Process for the preparation of storage-stable dye dispersions

摘要

This invention relates to a process for the preparation of storage-stable dye dispersions of alkali metal salts of anionic azo direct dyes by (a) preparing an aqueous slurry of an alkali metal salt of an azo direct dye, said salt having a solubility in water at 25 DEG C of about 0.1 to about 15% by weight, by azo coupling one or more aromatic diazonium salts with one or more couplers while maintaining a pH of at least about 5 by adding a basic alkali metal compound in the absence of a nitrogen-containing base; (b) optionally, stirring the aqueous slurry at a temperature of about 5 DEG C to about 100 DEG C for up to about six hours; (c) optionally, cooling the aqueous slurry to a temperature of about 5 DEG C to about 40 DEG C; and (d) adding to the aqueous slurry a viscosity enhancing agent in an amount sufficient to obtain a viscosity of about 500 to about 5000 centipoise and 0 to about 10% by weight, based on the total weight of the dye dispersion, of a humectant.