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.