COMPOSITION

The present invention relates to a cosmetic composition, in particular a hair composition, comprising i) one or more particular dicarbonyl compounds and/or derivatives thereof and/or hydrates thereof and/or salts thereof and ii) at least one amino silicone, the composition having a pH of less than or equal to 4, and also to a process for straightening the hair using this composition.

In the hair field, consumers wish to have available compositions which make it possible to introduce a temporary change to their head of hair, while targeting good remanence of the effect produced. In general, it is desirable for the change to withstand shampooing operations for a minimum of 15 days, indeed even more, depending on the nature of the said change.

Treatments already exist for modifying the colour or the shape of the hair and also, to some extent, the texture of the hair. One of the known treatments for modifying the texture of the hair consists of the combination of heat and of a formaldehyde- comprising composition. This treatment is especially effective for imparting a better appearance to damaged hair and/or for treating long hair and curly hair.

The action of formaldehyde is associated with its ability to crosslink proteins by reaction with the nucleophilic sites thereof. The heat used may be that of an iron (flat tongs or crimping iron), the temperature of which may generally be up to 200°C or more. However, it is increasingly sought to avoid the use of such substances, which may prove to be aggressive to the hair and other keratin materials.

Patent application WO 201 1/104 282 thus proposed a novel process for semipermanently straightening the hair, which consists in applying an a-keto acid solution to the hair for 15 to 120 minutes, then drying and, finally, straightening the head of hair with an iron at a temperature of about 200°C. The a-keto acid employed is preferably glyoxylic acid.

However, it has been found that the use of glyoxylic acid can result in some significant limitations; in particular, its pH of action is acidic, in particular of the order of 4, which does not allow it to be used at high concentration and which may not be well tolerated, in particular when the scalp is sensitive and/or irritated. Its volatility, amplified by the use of heat (iron), can also be a problem. Furthermore, cosmetic formulations having an acidic pH may impair the hair and/or impair its colour. It is already known practice to use glyoxylic acid esters in hair compositions, in particular in hair dye compositions, as described in document DE19859722, and in reducing compositions, as described in document DE19860239.

However, the efficacy of these compounds is not yet sufficient.

The purpose of the invention is to develop a straightening/relaxing composition which is stable over time and which makes it possible to straighten/relax and/or reduce the volume of the hair in an efficient and persistent manner while limiting damage to the hair, while at the same time retaining comfort at the time of application for the user of the composition, but also for the hairdresser who applies it.

Thus, a subject of the present invention is a cosmetic composition comprising: i) one or more dicarbonyl compounds corresponding to formula (I) below, and/or derivatives thereof and/or hydrates thereof and/or salts thereof:

(I)

in which formula (I):

R represents an atom or group chosen from i) hydrogen, ii) carboxyl -C(O)OH, iii) linear or branched C1 -C6 alkyl which is optionally substituted, preferably with at least one hydroxyl -OH radical or halogen such as Br, iv) optionally substituted phenyl, v) optionally substituted benzyl, iv) and v) preferably being optionally substituted with at least one -OH or -C(O)OH radical, vi) an indolyl radical and vii) an imidazolylmethyl radical and tautomers thereof such as with ^* representing the part linked to the rest of the molecule; and ii) at least one amino silicone, the composition having a pH of less than or equal to 4.

A subject of the invention is also a process for straightening keratin fibres, especially the hair, which comprises the application to the hair of a composition comprising:

i) one or more dicarbonyl compounds corresponding to formula (I) below, and/or derivatives thereof and/or hydrates thereof and/or salts thereof: in which formula (I):

R represents an atom or group chosen from i) hydrogen, ii) carboxyl-C(O)OH, iii) linear or branched C1 -C6 alkyl which is optionally substituted, preferably with at least one hydroxyl -OH radical, carboxyl -C(O)-OH radical or halogen such as Br, iv) optionally substituted phenyl, v) optionally substituted benzyl, iv) and v) preferably being optionally substituted with at least one -OH or -C(O)OH radical, vi) an indolyl radical and vii) an imidazolylmethyl radical and tautomers thereof such as: with ^* representing the part linked to the rest of the molecule, and

ii) at least one amino silicone,

the composition having a pH of less than or equal to 4

, followed by a straightening step using a straightening iron.

