Patent ID: 7332565

Claim:
A method for reducing an amount of residual monomer in an aqueous polymer dispersion, comprising: treating the aqueous polymer dispersion with an initiator system; wherein: the initiator system comprises: a) from 0.001 to 5% by weight, based on a total monomer amount used to prepare the polymer dispersion, of an inorganic salt of persulfuric acid; b) from 0.005 to 5% by weight, based on the total monomer amount used to prepare the polymer dispersion, of a methyl ketone; and c) optionally, catalytic amounts of at least one metal ion that is able to exist in a plurality of valence states; and the methyl ketone is a compound of the formula R1—C(═O)—CH 3 , where R1 is: an unsubstituted C 1 to C 5 alkyl group; a C 1 to C 5 alkyl groups substituted with one or more functional groups selected from the group consisting of halogens and alkoxy groups —O—R 2 , where R 2 is an unsubstituted C 1 to C 5 alkyl group; or an olefinically unsaturated group selected from the group consisting of 1-propenyl, 2-propenyl, isopropenyl, 1-butenyl, 2-butenyl, 3-butenyl, 1-methyl-1-propenyl, 1-methyl-2-propenyl, 2-methyl-1-propenyl, 2-methyl-1-propenyl, 1-pentenyl, 2-pentenyl, 3-pentenyl, 4-pentenyl, 1-methyl-1-butenyl, 1-methyl-2-butenyl, 1-methyl-3-butenyl, 2-methyl-1-butenyl, 2-methyl-2-butenyl, 2-methyl-3-butenyl, 3-methyl-1-butenyl, 3-methyl-2-butenyl, 3-methyl-3-butenyl, 1-ethyl-1-propenyl, 1-ethyl-2-propenyl, 2-ethyl-1-propyl-, 2-ethyl-2-propenyl, 1,2-dimethyl-1-propenyl, 1,2-dimethyl-2-propenyl, 1,1-dimethyl-1-propenyl and 2,2-dimethyl-1-propenyl groups.