Process for preparing ethylene copolymers suitable for producing foils or tubes

摘要

The invented process for preparing ethylene copolymers suitable for producing tubes and foils is characterized in that a substantially innovated catalytic system containing silyl chromate compound is used for initiation polymerization of 1-alkene monomer. The principle of the catalytic system synthesis is to ensure interaction of silyl chromate containing OH groups of silica with both ester groups so that an active center having cyclic structure (chart A) takes place. The catalytic system is prepared by successive interaction of the following components: (a) silyl chromate compound being totally freed of water and oxygen prior contact with a porous carrier, (b) a carrier containing a suitable type and optimal concentration of OH groups, (c) alkylating agent being represented by a combination of an organometallic compound of aluminium (Re4O)AlRe2Re3 and an organomagnesium compound (Re3MgRe2), whereby the ratios between the individual components are within the following range: amount of silyl chromate on the carrier ranges from 0.05 to 1.0 percent by weight of the carrier, molar ratio between the total amount of organometallic compounds (ORG) to silyl chromate expressed schematic by the relation ORG/Cr is within the range of 0.5 to 20, the most suitable of 1 to 10, and mutual molar ratio of the organoaluminium and the organomagnesium compounds Al : Mg ranges from 10 : 0.1 to 0.1 : 10.