Stjerne-blokk-kopolymer av en vinylaromatisk monomer og et konjugert dien, dets fremstilling samt blandinger inneholdende kopolymerene og krystallinsk polystyren

摘要

Star-shaped block copolymer of general formula [S1-S2-(B1/S3)-B2]m-X-[B2-(B1/S3)-S2 ]n in which X denotes a polyfunctional radical originating from a coupling agent, m and n denote nonzero integers such that m + n is equal to 3 or 4, each of S1 and S2 denotes a block of a polymer of at least one vinylaromatic monomer, B2 denotes a block of a polymer of at least one conjugated diene, (B1/S3) denotes a block of a statistical copolymer of at least one vinylaromatic monomer and of at least one conjugated diene, 40 to 75 % by weight of (B1/S3) consisting of units originating from vinylaromatic monomer, characterised in that the block B2 contains more than 40 % by weight and less than 90 % by weight of all conjugated diene present in the said star-shaped block copolymer. The invention also relates to the process for obtaining this copolymer. The compositions including this copolymer and crystal polystyrene exhibit remarkable mechanical properties and transparency.