Abstract: A process for producing .alpha.-olefin polymers characterized by employing an organomagnesium compound in the preparation of a preactivated catalyst therefor is provided. The resulting polymers have particularly a higher rigidity in addition to various superior properties. The process comprises reacting a trivalent metal halide with a divalent metal compound to obtain a solid product (I); reacting this product with an organomagnesium compound, an electron donor (ED) and an electron acceptor (EA), once to 10 times, and at that time, using TiCl.sub.4 at least once as the (EA) to obtain a solid product (II); combining this product with an organoaluminum compound (OAl) and an (ED), and at that time, subjecting a combination of (II) and (OAl) or that of (II), (OAl) and (ED) to polymerization treatment with an .alpha.-olefin, and in the case of the former combination, further adding (ED), to obtain a preactivated catalyst; and polymerizing .alpha.-olefin(s) in the presence of this catalyst.

Abstract: A process for producing .alpha.-olefin polymers is provided, which comprises: reacting an organoaluminum compound with an electron donor in a specified ratio in a solvent at a specified temperature to obtain a solid product (I); reacting solid product (I) with TiCl.sub.4 at a specified temperature in a specified ratio of Al/Ti and then removing a liquid portion from the resulting material followed by washing to obtain a solid product (II) having no free TiCl.sub.4 ; reacting solid product (II) with an electron donor and an electron acceptor in a specified ratio at a specified temperature to obtain a solid product (III); and polymerizing .alpha.-olefin(s) in the presence of a catalyst comprising a combination of solid product (III) with an organoaluminum compound. This process provides a catalyst having a high storing and thermal stability and a polymer having a uniform particle size.