| abstract |
Block polymers in which one of the blocks is a copolymer of (A) butadiene, isoprene or piperylene and (B) a vinyl substituted aromatic hydrocarbon and another block is a homopolymer of a vinyl substituted aromatic hydrocarbon are made by contacting a mixture of the diene and the vinyl aromatic hydrocarbon with a catalyst having the formula RLi wherein R is an alkyl, cycloalkyl, aralkyl, alkaryl, alkylcycloalkyl or cycloalkylalkyl radical in the presence of an aromatic, paraffinic or cycloparaffinic hydrocarbon diluent. Vinyl aromatic hydrocarbons specified are styrene, methylstyrenes and vinyl naphthalenes. Polymerization may be terminated at less than complete conversion. The resulting products may be cured in a conventional sulphur-containing vulcanization recipe. Reference has been directed by the Comptroller to Specifications 817,693 and 817,695. |