Agent for oxidative dyeing of hair

Use is made in the oxidative dyeing of hair of a preliminary coloring stage of the general formula ##STR1## wherein R signifies COOR', CONH.sub.2, CONHR', CONR'.sub.2, CONH--NH.sub.2, CONH--OH, CN, CH.sub.2 OH, CHO, CH(OH)(OR'), CH(OR').sub.2 and R' represents an alkyl group with 1 to 5 carbon atoms. The preliminary coloring stages as per formula (I) may be contained in the hair dyeing agents singly or in a mixture with known preliminary coloring stages and/or direct-acting hair dyeing agents. The hair dyeing agents may, in particular, additionally contain amino acids present in nature, their esters and/or their amides. The hair dyeing agents as described, are well compatible physiologically and it will particularly be brown to reddish-brown colorings having a natural effect, that may be obtained by their use.

For the dyeing of hair, it is the so-called oxidative colorants that have 
obtained essential importance by reason of their being fast to light and 
washing. To produce the oxidative colorants, certain aromatic compounds 
capable of oxidative coupling are being applied onto the hair as 
preliminary coloring stages. These will partially penetrate the hair and 
be oxidized therein to the desired colorant, either by atmospheric oxygen 
or, particularly, by the addition of chemical oxidants such as hydrogen 
peroxide. 
Mainly the derivatives of diamino or hydroxyamino compounds of benzene, 
naphthalene, pyridine, pyrimidine, pyrazolone, indol and chinoline serve 
as preliminary coloring stages. In part due to physiological reasons, the 
aforenoted materials are not entirely unobjectionable. 
Deriviatives of diphenol and naphthol are also known as preliminary 
coloring stages. However, no intensive hair dyeing has been achieved so 
far with representatives of these classes of substances known hitherto as 
preliminary coloring stages. 
Also, as knowledge concerning the formation of hair pigment has been 
obtained, the use of tyrosine,Dopa.sup.+), and Dihydroxyindols for the 
dyeing of hair has been described. Preparations on the basis of these 
compounds, which are physiologically the most suitable for use as 
preliminary coloring stages, could not, however, for various reasons, gain 
acceptance in practice. 
FNT .sup.+) Dopa=L-.beta.-(3,4-dihydroxy-phenyl)-alanine 
Numerous particular demands are put forward with respect to oxidative 
colorants used for dyeing human hair. They must be unobjectionable as to 
toxicology and dermatology, and allow for colorings of the desired 
intensity. It is furthermore necessary that a wide spectrum of various 
coloring nuances be obtained by a combination of such compounds as are 
suitable for preliminary coloring stages. In addition, the hair colorings 
that can be obtained are required to demonstrate good fastness to light 
and resistance to permanent-wave treatment, acids and rubbing. Such 
colorings must, at any rate, remain stable against the influence of light, 
rubbing and chemical agents, for a period of at least four to six weeks. 
The plurality of the demands as put forward are not met to complete 
satisfaction by the compounds used at present as preliminary coloring 
stages in oxidative hair dyeing agents. 
The task existed therefore, to prepare agents for oxidative dyeing of hair, 
based upon such compounds serving as preliminary coloring stages which, 
physiologically have more suitable properties when compared to known 
compounds used as preliminary coloring stages. These compounds should, 
furthermore, possess good fastness to wearing and a sufficient intensity 
of the colorings, either alone, or in combination with other compounds 
known as preliminary coloring stages. 
The object of the invention is, therefore, an agent for oxidative dyeing of 
hair, characterized by containing as preliminary coloring stage, a minimum 
of one compound of the general formula 
##STR2## 
wherein R signifies COOR', CONH.sub.2, CONHR', CONR'.sub.2, 
CONH--NH.sub.2, CONH--OH, CN, CH.sub.2 OH, CHO, CH(OH)(OR'), CH(OR').sub.2 
and R' represents an alkyl group with 1 to 5 carbon atoms. 
