Associative thickeners based on methacrylate
Provided is a process for the preparation of methacrylate-based polymers soluble in aqueous medium, which can be used, in particular, as associative and non-associative thickeners.
1. A process for the preparation of polymers P, the process comprising polymerizing at least one polymer A and at least one polymer B, wherein
(A) polymer A comprises, in polymerized-in form:
a1) 30 to 70% by weight of C 1 -C 4 -alkyl(meth)acrylate,
a2) 30 to 70% by weight of (meth)acrylic acid,
a3) 0.1 to 20% by weight of monomers substituted with a C 8 -C 30 -radical, and
a4) 0 to 20% by weight of further monomers different from a1) to a3), provided that the amounts of a1) to a4) add up to 100% by weight; and
(B) polymer B comprises, in polymerized-in form:
b1) at least one monomer b1) which carries at least one amide group, and
b2) optionally further monomers b2) different from b1);
wherein one of the polymers A or B is prepared in the presence of the other polymer in each case and
wherein the preparation of polymer A or B is started when in the region of from 10 to 50% by weight if all monomers to be used for the preparation of the other polymer in each case have been polymerized and is ended before more than 80% by weight of the amount of all monomers to be used for the preparation of the other polymer have been polymerized.
2. The process according to claim 1 , wherein the preparation of the polymers A and B takes place by radical emulsion polymerization.
3. The process according to claim 1 , wherein the polymer P comprises the polymers A and B in a weight ratio A:B in the range from 50:50 to 98:2.
4. The process according to claim 1 , wherein at least one monomer b1) is methacrylamide.
5. The process according to claim 1 , wherein a1) comprises ethyl acrylate and a2) comprises methacrylic acid.
6. The process according to claim 2 , wherein the polymer P comprises the polymers A and B in a weight ratio A:B in the range from 50:50 to 98:2.