SYNTHESIS OF HIGH-MOLECULAR-WEIGHT ELASTOMERIC POLYPROPYLENE WITH HALF-TITANOCENE/MAO CATALYSTS

摘要

Propylene polymerizations in the presence of various monocyclopentadienyltitanium compounds and MAOs have been investigated. It was found that the content of residual trimethylaluminum (TMA) in MAO has a determinative effect on catalytic activity for the polymerization. An excess of TMA in the catalyst systems reduces the Ti species to inactive lower valent states. By substituting hydrogen at cyclopentadienyl ring by more electron releasing methyl, the titanocene afford atactic polypropylene with increasing molecular weight by one order of magnitude. Esterified or alkylated titanocenes with appropriate -OR and -R ligands give higher molecular weight polypropylene than the corresponding halide. The produced polypropylenes with the molecular weight range of 20～100 x 10~4 exhibit good elasticity.