The total content of these compounds according to formula (I), serving as 
preliminary coloring stage, should amount to approximately 0.1 to 6 
percent by weight, preferably 1 to 4 percent by weight. 
Examples of suitable compounds, contained as preliminary coloring stages in 
the hair dyeing agents of the aforenamed general formula (I) are, in 
particular 
Homogentistic acid amide, 
Homogentisic acid dimethylamide, 
Homogentisic acid methylester, 
Homogentisic acid ethylester, 
Homogentisic acid isopropylester and 
Homogentisic hydroxamic acid (2,5-Dioxyphenyl acetohydroxamic acid). 
Furthermore, the agents for dyeing hair of the present application may, in 
particular, contain as preliminary coloring stages, such aromatic 
compounds as occur in nature, but also other aromatic compounds having a 
minimum of one hydroxy group in the molecule, and which may additionally 
have a nitrogen atom or a plurality of nitrogen atoms in the molecule. 
Examples of such compounds are: 
(a) aromatic compounds containing in the molecules a minimum of one hydroxy 
group such as orcin, hydroquinone, pyrogallol, hydroxy-hydroquinone, 
protecatechualdehyde, thymol, guajacol, arbutin, pyrocatechol, juglone, 
lawsone, vanillin, pulvinic acid, hydroxycoumarin, flavonoids, and 
grevillines, derivatives of salicylic acid, caffeic acid, chlorogenic 
acid, as well as, 
(b) aromatic compounds with at least one hydroxy group and additionally a 
minimum of one nitrogen atom in the molecule, such as Dopa, tyrosine, 
kynurenic acid and xanthurenic acid, derivatives of anthranilic acid, 
nicotinic acid, isonicotinic acid, picolinic acid, pyrrols, pyrimidines, 
purines, betalainic acids, kynurenin, and ommatins. 
These compounds may be used in a ratio of 0.1 to 1 mol, relative to 1 mol 
of the compounds of the general formula (I) contained as preliminary 
coloring stages in the agents described herein. 
The total quantity of compounds serving as preliminary coloring stages in 
the hair dyeing agents according to the invention will suitably amount to 
approximately 0.1 to 6 percent by weight, preferably 1 to 4 percent by 
weight. 
It is, furthermore, possible for the hair dyeing agents to additionally 
contain usual direct-acting hair colorants. 
To increase the coloring depth of the hair colorings, the dyeing agents 
according to the the present application may, furthermore, contain amino 
acids occurring in nature, their esters with lower alcohols and/or their 
amides as well as mono or dialkyl amides, wherein the alkyl group bonded 
to the nitrogen of the amide, will have 1 to 5 carbon atoms. Examples 
thereof are the amino acids: glycine, alanine, proline, hydroxy proline, 
serine, cysteine, histidine and tryptophane, their esters with lower 
alcohols as well as their respective amides or mono or dialkyl amides, 
wherein the alkyl group bonded to the nitrogen of the amide will have 1 to 
5 carbon atoms. The amino acids and their aforenamed derivatives may be 
contained in the agents particularly in a proportion of 0.05 to 1 mol 
relative to 1 mol of the compounds present therein as preliminary coloring 
stages. 
Finally, there may additionally be present in the hair dyeing agents usual 
cosmetic additives, for instance antioxidants such as ascorbic acid or 
sodium sulfite, alkalizing agents such as alkaline hydroxides, ammonium 
or, respectively, alkaline carbonate and ammonium, or, respectively, 
alkaline hydrogen carbonate, organic acids such as, for instance, acetic 
acid, lactic acid and citric acid, solvents, perfumes, swelling agents, 
wetting agents, emulgators, thickeners, hair-care substances and others. 
