| 摘要 |
PURPOSE:To prevent a change into the unstable state of bubbles by bringing a columnar bubble stabilizing body, through which a refrigerant is passed, into contact with the inside of a constricting section when high-density polyethylene is extruded annularly, constricted once and inflated. CONSTITUTION:A refrigerant path 7 is formed properly into a bubble stabilizing body 2, and a refrigerant holding the bubble stabilizing body 2 at a specified temperature passes through a hole bored to a die. The inner surface of a comparatively fine constriction 4 shaped through high-speed molding is brought into contact with the surface of a bubble stabilizing body 2 cooled and cooled, and cooled by air blown off from an air ring 3 from an outer surface. Consequently, bubbles quickly reach a frost line, and take-off speed under the state in which bubbles are held stably is increased remarkably. Accordingly, since the bubble stabilizing body is also cooled from the inside in the constriction section, not only the quantity of cooling air cooling the outside need not be augmented but also the position of the frost line of bubbles is lowered, thus preventing a change into the unstable state of bubbles by cooling air. |
