Process for preparing an impact resistant thermoplastic graft copolymer composition

A process for the preparation of an impact resistant thermoplastic graft copolymer composition from a small particle sized synthetic rubber latex, comprising the steps of:

• 1. agglomerating 100 parts by weight in terms of the solids content of a synthetic rubber latex (A) selected from the group consisting of polybutadiene, copolymers containing at least 50% by weight 1,3-butadiene, butadiene-unsaturated nitrile copolymers, butadiene-acrylate copolymers, butadiene-methacrylate copolymers, terpolymers or multipolymers containing at least 50% by weight 1,3-butadiene, polychloroprene, chloroprene copolymer and a homopolymer or copolymer of at least 50% by weight of alkyl acrylate having 1 to 12 carbon atoms in the alkyl group containing small-sized rubber particles by adding 0.1 - 5 parts by weight, in terms of the solids content, of a carboxylic acid containing copolymer latex (B) having a pH of at least 4, said copolymer latex being prepared by polymerizing a mixture of monomers comprising 5 - 20% by weight of at least one monomer selected from the group consisting of acrylic acid, methacrylic acid, itaconic acid and crotonic acid and 95 - 80% by weight of alkyl acrylate having 1 to 12 carbon atoms in the alkyl group, in the presence of at least one anionic emulsifier, and adjusting the pH of the mixed latexes (A) and (B) to not less than 6;
• 2. stabilizing the agglomerated latex with at least one nonionic emulsifier in an amount of 0.1 - 5% by weight of the dry rubber to be stabilized;
• and
• 3. grafting 93 - 30 parts by weight of a monomer or mixture of monomers, which is capable of producing a glassy thermoplastic polymer having a glass transition temperation of not less than 50.degree. C in the presence of or onto 7 - 70 parts by weight in terms of solids content of the agglomerated and stabilized synthetic rubber latex.