WO2015198923A1

WO2015198923A1 - Composition for keratin fibers

Info

Publication number: WO2015198923A1
Application number: PCT/JP2015/067380
Authority: WO
Inventors: Shiho MIYAKE; Hidetoshi Yamada; Daisuke Misu
Original assignee: L'oreal
Priority date: 2014-06-24
Filing date: 2015-06-10
Publication date: 2015-12-30
Also published as: JP2016008190A

Abstract

The present invention relates to a composition for dyeing keratin fibers, comprising: (a) at least one direct dye; (b) at least one aprotic polar solvent; and (c) at least one sulfur-containing reducing agent. The composition according to the present invention can prevent or reduce skin staining by the direct dye on the skin such as scalp, as well as the stiffness of the keratin fibers, while providing the keratin fibers with good cosmetic effects such as good coloring properties.

Description

DESCRIPTION

COMPOSITION FOR KERATIN FIBERS

TECHNICAL FIELD

The present invention relates to a composition for keratin fibers, in particular for dyeing keratin fibers with at least one direct dye, as well as a process using the same.

BACKGROUND ART

It is known to dye keratin fibers and in particular human hair with dyeing compositions containing oxidative coloring precursors, generally called oxidative bases, such as ortho- or

para-phenylenediamines, ortho- or para-aminophenols and heterocyclic compounds. These oxidative bases are generally combined with couplers. These bases and these couplers are colorless or weakly colored compounds which, combined with oxidizing products, can give rise to colored compounds through an oxidative condensation process.

This type of coloring by oxidation makes it possible to get colors with very high visibility, coverage of white hair and in a wide variety of shades but it results in damage to the keratin fibers by the use of oxidizing agents (in particular by repeated application or by combination with other hair treatments).

On the other hand, it is also known to dye keratin fibers and in particular human hair with dyeing compositions containing direct dyes. Conventional direct dyes are in particular the following: benzene nitrates, anthraquinones, nitropyridines, azos, xanthines, acridinies, azinies, and triarylmethane type or natural colorings.

For example, JP-A-2000-186018, JP-A-2006-342159 and WO 2010/032034 (JP-T-2012-502896) disclose a composition for dyeing hair, including a direct dye.

The hair coloration using direct dyes has advantages over the hair coloration using oxidative dyes: it has no allergic issue, no damage to the hair, and it gives vivid color visibility.

DISCLOSURE OF INVENTION

However, skin staining has been an inevitable drawback of the hair coloration performance using direct dyes. In addition to the skin staining, hair stiffness caused by the acidic condition for direct dyes is also an issue for the hair coloration with direct dyes.

An objective of the present invention is to provide a composition for keratin fibers, in particular for dyeing keratin fibers, which uses a direct dye, but can prevent or reduce skin staining by the direct dye on the skin such as scalp, preferably as well as the stiffness of the keratin fibers, while providing the keratin fibers with good cosmetic effects such as good coloring properties.

The above objective can be achieved by a composition for dyeing keratin fibers, comprising: (a) at least one direct dye;

(b) at least one aprotic polar solvent; and

(c) at least one sulfur-containing reducing agent.

The (a) direct dye may be selected from the group consisting of acidic direct dyes, basic direct dyes and neutral direct dyes.

The (a) direct dye may be selected from the group consisting of:

the diaryl anionic azo dyes of formula (II) or (IT):

in which formulae (II) and (IT):

R₇, Re, R9, R₁₀, R'7, R's, R'9 and R'io, which may be identical or different, represent a hydrogen atom or a group chosen from:

- alkyl;

alkoxy, alkylthio;

hydroxyl, mercapto;

nitro;

R°-C(X)-X'-, R°-X'-C(X)-, R°-X'-C(X)-X"- with R° representing a hydrogen atom or an alkyl or aryl group; X, X' and X", which may be identical or different, representing an oxygen or sulfur atom, or NR with R representing a hydrogen atom or an alkyl group; (0)₂S(0^")-, X^"1" with X^1" representing an organic or mineral cationic counter ion;

- R"-S(0)₂-, with R" representing a hydrogen atom or an alkyl, aryl, (di)(alkyl)amino or aryl(alkyl)amino group; preferably a phenylamino or phenyl group;

R"'-S(0)₂-X'- with R'" representing an alkyl or optionally substituted aryl group;

(di)(alkyl)arnino; aryl(alkyl)amino optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (0)₂S(0^")-, X⁺ and iv) alkoxy with X^"1";

optionally substituted heteroaryl; preferably a benzothiazolyl group;

cycloalkyl; especially cyclohexyl,

- Ar-N=N- with Ar representing an optionally substituted aryl group, preferably a phenyl optionally substituted with one or more alkyl, (0)₂S(0^")-, X^4" or phenylamino groups; or alternatively two contiguous groups R₇ with Rg or ¾ with R9 or R9 with Rio together form a fused benzo group A'; and R'₇ with R'g or R'g with R'9 or R'9 with R'io together form a fused benzo group B'; with A' and B' optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (0)₂S(0^")-, X*; iv) hydroxyl; v) mercapto; vi)

(di)(alkyl)amino; vii) R°-C(X)-X'-; viii) R°-X'-C(X)-; ix) R°-X'-C(X)-X"-; x) Ar-N=N- and xi) optionally substituted aryl(alkyl)amino;

W represents a sigma bond σ, an oxygen or sulfur atom, or a divalent radical i) -NR-, or ii) methylene -C(Ra)(Rb)- with Ra and R_b, which may be identical or different, representing a hydrogen atom or an aryl group, or alternatively Ra and R form, together with the carbon atom that bears them, a spiro cycloalkyl; preferably W represents a sulfur atom or Ra and R_b together form a cyclohexyl;

wherein formulae (II) and (ΙΓ) comprise at least one sulfonate (0)2S(0^")-, X*^" or phosphonate (0)P(0₂ ^") 2X⁺or carboxylate (0)C(0 , X* radical on one of the rings A, A', B, B' or C;

and

the anthraquinone dyes of formulae (III) and (III'):

in which formulae (III) and (ΠΓ):

R22, R23, R24, R25, R26 and R27, which may be identical or different, represent a hydrogen or halogen atom or a group chosen from:

alkyl;

hydroxyl, mercapto;

alkoxy, alkylthio;

- aryloxy or arylthio optionally substituted, preferably substituted with one or more groups chosen from alkyl and (0)₂S(0^")-, X* with X^ representing an organic or mineral cationic counter ion; aryl(alkyl)amino optionally substituted with one or more groups chosen from alkyl and

(di)(alkyl)amino;

(di)(¾ydroxyalkyl)amino;

- (OfcSCOy. X*;

Z' represents a hydrogen atom or a group NR₂₈R₂₉ vvith R₂₈ and R₂₉, which may be identical or different, representing a hydrogen atom or a group chosen from:

alkyl;

polyhydroxyalkyl such as hydroxyethyl;

- aryl optionally substituted with one or more groups, particularly i) alkyl such as methyl,

H-dodecyl, n-butyl; ii) (0)₂S(0^')-, *^"; iii) R°-C(X)-X'-, R°-X'-C(X)-, R°-X'-C(X)-X"-, preferably R° represents an alkyl group;

cycloakyl; especially cyclohexyl;

Z represents a group chosen from hydroxyl and NR'₂₈R'₂₉ with R'₂₈ and R'₂₉, which may be identical or different, representing the same atoms or groups as R₂₈ and R₂₉;

wherein formulae (ΠΙ) and (ΙΙΓ) comprise at least one sulfonate group (0)₂S(0^")-, X*.

The amount of the (a) direct dye in the composition according to the present invention may range from 0.001% to 5% by weight, preferably from 0.01% to 3% by weight, and more preferably from 0.05% to 2% by weight, relative to the total weight of the composition.

The (b) aprotic polar solvent may be selected from the group consisting of propylene carbonate, N-methylpyrrolidone, N-ethylpyrrolidone, dimethylsulfone, 2-propanone, dimethylsulfoxide, dirnethylformamide, ethyl acetate, dimethylacetarnide and mixtures thereof.

The amount of the (b) aprotic polar solvent in the composition according to the present invention may range from 1% to 50% by weight, preferably from 5% to 40% by weight, and more preferably from 10% to 30% by weight, relative to the total weight of the composition. The (c) sulfur-containing reducing agent may be selected from the group consisting of

2-mercapto-4-butanolide, glutathione, thioglycolic acid, 3-mercaptopropionic acid, thiolactic acid, L-cysteine, cysteamine, thioglycerol, L-cysteine methyl ester, L-cysteine ethyl ester,

mercaptosuccinic acid, glycerol monothioglyclate, N-acetyl-L-cysteine and mixtures thereof. The amount of the (c) sulfur-containing reducing agent in the composition according to the present invention may range from 0.1% to 20% by weight, preferably from 0.5% to 10% by weight, and more preferably from 1 to 5% by weight, relative to the total weight of the

composition. The composition according to the present invention may further comprise water.

