2-methyl-6-pentylphenol (isomers),
2-ethyl-6-propylphenol (isomers), 2-ethyl-6-butylphenol (isomers),
2-ethyl-6-pentylphenol (isomers), 2-propyl-6-butyl phenol (isomers),
2-ethyl-4-methylphenol (isomers), 2-ethyl-4-propyl phenol (isomers),
2-ethyl-butylphenol (isomers), 2-ethyl-4-pentyl phenol (isomers),
2-ethyl-4-hexylphenol (isomers), 2-ethyl-4-heptylphenol (isomers),
2-ethyl-4-octylphenol (isomers), 2-ethyl-4-phenylphenol (isomers),
2-ethyl-4-cumylphenol (isomers), 2-propyl-4-methylphenol (isomers),
2-propyl-4-ethylphenol (isomers), 2-propyl-4-butylphenol (isomers),
2-propyl-4-pentylphenol (isomers), 2-propyl-4-hexylphenol (isomers),
2-propyl-4-hetpylphenol (isomers), 2-propyl-4-octylphenol (isomers),

The aromatic hydroxy compounds are preferably aromatic hydroxy
compounds having a standard boiling point higher than the standard boiling
point of a hydroxy compound corresponding to an aliphatic alkoxy group,
aryloxy group or aralkyloxy group that composes the ester group of the
carbamic acid ester described below. The term "standard boiling point" as
referred to in the present invention indicates the boiling point at 1 atmosphere.

There are no particular limitations on the carbamic acid ester used in the
isocyanate production process of the present embodiment, and an aliphatic
carbamic acid ester is used preferably. Examples of aliphatic carbamic acid
esters include compounds represented by the following formula (11):

(wherein R7 represents a group selected from the group consisting of an
aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to
20 carbon atoms, the group containing an atom selected from a carbon atom
and an oxygen atom, and having a number of atoms equal to n,
R8 represents an aliphatic group having 1 to 8 carbon atoms containing
an atom selected from a carbon atom and an oxygen atom, and
n represents an integer of 1 to 10).
In formula (11) above, n is preferably a number selected from integers of
2 or more, and more preferably an aliphatic polycarbamic acid ester in which n
is 2.

Examples of R7 in formula (11) include linear hydrocarbon groups such
as methylene, dimethylene, trimethylene, tetramethylene, pentamethylene,
hexamethylene, octamethylene or the like; unsubstituted acyclic hydrocarbon
groups such as cyclopentane, cyclohexane, cycloheptane, cyclooctane,
bis(cyclohexyl)alkane or the like; alkyl-substituted cydohexanes such as
methylcyclopentane, ethylcydopentane, methylcyclohexane (isomers),
ethylcyclohexane (isomers), propylcyclohexane (isomers), butylcyclohexane
(isomers), pentylcydohexane (isomers), hexylcyclohexane (isomers) or the
like; dialkyl-substituted cydohexanes such as dimethylcyclohexane (isomers),
diethylcyclohexane (isomers), dibutylcydohexane (isomers) or the like;
trialkyl-substituted cydohexanes such as 1,5,5-trimethylcyclohexane,
1,5,5-triethylcyclohexane, 1,5,5-tripropylcyclohexane (isomers),
1,5,5-tributylcyclohexane (isomers) or the like; monoalkyl-substituted benzenes
such as toluene, ethylbenzene, propylbenzene or the like; dialkyl-substituted
benzenes such as xylene, diethylbenzene, dipropylbenzene or the like; and
aromatic hydrocarbons such as diphenylalkane, benzene or the like. In
particular, hexamethylene, phenylene, diphenylmethane, toluene, cyclohexane,
xylene, methylcyclohexane, isophorone and dicyclohexylmethane are used
preferably.
Examples of R8 include alkyl groups in which the number of carbon
atoms constituting the group is selected from an integer of 1 to 8, such as a
methyl group, an ethyl group, a propyl group (isomers), a butyl group (isomers),
a pentyl group (isomers), a hexyl group (isomers), a heptyl group (isomers), an
octyl group (isomers) or the like; and cydoalkyl groups in which the number of
carbon atoms constituting the group is selected from an integer of 5 to 14,

such as a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a
cyclooctyl group, a dicyclopentyl group (isomers), a dicyclohexyl group
(isomers), a cyclohexyl-cydopentyl group or the like.
Examples of alkyl polycarbamates represented by the above-mentioned
formula (11) include alkyl carbamates such as N,N'-hexanediyl-bis-carbamic
acid dimethyl ester, N,N'-hexanediyl-bis-carbamic acid diethyl ester,

3-(methoxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
methyl ester, 3-(ethoxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid ethyl ester,
3-(propyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
propyl ester (isomers),
3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
butyl ester (isomers).

3-(pentyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
pentyl ester (isomers),
3-(hexyloxycarbonylannino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
hexyl ester (isomers),
3-(heptyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
heptyl ester (isomers),
3-(octyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
octyl ester (isomers), toluene-dicarbamic acid dimethyl ester (isomers),
toluene-dicarbamic acid diethyl ester (isomers), toluene-dicarbamic acid
dipropyl ester (isomers), toluene-dicarbamic acid dibutyl ester (isomers),
toluene-dicarbamic acid dipentyl ester (isomers), toluene-dicarbamic acid
dihexyl ester (isomers), toluene-dicarbamic acid diheptyl ester (isomers),
toluene-dicarbamic acid dioctyl ester (isomers),
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dimethyl ester,
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid diethyl ester,
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dipropyl ester,
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester,
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dipentyl ester,
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dihexyl ester,
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid diheptyl ester,
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dioctyl ester or the like.
Among these, alkyl carbamates in which R7 in formula (11) above is a
group selected from the group consisting of an alkyl group having 1 to 20
carbon atoms and a cydoalkyl group having 5 to 20 carbon atoms are used
preferably, while alkyl carbamates represented by any of the following formulas

(12) to (14) are used particularly preferably:

(wherein R8 is the same as defined above).
Examples of alkyl polycarbamates represented by formula (12) include
N,N'-hexanediyl-bis-carbamic acid dimethyl ester,
N,N'-hexanediyl-bis-carbamic acid diethyl ester, N,N'-hexanediyl-bis-carbamic
acid dibutyl ester (isomers), N,N'-hexanediyl-bis-carbamic acid dipentyl ester
(isomers), N,N'-hexanediyl-bis-carbamic acid dihexyl ester (isomers) and
N,N'-hexanediyl-bis-carbamic acid dioctyl ester (including isomers). In
addition, examples of alkyl polycarbamates represented by formula (13)
include dimethyl-4,4'-methylene-dicyclohexyl carbamate,
diethyl-4,4'-methylene-dicyclohexyl carbamate,
dipropyl-4,4'-methylene-dicyclohexyl carbamate (isomers),
dibutyl-4,4'-methylene-dicyclohexyl carbamate (isomers),
dipentyl-4,4'-methylene-dicyclohexyl carbamate (isomers),
dihexyl-4,4'-methylene-dicyclohexyl carbamate (isomers),
diheptyl-4,4'-methylene-dicyclohexyl carbamate (isomers) and
dioctyl-4,4'-methylene-dicyclohexyl carbamate (isomers). Moreover,

examples of alkyl polycarbamates represented by formula (14) Include alkyl
polycarbamates such as
3-(methoxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
methyl ester, 3-(ethoxycarbonylamlno-methyl)-3,5,5-trimethylcyclohexyl
carbamic add ethyl ester,
3-(propyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
propyl ester (isomers),
3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
butyl ester (isomers),
3-(pentyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
pentyl ester (isomers),
3-(hexyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
hexyl ester (isomers),
3-(heptyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
heptyl ester (isomers),
3-(octyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic acid
octyl ester (isomers) or the like.
A known method can be used to produce the carbamic acid esters. For
example, carbamic esters may be produced by reacting amine compounds
with carbon monoxide, oxygen and aliphatic alcohols or aromatic hydroxy
compounds, or reacting amine compounds with urea and aliphatic alcohols or
aromatic hydroxy compounds. In the present embodiment, the carbamic acid
esters are preferably produced by reacting carbonic acid esters and amine
compounds.
The following provides an explanation of the production of alkyl

carbamates by reacting dialkyl carbonates and amine compounds.
Dialkyl carbonates represented by the following formula (21) can be used
for the dialkyl carbonates:

(wherein R17 represents a linear or branched alkyl group having 1 to 8 carbon
atoms).
Examples of R17 include alkyl groups in a form of aliphatic hydrocarbon
groups in which the number of carbon atoms constituting the group is a
number selected from an integer of 1 to 8, such as a methyl group, an ethyl
group, a propyl group (isomers), a butyl group (isomers), a pentyl group
(isomers), a hexyl group (isomers), a heptyl group (isomers), an octyl group
(isomers) or the like. Examples of such dialkyl carbonates include dimethyl
carbonate, diethyl carbonate, dipropyl carbonate (isomers), dibutyl carbonate
(isomers), dipentyl carbonate (isomers), dihexyl carbonate (isomers), diheptyl
carbonate (isomers) and dioctyl carbonate (isomers). Among these, a dialkyl
carbonate in which the number of carbon atoms constituting the alkyl groups is
a number selected from an integer of 4 to 6 is used particularly preferably.
Amine compounds represented by the following formula (22) are
preferably used for the amine compounds:

(wherein R7 represents a group selected from the group consisting of an
aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to
20 carbon atoms, the group containing an atom selected from a carbon atom
and an oxygen atom, and having a valence of n, and

n represents an integer of 1 to 10).
In formula (22) above, a polyamine compound is used in which n is
preferably 1 to 3 and more preferably n is 2.
Examples of such polyamine compounds include aliphatic diamines such
as hexamethylene diamine, 4,4'-methylenebis(cyclohexylamine) (isomers),
cydohexane diamine (isomers), 3-aminomethyl-3,5,5-trimethylcyclohexyl
amine (isomers) or the like; and aromatic diamines such as phenylene diamine
(isomers), toluene diamine (isomers), 4,4'-methylene dianiline (isomers) or the
like. Among these, aliphatic diamines such as hexamethylene diamine,
4,4'-methylenebis(cyclohexylamine) (isomers), cydohexane diamine (isomers),
3-aminomethyl-3,5,5-trimethylcyclohexyl amine (isomers) or the like are used
preferably, while hexamethylene diamine, 4,4'-methylenebis(cyclohexylamine)
and 3-aminomethyl-3,5,5-trimethylcyclohexyl amine are used more preferably.
Reaction conditions vary according to the reacted compounds, and
although the dialkyl carbonate is preferably in excess based on the amino
groups of the amine compound to accelerate the reaction rate and complete
the reaction quickly at a stoichiometric ratio of the dialkyl carbonate to amino
groups of the amine compound within a range of from 2 to 1000 times, the
range is preferably from 2 to 100 times and more preferably from 2.5 to 30
times in consideration of the size of the reaction vessel. The reaction
temperature is generally within the range of from normal temperature (20°C) to
300°C, and although higher temperatures are preferable in order to accelerate
the reaction rate, since undesirable reactions may conversely occur at high
temperatures, the reaction temperature is preferably within the range of from
50 to 150°C. A known cooling apparatus or heating apparatus may be

installed in the reaction vessel to maintain a constant reaction temperature. In
addition, although varying according to the types of compounds used and
reaction temperature, the reaction pressure may be decreased pressure,
normal pressure or increased pressure, and the reaction is generally carried
out at a pressure within the range of from 20 to 1 x 106 Pa. There are no
particular limitations on the reaction time (residence time in the case of a
continuous method), and is generally from 0.001 to 50 hours, preferably from
0.01 to 10 hours and more preferably from 0.1 to 5 hours. In addition, the
reaction can also be completed by confirming that a desired amount of alkyl
carbamate has been formed by, for example, liquid chromatography after
sampling the reaction liquid. In the present embodiment, a catalyst can be
used as necessary, and examples of catalysts that can be used include organic
metal compounds and inorganic metal compounds of tin, lead, copper or
titanium, and basic catalysts such as alkylates of alkaline metals or alkaline
earth metals in the form of methylates, ethylates and butyrates (isomers) of
lithium, sodium, potassium, calcium, or barium. Although the use of a
reaction solvent is not necessarily required in the present embodiment, a
suitable inert solvent is preferably used as a reaction solvent for the purpose of
facilitating the reaction procedure, examples of which include alkanes such as
hexane (isomers), heptane (isomers), octane (isomers), nonane (isomers),
decane (isomers) or the like; aromatic hydrocarbons and alkyl-substituted
aromatic hydrocarbons such as benzene, toluene, xylene (isomers), ethyl
benzene, diisopropyl benzene (isomers), dibutyl benzene (isomers),
naphthalene or the like; aromatic compounds substituted with a halogen or
nitro group such as chlorobenzene, dichlorobenzene (isomers), bromobenzene.

dibromobenzene (isomers), chloronaphthalene, bromonaphthalene,
nitrobenzene, nitronaphthalene or the like; polycyclic hydrocarbon compounds
such as diphenyl, substituted diphenyl, diphenyl methane, terphenyl,
anthracene, dibenzyl toluene or the like; aliphatic hydrocarbons such as
cyclohexane, cyclopentane, cyclooctane, ethylcyclohexane or the like; ketones
such as methyl ethyl ketone, acetophenone or the like; esters such as dibutyl
phthalate, dihexyl phthalate, dioctyl phthalate, benzylbutyl phthalate or the like;
ethers and thioethers such as diphenyl ether, diphenyl sulfide or the like; and
sulfoxides such as dimethylsulfoxide, diphenylsulfoxide or the like. These
solvents can be used alone or two or more types can be used as a mixture.
In addition, the dialkyl carbonate used in excess based on amino groups of the
amine compound is also preferably used as a solvent in the reaction.
A known tank reactor, column reactor or distillation column can be used
for the reaction vessel, and although known materials may be used for the
reaction vessel and lines provided they do not have a detrimental effect on the
starting substances or reactants, SUS304, SUS316 or SUS316L and the like
can be used preferably since they are inexpensive.

In the isocyanate production process of the present embodiment,
carbamic acid esters and aromatic hydroxy compounds are first reacted to
obtain aryl carbamates having a group derived from the aromatic hydroxy
compounds. This reaction involves an exchange between an aliphatic alkoxy
group or aralkyloxy group constituting the ester group of the carbamic acid
ester and an aryloxy group derived from the aromatic hydroxy compounds

resulting in the formation of the corresponding aryl carbamate and a hydroxy
compound derived from the carbamic acid ester (and is referred to as a
transesterification reaction in the present description).
Although varying according to the reacted compounds, the reaction
conditions of this transesterification reaction are such that the aromatic
hydroxy compound is used within the range of from 2 to 1000 times the ester
group of the carbamic acid ester when expressed as the stoichiometric ratio.
As a result of conducting extensive studies, the inventors of the present
invention surprisingly found that by using the aromatic hydroxy compounds
having a substituent at at least one ortho position with respect to the hydroxyl
group in this transesterification reaction as described above, side reactions as
previously-described attributable to the carbamic acid ester and / or product in
the form of the aryl carbamate can be inhibited in the transesterification
reaction. In the transesterification reaction, although the aromatic hydroxy
compound is preferably used in excess based on the ester group of the
carbamic acid ester in order to inhibit side reactions attributable to the
carbamic acid ester and / or product in the form of the aryl carbamate as well
as allow the reaction to be completed quickly, the aromatic hydroxy compound
is preferably used within the range of from 2 to 100 times and preferably within
the range of from 5 to 50 times in consideration of the size of the reaction
vessel. The reaction temperature is generally within the range of from 100 to
300°C, and although high temperatures are preferable in order to increase the
reaction rate, since there conversely may be greater susceptibility to the
occurrence of side reactions at high temperatures, the reaction temperature is
preferably within the range of from 150 to 250°C. A known cooling apparatus

or heating apparatus may be installed in the reaction vessel to maintain a
constant reaction temperature. In addition, although varying according to the
types of compounds used and reaction temperature, the reaction pressure may
be decreased pressure, normal pressure or increased pressure, and the
reaction is generally carried out at a pressure within the range of from 20 to 1 x
106 Pa. There are no particular limitations on the reaction time (residence
time in the case of a continuous method) and is generally from 0.001 to 100
hours, preferably from 0.01 to 50 hours and more preferably from 0.1 to 30
hours. In addition, the reaction can also be completed by confirming that a
desired amount of aryl carbamate has been formed by, for example, liquid
chromatography after sampling the reaction liquid. In the present
embodiment, the catalyst is used at from 0.01 to 30% by weight and preferably
at from 0.5 to 20% by weight based on the weight of the carbamic acid ester.
For example, organic metal catalysts such as dibutyl tin dilaurate, ferrous
octoate or stannous octoate, or amines such as 1,4-diazabicyclo[2,2,2]octane,
triethylenediamine or triethylamine are suitable for use, while organic metal
catalysts such as dibutyl tin dilaurate, ferrous octoate or stannous octoate are
particularly preferable. These compounds may be used alone or two or more
types may be used as a mixture. Although the use of a reaction solvent is not
necessarily required in the present embodiment, a suitable inert solvent is
preferably used as a reaction solvent for the purpose of facilitating the reaction
procedure, examples of which include alkanes such as hexane (isomers),
heptane (isomers), octane (isomers), nonane (isomers), decane (isomers)or
the like; aromatic hydrocarbons and alkyl-substituted aromatic hydrocarbons
such as benzene, toluene, xylene (isomers), ethylbenzene, diisopropyl-

benzene (isomers), dibutylbenzene (isomers), naphthalene or the like;
aromatic compounds substituted with a halogen or nitro group such as
chlorobenzene, dichlorobenzene (isomers), bromobenzene, dibromobenzene
(isomers), chloronaphthalene, bromonaphthalene, nitrobenzene,
nitronaphthalene or the like; polycyclic hydrocarbon compounds such as
diphenyl, substituted diphenyl, diphenyl methane, terphenyl, anthracene,
dibenzyltoluene (isomers) or the like; aliphatic hydrocarbons such as
cyclohexane, cyclopentane, cyclooctane, ethylcydohexane or the like; ketones
such as methyl ethyl ketone, acetophenone or the like; esters such as dibutyl
phthalate, dihexyl phthalate, dioctyl phthalate, benzylbutyl phthalate or the like;
ethers and thioethers such as diphenyl ether, diphenyl sulfide or the like; and
sulfoxides such as dimethylsulfoxide, diphenylsulfoxide or the like; and,
silicone oil. These solvents can be used alone or two or more types can be
used as a mixture.
As has been described above, although the transesterification reaction in
the present embodiment involves the exchange between the aliphatic alkoxy
group constituting the ester group of the carbamic acid ester and the aryloxy
group derived from the aromatic hydroxy compound resulting in the formation
of the corresponding aryl carbamates and the alcohols, the transesterification
reaction is an equilibrium reaction. Thus, in order to efficiently produce the
aryl carbamates by this transesterification reaction, it is preferable to remove
the products from the reaction system. Since the compounds having the
lowest standard boiling point in the reaction system are the alcohols formed by
the transesterification reaction, the alcohols are preferably removed from the
reaction system by a method such as distillative separation.

