Waterless dyeing with plant-based natural dyes as colorants

The search for waterless dyeing technologies led to the use of liquid (supercritical) carbon dioxide as a medium for dyeing synthetic fibers with the disperse dye family. The structural similarities between certain plant-based dyes and synthetic disperse dyes led us to explore textile dyeing with natural dyes in liquid carbon dioxide. In our initial studies, we found that anthraquinone dyes (e.g. Dermocybin and Emodin) extracted from mushrooms dyed polyester and nylon fibers in liquid carbon dioxide in 30 min. Our work has now been extended to plant extracts containing madder, weld, woad, or logwood, and to aliphatic polyenes (e.g. beta-carotene and lycopene), all at 0.5-1.0% (weight of dye/weight of fabric; (w/w)) shade depths. The best results (dye uptake levels) from the former group of dyes were obtained using madder and logwood, with weld giving no dye uptake. To enhance color depths from weld, we treated a weld extract with amylase enzyme solution, to enhance solubility in carbon dioxide by cleaving off the glucose group(s). As anticipated, enzyme treatment led to a canary yellow shade on polyester at 1% (w/w). Regarding the aliphatic polyenes, results showed better dye uptake on polyester at 3500 psi and 110°C, giving a red shade from lycopene at 1% (w/w). Coloristic data obtained are reported in this paper.