GB1250768A - - Google Patents

Abstract

1,250,768. Moulding expanded thermoplastics articles. MONSATOR HAUSHALTGROSSGERATE KOMBINAT VEB. 8 Nov., 1968, No. 47548/68. Heading B5A. Components of expanded thermoplastics material are made by charging a mould cavity with thermoplastic material containing blowing agent, closing the mould to render the cavity pressure-tight and introducing a heating medium to the cavity from at least one side of the mould through nozzles, the heating medium being introduced through different nozzles at different rates of flow. The nozzles may extend into the mould cavity and the nozzles are connected in groups to a set of inlets through which the heating medium, e.g. steam, is supplied at different rates. Some of the nozzles may function initially as exhausts to remove air, these nozzles being closed and the pressure in the mould allowed to increase during the forming. The mould may be cooled and may be lined with a low thermal conductivity material, e.g. a plastics or elastomeric material or with a layer of a good conductor spaced from the mould wall by insulating bridges. As shown, the mould comprises a moulding box 2 and a cover 4, strengthened by ribs 3. An insert 5 is introduced into the mould, unexpanded material is placed in the mould and the mould is closed. Three nozzle systems pass through the cover 4 and are connected respectively to feeds 6, 7 and 8. Heating medium is supplied to the mould through feeds 7 and 8 and feed 6 is initially open to the atmosphere to permit expulsion of air and heating medium condensate. The nozzles 6 are then closed and the heating medium introduced through passages 7 and 8 at rates which heat and expand the plastics material uniformly. The steam supply is then stopped, the mould cooled conventionally and the moulding removed.