WO2014131870A1 - Process for dyeing and/or bleaching keratin fibres using an oxidizing composition in the form of an oil-in-water nanoemulsion - Google Patents

Abstract

The present invention relates to a process for dyeing and/or bleaching keratin fibres using an oxidizing composition in the form of an oil-in-water nanoemulsion comprising one or more oxidizing agents, one or more surfactants, one or more fatty substances and water; the number-average size of the oil droplets in the said nanoemulsion being less than or equal to 100 nm.

Description

Process for dyeing and/or bleaching keratin fibres using an oxidizing composition in the form of an oil-in-water nanoemulsion The present invention relates to a process for dyeing and/or bleaching human keratin fibres such as the hair, using an oxidizing cosmetic composition in the form o f an oil-in-water nanoemulsion.

More precisely, a subj ect of the present invention is a process for dyeing and/or bleaching keratin fibres using an oxidizing composition in the form o f an oil-in-water nanoemulsion comprising one or more oxidizing agents, one or more surfactants, one or more fatty substances and water; the number-average size of the oil droplets in the said nanoemulsion being less than or equal to 100 nm.

Many people have for a long time sought to modify the colour of their hair, and especially to bleach it or on the contrary to dye it in order, for example, to mask their grey hair.

Two types of dyeing mainly exist for dyeing human keratin fibres.

The first type of dyeing is referred to as permanent dyeing or oxidation dyeing, which uses dye compositions containing oxidation dye precursors, generally referred to as oxidation bases. These oxidation bases are co lourless or weakly co loured compounds, which, when combined with oxidizing products, may give rise to coloured compounds via a process o f oxidative condensation.

It is also known that the shades obtained with these oxidation bases can be varied by combining them with couplers or coloration modifiers. The variety o f mo lecules used as oxidation bases and couplers allows a wide range of colours to be obtained.

The second type o f dyeing is referred to as semi-permanent dyeing or direct dyeing, which consists in applying to the keratin fibres direct dyes, which are coloured and colouring mo lecules that have affinity for the said fibres, in leaving them on the fibres for a time, and then in rinsing them o ff. In order to perform these co lorations, the direct dyes generally used are chosen from nitrobenzene, anthraquinone, nitropyridine, azo, xanthene, acridine, azine and triarylmethane direct dyes .

This type o f process does not require the use o f an oxidizing agent to develop the coloration. However, it is possible to use such an agent in order to obtain a lightening effect along with the co loration. Such a process is then referred to as a direct dyeing or semi-permanent dyeing under lightening conditions.

Processes of permanent or semi-permanent dyeing under lightening conditions thus require the use, along with the dye composition, of an aqueous composition comprising at least one oxidizing agent, under alkaline pH dyeing conditions in the vast majority o f cases .

Conventional processes for bleaching human keratin fibres consist in using an aqueous composition comprising at least one oxidizing agent. The role o f this oxidizing agent is to degrade the melanin o f the hair, which, depending on the nature of the oxidizing agent and on the pH conditions, leads to more or less pronounced lightening of the fibres .

Thus, for relatively weak lightening, the oxidizing agent is generally hydrogen peroxide. When more substantial lightening is desired, peroxygenated salts, for instance persulfates, are usually used in the presence of hydrogen peroxide.

In order to improve the performance qualities of processes for dyeing and/or bleaching human keratin fibres, it has been proposed to use in dye compositions a substantial amount of one or more fatty substances.

However, the compositions used in the prior art processes are not entirely satisfactory, and their properties can be improved in particular as regards the working qualities, especially in terms of texture, ease of mixing with dye compositions and/or ease of application and spreading on the hair and/or intensity or homogeneity of dyeing or bleaching. The Applicant has now discovered that the use of an oil-in- water nanoemulsion comprising an oxidizing agent in a process for dyeing and/or bleaching keratin fibres makes it possible to overcome the above drawbacks and has improved properties .

One subj ect of the present invention is thus a process for dyeing and/or bleaching keratin fibres using an oxidizing composition in the form o f an oil-in-water nanoemulsion comprising one or more oxidizing agents, one or more surfactants, one or more fatty substances and water; the number-average size of the oil droplets in the said nanoemulsion being less than or equal to 100 nm.

The composition used in the process according to the present invention has very good working qualities, and especially a particularly pleasant texture.

Furthermore, this composition is easy to apply and to spread on the locks of hair, in particular on the roots.

In addition, it does not run and remains well located at the points o f application and spreads easily from the roots to the ends .

Finally, the oxidizing composition may easily be mixed with one or more dyeing or bleaching compositions . The use of such a mixture in the process according to the invention makes it possible to obtain a superior quality, especially in terms of intensity, homogeneity and selectivity o f the dyeing obtained or in terms of intensity and homogeneity of the bleaching obtained.

Other characteristics and advantages of the invention will emerge more clearly on reading the description and the examples that fo llow.

According to the invention, the oxidizing composition is in the form of an oil-in-water nanoemulsion.

According to the present invention, the term "oil-in-water nanoemulsion" denotes a true emulsion, i. e. a thermodynamically unstable dispersion of oil droplets in a continuous aqueous phase.

Nanoemulsions are to be distinguished from microemulsions, which are thermo dynamically stable dispersions in the form o f micelles of oil-swo llen surfactants, and which form spontaneously by simple mixing o f the constituents, without substantial input of energy.

The number-average size of the oil droplets in the nanoemulsions used in the process according to the invention is less than or equal to 100 nm.

In a particularly preferred manner, the number-average size o f the oil droplets o f the nanoemulsion used in the process according to the invention ranges from 1 0 to 90 nm, better still from 20 to 80 nm and more preferentially from 40 to 60 nm.

The number-average size of the particles may be determined in particular according to the known method of quasi-elastic light scattering. As a machine that may be used for this determination, mention may be made of the Brookhaven brand machine equipped with an SX 200 optical bed (with a 532 nm laser) and a BI 9000 correlator. This machine gives a measurement of the mean diameter by photon correlation spectroscopy (PCS), which makes it possible to determine the number-average diameter from the polydispersity factor, which is also measured by the machine.

The nanoemulsion may also be characterized by measuring its turbidity according to the NTU method using a 21 OOP mo del turbidimeter from the company Hach, at room temperature. The turbidity o f the nanoemulsions used in the process o f the invention is generally less than 400 NTU units and preferably between 50 and 250 NTU units.

A nanoemulsion generally has a transparent to blueish or translucent appearance, in the absence of opacifying or nacreous additional compound(s).

In the process according to the invention, the reduction in the size o f the oil globules makes it possible especially to promote the penetration o f the active ingredients o f the oxidizing composition into the keratin materials, for example through the surface layers o f the hair (vehicle effect) . As indicated previously, the oxidizing composition used in the process according to the invention comprises one or more oxidizing agents .

Advantageously, the oxidizing agent used in the context of the invention is a chemical oxidizing agent other than atmospheric oxygen.

The said oxidizing agent(s) are preferably chosen from the group formed by hydrogen peroxide, urea peroxide, alkali metal bromates or ferricyanides, peroxygenated salts, for instance persulfates, perborates, peracids and precursors thereo f and alkali metal or alkaline-earth metal percarbonates, and most particularly hydrogen peroxide.

The oxidizing agent(s) may represent from 0.01 % to 20%, preferably from 0. 1 % to 10% and better still from 2% to 8% by weight, relative to the total weight of the oxidizing composition.

The oxidizing composition used in the process according to the invention comprises one or more surfactants which may be chosen especially from nonionic, cationic, anionic and amphoteric or zwitterionic surfactants .

The said surfactant(s) according to the invention preferably comprise one or more nonionic surfactants .

The nonionic surfactant(s) that may be used in the oxidizing composition are described, for example, in the Handbook of Surfactants by M .R. Porter, published by Blackie & Son (Glasgow and London), 1991 , pp . 1 16- 178.

Examples of nonionic surfactants that may be mentioned include the fo llowing nonionic surfactants :

- oxyalkylenated (Cs- C 24)alkylphenols;

- saturated or unsaturated, linear or branched, oxyalkylenated or glycerolated C 8 - C40 alcoho ls, comprising one or two fatty chains;

- saturated or unsaturated, linear or branched, oxyalkylenated C 8 - C30 fatty acid amides;

- esters of saturated or unsaturated, linear or branched, C 8 - C30 acids and of polyethylene glycols; - esters of saturated or unsaturated, linear or branched, C₈ - C30 acids and of sorbitol, preferably oxyethylenated;

- fatty acid esters o f sucrose;

- (C₈-C3o)alkyl(poly)glucosides, (C₈-C3o)alkenyl(poly)glucosides, which are optionally oxyalkylenated (0 to 10 oxyalkylene units) and comprising from 1 to 15 glucose units, (Cs- C3 o)alkyl (poly)glucoside esters;

- saturated or unsaturated, oxyethylenated plant oils;

- condensates of ethylene oxide and/or of propylene oxide, inter alia, alone or as mixtures;

- N-(C₈-C3o)alkylglucamine and N-(C₈-C3o)acylmethylglucamine derivatives;

- aldobionamides;

- amine oxides;

- oxyethylenated and/or oxypropylenated silicones;

- and mixtures thereof.

