The Chemistry of Dyestuff. Dyestuffs. XXIV. Sulphide Dyestuffs.

A Manual for Students of Chemistry and Dyeing
By
M. Fort, M.Sc. (Leeds) Late Lecturer in Dyeing in the Bradford Technical College and L. L. Lloyd, Ph.D. (Bern) Lecturer in Organic and Technical Chemistry in the Bradford Technical College
Cambridge: at the University Press 1919
(First edition 1917, reprinted 1919)The first member of this series, Cachou de Laval, an impure and unstable brown dyestuff, was prepared in 1873 by Croissant and Bretonniere by heating vegetable substances, such as sawdust, starch, straw, along with sodium hydroxide and sulphur or sodium sulphide and sulphur. Later it was found that animal and human excrement also gave similar results by fusion with sodium sulphide and sulphur. Cachou de Laval, it was found, acted as a mordant for fixing the basic dyestuffs and also giving different shades (saddenings) by after-treatment with iron or copper mordanting salts. The property _of fixing basic dyestuffs is a property possessed by nearly all sulphide dyestuffs, many also having the power of fixing acid and direct cotton dyestuffs, properties of great value in cotton dyeing.

In 1893. R. Vidal produced a sulphide black, Vidal Black (P.), from para-amido-phenol, to which he gave the following formula: [-] and at about the same period R. Bohn discovered Fast Black B (B.), which was obtained from 1.8-dinitronaphthalene. This was the opening of the sulphide era, and during the following ten years almost every organic substance was subjected to sulphide condensation. The varying proportions of sulphur to sodium sulphide, the proportion of the sodium polysulphide produced, the reaction temperature, and the aftertreatment of the reaction mass, all play important parts.

The constitution of the sulphide dyestuffs is not yet known. They appear to be thiazine derivatives or similarly constituted polysulphides, possessing the property of dissolving in sodium sulphide solution, the dyestuff being converted by alkaline reduction into the leuco form, and in this form it is absorbed by vegetable fibres and re-oxidised on the fibre, this being aided in some cases by after-treatment with chrome or copper salts.

The sulphide, unlike the vat dyes, re-oxidise to some extent during dyeing.

The sulphide dyes are very insoluble amorphous bodies, giving on reduction thio-oxy derivatives, which are soluble in alkali. Green and Meyenberg found that by oxidising a mixture of a para-diamine or a paraamido-phenol and a large excess of sodium thiosulphate with cold potassium bichromate, a dior tetra-thiosulphonic acid is obtained.
[-]

On oxidising either of these compounds with bichromate along with amines, amido-phenols, etc., indamine sulphonic acids are obtained which, on boiling with dilute mineral acids, give products of this series. This method of preparation points to the presence of the thiazine ring in these dyestuffs.

There are practically two methods employed for the preparation of these dyes:
I. Baking.
II. Boiling under reflux condenser.

The latter favours the production of purer products and minimises the quantity of free sulphur in the final product. The dyes are separated by acid precipitation or air oxidation, the latter method yielding the better product.

Sulphide Yellows. - These dyestuffs are generally obtained from meta-toluylene-diamine, or its derivatives, by heating with sodium poly sulphide. The lower the temperature at which the condensation takes place, as a rule, the brighter is the colour of the dyestuff that is produced. In the case of the yellow sulphide dyestuffs the reaction products are often too insoluble to be used directly in the dyebath. By heating with sodium sulphide at about 120° to l25°C. the compounds are rendered more soluble, and may then be evaporated to a solid product or they may be precipitated by acid.

Dehydrothiotoluidine also gives yellows by a sulphide melt treatment, the shade being improved by addition of benzidine or its homologues to the melt.

By raising the temperature for the condensation of m-toluylene-diamine with sulphur, the colour of the final product tends to become more orange or brown.

Meta-toluylene-diamihe is employed for the production of Immedial Yellow D, Immedial Orange C (C.) and Thion Yellow G (K.). Thiourea derivatives of the above substance are employed for the production of Kryogene Yellow (B.) with or without the addition of benzidine. Para-phenylene-diamine, along with paraamido acetanilide and benzidine, also gives yellow to bronze sulphide dyestuffs, e.g., Thiophor Yellow Bronze G (J.).

Sulphide Browns. - Of these dyestuffs only a few are of real commercial value, in spite of the immense number of organic compounds from which they may be obtained.

Kryogene Brown (B.) is obtained from 1.8-dinitronaphthalene by treatment with sodium bisulphite, followed by condensation by means of sulphur and sodium sulphide.

Thional Brown (S.) results when certain arylamido derivatives of β-naphthoquinone are condensed at 240° to 280°C. by treatment with sodium polysulphides.

