Colouring compositions containing dyes of the triarylmethane series

摘要

Dyestuff compositions for duplicating and typewriting comprise at least one leuco triarylmethane dye as defined below together with a quaternary ammonium hydroxide in quantity sufficient to stabilize the leuco compound against photochemical oxidation, oxidation to the dye taking place after the compositions have been applied to a stratum. The leuco compounds have the formula:- wherein X is H or methyl, R represents phenyl, tolyl, xylyl, mononitrophenyl, mono- and dichlorphenyl, 1 - p - phenylamino - naphthyl, 1 - p - monoalkylamino-or dialkylamino - naphthyl, or an aminophenyl or aminotolyl radical, said aminophenyl or aminotolyl radical may have one or both of the hydrogen atoms of their amino groups substituted by alkyl of less than 5 carbon atoms, acetyl, 2 - hydroxyethyl, 2 -cyanoethyl, benzyl, or phenyl, and R1, R2, R3, and R4 represent hydrogen, alkyl of less than five carbon atoms, 2 - hydroxyethyl 2 - cyanoethyl, benzyl or phenyl, said leuco compounds being devoid of sulpho, carboxy, or phenolic hydroxy groups. Preferably, sufficient quaternary ammonium hydroxide is added to give a pH of not less than 8 to a 1 per cent solution of the composition in ethanol at room temperature. The two ingredients are mixed by (1) stirring a solution of the purified leuco compound in an organic solvent with an aqueous solution of the base, (2) mixing both in an organic solvent and precipitating by cooling or diluting with a non-solvent for the leuco compound. (3) forming the leuco compound by alkaline reduction of the dye or by synthesis and mixing with an aqueous solution of the base without isolation. In examples:- (1) the leuco compounds of ethyl violet and crystal violet, prepared by reduction of the commercial colour, are each mixed in ethanol with aqueous benzyl trimethylammonium hydroxide; (2) the neutralized synthesis reaction mixtures from p-diethylaminobenzaldehyde and diethylaniline or N-diethyl - o - toluidine are each mixed with aqueous choline and those from p - diethylaminobenzaldehyde and N - ethyl -N - benzylaniline or N - ethyl - N - (b - hydroxyethyl) - o - toluidine or N - (b - cyanoethyl) - N - methyl - aniline (in this latter case p - dimethylaminobenzaldehyde may replace p-diethylaminobenzaldehyde) are each mixed with aqueous benzyl trimethylammonium hydroxide; (3) di (p-dimethylamino - phenyl) hydrol is condensed with diethylaniline and the separated leuco compound recrystallized from isopropanol in presence of benzyl trimethylammonium hydroxide; (4) di (p - di - n - butylaminophenyl) - methane is converted to the hydrol by action of lead peroxide and this hydrol is condensed with di - n - butylaniline, diethylaniline, N - ethyl - N - methyl - aniline, or N - b - cyanoethyl - N - methyl aniline and the neutralized product is mixed with benzyl trimethylammonium hydroxide; (5) Victoria Blue BO, Brilliant Green, New fuchsine and paraleucaniline, are reduced to their leuco compounds with zinc dust and sodium hydrosulphite and without isolation are admixed with aqueous benzyl trimethylammonium hydroxide, and fuchsine is similarly reduced and admixed with choline; (6) the neutralized condensation products from benzaldehyde and N - ethyl - N - benzylaniline, o - chlorbenzaldehyde and N.N - diethylaniline, p -chlorbenzaldehyde and N.N - dimethylani line, and p - chlorbenzaldehyde and N - ethyl - N - benzylaniline are mixed with benzyl trimethylammonium hydroxide. Other dyes and bases are listed. Examples describe the preparation of colourless transfer sheets for single or multiple reproduction, which may be developed with a chloranil - dioxane - alcohol solution, using compositions comprising the stabilized dyes of the invention, octadecyl and hexadecyl amines, paraffin wax, aluminium stearate, carnauba wax, and "Vaseline" (Registered Trade Mark) and if desired other non-smudging azo dyes.