| 摘要 |
PURPOSE:To obtain polyvinyl alcohol film transparent and excellent in gas barrier property by a method in which polyvinyl alcohol resin is treated in a specified manner, and has 55% or more crystallinity index obtained by a differential scanning calorimeter. CONSTITUTION:The polyvinyl alcohol film oriented uniaxially or biaxially so that is drawing magnification at least in one direction becomes 5-10, is heat-treated in the temperature range equal to the drawing temperature or higher and equal to or lower than the melting point of base resin. Next, the heat-treated film is treated to be left in high humidity condition until its moisture content becomes 5-20%. If the moisture content is shifted from said range, the crystallinity index is not almost improved. Then, the film with 5-20wt% moisture content is heated and dried, until said moisture content becomes 1wt% or less. When the moisture content exceeds 1wt%, its crystallinity index is not improved, and the gas barrier property is not also improved. If necessary, further a second and a third processes are repeatedly achieved, whereby a polyvinyl alcohol film more excellent in recrystallization property may be obtained. |
