Study On Phase Equilibrium And Dyeing Properties In Supercritical CO₂

Supercritical CO₂ dyeing is a new waterless dyeing technology, which used industrial emissions of CO₂. And dyestuff is dissolved in supercritical CO₂. After more than ten years’ research at home and abroad, it has made some achievements of the current stage. But dye solubility data in supercritical CO₂ and distribution coefficient of dye in the fabric have not been system research and the reports, affecting dyeing technology theoretical basis in supercritical CO₂. Therefore, the study of phase equilibrium and dyeing properties in supercritical CO₂ is proposed in the paper, and the main contents include:A kind of supercritical carbon dioxide dyeing and solubility experiment measurement device and method were studied in this paper. On the basis of previous studies, analyzing the mechanism of supercritical CO₂ dyeing further. The solubility of Disperse Red 127-Supercritical CO₂ binary phase equilibrium system was measured with continuous direct sampling method. In experimental conditions, the solubility of Disperse Red 127 range is 1.842-3.373 ×10-6mol/mol. It is showed that at the same temperature, when the system pressure was lower, the increase rate of solubility was slower, but the pressure is higher, the increase rate of solubility was quickly. At the same pressure, with the increasing of the temperature, the solubility increased smoothly. Relative to the temperature, the system pressure had a greater impact on the dye solubility. As the pressure going up, the solubility increased gradually. Between 23MPa and 24MPa, the growth of solubility was obvious. The results showed that the turning point of Disperse Red 127 pressure was 23MPa.Distribution coefficient of disperse dyes was expounded between fiber and supercritical CO₂. Combining with the dyeing data of Disperse Red 127 and cotton/polyester （65/35） fabric in supercritical CO₂, it was showed that in the experimental conditions of temperature for 373.2-388.2K, pressure for 21-25MPa, the distribution coefficient of Supercritical CO₂-Dye-Fabric ternary phase equilibrium system was 1.006-7.178. As the temperature was 388.2 K, pressure was 23 MPa; distribution coefficient was highest, showing that dyes in fabric had a good affinity. The solubility of dye was larger, the impetus of dyeing and mass transfer was larger, and the dyeing sped up, so it could get good dyeing effect. Dye strength in fibers is higher than in supercritical CO₂, which was about 102-104 orders of magnitude. Because of supercritical CO₂ dyeing was an exothermic chemical process, at the same pressure, raising temperature will reduce distribution coefficient.Finally, the calculation model of Disperse dye solubility was built. Chrastil associating model, cube state model PR equation and Van der Waals mixed rules were used to do experimental data correlation. Through the model above, the average relative error between the calculated value and experimental value was less than 10%. It was proved to be successful through correlation calculation. In general, in experimental conditions, Chrastil model is superior to cube state model PR equation.