| abstract |
Diene polymers having a high content of cis-1,4 addition are prepared by polymerizing a 1,3-diene monomer in a hydrocarbon solvent in the presence of a catalyst composition comprising (a) a carboxylated metal oxy borate compound in which the metal is nickel or cobalt, (b) an organometallic compound of a metal of Groups I, II, and III of the Periodic System, and (c) one or more fluorine containing compounds selected from the group consisting of boron trifluoride complexes with ethers, alcohols or mixtures thereof; hydrogen fluoride; hydrogen fluoride complexes with ethers, alcohols, or mixtures thereof and mixtures of said compounds. The resultant polymers exhibit good green strength and tack and are particularly suitable for use as tire rubbers. |