Patent ID: 6214965
Filing Date: 2001-04-10
Classification: C04B,C08G

Abstract:
-1.5 in molar ratio and its pH to 8.0-13.5, and thereafter heating the aqueous solution at 50-90.degree. C. to conduct the reaction until free sulfanilic acid decreases to 40-90 mol % of the amount of sulfanilic acid charged;Step (B): a step of adding an inorganic acid to the reaction liquid obtained in the step (A) to adjust its pH to 6.0-8.0, and thereafter heating the reaction liquid at 50-90.degree. C. to conduct the reaction until free sulfanilic acid decreases to 20-60 mol % of the amount of sulfanilic acid charged;Step (C): a step of adjusting a pH of the reaction liquid obtained in step (B) to 7.0-