In the present invention, the dicarbonyl compounds of formula (I) may be in free form, but also in the form of salts or in their hydrate forms, preferably in free form or in the form of hydrates.

As "derivatives" of the dicarbonyl compounds of formula (I), mention may be made of esters of the carboxyl group(s), amides of the carboxyl group(s), and (thio)acetals and hemi(thio)acetals of the carbonyl function(s) of the compounds of formula (I), in free form or optionally in the form of salts or of hydrates, preferably in free form or in the form of hydrates.

The composition of the invention is stable. The composition of the invention, and the process for treating keratin fibres using ingredients i) and iii) as defined previously allow good straightening of keratin fibres while limiting damage to these keratin fibres, even when the application of the composition(s) is followed by heat treatment, in particular by means of a hair-straightening iron, and have an appreciated working quality, in particular without excessive vaporization of the composition at the time of straightening. The composition and the process for treating keratin fibres according to the invention also make it possible to limit the change in the colour of the fibres and also the problems of breaking of the said fibres such as the hair. The composition and the process of the invention will also improve the physical properties of the hair, by reducing the frizziness effect in a long-lasting manner.

In the text hereinbelow, the term "at least one" is equivalent to the term "one or more".

Preferably, the composition according to the invention comprises neither a colouring agent nor a reducing agent.

According to the present invention, the term "colouring agents" means agents for colouring keratin fibres such as direct dyes, pigments or oxidation dye precursors (bases and couplers). If they are present, their content does not exceed 0.001 % by weight relative to the total weight of the composition. Indeed, at such a content, only the composition would be dyed, i.e. no dyeing effect would be observed on the keratin fibres.

It is recalled that oxidation dye precursors, oxidation bases and couplers are colourless or sparingly coloured compounds, which, via a condensation reaction in the presence of an oxidizing agent, give a coloured species. With regard to direct dyes, these compounds are coloured and have a certain affinity for keratin fibres.

According to the present invention, the term "reducing agent" means an agent that is capable of reducing the disulfide bonds of the hair, such as compounds chosen from thiols, alkali metal sulfites, hydrides and phosphines. Preferably, the dicarbonyl compound(s) corresponding to formula (I) and/or derivatives thereof and/or hydrates thereof and/or salts thereof are chosen from the dicarbonyl derivatives corresponding to formula (I) in which R represents i) a hydrogen atom or ii) a linear or branched C1 -C6 alkyl group optionally substituted with a carboxyl group.

More preferably, they are chosen from glyoxylic acid and pyruvic acid, a derivative thereof, salts thereof and hydrates thereof and more preferentially from glyoxylic acid, derivatives thereof and the hydrate form thereof. As glyoxylic acid derivatives, mention may be made of glyoxylic acid esters, glyoxylic acid amides, glyoxylic acid (thio)acetals and hemi(thio)acetals, and glyoxylic acid ester (thio)acetals and hemi(thio)acetals.

The esters and amides may be synthesized via conventional esterification or amidation processes from the corresponding acids well known to those skilled in the art. Preferentially, the dicarbonyl compound(s) of formula (I) of the invention are chosen from glyoxylic acid and derivatives thereof and the hydrate forms of these compounds. Mention may first of all be made of glyoxylic acid and also the hydrate form thereof (HO)2CH-C(O)-OH, such as, for example, the glyoxylic acid in aqueous solution at 50% sold by the company Merck.

The glyoxylic acid esters are, for example, obtained from glyoxylic acid and a mono- or polyalcohol.

The term "mono- or polyalcohoP' means an organic compound comprising a hydroxyl group (monoalcohol) or at least two hydroxyl groups (polyalcohol or polyol), it being possible for the said hydroxylated organic compound to be aliphatic, acyclic, linear or branched, or (hetero)cyclic, such as sugars (mono- or polysaccharides) or sugar alcohols.

More particularly, the polyalcohol comprises from 2 to 100 hydroxyl groups, preferentially from 2 to 20 hydroxyl groups, even more preferentially from 2 to 10 hydroxyl groups and better still 2 or 3 hydroxyl groups.