The amount of the water in the composition according to the present invention may range from 10% to 80% by weight, preferably from 20% to 85% by weight, and more preferably from 30 to 70% by weight, relative to the total weight of the composition. The pH of the composition according to the present invention in this case may range from 3 to 7, preferably from 4 to 7 and more preferably from 5 to 7.

The composition according to the present invention may further comprise (d) at least one protein denaturant comprising at least one nitrogen atom.

The (d) protein denaturant comprising at least one nitrogen atom may be selected from the group consisting of urea, guanidine and its salts, thiourea, biuret, thiobiuret, ammonia,

monoethanolamine, tf emanolamine, and mixtures thereof. The amount of the (d) protein denaturant comprising at least one nitrogen atom in the composition according to the present invention may range from 0.1 to 20% by weight, preferably from 0.5 to 15% by weight, and more preferably from 1 to 10% by weight, relative to the total weight of the composition. It is preferable that the composition according to the present invention be obtained prior to use by mixing a first composition comprising (a) at least one direct dye, and a second composition comprising (b) at least one aprotic polar solvent and (c) at least one sulfur-containing reducing agent, preferably in a weight ratio of the first compositionrthe second composition ranges from 1 : 1 to 10 : 1 , more preferably from 1 : 1 to 7 : 1 , and even more preferably from 1 : 1 to 5 : 1.

The present invention also relates to a process for dyeing keratin fibers, comprising the step of applying the composition according to the present invention.

The present invention also relates to a kit for dyeing keratin fibers such as hair comprising a first composition comprising (a) at least one direct dye, and a second composition comprising (b) at least one aprotic polar solvent and (c) at least one sulfur-containing compound.

BEST MODE FOR CARRYING OUT THE INVENTION After diligent research, the inventors have discovered that it is possible to provide a composition for keratin fibers, in particular for dyeing keratin fibers, which includes a direct dye, but can prevent or reduce skin staining by the direct dye on the skin such as scalp, as well as the stiffness of the keratin fibers, while providing the keratin fibers with good cosmetic effects such as good coloring properties.

Thus, the composition according to the present invention comprises:

(a) at least one direct dye;

(b) at least one aprotic polar solvent; and

(c) at least one sulfur-containing reducing agent.

The composition according to the present invention is preferably a cosmetic composition for keratin fibers.

It is preferable that the composition according to the present invention further comprises (d) at least one protein denaturant comprising at least one nitrogen atom. Due to the presence of the (d) protein denaturant comprising at least one nitrogen atom, the composition according to the present invention can furthermore prevent or reduce the stiffness of the keratin fibers, without any conventional conditioning agent. Hereafter, each of the phases constituting the composition according to the present invention will be described in a detailed manner.

[Direct Dye] The composition according to the present invention includes at least one direct dye. Two or more direct dye may be used in combination. Thus, a single type of direct dye or a combination of different types of direct dyes may be used.

A direct dye means a colored substance which does not require the use of an oxidizing agent in order to develop its color.

The direct dye may be a natural direct dye or a synthetic direct dye.

The expression "natural direct dye" is understood to mean any dye or dye precursor that is naturally occurring and is produced by extraction (and optionally purification) from a plant matrix optionally in the presence of natural compounds such as ash or ammonia.

As natural direct dye, mention may be made of quinone dyes (such as lawsone and juglone), alizarin, purpurin, laccaic acid, camiinic acid, kermesic acid, purpurogallin, protocatechaldehyde, indigoids such as indigo, sorghum, isatin, betanin, curcuminoids (such as curcumin), spinulosin, various types of chlorophyll and chlorophyllin, hematoxylin, hematein, brazilein, brazilin, safflower dyes (such as carthamin), fiavonoids (such as rutin, quercetin, catechin, epicatechin, morin, apigenidin, and sandalwood), anthocyans (such as apigeninidin and apigenidin), carotenoids, tannins, orceins, santalins and cochineal carmine.

It is also possible to use extracts or decoctions containing natural direct dye(s), in particular henna-based extracts, curcuma longa extract, sorghum leaf-sheath extract, haematoxylon campechianum extract, green tea extract, pine bark extract, cocoa extract, and logwood extract. It is preferable that the natural direct dye be chosen from the group consisting of curcuminoids, santalins, chlorophyllin, haematoxylin, haematein, brazilein, brazilin, sorghum, laccaic acid, lawsone, juglone, alizarin, purpurin, carrninic acid, kermesic acid, purpurogallin,

protocatechaldehyde, indigoids, isatin, spinulosin, apigenidin, orcein, betanin, fiavonoids, anthocyans, and extracts or decoctions containing these compounds.

Alternatively, the natural direct dyes may be preferably chosen, for example, from hydroxylated quinones, indigoids, hydroxyflavones, santalins A and B, isatin and its derivatives, and brasilin and its hydroxylated derivative. The hydroxylated quinones are preferably benzoquinones, naphthoquinones, and mono- or polyhydroxylated anthraquinones which are optionally substituted with groups such as alkyl, alkoxy, alkenyl, chloro, phenyl, hydroxyalkyl and carboxyl.

The naphthoquinones are preferably lawsone, juglone, flaviolin, naphthazarin, naphthopurpurin, lapachol, plumbagin, chloroplumbagin, droserone, shikonin,

2- hydroxy-3-methyl-l,4-naphthoquinone, 3,5-dihydroxy-l,4-naphthoquinone,

2,5-dihydroxy-l,4-naphthoquinone, 2-methoxy-5-hydroxy-l,4-naphthoquinone and

3- methoxy-5-hydroxy- 1 ,4-naphthoquinone. The benzoquinones are preferably spinulosin, atromentin, aurentioglyocladin,

2,5-dihydroxy-6-methylbenzoquinone, 2-hydroxy-3-methyl-6-methoxybenzoquinone, 2,

5-dihydroxy-3,6-diphenylbenzoquinone, 2,3-dimethyl-5-hydroxy-6-methoxybenzoquinone and 2,5-dihydroxy-6-isopropylbenzoquinone. The anthraquinones are preferably alizarin, quinizarin, purpurin, carminic acid, chrysophanol, kermesic acid, rhein, aloe emodin, pseudopurpurin, quinizarincarboxylic acid, frangula emodin, 2-methylquinizarin, 1-hydroxyanthraquinone and 2-hydroxyanthraquinone.

The indigoids are preferably indigo, indirubin, isoindigo and Tyrian purple.

The hydroxyflavones are preferably quercetin and morin.

The expression "synthetic direct dye" is understood to mean any dye or dye precursor that is produced by chemical synthesis.

In terms of ionic nature, the synthetic direct dye may be selected from the group consisting of acidic (anionic) direct dyes, basic (cationic) direct dyes and neutral (noninic) direct dyes, which covers all possible types of direct dyes, such as so-called nitro dyes, HC dyes, azo, methine, carbonyl, azine, nitro(hetero)aryl types or tri(hetero)arylmethane direct dyes, porphyrins and phthalocyanines, alone or as mixtures. Acidic direct dyes have an anionic moiety in their chemical structure. Basic direct dyes have a cationic moiety in their chemical structure.

Neutral direct dyes are nonionic.

More particularly, the azo dyes comprise an -N=N- functional group, the two nitrogen atoms of which are not simultaneously involved in a ring. However, it is not ruled out for one of the two nitrogen atoms of the -N=N- sequence to be involved in a ring.

The dyes of the family of the methines are more particularly compounds comprising at least one sequence chosen from >C=C< and -N=C<, the two atoms of which are not simultaneously involved in a ring. However, it is specified that one of the nitrogen or carbon atoms of the sequences can be involved in a ring. More particularly, the dyes of this family result from compounds of the following types: true methine (comprising one or more abovementioned -C=C- sequences); azomethine (comprising at least one or more -C=N- sequences) with, for example, the azacarbocyanines and their isomers, the diazacarbocyanines and their isomers, the tetraaza- carbocyanines; mono- and diarylmethane; indoarnines (or diphenylamines); indophenols; indoanilines.

As regards the dyes of the family of the carbonyls, mention may be made, for example, of synthetic dyes chosen from acridone, benzoquinone, anthraquinone, naphthoquinone,

benzanthrone, anthranthrone, pyranthrone, pyrazolanthrone, pyrirnidinoanthrone, flavanthrone, indanthrone, flavone, (iso)violanthrone, isoindolinone, benzimidazolone, isoquinoli one, anthrapyridone, pyrazoloquinazolone, perinone, quinacridone, quinophthalone, naphthalimide, anthrapyrimidine, diketopyrrolopyrrole or coumarin dyes. As regards the dyes of the family of the cyclic azines, mention may in particular be made of azine, xanthene, thioxanthene, fluorindine, acridine, (di)oxazine, (di)thiazine or pyronine dyes.

