ZEOLITE-SUPPORTED POLYMERIZATION CATALYSTS - COPOLYMERIZATION OF ETHYLENE AND ALPHA-OLEFINS WITH METALLOCENES SUPPORTED ON HY ZEOLITE

Copolymerization of ethylene with higher alpha-olefins, such as 4-meth yl-1-pentene, 1-hexene, 1-octene and 1-dodecene, was carried out with both aspecific and isospecific bridged metallocene complexes, comparin g the catalytic behaviour following metallocene supportation on methyl alumoxane-pretreated HY zeolite (SiO2/Al2O3 = 5.7). A decrease in spec ific activity was generally observed after adsorption on zeolite of bo th non bridged and ansa-metallocene complexes, though molecular weight s of the copolymers were found to be higher especially when employing alpha-olefins as polymerization solvents. On the other side, the incor poration of the alpha-olefin comonomer was reduced in the case of supp orted biscyclopentadienylzirconium dichloride, whereas similar content s of olefin units were incorporated in the copolymers prepared with so luble or supported ansa-zircono- or hafnocene. NMR analysis and DSC de termined melting points of the produced copolymers are connected with a shape selectivity effect promoted by the support. (C) 1998 Elsevier Science B.V.