Kabushiki Kaisha Ueno Seiyaku Oyo Kenkyujo

Shigeru Itoh

Ryuzo Ueno

Hiroaki Tsuchiya

Shine Fujimoto

Yumiko Komatsu

Ichiro Yamamoto

Highly pure benzyl esters of aromatic hydroxycarboxylic acids are produced in high yields by reacting an aromatic hydroxycarboxylic acid or its lower alkyl ester with a benzyl alcohol in the presence of an organotin compound of the general formula ##STR1## wherein R's are identical or different and each represents an alkyl group having 1 to 8 carbon atoms or an aryl group, and Z represents an oxygen or sulfur atom, an organotin compound of the general formula

Process for producing benzyl esters of aromatic hydroxycarboxylic acids

A process for producing an azo pigment, which comprises coupling an aromatic diazonium compound with 3-hydroxy-2-naphthoic acid and at least one bis-naphthylmethane, and optionally, making the resulting pigment.

Process for producing azo pigments

The color of azo pigments derived from 2-hydroxynaphthalene-3-carboxylic acid or its salts are improved by the coupling reaction of a diazonium compound of an aromatic aminosulfonic acid with a coupling component which is a mixture of (1) 2-hydroxynaphthalene-3-carboxylic acid or its salt, (2) .beta.-naphthol or its salt, and (3) a phenolic by-product having a molecular weight of about 300 and containing about 1 equivalent of phenolic hydroxy groups. The phenolic by-product can be obtained by evaporating .beta.-naphthol from a tarry substance formed as a by-product during the reaction of an alkali .beta.-naphtholate with carbon dioxide, extracting the residue with an alkali and precipitating the soluble matter with an acid. The color or tone of the azo pigment is stabilized by the use of the coupling component. The azo pigments range from those having dark color and a greater degree of transparency which are suitable for use in printing inks to those having increased brightness which are suitable for use in paints.

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Nishinomiya, Japan

Shigeru Itoh