COMPARISON OF ZIRCONOCENE AND HAFNOCENE CATALYSTS FOR THE POLYMERIZATION OF ETHYLENE AND 1-BUTENE

In polymerizations with ethylene and copolymerizations with ethylene a nd 1-butene the catalyst system rac-ethylene(bisindenyl)zirconium dich loride (rac-Et(Ind)2ZrCl2)/methylaluminoxane (MAO) shows lower activit ies than the analogous Hafnium catalyst. The polymers obtained with th e hafnium-catalyst have average molar masses up to ten times higher th an those synthesized with the zirconium compound. It is remarkable tha t rac-Et(Ind)2HfCl2 is much more able to incorporate the comonomer. Th is is expressed by the copolymerization parameters. At a polymerizatio n temperature of +30-degrees-C, e. g., the r1-parameter of the hafnium -catalyst is 5,4, the corresponding parameter of the zirconium catalys t is 19,4. Polymerizations with a catalyst mixture rac-Et(Ind)2(Hf, Zr )Cl2 (containing 95% rac-Et(Ind)2HfCl2 and 5% rac-Et(Ind)2ZrCl2) show that each catalyst compound produces its own polymer independently.