Patent GB-630564-A (GB)
Title: Improvements in and relating to the manufacture of azo dyestuffs
IPC: C09B45/18
Filed: 1946-07-30
Abstract: o-Aminophenols substituted by a thiophenol group in p-position to the amino group are produced from 3-chloro-6-nitrophenols (themselves obtainable by the action of alkali on a 4-chloro-1 : 2-dinitrobenzene) by the action of a soluble sulphide, whereby depending on the conditions, the amine may be obtained directly, or there may be first formed the corresponding nitrohydroxy-thiophenol which is reduced to the amine (e.g. with a soluble sulphide, sodium hydrosulphite or zinc), if desired after reoxidation to a dinitro-dihydroxy-disulphide for each of purification.  In examples: (1) sodium 3-chloro-6-nitrophenate is refluxed with excess of sodium sulphide in aqueous solution, to produce, on acidification, 4-amino-3-hydroxy-thiophenol; (2) 3 : 4-dichloro-6-nitrophenol and 2 : 3 : 4-trichloro-6-nitrophenol (obtained by the action of dilute caustic soda on 3 : 4 : 5-trichloro-1 : 2-dinitrobenzene) similarly yield 6 - chloro - and 2 : 6 - dichloro - 4 - amino - 3-hydroxythiophenol; (3) 2 : 3 : 4-trichloro-6-nitrophenol is dissolved in dilute caustic soda and refluxed with an equimolecular proportion of sodium sulphide to form on acidification 2 : 6 - dichloro - 4 - nitro - 3 - hydroxythiophenol, which is dissolved in dilute caustic soda and reduced to the amine by means of sodium hydrosulphite; (4) the sodium salt of 3-chloro-6-nitrophenol is refluxed with an equimolecular proportion of sodium sulphide in aqueous solution, and the resulting 4-nitro-3-hydroxythiophenol is oxidized with ferric chloride to 4 : 41-dinitro-5 : 51-dihydroxydiphenyl disulphide which is dissolved in dilute caustic soda and reduced with sodium sulphide to 4-amino-3-hydroxythiophenol; 3 : 4-di-chloro-6-nitrophenol similarly gives 2-chloro-5-hydroxy - 4 - aminothiophenol.  The samples schedule describes the preparation of 4-amino-3 - hydroxy - 2 - methylthiophenol from 4-nitro - 3 - hydroxy - 2 - methyl - 1 - chlorobenzene (obtainable by the action of soda on 2-chloro-5 : 6-dinitrotoluene).  Specifications 370,705 and 377,348 are referred to.  3-Amino-4-hydroxythiophenol is obtainable by reducing 3 - nitro - 4 - hydroxybenzene - 1-sulphochloride with zinc and hydrochloric acid.ALSO:Azo dyestuffs are manufactured by diazotizing an amine of the benzene series, substituted by a thiophenol or disulphide group and also by a hydroxy group in o-position to the amino group, and coupling with any coupling component, especially one coupling in o-position to a hydroxy group, if desired in the presence of a solvent such as pyridine.  The products dye fibres and other objects, particularly cellulosic substances, e.g. cotton, regenerated cellulose fibres or the material sold under the Registered Trade Mark "Cellophane," from a bath of water-soluble metal sulphide, yielding yellow to red, granate, violet and black dyeings which may be after-treated with compounds of heavy metals. Components specified are:-diazo components: 4-amino-3-hydroxythiophenol and its 6-chloro- and 2 : 6-dichloro-derivatives; coupling components: b -naphthol, 2 : 6-, 2 : 7-, 1 : 5- and 1 : 8-dihydroxynaphthalene, 5 - hydroxy - 1 - aminonaphthalene (coupled alkaline), acetoacetic anilide and m-xylidide, 4 : 41-di-(acetoacetylamino)-3 : 31-dimethyldiphenyl, 1-phenyl-3-methyl-5-pyrazolone, 3-hydroxydiphenylamine, 2 : 3-hydroxynaphthoic anilide, o-toluidide, o-anisidide and b  - naphthylamide, 1 - (21 - hydroxy - 31 - anthracenoyl) - amino - 2 - methylbenzene, resorcinol, 4 - chloro - 1 - hydroxynaphthalene and 3 - chloro - 2 - hydroxynaphthalene.  An example and a table describe dyestuffs from these components.  In further examples, cotton yarn is dyed marine blue with the dyestuff 4-amino-3-hydroxythiophenol --> b -naphthol from a bath containing sodium sulphide and sodium sulphate; and the resulting dyeing is treated with an aqueous solution of copper sulphate containing acetic acid, or ammonium hydroxide, or tartaric acid and soda.  Specifications 370,705 and 377,348 are referred to.  Samples have been furnished under Sect. 2(5) of the following dyestuffs: (a) 3-amino-4-hydroxythiophenol --> b  - naphthol; (b) 4 - amino - 3 - hydroxy - 2 - methylthiophenol --> b -naphthol; (c) 4 - amino - 3 - hydroxythiophenol --> b -naphthylamine; (d) 4-amino-3-hydroxythiophenol --> b -hydroxynaphthoic acid; (e) 4-amino-3-hydroxythiophenol --> sodium-2-naphthol-6-sulphonate.