Patent GB-666047-A (GB)
Title: Manufacture of new monoazo dyestuffs
IPC: C09B45/16
Filed: 1949-09-02
Abstract: Monoazo dyestuffs of the general formula <FORM:0666047/IV (c)/1> (wherein A represents an acylamino group and R the residue of 2 : 8-dihydroxynaphthalene-6-sulphonic acid coupled in the 1- or 7-position) are manufactured by (a) coupling a diazotized 4 - nitro - 6 - acylamino - 2 - aminophenol with 2 : 8 - dihydroxynaphthalene - 6 - sulphonic acid, or (b) treating a dyestuff of the general formula above, but in which A represents a nitro group, with an alkali sulphide or hydrosulphide to reduce the nitro group at A to an amino group and acylating this by means of an acid halide or anhydride. The acyl residue may be one of aromatic or aliphatic nature (e.g. benzoyl, m- or p-nitrobenzoyl, p-chlorobenzoyl, phthaloyl, benzenesulphonyl, p-toluenesulphonyl, m-sulphobenzoyl, acetyl, propionyl, butyryl or a carbalkoxy residue Alkyl-O-CO-), the preferred type being of the formula X-CO- where X represents a hydrocarbon radical of at most 6 carbon atoms.  The coupling in method (a) may be effected in a neutral or preferably alkaline medium (e.g. in the presence of an alkali metal carbonate or hydroxide or an alkaline-earth metal hydroxide) and takes place in the 1- or 7-position depending on the precise conditions.  The products may be treated with agents yielding metal, especially chromium.  Chroming in substance may be carried out with a salt of trivalent chromium, preferably a salt with a weak acid, such as the formate or acetate. Dyeings on animal fibres (e.g. leather, silk and especially wool) and on artificial fibres of superpolyamides or superpolyurethanes are advantageously produced by metallizing on the fibre or in the dyebath.  The after-chromed dyeings on wool are grey when coupling in method (a) has been effected in the presence of calcium hydroxide or a large excess of sodium hydroxide, whereas dyestuffs prepared by coupling with the mono-sodium salt of 2 : 8-dihydroxynaphthalene-6-sulphonic acid in the presence of about one equivalent of sodium hydroxide or magnesium hydroxide yield olive tints.  Examples (1) and (2) describe the use, in method (a), of diazo components in which the 6-acylamino group is acetyl, benzoyl or n-butyryl.  In further examples: (3) 4 : 6-dinitro-2-aminophenol is diazotized and coupled in the presence of sodium hydroxide with sodium 2 : 8 - dihydroxynaphthalene - 6 - sulphonate, and the product is reduced with sodium hydrosulphide and acetylated with acetic anhydride; (4) wool is dyed an olive tint by the after-chroming process with the dyestuff obtained by coupling diazotized 4-nitro - 6 - acetylamino - 2 - aminophenol with sodium 2 : 8 - dihydroxynaphthalene - 6-sulphonate in the presence of magnesium hydroxide. Specifications 19810/07, [Class 2], and 421,421 are referred to.  The Specification as open to inspection under Sect. 91 comprises also the use, as coupling components, of 2 : 6- and 2 : 7-dihydroxynaphthalene, yielding dyestuffs which can be applied by the single bath chroming process.  Additional examples describe the coupling of each of these compounds with 4-nitro-6-acetyl-amino-2-aminophenol, and the dyeing of wool olive green with the product from 2 : 6-dihydroxynaphthalene.  This subject-matter does not appear in the Specification as accepted.