ELASTOMERIC GRAFT COPOLYMER HAVING CORE-SHELL-STRUCTURE

Elastomeric particulate copolymers having a core/shell structure composed of a core (a) comprising an organosilicon polymer and an organopolymeric shell (c) or two shells (b) and (c), the inner shell (b) comprising an organosilicon polymer, and the copolymer being composed of (a) from 0.05 to 95 percent by weight, based on the total weight of the copolymer, of a core polymer (R2SiO2/2)x.(RSiO3/2)y.(SiO4/2)z where x=0 to 99.5 mol%, y=0.5 to 100 mol% and z=0 to 50 mol%, (b) from 0 to 94.5 percent by weight, based on the total weight of the copolymer, of a polydialkylsiloxane shell comprising (R2SiO2/2) units, and (c) from 5 to 95 percent by weight, based on the total weight of the copolymer, of a shell comprising an organopolymer of monoolefinically unsaturated monomers, and the particles have a particle size of from 10 to 300 nm and a monomodal particle size distribution having a maximum polydispersity index sigma 2=0.2. The invention furthermore relates to a process for preparing the graft copolymers. The graft copolymers of this invention are particularly suitable for use as modified thermoplastics or for use as additives for modifying polymers.