HYDROXYINDOLES AND THEIR USE IN DYEING

Abstract: Monohydroxyindoles and UV light or a chemical oxidant such as sodium periodate are used, simultaneously or sequentially, to dye hair or skin.

Description: FIELD OF THE INVENTION This invention relates to the use of hydroxylated indoles in dyeing. BACKGROUND OF THE INVENTION In the past thirty years, a variety of chemical systems for dyeing hair and skin have been developed. The most commercially successful of these has utilized phenylenediamine combined with various couplers and modifiers together with hydrogen peroxide as an oxidant. However, this system suffers from a number of problems. Phenylenediamine is a known sensitizer, hair is then damaged by repeated exposure to alkaline peroxide, and the color produced may fade over time to an undesirable off-shade. Further, p-phenylenediamine is oxidized in the presence of resorcinol by hydrogen peroxide to a mutagen that is percutaneously absorbed; see Crebelli et al , (1981) Fd. Cosmet. Toxicol. 19: 79-84. The most important pathway for the formation of melanin in vivo involves oxidation of dopa to dopaquinone which in turn cyclizes to form leucodopachrome. Leucodopachrome is oxidized to dopachrome which rearranges with the loss of carbon dioxide to yield 5,6-dihydroxyindole which subsequently undergoes oxidative polymerisation to form melanin. EP-A-0161073 discloses the formation of a melanin-like dye, using dopamine as the dye precursor and sodium iodate or sodium periodate as the oxidant. US-A-4021538 (which is related) discloses the dyeing of hair or skin, using esters of dopa owing to their solubility in both water and lipid solvents. US-A-4390341 concerns a composition for colouring hair or skin which employs, inter alia , acylated dopamine or acylated tyrosine derivates and omega-amino-acids. US-A-4609544 discloses a method of tanning human skin, using a composition comprising a cosmetic base, a dye precursor (of which an example is 5-hydroxyindole), a peroxidase and H₂O₂. US-A-4515773 discloses a method for tanning skin, using a composition comprising a cosmetic base, 5-hydroxyindole or another dye precursor, and tyrosinase. C.A. 90 (1979) 92263x discloses a hair dye comprising sulfite or bisulfite, a promoter, a hydroxy compound such as 5-hydroxyindole, and a water-soluble Fe or Cu salt. DE-A-2455376 discloses a three-part hair dye composition, the parts respectively comprising dithiothreitol/dithioerythritol,tyrosine/dihydroxyphenylalanine and 5-hydroxyindole or a similar compound, and a persulphate, together with a tyrosinase. EP-A-0161073 discloses a hair dye comprising an organic dye penetrant, dopamine or dopa, and iodate or periodate. US-A-2934396 concerns a composition for colouring hair and other keratinous material, which employs 5,6-dihydroxyindole as the dye precursor. US-A-4208183 discloses that commercial exploitation of 5,6-dihydroxy indole dyestuffs is limited due to the lack of stability during storage of 5,6-dihydroxyindole. SUMMARY OF THE INVENTION According to the present invention, a hydroxyindole dye precursor and an oxidant provide a dye composition suitable for dyeing hair or skin. The invention is based on the surprising discovery that the hydroxyindoles can be oxidized with sodium periodate or another oxidant, advantageously and desirably, to melanin-like dyes of varying shades. While a number of oyidants caused dye formation for topical applications, it has been found, surprisingly, that only sodium periodate (but not sodium iodate) effected dye formation inside the hair shaft. Hair dyed by a dyeing process according to the invention can be stable to multiple shampooing, without toxic effects and with minimal or no damage to the hair by comparison with the damage caused by phenylenediamine-type dyes. The colour which is produced is stable to washing, without forming the red or green overtones which are often observed after repeated washing or perming of hair coloured with commercially-avaiable phenylenediamine-based dyes. It appears that hair dyed according to the invention is protected against damage by ultra-violet light. Finally, the hydroxyindoles which are used are apparently more storage stable than dihydroxyindoles such as 5,6-dihydroxyindole. DETAILED DESCRIPTION OF THE INVENTION The hydroxyindole dye precursors which are used in the present invention have the formula wherein R₁ is H or C₁₋₄ alkyl; and R₂, R₃, R₄, R₅, R₆ and R₇ are independently selected from H, C₁₋₄ alkyl, NH₂, OH, COOH, (C₁₋₄ alkoxy)carbonyl, CONH₂, Cl, Br, I, F, C₁₋₄ alkoxy, CH₂OH, CH₂NH₂, (C₁₋₄ alkyl)-aminocarbonyl and di(C₁₋₄ alkyl)aminocarbonyl, provided that one and only one of R₄, R₅, R₆ and R₇ is OH. These dye precursors can be used alone or as a mixture of two or more. Preferred dye precursors for use in the invention (and the colours they give, e.g. when oxidised by sodium periodate at room temperature) are 4-hydroxyindole (black), 5-hydroxyindole (dark chestnut brown), 6-hydroxyindole (dark brown), 7-hydroxyindole (red-brown), 5-hydroxyindole-3-acetic acid (light brown), 5-hydroxyindole-2-carboxylic acid (light brown), 5-hydroxy-3(hydroxyethyl)indole and 5-hydroxy-2-(hydroxymethyl)indole. Indole itself gives no colour, while indole-5-carboxylic acid and indole-3-acetic acid and its ethyl ester all give a light brown colour. The chemical oxidant is selected from periodic acid, water-soluble salts of periodate and isolated equilibrium species of periodate. Specifically, periodic acid and its lithium, sodium (preferred), potassium, rubidium, cesium, magnesium, calcium, strontium, bromine, lanthanum, manganese, iron, copper, zinc and aluminium salts can be used. Other equilibrium states of periodate are as follows: In aqueous solution (pH = 0-7), periodic acid exists as an equilibrium mixture between the free acid (H₅IO₆) and its various ions. Changing the pH, dilution, or mixing with an organic solvent would be expected to shift any of various equilibria, e.g. the following: H₅IO₆ = H₄IO₆⁻ + H⁺ H₄IO₆⁻ = IO₄⁻ + 2H₂O H₄IO₆⁻ = H₃IO₆²⁻ + H⁺ H₃IO₆²⁻ = H₂IO₆³⁻ + H⁺ 2H₃IO₆²⁻ = H₂I₂O₁₀⁴⁻ + 2H₂O (pH = 10) Any of these chemical species and many others could be trapped and isolated and when placed into solution would re-equilibrate to the other chemical species. A screening of oxidants was performed with hydroxyindoles to determine if they would promote the formation of a melanin-like dye. Several oxidants promoted the polymerization of hydroxyindoles in solution, namely, oxygen in the presence of UV light, sodium periodate, potassium permanganate, sodium hypochlorite, potassium ferricyanide, potassium dichromate, ammonium persulfate, silver oxide, Fentons reagent, ferric chloride, lead (IV) oxide, and cesium (IV) sulfate. However, surprisingly, sodium periodate was the most efficient oxidant for melanin dye formation inside the hair. Currently commercially available hair dye products are formulated so that the dye precursors are stored in one bottle and the oxidant is stored in a second bottle. Immediately before use the two are mixed together and subsequently applied to the hair. After an appropriate interval of time the hair is rinsed and washed, leaving the hair dyed. Since only one solution is applied to the hair and the process requires only a rinse at the end, this has been defined as a one-step process. Sodium periodate cannot be employed as the oxidant in the one-step process since the dye precursors require sufficient time to penetrate into the hair fibers before sodium periodate is introduced into the dye bath. Two hair dye processes have been developed to overcome the dye precursor penetration-time problem. The first process, designated the two-step process, requires applying the dye precursor to the hair, waiting about 3 to about 30 min, rinsing the hair, applying the periodate solution to the hair, waiting about 3 to about 30 min, and then rinsing the hair. In the two-step process a surfactant such as 1% sodium dodecyl sulfate (SDS) may be included in the formulations. The second process, designated the one and one-half step process, eliminates the intermediate rinse between the application of the dye precursor mixture and the application of the sodium periodate mixture to the hair. For best results a surfactant such as about 0.1-10% SDS should be included in the formation when the one and one-half step process is utilized, to prevent unwanted surface coating of the hair fibers with dye material. The one and one-half step process may be converted to a one-step process by utilizing chemical as well as physical methods of delaying periodate introduction into the dye bath, e.g., utilizing slightly soluble salts of periodate, utilizing liposome technologies, or utilizing microencapsulation technologies. Generally, the dyeing system of the subject invention can be applied to hair in the following