Influence of trialkylaluminum reagents on the propylene polymerization behavior of bridged and unbridged 2-arylindene metallocene polymerization catalysts

Trialkylaluminum reagents such as triisobutylaluminum (TIBA) and trimethyla luminum (TMA) influence the propylene polymerization behavior of methylalum inoxane (MAO)-activated dimethylsilyl[bis(2-phenylindenyl)]zirconium dichlo ride (1). TIBA selectively decreases the productivity of the meso diastereo mer 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 t o polymer blends prepared in the absence of TIBA. In contrast, added trimet hylaluminum decreases the productivity of both 1-rac and l-meso. Similar tr ends in reactivity with AlR3 are observed for unbridged bis(2-phenylindenyl )zirconium dichloride (2) compared to a mixture of the bridged catalysts co ntaining 57% 1-rac. Mechanical testing indicates that polypropylene from 2 has superior elastomeric properties to reactor blends prepared from mixture s of 1-rac and 1-meso in the presence and absence of trialkylaluminum reage nts. Reactor blends prepared without AlR3 exhibit poorer recovery at 100% a nd 300% strain than that of the elastomeric polypropylene from 2. The react or blends prepared in the presence of TIBA exhibit pronounced yielding and necking during testing, characteristic of a softened plastic.