The oxyalkylene units are more particularly oxyethylene or oxypropylene units, or a combination thereof, preferably oxyethylene units.

The number o f mo les of ethylene oxide and/or propylene oxide preferably ranges from 1 to 250, more particularly from 2 to 100 and better still from 2 to 50; the number of mo les o f glycero l ranges especially from 1 to 50 and better still from 1 to 10.

Advantageously, the nonionic surfactants according to the invention do not comprise any oxypropylene units .

As examples of glycerolated nonionic surfactants, use is preferably made of monoglycerolated or polyglycerolated C8 - C40 alcoho ls, comprising from 1 to 50 mo l o f glycero l and preferably from 1 to 10 mo l o f glycerol.

As examp les of compounds o f this type, mention may be made of lauryl alcoho l containing 4 mo l of glycerol (INCI name : Polyglyceryl-4 Lauryl Ether), lauryl alcohol containing 1 .5 mo l o f glycerol, oleyl alcoho l containing 4 mol o f glycerol (INCI name : Polyglyceryl-4 Oleyl Ether), oleyl alcohol containing 2 mo l o f glycerol (INCI name: Polyglyceryl-2 Oleyl Ether), cetearyl alcohol containing 2 mol of glycerol, cetearyl alcohol containing 6 mol of glycerol, oleyl/cetyl alcohol containing 6 mol of glycerol, and octadecanol containing 6 mol of glycerol.

Among the glycerolated alcohols, it is more particularly preferred to use the Cs/Cio alcohol containing 1 mol of glycerol, the C10 C12 alcohol containing 1 mol of glycerol and the C₁₂ alcohol containing 1.5 mol of glycerol.

The nonionic surfactant(s) according to the invention are preferentially chosen from:

- oxyethylenated C8-C40 alcohols comprising from 1 to 100 mol of ethylene oxide, preferably from 2 to 50 and more particularly from 2 to 40 mol of ethylene oxide and comprising one or two fatty chains;

- saturated or unsaturated oxyethylenated plant oils comprising from 1 to 100 and preferably from 2 to 50 mol of ethylene oxide;

(C8-C3o)alkyl(poly)glucosides, which are optionally oxyalkylenated (0 to 10 OE) and comprising 1 to 15 glucose units;

- monoglycerolated or polyglycerolated C8-C40 alcohols, comprising from 1 to 50 mol of glycerol and preferably from 1 to 10 mol of glycerol.

saturated or unsaturated, linear or branched, oxyalkylenated C8-C30 fatty acid amides;

- esters of saturated or unsaturated, linear or branched, C₈-

C30 acids and of polyethylene glycols;

- and mixtures thereof.

Even more preferentially, the nonionic surfactant(s) according to the invention are chosen from:

- saturated or unsaturated, linear or branched, oxyalkylenated C8-C40 alcohols, comprising one or two fatty chains, especially ceteareth-60 myristyl glycol;

- (C8-C3o)alkyl(poly)glucosides, especially caprylyl/capryl glucoside; - esters of saturated or unsaturated, linear or branched, C₈- C30 acids and of polyethylene glycols and especially PEG- 8 isostearate;

- and mixtures thereof.

The oxidizing composition used in the process according to the invention may comprise one or more cationic surfactants .

The term "cationic surfactant" means a surfactant that is positively charged when it is contained in the composition used in the process according to the invention. This surfactant may bear one or more positive permanent charges or may contain one or more cationizable functions in the oxidizing composition.

The cationic surfactant(s) are preferably chosen from optionally polyoxyalkylenated, primary, secondary or tertiary fatty amines, or salts thereof, and quaternary ammonium salts, and mixtures thereo f.

The fatty amines generally comprise at least one C 8 - C30 hydrocarbon-based chain.

Examples of quaternary ammonium salts that may especially be mentioned include :

- those corresponding to the general formula (I) below :

(I)

in which the groups Rs to Rn , which may be identical or different, represent a linear or branched aliphatic group comprising from 1 to 30 carbon atoms, or an aromatic group such as aryl or alkylaryl, at least one of the groups Rs to Rn denoting a group comprising from 8 to 30 carbon atoms and preferably from 12 to 24 carbon atoms. The aliphatic groups may comprise heteroatoms especially such as oxygen, nitrogen, sulfur and halogens. The aliphatic groups are chosen, for example, from C 1 - C30 alkyl, C 1 - C30 alkoxy, polyoxy(C2-Ce)alkylene, C 1 - C30 alkylamide, (C i 2-C22)alkylamido(C2- C₆)alkyl, (C i ₂-C₂₂)alkyl acetate and C ₁ - C 30 hydroxyalkyl groups; X^" is an anion chosen from the group of halides, phosphates, acetates, lactates, (C i - C4)alkyl sulfates, and (C i - C4)alkyl- or (C i - C4)alkylarylsulfonates.

Among the quaternary ammonium salts of formula (I), those that are preferred are, on the one hand, tetraalkylammonium salts, for instance dialkyldimethylammonium or alkyltrimethylammonium salts in which the alkyl group contains approximately from 12 to 22 carbon atoms, in particular behenyltrimethylammonium, distearyldimethylammonium, cetyltrimethylammonium or benzyldimethylstearylammonium salts, or, on the other hand, the palmitylamidopropyltrimethylammonium salt, the stearamidopropyltrimethylammonium salt, the stearamidopropyldimethylcetearylammonium salt, or the stearamidopropyldimethyl(myristyl acetate)ammonium salt sold under the name Ceraphyl® 70 by the company Van Dyk. It is particularly preferred to use the chloride salts of these compounds .

- quaternary ammonium salts o f imidazo line, for instance those of formul (II) below:

(II)

in which Ri ₂ represents an alkenyl or alkyl group containing from 8 to 30 carbon atoms, derived for examp le from tallow fatty acids, Ri ₃ represents a hydrogen atom, a C ₁ - C4 alkyl group or an alkenyl or alkyl group containing from 8 to 30 carbon atoms, R1 4 represents a C ₁ - C4 alkyl group, R1 5 represents a hydrogen atom or a C ₁ - C4 alkyl group, X^" is an anion chosen from the group consisting o f halides, phosphates, acetates, lactates, alkyl sulfates, alkylsulfonates or alkylarylsulfonates in which the alkyl and aryl groups respectively preferably comprise from 1 to 20 carbon atoms and from 6 to 30 carbon atoms. R12 and R13 preferably denote a mixture of alkenyl or alkyl groups containing from 12 to 21 carbon atoms, derived for example from tallow fatty acids, R14 preferably denotes a methyl group, and R1 5 preferably denotes a hydrogen atom. Such a product is so ld, for example, under the name Rewoquat^® W 75 by the company Rewo;

- di- or triquaternary ammonium salts, in particular of formula

(III) :

Rl6 -N-(CH₂)₃-N-R₂₁ 2X-

^R1S ^R20

(III)

in which Ri ₆ denotes an alkyl radical comprising approximately from 1 6 to 30 carbon atoms which is optionally hydroxylated and/or interrupted by one or more oxygen atoms, R17 is chosen from hydrogen or an alkyl radical comprising from 1 to 4 carbon atoms or an

(Rl 6a) (Rl 7a) (Rl 8 a)N-(CH₂)3 - group, R_{1 6}a, Rl 7a, Rl 8 a, Rl 8 , Rl 9 , R20 and

R21 , which may be identical or different, are chosen from hydrogen or an alkyl radical comprising from 1 to 4 carbon atoms and X^" is an anion chosen from the group of the halides, acetates, phosphates, nitrates and methyl sulfates . Such compounds are, for examp le, Finquat CT-P , available from the company Finetex (Quaternium 89), and Finquat CT, available from the company Finetex (Quaternium 75) .

- quaternary ammonium salts containing at least one ester function, such as those o f formula (IV) below :

in which: R22 is chosen from Ci-C₆ alkyl groups and Ci-C₆ hydroxyalkyl or dihydroxyalkyl groups;

R23 is chosen from:

O

- the group ²⁶

- groups R27, which are linear or branched, saturated aturated C1-C22 hydrocarbon-based groups,

- a hydrogen atom,

R25 is chosen from:

O

- the group ²⁸

- groups R29, which are linear or branched, saturated or unsaturated Ci-C₆ hydrocarbon-based groups,

- a hydrogen atom,

R24, R26 and R28, which may be identical or different, are chosen from linear or branched, saturated or unsaturated C7-C21 hydrocarbon-based groups;

r, s and t, which may be identical or different, are integers ranging from 2 to 6;

y is an integer ranging from 1 to 10;

x and z, which may be identical or different, are integers ranging from 0 to 10;

X^" is a simple or complex, organic or mineral anion;

with the proviso that the sum x + y + z is from 1 to 15, that when x is 0 then R₂₃ denotes R27, and that when z is 0 then R₂₅ denotes The alkyl groups R22 may be linear or branched, and more particularly linear.