The preparation may be made available as a solution, preferably, however, 
as a cream, a gel or an emulsion. Its composition represents a mixture of 
the colorants with usual constituents of such preparations. The usual 
constituents of creams, gels or emulsions coming into consideration will, 
for instance, be wetting agents or emulgators from the categories of 
anionic, cationic or non-ionogenic surfactants such as sulfates of fatty 
alcohols, alkyl sulfonates, alkylbenzene sulfonates, salts of alkyl 
trimethyl ammonia, oxethylated fatty alcohols, oxethylated nonylphenols, 
fatty acid alkanol amides and, furthermore, thickeners such as higher 
fatty alcohols, starch, cellulose derivatives, paraffin oil and fatty 
acids, as well as hair-care substances such as lanolin derivatives, 
cholesterol and pantothenic acid. The constituents as noted are used in 
quantities as usual for these purposes, i.e. wetting agents and emulgators 
in concentrations of approximately 0.5 to 30 percent by weight, while 
thickeners may be present in the preparations in a quantity of 
approximately 0.1 to 25 percent by weight. 
Depending upon their composition, the dyeing agents according to the 
invention may react weakly acidic, neutral or alkaline. They are, in 
particular, of a pH value in the alkaline range of 7.5 to 11, adjustment 
being preferably made with ammonia, or ammonium hydrogen carbonate. Use 
may also be made of organic amines such as mono or triethanolamine. 
Application may be made, depending upon the pH value of these agents as per 
invention, (A) in one, (B) in two, or (C) in three stages. 
(A) In the one-stage process, the hair dyeing agent is mixed with an 
oxidant shortly before use, and the mixture applied onto the hair. Coming 
into consideration as oxidants for developing the hair coloring are, 
mainly, peroxodisulfates or hydrogen peroxide, the latter, for instance, 
as 3% aqueous solution, or, respectively, additive compounds of the latter 
with urea, melamin or sodium borate. The application temperatures of these 
hair dyeing agents are in the range from 20.degree. to 50.degree. C. After 
an application period of approximately 20 to 40 minutes, preferably 30 
minutes, the hair is rinsed with the aqueous solution of a weakly organic 
acid, for instance a solution of citric acid or tartaric acid which, in 
given instances, may additionally contain EDTA.sup.+), and final rinsing 
is made with water. 
FNT .sup.+) EDTA=Ethylenediaminetetraacetate 
This process is particularly suitable for the application of such hair 
dyeing agents according to the invention that are set to a pH value of 
approximately 9 to 10. 
(B) The two-stage process is suitable for the application of the hair 
dyeing agents described herein, particularly when these are of a pH value 
between 7 and 8. The hair dyeing agent is therein applied onto the hair in 
the first stage, and allowed to act at a temperature of 20.degree. to 
50.degree. C. for approximately 10 to 20 minutes. In the following second 
stage, a 1 to 8% alkaline solution of a suitable oxidant is applied onto 
the hair, whereby the pH value of the mixture acting upon the hair will 
rise to approximately 9.5. This solution is also allowed to act for 
approximately 10 to 20 minutes. Subsequently, the hair is rinsed with the 
aqueous solution of a weak organic acid, as for instance citric acid or 
tartaric acid containing in given instances also EDTA, and final rinsing 
is made with water. 
(C) The three-stage process is suitable for such hair dyeing agents as per 
invention which have a pH value within the weakly acidic range. Herein, 
the hair dyeing agent is applied onto the hair in the first stage and 
allowed to act for approximately 10 minutes at a temperature of 
approximately 35.degree. to 45.degree. C. In the second process stage, an 
oxidant, for instance a 10% suspension of ammonium peroxodisulfate is 
brought onto the hair and also allowed to act for about 10 minutes at the 
same temperature. Finally, in the third process stage, the aqueous 
solution of an alkalizing agent is distributed onto the hair and allowed 
to act for approximately 15 minutes at the same temperature. Subsequently, 
the hair is first rinsed with an aqueous solution of a weak organic acid, 
such as of citric acid or tartaric acid containing, in given instances, 
also EDTA, and final rinsing is made thereupon with water.