Pilot scale water free dyeing of pure cotton under supercritical carbon dioxide

Supercritical carbon dioxide (scCO2) is a green, safe and environmentally friendly medium in textile dyeing. It is, indeed representing a salient advancement in modern dyeing of textiles. However, to the authors' knowledge, current methods of dyeing 100% unmodified cotton fabrics under supercritical medium up to pilot scale encounter many problems, challenges and a variety of severe shortages. Thus, the aim of the current work is to develop a method for dyeing unmodified 100% cotton fabrics using vinyl sulphone reactive disperse dye under scCO2. Two types of cotton (woven & knitted) fabrics were dyed with N,N‑diethyl-4-((4-vinylsulfonyl)phenyl)diazenylaniline disperse reactive dye, in the presence of disodium edetate as a swelling agent under scCO2. The results indicate that vinyl sulphone dye has high color strength (K/S) values on cotton fabrics using the organic electrolyte (disodium edetate). The system parameters, mainly temperature, pressure, time were investigated. The proposed methodology has been confirmed by carrying out a pilot-scale experiment using the optimum conditions obtained from lab-scale. The results proved that dyeing cotton under scCO2 medium on pilot level is possible. However, more efforts are needed to develop more dyestuffs with different colors that suitable for cotton dyeing.