The nitro(hetero)aromatic dyes are more particularly nitrobenzene or nitropyridine direct dyes. As regards the dyes of porphyrin or phthalocyanine type, use may be made of cationic or noncationic compounds optionally comprising one or more metals or metal ions, such as, for example, alkali and alkaline earth metals, zinc and silicon.

Mention may be made, as examples of synthetic direct dyes which are particularly suitable, of nitrobenzene dyes, azo, azomethine or methine direct dyes, azacarbocyanines, such as

tetraazacarbocyanines (tetraazapentamethines), quinone and in particular anthraquinone, naphthoquinone or benzoquinone direct dyes, or azine, xanthene, triarylmethane, indoarnine, phthalocyanine and porphyrin direct dyes, alone or as mixtures. More preferably still, these synthetic direct dyes are chosen from nitrobenzene dyes, azo, azomethine or methine direct dyes and tetraazacarbocyanines (tetraazapentamethines); alone or as mixtures.

Mention may be made, among the azo, azomethine, methine or tetraazapentamethine direct dyes which can be used according to the invention, of the cationic dyes described in Patent

Applications WO 95/15144, WO 95/01772 and EP 714 954; FR 2 189 006, FR 2 285 851, FR-2 140 205, EP 1 378 544 and EP 1 674 073.

Thus, mention may be made of the cationic direct dyes corresponding to the following formulae:

in which:

D represents a nitrogen atom or the -CH group,

Ri and R₂, which are identical or different, represent a hydrogen atom; a Q-C₄ alkyl radical which can be substituted by a -CN, -OH or -NH₂ radical or can form, with a carbon atom of the benzene ring, an optionally oxygen-comprising or nitrogen-comprising heterocycle which can be substituted by one or more Q-C₄ alkyl radicals; or a 4'-arninophenyl radical,

R₃ and R'₃, which are identical or different, represent a hydrogen atom, a halogen atom chosen from chlorine, bromine, iodine and fluorine, a cyano radical, a Q-C₄ alkyl radical, a Q-C₄ alkoxy radical or an acetyloxy radical,

X^" represents an anion, preferably chosen from chloride, methyl sulphate and acetate,

A represents a group chosen from the following structures:

in which R4 represents a CrC₄ alkyl radical which can be ub tituted by a hydroxyl radical;

in which:

R₅ represents a hydrogen atom, a Q-C4 alkoxy radical or a halogen atom, such as bromine, chlorine, iodine or fluorine,

¾ represents a hydrogen atom or a Ci-C₄ alkyl radical or forms, with a carbon atom in the benzene ring, a heterocycle which optionally comprises oxygen and/or is optionally substituted by one or more Ci-C₄ alkyl groups,

R₇ represents a hydrogen atom or a halogen atom, such as bromine, chlorine, iodine or fluorine, Di and D₂, which are identical or different, represent a nitrogen atom or the -CH group, m = 0 or 1 ,

X^" represents a cosmetically acceptable anion preferably chosen from chloride, methyl sulphate and acetate,

E represents a group chosen from the following structures:

in which R' represents a C1-C4 alkyl radical;

when m = 0 and when Ό_\ represents a nitrogen atom, then E can also denote a group with the following structure:

R'

N

/

N+

I

R'

in which R' represents a Q-C₄ alkyl radical.

The synthetic direct dye may be selected from fluorescent dyes. Two or more types of the fluorescent dye may be used in combination. The use of some fluorescent dyes may make it possible to obtain, on dark hair, colors which are more visible than with conventional hydrophilic or hydrophobic direct dyes. Furthermore, these fluorescent dyes, when applied to dark hair, may also make it possible to lighten the hair without damaging it. As used herein, the term "fluorescent dyes" is understood to mean fluorescent compounds and optical brighteners. In at least one embodiment, the fluorescent dye is soluble in the medium of the composition.

Fluorescent dyes are fluorescent compounds which absorb visible radiation, for example, wavelengths ranging from 400 to 800 nm, and which are capable of re-emitting light in the visible region at a higher wavelength. According to one embodiment, the fluorescent dyes useful for the present invention re-emit orange-colored fluorescent light. They exhibit, for instance, a maximum re-emission wavelength ranging from 500 to 700 nm.

Non-limiting examples of fluorescent dyes include compounds known in the art, for example, those described in Ullmann's Encyclopedia of Industrial Chemistry, Release 2004, 7th edition, "Fluorescent Dyes" chapter.

The optical brighteners of the present disclosure, also known under the name of "brighteners", or "fluorescent brighteners", or "fluorescent brightening agents" or "FWA", or "fluorescent whitening agents", or "whiteners", or "fluorescent whiteners", are colorless transparent compounds as they do not absorb in visible light but only in ultraviolet light (wavelengths ranging from 200 to 400 nanometers) and convert the energy absorbed into fluorescent light of higher wavelength emitted in the visible part of the spectrum, generally in the blue and/or green, that is to say in wavelengths ranging from 400 to 550 nanometers.

Optical brighteners are known in the art, for example, they are described in Ullmann's

Encyclopedia of Industrial Chemistry (2002), "Optical Brighteners" and Kirk-Othmer

Encyclopedia of Chemical Technology (1995): "Fluorescent Whitening Agents". The fluorescent dyes which can be used in the composition of the present disclosure include compounds known from the art, for example, those described in French Patent No. 2 830 189.

Soluble fluorescent compounds that may especially be mentioned include those belonging to the following families: naphthalimides, coumarins, xanthenes and in particular

xanthenodiquinolizines and azaxanthenes; naphtholactams; azlactones; oxazines; thiazines;

dioxazines; azo compounds; azomethines; methines; pyrazines; stilbenes; ketopyrroles; pyrenes.

If present, the fluorescent dyes are preferred, more particularly, those re-emitting orange-colored fluorescent light.

According to an embodiment, it is preferable that the (a) direct dye be selected from acidic direct dyes. The anionic direct dyes are commonly known as "acidic direct dyes" for their affinity with alkaline substances (see, for example, "Industrial Dyes, Chemistry, Properties, Application", Klaus Hunger Ed. Wiley- VCH Verlag GmbH & Co KGaA, Weinheim 2003). Anionic or acid dyes are known in the literature (see, for example, " Ullman 's Encyclopedia of Industrial Chemistry", Azo Dyes, 2005 Wiley- VCH Verlag GmbH & Co. KGaA, Weinheini 10.1002/14356007.a03 245, point 3.2; ibid, Textile Auxiliaries, 2002 Wiley- VCH Verlag GmbH & Co. KGaA, Weinheim 10.1002/14356007.a26 227 and "Ashford's Dictionary of Industrial Chemicals", Second Edition, p. 14-p. 39, 2001).

The term "anionic direct dyes" means any direct dye comprising in its structure at least one sulfonate group S0₃ ^" and/or at least one carboxylate group C(0)0^" and/or at least one phosphonate group Ρ(=0)ΟΌ^" and optionally one or more anionic groups G^" with G^", which may be identical or different, representing an anionic group chosen from alkoxide O^", thioalkoxide S^", phosphonate, carboxylate and thiocarboxylate: C(Q)Q'^~ with Q and Q', which may be identical or different, representing an oxygen or sulfur atom; preferably, G^" represents a carboxylate, i.e. Q and Q' represent an oxygen atom.

The preferred anionic dyes of formula of the invention are chosen from acidic nitro direct dyes, acidic azo dyes, acidic azine dyes, acidic triarylmethane dyes, acidic indoamine dyes, acidic anthraquinone dyes, anionic styryl dyes, and indigoids and acidic natural dyes; each of these dyes containing at least one sulfonate, phosphonate or carboxylate group bearing a cationic counterion X*, where X^1" represents an organic or mineral cationic counter ion preferably chosen from alkali and alkaline-earth metals, such as Na⁺ and K⁺

Preferred acid dyes may be chosen from the dyes below. The diaryl anionic azo dyes of formula (II) or (ΙΓ):

in which formulae (II) and (ΙΓ):

R₇, Rs, R9, Rio, R'7, R's, R'9 and R'io, which may be identical or different, represent a hydrogi atom or a group chosen from:

alkyl;

alkoxy, alkylthio;

hydroxyl, mercapto; nitro;

R°-C(X)-X'-, R°-X'-C(X)-, R°-X'-C(X)-X"- with R° representing a hydrogen atom or an alkyl or aryl group; X, X' and X", which may be identical or different, representing an oxygen or sulfur atom, or NR with R representing a hydrogen atom or an alkyl group; - (0) S(0^")-, X⁺ as defined previously;

(O)CO^"-, X^ as defined previously;

(0)P(0₂ ^~)-, 2X* as defined previously;

R"-S(0)₂-, with R" representing a hydrogen atom or an alkyl, aryl, (di)(alkyl)amino or aryl(alkyl)amino group; preferably a phenylamino or phenyl group;

