Search results for "propylene polymerization"
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Comparison of the generation II with IV heterogeneous Ziegler-Natta catalysts used in propylene polymerizations
1998
An unsupported TiCl3-based catalyst (generation II), modified with n-butyl ether and AlEt2Cl3, was compared with a MgCl2/dibutyl phthalate/AlEt3/cyclohexylmethyldimethoxysilane catalyst system (generation IV) in propylene polymerizations. The latter (magnesium-supported) was fund to be more than 20 times as active as the former and more stereospecific, but to yield PP with a lower molecular weight (Table 2). The kinetics of the polymerizations studied with either of the catalyst, and involving the determination of concentrations of active sites [C0*] and elementary reaction rate constants (Table 4) based on earlier kinetic models, showed the C0*-values in the magnesium-supported catalyst to…
Nature of activating effect of two‐step polymerization of propylene
1999
The prepolymerization effect on propylene polymerization in the presence of a TiCl3‐based catalyst, modified by di‐n‐buthyl ether, was studied. The influence of prepolymerization on the electron spin resonance spectra and morphology of the catalyst, as well as the properties and the morphology of both prepolymer and regular polymerization products, was investigated. The polymer morphology was evaluated through scanning electron microscopy, polymer bulk density, and particle size distribution. Some evidence of the enhancement effect of prepolymerization on the catalyst activity and stereospecificity was obtained. No influence from prepolymerization was observed on molecular weight and its di…