GB730221A - Improvements in or relating to artificial leather - Google Patents

Abstract

730,221. Artificial leather. EBERLE, H., and SALADIN, O. Nov. 18, 1952 [Nov. 19, 1951; Nov. 13, 1951; Nov. 30, 1951], No. 29053/52. Class 140. Artificial leather, which is permeable to air and steam, but sufficiently impermeable to water, is produced by covering a fibrous support with a layer of a dispersion of an olefinic polymer containing 5-30 per cent water and evaporating the volatile components from the layer by heating to a temperature higher than 120‹ C. to produce a network of pores in the layer. The resin layer may be gelatinized. The fibrous support may be highly absorbent woven or knitted fabrics, fleeces, or paper and the olefinic polymer may be polyvinyl chloride, copolymers of vinyl chloride and vinyl acetate, or mixtures of vinyl and methacrylic acid ester polymers. The coated support may be subjected to electric spark discharge to increase the porosity, and may be given a final coating of non-porous olefinic polymer plastisol, which is also rendered porous by electric spark discharge treatment. Inorganic or organic gas-releasing compounds may be dissolved or dispersed in the aqueous dispersions, or their solutions may be used in place of water for making the dispersions, to release gas by heat or added acid during the entire drying and gelatinization treatments, with simultaneous evaporation of water, to increase the porosity. Suitable compounds are sodium bicarbonate, or ammonium carbonate, bicarbonate or carbamate. Fibrous material of animal, vegetable or synthetic origin, e.g. wool dust, cotton, cellulose, shredded or powdered leather, staple length being 1 mm., may also be added to the dispersions to increase the porosity. The porous product may be impregnated to increase the water repellency by oiling or greasing with cream or with aqueous paraffin dispersions. In examples: (1) extruded polyvinyl chloride is mixed with pigment, dioctyl phthalate and a mixture of higher molecular weight hydrocarbons and the mixture homogenized in a three-roll mill to form a pasty mass a which is stirred with water until a spreadable mass b is obtained; the mass b is coated on cotton dried at 140‹ C., gelatinized at 150-175‹ C., grained, subjected to electric discharge, and greased; the resulting product is dried at 140‹ C., overcoated with the pasty mass a, gelatinized at 175‹ C., grained, and again subjected to electric discharge; (2) a mixture of polyvinyl chloride and polymethyl methacrylate is used; (3) a mixture of a vinyl chloride-vinyl acetate copolymer and polyvinyl chloride is used; (4) the pasty mass a of (1) is stirred with an aqueous solution of ammonium bicarbonate to form a spreadable dispersion; (5) a pasty mass similar to a of (1) has cotton shearing dust added, and is stirred with an aqueous solution as in (4).