Supercritical CO₂ Water‑Free Dyeing Technology
Supercritical CO₂ Water‑Free Dyeing Equipment System Selected into National Catalogue
A supercritical CO₂ water‑free dyeing equipment system, developed by a domestic company, was successfully included in the Ministry of Water Resources’ “Catalogue of Advanced, Mature, and Applicable Water‑Saving Technologies and Equipment (2025).” This technology enables the entire dyeing process to be carried out without water or chemical auxiliaries, realising a disruptive shift from “aqueous dyeing” to “gas‑phase dyeing.”
The technical principle: supercritical CO₂ (temperature >31.1°C, pressure >7.38 MPa) is used as the dyeing medium to dissolve disperse dyes and uniformly diffuse them into the fibre interior – no water is needed. After dyeing, depressurisation rapidly vaporises CO₂, which is then separated from residual solid dye and recycled. The CO₂ recycling rate exceeds 97%, and the dye utilisation rate also approaches 97%. The entire process consumes zero water, produces zero wastewater, requires no drying, and significantly reduces overall energy consumption. The dyeing cycle is shortened from the traditional 8‑12 hours to about 3 hours.
This technology can reduce comprehensive costs by 50‑60%, shorten the dyeing cycle by 50%, and provide a product premium of 30‑50%, offering substantial economic benefits.
Related Research and Patents on Supercritical CO₂ Dyeing
Academic studies have examined the use of supercritical CO₂ as a medium with Disperse Orange 30 for water‑free dyeing of polyester yarn packages, investigating the effects of winding tension, winding angle, and package mass on colour depth. Other research has established practical screening strategies for trichromatic disperse dyes in supercritical CO₂ dyeing.
Patent applications cover a supercritical CO₂ water‑free combination dyeing process for nylon and its dye compositions (e.g., mixtures of C.I. Disperse Yellow 54 with C.I. Disperse Red 60, or with C.I. Disperse Blue 60), with stepwise temperature ramping and two‑stage circulation dyeing. Other patents relate to supercritical dyeing methods and apparatus for foam particles, where CO₂ is injected into dyeing and colour‑mixing autoclaves. All these processes are completely water‑free, environmentally friendly, require no post‑treatment, are energy‑efficient, and allow high CO₂ recycling with low operating costs.