Patent ID: 7312277

Claim:
A mass polymerized rubber-modified monovinylidene aromatic copolymer composition comprising: (i) a continuous matrix phase comprising a copolymer of a monovinylidene aromatic monomer and an ethylenically unsaturated nitrile monomer and (ii) a rubber component dispersed as discrete rubber particles in the matrix comprising (a) a polybutadiene rubber with a 5 weight percent solution viscosity in styrene at 25° C. of between 15 to 120 cP and (b) a styrene and butadiene block copolymer rubber wherein the rubber component has a polybutadiene content (PBD c ) equal to or greater than about 14 weight percent based on the weight of the copolymer composition and the matrix copolymer has a weight average molecular weight (Mw Matrix) represented by the formula: (Mw Matrix)≧510−22 *PBD c .