WO2004056331A1

WO2004056331A1 - Composition for dyeing keratin fibres, comprising at least one free-radical compound of nitroxyl type and at least one primary or secondary alcohol

Info

Publication number: WO2004056331A1
Application number: PCT/EP2003/015039
Authority: WO
Inventors: Grégory Plos
Original assignee: L'oreal
Priority date: 2002-12-23
Filing date: 2003-12-19
Publication date: 2004-07-08
Also published as: AU2003294974A1; DE10393955T5

Abstract

The present invention relates to a dye composition for dyeing keratin fibres, in particular human keratin fibres such as the hair, comprising at least one free-radical compound of the nitroxyl type, at least one primary or secondary alcohol, optionally a nucleophilic agent, and optionally an oxidation catalyst. The invention also relates to the use of this composition for dyeing keratin fibres, and also to the process for dyeing keratin fibres using this composition.

Description

COMPOSITION FOR DYEING KERATIN FIBRES, COMPRISING AT

LEAST ONE FREE-RADICAL COMPOUND OF NITROXYL TYPE AND AT

LEAST ONE PRIMARY OR SECONDARY ALCOHOL

The present invention relates to a dye composition for dyeing keratin fibres, in particular human keratin fibres such as the hair, comprising at least one free-radical compound of nitroxyl type, at least one primary or secondary alcohol, optionally a nucleophilic agent, and optionally an oxidation catalyst .

Two modes of dyeing exist in the field of: dyeing keratin fibres, in particular human keratin fibres such as the hair, these modes each having their advantages and drawbacks : - direct dyeing or semi -permanent dyeing consists in introducing the colour via a coloured molecule, which is adsorbed onto the surface of the keratin fibres and/or penetrates by diffusion into the surface layers of these fibres. One of the advantages of this type of dyeing is that mixing is not necessary at the time of application. The leave-in times are generally fairly short and the mild dyeing conditions preserve the integrity of the keratin fibres, but the colorations obtained by this mode of dyeing show poor wash fastness and fade out after shampooing only 4 or 5 times. Furthermore, the ranges of shades obtained are generally small; - oxidation dyeing or permanent dyeing uses the oxidative condensation of colourless or weakly coloured molecules, known as oxidation bases, such as ortho- or para-phenylenediamines, ortho- or para-aminophenols or heterocyclic compounds in the presence of an oxidizing agent. This reaction leads to the formation of insoluble coloured polymer compounds which are trapped in the keratin fibres. The main advantage of oxidation dyeing lies in the longevity of the colorations obtained, in particular in the fastness to washing and to external agents such as light, bad weather, permanent waving, perspiration and rubbing, and also in the production of a wide range of shades. However, this type of dyeing entails mixing the oxidizing agent, generally aqueous hydrogen peroxide, with oxidation bases at the time of use. Furthermore, the chemical dyeing conditions, such as the pH and an oxidizing medium, result in degradation of the keratin fibres. Moreover, this mode of dyeing requires relatively long leave-in times.

To improve the fastness with respect to repeated shampooing and to reduce the sensitization of the hair by the use of an oxidizing agent, it has been proposed to dye the hair without an oxidizing agent, by reacting an aldehyde or a ketone with a nucleophile. In particular, patents FR 2 787 708, FR 2 787 707, FR 2 787 705 and FR 2 787 706 describe the combination of an aldehyde or a ketone with, respectively, an activated methylene, a cationic derivative, an aliphatic cationic amine and a heterocyclic cationic amine . However, these systems for dyeing via coloured reactions require the mixing, before application, of the aldehyde or the ketone and of the nucleophile, which cannot be stored in the same container without the coloured reaction starting. The aim of the present invention is to provide a novel system for dyeing keratin fibres that does not require the mixing of an aldehyde or a ketone with a nucleophile at the time of application, that has good fastness properties, in particular with respect to repeated washing, and that does not degrade hair fibres.

This aim is achieved with the present invention, one subject of which is a dye composition for the oxidation dyeing of keratin fibres, comprising, in a medium that is suitable for dyeing:

- at least one free-radical compound of nitroxyl type as oxidation mediator;

- at least one primary or secondary alcohol of formula (I) , (II) or (III) and / or one of the addition salts thereof:

which:

- x and A₂, which may be identical or different, represent an aliphatic chain of 2 to 50 carbon atoms optionally comprising one or more hetero atoms chosen from nitrogen, sulphur, oxygen and phosphorus;

- A and A₂ together form: - an unsaturated, aromatic or non-aromatic, fused or non-fused monocarbocyclic or polycarbocyclic group containing from 6 to 50 carbon atoms;

