scCO₂ and liquid CO₂ have several applications in textile production supply chain:

 

(a) Dyeing,

(b) Pre-treatments (scouring)

(c) Post-treatments (infusion of functional additives)

 

scCO₂ is well suited as an environmentally friendly solvent/medium for dyeing textiles in the form of yarn, thread or fabric.  We have developed an efficient process for polyester dyeing. scCO₂ is ideally suited for dyeing polyester because many of the disperse dyes used for dyeing polyester are soluble in scCO₂. In addition, the disperse dyes are not soluble in water; hence they are mixed with large amounts of surfactants or modifiers so the dyes can be dispersed in water. With scCO₂ as solvent, no surfactants or modifiers are needed hence press-cake or crude dyes can be dissolved directly in the scCO₂, thereby reducing dye costs and eliminating a large amount of additives that would conventionally end up in the waste water stream.

The eCO₂Dye general process for dyeing in scCO₂ is a batch process and is shown in the diagram.

 

 

The key Process Steps are

 

• Load DRY textiles and dyes into pre-heated dyeing vessel

• Pump CO₂ to the desired pressure as a liquid

• Bring vessel to pressure with CO₂ at supercritical conditions

• scCO₂ is circulated in the system for about 30 minutes to complete the dyeing

• Dyed textile is leveled in the dyeing vessel

• CO₂ is depressurized. The CO₂ is recycled for re-use. More than 95% of the CO₂ is recycled.

• Dyed textile is removed DRY from the vessel.

•        The system is now ready for the next cycle.

 

Dyeing in scCO₂ is done in a temperature range of 80 to 120^oC; the pressure in dyeing vessel is in the range of 200 to 250 bar. The specific dyeing conditions are selected based on the desired color for the textile. The overall process time is 60 to 90 minutes, depending on the color and the size of the dyeing system.