Patent ID: 7138456

Claim:
A process for the preparation of a block copolymer having one or more mono alkenyl arene polymer blocks and one or more controlled distribution copolymer blocks of a conjugated diene and a mono alkenyl arene, comprising the steps: a. polymerizing a mono alkenyl arene in a first reactor in the presence of an inert hydrocarbon solvent and an organolithium initiator whereby a living polymer block A1 terminated with a lithium ion is formed; b. adding to a second reactor an inert hydrocarbon solvent, 80 to 100% of the mono alkenyl arene monomer desired in the copolymer block B1, between 30 and 60% of the conjugated diene monomer desired in the copolymer block B1, and an effective amount of a distribution agent; c. transferring the living homopolymer block A1 to the second reactor and starting the polymerization of the mono alkenyl arene monomer and conjugated diene monomer added in step b; d. after about 10 to about 60 mol percent of the monomers of step c have been polymerized, continuously adding the remaining amount of conjugated diene monomer and mono alkenyl arene to the second reactor at a rate that maintains the concentration of the conjugated diene monomer at no less than about 0.1% weight until about 90% of the monomers in block B1 have been polymerized, thereby forming a living block copolymer A1B1.