| 摘要 |
Device has an outer and inner extrusion nozzle sections which move relative to each other. The entire nozzle head may also rotate. The nozzle aperture defined by the sections has one or more uneven areas so that by relative motion, the sections produce tubular film having non uniform thickness. Spec., the two layers of the sheath-type foil are combined by rolling in a roller which has a dielectric of silicone or a fluorine polymer.
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