PROCESS FOR THE PREPARATION OF PHENYLENE-BIS-BENZIMIDAZOLE-TETRASULPHONIC ACID DISODIUM SALT

摘要

Phenylene-bis-benzimidazole-tetrasulphonic acid disodium salt which is largely free from impurities can be prepared by reacting o-phenylenediamine with terephthalic acid and chlorosulphonic acid in the presence of strong acids with a reaction time of 10 to 15 hours.