SILICA-GEL SUPPORTED ZIRCONOCENE DICHLORIDE METHYLALUMOXANE CATALYSTS FOR ETHYLENE POLYMERIZATION - EFFECTS OF HETEROGENATION ON ACTIVITY, POLYMER MICROSTRUCTURE AND PRODUCT MORPHOLOGY

The system zirconocene dichloride/methylalumoxane was supported on silica in order to provide ethylene polymerization catalysts for suspension or gas phase processes. Highest activity was found for a sandwich-like, three layer anchoring of the zirconium centers on the support surface. The new catalyst systems show a decrease of activity compared to polymerization experiments in homogeneous phase. However, the molecular weights are increased and the weight distributions remain narrow by immobilization of the active catalyst sites. Those supported metallocene catalysts could find application for the synthesis of polyethylene materials with controlled rheology.