- an aromatic or non-aromatic, fused or non- fused, 5- to 30-membered monoheterocyclic or polyheterocyclic group containing one or more hetero atoms chosen from nitrogen, sulphur, oxygen and phosphorus;

- these chains or rings optionally being substituted with the following groups: halo; Cι-C₄ alkyl optionally substituted with one or more hydroxyl, Cι-C₄ alkoxy, carboxyl, hydrogenocarbonyl or C!-C₄ alkoxycarbonyl groups; hydroxyl; C_3.-C₄ alkoxy; amino; C₁-C₄ monoalkylamino or dialkylamino; hydrogenocarbonyl; Cι-C₄ alkylcarbonyl; C_ι-C₄ alkoxycarbony1 ; nitro; sulphonato; imidazolio; pyridinio; benzothiazolio; trialkylammonio;

- Ri represents a hydrogen atom; a Cx-Cj alkyl grou ;

- R₂ represents a hydrogen atom; a halo group; a C_ι-C₄ alkyl group optionally substituted with one or more hydroxyl, C₁-C4 alkoxy, carboxyl, hydrogenocarbonyl or C!-C₄ alkylcarbonyl groups; a hydroxyl group; a C₁-C₄ alkoxy group; a C₁-C₄ monoalkylamino or dialkylamino group; a C₁-C₄ alkoxycarbonyl group; a C1-C₄ hydrogenocarbonyl- alkylcarbonyl group; a group of -CHR3-OH type in which R₃ may be a hydrogen atom or a C1-C₄ alkyl group .

This system makes it possible to generate the aldehyde or ketone at the time of use of the composition on the hair, in the presence of an oxidizing agent, which may be atmospheric oxygen. The aldehyde or ketone thus obtained can then react with a nucleophile present in the hair or in the composition. A subject of the present invention is also a process for dyeing keratin fibres, in particular human keratin fibres such as the hair, using the above composition, and also a device for performing this process.

A subject of the present invention is also the use of the composition of the invention for the oxidation dyeing of keratin fibres.

In the context of the present invention, the term "alkyl radical" (alk) means a linear or branched radical, for example methyl, ethyl, n-propyl, isopropyl or butyl. An alkoxy radical is a radical alk-O-, an alkylcarbonyl radical is a radical alk-CO-, an alkoxycarbonyl radical is a radical alk-O-CO-, a monoalkylamino or dialkylamino radical is a radical (alk)_nN- with n = 1 or 2, a hydrogenocarbonylalkyl- carbonyl radical is a radical H-CO-alk-CO- with the alkyl radical having the definition given above.

A sulphonato radical is an -S0₃ ^" radical . A trialkylammonio radical is a radical (alk)₃N⁺- with the alkyl radical having the definition given above. The imidazolio, pyridinio and benzothiazolio radicals are the cationic radicals corresponding to the imidazolium, pyridinium and benzothiazolium cations.

A halo group denotes a halogen atom chosen from chlorine, bromine, iodine and fluorine.

A fused or non-fused, aromatic or non- aromatic monocarbocyclic or polycarbocyclic group containing from 6 to 50 carbon atoms may be, for example, a benzene, naphthalene, anthracene or cyclohexane ring system. A 5- to 30-membered aromatic or non-aromatic, fused or non-fused, monoheterocyclic or polyheterocyclic group containing one or more hetero atoms may be, for example, a thiophene, benzofuran, benzothiophene, indole, bispyridine, benzopyran, quinoline, pyrazole, pyridine, pyrrole, furan, imidazole or benzimidazole ring system. The polyheterocycle may be fused or substituted with one or more carbocycles . According to one particular embodiment of the invention, the primary or secondary alcohol is chosen such that the radicals Ai and A₂ together form a benzene nucleus .

Preferably, the primary or secondary alcohol is chosen from benzyl alcohol, 2-methylbenzyl alcohol, 2-aminobenzyl alcohol, 3-aminobenzyl alcohol, 4- aminobenzyl alcohol, 2-hydroxybenzyl alcohol, 1,2- di (hydroxymethyl) benzene, 1, 3-di (hydroxymethyl) benzene and 1 , 4-di (hydroxymethyl) benzene . According to one particular embodiment of the invention, the free-radical compound of nitroxyl type is a 2,2' , 6, 6' -tetramethyl-N-oxylpiperidine derivative of formula (IV) and / or one of the addition salts thereof :

in which R₃ and R₄, independently of each other, represent a monovalent group chosen from a hydrogen atom; a C_ι-C₄ alkyl group; a hydroxyl group; a Cι-C₄ alkoxy group; a carboxyl group; a Cx- j alkoxycarbonyl group; a hydrogenocarbonyl group; an amino group; a C₁-C₄ acylamino group; a C₁-C4 haloacylamino group; an isothiocyanato group; a maleimido group; a phosphonyloxy group; a Ci- j alkoxyhalophosphonyloxy group; a 4-nitrobenzoyloxy group; or R₃ and R₄ form, with the carbon atom to which they are attached, a carbonyl group.

