| 摘要 |
The invention relates to a process for the preparation of a highly stereoregular and melt processable alpha -olefin polymer product. The product is obtained by (i) producing a low melt flow rate polymerization product by contacting an alpha -olefin under polymerization conditions with a first high activity polymerization catalyst system comprising a transition metal compound, a first organometal compound and a stereoregulating external electron donor, and little or no hydrogen termination agent; (ii) producing in one or more steps a high melt flow rate polymerization product by contacting an alpha -olefin under polymerization conditions with a second high activity polymerization catalyst system comprising a transition metal compound, a second organometal compound and a stereoregulating external electron donor, and a hydrogen termination agent; and (iii) integrating or combining the low and high melt flow rate polymerization products. A surprisingly good yield of the high melt flow rate polymerization product is achieved if the second organometal compound contains, on an atom basis, more halogen per metal than the first organometal compound. |
