PRODUCTION OF PROPYLENE POLYMER

PURPOSE:To obtain a crystalline polymer in high yields, by polymerizing propylene by using a highly efficient catalyst containing an organoaluminum compound and a propylene polymer and prepared by subjecting a specified solid titanium trichloride catalyst complex to a specified treatment. CONSTITUTION:A solid titanium trichloride catalyst complex having an alminum content, in terms of a Ti/Al atomic ratio, of at most 0.15 and containing a complexing agent is subjected to a contact treatment with propylene in the presence of an inert solvent, an organoaluminum compound (e.g., dimethylaluminum chloride) and a compound of the formula (wherein R and R are each a 1-3 C alkyl, and R is a 1-20 C alkyl) to form 0.1-100g of propylene polymer per gram of solid titanium trichloride on the complex, whereby a catalyst containing an organoaluminum compound and a propylene polymer-containing solid titanium trichloride is formed. Propylene, alone or together with a small amount of an alpha-olefin, is polymerized by using the above catalyst.