Examples that may be mentioned include 2 , 2 ' , 6 , 6 ' -tetramethyl-N-oxylpiperidine, 4-hydroxy- 2,2' , 6, 6' -tetramethyl-N-oxylpiperidine, 4-amino- 2,2' ,6,6' -tetramethyl-N-oxylpiperidine, 4-acetamido- 2,2' ,6,6' -tetramethyl-N-oxylpiperidine, 4- (2- bromoacetamido) -2,2' ,6,6' -tetramethyl-N-oxylpiperidine, 4- (2-iodoacetamido) -2,2' ,6,6' -tetramethyl-N- oxylpiperidine, 4-ethoxyfluorophosphonyloxy-2 , 2 ' ,6,6'- tetramethyl-N-oxylpiperidine, 4-isothiocyanato- 2,2' , 6, 6' -tetramethyl-N-oxylpiperidine, 4-maleimido- 2,2' , 6, 6' -tetramethyl-N-oxylpiperidine, 4- (4- nitrobenzoyloxy) -2,2' ,6,6' -tetramethyl-N- oxylpiperidine, 4-oxo-2,2' ,6,6' -tetramethyl-N- oxylpiperidine and 4-phosphonyloxy-2 , 2 ' , 6 , 6 ' - tetramethyl-N-oxylpiperidine. 2,2' ,6,6' -Tetramethyl-N- oxylpiperidine, or TEMPO, is particularly preferred.

According to a second particular embodiment of the invention, the free-radical compound of nitroxyl type is N,N-diphenylnitroxyl of formula (V) :

According to a third particular embodiment of the invention, the free-radical compound of nitroxyl type is N,N-di-tert-butylnitroxyl of formula (VI) :

(VI).

According to a fourth particular embodiment of the invention, the free-radical compound of nitroxyl type is 3-carbamoylproxylene of formula (VII) :

According to yet a different embodiment of the invention, the free-radical compound of nitroxyl type is in the form of a polymer containing at least one of the units of formula (VIII) or (IX) below:

In general, the addition salts that may be used in the context of the invention are chosen especially from the addition salts with an acid, such as the hydrochlorides, hydrobromides, sulphates, citrates, succinates, tartrates, lactates, tosylates, benzene- sulphonates, phosphates and acetates, and the addition salts with a base, such as sodium hydroxide, potassium hydroxide, ammonia, amines or alkanolamines . The concentration of primary or secondary alcohol is generally between 0.01% and 30% by weight and preferably between 0.05% and 20% by weight relative to the total weight of the composition. The concentration of free-radical compound of nitroxyl type is generally between 0.01% and 30% by weight and preferably between 0.05% and 20% by weight relative to the total weight of the composition.

The dye composition of the invention may also comprise a nucleophilic agent.

According to one particular embodiment, the nucleophilic agent contains at least one amine, alcohol or activated methylene function. This nucleophilic agent is preferably an aromatic compound substituted with an amine, alcohol or activated methylene function. The nucleophilic agent is preferably chosen from para-phenylenediamines, para-aminophenols, ortho- phenylenediamines, ortho-aminophenols, meta-phenylene- diamines, meta-aminophenols, aminonaphthalenes, aminohydroxynaphthalenes, triaminobenzenes, tetraamino- benzenes, diaminophenols, triaminophenols, nitro-para- phenylenediamines, nitro-ortho-phenylenediamines, nitro-meta-phenylenediamines, nitroaminophenols, aminopyridines, aminohydroxypyridines, nitroanilines, diaminodiphenylamines, aminopyrimidines, diamino- pyrazoles, triaminopyrazoles, aminoindazoles, aminoindoles, aminobenzimidazoles, monohydroxyindoles, dihydroxyindoles, dihydroxybenzenes, trihydroxy- benzenes, hydroxynaphthalenes, monohydroxyindolines, dihydroxyindolines, basic amino acids, oligopeptides, protein hydrolysates, barbituric acids and pyrazolones. When the composition comprises a nucleophilic agent, it is present in an amount generally of between 0.01% and 30% by weight and preferably between 0.05% and 20% by weight relative to the total weight of the composition. The composition of the invention may furthermore contain at least one oxidation catalyst . This catalyst is preferably an oxidase enzyme, preferably a laccase or a peroxidase .

The oxidase enzymes are obtained by extraction or via biotechnology.

