Patent GB-415924-A (GB)
Title: Process of dyeing leather
IPC: D06P3/32
Filed: 1933-12-05
Abstract: Leather is dyed brown to brown-violet to black-brown shades by treating it with a copper compound of an azo-dyestuff constructed according to the scheme R1 --> R2 \sM R3, where R1 is an amino-compound containing a lake-forming group, R2 is a benzene derivative containing at least two hydroxyl-groups and capable of being twice coupled and R3 is an aminoazo-compound in which the amino-group belongs to a monoaryl residue.  The compounds R1 may be amino-compounds of the benzene or naphthalene series containing an o-hydroxy-, carboxyl- or alkoxy-group or containing a salicylic acid grouping, e.g. o-aminophenols, o-aminonaphthols, o-aminoalkoxybenzenes, o-aminoalkoxynaphthalenes, anthranilic acids, o-aminonaphthalenecarboxylic acids, aminosalicylic acids, and the sulpho-, nitro-, alkyl- and halogen-substitution products thereof. R2 may be 1 : 3-dioxybenzene, 1 : 3-dioxybenzene-4- or 5-carboxylic acid, 1 : 2 : 3-trioxybenzene-5-carboxylic acid, or a sulpho-, nitro-, alkyl- or halogen-substitution product thereof capable of coupling twice.  R3 may be 4-aminoazobenzene-4<1>-sulphonic acid, 3 : 2<1>-dimethyl-4-aminoazobenzene-4<1>-sulphonic acid or 4<1>-oxy-4-aminoazobenzene-3<1>-carboxylic acid.  The coupling may be effected in any order and, according to the selected order and the nature of the diazo-compound, may be effected in neutral, acid or alkaline medium, e.g. a medium containing sodium carbonate or bicarbonate, alkaline - earth hydroxide, caustic alkali, ammonia, pyridine, acetic acid or hydrochloric acid.  The copper compounds may be made by treating the dyestuff with various agents yielding copper, e.g. copper sulphate, copper chloride, tetrammine-cupric sulphate or copper acetate, if desired in the presence of an organic base, e.g. pyridine.  The agent yielding copper may be caused to react on the monoazo-dyestuff containing the lake-forming group, or on a finished polyazo dyestuff either in the dyebath or in the course of manufacture of the dyestuff.  In examples: (1) neutralized chrome leather (box willow calf, chrome sides, glazed kid, full chrome sheep) is dyed a dull brown with the copper compound of the dyestuff 2-amino-1-oxybenzene-4-sulphonic acid --> 1 : 3-dioxybenzene \sM 3 : 2<1>-dimethyl-4-aminoazobenzene-4<1>-sulphonic acid; (2) well fulled vegetable-tanned sheep or goat skins are similarly dyed, formic acid being added in the later stages.  A table shows the colours produced by copper compounds of additional dyes, further components specified being: R1 : 2-amino-4 : 6-dinitro-1-oxybenzene and 6-amino-4-sulpho-1-oxybenzene-2-carboxylic acid; R2 : 1 : 3-dioxybenzene-4-carboxylic acid; R3 : 4-aminoazobenzene - 4<1> - sulphonic acid, dehydrothiotoluidinesulphonic acid-azo-1-amino-8-oxynaphthalene-3 : 6-disulphonic acid, 4-nitro-1-aminobenzeneazo - 1 - amino - 8 - oxynaphthalene - 3 : 6-disulphonic acid, 4-amino-4<1>-oxyazobenzene-3<1>-carboxylic acid, 4-amino-3-methoxyazobenzene - 3<1> - sulphonic acid, aminobenzeneazo - 1 - aminonaphthalene - 6 - (7) - sulphonic acid and 4-nitro-1-aminobenzeneazo-1-aminonaphthalene-6-sulphonic acid.