bimodal star blokcopolymere with good optical and elastic properties, and method for manufacture thereof

摘要

Bimodal star-block copolymers are disclosed containing from 60 to 90% by weight of an aromatic vinyl monomer and from 40 to l0% by weight of a conjugated diene, said copolymers having the general formula: (S-S1-B/S2-B1)m -X-(B1-S2/B-S1)n wherein X is a polyfunctional radical m and n are integers (being m/=n) the sum of which is from 3 to 20 and equal to the functionality degree of the radical X, S and S1 are polymer blocks of an aromatic vinyl monomer, B1 is an elastomeric copolymer of conjugated diene units, containing up to 20% of all the diene units of the copolymer, and B/S2 and S2/B are blocks of copolymers of aromatic vinyl monomer and conjugated diene of the random and/or tapered type.