The Dyeing and Printing of Textile Fibres

The split into the various textile dyestuff application areas has, over recent years, seen a shift towards the two main outlets of disperse dyes for polyester and reactive dyes for cellulosics (mainly cotton), at the expense of directs and vat dyes for cotton, cationic dyes for acrylics and acid dyes for polyamide. The latter fibre has shown a comeback in recent years with the popularity of microfibres in sports and leisure wear. The position in 1998, with disperse dyes dominating in value terms, was as shown in Table 2.6. 

There are three basic ways of applying dyes to a textile substrate  

Cotton and Other Cellulosic Fibres. The dominant natural cellulosic fibre is cotton, the other natural cellulosic fibres, or bast fibres, include flax, linen, jute and ramie. The so-called regenerated fibres, which include viscose, modal fibres and lyoceU (Tencel), are made by various chemical treatments of cellulosic substrates. The dyeing and printing of cellulosic fibres and materials is carried out using, in decreasing order of scale and importance, reactive, direct and vat dyes.  

The overall process for the dyeing with vat dyes produces a large load on the effluent because of the chemical reducing agent. More environmentally friendly alternatives to hydros have been proposed, e.g. the biodegradable hydroxyacetone, but cost 

The reactive functional groups fall into two classes  

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