Influence of Trialkylaluminum Reagents on the Propylene Polymerization Behavior of Bridged and Unbridged 2-Arylindene Metallocene Polymerization Catalysts

Abstract

Trialkylaluminum reagents such as triisobutylaluminum (TIBA) and trimethylaluminum (TMA) influence the propylene polymerization behavior of methylaluminoxane (MAO)-activated dimethylsilyl[bis(2-phenylindenyl)]zirconium dichloride ( 1 ). TIBA selectively decreases the productivity of the meso diastereomer of 1 ( 1-meso ). This is manifested in an increase in the isotacticity of polypropylene blends prepared from mixtures of 1-rac and 1-meso compared to polymer blends prepared in the absence of TIBA. In contrast, added trimethylaluminum decreases the productivity of both 1-rac and 1-meso . Similar trends in reactivity with AlR 3 are observed for unbridged bis(2-phenylindenyl)zirconium dichloride ( 2 ) compared to a mixture of the bridged catalysts containing 57% 1-rac . Mechanical testing indicates that polypropylene from 2 has superior elastomeric properties to reactor blends prepared from mixtures of 1-rac and 1-meso in the presence and absence of trialkylaluminum reagents. Reactor blends prepared without AlR 3 exhibit poorer recovery at 100% and 300% strain than that of the elastomeric polypropylene from 2 . The reactor blends prepared in the presence of TIBA exhibit pronounced yielding and necking during testing, characteristic of a softened plastic.