Waterless and Low-Impact Dyeing Technologies
topic
Supercritical CO₂ (scCO₂) dyeing of polyester: CO₂ above Tc (31.1°C) and Pc (73.8 bar) acts as non-polar solvent for disperse dyes; at 120–180°C and 200–300 bar, dyes dissolve and diffuse into swollen PET. No water, no effluent, CO₂ recycled (>95% recovery). Dye exhaustion >95%. Commercial installations: DyeCoo (Netherlands). Other low-impact routes: foam dyeing (10:1 liquor ratio reduction), waterless padding with microemulsion, plasma-assisted dyeing.
Role
Waterless dyeing technology represents a potential step-change in polyester dyeing sustainability, eliminating the largest water and effluent burden of polyester processing. ScCO₂ dyeing chemistry integrates supercritical fluid thermodynamics, polymer swelling, and disperse dye dissolution — a rich academic topic.