MANUFACTURE OF POLYPROPYLENE

PURPOSE:To obtain a polypropylene in high catalytic activity with markedly low content of amorphous by-product, by first carrying out a preliminary polymerization, in a particular condition, of propylene (and another olefin) followed by polymerization of the propylene in the presence of the resulting catalyst- polymer composition. CONSTITUTION:First, in the presence of a catalyst comprising (A) titanium trichloride and (B) an organoaluminum compound (pref. diethylaluminum monochloride), a preliminary polymerization of (C) propylene singly or in combination with (D) another olefin is carried out in such a manner that the polymerization rate is 4-70g polymer per g of the component (A) per hr., also the amount of the resulting polymer being 3-100g per g of the component (A), follwed by performing the full-scale polymerization of the component (C) in the presence of the catalyst-polymer composition produced above, thus obtaining the objective polymer. It is recommended that said full-scale polymerization be conducted at temperatures higher than those in the preliminary one.