| 摘要 |
PURPOSE:To heighten remarkably the production yield of films as the result of the improvement of the stability of succeeding orientation by a method in which when a biaxially oriented polyoxymethylene film is produced, a blank sheet is rolled between a pair of rolls with mutually different prepheral speeds in the rolling process thereof. CONSTITUTION:When the biaxially oriented film composed of polyoxymethylene polymer is produced, a melted and solidified blank sheet or film 1 is rolled under such sufficient pressure that its draft (r) satisfies the formulas 1, 2 between a pair of rollers 2a, 2b which are rotated at mutually different peripheral speeds, and then it is biaxially oriented. (in formulas, (t0) shows the thickness of the film or the sheet before rolling, and (t) shows the thickness of the film or the sheet after rolling). In the case of successively biaxially orienting method, the method in which first, transverse orientation is carried out, and next, longitudinal orientation is carried out is preferable. Then, the draw ratio in each direction is at least 3 times and preferably at least 5 times in transverse direction, and at least 1.1 times and preferably at least 5(1-r) times in longitudinal direction. |