manner. ( Two-step process ) The hair is contacted with an aqueous solution (which can include 0.1-10% of a surfactant such as SDS or CYCLOPOL SBFA 30 [Registered Trade Mark, Cyclo Chemical Co., Miami, FL]) of about 0.1 to about 10% of a hydroxyindole dye precursor (for convenience the bath ratio [liquid:hair] can be 0.1:1 to 5:1) at room temperature for about 3 to about 30 min. The hair is rinsed with water, patted dry, and then contacted with a solution of about 3 to about 15% of sodium periodate (for convenience the bath ratio [liquid:hair] can be 0.5:1 to 5:1), which can include 0.1-10% of a surfactant such as SDS or CYCLOPOL SBFA 30 at about 20 to about 30°C for about 5 to about 30 min. Dyeing is terminated by rinsing the hair with water, followed, if desired, by one or two one-minute washings with a commercially-available mild shampoo. The hair then can be combed out and blown dry, if desired. (One and one-half step process) The hair is contacted with an aqueous solution (which can include 0.1-10% of a surfactant such as SDS or CYCLOPOL SBFA 30) of about 0.1 to about 10% of a hydroxyindole dye precursor (for convenience the bath ratio [liquid:hair] can be 0.5:1 to 5:1) at room temperature for about 3 to about 30 min. The hair is subsequently contacted with a solution of about 3 to about 15% of sodium periodate (for convenience the bath ratio [liquid:hair] can be 0.5:1 to 5:1), which can include 0.1-10% of a surfactant such as SDS or CYCLOPOL SBFA 30 at about 20 to about 30°C for about 5 to about 30 min. Dyeing is terminated by rinsing the hair with water, followed, if desired, by one or two one-minute washings with a commercially-available mild shampoo. The hair then can be combed out and blown dry, if desired. Formation of Dyes Utilizing Hydroxyindoles A variety of indole derivatives were tested on hair. The presence of a hydroxyl group on the aromatic ring is required in order to form a dye. 4-, 5-, 6-, and 7-Hydroxyindoles were found to form a black, dark brown, dark brown, and red-brown dye, respectively. The intensity or shades of color desired will dictate the choice of dye precursor. The addition of an acetate or carboxylate group to the 2- or 3- position of the indole ring reduces the color of the dye formed as seen with indole-5-hydroxy-3-acetic acid and indole-5-hydroxy-2-carboxylic acid. At 25°C 5-hydroxyindole (2%), 4-hydroxyindole (1%), 6-hydroxyindole (2%) and 7-hydroxyindole (2%) were found to form a dark brown, black, dark brown, and red-brown dye, respectively, inside hair in the dye process when allowed to penetrate hair for 3-15 min and subsequently oxidized with sodium periodate. The formation of melanin-like dye inside the hair (as assessed by light and electron microscopy) can therefore by accomplished utilizing 4-, 5-, 6-, or 7-hydroxyindoles at low concentration employing a room temperature process of a total of about 20 min. Increasing the temperature to 34°C shortened the total dye time required but did not significantly enhance color formation. A permanent coloring system for hair should produce a dye which is resistant to multiple shampooing. The stability of melanin-like dye in hair formed by either 4-, 5-, 6-, or 7-hydroxyindole to shampooing was investigated. Tresses were exposed to either 4-hydroxyindole (1%), 5-hydroxyindole (2%), 6-hydroxyindole (2%) or 7-hydroxyindole (2%) for 15 min followed by a rinse and then by a 15-min oxidation by sodium periodate (15%). Tresses which were washed either one time (wash/rinse/wash/rinse) or ten times were indistinguishable from each other. Thus, the dye formed by either 4-, 5-, 6-, or 7-hydroxyindole in the hair is stable to shampooing. Upon light microscopic examination of cross sections of hair fibers treated with hydroxyindoles and the oxidants that showed effectiveness in converting the hydroxyindoles to melanin-like dyes in solution, only the hair fibers treated with periodate or its salts visually contained dye material within the fiber with little or no damage to the hair cuticle, and little to no coating of the dye on the hair surface. Potassium permanganate effected some dye formation within the hair fibers examined; however, the cuticles of the hair fibers treated were severely damaged during the dyeing process. Mixtures of 4-hydroxyindole (0.1-10%) and 5-hydroxyindole (0.1-10%), 6-hydroxyindole (0.1-10%), or 7-hydroxyindole (0.1-10%) will give a color range from black to light auburn. 