Abstract: Method of preparation of ethylene copolymers suitable for manufacturing films or pipes so characterized that for the initiation of polymerization of ethylene and 1-alkene monomer a substantially innovated catalyst system containing silyl chromate compound is used. The catalyst system, containing a high yield structure A, is prepared by a sequential interaction of the following components: a) a silyl chromate compound completely freed from water and oxygen prior to its contact with the porous support, b) a support containing a suitable type and optimum concentration of hydroxyl groups, and c) an alkylating agent, being a combination of organometal compounds of aluminum (RO)AlR2 and magnesium (R1MgR2), the ratios between the components in the catalyst vary in the following ranges: content of silyl chromate on the support varies from 0.05 to 0.35% of the support weight, ratio between the total amount of organometals (ORG) to silyl chromate (expressed in terms of ORG/Cr) varies between 0.

Abstract: The supported catalyst for the polymerization of 1-alkenes is obtained by a consecutive depositing on the insert inorganic oxide of silicium and/or aluminium at least one organic compound of aluminium, at least one compound of titanium and vanadium and at least one organic compound of aluminium and/or magnesium. It can be phlegmatized by 0.5-50% w/w of the paraffinic hydrocarbon having melting point 25-150.degree. C., which is coated either together with active components of the catalyst or separately. The catalyst polymerize and copolymerize ethylene without any additional activation.