- R'"-S(0)₂-X'- with R'" representing an alkyl or optionally substituted aryl group, X' as defined previously;

(di)(alkyl)amino;

aryl(alkyl)amino optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (0)₂S(0 , X^1" and iv) alkoxy with X^1";

- optionally substituted heteroaryl; preferably a benzothiazolyl group;

cycloalkyl; especially cyclohexyl,

Ar-N=N- with Ar representing an optionally substituted aryl group, preferably a phenyl optionally substituted with one or more alkyl, (0) S(0^")-, X⁺ or phenylamino groups; or alternatively two contiguous groups R₇ with ¾ or ¾ with R9 or R9 with Rio together form a fused benzo group A'; and R'7 with R's or R's with R'9 or R' with R'io together form a fused benzo group B'; with A' and B' optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (0)₂S(0^")-, X⁺; iv) hydroxyl; v) mercapto; vi) (di)(alkyl)amino; vii) R°-C(X)-X'-; viii) R°-X'-C(X)-; ix) R°-X'-C(X)-X"-; x) Ar-N=N- and xi) optionally substituted aryl(alkyl)amino; with X^4", R°, X, X', X" and Ar as defined previously;

W represents a sigma bond σ, an oxygen or sulfur atom, or a divalent radical i) -NR- with R as defined previously, or ii) methylene -C(Ra)(Rt>)- with R¾ and R_b, which may be identical or different, representing a hydrogen atom or an aryl group, or alternatively Ra and Rb form, together with the carbon atom that bears them, a spiro cycloalkyl; preferably W represents a sulfur atom or Ra and R_b together form a cyclohexyl;

it being understood that formulae (II) and (IT) comprise at least one sulfonate (0)₂S(0^")-, X* or phosphonate (0)P(0₂ ^") 2X* or carboxylate (O)C(O^')-, X⁺ radical on one of the rings A, A', B, B' or C with ^1" as defined previously. As examples of dyes of formula (II), mention may be made of Acid Red 1 , Acid Red 4, Acid Red 13, Acid Red 14, Acid Red 18, Acid Red 27, Acid Red 32, Acid Red 33, Acid Red 35, Acid Red 37, Acid Red 40, Acid Red 41 , Acid Red 42, Acid Red 44, Acid Red 68, Acid Red 73, Acid Red 135, Acid Red 138, Acid Red 184, Food Red 1, Food Red 13, Food Red 17, Acid Orange 6, Acid Orange 7, Acid Orange 10, Acid Orange 19, Acid Orange 20, Acid Orange 24, Acid Yellow 9, Acid Yellow 36, Acid Yellow 199, Food Yellow 3 ; Acid Violet 7, Acid Violet 14, Acid Blue 113, Acid Blue 117, Acid Black 1, Acid Brown 4, Acid Brown 20, Acid Black 26, Acid Black 52, Food Black 1, Food Black 2, Pigment Red 57;

and as examples of dyes of formula (ΙΓ), mention may be made of Acid Red 111, Acid Red 134, Acid yellow 38; The anthraquinone dyes of formulae (III) and (ΠΓ):

in which formulae (ΠΙ) and (ΠΓ):

alkyl;

hydroxyl, mercapto;

alkoxy, alkylthio;

aryloxy or arylthio optionally substituted, preferably substituted with one or more groups chosen from alkyl and (0)₂S(0^")-, X* with ^ as defined previously;

aryl(alkyl)amino optionally substituted with one or more groups chosen from alkyl and

(0)₂S(0^")-, with X^1" as defined previously;

(di)(alkyl)amino ;

(di)(hydroxyalkyl)amino;

- (0)2S(0^")-, X with X^4" as defined previously;

Z' represents a hydrogen atom or a group NR₂₈R₂9 with R₂₈ and R₂₉, which may be identical or different, representing a hydrogen atom or a group chosen from:

alkyl;

polyhydroxyalkyl such as hydroxyethyl;

H-dodecyl, n-butyl; ii) (0)₂S(0>, X⁺ with X as defined previously; iii) R°-C(X)-X'-,

R°-X'-C(X)-, R°-X'-C(X)-X"- with R°, X, X' and X" as defined previously, preferably

R° represents an alkyl group;

cycloakyl; especially cyclohexyl;

Z represents a group chosen from hydroxyl and N '2₈R'₂9 with R'₂₈ and R'29, which may be identical or different, representing the same atoms or groups as R₂₈ and R₂₉ as defined previously; it being understood that formulae (ΙΠ) and (ΠΓ) comprise at least one sulfonate group (0)₂S(0 , X* with X ^' as defined previously.

As examples of dyes of formula (ΙΠ), mention may be made of Acid Blue 25, Acid Blue 43, Acid Blue 62, Acid Blue 78, Acid Blue 129, Acid Blue 138, Acid Blue 140, Acid Blue 251, Acid Green 25, Acid Green 41 , Acid Violet 42, Acid Violet 43, Mordant Red 3; EXT Violet 2,

and as examples of dyes of formula (III'), mention may be made of Acid Black 48; The quinoline-based dyes of formula (IV):

in which formula (IV):

R6i represents a hydrogen or halogen atom or an alkyl group;

!½, I½ and R64, which may be identical or different, represent a hydrogen atom or a group (0)₂S(0^")-, ^1" with X* as defined previously;

or alternatively R with ¾₂, or Ra with R64, together form a benzo group optionally substituted with one or more groups (0)₂S(0^")-, * with X* as defined previously;

G represents an oxygen or sulfur atom or a group NRe with Re representing a hydrogen atom or an alkyl group; particularly G represents an oxygen atom;

it being understood that formula (IV) comprises at least one sulfonate group (0)₂S(0^")-, X^ with X as defined previously.

As examples of dyes of formula (IV), mention may be made of Acid Yellow 2, Acid Yellow 3 and Acid Yellow 5.

It is preferable that the direct dye be selected from acidic direct dye such as Acid Black 1 , Acid Violet 43 and Acid Orange 7.

The composition according to the present invention may contain the direct dye(s) in an amount of from 0.001% to 5% by weight, preferably from 0.01 to 3% by weight, and more preferably 0.05 to 2% by weight, relative to the total weight of the composition.

[Aprotic Polar Solvent]

The composition according to the present invention includes at least one aprotic polar solvent. Two or more aprotic polar solvent may be used in combination. Thus, a single type of aprotic polar solvent or a combination of different types of aprotic polar solvents may be used.

The term "aprotic polar solvent" means a polar solvent which does not contain acidic hydrogen and does not act as a hydrogen bond donor. As the aprotic polar solvent, an ether-based solvent such as diethyl ether, tetrahydrofuran, and dioxane; a ketone-based solvent such as 2-propanone; a sulfoxide-based solvent such as dimethylsulfoxide and diethylsulfoxide; an amide-based solvent such as N,N-dimethylformamide, N,N-diethylformamide, N,N-dimethylacetamide, N,N-diethylacetamide, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, or the like; an ester-based solvent such as ethyl acetate,

garnma-butyrolactone or the like; an ether ester-based solvent such as propylene glycol

monomethyl ether acetate, ethylene glycol monomethyl ether acetate, or the like;

hexamethylphosphoamide and the like; acetonitrile and the like, may be preferably used.

As the aprotic polar solvent, mention may be made of, alkylene carbonate of the following chemical formula ( 1 ) :

wherein

R" represents a hydrogen atom, a (Ci-C₈) alkyl group, a (Q-C4) hydroxyalkyl group.

As the alkylene carbonate, mention may be made of ethylene carbonate (R"=H), propylene carbonate (R" ¾), glycerol carbonate (R"=CH₂OH), or else butylene carbonate (R"=CH₂CH₃). Among the alkylene carbonates, propylene carbonate is preferred.

It may be preferable that the (b) aprotic polar solvent be selected from the group consisting of propylene carbonate, N-methylpyrrolidone, N-ethylpyrrolidone, dimethylsulfone, 2-propanone, dimethylsulfoxide, dimethylformamide, ethyl acetate, dimethylacetamide and mixtures thereof.

The composition according to the present invention may contain the aprotic polar solvent(s) in an amount of from 1% to 50% by weight, preferably from 5 to 40% by weight, and more preferably 10 to 30% by weight, relative to the total weight of the composition.

[Sulfur-Containing Reducing Agent]

The composition according to the present invention includes at least one sulfur-containing reducing agent. Two or more sulfur-containing reducing agents may be used in combination. Thus, a single type of sulf ir-contairiing reducing agent or a combination of different types of sulfur-containing reducing agents may be used.

The term "sulfur-containing reducing agent" means a reducing agent with at least one sulfur atom. It is preferable that a thiol-based reducing agent be used as the sulf ir-containing reducing agent.

