Sugai Chemical Industry Co., Ltd.

Koji Nishihara

Takeshi Hashimoto

Shunsaku Tanaka

Terumasa Akashi

Katsuhiko Sato

A process for producing 4,4'-dihydroxydiphenyl which comprises subjecting to alkali fusion 1 mol of 4,4'-diphenyldisulfonic acid and/or potassium 4,4'-diphenyldisulfonate together with 4 to 10 mol of potassium hydroxide and 0.1 to 2 mol of potassium sulfate. Alternatively, the process may comprise subjecting to alkali fusion 4,4'-diphenyldisulfonic acid in the presence of potassium hydroxide, controlling to 20 to 25% the potassium hydroxide concentration in the reaction mixture, and separating dipotassium salt of 4,4'-dihydroxydiphenyl.

Process for producing 4',4-dihydroxydiphenyl

A process for producing 4,4'-diphenyldisulfonic acid is disclosed, which comprises the steps of adding a sulfonating agent to molten diphenyl at a temperature within a range of 130.degree. to 145.degree. C., and when crystallization commences of 4,4'-diphenyldisulfonic acid within such temperature range, cooling the reaction mixture to a temperature within a range of 115.degree. to 127.degree. C., and letting the disulfonation reaction complete while the reaction mixture is maintained within the cooled temperature range. A process for producing monopotassium 4,4'-diphenyldisulfonate is also disclosed, in which steps are taken of adding a sulfonating agent to diphenyl, then controlling the sulfuric acid concentration to 45 to 55%, and while the reaction mixture is heated to at least 140.degree. C., adding at least a stoichiometric amount of a potassium salt of an inorganic acid.

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Wakayama, Japan

Koji Nishihara