Synthesis of Stereoblock Elastomeric Polypropylenes using (2-PhInd)2ZrCl2Metallocene Catalyst in the Presence of Co-catalyst Mixtures: Part I. Study of Activity and Molecular Weight

One of the main issues in the polymerization of alpha-olefins using multi-catalyst systems is the interaction of different species present in the reaction media. The interaction ofco-catalysts, active species, and other side products present in the media are still under debate [1]. The topic of co-catalystsseems especially important because the co-catalyst agents can perform distinct functions [2]. For example, electron deficient MAO (methylaluminoxane) will accept an anion and activatea metallocene catalyst [2]. In contrast, AlR3 (R=Et or i-Bu) is used to activate classical Ziegler-Natta catalyst by transferringan alkyl group to the transition metal center [3]. In the present work the effect of adding different aluminumalkyls to the polymerization medium is investigated regardingthe polymerization of propylene by the metallocene catalyst (2-PhInd)2ZrCl2.Catalyst activities and viscometric molecular weights (Mv) of all produced polypropylenes are measured as a function of the mole percent of added aluminum alkyls.