Process for dyeing keratinous fibres, at acid pH using 6- or 7-monohydroxyindoles and the compositions employed

An agent for dyeing keratinous fibers comprising at least two components,

• one component (A) consisting of an aqueous composition containing, in a medium suitable for dyeing said fibers, (i) as a coupler at least one 5-, 6- or 7-hydroxyindole derivative having the formula ##STR6## wherein R.sub.1 represents hydrogen or C.sub.1 -C.sub.4 alkyl,
• R.sub.2 and R.sub.3, each independently, represent hydrogen, C.sub.1 -C.sub.4 lower alkyl, carboxyl or alkoxy carbonyl,
• X represents hydrogen, C.sub.1 -C.sub.4 lower alkyl, C.sub.1 -C.sub.8 alkoxy, halogen, C.sub.2 -C.sub.20 acyloxy or acetylamino, or a salt of the derivative of formula I, said derivative of formula I being present in an amount ranging from 0.05 to 4 percent by weight based on the total weight of said component (A) and (ii) an oxidation dye precursor selected from the group consisting of a paraphenylenediamine, a para-aminophenol, a para-heterocyclic precursor, an ortho-aminophenol and an ortho-phenylenediamine, said coupler and said oxidation dye precursor being present in an amount ranging from 0.3 to 7 percent by weight based on the total weight of said component (A), and
• another component (B) consisting of an aqueous composition containing in a medium suitable for dyeing said fibers an oxidizing agent selected from the group consisting of hydrogen peroxide, urea peroxide, an alkaline metal bromate and a per salt, and present in an amount effective to dye said fibers,
• the pH of the mixture of 90 to 10 weight percent of said component (A) and 10 to 90 weight percent of said (B) having a pH less than 7.

A multi-compartment kit for dyeing keratinous fibers comprising a first compartment containing a component (A) consisting of a composition containing, in a medium suitable for dyeing said fibers, (i) as a coupler at least 5-, 6-, 7-hydroxyindole derivative having the formula ##STR7## wherein R.sub.1 represents hydrogen or C.sub.1 -C.sub.4 alkyl,

• R.sub.2 and R.sub.3, each independently, represent hydrogen, C.sub.1 -C.sub.4 lower alkyl, carboxyl or alkoxycarbonyl,
• X represents hydrogen, C.sub.1 -C.sub.4 lower alkyl, C.sub.1 -C.sub.18 alkoxy, halogen, C.sub.2 -C.sub.20 acyloxy or acetylamino, or a salt of the derivative of formula I, said derivative of formula I being present in an amount ranging from 0.05 to 4 percent by weight based on the total weight of said component (A) and (ii) an oxidation dye precursor selected from the group consisting of a paraphenylenediamine, a para-aminophenol, a para-heterocyclic precursor, an ortho-aminophenol and an ortho-phenylenediamine, said coupler and said oxidation dye precursor being present in an amount ranging from 0.3 to 7 weight percent based on the total weight of said component (A), and a second compartment containing a component (B) consisting of a composition containing in a medium suitable for dyeing said fibers an oxidizing agent selected from the group consisting of hydrogen peroxide, urea peroxide, an alkaline metal bromate and a persalt and present in an amount effective to dye said keratinous fibers.

A ready-for-use composition for dyeing keratinous fibers comprising in a medium suitable for dyeing said fibers a combination of

• (a) at least one 5-, 6- or 7-hydroxyindole derivative having the formula ##STR8## wherein R.sub.1 represents hydrogen or C.sub.1 -C.sub.4 alkyl,
• R.sub.2 and R.sub.3, each independently, represent hydrogen, C.sub.1 -C.sub.4 lower alkyl, carboxyl or alkoxycarbonyl,
• X represents hydrogen, C.sub.1 -C.sub.4 lower alkyl, C.sub.1 -C.sub.18 alkoxy, halogen, C.sub.2 -C.sub.20 acyloxy or acetylamino,
• or a salt of the derivative of formula I,
• said derivative of formula I being present in an amount ranging from said 0.01 to 3.5 percent by weight based on the total weight of said composition,
• (b) an oxidation dye precursor selected from the group consisting of a paraphenylenediamine, a para-aminophenol, a para-heterocyclic precursor, an ortho-aminophenol and an ortho-phenylenediamine, and
• (c) an oxidizing agent selected from the group consisting of hydrogen peroxide, urea peroxide, an alkaline metal bromate and a persalt,
• said oxidation dye precursor (b) and said oxidizing agent (c) being present in an amount effective to dye said keratinous fibers,
• said composition being free of iodide ions and nitrite ions in an amount sufficient to oxidize said derivative of formula I or said oxidation dye precursor,
• said composition having a pH less than 7.