Study On The Compatibility Of Pet Fibric Dyed With Trichrome Disperse Dyes In Supercritical CO₂

Comparing with the conventional aqueous dyeing processes, the supercritical fluid dyeing is a water-free and auxiliaries-free processing and has many other advantages such as shorter dyeing time, full utility of dyes, energy savings and being more environmentally friendly. With these advantages, the commercialization of the supercritical CO₂ fluid(SCFCO₂) technology will be of great benefit to promote the clean production, water savings, energy savings, and the environmental protection for dyeing and finishing plants. Most of the published literatures deal only with the behavior of individual dye in SCFCO₂, but dyeing with combination of differernt dyes, which is of great importance in industrial practice, has remain unknown. This research was carried out on the pilot-scale SCFCO₂ dyeing equipment to study the coloration of polyester(PET) in SCFCO₂ using the combination of dyes, with the temperature of 120℃and the pressure of 25Mpa.Based on the developed dyeing prototype, the kinetic of dyeing of polyester with C.I. Disperse Red 60 in SCF CO₂ were studied. The apparent diffusion coefficient of the dye in PET in SCFCO₂ increased with the increase of temperature; the activation energy calculated with the Arrhenius equation was lower than that in traditional aqueous dyeing process. The thermodynamic of dyeing of polyester with C.I. Disperse Red 60 in SCFCO₂ were also investigated. Similar to the aqueous dyeing, the SCFCO₂ dyeing process of PET with C.I. Disperse Red 60 is also an exothermic reaction. The thermodynamic affinity of the dye decreased with the increase of temperature.As the dyeing mechanism in SCFCO₂ and traditional aqueous process were similar, C.I. Disperse Orange 30, C.I. Disperse Red 167 and C.I. Disperse Blue 79, which were known as the trichrome disperse dyes for aqueous dyeing, were chosen to study for combination dyeing in SCFCO₂. The results showed that the individual dye uptake rate of three kinds of dyes in SCFCO₂ dyeing are almost consistent with that in aqueous dyeing. The building up properties are similar to that of aqueous dyeing. A good compatibility was found with these thress dyes. In the combination dyeing of these dyes, the dyeing process was actually a distribution process of the dye between the fiber and the fluid, and the amount of dye on the fiber of C.I. Disperse Orange 30, C.I. Disperse Blue 79 and C.I. Disperse Red 167 were a bit lower than that of the individual ones.The shade of the three dyes in SCFCO₂ dyeing were large different with that of aqueous dyeing, so the existing aqueous-based color-matching system was not suitable for SCFCO₂ dyeing. Due to the interactions between mixed dyes in SCFCO₂ dyeing, a correctiong cofficient was indroduced to reduce the deviation of the theoretical K/S value from Kubelka-Munk theory and actual measured K/S value were found, in order to estabilish the color-matching system based on this study's data.