GB1204764A - Process for the continuous solution polymerization of 1,3-butadiene - Google Patents

Abstract

1,204,764. Polybutadiene. SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ N.V. 18 June, 1969 [20 June, 1968], No. 29380/68. Headings C3G and C3P. 1,3-Butadiene is polymerized continuously in a homogeneous reaction mixture in a reactor in the presence of one or more hydrocarbon solvents and a catalyst formed from a hydrocarbon soluble organic cobalt compound and a hydrocarbylaluminium chloride compound, the cobalt concentration in the reactor being less than 5 p.p.m. by weight of the reaction mixture, by a process comprising adding the cobaltcontaining compound to one or more liquid streams, providing that all streams entering the reactor provide an average cobalt concentration which is at least one times the cobalt concentration in the reactor, the cobalt concentration in any cobalt stream when entering the reactor is less than 4 times the cobalt concentration in the reactor and that the cobalt-containing compound and the aluminium-containing compound are not added to one and the same stream having a 1,3-butadiene content of more than 1% by weight. The two catalyst components are preferably fed to one or more liquid solvent recycle streams and are preferably cobalt acetylacetonate and a hydrocarbylaluminium chloride compound which has been prepared by reacting a dihydrocarbylaluminium monochloride with water. In a preferred embodiment at least two liquid recycle streams are applied (A) benzene, having a 1,3-butadiene content of not more than 1 % w. and (B) butene, having at least 90% of the 1,3-butadiene feed and at least 90% of the unconverted 1,3- butadiene. In the examples 1,3-butadiene is continuously polymerized in a mixed solvent of benzene and butene in the presence of a catalyst comprising cobalt (II) acetylacetonate and a reaction product of diethylaluminium chloride. The polymerization is terminated by the addition of ethanol and as an anti-oxidant, a phenol. The mixture is steam stripped to remove the polymer from the stripped off solvent mixture and unreacted monomer, the stripped off mixture being purified by distillation to produce a larger stream of butene-1 and butadiene, and a smaller stream of benzene. These streams are recycled to the reactor, the benzene stream being mixed with a water containing stock solution and diethylaluminium chloride, and the butene stream, which contained butadiene feed, being mixed with the cobalt containing catalyst components. The resultant polymer, which has a high cis,1,4 content, is further polymerized by dissolving in styrene and further polymerizing with lauroyl peroxide to form a high impact polystyrene. A mixture of 1,3- butadiene and less than 10% by weight of isoprene may also be polymerized by the above described process. A solution of 6 % w. butadiene rubber, obtained by the above process, and 0.1% w. of lauroyl peroxide as initiator, in styrene was prepolymerized in a N 2 atmosphere at 90‹ C. and postpolymerized at 180‹ C. to produce a high impact polystyrene.