METHOD OF MOULDING HEAT-EXPANDABLE THERMO-PLASTICS MATERIAL, AND MOULDS THEREFOR

摘要

1,261,718. Moulding foamed articles from expandable thermoplastic beads. PROFILE EXPANDED PLASTICS Ltd. 19 Sept., 1969 [26 Sept., 1968; 5 June, 1969], Nos. 45717/68 and 28474/69. Heading B5A. Thermoplastic, heat expandable beads are expanded by a heated fluid in a metal mould which is vented through apertures in plugs which have a low thermal conductivity so that beads in the centre of the mould fuse before those adjacent the plug. The plugs are preferably made of nylon 66 and comprise means, e.g. a flange or external screw thread, for fixing them in the mould and an internal bore closed except for slits at the end adjacent the inside of the mould. Some of the plugs may be connected to an exhaust manifold to assist the venting of the mould. In the embodiment shown in Fig. 1 comprising a two-part mould 10, 11 fitted with plugs 15, some of the plugs are connected via pipes 30 to a manifold 28 which is partially evacuated or vented to atmosphere. The other plugs serve as inlets for steam which is supplied at a pressure of 14-20 p.s.i.g. to enclosure 37 surrounding the mould. In a second embodiment (Fig. 6) all the plugs serve as both inlets and vents. The mould halves 46, 49 are mounted on fixed jaw 45 and movable jaw 48 and define steam chests 47, 50. Steam is supplied from pipe 55 under pressure to pipes 52, 53 and passes into the steam chests and through plugs 40 into the heads. The mould is then connected to atmosphere via pipe 56SP1/SP and steam pressure inside the mould causes it to vent. The mould halves are cooled by water from sprays 58 and the mould is opened by lowering movable jaw 48 with the lower mould half.