Among the laccases that may be used according to the invention, mention may be made of laccases that may be obtained from plants: Anacardiacea plants, Podocarpacea plants, Rosmarinus off. , Solanum tuberosum, Iris sp. , Coffea sp. , Daucus carrota, Vinca minor, Persea Americana, Catharenthus roseus, Musa sp. , Malus pumila, Gingko biloba, Monotropa hypopithys , Aesculus sp. , Acer pseudoplatanus , Prunus persica, Pistacia palaestina and rom microorganisms : Polyporus versicolor, Rhizoctoniapraticola, Rhus vernicifera, Scytalidium, Polyporus pinsitus, Myceliophtora thermophila, Rhizoctonia solani, Pyricularia orizae, Trametes versicolor, Fomes fomentarius , Chaetomium thermophile, Neurospora crassa, Colorius versicol, Botrytis cinerea, Rigidoporus lignosus , Phellinus noxius, Pleurotus ostreatus, Aspergillus nidulans, Podospora anserina, Agaricus bisporus, Ganoderma lucidum, Glomerella cingulata, Lactarius piperatus, Russula delica, Heterobasidion annosum, Thelephora terrestris, Cladosporium cladosporioides , Cerrena unicolor, Coriolus hirsutus, Ceriporiopsis subvermispora, Coprinus cinereus, Panaeolus papilionaceus , Panaeolus sphinctrinus , Schizophyllum commune, Dichomitius squalens, Acremonium murorum, and variants thereof .

Among the peroxidases that may be used according to the invention, mention may be made of peroxidases that may be obtained from microorganisms : Aspergillus oryzae, Caldariomyces fumago, Inonotus weirii, Aspergillus flavus, Trametes versicolor, Aspergillus ochraceus, Phanerochaete chrysosporium, Geotrichum candidum, Aspergillus parasiticus,

Cochiliobolus heterostrophus , Phellinus pini, Phellinus chrysoloma, Phellinus weirii, Phytophthora palmivora, Merulius tremellosus, Phanerochaete flavido-alba, Phlebia radiata, Ceriporiopsis subvermispora, Junghuhnia separabilima, Phanerochaete sordida, Pleurotus eryngii, Bjerkandera sp. , Phlebia ochraceofulva, Nematoloma frowardii, Dichomitus squalens, Phanerochaete chrysosporium, Pycnoporus cinnabarinus , Bjerkandera adusta, Trametes hirsuta, Arthromyces ramosus, and variants thereof, and from plants: horseradish, Arachis hypogea (peanut), Raphanus sativus (Japanese radish) , Sphagnum magellani, Nicotiana tabacum.

When the composition comprises an oxidation catalyst, it is present in an amount generally of between 0.01% and 30% by weight and preferably between 0.05% and 20% by weight relative to the total weight of the composition.

The dye composition in accordance with the invention may also contain one or more direct dyes that may be chosen especially from nitrobenzene dyes, azo direct dyes and methine direct dyes. These direct dyes may be of nonionic, anionic or cationic nature.

The composition of the present invention may also comprise one or more oxidation bases conventionally used in oxidation dyeing. The composition of the present invention may further comprise one or more couplers conventionally used in oxidation dyeing.

The medium that is suitable for dyeing, also known as the dye support, generally consists of water or a mixture of water and at least one organic solvent to dissolve the compounds which would not be sufficiently soluble in water. The alcohols which are useful in the invention may serve as solvents . The composition may however contain other alcohols as organic solvent. Mention may be made, for example, of C₁-C₄ lower alkanols, such as ethanol and isopropanol; polyols and polyol ethers such as 2-butoxyethanol, propylene glycol, propylene glycol monomethyl ether, diethylene glycol monoethyl ether and monomethyl ether, and mixtures thereof .

The solvents are present in proportions preferably of between 1% and 40% by weight approximately relative to the total weight of the dye composition, and even more preferably between 5% and 30% by weight approximately.

The composition in accordance with the invention can also contain various adjuvants conventionally used in compositions for dyeing the hair, such as anionic, cationic, nonionic, amphoteric or zwitterionic surfactants or mixtures thereof, anionic, cationic, nonionic, amphoteric or zwitterionic polymers or mixtures thereof, inorganic or organic thickeners, and in particular anionic, cationic, nonionic or amphoteric associative polymeric thickeners, antioxidants, penetration agents, sequestering agents, fragrances, buffers, dispersing agents, packaging agents such as, for example, silicones, which may or may not be volatile or modified or unmodified, film-forming agents, ceramides, preserving agents and opacifiers.

The above adjuvants are generally present in an amount for each of them of between 0.01% and 20% by weight relative to the weight of the composition.

