Use of 2,4‐Dihydroxybenzophenone‐2‘‐ammonium Sulphonate to Prevent the Yellowing of Wool by Ultraviolet Radiation

The use of 2,4‐dihydroxybenzophenone‐2′‐ammonium sulphonate (das) to prevent the yellowing of wool by ultraviolet radiation is discussed. The optimum conditions of application of this absorber to wool have been determined. The Yellowness Index, a measure of the degree of yellowing, was used to determine the effect of the concentration of das on its protective action against ultraviolet radiation. Exposure in a Xenotest apparatus indicated that initially bleaching occurred, followed by yellowing, which decreased with increase in the concentration of das. The washing and dry‐cleaning fastness properties of das on wool were assessed and the effect of dye on these properties was also determined, das has poor washing fastness, but this can be improved by mordanting the wool before treatment with das. This absorber does not significantly improve the light fastness of acid dyes on wool.