5-Hydroxyindole (0.1-10%) was found to produce progressively darker browns and, eventually, black through the addition of 3-methylcatechol (0.1-10%), 3-methoxycatechol (0.1-10%), or 3,6-dimethylcatechol (0.1-10%) followed by oxidation by sodium periodate (15%). 4-Hydroxyindole (1%) was found to produce progressively lighter colors with increasing red highlights through the addition of dopamine (2-5%) when penetration of precursors was done at high pH (9.2). Therefore a range of colors from light brown to black can be obtained through combinations of 4-hydroxyindole, 5-hydroxyindole, 6-hydroxyindole, and 7-hydroxyindole with each other or various other dye precursors. If desired, a thickening agent can be incorporated into the dyeing combinations to minimize dripping from the hair. Suitable thickeners include water-soluble resins and gums, for example carrageenan, guar gum or locust bean gum; also polymers, such as Carbopol 934 (Registered Trade Mark BFGoodrich Chemical Group, Cleveland, OH) or polyvinyl alcohol; or inorganic materials, for example, Veegum (Registered Trade Mark Vanderbilt Company, Norwalk, CN), nonoxynol-4, nonoxynol-9 (Registered Trade Marks Heterene Chemical Co., Paterson, NJ) or combinations of nonoxynols. A particularly useful thickening agent is polyethylene glycol-150 distearate (PEG-150 distearate) (Heterene). For example, a 10% solution of PEG-150 distearate is compatible with the dyeing reaction and gives a commercially useful thickened product. Thickening agents can be used in a variety of combinations. The thickener can be present at about 0.1 to about 25% by weight, relative to the total weight of the dye composition. The dyeing time generally can be shortened by dyeing the hair at temperatures above room temperature. For example, more rapid dyeing can be realized at 35°C than at 20°C. Higher temperatures can be achieved by a variety of methods, including covering the head with a plastic cap during the dyeing reaction; warming of the dye precursor and oxidant solutions before application, either with an external device or with an exothermic reaction initiated by mixing of, for example, the precursor and oxidant solution; with an infrared lamp; or by other means well known in the hair dyeing art. Anionic, cationic, non-ionic or amphoteric water-soluble surface-active agents also can be included in the dye composition. Surface-active agents such as TEA lauryl sulfate, CYCLOPOL SBFA 30, SIPONIC L-4 and SIPONIC L-25 (Registered Trade Marks both supplied by Alcolac, Baltimore, MD), sodium lauryl sulfate, phosphate esters, sodium lauryl ether sulfo succinate, and SDS are examples of such agents known to the art which can be included in the formation. The surface-active agents are preferably present in the dye composition in a proportion of about 0.1 to about 15% by weight. Advantageously, a stabilizer can be added to the hydroxyindole composition. A suitable stabilizer is the reducing agent sodium metabisulfite at a concentration of 1 to about 5 mM. Other reducing agents such as sodium sulfite, ascorbic acid, and the like, can be used. The subject dye composition can be used in various forms, for example, liquid, cream, gel or an aerosol, or in any other form that is suitable for dyeing hair. Following are examples that illustrate products of the invention and procedures. These examples should not be construed as limiting. All percentages are by weight and all solvent mixture proportions are by volume unless otherwise noted. Example 1--Dyeing Gray Hair to Brown Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1-10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing 1 to 10% 5-hydroxyindole plus a reducing agent (0.1% ascorbic acid) to prevent premature oxidation of dye precursor (pH 3 to 9) for about 3 to about 15 min at about 20°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to about 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 30 min, after which the hair is rinsed. The hair now has a pleasing and stable brown color with red highlights. Example 2--Dyeing Gray Hair to Red or Red-Brown Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1-10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 1 to 5% 7-hydroxyindole plus 0.1% ascorbic acid (pH 3 to 9) for about 3 to about 15 min at about 20°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to about 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 