Multicenter nature of titanium‐based Ziegler–Natta catalysts: Comparison of ethylene and propylene polymerization reactions

• DOI: 10.1002/pola.10714
• Publication Date: 2003-05-07T10:11:15Z
• Authors: Yury V. Kissin
• Keywords: Tacticity; Ziegler–Natta catalyst; Polypropylene; Ethylene propylene rubber; Propene

Abstract This article discusses the similarities and differences between active centers in propylene ethylene polymerization reactions over same Ti‐based catalysts. These correlations were examined by comparing kinetics of both monomers two different catalyst systems, δ‐TiCl 3 ‐AlEt TiCl 4 /DBP/MgCl 2 /PhSi(OEt) , molecular weight distributions respective polymers, consecutive ethylene/propylene propylene/ethylene homopolymerization reactions, examining IR spectra “impact‐resistant” polypropylene (a mixture isotactic an copolymer). The results these experiments indicated that catalysts contain families centers. first family, which are relatively unstable kinetically, capable polymerizing copolymerizing all olefins. family includes from four to six populations differ their stereospecificity, average weights polymer molecules they produce, values reactivity ratios olefin copolymerization reactions. second (two centers) efficiently polymerize only ethylene. They do not homopolymerize α‐olefins and, if used ethylene/α‐olefin incorporate α‐olefin very poorly. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Chem 41: 1745–1758,