Process for producing propylene-ethylene block copolymer

Abstract

A propylene-ethylene block copolymer in the presence of a catalyst comprises as main components, a solid titanium-containing catalytic component and an organoaluminum compound having the formula AIR.sub.m.sup.1 Cl.sub.3-m (R.sup.1 represents a C.sub.1-20 hydrocarbon moiety; and m is 3.gtoreq.m>1.5) by producing a homopolymer of propylene or a propylene-ethylene copolymer by polymerizing propylene or both propylene and ethylene at a vapor phase propylene concentration of 90 mol % or higher based on the sum of propylene and ethylene in a first step and producing a propylene-ethylene block copolymer by copolymerizing propylene and ethylene at a vapor phase propylene concentration of less than 90 mol % based on the sum of propylene and ethylene in the presence of the polymer resulted in the first step and the catalyst in a second step is produced by newly adding an aluminum compound having the formula AlR.sub.n.sup.2 X.sub.3-n (R.sup.2 represents a C.sub.1-20 hydrocarbon moiety; X represents a halogen atom and n is 1.5.gtoreq.n.gtoreq.0) to the components for the copolymerization in the second step.

Dependencies are inferred from the claim text.