PROCESS FOR BULK POLYMERIZING BUTADIENE

PROCESS FOR BULK POLYMERIZING BUTADIENE High cis-1,4-polybutadiene is a synthetic rubber that is commonly utilized in manufacturing tires. It is usually made commercially by employing solution polymerization techniques. However, it has been unexpectedly found that 1,3-butadiene can be polymerized into high cis-1,4-polybutadiene in a continuous bulk polymerization process while attaining very high conversions. This continuous bulk polymerization process comprises: (1) charging into a reaction zone the 1,3-butadiene; a catalyst system comprising (a) an organoaluminum compound, (b) a soluble nickel containing compound, and (c) a fluorine containing compound; (2) allowing the 1,3-butadiene to polymerize into high cis-1,4-polybutadiene to a conversion of at least about 60 percent while utilizing conditions under which there is sufficient evaporative cooling in said reaction zone to maintain a temperature within the range of 10.degree.C to 130.degree.C; and (3) continuously withdrawing said high cis-1,4-polybutadiene from said reaction zone. In order to reduce the molecular weight of the high cis-1,4-polybutadiene, the polymerizations of this invention are generally conducted in the presence of at least one molecular weight regulator selected from the group consisting of .alpha.-olefins, cis-2-butene, trans-2-butene, allene, 1,4-pentadiene, 1,5-hexadiene, 1,6-heptadiene, 1,2,4-trivinylcyclohexene, 4-vinyl-1-cyclohexene, 1-trans-4-hexadiene, and hydrogen.