Antioxidant‐assisted coloration of wool with xanthophylls extracted from corn distillers’ dry grain

Abstract

Xanthophylls extracted from corn distillers’ dry grain were successfully applied to dye wool fabrics. As a readily available and cost‐effective grain processing byproduct, corn distillers’ dry grain contains appreciable amounts of isolable xanthophyll colourants, which can potentially be used in textile coloration. However, the application of xanthophylls as textile colourants has been limited, possibly owing to their hydrophobic nature and lack of stability at higher temperatures. In the present work, dyeing of wool fabrics with xanthophyll dyes was performed in the presence of a solubilising agent (diglyme) and an antioxidant (butylated hydroxytoluene). Dyeing conditions were modelled and optimised by the one‐factor‐at‐a‐time method and response surface methodology. Depth of shade of the wool fabrics dyed with 0.33 g l−1 of xanthophylls could be as high as 10.9 ± 0.5, while the colour fastness to laundering and crocking was better than grade 4. The prominent effect of butylated hydroxytoluene on depth of shade (K/S) was further studied using functionally and structurally related model compounds. The K/S‐enhancing ability of butylated hydroxytoluene was found to be a synergistic result of its antioxidising and complexing abilities. Lab‐extracted xanthophylls of various purities were applied to wool fabrics using the optimised dyeing and aftertreatment conditions. Depth of shade but not colour fastness was significantly affected by the impurities in xanthophylls extracted from corn distillers’ dry grain. The strategy developed by this work not only extends the scope of xanthophyll application into textile coloration but also could be used for other hydrophobic and unstable natural colourants.