| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for producing a propylene-based block copolymer excellent in balance between rigidity and impact resistance by using an inexpensive apparatus low in installed cost and operation cost while maintaining a high productivity. SOLUTION: This continuous production method consists of a first-stage polymerization process carried out in the presence of a magnesium, titanium and halogen-based stereoregulation catalyst by a single polymerizer and a second-stage polymerization process for sending the prepared polymer to a propylene/anα-olefin copolymerization tank and copolymerizing propylene with theα-olefin except propylene in a vapor phase and satisfies the following requisites. (1) When the particle diameter distribution of the solid catalyst component is approximated by Rosin-Rammler distribution, an (n) order showing the particle diameter distribution is n>=5. (2) When a polymer slurry pulled out from the firs-stage polymerizer is classified into a slurry containing a large amount of particles having larger diameters and a slurry containing a large amount of particles having smaller diameters, the former is transported to the second-stage polymerization process and the latter is returned to the first-stage polymerization process.
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