OLEFIN POLYMERISATION
1419501 Olefin polymerization catalysts INTERNATIONAL SYNTHETIC RUBBER CO Ltd 2 March 1973 [3 March 1973 11 Jan 1973] 10188/72 and 1601/73 Heading C3P Alpha-monoolefins are polymerized in a hydrocarbon diluent in the presence of a catalyst comprising (1) an intimate mixture of (a) a trivalent halide of titanium, zirconium or hafnium, and (b) a compound of a Group V(a) or VI(a) transition metal, in which the mole ratio of (a) to (b) is between 10 : 1 and 100 : 1 and (2) an aluminium trihydrocarbyl or a hydrocarbylaluminium halide. The dispersion (1) is obtained by mixing the specified ingredients, followed by subjecting the mixture to shear, e.g. milling in the presence of a diluent. The polymers may be recovered by injection into hot water to form crumbs. A thiodipropionate or a metal soap may be added before final recovery of the polymer. In examples, polypropylene or ethylene-propylene copolymer is obtained by polymerization in the presence of a component (1) obtained by ball-milling in a hydrocarbon diluent a mixture of TiCl 3 and VOCl 3 and, as component (2), AlEt 3 and Et 2 AlCl. In some cases hydrogen, ethyltrichloroacetate or butylperchlorocrotonate modifiers are also included.