| 摘要 |
PURPOSE:To obtain polypropylene sheet, the sagging at the heating for differential pressure forming of which is small and out of which a vessel excellent in the uniformity of wall thickness and impact strength can be obtained, by a method wherein ultrahigh molecular weight crystalline polypropylene power having specified intrinsic viscosity is turned into sheet with revolving rolls, the temperature of which is set within the specified temperature range above its melting point. CONSTITUTION:The crystalline polypropylene used for the manufacturing method concerned has intrinsic viscosity in tetralin at 140 deg.C of 4-50dl/g. The polypropylene powder is continuously compression-molded into sheet with one pair of a plurality of pairs of metal pinch rolls 5-8. At this time, the surface temperature of the rolls 5-8 is set to be higher than its crystalline melting point (Tm) and lower than Tm+110 deg.C. Tm is the crystalline melting end temperature of the DSC curve obtained when the temperature is raised at the rate of 5 deg.C/min. If the surface temperature of the rolls is help below Tm, the mechanical strength of the formed article made of the obtained sheet is remarkably low. If the surface temperature of the rolls is held above Tm+110 deg.C, the stable forming of the obtained sheet becomes impossible. |
