| 摘要 |
PURPOSE:To produce a cylindrical laminated film that is free from curl and excellent in transparency, by using crystalline thermoplastic resins that can provide a special relationship between an inner layer and an outer layer, and performing down-flow water-cooled inflation forming. CONSTITUTION:As a crystalline thermoplastic resin for an inner layer is used a resin having a melting point relatively higher, preferably 5 deg.C or more higher, than the crystalline thermoplastic resin for an outer layer. The resin for the inner layer, the resin for the outer layer and, if required, various additives are fed to an extruder 1, and after they are melted and mixed, they are introduced into a circular and a die 2. Then they are extruded downward and is subjected to down-flow water-cooled inflation forming (for example, blowing is effected by an air ring 3 and cooling water 4 is directly brought in contact with the bulb). The cooling temperature is 10-40 deg.C, and the blow-up ratio is 0.8-3. The layer thickness ratio of the outer layer to the inner layer is to be in the range of 30:70- 97:3. |
