Patent GB-823706-A (GB)
Title: Improvements in and relating to coating processes
Inventor: JONES EDWARD RICHARD STANLEY
IPC: B32B15/08
Filed: 1956-03-29
Abstract: A process for uniting an organic thermoplastic material to a surface to form a coating thereon comprises placing the object to be coated inside a length of tubing of thermoplastic material, sealing the tubing at one end either to itself or round a portion of said object, withdrawing air through the other end of the tubing, and progressively melting the thermoplastic material from the sealed end towards the end from which air is being withdrawn. The coating material may be polythene, polyvinyl chloride or natural or synthetic rubber; and the tubing may be stretched before the article is placed inside it.  The article to be coated may be of copper or other metal and may be an electrical conductor (a bus-bar in the example) or may be of plastics, wood, glass or ceramics.  An adhesive may be first applied to the surface to be coated.  For coating metals with polythene, the metal may first be coated with a thin coating of polythene which is then oxidized by baking, and the main polythene coating applied by the above method.  The coating material may contain antioxidants, pigments, carbon black, &c.  Two or more layers may be applied by repeating the process.  According to the Provisional Specification, the method comprises bringing the thermoplastic material, not necessarily in the form of a tube, in the heat-softened state progressively into contact with the surface to be coated while maintaining a pressure substantially below atmospheric in the space between the thermoplastic material and the surface to be coated, immediately in front of the advancing line of contact between the thermoplastic material and said surface.  A prefabricated section of the organic thermoplastic material may be progressively melted and applied to the surface to be coated, while a reduced pressure is maintained at the interface.  Tubes and similar elongated hollow articles can be lined with organic thermoplastic material by inserting a length of tubing of the thermoplastic material, sealing it at one end to the article to be lined, evacuating the space between the thermoplastic tubing and the article to be lined, and progressively melting the thermoplastic material by the application of heat, starting from the end at which it has previously been sealed to the article to be lined.  The known vacuum-moulding technique may be adapted by placing an article to be coated in a mould or other vessel that can be evacuated with its surface to be coated towards a sheet of thermoplastic material clamped over the vessel, and progressively softening the sheet and drawing it into contact with the surface to be coated.  The method can also be adapted to extrusion coating by maintaining a reduced pressure in the space between the extruded coating and the surface.  The method may be used for the covering of fibrous cords or ropes.  Specification 766,813 is referred to.ALSO:According to the Provisional Specification, extrusion coating techniques may be modified by extruding an organic thermoplastic material in the heat softened state directly on to the surface to be coated while a reduced pressure is maintained in the space between the extruded coating and the surface.  Cables may be formed in this way.  The take-off speed is adjusted in accordance with the viscosity of the softened thermoplastic material, to counteract the tendency of the thermoplastic material to be sucked into the aperture in the core of the die, through which the uncoated structure enters.  The coating material may be polythene, polyvinyl chloride or natural or synthetic rubber.  An adhesive may be first applied to the surface to be coated.  The coating material may contain antioxidants, pigments, carbon black &c. Specification 766,813 is referred to.