In addition, the transesterification reaction is preferably carried out with a
continuous method to allow the transesterification reaction to proceed
efficiently. Namely, a method is preferably used in which the carbamic acid
esters and the aromatic hydroxy compounds are supplied continuously to the
reaction vessel to carry out the transesterification reaction, the alcohols formed
are removed from the reaction vessel in the form of the gaseous components,
and reaction liquids containing the formed aryl carbamates and the aromatic
hydroxy compounds are continuously removed from the bottom of the reaction
vessel. In the case of carrying out the transesterification reaction according to
this method, in addition to promoting the transesterification reaction, there is
also the surprisingly effect of being able to improve the final yield of
isocyanates by inhibiting side reactions as previously described.
Although known materials may be used for the reaction vessel and lines
used to carry out the transesterification reaction provided they do not have a
detrimental effect on the starting substances or reactants, SUS304, SUS316 or
SUS316L and the like can be used preferably since they are inexpensive.
There are no particular limitations on the type of reaction vessel, and a known
tank reactor or column reactor can be used. A reaction vessel is preferably
used that is provided with lines for extracting a low boiling point reaction
mixture containing alcohol formed in the transesterification reaction from the
reaction vessel in the form of the gaseous components, and for removing
mixed liquids containing the produced aryl carbamates and aromatic hydroxy
compounds from the lower portion of the reaction vessel in the form of a liquid.
Various known methods are used for such a reaction vessel, examples of
which include types using reaction vessels containing a stirring tank, a

multistage stirring tank, a distillation column, a multistage distillation column, a
multitubular reactor, a continuous multistage distillation column, a packed
column, a thin film evaporator, a reactor provided with a support inside, a
forced circulation reactor, a falling film evaporator, a falling drop evaporator, a
trickle flow reactor, a bubble column, and types using combinations thereof.
Methods using the thin film evaporator or columnar reactor are preferable from
the viewpoint of efficiently shifting the equilibrium to the products side, while a
structure having a large gas-liquid contact area is preferable for being able to
rapidly transfer the alcohol formed to the gaseous phase.
The multistage distillation column refers to a distillation column having
multiple stages in which the number of theoretical plates of distillation is 2 or
more, and any multistage distillation column may be used provided it allows
continuous distillation. Any multistage distillation column can be used for the
multistage distillation column provided it is ordinarily used as a multistage
distillation column, examples of which include tray column types using a
bubble tray, a porous plate tray, a valve tray, a counter-current tray or the like,
and packed column types packed with various types of packing materials such
as a raschig ring, a lessing ring, a pole ring, a Berl saddle, an Interlock saddle,
a Dixon packing, a McMahon packing, Helipack, a Sulzer packing, Mellapak or
the like. Any packed column can be used provided the column is packed with
known packing materials as described above. Moreover, a combination
tray-packed column type is also used preferably that combines a tray portion
with the portion packed with the packing materials. The reaction vessel is
preferably provided with a line for supplying a mixture containing the carbamic
acid esters and the aromatic hydroxy compounds, a line for removing the

gaseous phase components containing alcohols formed by the
transestehfication reaction, and a line for extracting mixed liquids containing
the carbamic acid esters and aromatic hydroxy compounds, and the line for
removing the gaseous phase components containing the alcohols is preferably
at a location that allows the gaseous phase components in the reaction vessel
to be removed, and the line for extracting the mixed liquids containing the aryl
carbamates and the aromatic hydroxy compounds is particularly preferably
located there below.
A line for supplying inert gas and / or liquid inert solvent from the lower
portion of the reaction vessel may be separately attached, and in the case the
mixed liquids containing the formed aryl carbamates and the aromatic hydroxy
compounds contain unreacted carbamic acid esters, a line may be attached for
recirculating all or a portion of the mixed liquids to the reaction vessel. Note
that in the case of using the above-mentioned inert solvent, the inert solvent
may be in the form of a gas and / or a liquid.
The gaseous components containing alcohols extracted from the reaction
vessel may be purified using a known method such as a distillation column,
and the azeotropic and / or accompanying aromatic hydroxy compound and
the like may be recycled. Equipment for warming, cooling or heating may be
added to each line in consideration of clogging and the like.

The aryl carbamates preferably produced by the transesterification
reaction are aryl carbamates represented by any of the following formulas (15)
to (17):

(wherein ring B represents a structure which may have a substituent and which
contains at least one structure selected from the group consisting of a benzene
ring, a naphthalene ring and an anthracene ring,
R9 represents a group other than a hydrogen atom in a form of an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group
containing an atom selected from a carbon atom, an oxygen atom and a
nitrogen atom, and
R10 represents an aliphatic alkyl group having 1 to 20 carbon atoms, an
aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl group having 6 to
20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl
group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20
carbon atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the

aralkyl and aralkyoxy groups containing an atom selected from a carbon atom,
an oxygen atom and a nitrogen atoms).
Among these, more preferably produced aryl carbamates are aryl
carbamates represented by any of the following formulas (18) to (20);

(wherein R9 represents a group other than a hydrogen atom in a form of an
alkyl group having 1 to 20 carbon atoms, an alkoxy group having 1 to 20
carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group
having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or
an aralkyloxy group having 7 to 20 carbon atoms, the group containing an
atom selected from a carbon atom, an oxygen atom and a nitrogen atoms, and
each of R10, R11, R12 and R13 independently represents a hydrogen atom
or an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy
group having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms,
an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20

carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic
alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl, and the aralkyoxy
groups containing an atom selected from a carbon atom, an oxygen atom and
a nitrogen atom).

include 3-((2-ethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2-ethylphenyl)ester,
3-((2-propylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2-propylphenyl)ester (isomers),
3-((2-butylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic
acid (2-butylphenyl)ester (isomers),
3-((2-pentylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic
acid (2-pentylphenyl)ester (isomers),
3-((2-hexylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic
acid (2-hexylphenyl)ester (isomers),
3-((2-heptylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic
acid (2-heptylphenyl)ester (isomers),
3-((2-octylphenoxy)carbonyiamino-methyl)-3,5,5-trimethyicyclohexyl carbamic
acid (2-octylphenyl)ester (isomers),
3-((2-cumyiphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl carbamic
acid (2-cumyiphenyi)ester (isomers),
3-((2,4-diethylphenoxy)carbonylamino-methyi)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-diethylphenyl)ester,
3-((2,4-dipropylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-dipropylphenyl)ester (isomers),
3-((2,4-dibutylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-dibutylphenyl)ester (isomers),
3-((2,4-dipentylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-dipentylplnenyl)ester (isomers),
3-((2,4-dihexylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl

carbamic acid (2,4-dihexylphenyl)ester (isomers),
3-((2,4-diheptylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-diheptylphenyl)ester (isomers),
3-((2,4-dioctylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-dioctylphenyl)ester (isomers),
3-((2,4-dicumylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-dicumylphenyl)ester,
3-((2,6-dimethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,6-dimethylphenyi)ester,
3-((2,6-diethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,6-diethylphenyl)ester,
3-((2,6-dipropylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,6-dipropylphenyl)ester (isomers),
3-((2,4,6-trimethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4,6-trimethylphenyl)ester,
3-((2,4,6-triethylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4,6-triethylphenyl)ester, and
3-((2,4,6-tripropylphenoxy)carbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4,6-tripropylphenyl)ester (isomers).
The aryl carbamates produced in the transesterification reaction may be
subjected to the subsequent thermal decomposition reaction while still as a
mixed liquid containing aryl carbamates and aromatic hydroxy compounds
which are removed from the reactor, or the aryl carbamates may be subjected
to the thermal decomposition reaction after purifying from the mixed liquid. A
known method can be used to purify the aryl carbamate from the reaction

liquid, examples of which include removal of the aromatic hydroxy compounds
by distillation, washing with solvents and purification of the aryl carbamates by
crystallization.
Since the aryl carbamates of the present embodiment are carbamic acid
esters composed of aromatic hydroxy compounds and isocyanates, the
thermal decomposition temperature is low as is generally known. In addition,
the aryl carbamates of the present embodiment are surprisingly extremely
resistant to the occurrence of side reactions (such as a reaction resulting in the
formation of a urea bond as previously described) at high temperatures (such
as 180°C) at which thermal decomposition is carried out. Although the
mechanism by which side reactions are inhibited is unclear, as was previously
described, it is presumed that a substituent at the ortho position relative to the
hydroxyl group sterically protects a urethane bond, thereby hindering the
reaction between a different carbamic acid ester and the urethane bond.
Moreover, although the aromatic hydroxy compounds formed by the
thermal decomposition reaction of the aryl carbamates of the present
embodiment are aromatic hydroxy compounds having a substituent at the
ortho position relative to a hydroxyl group, since the reaction rate between the
aromatic hydroxy compounds and isocyanates are surprisingly late, namely the
reverse reaction rate in the thermal decomposition reaction is slow, when
carrying out the thermal decomposition reaction on the aryl carbamates, there
is the advantage of being able to easily separate the aromatic hydroxy
compounds and the isocyanates.

The following provides an explanation of the aryl carbamate
decomposition reaction of the present embodiment.
The decomposition reaction of the present embodiment is a thermal
decomposition reaction by which corresponding isocyanates and aromatic
hydroxy compounds are formed from the aryl carbamates.
The reaction temperature is generally within the range of from 100 to
300°C, and although a high temperature is preferable for increasing the
reaction rate, since side reactions as described above may be conversely
caused by the aryl carbamates and / or the reaction products in the form of the
isocyanates, the reaction temperature is preferably within the range of from
150 to 250°C. A known cooling apparatus or heating apparatus may be
installed in the reaction vessel to maintain a constant reaction temperature. In
addition, although varying according to the types of compounds used and
reaction temperature, the reaction pressure may be decreased pressure,
normal pressure or increased pressure, and the reaction is normally carried out
at a pressure within the range of from 20 to 1 x 106 Pa. There are no
particular limitations on the reaction time (residence time in the case of a
continuous method) and is generally from 0.001 to 100 hours, preferably from
0.01 to 50 hours and more preferably from 0.1 to 30 hours. A catalyst can be
used in the present embodiment, and the catalyst is used at from 0.01 to 30%
by weight and preferably at from 0.5 to 20% by weight based on the weight of
the aryl carbamates. For example, organic metal catalysts such as dibutyl tin
dilaurate, ferrous octoate, stannous octoate or the like, or amines such as
1,4-diazabicyclo[2,2,2]octane, triethylenediamine, triethylamine or the like are
suitable for use as catalysts, while organic metal catalysts such as dibutyl tin

dilaurate, ferrous octoate, stannous octoate or the like are particularly
preferable. These compounds may be used alone or two or more types may
be used as a mixture. In the case of using the catalysts in the
above-mentioned transesterification reaction, the catalysts contained in the
mixed liquid following the transesterification reaction may be used as a catalyst
in the thermal decomposition reaction or catalysts may be freshly added to the
aryl carbamates when the thermal decomposition reaction is carried out.
Although the use of a reaction solvent is not necessarily required in the present
embodiment, a suitable inert solvent can be used as a reaction solvent for the
purpose of facilitating the reaction procedure, examples of which include
alkanes such as hexane (isomers), heptane (isomers), octane (isomers),
nonane (isomers), decane (isomers) or the like; aromatic hydrocarbons and
alkyl-substituted aromatic hydrocarbons such as benzene, toluene, xylene
(isomers), ethyl benzene, diisopropyl benzene (isomers), dibutyl benzene
(isomers), naphthalene or the like; aromatic compounds substituted with a
halogen or nitro group such as chlorobenzene, dichlorobenzene (isomers),
bromobenzene, dibromobenzene (isomers), chloronaphthalene,
bromonaphthalene, nitrobenzene, nitronaphthalene or the like; polycyclic
hydrocarbon compounds such as diphenyl, substituted diphenyl, diphenyl
methane, terphenyl, anthracene, dibenzyl toluene (isomers) or the like;
aliphatic hydrocarbons such as cydohexane, cyclopentane, cyclooctane,
ethylcyclohexane or the like; ketones such as methyl ethyl ketone,
acetophenone or the like; esters such as dibutyl phthalate, dihexyl phthalate,
dioctyl phthalate, benzylbutyl phthalate or the like; ethers and thioethers such
as diphenyl ether, diphenyl sulfide or the like; and sulfoxides such as

dimethylsulfoxide, diphenylsulfoxide or the like; and, silicone oil. These
solvents can be used alone or two or more types can be used as a mixture.
As was previously described, although the thermal decomposition
reaction of the present embodiment is a reaction by which the corresponding
isocyanates and the aromatic hydroxy compounds are formed from the aryl
carbamates, the thermal decomposition reaction is an equilibrium reaction.
Thus, in order to efficiently obtain isocyanates in this thermal decomposition
reaction, it is preferable to remove at least one of the products of this thermal
decomposition reaction in the form of the isocyanates and the aromatic
hydroxy compounds from the thermal decomposition reaction system in the
form of a gaseous component by a method such as distillation. Whether the
isocyanates or aromatic hydroxy compounds are removed as the gaseous
components can be arbitrarily determined according to the compounds used,
and for example, the respective standard boiling points of the isocyanates and
the aromatic hydroxy compounds are compared followed by removing the
compounds having the lower standard boiling point in the form of the gaseous
components.
The aryl carbamates are also susceptible to the occurrence of side
reactions as described above in the case of being held at a high temperature
for a long period of time, although to a much lower degree than carbamic acid
esters. In addition, the above-mentioned side reactions may also be induced
by the isocyanates formed by the thermal decomposition reaction. Thus, the
time during which the aryl carbamates and the isocyanates are held at a high
temperature is preferably as short as possible, and the thermal decomposition
reaction is preferably carried out by the continuous method. The continuous

method refers to a method in which the aryl carbamates are continuously
supplied to a reaction vessel where it is subjected to a thermal decomposition
reaction, and at least either the formed isocyanates or aromatic hydroxy
compounds are removed from the reaction vessel in the form of a gaseous
component.
Although known materials may be used for the reaction vessel and lines
used to carry out the thermal decomposition reaction provided they do not
have a detrimental effect on the aryl carbamate or the products in the form of
the aromatic hydroxy compounds and isocyanates, SUS304, SUS316 or
SUS316L and the like can be used preferably since they are inexpensive.
There are no particular limitations on the type of reaction vessel, and a known
tank reactor or column reactor can be used. A reaction vessel is preferably
used that is provided with lines for extracting a low boiling point mixture
containing at least either the isocyanates or aromatic hydroxy compounds
formed in the thermal decomposition reaction from the reaction vessel in the
form of the gaseous components, and for removing mixed liquids containing
unreacted aryl carbamates and the compounds not extracted in the form of the
gaseous components from the lower portion of the reaction vessel. Various
known methods are used for such reaction vessels, examples of which include
types using reaction vessels containing a stirring tank, a multistage stirring tank,
a distillation column, a multistage distillation column, a multitubular reactor, a
continuous multistage distillation column, a packed column, a thin film
evaporator, a reactor provided with a support inside, a forced circulation
reactor, a falling film evaporator, a falling drop evaporator, a trickle flow reactor
or a bubble column, and types using combinations thereof. Methods using

the thin film evaporator or columnar reactor are preferable from the viewpoint
of rapidly removing low boiling point components from the reaction system,
while a structure having a large gas-liquid contact area is preferable for rapidly
transferring the low boiling point components formed to the gaseous phase.
The reaction vessel is preferably provided with a line for supplying the
aryl carbamates, a line for removing a gaseous component containing at least
either the isocyanates or aromatic hydroxy compounds formed by the thermal
decomposition reaction, and a line for removing a mixed liquid containing the
compounds not removed as a gaseous component and unreacted aryl
carbamates, the line for removing the gaseous components containing at least
either the isocyanates or aromatic hydroxy compounds is preferably located at
a location that allows the gaseous components in the reaction vessel to be
removed, and the line for extracting the mixed liquids containing the
compounds not removed as the gaseous components and the unreacted aryl
carbamates is particularly preferably located there below.
In addition, a line for supplying inert gas and / or liquid inert solvent from
the lower portion of the reaction vessel may be separately attached, and a line
may also be attached for recirculating all or a portion of the mixed liquid
containing the unreacted aryl carbamates and the compounds not removed as
the gaseous components to the reaction vessel. Equipment for warming,
cooling or heating may be added to each line in consideration of clogging and
the like. Furthermore, in the case of using the above-mentioned inert solvent,
the inert solvent may be in the form of a gas and / or a liquid.
The isocyanate obtained by the above-mentioned production process can
be preferably used as a production raw material of polyurethane foam, paints,

adhesives and the like. Since this process enables isocyanates to be
efficiently produced without using extremely toxic phosgene, the present
invention is industrially extremely significant.
EXAMPLES
Although the following provides a detailed explanation of the present
invention based on examples thereof, the scope of the present invention is not
limited by these examples.

