Method for producing water-soluble or water-swellable polymerizates with a very low residual monomer content, products produced according to this method and the use thereof
View Patent ↗The invention relates to a process for producing water-soluble or water-swellable polymer products from acrylic acid and/or acrylic acid derivatives partially or completely neutralized with nitrogen compounds and with exceedingly low levels of residual monomers, which process is characterized by subsequent heating of the polymer product at temperatures of from 120 to 240° C. The polymers produced accordingly are suitable for use as flocculants, dispersants and absorbers.
1. A process for producing a water-soluble or water-swellable polymer or copolymer comprising:
providing an acid monomer alone, or in combination with at least one comonomer;
partially or completely neutralizing said at least one monomer with at least one basic nitrogen compound;
free-radical polymerizing said at least one monomer alone, or in combination with said at least one comonomer to form said water-soluble or water-swellable polymer or copolymer,
wherein said free-radical polymerization is started at a temperature of from 0 to 50° C and is performed in aqueous solution at a maximum temperature of no more than 102-104° C, to provide an aqueous polymer or copolymer solution or an aqueous polymer or copolymer gel; and,
subsequent to completion of said free-radical polymerization, heating said water-soluble or water-swellable polymer or copolymer at a temperature of from 120° to 240° ;
wherein said heating is caried out for a time period between 10 minutes and 2 hours;
wherein the water-soluble or water-swellable polymer or copolymer has a content of residual monomer of less than 50 ppm.
2. The process according to claim 1 , wherein said nitrogen compound is selected from the group consisting of ammonia, ammonium hydroxide, hydroxylamine, alkanolamines, alkylamines and mixtures thereof.
3. The process according to claim 1 , wherein said nitrogen compound is selected from the group consisting of ammonia, ammonium hydroxide, monoethanolamine, diethanolamine and mixtures thereof.
4. The process according to claim 1 , wherein said at least one acid monomer is neutralized with said nitrogen compound up to a neutralization level of from 10 to 100%.
5. The process according to claim 1 , wherein monomers based on acrylic acid, methacrylic acid or derivatives of these carboxylic acids are subjected to polymerization.
6. The process of claim 1 , wherein said comonomer is vinyl acetate.
7. The process according to claim 1 , wherein at least one crosslinker based on a bi- or polyfunctional monomer is used in addition.
8. The process according to claim 1 , wherein the polymer or copolymer is heated at a temperature of from 140 to 180° C.
9. The process according to claim 1 , wherein the water-soluble or water-swellable polymer or copolymer has a content of residual monomer of less than 30 ppm.
10. The process according to claim 1 , wherein the water-soluble or water-swellable polymer or copolymer has a content of residual content of acrylamide of less than 10 ppm.
11. The process according to claim 1 , wherein said nitrogen compound is selected from the group consisting of ammonia, ammonium hydroxide, aliphatic monoamines, aliphatic polyamines, cycloaliphatic monoamines, cycloaliphatic polyamines, aromatic monoamines, aromatic polyamines, heterocyclic amines, hydroxylamine, alkanolamines and mixtures thereof.
12. The process according to claim 1 , wherein said at least one monomer is selected from the group consisting of acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, vinyl sulfonic acid, acrylamidopropanesulfonic acid, and mixtures thereof.
13. The process according to claim 1 , wherein said at least one comonomer is selected from the group consisting of acrylonitrile, methacrylonitrile, N,N-dimethylacryl amide, vinylpyrrolidone, vinylpyridine, vinyl acetate, hydroxyl group-containing esters of polymerizable acids, amino group-containing esters of polymerizable acids, amino group-containing amides of polymerizable acids, ammonium group-containing esters of polymerizable acids, ammonium group-containing amides of polymerizable acids, C 1 -C 10 alcohol esters of acrylic acid, C 1 -C 10 alcohol esters of methacrylic acid, C 1 -C 10 alcohol esters of a mixture of acrylic acid and methacrylic acid, esters of acrylic acid and methacrylic acid with styrene, esters of methacrylic acid with styrene, esters of methacrylic acid with alkylated styrene, esters of a mixture of acrylic acid and methacrylic acid with alkylated styrene.
14. The process according to claim 8 , wherein said heating is carried out for a time period between 10 minutes and 1 hour.
15. The process according to claim 1 , wherein said heating is carried out for a time period between 10 minutes and 1 hour.
16. The process according to claim 1 , wherein said free radical polymerization is started at a temperature of from 5 to 25° C.
17. The process according to claim 1 , wherein the polymer or copolymer is heated at a temperature of 160° C or 180 ° C.
18. The process according to claim 1 , wherein said heating is carried out for a period between 10 minutes and 90 minutes.