The thiol-based reducing agent may preferably be chosen from the group consisting of

thioglycolic acid and derivatives thereof, in particular esters thereof such as glycerol or glycol monothioglycolate; dithioglycolic acid and derivatives thereof in particular esters thereof such as glycerol or glycol dithioglycolate; thiolactic acid and derivatives thereof, in particular esters thereof such as glycerol monothiolactate; 3-mercaptopropionic acid and derivatives thereof, in particular esters thereof such as glycerol 3-mercaptopropionate and ethyleneglycol 3-mercaptopropionate; cysteamine and derivatives thereof, in particular C_1-4 acyl derivatives thereof such as N-acetylcysteamine and N-propionylcysteamine; thioglycerol, for example mono-thioglycerol and derivatives thereof, in particular esters; cysteine and derivatives thereof, in particular esters such as N-acetylcysteine, N-alkanoylcysteine and cysteine alkyl esters;

glutathione in the reduced form; mercaptosuccinic acid; and salts thereof.

As the above salts, mention may be made of, for example, ammonium salts; primary-, secondary- or tertiary-arnine salts; alkaline metal salts; and, alkaline earth metal salts. As the primary-, secondary- or tertiaiy-arnine, for example, monoemanolamine, di-isopropanolamine or triethanolamine, respectively, may be mentioned.

Other suitable examples of the thiol-based reducing agent that may be used in the composition according to the present invention include, but are not limited to, sugar N-mercapto alkyl amides, such as N-(mercapto-2-ethyl)gluconamide, β-mercaptopropionic acid and derivatives thereof, thiomalic acid, pantheteine, N-(mercaptoalkyl)o-hydroxyalkyl amides, such as those described in European Patent Application No. 0 354 835 andN-mono- or N,N-dialkylmercapto 4-butyramides, such as those described in European Patent Application No. 0 368 763, aminomercaptoalkyl amides, such as those described in European Patent Application No. 0 432 000 and

alkylaminomercaptoalkylamides, such as those described in European Patent Application No. 0 514 282, (2/3) hydroxy-2 propyl tbioglycolate and, hydroxy-2 methyl- 1 ethyl thioglycolate-based mixture (67/33) described in French Patent Application No. 2 679 448.

The thiol-based reducing agent may be a compound represented by the following chemical formula (2):

Y

wherein

X is a structure selected from the group consisting of -0-, -S-, -NH- and -NR¹-;

R¹ is an alkyl group of 1 to 6 carbon atoms;

R is a hydrogen atom or an alkyl group of 1 to 6 carbon atoms;

Y is an oxygen atom or a sulfur atom; and

R is a divalent organic residue optionally having a mercapto group.

X is preferably -0-, -NH-, -NCH₃- or -S- in view of preparation of a perm solution, in which case the compound shows relatively high solubility in the perm aqueous solution.

Y is an oxygen atom or a sulfur atom, and is more preferably an oxygen atom in view of industrial availability and handling properties.

R² may be a hydrogen atom, a methyl group, an ethyl group or a propyl group, and is preferably a hydrogen atom, a methyl group or an ethyl group.

R is a divalent organic residue optionally having a mercapto (-SH) group. R is not particularly limited as long as it is a divalent organic group, and is preferably an alkylene group. The main chain of the alkylene group preferably has 2 to 6 carbon atoms. The divalent organic residue may have a branch or a side chain. Examples of the side chains include alkyl groups and alkenyl groups.

If R is substituted with a mercapto group, one or more mercapto groups may be present.

Preferable examples of R include ethylene and propylene groups because of easy industrial availability.

Specific examples of the compounds represented by the above chemical formula (2) include 2-mercapto-3-propiolactone, 2-mercapto-2-methyl-3-propiolactone,

2-mercapto-3-methyl-3-propiolactone, 2-mercapto-3-ethyl-3-propiolactone,

2-mercapto-2,3-dimethyl-3-propiolactone, 2-mercapto-3-propiolactam,

2-mercapto-2-rriethyl-3 -propiolactam, 2-mercapto-3 -methyl-3 -propiolactam,

2-mercapto-3-ethyl-3-propiolactam, 2-mercapto-2,3-dimethyl-3-propiolactam,

2-mercapto-3-propiothiolactone, 2-mercapto-2-methyl-3-propiothiolactone,

2-mercapto-3-methyl-3-propiothiolactone, 2-mercapto-3-ethyl-3-propiothiolactone,

2-mercapto-2,3-dimethyl-3-propiothiolactone, 2-mercapto-4-butyrolactone (another name: 2-mercapto-4-butanolide), 2-mercapto-2-memyl-4,4-dimethyl-4-butyrolactone,

2-mercapto-3-(2-propenyl)-4-butyrolactone, 2-mercapto-4-methyl-4-butyrolactone,

2-mercapto-2-methyl-4-butyrolactone, 2-mercapto-3-methyl-4-butyrolactone,

2-mercapto-4-methyl-4-butyrolactone, 2-mercapto-3,4-dimethyl-4-butyrolactone,

2-mercapto-2-ethyl-4-butyrolactone, 2-mercapto-3-ethyl-4-butyrolactone,

2-mercapto-4-ethyl-4-butyrolactone, 2-mercapto-4-butyrothiolactone,

2-mercapto-2-methyl-4-butyrothiolactone, 2-mercapto-3 -methyl-4-butyrothiolactone,

2-mercapto-4-methyl-4-butyrothiolactone, 2-mercapto-3 ,4-dimethyl-4-butyrothiolactone, 2-mercapto-2-ethyl-4-butyrothiolactone, 2-mercapto-3 -ethyl-4-butyrothiolactone,

2-mercapto-4-ethyl-4-butyrothiolactone, 2-mercapto-4-butyrolactam,

2-mercapto-2-methyl-4-butyrolactam, 2-mercapto-3-methyl-4-butyrolactam,

2-mercapto-4-methyl-4-butyrolactam, 2-mercapto-3,4-dimethyl-4-butyrolactam,

2-mercapto-2-ethyl-4-butyrolactam, 2-mercapto-3-ethyl-4-butyrolactam,

2-mercapto-4-ethyl-4-butyrolactam, 2-mercapto-5-valerolactone,

2-mercapto-2-methyl-5-valerolactone, 2-mercapto-3-methyl-5-valerolactone,

2-mercapto-4-methyl-5-valerolactone, 2-mercapto-5-methyl-5-valerolactone,

2-mercapto-2-ethyl-5-valerolactone, 2-mercapto-3-ethyl-5-valerolactone,

2-mercapto-4-ethyl-5-valerolactone, 2-mercapto-5-ethyl-5-valerolactone,

2-mercapto-5-valerolactam, 2-mercapto-2-methyl-5-valerolactam,

2-mercapto-3-methyl-5-valerolactam, 2-mercapto-4-methyl-5-valerolactam,

2-mercapto-5-methyl-5-valerolactam, 2-mercapto-2-ethyl-5-valerolactam,

2-mercapto-3-ethyl-5-valerolactam, 2-mercapto-4-ethyl-5-valerolactam,

2-mercapto-5-ethyl-5-valerolactam, 2-mercapto-5-valerothiolactone, 2-mercapto-2-methyl-5-valerothiolactone, 2-mercapto-3-methyl-5-valerothiolactone, 2-mercapto-4-methyl-5-valerothiolactone, 2-mercapto-5-methyl-5-valerothiolactone,

2-mercapto-2-ethyl-5-valerothiolactone, 2-mercapto-3-ethyl-5-valerothiolactone,

2-mercapto-4-ethyl-5-valerothiolactone, 2-mercapto-5-ethyl-5-valerothiolactone,

2-mercapto-6-hexanolactone, 2-mercapto-2-methyl-6-hexanolactone,

2-mercapto-3-methyl-6-hexanolactone, 2-mercapto-4-methyl-6-hexanolactone,

2-mercapto-5-methyl-6-hexanolactone, 2-mercapto-6-methyl-6-hexanolactone,

2-niercapto-6-hexanolactam, 2-mercapto-2-methyl-6-hexanolactam,

2-mercapto-3-methyl-6-hexanolactam, 2-mercapto-4-methyl-6-hexanolactam,

2-mercapto-5-methyl-6-hexanolactam, 2-mercapto-6-methyl-6-hexanolactam,

2-mercapto-6-hexanothiolactone, 2-mercapto-2-methyl-6-hexanothiolactone,

2-mercapto-3-methyl-6-hexanothiolactone, 2-mercapto-4-methyl-6-hexanothiolactone,

2-mercapto-5-methyl-6-hexanothiolactone, 2-mercapto-6-methyl-6-hexanothiolactone,

2-mercapto-7-heptanolactone, 2-mercapto-7-heptanothiolactone, 2-mercapto-7-heptanolactam, 2-mercapto-8-octanolactone, 2-mercapto-8-octanothiolactone, 2-mereapto-8-octanolaetam, 2-mercapto-9-nonalactone, 2-mercapto-9-nonathiolactone, 2-mercapto-9-nonalactam, and N-methyl or N-ethyl derivatives of these lactams.

