In spite of the essential simplicity of reactive dyeing methods, there are few instances where dyes based on one type of reactive system show fully satisfactory compatibility with those of another type. Even if competing dyes have identical chromophoric groupings, there may well be marked differences in application behaviour and fastness properties of the resulting dyeings. In selecting a range of reactive dyes for batchwise dyeing, however, the dyer has considerable freedom of choice since almost all required hues are fully represented in every range. Selection is largely based on application technique and consideration of the end use of the material.
Reactive dyes can be applied by any conventional batchwise dyeing method for cellulosic materials, including circulating-liquor machines for loose stock, yarn or woven fabrics, as well as jets, winches or jigs for piece dyeing. The conventional dyeing process entails three stages:
Numerous variants of this basic procedure in terms of chemical concentrations and fixation conditions have been devised to take account of the characteristic properties of the numerous ranges of reactive dyes now available.
Considerable research over several decades has led to the present selection of processes to apply each range of dyes in such a way that optimal fixation efficiency and level dyeing are achieved. In recent years these studies have been concerned particularly with dyes that contain bifunctional reactive systems. For example, a detailed investigation of levelling characteristics has compared a bis(vinylsulphone) and a bifunctional aminochlorotriazine–vinylsulphone with several conventional monofunctional vinylsulphone dyes [1]. Factors controlling the rates of exhaustion and level dyeing behaviour have been analysed to define optimised conditions recommended for batchwise dyeing with Procion H-EXL (Zeneca) bis(aminochlorotriazine) dyes [2] or with Sumifix Supra (NSK) aminochlorotriazine–vinylsulphone dyes [3].
Reactive dyes can be applied by any conventional batchwise dyeing method for cellulosic materials, including circulating-liquor machines for loose stock, yarn or woven fabrics, as well as jets, winches or jigs for piece dyeing. The conventional dyeing process entails three stages:
- Exhaustion from an aqueous bath containing electrolyte, normally under neutral conditions.
- Addition of alkali to promote further uptake and chemical reaction of absorbed dye with the fibre at the optimal pH and temperature.
- Washing of the dyed material to remove electrolyte, alkali and unfixed dye.
Numerous variants of this basic procedure in terms of chemical concentrations and fixation conditions have been devised to take account of the characteristic properties of the numerous ranges of reactive dyes now available.
Considerable research over several decades has led to the present selection of processes to apply each range of dyes in such a way that optimal fixation efficiency and level dyeing are achieved. In recent years these studies have been concerned particularly with dyes that contain bifunctional reactive systems. For example, a detailed investigation of levelling characteristics has compared a bis(vinylsulphone) and a bifunctional aminochlorotriazine–vinylsulphone with several conventional monofunctional vinylsulphone dyes [1]. Factors controlling the rates of exhaustion and level dyeing behaviour have been analysed to define optimised conditions recommended for batchwise dyeing with Procion H-EXL (Zeneca) bis(aminochlorotriazine) dyes [2] or with Sumifix Supra (NSK) aminochlorotriazine–vinylsulphone dyes [3].
References:
- N Harada et al., J.S.D.C., 107 (1991) 363.
- M J Bradbury, P S Collishaw and D A S Phillips, J.S.D.C., 108 (1992) 430.
- K Imada and N Harada, J.S.D.C., 108 (1992) 210.
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