Comparison of Electron Microscopic and Kinetic Studies of Supported Metallocene and Classical Ziegler Catalysts for Polypropylene Polymerization

摘要

This article treats the comparison of a conventional Ziegler-catalyst with a novel SiO_2-supported metallocene (SiO_2/MAO/rac-Me_2Si-[IndR_2]_2ZrCl_2) concerning their different impact on the slurry polymerization of polypropylene. Electron microscopic and kinetic studies of early polymerization stages show a different polymerization- and fragmentation behaviour. The Ziegler-catalyst causes a fragmentation according to the "multigrain-model" of RAY and YERMARKOV and leads to a constantly high activity level during the whole reaction. The metallocene-catalyst on the other hand induces a short prepolymerization period, followed by a larger induction period before it reaches the maximum activity plateau. The fragmentation agrees with the newly developed "particle growth model" of FINK et al.