Sulphur dyes fastness

A similar study of the dye Cl Sulphur Orange 1, obtained by heating 2,4-diaminotoluene with sulphur led to the isolation of compound 6.136 after reaction of the alkali melt of the dye with chloroacetic acid. It was concluded that the commercial dye is a polybenzothiazole. The final hue of the product depends on the temperature and the duration of the sulphurisation the use of a smaller proportion of sulphur produces Cl Sulphur Brown 10. A similar product (Cl Sulphur Brown 8) is obtained when 2,4-dinitrotoluene is baked with sodium polysulphide. A brown sulphur dye of high fastness to light (Cl Sulphur Brown 52) results when the polycyclic hydrocarbon decacyclene (6.137) is baked with sulphur at 350 °C [57]. 

Improves wetfastness and Peroxide wash fastness of sulphur dyeings. 

The sulphur dyes are cheap and easy to apply. Their wet-fastness is good and the light-fastness satisfactory, as shown in Table 19.1. They therefore provide a cheap method of dyeing cellulosic fibres with a wet-fastness better than the direct dyes. Some of the yellows have only poor light-fastness, such as Thional Yellow G (C.l. sulphur yellow 2), which is rated as 2. The sulphur dyes all have poor fastness to chlorine and are no use for elfect... 

Sulphur dyes are after-treated with copper sulphate or, more commonly, with copper sulphate together with potassium or sodium dichromate and acetic acid. The treatment improves light-fastness and, in some cases, wash-fastness, to a small extent. When copper sulphate alone is used the process consists of running, after rinsing, at 70°C (160°F) for 20 to 30 minutes in a liquor containing... 

Sulphur dyes cannot be applied to protein fibres by normal methods on account of the strongly alkaline nature of the dye liquors. Wool is never dyed with these dyestuffs, but a reasonably fast black was obtained on wool and cotton unions by adding 5 per cent on the weight of the goods of a protective colloid such as glue or boiled starch. 

Vidal and other sulphur blacks have been used for dyeing fast shades on pure silk by the method patented by Lodge and Evans. The process is based on the fact that Vidal Black can be converted into its leuco compound, which is soluble in ammonium sulphide, by the action of sulphites or bisulphites. In practice the leuco compound is prepared and dissolved in sodium sulphide, which is then converted into ammonium sulphide by the addition of ammonium sulphate. 

Sulphur dyes may be topped with basic dyes and, because the former act as mordants, the resultant wet-fastness is good. From 0-1 to 0-5 per cent of the basic dye is used, together with 2 to 5 per cent of acetic acid. The goods are entered into a cold bath in which the acid has already been placed. The temperature is raised slowly to 50°C (122°F), during which time the dye is added in portions. 

Sulphur dyes. Sulphur dyes, in use for over 90 years, are still used in large quantities on cotton goods for fast, though not bright colours, mostly blacks, browns and deep blues. The dyes are complex mixtures of uncertain composition to which precise chromophores cannot be assigned. 

The fact that the aftertreatment of direct dyes has a long history is not surprising since wet fastness within this class is not particularly good. Their prime advantages are ease of application and economy compared with dyes of higher fastness (reactive, sulphur or vat) -hence the continued search for highly effective aftertreatments that improve wet fastness... 

Levelling acid dyes and particularly 1 1 metal-complex types generally require an exceptionally low pH in order to promote exhaustion and levelling up to 3% o.w.f. sulphuric acid is most commonly used for levelling acid dyes, although hydrochloric, formic and phosphoric acids are also effective. In the case of conventional 1 1 metal-complex dyes it is essential to use a sufficient excess of acid over and above the typical 4% o.w.f. sulphuric acid normally absorbed by the wool, otherwise there may be a tendency towards tippy dyeings and lower wet fastness. The actual excess required depends on applied depth and liquor ratio [2] typical recommendations are given in Table 12.2. 

Another terminal bidentate ligand that has been exploited occasionally in bright disazo direct dyes is the sulphated 8-hydroxyquinoline residue (5.15). On aftercoppering, fastness to light and wet tests is enhanced by hydrolysis catalysed by the copper(II) ion and formation of a bidentate 1 2 complex (Scheme 5.3). Apparently, electron withdrawal by sulphur facilitates removal of the sulphite grouping and approach of the copper(II) cation [10]. 

