Optimisation of the synthesis of a water-soluble sulfur black dye

A water-soluble sulfur black dye containing carboxylic acid groups was prep ared by reducing C.I. Sulfur Black 1 to its leuco form followed by reaction with chloroacetic acid. In conducting this reaction, variables studied inc luded the order of adding reactants, the amount of Na2S and chloroacetic ac id employed, and the time and temperature of the reaction. It was found tha t the carboxylic acid group content and reaction yield were, maximized by c ontrolling the amount of Na2S and chloroacetic acid employed, and by conduc ting the reaction for 2 h at 60 degreesC. (C) 2001 Elsevier Science Ltd. Al l rights reserved.