OVERVIEW

It is probable that history will judge the development of reactive dyes to have been the most significant innovation in textile dyeing technology of the 20th century. As a consequence of their particular importance, and because they make use of some interesting organic chemistry, this chapter is devoted entirely to a consideration of the chemical principles involved in the application of reactive dyes. Reactive dyes, after application to the fibre, are induced to react chemically to form a covalent bond between the dye and the fibre. This covalent bond is formed between a carbon atom of the dye molecule and an oxygen, nitrogen or sulfur atom of a hydroxy, amino or thiol group on the polymer. Because of the strength of the covalent bond, reactive dyes once applied to the textile material resist removal and as a consequence show outstanding washfastness properties. Initially, reactive dyes were introduced commercially for application to cellulosic fibres, and this remains by far their most important use, although dyes of specific types have also been developed for application to protein and polyamide fibres. The potential to apply reactive dyes to other fibre types, including polyester and polypropylene, has been demonstrated technically although they are not as yet a commercial reality.

The concept of attempting to link dye molecules covalently to fibre molecules to produce colours with superior fastness to washing had been envisaged long before the 1950s when the major breakthrough took place. Prior to this, however, attempts at dye fixation employed rather vigorous...