Preferably, R22 denotes a methyl, ethyl, hydroxyethyl or dihydroxypropyl group, and more particularly a methyl or ethyl group.

Advantageously, the sum x + y + z is from 1 to 10. When R₂3 is an R₂₇ hydrocarbon-based group, it may be long and may contain from 12 to 22 carbon atoms, or may be short and may contain from 1 to 3 carbon atoms.

When R₂₅ is an R₂₉ hydrocarbon-based group , it preferably contains 1 to 3 carbon atoms .

Advantageously, R₂₄, R₂₆ and R₂s , which may be identical or different, are chosen from linear or branched, saturated or unsaturated C _{1 1} -C_{2 1} hydrocarbon-based groups, and more particularly from linear or branched, saturated or unsaturated C n -C_{2 1} alkyl and alkenyl groups .

Preferably, x and z, which may be identical or different, are equal to 0 or 1 .

Advantageously, y is equal to 1 .

Preferably, r, s and t, which may be identical or different, are equal to 2 or 3 , and even more particularly are equal to 2.

The anion X^" is preferably a halide (chloride, bromide or iodide) or an alkyl sulfate, more particularly methyl sulfate . However, use may be made o f methanesulfonate, phosphate, nitrate, tosylate, an anion derived from an organic acid, such as acetate or lactate, or any other anion compatible with the ammonium containing an ester function.

The anion X^" is even more particularly chloride or methyl sulfate.

Use is made more particularly, in the composition according to the invention, of the ammonium salts o f formula (IV) in which:

R₂₂ denotes a methyl or ethyl group,

x and y are equal to 1 ;

z is equal to 0 or 1 ;

r, s and t are equal to 2;

R₂3 is chosen from:

O - the group ^²⁶ ^

- methyl, ethyl or C i ₄-C₂₂ hydrocarbon-based groups,

- a hydrogen atom; R25 is chosen from:

- the group

- a hydrogen atom;

R24, R26 and R₂8, which may be identical or different, are chosen from linear or branched, saturated or unsaturated C₁₃-C₁₇ hydrocarbon-based groups, and preferably from linear or branched, saturated or unsaturated C₁₃-C₁₇ alkyl and alkenyl groups.

The hydrocarbon-based groups are advantageously linear.

Mention may be made, for example, of compounds of formula (IV), such as diacyloxyethyldimethylammonium, diacyloxyethyl(hydroxyethyl)methylammonium,

monoacyloxyethyldi(hydroxyethyl)methylammonium,

triacyloxyethylmethylammonium or monoacyloxyethyl(hydroxyethyl)dimethylammonium salts (in particular chloride or methyl sulfate), and mixtures thereof. The acyl groups preferably contain 14 to 18 carbon atoms and are obtained more particularly from a vegetable oil, such as palm oil or sunflower oil. When the compound contains several acyl groups, these groups may be identical or different.

These products are obtained, for example, by direct esterification of triethanolamine, triisopropanolamine, an alkyldiethanolamine or an alkyldiisopropanolamine, which are optionally oxyalkylenated, with Cio-C₃o fatty acids or with mixtures of Cio-C₃o fatty acids of plant or animal origin, or by transesterification of the methyl esters thereof. This esterification is followed by quaternization using an alkylating agent such as an alkyl (preferably methyl or ethyl) halide, a dialkyl (preferably methyl or ethyl) sulfate, methyl methanesulfonate, methyl para-toluenesulfonate, glycol chlorohydrin or glycerol chlorohydrin.

Such compounds are, for example, sold under the names

Dehyquart^® by the company Henkel, Stepanquat^® by the company Stepan, Noxamium by the company Ceca or Rewoquat WE 1 8 by the company Rewo-Witco .

The oxidizing composition used in the process according to the invention may contain, for example, a mixture o f quaternary ammonium monoester, diester and triester salts with a weight majority of diester salts .

Use may also be made o f the ammonium salts containing at least one ester function that are described in patents US-A-4 874 554 and US-A-4 137 1 80.

Use may be made o f behenoylhydroxypropyltrimethylammonium chloride, provided by Kao under the name Quatarmin BTC 13 1 .

Preferably, the ammonium salts containing at least one ester function contain two ester functions.

Among the quaternary ammonium salts containing at least one ester function, which can be used, it is preferred to use dipalmitoylethylhydroxyethylmethylammonium salts.

The cationic surfactants are preferably chosen from those of formula (I) and those of formula (IV), and even more preferentially from those o f formula (I) .

The oxidizing composition used in the process according to the invention may comprise one or more anionic surfactants .

The term "anionic surfactant" means a surfactant comprising, as ionic or ionizable groups, only anionic groups . These anionic groups are preferably chosen from the fo llowing groups :

-COOH, -COO^", - S O3H, - S O3 ^", -O S O3 H, -O S O3^", -PO2H2 , -PO₂H^", -PO₂ ^{2 "}, -P(OH)₂, =P(0)OH, -P(OH)0^", =P(0)0^", =POH, =PO , the anionic parts comprising a cationic counterion such as an alkali metal, an alkaline-earth metal or an ammonium.

As examples of anionic surfactants that may be used according to the invention, mention may be made of alkyl sulfates, alkyl ether sulfates, alkylamido ether sulfates, alkylaryl polyether sulfates, monoglyceride sulfates, alkylsulfonates, alkylamidesulfonates, alkylarylsulfonates, a-o lefin sulfonates, paraffin sulfonates, alkyl sulfosuccinates, alkyl ether sulfosuccinates, alkylamide sulfosuccinates, alkyl sulfoacetates, acylsarcosinates, acylglutamates, alkyl sulfo succinamates, acylisethionates and N-acyltaurates, polyglycoside polycarboxylic acid and alkyl monoester salts, acyl lactylates, salts of D-galactoside uronic acids, salts of alkyl ether carboxylic acids, salts of alkylaryl ether carboxylic acids, salts o f alkylamido ether carboxylic acids, and the corresponding non-salified forms o f all these compounds; the alkyl and acyl groups of all these compounds comprising from 6 to 40 carbon atoms and the aryl group denoting a phenyl group .

These compounds can be oxyethylenated and then preferably comprise from 1 to 50 ethylene oxide units.

The salts o f C₆ - C24 alkyl monoesters of polyglycoside- polycarboxylic acids may be chosen from C₆ - C24 alkyl po lyglycoside- citrates, C₆ - C24 alkyl polyglycoside-tartrates and C₆ - C24 alkyl poly glycoside-sulfo succinates .

When the anionic surfactant(s) are in salt form, they may be chosen from alkali metal salts such as the sodium or potassium salt and preferably the sodium salt, ammonium salts, amine salts and in particular amino alcohol salts, or alkaline-earth metal salts such as the magnesium salts .

Examples o f amino alcoho l salts that may especially be mentioned include monoethano lamine, diethanolamine and triethanolamine salts, monoisopropanolamine, diisopropanolamine or triisopropanolamine salts, 2-amino-2-methyl- 1 -propanol salts, 2- amino-2-methyl- 1 ,3 -propanediol salts and tris(hydroxymethyl)amino methane salts.

Alkali metal or alkaline-earth metal salts, and in particular sodium or magnesium salts, are preferably used.

Among the anionic surfactants mentioned, use is preferably made o f (C₆ - C24)alkyl sulfates, (C₆ - C24)alkyl ether sulfates comprising from 2 to 50 ethylene oxide units, in particular in the form o f alkali metal, ammonium, amino alcohol and alkaline-earth metal salts, or a mixture of these compounds. In particular, it is preferred to use (C i ₂-C₂o)alkyl sulfates, (C _{1 2}- C₂o)alkyl ether sulfates comprising from 2 to 20 ethylene oxide units, especially in the form o f alkali metal, ammonium, amino alcoho l and alkaline-earth metal salts, or a mixture of these compounds . Better still, it is preferred to use sodium lauryl ether sulfate containing 2.2 mo l o f ethylene oxide.

The oxidizing composition used in the process according to the invention may comprise one or more amphoteric or zwitterionic surfactants .

In particular, the amphoteric or zwitterionic surfactant(s), which are preferably non-silicone, which may be used in the present invention may especially be derivatives of optionally quaternized aliphatic secondary or tertiary amines, in which derivatives the aliphatic group is a linear or branched chain comprising from 8 to 22 carbon atoms, the said amine derivatives containing at least one anionic group, for instance a carboxylate, sulfonate, sulfate, phosphate or phosphonate group .

Mention may be made in particular of (C₈-C₂o)alkylbetaines, (C₈-C₂o)alkylsulfobetaines, (C₈-C₂o)alkylamido(C3 -C₈)alkylbetaines and (C₈-C₂o)alkylamido(C6-C₈)alkylsulfobetaines.

