Electron donors in a Ziegler-Natta catalyst for the production of high melt flow copolymers

摘要

The present invention provides a catalyst system that exhibits unexpected control of desired properties in copolymer product. The catalyst system includes a conventional supported Ziegler-Natta catalyst in combination with an electron donor described by the formula:wherein R1 is a linear alkyl group attached to the silicon atom; R2 and R3 are alkyl or aryl groups and R4 is a linear alkyl attached to the silicon atom, R1 and R4 are the same or different. R1 and R4 are preferably linear carbon groups of 4-13 carbon atoms, more preferably 4-7 carbon atoms; most preferably R1 and R4 are the same and are n-butyl groups. The system exhibits good control over the melt flow index of the copolymer products.