| 摘要 |
PROBLEM TO BE SOLVED: To obtain a propylene block copolymer that can be produced in a low cost, as high productivity is retained, and has a high rubber content and excellent powder properties. SOLUTION: This continuous production process for a propylene block copolymer comprises a first polymerization step in whichα-olefin mainly comprising propylene is polymerized in the presence of a stereospecific polymerization catalyst consisting of a solid catalyst containing magnesium, titanium, a halogen and an electron donor, an organoaluminum compound and, when necessary, an electron donor in the presence of hydrogen in a single polymerization tank, and a second polymerization step in which the polymer prepared in the first step is sent thereto and the copolymerization of propylene andα-olefin other than propylene is carried out substantially in the vapor phase in the presence of the stereospecific polymerization catalyst used in the first step. In this case, the polymer sent from the first polymerization step to the second polymerization step has an average particle size of >=600μm.
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