A 1 l sulfonating flask equipped with stirrer, condenser, internal thermometer and dropping funnel is charged at 80° C. with 83.7 g (0.14 mol) of 4-{4,6-bis[4-(2-ethylhexyloxy)phenyl]-s-triazin-2-yl}-1,3-dihydroxybenzene together with 500 ml of methylcellosolve. 18.1 g of 30% sodium hydroxide solution (0.16 mol) are added, stirring is continued for 15 minutes, and a solution of 31.4 g (0.16 mol) of 3-bromomethylheptane and 30 ml of methylcellosolve is then added dropwise over a period of 30 minutes. After 24 hours of stirring at 110° C., alkylation is complete (thin-layer chromatogram). The mixture is evaporated to dryness in vacuo, the residue is dissolved in 500 ml of toluene, the resulting solution is filtered, and the filtrate is extracted with water. The organic phase is dried over sodium sulfate and the solvent is distilled off to give 100.9 g of a red-brown oil. The crude product is dissolved in 200 ml of 97.5:2.5 toluene/ethyl acetate and purified by chromatographing it through silica gel (10 cm×40 cm). This gives 79.4 g (80% of theory) of the compound of the formula ##STR26## as a honey-like, red-brown resin.
