| abstract |
Finely divided, cationic, aqueous polymer dispersion which is obtainable by emulsion polymerisation of ethylenically unsaturated monomers in an aqueous liquid containing a cationic prepolymer as a dispersant, wherein the cationic prepolymer is prepared in the presence of at least one polymerisation initiator by polymerisation of (a) from 15 to 45% by weight of at least one ethylenically unsaturated monomer comprising at least one quaternary ammonium group; (b) from 5 to 80% by weight of at least one optionally substituted styrene; (c) from 0 to 50% by weight of at least one C 1-12 alkyl (meth) acrylate; (d) from 0 to 10% by weight of at least one ethylenically unsaturated monomer comprising an acid group; (e) from 0 to 10% by weight of at least one ethylenically unsaturated monomer comprising an amine group; and (f) from 0 to 20% by weight of at least one non-ionic ethylenically unsaturated monomer differing from (b), (c) and (e), the sum of (a)+(b)+(c)+(d)+(e)+(f) being 100% by weight, in a first emulsion polymerisation in the presence of at least one non-ionic emulsifier, and thereafter, in the aqueous liquid containing the cationic prepolymer a second emulsion polymerisation is carried out, in the presence of at least one polymerisation initiator, of a monomer mixture comprising (i) from 10 to 70% by weight of at least one of an optionally substituted styrene or (meth) acrylonitrile; (ii) from 30 to 90% by weight of at least one CMS alkyl (meth) acrylate; (iii) from 0 to 30% by weight of at least one vinyl ester of linear or branched C 1-30 carboxylic acids; and (iv) from 0 to 30% by weight of at least one non-ionic ethylenically unsaturated monomer differing from (i), (ii) and (iii), the sum of (i)+(ii)+(iii)+(iv) being 100% by weight, and the first emulsion polymerisation and/or the second emulsion polymerisation is optionally carried out in the presence of from 0 to 10% by weight of at least one polymerisation regulator. The polymer dispersions according to the present invention are suitable for use as sizing agents for paper, board and card board. |