| 摘要 |
PROBLEM TO BE SOLVED: To provide a method capable of reducing the content of a metal ion to <50 ppb from a naphthol novolak and its derivative containing several thousand ppb metal ion. SOLUTION: The method for producing naphthol novolak and its derivative comprises (1) a step of preparing an organic solvent solution by dissolving a naphthol novolak and its derivative into an organic solvent, (2) a step of recovering an organic layer by bringing the organic solvent solution into contact with an acidic water solution and (3) a step of further recovering the organic layer by bringing the organic layer into contact with an ion exchange water in this order, and the method also comprises repeating the step (3) three or more times. COPYRIGHT: (C)2008,JPO&INPIT
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