Cl Sulphur Black 1, which is produced from the relatively simple intermediate 2,4-dinitrophenol and aqueous sodium polysulphide. A similar product (Cl Sulphur Black 2) is obtained from a mixture of 2,4-dinitrophenol and either picric acid (6.148 X = N02) or picramic acid (6.148 X = NH2). A black dye possessing superior fastness to chlorine when on the fibre (Cl Sulphur Black 11) can be made from the naphthalene intermediate 6.149 by heating it in a solution of sodium polysulphide in butanol. An equivalent reaction using the carbazole intermediate 6.150 gives rise to the reddish blue Cl Vat Blue 43 (Hydron blue). This important compound, which also possesses superior fastness properties, is classified as a sulphurised vat dye because it is normally applied from an alkaline sodium dithionite bath. Interestingly, inclusion of copper(II) sulphate in the sulphurisation of intermediate 6.150 leads to the formation of the bluish black Cl Sulphur Black 4. 

Polysulfide melt dyes, which are applied chiefly with dithionite and commonly show a higher degree of fastness, are called sulfur vat dyes. They include such dyes as C.I. Vat Blue 43 and C.I. Sulphur Black 11. 

With respect to both application and fastness, a distinction is made between sulfur dyes and sulfur vat dyes. The latter include dyes of the type Hydron Blue C.I. Vat Blue 43, 53630 [1327-79-3]) and Indocarbon C.I. Sulphur Black 11, 53290 [1327-14-6]). 

Metaxylidine gives similar compounds if treated with sulphur. One of these, M.P. 107°, possesses one amido-group capable of being diazotised, and certain of the azo-dyes prepared with it form the various brands of Erica. These dyestuffs have the remarkable property of dyeing cotton from a bath containing sulphate of soda, producing pleasing pink shades of considerable fastness. 

The amidoazobenzene hydrochloride came into the market formerly, as a yellow dye, under tire name of Aniline Yellow. At present, it is scarcely used, but there is prepared from it, by heating with sulphuric acid, a mono- or di-sulphonic acid, which in the form of its alkali salts finds application as a dye under the name of Acid Yellow, or Fast Yellow. As already mentioned under the dis-azo dyes, from the diazo-compound of this dye, Biebrich Scarlet may be made-by combination with /3-naphthol. Finally, the amidoazobenzene is still used for the preparation of the Induline dyes. 

Covalent bonds. The covalent bond between carbon atoms in most organic compounds is very stable. It has been realized for a long time that great wet fastness would be obtained if dye molecules could be anchored to textile fibres by covalent bonds. During the last decade this has been achieved with the aid of certain reactive groups such as cyanuryl chloride, trichloropyrimidyl, sulphonethanolamide sulphuric acid ester, and vinyl sulphone. 

The members of this group are complex organic compounds containing sulphur. They are used to dye cheap shades of high wet-fastness on cellulosic fibres. The colours, however, lack brightness. 

The most significant assistant in the application of these dyes is the acid added to the dyebath. Many acid dyes will not exhaust on wool at all unless the dyebath has been acidified. If, for example, wool is boiled gently for half an hour with 5 per cent of Acid Magenta, it is only faintlystained. When 4 to 5 per cent of sulphuric acid is also added, however, the wool is dyed a heavy shade, and exhaustion is virtually complete. Some experiments reported by Lister (J.S.D.C., 1949, 98) show the relationship between acid and exhaustion of Azo Rhodine 2G (C.I. acid red 1) and Xylene Fast Yellow P (C.I. ACID YELLOW 61) on purified wool. 

If a correction to the shade is necessary and the standard of fastness is to be maintained, the most convenient procedure is to cool the liquor to 60°C (140°F) and add sufficient sodium acetate to convert any free sulphuric to acetic acid, and then correct with an acid mordant or a premetallized dye. If the amount of dye required is not great the wool will already contain sufficient Cr Os to combine with the acid mordant dye. A few dyes suitable for shading are shown below. 

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