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EFFECTS OF EXTERNAL DONOR ON ACTIVE CENTER DISTRIBUTION OF SUPPORTED ZIEGLER-NATTA CATALYST

Chinese Journal of Polymer Science 1997年第3期15卷 217-225页

作者：范志强 m.carmelasacchi PaoloLocatelli Department of Polymer Science and Engineering Zhejiang University Hangzhou 310027 Istituto di Chimica delle macromolecole CNR 20133 Milan Italy

The composition distribution (CD) and microisotacticity distribution (ID) of propene/1-hexene copolymer synthesized by mgCl2/DIBP/TiCl4 (DIBP: diisobutyl phthalate) were determined by fractionating the copolymers according to crystallinity and characterizing the fractions by (CNmR)-C-13. The effects of two alkoxysilane donors, triethoxyphenylsilane (PTES) and dimethoxydi-tert-butylsilane (TBmS), on CD and ID of the copolymers were compared. Three main parts in the CD diagram of each copolymer were distinguished, which were correlated to active center distribution (ACD) based on three groups of different active centers. By studying the changes in l-hexene content, microisotacticity and reactivity ratio product of three typical fractions, the effects of external donor on ACD were better elucidated. It was found that TBmS shows much stronger effects on ACD than PTES. In the former system, most fractions were produced on active centers with relatively lower r(1)r(2), higher reactivity to I-hexene, and higher stereospecificity as compared to the system without external donor. It is concluded that the observed very extensive changes in ACD are mainly resulted by the formation of new types of active centers, possibly by coordination of external donor to certain positions on the catalyst.

关键词： supported Ziegler-Natta catalyst propene/1-hexene copolymer external donor active center distribution

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