Patent ID: 6258131
Filing Date: 2001-07-10
Classification: A61K,A61Q,D06P

Abstract:
A process for preserving the dyeing capacity of a dyeing agent in an aqueous medium, said dyeing agent consisting of an indole, said indole having the formula ##STR10##whereinR.sub.1, R.sub.2, R.sub.3 and R.sub.4, each independently, represent hydrogen or C.sub.1 -C.sub.4 lower alkyl with the proviso that R.sub.1, R.sub.2 and R.sub.3 represent hydrogen when R.sub.4 represents alkyl, said process comprising adjusting the pH of said aqueous medium to a pH.sub.C value of between 5 and 10 by adding thereto a pH regulating agent containing two components (A) and (B), said component (A) being triethanolamine and said component (B) being a pH regulating agent having a dissociation constant, K.sub.CB, in an aqueous solution at 25.degree. C., of 2<pK.sub.CB.ltoreq.pH.sub.C, the weight ratio of said component (A) to said component (B) being greater than 1 and the molar ratio of said component (A) to said component (B) being greater than or equal to 2 and less than 15.