Patent ID: 8901227

Claim:
A finely divided, cationic, aqueous polymer dispersion, obtained by a process comprising: (I) solution polymerizing, in a partly to completely water-miscible solvent, in the presence of a polymerization initiator, a first monomer mixture comprising (a) 15 to 40% by weight of a mixture comprising (a1) a (meth)acrylate comprising at least one selected from the group consisting of an amino group and a quaternary ammonium group, and (a2) a (meth)acrylamide comprising at least one selected from the group consisting of an amino group and a quaternary ammonium group, (b) 40 to 85% by weight of at least one optionally substituted styrene, (c) 0.5 to 5% by weight of at least one ethylenically unsaturated monomer comprising an acid group, and (d) 0 to 20% by weight of at least one nonionic, ethylenically unsaturated monomer differing from (b), wherein a sum of (a)+(b)+(c)+(d) is 100% by weight, to obtain a cationic prepolymer; then (II) adding water to a solution/dispersion of the cationic prepolymer, to obtain an aqueous solution of the cationic prepolymer; and thereafter (III) in the aqueous solution of the prepolymer, emulsion polymerizing, in the presence of the polymerization initiator, a second monomer mixture comprising (i) 0 to 29% by weight of styrene, and (ii) 71 to 100% by weight of n-butyl acrylate, tert-butyl acrylate, or a mixture of n-butyl acrylate and tert-butyl acrylate in a weight ratio range of 3:1 to 1:3, wherein a sum of (i)+(ii) is 100% by weight, and wherein at least one selected from the group consisting of the solution polymerizing (I) and the emulsion polymerizing (III) is performed in the presence of 0 to 10% by weight of at least one polymerization regulator.