Thermoplastic molding material based on graft copolymers with bimodal particle size distribution and a two-step graft shell

Claim 1

A thermoplastic molding material containing A. a first graft copolymer A comprising A1: from 55 to 75% by weight, based on A, of an elastomeric, crosslinked acrylate polymer A1 having a mean particle diameter (weight average) of from 50 to 150 nm as the graft base, and A2: from 45 to 25% by weight, based on A, of a graft shell A2 made from a vinyl-aromatic monomer and a polar, copolymerizable, ethylenically unsaturated monomer in a weight ratio of from 80:20 to 65:35, B: a second, separately prepared graft copolymer B comprising B1: from 50 to 80% by weight, based on B, of an elastomeric, crosslinked acrylate polymer B1 which is different from A1 and has a mean particle diameter (weight average) in the range from 200 to 700 nm as the graft base, B2: a first graft shell B2 comprising from 5 to 30% by weight, based on B, of a vinyl-aromatic monomer and B3: a second graft shell B3 comprising from 15 to 40% by weight, based on B, of a mixture of a vinyl-aromatic monomer B31 and a polar, copolymerizable, ethylenically unsaturated monomer B32 in a B31:B32 weight ratio of from 90:10 to 60:40, and C: a hard matrix C comprising a copolymer or mixture of two copolymers prepared from monomers selected from the group consisting of styrene, α-methylstyrene, acrylonitrile, methyl methacrylate and phenylmaleimide, wherein the A1:B1 weight ratio of the graft bases is in the range from 95:5 to 35:65, and the proportion of A1 plus B1 in the graft bases is from 10 to 35% by weight, based on the molding material comprising A, B and C.