Two different, on the same silica supported metallocene catalysts, activated by various trialkylaluminums – a kinetic and morphological study as well as an experimental investigation for building stereoblock polymers

Abstract

The main focus of this study is the development of new polypropylene macromolecules. The simultaneous supporting of two metallocenes that manufacture polyolefins of different tacticity on the same silica should yield stereoblock polymers of polypropylene, if a chain transfer between the active species takes place. As chain transfer agents two aluminumalkyls (cocatalyst and scavenger) of distinct steric demands were chosen. Two catalyst systems were studied. The first was based on a PQ-silica/MAO on which the two metallocene catalysts rac-Me₂Si[Ind]₂ZrCl₂ (isotactic working species) and i-Pr[FluCp]-ZrCl₂ (syndiotactic working species) were fixed. For the second the components rac-Me₂Si[IndR₂]₂ZrCl₂ and i-Pr[FluCp]-ZrCl₂ were fixed to a Grace Silica/MAO-support. The influence of the type of silica, of MAO-content, of the kind of scavenger and of the supporting procedure on the microstructure, the kinetics and the morphology of the product were investigated.