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.

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.

eCO₂Dye has demonstrated dyeing of other man-made textiles including acrylics, nylon and polylactic acid in scCO₂. A limited number of dyes have been selected for dyeing these materials.

While our focus has been on polyester, eCO₂Dye has demonstrated success on other man-made textiles.

Pre-Treatments

scCO₂ for Scouring : Cleaning of yarns and fabrics done prior to dyeing or printing

Production of yarns and converting these into fabrics by weaving or knitting processes requires use of various oils, waxes, lubricants and other additives to facilitate in the fabrication steps.  The processing aids are removed from the textile to obtain high quality dyeing or printing on the textile. Processing aids are used for all textile materials – natural and man-made, though they may differ chemically depending on the material.

Conventionally the above processing aids are removed by washing with water, surfactants, caustic soda, emulsifiers

•  Large water use – as much as 40 l/kg textile
•  Extracted materials end up in waste water
•  Typically >90% of extraneous materials removed

In our work we have shown both in the lab and the pilot scale that scouring is technically viable and amenable to commercialization for natural and man-made textile materials.

Post-treatments

Textiles are frequently treated with additives which allow properties of the fabric, for example, to be modified to improve customer liking for the textile or for improving the performance of the textile in machine handling.

eCO₂Dye has worked with numerous additives such as silicone oils that can be infused into the textile to improve the “feel or softness” of the textile fabric.  We also offer treatments for yarns that reduce the friction of the surface of yarns to enhance the processing of the yarn in knitting and weaving operations.

Natural Textile Materials

Typically the dyes used for dyeing natural textiles (cotton, silk, wool) do not dissolve in scCO₂ and hence dyeing these materials in scCO₂ is not straightforward.  Dyes and processes for this purpose are being developed. eCO₂Dye is developing novel technologies which will allow cotton to be dyed in scCO₂.