Carbon dioxide as a solvent is well suited for use in textile operations such as scouring, dyeing and post-treatments because it can be used a solvent whose density (hence solvent properties) can be modified by simply changing the temperature and pressure of the carbon dioxide. Carbon dioxide above its supercritical condition has the following attributes:
• scCO2 is a solvent that can dissolve dyes, oils, surfactants, waxes etc.
• Solvent properties are tunable
• Behaves mostly like non-polar solvent e.g. alkanes (low dielectric constant and dipole moment)
• Has some quadrupolar characteristics; behaves like dioxane
• scCO2 has some “Polar” attributes: Capable of weak Lewis acid and base interactions;
Hydrogen bonding e.g. with amines; Fluorocarbon interactions
• Low cost
• Safe, environmentally benign/non-toxic,
• Readily recyclable
• Does not oxidize
• Pressure reduction converts to gas hence removal of scCO2 as solvent does not require
scCO2 for Dyeing
• Conventional drying required to remove solvents such as water