Sustainable low liquor ratio dyeing of wool with acid dyes: Effect of auxiliaries on agglomeration of dye molecules in a dyebath and dyeing uniformity

The use of a low-liquor ratio (1:10 or less) in the dyeing of wool has several economic and environmental benefits, such as lower energy usage and smaller quantity of auxiliaries are required compared to the traditional dyeing method. However, the reduction in liquor ratio increases the occurrence of agglomeration of dyes causing uneven dyeing. The aim of this study is to develop a low-liquor dyeing method for wool with acid dyes that could potentially be applied to larger scale industrial practices. In this work, the feasibility of application of several chemical auxiliaries to prevent the agglomeration of dyes in dyebaths and also for improving the dyeing uniformity in the low liquor ratio dyeing of wool fabric with three acid dyes, has been investigated. Optical microscopy was used to evaluate the performance of various auxiliaries to prevent the agglomeration of dyes in a dyebath. The dyeing uniformity was assessed by measuring the colour difference in various parts of the same dyed fabric by a hand-held reflectance spectrophotometer. It was found that Teric G12A6 showed the best results in terms of prevention from the agglomeration of dyes and the dyeing uniformity produced for all three acid dyes investigated. The low liquor ratio dyeing of wool fabrics with acid dyes using Teric G12A6 as a dye agglomeration preventer is equally efficient as the traditional high liquor ratio dyeing in terms of colour strength and uniformity in dyeing. The developed method could reduce dyeing cost and environmental footprint compared to the traditional dyeing of wool

Sustainable Ultrasound-Assisted Ultralow Liquor Ratio Dyeing of Wool Textiles with an Acid Dye

Conventional wool dyeing is an energy-hungry process as the dyeing is carried out at boil using a high liquor ratio. It can be energy efficient if dyeing can be carried out at low temperatures or if the liquor ratio can be reduced. Ultralow liquor ratio dyeing (materials to liquor ratio of 1:5) is advantageous as it considerably reduces consumption of auxiliary chemicals and energy in dyeing. However, at that low liquor ratio dye molecules form agglomerates causing low dye-uptake and uneven dying. In this work, the feasibility of using ultrasound in conjunction with a range of textile auxiliaries for the prevention from dye agglomeration has been investigated for the dyeing of wool with an acid dye. Three ultrasonic baths with different ultrasonic power were used to investigate the effect of ultrasonic power on dyeing performance. It was found that citric acid in conjunction with ultrasound prevented the formation of dye agglomeration in a dyebath and also produced deeper shades and uniform dyeings compared to the dyeing without ultrasound. The depth of shade increased with an increase in ultrasound power. The application of ultrasound did not cause any loss in tensile strength of the fabric, suggesting there was no fiber damage. The developed technique could be used in the textile industry to make wool dyeing even more sustainable than it is at present