Title of Invention	A PROCESS FOR PREPARING A STABLILIZED HYDROXYLAMINE SOLUTION
Abstract	ABSTRACT 2219/MAS/96 A process for preparing a stabilized hydroxylamine solution The present invention relates to a process for preparing a stabilized hydroxylamine solution which comprises adding at least one compound of the formula I in which A and R1 to R4are as defined in the description to the said solution.

Full Text

The present invention relates tc a process fo preparing a stabilized hydroxylamine solution. r Hydroxylamine, especially in the form of its salt with sulfuric acid, is an important intermediate for the chemical industry, and is widely employed in chemical syntheses. It is frequently necessary to employ hydroxylamine in the form of a solution of the free base, which is generally liberated from a hydroxylammonium salt such as, for example, hydroxylammonium sulphate or hydroxylammonium chloride, by the action of an appropriate base, such as ammonia, sodium hydroxide solution or an alcoholate. Neutral and alkaline hydroxylamine solutions are unstable and decompose to form ainmonia, nitrogen, oxides of nitroger, and water, so that their transportation or storage is highly problematic. The rate of decomposition increases with rising temperature, rising pH and rising concentration of catalytically active impurities. In order to avoid the decomposition of the hydroxylamine, a stabilizer is added to the solutions. Numerous stabilizers for hydroxylamine are already known. Proposals which have been made are: thioglycolic acid (JP-A-58069843), glycerol monoethers and ethylene oxide adducts thereof (DE-A-29 19 554), hydroxyar.thraquinones (DE-A-33 43 600), hydroxyguinolines (DE-A-33 45 734), polyhydroxyhexano-1,4-lactone (DE-A-33 45 733), anthocyar.ins (DE-A-33 47 260), hydroxyguinaldines, flavones, benzonitrile, N-phenyl-N-hydroxythiourea (DE-A-36 01 803), flavans (DE-A-33 43 599), thiosulfates, mercaptobenzothiazoles, mercaptoalkanols, mercaptothiazolines, thiuram disulfides, thioureas {EP-A-516 933), the tetrasodium salt of ethylenediaminetetraacetic acid, the trisodium salt of N-hydroxyethylethylenediaminetriacetic acid, polyvinylpyrrolidone or poly-N-vinyl-5-ethyl-2-oxa2olidinone (US-A-3,145,082), amdde oximes {US-A-3,4 80,391), hydroxamic acids (US-3,480,391), hydroxyureas (US-3,544,270), dipyridyl compounds (JP-A-^58069842), aminoquinolines (JP-A- 58069844), phenanthrolines (JP-A- 58069841), and polyhydroxyphehols (JP-A- 4878099}. However, none of the stabilizers proposed to date has been able to provide hydroxylamine solutions with sufficient stabilization for no notable decomposition of the hydroxylamine to occur, especially during storage. It is therefore an object of the present invention to provide a better means of stabilizing hydroxy1amine solutions. We have now found that this object is achieved, surprisingly, by using as stabilizer at least one compound of the formula I; R1R2N-A-NR3R4 (I) in which A is alkylene, alkenylene, alkynylene, cycloalkylene, cycloalkenylene, arylene, o-, m~ or p-xylylene, a 5- or 6-membered saturated or unsaturated heterocycle having a nitrogen atom, said radicals being able to contain 1, 2 or 3 substituents which are selected independently of one another from alkyl, alkoxy and hydroxyl, cr is — X-f-NR—BH— n -n which B and X are -CHjCHj- or -CH2CH2CH2-, n is 10 - 50,000, R is H, alkyl, ethylene or propylene which is substituted ~y OH, NH2, NHC0R5 or COOH, or is CSSH, CHaCN or CH2PO3H2, cr is a bridge to a nitrogen atom of another polyethyleneimine or polypropyleneindne chain, the bridge r>eing formed by —^NR-&H— or o CHj-CHOH-CHj-f-O CH2 CH2-J— CH2-CHOH-CH2- R5 .