Silica-supported metallocenes: Effect of the preparation procedure on the morphology of polyethylene particles

Polyethylene (PE) particles are produced by a catalyst prepared by contacting a (C₄H₉Cp)₂-ZrCl₂/MAO pre-mixing solution with SiO² support. These particles have a large granular size and very few fine particles compared with those derived from a catalyst prepared by adsorption of (C₄H₉Cp)₂ZrCl₂ onto methylaluminoxane modified SiO₂. The amount of Al in the pre-mixing catalyst has an important effect on its activity and the PE particle size distribution. The optimal concentration is about 30 wt.-%. The PE particles produced using a premixing catalyst consist of globules with randomly oriented fiber structure on the surface, whereas those produced using adsorption catalysts have worm-like fibrils protruding from the PE globule surface.