Optimization of an ecofriendly dyeing process in an industrialized supercritical carbon dioxide unit for acrylic fibers

The feasibility of using supercritical CO 2 as a cleaning dyeing medium to dye acrylic fibers was investigated on an industrialized unit. The influence of dyeing temperature, dyeing pressure, dyeing time, and dye concentration on the K/ S values of acrylic fibers was examined using the fractional factorial design of experiments. A second-order polynomial model was established to analyze the interactions between distinct parameters and to obtain the optimal K/ S values. The results showed that an excellent dyeing effect of acrylic fibers was obtained in the industrialized supercritical CO 2 unit, but the dyeing effect was easily affected by variations of the dyeing parameters. In the experimental range, a calculated K/ S value could be up to 6.14 with the dyeing temperature of 100℃, dyeing pressure of 26 MPa, dyeing time of 60 min, and dye concentration of 3%. The dyed acrylic fibers presented good color fastness to washing, rubbing, and light. Furthermore, a commercially acceptable levelness and reproducibility for acrylic fibers were obtained in the supercritical CO 2 dyeing process.