Patent ID: 7449518

Claim:
A process for the preparation of block copolymers comprising: a. adding an alpha-alkyl-vinyl-aromatic monomer to an inert solvent; b. adding a polymerization modifier selected from the group consisting of diethyl ether, ortho-dimethoxy-benzene and diethoxy-propane; c. adding an anionic polymerization initiator selected from the group consisting of alkyl lithium compounds and organo-lithium compounds; d. adding monovinyl-aromatic monomer continuously and copolymerizing said monovinyl-aromatic and alpha-alkyl-vinyl-aromatic monomers to form a living glassy block at a temperature from 35 to 60° C. wherein said copolymerization is conducted in such a manner as to maintain a high concentration of alpha-alkyl-vinyl-aromatic monomer relative to monovinyl-aromatic monomer for the majority of the copolymerization achieving at least 45% conversion of the alpha-alkyl-vinyl-aromatic monomer such that at the end of this copolymerization step d, the solids content is from 20 to 50 wt % such that the concentration of living polymer-Li chain ends is from 500 to 2500 ppm and wherein the amount of alpha-alkyl-vinyl-aromatic monomer is from 25 to 50 mol % on the basis of the total amount of monovinyl-aromatic and alpha-alkyl-vinyl-aromatic monomers; e. adding a conjugated diene or a mixture of conjugated dienes; and f. polymerizing said conjugated diene or mixture of conjugated dienes to form a living elastomeric block wherein the conversion of the conjugated diene or mixture of conjugated dienes is at least 90%.