-here o and p independently of one another are 1 - 15, .s H, Ci-CiB-alkyl or :3R6C0R6 where R' is Cij-Cje-alkyl, R^» ^~ rz-- and R* independently of one another are H, CH2COOH, rH2P03H2, alkyl, acyl, CH2CH2OH, CH2CH2NH2 z;r CH2— R' ft' is OH, SH, NH;, CN, COOH, alkyl or alkoxy, or the salts thereof, with the exceptions of ethylenediaminetetraacetic acid and N-hydroxyethylenediaminetriacetic acid and salts thereof. I'he present invention therefore provides stabilized hydroxylaraine jolutions comprising hydroxylamine and at least one compound of :he formula I. The novel solutions comprise hydroxylamine in essentially pure form as a free base or as an at least partially neutralized lydroxylamine salt; in other words, free hydroxylamine is mixed rfith the hydroxylamine salt. The stabilizers employed in accordance with the invention can be ased to stabilize all types of hydroxylamine solutions. They may be aqueous solutions or solutions of hydroxylamine in an organic solvent such as methanol, ethanol, n~propanol, isopropanol, acetone, tetrahydrofuran, etc., or may be mixtures of water and organic solvents. The stabilizers employed in accordance with the invention are also soluble in the solvents in which hydroxylamine is soluble. If appropriate, solubility can be obtained by the choice of appropriate groups R^ to R4 and A. Hydroxylamine solutions are in general obtained by reacting a hydroxylammonium salt, especially hydroxylammonium sulfate, hydroxylammonium chloride and hydroxylammonium phosphate,, with an appropriate base, such as ammonia, sodium hydroxide, potassium hydroxide or calcium hydroxide. In the case of complete neutralization of the hydroxylainmonium salt a solution is obtained which comprises free hydroxylamine and the salt derived from the base cation and the acid anion which is present in the hydroxylaBimoniuro salt. The salt can be separated off completely or partially. The hydroxylammonium salt can also be neutralized only partially with the base. In this case a solution is obtained which comprises not only free hydroxylamine and the salt mentioned but also unreacted hydroxylammonium salt. All of these solutions can be stabilized in accordance with the invention, the nature of the anion in the hydroxylammonium salt not being critical. In the context of the present invoition, alkyl is a straight-chain or branched radical of preferably 1 to 18 carbon atoms, especially 1 to 6 carbon atoms and, in particular, 1 to 4 carbon atoms. The same comments apply to the alkyl group in alkoxy. Alkylone is a straight-chain or branched divalent radical of, preferably, 2 to 6 carbon atoms, especially 2 to 4 carbon atoms. Alkenylene and aikynylene are straight-chain or branched divalent radicals of, preferably, 3 to 6 carbon atoms and, in particular, 3 or 4 carbon atoms. rycloalkylene and cycloalkenylene are preferably cyclopentylene Dr cyclohexylene or, respectively, cyclopentenylene or cyclo-hexenylene. Rrylene is preferably an aromatic Ce-Cjo hydrocarbon radical or phenylene. The saturated or unsaturated heterocycle is preferably pyrrolidinylene, piperidinylene, pyrrolylene or pyridinylene. The heterocycle is attached by carbon atoms to the two nitrogen atoms of the formula I. Acyl is straight-chain or branched and preferably has 1 to 19 carbon atoms. A is preferably alkylene, cycloalkylene, arylene or — X-e-NR—BH— n and in particular is alkylene, cycloalkylene or — X-f-NR—BH— In this case the radicals R^ to R* independently of one another are preferably CH2COOH, CH2CH20H, CHjCHjNHz or L jj and in particular are CHjCOOH °J^ L Jj R' is preferably in the ortho position and in particular is OH, COOH or a branched (bulky) alkyl radical, such as isopropyl, tert-butyl etc. The stabilizers according to the invention can also be employed in the form of salts. Particularly suitable salts -re alkali metal salts, such as sodium salts or potassium salts, or ammonium salts, if acidic functions are present, including the salts with amines, such as triethylamine or trlethanolamine, and with hydroxylamine. The latter may arise if the