Surfactants for particulate soil removal in dry-cleaning with high-pressure carbon dioxide

The removal of particulate soils from textile in dry-cleaning with CO ₂ is insufficient compared to perchloroethylene (PER). Especially the removal of relatively small particles (<20 μm) poses a problem. Various anionic and amine based surfactants have been investigated to enhance the removal of particulate, but also of non-particulate soils in dry-cleaning with high-pressure CO₂. The cleaning performance index for relatively small particulate soil (CPI_part) increased from 24% (when no surfactants were used) to a maximum of 51% (when surfactants were used), which shows that particle removal is possible in CO₂ dry-cleaning. The use of these surfactants, however, does not bring particle removal up to the level of PER (CPI_part of 68%). The removal of non-particulate soils in CO₂ with water, surfactant and co-solvent is better than in PER. The overall results using the investigated surfactants are promising; the overall result increases from 70% (when no surfactants are used) to 87% (when surfactants are used) compared to the level when using PER. Surfactant particles were formed in all experiments. In the case of the amines, these particles may be formed by reaction. The formed charged surfactant particles are probably responsible for the removal of the soil particles from the textile. The charged surfactant particles may adhere to the soil particles and/or fabric, thereby establishing an element of repulsion and/or a steric barrier. The use of a co-solvent (iso-propanol) had a positive effect on the removal of particulate and non-particulate soils when using amines. However, when anionic surfactants were used, the addition of a co-solvent had a pronounced negative effect on particulate soil removal.