GB1181850A - Industrial Process for Bleaching Bast Fibres by Applying Chlorinated Derivatives of Cyanuric Acid - Google Patents

Abstract

1,181,850. Bleaching bast fibres. OFFICE NATIONAL INDUSTRIEL DE L'AZOTE. 5 Sept., 1967 [6 Spet., 1966], No. 40604/67. Heading D1P. Textile materials made from bast fibres, e.g. linen, hemp or jute, are bleached by a continuous or semicontinuous process comprising impregnating them with an aqueous alkaline solution containing 40-60 g/l of alkali and subjecting them to a steam treatment, impregnating them with an aqueous solution containing a chlorinated derivative of cyanuric acid and oxidising the resultant material with hydrogen peroxide. Fabric may be passed loosely at high speed into a washing machine where it is contacted with boiling water optionally containing detergents or wetting agents, wrung out, impregnated with an aqueous solution containing 40-60 g/l caustic soda, 90-100% wrung out, passed to a vaporiser having a steam atmosphere at 100‹C and then disposed in folds in a ripening apparatus where it stays for 10-20 minutes at 100‹C. It is then washed, rinsed, passed to an aqueous bath containing the chlorinated cyanuric acid, e.g. a mixture containing trichlorocyanuric acid, cyanuric acid and a carbonate or alkaline bicarbonate, or an alkaline salt of dichlorocyanuric acid to which an acid such as acetic, formic or phosphoric acid is added, containing 7-15 g/l of available chlorine and having a pH of 4-5, wrung out at 100-110%, deposited in folds in a second ripening apparatus where it remains for 10-20 minutes at a temperature between atmospheric and 50‹C and is then washed with boiling water and wrung out. The fabric is then passed through an aqueous alkaline bath of hydrogen peroxide stabilised with sodium silicate, passed into a vaporiser where its temperature is raised to 100‹C, deposited in folds in a third ripening apparatus where it remains for 10-20 minutes at 100‹C and washed. Alternatively the second step with the solution of the chlorinated cyanuric acid may be effected by winding the fabric impregnated with the solution of the chlorinated cyanuric acid on a slowly rotating drum at 20-50‹C for 1-2 hours and then unwinding it, wringing it and, washing and treating it with hydrogen peroxide. The fabric may be given a preliminary treatment comprising impregnating it with an aqueous solution of a chlorinated derivative of cyanuric acid containing 7-15 g/l of available chlorine and having a pH of 4-5 at 20-50‹C., depositing it in the form of folds in a ripening apparatus or winding it on a slowly rotating drum for 1-3 hours, washing hot, rinsing and wringing out.