Comparative value of fatty acids and resin acids of tall oil in soaps

Abstract

SummaryA study has been made of the detergency and foaming power of soaps made from a typical acid‐refined American tall oil. Sodium soap of tall oil, straight tall oil fatty‐acid soap, and straight tall oil resin‐acid soap were evaluated. The effect of fatty acid‐resin acid ratio was determined by using mixtures of those soaps. Sodium rosinate, sodium oleate, and mixtures of these soaps were used as comparison standards. Curves plotted show wash‐test data and foaming values as functions of the ratio of fatty soap to resin soap.The data indicate in terms of detergency: a) tall oil soap has a higher value than sodium rosinate; b) sodium oleate is better than tall oil fatty‐acid soap, but the latter is approximately equivalent to soaps from various unsaturated vegetable oils; c) both tall oil resin‐acid soap and rosin soap have low detergency on cotton; d) the detergency of most mixtures of tall oil fatty‐acid and resin‐acid soaps at lower concentrations is greater than would be predicted from the individual soaps, indicating a synergistic effect.As a rough approximation, tall oil soap without unsaponifiables is equivalent to a corresponding mixture of sodium oleate and sodium rosinate. The presence of unsaponifiables lowers both detergency and foaming. Tall oil soap is somewhat less sensitive to hard water than sodium oleate.Significant differences between detergencies of soaps, and especially between soap mixtures, are obscured when launderometer tests are run at moderate soap concentrations. These differences are readily detected at lower concentrations.