Silica supported metallocene/MAO-systems: comparison of the polypropylene growth during bulk phase polymerization with slurry phase experiments

摘要

A kinetic investigation of the bulk phase propylene polymerization with a silica supported metallocene/MAO system has been carried out. In spite of the high monomer concentration and the resulting high activity it was possible to distinguish between different polymerization phases producing polymers with differing properties. Similar to prior experiments in slurry phase we noticed an induction period at lower reaction temperatures. Even at the drastic conditions of polymerizing in the liquid monomer we were able to prove strong initial diffusion limitation toward the monomer resulting from a polymer layer formed during the first minutes. The use of an 1-octene prepolymerized catalyst system leads to a markedly improved activity. This arises from a better monomer diffusion through the more amorphous poly(1-octene) layer compared to a highly isotactic polypropylene layer. [References: 10]