| 摘要 |
PURPOSE:To obtain a biaxially oriented film low in anisotropy, good in dimensional stability and used in food packing or the like, by specifying a temp. condition in performing such a process that an unoriented film of nylon 12 is oriented by inflation and simultaneously subjected to biaxial orientation and the resulting oriented film is further set under heating. CONSTITUTION:A tubular unoriented film obtained by cooling molten nylon 12 extruded into a tubular shape is inflated and stretched and simultaneously subjected to biaxial orientation by applying gas pressure to the interior of the tube within a stretchable temp. region and the oriented film is set under heating. In this case, the surface temp. of the film at the begining of inflation is regulated to 60-80 deg.C and a temp. gradient is taken so as to bring the surface temp. of the film at the 1/2-1/3 advance position of an orientation region from the begining of inflation to the finishing point thereof to a max. temp. to adjust the temp. to 80-90 deg.C. In addition, the temp. gradient wherein the surface temp. of the film in the orientation region from the max. temp. position to the finishing point of inflation is fallen 5-10 deg.C from the max. temp. is kept to obtain a film with tensile strength of 1,500kg/cm<2> or more in all directions and hot water shrinkage ratio of 3% or less at 100 deg.C. |
