| 摘要 |
PURPOSE:To improve the impact resistance and flow of a block copolymer and at the same time to decrease the amount of a low-crystalline component by-product, by performing the block copolymerization in two steps in the presence of a catalyst comprising a combination of a solid composition comprising Mg, Ti and a halogen with an organoaluminum compound and two specified silicon compounds. CONSTITUTION:As catalyst components, a solid composition (A) essentially consisting of Mg, Ti and a halogen, an organoaluminum compound (B), a compound (C-1) having at least one Si-bonded aromatic substituent and at least one Si-O-C bond and a compound (C-2) having no Si-bonded aromatic substituent and at least one Si-O-C bond are used. In the first step, a propylene homopolymer or a propylene copolymer of an ethylene content <=5wt% is formed in an amount corresponding to 60-95wt% of the total weight of polymer to be produced, in the presence of catalyst components A, B and C-1. In the second step, component C-2 is added and a copolymer of an ethylene content of 20-100wt% is produced so as to obtain an overall ethylene content of 3-40wt%.
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