抄録
The most important hair colorants on the market are the oxidation dyes because of their effective coloring. They consist of primary intermediates, oxidants, and couplers. In most cases, hydrogen peroxide is employed as the oxidants, but it has resulted in damage to hair. Therefore, there has been much hope of finding a better and safer hair colorant. In our studies, we have found a hair colorant in which the primary intermediates are oxidized in the presence of silver ions used as a catalyst without hydrogen peroxide.
In order to dye hair, oxidation of the intermediates must take place within the hair. If the oxidative reaction is completed outside of the hair strand, the enlarged dye molecules will not diffuse within the hair strand. If the reaction proceeds slowly, it is too time-consuming for hair coloring. We have succeeded in controlling the elution rate of silver ion catalyzing the oxidation reaction by holding it within the zeolite. By controlling the contents of silver in zeolite, the contents of the silver-zeolite in dyeing system, and the composition of the solvent, the elution rate can be best controlled for dyeing the hair.
The hair coloring products using silver-zeolite as an oxidation catalyst were shown to be safer in the mutagenicity tests which we have conducted. We have also found less damage of the dyed hair surface than with conventional hair deys using hydrogen peroxide.
