Patent GB-422556-A (GB)
Title: Stripping dyed textiles
IPC: D06P5/13
Filed: 1933-04-07
Abstract: Dyeings with alizarine or basic colours are stripped by treating the dyed material with an alkaline, acid or neutral liquor containing either (a) an amine, free from hydroxy groups, esterified or etherified hydroxy groups or heterocyclic oxygen, having attached directly or indirectly to the nitrogen atom a straight or branched chain of not less than 10 carbon atoms, or (b) a salt of such an amine, or (c) a quaternary ammonium salt, free from hydroxy groups, derived from a long chain (i.e. of not less than 10 carbon atoms) fatty acid monoamide of an arylene or alkylene diamine, or (d) a quaternary ammonium salt, free from hydroxy groups, having attached directly to the pentavalent nitrogen atom an unbroken chain of not less than 10 carbon atoms. The stripping may be effected in presence or absence of a reducing agent and/or soap or other detergent. Vegetable fibres are advantageously subjected to a supplementary chlorine bleach and animal fibres to a supplementary peroxide bleach. Specified amines and amine salts are b -diethylaminoethyloleyl amide, its acetate and hydrochloride, heptadecylamine and its hydrochloride. Specified quaternary ammonium salts are octadecyl- and cetyl-pyridinium bromides (cf. Specification 379,396), cetylpyridinium chloride (cf. Specification 392,763), octadecyltrimethylammonium iodide, cetyltrimethyl- and cetyltriethyl-ammonium bromides, cetyltrimethylammonium iodide, p - stearoamidophenyltrimethylammonium sulphate and b -stearoamidoethyldiethylamine methosulphate (cf. Specification 294,582, [Class 2 (iii)]).  The following examples are specified. (1) Cotton dyed with turkey red is stripped to a pale brown by treatment for 30 minutes with a boiling dilute caustic soda solution containing sodium hydrosulphite and cetyl trimethylammonium bromide and is thereafter cleared to a white by treatment for 15--30 minutes at room temperature in dilute sodium hypochlorite.  (2) Wool dyed a full red with alizarine on an aluminium mordant is stripped to a very pale pink by treatment for 20 minutes with a boiling dilute acetic acid solution containing Formosul and cetyltrimethylammonium bromide.  (3) Cotton dyed with Auramine O on a tannin mordant is completely stripped by treatment for 30 minutes with a boiling dilute aqueous solution of octadecylpyridinium bromide.  (4) Cotton dyed with Rhodamine 6GBS on a tannin mordant is stripped to a very pale pink by treatment for 30 minutes with a boiling dilute aqueous solution of cetyltrimethylammonium bromide.  (5) Cotton dyed with Magenta P on a tannin mordant is stripped to a very weak bluish red by treatment for 30 minutes with a boiling dilute aqueous solution of the acetate of b -diethylaminoethyloleylamide.  (6) Natural silk dyed with Acronol yellow T is stripped to a very pale yellow by treatment for 30 minutes with a boiling dilute aqueous solution of cetyltrimethylammonium bromide.  (7) Natural silk dyed with Auramine O is almost completely stripped by treatment as in (6). Specification 400,239 also is referred to.  Octadecyltrimethylammonium iodide is obtained by combining octadecyl iodide with trimethylamine.