compounds of the formula I are introduced into the hydroxylamine solution to be stabilized. Also suitable are acid addition salts with inorganic acids, such as HF, HCl, HBr, H2SO4, H3p04, etc., if basic functions are present. A further preferred embodiment is a stabilized solution comprising as stabilizer a compound of the formula I in which A is alJtylene or cycloalkylene and Ri to R CH2— where R' is as defined above and in particular is OH, SH or NH;, If A is X-hHR—B-j- the compounds of the formula I are polyethyleneimine or polypropyleneimine polymers, which are in general weakly crosslinked. The repeating units of said formula may be identical ^or different. This applies in particular when units are present which ars substituted on the nitrogen atom, i.e. R is other than hydrogen in at least some of the units. The chosen degree of substitution can lie within a wide range and is in general in the range from 5 to 98 %. The slight crosslinking which is the result of the preparation of the polyethyleneimines and polypropyleneimihes can be increased by polyether bridges between the polymers. The polyether bridge is formed by alkylating some of the nitrogen atoms with epichlorohydrine followed by ethoxylation. In the case of polyethyleneimine or polypropyleneimine polymers, the radicals Ri to R* are preferably H or alkyl. The weight average molecular weight of the polymers can be chosen within a wide range, and is generally in the range from 800 to 2,000,000, in particular from 1,000 to 1,500,000 and, in the case of more highly crosslinked polymers, in the range from 50,000 to 2,000,000. In accordance with a further preferred embodiment, the stabilized hydroxy1amine solution comprises at least one compound of the formula I in which A is — X-f-NR— BH— B and X are CHjCH;-, R is CHjCOOH, CHjCHjCOOH, CHjCH^OH, CH2CH2NH2, NHC0R5 or CSSH or is a bridge as defined above, R^ is as defined above and Ri to R* are H or alkyl. Particularly preferred compounds in this context are: a weakly crosslinked polyethyleneimine with an average molecular weight in the range from 1,000 to 2,000,000; carboxymethylated polyethyleneimines with a degree of substitution of from 25 to 98 % and an average molecular weight in the range from 1,500 to 1,500,000; carboxyethylated polyethyleneimines with a degree of substitution of from 5 to 50 % and an average molecular weight in the range from 1,000 to 1,500,000; partially amidated polyethyleneimines(one or two of the radicals Ri to R* are Cj to Cig-acyl) with a degree of substitution of from 5 to 50% and an average molecular weight in the range from 1,000 to 1,500,000; polyether-crosslinked polyethyleneimines with an average molecular weight in the range from 50,000 to 1,500,000; hydrophobically modified polyethyleneimines (R = -CH2CH2NHCOR5, where RS is CHR^CORS and R* is Cu to Cig-alkyl, especially hexadecyl) with a degree of substitution of from 1 to 7 % and an average molecular weight in the range from 1,500 to 1,500,00 [sic]. These polymers are obtainable by reacting the corresponding ethyleneimines (R = CH2CH2NH2) with the corresponding alkyl diketenes; hydroxyethyl-substituted polyethyleneimines with a degree of substitution of 80 to 100 % and an average molecular weight in the range from 1 to 2,000,000; polyethyleneimine dithiocarbamates (R ~ CSSH] with a degree of substitution of from 30 to 60 % and an average molecular weight of from 2,000 to 1,000,000, and the sodium salts thereof. Some of the above polyethyleneimines are commercially obtainable, and are marketed, for example, by BASF AG under the name LUPASOL®. According to a further preferred embodiment the stabilized, hydroxylamine solution comprises as stabilizer a compound of the formula I in which A is cyclohexylene or -CHjCHz- and Ri to R* are CHjCOOH or -CH2— preferably CHjCOOH, where R' is OH, SH, NH; or COOH. With particular