1) NMR Analysis
Apparatus: JNM-A400 FT-NMR system, JEOL Ltd., Japan
(1) Preparation of 1H and 13C-NMR Analysis Samples
About 0.3 g of sample solution were weighed followed by the addition of
about 0.7 g of heavy chloroform (99.8%, Aldrich Corp., USA) and about 0.05 g
of internal standard in the form of tetramethyl tin (guaranteed reagent, Wako
Pure Chemical Industries, Ltd., Japan) and mixing to uniformity to obtain
solutions used as NMR analysis samples.
(2) Quantitative Analysis
Analyses were performed for each standard and quantitative analyses
were performed on the analysis sample solutions based on the resulting
calibration curve.
2) Liquid Chromatography
Apparatus: LC-1 OAT system, Shimadzu Corp., Japan
Column: Silica-60 column, Tosoh Corp., Japan, two columns connected
in series

Developing solvent: Mixed liquid of hexane / tetrahydrofuran (80/20) (v/v)
Solvent flow rate: 2 mL / min
Column temperature: 35°C
Detector: R.I. (refractometer)
(1) Liquid Chromatography Analysis Samples
About 0.1 g of sample were weighed followed by the addition of about 1 g
of tetrahydrofuran (dehydrated, Wako Pure Chemical Industries, Ltd., Japan)
and about 0.02 g of internal standard in the form of bisphenol A (guaranteed
reagent, Wako Pure Chemical Industries, Ltd., Japan) and mixing to uniformity
to obtain solutions used as liquid chromatography analysis samples.
(2) Quantitative Analysis
Analyses were performed for each standard and quantitative analyses
were performed on the analysis sample solutions based on the resulting
calibration curve.
3) Gas Chromatography
Apparatus: GC-2010, Shimadzu Corp., Japan
Column: DB-1 column, Agilent Technologies Corp., USA, length: 30 m,
inner diameter: 0.250 mm, film thickness: 1.00 μm
Column temperature: Held at 50°C for 5 minutes followed by increasing
at the rate of 10°C / min to 200°C; held at 200°C for 5 minutes followed by
increasing at the rate of 10°C / min to 300°C
Detector: FID
(1) Gas Chromatography Analysis Samples
About 0.05 g of sample were weighed followed by the addition of about 1
g of acetone (dehydrated, Wako Pure Chemical Industries, Ltd., Japan) and

about 0.02 g of internal standard in the form of toluene (dehydrated, Wako
Pure Chemical industries, Ltd., Japan) and mixing to uniformity to obtain
solutions used as gas chromatography analysis samples.
(2) Quantitative Analysis
Analyses were performed for each standard and quantitative analyses
were performed on the analysis sample solutions based on the resulting
calibration curve.
[Reference Example 1] Production of Bis(3-methylbutyl) Carbonate
Step (1-1): Production of Dialkyl Tin Catalyst
625 g (2.7 mol) of di-n-butyl tin oxide (Sankyo Organic Chemicals Co.,
Ltd., Japan) and 2020 g (22.7 mol) of 3-methyl-1-butanol (Kuraray Co., Ltd.,
Japan) were placed in a 5000 mL volumetric pear-shaped flask. The flask
was connected to an evaporator (R-144, Shibata Co., Ltd., Japan) to which
was connected an oil bath (OBH-24, Masuda Corp., Japan) equipped with a
temperature controller, a vacuum pump (G-50A, Ulvac Inc., Japan) and a
vacuum controller (VC-10S, Okano Seisakusho Co., Ltd., Japan). The purge
valve outlet of this evaporator was connected to a line containing nitrogen gas
flowing at a normal pressure. After closing the purge valve of the evaporator
to reduce pressure inside the system, the purge valve was opened gradually to
allow nitrogen to flow into the system and return to normal pressure. The oil
bath temperature was set to about 145°C, the flask was immersed in the oil
bath and rotation of the evaporator was started. After heating for about 40
minutes in the presence of atmospheric pressure nitrogen with the purge valve
of the evaporator left open, distillation of 3-methyl-1-butanol containing water
began. After maintaining in this state for 7 hours, the purge valve was closed,

pressure inside the system was gradually reduced, and excess
3-methyl-1-butanol was distilled with the pressure inside the system at 74 to 35
kPa. After the fraction no longer appeared, the flask was taken out of the oil
bath. After allowing the flask to cool to the vicinity of room temperature
(25°C), the flask was taken out of the oil bath, the purge valve was opened
gradually and the pressure inside the system was returned to atmospheric
pressure. 1173 g of reaction liquid were obtained in the flask. Based on the
results of 119Sn-, 1H- and 13C-NMR analyses, 1,1,3,3-tetra-n-butyl-
1,3-bis(3-methylbutyloxy) distannoxane was confirmed to have been obtained
at a yield of 99% based on di-n-butyl tin oxide. The same procedure was then
repeated 12 times to obtain a total of 10335 g of
1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane.
Step (1-2): Production of Bis(3-methylbutyl) Carbonate
Bis(3-methylbutyl) carbonate was produced in a continuous production
apparatus like that shown in FIG. 1.
1,1,3,3-tetrabutyl-1,3-bis(3-methylbutyloxy) distannoxane produced in the
manner described above was supplied at the rate of 4388 g / hr from a transfer
line 4 into a column-type reaction vessel 102 packed with Metal Gauze CY
Packing (Sulzer Chemtech Ltd., Switzerland) and having an inner diameter of
151 mm and effective length of 5040 mm, and 3-methyl-1-butanol purified with
a distillation column 101 was supplied at the rate of 14953 g / hr from a
transfer line 2. The liquid temperature inside reaction vessel 102 was
controlled to 160°C by a heater and a reboiler 112, and the pressure was
adjusted to about 120 kPa-G with a pressure control valve. The residence
time in the reaction vessel was about 17 minutes. 3-Methyl-1-butanol

containing water at the rate of 15037 g / hr from tine top of tine reaction vessel
via a transfer line 6, and 3-methyl-1-butanol at the rate of 825 g / hr via feed
line 1, were pumped to distillation column 101 packed with Metal Gauze CY
Packing and provided with a reboiler 111 and a condenser 121 to carry out
distillative purification. In the top of distillation column 101, a fraction
containing a high concentration of water was condensed by condenser 121
and recovered from a recovery line 3. Purified 3-methyl-1-butanol was
pumped to column-type reaction vessel 102 via transfer line 2 located in the
bottom of distillation column 101. An alkyl tin alkoxide catalyst composition
containing di-n-butyl-bis(3-methylbutyloxy) tin and
1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane was obtained from
the bottom of column-type reaction vessel 102, and supplied to a thin film
evaporator 103 (Kobeico Eco-Solutions Co., Ltd., Japan) via a transfer line 5.
The 3-methyl-1-butanol was distilled off in thin film evaporator 103 and
returned to column-type reaction vessel 102 via a condenser 123, a transfer
line 8 and transfer line 4. The alkyl tin alkoxide catalyst composition was
pumped from the bottom of thin film evaporator 103 via a transfer line 7 and
supplied to an autoclave 104 while adjusting the flow rate of
di-n-butyl-bis(3-methylbutyloxy) tin and 1,1,3,3-tetra-n-
butyl-1,3-bis(3-methylbutyloxy) distannoxane to about 5130 g / hr. Carbon
dioxide was supplied to the autoclave by a transfer line 9 at the rate of 973 g /
hr, and the pressure inside the autoclave was maintained at 4 MPa-G. The
temperature inside the autoclave was set to 120°C, the residence time was
adjusted to about 4 hours, and a reaction between the carbon dioxide and the
alkyl tin alkoxide catalyst composition was carried out to obtain a reaction liquid

containing bis(3-methylbutyl) carbonate. This reaction liquid was transferred
to a decarbonization tank 105 via a transfer line 10 and a control valve to
remove residual carbon dioxide, and the carbon dioxide was recovered from a
transfer line 11. Subsequently, the reaction liquid was transferred to a thin
film evaporator (Kobelco Eco-Solutions Co., Ltd., Japan) 106 set to about
142°C and about 0.5 kPa via a transfer line 12 and supplied while adjusting the
flow rate of 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane to
about 4388 g / hr to obtain a fraction containing bis(3-methylbutyl) carbonate.
On the other hand, the evaporation residue was circulated to column-type
reaction vessel 102 via transfer line 13 and transfer line 4 while adjusting the
flow rate of 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane to
about 4388 g / hr. The fraction containing bis(3-methylbutyl) carbonate was
supplied to a distillation column 107 packed with Metal Gauze CY packing and
equipped with a reboiler 117 and a condenser 127 via a condenser 126 and a
transfer line 14 at the rate of 959 g / hr followed by distillative purification to
obtain 99 wt% bis(3-methylbutyl) carbonate from a recovery line 16 at the rate
of 944 g / hr When the alkyl tin alkoxide catalyst composition of a transfer
line 13 was analyzed by 119Sn-, 1H- and 13C-NMR analysis, it was found to
contain 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane but not
contain di-n-butyl-bis(3-methylbutyloxy) tin. After carrying out the
above-mentioned continuous operation for about 240 hours, alkyl tin alkoxide
catalyst composition was extracted from an extraction line 16 at the rate of 18
g / hr, while 1,1,3,3-tetra-n-butyl-1,3-bis(3-methylbutyloxy) distannoxane
produced according to the above process was supplied from a feed line 17 at
the rate of 18 g / hr.

[Reference Example 2] Production of Dibutyl Carbonate
Step (11-1): Production of Dialkyl Tin Catalyst
692 g (2.78 mol) of di-n-butyl tin oxide and 2000 g (27 mol) of 1-butanol
(Wako Pure Chemical Industries, Ltd., Japan) were placed in a 3000 mL
volumetric pear-shaped flask. The flask containing the white, slurry-like
mixture was attached to an evaporator to which was connected an oil bath
equipped with a temperature controller, a vacuum pump and a vacuum
controller. The purge valve outlet of this evaporator was connected to a line
containing nitrogen gas flowing at normal pressure. After closing the purge
valve of the evaporator to reduce pressure inside the system, the purge valve
was opened gradually to allow nitrogen to flow into the system and return to
normal pressure. The oil bath temperature was set to about 126°C, the flask
was immersed in the oil bath and rotation of the evaporator was started. After
rotating and heating for about 30 minutes at normal pressure with the purge
valve of the evaporator left open, the mixture boiled and distillation of the low
boiling point component began. After maintaining in this state for 8 hours, the
purge valve was closed, pressure inside the system was gradually reduced,
and residual low boiling point component was distilled off with the pressure
inside the system at 76 to 54 kPa. After the low boiling point component no
longer appeared, the flask was taken out of the oil bath. The reaction liquid
was in the form of a clear liquid. The flask was subsequently taken out of the
oil bath, the purge valve was opened gradually and the pressure inside the
system was returned to normal pressure. 952 g of reaction liquid were
obtained in the flask. Based on the results of 119Sn-, 1H- and 13C-NMR
analyses, a product in the form of 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy)

distannoxane was obtained at a yield of 99% based on di-n-butyl tin oxide.
The same procedure was then repeated 12 times to obtain a total of 11480 g of
1,1,3,3-tetra-n-butyl-1,3-di(butyloxy) distannoxane.
Step (11-2): Production of Dibutyl Carbonate
Carbonic acid ester was produced in a continuous production apparatus
like that shown in FIG. 1. 1,1,3,3-Tetra-n-butyl-1,3-di(n-butyloxy)
distannoxane produced in step (11-1) was supplied at the rate of 4201 g / hr
from transfer line 4 into a column-type reaction vessel packed with Mellapak
750Y packing (Sulzer Chemtech Ltd., Switzerland) and having an inner
diameter of 151 mm and effective length of 5040 mm, and 1-butanol purified
with distillation column 101 was supplied to column-type reaction vessel 102 at
the rate of 24717 g / hr from feed line 2. The liquid temperature inside the
reaction vessel was controlled to 160°C by a heater and reboiler 112, and the
pressure was adjusted to about 250 kPa-G with a pressure control valve. The
residence time in the reaction vessel was about 10 minutes. 1-Butanol
containing water at the rate of 24715 g / hr from the top of the reaction vessel
via transfer line 6, and 1-butanol at the rate of 824 g / hr via feed line 1, were
pumped to distillation column 101 packed with Metal Gauze CY packing
(Sulzer Chemtech Ltd., Switzerland) and provided with reboiler 111 and
condenser 121 to carry out distillative purification. In the top of distillation
column 101, a fraction containing a high concentration of water was condensed
by condenser 121 and recovered from transfer line 3. Purified 1-butanol was
pumped via transfer line 2 located in the bottom of distillation column 101. An
alkyl tin alkoxide catalyst composition containing di-n-butyl tin di-n-butoxide
and 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane was obtained from

the bottom of column-type reaction vessel 102, and supplied to thin film
evaporator 103 (Kobelco Eco-Solutions Co., Ltd., Japan) via a transfer line 5.
The 1-butanol was distilled off in thin film evaporator 103 and returned to
column-type reaction vessel 102 via condenser 123, transfer line 8 and
transfer line 4. The alkyl tin alkoxide catalyst composition was pumped from
the bottom of thin film evaporator 103 via transfer line 7 and supplied to
autoclave 104 while adjusting the flow rate of the active components in the
form of dibutyl tin dibutoxide and 1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy)
distannoxane to about 4812 g / hr Carbon dioxide was supplied to the
autoclave by feed line 9 at the rate of 973 g / hr, and the pressure inside the
autoclave was maintained at 4 MPa-G. The temperature inside the autoclave
was set to 120°C, the residence time was adjusted to about 4 hours, and a
reaction between the carbon dioxide and the alkyl tin alkoxide catalyst
composition was carried out to obtain a reaction liquid containing dibutyl
carbonate. This reaction liquid was transferred to decarbonization tank 105
via transfer line 10 and a control valve to remove residual carbon dioxide, and
the carbon dioxide was recovered from transfer line 11. Subsequently, the
reaction liquid was pumped to thin film evaporator 106 (Kobeico Eco-Solutions
Co., Ltd., Japan) set to about 140°C and about 1.4 kPa via transfer line 12 and
supplied while adjusting the flow rate of the
1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane to about 4201 g / hr to
obtain a fraction containing dibutyl carbonate. On the other hand, the
evaporation residue was circulated to column-type reaction vessel 102 via
transfer line 13 and transfer line 4 while adjusting the flow rate of
1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane to about 4201 g / hr. The

fraction containing dibutyl carbonate was supplied to distillation column 107
packed with Metal Gauze CY packing (Sulzer Chemtech Ltd., Switzerland) and
equipped with reboiler 117 and condenser 127 via condenser 126 and a
transfer line 14 at the rate of 830 g / hr followed by distillative purification to
obtain 99 wt% bis(3-methylbutyl) carbonate from recovery line 16 at the rate of
814 g / hr. When the alkyl tin alkoxide catalyst composition of transfer line 13
was analyzed by 119Sn-, 1H- and 13C-NMR analysis, it was found to contain
1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane but not contain di-n-butyl
tin di-n-butoxide. After carrying out the above-mentioned continuous
operation for about 600 hours, alkyl tin alkoxide catalyst composition was
extracted from extraction line 16 at the rate of 16 g / hr, while
1,1,3,3-tetra-n-butyl-1,3-di(n-butyloxy) distannoxane produced in step (11-1)
was supplied from feed line 17 at the rate of 16 g / hr.
[Example 1]
Step (1-1): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(3-methylbutyl) Ester
1818 g (9.0 mol) of bis(3-methylbutyl) carbonate and 208.8 g (1.8 mol) of
hexamethylene diamine (Aldrich Corp., USA) were placed in a 5 L volumetric
fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser
and three-way valve were attached to the flask. After replacing the inside of
the system with nitrogen, the four-mouth flask was immersed in an oil bath
(OBH-24, Masuda Corp., Japan) heated to 80°C followed by the addition of 3.5
g of sodium methoxide (28% methanol solution, Wako Pure Chemical
Industries, Ltd., Japan) to start the reaction. Samples of the reaction liquid

