Patent GB-692184-A (GB)
Title: Improvements in or relating to crease proofing cotton and linen fabrics
IPC: D06M11/56
Filed: 1948-09-02
Abstract: Cotton and linen fabrics are impregnated with an aqueous solution of a polybasic acid and a nitrogen-containing compound basic toward the acid, baked to produce a complex of the acid, nitrogen compound and cellulose, swollen and finally neutralized. The treated fabric is crease-resistant.  The acid may have at least two replaceable hydrogen atoms or at least three replaceable hydrogen atoms only one of which is replaced by a metal.  Thus any acid of phosphorus or sulphur with at least two replaceable hydrogens, free of constituents yielding active oxygen or chlorine during the processing, substantially non-volatile and not containing organic groups of more than 4 carbon atoms, and salts of such acids wherein the replaceable hydrogens are replaced by an anion volatile during the process to give the acid may be employed.  The acid may also be a polycarboxylic acid having a molecular weight not over 200 such as phthalic, malonic, succinic or glutaric acid.  It may be used in concentrations of between 2 and 30 per cent by weight of the solution.  The preferred range is from 2 to 16 per cent with 100 per cent pick-up on the fabric, but concentrations above 16 per cent are preferred when using organic acids.  The nitrogen - containing compound may be an organic base having an atomic ratio of carbon to nitrogen of not more than 2 to 1, such as urea, dicyandiamide, biuret, acetamide, cyanoacetamide, guanidine bicarbonate, aminoguanidine carbonate, biguanide, guanidine, or mixtures thereof.  For ease of control, strong bases may be mixed with more weakly basic compounds. Preferably the base is used in amounts of 1 to 4 mols. per mol. of acid; higher amounts up to 10 mols. are permissible.  The temperature of baking may be between 400 DEG  and 280 DEG  F. (preferably 350 DEG to 300 DEG  F.) and the time of baking from 2 to 30 minutes (preferably 4 to 15 minutes).  The conditions of treatment, concentration, &c. may be selected so that sufficient of the acid-forming element or acyl radical will remain in the fabric after washing and drying.  In the case of orthophosphoric acid, the cured, washed and dried fabric may contain from 0.5 to 5 per cent of phosphorus, equivalent to 1.5 to 15 per cent of acid.  The proportion of nitrogen carried into the fabric varies with the basic compound used; for urea it may be 0.25 to 1.5 per cent by weight of the dry fabric, and with more complex compounds from 0.5 to 6 per cent. During the curing a pH of 2 to 7 should be reached on the fabric. After curing or baking, and, if desired, washing or washing and drying, the fabric is swollen, preferably with 30 per cent sodium hydroxide solution for 45 seconds at room temperature.  The concentration may, however, vary from 10 to 50 per cent and the time of swelling from 5 to 180 seconds. Preferably the fabric is under tension and is immediately washed after swelling whilst still under tension and neutralized with a weakly acidic solution or sodium bicarbonate.  Other conventional swelling agents except those liberating free halogens may be used, such as caustic soda-cuprammonium, caustic soda-sodium zincate, or concentrated calcium thiocyanate.  Caustic soda supercooled to -10 DEG  C. may also be employed.  The fabric, after washing and neutralizing, is finally dried.  Prior to, or after drying, the fabric may be treated with a solution of a softening agent.  If desired, aldehydes such as formaldehyde (paraformaldehyde, hexamethylene tetramine) or glyoxal may be incorporated in the solution containing the acid and nitrogen-containing compound, in amounts from 0.2 to 3 mols. of aldehyde per mol. of acid on the basis of phosphoric acid.  Part or all of the aldehyde and some of the nitrogen-containing compound may be replaced by water-soluble condensates such as those of urea-formaldehyde, urea-glyoxal, and melamine-formaldehyde, added either directly to the impregnating solution or used as a pretreatment.  In these circumstances, it is preferred to adjust the pH of the solution to neutral or slightly alkaline with ammonia to prevent condensation and consequent precipitation of the resin.  In an example an impregnating solution is prepared from 60 lbs. of 75 per cent orthophosphoric acid, 40 lbs. of dicyandiamide, 120 lbs. of urea, 60 lbs. of 28 per cent ammonia and 80 lbs. of 37 per cent formaldehyde, made up to 100 U.S. gallons with water.  A printed cotton fabric is impregnated, squeezed, dried and baked for 6 minutes at 320 DEG  F.  It is then swollen with 30 per cent caustic soda in a mercerizer, washed with warm water while still under tension, and then with sodium bicarbonate solution.  It is finally impregnated with a 2 per cent solution of a cationic softener, squeezed and dried.  Specifications 604,197 and 648,883, [both in Group VIII], are referred to.  The Specification as open to inspection under Sect. 91 also includes an example in which the impregnating solution is prepared from 200 lbs. of sulphamic acid and 200 lbs. urea made up to 100 gallons with water.  This subject-matter does not appear in the Specification as accepted.