IE32745L - Moulding plastics articles. - Google Patents

Abstract

1,259,349. Moulding filled articles. LIBBEYOWENS-FORD CO. 19 Feb., 1969 [27 Feb., 1968], No. 8954/69. Heading B5A. General method.-Articles are moulded by providing an assembly of filler particles which are tightly packed into contact under pressure and provide pores between adjacent particles which are then filled, after release of the compacting pressure, by injecting thermoplastics or thermosetting liquid or powder resin into the assembly. The assembly may comprise a non-self-sustaining assembly which may be compacted around removable cores and/or inserts in the mould cavity. Alternatively, the particles may be cohered into a self-sustaining form by an adhesive, e.g. sodium silicate or a plastics which may be the same or different from that injected into the pores, or by sintering. Heat, solvent, or vibrationally removable cores may be employed and they may be coated to provide a shell or encased in a shell which remains in the article. Examples.-A self-sustaining preform 41 (Example 1) is formed by filling, by pouring or blowing, a preform cavity 25 with spherical aluminum pellets coated with sodium silicate, and compacting the particles, e.g. at 5 p.s.i., around a removable core 36. CO 2 gas is introduced into the assembly from conduit 39 through a mould cover 37 held in place by an upper platen 54. The preform is removed from the mould cavity 25 and after heating, e.g. to 100‹ F., is located within a close fitting cavity, Figs. 6 and 7 (not shown), of an injection mould heated also to 100‹ F. and into which NYLON 6 is injected at 525‹ F. and 20,000 p.s.i. from a horizontal cylinder screw-ram machine. The removable core 36 comprises sand grains bound together with CO 2 hardened sodium silicate, dipped into precoating material and then sprayed with polyvinyl alcohol release agent; a shell of epoxy resin, which remains in the article, may be coated on the core. The core 36 is removed either by a jet of water directed thereat in a water container, or by mechanical vibration of the article. The preform 41 (Example 2) may also be moulded in the cavity 25 from randomly shaped and sized aluminium particles wetted with silane and mixed with phenolic resin moulding powder, the mould being heated by resistance heaters 40 and hot air introduced into the cavity 25. The preform at 70‹ F. was introduced into the close fitting injection mould at the same temperature, and polyethylene injected thereinto at 410‹ to 475‹ F. at 20,000 p.s.i. A preform 41 formed as in either Example I or II may be injected with thermosetting resin, from either a horizontal or vertical cylinder machine. A preform 56 (Example 4) of sodium silicate bound aluminium particles, and incorporating a threaded member 57, may in addition be provided with a coating of the injected resin by locating it by the member 57 within a cavity 65 of a vertical cylinder injection machine into which polyvinyl chloride resin is injected through gates 68, the preform and mould being respectively at 70‹ and 50‹ F. and the injection being at 325‹ F. and 12,000 p.s.i. The polyvinyl chloride (Example 5) may comprise material containing azodicarbamide foaming agent injected at 15,000 p.s.i. to produce an unfoamed filling of the preform 56 and a similar exterior surface, with an intermediate foamed region. The surface of cavity 65 may be configured to simulate leather or fabric. It is stated that the particulate fillers may also be elongated, or of cube or plate form, and may also comprise wood, steel, sponge iron particles, walnut shells, acrylonitrile-butadiene-styrene resin, glass beads, asbestos, and marble and stone. The injected resins may also comprise polyethylene, polypropylene, acrylics, polystyrene, acrylonitrile - butadiene - styrene, polyurethane, synthetic rubbers, polyesters, polycarbonates, epoxies, and silicones. [GB1259349A]