Among the optionally quaternized secondary or tertiary aliphatic amine derivatives that may be used, as defined above, mention may also be made of the compounds having the respective structures (V) and (VI) below: a-CONHCH₂CH₂- N⁺(R_b)(R_c)-CH₂COO^", M⁺ , X^" (V) in which formula:

- R_a represents a C 1 0 - C30 alkyl or alkenyl group derived from an acid R_aCOOH preferably present in hydro lysed coconut oil, or a heptyl, nonyl or undecyl group;

- Rb represents a beta-hydroxyethyl group; and

- R_c represents a carboxymethyl group; - M represents a cationic counterion derived from an alkali metal or alkaline-earth metal, such as sodium, an ammonium ion or an ion derived from an organic amine, and

- X^" represents an organic or mineral anionic counterion, such as that chosen from halides, acetates, phosphates, nitrates, (Ci-

C₄)alkyl sulfates, (Ci-C₄)alkyl- or (Ci-C₄)alkylarylsulfonates, in particular methyl sulfate and ethyl sulfate; or alternatively M⁺ and X^" are absent; a'-CONHCH₂CH₂-N(B)(B') (VI) in which formula:

- B represents the group -CH₂CH₂OX';

- B' represents the group -(CH₂)_ZY', with z = 1 or 2; - X* represents the group -CH₂COOH, -CH₂-COOZ',

-CH₂CH₂COOH, -CH₂CH₂-COOZ', or a hydrogen atom;

- Y* represents the group -COOH, -COOZ',

-CH₂CH(OH)S0₃H or the group CH₂CH(OH)S0₃-Z' ;

- Z' represents a cationic counterion derived from an alkali metal or alkaline-earth metal, such as sodium, an ammonium ion or an ion derived from an organic amine;

- R_a' represents a Cio-C₃o alkyl or alkenyl group of an acid R_a'-COOH which is preferably present in coconut oil or in hydrolysed linseed oil, or an alkyl group, especially a C₁₇ group, and its iso form, or an unsaturated C₁₇ group.

These compounds are classified in the CTFA dictionary, 5th edition, 1993, under the names disodium cocoamphodiacetate, disodium lauroamphodiacetate, disodium caprylamphodiacetate, disodium capryloamphodiacetate, disodium cocoamphodipropionate, disodium lauroamphodipropionate, disodium caprylamphodipropionate, disodium capryloamphodipropionate, lauroamphodipropionic acid and cocoamphodipropionic acid. By way o f example, mention may be made o f the cocoamphodiacetate sold by the company Rhodia under the trade name Mirano l® C2M Concentrate.

Use may also be made o f the compounds of formula (VII) : a "-NHCH(Y' ')-(CH₂)_nCONH(CH₂)_n '-N(R_d)(R_e) (VII) in which formula:

- Y" represents the group -COOH, -COOZ " ,

-CH₂CH(OH)S0₃H or the group CH₂CH(OH)S0₃-Z " ;

- Rd and R_e represent, independently of each other, a C ₁ - C 4 alkyl or hydroxyalkyl radical;

- Z" represents a cationic counterion derived from an alkali metal or alkaline-earth metal, such as sodium, an ammonium ion or an ion derived from an organic amine;

- R_a" represents a C i o-C₃o alkyl or alkenyl group of an acid R_a"-COOH which is preferably present in coconut oil or in hydrolysed linseed oil;

- n and n' denote, independently o f each other, an integer ranging from 1 to 3.

Among the compounds o f formula (VII), mention may be made of the compound classified in the CTFA dictionary under the name sodium diethylaminopropyl cocoaspartamide and sold by the company Chimex under the name Chimexane HB .

These compounds may be used alone or as mixtures.

Among the amphoteric or zwitterionic surfactants mentioned above, use is preferably made of (C ₈ -C₂o)alkylbetaines such as cocoylbetaine, (C₈ -C₂o)alkylamido(C₃ - C₈)alkylbetaines such as cocamidopropylbetaine, and mixtures thereof, and the compounds of formula (VII) such as the sodium salt of diethylaminopropyl laurylamino succinamate (INCI name : sodium diethylaminopropyl cocoaspartamide).

Among all the surfactants mentioned, use is preferably made o f one or more nonionic surfactants . In a preferred embodiment, the oxidizing composition used in the process according to the invention comprises one or more nonionic surfactants and one or more cationic surfactants .

In general, the surfactant(s) represent from 1 % to 50%, preferably from 5 % to 40% and better still from 10% to 30% by weight relative to the total weight of the oxidizing composition.

As indicated previously, the oxidizing composition used in the process according to the invention comprises one or more fatty substances.

The term "fatty substance" means an organic compound that is inso luble in water at ordinary temperature (25 °C) and at atmospheric pressure (760 mmHg) (so lubility o f less than 5 %, preferably less than 1 % and even more preferentially less than 0. 1 %) . The fatty substances have in their structure at least one hydrocarbon-based chain comprising at least 6 carbon atoms or a sequence of at least two siloxane groups . In addition, the fatty substances are generally soluble in organic so lvents under the same temperature and pressure conditions, for instance chloroform, dichloromethane, carbon tetrachloride, ethanol, benzene, toluene, tetrahydrofuran (THF), liquid petroleum j elly or decamethylcyclopentasiloxane.

The fatty substances of the invention preferably do not contain any salified carboxylic acid groups .

Particularly, the fatty substances o f the invention are neither oxyalkylenated nor glycerolated ethers .

The term "oil" means a " fatty substance" that is liquid at room temperature (25 °C) and at atmospheric pressure (760 mmHg; i. e. 1 .013 x 10^s Pa) .

The term "non-silicone oil" means an oil not containing any silicon atoms (Si) and the term " silicone oil" means an oil containing at least one silicon atom.

More particularly, the fatty substances are chosen from C₆ - C i 6 hydrocarbons, hydrocarbons containing more than 16 carbon atoms, non- silicone oils of animal origin, plant or synthetic oils o f triglyceride type, fluoro oils, fatty alcoho ls, fatty acid and/or fatty alcoho l esters other than triglycerides and plant waxes, non-silicone waxes other than fatty alcoho ls, and silicones, and mixtures thereof.

It is recalled that the fatty alcoho ls, esters and acids more particularly contain at least one saturated or unsaturated, linear or branched hydrocarbon-based group comprising 6 to 30 and better still from 8 to 30 carbon atoms, which is optionally substituted, in particular by one or more hydroxyl groups (in particular 1 to 4) . If they are unsaturated, these compounds may comprise one to three conjugated or unconjugated carbon-carbon double bonds .

As regards the C₆ - C i 6 hydrocarbons, they may be linear, branched, and optionally cyclic, and are preferably chosen from alkanes. Examples that may be mentioned include hexane, dodecane, undecane, tridecane, and isoparaffins, for instance isohexadecane, isododecane and isodecane.

The linear or branched hydrocarbons of mineral or synthetic origin, containing more than 16 carbon atoms, are preferably chosen from liquid paraffins, petroleum j elly, liquid petroleum j elly, polydecenes, squalane, and hydrogenated polyisobutene such as Parleam^®.

A hydrocarbon-based oil o f animal origin that may be mentioned is perhydrosqualene.

The triglyceride oils of plant or synthetic origin are preferably chosen from liquid fatty acid triglycerides containing from 6 to 30 carbon atoms, for instance heptanoic or octanoic acid triglycerides, or alternatively, for example, sunflower oil, corn oil, soybean oil, pumpkin oil, grapeseed oil, sesame seed oil, hazelnut oil, apricot oil, macadamia oil, arara oil, castor oil, avocado oil, caprylic/capric acid triglycerides, for instance those sold by the company Stearineries Dubois or those sold under the names Miglyol® 8 10, 8 12 and 8 1 8 by the company Dynamit Nobel, jojoba oil and shea butter oil.

Use will preferably be made of triglyceride oils of plant origin. The fluoro oils may be chosen from perfluoromethylcyclopentane and perfluoro- 1 ,3 -dimethylcyclohexane, so ld under the names Flutec® PC I and Flutec® PC3 by the company BNFL Fluorochemicals; perfluoro- 1 ,2-dimethylcyclobutane; perfluoroalkanes such as dodecafluoropentane and tetradecafluorohexane, sold under the names PF 5050® and PF 5060® by the company 3M, or bromoperfluorooctyl sold under the name Foralkyl® by the company Atochem; nonafluoromethoxybutane and nonafluoroethoxyisobutane; perfluoromorpholine derivatives such as 4-trifluoromethyl perfluoromorpholine sold under the name PF 5052® by the company 3M.

The fatty alcohols that are suitable for use in the invention are more particularly chosen from linear or branched, saturated or unsaturated alcohols comprising from 6 to 30 carbon atoms and preferably from 8 to 30 carbon atoms. Examples that may be mentioned include cetyl alcohol, stearyl alcohol and the mixture thereof (cetylstearyl alcohol), octyldodecanol, 2-butyloctanol, 2- hexyldecanol, 2-undecylpentadecanol, oleyl alcohol and linoleyl alcohol.

As regards the fatty acid and/or fatty alcohol esters, which are advantageously different from the triglycerides mentioned above, mention may be made especially of esters of saturated or unsaturated, linear or branched Ci-C₂₆ aliphatic mono- or polyacids and of saturated or unsaturated, linear or branched Ci-C₂₆ aliphatic mono- or polyalcohols, the total carbon number of the esters being greater than or equal to 6 and more advantageously greater than or equal to 10.