were suitably collected and subjected to NMR analysis, and the reaction was
terminated at the point hexamethylene diamine was no longer detected. As a
result of analyzing the resulting solution by liquid chromatography, the solution
was found to contain 29.9% by weight of N,N'-hexanediyl-bis-carbamic acid
di(3-methylbutyl) ester.
Step (1-2): Distillation of Low Boiling Point Component
The solution obtained in step (1-1) was placed in a 5 L volumetric flask
equipped with a three-way valve, condenser, distillate collector and
thermometer, and the inside of the flask was replaced with nitrogen in a
vacuum. The flask was immersed in an oil bath heated to about 130°C.
Distillation was carried out while gradually reducing the pressure in the flask to
a final pressure of 0.02 kPa. 1410 g of distillate were obtained. As a result
of analyzing by gas chromatography, the distillate was found to be a solution
containing 78.3% by weight of bis(3-methylbutyl) carbonate and 21.4% by
weight of isoamyl alcohol. In addition, as a result of analyzing the resulting
distillation residue in the flask by liquid chromatography, the distillation residue
was found contain 98.0% by weight of N,N'-hexanediyl-bis-carbamic acid
di(3-methylbutyl) ester.
Step (1-3): Production of N,N'-h6xanediyl-bis-carbamic Acid
Di(2,4-di-tert-amylphenyl) Ester by Transesterification
A transesterification reaction was carried out in a reaction apparatus like
that shown in FIG. 2.
111 g of dibutyl tin dilaurate (chemical grade, Wako Pure Chemical
Industries, Ltd., Japan) and 4119 g of 2,4-di-tert-amylphenol (Tokyo Chemical
Industry Co., Ltd., Japan) were added to 618 g of the distillation residue

obtained in step (1-2) and stirred to obtain a homogeneous solution which was
then placed in a feed tank 201. A thin film distillation apparatus 202 (Kobelco
Eco-Solutions Co., Ltd., Japan) having heat-conducting surface area of 0.2 m2
was heated to 240°C, and the inside of the thin film distillation apparatus was
replaced with a nitrogen atmosphere at atmospheric pressure. The solution
was supplied to the thin film distillation apparatus via supply line 21 at the rate
of about 1200 g / hr. A mixed gas containing 3-methyl-1-butanol and
2,4-di-tert-amylphenol was extracted from a line 25 provided in the upper
portion of the thin film distillation apparatus 202, and supplied to a distillation
column 203 packed with Metal Gauze CY Packing (Sulzer Chemtech Ltd.,
Switzerland). The 3-methyl-1-butanol and 2,4-di-tert-amylphenol were
separated in the distillation column 203, and the 2,4-di-tert-amylphenol was
returned to the upper portion of thin film distillation apparatus 202 by a line 26
provided in the bottom of distillation column 203. The reaction liquid was
extracted from a line 22 provided in the bottom of thin film distillation apparatus
202 and returned to feed tank 201 via a line 23.
After carrying out this step for 62 hours, the reaction liquid was extracted
from a line 24. 4532 g of extracted liquid were extracted, and 304 g of
solution were recovered from a line 27 provided in the upper portion of
distillation column 203.
As a result of analyzing the extracted reaction liquid by liquid
chromatography, the reaction liquid was found to contain 24.2% by weight of
N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester. In addition,
as a result of analyzing the solution recovered from line 27 by 1H- and
13C-NMR analysis, the solution was found to contain 98% by weight of

3-nnethyl-1-butanol.
Step (1-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl)
Ester
A thermal decomposition reaction was carried out in a reaction apparatus
like that shown in FIG. 2.
A thin film distillation apparatus 302 (Kobelco Eco-Solutions Co., Ltd.,
Japan) having a heat-conducting surface area of 0.2 m2 was heated to 200°C
and the pressure within the thin film distillation apparatus was set to about 1.3
kPa. The solution obtained in step (1-3) was placed in a feed tank 301 and
supplied to the thin film distillation apparatus at the rate of about 980 g / hr via
a line 31. A liquid component was extracted from a line 33 provided in the
bottom of thin film distillation apparatus 302 and returned to feed tank 301 via a
line 34. A gaseous component containing hexamethylene diisocyanate and
2,4-di-tert-amylphenol was extracted from a line 32 provided in the upper
portion of a thin film distillation apparatus 302. The gaseous component was
introduced into a distillation column 303 followed by separation into
hexamethylene diisocyanate and 2,4-di-tert-amylphenol, and a portion of the
2,4-di-tert-amylphenol was returned to feed tank 301 through line 34 via a line
36 provided in the bottom of distillation column 303. When this reaction was
carried out for 13 hours, 266 g of a solution were recovered from a line 35, and
as a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution
was found to contain 99% by weight of hexamethylene diisocyanate. The
yield based on hexamethylene diamine was 88%.
[Example 2]

Step (2-1): Production of N,N'-hexanecliyl-bis-carbamic Acid
Di(3-methylbutyl) Ester
A solution containing 12.8% by weight of N,N'-hexanediyl-bis-carbamic
acid di(3-methylbutyl) ester was obtained by carrying out the same method as
step (1-1) of Example 1 with the exception of adding 2230 g of
3-methyl-1-butanol to a 5 L volumetric four-mouth flask and then adding 1515 g
(7.5 mol) of bis(3-methylbutyl) carbonate and 174 g (1.5 mol) of
hexamethylene diamine thereto and using 28.9 g of sodium methoxide. The
solution was passed through a column packed with an ion exchange resin
(Amberlyst 15 Dry, Rohm and Haas Co., USA) and 3919 g of solution were
recovered.
Step (2-2): Distillation of Low Boiling Point Component
3373 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (2-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 27.0% by
weight of bis(3-methylbutyl) carbonate and 72.9% by weight of
3-methy 1-1-butanol. In addition, as a result of analyzing by liquid
chromatography, the distillation residue in the flask was found to contain 92.1%
by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester.
Step (2-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(2,4-di-tert-butylphenyl) Ester by Transesterification
3351 g of a reaction liquid were extracted from line 24 by carrying out the
same method as step (1-3) of Example 1 with the exception of using 544 g of
the distillation residue obtained in step (2-2) instead of the distillation residue

obtained in step (1-2), using 92 g of dibutyl tin diiaurate, using 2999 g of
2,4-di-tert-butylphenol (Wako Pure Chemical Industries, Ltd., Japan) instead of
2,4-di-tert-amylphenol, and carrying out the reaction for 70 hours. In addition,
246 g of a solution were recovered from line 27 provided in the upper portion of
distillation column 203. The extracted reaction liquid contained 24.2% by
weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-butylphenyl) ester.
Step (2-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-butylphenyl)
Ester
225 g of a solution were recovered from line 35 by carrying out the same
method as step (1-4) of Example 1 in a reaction apparatus like that shown in
FIG. 2 with the exception of heating thin film distillation apparatus 302 to 200°C,
setting the pressure within the thin film distillation apparatus to about 1.3 kPa,
supplying the solution obtained in step (2-3) to the thin film distillation
apparatus at the rate of about 980 g / hr via line 31, and carrying out the
reaction for 11 hours. As a result of analyzing the solution by 1H- and
13C-NMR analysis, the solution was found to contain 99% by weight of
hexamethylene diisocyanate. The yield based on hexamethylene diamine
was 89%.
[Example 3]
Step (3-1): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(3-methylbutyl) Ester
2754 g of a solution containing 21.6% by weight of N,N'-hexanediyl-bis-
carbamic acid di(3-methylbutyl) ester were obtained by carrying out the same
method as step (1-1) of Example 1 with the exception of using 2545 g (12.6

mol) of bis(3-methylbutyl) carbonate and 209 g (1.8 mol) of hexamethylene
diamine along with the stirrer, and using 3.5 g of sodium methoxide.
Step (3-2): Distillation of Low Boiling Point Component
2150 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (3-1) instead of the solution obtained in step (1-1). As a result of
analyzing the distillate by gas chromatography, the distillate was found to
contain 85.6% by weight of bis(3-methylbutyl) carbonate and 14.0% by weight
of 3-methyl-1-butanol. In addition, as a result of analyzing by liquid
chromatography, the distillation residue in the flask was found to contain 98.4%
by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester.
Step (3-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(2,4-di-tert-amylphenyl) Ester by Transesterification
4834 g of a reaction liquid were extracted from line 24 by carrying out the
same method as step (1-3) of Example 1 with the exception of using 602 g of
the distillation residue obtained in step (3-2) instead of the distillation residue
obtained in step (1-2), using 109 g of dibutyl tin dilaurate, using 4431 g of
2,4-di-tert-amylphenol and carrying out the reaction for 70 hours. In addition,
297 g of a solution were recovered from line 27 provided in the upper portion of
distillation column 203. The extracted reaction liquid contained 22.2% by
weight of N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester.
Step (3-4): Distillation of 2,4-di-tert-amylphenol
A vacuum pump and a vacuum controller were attached to a molecular
distillation apparatus having a jacketed heating unit operated by oil circulation
(80 molecular distillation apparatus, Asahi Seisakusho Co., Ltd., Japan), and

the purge line of the vacuum controller was connected to a nitrogen gas line.
The air inside the molecular distillation apparatus was replaced with nitrogen
and the heating unit was heated to 150°C with an oil circulator. The pressure
in the molecular distillation apparatus was reduced to 0.3 kPa, and the solution
obtained in step (3-3) was fed to the molecular distillation apparatus at the rate
of about 5 g / min while rotating the wiper of the molecular distillation apparatus
at about 300 rpm to distill off the 2,4-di- tert-amylphenol. 1291 g of a high
boiling point substance were recovered in a high boiling point sample collector
held at 120°C and as a result of analyzing by liquid chromatography, was
found to contain 83.1% by weight of N,N'-hexanediyl-bis-carbamic acid
di(2,4-di-tert-amylphenyl) ester.
Step (3-5): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl)
Ester
A thermal decomposition reaction was carried out in a reaction apparatus
like that shown in FIG. 2.
290 g of a solution were recovered from line 35 by carrying out the same
method as step (1-4) of Example 1 with the exception of feeding a mixed liquid
in the form of a slurry comprising a mixture of 1289 g of the carbamic acid
ester-containing substance obtained in step (3-4) and 3422 g of benzylbutyl
phthalate (guaranteed reagent, Wako Pure Chemical Industries, Ltd., Japan) to
feed tank 301, supplying to the thin film distillation apparatus at the rate of
about 980 g / hr and reacting for 14 hours. As a result of analyzing the
solution by 1H- and 13C-NMR analysis, the solution was found to contain 99%
by weight of hexamethylene diisocyanate. The yield based on

hexamethylene diamine was 83%.
[Example 4]
Step (4-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl
Ester
A solution containing 30.8% by weight of N,N'-hexanediyl-bis-carbamic
acid dibutyl ester was obtained by carrying out the same method as step (1-1)
of Example 1 with the exception of using 1479 g (8.5 mol) of dibutyl carbonate
produced according to the method of Reference Example 2 and 197 g (1.7
mol) of hexamethylene diamine (Aldrich Corp., USA), and using 3.3 g of
sodium methoxide (28% methanol solution, Wako Pure Chemical Industries,
Ltd., Japan) in a 5 L volumetric four-mouth flask.
Step (4-2): Distillation of Low Boiling Point Component
1156 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (4-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 78.5% by
weight of dibutyl carbonate and 20.8% by weight of n-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 98.8% by weight of N,N'-hexanediyl-bis-carbamic
acid dibutyl ester.
Step (4-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(2,4-di-tert-amylphenyl) Ester by Transesterification
4929 g of a reaction liquid were extracted from line 24 by carrying out the
same method as step (1-3) of Example 1 with the exception of using the
distillation residue obtained in step (4-2) instead of the distillation residue

obtained in step (1-2), using 82 g of dibutyl tin diiaurate, adding 4566 g of
2,4-di-tert-amyiphenol followed by stirring to obtain a homogeneous solution
that was then fed to feed tank 201, heating thin film distillation apparatus 202
having a heat-conducting surface area of 0.2 m2 to 240°C and reacting for 86
hours. 233 g of a solution were recovered from line 27 provided in the upper
portion of distillation column 203.
When the extracted reaction liquid was analyzed by liquid
chromatography, the reaction liquid was found to contain 20.4% by weight of
N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester. In addition,
when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR
analysis, the solution was found to contain 99.9% by weight 1-butanol.
Step (4-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert-amylphenyl)
Ester
A thermal decomposition reaction was carried out in a reaction apparatus
like that shown in FIG. 2.
248 g of a solution were recovered from line 35 by carrying out the same
method as step (1-4) of Example 1 with the exception of using the solution
extracted from line 24 in step (4-3) instead of the solution extracted from line
24 in step (1-3) and reacting for 14 hours. As a result of analyzing the
solution by 1H- and 13C-NMR analysis, the solution was found to contain 99%
by weight of hexamethylene diisocyanate. The yield based on
hexamethylene diamine was 87%.
[Example 5]
Step (5-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl

Ester
2091 g of a solution containing 26.2% by weight of N,N'-hexanediyl-bis-
carbamic acid dibutyl ester was obtained by carrying out the same method as
step (1-1) of Example 1 with the exception of using 1879 g (10.8 mol) of dibutyl
carbonate and 209 g (1.8 mol) of hexamethylene diamine, adding a stirrer and
adding 3.5 g of sodium methoxide.
Step (5-2): Distillation of Low Boiling Point Component
1537 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (5-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 82.9% by
weight of dibutyl carbonate and 16.6% by weight of n-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 99.0% by weight of N,N'-hexanediyl-bis-carbamic
acid dibutyl ester.
Step (5-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(2,6-dimethylphenyl) Ester by Transesterification
3554 g of a reaction liquid were extracted from line 24 by carrying out the
same method as step (1-3) of Example 1 with the exception of using 548 g of
the distillation residue obtained in step (5-2) instead of the distillation residue
obtained in step (1-2), using 3142 g of 2,6-dimethylphenol (Aldrich Corp., USA)
instead of 2,4-di-tert-amylphenol, using 109 g of dibutyl tin dilaurate, making
the temperature of thin film distillation apparatus 202 200°C and carrying out
the reaction for 225 hours. In addition, 239 g of a solution was recovered
from line 27 provided in the upper portion of distillation column 203. The

extracted reaction liquid contained 18.7% by weight of
N,N'-hexanediyl-bis-carbamic acid di(2,6-dimethylphenyl) ester.
Step (5-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-dimethylphenyl)
Ester
A thermal decomposition reaction was carried out in a reaction apparatus
like that shown in FIG. 4.
A thin film distillation apparatus 402 (Kobelco Eco-Solutions Co., Ltd.,
Japan) having a heat-conducting surface area of 0.2 m2 was heated to 200°C
and the pressure within the thin film distillation apparatus was set to about 1.3
kPa. The solution obtained in step (5-3) was placed in a feed tank 401 and
supplied to the thin film distillation apparatus at the rate of about 680 g / hr via
a line 41. A liquid component was extracted from a line 43 provided in the
bottom of thin film distillation apparatus 402 and returned to feed tank 401 via a
line 44. A gaseous component containing hexamethylene diisocyanate and
2,6-dimethylphenol was extracted from a line 42 provided in the upper portion
of thin film distillation apparatus 402. The gaseous component was
introduced into a distillation column 403 followed by separation into
hexamethylene diisocyanate and 2,6-dimethylphenol, the 2,6-dimethylphenol
was extracted from a line 45 via the top of the distillation column 403, and a
gaseous component containing hexamethylene diisocyanate was extracted
from a line 47 provided in the distillation column 403. On the other hand, a
high boiling point substance was extracted from a line 46 provided in the
bottom of the distillation column, and a portion was returned feed tank 401
through line 44. The gaseous component containing hexamethylene

diisocyanate extracted from line 47 was pumped to a distillation column 404,
and the hexamethylene diisocyanate was distilled off and separated in the
distillation column 404. A high boiling point substance was extracted from a
line 48 provided in the distillation column 404, and a portion was returned to
feed tank 401 through line 44. On the other hand, a gaseous component was
extracted from a line 49, and hexamethylene diisocyanate was extracted from
a line 52 via a condenser. After reacting for 11 hours, 249 g of a solution
containing 99% by weight of hexamethylene diisocyanate was recovered from
line 47. The yield based on hexamethylene diamine was 82%.
[Example 6]
Step (6-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dimethyl
Ester
A solution containing 39.0% by weight of N,N'-hexanediyl-bis-carbamic
acid dimethyl ester therein was obtained by carrying out the same method as
step (1-1) of Example 1 with the exception of using 765 g (8.5 mol) of dimethyl
carbonate (Aldrich Corp., USA) and 197 g (1.7 mol) of hexamethylene diamine,
and using 3.3 g of sodium methoxide in a 2 L volumetric four-mouth flask.
Step (6-2): Distillation of Low Boiling Point Component
582 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (6-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 80.8% by
weight of dimethyl carbonate and 17.9% by weight of methanol. In addition,
as a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 98.9% by weight of N,N'-hexanediyl-bis-carbamic

acid dimethyl ester.
Step (6-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(2,4-di-tert-amylphenyl) Ester by Transesterification
4517 g of a reaction liquid were extracted from line 24 by carrying out the
same method as step (1-3) of Example 1 with the exception of using 376 g of
the distillation residue in the flask obtained in step (6-2) instead of the
distillation residue in the flask obtained in step (1-2), using 82 g of dibutyl tin
dilaurate, using 4161 g of 2,4-di-tert-amylphenol and carrying out the reaction
for 86 hours. 100 g of a solution were recovered from line 27 provided in the
upper portion of distillation column 203.
When the extracted reaction liquid was analyzed by liquid
chromatography, the reaction liquid was found to contain 22.1% by weight of
N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester. In addition,
when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR
analysis, the solution was found to contain 99.4% by weight methanol.
Step (6-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,4-di-tert~amylphenyl)
Ester
242 g of a solution were recovered from line 35 by carrying out the same
method as step (1-4) of Example 1 with the exception of using the solution
extracted from line 24 in step (6-3) instead of the solution extracted from line
24 in step (1-3), and carrying out the reaction for 13 hours. As a result of
analyzing the solution by 1H- and 13C-NMR analysis, the solution was found to
contain 99% by weight of hexamethylene diisocyanate. The yield based on
hexamethylene diamine was 85%.

