High-impact polystyrene composition and production thereof

Claim 1

A high-impact polystyrene composition comprising a major amount of (1) polystyrene or (2) a copolymer of styrene and at least one monomer copolymerizable with styrene, the amount of said monomer being at most 50% by weight based on the total weight of the styrene and the monomer, and a minor amount of a diene polymer, the diene polymer having been prepared from more than 50% by weight of 1,3-butadiene and less than 50% by weight of at least one conjugated diolefin selected from the group consisting of isoprene; 1,3-pentadiene; 2,3-dimethyl-1,3-butadiene; 2-ethyl-1,3-butadiene; 2,3-diethyl-1,3-butadiene; 2-phenyl-1,3-butadiene; and 2,3-diphenyl-1,3-butadiene; by solution polymerization using an organic lithium compound as catalyst and having been grafted onto the polystyrene or styrene copolymer by free-radical polymerization and forming a two-phase structure, and the diene polymer having a (1) 1,2-vinyl content of more than 15 to 35% and cis-1,4 content of 20 to 45%, and (2) Mooney viscosity (ML 1+4 ) of 25 to 85, solution viscosity of styrene containing 5% by weight of the diene polymer (SV) at 25° C. being 50 to 200 cps, and 1.5 ML 1+4 ≦ SV <3.0 ML 1+4 .