Of these, 2-mercapto-4-butyrolactone (another name: 2-mercapto-4-butanolide),

2-mercapto-4-butyrothiolactone, 2-mercapto-4-butyrolactam,

N-methyl-2-mercapto-4-butyrolactam, N-ethyl-2-mercapto-4-butyrolactam,

N-(2-methoxy)ethyl-2-mercapto-4-butyrolactam, N-(2-ethoxy)ethyl-2-mercapto-4-butyrolactam, 2-mercapto-4-methyl-4-butyrolactone, 2-mercapto-4-ethyl-4-butyrolactone,

2-mercapto-5-valerolactone, 2-mercapto-5-valerolactam, N-methyl-2-mercapto-5-valerolactam, N-ethyl-2-mercapto-5-valerolactam, N-(2-methoxy)ethyl-2-mercapto-5-valerolactam,

N-(2-ethoxy)ethyl-2-mercapto-5-valerolactam and 2-mercapto-6-hexanolactam are preferable in view of penning performance and industrial production. The permanent waving agent contains at least one such mercapto compound. These compounds may be produced by known methods. For example, such compounds can be synthesized by halogenating lactone compounds or lactam compounds followed by introduction of mercapto groups.

Mercaptolactones and mercaptothiolactones may be synthesized by a series of steps in which commercially available lactones or thiolactones are halogenated in accordance with a method described in J. Am. Chem. Soc. 1945, 67, 2218-2220, and the synthesized halides or commercially available halides are produced into objective lactone derivatives by a method described in Ann. 1960, 639, 146-56. Mercaptolactams may be synthesized by a series of steps in which halides are synthesized by a method described in J. Am. Chem. Soc. 1958, 80, 6233-6237, and the resultant halides are synthesized into objective lactam derivatives by a method described in Ann. 1960, 639, 146-56, similarly to the production of lactones. It may be preferable that the (c) sulftir-containing reducing agent be selected from the group consisting of 2-mercapto-4-butanolide, glutathione, thioglycolic acid, 3-mercaptopropionic acid, thiolactic acid, L-cysteine, cysteamine, thioglycerol, L-cysteine methyl ester, L-cysteine ethyl ester, mercaptosuccinic acid, glycerol monothioglyclate, N-acetyl-L-cysteine and mixtures thereof.

The composition according to the present invention may contain the sulfur-contaiiiing reducing agent in the composition according to the present invention may range from 0.1% to 20% by weight, preferably from 0.5% to 10% by weight, and more preferably from 1 to 5% by weight, relative to the total weight of the composition.

[Protein denaturant comprising at least one nitrogen atom]

It is preferable that the composition according to the present invention further comprise (d) at least one protein denaturant comprising at least one nitrogen atom. Two or more protein denaturants comprising at least one nitrogen atom may be used i combination. Thus, a single type or a combination of different types may be used.

The term "protein denaturant" means a substance which changes 3D protein conformation, but does not cleave the covalent bonds or amide bonds, nor collapse primary protein structure.

It is preferable that the protein denaturant comprising at least one nitrogen atom is not a polymer, but a low molecular weight compound.

As examples of the protein denaturant comprising at least one nitrogen atom, mention may be made of ammonia and organic amines.

In some embodiments, the organic amine may comprise a primary, secondary, or tertiary amine function, and at least one linear or branched Q-Q alkyl group bearing at least one hydroxyl radical. Organic amines may be, in some embodiments, chosen from alkanolamines such as mono-, di- or trialkanolamines, comprising one to three identical or different C₁-C₄ hydroxyalkyl radicals.

Among the compounds of this type that may be mentioned, in a nonlimiting manner, are monoethanolamine, diemanolamine, triemanolamine, monoisopropanolamine,

diisopropanolamine, N-dimemylanimoemanolamine, 2-amino-2-methyl- 1 -propanol,

triiso-propanolamine, 2-arnino-2-methyl- 1 ,3 -propanediol, 3-amino- 1 ,2-propanediol,

3-oimemylamino-l,2-propanediol and tris(¾ydroxymethylamino)methane.

In some embodiments, the organic amines having the following chemical formula (3):

^ N - W- N

R^y (3)

in which

W is a C]-C₆ alkylene residue optionally substituted with a hydroxyl group or a Cj-C₆ alkyl radical;

Rx, Ry, Rz and Rt, which may be identical or different, represent a hydrogen atom or a -C alkyl, Ci-C₆ hydroxyalkyl or C_\-Ce aminoalkyl radical, may also be suitable for use. Examples of such amines that may be mentioned include, but are not limited to,

1,3-diaminopropane, l,3-diamino-2-propanol, spermine, and spermidine.

According to some embodiments, the protein denaturant comprising at least one nitrogen atom is chosen from amino acids.

The amino acids that may be used are of natural or synthetic origin, in L, D or racemic form, and comprise at least one acid function chosen from carboxylic acid, sulfonic acid, phosphonic acid, and phosphoric acid functions. The amino acids may be in their neutral or ionic form. As amino acids, mention, in a nonlimiting manner, may be made of aspartic acid, glutamic acid, alanine, arginine, orruthine, citrulline, asparagine, carnitine, cysteine, glutamine, lysine, histidine, lysine, isoleucine, leucine, methionine, N-phenylalanine, proline, serine, taurine, threonine, tryptophan, tyrosine, and valine. In some embodiments, the amino acids may be chosen from basic amino acids comprising an additional amine function optionally included in a ring or in a ureido function.

Such basic amino acids may be chosen, in some embodiments, from those corresponding to the following chemical formula (4):

wherein

R denotes a group chosen from: (CH₂)₂NH₂; -(CH₂)NHCONH²; and

In some embodiments, the compounds corresponding to the above chemical formula are histidine, lysine, arginine, ornithine, and citrulline.

In some embodiments, the protein denaturant comprising at least one nitrogen atom is chosen from organic amines of heterocyclic type. Besides histidine that has already been mentioned in the amino acids, mention, in a nonlimiting manner, may be made of pyridine, piperidine, imidazole, triazole, tetrazole, and benzimidazole.

In some embodiments, the protein denaturant comprising at least one nitrogen atom is chosen from amino acid dipeptides. As amino acid dipeptides, mention, in a nonlimiting manner, may be made of carnosine, anserine, and baleine.

In some embodiments, the protein denaturant comprising at least one nitrogen atom is chosen from compounds comprising a guanidine function. Exemplary protein denaturants comprising at least one nitrogen atom include, but are not limited to, guanidine, arginine, creatine, creatinine, 1,1-dimethylguanidine, 1,1-diethylguanidine, glycocyamine, metformin, agmatine,

N-amidinoalanine, 3-guanidinopropionic acid, 4-guanidinobutyric acid, and

2-([ammo(mimo)methyl]arnino)ethane- 1 -sulfonic acid. In some embodiments, the protein denaturants comprising at least one nitrogen atom are chosen from alkanolarnines, basic amino acids, compounds comprising a guanidine function, and mixtures thereof.

In some embodiments, the protein denaturants comprising at least one nitrogen atom are chosen from urea and its derivatives such as N-(2-hydroxyethyi)urea, biuret and its derivatives, and mixtures thereof.

It may be preferable that the (d) protein denaturant comprising at least one nitrogen atom be selected from the group consisting of urea, guanidine and its salts, thiourea, biuret, thiobiuret, ammonia, monoemanolamine, rriemanolamine, and mixtures thereof.

The amount of the protein denaturant comprising at least one nitrogen atom in the composition according to the present invention may range from 0.1 to 20% by weight, preferably from 0.5 to 15% by weight, and more preferably from 1 to 10% by weight, relative to the total weight of the composition.

[Other Ingredient]

The composition according to the present invention may further comprise water.

The pH of the composition according to the present invention may be adjusted to the desired value using acidifying or basifying agents commonly used in dyeing keratinous fibers or else using conventional buffer systems. Among the acidifying agents, mention may be made, by way of example, of mineral or organic acids such as hydrochloric acid, ortho-phosphoric acid, sulfuric acid, carboxylic acids such as acetic acid, tartaric acid, citric acid, lactic acid and sulfonic acids.

Among the basifying agents, mention may be made, by way of example, of ammonium hydroxide, alkali metal carbonates, alkanolarnines such as mono-, di- and triethanolamines and also their derivatives, sodium or potassium hydroxide and compounds of formula below:

R1 R3

\ /

N-R-N

/ \

R2 R4

wherein

R denotes an alkylene such as propylene optionally substituted by a hydroxyl or a Q-C₄ alkyl radical, and R_1; R₂, R₃ and R4 independently denote a hydrogen atom, an alkyl radical or a Q-C₄ hydroxyalkyl radical, which may be exemplified by 1,3-propanediarnine and derivatives thereof. Arginine, urea and monoemanolamine are preferable. They can also function as the protein denaturant.

