| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for selectively recovering unreacted 6-hydroxy-2-naphthoic acid through removing byproducts in a method for producing 6,6'-(ethylenedioxy)bis-2-naphthoic acid. SOLUTION: The method of recovering 6-hydroxy-2-naphthoic acid in the method of producing 6,6'-(ethylenedioxy)bis-2-naphthoic acid comprising processes (1) to (4) described below, comprises a process of adding a prescribed amount of an alkaline earth metal salt to a first mother liquid obtained in the process (3) relative to a mole of an alkali metal 6-(2-hydroxyethoxy)-2-naphthoate contained in the first mother liquid to form a precipitate, a process of precipitating 6-hydroxy-2-naphthoic acid by acidifying a second mother liquid obtained by removing the precipitate from the first mother liquid, and a process of separating the precipitated 6-hydroxy-2-naphthoic acid. (1) A process of reacting 6-hydroxy-2-naphthoic acid with a basic alkali metal compound to prepare an aqueous solution of dialkali metal 6-hydroxy-2-naphthoate, (2) a process of causing the aqueous solution of the metal salt obtained in the process (1) to react with a 1,2-dihalogenated ethane to prepare an alkali metal 6,6'-(ethylenedioxy)bis-2-naphthoate, (3) a process of separating the reaction liquid in the process (2) into the above alkali metal salt and the first mother liquid, and (4) a process of reacting the alkali metal salt obtained in the process (3) with an acid, to form 6,6'-(ethylenedioxy)bis-2-naphthoic acid. COPYRIGHT: (C)2009,JPO&INPIT
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