CATALYST SYSTEM TO PRODUCE HIGHLY CRYSTALLINE POLYPROPYLENE

摘要

The present invention provides a catalyst system that exhibits control of desired properties in the polymer product. The catalyst system includes a conventional supported Ziegler-Natta catalyst in combination with an electron donor having the general formula SiR_m(OR′)_4-m where R is selected from the group consisting of an alkyl group, a cycloalkyl group, an aryl group and a vinyl group; R′ is an alkyl group; and m is 0-3, wherein when R is an alkyl group, R may be identical with R′; when m is 0, 1 or 2, the R′ groups may be identical or different; and when m is 1, 2 or 3, the R groups may be identical or different. The system easily achieves efficiencies over 30 kg/g-cat·h. The system also exhibits good control over the xylene solubles of the polymer products and produces a highly crystalline polymer product. The electron donor is preferably described by the formula: chemistry chemdraw filechemistry mol file;wherein R₁ is an alkyl or cycloalkyl group containing a primary, secondary or tertiary carbon atom attached to the silicon atom; R₂ and R₃ are alkyl or aryl groups; and R₄ is an alkyl or cycloalkyl group with a secondary or tertiary carbon atom attached to the silicon atom. More preferably, R₁ and R₄ are both cycloalkyl groups and are both the same. Most preferably, R₁ and R₄ are both cyclopentyl groups and R₂ and R₃ are both methoxy groups. Specifically, the electron donor may be dicyclopentyldimethoxysilane.