The composition according to the present invention may comprise at least one organic solvent. The organic solvent is preferably water-miscible. As the organic solvent, there may be mentioned, for example, Ci-C₄ alkanols, such as ethanol and isopropanol; polyols and polyol ethers such as glycerol, 2-butoxyethanol, propylene glycol, monomethyl ether of propylene glycol, monoethyl ether and monomethyl ether of diethylene glycol; and aromatic alcohols such as benzyl alcohol and phenoxyethanol; analogous products; and mixtures thereof.

The organic solvents may be present in an amount ranging from 0.01 to 15% by weight, preferably from 0.1 to 10% by weight, and more preferably from 1 to 5% by weight, relative to the total weight of the composition.

The composition according to the present invention may comprise at least one thickening agent. The thickening agent may be selected from organic and inorganic thickeners. The organic thickeners may be chosen at least one of:

(i) associative thickeners;

(ii) crosslinked acrylic acid homopolymers;

(iii) crosslinked copolymers of (meth)acrylic acid and of (Q-C^alkyl acrylate;

(iv) nonionic homopolymers and copolymers comprising at least one of ethylenically

unsaturated ester monomers and ethylenically unsaturated amide monomers;

(v) ammonium acrylate homopolymers and copolymers of ammonium acrylate and of

acrylamide;

(vi) polysaccharides such as cellulose and its derivatives; and

(vii) C₁₂-C₃₀ fatty alcohols.

The thickening agent is preferably selected from polysaccharides such as starch, xanthan gum, and hydroxyethylcellulose.

As used herein, the expression "associative thickener" means an amphiphihc thickener comprising both hydrophilic units and hydrophobic units, for example, comprising at least one C₈-C₃o fatty chain and at least one hydrophilic unit.

The viscosity of the composition according to the present invention is not particularly limited. The viscosity can be measured at 25 °C with viscosimeters or rheometers preferably with coneplan geometry. Preferably, the viscosity of the composition according to the present invention can range, for example, from 1 to 2000 Pa.s, and preferably from 1 to 1000 Pa.s at 25 °C and Is^"1.

The thickening agent may be present in an amount ranging from 0.001 to 10% by weight, and preferably from 0.01 to 10% by weight, such as from 0.1 to 5% by weight, relative to the total weight of the composition.

The compositions used for the present invention may also contain various adjuvants

conventionally used in compositions for dyeing hair, such as anionic, non-ionic, cationic, amphoteric or zwitterionic polymers, or mixtures thereof, antioxidants, penetrating agents, sequestering agents, fragrances, buffers, dispersing agents, conditioning agents, film-fonning agents, ceramides, preservatives and opacifying agents.

The form of the composition according to the present invention is not particularly limited, as long as it is water-based, and may take various forms such as an emulsion, an aqueous gel, an aqueous solution, or the like.

[Preparation]

The composition can be prepared by mixing (a) at least one direct dye; (b) at least one aprotic polar solvent; and (c) at least one sulfur-containing reducing agent, as essential ingredients, as well as optional ingredient(s) as explained above.

The method and means to mix the above essential and optional ingredients are not limited. Any conventional method and means can be used to mix the above essential and optional ingredients to prepare the composition according to the present invention.

The composition according to the present invention is preferably a ready-to-use composition.

For the purposes of the present invention, the expression "ready-to-use composition" is defined herein as a composition to be applied immediately to keratin fibers such as hair. Said

"ready-to-use composition" may be stored in unmodified form before use, or may result from the extemporaneous mixing of two or more separate compositions. In one embodiment, one of the separate compositions may comprise (a) at least one direct dye, and another of the separate compositions may comprise (b) at least one aprotic polar solvent and (c) at least one

sdfur-containing reducing agent. In this embodiment, it is preferable that the composition according to the present invention be obtained prior to use by mixing a first composition comprising (a) at least one direct dye, and a second composition comprising (b) at least one aprotic polar solvent and (c) at least one sulfur-containing reducing agent, preferably in a weight ratio of the first compositio the second composition ranges from 1 :1 to 10:1, more preferably from 1:1 to 7:1, and even more preferably from 1:1 to 5:1.

[Process]

The present invention also relates to a process using the composition according to the present invention. The process according to the present invention preferably is intended for dyeing keratin fibers such as hair. Thus, the present invention relates to a process for dyeing keratin fibers, comprising the step of applying the composition according to the present invention.

The keratin fibers to which the composition according to the present invention has been applied can be left for an appropriate time which is required to treat the keratin fibers. The time length for the treatment is not limited, but it may be from 1 minute to 1 hours, preferably 1 minute to 30 minutes, and more preferably 1 minute to 15 minutes. For example, the time for dyeing the keratin fibers may be from 1 to 20 minutes, preferably 5 to 15 minutes.

The keratin fibers may be treated at a room temperature. Alternatively, the keratin fibers can be heated at 25C to 65°C, preferably 30°C to 60 °C, more preferably35 °C to 55°C, more preferably 40 °C to 50 °C, during the step of applying the composition according to the present invention to the keratin fibers, and/or the step of leaving the keratin fibers to which the composition according to the present invention has been applied. The keratin fibers may be rinsed after the step of applying the composition according to the keratin fibers onto the keratin fibers and/or after the step of leaving the keratin fibers to which the composition according to the present invention has been applied.

The present invention may also relate to the use of the composition according to the present invention for dyeing keratin fibers such as hair.

The present invention may also relate to a kit for dyeing keratin fibers such as hair, comprising: a first composition comprising (a) at least one direct dye, and

a second composition comprising (b) at least one aprotic polar solvent and (c) at least one sulfur-containing reducing agent.

EXAMPLES

The present invention will be described in a more detailed manner by way of examples.

However, these examples should not be construed as limiting the scope of the present invention. Examples 1-14 and Comparative Examples 1-9

[Preparation]

Each of the first and second agents according to Examples 1-14 (Ex. 1 to Ex. 14) and Comparative Examples 1-9 (Comp. Ex. 1 to Comp. Ex. 9) was respectively prepared by mixing the ingredients shown in Tables 1-3 at room temperature, and were poured into transparent vessels with the same volume. The numerical values for the amounts of the ingredients are all based on "% by weight" as active raw materials.

[Evaluation of Color Difference]

After homogeneously mixing the first and second agents using a brush in a weight ratio shown in Tables 1-3, the composition thus obtained was evenly applied onto lg of tress of 90% gray human natural hair. The tress was then left for 15 minutes at 40°C, followed by washing with water, shampooing, rinsing once and drying the tress. The difference in color of the tress before and after the above dyeing process was evaluated by using Minolta CM-580. ΔΕ (between the color of the undyed original tress and the color of the dyed tress under L a b system) was calculated. Evaluation was carried out in accordance with the following criteria.

Large ΔΕ value indicates good dyeing performance.

A: ΔΕ value greater than 45.

B : ΔΕ value between 40 to 45.

C: ΔΕ value below 40.

The results are shown in Tables 1-3. [Evaluation of Skin Staining] The skin staining of the composition was subjected to the sensory evaluation by 10 experts.

After homogeneously mixing the first and second agents using a brush in a weight ratio shown in Tables 1 -3, the composition thus obtained was applied onto the surface of a forearm of 10 human experts. The. applied surface was left for 15 minutes at room temperature, followed by thoroughly washing out the composition with water, and drying the surface. Evaluation was carried out in accordance with the following criteria.

A: At least 80% of 10 experts recognized skin staining to be absolutely unnoticeable.

B: At least 50% but less than 80% of 10 experts recognized skin staining to be absolutely unnoticeable.

C: At least 20% but less than 50% of 10 experts recognized skin staining to be absolutely unnoticeable.

D: Less than 20% of 10 experts recognized skin staining to be absolutely unnoticeable.

The results are shown in Tables 1-3. Table 1

Spiera : 2-Mercapto-4-Butanolide marketed by Showa Denko, Japan

Table 2

Spiera : 2-Mercapto-4-Butanolide marketed by Showa Denko, Japan

Table 3

Table 3

(continued)

Spiera : 2-Mercapto-4-Butanolide marketed by Showa Denko, Japan

It can be recognized from the experimental results shown in Tables 1 -3 that a combination of (b) at least one aprotic polar solvent and (c) at least one sulfur-containing reducing agent is necessary to provide a composition for keratin fibers, in particular for dyeing keratin fibers, which uses the (a) direct dye, but can prevent or reduce skin staining by the (a) direct dye on the skin such as scalp, while providing good cosmetic effects such as good coloring properties.

[Evaluation of Hair Smoothness]

The smoothness of the dyed hair was subjected to the sensory evaluation by 5 panels. The dyed hair tress used in [Evaluation of Color Difference] was scored in accordance with the following criteria. 1 : Hair was not smooth at all

2: Hair was not smooth

3: Hair was medium

4: Hair is smooth

5: Hair is very smooth

The score was then averaged. The results are shown in Table 4.