[Example 7]
Step (7-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dimethyl
Ester
934 g of a solution containing 42.4% by weight of
N,N'-hexanediyl-bis-carbamic acid dimethyl ester was obtained by carrying out
the same method as step (1-1) of Example 1 with the exception of using 729 g
(8.1 mol) of dimethyl carbonate and 209 g (1.8 mol) of hexamethylene diamine,
and using 0.35 g of sodium methoxide.
Step (7-2): Distillation of Low Boiling Point Component
533 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (7-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 77.8% by
weight of dimethyl carbonate and 20.6% by weight of methanol, in addition,
as a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 99.7% by weight of N,N'-hexanediyl-bis-carbamic
acid dimethyl ester.
Step (7-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(2,6-di-methylphenyl) Ester by Transesterification
3537 g of a reaction liquid were extracted from line 24 by carrying out the
same method as step (1-3) of Example 1 with the exception of using 395 g of
the distillation residue obtained in step (7-2) instead of the distillation residue
obtained in step (1-2), using 108 g of dibutyl tin dilaurate, using 3133 g of
2,6-dimethylphenol instead of 2,4-di-tert-amylphenol, heating the thin film
distillation apparatus 202 to 200°C and carrying out the reaction for 250 hours.

In addition, 100 g of a solution were recovered from line 27 provided in the
upper portion of distillation column 203. The extracted reaction liquid
contained 18.3% by weight of N,N'-hexanediyi-bis-carbamic acid
di(2,6-di-methylphenyl) ester.
Step (7-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-di-methylphenyl)
Ester
243 g of a solution containing 99% by weight of hexamethylene
diisocyanate were recovered from line 52 by carrying out the same method as
step (5-4) of Example 5 with the exception of using the reaction liquid obtained
from line 24 in step (7-3) instead of the solution obtained in step (5-3), and
carrying out the reaction for 16 hours. The yield with respect to
hexamethylene diamine was 81 %.
[Example 8]
Step (8-1): Production of
3-((3-methylbutyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic
Acid (3-methylbutyl) Ester
1980 g (9.8 mol) of bis(3-methylbutyl) carbonate and 239 g (1.8 mol) of
3-aminomethyl-3,5,5-trimethylcyclohexylamine (Aldrich Corp., USA) were
placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask,
and a Dimroth condenser and three-way valve were attached to the flask.
After replacing the inside of the system with nitrogen, the four-mouth flask was
immersed in an oil bath (OBH-24, Masuda Corp., Japan) heated to 100°C
followed by the addition of 2.7 g of sodium methoxide (28% methanol solution,
Wako Pure Chemical Industries, Ltd., Japan) to start the reaction. Samples of

the reaction liquid were suitably collected and subjected to NMR analysis, and
the reaction was terminated at the point
3-aminomethyl-3,5,5-trimethylcyclohexylamine was no longer detected. As a
result of analyzing the resulting solution by liquid chromatography, the solution
was found to contain 23.9% by weight of
3-((3-methylbutyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (3-methylbutyl) ester.
Step (8-2): Distillation of Low Boiling Point Component
1683 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (8-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 85.4% by
weight of bis(3-methylbutyl) carbonate and 13.8% by weight of
3-methyl-1-butanol. In addition, as a result of analyzing by liquid
chromatography, the distillation residue in the flask was found to contain 99.4%
by weight of 3-((3-methylbutyl)oxycarbonylamino-
methyl)-3,5,5-trimethylcyclohexylcarbamic acid (3-methylbutyl) ester.
Step (8-3): Production of
3-((2,4-di-tert-amylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic Acid (2,4-di-tert-amylphenyl) Ester by Transesterification
5034 g of a reaction liquid were extracted from line 24 and 221 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of using 530 g of the distillation residue obtained in step (8-2)
instead of the distillation residue obtained in step (1-2), using 84 g of dibutyl tin

dilaurate, using 4645 g of 2,4-di-tert-amylphenol, heating the thin film
distillation apparatus 202 to 240°C, supplying the solution to the thin film
distillation apparatus via feed line 21 at the rate of about 1200 g / hr, and
carrying out the reaction for 75 hours.
When the extracted reaction liquid was analyzed by liquid
chromatography, the reaction liquid was found to contain 17.2% by weight of
3-((2,4-di-tert-amylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-di-tert- amylphenyl) ester. In addition, when the solution
recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the
solution was found to contain 99% by weight of 3-methyl-1-butanol.
Step (8-4): Production of Isophorone Diisocyanate by Thermal
Decomposition of 3-((2,4-di-tert-amylphenyl)oxycarbonylamino-methyl)-3,5,5-
trimethylcyclohexylcarbamic Acid (2,4-di-tert-amylphenyl) Pentyl Ester
257 g of a solution containing 99% by weight of isophorone diisocyanate
were recovered from line 52 by carrying out the same method as step (5-4) of
Example 5 with the exception of heating the thin film distillation apparatus 402
to 200°C, making the pressure in the thin film distillation apparatus about 1.3
kPa, feeding the solution obtained in step (8-3) to feed tank 401, supplying to
the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and
carrying out the reaction for 11 hours. The yield based on
3-aminomethyl-3,5,5-trimethylcyclohexylamine was 83%.
[Example 9]
Step (9-1): Production of
3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic Acid
Butyl Ester

The same method as step (8-1) of Example 8 was carried out with the
exception of using 2349 g (13.5 mol) of dibutyl carbonate, 255 g (1.5 mol) of
3-aminomethyl- 3,5,5-trimethylcyclohexyiamine and 2.9 g of sodium methoxide.
As a result of analyzing the resulting solution by liquid chromatography, the
solution was found to contain 20.0% by weight of
3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid butyl
ester therein.
Step (9-2): Distillation of Low Boiling Point Component
2075 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (9-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 89.2% by
weight of dibutyl carbonate and 10.0% by weight of n-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 98.7% by weight of
3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid butyl
ester.
Step (9-3): Production of
3-((2,4-di-tert-butylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic Acid (2,4-di-tert-butylphenyl) Ester by Transesterification
4077 g of a reaction liquid were extracted from line 24 and 197 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of using 525 g of the distillation residue obtained in step (9-2),
using 89 g of dibutyl tin dilaurate, using 3751 g of 2,4-di-tert~butylphenol to

obtain a homogeneous solution, heating the thin film distillation apparatus 202
to 240°C, replacing the inside of the thin film distillation apparatus with nitrogen
at atmospheric pressure, supplying the solution to the thin film distillation
apparatus via supply line 21 at the rate of about 1200 g / hr and carrying out
the reaction for 84 hours.
When the recovered reaction liquid was analyzed by liquid
chromatography, the reaction liquid was found to contain 20.7% by weight of
3-((2,4-di-tert-butylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexyl
carbamic acid (2,4-di-tert-butylphenyl) ester. In addition, when the solution
recovered from line 27 was analyzed by 13H- and 13C-NMR analysis, the
solution was found to contain 98% by weight of 1-butanol.
Step (9-4): Production of Isophorone Diisocyanate by Thermal
Decomposition of 3-((2,4-di-tert-butylphenyl)oxycarbonylamino-methyl)-3,5,5-
trimethylcyclohexylcarbamic Acid (2,4-di-tert-butylphenyl) Ester
271 g of a solution containing 99% by weight of isophorone diisocyanate
were recovered from line 52 by carrying out the same method as step (5-4) of
Example 5 with the exception of heating the thin film distillation apparatus 402
to 200°C, making the pressure in the thin film distillation apparatus about 1.3
kPa, feeding the solution obtained in step (9-3) to feed tank 401, supplying to
the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and
carrying out the reaction for 11 hours. The yield based on
3-aminomethyl-3,5,5-trimethylcyclohexylamine was 82%.
[Example 10]
Step (10-1): Production of 3-(butyloxycarbonylamino-methyl)-3,5,5-
trimethylcyclohexylcarbamic acid Butyl Ester

A solution containing 25.1% by weight of
3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbannic acid butyl
ester was obtained by carrying out the same method as step (8-1) of Example
8 with the exception of using 1949 g (11.2 mol) of dibutyl carbonate, 272 g (1.6
mol) of 3-aminomethyl-3,5,5-trimethylcyclohexylamine and 3.1 g of sodium
methoxide.
Step (10-2): Distillation of Low Boiling Point Component
1657 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (10-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 85.7% by
weight of dibutyl carbonate and 13.4% by weight of n-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 98.9% by weight of
3-(butyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid butyl
ester.
Step (10-3): Production of
3-((2,4,6-tri-methylphenyl)oxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylc
arbamic Acid (2,4,6-tri-methylphenyl) Ester by Transesterification
3067 g of a reaction liquid were extracted from line 24 and 208 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 76 g of dibutyl tin dilaurate to 560 g of the distillation
residue obtained in step (10-2), adding 2645 g of 2,4,6-trimethylphenol (Aldrich
Corp., USA) and using in the form of a homogeneous solution, heating the thin

film distillation apparatus 202 to 220°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the
solution to the thin film distillation apparatus via supply line 21 at the rate of
about 120 g/hr and carrying out the reaction for 180 hours.
When the extracted reaction liquid was analyzed by liquid
chromatography, the reaction liquid was found to contain 22.7% by weight of
3-((2,4,6-tri-methylphenyl)oxycarbonylamino-methyl)-3,5,5-
trimethylcyclohexylcarbamic acid (2,4,6-trimethylphenyl) ester. In addition,
when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR
analysis, the solution was found to contain 99% by weight of 1-butanol.
Step (10-4): Production of Isophorone Diisocyanate by Thermal
Decomposition of 3-((2,4,6-trimethylphenyl)oxycarbonylamino-methyl)-3,5,5-
trimethylcyclohexylcarbamicAcid (2,4,6-trimethylphenyl) Ester
286 g of a solution containing 99% by weight of isophorone diisocyanate
were recovered from line 52 by carrying out the same method as step (5-4) of
Example 5 with the exception of heating the thin film distillation apparatus 402
to 200°C, making the pressure in the thin film distillation apparatus about 1.3
kPa, feeding the solution obtained in step (10-3) to feed tank 401, supplying to
the thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and
carrying out the reaction for 14 hours. The yield based on
3-aminomethyl-3,5,5-trimethylcyclohexylamine was 81%.
[Example 11]
Step (11-1): Production of
3-(methyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid
Methyl Ester

A solution containing 33.6% by weight of
3-(methyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbannic acid
methyl ester was obtained by carrying out the same method as step (8-1) of
Example 8 with the exception of using 1323 g (14.7 mo!) of dimethyl carbonate,
357 g (2.1 mol) of 3-aminomethyl-3,5,5-trimethylcyclohexylamine and 4.1 g of
sodium methoxide.
Step (11-2): Distillation of Low Boiling Point Component
1111 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (11-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 86.7% by
weight of dimethyl carbonate and 11.3% by weight of methanol. In addition,
as a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 99.1% by weight of
3-(methyloxycarbonylamino-methyl)-3,5,5-trimethylcyclohexylcarbamic acid
methyl ester.
Step (11-3): Production of 3-((2,4,6-tri-methylphenyl)oxycarbonylamino-
methyl)-3,5,5-trimethylcyclohexylcarbamic Acid (2,4,6-tri-methylphenyl) Ester
by Transesterification
A transesterification reaction was carried out in a reaction apparatus like
that shown in FIG. 2.
4457 g of a reaction liquid were extracted from line 24 and 118 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 99 g of dibutyl tin dilaurate and 4006 g of

2,4,6-trimethylphenol to 567 g of the distillation residue obtained in step (11-2)
and using in the form of a homogeneous solution, heating the thin film
distillation apparatus 202 to 220°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the
solution to the thin film distillation apparatus via supply line 21 at the rate of
about 1200 g / hr and carrying out the reaction for 90 hours.
When the reaction liquid was analyzed by liquid chromatography the
reaction liquid was found to contain 20.5% by weight of
3-((2,4,6-tri-methylphenyl)oxycarbonylamino-methyl)-3,5,5-
trimethylcyclohexylcarbamic acid (2,4,6-trimethylphenyl) ester. In addition,
when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR
analysis, the solution was found to contain 99% by weight of methanol.
Step (11-4): Production of Isophorone Diisocyanate by Thermal
Decomposition of 3-((2,4,6-trimethylphenyl)oxycarbonylamino-methyl)-3,5,5-
trimethylcyclohexylcarbamicAcid (2,4,6-trimethylphenyl) Ester
368 g of a solution containing 99% by weight of isophorone diisocyanate
were recovered from line 47 by carrying out the same method as step (5-4) of
Example 5 with the exception of heating the thin film distillation apparatus 402
to 200°C, making the pressure in the thin film distillation apparatus about 1.3
kPa, feeding the solution obtained in step (11-3) to feed tank 401, supplying to
the thin film distillation apparatus via line 41 at the rate of about 900 g / hr, and
carrying out the reaction for 13 hours. The yield based on
3-aminomethyl-3,5,5-trimethylcyclohexylamine was 79%.
[Example 12]
Step (12-1): Production of

Bis(3-methylbutyl)-4,4'-methylene-dicyclohexyl Carbamate
1313 g (6.5 mol) of bis(3-methylbutyl) carbonate and 273 g (1.3 mol) of
4,4'- methylenebis(cyclohexylamine) (Aldrich Corp., USA) were placed in a 5 L
volumetric fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth
condenser and three-way valve were attached to the flask. After replacing the
inside of the system with nitrogen, the four-mouth flask was immersed in an oil
bath (OBH-24, Masuda Corp., Japan) heated to 100°C followed by the addition
of 2.5 g of sodium methoxide to start the reaction. Samples of the reaction
liquid were suitably collected and subjected to NMR analysis, and the reaction
was terminated at the point 4,4'-methylenebis(cyclohexylamine) was no longer
detected. As a result of analyzing the resulting solution by liquid
chromatography, the solution was found to contain 34.3% by weight of
bis(3-methylbutyl)-4,4'-methylene-dicyclohexyl carbamate.
Step (12-2): Distillation of Low Boiling Point Component
1034 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (12-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 77.8% by
weight of bis(3-methylbutyl) carbonate and 21.2% by weight of
3-methyl-1-butanol. In addition, as a result of analyzing by liquid
chromatography, the distillation residue in the flask was found to contain 99.0%
by weight of bis(3-methylbutyl)-4,4'-methylene- dicyclohexyl carbamate.
Step (12-3): Production of Bis(2,4-di-tert-amylphenyl)-4,4'-methylene-
dicydohexyl Carbamate by Transesterification
4702 g of a reaction liquid were extracted from line 24 and 210 g of a

solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 79 g of dibutyl tin dilaurate and 4358 g of
2,4-di-tert-amylphenol to 547 g of the distillation residue obtained in step (12-2)
and using in the form of a homogeneous solution, heating the thin film
distillation apparatus 202 to 260°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the
solution to the thin film distillation apparatus via supply line 21 at the rate of
about 1200 g / hr and carrying out the reaction for 58 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 18.2% by weight of
bis(2,4-di-tert-amylphenyl)-4,4'-methylene-dicyclohexyl carbamate. In
addition, when the solution recovered from line 27 was analyzed by 1H- and
13C-NMR analysis, the solution was found to contain 99% by weight of
3-methyl-1-butanol.
Step (12-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of Bis(2,4-di-tert-amylphenyl)-4,4'-methylene-dicyclohexyl
Carbamate
287 g of a substance containing 99% by weight of 4,4'-methylene-
di(cyclohexylisocyanate) were recovered from line 47 by carrying out the same
method as step (5-4) of Example 5 with the exception of heating the thin film
distillation apparatus 402 to 210°C, making the pressure in the thin film
distillation apparatus about 0.13 kPa, feeding the solution obtained in step
(12-3) to feed tank 401, supplying to the thin film distillation apparatus via line
41 at the rate of about 680 g / hr, and carrying out the reaction for 11 hours.