Needless to say, a person skilled in the art will take care to select this or these optional additional compounds such that the advantageous properties intrinsically associated with the oxidation dye composition in accordance with the invention are not, or are not substantially, adversely affected by the addition (s) envisaged.

The pH of the dye composition in accordance with the invention is generally between about 3 and 11 and preferably between about 4 and 10. It may be adjusted to the desired value using acidifying or basifying agents usually used in the dyeing of keratin fibres, or alternatively using standard buffer systems. Among the acidifying agents which may be mentioned, for example, are inorganic or organic acids such as hydrochloric acid, orthophosphoric acid, sulphuric acid, carboxylic acids such as acetic acid, tartaric acid, citric acid and lactic acid, and sulphonic acids . Among the basifying agents which may be mentioned, for example, are aqueous ammonia, alkaline carbonates, alkanolamines such as mono-, di- and triethanolamine and derivatives thereof, sodium hydroxide, potassium hydroxide and the compounds of formula (X) below:

(X)

in which W is a propylene residue which is optionally substituted with a hydroxyl group or a Cι-C₄ alkyl radical; R_a, Rb, Rc and R_d, which may be identical or different, represent a hydrogen atom, a C₁-C4 alkyl radical or a Cτ.-C4 hydroxyalkyl radical. The dye composition according to the invention may be in various forms, such as in the form of liquids, creams or gels, or in any other form that is suitable for dyeing keratin fibres, and especially human hair. The process for dyeing keratin fibres of the present invention consists in applying to the keratin fibres a composition comprising, in a medium that is suitable for dyeing, at least one free-radical compound of nitroxyl type, at least one primary or secondary alcohol, optionally a nucleophilic agent, and optionally an oxidation catalyst, and in developing the colour using an oxidizing agent .

According to one particular embodiment of the process of the invention, the oxidizing agent is present in an oxidizing composition that is applied simultaneously or sequentially to the keratin fibres.

According to another particular embodiment of the process of the invention, the oxidizing agent is added to the dye composition just at the time of its application.

According to one variant, the process of the invention consists in applying to the keratin fibres, sequentially and in any order, a first composition comprising, in a medium that is suitable for dyeing, at least one free-radical compound of nitroxyl type and at least one primary or secondary alcohol and a second composition comprising, in a medium that is suitable for dyeing, at least one nucleophilic agent, one of the two compositions or both of them optionally comprising an oxidation catalyst, and then in applying an oxidizing composition comprising, in a medium that is suitable for dyeing, at least one oxidizing agent.

In these various embodiments, the application of each of the compositions may optionally be followed by a rinsing operation.

The action time for each of the compositions is generally between 5 minutes and 1 hour and preferably between 5 minutes and 30 minutes. The application temperature is generally set at between room temperature and 80°C and preferably between room temperature and 60°C. The oxidizing agents used in the present invention are, for example, hydrogen peroxide, urea peroxide, persalts such as percarbonates, persulphates, perborates, 3-chloroperbenzoates and metal salts such as copper or iron salts, for instance copper II chloride .

If the oxidizing agent is present in an oxidizing composition, this composition may also contain various adjuvants conventionally used in hair dye compositions and as defined above, and its pH may be between 3 and 12 and preferably between 5 and 11. The oxidizing agent concentration is generally such that when the oxidizing composition is mixed with the other compositions, the oxidizing agent concentration in the composition obtained is between 0.01% and 30% by weight and preferably between 0.05% and 20% by weight relative to the total weight of the composition.

The various compositions applied to the keratin fibres may be in various forms, such as in the form of liquids, creams or gels, or in any other form that is suitable for dyeing keratin fibres, and especially human hair.

The oxidizing agent may also be atmospheric oxygen. In this case, the composition is stored in an anaerobic medium and is placed in contact with air at the time of use for dyeing keratin fibres. The invention then has an additional advantage, which is that of not requiring mixing at the time of application.

A subject of the present invention is also a multi-compartment device for performing the process for dyeing keratin fibres described above .

The multi-compartment device of the invention contains, in a first compartment, a composition comprising, in a medium that is suitable for dyeing, at least one free-radical compound of nitroxyl type, at least one primary or secondary alcohol, optionally a nucleophilic agent and optionally an oxidation catalyst, and, in a second compartment, a composition comprising, in a medium that is suitable for dyeing, at least one oxidizing agent. According to one variant, the device contains, in a first compartment, a composition comprising, in a medium that is suitable for dyeing, at least one free-radical compound of nitroxyl type and at least one primary or secondary alcohol, in a second compartment, a composition comprising, in a medium that is suitable for dyeing, at least one oxidizing agent, and, in a third compartment, a composition comprising, in a medium that is suitable for dyeing, at least one nucleophilic agent. According to one particular embodiment, one of the compositions present in the first and the third compartment or both comprises an oxidation catalyst . According to one variant, the device contains, in a first compartment, a composition comprising, in a medium that is suitable for dyeing, at least one free-radical compound of nitroxyl type, at least one primary or secondary alcohol and at least one nucleophilic agent, in a second compartment, a composition comprising, in a medium that is suitable for dyeing, at least one oxidizing agent, and, in a third compartment, a composition comprising, in a medium that is suitable for dyeing, at least one oxidation catalyst.