Among the monoesters, mention may be made of dihydroabietyl behenate; octyldodecyl behenate; isocetyl behenate; cetyl lactate; C₁₂- Ci5 alkyl lactate; isostearyl lactate; lauryl lactate; linoleyl lactate; oleyl lactate; (iso)stearyl octanoate; isocetyl octanoate; octyl octanoate; cetyl octanoate; decyl oleate; isocetyl isostearate; isocetyl laurate; isocetyl stearate; isodecyl octanoate; isodecyl oleate; isononyl isononanoate; isostearyl palmitate; methyl acetyl ricinoleate; myristyl stearate; octyl isononanoate; 2-ethylhexyl isononate; octyl palmitate; octyl pelargonate; octyl stearate; octyldodecyl erucate; oleyl erucate; ethyl and isopropyl palmitates, 2-ethylhexyl palmitate, 2-octyldecyl palmitate, alkyl myristates such as isopropyl, butyl, cetyl, 2- octyldodecyl, myristyl or stearyl myristate, hexyl stearate, butyl stearate, isobutyl stearate; dio ctyl malate, hexyl laurate, 2-hexyldecyl laurate.

Still within the context of this variant, esters of C4 - C22 dicarboxylic or tricarboxylic acids and of C 1 - C22 alcoho ls and esters of mono-, di- or tricarboxylic acids and of C2 - C26 di-, tri-, tetra- or pentahydroxy alcohols may also be used.

Mention may in particular be made of: diethyl sebacate; diisopropyl sebacate; diisopropyl adipate; di(n-propyl) adipate; dioctyl adipate; diisostearyl adipate; dio ctyl maleate; glyceryl undecylenate; octyldodecyl stearoyl stearate; pentaerythrityl monoricino leate; pentaerythrityl tetraisononanoate; pentaerythrityl tetrapelargonate; pentaerythrityl tetraisostearate; pentaerythrityl tetraoctanoate; propylene glyco l dicaprylate; propylene glycol dicaprate; tridecyl erucate; triisopropyl citrate; triisostearyl citrate; glyceryl trilactate; glyceryl trioctanoate; trioctyldodecyl citrate; trio leyl citrate; propylene glyco l dioctanoate; neopentyl glyco l diheptanoate; diethylene glycol diisononanoate; and polyethylene glyco l distearates .

Among the esters mentioned above, use is preferably made o f ethyl, isopropyl, myristyl, cetyl or stearyl palmitate, 2-ethylhexyl palmitate, 2-octyldecyl palmitate, alkyl myristates, such as isopropyl, butyl, cetyl or 2-octyldodecyl myristate, hexyl stearate, butyl stearate, isobutyl stearate, dioctyl malate, hexyl laurate, 2-hexyldecyl laurate, isononyl isononanoate or cetyl octanoate.

The oxidizing composition may also comprise, as fatty ester, sugar esters and diesters of C6 - C30 and preferably C 12 - C22 fatty acids . It is recalled that the term "sugar" means oxygen-bearing hydrocarbon- based compounds containing several alcohol functions, with or without aldehyde or ketone functions, and which comprise at least 4 carbon atoms. These sugars may be monosaccharides, oligosaccharides or polysaccharides .

Examples o f suitable sugars that may be mentioned include sucrose (or saccharose), glucose, galactose, ribose, fucose, maltose, fructose, mannose, arabinose, xylose and lactose, and derivatives thereo f, especially alkyl derivatives, such as methyl derivatives, for instance methylglucose.

The sugar esters of fatty acids may be chosen especially from the group comprising the esters or mixtures of esters of sugars described previously and of linear or branched, saturated or unsaturated C6 - C30 and preferably C 1 2 - C22 fatty acids . If they are unsaturated, these compounds may comprise one to three conjugated or unconjugated carbon-carbon double bonds.

The esters according to this variant may also be chosen from monoesters, diesters, triesters, tetraesters and po lyesters, and mixtures thereo f.

These esters may be, for example, o leates, laurates, palmitates, myristates, behenates, cocoates, stearates, linoleates, linolenates, caprates and arachidonates, or mixtures thereof such as, especially, oleopalmitate, oleostearate and palmitostearate mixed esters .

More particularly, use is made of monoesters and diesters and in particular mono- or di-o leate, -stearate, -behenate, -oleate/palmitate, -lino leate, -lino lenate or -oleate/stearate of sucrose, glucose or methylglucose.

Mention may be made, by way o f examp le, of the product sold under the name Glucate^® DO by the company Amercho l, which is a methylglucose dio leate .

Examples o f esters or mixtures of esters of sugar and of fatty acid that may also be mentioned include :

- the products sold under the names F 160, F 140, F 1 10, F90,

F70 and SL40 by the company Crodesta, respectively denoting sucrose palmitate/stearates formed from 73 % monoester and 27% diester and triester, from 61 %> monoester and 39% diester, triester and tetraester, from 52% monoester and 48% diester, triester and tetraester, from 45 % monoester and 55 % diester, triester and tetraester, from 39% monoester and 6 1 % diester, triester and tetraester, and sucrose mono laurate; - the products sold under the name Ryoto Sugar Esters, for example referenced B370 and corresponding to sucrose behenate formed from 20% monoester and 80%> diester-triester-polyester;

- the sucrose mono-dipalmitate/stearate sold by the company Goldschmidt under the name Tegosoft^® PSE .

The non-silicone wax(es) other than fatty alcoho ls are chosen especially from carnauba wax, candelilla wax, esparto wax, paraffin wax, ozokerite, plant waxes, such as olive tree wax, rice wax, hydrogenated jojoba wax or absolute flower waxes, such as the blackcurrant blossom essential wax sold by the company Bertin (France), or animal waxes, such as beeswaxes or modified beeswaxes (cerabellina); other waxes or waxy raw materials that can be used according to the invention are in particular marine waxes, such as the product sold by the company Sophim under the reference M82, polyethylene waxes or polyolefin waxes in general.

The fatty substance(s) according to the invention may be chosen from silicones.

The silicones that can be used in accordance with the invention may be in the form o f oils, waxes, resins or gums .

Preferably, the silicone(s) are chosen from polydialkylsiloxanes, in particular po lydimethylsiloxanes (PDMSs), and organomodified polysiloxanes comprising at least one functional group chosen from amino groups, aryl groups and alkoxy groups .

Silicones are defined in greater detail in Walter No ll ' s Chemistry and Technology of Silicones ( 1968), Academic Press . They may be vo latile or non- vo latile.

The vo latile silicones are more particularly chosen from silicones with a boiling point of between 60°C and 260°C , and even more particularly silicones chosen from:

(i) cyclic po lydialkylsiloxanes comprising from 3 to 7 and preferably from 4 to 5 silicon atoms. These are, for example, octamethylcyclotetrasiloxane sold in particular under the name Volatile Silicone^® 7207 by Union Carbide or Silbione^® 70045 V2 by Rhodia, decamethylcyclopentasiloxane sold under the name Volatile Silicone* 7158 by Union Carbide, and Silbione* 70045 V5 by Rhodia, and mixtures thereof.

Mention may also be made o f cyclocopolymers of the dimethylsiloxane/methylalkylsiloxane type, such as Volatile Silicone® FZ 3 109 so ld by the company Union Carbide, of formula:

with D" : ^— Si - O— with D' : - Si - O—

CH₃ C₈ H₁₇

Mention may also be made o f mixtures o f cyclic polydialkylsiloxanes with organosilicon compounds, such as the mixture of octamethylcyclotetrasiloxane and tetra(trimethylsilyl)pentaerythrito l (50/50) and the mixture of octamethylcyclotetrasiloxane and oxy- 1 , 1 ' -bis(2 ,2,2 ' ,2 ' ,3 ,3 ' - hexatrimethylsilyloxy)neopentane;

(ii) linear vo latile po lydialkylsiloxanes containing 2 to 9 silicon atoms and having a viscosity o f less than or equal to 5 x 10^"6 m²/s at 25 °C . An example is decamethyltetrasiloxane so ld in particular under the name SH 200 by the company Toray Silicone . Silicones belonging to this category are also described in the article published in Cosmetics and Toiletries, Vol. 91 , Jan. 76, pp . 27-32 , Todd & Byers, Volatile Silicone Fluids for Cosmetics .

The non-vo latile silicones that may be used according to the invention may preferably be non-volatile po lydialkylsiloxanes, polydialkylsiloxane gums and resins, polyorganosiloxanes modified with organic functional groups chosen from amine groups, aryl groups and alkoxy groups, and also mixtures thereof.

The organomodified silicones that may be used in accordance with the invention are silicones as defined above and comprising in their structure one or more organofunctional groups attached via a hydrocarbon-based group . The organomodified silicones may be polydiarylsiloxanes, in particular polydiphenylsiloxanes, and polyalkylarylsiloxanes functionalized with the organo functional groups mentioned previously.