Preferably, the mono- or polyalcohol is chosen from methanol, ethanol, propanol, isopropanol, butanol, hexanol, ethylene glycol, glycerol, dihydroxyacetone, glucose, sorbitol and menthol.

Esters that may in particular be mentioned include methyl glyoxylate, ethyl glyoxylate, glyceryl glyoxylate, dihydroxyacetone glyoxylate, glyceryl diglyoxylate or triglyoxylate, sorbitol mono-, di- or triglyoxylate, glucose mono-, di- or triglyoxylate, menthyl glyoxylate, and the acetals, hemiacetals and hydrates thereof.

The glyoxylic acid amides are obtained, for example, from glyoxylic acid and an organic mono- or polyamine. The term "mono- or polyamine" means an organic compound comprising an amino (monoamine) group or at least two (and preferably from 2 to 100, better still from 2 to 20) amino groups, it being possible for the said organic compound to be aliphatic, acyclic, linear or branched or (hetero)cyclic. The term "amino" group means a primary amine group -NH ₂ or a secondary amine group >NH.

Preferably, the mono- or polyamine is aliphatic. This amine is preferably chosen from methylamine, ethylamine, propylamine, isopropylamine, butylamine, hexylamine, monoethanolamine, monopropanolamine, propane-1 ,2,3-triamine and diaminoacetone.

Mention may be made in particular of glyoxylic acid /V- -hydroxyethylamide and glyoxylic acid Ν-γ-hydroxypropylamide and the acetals, hemiacetals and hydrates thereof.

The glyoxylic acid (thio)acetals and hemi(thio)acetals may be obtained, for example, from the reaction of alcohols, for the acetals or hemiacetals, or of thiols, for the thioacetals or hemithioacetals, with blocked forms of glyoxylic acid, followed by hydrolysis. The alcohols may be the same as those mentioned for the esters. The thiols may be equivalents (referred to as mono- or polythiols) to the mono- or polyalcohols mentioned above, except for the fact that the hydroxyl function(s) of the said mono- or polyalcohols are replaced with one or more thiol functions SH of the mono- or polythiols. The acetals or thioacetals may also be cyclic (thio)acetals.

Mention may in particular be made of dimethoxyacetic acid, diethoxyacetic acid, 1 ,3-dioxane-2-carboxylic acid and 1 ,3-dioxolane-2-carboxylic acid.

The salts may be salts derived from the interaction of the compounds of formula (I) with acids or bases, it being possible for the acids or bases to be of organic or mineral nature.

Preferably, the salts are salts derived from the interaction of the compounds of formula (I) with bases. Mention will be made in particular of the salts of alkali metals or alkaline-earth metals and in particular the sodium salts.

According to one embodiment, the composition of the invention comprises from 0.1 % to 20% of one or more dicarbonyl compounds corresponding to formula (I) and/or derivatives thereof and/or hydrates thereof and/or salts thereof, preferably at least 3% by weight and preferentially from 3% to 10% by weight relative to the total weight of the composition.

The composition according to the invention also comprises one or more amino silicones.

The term "amino silicone" means any silicone comprising at least one primary, secondary or tertiary amine function or a quaternary ammonium group. Preferably, the amino silicone(s) used in the cosmetic composition according to the present invention comprise in their structure at least 4 silicon atoms.

In the text hereinbelow, the term "silicone" is intended to denote, in accordance with what is generally accepted, any organosilicon polymer or oligomer of linear or cyclic, branched or crosslinked structure, of variable molecular weight, obtained by polymerization and/or polycondensation of suitably functionalized silanes, and consisting essentially of a repetition of main units in which the silicon atoms are linked together via oxygen atoms (siloxane bond -Si-O-Si-), optionally substituted hydrocarbon-based radicals being directly linked via a carbon atom to the said silicon atoms. The hydrocarbon-based groups that are the most common are alkyl groups, especially of C1-C10, and in particular methyl, fluoroalkyl groups, the alkyl part of which is of C1-C10, and aryl groups and in particular phenyl . The amino silicones used in the composition according to the present invention may be chosen from the silicones [al to (§1 below:

(a) the compounds corresponding to formula (la) below:

