Why is desensitisation using supercritical CO2 better?
Supercritical CO2 desensitisation offers a number of advantages over traditional processes.
Supercritical CO2 is a dry process, eliminating the need for any drying stage, and therefore the high electricity consumption associated with a very high temperature rise (generally over 120°C).
Not a single drop of water is required. As a result, it eliminates the need to use running water and the obligatory, costly steps involved in treating wastewater before it is discharged into wastewater treatment plants. Indeed, de-sensitisation water contains a high level of hydrocarbon oil, which, without pre-treatment by the manufacturer, would abnormally degrade the quality of the water collected in treatment plants.
Supercritical CO2 is chemically neutral. It is not corrosive, does not deform fibres and does not affect the mechanical properties of textiles.
It will concentrate on extracting sizing oils without affecting the rest.
The shrinkage rate is lower than with aqueous solutions. Following numerous tests on all types of textile compositions, we have observed a shrinkage of the textile of 1 to 2.5%, unlike water-based cleaning and degreasing solutions for which the shrinkage observed is on average 4% or more.
Supercritical CO2 desensitisation time in a Dense Fluid Degreasing machine is reduced by a factor of 2 to 10, depending on the process.
Unlike processes using perchloroethylene or those based on water and additives, the supercritical CO2 desensitisation process cannot be continuous and must be batch-based.
This difference is due to the fact that the process is carried out in an autoclave.
What materials are compatible with supercritical CO2?
Supercritical CO2 desensitisation technology is compatible with most synthetic or natural materials used in the manufacture of textiles, whether technical textiles, clothing, geotextiles or furnishings.
Here is a non-exhaustive list of synthetic materials frequently used in the textile industry and compatible with supercritical CO2 desensitisation technology.
- Polyester (PE)
- Polypropylene (PP)
- Polyethylene terephthalate (PET)
- Poly L-Lactic Acid (PLA, PDLA, PLLA)
- Viscose
- Elastane
Here is a non-exhaustive list of natural materials used in the textile industry and compatible with supercritical CO2 desensitisation technology.
- Sheep wool
- Cashmere wool
- Silk
- Alpaca wool
- Cotton
- Hemp
- Linen
Goodto know: Supercritical CO2 desensitisation is compatible with recycled fibres from fishing nets, water bottles, etc.
Material alterations have been observed in the presence of rubber and polyurethane. In the first case, the rubber swells under pressure and does not regain its initial shape, and in the second case, a chemical reaction causes the polyurethane to 'foam'.
Is supercritical CO2 desensitisation technology compatible with all web width sizes?
Supercritical CO2 desensitisation is suitable for all web sizes and roll or bobbin diameters.
Our supercritical CO2 desensitising machines are designed to handle all types of textiles (synthetic and natural fibres). The dimensions of the autoclave and the technical unit are adapted to the size of the web.
It is possible to build autoclaves capable of handling narrow widths up to large widths (5 metres or more).
In the case of desensitisation using supercritical CO2, the diameter of the autoclave will be only slightly larger than the diameter of the roll.
The main difference with machines such as "Jiggers" or dye autoclaves, which are sometimes also used for desensitisation, is the diameter of the fabric rolls. This can be reduced by reducing the diameter of the warp beam or pierced mandrel on which the textile is wound.
How can supercritical CO2 desensitisation be faster than other processes?
The time taken for a desensitisation cycle using supercritical CO2 is naturally comparatively shorter than for most existing desensitisation processes.
The only exception is desensitisation using perchloroethylene, but this will gradually be banned in view of the hazardous and carcinogenic nature of this petroleum-derived solvent.
Compared with "Jiggers" type machines, or with desensitisation carried out in dyeing autoclaves using water and detergent, the supercritical CO2 process will reduce treatment time by at least 50%.
In the case of "Jiggers", the drying stage that necessarily follows aqueous desensitisation can also be eliminated.
In addition to these process differences, Qarboon's Design Office and engineers are able to carry out specific dimensioning to further reduce cycle times. For example, it is possible to deliberately increase the size of high-pressure equipment to speed up the pressure build-up and decompression process.
Is treatment necessary before or after textile desensitisation using supercritical CO2?
By using supercritical CO2 technology to de-densify rolls, bobbins, hanks and unbleached fabrics of any width, no pre-treatment or post-processing is required. The textile is at ambient temperature and no waiting time or delay before the industrial process continues is necessary. This is made possible by the type of treatment:
- the process is dry, so no drying is required
- the process is at low temperature (35°C ~ 50°C)
- the fibres are not deformed, the characteristics of the textile are preserved and it can be handled without delay.