30 min, after which the hair is rinsed. The hair now has a pleasing and stable red to red-brown color. Example 3--Dyeing Gray Hair to Red-Brown Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1-10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 1% to about 2% 5-hydroxyindole plus about 0.1% to about 1% 7-hydroxyindole plus 0.1% ascorbic acid (pH 3 to 9) for about 3 to about 15 min at about 20°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 30 min, after which the hair is rinsed. The hair now has a pleasing and stable red-brown color. Example 4--Dyeing Gray Hair to Black Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1-10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) of about 0.5% to about 3% 4-hydroxyindole plus 0.1% ascorbic acid (final pH 3 to 9) for about 3 to 15 min at about 20°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to about 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 20 min, after which the hair is rinsed. The hair now has a pleasing and stable black color. Example 5--Dyeing Gray Hair to Black Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 1% to about 3% 5-hydroxyindole plus about 1 to about 3% 3-methylcatechol plus about 0.1% ascorbic acid (final pH 3-9) for about 3 to about 15 min at 20°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 20 min, after which the hair is rinsed. The hair now has a pleasing and stable black color. Example 6--Dyeing Gray Hair to Brown Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1-10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 0.1 to about 2% 4-hydroxyindole plus about 2 to about 3% dopamine plus 0.1% ascorbic acid (final pH 7-10) for about 3 to about 15 min at about 20°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to about 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 20 min, after which the hair is rinsed. The hair now has a pleasing and stable brown color. Example 7--Dyeing Gray Hair to Black Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 1% to about 3% 5-hydroxyindole plus about 1 to about 3% 3-methoxycatechol plus about 0.1% ascorbic acid (final pH 3 to 9) for about 3 to about 15 min at 35°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to about 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 20 min at 35°C, after which the hair is rinsed. The hair now has a pleasing and stable black color. Example 8--Dyeing Gray Hair to Dark Brown Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 1 to 10% 6-hydroxyindole plus 0.1% ascorbic acid (final pH 3 to 9) for about 3 to about 15 min at about 25°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to about 15 % sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 20 min. The hair now has a pleasing and stable dark brown color. Example 9--Dyeing Gray Hair to Brown Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 0.1% to about 2% 4-hydroxyindole plus about 1 to about 2% 7-hydroxyindole plus 0.1% ascorbic acid (final pH 3-9) for about 3 to about 15 min at about 20°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to about 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 20 min, after which the hair is rinsed. The hair now has a pleasing and stable brown color with red highlights. Example 10--Dying Gray Hair to Brown Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 1 to about 2% 5-hydroxyindole plus about 0.1 to about 1% 3-methylcatechol plus 0.1% ascorbic acid (pH 3-9) for about 3 to about 15 min at about 20°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 3 to about 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 20 min, after which the hair is rinsed. The hair now has a pleasing and stable brown color. Example 11--Dyeing Gray Hair to Black Gray hair is contacted with an aqueous solution (which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) containing about 1 to about 2% 6-hydroxyindole plus about 0.1 to about 1% 3-methoxycatechol plus 0.1% ascorbic acid (pH 3 to 9) for about 5 to about 15 min at about 25°C. The hair may or may not be rinsed for 30 sec. The hair is then contacted with a solution of about 5 to about 15% sodium periodate (pH 2.5 to 5.5, which may contain a surfactant such as 0.1 to 10% SDS or CYCLOPOL SBFA 30 and/or a thickening agent such as 5 to 10% PEG-150 distearate) and the treatment allowed to proceed for about 10 to about 20 min, after which the hair is rinsed. The hair now has a pleasing and stable brown color.

