Title of Invention	"A METHOD FOR COPOLYMERISATION AND HOMOPOLYMERISATION OF OLIGOMERIC WASTES GENERATED FROM NYLON-6 PRODUCTION"
Abstract	A method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, and products thereof is disclosed which comprises: (i) heating oligomeric waste in presence of water under nitrogen blanket and autogenous pressure at a temperature of 135°C to 180°C, (ii) adding predetermined amount of respective monomer I after increasing temperature if desired, (iii) subsequently adding predetermined amount of respective monomer II after 30 minutes, after raising the temperature, followed by raising the temperature and allowing to continue reaction for completion with or without applying vacuum for copolymer preparation.

Title of Invention

"A METHOD FOR COPOLYMERISATION AND HOMOPOLYMERISATION OF OLIGOMERIC WASTES GENERATED FROM NYLON-6 PRODUCTION"

Abstract

A method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, and products thereof is disclosed which comprises: (i) heating oligomeric waste in presence of water under nitrogen blanket and autogenous pressure at a temperature of 135°C to 180°C, (ii) adding predetermined amount of respective monomer I after increasing temperature if desired, (iii) subsequently adding predetermined amount of respective monomer II after 30 minutes, after raising the temperature, followed by raising the temperature and allowing to continue reaction for completion with or without applying vacuum for copolymer preparation.

