Dyeing with sulfur dyes

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Dyeing with sulfur dyes

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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 [2] and nylon [3].

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.

Introduction
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
Bibliography

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[...] 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. [...]

[...] Sulfur dyes can also be oxidized in the acidic media with 5-7 g/l H202 at about 60°C for the continuous dyeing method and H202 for the exhaust method along with acetic acid (pH 4.0 - 4.5 ) at 50°C. Addition of p - nitro aniline or meta- toluenediamine to the peroxide oxidation bath for sulfur dyes improve the wash fastness of the dye. Sodium chiorite/bromate as oxidizing agents Sodium chlorite is a strong oxidizing agent and sodium bromate does not cause complete oxidation of sulfur red-browns. [...]

[...] Nitro process Nitro process uses inert nitorgen into the dyeing vessel, thus bringing about a substantial reduction in the amount of reducing agent. The introduction of piece in the air feed time to the dyeing machine, au nitrogen can be supplied atternatively. The dye bath is prepared at 50°C including a wetting agent, alkali and glucose. Diresul EV dye (Clariant) is added and uniformly distributed. The dye bath is heated up to 95°C and air in dyeing machine is substituted by N2. [...]

[...] One-bath pad-steam continuous dyeing In this system, the goods are padded with pre-reduced sulfur dye solution at 38°C except black shade. The padded goods are steamed at 102-104°C with saturated steam for 30-60 see, washed at elevated temperature from 40-60°C, oxidized, soaped and rinsed. Two -bath padding method A noteworthy variation on this system is the pad-dry-develop method which dispenses with normal steamer. Processes which entail pad-dry- chemical pad-steam or jig development are best served for the C. I. Soluble Sulfur dyes or the dispersed conventional dye types. [...]

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