GB1096453A - Improvements relating to surface coatings - Google Patents

Abstract

A method of coating a surface with flake-like particles which surface is capable of retaining the particles when pressed thereon consists of causing the particles to impinge on the surface in an edge-on position and pressing the upstanding particles down on to the surface. The particles may be mica particles, and they may be applied by electrostatic deposition to a sheet or layer of plastics film or foil, or a woven or non woven fabric, e.g. of natural or synthetic fibres such as cotton, rayon, nylon, polyester or glass. The surface to be coated with mica may be treated with a natural or synthetic resin, which may be cured or semi-cured, then coated with a resin dissolved or dispersed in a solvent or aqueous medium to produce a soft, tacky face to which the mica particles will adhere. The mica flakes may then be fed into a vibratory hopper which is positioned over the surface to be coated and has a base incorporating a fine slotted grid charged by a high voltage generator, such that when the hopper is vibrated the flakes are caused to discharge through the grid or to the surface in an edge-on position. An earthed plate over which the material being coated is supported forms the other pole for the electrostatic field. The material is then passed between two pressure rollers. The spacing between the impinging flakes may be such that when pressure is applied, each flake overlaps its neighbour to form a continuous layer. Further layers of adhesive resin and mica may be applied. The mica coated materials may be used for the insulation of electrical machines, and if semi-cured resin has been employed in the coating procedure, the curing may be completed at this stage.ALSO:A method of coating a surface with flakelike particles which surface is capable of retaining the particles when pressed thereon consists of causing the particles to impinge on the surface in an edge-on position and pressing the upstanding particles down on to the surface. The particles may be mica particles, and they may be applied by electrostatic deposition to a sheet or layer of plastics film or foil, or a woven or non woven fabric e.g. of natural or synthetic fibres such as cotton, rayon, nylon, polyester or glass. The surface to be coated with mica may be treated with a natural or synthetic resin, which may be cured, or semicured, then coated with a resin dissolved or dispersed in a solvent or aqueous medium to produce a soft, tacky face to which the mica particles will adhere. The mica flakes may then be fed into a vibratory hopper which is positioned over the surface to be coated and has a base incorporating a fine slotted grid charged by a high voltage generator, such that when the hopper is vibrated the flakes are caused to discharge through the grid or to the surface in an edge-on position. An earthed plate over which the material being coated is supported forms the other pole for the electrostatic field. The material is then passed between two pressure rollers. The spacing between the impinging flakes may be such that when pressure is applied, each flake overlaps its neighbour to form a continuous layer. Further layers of adhesive resin and mica may be applied. The mica coated materials may be used for the insulation of electrical machines, and if semicured resin has been employed in the coating procedure, the curing may be completed at this stage.