| 摘要 |
PURPOSE:To obtain a packaging film, which has automatic stretch packability and, at the same time, is excellent in stretchability and recovery properties from deformation, by a method wherein the film thickness, birefringence, the ratio between the longitudinal and lateral heat shrinkage factor and 100% recoverable maximum strain are provided. CONSTITUTION:The film concerned is set to have the thickness of 6-100mum, the birefringence DELTAnA represented by DELTAnA=¦nMD-nTD¦, in nMD and nTD are respectively the refractive indices to the extrusion direction and to the widthwise direction, of 0.6X10<-3>-8X10<-3>. If the orientation of molecular chain is large, the stretching in the oriented direction becomes poor. Further, the ratio between the heat shrinkage factor in the extrusion direction and that in the widthwise direction after being left in silicone oil with 140 deg.C for three minutes is set to be 0.65-1.5. Furthermore, the 100% recoverable maximum strain, which is measured by pushing a hemisphere with the radius of 20mm at the center of a circular sample fixed under tension with the diameter of 100mm and then removing the hemisphere from the sample, is set to be 18mm or more. The film is preferably inflation-molded with polyolefin-based resin. |
