Kaminsky catalyst

Under Kaminsky catalysts are mixtures of a metallocene dihalide with methylaluminoxane (MAO). These catalysts allow the polymerization of olefins. The catalyst systems were developed in the 1980s by Walter Kaminsky and Hansjörg Sinn at the University of Hamburg.

The catalysts are suitable for both academic research and for industrial production of polyolefin plastics is of great importance, since variation of the ligand and the catalyst symmetry, the activity and selectivity of the catalysts in terms of tacticity and molecular weight distribution of the polymers obtained in wide limits can be varied.

Representation

The metallocenes used by Kaminsky and Sinn are complexes of transition metals of the titanium group. The compounds are usually easily accessible from the element chlorides and sodium cyclopentadienyl or its derivatives.

Reactions

Polyethylene

The Kaminsky catalyst systems produce at room temperature and atmospheric pressure of ethylene with a high catalytic activity polyethylene. At higher ethene pressure, the activity continues to increase so that eg at temperatures of about 95 ° C and pressures of approximately 8 bar ethylene per gram of zirconium in a yield of 40.000 kg of polyethylene is obtained. Due to the low concentration of these catalyst can remain in the finished product and does not affect the processing performance and the stability of the products. The molecular weight distribution is narrower than that obtained with conventional Ziegler catalysts.

Polypropylene

Through the use of C2 -chiral metallocenes from Brintzinger type (2) in which two indenyl ligands are bridged, succeeded in producing high - stereoselectively polymerized α -olefins. 1 is the metallocene used in the polymerization of propylene, atactic polypropylene is obtained, while the catalyst 2 to isotactic with C2 - symmetry and complex 3 with Cs symmetry leads to the syndiotactic polypropylene.

Copolymerisation

By modification of the metallocene also catalysts for the selective co- Polymersisation different olefins can be produced. Thus, the properties of ethylene -propylene, ethylene-1- octene, or copolymers can be varied on the basis of ethylene-norbornene in a wide range.

Heterogenization

The homogeneous Kaminsky catalysts can be heterogenize with the aim to replace these as a replacement for conventional Ziegler -Natta catalysts in existing production facilities. The heterogeneity also allows a reduction in the MAO / metallocene ratio by several orders of magnitude.

Different methods can be applied for the heterogeneity of the catalyst system. The fixing can be carried out from the suspension and from the gas phase. The complex may be covalently bound via the ligand to the support material as are present only in the form of physisorbed. As support aluminum oxide, magnesium chloride, silica, zeolites and polymers such as polystyrene or silicone can be used.