Patent ID: 7662871

Claim:
An aqueous paper size composition, which comprises: dispersed polymer particles; at least one degraded starch having a molecular weight Mn of from 500 to 40,000; at least one water soluble catalyst; and at least one complexing agent; wherein the dispersed polymer particles comprise a copolymer consisting of (a) from 50 to 99% by weight of styrene and/or methylstyrene, (b) 1 to 50% by weight of 1,3-butadiene and/or isoprene and (c) from 0 to 40% by weight of other ethylenically unsaturated copolymerizable monomers, the sum of the monomers (a), (b) and (c) always being 100%, the copolymer is obtained by free radical copolymerization in the presence of from 10 to 40% by weight, based on the weight of monomers (a), (b) and (c), of the at least one degraded starch having a molecular weight Mn of from 500 to 40,000, the at least one water soluble redox catalyst comprises hydrogen peroxide and at least one heavy metal salt selected from the series consisting of cerium, manganese and iron(II) salts, and the mean particle size of the dispersed polymer particles is from 50 to 100 nm.