The yield based on 4,4'-methylenebis(cyclohexylamine) was 84%.
[Example 13]
Step (13-1): Production of
Bis(3-methylbutyl)-4,4'-methylene-dicyclohexyl Carbamate
A solution containing 29.4% by weight of
bis(3-methylbutyl)-4,4'-methylene-dicyclohexyl carbamate was obtained by
carrying out the same method as step (12-1) of Example 12 with the exception
of using 1818 g (9.0 moi) of bis(3-methylbutyl) carbonate, 315 g (1.5 mol) of
4,4'-methylenebis(cyclohexylamine) and 2.9 g of sodium methoxide.
Step (13-2): Distillation of Low Boiling Point Component
1490 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (13-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 82.6% by
weight of bis(3-methylbutyl) carbonate and 16.8% by weight of
3-methyl-1-butanol. In addition, as a result of analyzing by liquid
chromatography, the distillation residue in the flask was found to contain 98.0%
by weight of bis(3-methylbutyl)-4,4'-methylene- dicyclohexyl carbamate.
Step (13-3): Production of Bis(2,4-di-tert-butylphenyl)-4,4'-methylene-
dicyclohexyl Carbamate by Transesterification
4987 g of a reaction liquid were extracted from line 24 and 238 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 90 g of dibutyl tin dilaurate and 4511 g of
2,4-di-tert-butylphenol to 633 g of the distillation residue obtained in step (13-2)

and using in the form of a homogeneous solution, heating the thin film
distillation apparatus 202 to 240°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the
solution to the thin film distillation apparatus via supply line 21 at the rate of
about 1200 g/hr and carrying out the reaction for 78 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 18.3% by weight of
bis(2,4-di-tert-butylphenyl)-4,4'-methylene-dicyclohexyl carbamate. In
addition, when the solution recovered from line 27 was analyzed by 1H- and
13C-NMR analysis, the solution was found to contain 99% by weight of
3-methyl-1-butanol.
Step (13-4): Production of 4,4'-methylene-di(cyclohexylisocyanate) by
Thermal Decomposition of
Bis(2,4-di-tert-butylphenyl)-4,4'-methylene-dicyclohexyl Carbamate
325 g of a substance containing 99% by weight of 4,4'-methylene-
di(cyclohexylisocyanate) were recovered from line 52 by carrying out the same
method as step (5-4) of Example 5 with the exception of heating the thin film
distillation apparatus 402 to 210°C, making the pressure in the thin film
distillation apparatus about 0.13 kPa, feeding the solution obtained in step
(13-3) to feed tank 401, supplying to the thin film distillation apparatus via line
41 at the rate of about 680 g / hr, and carrying out the reaction for 14 hours.
The yield based on 4,4'-methylenebis(cyclohexylamine) was 83%.
[Example 14]
Step (14-1): Production of Dibutyl-4,4'-methylene-dicyclohexyl
Carbamate

A solution containing 29.0% by weight of
dibutyl-4,4'-methylene-dicyclohexyl carbamate was obtained by carrying out
the same method as step (12-1) of Example 12 with the exception of using
1696 g (9.8 mol) of dibutyl carbonate, 315 g (1.5 mol) of
4,4'-methylenebis(cyclohexy!amine) and 2.9 g of sodium methoxide.
Step (14-2): Distillation of Low Boiling Point Component
1409 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (14-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 84.0% by
weight of dibutyl carbonate and 14.9% by weight of n-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 97.3% by weight of
dibutyl-4,4'-methylene-dicyclohexyl carbamate.
Step (14-3): Production of Bis(2,6-dimethylphenyl)-4,4'-methylene-
dicyclohexyl Carbamate by Transesterification
3923 g of a reaction liquid were extracted from line 24 and 194 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 89 g of dibutyl tin dilaurate and 3447 g of
2,6-dimethylphenol to 595 g of the distillation residue obtained in step (14-2)
and using in the form of a homogeneous solution, heating the thin film
distillation apparatus 202 to 200°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the
solution to the thin film distillation apparatus via supply line 21 at the rate of

about 1200 g / hr and carrying out the reaction for 350 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 16.8% by weight of
bis(2,6-dimethylphenyl)-4,4'- methylene-dicyclohexyl carbamate. In addition,
when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR
analysis, the solution was found to contain 97% by weight of 1-butanol.
Step (14-4): Production of 4,4'-methylene-di(cyclohexylisocyanate) by
Thermal Decomposition of Bis(2,6-dimethylphenyl)-4,4'-methylene-dicyclohexyl
Carbamate
313 g of a solution containing 99% by weight of 4,4'-methylene-
di(cyclohexylisocyanate) were recovered from line 52 by carrying out the same
method as step (5-4) of Example 5 with the exception of heating the thin film
distillation apparatus 402 to 210°C, making the pressure in the thin film
distillation apparatus about 0.13 kPa, feeding the solution obtained in step
(14-3) to feed tank 401, supplying to the thin film distillation apparatus via line
41 at the rate of about 700 g/hr, and carrying out the reaction for 15 hours.
The yield based on 4,4'-methylenebis(cyclohexylamine) was 80%.
[Example 15]
Step (15-1): Production of Dibutyl-4,4'-methylene-dicyclohexyl
Carbamate
A solution containing 27.0% by weight of
dibutyl-4,4'-methylene-dicyclohexyl carbamate was obtained by carrying out
the same method as step (12-1) of Example 12 with the exception of using
1705 g (9.8 mol) of dibutyl carbonate, 294 g (1.4 mol) of
4,4'-methylenebis(cyclohexylamine) and 0.27 g of sodium methoxide (28%

methanol solution, Wako Pure Chemical Industries, Ltd.).
Step (15-2): Distillation of Low Boiling Point Component
1643 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (15-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 87.7% by
weight of dibutyl carbonate and 11.7% by weight of n-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 99% by weight of
dibutyl-4,4'-methylene-dicyclohexyl carbamate.
Step (15-3): Production of Bis(2-tert-butylphenyl)-4,4'-methylene-
dicydohexyl Carbamate by Transesterification
4256 g of a reaction liquid were extracted from line 24 and 181 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 84 g of dibutyl tin dilaurate and 3980 g of
2-tert-butylphenol to 562 g of the distillation residue obtained in step (15-2) and
using in the form of a homogeneous solution, heating the thin film distillation
apparatus 202 to 220°C, replacing the inside of the thin film distillation
apparatus with nitrogen at atmospheric pressure, supplying the solution to the
thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr
and carrying out the reaction for 180 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 15.5% by weight of
bis(2-tert-butylphenyl)-4,4'-methylene-dicyclohexyl carbamate. In addition.

when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR
analysis, the solution was found to contain 99% by weight of 1-butanol.
Step (15-4): Production of 4,4'-methylene-di(cyclohexylisocyanate) by
Thermal Decomposition of Bis(2-tert-butylphenyl)-4,4'-methylene-dicyclohexyl
Carbamate
287 g of a solution containing 99% by weight of 4,4'-methylene-
di(cyclohexylisocyanate) were recovered from line 52 by carrying out the same
method as step (5-4) of Example 5 with the exception of heating the thin film
distillation apparatus 402 to 210°C, making the pressure in the thin film
distillation apparatus about 0.13 kPa, feeding the solution obtained in step
(15-3) to feed tank 401, supplying to the thin film distillation apparatus via line
41 at the rate of about 710 g / hr, and carrying out the reaction for 14 hours.
The yield based on 4,4'-methylenebis(cyclohexylamine) was 78%.
[Example 16]
Step (16-1): Production of Dimethyl-4,4'-methylene-dicyclohexyl
Carbamate
A solution containing 28.2% by weight of
dimethyl-4,4'-methylene-dicyclohexyl carbamate was obtained by carrying out
the same method as step (1-1) of Example 1 with the exception of using 1440
g (16.0 mol) of dimethyl carbonate, 336 g (1.6 mol) of
4,4'-methylenebis(cyclohexylamine) and 1.5 g of sodium methoxide (28%
methanol solution, Wako Pure Chemical Industries, Ltd.).
Step (16-2): Distillation of Low Boiling Point Component
1271 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in

step (16-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 91.3% by
weight of dimethyl carbonate and 7.7% by weight of methanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 99.4% by weight of
dibutyl-4,4'-methylene-dicyclohexyl carbamate.
Step (16-3): Production of Bis(2,4-di-tert-amylphenyl)-4,4'-methylene-
dicyclohexyl Carbamate by Transesterification
5151 g of a reaction liquid were extracted from line 24 and 88 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 97 g of dibutyl tin dilaurate and 4645 g of
2,4-di-tert-amylphenol to 501 g of the distillation residue obtained in step (16-2)
and using in the form of a homogeneous solution, heating the thin film
distillation apparatus 202 to 240°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the
solution to the thin film distillation apparatus via supply line 21 at the rate of
about 1200 g / hr and carrying out the reaction for 80 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 19.5% by weight of
bis(2,4-di-tert-amylphenyl)-4,4'-methylene-dicyclohexyl carbamate. In
addition, when the solution recovered from line 27 was analyzed by 1H- and
13C-NMR analysis, the solution was found to contain 99% by weight of
methanol.
Step (16-4): Production of Hexamethylene Diisocyanate by Thermal

Decomposition of Bis(2,4-di-tert-amylphenyl)-4,4'-methylene-dicyc!ohexyl
Carbamate
The same method as step (5-4) of Example 5 was carried out with the
exception of heating the thin film distillation apparatus 402 to 210°C, making the
pressure in the thin film distillation apparatus about 0.13 kPa, feeding the
solution obtained in step (16-3) to feed tank 401, supplying to the thin film
distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out
the reaction for 16 hours. 323 g of a solution containing 99% by weight of
4,4'-methylene-di(cyclohexylisocyanate) were recovered from line 52. The
yield based on 4,4'-methylenebis(cyclohexylamine) was 77%.
[Example 17]
Step (17-1): Production of Toluene-2,4-dicarbamic Acid
Bis(3-methylbutyl) Ester
1818 g (9.0 mol) of bis(3-methylbutyl) carbonate and 220 g (1.8 mol) of
2,4-toluene diamine (Aldrich Corp., USA) were placed in a 5 L volumetric
fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser
and three-way valve were attached to the flask. After replacing the inside of
the system with nitrogen, the four-mouth flask was immersed in an oil bath
(OBH-24, Masuda Corp., Japan) heated to 80°C followed by the addition of
0.35 g of sodium methoxide (28% methanol solution, Wako Pure Chemical
Industries, Ltd.) to start the reaction. Samples of the reaction liquid were
suitably collected and subjected to NMR analysis, and the reaction was
terminated at the point 2,4-toluenediamine was no longer detected. As a
result of analyzing the resulting solution by liquid chromatography, the solution
was found to contain 29.7% by weight of toluene-2,4-dicarbamic acid

bis(3-methylbutyl) ester.
Step (17-2): Distillation of Low Boiling Point Component
1422 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (17-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 78.2% by
weight of bis(3-methylbutyl) carbonate and 21.2% by weight of
3-methyl-1-butanol. In addition, as a result of analyzing by liquid
chromatography, the distillation residue in the flask was found to contain 98.0%
by weight of toluene-2,4-dicarbamic acid bis(3-methylbutyl) ester.
Step (17-3): Production of Toluene-2,4-dicarbamic acid
bis(2,4-di-tert-amylphenyl) Ester by Transesterification
5258 g of a reaction liquid were extracted from line 24 and 289 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 109 g of dibutyl tin dilaurate and 4835 g of
2,4-di-tert-amylphenol to 615 g of the distillation residue obtained in step (17-2)
and using in the form of a homogeneous solution, heating the thin film
distillation apparatus 202 to 240°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the
solution to the thin film distillation apparatus via supply line 21 at the rate of
about 1200 g / hr and carrying out the reaction for 70 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 20.0% by weight of toluene-2,4-dicarbamic
acid bis(2,4-di-tert-amylphenyl) ester. In addition, when the solution

recovered from line 27 was analyzed by 1H- and 13C-NMR analysis, the
solution was found to contain 98% by weight of 3-methyl-1-butanol.
Step (17-4): Production of Toluene-2,4-diisocyanate by Thermal
Decomposition of Toluene-2,4-dicarbamic Acid Bis(2,4-di-tert-amylphenyl)
Ester
The same method as step (1-4) of Example 1 was carried out with the
exception of heating the thin film distillation apparatus 302 to 200°C, making
the pressure in the thin film distillation apparatus about 1.3 kPa, feeding the
solution obtained in step (17-3) to feed tank 301, supplying to the thin film
distillation apparatus via line 31 at the rate of about 1000 g / hr, and carrying
out the reaction for 15 hours. 267 g of a solution were recovered from line 35,
and as a result of analyzing the solution by 1H- and 13C-NMR analysis, the
solution was found to contain 99% by weight of toluene-2,4-diisocyanate. The
yield based on 2,4-toluene diamine was 85%.
[Example 18]
Step (18-1): Production of
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Dibutyl Ester
1774 g (10.2 mol) of dibutyl carbonate and 336 g (1.7 mol) of
4,4'-methylene dianiline (Aldrich Corp., USA) were placed in a 5 L volumetric
fourth-mouth flask, a stirrer was placed in the flask, and a Dimroth condenser
and three-way valve were attached to the flask. After replacing the inside of
the system with nitrogen, the four-mouth flask was immersed in an oil bath
(OBH-24, Masuda Corp., Japan) heated to 80°C followed by the addition of 3.3
g of sodium methoxide (28% methanol solution, Wako Pure Chemical
Industries, Ltd.) to start the reaction. Samples of the reaction liquid were

suitably collected and subjected to NMR analysis, and the reaction was
terminated at the point 4,4'-methylene dianiline was no longer detected. As a
result of analyzing the resulting solution by liquid chromatography, the solution
was found to contain 30.8% by weight of
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester.
Step (18-2): Distillation of Low Boiling Point Component
1452 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (18-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 82.7% by
weight of dibutyl carbonate and 16.6% by weight of 1-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 98.5% by weight of
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester.
Step (18-3): Production of
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Bis(2,4-di-tert-amylphenyl)
Ester by Transesterification
4322 g of a reaction liquid were extracted from line 24 and 226 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 103 g of dibutyl tin dilaurate and 3799 g of
2,4-di-tert-amylphenol to 656 g of the distillation residue obtained in step (18-2)
and using in the form of a homogeneous solution, heating the thin film
distillation apparatus 202 to 240°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the

solution to the thin film distillation apparatus via supply line 21 at the rate of
about 1200 g / hr and carrying out the reaction for 62 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 25.3% by weight of
N,N'-(4,4'-methanediyl-diphenyl)- biscarbamic acid bis(2,4-di-tert-amylphenyl)
ester. In addition, when the solution recovered from line 27 was analyzed by
1H- and 13C-NMR analysis, the solution was found to contain 99% by weight of
1-butanol.
Step (18-4): Production of 4,4'-diphenylmethane Diisocyanate by
Thermal Decomposition of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid
Bis(2,4-di-tert-amylphenyl) Ester
When the thin film distillation apparatus 402 was heated to 210°C, the
pressure in the thin film distillation apparatus was made to be about 0.1 kPa,
the solution obtained in step (18-3) was fed to feed tank 401, supplied to the
thin film distillation apparatus via line 41 at the rate of about 680 g / hr, and the
reaction was carried out for 11 hours, 351 g of a solution containing 99% by
weight of 4,4'-diphenylmethane diisocyanate were recovered from line 52.
The yield based on 4,4'-methylene dianiline was 83%.
[Example 19]
Step (19-1): Production of
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Dibutyl Ester
A solution containing 26.7% by weight of
N,N'-(4,4'-methanediyl-diphenyl)- biscarbamic acid dibutyl ester was obtained
by carrying out the same method as step (18-1) of Example 18 with the
exception of using 1583 g (9.1 mol) of dibutyl carbonate, 257 g (1.3 mol) of