Table 4

It can be recognized from the experimental results shown in Table 4 that, the composition according to the present invention can also enhance the smoothness of the keratin fibers (i.e., the composition according to the present invention can prevent or reduce the stiffness of the keratin fibers), and that when the (d) at least one protein denaturant comprising at least one nitrogen atom is included, the composition according to the present invention can furthermore enhance the smoothness of the keratin fibers, without any conventional conditioning agent.

Claims

A composition for dyeing keratin fibers, comprising:

(a) at least one direct dye;

(b) at least one aprotic polar solvent; and

(c) at least one sulfur-containing reducing agent.

The composition according to Claim 1 , wherein the (a) direct dye is selected from the group consisting of acidic direct dyes, basic direct dyes and neutral direct dyes.

The composition according to Claim 1, wherein the (a) direct dye is selected from the group consisting of:

the diaryl anionic azo dyes of formula (II) or (ΙΓ):

in which formulae (II) and (ΙΓ):

R₇, Re, R9, R₁₀, R'7, R'8, R'9 and R'io, which may be identical or different, represent a hydrogen atom or a group chosen from:

alkyl;

alkoxy, alkylthio;

hydroxy 1, mercapto;

nitro;

R°-C(X)-X'-, R°-X'-C(X)-, R°-X'-C(X)-X"- with R° representing a hydrogen atom or an alkyl or aryl group; X, X' and X", which may be identical or different, representing an oxygen or sulfur atom, or NR with R representing a hydrogen atom or an alkyl group;

(0)₂S(0^")-, X⁺ with X⁺ representing an organic or mineral cationic counter ion;

(0)CO^'-, X⁺;

(0)P(0₂ , 2X⁺;

R"-S(0)₂-, with R" representing a hydrogen atom or an alkyl, aryl,

(di)(alkyl)amino or aryl(alkyl)amino group; preferably a phenylamino or phenyl group;

R"'-S(0)₂-X'- with R'" representing an alkyl or optionally substituted aryl group; (di)(alkyl)amino;

aryl(alkyl)amino optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (0)₂S(0^")-, X⁺ and iv) alkoxy with X⁺;

optionally substituted heteroaryl; preferably a benzothiazolyl group;

cycloalkyl; especially cyclohexyl,

Ar-N=N- with Ar representing an optionally substituted aryl group, preferably a phenyl optionally substituted with one or more alkyl, (0)₂S(0^")-, X⁺ or phenylamino groups;

or alternatively two contiguous groups R₇ with R_¾ or ¾ with R9 or R9 with Rto together form a fused benzo group A'; and R'₇ with R'₈ or R'₈ with R'9 or R'9 with R'10 together form a fused benzo group B' ; with A' and B' optionally substituted with one or more groups chosen from i) nitro; ii) nitroso; iii) (0)₂S(0^")-, X⁺; iv) hydroxyl; v) mercapto; vi) (di)(alkyl)amino; vii) R°-C(X)-X'-; viii) R°-X'-C(X)-; ix) R°-X'-C(X)-X"-; x) Ar-N=N- and xi) optionally substituted aryl(alkyl)amino;

W represents a sigma bond σ, an oxygen or sulfur atom, or a divalent radical i) -NR-, or ii) methylene -C(R_a)(Rt_>)- with R_a and Rb, which may be identical or different, representing a hydrogen atom or an aryl group, or alternatively R_a and R_b form, together with the carbon atom that bears them, a spiro cycloalkyl; preferably W represents a sulfur atom or R_a and Rb together form a cyclohexyl;

wherein formulae (II) and (ΙΓ) comprise at least one sulfonate (0)₂S(0^")-, X⁺ or phosphonate (0)P(0₂ ^") 2X⁺ or carboxylate (O)C(O^')-, X⁺ radical on one of the rings A, A, B, B' or C;

and

the anthraquinone dyes of formulae (III) and (ΙΙΓ) :

in which formulae (III) and (III'):

R22, R23, R24, R25, R26 and R₂₇, which may be identical or different, represent a hydrogen or halogen atom or a group chosen from:

alkyl;

hydroxyl, mercapto;

alkoxy, alkylthio;

aryloxy or arylthio optionally substituted, preferably substituted with one or more groups chosen from alkyl and (0)₂S(0^")-, X⁺ with X⁺ representing an organic or mineral cationic counter ion; aryl(alkyl)amino optionally substituted with one or more groups chosen from alkyl and (0)₂S(0>, X⁺;

(di)(alkyl)amino;

(di)(hydroxyalkyl)amino;

(0)₂S(0-)-, X⁺;

Z' represents a hydrogen atom or a group NR₂₈R₂₉ with R₂₈ and R₂₉, which may be identical or different, representing a hydrogen atom or a group chosen from:

alkyl;

polyhydroxyalkyl such as hydroxyethyl;

aryl optionally substituted with one or more groups, particularly i) alkyl such as methyl, «-dodecyl, >?-butyl; ii) (0)₂S(0>, X⁺; iii) R°-C(X)-X'-,

R°-X'-C(X)-, R°-X'-C(X)-X"-, preferably R° represents an alkyl group; cycloakyl; especially cyclohexyl;

Z represents a group chosen from hydroxyl and NR'₂gR'₂₉ with R'₂₈ and R'₂₉, which may be identical or different, representing the same atoms or groups as R₂₈ and R₂₉; wherein formulae (III) and (ΙΙΓ) comprise at least one sulfonate group (0)₂S(0^")-,

X⁺.

4. The composition according to any one of Claims 1 to 3, wherein the amount of the

(a) direct dye ranges from 0.001% to 5% by weight, preferably from 0.01% to 3% by weight, and more preferably from 0.05% to 2% by weight, relative to the total weight of the composition.

5. The composition according to any one of Claims 1 to 4, wherein the (b) aprotic polar solvent is selected from the group consisting of propylene carbonate,

N-methylpyrrolidone, N-ethylpyrrolidone, dimethylsulfone, 2-propanone, dimethylsulfoxide, dimethylformamide, ethyl acetate, dimethylacetamide and mixtures thereof.

6. The composition according to any one of Claims 1 to 5, wherein the amount of the

(b) aprotic polar solvent ranges from 1% to 50% by weight, preferably from 5% to 40% by weight, and more preferably from 10% to 30% by weight, relative to the total weight of the composition.

7. The composition according to any one of Claims 1 to 6, wherein the (c)

sulfur-containing reducing agent is selected from the group consisting of

2-mercapto-4-butanolide, glutathione, thioglycolic acid, 3-mercaptopropionic acid, thiolactic acid, L-cysteine, cysteamine, thioglycerol, L-cysteine methyl ester, L-cysteine ethyl ester, mercaptosuccinic acid, glycerol monothioglyclate,

N-acetyl-L-cysteine and mixtures thereof.

8. The composition according to any one of Claims 1 to 7, wherein the amount of the

(c) sulfur-containing reducing agent ranges from 0.1% to 20% by weight, preferably from 0.5% to 10% by weight, and more preferably from 1 to 5% by weight, relative to the total weight of the composition.

9. The composition according to any one of Claims 1 to 8, further comprising water.

10. The composition according to Claim 9, wherein the amount of the water ranges from 10% to 80% by weight, preferably from 20% to 85% by weight, and more preferably from 30 to 70% by weight, relative to the total weight of the composition.

11. The composition according to Claim 9 or 10, wherein the pH of the composition

ranges from 3 to 7, preferably from 4 to 7 and more preferably from 5 to 7.

12. The composition according to any one of Claims 1 to 11, further comprising (d) at least one protein denaturant comprising at least one nitrogen atom.

13. The composition according to Claim 12, wherein the (d) protein denaturant

comprising at least one nitrogen atom is selected from the group consisting of urea, guanidine and its salts, thiourea, biuret, thiobiuret, ammonia, monoethanolamine, triethanolamine, and mixtures thereof.

14. The composition according to Claim 12 or 13, wherein the amount of the (d) protein denaturant comprising at least one nitrogen atom ranges from 0.1 to 20% by weight, preferably from 0.5 to 15% by weight, and more preferably from 1 to 10% by weight, relative to the total weight of the composition.

15. The composition according to any one of Claims 1 to 14, wherein the composition is obtained prior to use by mixing a first composition comprising (a) at least one direct dye, and a second composition comprising (b) at least one aprotic polar solvent and (c) at least one sulfur-containing reducing agent, preferably in a weight ratio of the first composition:the second composition ranges from 1 :1 to 10:1, more preferably from 1:1 to 7: 1, and even more preferably from 1: 1 to 5: 1.

16. A process for dyeing keratin fibers, comprising the step of

applying the composition according to any one of Claims 1 to 15 to the keratin fibers.

17. A kit for dyeing keratin fibers such as hair comprising a first composition comprising (a) at least one direct dye, and a second composition comprising (b) at least one aprotic polar solvent and (c) at least one sulfur-containing compound.