(R ana-a-SilOSindn-IOSiiTWR z-Jm-OSin^-iR a (la) in which formula (la):

• T represents a hydrogen atom or a phenyl, hydroxyl (-OH) or Ci-Cs alkyl group, and preferably methyl, or a Ci-Cs alkoxy, preferably methoxy,

• a denotes the number 0 or an integer from 1 to 3, and preferably 0,

· b denotes 0 or 1 , and in particular 1 ,

• m and n are integers such that the sum (n + m) can range especially from 1 to 2000 and in particular from 50 to 150, it being possible for n to denote a number from 0 to 1999 and in particular from 49 to 149, and for m to denote a number from 1 to 2000 and in particular from 1 to 10,

· Ri is a monovalent group of formula -C _q H _2q L in which q is an integer from 2 to 8 and L is an optionally quaternized amino group chosen from the following groups:

-N(R ₂ )-CH2-CH2-N(R ₂ )2,

-N(R ₂ ) ₂ ,

-N ⁺ (R ₂ ) ₃ Q-,

-N ⁺ (R ₂ ) (H) ₂ Q-,

-N ⁺ (R ₂ ) ₂ HQ-,

-N(R ₂ )-CH2-CH2-N ⁺ (R ₂ )(H)2 Q ^" ,

in which R ₂ may denote a hydrogen atom, a phenyl group, a benzyl group or a saturated monovalent hydrocarbon-based group, for example a C1-C20 alkyl group, and Q ^" represents an anionic counterion such as a halide ion, for instance fluoride, chloride, bromide or iodide.

In particular, the amino silicones corresponding to the definition of formula (la) are chosen from the compounds corresponding to formula (Ma) below:

in which formula (Ma):

• R, R' and R", which may be identical or different, denote a Ci-C ₄ alkyl group, preferably methyl, a Ci-C ₄ alkoxy group, preferably methoxy, or hydroxyl,

• A represents a linear or branched C3-C8 and preferably C3-C6 alkylene group,

• m and n are integers that are dependent on the molecular weight and whose sum is between 1 and 2000 inclusive.

According to a particular embodiment of the invention, the amino silicones are of formula (Ma) with R, R' and R", which may be identical or different, each representing a Ci-C ₄ alkyl or hydroxyl group, A represents a C3 alkylene group and m and n are such that the weight-average molecular mass of the compound is between 5000 and 500 000 inclusive. Compounds of this type are referred to in the CTFA dictionary as "amodimethicones".

According to another particular embodiment of the invention, the amino silicones are of formula (Ma) with R, R' and R", which may be identical or different, each representing a Ci-C ₄ alkoxy or hydroxyl group, at least one of the groups R or R" is an alkoxy group and A represents a C3 alkylene group. The hydroxyl/alkoxy mole ratio is preferably between 0.2/1 and 0.4/1 inclusive and advantageously equal to 0.3/1 . Moreover, m and n are such that the weight-average molecular mass of the compound is between 2000 and 10 ⁶ inclusive. More particularly, n is between 0 and 999 inclusive and m is between 1 and 1000 inclusive, the sum of n and m being between 1 and 1000 inclusive.

In this category of compounds, mention may be made, inter alia, of the product Belsil®ADM 652 sold by the company Wacker.

According to yet another particular embodiment of the invention, the amino silicones are of formula (Ma) with R and R", which are different, each representing a Ci-C ₄ alkoxy or hydroxyl group, at least one of the groups R or R" being an alkoxy group, R' representing a methyl group and A representing a C3 alkylene group. The hydroxyl/alkoxy mole ratio is preferably between 1/0.8 and 1/1 .1 inclusive and advantageously is equal to 1/0.95. Moreover, m and n are such that the weight-average molecular mass of the compound is between 2000 and 200 000 inclusive. More particularly, n is between 0 and 999 inclusive and m is between 1 and 1000 inclusive, the sum of n and m being between 1 and 1000.

More particularly, mention may be made of the product Fluid WR® 1300 sold by the company Wacker.

It should be noted that the molecular mass of these silicones is determined by gel permeation chromatography (room temperature, polystyrene standard; μ styragem columns, THF eluent, flow rate of 1 mm/m, 200 μΙ of a solution containing 0.5% by weight of silicone in THF are injected, and detection is performed by refractometry and UV-metry).