4,4'-methylene dianiline and 2.5 g of sodium methoxide (28% methanol
solution, Wako Pure Chemical Industries, Ltd.).
Step (19-2): Distillation of Low Boiling Point Component
1342 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (19-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography the distillate was found to contain 85.5% by
weight of dibutyl carbonate and 13.6% by weight of 1-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 98.6% by weight of
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester.
Step (19-3): Production of
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid Bis(2,6-dimethylphenyl)
Ester by Transesterification
2824 g of a reaction liquid were extracted from line 24 and 160 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 74 g of dibutyl tin dilaurate and 2441 g of
2,6-dimethylphenol to 475 g of the distillation residue obtained in step (19-2)
and using in the form of a homogeneous solution, heating the thin film
distillation apparatus 202 to 200°C, replacing the inside of the thin film
distillation apparatus with nitrogen at atmospheric pressure, supplying the
solution to the thin film distillation apparatus via supply line 21 at the rate of
about 1200 g / hr and carrying out the reaction for 662 hours.
When the reaction liquid was analyzed by liquid chromatography the

reaction liquid was found to contain 18.9% by weight of toluene-2,4-dicarbamic
acid bis(2,6-dimethylphenyl) ester. In addition, when tine solution recovered
from line 27 was analyzed by 1H- and 13C-NMR analysis, the solution was
found to contain 99% by weight of 1-butanol.
Step (19-4): Production of 4,4'-diphenylmethane Diisocyanate by
Thermal Decomposition of N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic Acid
Bis(2,6-dimethylphenyl) Ester
244 g of a solution containing 99% by weight of 4,4'-diphenylmethane
diisocyanate was recovered from line 52 by carrying out the same method as
step (5-4) of Example 5 with the exception of heating the thin film distillation
apparatus 402 to 210°C, making the pressure in the thin film distillation
apparatus to be about 0.1 kPa, feeding the solution obtained in step (19-3) to
feed tank 401, supplying to the thin film distillation apparatus via line 41 at the
rate of about 700 g / hr, and carrying out the reaction for 13 hours. The yield
based on 4,4'-methylene dianiline was 75%.
[Example 20]
Step (20-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl
Ester
A solution containing 22.7% by weight of N,N'-hexanediyl-bis-carbamic
acid dibutyl ester was obtained by carrying out the same method as step (1-1)
of Example 1 with the exception of using 2192 g (12.6 mol) of dibutyl
carbonate, 209 g (1.8 mol) of hexamethylene diamine and 3.5 g of sodium
methoxide (28% methanol solution, Wako Pure Chemical Industries, Ltd.).
Step (20-2): Distillation of Low Boiling Point Component
1845 g of a distillate were obtained by carrying out the same method as

step (1-2) of Example 1 with the exception of using the solution obtained in
step (20-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 85.9% by
weight of dibutyl carbonate and 13.6% by weight of 1-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 98.6% by weight of
N,N'-(4,4'-methanediyl-diphenyl)-biscarbamic acid dibutyl ester.
Step (20-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(2,6-di-tert-butylphenyl) Ester by Transesterification
5395 g of a reaction liquid were extracted from line 24 and 206 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of obtaining a homogeneous solution of 550 g of the distillation
residue obtained in step (20-3), 109 g of dibutyl tin dilaurate and 4950 g of
2,6-di-tert-butylphenol, heating the thin film distillation apparatus 202 to 240°C,
and carrying out the reaction for 86 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 14.9% by weight of
N,N'-hexanediyl-bis-carbamic acid di(2,6-di-tert-butylphenyl) ester. In addition,
when the solution recovered from line 27 was analyzed by 1H- and 13C-NMR
analysis, the solution was found to contain 99% by weight of 1-butanol.
Step (20-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2,6-di-tert-butylphenyl)
Ester
The same method as step (1-4) of Example 1 was carried out with the

exception of heating the thin film distillation apparatus 302 was heated to
200°C, making the pressure in the thin film distillation apparatus to be about
1.3 kPa, feeding the solution obtained in step (20-3) was fed to feed tank 301,
supplying to the thin film distillation apparatus via line 31 at the rate of about
980 g / hr, and carrying out the reaction for 13 hours. 210 g of a solution were
recovered from line 35. As a result of analyzing the solution by 1H- and
13C-NMR analysis, the solution was found to contain 99% by weight of
hexamethylene diisocyanate. The yield based on hexamethylene diamine
was 70%.
[Example 21]
Step (21-1): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(3-methylbutyl) Ester
A solution containing 24.0% by weight of N,N'-hexanediyl-bis-carbamic
acid di(3-methylbutyl) ester was obtained by carrying out the same method as
step (1-1) of Example 1 with the exception of using 2290 g (11.3 mol) of
bis(3-methylbutyl) carbonate, 208.8 g (1.8 mol) of hexamethylene diamine and
3.5 g of sodium methoxide (28% methanol solution, Wako Pure Chemical
Industries, Ltd.).
Step (21-2): Distillation of Low Boiling Point Component
1891 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (21-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 83.6% by
weight of bis(3-methylbutyl) carbonate and 16.1% by weight of
3-methyl-1-butanol. In addition, as a result of analyzing by liquid

chromatography, the distillation residue in the flask was found to contain 98.6%
by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester.
Step (21-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(2-phenylphenyl) Ester by Transesterification
3977 g of a reaction liquid were extracted from line 24 and 276 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 110 g of dibutyl tin dilaurate and 3545 g of
2-phenylphenol to 606 g of the distillation residue obtained in step (21 -2) and
using in the form of a homogeneous solution, heating the thin film distillation
apparatus 202 to 240°C, replacing the inside of the thin film distillation
apparatus with nitrogen at atmospheric pressure, supplying the solution to the
thin film distillation apparatus via supply line 21 at the rate of about 1200 g / hr
and carrying out the reaction for 80 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 20.0% by weight of
N,N'-hexanediyl-bis-carbamic acid di(2-phenylphenyl) ester. In addition, when
the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis,
the solution was found to contain 99% by weight of 3-methyl-1-butanol.
Step (21-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(2-phenylphenyl)
Ester
241 g of a solution were recovered from line 35 by carrying out the same
method as step (1-4) of Example 1 with the exception of heating the thin film
distillation apparatus 302 to 200°C, making the pressure in the thin film

distillation apparatus to be about 1.3 kPa, feeding the solution obtained In step
(21-3) to feed tank 301, supplying to the thin film distillation apparatus via line
31 at the rate of about 980 g / hr, and carrying out the reaction for 13 hours.
As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution
was found to contain 99% by weight of hexamethylene diisocyanate. The
yield based on hexamethylene diamine was 80%.
[Example 22]
Step (22-1): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(3-methylbutyl) Ester
A solution containing 23.8% by weight of N,N'-hexanediyl-bis-carbamic
acid di(3-methylbutyl) ester was obtained by carrying out the same method as
step (1-1) of Example 1 with the exception of using 2163 g (10.7 mol) of
bis(3-methylbutyl) carbonate, 197 g (1.7 mol) of hexamethylene diamine and
3.3 g of sodium methoxide (28% methanol solution, Wako Pure Chemical
Industries, Ltd.).
Step (22-2): Distillation of Low Boiling Point Component
1783 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (22-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 83.5% by
weight of bis(3-methylbutyl) carbonate and 16.0% by weight of
3-methyl-1-butanol. In addition, as a result of analyzing by liquid
chromatography, the distillation residue in the flask was found to contain 97.1 %
by weight of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester.
Step (22-3): Production of N,N'-hexanediyl-bis-carbamic Acid

Di(2,4-bis(a,a-dimethylbenzyl)phenyl) Ester by Transesterification
4689 g of a reaction liquid were extracted from line 24 and 259 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of adding 103 g of dibutyl tin dilaurate and 4385 g of
2,4-bis(a,a-dimethylbenzyl)phenol (Aldrich Corp., USA) to 575 g of the
distillation residue obtained in step (22-2) and using in the form of a
homogeneous solution, heating the thin film distillation apparatus 202 to 240°C,
replacing the inside of the thin film distillation apparatus with nitrogen at
atmospheric pressure, supplying the solution to the thin film distillation
apparatus via supply line 21 at the rate of about 1200 g/hr and carrying out the
reaction for 80 hours.
When the reaction liquid was analyzed by liquid chromatography, the
reaction liquid was found to contain 25.8% by weight of
N,N'-hexanediyl-bis-carbamic acid di(2,4-bis(α,α-dimethylbenzyl)phenyl ester
In addition, when the solution recovered from line 27 was analyzed by 1H- and
13C-NMR analysis, the solution was found to contain 99% by weight of
3-methyl-1-butanol.
Step (22-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid
Di(2,4-bis(aa-dimethylbenzyl)phenyl) Ester
220 g of a solution were recovered from line 35 by carrying out the same
method as step (1-4) of Example 1 with the exception of heating the thin film
distillation apparatus 302 to 200°C, making the pressure in the thin film
distillation apparatus to be about 1.3 kPa, feeding the solution obtained in step

(22-3) to feed tank 301, supplying to the thin film distillation apparatus via line
31 at the rate of about 980 g / hr, and carrying out the reaction for 18 hours.
As a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution
was found to contain 99% by weight of hexamethylene diisocyanate. The
yield based on hexamethylene diamine was 77%.
[Example 23]
Hexamethylene diisocyanate was produced in a reaction apparatus like
that shown in FIG. 5.
Step (23-1): Production Process of N,N'-hexanediyl-bis-carbamic Acid
Di(3-methylbutyl) Ester
A stirring tank 601 (internal volume: 5 L) was heated to 80°C.
Bis(3-methylbutyl) carbonate was transferred to the stirring tank 601 from a line
60 at the rate of 678 g / hr with a line 62 closed, and a mixed solution of
hexamethylene diamine, 3-methyl-1-butanol and sodium methoxide (28%
methanol solution) (mixing ratio: hexamethylene diamine 50
parts/3-methyl-1-butanol 50 parts / sodium methoxide 0.42 parts) was
simultaneously transferred from a line 61 at the rate of 112 g / hr. After 4
hours, line 62 was opened with a line 63 closed, and transfer of the reaction
liquid to a tank 602 was started at the rate of 790 g / hr. Line 62 was
maintained at 80°C to prevent precipitation of solids from the reaction liquid.
When the reaction liquid transferred to a line 602 was analyzed by liquid
chromatography, the reaction liquid was found to contain 20.3% by weight of
N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester.
Step (23-2): Low Boiling Point Component Distillation Process
A thin film distillation apparatus 603 (heat-conducting surface area of 0.2

m2, Kobelco Eco-Solutions Co., Ltd., Japan) was heated to 150°C and the
pressure inside the apparatus was made to be about 0.02 kPa.
The solution stored in tank 602 was transferred to thin film distillation
apparatus 603 from line 63 at the rate of 790 g / hr where a low boiling point
component contained in the solution were distilled off. The low boiling point
component that had been distilled off was extracted from the thin film
distillation apparatus 603 via a line 64. On the other hand, a high boiling point
component was extracted from the thin film distillation apparatus 603 via a line
65 maintained at 150°C, and transferred to a stirring tank 604 maintained at
120°C. At the same time, 2,4-di-tert-amylphenol was transferred via a line 66
to stirring tank 604 at the rate of 1306 g / hr, and dibutyl tin dilaurate was
transferred to stirring tank 604 via a line 67 at the rate of 29 g / hr.
The mixed liquid prepared in stirring tank 604 was transferred to a tank
605 via a line 68 with a line 69 closed, and stored in the tank 605. When the
solution stored in the tank 605 was analyzed by liquid chromatography, the
solution was found to contain 10.7% by weight of N,N'-hexanediyl-bis-carbamic
acid di(3-methylbutyl) ester.
Step (23-3): Production Process of N,N'-hexanediyl-bis-carbamic Acid
Di(2,4-di-tert-amylphenyl) Ester by Transesterification
A thin film distillation apparatus 606 (heat-conducting surface area of 0.2
m2, Kobelco Eco-Solutions Co., Ltd., Japan) was heated to 240°C.
A transesterification reaction was carried out by transferring a mixed
liquid of N,N'-hexanediyl-bis-carbamic acid di(3-methylbutyl) ester,
2,4-di-tert-amylphenol and dibutyl tin dilaurate stored in tank 605 to thin film
distillation apparatus 606 via a line 69 at the rate of 1496 g / hr with a line 72

closed. A mixed gas containing 3-methyl-1 -butanol and 2,4-di-tert-amylphenol
was extracted from a line 73 provided in the upper portion of the thin film
distillation apparatus 606, and supplied to a distillation column 607. The
3-methyl-1-butanol and 2,4-di-tert-amylphenol were separated in the distillation
column 607, and the 2,4-di-tert-amylphenol was returned to the upper portion
of thin film distillation apparatus 606 via a line 74 provided in the bottom of
distillation column 607. A reaction liquid was extracted from a line 70
provided in the bottom of the thin film distillation apparatus 606, and supplied
to thin film distillation apparatus 606 via a line 71. When the
N,N'-hexanediyl-bis-carbamic acid di(2,4-di-tert-amylphenyl) ester in the
reaction liquid extracted from line 70 reached 20.3% by weight, line 72 was
opened with line 75 closed and the reaction liquid was transferred to a tank
608.
Step (23-4): Production Process of Hexamethylene Diisocyanate by
Thermal Decomposition of N,N'-hexanediyl-bis-carbamic Acid
Di(2,4-di-tert-amylphenyl) Ester
The solution stored in tank 608 was supplied to a thin film distillation
apparatus 609 (heat-conducting surface area of 0.2 m2, Kobelco Eco-Solutions
Co., Ltd., Japan) heated to 200°C and set to an internal pressure of about 1.3
kPa via line 75 at the rate of 1395 g / hr. A gaseous component containing
hexamethylene diisocyanate was extracted from a line 77 provided in the
upper portion of the thin film distillation apparatus 609 and supplied to a
distillation column 610. Distillative separation was carried out in distillation
column 610, and hexamethylene diisocyanate was recovered from a line 79 at
the rate of 72 g / hr.

[Comparative Example 1]
Step (A-1): Production of N,N'-hexanedlyl-bis-carbamic Acid Dimethyl
Ester
1044 g of a solution containing 29.6% by weight of N,N-hexanediyl-bis-
carbamic acid methyl ester were obtained by carrying out the same method as
step (1-1) of Example 1 with the exception of using 882 g (9.8 mol) of dimethyl
carbonate and 162 g (1.4 mol) of hexamethylene diamine, adding a stirrer, and
using 2.7 g of sodium methoxide.
Step (A-2): Distillation of Low Boiling Point Component
729 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (A-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 87.5% by
weight of dimethyl carbonate and 11.7% by weight of methanol. As a result of
analyzing by liquid chromatography, the distillation residue in the flask was
found to contain 98.2% by weight of N,N'-hexanediyl-bis-carbamic acid
dimethyl ester.
Step (A-3): Production of N,N'-hexanediyl-bis-carbamic Acid Diphenyl
Ester by Transesterification
4101 g of a reaction liquid were extracted from line 24 and 65 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of using 316 g of the distillation residue obtained in step (A-2)
instead of the distillation residue obtained in step (1-2), using 85 g of dibutyl tin
dilaurate and 3770 g of phenol (for nucleic acid extraction, Wako Pure

Chemical Industries, Ltd., Japan), setting the heating unit of the thin film
distillation apparatus to 180°C and carrying out the reaction for 430 hours.
The extracted reaction liquid contained 8.7% by weight of
N,N'-hexanediyl-bis-carbamic acid diphenyl ester.
Step (A-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Diphenyl Ester
The same method as step (5-4) of Example 5 was carried out with the
exception of heating thin film distillation apparatus 402 to 200°C, making the
pressure inside the thin film distillation apparatus about 1.3 kPa, feeding the
solution obtained in step (A-3) to feed tank 401, supplying to the thin film
distillation apparatus via line 41 at the rate of about 680 g / hr, and carrying out
the reaction for 11 hours. 134 g of a solution containing 99% by weight of
hexamethylene diisocyanate was recovered from line 47. The yield based on
hexamethylene diamine was 57%. In addition, a black solid was adhered to
the sidewalls of the thin film distillation apparatus 402 following completion of
step (A-4).
[Comparative Example 2]
Step (B-1): Production of N.N'-hexanediyl-bis-carbamic Acid
Di(3-methylbutyl) Ester
2146 g of a solution containing 23.1% by weight of N,N-hexanediyl-bis-
carbamic acid di(3-methylbutyl) ester were obtained by carrying out the same
method as step (1-1) of Example 1 with the exception of using 1970 g (9.8 mol)
of bis(3-methylbutyl) carbonate and 174 g (1.5 mol) of hexamethylene diamine,
adding a stirrer, and using 2.9 g of sodium methoxide.
Step (B-2): Distillation of Low Boiling Point Component

1631 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (B-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 84.2% by
weight of bis(3-methylbutyl) carbonate and 15.4% by weight of
3-methyl-1-butanol. In addition, as a result of analyzing by liquid
chromatography, the distillation residue in the flask was found to contain 96.7%
by weight of N,N'-hexanediyl-bis-carbamic acid bis(3-methylbutyl) ester.
Step (B-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(4-methylphenyl) Ester by Transesterification
4978 g of a reaction liquid were extracted from line 24 and 185 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of using 510 g of the distillation residue obtained in step (B-2)
instead of the distillation residue obtained in step (1-2), using 91 g of dibutyl tin
dilaurate and 4645 g of 4-methylphenol (Aldrich Corp., USA), and carrying out
the reaction for 58 hours. The extracted reaction liquid contained 8.1% by
weight of N,N'-hexanediyl-bis-carbamic acid di(4-methylphenyl) ester.
Step (B-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(4-methylphenyl) Ester
A thermal decomposition reaction was carried out in a reaction apparatus
like that shown in FIG. 4.
Thin film distillation apparatus 402 (Kobelco Eco-Solutions Co., Ltd.,
Japan) having a heat-conducting surface area of 0.2 m2 was heated to 200°C
and the pressure inside the thin film distillation apparatus was made to be

about 1.3 kPa. The solution obtained in step (B-3) was fed to feed tank 401
and supplied to the thin film distillation apparatus via line 41 at the rate of
about 680 g / hr. A liquid component was extracted from line 43 provided in
the bottom of the thin film distillation apparatus 402, and returned to feed tank
401 via line 44. A gaseous component containing hexamethylene
diisocyanate and 4-methylphenol was extracted from line 42 provided in the
upper portion of thin film distillation apparatus 402. The gaseous component
was fed to distillation column 403 where the hexamethylene diisocyanate and
4-methylphenol were separated, the 4-methylphenol was extracted from line 45
connected to the top of distillation column 403, the hexamethylene
diisocyanate was extracted from line 47 provided at an intermediate stage of
distillation column 403, a high boiling point substance was extracted from line
46 provided in the bottom of distillation column 403, and a portion was returned
to feed tank 401 via line 44. When the reaction was carried out for 11 hours,
114 g of a solution containing 99% by weight of hexamethylene diisocyanate
was recovered from line 47. The yield based on hexamethylene diamine was
57%. In addition, a black solid was adhered to the sidewalls of the thin film
distillation apparatus 402 following completion of step (B-4).
[Comparative Example 3]
Step (C-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl
Ester
1818 g (10.5 mol) of dibutyl carbonate produced using the method of
Reference Example 2 and 220 g (1.9 mol) of hexamethylene diamine were
placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask,
and a Dimroth condenser and three-way valve were attached to the flask.

