Abstract: There is described an improved process for the discontinuous suspension polymerization of alkenyl-aromatic compounds, which comprises re-using the aqueous polymerization medium, after separation of the polymer beads, as the polymerization medium of a subsequent polymerization. Monomer-soluble and water-soluble initiators and, optionally fresh water and dispersing agent, are added. Re-using the aqueous polymerization medium does not negatively affect the color and mechanical properties of the polymer obtained. The process of the invention results in considerable saving of energy.

Abstract: There is disclosed an improved bulk-suspension process for polymerizing vinyl aromatic monomers in the presence of an ethylene-propylene-nonconjugated diene-rubber, which comprises using, in the suspension polymerization step, peroxy-carbonic esters as the polymerization initiator. The process of the invention yields products having improved notched impact strength, weatherability and elongation at break combined with a good shear stability.

Abstract: The invention relates to novel impact resistant graft copolymers of a vinyl aromatic on an ethylene/propylene/tercomponent rubber especially characterized by an improved notched impact strength and resistance to atmospheric corrosion, and a process for their preparation. Said copolymers are obtained by a two-step mass/suspension polymerization process characterized by the presence of oxygen, preferably by the presence of air, at a pressure of from 0.05 to 10 atmospheres gauge during the course of the mass polymerization step.