Patent GB-1329724-A (GB)
Title: Monograin layer membrane
IPC: B32B5/16
Filed: 1970-09-15
Abstract: 1329724 Membrane PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 15 Sept 1970 [18 Sept 1969] 44015/70 Headings B2E and B1X A mono-grain layer membrane comprises a layer of grains having a thickness of one grain diameter, which grains are embedded in a synthetic resin film in which part of the surfaces of the grains on at least one side of the membrane are not coated with synthetic resin, and wherein the grains are located in the apertures of a piece of wire gauze which is embedded in the synthetic resin film together with the grains. The grains may consist of ionexchange material such as cation-exchange or anion-exchange resins, electrically conducting materials such as carbon or metals, or semiconductor materials, molecular sieves or materials which exclusively pass cations or anions of a certain size. The wire gauze must have apertures of size not less than the diameter of the smallest grain and may be manufactured from wires of natural or synthetic polymers such as natural silk, nylon, polyester, polyvinylidene chloride, glass fibres, metals, alloys such as stainless steel, phosphor bronze, nickel and nickel alloys. Combinations of metal wires and wires of other materials may be used. The wire gauze may be obtained by weaving or by interconnecting, e.g. by knoting, welding or electro-deposition with a metal of two or more layers of mutually parallel wires on their points of intersection, which wires are located relatively to one another at a given angle in the successive layers. Pieces of wire gauze from synthetic resin may be obtained by extrusion. The apertures in the wire gauze may be square or hexagonal and the apertures may have mutually different shapes and dimensions accommodating grain materials having different functions. The wire gauze may also be a material obtained by the provision of a large number of apertures in a metal or synthetic resin film. Preferably each aperture accommodates one grain. The synthetic resin may be polyester resins, polycarbonate resins, polyamide, phenol formaldehyde, polyurethane and epoxy rins. As shown informing an initial membrane (see Fig. 3), an adhesive layer 2, e.g. a highly viscous solution of natural and synthetic rubber such as polyisoprene is applied to a substrate 1, e.g. a glass or metal plate and the wire gauze 3 is laid on this layer. Grains 4 are scattered on the wire gauze and after removal of superfluous grains, a solution of synthetic resin 5 or of materials which form the synthetic resin in situ is poured out on to the grains 4 and the solvent subsequently removed. If necessary part of the resulting film is removed, e.g. by scouring, dissolving it partially, saponifying it or etching it away to expose the surface of the grains. The membrane is then detached from the substrate 1, e.g. by dissolving the adhesive layer 2 (see Fig. 5). In another embodiment a wire gauze is used whose wires are already coated with a thermoplastic synthetic resin or a thermosetting synthetic resin in the B-stage. The wire gauze is then laid on the adhesive layer, grains scattered on the wire gauze, the resulting assembly heated to soften the synthetic resin on the wire gauze and form a coherent film. The synthetic resin on the wire gauze may be used to fix the grains temporarily and these are scattered thereon, e.g. by treating it with a solvent to make it tacky. Alternatively the wire gauze may be coated with an adhesive to accommodate the grains in the apertures and the synthetic resin film subsequently formed by coating the assembly with a solution of synthetic resin. The grains may be provided in the membrane according to desired patterns utilizing photoresist techniques.