| 摘要 |
PURPOSE: To obtain a copolymer excellent in clarity, resistance to whitening due to impact, molding shrinkage, and resistance to whitening due to folding by producing a propylene-ethylene block copolymer by vapor phase polymn. under specified conditions. CONSTITUTION: This copolymer is obtd. by using a stereospecific catalyst comprising a titanium-contg. solid catalyst component, an organoaluminum compd., and if necessary, an organosilicon compd and by polymerizing propylene therewith to produce a homopolymer in an ant. of 70-20wt.% of the finally resulting copolymer and then copolymerizing a mixture of ethylene and propylene to produce 80-30wt.% of the copolymer under such conditions that the ethylene content of the copolymer becomes 25-65wt.%. The copolymer is produced in such a manner that the intrinsic viscosity ([η]PP and wt. (WPP) of the homopolymer part and the intrinsic viscosity ([η]RC) and wt. (WRC) of the copolymer part satisfy the relations: ([η]RC/[η]PP)×(WPP/WRC)=0.2 to 2.0 and [η]RC<6.5 and that the ratio of the melt flow rate of the homopolymer part to that of the copolymer part is in the range of 0.3-4.
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