Improvement in productivity and molecular weight of polypropene-block-poly(ethene-co-propene) obtained by a modified stopped-flow method using various external electron donors
ANGEWANDTE MAKROMOLEKULARE CHEMIE(1999)
摘要
The efficiencies of various types of external electron donors to improve the productivity and molecular weight of the block copolymer, polypropene-block-poly(ethene-co-propene) obtained by a modified stopped-flow method were investigated, directed toward commercial production. Five alkoxysilanes having different structures, and a piperidine compound were employed as external donors. In all cases, an increase in the activity and weight-average molecular weight was observed on addition of the external donor at a Si/Ti mole ratio of ca. 1.0. Diisopropyldimethoxysilane was considered to be the most suitable donor for the synthesis of the block copolymer, due to its higher initial activity and properties, giving a polymer having higher molecular weight. An improvement in the molecular weight with considerable catalyst deactivation was apparently observed by increasing the Si/Ti mole ratio and decreasing the triethylaluminum (TEA) concentration. The results in this paper are an indication that a suitable choice of the kinds of external donors, Si/Ti mole ratio, and TEA concentration an needed to obtain block copolymers with desirable performance.
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关键词
molecular weight
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