| 摘要 |
PURPOSE:To obtain a film which is excellent in thermal dimensional stability and has high cushioning properties and whiteness by a method wherein the heat shrinkage, the specific gravity and the shape factor of non-compatible polymer dispersed in polyester are set within the specified range. CONSTITUTION:Of the polyester film concerned, its heat shrinkage factor at 150 deg.C is set to be below 2 % and its specific gravity is set to be 0.95 or below. Further, non-compatible polymer is dispersedly mixed in the polyester film and the preferable shape factor of the non-compatible polymer in the film is 1- 4. Furthermore, the preferable color tone b-value measured with the color difference meter is -3 or below. The effect for reducing the specific gravity of the film is obtained by adding specific gravity reducing agent such as polyeth ylene glycol or the like to polyester. Further, the non-compatible polymer is polymer, which is selected from the group consisting of methyl butene polymer, methyl pentene polymer, styrene-based polymer, fluorine-based polymer, cellulose acetate polymer and cellulose propionate polymer, and which has a melting point of 200 deg.C or higher. |
