Patent GB-1273445-A (GB)
Title: Synthetic microporous sheet material
Inventor: CRAVEN JAMES MILTON
IPC: C08G64/18
Filed: 1969-06-25
Abstract: 1,273,445. Leather substitutes. E.I. DU PONT DE NEMOURS & CO. 25 June, 1969, No. 32114/69. Heading B2E. [Also in Division C3]  A water vapour permeable, coriaceous, synthetic microporous sheet material comprises a porous substrate comprising a layer of fibrous material impregnated with a synthetic polymer having adhered thereto a microporous synthetic polymer coating (A), and a non-porous vapour permeable finish (B) having a thickness of 0.1-5 mils in superimposed adherence with microporous coating (A) and comprising an elastomeric polymer containing (a) at least 40% by weight of soft polymeric segments derived from a polymer having a molecular weight of 500-1,000,000 selected from polyalkylene ether glycols having a glass transition temperature of -40C to -90C, polysiloxanes having a glass transition temperature of -60 to -150C, polyvinyl alkyl ethers having a glass transition temperature of -20 to -60C, polyalkyl acrylates having a glass transition temperature of -20 to -70C in which the alkyl group has 1-8 carbon atoms and hydrocarbon copolymers having a glass transition temperature of -30 to -80C in which the hydrocarbon units have 2-12 carbon atoms, and containing 10-50% by weight of oxygen, nitrogen or a mixture of oxygen and nitrogen, and (b) 0-60% by weight of hard polymeric segments derived from polyureas, polyurethanes, chain extended polyurethanes, polycarbonates, polyesters, polysiloxanes or vinyl addition polymers, e.g. of styrene or acrylonitrile, which have a glass transition temperature above 50C, a crystalline melting point above 100C or a softening temperature above 100C, the elastomeric polymer being characterized by a non-porous unsupported film formed thereof having a permeability constant for water vapour of at least 3000, a stress at 100% elongation of 50-4000 pounds per square inch, a permanent set of less than 20% and a tensile strength of at least 3000 pounds per square inch. The porous substrate may comprise a woven, non- woven or knitted fabric made from polyester, polyamide, polyesteramide, acrylic, viscose rayon, wool, cotton or glass fibres impregnated with a synthetic polymer. The polymer used to form microporous coating A may have a secant tensile modulus at 5% elongation of above 600 pounds per square inch during the entire processing cycle from the time the polymer is coagulated into a microporous structure until it is dried and may be a polyurethane prepared from a polyalkylene ether glycol or hydroxylterminated polyester and an organic diisocyanate, which may contain polyurea units and may be used in admixture with a vinyl chloride polymer. The coatings may be applied by spraying, rollers, dipping, swabbing, brushing, padding or printing. The elastomeric polymer coating (B) may also contain polyvinyl butyral, a silicone resin, a pigment, e.g. titanium dioxide, metal hydroxides, chromates, silicates, sulphides, sulphates, carbonates, carbon black, copper phthalo-cyanine, lakes and metal flake pigments, and antioxidants, e.g. 4, 4'-butylidene-bis (6-tertiarybutyl-m-cresol) and 2, 2'-methylene-bis-(4-methyl-6-tertiary-butylphenol). The sheet material may be further coated with an acrylic polymer which may be a terpolymer containing 1-6% by weight of an α, #-unsaturated monovinylidene carboxylic acid, e.g. acrylic or methacrylic acid, an acrylic acid ester and a methacrylic acid ester, the carboxyl groups of which may be reacted with an alkylene imine and which may contain a pigment, and with a final coating of cellulose acetate butyrate, and may be embossed.