Dyeing with sulfur dyes
- Chemical constitution of sulfur dyes
- Dyeing with sulfur dyes
- Classification of sulfur dyes
- The reduction of sulfur dyes
- Dyeing of cotton with soluble form of sulfur dyes
- Two -bath padding method
Sulfur dyes are mainly used for dyeing cellulosic fibers for corduroy articles, work wears and men's outer wear (woven and knitted goods) and lcisurewcar. Polyester/cotton blend fabric is another important area of application of sulfur dyes. Silk, paper and leather are also dyed to a limited extent. Sulfur dyes are much used for raincoat and other matcraIs which are subsequently rubber coated and vulcanized. Current literature shows a wider area of sulfur dyes for dyeing various fibers such as Tencel [11, silk  and nylon .
The consumption of sulfur dyes for the dyeing of cellulosics is estimated at 70,000 ton per annum. By far the largest proportion of this quantity is sulfur blacks for heavy shades to get umbrella cloth. Sulfur blue is also most important member of this class for dyeing knitwear. The remaining proportion is made up of yellows, browns, greens and red browns. Sulfur dyes represent a wide range of shade having good to excellent fastness to washing and light at relatively low cost compared to any other class of dye. Most sulfur dyes give dull shades and hence they can be dyed on unbleached or even grey material. Sulfur blues and greens are brightest and the best of the sulfur dyes. Sulfur dyes are not fast to chlorine bleach.
[...] Some of the well-known dyes based on above mentioned chromo are given below: Dyeing with Sulfur Dyes Suiphurised vat dyes (Hidron Blue, C. I. Vat Blue 43, Ci. Sulfur Black 11 and Indocarbon C occupy an intermediate position between vat dyes and sulfur dyes in that like vat dyes, they are applied preferentially from a sodium dithionite/sodium hydroxide bath and have superior chlorine fastness properties. Other sulfur dyes that include C Condense Sulfur dyes, copper plthalocyanine, dioxazinc intermediate, azo -disuLphide dye, introduction of brown dyes from decacyciene and its polynitro derivatives etc. [...]
[...] NaHS + NaOH Dyeing with Sulfur Dyes A mixture of sodium bisulphite along with Na2S gives beneficial results in certain cases. Bisuiphites keep the dye bath in reduced condition and hence prevent or retard surface oxidation. Some other agents suggested include thioglycolic acid, thiosalicylic acid and pseudothiohydantoin. Though good results are obtained, hut in some cases Na2S is necessary to obtain satisfactory affinity and good color value. Molleskal SF (BASF), based on 3-mercaptoethanol along with NaQH is suggested for the application of uilphitr dyes by exhaust method and by the one-bath pad-steam process [61. [...]
[...] Dyeing of cotton with soluble form of sulfur dyes The reduced form of sulfur dyes have affinity towards cellulose and promote exhaustion. The reduced sulfur dye is added to the dye bath to which 2-5 g/l sodium polysuiphide is added as an anti-oxidant. Other dye bath additives, such as alkali stable wetting and antifoam auxiliaries are Dyeing with Sulfur Dyes added. Non-ionic auxiliaries can interact with sulfur dyes and form a soluble complex which have virtually no substantivity for cotton. [...]