preference these compounds are trans-1, 2-diaminocyclohexane-N,N,N ' ,N'--tetraacetic acid and/or N,N' -di( 2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid and the salts thereof. The compounds of the formula I are known and commercially available or can be prepared by analogy with known methods. The novel stabilized hydroxylamine solutions comprise the compounds of formula I in a quantity which is sufficient for stabilization. They preferably contain from 0.001 to 20 % by weight (from a 0 to 200,000 ppm), in particular from 0.001 to 10 by weight, particularly preferably from 0.01 to 5 % by weight, very particularly preferably from 0.02 to 2 % by weight, of a compound of the formula I, based on the hydroxylamine content. The concentration of hydroxylamine is in general 1 - 100 % by weight, in particular 1 - 70 * by weight, based on the overall weight of the solution. The stabilizer can be added prior to or following neutralization of the hydroxylamine salt, but preferably prior to the neutralization. The compounds of the formula I are effective in a wide temperature range. For instance, they stabilize hydroxylamine solutions at fron--20»C to ISO^C, preferably at -lOoc - lOOoc. However, they are also suitable as stabilizers at markedly higher temperatures, under the pressures which are necessary to liquefy the solution. Accordingly, the present invention provides a process for preparing astabihzed hydroxylamine solution comprising the step of adding a stabilizer selected from at least one compound of the formula I R'R^N-A-NR^R^ (I) in which A is C2-C6-alkylene, Ca-Q-alkenylene, Cs-Ce-alkynylene, Cs-Q-cycloalkylene, C5-Ce-cycloalkenylene, an aromatic Ce-Cio-hydrocarbon radical, phenylene, o-m- or p-xylylene, a 5- or 6-membered saturated or unsaturated heterocycle having a nitrogen atom, said radicals being able to contain 1, 2 or 3 substituents which are selected independently of one another from Ci-Cig-alkyl, Ci-Cig-alkoxy or hydroxyl, or is _X-t-NR-BH-n in which B and X are -CH2CH2- or -CH2CH2CH2-, n is 10 - 50,000, R is H, CrC|8-alkyl, ethylene or propylene which is substituted by OH, NH2, NHCOR^ or'COOH, or is CSSH, CH2CN or CH2PO3H2, or is a bridge to a nitrogen atom of another polyethyleneimine or polyproyleneimine chain, the bridge being formed by —f—NR-BH-o or CH2-CHOH-CH2—t—O-CH2-CH2—^—CH2-CHOH-CH2-where 0 and p independently of one another are 1 - 15, RMSH, Ci-C,8-alkyIor CHR'COR^ where R' is Ci2-C,8-aIkyI, R', R^ R^ and R" independently of one another are H, CH2COOH, CH2PO3H2, C,-C,f R , R , R and R independently of one alkyl, C|-C|9-acyl, CH2CH2OH, CH2CH2NH2 or where R' is OH, SH, NH2, CN, CQOH, C,-Ci8-alkyl or Ci-Cig-alkoxy, or the salts thereof, with the exceptions of ethyienediaminetetracetic acid and N-hydroxyethylenediaminetriacetic acid and salts thereof to a hydroxyiamine solution. The examples which follow illustrate the invention without limiting it. The determination of the hydroxyiamine concentrations R' is preferably in the ortho position and in particular is OH, COOH or a branched (bulky) alkyl radical, such as isopropyl, tert-butyl etc. is — X-f-NR— BH— B and X are CHjCH;-, R is CHjCOOH, CHjCHjCOOH, CHjCH^OH, CH2CH2NH2, NHC0R5 or CSSH or is a bridge as defined above, R^ is as defined above and Ri to R* are H or alkyl. Particularly preferred compounds in this context are: a weakly crosslinked polyethyleneimine with an average molecular weight in the range from 1,000 to 2,000,000; carboxymethylated polyethyleneimines with a degree of substitution of from 25 to 98 % and an average molecular weight in the range from 1,500 to 1,500,000; carboxyethylated polyethyleneimines with a degree of substitution of from 5 to 50 % and an average molecular weight in the range from 1,000 to 1,500,000; partially amidated polyethyleneimines(one or two of the radicals Ri to R* are Cj to Cig-acyl) with