VANADIUM-BASED ZIEGLER-NATTA CATALYST SUPPORTED ON MGCL2(THF)(2) FOR ETHYLENE POLYMERIZATION

A supported magnesium-vanadium-aluminium catalyst was prepared by depo siting with the use of a milling technique - VOCl3 on the MgCl3(THF)(2 ) support and subsequent activation with diethylaluminium chloride. Ca talytic activity of the obtained system for ethylene polymerization wa s evaluated as a function of Mg/V and Al/V ratios as well as catalyst ageing time and polymerization temperature. High concentrations of THF in the catalytic system and considerable excess of an organoaluminium co-catalyst were found to have no deactivating action on vanadium act ive sites. The catalyst obtained is stable and its activity for ethyle ne polymerization is high. It yields polyethylene with higher molecula r weight and higher melting point than offered by the materials produc ed with the use of a corresponding unsupported vanadium catalyst or a titanium-based system on the same magnesium support. Kinetic investiga tions confirmed stability of this catalyst irrespective of its concent ration in the polymerization medium or of monomer concentration. Moreo ver, analysis of the kinetic findings revealed that over 80% of vanadi um employed forms active polymerization sites.