Patent ID: 6235810
Filing Date: 2001-05-22
Classification: C08F,Y10S

Abstract:
A process for preparation of hollow polymer particle latexes by emulsion copolymerization with water soluble initiator and anionic surfactant, characterized in the following stages:a) preparation by emulsion polymerization of a seed latex of a copolymer containing methyl methacrylate and methacrylic acid monomer units;b) preparation by emulsion polymerization of a latex of a highly carboxylated copolymer containing methyl methacrylate monomer units, monoethylenically unsaturated carboxylic acid monomer units and a cross-linking agent and optionally containing vinyl aromatic monomer units, in the presence of the seed latex prepared in stage(a);c) in the presence of the preparation by emulsion polymerization of an intermediate shell comprising a copolymer of methyl methacrylate, an acrylic acid ester, a monoethylenically unsaturated carboxylic acid and a cross-linking agent, and optionally containing vinyl aromatic monomer units, wherein said intermediate shell copolymer is prepared in the presence of the highly carboxylated latex synthesized at stage (b), and has a glass transition temperature below 80.degree. C.;d) swelling the particles prepared at stage (c) by the addition of a volatile basic compound;e) preparation by emulsion polymerization of a hard shell in the presence of the swollen expanded particles prepared in stage (d), said hard shell comprising a copolymer of a vinyl aromatic compound, acrylonitrile and/or methyl methacrylate, and a cross-linking agent, said hard shell having a glass transition temperature above 80.degree. C.; andf) optional preparation of an external shell.