Full Text	Field of the Invention: The present invention relates to a method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, Particularly, it relates to the method for copolymerisation and homopolymerisation of oligomeric wastes obtained from nylon-6 production. More particularly, it relates to the method for homopoymerisation and copolymerisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant and prodcuts thereof. Even more particularly it relates to the method for utilisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant to develop useful polymers by way of copolymerisation and homopolymerisation thereof. Still more particularly the invention relates to a method of polymerization without employing flow agent or plasticizers thereby making the process cost effective. Further, the polymers obtained are with suppressed melting point. Background of the Invention: The copolymeristion or the homopolymerisation of the monomers, particularly of caprolactam monomers, more particularly of pure caprolactam monomers, or of oligomers, particularly of pure oligomers, or of pure oligomers obtained from pure caprolactam monomers is known in the art. The main drawback of such known methods is that, these methods involve addition of flow agents and/or plascticisers to result in nylon-6 or nylon-6 type polymers with desired properties, which not only adds to additional step of the reaction but also the cost of the production. The another drawback of such known methods is that, these methods do not result in nylon-6 or nylon-6 type polymers with suppressed melting point. Still another drawback of such known methods is that, these methods do not teach any method to utilise the nylon-6 oligomeric wastes, preferably obtained from caprolactam distillation still or from caprolactam recovery plant, which presently go unused and hence are required to be dumped in landfills. The above drawbacks of such known methods and need to utilise the nylon-6 oligomeric wastes, preferably obtained from caprolactam distillation still or from caprolactam recovery plant in order to avoid dumping of such wastes, has compelled to look for a process which can not only over come the above stated drawbacks of the prior art but also can teach a method to utilise the nylon-6 oligomeric wastes, preferably obtained from caprolactam distillation still or from caprolactam recovery plant. Need of the Invention: Therefore, there is need to develop a method for copolymerisation of oligomeric wastes, particularly for copolymerisation of oligomeric wastes obtained from nylon-6 production, more particularly for copolymerisation and for homopolymerisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant, even more particularly for utilistion of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant, and to have products, which can overcome drawbacks of such known methods. Objects of the Invention: This is the main object of the present invention to make a disclosure of a method for copolymerisation of oligomeric wastes, particularly for copolymerisation of oligomeric wastes obtained from nylon-6 production, more particularly for copolymerisation and for homopoymerisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant, even more particularly for utilisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant, and of products thereof, which can overcome drawbacks of such known methods as described herein above. There is another an object of this invention to make a disclosure of method, as stated herein above, which has proved to be economical as a result of the present invention. This is yet another object of this invention to make a complete disclosure of a method, as stated herein above, which can eliminate the use of additional flow agents and/or plasticisers and hence can eliminate requirement of the additional step of the process. Yet another object of the present invention is to make a complete disclosure of a method, as stated herein above, which can produce the nylon-6 or nylon-6 polymers having suppressed melting point. Further objects and the preferred embodiments of the present invention will be more apparent from the following description. Brief description of the Invention: Accordingly, the present invention provides a method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, comprises: (i) heating oligomeric waste in presence of water under nitrogen blanket and autogenous pressure at a temperature of 135°C to 180°C, (ii) adding respective monomer I such as herein described after increasing temperature as mentioned in step (i) if desired, (iii) subsequently adding respective monomer II such as herein described after 30 minutes, after raising the temperature, followed by raising the temperature to a range of 250°C to 290°C, and allowing to continue reaction for completion with or without applying vacuum for copolymer preparation. Further, the present invention also makes a complete disclosure of a method for homopolymerisation of the said oligomeric waste, wherein the heating under step (i) is carried out at a temperature in the range of 135°C to 180°C, for about 2 to 4 hours till completion of reaction for homopolymerisation repparation. The temperature in step (ii) may be raised to about 180 to 220°C if so required. Monomer I may be such as diamine exemplified by hexamethylene diamine or diol exemplified by ethylene glycol. The temperature in step (iii) may be raised to 260°C and maintained for about 5 to 10 hours preferably for 6 to 7 hours. More specifically the type of monomer to be added, the temperature and period of the reaction is regulated by the type of polymer to be obtained. The reaction may preferably be conducted under stirring. Further embodiments of the presently disclosed process will be more apparent from the following description, which is not intended to limit the scope of this invention. Detail description of the Invention: Accordingly, this invention makes a complete disclosure of a method for copolymerisation and for homopolymerisation of oligomeric wastes obtained from nylon-6 production, as stated herein above, wherein the weighed amount of oligomeric waste consisting of cyclic and linear oligomers is taken in a reactor, which in-turn is placed on a hating bath, preferably consisting of triethylene glycol/cooking oil, a weighted amount of water is added to the weighed amount of oligomeric waste and an inert gas, preferably nitrogen gas is flushed in to the said reactor, which in-turn is heated to raise the temperature, preferably to about 180 to 200°C and maintained at this temperature for about 2 to 4 hrs followed by addition of weighed amount of desired monomer-I and again raising the temperature to about 220°C and maintaining at this temperature for about 30 minutes followed by addition of weighed amount of desired monomer-II and again raising the temperature to about 260°C and maintaining at this temperature for about 5 to 10 hrs, preferably for about 6 to 7 hrs with or without vacuum, which results in the desired