Method for producing novel rubbery polymers from diene monomers

Claim 1

In the production of a polymer wherein a conjugated diolefin monomer is polymerized with up to about 30% by weight of a monovinyl aromatic hydrocarbon monomer by supplying monomer to a polymerized together with a solvent to a polymerizer together with a catalyst selected from the group consisting of lithium, methyl lithium, ethyl lithium, butyl lithium, amyl lithium, hexyl lithium, 2-ethylhexyl lithium, phenyl lithium, tolyl lithium, xylyl lithium, naphthyl lithium, methylene dilithium, tetramethylene dilithium, dilithium benzene and dilithium naphthalene, at a temperature of about 20° to 150°C and a pressure sufficient to keep the solvent in liquid state, withdrawing from said polymerizer a solution of living polymer substantially free of monomer, recirculating to said polymerizer some of the withdrawn polymer-containing solution, and subsequently removing the solvent from the withdrawn polymer-containing solution, the improvement which comprises supplying said monomer continuously, withdrawing said polymer-containing solution continuously, continuously recirculating said withdrawn solution to the extent of about 20 to 80%, and discontinuing polymerization of the balance of the withdrawn solution, whereby the final polymer has a broad monomodal molecular weight distribution, a ratio of weight average molecular weight to number average molecular weight of 3 to 10, a Mooney viscosity of about 30 to 150 and a 1,4-linkage conjugated diolefin unit content of at least about 60%.