Patent GB-784503-A (GB)
Title: Process for producing an article or surface with a protective covering of thermoplastic material
Inventor: MONCRIEFF LESLIE JOHN
IPC: B29C51/16
Filed: 1953-08-28
Abstract: <PICT:0784503/III/1> A flat or profiled base is coated by drawing a heat-softened thermoplastic film or sheet into contact with the base by rapidly withdrawing air from between the two, and thereafter cooling the thermoplastic material, the structure of the base being such as to provide channels for the further withdrawal of air from between it and the thermoplastic sheet after they have made contact. The base material may be porous, e.g. woven, knitted, pile, or felted fabric, wire gauze, porous metal, unglazed paper, blotting paper, or cardboard, or may have a granular or scored surface, e.g. granule-coated abrasive paper, embossed cardboard, embossed cellulose acetate, or metal scored with V-shaped grooves.  The base may be flat or curved, e.g. a dish- or cup-shaped papier mache article, or may be a showcard to which objects are fixed for display in shops or museums.  The base may be nonporous, e.g. wood, metal, or thermoplastic material, perforated over the areas to be covered by the objects, and may be heated from the uncovered side to assist bonding.  The objects may be covered with an adhesionresisting film such as regenerated cellulose or polytetrafluorethylene, coated with a silicone parting agent, or protected by spacing members which prevent the film from contacting the object.  The thermoplastic film, which may be transparent or opaque, coloured or colourless, printed or decorated, may be of a cellulose derivative such as cellulose acetate or acetate butyrate, ethyl or benzyl cellulose, one of a number of specified vinyl and acrylic resins, rubber hydro-chloride, certain polyesters, polyamides, and polyesteramides.  The backing on which the objects are mounted may be white or coloured, printed or decorated, and, if a fabric, may be of cellulose acetate, regenerated cellulose, silk, or cotton. An adhesive may be applied to the film or in a discontinuous layer, e.g. sprayed, to the surface to be coated. As shown, objects 10 are arranged on a porous base sheet 11 provided with a porous coating 12 of a thermoplastic adhesive.  The base sheet is laid on a perforated plate 13 supported by blocks 14 in a vessel 15 connected by a large bore pipe 16 provided with a quick-opening valve 17 to a large, closed vacuum vessel.  A thin thermoplastic sheet 19 clamped around its edges between the edge 18 of the vessel 15 and a rubber gasket 20 by a frame 21, is heated by an electric heater 22 until plastic.  The valve 17 is opened and the sheet 19 is sucked down into contact with the coated base sheet 11 to which it adheres.  Articles may be mounted between a thermoplastic foil of cellulose acetate and a scored metal plate, the foil stripped off, trimmed, the articles replaced in their cavities and a backing sheet of cellulose acetate cemented to the assembly instead of the metal plate.  The adhesive may be polyvinyl acetate, polyvinyl chloride-acetate, polyvinyl chloride, polyethyl or methyl acrylate, plasticised ethyl cellulose, cellulose acetate-butyrate, nitrile synthetic rubbers, cyclized rubber, or chlorinated rubber.  Abietic acid and its derivatives, alkyd resins, urea- and melamine-formaldehyde resins may be added.