copolymer. In accordance to the preferred embodiment of the present invention, the continuous stirring and continuous flow of nitrogen gas is ensured. Further, in accordance to another preferred embodiment of this invention, during the addition of the monomers nitrogen is blowed under high pressure so as to avoid entry of oxygen. Still further, according to another preferred embodiment of this invention, the addition of monomers is done carefully, so as to avoid their sticking to the walls of the reactor, which can be further ensured by stopping the stirring temporarily. Still further a precaution to be taken is that the stirrer, preferably glass stirrer is immersed completely in the reacting material and uninterrupted stirring is ensured to ensure the uniform polymerization. The temperature profile for copolymerisation of oligomeric waste for preparation of copolymer of polyamide along with the sequence of addition of monomers, in accordance to one of the preferred embodiments of the present invention, is shown below: (Structure Removed) In accordance to one of the preierred embodiments of the present invention, the diamine, referred to as monomer-1 is preferably hexamethylene diamine and diacid, referred to as monomer-II is adipic acid. Such combination of said monomer-I and said monomer-II will result in preparation of copolymer of nylon, referred to as nylon6-nylon66, wherein nylon6 represents oligomeric waste and nylon66 represents said monomers. The selection of said monomer-I and/or said monomer-II would depend upon copolymer to be manufactured. The temperature profile for copolymerisation of oligomeric waste for preparation of copolymer of nylon and polyester along with the sequence of addition of monomers, in accordance to one of the preferred embodiments of the present invention, is shown below: (Structure Removed) In accordance to one of the preferred embodiments of the present invention, the diacid, referred to as monomer-I is preferably ethylene glycol and diacid, referred to as monomer-II is terephthalic acid and such combination of said monomer-I and said monomer-II will result in preparation of copolymer of nylon and polyester, referred to as, nylon6-PET, wherein nylon6 represents oligomeric waste and PET represents said monomers. The selection of said monomer-I and/or said monomer-II will depend upon desire of copolymer to be manufactured. In accordance to the preferred embodiment of the present invention the raising of temperature, preferably to about 180°C to 200°C and maintaining at this temperature for about 2 to 4 hrs result in increase of NH2 group from 50 meq/kg to about 125 to 250 meq/kg, which indicates opening if chain of some of the cyclic oligomers, which were obtained in the said oligomeric waste. Further, in accordance to one of the preferred embodiments of the present invention, the said oligomeric waste, as stated herein above, is heated first to a temperature of about 135 to 140°C and maintained at this temperature and then subsequently further heated to raise the temperature, preferably to about 180 to 200°C and maintained at this temperature for about 2 to 4 hrs. Further, according to the preferred embodiment of this invention, said monomer-II is added and the temperature is again raised to about 260°C and maintaining at this temperature for about 5 to 10 hrs, preferably for about 6 to 7 hrs, however, the present invention is not restricted by the time period for which the temperature of about 260°C is maintained, which will depend upon the copolymer required to be prepared. In accordance to one of the preferred embodiments of the presently disclosed method, if the step of opening of the cyclic oligomer of the oligomeric waste is avoided, it will result in preparation of homopolymers of the oligomeric waste, that is of nylon, and such homopolymerisation process. In accordance to the preferred embodiment, this invention consists of flushing of nitrogen in the empty reactor to which oligomeric waste is added, preferably in the semi-solid form. More preferably, while nitrogen flushing is on, preferably at an uniform rate of flow, the waste is added. The said reactor is then fixed with a stirrer, preferably with a flexible stirrer, and placed on an heating arrangement, preferably on triethylene glycol or ordinary cooking oil bath, which in-turn is heated, preferably to about 180°C to 200°C, to allow elimination of water contents of the said oligomeric waste, preferably for about 1 to 2 his till partial elimination of water. The said reactor is transferred preferably while hot and more preferably at a temperature of about 180°C, to a metal bath, where it is heated and continuously stirred at further increased temperature of about 250°C to 290°C, preferably about 270°C, which is attained in about 30 min and allowed to remain at this temperature for about 4 to 8 hrs, preferably about 6 hrs. In accordance to one of the preferred embodiments of the present invention, the last step of copolymerisation or the homopolymerisation processes, as described herein above, can be carried partially or completely under vacuum. In accordance to one of the preferred embodiments of the presently disclosed method, the said monomer-I is preferably diamine or diol, depending upon the desire of copolymerisation, which is added preferably after heating in a water bath. In accordance to another preferred embodiment of the presently disclosed method, the said monomer-II is preferably diacid. According to preferred embodiment of this invention, a weighed amount of desired monomer-II is added after addition of weighed amount of desired monomer-I, however, the present invention is not restricted by first addition of said monomer-I or of said monomer-II, which will depend upon the coplymer, required to be prepared. The presently disclosed process has been used to prepare number of homopolymers and number of coplymers using said oligomeric waste and combination of said monomers (monomer-I and monomer-II) in different ratios. The homopolymers prepared in accordance to the presently disclosed method are referred herein as homopolymer, and the coplymers prepared in accordance to the presently disclosed method are referred herein as N66-N6, if these are copolymers of polyamide, particularly copolymers of nylon, wherein N66 represents the said monomers and N6 represents the said oligomeric waste, and as PET-N6, if these are copolymers of nylon and polyester, wherein PET represents the said monomers and N6 represents the said oligomeric waste and in general are referred herein after to as polymers. The copolymers or homopolymers in particular, or the polymers in general, obtained in accordance to the preferred embodiments of the process of the present invention have been characterised for their viscosity/molecular weight, weight loss on heating, melting point range and have been tested for end use application particularly for application as hot melt adhesive. The polymers, obtained in accordance to the preferred embodiments of the