Process of preparing A-B-C elastomeric block copolymers

Claim 1

In a process for the preparation of block copolymers of the general formula A--B--C including polymerizing at least one monomer to form a living polymer block A, adding a further monomer and continuing polymerization to form polymer block B bound to polymer block A, and continuing polymerization while adding at least one monomer to form terminal polymer block C, thereby producing an A--B--C block copolymer, wherein each of polymer blocks A and C consists of a non-elastomer homopolymer or copolymer having a glass transition temperature over 25°C. and a number average molecular weight between 200 and 100,000, and polymer block B consists of a conjugated diene having a glass transistion temperature below -10° C. and a number average molecular weight between 25,000 and 1,000,000; and wherein the contaminants contained in the monomers forming blocks A and C are deactivated, the improvement comprising introducing the conjugated diene monomer forming polymer block B containing therein contaminants which have not been deactivated and are capable of killing 1-50% of the living polymer block A.