| 摘要 |
PURPOSE:To eliminate the adhesion of polymer to the under surface of a mouthpiece and consequently form a film with no fluctuation in thickness by a method wherein the forming mouthpiece of thermoplastic polymer is coated with ceramic having the specified wetting angle to the polymer. CONSTITUTION:The under surface of a metal T-die mouthpiece is coated with ceramic, the wetting angle of which to thermoplastic polymer is 70 deg. or more. The thermoplastic polymer is extruded through the above-mentioned mouthpiece and cooled and solidified on a cooling drum and, in succession, stretched biaxially and finally heat-treated. No adhered matter consisting of decomposition product of the thermoplastic polymer is shown on the mouthpiece and consequently biaxially stretched film with no projected mouthpiece streak at all is obtained. In addition, no breakage of film occurs. |
