Bis(5 -cyclohexyl-4-hydroxy-2-methylphenyl)-3,4-dihydroxyphenylmethane(1.0 mole), naphthoquinone-1,2-diazido-5-sulfonyl chloride (2.0 moles) and methanesulfonyl chloride(0.5 moles) were dissolved in dioxane (4,000 g). To the resulting solution, dioxane (1,500 g) having triethylamine (500 g) dissolved therein was added dropwise over 40 minutes at a controlled temperature not higher than 35° C. The precipitating salt was separated by filtration and the thus recovered reaction product was washed and dried to yield a mixed ester of bis(5-cyclohexyl-4-hydroxy-2-methylphenyl)-3,4-dihydroxyphenylmethane with naphthoquinone-1,2-diazido-5-sulfonic acid and methanesulfonic acid; the average degree of esterification was 50% for the quinonediazidosulfonate ester and 12% for the methanesulfonate ester.