According to another variant, the device contains, in a first compartment, a composition comprising, in a medium that is suitable for dyeing, at least one free-radical compound of nitroxyl type and at least one primary or secondary alcohol, in a second compartment, a composition comprising, in a medium that is suitable for dyeing, at least one oxidizing agent, in a third compartment, a composition comprising, in a medium that is suitable for dyeing, at least one nucleophilic agent, and, in a fourth compartment, a composition comprising, in a medium that is suitable for dyeing, at least one oxidation catalyst.

A subject of the present invention is also an anaerobically packaged aerosol containing a composition comprising, in a medium that is suitable for dyeing, at least one free-radical compound of nitroxyl type, at least one primary or secondary alcohol, optionally a nucleophilic agent and optionally an oxidation catalyst .

The primary or secondary alcohol does not react with the nucleophilic compound and may be stored in the same container as the said compound.

A subject of the present invention is also the use for dyeing keratin fibres of a composition comprising, in a medium that is suitable for dyeing, at least one free-radical compound of nitroxyl type, at least one primary or secondary alcohol, optionally a nucleophilic agent, optionally an oxidation catalyst and optionally an oxidizing agent.

The examples that follow serve to illustrate the invention without, however, being limiting in nature .

EXAMPLES

In the examples that follow, the amounts of the compounds are expressed in grams per 100 g of composition (%) or in moles per 100 g of composition (mol%) . Example 1

Compositions .1 and 2 are applied to white hair with a leave-in time of 30 minutes, to dewhiten them.

Claims

1. Dye composition for the oxidation dyeing of keratin fibres, comprising, in a medium that is suitable for dyeing:

- at least one free-radical compound of nitroxyl type as oxidation mediator;

- at least one primary or secondary alcohol of formula (I) , (II) or (III) and / or one of the addition salts thereof :

in which:

- i and A₂, which may be identical or different, represent an aliphatic chain of 2 to 50 carbon atoms optionally comprising one or more hetero atoms chosen from nitrogen, sulphur, oxygen and phosphorus ;

- Ai and A₂ together form: - an unsaturated, aromatic or non-aromatic, fused or non-fused monocarbocyclic or polycarbocyclic group containing from 6 to 50 carbon atoms; - an aromatic or non-aromatic, fused or non- fused, 5- to 30-membered monoheterocyσlic or polyheterocyclic group containing one or more hetero atoms chosen from nitrogen, sulphur, oxygen and phosphorus;

- these chains or rings optionally being substituted with the following groups: halo; C_ι-C₄ alkyl optionally substituted with one or more hydroxyl, Cι-C₄ alkoxy, carboxyl, hydrogenocarbonyl or C_ι-C₄ alkoxycarbonyl groups; hydroxyl; C₁-C₄ alkoxy; amino; C₁-C₄ monoalkylamino or dialkylamino; hydrogenocarbonyl; C₁-C₄ alkylcarbonyl; C₁-C₄ alkoxycarbonyl; nitro; sulphonato; imidazolio; pyridinio; benzothiazolio; and trialkylammonio;

- Ri represents a hydrogen atom; a C₁-C₄ alkyl group;

- R₂ represents a hydrogen atom; a halo group; a C₁-C₄ alkyl group optionally substituted with one or more hydroxyl, C_x-C₄ alkoxy, carboxyl, hydrogenocarbonyl or C₁-C₄ alkylcarbonyl groups; a hydroxyl group; a Ci-Gj alkoxy group; a C₁-C₄ monoalkylamino or dialkylamino group; a C₁-C₄ alkoxycarbonyl group; a C1-C4 hydrogenocarbonyl- alkylcarbonyl group; a group of -CHR3-OH type in which R₃ may be a hydrogen atom or a C₁-C₄ alkyl group .

2. Composition according to Claim 1, in which the primary or secondary alcohol is such that A_x and A₂ together form a benzene nucleus .

