| 摘要 |
1,157,842. Extruding foamed plastics materials, STAMICARBON N.V. Jan. 17, 1967 [Jan. 21, 1966], No. 2529/67. Heading B5A. In an extrusion die for use with foamed plastics the die slot 1 is provided with enlarged portions 2 which diverge in the downstream direction and run parallel to one another and to the direction of extrusion. The product, which may be a sheet or tube, is thereby provided with localized surface elevations, Fig. 4 (not shown), but is substantially free from wrinkles. Typical values for the dimensions a, b, c, d and e are given, e.g. 0À25 mm. for e, a general requirement being that foaming should not occur until the plastics has emerged from the die. In a second embodiment, Fig. 5 (not shown), a fluted roller 3 is situated at the die orifice and is rotated by the material or otherwise. A product is formed having surface elevations running transverse to the direction of extrusion. Two rollers may be used to produce a sheet having elevations on both surfaces, and a polygonally cross-sectioned tube may be produced by providing a roller at each side of the polygon. In examples the plastics material is polyethylene or a polyethylene/polystyrene mixture with, as additives, micro crystalline wax and titanium oxide or calcium carbonate. The product may be used for packaging. |
