Sulpher dyes are highly coloured, water insoluble compounds and have to be converted in to water soluble substantive forms (lucoforms) before application to the textile materials. This conversion is carried out by a treatment with a reducing agent like dilute aqueous Na2S. Since this lucoform of Sulpher dye is substantive to cellulosic materials. They are absorbed on the fibre surface. Then they are reconverted original water insoluble form of dye by oxidation. This oxidation is carried out by “airing” (exposure to air) or by using an oxidizing agent like Na-dichromate (Na2Cr2O7).Sulpher gives best result (Bright Tone) when they are used to produce black, Black & brown shades but red shades cannot be obtained by Sulpher dyes.
Friday, May 18, 2012
11:44 PM
Dyeing of Cotton Fabric with Sulpher Dyes | Method of Manufacture of Sulpher Dye | Characteristics of Sulpher Dyes
Method of manufacture of Sulpher dye:
Aromatic Hydro Carbon
Containing Hydroxy amino or nitro group - Thionation Sulphorization - Sulpher Dye
Trade Names:
Trade Names | Name of Manufacturer | Country of origin |
Calcogen | Dyes Dept. American Cyanamid Co. | USA |
Pyrogene | Ciba | Switzerland |
Thional | Sandoz | Switzerland |
Solfo | ACNA | Italy |
Sulfogene | Du pont | USA |
Thional | Imperial | UK |
Mitsui Sulpher | Mitsui Chemicals Ind. Co. Ltd | Japan |
Characteristics of Sulpher Dyes:
The main properties and characteristics features of Sulpher dyes are mentioned below:- Sulpher dyes have Sulpher linkage within their molecules. Sulpher dyes are highly colouerd water insoluble dyes. Some dyes are partially soluble in water. They have no direct affinity towards cellulosic fibres. To make them substantive they are to be converted in to soluble lucoform by treating them with reducing agents (Like dilute Na2S solution)
Sulpher dyes have good light fastness with rating about 4. This light fastness may be improved by an after treatment with metallic salt. These dyes have excellent wash fastness with rating about 3-4. This good wash fastness is due to its larger molecular size & insolubility in water. They are not applicable to wool due to strong alkaline condition. They are exclusively amorphous, few of them show crystallinity.
Classification of Sulpher Dyes:
Sulpher dyes may be classified in many ways:- But according to their solubility there are essentially 3 classes of Sulpher dyes as below:-
- Conventional or Water insoluble dyes
- Leuco Sulpher dyes (Partially soluble) and
- Solubilised Sulpher dyes.
i) Method i
ii) Method ii
iii) Method iii
iv) Method iv
v) Method v
vi) Method vi
Features of Sulpher Dye
- Amorphous Colloidal materials.
- High molecular weight with various composition
- Complex molecular structure –heterocyclic molecules containing Sulpher linkage.
- Decomposed by acids, with the liberation of H2S.
- Characterized by thiozine ring, containing Sulpher atom.
Chemistry of dyeing with Sulpher Dye:
The Sulpher dyes contain Sulpher linkage within their molecules. They are insoluble in water but can be made soluble in water by treating them with reducing agents. This also makes them substantive towards cellulosic fibres. Na2S acts as reducing agent that breaks the Sulpher linkage and break down the longer molecules in to simple components which can penetrate the material (fiber/fabric) surface easily.
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Textile Technology: Dyeing of Cotton Fabric with Sulpher Dyes | Method of Manufacture of
Sulpher Dye | Characteristics of Sulpher Dyes
Sulpher dyes are highly coloured, water insoluble compounds and have to be converted in to water soluble substantive forms (lucoforms) befor...
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