Novel sustainable synthesis of dyes for clean dyeing of wool and cotton fibres in supercritical carbon dioxide

Abstract

This is a repository copy of Novel sustainable synthesis of dyes for clean dyeing of wool and cotton fibres in supercritical carbon dioxide.

Recent advances in supercritical fluid dyeing

“…Significant results have been obtained as far as the F of the dyes on cotton, silk and wool is concerned. The choice of modifying disperse dyes with appropriate reactive groups able to bind with the textiles functionalities seems to be the winning strategy, which has allowed F values of up to 98%‐100% to be obtained 65,67,70 . However, the intensity of coloration is still much lower with respect to PET and other synthetic polymers.…”

“…It is evident that the coloration of hydrophilic materials in the non‐polar supercritical environment suffers from a lack of solvent swelling of the fibres, which is confirmed by the fact that many researchers are trying to make the technology work by using pretreatments or other wet processes 57,64‐67,77,79,80 . This is the downside of SFD.…”

“…Coloration efficiency is generally quantified by means of the K / S and the fixation efficiency ( F ) 57,63‐70 . Two K / S values are generally evaluated: the first one on the “just‐dyed” samples, the second after treating the textiles with an appropriate high temperature solvent extraction to remove the unfixed dye.…”

“…This allows this compound to be used to transfer hydroxyl or carbonate anions from the liquid phase to the supercritical and substrate solid phases, thus achieving good fixation of the reactive dye 57 . Recently, Luo et al 67 employed the same vinylsulphone dyestuff investigated by Long's research group 57,73 to dye wool and cotton in supercritical carbon dioxide after a water pretreatment, but without any kind of catalytic activation. The pretreatment consisted of soaking the textiles in water at room temperature: the amount of water ranged from 0% to 100% owf.…”

A salt-free and water-saving approach as a green alternative to conventional reactive dyeing of cotton

“…Many researchers have realized the importance of developing a green approach for reactive dyeing of cotton. Though supercritical carbon dioxide has the potential to replace water (Fernandez Cid et al 2005;Long et al 2014;Luo et al 2018) nonpolar ScCO2 cannot effectively swell cotton characterized by high polarity, leading to low dye sorption and poor color build-up (Cid et al 2007). Furthermore, the dyeing technology is expensive as high pressure is required, which greatly limits large-scale industrial application of ScCO2 dyeing.…”