Patent ID: 7390856

Claim:
A method for making selectively hydrogenated block copolymers of vinyl aromatic hydrocarbons and conjugated dienes comprising: a) anionically polymerizing vinyl aromatic hydrocarbons and conjugated dienes to produce block copolymers with living chain ends; b) terminating the living chain ends with an alcohol, or a mixture of hydrogen and alcohol to prepare a terminated block copolymer; and c) contacting the terminated block copolymers with hydrogen at a temperature of from 20 to 175° C. in the presence of a catalyst prepared by combining a cobalt carboxylate with an aluminum alkyl, wherein the alcohol is a linear alcohol or a mixture of a linear alcohol and a branched alcohol, and wherein (i) if the polymer is terminated with the linear alcohol, the linear alcohol is used to terminate the living chain ends in an amount such that the alcohol:living chain end molar ratio is from 0.05 to 1.2; (ii) if the polymer is terminated with the mixture of a linear alcohol and a branched alcohol, the linear alcohol is used to terminate the living chain ends in an amount such that the linear alcohol:living chain end molar ratio is from 0.05 to 1.2, and wherein the linear alcohol is methanol, ethanol, n-propanol, n-butanol, n-pentanol or a mixture thereof.