GB778661A - Improvements in or relating to processes for the manufacture of electrical surface-heating devices - Google Patents

Abstract

778,661. Laminates. BRISTOL AIRCRAFT, Ltd. March 23, 1954 [Dec. 23, 1952], No. 32662/52. Drawings to Specification. Class 140. [Also in Groups XI and XXXVI] A method of making a sheet of composite material, e.g. for an electric heating mat, consisting of a layer of nickel or nickel alloy foil adhering to a flexible layer of electrically insulating material, comprises electrodepositing a layer of the foil on a receptive conducting surface which is polished so that the foil adheres weakly thereto, bonding to the foil a flexible layer of the insulating material, and then simultaneously stripping the bonded layers of foil and material from the former. The receptive area is on the surface of a stainless steel plate. After electroplating with nickel or a nickel alloy (see Group XXXVI), the plate is marked out in areas and each area is coated with an adhesive containing ethylene dichloride, a thermosetting phenolic base resin, and industrial spirit. Two sheets of brown paper are impregnated with a partly cured thermosetting resin, e.g. with the adhesive described above, dried and tacked in place over each area. A sheet of tissue paper and a sheet of brown paper are then laid over all the areas and tacked in place. The composite sheet is then bonded together by heat and pressure, e.g. in excess of 100 lbs./square inch at 140‹ C. for 30 minutes and allowed to cool. The tissue and upper brown paper sheets are scraped off, foil on the receptive area severed from the rest of the foil on the plate by filing, and the foil and impregnated paper together removed from the plate. The exposed foil is printed with a positive of the pattern required, is suitably masked, and the unmasked foil removed electrolytically or chemically, e.g. as described in Specification 639,178, [Group XI]. In a modified process, an ink negative of the pattern is applied by silk printing or by stencils to the receptive area, the periphery of which is masked, and the plate electroplated as before. A sheet of glass fabric impregnated under slight tension with an uncured or partly cured resin, e.g. epoxy or ethoxylene resin is laid on the foil and subjected to heat and pressure as before, cooled under pressure, and the foil and fabric stripped from the plate. A second sheet of glass fabric, impregnated in the same manner as the first, is laid on the exposed foil and the whole heated for 15 minutes to 120‹ C. at at least 3 Ibs./square inch. If desired, in the modified process, after electroplating, the foil may be sprayed with uncured or partly cured thermosetting resin, e.g. epoxy or ethoxylene resin, which is allowed to set, and foil and resin are removed from the plate. Glass fabric sheets are then impregnated as before and bonded to each side of the coated foil as described above. The composite material formed by any of the above processes is bonded to a surface through a resin interlayer, e.g. with a resin-impregnated glass fibre layer at each face of the composite material.