Transfer and Isomerization Reactions in Propylene ... - ACS Publications

Chapter 11

Downloaded by UNIV OF CALIFORNIA SANTA BARBARA on March 19, 2018 | https://pubs.acs.org Publication Date: August 10, 2000 | doi: 10.1021/bk-2000-0760.ch011

Transfer and Isomerization Reactions in Propylene Polymerization with the Isospecific, Highly Regiospecific rac-Me C(3-t-Bu-1-Ind) ZrCl /MAO Catalyst 2

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Isabella Camurati, Anna Fait, Fabrizio Piemontesi, Luigi Resconi , and Stefano Tartarini 1

Montell Polyolefins, Centro Ricerche G. Natta, 44100 Ferrara, Italy

The influence of polymerization temperature, propylene concentration and hydrogen on the polymerization performance of the isospecific, highly regiospecific rac-Me C(3-t-Bu-1-Ind) ZrCl / MAO (1/MAO) catalyst has been investigated. Propagation follows the rate law Rp=(a[M]+b[M] )/(c+d[M]).1/MAOis more stereospecific compared to unsubstituted bisindenyl complexes, e.g rac­ -C H (1-Ind) ZrCl / MAO (2/MAO), but growing-chain-end isomerization (epimerization) is faster in 1/MAO (ca 10% of stereoerrors of type mrrm are due to epimerization in liquid monomer at 50 °C) than in 2/MAO. H NMR end group analysis shows that chain transfer occurs by β-methyl (prevalent) and β-hydrogen transfer reactions. 2

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Chiral, C -symmetric awsa-zirconocenes produce polypropylenes with microstructures ranging from almost atactic to almost perfectly isotactic, and often containing isolated regioirregularities.[/,2] The wide range of molecular properties of these polypropylenes is due not only to the variability of the ansa-n-\\gzn