Patent ID: 7812106

Claim:
A process for preparing a polymer emulsion by emulsion polymerization, comprising: (a) providing an aqueous emulsion, the emulsion comprising: (i) a major amount, based on the polymerizable components of the emulsion, of at least one substantially water-insoluble olefinically unsaturated monomer; (ii) from about 1% to about 6% by weight of a water-soluble monomer, based on the combined weight of the monomers (i) and (ii), selected from the group consisting of acrylonitrile, methacrylonitrile, C1-C8 semiesters of maleic acid, C1-C8 semiesters of fumaric acid, acrylic acid, methacrylic acid, maleic acid, fumaric acid, crotonic acid, itaconic acid, acrylamide, N-methylolacrylamide and combinations thereof; (iii) at least one copolymerizable emulsifier; and (iv) water, wherein the copolymerizable emulsifier comprises at least one olefinically unsaturated ester of formula (I): HOOC—CH═CH—COO—(BO) z (PO) y (EO) x —R 1 (I) wherein R 1 represents an alkyl group or alkenylphenol group having from 8 to 24 carbon atoms, BO represents a butylene oxide unit, PO represents a propylene oxide unit and EO represents an ethylene oxide unit and each of x, y and z independently represents a number of from 0 to 50, with the proviso that at least one of x, y and z is not 0, and wherein the carboxylic acid group is completely or partly neutralized; and (b) emulsion polymerizing at least a portion of said aqueous emulsion (a) to form a polymer emulsion.