| 摘要 |
The invention is a process for preparing .alpha.-olefin polymers or copolymers having improved stereoregularity and bulk density. The process involves polymerising or copolymerizing .alpha.-olefins in the presence of a catalyst comprising (A) a solid titanium complex catalyst component and (B) an organometallic compound of a metal of groups I to III of the Periodic Table. The polymerization or copolymerization is carried out in two steps: (a) a first step where at least about 100 millimoles, per millimole of titanium atom, of an .alpha.-olefin is polymerized or copolymerized at a temperature less than about 50.degree.C, to form a polymer of copolymer the amount of which is not more than about 30% by weight based on the final product obtained in the second step, and (b) a second step where the final product is formed at at temperature highter than the temperature of the first step and from about 50.degree.C, to about 90.degree.C. |
