| 摘要 |
PROBLEM TO BE SOLVED: To make thickness of a thin film of thermoplastic resin uniform and to prevent occurrence of perforation and rupture or the like by driving a cylindrical thin film of thermoplastic resin in the direction for passing the cylindrical thin film on the surface of a mandrel. SOLUTION: A cylindrical film F of linear low density polyethylene extruded from an extruder is vertically stretched by a vertical stretching device L to produce a vertically stretched cylindrical film F1. Thereafter, the cylindrical film F1 is lifted until necessary height by a guide roll and moved in the nearly horizontal direction. The course thereof is rectangularly curved by a turn roll R1 and downward moved. The outside diameters D1-D4 of a first-fourth mandrels M1-M4 are gradually enlarged and the film F1 is horizontally stretched gradually by passing it through the respective mandrels M1-M4. Further, the cylindrical film F1 passed through the circumferences of mandrels M1, M2, M3 is heated by infrared heaters H1, H2, H3. |
