| 摘要 |
1,184,688. Extruding foamed plastics. UGINE KUHLMANN. 5 Sept., 1967 [7 Sept., 1966; 2 March, 1967], No. 40453/67. Heading B5A. [Also in Divisions C3 and F2] A hollow extrudate of foamable plastics is extruded from an extrusion head 4, Fig. 12, comprising a mandrel 5 into a temperaturecontrolled sizing die 7 where expansion of the plastics takes place inwardly of the extrudate to fill or decrease in volume cavity 15b. The nature of the final product, i.e. whether hollow or solid, depends on various parameters, chief amongst which is the draw-off speed of caterpillars 80. Sizing die 7 may be electrically heated, or as shown, have fluid-flow chambers 9; the temperature of the die in any event is maintained below the gelling point of the plastics and a smooth non-cellular skin 13 is formed on the extrudate. Suction may be applied to the extrudate via apertures in the sizing die, see Fig. 5 (not reproduced), and also to the cavity in the extrudate via a conduit in the die head mandrel, see Fig. 4 (not reproduced). In the embodiment of Fig. 12, the draw-off speed of caterpillars 80 is varied to produce a product having alternate hollow and solid portions. Hollow bricks may be formed by cutting into lengths such a product when of rectangular cross-section. In the embodiment of Fig. 6, a tube having a bore of constant cross-section is obtained by using an extrusion head having two mandrels 44b, 45 and a sizing die 47 having a single mandrel 47b, the separate layers of plastics formed by mandrel 45 expanding in die 47 to fill the cavity therebetween. Other embodiments describe the formation of a product of T-cross-section, Figs. 4 and 5 (not shown), and of rectangular or biconcave cross-section, Figs. 9-11 (not shown). Inward expansion of the extrudate may be on to a solid core, e.g. an electrical conductor. Plastics specifically mentioned are polystyrene, styrene acrylonitrile copolymers, acrylonitrile-butadiene styrene copolymers, PVC and mixtures of PVC with acrylonitrile butadiene styrene, polymethylmethacrylate, polyamides, polyethylene, polypropylene, polycarbonate, cellulose propionate and polyurethane. Twenty one examples are given and these include descriptions of the production of longitudinally ribbed rods and rods where such ribbing has been smoothed to give the surface a fibrous appearance. |
