Process for nonaqueous dispersion polymerization of butadiene in the presence of polymeric dispersing agents

DETAILED DESCRIPTION Butadiene can be polymerized to a very high (95% or greater) cis-1,4-polybutadiene in a nonaqueous liquid dispersion medium containing random copolymers of butadiene and styrene to produce very high cis-1,4-polybutadiene.
The nonaqueous medium in which this polymerization is run must be a very poor solvent for very high cis-1,4-polybutadiene.
Some representative examples of nonaqueous media that can be employed in which the very high cis-1,4-polybutadiene is essentially insoluble include: n-butane, isobutane, n-pentane, isopentane, neopentane, 2-methylpentane, 2,2-dimethylbutane, 2,2-dimethylpentane, 2,4-dimethylpentane, 2,2,4-trimethylpentane, 2,2,3-trimethylbutane, isobutylene, 1-butene, 3-methyl-1-butene, trans-2-butene and any mixture of any or all of these nonaqueous media.
Minor amounts of other hydrocarbons, which by themselves are solvents for very high cis-1,4-polybutadiene, can also be present in such a nonaqueous dispersion media; however, their presence is detrimental since even small amounts of solvent will cause swelling of the cis-1,4-polybutadiene and result in an increase in viscosity.
The presence of large amounts of solvents for cis-1,4-polybutadiene will lead to the formation of a cement-like composition.
Since it is desirable for these nonaqueous dispersions to have a very low viscosity it is advantageous to minimize the amount of solvents for cis-1,4-polybutadiene in the nonaqueous medium.
The liquid nonaqueous dispersion media should contain less than about 5% aromatic and cycloaliphatic hydrocarbons (which are good solvents for cis-1,4-polybutadiene) such as, benzene, toluene, cyclohexane, methylcyclohexane and the like.
The nonaqueous medium must contain less than about 20% aliphatic hydrocarbons that are fair solvents for high cis-1,4-polybutadiene in order to be effective as a nonaqueous medium in the polymerization of high cis-1,4-polybutadiene.
Some representative examples of such aliphatic hydrocarbons include: hexane, 3-methylpentane, 2,3-dimethylbutane, heptane, octane, 2,3-dimethylpentane, and 2,3,4-trimethylpentane