Polymerization of propylene by mixed Ziegler-Natta and metallocene catalysts

Abstract

The polymerization of propylene using a mixture of racemic metallocenes and Ziegler–Natta catalysts was investigated. The polypropylene was obtained as a mixture of a fine powder and beads, with the powder being absorbed partially on the beads. The relative amount of the powder can be controlled by the concentration of the metallocene. The compatibility between the components of the mixed catalytic systems and the effect of the components on the rate of polymerization and on the properties of the new polymers were studied. The metallocene system dramatically affects the melt viscosity, isotacticity and molecular weight of the polymers. The two catalytic systems are able to act jointly, producing different polymers, for which separate melting and crystallization temperatures are obtained. © 1998 John Wiley & Sons, Ltd.

Melt viscoelasticity of polypropylenes prepared under different polymerization regimes

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Ziegler‐Natta/Metallocene Hybrid Catalyst for Ethylene Polymerization

“…Several reviews and patents have been published about recent advances in olefin polymerization using binary catalyst systems 9–15. Catalysts can be combined in three ways: (1) in the catalyst transition, the second catalyst is introduced to the reactor in the middle of polymerization and can continue polymerization with or without (by deactivating) the first catalyst;16–19 (2) in the catalyst mixture, two independent catalysts are introduced to the reactor and start the polymerization together;16–27 (3) two catalysts can also be loaded on a support to form a new catalyst, named a hybrid catalyst 28–44…”

“…However, polyolefins are mostly obtained using Ziegler‐Natta catalysts, and less work has been done on the combination of different catalysts with these traditional catalysts 16–21, 36–44. There is great potential in combining different metallocene catalysts with Ziegler‐Natta catalysts, not only in order to introduce a metallocene catalyst into traditional processes, but also to combine the advantages of both catalytic systems.…”