Patent GB-845896-A (GB)
Title: Improvements relating to the preparation of impregnated sheet materials and laminates
IPC: B32B27/00
Filed: 1957-02-13
Abstract: 845,896. Laminates; impregnating materials for electric insulation. GENERAL ELECTRIC CO. Feb. 13, 1957 [Feb. 21, 1956], No. 4896/57. Class 140. Absorbent sheet-material, of low tensile strength, such as mica mat, short-fibre asbestos, bentonite, glass fibres, or acrylonitrile or polyester fibre, is impregnated or laminated by applying a natural or synthetic resin or resinforming monomer to one or more sheet backing materials, winding the backing material or materials into a roll with a layer or interlayer of the sheet material, and holding the roll, with or without heat treatment, until the sheet is impregnated with the resinous material. One or more of the backing sheets may then be removed or these sheets may form part of the final product. The backing materials may comprise paper, glass threadreinforced paper, cotton cloth, glass cloth, cellulose acetate film or fabric, or a film of polyester such as polyethylene terephthalate or polycarbonate. The resins used may be phenol, urea, or melamine-formaldehyde condensation products, alkyd, or oil-modified alkyd resins, vinyl resins, mixtures of alkyd resins with vinyl esters or of polyesters with epoxide resins, silicone resins such as methyl or phenyl siloxane polymers, or natural resins such as shellac. Examples of alkyd resins given are the reaction products of glycerine, pentaerythritol or ethylene glycol with phthalic or maleic acids or their anhydrides, with or without coconut, castor, soya or linseed oil or oil acids as modifying- agents. Alkyd-vinyl ester mixtures which may be used comprise those disclosed in Specifications 563,624 and 558,136, namely blended or heat-reacted mixtures of polyvinyl ester resin, a maleic anhydride-pentaerythritol resin, and a resin obtained by reacting glycerine with 3,6- endomethylene - A - 4 - tetrahydrophthalic anhydride. Polyester-epoxide resins disclosed in Specification 732,260 may also be used; these comprise mixtures of the reaction products of glycerine and aliphatic dicarboxylic acids containing 5-10 carbon atoms, which contain free carboxyl groups, with epoxide resins. Other suitable resins comprise polymerized methyl, ethyl, butyl or octyl acrylates cross-linked with 5-50% of a polyester cross-linking agent. Examples describe: (1) laminates bonded with various synthetic resins and having interlayers of mica mat and outer layers of (a) rope paper and glass thread reinforced rope paper, (b) both of rope paper, (c) both of polyethylene terephthalate film, to one of which a layer of glass cloth may be bonded; (2) laminates of paper having a surface layer or an interlayer of mica mat, the paper layer or layers being removed after impregnation of the mica mat, the impregnants being (a) a copolymer of 2-ethylhexyl acrylate and the reaction product of maleic anhydride, adipic acid and diethylene glycol, (b) an alcoholic solution of shellac. The products may be used for electric insulation, as decorative surfaces and as light diffusing panels. Specification 539,982 and U.S.A. Specification 2,549,880 also are referred to.