A study of neutral fixation (pH7) of a variety of reactive dyes on cotton has demonstrated that promising overall total fixation efficiencies can be obtained by increasing electrolyte concentration, by working at the lowest possible liquor ratios and by dyeing at 100 °C for fluoro-triazine and vinylsulphone derivatives and at 140 °C for the less reactive monochloro-triazine derivatives. Because of the neutral dyeing conditions, the risk of hydrolysis of dyes can be minimized. Even in this new dyeing process, the temperature, and the concentration of electrolyte used are higher than those in the conventional dyeing method. However because of the low liquor ratio employed, less energy is used to heat the dyebath solution and a lower amount of chemicals is used. The smaller volume of water used for dyeing, and reduction in waste effluents potentially reduces the cost of waste water treatment after dyeing. The neutral exhaust application of reactive dyes to cellulosic fibres gave dyeings with excellent reproducibility, levelness, and penetration.Moreover, since all the chemicals such as dyes, electrolyte, and acetate can be put into the dyeing solution at the same time, it is possible to simplify the dyeing process and save operation costs.The work carried out for this study has been on a bench scale, but the results obtained show promise for commercial scale application.
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