Abstract: A process for the production of ethylenic polymers, characterized in that ethylene is homopolymerized or ethylene with .alpha.-olefin is copolymerized by the use of a catalyst system comprising:(A) a solid catalyst component prepared by treating (1) a solid ingredient containing at least a magnesium atom, a halogen atom and a transition metal element with (2) at least a cyclic organic compound; and(B) an organoaluminum compound; or(A) the solid catalyst component;(B) the organoaluminum compound; and(C) an electron donor compound; and the catalyst systewm as obtained in the above-described manner.Ethylenic polymers having a narrow distribution of molecular weight, having suitability for use in injection molding and having excellent powder characteristics can be produced, and by using this polymer, film having excellent optical characteristics can be produced.

Abstract: A process for polymerizing or co-polymerizing propylene in the presence of a catalyst consisting essentially of (A) a solid catalyst component which is prepared by contacting(1) a copulverized material obtained by copulverizing a magnesium dihalide compound together with an acyl halide with(2) a mixture or addition-reaction product of a tetravalent titanium compound containing at least one halogen atom with at least one electron donor compound selected from the group consisting of organic compounds containing a P--O bond, organic compounds containing an Si--O bond, ether compounds, nitrite ester compounds, sulfite ester compounds, alcohol compounds, phenol compounds and naphthol compounds,(B) a trialkyl aluminum compound, and (C) a carboxylic acid ester compound.