According to a particularly advantageous embodiment of the invention, the amino silicone is of formula (la) and in particular the polymer known in the CTFA dictionary as "trimethylsilyl amodimethicone", corresponding to formula (Ilia) belo

(CH ₃ ) ₃ SiO

in which formula (Ilia) n and m have the meanings given above in accordance with formula (la).

Such compounds are described, for example, in patent EP 95238. A compound of formula (la) is sold, for example, under the name Q2-8220 by the company OSI.

(b) the compounds corresponding to formula (lb) below: in which formula (lb):

R ³ represents a monovalent C1-C18 hydrocarbon-based group, and in particular a C1-C18 alkyl or C2-C18 alkenyl group, for example methyl,

R ⁴ represents a divalent hydrocarbon-based group, in particular a C1-C18 alkylene group or a divalent C1-C18, for example C Cs, alkylenoxy group, Q ^" represents an anionic counterion such as that chosen from halide ions, especially chloride,

r represents a mean statistical value from 2 to 20 and in particular from 2 to 8,

s represents a mean statistical value between 20 and 200 inclusive and in particular between 20 and 50 inclusive.

Such compounds are described more particularly in patent US 4 185 087.

A compound falling within this class is the product sold by the company Union Carbide under the name Ucar Silicone ALE 56.

(c) the quaternary ammonium silicones, especially of formula (lc):

OH 2 X OH

R, R,

Ro N C CH— CH— R ₆ †Si O Si R _c CH ₀ CH CH Rc

I

R, R,

r

(lc)

in which formula (lc):

• R6 represents a divalent hydrocarbon-based group, especially a C1-C18 alkylene group or a divalent C1-C18, for example C Cs, alkylenoxy group linked to the Si atom via an Si-C bond,

• R ₇ , which may be identical or different, represent a monovalent hydrocarbon-based group containing from 1 to 18 carbon atoms, and in particular a C1-C18 alkyl group, a C2-C18 alkenyl group or a ring comprising 5 or 6 carbon atoms, for example methyl,

• R ₈ , which may be identical or different, each represent a hydrogen atom, a monovalent hydrocarbon-based group containing from 1 to 18 carbon atoms, and in particular a C1-C18 alkyl group, a C2-C18 alkenyl group or a group -R6-N(H)-C(O)-R ₇ with R ₆ and R ₇ as defined previously,

• X ^" , which may be identical or different, represents an anionic counterion such as a halide ion, especially chloride, or an anionic counterion derived from an organic acid such as (CrC6)alkylcarboxylate, for instance acetate, mesylate, etc.,

• r represents a mean statistical value between 2 and 200 inclusive and in particular between 5 and 100. These silicones are described, for example, in patent application EP-A-0 530 974.

the amino silicones of formula (Id):

R,

1

H ₂ N-(C _m H _2m )-N-(C _n H _2n )-Si- O Si - O Si— R _c

R,

(Id) which formula (Id):

• Ri, R2, R3 and R ₄ , which may be identical or different, each denote a Ci-C ₄ alkyl group or an aryl group such as phenyl,

• R ₅ denotes a Ci-C ₄ alkyl group or a hydroxyl group,

• n and m, which may be identical or different, represent an integer between 1 and 5 inclusive, and

• x is such that the amine number is between 0.01 and 1 meq/g.

(el the amino silicones containing polyalkoxylene groups of formula (le):

in which formula (le):

• R ^a , R ^b , R ^c and R ^d , which may be identical or different, represent a hydroxyl or linear or branched (Ci-Cio)alkyl group, and preferably R ^a , R ^b , R ^c and R ^d represent a (Ci-Ce)alkyl group, which is more particularly linear, such as methyl;

• ALK and ALK', which may be identical or different, represent a linear or branched (Ci-Cio)alkylene group, which is preferably linear, such as propylene;

• A and B, which may be identical or different, represent an aminopolyalkoxy group below:

R ^e R ^f N-[ALK"-O] _z -[ALK"'-O]w-ALKa-N(R ⁹ )-[ALKb -O] _q - ^* with:

representing the point of attachment of the radical to the rest of the molecule via ALK or ALK';