homopolymerisation process of the present invention have shown intrinsic viscosity, herein after referred to as IV of about 0.37 dl/gm, when process carried under normal pressure, which corresponds to a molecular weight of about 4275. The homopolymerisation employing said last step under low vacuum results in a little better IV of about 0.40 dl/gm, which corresponds to molecular weight of about 4800. The copolymers, obtained in accordance to the preferred embodiments of the copolymerisation process of the present invention employing said diol or diamine and said diacid have shown interesting trend in intrinsic viscosity, that is the copolymers of type N66-N6 (2:1) show IV of about 0.412 dl/gm, of type N66-N6 (1:1) show IV of about 0.413 dl/gm, of type N66-N6 (1:2) show IV of about 0.340 dl/gm, of type N66-N6 (1:3) show IV of about 0.260 dl/gm, of type PET-N6 (1:1) show IV of about 0.338 dl/gm, of type PET-N6 (1:2) show IV of about 0.280 dl/gm, of type PET-N6 (1:3) show IV of about 0.231 dl/gm, wherein the figures in brackets refer to the molar ratio of the respective component. The above data is evident that all the polymers could attain a reasonable IV appropriate for their application as hot melt adhesive, which has been tested and the inferences given herein below. The homopolymers, obtained in accordance to the preferred embodiments of the homopolymeristion process of the present invention have shown three step weight loss in the studied temperature range of 70 to 570°C. The first weight loss is less than 17% in the temperature range of 70 to 330°C, the second weight loss is less than 68% in the temperature range of 330 to 468°C, the third weight loss is less than 15% in the temperature range of 468 to 570°C. The copolymers, as obtained in accordance to the preferred embodiments of the copolymerisation process of the present invention employing said diamine and said diacid, resulting in copolymer of type N66-N6 (1:1), have also shown three step weight loss in the studied temperature range of 120 to 600°C. The first weight loss is less than 5% in the temperature range of 120 to 330°C, the second weight loss is less than 85% in the temperature range of 330 to 485°C, the third weight loss is less than 9.8% in the temperature range of 485 to 600°C. Similarly, the copolymers, obtained in accordance to the preferred embodiments of the copolymerisation process of the present invention employing said diol and said diacid, resulting in copolymer of type PET-N6 (1:1), have also shown three step weight loss in the studied temperature range of 70 to 570°C. The first weight loss is less than 10% in the temperature range of 70 to 330°C, the second weight loss is less than 72% in the temperature range of 330 to 480°C, the third weight loss is less than 19% in the temperature range of 480 to 570°C. The said homopolymer has shown a broad melting range from about 162 to 214°C. The broad peak in the DSC graph is attributed to a variety of mixed species including cyclic oligomeric present in the polymer. In hot melt adhesive, the presence of cyclic oligomers is advantageous, as it helps in increasing the flowability of the molten adhesive and also helps in lowering the melting point of the composition. The said copolymers have shown a relatively narrow letting range. The copolymer of type N66-N6 (2:1) has shown melting point range from about 145 to 187°C, copolymer of type N66-N6 (1:1) has shown melting point range from about 145 to 183°C, copolymer of type N66-N6 (1:2) has shown melting point range from about 128 to 172°C, copolymer of type N66-N6 (1:3) has shown melting point range from about 124 to 165°C, and copolymer of type PET-N6 (1:1) has shown melting point range from about 141 to 197°C, copolymer of type PET-N6 (1:2) has shown melting point range from about 134 to 181°C, copolymer of type PET-N6 (1:3) has shown melting point range from about 99 to 153°C. The melting point of the presently developed polymers has shown decreasing tend with the addition of oligomeric waste component. The polymers, as obtained in accordance to the preferred embodiments of the presently disclosed process of the present invention have been tested for end use application, particularly for application as hot melt adhesive by known method and lap shear and T-peel tests have been performed in the known manner. The polymers have shown better adhesive strength, whicn may be attributed to the regular structure of the prepared polymers. The presently disclosed invention has been described with a set of specific reaction for polymerization of oligomeric waste, whichis not intended to limit the scope of the present invention. It is obvious that, a minor modification in the reaction conditions of the presently disclosed set of specific reaction for polymerization of oligomeric waste of the presently disclosed invention is possible without deviating from the scope of the present invention. We Claim: 1. A method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, comprises: (iv) heating oligomeric waste in presence of water under nitrogen blanket and autogenous pressure at a temperature of 135°C to 180°C, (v) adding respective monomer I such as herein described after increasing temperature as mentioned in step (i) if desired, (vi) subsequently adding respective monomer II such as herein described after 30 minutes, after raising the temperature, followed by raising the temperature to a range of 250°C to 290°C, and allowing to continue reaction for completion with or without applying vacuum for copolymer preparation. 2. A method as claimed in claim 1, wherein the heating under step (i) is carried out at a temperature in the range of 135°C to 180°C, for 2 to 4 hours till completion of reaction. 3. A method in claims 1 and 2, wherein The temperature in step (ii) may be raised to 180 to 220°C if so required. 4. A method as claimed in claim 1, wherein the monomer I used is such as diamine or diol. 5. A method as claimed in claims 1& 4, wherein the monomer I used is diamine such as hexamethylene diamine. 6. A method as claimed in claims 1 & 4, wherein the monomer I used is diol such as ethylene glycol. 7. A method as claimed in claim 1, wherein the temperature in step (iii) is raised to 260°C. 8. A method as claimed in claims 1 & 7, wherein the temperature in step (iii) is maintained for 5 to 10 hours preferably for 6 to 7 hours. 9. A method as claimed in claims 1, wherein monomer II used in step (iii) is diacid. 10. A method as claimed in claims 1 & 9, wherein the monomer II used is diacid exemplified by adipic acid or terephthalic acid. 11. A method as claimed in preceding claims, wherein the copolymerisation or homopolymerisation is carried out under stirring. 12. A method as claimed in preceding claims, wherein monomer I is diamine and monomer II is adipic acid. 13. A method as claimed in preceding claims, wherein monomer I is diol and monomer II is terephthalic acid. 14. A method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, substantially as herein described.

