GB844769A - Polymerisation process - Google Patents

Abstract

a -Olefins having at least three carbon atoms are polymerized with a catalyst system formed by mixing lithium borohydride with a titanium, zirconium or vanadium halide, e.g. a chloride. The olefin may be of formula R-CH=CH2, wherein R is an alkyl, cycloalkyl or aryl group, and specified compounds are propylene, butene, pentene, hexene, styrene and mixtures thereof. Chlorides disclosed are titanium tetra- and tri-chlorides, and vanadium and zirconium tetra-chlorides. Polymerization may be batchwise or continuous and is preferably in an inert medium such as pentane, hexane, cyclohexane, tetrahydro-naphthalene, decahydronaphthalene, benzene, xylene, o-dichlorobenzene, chlorinated naphthalene, petroleum ether or mixtures thereof. Oxygen and water are preferably excluded, e.g. by reaction in an atmosphere of argon. The catalyst components may be mixed in situ and may be preheated at a higher temperature than that used in the polymerization; preferred molar ratios are given. Subsequent to the polymerization the catalysts may be destroyed and the products purified by treatment with methanol and/or mineral acid, e.g. methanolic hydrochloric acid. The examples illustrate the addition of olefin during polymerization, and extraction of a product with diethyl ether. Highly crystalline polymers may be obtained. Comparison is made with a catalyst obtained from triethyl aluminium and titanium tetrachloride. Specification 827,464 is referred to.ALSO:Catalysts used in the polymerization of olefins (see Group IV(a)) are obtained by mixing lithium borohydride with a titanium, zirconium or vanadium halide, e.g. a chloride, such as titanium, vanadium or zirconium tetrachloride or titanium trichloride. Preferred molar ratios are given and the components may be mixed in situ and, if desired, may be preheated prior to polymerization. An inert medium is preferably present and specified are pentane, hexane, cyclohexane, tetrahydronaphthalene, decahydronaphthalene, benzene, xylene, o-dichlorobenzene, chlorinated naphthalene, petroleum ether and mixtures thereof. Subsequent to the polymerization the catalysts may be destroyed and the products purified by treatment with methanol and/or mineral acid, e.g. methanolic hydrochloric acid. Specification 827,464 is referred to.