R ^e , R ^f and R ⁹ , which may be identical or different, representing a hydrogen atom or a linear or branched (Ci-Cio)alkyl group, and preferably R ^e , R ^f and R ⁹ represent a hydrogen atom;

ALK" and ALK'", which may be identical or different, represent a linear or branched (Ci-Cio)alkylene group, preferably of C2 or C3; more particularly, ALK" represents a divalent group -CH ₂ -CH(CH ₃ )- and ALK'" represents an ethylene group;

ALK _a and ALK _b , which may be identical or different, represent a linear or branched (Ci-Cio)alkylene group, which is optionally substituted preferably with a hydroxyl group, and is preferably of C2 or C3; more particularly, ALK _a represents an ethylene or propylene group or a divalent group -CH ₂ -CH(CH ₃ )- and ALK _b represents a divalent group -CH ₂ -CH(OH)-CH ₂ -;

q, which may be identical or different, represent 0 or 1 , preferably 1 ; w, which may be identical or different, represent an integer, preferably the sum of the w values (w of A + w of B) having a mean value inclusively between 10 and 100, more particularly inclusively between 20 and 60 and more preferentially between 30 and 50, such as 40-41 ;

z, which may be identical or different, represent an integer, preferably the sum of the z values (z of A + z of B) having a mean value inclusively between 1 and 20, more particularly inclusively between 1 and 10 and more preferentially between 2 and 5, such as 3.

(I'e) the amino silicones containing polyalkoxylene groups consisting of polysiloxane block(s) and of polyalkoxylene block(s) comprising at least one amine group, in particular:

- those of formula (I'e):

in which formula (I'e):

• R ^a , R ^b , R ^c and R ^d , which may be identical or different, represent a hydroxyl or linear or branched (Ci-Cio)alkyl group, and preferably R ^a , R ^b , R ^c and R ^d represent a (Ci-C ₄ )alkyl group, which is more particularly linear, such as methyl;

• R and R", which may be identical or different, represent a linear or branched, optionally hydroxylated C2-C6 alkylene radical, optionally interrupted with an oxygen atom;

• a and b, which may be identical or different, represent a number ranging from 0 to 100;

• R' and R'", which may be identical or different, represent a hydrogen atom or a Ci-C ₄ alkyl radical such as a methyl radical;

• x denotes an integer ranging from 1 to 500 and y denotes an integer ranging from 1 to 10;

According to a particularly advantageous embodiment of the invention, the amino silicone is bisamino PEG/PPG-41 -3 aminoethyl PG-propyl dimethicone of formula

in which formula (l"e) m and n, which may be identical or different, represent an integer with the sum m + n having a mean value of 41 and o and p, which may be identical or different, represent an integer with the sum o + p having a mean value of 3.

- that containing units of formula (Me)

in which formula (Me)

• Ri to R ₄ , which may be identical or different, represent a Ci-C ₄ alkyl radical, preferably methyl; R and R", which may be identical or different, represent a linear or branched, optionally hydroxylated C ₂ -C6 alkylene radical, optionally interrupted with an oxygen atom;

a and b, which may be identical or different, represent an integer ranging from 0 to 100;

R' and R'", which may be identical or different, represent a hydrogen atom or a Ci-C ₄ alkyl radical such as a methyl radical; and

x denotes a number ranging from 1 to 500 and y denotes a number ranging from 1 to 10.

A compound falling within this category of amino silicones (e) is the product sold under the name Silsoft® A-843 by the company Momentive Performance Materials.

Among the amino silicones, mention may also be made of the silicone derived from the reaction between one or more copolymers of PEG-40/PPG-8 terminating with a 2-aminopropyl group and of bis-glycidoxypropyl dimethicone sold by the company Momentive Performance Materials under the name Silsoft® A+.

According to a particular embodiment of the invention, the amino silicones are used in combination with cationic and/or nonionic surfactants.

