摘要 |
1528728 Heat insulated film blowing head DEMAG KUNSTSTOFFTECHNIK ZWEIGNIEDERLASSUNG DER DEMAG AG 1 July 1977 [2 July 1976] 27748/77 Heading B5A Apparatus for producing a tubular film 5 of low density polyethylene, polypropylene, or polyamide comprises inner and outer extrusion die parts 4, 6<SP>1</SP>, defining an annular outlet 13 from which a tube of the material is extruded and inflated into the film, an annular air cooling outlet slit 12 surrounding the die part 6<SP>1</SP> and from which cooling air is directed axially of, and in the same direction as the film 5 to cool its exterior, and a heat barrier 18 between the extrusion and air outlets 13, 12 to reduce heat transfer therebetween. In the Fig. 1 embodiment (not shown), the heat barrier comprises an air gap (14) extending from the downstream face of the outer die part (6). In the Fig. 2 embodiment the barrier comprises a closed air gap 18 defined between the outer die part 6<SP>1</SP> and a ring 15, which defines the inner surface of the outlet 12 and channel 10 and has a highly polished heat reflecting surface facing the gap 18. In the Fig. 3 embodiment (not shown), the barrier comprises a layer of polytetrafluoroethylene on the exterior of the outer die part (6<SP>11</SP>). The film may comprise low density polyethylene, propylene, or polyamide. |