| 摘要 |
PURPOSE:To produce highly heat-shrinkable film having longitudinal and lateral heat shrinkage factors, which are well balanced with each other, by a method wherein film, which is produced by extruding mixed resin prepared by adding specified petroleum resin to polypropylene resin, is stretched by successive biaxial stretching. CONSTITUTION:Stock film, which is produced by extruding and forming melt extrusion composition, the resin component of which consists of 100 pts. wt. of polypropylene resin and 5 - 30 pts. wt. of petroleum resin is stretched by successive biaxial stretching so as to obtain film having longitudinal and lateral heat shrinkage factors of 35% or more respectively. As the petroleum resin- based hydrocarbon, petroleum resin, hydrogenated petroleum resin, terpene resin, hydrogenated terpene resin or the like is exampled. The normal order of the successive biaxial stretching of the stock film obtained by extrution molding or of processes for stretching longitudinally and laterally is from longitudinal stretching to lateral one. The preferable longitudinal stretching is performed at about 70 - 110 deg.C. The preferable lateral stretching is performed at about 90 - 130 deg.C or is set at stretching temperature, which is higher than the longitudinal stretching temperature by about 15 - 20 deg.C. |
