SUPPORTED ZIEGLER-NATTA CATALYST FOR ETHYLENE POLYMERISATION AND THE COPOLYMERISATION OF ETHYLENE WITH ALPHA-OLEFINS, ITS PREPARATION AND USE

摘要

A supported Ziegler-Natta catalyst active in ethylene polymerisation and in the copolymerisation of ethylene with alpha-olefins consists of: (A) a cocatalyst in the form of an organometallic compound of aluminium, and (B) a solid catalyst component obtained by: (i) impregnating a granular solid support with a solution of a titanium alcoholate Ti(OR)4 and magnesium chloride MgCl2 in a liquid aliphatic hydrocarbon, followed by evaporation of the hydrocarbon solvent; (ii) impregnating the support treated in (i) with a solution of magnesium chloride in a liquid aliphatic ester, followed by evaporation of the ester solvent; and (iii) activating the support treated in (ii) by contact with an alkyl aluminium halide. In a preferred embodiment, measured quantities of a silicon halide are introduced in stage (i) and/or (ii), this considerably improving catalytic activity. In a particular embodiment, zirconium or hafnium is introduced into the solid catalyst component (B) in addition to titanium, to obtain catalysts able to produce polyethylenes with a widened molecular weight distribution.