Full Text

Field of the Invention:
The present invention relates to a method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, Particularly, it relates to the method for copolymerisation and homopolymerisation of oligomeric wastes obtained from nylon-6 production. More particularly, it relates to the method for homopoymerisation and copolymerisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant and prodcuts thereof. Even more particularly it relates to the method for utilisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant to develop useful polymers by way of copolymerisation and homopolymerisation thereof. Still more particularly the invention relates to a method of polymerization without employing flow agent or plasticizers thereby making the process cost effective. Further, the polymers obtained are with suppressed melting point. Background of the Invention:
The copolymeristion or the homopolymerisation of the monomers, particularly of caprolactam monomers, more particularly of pure caprolactam monomers, or of oligomers, particularly of pure oligomers, or of pure oligomers obtained from pure caprolactam monomers is known in the art.
The main drawback of such known methods is that, these methods involve addition of flow agents and/or plascticisers to result in nylon-6 or nylon-6 type polymers with desired properties, which not only adds to additional step of the reaction but also the cost of the production.

The another drawback of such known methods is that, these methods do not result in nylon-6 or nylon-6 type polymers with suppressed melting point.
Still another drawback of such known methods is that, these methods do not teach any method to utilise the nylon-6 oligomeric wastes, preferably obtained from caprolactam distillation still or from caprolactam recovery plant, which presently go unused and hence are required to be dumped in landfills.
The above drawbacks of such known methods and need to utilise the nylon-6 oligomeric wastes, preferably obtained from caprolactam distillation still or from caprolactam recovery plant in order to avoid dumping of such wastes, has compelled to look for a process which can not only over come the above stated drawbacks of the prior art but also can teach a method to utilise the nylon-6 oligomeric wastes, preferably obtained from caprolactam distillation still or from caprolactam recovery plant.
Need of the Invention:
Therefore, there is need to develop a method for copolymerisation of oligomeric wastes, particularly for copolymerisation of oligomeric wastes obtained from nylon-6 production, more particularly for copolymerisation and for homopolymerisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant, even more particularly for utilistion of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant, and to have products, which can overcome drawbacks of such known methods.
Objects of the Invention:

This is the main object of the present invention to make a disclosure of a method for copolymerisation of oligomeric wastes, particularly for copolymerisation of oligomeric wastes obtained from nylon-6 production, more particularly for copolymerisation and for homopoymerisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant, even more particularly for utilisation of nylon-6 oligomeric wastes obtained from caprolactam distillation still or from caprolactam recovery plant, and of products thereof, which can overcome drawbacks of such known methods as described herein above.
There is another an object of this invention to make a disclosure of method, as stated herein above, which has proved to be economical as a result of the present invention.
This is yet another object of this invention to make a complete disclosure of a method, as stated herein above, which can eliminate the use of additional flow agents and/or plasticisers and hence can eliminate requirement of the additional step of the process.
Yet another object of the present invention is to make a complete disclosure of a method, as stated herein above, which can produce the nylon-6 or nylon-6 polymers having suppressed melting point.
Further objects and the preferred embodiments of the present invention will be more apparent from the following description.
Brief description of the Invention:
Accordingly, the present invention provides a method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, comprises:

(i) heating oligomeric waste in presence of water under nitrogen blanket and autogenous pressure at a temperature of 135°C to 180°C,
(ii) adding respective monomer I such as herein described after increasing
temperature as mentioned in step (i) if desired,
(iii) subsequently adding respective monomer II such as herein described after 30 minutes, after raising the temperature, followed by raising the temperature to a range of 250°C to 290°C, and allowing to continue reaction for completion with or without applying vacuum for copolymer preparation. Further, the present invention also makes a complete disclosure of a method for homopolymerisation of the said oligomeric waste, wherein the heating under step (i) is carried out at a temperature in the range of 135°C to 180°C, for about 2 to 4 hours till completion of reaction for homopolymerisation repparation. The temperature in step (ii) may be raised to about 180 to 220°C if so required.
Monomer I may be such as diamine exemplified by hexamethylene diamine or diol
exemplified by ethylene glycol.
The temperature in step (iii) may be raised to 260°C and maintained for about 5 to 10
hours preferably for 6 to 7 hours. More specifically the type of monomer to be added, the temperature and period of the reaction is regulated by the type of polymer to be obtained. The reaction may preferably be conducted under stirring.
Further embodiments of the presently disclosed process will be more apparent from the following description, which is not intended to limit the scope of this invention.
Detail description of the Invention:

Accordingly, this invention makes a complete disclosure of a method for copolymerisation and for homopolymerisation of oligomeric wastes obtained from nylon-6 production, as stated herein above, wherein the weighed amount of oligomeric waste consisting of cyclic and linear oligomers is taken in a reactor, which in-turn is placed on a hating bath, preferably consisting of triethylene glycol/cooking oil, a weighted amount of water is added to the weighed amount of oligomeric waste and an inert gas, preferably nitrogen gas is flushed in to the said reactor, which in-turn is heated to raise the temperature, preferably to about 180 to 200°C and maintained at this temperature for about 2 to 4 hrs followed by addition of weighed amount of desired monomer-I and again raising the temperature to about 220°C and maintaining at this temperature for about 30 minutes followed by addition of weighed amount of desired monomer-II and again raising the temperature to about 260°C and maintaining at this temperature for about 5 to 10 hrs, preferably for about 6 to 7 hrs with or without vacuum, which results in the desired copolymer.
In accordance to the preferred embodiment of the present invention, the continuous stirring and continuous flow of nitrogen gas is ensured.
Further, in accordance to another preferred embodiment of this invention, during the addition of the monomers nitrogen is blowed under high pressure so as to avoid entry of oxygen.
Still further, according to another preferred embodiment of this invention, the addition of monomers is done carefully, so as to avoid their sticking to the walls of the reactor, which can be further ensured by stopping the stirring temporarily. Still further a precaution to be taken is that the stirrer, preferably glass stirrer is immersed completely in the reacting material and uninterrupted stirring is ensured to ensure the uniform polymerization.

