Method for making an alkali-soluble emulsion copolymer

Abstract

An emulsion polymerization process for making a low molecular weight alkali-soluble copolymer of a water insoluble monoethylenically unsaturated aromatic monomer and methacrylic acid, includes heating an aqueous reaction mixture, said reaction mixture having a pH of less than or equal to about 4.5 and including from about 25 parts by weight to about 75 parts by weight of the water insoluble monoethylenically unsaturated aromatic monomer; from about 25 parts by weight to about 75 parts by weight methacrylic acid; a polymerization initiator; a reducing agent; a catalyst effective for promoting decomposition of the polymerization initiator in the presence of the reducing agent; and an amount of a chain transfer agent effective to limit copolymer weight average molecular weight to a range of about 2,000 to about 40,000; to a temperature greater than or equal to about 75.degree. C.; and maintaining the reaction mixture at a temperature greater than or equal to about 75.degree. C. for a period of time effective to allow formation of the copolymer.

Dependencies are inferred from the claim text.