a degree of substitution of from 5 to 50% and an average molecular weight in the range from 1,000 to 1,500,000; polyether-crosslinked polyethyleneimines with an average molecular weight in the range from 50,000 to 1,500,000; hydrophobically modified polyethyleneimines (R = -CH2CH2NHCOR5, where RS is CHR^CORS and R* is Cu to Cig-alkyl, especially hexadecyl) with a degree of substitution of from 1 to 7 % and an average molecular weight in the range from 1,500 to 1,500,00 [sic]. These polymers are obtainable by reacting the corresponding ethyleneimines (R = CH2CH2NH2) with the corresponding alkyl diketenes; hydroxyethyl-substituted polyethyleneimines with a degree of substitution of 80 to 100 % and an average molecular weight in the range from 1 to 2,000,000; polyethyleneimine dithiocarbamates (R ~ CSSH] with a degree of substitution of from 30 to 60 % and an average molecular weight of from 2,000 to 1,000,000, and the sodium salts thereof. Some of the above polyethyleneimines are commercially obtainable, and are marketed, for example, by BASF AG under the name According to a further preferred embodiment the stabilized, hydroxylamine solution comprises as stabilizer a compound of the formula I in which A is cyclohexylene or -CHjCHz- and Ri to R* are CHjCOOH or -CH2— preferably CHjCOOH, where R' is OH, SH, NH; or COOH. With particular preference these compounds are trans-1, 2-diaminocyclohexane-N,N,N ' ,N'--tetraacetic acid and/or N,N' -di( 2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid and the salts thereof. The compounds of the formula I are known and commercially available or can be prepared by analogy with known methods. The novel stabilized hydroxylamine solutions comprise the compounds of formula I in a quantity which is sufficient for stabilization. They preferably contain from 0.001 to 20 % by weight (from a 0 to 200,000 ppm), in particular from 0.001 to 10 by weight, particularly preferably from 0.01 to 5 % by weight, very particularly preferably from 0.02 to 2 % by weight, of a compound of the formula I, based on the hydroxylamine content. The concentration of hydroxylamine is in general 1 - 100 % by weight, in particular 1 - 70 * by weight, based on the overall weight of the solution. The stabilizer can be added prior to or following neutralization of the hydroxylamine salt, but preferably prior to the neutralization. which is carried out in the examples is done by redox titration. Examples: 20 ml of 50 I strength aqueous hydroxylamine solution were charged to a 50 ml round-bottomed glass flask, and 500 ppm (m/m) of stabilizer of formula I, based on the mass of hydroxylamine, were added in each case. The flask was maintained at room temperature or heated with an oil bath to 100°C and maintained at this temperature. The hydroxylamine contents of the stabilized solutions at room temperature and at 100°c were determined by redox titration after defined periods. For this purpose, defined quantities of sample were withdrawn from the solutions, boiled for 5 minutes with excess ammonium iron(III) salt solution in sulfuric acid, and the iron(II) salt formed was back-titrated with cerium(IV) salt solution. The end point was determined potentiometrically. Table 1 gives the results at room temperature while Table 2 gives those at lOO'^C. In order to demonstrate the outstanding stabilizing action of the compounds of formula I on hydroxylamine solutions, measurements with unstabilized hydroxylamine solutions, and with hydroxylamine solutions stabilized using ethylenediaminetetraacetic acid (EDTA), are shown for comparison. WE CLAIM". 