Process for the preparation of modified block copolymers

摘要

A process for preparing a modified block copolymer by graft-reacting at least one maleic acid compound with an aromatic vinyl compound/conjugated diene compound block copolymer containing at least one polymer block mainly composed of a conjugated diene compound and at least one polymer block mainly composed of an aromatic vinyl compound, the aromatic vinyl compound/conjugated diene compound weight ratio being within the range of 5/95 to 97/3, characterized in that said graft-reaction is carried out under conditions wherein the generation of radicals can be substantially inhibited. According to this process, it is possible to prevent gelation of the product in the graft-reaction, and the modified block copolymer obtained has excellent appearance characteristics, mechanical properties, and transparency.