Verfahren zur Copolymerisation von wenigstens zwei Olefinen

Copolymers of olefins, e.g. ethylene/propylene, and ethylene/1-butene, of controlled molecular weight, are made by copolymerizing a mixture of the olefins in the presence of a catalyst consisting of an organometallic compound of a metal of Group I, II, or III of the Periodic Table other than aluminium and beryllium, with a halogen compound of a transition metal belonging to Group IVa, Va, or VIa of the Mendeleeff Periodic Table, in which the molar ratio of the organometallic compound to the transition metal halide is from 1 to 10, and controlling the molecular weight of the copolymer by increasing the catalyst molar ratio to obtain a copolymer of lower intrinsic viscosity. During polymerization pressure is kept constant by introducing one of the olefins. The transition metal compound may be vanadium tetrachloride, and the organometallic is preferably selected from alkyl derivatives of zinc, cadmium, or mercury, e.g. zinc diethyl. The copolymers are vulcanizable under heat and pressure, in the presence of carbon black, butyl cumyl peroxide, and sulphur.