Patent GB-761348-A (GB)
Title: Process for the fast dyeing of anodically oxidised aluminium
IPC: C25D11/24
Filed: 1953-01-28
Abstract: Anodically oxidized aluminium or its alloys is fast dyed from an aqueous dyebath in which the dyestuff is a cobalt or copper compound of a monoazo dyestuff which contains at least two sulphonic acid groups and corresponds to the general formula:- <FORM:0761348/IV(b)/1> in which R1 represents a benzene residue bound in the 1-position to the hydroxyl group, in the 2-position to the azo linkage, and in the 6-position to the sulphonic acid group, and <FORM:0761348/IV(b)/2> represents the residue of a hydroxy compound bound to the azo linkage in a position vicinal to the hydroxyl group, and which residue contains two 6-membered rings fused together, having as members of the fused ring system 9 or 10 carbon atoms, and as a heteroatom at most one nitrogen atom in an a -position, at least one of the residues R1 and R2 containing a further sulphonic acid group.  The dyestuffs of the above formula may be prepared from diazotized 2-amino-1-hydroxybenzene-6-sulphonic acids and naphthols or hydroxy-quinolines.  The 2-amino-1-hydroxybenzene-6-sulphonic acid may contain a further substituent in the 4-position, such as 4-methyl-, 4-methoxy-, 4-bromo-, 4-chloro-, 4-nitro-, 4-acetylamino-, 4 - tertiaryamyl - 2 - amino - 1 - hydroxybenzene - 6 sulphonic acid, and 2 - amino-1 - hydroxybenzene - 4:6 - disulphonic acid.  Suitable naphthols include 2 - hydroxynaphthalene and nuclear substitution products, e.g. mono-sulphonic acids, thereof, and 1-hydroxynaphthols capable of coupling in the 2-position. Suitable hydroxyquinolines include N-methyl, N-n-butyl-, and N-phenyl-4-hydroxyquinolone-(2) and 2:4 dihydroxyquinoline Conversion to the cobalt or copper compound may be carried out by heating with a cobalt- or copperyielding agent while the dyestuffs are in the coupling mixture, or on the filtered or reprecipitated dyestuff.  The cobalt- or copper-yielding agent may be salt containing the metal as cation, e.g. the sulphate or acetate or it may be a complex metal compound, e.g. a metal-ammine complex such as copper tetrammine sulphates from ammonia, pyridine or monoethanolamine, or the metal may be contained in a complex anion as in complexes of cobalt or copper with alkali salts of aliphatic amino-carboxylic acids such as glycocoll, lactic acid and tartaric acid.  Other substances such as alcohol may be present.  Dyeing is carried out in an aqueous dyebath containing the cobalt or copper compound of the dyestuff; buffer salts or other additions for controlling the pH value may also be present. In an example, an aluminium article which has been anodically oxidized in a sulphuric acid bath, is treated for half-an-hour at 65 DEG C. in a bath containing 0.05 to 0.2 grams per litre of a dyestuff prepared by dissolving 46.3 parts of the sodium salt of the dyestuff obtained from diazotized 2-amino-1-hydroxybenzene-4:6 disulphonic acid and 2:4-dihydroxyquinoline in 150 parts of water and mixing with 20 parts of crystalline sodium acetate and 120 parts of a copper sulphate solution, containing 7.8 parts of copper, the whole being stirred for 30 minutes at 70-75 DEG C., and the copper complex precipitated by the addition of sodium chloride, filtered and dried.  Sodium acetate and acetic acid may be added to give the dyebath a pH value of about 5.  This gives a bronze colour, which is of excellent fastness to light after a sealing treatment in boiling water.  The corresponding cobalt compound gives a copper red tint.  The copper complex of the dyestuff from diazotized 2-amino-1-hydroxybenzene-4:6 disulphonic acid and b -naphthol gives bluish red tints.  Reddish violet tints are given by both the copper and cobalt compounds of the monoazo-dyestuff obtained from 4-chloro-2-amino-1-hydroxybenzene-6-sulphonic acid and 1-hydroxynaphthalene-4-sulphonic acid, bluish red by the compound of either metal with that obtained from 4-chloro-2-amino-1-hydroxybenzene-6-sulphonic acid and 2-hydroxynaphthalene-3:6 disulphonic acid, and a red tint from the copper, and a bluish red tint from the cobalt compounds with that obtained from 2-amino-1-hydroxybenzene-4:5 disulphonic acid and 2-hydroxy-naphthalene-6-sulphonic acid.