Claims: A dye composition which comprises, in a combined formulation for sequential use in dyeing hair, (1) a hydroxyindole dye precursor of the formula wherein R is H or C₁₋₄ alkyl; and R₂, R₃, R₄, R₅, R₆ and R₇ are independently selected from H, C₁₋₄ alkyl, NH₂, OH, COOH, (C₁₋₄ alkoxy)carbonyl, CONH₂, Cl, Br, I, F, C₁₋₄ alkoxy, CH₂OH, CH₂NH₂, (C₁₋₄ alkyl)aminocarbonyl and di(C₁₋₄ alkyl)aminocarbonyl, provided that one and only one of R₄, R₅, R₆ and R₇ is OH; and (2) an oxidant selected from periodic acid, water-soluble salts of periodate and isolated equilibrium species of periodate. A dye composition according to claim 1, wherein the oxidant is sodium periodate. A dye composition according to claim 2, wherein the hydroxyindole dye precursor is 4-hydroxyindole, 5-hydroxyindole, 6-hydroxyindole, 7-hydroxyindole, 5-hydroxyindole-3-acetic acid, 5-hydroxy-3-(hydroxyethyl)indole, 5-hydroxyindole-2-carboxylic acid or 5-hydroxy-2-(hydroxymethyl)indole A dye composition according to claim 2 or claim 3, which comprises 0.1 to 10% of the hydroxyindole dye precursor and 1 to 10% sodium periodate. A dye composition according to any preceding claim, which additionally comprises a thickener. A dye composition according to any preceding claim, which additionally comprises 0.1 to 4% of a colour modifier selected from 3-methylcatechol, 3-methoxycatechol and 3,6-dimethylcatechol. A dye composition according to any preceding claim, which additionally comprises 0.5 to 5 mM of a stabiliser A dye composition according to claim 7, wherein the stabiliser is ascorbic acid. A process for dyeing hair, which comprises applying to the hair, sequentially, a hydroxindole dye precursor as defined in claim 1 or claim 3; an oxidant as defined in claim 1; and, optionally, an additional component as defined in any of claims 5 to 8. A process for dyeing hair according to claim 9, which comprises (1) contacting the hair with the hydroxyindole dye precursor for 3 to 30 min; (2) rinsing the hair with water; (3) patting the hair dry; (4) contacting the rinsed, dried hair with a solution of 5 to 10% sodium periodate, at 20 to 30°C for 5 to 30 min; and (5) rinsing the dyed hair with water. A process according to claim 9, which comprises (1) contacting the hair with a dye composition comprising 0.1 to 10% of the hydroxyindole dye precursor and 0.1 to 10% of a surfactant; (2) after 3 to 15 min, working into the hair a solution of 5 to 10% sodium periodate, at 20 to 30°C, for 5 to 30 min; and (3) rinsing the dyed hair with water. A process according to claim 11, wherein the surfactant is selected from TEA laurylsulfate, sodium laurylsulfate, phosphate esters and sodium lauryl ether sulfosuccinate.

Inventors: CARROLL, JAMES, HERLIHY, WALTER C., MILLIS, CYNTHIA D.
Applicants: REPLIGEN CORPORATION
Application year: 1987
Main classification: A61K7
IPC codes: A61Q5, A61K8