| 摘要 |
<p>1,156,217. Cellular articles with unfoamed skin. IMPERIAL CHEMICAL INDUSTRIES Ltd. 19 April, 1968 [3 May, 1967(2) ; 15 Dec., 1967 (2)], Nos. 20590/67; 20591/67; 57082/67 and 57083/67. Heading B5A. Articles having a cellular core and an unfoamed surface skin are produced by injecting an unfoamable thermoplastic resin into a mould cavity and before the centre thereof has set, injecting a heated foamable thermoplastic composition into the cavity, and allowing it to foam and set. The mould walls are preferably cooled and the mould cavity may be enlarged to allow expansion, e.g. by instantaneously or gradually relieving the pressure holding the mould halves together, the enlarging preferably being effected by the expansion pressure. A removable insert, e.g. a rigid sheet, for example, wood, plywood, metal, hardboard or a high melting thermoplastic, for manufacture of luggage, chairs, panels &c. or flexible sheets, e.g. P.V.C. for car seats &c. may line the mould before injection. The foamable and unfoamable materials, which may be the same or different, may be polyethylene, polypropylene, polybutene, poly-4-methylpentene-1, copolymers thereof, plasticized or unplasticized vinyl chloride homo-polymers and copolymers, homopolymers or copolymers of styrene, or methyl methacrylate and linear polyesters, e.g. polyethylene terephthalate. They may be injected into the mould from two separate, synchronized injection barrels, or an injection machine may be used which has an inlet port in the barrel so that blowing agent may be injected into the thermoplastic material after a plug of thermoplastic unfoamable material has built up at the orifice, so as to form a plug of foamable material adjacent the unfoamable plug. A second amount of unfoamable material may be subsequently injected. The blowing agent may be a volatile organic liquid, or a solid which thermally decomposes to a gas inert to the thermoplastic material. The mould may be textured to give a surface finish to the article. The unfoamable material may contain additives to improve moisture, light and heat resistance.</p> |