By way of example, use may be made of the products sold under the names Xiameter® MEM-939 Emulsion and Xiameter® MEM-949 Emulsion sold by the company Dow Corning, which comprise, besides amodimethicone, a cationic surfactant which is a trimethylcetylammonium halide (generally chloride) and a nonionic surfactant of formula Ci ₃ H ₂ 7-(OC ₂ H )i ₂ -OH, known under the CTFA name Trideceth-12. Another commercial product that may be used according to the invention is the product sold under the name Wacker-Belsil® ADM LOG 1 , sold by the company Wacker, comprising, in microemulsion form, an amodimethicone of formula (Ma) in combination with Trideceth-5 and Trideceth-10. Other amino silicones may be used in the context of the invention, such as the product referenced in the CTFA dictionary under the name Polysilicone-9.

Preferably, the amino silicone(s) used in the cosmetic composition according to the invention are chosen from amino silicones bearing polyalkoxylene groups consisting of polysiloxane block(s) and polyalkoxylene block(s) comprising at least one amine group, in particular those of formulae (le), (I'e) and (l"e) or those containing units (Me). The amino silicone(s) used in the composition according to the invention may be present in an amount ranging from 0.01 % to 10%, better still from 0.1 % to 5% by weight, preferably from 0.5% to 3% by weight, and even more preferentially from 0.5% to 1 .5% by weight, relative to the total weight of the composition.

Preferably, the weight ratio between the amount of amino silicone(s), on the one hand, and the amount of dicarbonyl compounds corresponding to formula (I) and/or derivatives thereof, salts thereof and/or hydrates thereof ranges from 0.01 to 100, more preferentially from 0.01 to 20, better still from 0.05 to 10 and even better still from 0.05 to 1 .

The compositions according to the invention can be provided in any galenical form conventionally used and in particular in the form of an aqueous, alcoholic or aqueous/alcoholic solution or suspension or oily solution or suspension; of a solution or a dispersion of the lotion or serum type; of an emulsion, in particular having a liquid or semi-liquid consistency, of the O/W, W/O or multiple type; of a suspension or emulsion having a soft consistency of (O/W) or (W/O) cream type; of an aqueous or anhydrous gel, or of any other cosmetic form. These compositions can be packaged in pump-action sprays or in aerosol containers, in order to provide for application of the composition in the vaporized (lacquer) form or in the form of a mousse. Such packaging forms are indicated, for example, when it is desired to obtain a spray or a mousse, for the treatment of the hair. In these cases, the composition preferably comprises at least one propellant.

The compositions of the invention may be aqueous or anhydrous. They are preferably aqueous and then comprise water at a concentration ranging from 5% to 98%, better still from 5% to 90% and even better still from 10% to 90% by weight relative to the total weight of the composition.

The composition of the invention may also comprise at least one common cosmetic ingredient, chosen in particular from propellants; oils; solid fatty substances and in particular Cs-C ₄ o esters; Cs-C ₄ o acids; Cs-C ₄ o alcohols; surfactants; sunscreens; moisturizers; antidandruff agents; antioxidants; chelating agents; nacreous agents and opacifiers; plasticizers or coalescers; fillers; silicones other than the amino silicones and in particular polydimethylsiloxanes; polymeric or non-polymeric thickeners; gelling agents; emulsifiers; polymers, in particular conditioning or styling polymers; fragrances; basifying agents or acidifying agents; silanes; crosslinking agents. The composition can, of course, comprise several cosmetic ingredients appearing in the above list.

The composition may in particular comprise one or more organic solvents, in particular water-soluble solvents, such as C1-C ₇ alcohols; mention may in particular be made of C1-C ₇ aliphatic monoalcohols, C6-C ₇ aromatic monoalcohols, C3-C ₇ polyols or C3-C7 polyol ethers, which may be employed alone or as a mixture with water.

Depending on their nature and the purpose of the composition, the normal cosmetic ingredients can be present in normal amounts which can be easily determined by a person skilled in the art and which can be, for each ingredient, between 0.01 % and 80% by weight. A person skilled in the art will take care to choose the ingredients included in the composition and the amounts thereof so that they do not harm the properties of the compositions of the present invention.

The pH of the composition is less than 4 and preferably ranges from 1 to 3, better still from 1 .5 to 3 and even better still from 1 .7 to 3.

