| 摘要 |
PURPOSE:To make it possible to produce a product having excellent uniformity of thickness, by cooling a bubble of high temp. extruded from a circle nozzle during drawing it to the axial direction and by expanding the bubble at one operation after a specified operation. CONSTITUTION:A bubble 15 extruded from a circle nozzle 12 of a molding die 10 is directed to the downstream direction with very little change in the diameter and is passed through a lower stablizer 13a and an upper one 13b. The bubble 15 is oriented to the axial direction with very little increase in its diameter and is gradually cooled by the cooling wind blowing downward until the bubble temp. reaches about the upper limiting temp. at which orientation starts to remain. The height at which the radial expansion of the bubble 15 starts above the circle nozzle 12 is 7 to 12 times of the diameter of the circle nozzle 12. The expansion of the bubble 15 is carried out at one operation while the bubble temp. is kept within the temp. range where the orientation remains. It is possible by this means to enlarge the limiting output further and to improve the dimensional uniformity of the thickness. |