The temperature profile for copolymerisation of oligomeric waste for preparation of copolymer of polyamide along with the sequence of addition of monomers, in accordance to one of the preferred embodiments of the present invention, is shown below:

(Structure Removed)
In accordance to one of the preierred embodiments of the present invention, the diamine, referred to as monomer-1 is preferably hexamethylene diamine and diacid, referred to as monomer-II is adipic acid. Such combination of said monomer-I and said monomer-II will result in preparation of copolymer of nylon, referred to as nylon6-nylon66, wherein nylon6 represents oligomeric waste and nylon66 represents said

monomers. The selection of said monomer-I and/or said monomer-II would depend
upon copolymer to be manufactured.
The temperature profile for copolymerisation of oligomeric waste for preparation of
copolymer of nylon and polyester along with the sequence of addition of monomers, in
accordance to one of the preferred embodiments of the present invention, is shown
below:

(Structure Removed)
In accordance to one of the preferred embodiments of the present invention, the diacid, referred to as monomer-I is preferably ethylene glycol and diacid, referred to as monomer-II is terephthalic acid and such combination of said monomer-I and said

monomer-II will result in preparation of copolymer of nylon and polyester, referred to as, nylon6-PET, wherein nylon6 represents oligomeric waste and PET represents said monomers. The selection of said monomer-I and/or said monomer-II will depend upon desire of copolymer to be manufactured.
In accordance to the preferred embodiment of the present invention the raising of temperature, preferably to about 180°C to 200°C and maintaining at this temperature for about 2 to 4 hrs result in increase of NH2 group from 50 meq/kg to about 125 to 250 meq/kg, which indicates opening if chain of some of the cyclic oligomers, which were obtained in the said oligomeric waste.
Further, in accordance to one of the preferred embodiments of the present invention, the said oligomeric waste, as stated herein above, is heated first to a temperature of about 135 to 140°C and maintained at this temperature and then subsequently further heated to raise the temperature, preferably to about 180 to 200°C and maintained at this temperature for about 2 to 4 hrs.
Further, according to the preferred embodiment of this invention, said monomer-II is added and the temperature is again raised to about 260°C and maintaining at this temperature for about 5 to 10 hrs, preferably for about 6 to 7 hrs, however, the present invention is not restricted by the time period for which the temperature of about 260°C is maintained, which will depend upon the copolymer required to be prepared.
In accordance to one of the preferred embodiments of the presently disclosed method, if the step of opening of the cyclic oligomer of the oligomeric waste is avoided, it will result in preparation of homopolymers of the oligomeric waste, that is of nylon, and such homopolymerisation process.

In accordance to the preferred embodiment, this invention consists of flushing of nitrogen in the empty reactor to which oligomeric waste is added, preferably in the semi-solid form. More preferably, while nitrogen flushing is on, preferably at an uniform rate of flow, the waste is added. The said reactor is then fixed with a stirrer, preferably with a flexible stirrer, and placed on an heating arrangement, preferably on triethylene glycol or ordinary cooking oil bath, which in-turn is heated, preferably to about 180°C to 200°C, to allow elimination of water contents of the said oligomeric waste, preferably for about 1 to 2 his till partial elimination of water. The said reactor is transferred preferably while hot and more preferably at a temperature of about 180°C, to a metal bath, where it is heated and continuously stirred at further increased temperature of about 250°C to 290°C, preferably about 270°C, which is attained in about 30 min and allowed to remain at this temperature for about 4 to 8 hrs, preferably about 6 hrs.
In accordance to one of the preferred embodiments of the present invention, the last step of copolymerisation or the homopolymerisation processes, as described herein above, can be carried partially or completely under vacuum.
In accordance to one of the preferred embodiments of the presently disclosed method, the said monomer-I is preferably diamine or diol, depending upon the desire of copolymerisation, which is added preferably after heating in a water bath. In accordance to another preferred embodiment of the presently disclosed method, the said monomer-II is preferably diacid.
According to preferred embodiment of this invention, a weighed amount of desired monomer-II is added after addition of weighed amount of desired monomer-I, however, the present invention is not restricted by first addition of said monomer-I or of said monomer-II, which will depend upon the coplymer, required to be prepared.