The po lyalkylarylsiloxanes are particularly chosen from linear and/or branched polydimethyl/methylphenylsiloxanes and polydimethyl/diphenylsiloxanes with a viscosity ranging from l x l O^"5 to 5 x l 0^"2 m²/s at 25 °C .

Among these polyalkylarylsiloxanes, examples that may be mentioned include the products sold under the following names :

- the Silbione® oils o f the 70 641 series from Rhodia;

- the oils o f the Rhodorsi 1^® 70 633 and 763 series from Rhodia;

- the oil Dow Corning 556 Cosmetic Grade Fluid from Dow Corning;

- the silicones o f the PK series from Bayer, such as the product PK20;

- the silicones o f the PN and PH series from Bayer, such as the products PN 1000 and PH 1 000;

- certain oils o f the SF series from General Electric, such as SF 1023 , SF 1 154, SF 1250 and SF 1265.

Mention may also be made, among the organomodified silicones, of polyorganosiloxanes comprising :

- substituted or unsubstituted amine groups, such as the products sold under the names GP 4 Silicone Fluid and GP 71 00 by the company Genesee or the products sold under the names Q2 8220 and Dow Corning 929 or 939 by the company Dow Corning. The substituted amine groups are, in particular, C 1 - C 4 amino alkyl groups;

- alkoxylated groups, such as the product sold under the name Silicone Copolymer F-755 by SWS Silicones and Abil Wax® 2428 , 2434 and 2440 by the company Go ldschmidt.

More particularly, the fatty substances are chosen from compounds that are liquid or pasty at room temperature (25 ° C) and at atmospheric pressure.

Preferably, the fatty substance(s) are chosen from compounds that are liquid at a temperature of 25 °C and at atmospheric pressure. The fatty substances are advantageously chosen from C₆ - C i 6 alkanes, linear or branched hydrocarbons, of mineral or synthetic origin, containing more than 1 6 carbon atoms, non-silicone oils o f plant, mineral or synthetic origin, fatty alcohols, and fatty acid and/or fatty alcoho l esters, or mixtures thereof.

Preferably, the fatty substance(s) are chosen from linear or branched liquid hydrocarbons, of mineral or synthetic origin, containing more than 16 carbon atoms, and especially liquid petroleum j elly and hydrogenated po lyisobutene, C₆ - C i 6 alkanes, liquid fatty acid and/or fatty alcohol esters, and liquid fatty alcohols, and mixtures thereo f.

In general, the fatty substances may represent from 1 % to 60%, preferably from 2% to 50%>, better still from 5 % to 40%> by weight, even better still from 10% to 30% by weight and very preferentially from 12% to 25 % by weight relative to the total weight of the oxidizing composition.

The oxidizing composition used in the process in accordance with the invention may also comprise one or more cosmetic adjuvants.

For example, they may comprise one or more standard additives that are well known in the art, such as anionic, cationic, nonionic or amphoteric polymers or mixtures thereo f, agents for preventing hair lo ss, so lid fatty substances other than those mentioned previously, vitamins and provitamins including pantheno l, sunscreens, mineral or organic pigments, sequestrants, plasticizers, solubilizers, acidifying agents, mineral or organic thickeners, especially polymeric thickeners, opacifiers, antioxidants, hydroxy acids, nacreous agents, fragrances and preserving agents .

Needless to say, a person skilled in the art will take care to select this or these optional additional compound(s) such that the advantageous properties intrinsically associated with the composition used in the process according to the invention are not, or are not substantially, adversely affected by the envisaged addition(s). The above adjuvants may generally be present in an amount, for each o f them, of between 0 and 20% by weight relative to the total weight of the oxidizing composition.

The oxidizing composition used in the process according to the invention comprises water in a preferential content greater than or equal to 40%> by weight, preferably ranging from 40%> to 95 % by weight, more preferentially from 40% to 80% by weight and in particular from 40% to 70% by weight, relative to the total weight o f the oxidizing composition.

The oxidizing composition may also comprise one or more water-so luble organic solvents (solubility o f greater than or equal to 5 % in water at 25 °C and at atmospheric pressure).

Examples o f water-so luble organic solvents that may be mentioned include linear or branched and preferably saturated monoalcoho ls or dio ls, comprising 2 to 10 carbon atoms, such as ethyl alcoho l, isopropyl alcoho l, hexylene glycol (2-methyl-2,4- pentanedio l), neopentyl glyco l and 3 -methyl- 1 ,5 -pentanedio l, butylene glyco l, dipropylene glycol and propylene glyco l; aromatic alcoho ls such as phenylethyl alcohol; polyols containing more than two hydroxyl functions, such as glycero l; polyo l ethers, for instance ethylene glycol monomethyl, monoethyl and monobutyl ether, propylene glyco l or ethers thereof, for instance propylene glyco l monomethyl ether; and also diethylene glyco l alkyl ethers, especially C 1 - C 4 alkyl ethers, for instance diethylene glycol monoethyl ether or monobutyl ether, alone or as a mixture.

The water-so luble organic solvents, when they are present, generally represent between 1 % and 20% by weight relative to the total weight of the oxidizing composition, and preferably between 5 % and 10% by weight relative to the total weight of the oxidizing composition.

The pH o f the oxidizing composition used in the process according to the invention preferably ranges from 1 .5 to 9, better still from 1 .5 to 7 and even better still from 2 to 4. The compositions used in the process according to the invention may especially be in the form of fluid or thickened liquids, gels or creams .

The nanoemulsions used in the process according to the invention may be prepared by mixing water, the fatty substance(s) and the surfactant(s), with vigorous stirring, at a temperature preferably between approximately 20°C and 45 °C, followed by one or more steps of homogenization at high pressure, i.e . at a pressure preferably greater than or equal to 5 x 10⁷ Pa and preferably ranging from 6 x 10⁷ to 1 8 x l 0⁷ Pa. The shear will preferably be from 2 x l 0⁶ s^{" 1} to 5 x l 0⁸ s^{" 1} , and more preferentially from l x l O⁸ s^{" 1} to 3 x 10⁸ s^{" 1} .

According to a preferred embodiment of the nanoemulsions used in the process according to the invention, several successive high-pressure homogenization steps as described above are performed.

The nanoemulsions used in the process according to the invention may also be prepared with the aid o f a ternary phase diagram (fatty substance/surfactant/water), established beforehand, according to the fo llowing process :

(i) mixing with stirring of one or more fatty substances and o f one or more surfactants, at a temperature Tm and at normal atmospheric pressure;

(ii) addition o f water with stirring, so as to reach the nanoemulsion zone, detected beforehand by means o f the ternary phase diagram;

(iii) coo ling o f the composition to room temperature. The addition o f the water-soluble ingredients such as the oxidizing agent(s) takes place at the end of step (ii) or after step (iii) .

The temperature Tm is preferably between 20 and 100°C and better still between 20 and 85 °C .

It should be noted that the particle size of the nanoemulsion is conserved during and after this cooling.

In a first embodiment of the invention, the process according to the invention is a process for bleaching keratin fibres . In a first variant of this embodiment, the process according to the invention comprises a step of applying the oxidizing composition alone to the said fibres .

In a second variant of this embodiment, the process according to the invention comprises a step of applying the oxidizing

composition to the said fibres in combination with a second anhydrous composition comprising at least one peroxygenated salt.

It is indicated that the term " anhydrous" denotes a composition whose water content is less than 1 % and preferably less than 0.5 % by weight relative to the total weight of this composition.

Advantageously, the peroxygenated salt is chosen from persulfates, perborates and percarbonates of ammonium or of alkali metals, such as potassium or sodium; magnesium peroxide; alone or as a mixture.

Preferably, the second anhydrous composition comprises at least one persulfate as peroxygenated salt, and even more preferably at least one sodium and potassium persulfate.

Usually, the content of peroxygenated salt ranges from 10% to 70% by weight and preferably from 20% to 60% by weight relative to the weight of the second composition.

The second composition also preferably comprises at least one alkaline agent. More particularly, this alkaline agent is chosen from urea, alkali metal or alkaline-earth metal silicates, phosphates and bicarbonates, and in particular alkali metal metasilicates, or ammonia precursors such as ammonium salts, for instance chlorides, sulfates, phosphates or nitrates .

When it is used, the content of alkaline agent represents from 0.01 % to 40% by weight and preferably from 0. 1 % to 30% by weight relative to the weight of the second composition.

According to an advantageous embodiment, the second composition comprises at least one inert organic compound.

The inert organic compound(s) may be chosen from the fatty substances described above, which are present in the oxidizing composition. The preceding description o f the fatty substances given previously also applies to this second composition.

Preferably, if it is present, the inert organic compound is chosen from linear hydrocarbons of more than 16 carbon atoms, and fatty alcoho l and/or fatty acid esters.

Usually, the content of inert organic compound, when the second composition comprises the same, ranges between 5 % and 60% by weight of the second composition.

It should be noted that this second composition may be in the form of a powder or a paste.

