Dunkelspersers

Claim 1

A process for preparing an improved impact modifier composition comprising an intimate admixture of from about 99.5 to about 96 parts by weight of an elastomeric impact modifier polymer prepared by emulsion polymerization and from about 0.5 to about 4 parts by weight of a dunkelsperser polymer or copolymer formed from at least 50 weight percent of at least one monomer selected from the group consisting of styrene, substituted styrene, an olefin, and an unsaturated ester of an organic acid different from the methyl ester of methacrylic acid, said improved impact modifier composition being formed by a free radical initiated polymerization of said monomer or monomers in the presence of an adjusted emulsion containing said elastomeric impact modifier polymer by adding an emulsifier to reduce the surface tension of the emulsion containing said elastomeric impact modifier polymer to or below its critical micelle concentration; heating the adjusted emulsion to a temperature sufficient to initiate the subsequent free radical initiated polymerization of said monomer or monomers; adding to said heated, adjusted emulsion a second emulsion containing said monomer or monomers and at least one free radical initiator; allowing polymerization of said monomer or monomers to form a dunkelsperser polymer in intimate admixture with said elastomeric impact modifier polymer; and isolating the improved impact modifier composition from said emulsion.