The presently disclosed process has been used to prepare number of homopolymers and number of coplymers using said oligomeric waste and combination of said monomers (monomer-I and monomer-II) in different ratios. The homopolymers prepared in accordance to the presently disclosed method are referred herein as homopolymer, and the coplymers prepared in accordance to the presently disclosed method are referred herein as N66-N6, if these are copolymers of polyamide, particularly copolymers of nylon, wherein N66 represents the said monomers and N6 represents the said oligomeric waste, and as PET-N6, if these are copolymers of nylon and polyester, wherein PET represents the said monomers and N6 represents the said oligomeric waste and in general are referred herein after to as polymers.
The copolymers or homopolymers in particular, or the polymers in general, obtained in accordance to the preferred embodiments of the process of the present invention have been characterised for their viscosity/molecular weight, weight loss on heating, melting point range and have been tested for end use application particularly for application as hot melt adhesive.
The polymers, obtained in accordance to the preferred embodiments of the homopolymerisation process of the present invention have shown intrinsic viscosity, herein after referred to as IV of about 0.37 dl/gm, when process carried under normal pressure, which corresponds to a molecular weight of about 4275. The homopolymerisation employing said last step under low vacuum results in a little better IV of about 0.40 dl/gm, which corresponds to molecular weight of about 4800.
The copolymers, obtained in accordance to the preferred embodiments of the copolymerisation process of the present invention employing said diol or diamine and said diacid have shown interesting trend in intrinsic viscosity, that is the copolymers of type N66-N6 (2:1) show IV of about 0.412 dl/gm, of type N66-N6 (1:1) show IV of

about 0.413 dl/gm, of type N66-N6 (1:2) show IV of about 0.340 dl/gm, of type N66-N6 (1:3) show IV of about 0.260 dl/gm, of type PET-N6 (1:1) show IV of about 0.338 dl/gm, of type PET-N6 (1:2) show IV of about 0.280 dl/gm, of type PET-N6 (1:3) show IV of about 0.231 dl/gm, wherein the figures in brackets refer to the molar ratio of the respective component.
The above data is evident that all the polymers could attain a reasonable IV appropriate for their application as hot melt adhesive, which has been tested and the inferences given herein below.
The homopolymers, obtained in accordance to the preferred embodiments of the homopolymeristion process of the present invention have shown three step weight loss in the studied temperature range of 70 to 570°C. The first weight loss is less than 17% in the temperature range of 70 to 330°C, the second weight loss is less than 68% in the temperature range of 330 to 468°C, the third weight loss is less than 15% in the temperature range of 468 to 570°C.
The copolymers, as obtained in accordance to the preferred embodiments of the copolymerisation process of the present invention employing said diamine and said diacid, resulting in copolymer of type N66-N6 (1:1), have also shown three step weight loss in the studied temperature range of 120 to 600°C. The first weight loss is less than 5% in the temperature range of 120 to 330°C, the second weight loss is less than 85% in the temperature range of 330 to 485°C, the third weight loss is less than 9.8% in the temperature range of 485 to 600°C. Similarly, the copolymers, obtained in accordance to the preferred embodiments of the copolymerisation process of the present invention employing said diol and said diacid, resulting in copolymer of type PET-N6 (1:1), have also shown three step weight loss in the studied temperature range of 70 to 570°C. The first weight loss is less than 10% in the temperature range of 70 to 330°C, the second

weight loss is less than 72% in the temperature range of 330 to 480°C, the third weight loss is less than 19% in the temperature range of 480 to 570°C.
The said homopolymer has shown a broad melting range from about 162 to 214°C. The broad peak in the DSC graph is attributed to a variety of mixed species including cyclic oligomeric present in the polymer. In hot melt adhesive, the presence of cyclic oligomers is advantageous, as it helps in increasing the flowability of the molten adhesive and also helps in lowering the melting point of the composition.
The said copolymers have shown a relatively narrow letting range. The copolymer of type N66-N6 (2:1) has shown melting point range from about 145 to 187°C, copolymer of type N66-N6 (1:1) has shown melting point range from about 145 to 183°C, copolymer of type N66-N6 (1:2) has shown melting point range from about 128 to 172°C, copolymer of type N66-N6 (1:3) has shown melting point range from about 124 to 165°C, and copolymer of type PET-N6 (1:1) has shown melting point range from about 141 to 197°C, copolymer of type PET-N6 (1:2) has shown melting point range from about 134 to 181°C, copolymer of type PET-N6 (1:3) has shown melting point range from about 99 to 153°C.
The melting point of the presently developed polymers has shown decreasing tend with the addition of oligomeric waste component.
The polymers, as obtained in accordance to the preferred embodiments of the presently disclosed process of the present invention have been tested for end use application, particularly for application as hot melt adhesive by known method and lap shear and T-peel tests have been performed in the known manner. The polymers have shown better adhesive strength, whicn may be attributed to the regular structure of the prepared polymers.

