Abstract: The present invention provides a catalyst system and processes for preparing the system for use in ethylene polymerization and copolymerization. The catalyst system is obtained by dissolving any electron-donor activator and optionally, a metal halide adjusting agent, into a solution of magnesium halide in a solvent system consisting essentially of organic epoxy compounds and organic phosphorous compounds to form a homogeneous solution. At least one coprecipitator and a titanium halide or its derivative is then mixed to form a solid component, followed by incorporating in combination with an organic aluminum component prior to use in polymerizations. The electron donor activator is an ether or alcohol, and the coprecipitator is an organic acid, anhydride, ether, or ketone.

Abstract: The present invention provides a compound catalyst system useful for synthesizing polyethylenes or copolymers of ethylene having bimodal or broad molecular weight distributions, prepared by incorporating an organic alcohol as an electron-donor compound and an aluminoxane compound into the prior art compound catalyst systems, thereby promoting the activities of the two active centers, which leads to not only a large improvement in the activity of the catalyst system, but also the formation of polyethylenes and copolymers of ethylene having bimodal or broad molecular weight distributions, which in turn gives polymers having excellent processability and mechanical properties. A process for preparing the solid catalyst component used in the compound catalyst system according to the present invention and use of the compound catalyst system are also disclosed.