The second composition may also comprise one or more additives especially such as water-so luble thickening polymers, fillers such as clays or amorphous silica, binders such as vinylpyrrolidone, lubricants such as polyo l stearates or alkali metal or alkaline-earth metal stearates, and also oxygen-release control agents such as magnesium carbonate or oxide, dyes or matting agents such as titanium oxides, or alternatively anionic, nonionic, cationic or amphoteric surfactants, and vitamins.

By way o f illustration, the content of additive(s) generally represents from 0.01 % to 40% by weight and preferably from 0. 1 % to 30%) by weight relative to the weight of the second composition.

The second composition is preferably mixed, before applying to the fibres, with the oxidizing composition, for example with about 0.5 to 1 0 weight equivalents of the oxidizing composition.

In a second embodiment, the process according to the invention is a process for dyeing keratin fibres.

In a preferred variant of this embodiment of the invention, the process according to the invention consists in applying the oxidizing composition in combination with a dye composition.

More particularly, in this embodiment, the dyeing process according to the invention consists in applying the oxidizing

composition, simultaneously with or sequentially to , a dye

composition comprising one or more oxidation dyes and/or one or more direct dyes, and preferably one or more oxidation dyes . The dye composition used in this dyeing process may comprise :

- one or more standard oxidation dye precursors chosen especially from oxidation bases such as phenylenediamines,

bis (phenyl) alky lenediamines, para-aminophenols, ortho-aminopheno ls, heterocyclic bases and the addition salts thereof; optionally combined with one or more usual couplers, for instance meta-phenylenediamines, meta-aminopheno ls, meta-diphenols, naphthalene-based couplers or heterocyclic couplers, and also the addition salts thereo f, and/or

- one or more direct dyes chosen, for example, from synthetic or natural, cationic or nonionic direct dyes .

Examples of particularly suitable direct dyes that may be mentioned include nitrobenzene dyes; azo direct dyes; azomethine direct dyes; methine direct dyes; azacarbocyanin direct dyes, for instance tetraazacarbocyanines (tetraazapentamethines); quinone and in particular anthraquinone, naphthoquinone or benzoquinone direct dyes; azine direct dyes; xanthene direct dyes; triarylmethane direct dyes; indoamine direct dyes; indigoid direct dyes; phthalocyanine direct dyes, porphyrin direct dyes and natural direct dyes, alone or as mixtures . In particular, mention may be made o f direct dyes from among : azo; methine; carbonyl; azine; nitro (hetero)aryl; tri(hetero)arylmethane; porphyrin; phthalocyanine and natural direct dyes, alone or as mixtures.

The dye composition usually comprises dyes (oxidation dyes and/or direct dyes) in a content ranging, for example, from 0.0001 % to 10% by weight and preferably from 0.005 % to 5 % by weight relative to the weight of the dye composition.

The dye composition may also comprise other ingredients such as fatty substances, chosen especially from those listed previously.

It may also comprise at least one alkaline agent for example chosen from aqueous ammonia, alkali metal carbonates or bicarbonates, organic amines with a pKb at 25 °C of less than 12 , in particular less than 1 0 and even more advantageously less than 6; from the salts of the amines mentioned previously with acids such as carbonic acid or hydrochloric acid: it should be noted that it is the pKb corresponding to the function of highest basicity.

Preferably, the amines are chosen from alkanolamines, in particular comprising a primary, secondary or tertiary amine function, and one or more linear or branched Ci-Cs alkyl groups bearing one or more hydroxyl radicals; from oxyethylenated and/or oxypropylenated ethylenediamines, and from amino acids and compounds having the following formula:

^Rx\ /^Rz

N-W-N

Ry t

in which W is a Ci-C₆ alkylene residue optionally substituted with a hydroxyl group or a Ci-C₆ alkyl radical; Rx, Ry, Rz and Rt, which may be identical or different, represent a hydrogen atom or a Ci-C₆ alkyl, Ci-C₆ hydroxyalkyl or Ci-C₆ aminoalkyl radical.

According to one embodiment of the invention, the dye composition is used in the presence of aqueous ammonia and/or of at least one alkanolamine and/or of at least one basic amino acid, more advantageously of aqueous ammonia and/or of at least one alkanolamine, such as monoethanolamine, or mixtures thereof.

Advantageously, the content of alkaline agent(s) ranges from 0.01% to 30% by weight, preferably from 0.1% to 20% by weight and better still from 1% to 10% by weight relative to the weight of the dye composition. It should be noted that this content is expressed as NH₃ when the alkaline agent is aqueous ammonia.

The dye composition may also contain various adjuvants, such as, in a non-limiting manner, nonionic, cationic, anionic or amphoteric surfactants, and especially those mentioned previously in the context of the oxidizing composition; anionic, nonionic or amphoteric polymers or mixtures thereof; antioxidants; penetrants; sequestrants; fragrances; dispersants; film-forming agents; ceramides; preserving agents; opacifiers.

The above adjuvants may be present in an amount for each of them of between 0.01% and 20% by weight relative to the weight of the dye composition. The dye composition may also comprise water and/or one or more organic solvents .

Examples o f organic so lvents that may be mentioned include linear or branched, preferably saturated, monoalcohols or dio ls, comprising from 2 to 10 carbon atoms, such as ethyl alcoho l, isopropyl alcoho l, hexylene glyco l (2-methyl-2,4-pentanedio l), neopentyl glyco l and 3 -methyl- l ,5 -pentanedio l, butylene glyco l, dipropylene glycol and propylene glyco l; aromatic alcoho ls such as benzyl alcoho l and phenylethyl alcoho l; po lyo ls containing more than two hydroxyl functions, such as glycerol; polyo l ethers, for instance ethylene glycol monomethyl, monoethyl and monobutyl ethers, propylene glyco l or ethers thereof, for instance propylene glycol monomethyl ether; and also diethylene glyco l alkyl ethers, especially o f C 1 - C 4 , for instance diethylene glycol monoethyl ether or monobutyl ether, alone or as mixtures.

When they are present, the organic so lvents generally represent between 1 % and 40% by weight relative to the total weight of the dye composition, and preferably between 5 % and 30% by weight relative to the total weight of the dye composition.

Preferably, the dye composition is aqueous.

The pH of the dye composition generally ranges from 6 to 1 1 and even better still from 8.5 to 1 1 .

It can be adjusted by adding acidifying agents, such as hydrochloric acid, (ortho)phosphoric acid, sulfuric acid, boric acid, and also carboxylic acids, for instance acetic acid, lactic acid or citric acid, or sulfonic acids. Alkaline agents such as those previously mentioned may also be used.

Preferably, the process according to this second mode of the invention is performed by applying to the keratin fibres the oxidizing composition in the presence o f the abovementioned dye composition.

These two compositions may be applied one after the other, without intermediate rinsing, or alternatively mixed just before applying to the keratin fibres. The process may be repeated several times in order to obtain the desired coloration.

Irrespective o f the process used (dyeing, bleaching) and the number of compositions used, the composition(s) described previously, optionally mixed beforehand, is/are applied to wet or dry keratin fibres.

The composition(s) are usually left in place on the fibres for a time generally ranging from 1 minute to 1 hour and preferably from 5 minutes to 30 minutes.

The temperature during the process is conventionally between

20 and 80°C and preferably between 20 and 60°C .

After the treatment, the human keratin fibres are advantageously rinsed with water. They may optionally be washed with a shampoo , followed by rinsing with water, before being dried or left to dry.

The process according to the invention is preferably a process for the oxidation dyeing of keratin fibres.

The examp le that fo llows is given purely as an illustration o f the present invention.

EXAMPLE :

A cosmetic composition in the form of a nanoemulsion was prepared, in accordance with the invention, from the ingredients indicated in the table below (in which the contents are indicated in grams o f active material) :

PEG-8 1 .5

PEG-8 isostearate 13.5

Hydrogenated polyisobutene 15

Sodium stannate 0.04

EDTA 0.2

Tetrasodium pyrophosphate 0.03

Phosphoric acid qs pH 2.2

Water qs l OOg

The nanoemulsion o f the above composition was obtained from the knowledge of the surfactants/hydrogenated polyisobutene/water ternary phase diagram. The mixture of surfactants and of hydrogenated polyisobutene o f the above composition according to the invention was brought to a temperature of 60°C and the mixture was then diluted with the water of the formula at the same temperature. The composition was finally cooled to room temperature (20 to 25 °C) . The water-so luble compounds including the hydrogen peroxide are added either after addition of the water or after cooling to room temperature .

After this cooling to room temperature, the pH is then optionally adjusted to the desired value to obtain the desired composition.

A nanoemulsion in which the size o f the oil globules, measured by quasi-elastic light scattering, is less than 100 nm is obtained. This composition is stable on storage for at least 2 months at room temperature and at 45 ° C .

When applied alone, the composition o f the example allows the hair to be bleached.

When applied as a mixture with a dyeing cream containing oxidation dyes, it allows very satisfactory dyeing of the hair to be obtained.

The Applicant finds that the composition (or, if appropriate, the mixture) according to the example above has very good working qualities, and especially a particularly pleasant texture.

