GB674948A - Improvements in or relating to the production of a glazed finish on textile fabrics - Google Patents

Abstract

Water-soluble condensation products of the general formula <FORM:0674948/IV (b)/1> where R is methyl and n is 5 or 6, are prepared by reacting an excess of methanol with the reaction product of 1 mol. of melamine with at least 6 and preferably 7 to 9 mols. of formaldehyde. The hexamethylol melamine condensation product is preferably prepared at a pH slightly above 7 and at relatively low temperatures, viz. 50 DEG to 80 DEG C. The methylated methylol melamine condensation product may be used for fixing glazed finishes on textiles (see Group IV (c)). In an example, one mol. of melamine and 8 mols. of formaldehyde (37 per cent aqueous solution) are reacted at 70 DEG C. for about 40 minutes. The pH of the solution is adjusted to 7.5 by addition of caustic soda. After cooling to room temperature it is rendered strongly acid by addition of hydrochloric acid and then about 15 mols. of methanol are added. The mixture is heated at about 50 DEG C. for about 2 hours, cooled, the pH adjusted to 8 by addition of caustic soda and concentrated at about 60 DEG C. under vacuum of 28 inches Hg to form a 40 per cent resin solids solution. Precipitated salts are filtered off. The dry product corresponded on analysis to 1 mol. melamine, 6 mols. combined formaldehyde and 6 mols. combined methanol.ALSO:A textile fabric is treated with an aqueous solution or dispersion comprising a resin precondensate of general formula <FORM:0674948/IV (c)/1> where R represents the methyl group and n is 5 or 6, and is then dried to between 9 and 20 per cent moisture by weight based on the dried fabric, glazed by mechanical means and heated at elevated temperature to cure the resin precondensate in situ, in the presence of a curing catalyst. The process is applicable to fabrics of wool, cotton, regenerated cellulose, cellulose derivatives and casein and may be applied to staple fibre and continuous filament fabrics. The condensation product may be prepared by reacting one mol. of melamine with at least 6 and preferably 7 to 9 mols. of formaldehyde at a pH slightly above 7 at 50 DEG to 80 DEG C. to prevent polymerization. Etherification is carried out using sufficient methanol to form the penta-(methoxymethyl) or hexa(methoxymethyl) derivative. The etherified condensation product is used in its monomeric or lower polymeric form. The solution or dispersion may contain 7-30 per cent by weight, and may be applied to the fabric by impregnation or spraying. Excess solution is removed by a padder or hydroextractor leaving 7-14 per cent by weight, based on dry weight of the fabric, of resin solids on the fabric. The drying is carried out below 200 DEG F. to avoid any premature polymerization, 9-20 per cent by weight of moisture (based on the dry weight of the fabric) being left in the material. The latter is then glazed in known manner, 3 to 10 per cent of a lubricant (which may be incorporated in the impregnating bath) being employed, if desired. Suitable lubricants are water-soluble alkali-metal and ammonium salts of sulphonated mineral oils, sulphonated long-chain fatty alcohols such as cetyl and stearyl alcohol and sulphonated castor oil; water-soluble alkali-metal and ammonium salts of long-chain fatty acids such as sodium stearate, oleate and palmitate; water-soluble or dispersible polyethylene oxides of high molecular weight and the poly-reaction products of ethylene and propylene oxides with aryl and aralkyl alcohols. Water-insoluble lubricants such as carnauba wax, montan wax, sulphonated oils, sulphonated alcohols and fatty oils may be applied to the fabric after impregnation. The condensation catalyst is preferably dissolved in the impregnating bath, but it may, if desired, be applied at any stage of the process prior to curing. Suitable catalysts include ammonium chloride, sulphate and formate, diammonium phosphate, formic acid, oxalic acid, hydrochloric acid, sulphuric acid, nitric acid, and amino-alcohol salts of inorganic acids such as 2-amino-propanol-(1) hydrochloride and phosphate and 2-amino-butanol-(1) hydrochloride and phosphate. Desirably 3 to 15 per cent by weight of the catalyst, based on the weight of the condensation product, is used. The curing is carried out between 275 DEG and 350 DEG F., for from 1 to 10 minutes. In an example (all parts by weight), 250 parts of a 40 per cent solution of a resin product containing 1 mol. combined melamine, 6 mols. combined formaldehyde and 5.5 mols. combined methanol, 20 parts of a 35 per cent aqueous solution of ammonium chloride and 10 parts of the sodium salt of sulphonated castor oil are mixed with 720 parts of water to form a solution for the impregnation of a viscose fabric. The solution pick-up is 100 per cent. The fabric is dried to 15 per cent moisture using as little tension as possible and passed three times through a friction calender at 310 DEG F. The resin is then cured at about 310 DEG F. for 4 minutes. (For the preparation of the condensation product see Group IV (b).)