Selective control of dyeing and dyes´ compatibility using β-cyclodextrins

Abstract

Textile dyeing industry is still facing problems related with unlevelness and poor color reproducibility. Combined, those problems are an important issue on lack of enterprises’ competitiveness. It is commonly assumed that different dyes to be combined need to have similar dyeing rate in order to provide high levels of reproducibility. Moreover the dyeing cycles should be as short as possible. Thus, for a given color and dyeing conditions, it can be stated that a certain combination of dyes is compatible if the color depth on fabric increases with no changes in color hue during the dyeing process. Too high dyeing rates, often due to poor process control, are considered a major source of unlevelness related problems. Besides, color depth and hue color shifts, or in most situations, the combination of these two factors, occur more frequently when mixtures of incompatible dyes are used. Correction actions are required on those situations in order to obtain the desired color. Usually, the dyeing rate control is done by decreasing the temperature gradient during the heating phase, or by adding retarding agents (anionic or cationic) to the dyebath. Changes in the overall kinetics of dyeing were observed, resulting in modified exhaustion profiles. In these circumstances, dyes’ dyeing rate decreases below its optimum conditions and the processing time must be extended, allowing acceptable exhaustion levels. Furthermore, longer processes have a sustainability impact, since economic or environmental issues are involved. Alternative dyeing control systems that simultaneously sets the dyeing rate and improve dyes compatibility are required. In present work, a β-cyclodextrins based system is discussed. From the results, it can be concluded that β-cyclodextrins offer a promising setting dyeing rate mechanism for some trichromic dye mixtures. By controlling in an independent way, a specific dye with faster exhaustion profile in the mixture, the unlevelness dyeing probability decreases.