GB1384735A - Manufacture of sheet materials with reversible absorptivity for moisture vapour - Google Patents

Abstract

1384735 Porous coated sheet materials BADISCHE ANILIN-& SODA-FABRIK AG 24 March 1972 [25 March 1971] 13824/72 Heading B2E [Also in Division D1] Sheet materials capable of absorption and desorption of moisture vapour are produced by applying to substrate in an amount of 0.5-5 parts by weight per part by weight of substrate polymers containing at least 15 mole percent of free carboxyl groups directly attached 'to carbon atoms carrying at least one hydrogen atom in addition to the carboxyl group, and heating the substrate materials, together with the polymers applied thereto, to cross-linking temperature. Suitable polymers are acrylic acid homopolymers or a copolymer containing at least 15 mole percent of acrylic acid, maleic acid, fumaric acid or itaconic acid. Suitable comonomers which may be polymerised with these unsaturated acids are acrylates or methacrylates, vinyl esters, styrene, acrylonitrile, ethylene, propylene. A polymer may be applied together with a catalyst for a cross-linking reaction, e.g. ammonia or primary, secondary or tertiary amines. The polymer may be applied as an aqueous solution or dispersion, optionally together with aqueous solutions or dispersions of other polymers. The substrate may be non-woven fabric, woven or knitted fabric, felts, woven netting, foamed webs and may consist of polyamide, polyacrylonitrile, either alone or blended with other materials. The polymer may be applied by dipping, brushcoating, casting, spraying or padding, or by rolling. The cross-linking reaction may be effected in a press, the surface of the pressed material thereby 'being smoothed or grained, or alternatively the surface may be buffed or it may be smoothed in a subsequent pressing operation. At least some of the free acid groups still remaining after the cross-linking reaction may be utilised, e.g. by conversion to sodium salts or by treatment with ammonia gas. Alternatively the remaining free carboxyl groups after cross-linking may be reacted with polyfunctional compounds before they are neutralised to completion, e.g. they may be reacted with polyfunctional amines, isocyanates or polyvalent metal ions such as aluminium, chromium or calcium ions. The products may be used in upholstery or clothing, e.g. shoe uppers. There may be added to an aqueous solution of polyacrylic acid a dispersion based on polyvinylidene chloride, polyvinyl chloride, polyacrylate, polyvinyl ester or a polydiene. Further additives to the polymers may comprise plasticisers, fillers; dyes, fungicides; flame-proofing agents, finely ground foams, asbestos fibres. In a typical example a non-woven fabric made by needle-punching polycaprolactam staple fibres is passed through a bath consisting of an aqueous dispersion of polyacrylic acid containing diethanol amine, squeezed between rollers to remove excess liquor, dried in air at 80‹C and then maintained at 170‹C in air for 20 minutes. The web is then neutralised in 1% soda solution at room temperature.