| 摘要 |
<p>PROBLEM TO BE SOLVED: To realize a favorable stretch blow moldability by a method where in a polypropylene composition, the difference between the melt starting temperature and the melt finishing temperature of which is specified, is stretch blow-molded. SOLUTION: A polypropylene composition is set to have the difference between its melt starting temperature and its melt finishing temperature of 50 deg.C or more, especially of 70 deg.C or more. By copolymerizing the rubber component such as an ethylene, a butylene or the like with a homopolypropylene, a polypropylene copolymer is obtained. By means of only the polypropylene copolymer or of its blending with the homopolypropylene, the difference between the melt starting temperature and the melt finishing temperature is widened. Under the wider difference between the melt starting temperature and the melt finishing temperature, during a stretch blow molding, due to a stretch temperature, the polypropylene having a higher melting point does not melt and the polypropylene having a lower melting point melts or a mixed state of the molten polypropylene and the solidified polypropylene is present, resulting in realizing a polypropylene composition having a small sagging. The temperature range, in which a stretch blow molding can be possible, becomes winder, resulting in obtaining a favorable moldability.</p> |