3. Composition according to Claim 2 , in which the primary or secondary alcohol is chosen from benzyl alcohol, 2-methylbenzyl alcohol, 2-aminobenzyl alcohol, 3-aminobenzyl alcohol, 4-aminobenzyl alcohol, 2-hydroxybenzyl alcohol, 1, 2-di (hydroxymethyl) benzene, 1, 3-di (hydroxymethyl)benzene and 1,

4- di (hydroxymethyl) benzene . . Composition according to any one of the preceding claims, in which the free-radical compound of nitroxyl type is chosen from 2, 2' , 6, 6' -tetramethyl-N- oxylpiperidine derivatives; N,N-diphenylnitroxyl; N,N- di-tert-butylnitroxyl; 3-carbamoylproxylene; polymers containing at least one group derived from 2,2' ,6,6'- tetramethyl-N-oxylpiperidine .

5. Composition according to Claim 4, in which the free-radical compound of nitroxyl type is a 2 , 2 ' , 6 , 6 ' -tetramethyl-N-oxylpiperidine derivative of formula (IV) and / or one of the addition salts thereof :

in which R₃ and R₄, independently of each other, represent a monovalent group chosen from a hydrogen atom; a C₁-C₄ alkyl group; a hydroxyl group; a Cι-C₄ alkoxy group; a carboxyl group; a C!-C₄ alkoxycarbonyl group; a hydrogenocarbonyl group; an amino group; a C_ι-C₄ acylamino group; a C₁-C₄ haloacylamino group; an isothiocyanato group; a maleimido group; a phosphonyloxy group; a Cχ-C₄ alkoxyhalophosphonyloxy group; a 4-nitrobenzoyloxy group; or R₃ and R form, with the carbon atom to which they are attached, a carbonyl group.

6. Composition according to Claim 5, in which the free-radical compound of nitroxyl type is chosen from 2,2' , 6, 6' -tetramethyl-N-oxylpiperidine, 4- hydroxy-2 , 2 ' ,6,6' -tetramethyl-N-oxylpiperidine, 4- amino-2, 2' ,6,6' -tetramethyl-N-oxylpiperidine, 4- acetamido-2,2' , 6, 6' -tetramethyl-N-oxylpiperidine, 4- (2- bromoacetamido) -2,2' ,6,6' -tetramethyl-N-oxylpiperidine, 4- (2-iodoacetamido) -2,2' ,6,6' -tetramethyl-N- oxylpiperidine, -ethoxyfluorophosphonyloxy-2 , 2 ' , 6 , 6 ' - tetramethyl-N-oxylpiperidine, 4-isothiocyanato- 2,2' ,6,6' -tetramethyl-N-oxylpiperidine, 4~maleimido- 2,2' ,6,6' -tetramethyl-N-oxylpiperidine, 4- (4- nitrobenzoyloxy) -2,2' ,6,6' -tetramethyl-N- oxylpiperidine, 4-oxo-2,2' , 6, 6' -tetramethyl-N- oxylpiperidine and 4-phosphonyloxy-2 , 2 ' , 6, 6' - tetramethyl-N-oxylpiperidine .

7. Composition according to Claim 6, in which the free-radical compound of nitroxyl type is 2,2' ,6,6' -tetramethyl-N-oxylpiperidine .

8. Composition according to Claim 4, in which the free-radical compound of nitroxyl type is N,N-diphenylnitroxyl of formula (V) :

9. Composition according to Claim 4, in which the free-radical compound of nitroxyl type is N,N-di-tert-butylnitroxyl of formula (VI) :

10. Composition according to Claim 4, in which the free-radical compound of nitroxyl type is 3- carbamoylproxylene of formula (VII) :

(VII).

11. Composition according to Claim 4, in which the free-radical compound of nitroxyl type is in the form of a polymer containing at least one of the units of formula (VIII) or (IX) below:

12. Composition according to any one of the preceding claims, in which the concentration of primary or secondary alcohol is between 0.01% and 30% by weight relative to the total weight of the composition.

13. Composition according to any one of the preceding claims, in which the concentration of free- radical compound of nitroxyl type is between 0.01% and 30% by weight relative to the total weight of the composition.

1 . Composition according to any one of the preceding claims, comprising a nucleophilic agent.

15. Composition according to Claim 14, in which the nucleophilic agent contains at least one amine, alcohol or activated methylene function.

