High activity polyethylene catalysts which produce bimodal or trimodal product molecular weight distributions

摘要

A catalyst composition for copolymerizing ethylene and alpha-olefins is prepared by treating a silica carrier, in a non-polar hydrocarbon solvent, with a dialkyl magnesium compound, a halogen-containing compound and titanium tetrachloride, to form a catalyst precursor and activating the precursor with dimethylaluminum chloride. Also disclosed is a process for copolymerizing ethylene and alpha-olefins in the presence of the catalyst of the invention. The polymer products have multimodal molecular weight distributions unlike unimodal molecular weight distributions of polymers prepared with similar catalyst precursors but activated with different alkylaluminum activators, e.g., triethylaluminum or trimethylaluminum.