Nitrodiphenylamine dyes

The preferred dyes for cellulose acetate and triacetate are the disperse dyes. These consist mainly of azo, anthraquinonoid, and nitrodiphenylamine dyes that are insoluble or at best slightly soluble in hot aqueous dye-bath systems. These crystalline dyes must be ground to a very small particle size, e.g., 2 pm. They are then pasted with water and a wetting agent and added to the dye-bath through a fine mesh screen. A dispersing agent and a carrier or accelerant may be present in the dye-bath to enhance diffusion of the dye molecules into... 

An aqueous dispersion of a disperse dye contains an equilibrium distribution of solid dye particles of various sizes. Dyeing takes place from a saturated solution, which is maintained in this state by the presence of undissolved particles of dye. As dyeing proceeds, the smallest insoluble particles dissolve at a rate appropriate to maintain this saturated solution. Only the smallest moieties present, single molecules and dimers, are capable of becoming absorbed by cellulose acetate or polyester fibres. A recent study of three representative Cl Disperse dyes, namely the nitrodiphenylamine Yellow 42 (3.49), the monoazo Red 118 (3.50) and the anthraquinone Violet 26 (3.51), demonstrated that aggregation of dye molecules dissolved in aqueous surfactant solutions does not proceed beyond dimerisation. The proportion present as dimers reached a maximum at a surfactant dye molar ratio of 2 5 for all three dyes, implying the formation of mixed dye-surfactant micelles [52]. 

Only a limited range of nitro, azo and anthraquinone disperse dyes exhibit adequate fastness to dry heat, light and weathering for application on polyester automotive fabrics. The structure of Cl Disperse Yellow 86 was modified to incorporate UV absorbers of the benzophenone, benzotriazole or oxalanilide types into the dye molecule. The derived dyes showed better fastness properties than the parent unsubstituted dye. Positioning of the photostabilising moiety within the dye molecule had little influence on the light fastness obtained, however. Built-in benzophenone residues were more effective than the other two types [177]. Nevertheless, several further monoazo and nitrodiphenylamine disperse dye... 

The most important nitro dyes are the nitrodiphenylamines of general structure (6). 

Nitro Dyes. 2-Nitrodiphenylamines are readily obtained by condensation of derivatives of 2-nitrochlorobenzene 88-73-3] with suitable aromatic amines. Because of their accessibility and good lightfastness, these dyes became very important for dyeing cellulose acetate and, more recently, have gained a solid position as disperse dyes for polyester fibers. This is especially true for the reaction product of 1 mol of 3-nitro-4-chlorobenzenesulfonyl chloride [97-08-5] and 2 mol of aniline. An exhaustive review of the constitution and color of nitro dyes is given by Merian [40], The yellow nitroacridones may also be classified in this group. 

Nitro dyes are the most important class of direct hair dyes they are substituted derivatives of nitrobenzene or nitrodiphenylamine [3, Nitro and Nitroso Dyes]. By proper selection of donor groups and substitution site on the benzene ring, a spectrum of dyes from yellow to blue violet can be prepared [9, pp. 247-250], [40] (Scheme 3). 

Reduction of 2-nitrochIorobenzene-4-sulfonic acid gives o-chlorometanilic acid which is used in making azo dyes. The real technical value of nitrochlorobenzene-sulfonic acid, however, lies in the ability of its chlorine atom to be replaced by various groups. For example, o-nitrophenol-p-sulfonic acid is obtained by treatment wiui sodium hydroxide, and this product, on reduction, yields o-aminophenol-p-sulfonic acid. An ogously, nitrochlorobenzenesulfonic acid gives o-nitroanisole-p-sulfonic acid by treatment with alcoholic methanol, and from this is obtained o-anisidine-p-sulfonic acid. The action of ammonia on nitrochlorobenzenesulfonic acid produces o-nitroaniline-p>sulfonic acid aniline and its derivatives produce o-nitrodiphenylamine-p Sulfonic acids (cf. Table II). 

Nitrodiphenylamine is a solid. Otto Fuel II contains 2-nitrodiphenylamine to control the explosion of propylene glycol dinitrate. It is also used as a solvent dye. Other names for 2-nitrodiphenylamine are 2-nitrobenzamine, 2-nitro-N-phenyl, 2-nitro-N-phenylaniline, and Sudan Yellow 1339. 

Disperse colouring materials are used principally for colouring cellulose acetate, polyamide and polyester fibres. Their chemical structure is similar to that of the fat-soluble dyes. They belong to the compound classes of nitrodiphenylamine derivatives and azo- and anthraquinone dyes without a sulphonate group. They are more or less easily soluble in organic solvents but insoluble or difficultly soluble in water. Mixtures of disperse dyes can be separated on alumina columns, using solvents such as ether, methylene dichloride, ethyl acetate and tetrahydrofuran [71]. PC-separations on cellulose paper are incomplete [14, 30, 31, 73, 85]. Separations are better on acetyl-paper [29, 30, 43] or pre-treated paper [19, 20, 25, 44, 73]. 

An important dye in this class is the substituted nitrodiphenylamine, Disperse Yellow 42, which is used to dye polyester with very good lightfastness. 

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