| 摘要 |
PROBLEM TO BE SOLVED: To obtain a product, in which neither longitudinal contraction, nor scoreline, nor die score nor melt fracture develops, which is excellent in planeness by a method wherein the temperature of a support at casting position is set to be lower than the boiling point of a main solvent used in a dope by the specified range and a cast draw ratio is set within the specified range. SOLUTION: If the temperature of a support 3 at the position, against which a dope is cast, is equal to or higher than the boiling point of a main solvent in a dope, a cast dope film 1 immediately expands. Casting is executed under the condition that the temperature of the support 3 at casting position is set to be lower than the boiling point of the main solvent used in the dope by 0.5-55 deg.C or under the condition that the dope film neither expands nor gelates by low temperature and, at the same time, a cast draw ratio is set to be 1.0-3.0. If the temperature of the support 3 at the casting position is too low as compared with the boiling point of the main solvent in the dope, some of the main solvent tends to easily gelled, resulting in making it impossible to turn into a film as the case may be. |
