Objective Supercritical carbon dioxide fluid (ScCO2) dyeing of disperse dyes with low energy consumption and no effluent discharge in the dyeing process is an advanced industrial technology in line with sustainable development. However, some problems associated with the disperse dyes in this process, such as low dye uptake and incomplete dye chromatography caused by low solubility, greatly limit their further development. In view of these problems, this paper proposed to add appropriate cosolvent to the ScCO2 to improve its solubility, so as to reduce the impact of these problems on the dyeing process. Method Based on the interaction forces between disperse dye molecules and cosolvent molecules, a green cosolvent (methyl 5-(dimethylamino) - 2 - methyl - 5 - oxopentanoate) with high solubility for disperse dyes, high boiling point and non-volatile and non-toxic was selected as a dyeing auxiliary. Disperse yellow 163 and Disperse Blue 60 were selected as experimental dyes. The dyeing rates and K/S values of disperse dye filter cakes and disperse dye filter cakes with cosolvent blends were tested under different process conditions to evaluate their dyeing effects. The mechanical properties and color fastness of the dyed yarns were characterized to assess the effect of the cosolvent addition on the yarn properties. Results The influence of cosolvent on the fabric was studied through the reflectance curve of the dyed fabric. The results showed that the selected cosolvent has a significant influence on the brightness of the fabric, but it will not change the color and saturation of the fabric. With the addition of cosolvent, the K/S value of fabric dyed by Disperse Yellow 163 increased from 4.5 to 12.0, and that of fabric dyed by Disperse Blue 60 increased from 5.9 to 12.2, indicating that this cosolvent could be used in supercritical carbon dioxide fluid dyeing with disperse dyes. By changing the mass ratio of disperse dyes to liquid cosolvent, dyeing temperature and pressure, the influence of process conditions on the dye uptake of disperse dyes was investigated. The dye uptake of disperse dyes increased significantly after adding the cosolvent. When the mass ratio of dye and cosolvent was 1 • 20, the dyeing rate of Disperse Yellow 163 and Disperse Blue 60 reached 57.62 % and 70.97 %, respectively. With the increase of temperature, the dye uptake increased first and then decreased after adding cosolvent, reaching the maximum at 130 T. With the increase of pressure, the dye uptake of disperse dyes increased slightly. The dye uptake did not change significantly with the dyeing pressure above 27 MPa, and the optimum dyeing pressure was 27 MPa. The mechanical properties and color fastness of four different yarns were characterized. The breaking strength and the elongation at break did not change significantly, and the breaking strength of yarns is all about 250 cN and elongation at break is all about 20%. Color fastness to rubbing, color fastness to sunlight and color fastness to soaping of the yarn were all above 4 levels. Properties of yarns dyed with cosolvent met the production requirements. Conclusion In this study, methyl -5-(dimethylamino) - 2 - methyl - 5 - oxopentanoate was used as a dyeing cosolvent to effectively improve the dyeing rate of Disperse Yellow 163 and Disperse Blue 60 in the supercritical CO2 fluid dyeing process from a practical production problem. Meanwhile, the addition of the cosolvent only affected the brightness of the dyed yarn, and had no significant effect on the color phase and saturation. A suitable dyeing process was determined by the subsequent experiment conditions, i. e., the mass ratio of dye to co-solvent was 1 :20, the dyeing temperature was 130 T, and the dyeing pressure was 27 MPa. After the addition of cosolvent, the resulting fabric with increased color depth, no significant loss of mechanical properties, and excellent color fastness performance met the requirements of national standards. In summary, the addition of cosolvent caused no significant effect on yarn properties while improving the dyeing rate of disperse dyes with good application prospects in the field of ScCO2 dyeing. © 2024 China Textile Engineering Society. All rights reserved.
