Using Supercritical Fluids for Textile Dyeing

The conventional dyeing of textiles requires that an excess of dye is dissolved or in some way "taken-up" in an aqueous or solvent solution. The dye mix is then pumped into a vat containing holding the textile. Typically there is agitation or the dye is recirculated several times through the cloth. At the end of the cycle, the dye mix is pumped to the waste treatment facility. Dyes are notoriously difficult to treat. The process is decidedly unfriendly to the environment.

The use of supercritical CO₂ in textile dyeing is an environmentally friendly alternative. Instead of using an aqueous or solvent solution to "take-up" the dye, supercritical CO₂ is used. The process proceeds in the same manner as the conventional method, but instead of sending the spent mix to the waste treatment facility, the supercritical CO₂ /dye mix is depressurized. The CO₂ /to a gas and all the spent dye falls out and can be reused. In production systems the CO₂ is recycled for providing for a completely closed systems and an entirely environmentally friendly approach to textile dyeing.

The operation as shown above follows in this manner:

1. Supercritical CO₂ flows into the dye make-up vessel where it dissolves the dye.
2. It continues to the dye vessel which contains the textile cocoon.
3. Dyeing can continue in a static bath or a specially designed pump recirculates the mix several times through the cocoon.
4. At the end of the cycle, the mix flows to the dye collection vessel where depressurization occurs causing the spend dye to drop out.
5. The CO₂ can then be recycled and the "spent" dye reused.

Applications
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