The presently disclosed invention has been described with a set of specific reaction for polymerization of oligomeric waste, whichis not intended to limit the scope of the present invention. It is obvious that, a minor modification in the reaction conditions of the presently disclosed set of specific reaction for polymerization of oligomeric waste of the presently disclosed invention is possible without deviating from the scope of the present invention.

We Claim:
1. A method for copolymerisation and homopolymerisation of oligomeric wastes generated from nylon-6 production, comprises:
(iv) heating oligomeric waste in presence of water under nitrogen blanket and autogenous pressure at a temperature of 135°C to 180°C,
(v) adding respective monomer I such as herein described after increasing temperature as mentioned in step (i) if desired,
(vi) subsequently adding respective monomer II such as herein described after 30 minutes, after raising the temperature, followed by raising the temperature to a range of 250°C to 290°C, and allowing to continue reaction for completion with or without applying vacuum for copolymer preparation.
2. A method as claimed in claim 1, wherein the heating under step (i) is carried out
at a temperature in the range of 135°C to 180°C, for 2 to 4 hours till completion
of reaction.
3. A method in claims 1 and 2, wherein The temperature in step (ii) may be raised
to 180 to 220°C if so required.
4. A method as claimed in claim 1, wherein the monomer I used is such as diamine
or diol.
5. A method as claimed in claims 1& 4, wherein the monomer I used is diamine
such as hexamethylene diamine.
6. A method as claimed in claims 1 & 4, wherein the monomer I used is diol such
as ethylene glycol.
7. A method as claimed in claim 1, wherein the temperature in step (iii) is raised to
260°C.
8. A method as claimed in claims 1 & 7, wherein the temperature in step (iii) is
maintained for 5 to 10 hours preferably for 6 to 7 hours.

9. A method as claimed in claims 1, wherein monomer II used in step (iii) is
diacid.
10. A method as claimed in claims 1 & 9, wherein the monomer II used is diacid
exemplified by adipic acid or terephthalic acid.
11. A method as claimed in preceding claims, wherein the copolymerisation or
homopolymerisation is carried out under stirring.
12. A method as claimed in preceding claims, wherein monomer I is diamine and
monomer II is adipic acid.
13. A method as claimed in preceding claims, wherein monomer I is diol and
monomer II is terephthalic acid.
14. A method for copolymerisation and homopolymerisation of oligomeric wastes
generated from nylon-6 production, substantially as herein
described.

Documents:

749-del-1999-abstract.pdf

749-del-1999-claims.pdf

749-del-1999-correspondence-others.pdf

749-del-1999-correspondence-po.pdf

749-del-1999-description (complete).pdf

749-del-1999-form-1.pdf

749-del-1999-form-13.pdf

749-del-1999-form-19.pdf

749-del-1999-form-2.pdf

749-del-1999-form-6.pdf

749-del-1999-form-62.pdf

749-del-1999-gpa.pdf

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Patent Number

216390

Indian Patent Application Number

749/DEL/1999

PG Journal Number

13/2008

Publication Date

28-Mar-2008

Grant Date

12-Mar-2008

Date of Filing

18-May-1999

Name of Patentee

DEAN, INDUSTRIAL RESEARCH AND DEVELOPEMENT (IRD)

Applicant Address

INDIAN INSTITUTE OF TECHNOLOGY , DELHI(IITD), HAUZ KHAS, NEW DELHI, 110016, INDIA

Inventors:

#	Inventor's Name	Inventor's Address
1	ASHWINI KUMAR AGRAWAL	ASST. PROFESSOR DEPARTMENT OF TEXTILE TECHNOLOGY,INDIAN INSTITUTE OF TECHNOLOGY , DELHI, HAUZ KHAS, NEW DELHI, 110016, INDIA
2	PUSPA BAJAJ	PROFESSOR DEPARTMENT OF TEXTILE TECHNOLOGY,INDIAN INSTITUTE OF TECHNOLOGY , DELHI, HAUZ KHAS, NEW DELHI, 110016, INDIA
3	SAMRAT MUKHOPADHYAY	EX. STUDENT OF M.TECH, DEPARTMENT OF TEXTILE TECHNOLOGY,INDIAN INSTITUTE OF TECHNOLOGY , DELHI, HAUZ KHAS, NEW DELHI, 110016, INDIA
4	MS. PREETI LODHA	EX. STUDENT OF B.TECH, DEPARTMENT OF TEXTILE TECHNOLOGY,INDIAN INSTITUTE OF TECHNOLOGY , DELHI, HAUZ KHAS, NEW DELHI, 110016, INDIA

PCT International Classification Number

C08

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA