Patent GB-583043-A (GB)
Title: Manufacture of monoazo-dyestuffs
IPC: C09B45/16
Filed: 1943-12-22
Abstract: Monoazo dyestuffs are manufactured by coupling diazo-compounds of the benzene series containing a hydroxy group in o-position to the diazo-group with 2 : 6-dihydroxynaphthalenes which have no further substituents in the naphthalene nucleus and in which one hydroxy group is etherified to form an alkoxy (e.g. methoxy or ethoxy) group or a substituted alkoxy group (e.g. one in which the alkyl residue is that of a polyhydric alcohol, such as ethylene glycol or glycerol, or contains a group imparting solubility in water, such as a carboxyl group).  The resulting dyestuffs may be treated with an agent yielding metal (e.g. chromium), in substance (e.g. in acid, neutral or alkaline medium, with or without a suitable addition such as an acid, a neutral salt, a base, an acid-binding agent or an inert solvent, and with or without the application of pressure), in the dyebath or on the fibre (e.g. with the addition of a neutral chromlte and an ammonium salt to the dyebath).  The products may be used as pigment dyestuffs, or for dyeing or printing a variety of fibres, e.g. vegetable fibres such as cotton, viscose artificial silk and especially animal fibres such as wool, silk and leather; e.g. some of them dye wool by the after-chroming or single bath process in olive, olive-green or grey shades.  Examples (1) to (9) describe the preparation of the following dyestuffs: 4- (or 6-) nitro-2-aminophenol-6-(or 4-) sulphonic acid, 4 : 6-dinitro-2-aminophenol, 4 - chloro - 2 - aminophenol - 6 - sulphonic acid or 4-methyl-2-aminophenol-5- or 6-sulphonic acid (or a mixture of the last two compounds) --> 2-hydroxy-6-methoxynaphthalene; 4 : 6-dinitro-, 5-nitro- or 4-chloro-6-nitro-2-aminophenol, or 4-nitro- or 4-chloro-2-aminophenol-6-sulphonic acid --> glycerol a -mono-(6 - hydroxy - 2 - naphthyl) - ether; 5 - nitro- or 4-chloro-6-nitro-2-aminophenol --> 2-hydroxynaphthalene-6-oxyacetic acid.  In further examples: (10) the dyestuff 4-chloro-2-aminophenol-6-sulphonic acid --> 2-hydroxy-6-methoxynaphthalene is boiled with an aqueous solution of chromium fluoride; (11) the dyestuff 4-nitro-2-aminophenol-6-sulphonic acid --> 2-hydroxy-6-methoxynaphthalene is similarly chromed and the product is converted into its sodium salt by addition of sodium carbonate; (12) wool is dyed with the dyestuff 4-nitro-2-aminophenol-6-sulphonic acid --> 2-hydroxy-6-methoxynaphthalene from a bath containing acetic acid and Glauber salt and, during the later stages, sulphonic acid, and is after-treated in the same bath with potassium bichromate, yielding an olive shade; (13) wool is dyed grey-green with the product of (11) from a bath containing sulphuric acid.  Glycerol-a -mono-(6-hydroxy-2-naphthyl) ether is obtainable by heating 2 : 6-dihydroxynaphthalene with glycerol a -monochlorhydrin in aqueous potassium hydroxide solution.  2-Hydroxynaphthalene-6-oxyacetic acid is obtainable similarly from 2 : 6-dihydroxynaphthalene and potassium chloracetate.  The Specification as open to inspection under Sect. 91 comprises the use of any diazo compounds containing lake-forming groups (including those of the naphthalene series) and, as coupling component, any monoether of a dioxynaphthalene in which the hydroxyl groups are in b -position and both o-positions with respect to the free hydroxyl group are unsubstituted.  Additional examples describe the production of dyestuffs by coupling 2-hydroxy-6-methoxynaphthalene with 1 - diazo - 2 - naphthol - 4 - sulphonic acid or its 6-nitro derivative, and the conversion of the former of these dyestuffs to its chromium compound by refluxing with chromium fluoride solution.  This subject-matter does not appear in the Specification as accepted.