Abstract: A comparative study on the rinsability of surfactants was performed among four anionic surfactants which are commonly used in household laundry detergents.A comprehensive evaluation method was applied which was based on the foam decay in the rinse liquor and the initial/residual adsorption amount on the cloth during the model rinse process.The relationship between the rinsability of surfactant and its calcium ion stability was further investigated.The experimental results show that the calcium ion stabilities of surfactants have positive correlations with the foaming abilities of the model rinse liquor but negative correlations with the initial/residual adsorption amounts of surfactants on cloths.Therefore,the modified carboxylate surfactant (sodium N-lauroyl sarcosinate) with moderate calcium ion stability shows the best ability of easy rinsing,and the sulfonate surfactant (sodium dodecylbenzene sulfonate) is a little worse than it,but neither of the soap (sodium laurate) and the anionic-nonionic hybrid sulfate (sodium lauryl polyoxyethylene ether sulfate) are easy-rinse surfactants,whose calcium ion stabilities are low and high,respectively.These results have theoretical significance for molecular design of easy-rinse anionic surfactants and practical value for research and development of water-saving detergents.

Key words: anionic surfactant, rinsability, calcium ion stability, foam, amount adsorbed