Process for the preparation of a propylene block copolymer

摘要

The invention relates to a process for the preparation of a propylene block copolymer of high rigidity and excellent impact strength in which, in a first step, propylene or a mixture of propylene and another ethylenically unsaturated hydrocarbon monomer other than propylene is polymerised in the presence of a catalyst comprising a titanium-containing solid component (A), an organoaluminium compound-containing component (B) and an alkoxy silicon compound-containing component (C), and, in a second step, propylene and another ethylenically unsaturated hydrocarbon monomer are copolymerised in the gas phase in the presence of the first crystalline polymer from step (1), with re-use of the catalyst from the first polymerisation and in the presence of a saturated hydrocarbon having 6 or more carbon atoms, forming an elastomeric fraction in the form of a component of the crystalline polymer fraction mixture.