GB773794A - Improvements in or relating to the production and/or stabilisation of hydroquinones - Google Patents

Abstract

Quinones are reduced to hydroquinones and/or hydroquinones are stabilized by treating a quinone or hydroquinone with an aqueous alkaline solution of an alkali metal borohydride. Such solution may be used for dyeing keratinous material such as wool or hair, and the hydroquinone oxidized on the fibre, the pH being reduced to destroy the borohydride if desired, or the oxidation may take place in alkaline solution. A primary aliphatic or arylaliphatic amine and an antifoaming agent may be present in the dye solution. The rate of reduction to hydroquinone may be speeded up in some cases by the addition of alcohols. Quinones specified are benzoquinone, hydroxybenzoquinone, methoxybenzoquinone, 2-aminobenzoquinone, 2,5-bis - diethylamino-benzoquinone, anilinoquinone, 2,5-dihydroxybenzoquinone, 2,5-dimethoxybenzoquinone, chloroquinone, 1,4-naphthoquinone, lawsone, juglone, menaphthone, 2-amino - 1,4 - naphthoquinone, 1,2 - naphthoquinone-4-sulphonic acid sodium salt, 2,3-dichlor - 1,4 - naphthoquinone, naphthazarin, indigo, alizarin. In examples: (1) lawsone, juglone and naphthazarin are each ground with potassium borohydride and the mixtures added to water, the solutions are subsequently acidified or reduced in pH by addition of a buffer, and used to dye hair and wool cloth. Also in examples: (2) mixtures of (a) trihydroxybenzene and lawsone, (b) lawsone and juglone, (c) juglone and naphthazarin, and (d) lawsone, juglone and naphthozarin are similarly treated.ALSO:Quinones are reduced to hydroquinones and/or hydroquinones are stabilized by treating a quinone or hydroquinone with an aqueous alkaline solution of an alkali metal borohydride. Such solutions may be used for dyeing keratinous material such as wool or hair, and the hydroquinone oxidized on the fibre, the pH being reduced to destroy the borohydride if desired, or the oxidation may take place in alkaline solution. A primary aliphatic or arylaliphatic amine and an antifoaming agent may be present in the dye solution. The rate of reduction to hydroquinone may be speeded up in some cases by the addition of alcohols. Quinones specified are benzoquinone, hydroxy benzoquinone, methoxybenzoquinone, 2 - aminobenzo, quinone, 2.5 - bis - diethylamino - benzoquinone, anilinoquinone, 2.5 - dihydroxy-benzoquinone, 2.5 - dimethoxybenzoquinone, chloroquinone, 1.4 - naphthquinone, lawsone, juglone, menaphthone, 2-amino - 1.4 - naphtho quinone, 1.2 - naphthoquinone - 4 - sulphonic acid sodium salt, 2.3-dichlor- 1.4naphthoaquinone naphthazarin, indigo, alizarin. In examples, (1) lawsone, juglone and naphthazarin are each ground with potassium borohydride and the mixture added to water, the solutions are subsequently acidified or reduced in pH by addition of a buffer, and used to dye hair and wool cloth. Also in examples (2) mixtures of (a) trihydroxybenzene and lawsone, (b) lawsone and juglone, (c) juglone and naphthazarin, and (d) lawsone, juglone and naphthazarin are similarly treated.