In this work, the performance of the catalysts SiMe2(Ind)2ZrCl2, Et(Ind)2ZrCl2, SiMe2(Ind)2HfCl2 e Et(Ind)2HfCl2 on propylene polymerization using MAO as cocatalyst and employing a Statistic Experimental Planning Model was evaluated. The polymerizations were carried out at different temperatures and aluminum/transition metal molar ratios. The effect of these variables on the catalyst activity and on the polymer characteristics was investigated using the proposed models for each variable. A significant influence was observed of the experimental conditions on the catalyst activity in particular, but also on the weight-average molecular weight, melting point and isotacticity of the polypropylenes produced; the statistical analysis with the proposed models indicated higher catalyst activity for the zirconocenes, while the hafnocenes produced polypropylene with higher molecular weight. The complexes with dimethylsilane bridge produced polypropylene with higher molecular weight, stereoregularity and higher melting temperature in comparison with the corresponding polymers using the ethylidene bridge.
Ansa-metallocene; polypropylene; transition metal
