Solubilization and performance characteristics of Ca(LAS) 2

Properties of Binary Mixture of Cetyl Diphenyl Ether Disulfonate and Linear Alkylbenzene Sulfonate

The surface properties of the binary mixture of cetyl diphenyl ether disulfonate (C16-MADS) and linear alkylbenzene sulfonate (LAS) have been investigated by salinity and hardness tolerance, equilibrium surface tension, wettability, foam and emulsification measurements. The results show that with increasing mass ratio of LAS in the C16-MADS/LAS mixed system, the ability to reduce the surface tension of the solution is improved. The wetting performance is also improved. The critical micelle concentration (CMC) values are increased first, then decreased, and are higher than the ideal CMC values, which indicates that there is an antagonistic effect that is not conducive to the formation of mixed micelles between C16-MADS and LAS. In addition, the C16-MADS/LAS system improves the hard water resistance of LAS and reduces the foam properties of LAS.

Effect of Washing Conditions on Cleaning Action of Linear Alkylbenzene Sulfonate in Hard Water

The effects of water hardness on textile detergency in aqueous linear dodecylbenzene sulfonate (LAS) solutions were examined under various washing conditions. Plain-woven and towel cotton fabrics and plain-woven polyester fabric were soiled with a mixture of carbon black/oleic acid. The soiled fabrics were shake-washed in the LAS solution together with the original unsoiled fabrics. Surface reflectance measurements revealed that the soil removal and redeposition decreased and increased, respectively, with increasing water hardness. The identity of the mineral species (calcium or magnesium ions) in the hard water had no notable effect on the detergency. The addition of significant amounts of extra LAS did not fully compensate the reduction in detergency in hard water. Addition of softening agents and an alkali builder to the hard water limited the reduction in detergency, but the detergency was still lower than that in the absence of hardness salts. Moreover, a high wash temperature and repeated rinse procedure did not prevent the reduction in detergency in hard water. Finally, a washing test was carried out in hard water under the conditions considered to be effective for improving the detergent quality in hard water, based on the experimental results. The LAS detergency toward the cotton fabrics under these conditions was still poorer than that in the absence of hardness salts. We concluded that using soft wash water is the best choice for maximizing the cleaning power of detergents.

Effects of Water Hardness on Textile Detergency Performance in Aqueous Cleaning Systems

The effects of water hardness on textile detergency in aqueous solutions were systematically investigated using four surfactants: sodium oleate (OLNa), linear dodecylbenzene sulfonate (LAS), sodium dodecyl sulfate (AS), and polyoxyethylene (10) dodecyl ether (AE). Water hardness was adjusted according to the standard procedure described in IEC 60734:2012. As expected, by adding hardness salts the surface tension of the OLNa solution increased. Surprisingly, the addition of hardness salts lowers the surface tension for the LAS and AS solutions. In the case of the AE solution, hardness salt did not affect the surface tension. A decrease in transmittance and foamability after adding hardness salts was observed for every anionic surfactant solution, indicating that anionic surfactants can combine with divalent ions to form insoluble precipitates. Detergency experiments were performed using cotton plain-woven and towel fabrics soiled with a carbon black and oleic acid mixture. One piece each of untreated and soiled fabric were stacked and placed horizontally in detergent solution with or without hardness salts. As a mechanical action of soil removal, the shaking of 190 spm was applied. Soil removal and redeposition due to washing were evaluated from changes in values of the Kubelka-Munk function for both fabrics. With increasing water hardness, soil removal decreased and redeposition increased. In order of decreasing detergency, the surfactants were as follows: LAS > OLNa ≈ AS > AE. The results indicate that precipitates, formed by reaction of LAS or AS with hardness salts, are strongly adsorbed on the water surface because of their hydrophobicity, but they have no detergency power. The field emission scanning electron microscopic observation and X-ray photoelectron spectroscopic analysis showed that Ca(LAS)2 precipitation clung to fiber surfaces, and remained on the surfaces after washing. Significant changes in the cotton fabric due to washing were observed in mechanical properties and water absorbency.