Reactive Dyes for Textiles

Of various methods of achieving wet fastness in dyeings, direct chemical linkage of the dye to the fibre has not hitherto been employed in practice. The Procion dyes are a new class of dyes, which will react with cellulose in presence of alkali. The evidence for chemical reaction is reviewed. Being dyes of small molecular weight, their affinity for cellulose is low and diffusion inside cellulose fibres rapid, so that cold dyeing becomes feasible. Also, side‐reaction of the dyes with water is minimised at low temperatures. The importance of these properties in determining the preferred dyeing methods is discussed. Procion dyes can be applied in practice by continuous processes, including a method which entails only padding and drying. Novel batch dyeing methods have been developed. The dyes can also be applied by printing with a suitable thickener, and again a novel non‐steaming printing style has been evolved and a particularly interesting style using white and vat‐dye‐illuminated resists under Procion dyes. The fastness properties characteristic of chemical linkage are briefly reviewed.