Ultraviolet absorbers for retarding wool photo-degradation: Sulphonated long-chain substituted 2-hydroxybenzophenones

A series of sulphonated 2-hydroxybenzophenones containing 4-alkyloxy substituents of varying chain length has been synthesised and applied to wool fabrics. The higher members of the series, especially those with n-hexadecyloxy or n-octadecyloxy substituents, protect wool from photo-yellowing and photo-tendering more effectively than do the lower members. The higher members have the additional advantages that they are absorbed almost quantitatively during application and are not removed during laundering. The greater level of photo-protection provided by the higher members is unlikely to be due to their preferential location near the fibre surface, because redistribution of the absorber uniformly throughout the fibre does not reduce the level of protection. Other reasons for the observed differences in photo-protective behaviour are discussed.