High molecular weight homopolymers and copolymers of ethene

摘要

The present invention relates to high molecular weight homopolymers and copolymers of ethene, which homopolymer or copolymer is obtained by polymerizing the monomer(s) at a temperature of from 70 DEG to 150 DEG C. and under a pressure of from 2 to 150 bar in contact witha chromium trioxide catalyst, (1) loading a support based on silicon dioxide with (2) either chromium trioxide or a chromium compound capable of being converted to chromium trioxide under the conditions of stage (3) below and then (3) heating the resulting intermediate in a gas stream containing oxygen, the support (1) being a special silica xerogel obtained by extracting not more than 30% of the water from a silica hydrogel by means of an alkanol, an alkanone or a mixture thereof followed by drying, comminution and fractional screening.