After replacing the inside of the system with nitrogen, the four-mouth flask was
immersed in an oil bath (OBH-24, Masuda Corp.) heated to 80°C followed by
the addition of 3.7 g of sodium methoxide (28% methanol solution, Wako Pure
Chemical Industries, Ltd.) to start the reaction. Samples of the reaction liquid
were suitably collected and subjected to NMR analysis, and the reaction was
terminated at the point hexamethylene diamine was no longer detected. As a
result of analyzing the resulting solution by liquid chromatography, the solution
was found to contain 28.3% by weight of N,N'- hexanediyl-bis-carbamic acid
di butyl ester.
Step (C-2): Distillation of Low Boiling Point Component
1444 g of a distillate were obtained by carrying out the same method as
step (1-2) of Example 1 with the exception of using the solution obtained in
step (C-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 80.9% by
weight of dibutyl carbonate and 18.6% by weight of 1-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 98.0% by weight of N,N'-hexanediyl-bis-carbamic
acid dibutyl ester.
Step (C-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(4-octyl phenyl) Ester by Transesterification
6122 g of a reaction liquid were extracted from line 24 and 182 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of using 594 g of the distillation residue obtained in step (6-3)
instead of the distillation residue obtained in step (1-2), adding 114 g of dibutyl

tin dilaurate and 5611 g of 4-octylphenol and using in the form of a
homogeneous solution, feeding to feed tank 201, heating the thin film
distillation apparatus 202 having a heat-conducting surface area of 0.2 m2 to
240°C, and carrying out the reaction for 86 hours.
When the extracted reaction liquid was analyzed by liquid
chromatography, the reaction liquid was found to contain 11.5% by weight of
N,N'-hexanediyl-bis-carbamic acid di(4-octylphenyl) ester. In addition, when
the solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis,
the solution was found to contain 99.0% by weight of 1-butanol.
Step (C-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(4-octylphenyl) Ester
A thermal decomposition reaction was carried out in a reaction apparatus
like that shown in FIG. 3.
Thin film distillation apparatus 302 having a heat-conducting surface area
of 0.2 m2 was heated to 200°C and the pressure inside the thin film distillation
apparatus was made to be about 1.3 kPa. The solution obtained in step (C-3)
was fed to feed tank 301 and supplied to the thin film distillation apparatus via
line 31 at the rate of about 980 g / hr. A liquid component was extracted from
line 33 provided in the bottom of the thin film distillation apparatus 302, and
returned to feed tank 301 via line 34. A gaseous component containing
hexamethylene diisocyanate and 4-octylphenol was extracted from line 32
provided in the upper portion of thin film distillation apparatus 302. The
gaseous component was fed to distillation column 303 where the
hexamethylene diisocyanate and 4-octylphenol were separated, and a portion
of 4-octylphenol was returned to feed tank 301 through line 34 via line 36

provided in the bottom of distillation column 303. When the reaction was
carried out for 13 hours, 167 g of a solution were recovered from line 35, and
as a result of analyzing the solution by 1H- and 13C-NMR analysis, the solution
was found to contain 99% by weight of hexamethylene diisocyanate. The
yield based on hexamethylene diamine was 53%. In addition, a black solid
was adhered to the sidewalls of the thin film distillation apparatus 302 following
completion of step (C-4).
[Comparative Example 4]
Step (D-1): Production of N,N'-hexanediyl-bis-carbamic Acid Dibutyl
Ester
1914 g (11.0 mol) of dibutyl carbonate produced using the method of
Reference Example 2 and 232 g (2.0 mol) of hexamethylene diamine were
placed in a 5 L volumetric fourth-mouth flask, a stirrer was placed in the flask,
and a Dimroth condenser and three-way valve were attached to the flask.
After replacing the inside of the system with nitrogen, the four-mouth flask was
immersed in an oil bath heated to 80°C followed by the addition of 0.37 g of
sodium methoxide (28% methanol solution, Wako Pure Chemical Industries,
Ltd.) to start the reaction. Samples of the reaction liquid were suitably
collected and subjected to NMR analysis, and the reaction was terminated at
the point hexamethylene diamine was no longer detected. As a result of
analyzing the resulting solution by liquid chromatography, the solution was
found to contain 28.3% by weight of N,N'- hexanediyl-bis-carbamic acid dibutyl
ester.
Step (D-2): Distillation of Low Boiling Point Component
1532 g of a distillate were obtained by carrying out the same method as

step (1-2) of Example 1 with the exception of using the solution obtained in
step (D-1) instead of the solution obtained in step (1-1). As a result of
analyzing by gas chromatography, the distillate was found to contain 80.9% by
weight of dibutyl carbonate and 18.5% by weight of 1-butanol. In addition, as
a result of analyzing by liquid chromatography, the distillation residue in the
flask was found to contain 99.5% by weight of N,N'-hexanediyl-bis-carbamlc
acid dibutyl ester.
Step (D-3): Production of N,N'-hexanediyl-bis-carbamic Acid
Di(3-octyloxy) Ester by Transesterification
4203 g of a reaction liquid were extracted from line 24 and 250 g of a
solution were recovered from line 27 provided in the upper portion of distillation
column 203 by carrying out the same method as step (1-3) of Example 1 with
the exception of using 605 g of the distillation residue obtained in step (6-3)
instead of the distillation residue obtained in step (1-2), adding 120 g of dibutyl
tin dilaurate and 3727 g of 3-octanol (Aldrich Corp., USA) and using in the form
of a homogeneous solution, feeding to feed tank 201, heating the thin film
distillation apparatus 202 having a heat-conducting surface area of 0.2 m2 to
175°C, and carrying out the reaction for 180 hours.
When the extracted reaction liquid was analyzed by liquid
chromatography, the reaction liquid was found to contain 17.1% by weight of
N,N'-hexanediyl-bis-carbamic acid di(3-octyloxy) ester. In addition, when the
solution recovered from line 27 was analyzed by 1H- and 13C-NMR analysis,
the solution was found to contain 99.0% by weight of 1-butanol.
Step (D-4): Production of Hexamethylene Diisocyanate by Thermal
Decomposition of N,N'-hexanediyl-bis-carbamic Acid Di(3-octyloxy) Ester

A thermal decomposition reaction was carried out in a reaction apparatus
like that shown in FIG. 4.
Thin film distillation apparatus 402 (Kobelco Eco-Solutions Co., Ltd.,
Japan) having a heat-conducting surface area of 0.2 m2 was heated to 200°C
and the pressure inside the thin film distillation apparatus was made to be
about 1.3 kPa. The solution obtained in step (D-3) was fed to feed tank 401
and supplied to the thin film distillation apparatus via line 41 at the rate of
about 680 g / hr. A liquid component was extracted from line 43 provided in
the bottom of the thin film distillation apparatus 402, and returned to feed tank
401 via line 44. A gaseous component containing hexamethylene
diisocyanate and 3-octanol was extracted from line 42 provided in the upper
portion of thin film distillation apparatus 402. The gaseous component was
fed to distillation column 403 where the hexamethylene diisocyanate and
3-octanol were separated, the 3-octanol was extracted from line 45 connected
to the top of distillation column 403, hexamethylene diisocyanate was
extracted from line 47 provided in an intermediate stage of distillation column
403, a high boiling point substance was extracted from line 46 provided in the
bottom of distillation column 403, and a portion was returned to feed tank 401
via line 44. When the reaction was carried out for 11 hours, 149 g of a
solution containing 99% by weight of hexamethylene diisocyanate were
recovered from line 47. The yield based on hexamethylene diamine was 45%.
In addition, a black solid was adhered to the sidewalls of the thin film distillation
apparatus 402 following completion of step (D-4).
Industrial Applicability

Since the isocyanate production process according to the present
invention enables isocyanates to be efficiently produced without using
extremely toxic phosgene, the production process of the present invention is
extremely useful industrially and has high commercial value.

CLAIMS
1. A process for producing an isocyanate, comprising the steps of:
reacting a carbamic acid ester and an aromatic hydroxy compound to
obtain an aryl carbamate having a group derived from the aromatic hydroxy
compound; and
subjecting the aryl carbamate to a decomposition reaction,
wherein the aromatic hydroxy compound is an aromatic hydroxy
compound which is represented by the following formula (1) and which has a
substituent R1 at at least one ortho position of a hydroxyl group:

(wherein ring A represents an aromatic hydrocarbon ring in a form of a single
or multiple rings which may have a substituent and which have 6 to 20 carbon
atoms;
R1 represents a group other than a hydrogen atom in a form of an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group
containing an atom selected from a carbon atom, an oxygen atom and a
nitrogen atom; and R1 may bond with A to form a ring structure).

2. The process according to Claim 1, wherein the aromatic hydroxy
compound is a compound represented by the following formula (2):

(wherein ring A and R1 are the same as defined above,
R2 represents a hydrogen atom or an aliphatic alkyl group having 1 to 20
carbon atoms, an aliphatic alkoxy group having 1 to 20 carbon atoms, an aryl
group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon
atoms, an aralkyl group having 7 to 20 carbon atoms or aralkyloxy group
having 7 to 20 atoms, the aliphatic alkyl, the aliphatic alkoxy, the aryl, the
aryloxy, the aralkyl and the aralkyloxy groups containing an atom selected from
a carbon atom, an oxygen atom and a nitrogen atom, and R2 may bond with A
to form a ring structure).
3. The process according to Claim 2, wherein in the formula (2), a total
number of the carbon atoms constituting R1 and R2 is 2 to 20.
4. The process according to any one of Claims 1 to 3, wherein the ring
A of the aromatic hydroxy compound comprises a structure containing at least
one structure selected from the group consisting of a benzene ring, a
naphthalene ring and an anthracene ring.
5. The process according to Claim 4, wherein the aromatic hydroxy
compound is a compound represented by the following formula (3):

(wherein R1 and R2 are the same as defined above, and
each of R3, R4 and R5 independently represents a hydrogen atom or an
aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an
aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20
carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the aliphatic
alkyl, the aliphatic alkoxy, the aryl, the aryloxy, the aralkyl and the aralkyloxy
groups containing an atom selected from a carbon atom, an oxygen atom and
a nitrogen atom).
6. The process according to Claim 5, wherein the aromatic hydroxy
compound is such that in the formula (3), each of R1 and R4 independently
represents a group represented by the following formula (4), and R2, R3 and R5
represent a hydrogen atom:

(wherein X represents a branched structure selected from the structures
represented by the following formulas (5) and (6):

(wherein R6 represents a linear or branched alkyl group having 1 to 3 carbon
atoms).
7. The process according to Claim 5, wherein the aromatic hydroxy •
compound is such that in the formula (3), R1 represents a linear or branched
alkyl group having 1 to 8 carbon atoms, and each of R2 and R4 independently
represents a hydrogen atom or a linear or branched alkyl group having 1 to 8
carbon atoms.
8. The process according to any one of Claims 1 to 7, wherein the
carbamic acid ester is an aliphatic carbamic acid ester, and a low boiling point
component formed with the aryl carbamate is an aliphatic alcohol.
9. The process according to Claim 8, wherein the aliphatic carbamic
acid ester is an aliphatic polycarbamic acid ester.
10. The process according to Claim 8, further comprising the steps of:
continuously supplying the aliphatic carbamic acid ester and the aromatic
hydroxy compound to a reaction vessel so as to react the aliphatic carbamic
acid ester and the aromatic hydroxy compound inside the reaction vessel;
recovering a formed low boiling point component in a form of a gaseous
component; and
continuously extracting a reaction liquid containing the aryl carbamate

and the aromatic hydroxy compound from a bottom of the reaction vessel.
11. The process according to any one of Claims 1 to 10, wherein the
decomposition reaction is a thermal decomposition reaction, and is a reaction
in which a corresponding isocyanate and aromatic hydroxy compound are
formed from the aryl carbamate.
12. The process according to Claim 11, wherein at least one compound
of the isocyanate and aromatic hydroxy compound formed by the thermal
decomposition reaction of the aryl carbamate is recovered in a form of a
gaseous component.
13. The process according to Claim 8, wherein the aliphatic carbamic
acid ester is a compound represented by the following formula (7):

(wherein R7 represents a group selected from the group consisting of an
aliphatic group having 1 to 20 carbon atoms and an aromatic group having 6 to
20 carbon atoms, the group containing an atom selected from a carbon atom,
an oxygen atom and a nitrogen atoms, and having a valence of n,
R8 represents an aliphatic group which has 1 to 8 carbon atoms and
which contains an atom selected from a carbon atom, an oxygen atom and a
nitrogen atom, and

14. The process according to Claim 13, wherein the aliphatic carbamic
acid ester is such that R8 in the compound represented by the formula (7) is a
group selected from the group consisting of an alkyl group having 1 to 20
carbon atoms and a cycloalkyl group having 5 to 20 carbon atoms.
15. The process according to Claim 14, wherein the aliphatic carbamic
acid ester is at least one compound selected from the group consisting of
compounds represented by the following formulas (8), (9) and (10):

(wherein R8 is the same as defined above).

An object of the present invention is to provide a process that enables isocyanates to be stably produced over a long period of time at high yield
without encountering various problems as found in the prior art when producing isocyanates without using phosgene. The present invention
discloses a process for producing an isocyanate, comprising the steps of: reacting a carbamic acid ester and an aromatic hydroxy compound to obtain an aryi carbamate having a group derived from the aromatic hydroxy compound; and subjecting the aryl carbamate to a decomposition reaction, wherein the aromatic hydroxy compound is an aromatic hydroxy compound which is
represented by the following formula (1) and which has a substituent R1 at at least one ortho position of a hydroxyl group:
(wherein ring A represents an aromatic hydrocarbon ring in a form of a single
or multiple rings which may have a substitute and which have 6 to 20 carbon atoms;
R1 represents a group other than a hydrogen atom in a form of an aliphatic alkyl group having 1 to 20 carbon atoms, an aliphatic alkoxy group
having 1 to 20 carbon atoms, an aryl group having 6 to 20 carbon atoms, an aryloxy group having 6 to 20 carbon atoms, an aralkyl group having 7 to 20 carbon atoms or an aralkyloxy group having 7 to 20 carbon atoms, the group
containing an atom selected from a carbon atom, an oxygen atom and a nitrogen atom; and R1 may bond with A to form a ring structure).

Documents:

1684-KOLNP-2009-(05-10-2012)-ANNEXURE TO FORM 3.pdf

1684-KOLNP-2009-(05-10-2012)-CORRESPONDENCE.pdf

1684-KOLNP-2009-(05-10-2012)-OTHERS.pdf

1684-KOLNP-2009-(13-02-2013)-PETITION UNDER RULE 137.pdf

1684-KOLNP-2009-(18-10-2012)-ABSTRACT.pdf

1684-KOLNP-2009-(18-10-2012)-CLAIMS.pdf

1684-KOLNP-2009-(18-10-2012)-CORRESPONDENCE.pdf

1684-KOLNP-2009-(18-10-2012)-DESCRIPTION (COMPLETE).pdf

1684-KOLNP-2009-(18-10-2012)-DRAWINGS.pdf

1684-KOLNP-2009-(18-10-2012)-FORM-1.pdf

1684-KOLNP-2009-(18-10-2012)-FORM-2.pdf

1684-KOLNP-2009-(18-10-2012)-OTHERS.pdf

1684-KOLNP-2009-(18-10-2012)-PA.pdf

1684-kolnp-2009-abstract.pdf

1684-kolnp-2009-claims.pdf

1684-KOLNP-2009-CORRESPONDENCE 1.2.pdf

1684-KOLNP-2009-CORRESPONDENCE-1.1.pdf

1684-KOLNP-2009-CORRESPONDENCE-1.3.pdf

1684-kolnp-2009-correspondence.pdf

1684-kolnp-2009-description (complete).pdf

1684-kolnp-2009-drawings.pdf

1684-kolnp-2009-form 1.pdf

1684-kolnp-2009-form 18.pdf

1684-kolnp-2009-form 2.pdf

1684-kolnp-2009-form 3.pdf

1684-kolnp-2009-form 5.pdf

1684-kolnp-2009-international publication.pdf

1684-kolnp-2009-others pct form.pdf

1684-kolnp-2009-others.pdf

1684-KOLNP-2009-PCT IPER.pdf

1684-kolnp-2009-pct priority document notification.pdf

1684-kolnp-2009-pct request form.pdf

1684-KOLNP-2009-SCHEDULE.pdf

1684-kolnp-2009-specification.pdf

1684-KOLNP-2009-TRANSLATED COPY OF PRIORITY DOCUMENT.pdf

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Patent Number

255353

Indian Patent Application Number

1684/KOLNP/2009

PG Journal Number

07/2013

Publication Date

15-Feb-2013

Grant Date

13-Feb-2013

Date of Filing

06-May-2009

Name of Patentee

ASAHI KASEI CHEMICALS CORPORATION

Applicant Address

1-105 KANDA JINBOCHO, CHIYODA-KU, TOKYO 101-8101

Inventors:

#	Inventor's Name	Inventor's Address
1	NOBUHISA MIYAKE	1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440
2	MASAAKI SHINOHATA	1-2, YURAKU-CHO 1-CHOME, CHIYODA-KU, TOKYO 100-8440

PCT International Classification Number

C07C 263/04

PCT International Application Number

PCT/JP2007/072268

PCT International Filing date

2007-11-16

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	2007-091382	2007-03-30	Japan
2	2006-311049	2006-11-17	Japan
3	2006-311054	2006-11-17	Japan
4	2006-311048	2006-11-17	Japan
5	2006-311057	2006-11-17	Japan