| 摘要 |
PROBLEM TO BE SOLVED: To stably produce a tubular film of high quality at a high speed over a long time by bringing the inner surface of a molten resin into contact with an inner diameter equalizing device during a period when the molten resin reaches an expansion start point to form the tubular film. SOLUTION: Cooling devices 5,7 and devices 6-1, 6-2, 6-3 uniformizing the inner diameter of a molten resin are provided to an inflation molding apparatus. As the cooling devices 7, air ring devices are used and water is used in the cooling device 5 as a cooling medium and air is used in the air ring cooling device 7 as a cooling medium. The air ring cooling device 7 is arranged so that the air blown out of the device 7 impinges against the molten resin between the inner diameter uniformizing devices 6-1-6-3. Only the cooling device 7 is opperated to perform usual upward blow inflation molding and, subsequently, the cooling device 5 is operated to form an expansion start point position 2 above a die 1. The inner diameter uniformizing devices 6-1-6-3 are arranged between the expansion start point position and the die 1. |
