Process for preparing acrylate copolymers
The present invention relates to a method of producing polymers by free-radical polymerization in solution, wherein the polymerization initiator used is an ethanol-soluble initiator, and the solution polymerization is carried out in an alcoholic solvent which comprises 5 to 50% by weight of water.
1. A method of producing polymers which comprise, in copolymerized form, a) at least 50% by weight of olefinically unsaturated compounds selected from the group consisting of C 1 -C 18 -alkyl (meth)acrylates and b) at least a further monomer which is an olefinically unsaturated free-radically polymerizable compound containing urethane groups, by free-radical polymerization in solution, in an alcohol-comprising solvent which, based on the solvent, comprises 5 to 50% by weight of water, wherein the polymerization of a polymerization mixture comprising a) and b) in solution is carried out until a residual monomer content of at most 10% by weight is achieved, based on the solids content of the polymerization mixture, in the presence of at least one ethanol-soluble initiator, and a subsequent further polymerization of the polymerization mixture is carried out in the presence of at least one water-soluble initiator.
2. The method according to claim 1 , wherein the solvent comprises water in the range from 15 to 45% by weight.
3. The method according to claim 1 , wherein the solvent comprises alcohol in the range from 55 to 85% by weight.
4. The method according to claim 1 , wherein the alcohol is selected from the group consisting of: ethanol, isopropanol and mixtures thereof.
5. The method according to claim 1 , wherein a) is selected from the group consisting of: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate and mixtures thereof.
6. The method according to claim 1 , wherein the ethanol-soluble polymerization initiator is selected from the group consisting of: ethanol-soluble diazo and peroxide compounds.
7. The method according to claim 1 , wherein the ethanol-soluble polymerization initiator is selected from the group consisting of: benzoyl peroxide, tert-amyl peroxipivalate, 2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile), 2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl 2,2′-azobis(2-methylpropionate), 2,2′-azobis(2-methylbutyronitrile), 1,1′-azobis(cyclohexane-1-carbonitrile), 2,2′-azobis[N-(2-propenyl)-2-methylpropionamide], 1-[(cyano-1-methylethyl)azo] formamide, 2,2′-azobis(N-butyl-2-methylpropionamide), and 2,2′-azobis(N-cyclohexyl-2-methyl-propionamide).
8. The method according to claim 1 , wherein the temperature at which the polymerization is carried out is in the range from 30 to 120° C.
9. The method according to claim 1 , wherein, following the polymerization, the alcohol used as solvent is removed by distillation.
10. The method according to claim 9 , wherein the polymer is neutralized in a range from 20% to 100% before the distillation.
11. The method according to claim 2 , wherein the solvent comprises alcohol in the range from 55 to 85% by weight.
12. The method according to claim 2 , wherein the alcohol is selected from the group consisting of: ethanol, isopropanol and mixtures thereof.
13. The method according to claim 3 , wherein the alcohol is selected from the group consisting of: ethanol, isopropanol and mixtures thereof.
14. The method according to claim 2 , wherein a) is selected from the group consisting of: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate and mixtures thereof.
15. The method according to claim 3 , wherein a) is selected from the group consisting of: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate and mixtures thereof.
16. The method according to claim 4 , wherein a) is selected from the group consisting of: methyl (meth)acrylate, ethyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, tert-butyl (meth)acrylate and mixtures thereof.
17. The method according to claim 2 , wherein the ethanol-soluble polymerization initiator is selected from the group consisting of: ethanol-soluble diazo and peroxide compounds.
18. The method according to claim 3 , wherein the ethanol-soluble polymerization initiator is selected from the group consisting of: ethanol-soluble diazo and peroxide compounds.