Blends of styrene-butadiene copolymers

Abstract

Polymer blend comprising 95 to 100% of a component A) and 0 to 5% of additives, where A) is consisting of polymers A1) to A4): A1) 50 to 75% of a star shaped block copolymer A1 which comprises at least 2 terminal vinylaromatic hard blocks S and diene soft blocks B, where the proportion of the hard blocks S is from 65 to 90%, and Mn of block S is 35000 to 200000; A2) 5 to 15% of block copolymer A2 which comprises 2 terminal vinylaromatic hard blocks S1 and S2 and random copolymer blocks (B/S) consisting of 20 to 60% vinylaromatic monomers, and 80 to 40% dienes where the proportion of blocks S1 and S2 is 40 to 60%; and Mn of blocks S1 is 35000 to 200000, and Mn of blocks S2 is 5000 to 30000 and the molar S1/S2 ratio is 1:0.5 to 1:10; A3) 3 to 10% of an block copolymer A3 built up from vinylaromatic hard blocks S and from random soft blocks B/S consisting of 60 to 30% vinylaromatic monomers and 40 to 70% dienes, where the diene content is less than 50% and the proportion of the soft phase is at least 60%; and A4) 10 to 35% polystyrene A4; whereby the ratio of A1) to A2) to A3) is from 7 : [1.2 to 1.9] : [0.5 to 12], have particular mechanical properties.