Rubber-modified monovinylidene aromatic polymer compositions

An improved rubber-modified monovinylidene aromatic polymer composition comprising:

• (a) a matrix consisting of a homopolymer of a monovinylidene aromatic monomer, and
• (b) an elastomeric material (rubber), in an amount sufficient to toughen said composition, such elastomeric material being in the form of discrete particles dispersed throughout the matrix of the monovinylidene aromatic polymer and grafted with monovinyliden aromatic polymer;
• wherein the improvement comprises the dispersed rubber particles comprising the following three components:
• (1) a small particle component being from about 5 to about 85 weight percent of the rubber, the particles of this component having a volume average diameter of from about 0.04 to about 0.30 microns (.mu.);
• (2) a large eumulsion particle component being from about 5 to about 85 weight percent of the rubber, the particles of this component having a volume average diameter of from about 0.4 to about 3.0.mu.;
• and
• (3) a large mass particle component being from about 2 to about 90 weight percent of the rubber, comprising a rubber substrate having monovinylidene aromatic polymer grafted thereon and occuleded therein the rubber substrate comprising up to 9 percent by weight of a rubber-modified monovinylidene aromatic polymer prepared by a mass, mass-solution or mass-suspension polymerization process, which rubber-modified monovinylidene aromatic polymer is contained in the improved rubber-modified monovinylidene aromatic polymer composition the particles of this component having a volume average diameter of from aobut 0.6 to about 10.0.mu..