Analysis of Cleaning Process for Several Kinds of Soil by Probability Density Functional Method

A method of analyzing the detergency of various soils by assuming normal distributions for the soil adhesion and soil removal forces was developed by considering the relationship between the soil type and the distribution profile of the soil removal force. The effect of the agitation speed on the soil removal was also analyzed by this method. Washing test samples were prepared by soiling fabrics with individual soils such as particulate soils, oily dyes, and water-soluble dyes. Washing tests were conducted using a Terg-O-Tometer and four repetitive washing cycles of 5 min each. The transition of the removal efficiencies was recorded in order to calculate the mean value (μ_rl) and the standard deviation (σ_rl) of the removal strength distribution. The level of detergency and the temporal alteration in the detergency can be represented by μ_rl and σ_rl, respectively. A smaller σ_rl indicates a smaller increase in the detergency with time, which also indicates the existence of a certain amount of soil with a strong adhesion force. As a general trend, the values of σ_rl were the greatest for the oily soils, followed by those of the water-soluble soils and particulate soils in succession. The relationship between the soil removal processes and the soil adhesion force was expressed on the basis of the transition of the distribution of residual soil. Evaluation of the effects of the agitation speed on µ_rl and ơ_rl showed that σ_rl was not affected by the agitation speed; the value of µ_rl for solid soil and oily soil increased with increasing agitation, and the µ_rl of water-soluble soil was not specifically affected by the agitation speed. It can be assumed that the parameter ơ_rl is related to the characteristics of the soil and the adhesion condition, and can be applied to estimating the soil removal mechanism.