Thiocatechine (P.) is obtained by condensing one part of acetyl-para-phenylene-diamine with two parts of sulphur at 200° to 250°C. As soon as the violent reaction has ended and sulphuretted hydrogen is no longer given off, the mass is allowed to cool. It is soluble in sodium sulphide and dyes cotton catechu brown shades.

Sulphide Reds. Red is the only colour that is not satisfactorily represented in the sulphide dyestuffs. The red dyestuffs of the azine series, when heated with polysulphide, give those sulphide dyes which most nearly approach to red. Safranine is the one most commonly used. The introduction of copper, nickel and cobalt salts to the melts also tends to produce redder sulphide colours.

Immedial Bordeaux (C.) is obtained from a simple azine, amido-oxyphenazine, by a sulphide melt process.

Sulphide Greens. Many of the melts which give black sulphide dyestuffs give green dyestuffs when copper salts are added also. Two of the most important intermediate products for the production of these colours are l-phenylamido-4-p-oxyphenylamidonaphthalene-8-sulphonic acid [-] and 4-p-oxyphenylamido-l-amidonaphthalene sulphonic acid [-]

Sulphide Blues. - The blues are mainly obtained from indophenols. These compounds are easily produced by condensation of para-diamines, or para-amidophenols, with amines or phenols. Both benzene and naphthalene derivatives are largely used for this class. Para-oxypara-amidodiphenylamine obtained from aniline and para-amidophenol by oxidation with bichromate, or by oxidation of a mixture of phenol and para-phenylenediamine, and also para-phenylamino-para-oxy-diphenylamine obtained from diphenylamine and para-nitrosophenol, are both extensively used for the manufacture of sulphide blues.

Immedial Sky Blue (C.) is obtained by condensing dimethyl-p-amido-p-oxydiphenylamine with sodium polysulphide at 110° to 115°C. by heating under reflux condenser. Its probable formula is [-]


Sulphide Blacks. - A large variety of nitro-compounds may be used for sulphide black melts. 2.4dinitrophenol, 1.5 and 1.8or the mixture of these two dinitronaphthalenes, 1.5-dinitroanthraquinone, dinitrodiphenylamine, together with their oxy and chloro derivatives or corresponding derivatives of diphenylamine, are the main intermediate compounds used for sulphide blacks.

The preparation of sulphide blacks may be best understood, however, from actual examples.

Sulphur Black T (Ber.). 85 parts of crystallised sodium sulphide are dissolved in 100 parts of water; 30 parts of sulphur are dissolved in the above solution by heating on the water bath. To the above solution 20 parts of 2.4-dinitrophenol are gradually added and the reaction mass heated for 20 hours under reflux condenser. The solution is then tested by spotting a drop on filter paper; if the reaction is complete no yellow colour will be seen at the edge of the spot. If a yellow edge is shown boiling is continued until it is no longer produced. The dyestuff is obtained from this solution by precipitation by means of acid or aeration.

Immedial Black V (C.). 20 parts of 2.4-dinitro4'-oxy-diphenylamine are added slowly to a solution of 16 parts of sulphur in 44 parts of crystallised sodium sulphide. The reaction mass is now heated, in an oil bath, to 140°C. during five hours under reflux condenser. The solution becomes deep blue-black in colour, and about this stage a vigorous evolution of sulphuretted hydrogen takes place. As soon as this has subsided, the solution is diluted and air drawn or blown through it until no more dye is precipitated; it is then filtered, washed, and dried.
Unless carefully manufactured, sulphide dyes, especially blacks and browns, are liable to contain sulphur in a loosely combined form, which oxidises readily to free sulphuric acid, e.g., in the drying stove, or after dyeing when goods are subjected to heat and moisture, thus tendering the fabric. Alkaline impregnation of cloth has done much to diminish tendering from this cause, but still more is due to improvements in the methods of dye manufacture, e.g., the use of air precipitation instead of acid, the accurate adjustment of melt quantities and the replacement of baking methods by condensation in solution. The sulphide dyestuffs find their chief use on vegetable fibres, as the hot alkaline bath, from which they are dyed, acts unfavourably on animal fibres and tissues. A noteworthy fact in connection with the sulphide dyes, which in most respects possesses considerable fastness, is their small resistance to hypochlorites.

The following are among the best known brands of sulphide dyestuffs: Auronal (W-t-M.), Cross Dye (R.H.), Eclipse (G.), Immedial (C.), Katigen (By.), Kryogene (B.), Pyrogene (S.C.I.), Sulphur (Ber.), Thiogene (M.), Thion (K.), Thional (S.), Thionol (Lev.), Thiophor (J.), Thioxine (G.E.), Vidal (P.).