METHOD FOR PRODUCING WATER-SOLUBLE AZO DYE

PROBLEM TO BE SOLVED: To provide a means for simply and inexpensively producing a water-soluble azo dye having slight inorganic salt content and composed of a lithium salt of the water-soluble azo dye having various structures. SOLUTION: The method for synthesizing the water-soluble azo dye comprises forming the lithium salt by carrying out diazotization and coupling reaction by using lithium nitrite. In the synthetic method, diazotization and coupling reaction are preferably successively carried out in one tank by using lithium nitrite to form the lithium salt. In the method for producing the water-soluble azo dye, a poor solvent is further added to the reaction product after coupling reaction and crystallization and filtration are carried out in order to keep inorganic salt content to ≤1 mass%. COPYRIGHT: (C)2005,JPO&NCIPI