FINE-PARTICLE, CATIONIC, AQUEOUS POLYMER DISPERSIONS, METHOD FOR THE PRODUCTION THEREOF, AND USE THEREOF

Finely divided, cationic, aqueous polymer dispersions which are obtainable by emulsion polymerization of ethylenically unsaturated monomers in an aqueous solution of a cationic prepolymer as a dispersant, wherein first the cationic prepolymer is prepared in the presence of polymerization initiators by polymerization of (a) from 15 to 40% by weight of a mixture of at least two different (meth)acrylates which in each case have an amino group and/or quaternary ammonium group and/or (meth)acrylamides which in each case carry an amino group and/or quaternary ammonium group, (b) from 40 to 85% by weight of at least one optionally substituted styrene, (c) from 0.5 to 5% by weight of at least one ethylenically unsaturated monomer comprising acid groups and (d) from 0 to 20% by weight of at least one nonionic, ethylenically unsaturated monomer differing from (b), the sum of (a)+(b)+(c)+(d) being 100% by weight, in a solution polymerization in a partly to completely water-miscible solvent, and water is then added to the solution/dispersion of the prepolymer, and thereafter, in the aqueous solution of the prepolymer, an emulsion polymerization is carried out, in the presence of polymerization initiators, of a monomer mixture comprising (i) from 0 to 29% by weight of at least one optionally substituted styrene, (ii) from 50 to 100% by weight of at least one C1- to C18-(meth)acrylate, (iii) from 0 to 30% by weight of at least one vinyl ester of linear or branched C1-C30-carboxylic acids and (iv) from 0 to 30% by weight of at least one nonionic ethylenically unsaturated monomer differing from (i), (ii) and (iii), the sum of (i)+(ii)+(iii)+(iv) being 100% by weight, and the solution polymerization and/or emulsion polymerization is carried out in the presence of from 0 to 10% by weight of at least one polymerization regulator.