Comparison of zirconocene and hafnocene catalysts for the polymerization of ethylene and 1‐butene

In polymerizations with ethylene and copolymerizations with ethylene and 1‐butene the catalyst system rac ‐ethylene(bisindenyl)zirconium dichloride ( rac ‐Et(Ind) 2 ZrCl 2 )/methylaluminoxane (MAO) shows lower activities than the analogous Hafnium catalyst. The polymers obtained with the hafnium‐catalyst have average molar masses up to ten times higher than those synthesized with the zirconium compound. It is remarkable that rac ‐Et(Ind) 2 HfCl 2 is much more able to incorporate the comonomer. This is expressed by the copolymerization parameters. At a polymerization temperature of +30°C, e.g., the r 1 ‐parameter of the hafnium‐catalyst is 5,4, the corresponding parameter of the zirconium catalyst is 19,4. Polymerizations with a catalyst mixture rac ‐Et(Ind) 2 (Hf, Zr)Cl 2 (containing 95% rac ‐Et(Ind) 2 HfCl 2 and 5% rac ‐Et(Ind) 2 ZrCl 2 ) show that each catalyst compound produces its own polymer independently.