Process for producing mixture of block copolymers

Claim 1

A process for producing a block copolymer mixture of conjugated diene and vinylaromatic hydrocarbon which comprises two steps of a first step (A) of preparing (a) living polymer of conjugated diene, (b) random living copolymer of conjugated diene and vinylaromatic hydrocarbon, or (c) living block copolymer consisting of at least one of conjugated diene polymer blocks and at least one of vinylaromatic hydrocarbon polymer blocks, by polymerizing monomers of conjugated diene or conjugated diene and vinylaromatic hydrocarbon, in a ratio by weight of vinylaromatic hydrocarbon to conjugated diene of 0/100 to 60/40 and the monomers being present in an amount of 1 to 80% by weight of total monomers to be used through the two steps, using an organolithium compound as a catalyst and a solvent consisting mainly of aliphatic hydrocarbon the polymers not being inactivated with an inactivating agent, and a second step (B) of (1) preparing (d) vinylaromatic hydrocarbon polymer or (e) block copolymer consisting of at least one of vinylaromatic hydrocarbon polymer blocks and at least one of conjugated diene polymer blocks, and (2) simultaneously extending copolymer chains or polymer chains obtained in said step (A), by adding to the living (co)polymer obtained in said step (A), monomers of vinylaromatic hydrocarbon or vinylaromatic hydrocarbon and conjugated diene, in a ratio by weight of vinylaromatic hydrocarbon to conjugated diene of 100/0 to 65/35 and the monomers being present in an amount of 99 to 20% by weight of total monomers to be used through the two steps, and adding an organolithium compound as a catalyst and a solvent consisting mainly of an aliphatic hydrocarbon, and polymerizing the monomer(s) to simultaneously obtain polymers (d) or (e) and the polymers by extending the chains of polymers of step (A), thereby obtaining a resulting block copolymer mixture, said block copolymer mixture having a ratio of vinylaromatic hydrocarbon content of the ultimate block copolymers obtained by combining the monomer(s) added in said step (B), with the living polymer chains formed in said step (A) to vinylaromatic hydrocarbon content of the (co)polymers obtained only in said step (B), of at least 1/1.8, and a ratio of vinylaromatic hydrocarbon portion to conjugated diene portion in said resulting block copolymer mixture, of 60/40 to 95/5.