Patent GB-882892-A (GB)
Title: Process of producing foldable, highly water-resistant, stiffened sheet material of very high dimensional stability which can be printed by means of lithographic printing methods
IPC: D06M15/423
Filed: 1958-09-05
Abstract: 882,892. Coated fabrics. RADUNER & CO., A. G. Sept. 5, 1958 [Sept. 16, 1957], No. 28630/58. Class 140. A stiffened sheet material which can be printed lithographically as paper and has very high dimensional stability as well as high resistance to mechanical wear, is produced by first removing impurities from woven fabric or textile sheet material which may be an unwoven fabric consisting wholly or predominantly of organic fibres having at 20 C. and 65% relative humidity a water take-up of less than 1.5%, preferably less than 0.5%, if desired by treatment causing chemical and/or physical changes limited to the surface of the fibres, applying a composite improving agent which is a solution, dispersion or emulsion consisting of a precondensate of a thermosetting resin, a cross-linking agent capable of cross-linking two or more hydroxy groups, at least one polymeric compound capable of being rendered insoluble by reaction with the cross-linking agent, at least one catalyst capable of catalysing the curing of the resin and the cross-linking action of the cross-linking agent, and effecting the cure of the resin precondensate and the reaction of the cross-linking agent by subsequently applying heat, the fabric or material being subjected in any desirable phase of the process but prior to the curing of the precondensate and preferably after the removal of the impurities, to tensioning in both directions and, if desired, to mechanical deformation, preferably by calendering, under temperature conditions which prevent yarns from being fused together at yarn intersections due to pressure exerted by the mechanical deformation. Materials may be woven from single yarns or twisted yarns spun from filaments or cut staple fibres, or may be produced by bonding random or oriented fibres together by means of a polymeric material, e.g. polymers of acrylic compounds. The fibres may be of polymeric esters of dihydroxy compounds and a dicarboxylic acid such as polyethylene terephthalate, polymers or copolymers of acrylic or vinyl compounds, e.g. acrylonitrile, vinyl chloride, vinylidene chloride, vinyl alcohol, ethylene, methyl substituted ethylene, or copolymers of such compounds with vinyl acetate, and vinylnitrogen compounds, polyamides, e.g. polymeric omega amino n-dodecyclic acid, or polyurethanes produced from glycols having at least four CH 2  groups between hydroxy groups and di-isocyanates having at least six CH 2  groups between the isocyanate groups, or cellulose derivatives such as cellulose triacetate. The impurities, of which examples are given, may be removed by subjecting the material to the action of compounds capable of dissolving, strongly swelling, or reacting with the fibre material under conditions producing only surface changes in the fibre, e.g. using alkali hydroxides, acids or acidic compounds, solutions, emulsions or vapours of compounds capable of dissolving the fibre material, superficial saponification with compounds of alkaline reaction, and phenolic compounds. These compounds may be added to scouring baths, bleaching liquors or other wet treatment baths or may be applied separately. The composite improving agent may be applied by padding, coating, spraying or printing and may comprise as precondensate of a thermo-setting resin, an aminoplast precondensate such as reaction products of nitrogenous compounds with aldehydes, e.g. melamine, urea, substituted urea, di-cyandiamide, hydantoins with formaldehyde, glyoxal and acrolein; and reaction products of ketones or phenolic compounds with formaldehyde. Cross-linking agents suitable are aldehydes and di-aldehydes having not more than three carbon atoms or derivatives thereof, di- or poly-epoxy compounds or derivatives thereof, di-isocyanates or derivatives thereof, or compounds capable of releasing such compounds. Polymeric compounds specified are starch or derivatives thereof, polyvinyl alcohol, or derivatives thereof, polyesters having hydroxy end groups or other polymeric bodies carrying a plurality of hydroxy groups or other funetional groups capable of reacting with the cross-linking agent. The ratio between the combined weights of the resin precondensate plus cross-linking agent and the polymeric compound may vary from 1 : 2 to 2 : 1, and the ratio between resin precondensate and cross-linking agent may vary from 1 : 10 to 10 : 1. Other known materials, e.g. fillers, pigments, abrasives, softening agents, dyestuffs, hydrophobing agents, silicones, plastifying agents flame-proofing agents and compounds sensitive to light or other radiation, may also be present in the coating. Mechanical deformation may be effected by means of heated calender bowls, plane or engraved, or by heated plates, the temperature during deformation being at least 20 C. below the softening point of the fibre material to prevent the yarns from being fused together at their intersections. The stiffened sheet material may be printed by lithographic printing methods or coated with compounds sensitive to light.