Polymerization of propene in the presence of MgCl₂‐supported Ziegler‐Natta catalysts, 2. Effects of the co‐catalyst composition

Abstract

Abstract As a part of a study on the polymerization of propene in the presence of MgCl 2 ‐supported catalysts, new results were obtained when polymerizing at variable ethyl benzoate (EB)/alkylaluminium and alkylaluminium/Ti mole ratios. The pre‐treatment of MgCl 2 with the Lewis base is essential to achieve high stereoregularities without an unacceptable decrease of polymerization rate, apparently because it prevents the formation of nonstereospecific active sites of low Lewis acidity, which require high EB/alkylaluminium mole ratios in the co‐catalyst in order to be poisoned. The data may be explained in the framework of a model of catalytic sites preliminarily presented in Part 1 of this series.