Patent GB-364147-A (GB)
Title: Manufacture of azo-dyestuffs containing chromium
IPC: C09B45/01
Filed: 1930-09-26
Abstract: Azo dyes, soluble chromium compounds of; acid wool dyes, dyeing with; printing.--Azo dyestuffs containing chromium are obtained by treating the dyes from diazotized 1 : 2-aminonaphthol-4-sulphonic acid or its nitrated derivative and a - or b -naphthol in boiling aqueous solution with an agent yielding chromium in presence of a proportion of alkali metal ions having no salting-out action on the dyestuff until a dyestuff not precipitated by a saturated solution of common salt is formed and thereafter evaporating the reaction solution at a lower temperature, if necessary after filtration and advantageously under reduced pressure.  As chroming agents are specified chromium chloride, fluoride, sulphate, sulphite, acetate, formate, oxalate, hydroxide, and aromatic sulphonates, and mixtures of any of these, with or without the usual additions.  The chroming may be effected under pressure. The products are in part precipitated in a dyebath containing sulphuric acid and are therefore applicable in a weakly acid bath according to the process of Specification 364,148 with subsequent development in a bath of increased acidity; they are suitable for dyeing animal fibres and leather, for colouring varnishes and for printing in presence of chromium acetate, their ready solubility in water enabling the use of a highly concentrated printing paste.  The following examples are specified.  (1) and (2) The dyestuff from nitrated 1 : 2-diazonaphthol-4-sulphonic acid and b -naphthol is boiled in an open vessel with an aqueous solution of chromium fluoride containing sodium formate (different proportions specified in the two examples) until no dyestuff is precipitated on adding a saturated solution of common salt to a test portion, and the reaction mixture is then, after filtration if necessary, evaporated under reduced pressure.  (3) The dyestuff from nitrated 1 : 2-diazonaphthol-4-sulphonic acid and b -naphthol, dissolved in dilute caustic soda, is boiled for 3 hours under reflux with an aqueous solution of chromium sulphite and for a further \ba1/2\be hour with a further addition of chromium sulphite, and the solution is filtered and evaporated under reduced pressure; the product dyes wool deep fast black tints from an acid bath.  (4) The dyestuff from nitrated 1 : 2-diazonaphthol-4-sulphonic acid and b -naphthol, dissolved in dilute caustic soda, is boiled for 6 hours under reflux with an aqueous solution of chromium sulphate and sodium bisulphite, and the solution is neutralized with sodium carbonate, filtered, and evaporated under reduced pressure; the product dyes wool fast black tints from an acid bath.  (5) The dyestuff from nitrated 1 : 2-diazonaphthol-4-sulphonic acid and a -naphthol is boiled for 1 hour with an aqueous solution containing chromium oxalate, chromium fluoride and sodium formate, filtered, and evaporated under reduced pressure; the product dyes wool fast black tints. (6) The dyestuff from nitrated 1 : 2-diazonaphthol-4-sulphonic acid and a -naphthol is boiled for \ba1/2\be hour with an aqueous solution containing chromium oxalate, chromium fluoride, and sodium formate, filtered, and evaporated on the water bath; the product gives on wool from a formic acid bath blackish brown dyeings which are developed by sulphuric acid to well equalized pure black tints.  (7) The dyestuff 1 : 2-aminonaphthol-4-sulphonic acid --> a -naphthol is boiled for 3 hours under reflux with an aqueous solution of chromium fluoride containing sodium formate and the solution is evaporated under reduced pressure; the product dyes wool from a weakly acid bath blue tints which are rendered fast by development with sulphuric acid. Other chroming mixtures may be used in any of the foregoing examples, e.g. chromium fluoride and sodium sulphite, chromium acetate and sodium acetate, chromium sulphate, sodium bisulphite and sodium acetate, chromium fluoride and chromium oxalate, chromium fluoride, chromium formate and sodium formate, chromium oxalate and sodium acetate, or a chromium salt and an aromatic sulphonic acid.  The Specification as open to inspection under Sect. 91 (3) (a) comprises also any treatment of the parent azo dyestuffs with agents yielding chromium which yields a product suitable for dyeing from a weakly acid bath and for subsequent development by increasing the acidity of the bath, whether or not such product is capable of being salted out, and includes the following further examples: (1) The dyestuff from nitrated 1 : 2 - diazonaphthol - 4 - sulphonic acid and b -naphthol is heated at 80-85 DEG  C. with an aqueous solution containing sodium sulphide, chromic oxide paste and caustic soda until the product has the required properties, whereupon the solution is diluted and neutralized with sodium bisulphite at 50-60 DEG  C. and the product is salted out; it dyes wool a fast black.  (2) The dyestuff obtained from nitrated 1 : 2-diazonaphthol-4-sulphonic acid and b -naphthol and reduced by heating with sodium sulphide is boiled for 4 hours under reflux with an aqueous solution containing caustic soda, chromium fluoride, chromium oxalate and sodium acetate, whereafter the solution is filtered and the product is salted out; it dyes wool from an acid bath very fast blue-green to black.  This subject-matter does not appear in the Specification as accepted.