1. A process for preparing a stabilized hydroxylamine solution comprising the step of adding a stabilizer selected from at least one compound of the formula I 0) in which A is C2-C6-alkylene, C3-C6-alkenylene, C3-C6-alkynylene, C5-C6-cycloalkylene, C5-C6-cycloalkenylene, an aromatic C6-C10-hydrocarbon radical, phenylamino, o-m- or p-xylylene, a 5- or 6-membered saturated or unsaturated heterocycle having a nitrogen atom, said radicals being able to contain 1, 2 or 3 substituents which are selected independently of one another from C1-C18-alkyl, C1-C18-alkoxy or hydroxyl, or is in which B and X are -CH2CH2- or -CH2CH2CH2-, n is 10 - 50,000, R is H, C1-C18-alkyl, ethylene or propylene which is substituted by OH, NH2, NHCOR5 or COOH, or is CSSH, CH2CN or CH2P03H2, or is a bridge to a nitrogen atom of another polyethylene mine or polyproyleneimine chain, the bridge being formed by or where b and p independently of one another are 1 - 15, R5 isH, C1-C18-alkylor CHR6COR6 where R6 is C12-C18-alkyI, R1, R2, R3 and R6 independently of one another are H, CH2COOH, CH2P03H2, C1-C18-alkyl, C1-C19-acyl, CH2CH2OH, CH2CH2NH2 or where R7 is OH, SH, NH2, CN, COOH, C1-CI8-alkyl or C1-Cl8-alkoxy, or the salts thereof, with the exceptions of ethylenediaminetetracetic acid and N- hydroxyethylenediaminetriacetic acid and salts thereof to a hydroxylamine solution. 2. The process as claimed in claim 1, wherein the stabilizer comprises at least one compound of the formula I or a salt thereof in which A is C2-C6-alkylene, C3-C6-alkenylene, C5-C6-cycloalkylene, an aromatic C6-C10-hydrocarbon radical, phenylamino or B and X are -CH2CH2- and n, R, and R1 to R4 are as defined in claim 1. 3. The process as claimed in claim 2, wherein the stabilizer comprises at least one compound of the formula I or a salt thereof in which A is C2-C6-alkylene, C5-C6-cycloalkylene or and B, X, n and R1 to R4 are as defined in claim 2. 4. The process as claimed in claim 1, wherein the stabilizer comprises at least one compound of the formula I or a salt thereof in which A is C2-Ce-alkylene or C5-C6-cycloalkylene and R1 to R4 independently of one another are CH2COOH, CH2P03H2 or where R7 is as defined in claim 1. 5. The process as claimed in claim 4, wherein the stabilizer comprises at least one compound of the formula I or a salt thereof in which A is cyclohexylene or -CH2CH2- and R1 to R4 independently of one another are CH2COOH or where R7 is OH, SH, NH2 or COOH. 6. The process as claimed in claim 5, wherein the stabilizer is trans-l,2-diaminocyclohexane-N,N,N',N'-tetraacetic acid and/or N,N'-di(2-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid. 7. The process as claimed in claim 1, wherein the stabilizer comprises at least one compound of the formula I or a salt thereof in which A is B and X are -CH2CH2-, n is 10 to 50,000, R is CH2COOH, CH2CH2COOH, CH2CH2OH, CH2CH2NH2, NHCOR5 or CSSH or is a bridge as defined in claim 1 to a nitrogen atom of another polyethylene mine or polypropylene mine chain, R5 is as defined in claim 1 and R1 to R4 independently of one another are H, Ci-Ci8-alkyl or Ci-C19-acyl. 8. The process as claimed in any of the preceding claims, wherein the stabilizer is the hydroxylamine salt of a compound of the formula I containing acidic groups. 9. The process as claimed in any of the preceding claims, wherein 0.001 - 20% by weight, in particular 0.001 - 10% by weight, preferably 0.01 to 5% by weight, particularly preferably 0.02-2% by weight, of stabilizer, based on hydroxylamine, is brought into contact with the hydroxylamine solution. 10. A process for preparing a stabilized hydroxylamine solution substantially as herein described.

Documents:

2219-mas-1996 abstract duplicate.pdf

2219-mas-1996 abstract.pdf

2219-mas-1996 claims duplicate.pdf

2219-mas-1996 claims.pdf

2219-mas-1996 correspondence-others.pdf

2219-mas-1996 correspondence-po.pdf

2219-mas-1996 description (complete) duplicate.pdf

2219-mas-1996 description (complete).pdf

2219-mas-1996 form-2.pdf

2219-mas-1996 form-26.pdf

2219-mas-1996 form-4.pdf

2219-mas-1996 form-6.pdf

2219-mas-1996 others.pdf

2219-mas-1996 petition.pdf