Ziegler-Natta-katalysator

摘要

A Zeigler-Natta type catalyst suitable for polmerising propylene comprising a preactivated support coated with 0.1 to 10g of homopolymer or copolymer of propylene. The preactivated support which comprises magnesium chloride and 1 to 20% by mol of an electron donor free from labile hydrogen and from ester function, is in the form of spherical particles having a mean diameter by mass of 10 to 100 microns and a ratio of the mean diameter by mass to the mean diameter by number of less than 2.0. The preactivated support is treated with at least one internal electron donor compound and coated by contacting the treated support with an alkyl aluminium halide and propylene, optionally together with ethylene and/or a C4-8 alpha-olefin, in the absence of an external electron donor compound.