Relation between mechanism of soil removal from fabrics and a parameter derived from probability density functional method for washing force analysis

The probability density functional method is one of the washing force analysis methods that combines the classical kinetic analysis of detergency method and risk calculation method using probability density function. This paper discusses the relation between soil removal mechanisms and the value of σ rl, which is one of the two parameters used in the probability density functional method. Four repetitive washing tests were conducted using test fabrics soiled with iron(III) oxide, carbon black, four kinds of water-soluble dyes and three kinds of oily dyes, and the removal (%) was analyzed with the probability density functional method. The results show that the range of σ rl varied with removal mechanisms; mechanical removal of particle soil (0.01–0.6), dissolution into water of water-soluble soil (0.3–1.4), solubilization of oily soil into surfactant micelle (1.0–2.0) and emulsification or dispersion of oily soil (≥3.0). This tendency can be used for estimating the removal mechanism of any washing system where the soil type is unknown.