Patent ID: 6121393
Filing Date: 2000-09-19
Classification: C08F

Abstract:
A process for polymerizing propylene or copolymerizing at least 70 mole % propylene with another alpha-olefin which comprises preliminarily polymerizing propylene in the presence of(A') a highly active solid titanium catalyst component containing magnesium, titanium and halogen atoms,(B) an organoaluminum compound, and(C) a catalyst component consisting of branched chain alkyl chlorides having up to 20 carbon atoms or titanium tetrachloride,wherein the components (A'), (B) and (C) are contacted in the presence or absence of propylene, prior to the preliminary polymerization; andpolymerizing propylene or copolymerizing at least 70 mole % propylene with another alpha-olefin in the presence of the resulting catalyst formed in the preliminary polymerization;wherein said preliminary polymerization is carried out in suspension with an inert hydrocarbon medium by polymerizing 1 to 100 g of propylene, per 1 g of the component (A'), and the preliminarily polymerized catalyst in suspension is separated from the suspension; andwherein, in the case when the catalyst component (C) is titanium tetrachloride, the proportion of the transition atom in the component (C) is 0.1 to 10 gram.multidot.atom per gram.multidot.atom of titanium in the component (A').