16. Composition according to Claim 15, in which the nucleophilic agent is an aromatic compound.

17. Composition according to Claim 15, in which the nucleophilic agent is chosen from para- phenylenediamines, para-aminophenols, ortho-phenylene- diamines, ortho-aminophenols, meta-phenylenediamines, meta-aminophenols, aminonaphthalenes, aminohydroxy- naphthalenes, triaminobenzenes, tetraaminobenzenes, diaminophenols, triaminophenols, nitro-para- phenylenediamines, nitro-ortho-phenylenediamines, nitro-meta-phenylenediamines, nitroaminophenols, aminopyridines, aminohydroxypyridines, nitroanilines, diaminodiphenylamines, aminopyrimidines, diamino- pyrazoles, triaminopyrazoles, aminoindazoles, aminoindoles, aminobenzimidazoles, monohydroxyindoles, dihydroxyindoles, dihydroxybenzenes , trihydroxy- benzenes, hydroxynaphthalenes, monohydroxyindolines, dihydroxyindolines, basic amino acids, oligopeptides, protein hydrolysates, barbituric acids and pyrazolones.

18. Composition according to any one of

Claims 14 to 17, in which the concentration of nucleophilic agent is between 0.01% and 30% by weight relative to the total weight of the composition.

19. Composition according to any one of the preceding claims, comprising an oxidation catalyst.

20. Composition according to Claim 19, in which the oxidation catalyst is chosen from oxidase enzymes such as laccase and peroxidase.

21. Composition according to Claim 19 or 20, in which the concentration of oxidation catalyst is between 0.01% and 30% by weight relative to the total weight of the composition.

22. Composition according to any one of the preceding claims, comprising an oxidizing agent.

23. Composition according to Claim 22, in which the oxidizing agent is chosen from hydrogen peroxide, urea peroxide, persalts and metal salts.

24. Composition according to Claim 22 or 23, in which the concentration of oxidizing agent is between 0.01% and 30% by weight relative to the total weight of the composition.

25. Process for dyeing keratin fibres, characterized in that a composition comprising, in a medium that is suitable for dyeing, at least one free- radical compound of nitroxyl type as defined in any one of Claims 1 and 4 to 11 and at least one primary or secondary alcohol as defined in any one of Claims 1 to 3 is applied to the keratin fibres and the colour is developed using an oxidizing agent.

26. Process according to Claim 25, in which the composition also comprises a nucleophilic agent as defined in any one of Claims 14 to 17.

27. Process according to Claim 25 or 26, in which the composition also comprises an oxidation catalyst as defined in Claim 19 or 20.

28. Process according to Claim 25, in which a second composition comprising, in a medium that is suitable for dyeing, at least one nucleophilic agent as defined in any one of Claims 14 to 17 is applied to the keratin fibres.

29. Process according to Claim 28, in which at least one of the compositions applied to the keratin fibres comprises an oxidation catalyst as defined in Claim 19 or 20.

30. Process according to any one of Claims 25 to 29, in which the oxidizing agent is present in an oxidizing composition applied simultaneously or sequentially.

31. Process according to Claim 30, in which the oxidizing agent is chosen from hydrogen peroxide, urea peroxide, persalts and metal salts.

32. Process according to Claim 30 or 31, in which the keratin fibres are rinsed between the application of each of the compositions.

33. Process according to any one of Claims 25 to 27, in which the oxidizing agent is added to the dye composition just at the time of application.

34. Process according to Claim 33, in which the oxidizing agent is chosen from atmospheric oxygen, hydrogen peroxide, urea peroxide, persalts and metal salts .

35. Multi-compartment device containing, in a first compartment, a composition comprising, in a medium that is suitable for dyeing, at least one free- radical compound of nitroxyl type as defined in any one of Claims 1 and 4 to 11 and at least one primary or secondary alcohol as defined in any one of Claims 1 to 3, and, in a second compartment, a composition comprising, in a medium that is suitable for dyeing, at least one oxidizing agent.

36. Device according to Claim 35, in which the composition present in the first compartment also comprises a nucleophilic agent as defined in any one of Claims 14 to 17.

37. Device according to Claim 35 or 36, in which the composition present in the first compartment also comprises an oxidation catalyst as defined in Claim 19 or 20.

38. Device according to Claim 35, containing, in a third compartment, a composition comprising, in a medium that is suitable for dyeing, at least one nucleophilic agent as defined in any one of Claims 14 to 17.

39. Device according to Claim 38, in which one of the compositions present in the first and third compartment or both also comprises an oxidation catalyst as defined in Claim 19 or 20.

40. Device according to Claim 36, containing, in a third compartment, a composition comprising, in a medium that is suitable for dyeing, at least one oxidation catalyst as defined in Claim 19 or 20.

41. Device according to Claim 38, in which a fourth compartment contains a composition comprising, in a medium that is suitable for dyeing, at least one oxidation catalyst as defined in Claim 19 or 20.

4 . Anaerobically packaged aerosol containing a composition as defined in any one of Claims 1 to 21.

43. Use for dyeing keratin fibres of a composition as defined in any one of Claims 1 to 24.