The composition (or, if appropriate, the mixture) according to the example above was applied to locks of hair. The Applicant finds that the composition (or, if appropriate, the mixture) is easy to apply and to spread onto the locks of hair.

In addition, the said composition (or, if appropriate, the mixture) does not run and remains well located at the points o f application and spreads easily from the roots to the ends .

Claims

1 . Process for dyeing and/or bleaching keratin fibres using an oxidizing composition in the form of an oil-in-water nanoemulsion comprising one or more oxidizing agents, one or more surfactants, one or more fatty substances and water; the number-average size of the oil droplets in the said nanoemulsion being less than or equal to 100 nm.

2. Process according to Claim 1 , characterized in that the oxidizing agent(s) are chosen from hydrogen peroxide, urea peroxide, alkali metal bromates or ferricyanides and peroxygenated salts, and is preferably hydrogen peroxide.

3. Process according to any one o f the preceding claims, characterized in that the said oxidizing agent(s) represent from 0.0 1 % to 20%, preferably from 0. 1 % to 10% and better still from 2% to 8 % by weight relative to the total weight of the oxidizing composition.

4. Process according to any one of the preceding claims, characterized in that the said surfactant(s) comprise one or more nonionic surfactants preferably chosen from:

- oxyalkylenated (Cs- C 24)alkylphenols;

- saturated or unsaturated, linear or branched, oxyalkylenated or glycerolated C₈ - C40 alcohols, comprising one or two fatty chains;

- saturated or unsaturated, linear or branched, oxyalkylenated C8 - C30 fatty acid amides;

- esters of saturated or unsaturated, linear or branched, C₈- C30 acids and of po lyethylene glyco ls;

- esters of saturated or unsaturated, linear or branched, C₈-

C30 acids and of sorbito l, preferably oxyethylenated;

- fatty acid esters o f sucrose;

- (C₈-C3o)alkyl(poly)glucosides, (C₈-C3o)alkenyl(poly)glucosides, which are optionally oxyalkylenated (0 to 10 oxyalkylene units) and comprising from 1 to 15 glucose units, (Cs- C3 o)alkyl (poly)glucoside esters;

- saturated or unsaturated, oxyethylenated plant oils; - condensates of ethylene oxide and/or of propylene oxide, inter alia, alone or as mixtures;

- N-(C₈-C3o)alkylglucamine and N-(C₈-C3o)-acylmethylglucamine derivatives;

- aldobionamides;

- amine oxides;

- oxyethylenated and/or oxypropylenated silicones;

- and mixtures thereof.

5. Process according to the preceding claim, characterized in that the said nonionic surfactant(s) are chosen from:

- saturated or unsaturated, linear or branched, oxyalkylenated C₈ - C40 alcoho ls, comprising one or two fatty chains;

- (C₈ - C3 o)alkyl(poly)glucosides;

- esters of saturated or unsaturated, linear or branched, C₈- C30 acids and of po lyethylene glyco ls;

- and mixtures thereof.

6. Process according to any one of the preceding claims, characterized in that the oxidizing composition contains one or more cationic surfactants, preferably chosen from those corresponding to the fo llowing formulae :

- those corresponding to the following general formula (I) :

(I) in which the groups Rs to Rn , which may be identical or different, represent a linear or branched aliphatic group comprising from 1 to 30 carbon atoms, or an aromatic group such as aryl or alkylaryl, at least one of the groups Rs to Rn denoting a group comprising from 8 to 30 carbon atoms and preferably from 12 to 24 carbon atoms; X^" is an anion chosen from the group of halides, phosphates, acetates, lactates, (Ci-C4)alkyl sulfates, and (Ci-C4)alkyl- or (Ci-C4)alkylarylsulfonates;

- quaternary ammonium salts of imidazoline, for instance those of formula (II) below:

in which R12 represents an alkenyl or alkyl group containing from 8 to 30 carbon atoms, R13 represents a hydrogen atom, a C1-C4 alkyl group or an alkenyl or alkyl group containing from 8 to 30 carbon atoms, R14 represents a C1-C4 alkyl group, R15 represents a hydrogen atom or a C1-C4 alkyl group; X^" is an anion chosen from the group of halides, phosphates, acetates, lactates, alkyl sulfates, alkylsulfonates or alkylarylsulfonates in which the alkyl and aryl groups respectively preferably comprise from 1 to 20 carbon atoms and from 6 to 30 carbon atoms;

- di- or triquaternary ammonium salts, in particular of formula (III):

Rl6 -N-(CH₂)₃-N-R₂₁ 2X-

^R1S ^R20

(III)

in which Ri₆ denotes an alkyl radical comprising approximately from 16 to 30 carbon atoms which is optionally hydroxylated and/or interrupted by one or more oxygen atoms, R17 is chosen from hydrogen or an alkyl radical comprising from 1 to 4 carbon atoms or an

(Rl6a)(Rl7a)(Rl8a)N-(CH₂)3 group, R₁₆a, Rl7a, Rl8a, Rl8, Rl9, R₂0 and

R₂i, which may be identical or different, are chosen from hydrogen or an alkyl radical comprising from 1 to 4 carbon atoms and X^" is an anion chosen from the group of halides, acetates, phosphates, nitrates and methyl sulfates;

- quaternary ammonium salts containing at least one ester function, such as those of formula (IV) below:

in which:

R22 is chosen from Ci-C₆ alkyl groups and Ci-C₆ hydroxyalkyl or dihydroxyalkyl groups;

R23 is chosen from:

- the group

- groups R27, which are linear or branched, saturated unsaturated C1-C22 hydrocarbon-based groups,

- a hydrogen atom,

R25 is chosen from:

- the group

- groups R29, which are linear or branched, saturated or unsaturated Ci-C₆ hydrocarbon-based groups,

- a hydrogen atom,

R24, R26 and R28, which may be identical or different, are chosen from linear or branched, saturated or unsaturated C7-C21 hydrocarbon-based groups;

r, s and t, which may be identical or different, are integers ranging from 2 to 6;

y is an integer ranging from 1 to 10;

x and z, which may be identical or different, are integers ranging from 0 to 10;

X^" is a simple or complex, organic or mineral anion; with the proviso that the sum x + y + z is from 1 to 1 5 , that when x is 0 then R₂₃ denotes R₂₇, and that when z is 0 then R₂₅ denotes

7. Process according to the preceding claim, characterized in that the said cationic surfactant(s) are chosen from those of formula

(I) and those of formula (IV), preferably from those of formula (I) .

8. Process according to any one of the preceding claims, characterized in that the said surfactant(s) represent from 1 % to 50%, preferably from 5 % to 40% and better still from 10% to 30% by weight relative to the total weight of the oxidizing composition.

9. Process according to any one of the preceding claims, characterized in that the fatty substance(s) are chosen from C₆ - C i 6 hydrocarbons, hydrocarbons containing more than 16 carbon atoms, non-silicone oils o f animal origin, plant or synthetic oils o f triglyceride type, fluoro oils, fatty alcoho ls, fatty acid and/or fatty alcoho l esters other than triglycerides and plant waxes, non-silicone waxes other than fatty alcoho ls, and silicones, and mixtures thereo f.

10. Process according to any one o f the preceding claims, characterized in that the fatty substance(s) are chosen from compounds that are liquid at a temperature of 25 °C and at atmospheric pressure.

1 1 . Process according to the preceding claim, characterized in that the fatty substance(s) are chosen from linear or branched liquid hydrocarbons, of mineral or synthetic origin, containing more than 16 carbon atoms, and especially liquid petroleum j elly and hydrogenated polyisobutene, C₆ - C i 6 alkanes, liquid fatty acid and/or fatty alcoho l esters, and liquid fatty alcoho ls, and mixtures thereo f.

12. Process according to any one of the preceding claims, characterized in that the said fatty substance(s) represent from 1 % to 60%, preferably from 2% to 50%, better still from 5 % to 40% by weight, even better still from 1 0%> to 30%> by weight and very preferentially from 12% to 25 % by weight, relative to the total weight of the oxidizing composition.

13. Process according to any one of the preceding claims, characterized in that the oxidizing composition has a water content greater than or equal to 40% by weight, preferably ranging from 40% to 95 % by weight, more preferentially ranging from 40% to 80% by weight and in particular ranging from 40% to 70% by weight relative to the total weight of the oxidizing composition.

14. Process according to any one of the preceding claims, characterized in that the pH o f the oxidizing composition ranges from 1 .5 to 9, better still from 1 .5 to 7 and even better still from 2 to 4.

15. Bleaching process according to any one of the preceding claims, characterized in that it comprises a step of applying to the keratin fibres the oxidizing composition alone or as a mixture with a second anhydrous composition comprising at least one peroxygenated salt.

16. Dyeing process according to any one of Claims 1 to 14, characterized in that it consists in applying the oxidizing composition simultaneously with or sequentially to a dye composition comprising one or more oxidation dyes and/or one or more direct dyes, and preferably one or more oxidation dyes .