| 摘要 |
PROBLEM TO BE SOLVED: To facilitate speedup and the saving of a space and to perform stretching by setting the product part and edge parts of the film to uniform temp. by heating the plastic film to temp. higher than preheating temp. necessary for raising the temp. of the film to objective stretching temp. SOLUTION: A plastic film 1 is fed from the upstream side in the feed direction of the plastic film 1 to the downstream side thereof through preheating rolls 2-6 equipped with heat treatment devices to be raised in its temp. to an objective stretching temp. When the temp. before the preheating of the film 1 is rapidly raised to the objective stretching temp. from 80 deg.C, for example, to a temp. of 110 deg.C, the set temp. of the preheating roll on the upstream side in the feed direction of the plastic film 1 is set to temp. higher than the objective set temp. For example, the temp. of a product part is raised to temp. higher than the objective stretching temp., for example, by 3 deg.C and the edge part of the film is rapidly raised in temp. and, thereafter, the temp. of the preheating roll is set to the objective set temp. to eliminate the temp. difference between the product part and the edge part at a time of stretching. |