It may be adjusted to the desired value by means of acidifying and/or basifying agents usually used for treating keratin fibres.

The basifying agent may be chosen from mineral or organic or hybrid alkaline agents, or mixtures thereof.

The mineral alkaline agent(s) are preferably chosen from aqueous ammonia, alkali metal carbonates or bicarbonates such as sodium or potassium carbonate and sodium or potassium bicarbonate, sodium hydroxide or potassium hydroxide, or mixtures thereof.

The organic alkaline agent(s) are preferably chosen from organic amines with a pKb at 25°C of less than 12, preferably less than 10 and even more advantageously less than 6. It should be noted that it is the pKb corresponding to the function of highest basicity.

Hybrid compounds that may be mentioned include the salts of the amines mentioned previously with acids such as carbonic acid or hydrochloric acid.

The organic alkaline agent(s) are chosen, for example, from amine derivatives such as alkanolamines, oxyethylenated and/or oxypropylenated ethylenediamines, amino acids of amines such as 1 ,3-diaminopropane, 1 ,3-diamino-2-propanol, spermine or spermidine.

The term "alkanolamine" means an organic amine 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. Sodium hydroxide is in particular suitable for use in the invention.

The acidifying agent may be chosen from mineral or organic acids, for instance hydrochloric acid, phosphoric acid or lactic acid.

The composition according to the invention is preferably in the form of styling or care gels, care lotions or creams, conditioners, masks or sera. The composition according to the invention may be obtained by mixing several compositions.

The process of the invention comprises the application of the composition described previously, followed by a step of straightening the hair with an iron. Straightening with an iron is known from the prior art. It consists in straightening the hair with flat heating tongs, which are generally metallic. The straightening irons are generally used at a temperature ranging from 150 to 250°C.

The process of the invention may comprise other intermediate steps aimed at improving the straightening of the hair.

According to a particular embodiment, the process of the invention comprises the application of the composition of the invention to dry hair, and a time of contact of the composition with the hair of between 10 and 60 minutes, preferably between 20 and 40 minutes. After this leave-on time, straightening with a brush and with a hairdryer (blow-drying) is performed. The hair is then straightened with a straightening iron at a temperature of between 150 and 250°C, preferably from 210 to 230°C. In another variant, the process for straightening keratin fibres, such as the hair, may comprise the successive application to the said fibres, and in any order with or without intermediate rinsing,

- of a composition comprising i) one or more dicarbonyl compounds corresponding to formula (I) and/or derivatives thereof and/or hydrates thereof and/or salts thereof as defined previously;

- of a composition comprising ii) one or more amino silicones as defined previously;

- being followed by a straightening step using a straightening iron at a temperature of at least 150°C, preferably ranging from 150 to 250°C.

According to one particular mode of the invention, i) is applied to the fibres, then ii).

According to another particular embodiment, ii) is applied first, and then i).

The process of the invention may also comprise the application of other hair agents as a pretreatment or post-treatment. In particular, it may comprise the application of a conditioning care product as a post-treatment.

According to another embodiment, the hair straightening process comprises a step of washing the hair and then of drying with a hairdryer before applying the composition of the invention. According to this particular embodiment, the steps described above are then encountered, such as the contact time of the composition, the blow-drying, the straightening with a straightening iron, the application of a conditioning agent and the rinsing, all these steps possibly being performed independently of each other. According to a particular embodiment, the straightening with the straightening iron is performed in several passes on the hair, in general 8 to 10 passes.

The process of the present invention is performed without a step of permanent reshaping at basic pH or based on a reducing agent.

Examples The composition below was prepared (weight % of starting material in unmodified form relative to the total weight of the composition):

Ingredients %

Hydroxypropylmethylcellulose (Methocel F4M from OW

1

Chemical)

Glyoxylic acid (50% aqueous solution) 16

Disodium cocoamphodiacetate (sodium A/-cocoylamidoethyl-/V- ethoxycarbonylmethyl glycinate) as an aqueous 30% solution 2

(Miranol C2M Cone. NP from Rhodia)

Polyquaternium-37(and) propylene glycol dicaprylate/dicaprate

2.5 (and)PPG-l , Trideceth 6 (Salcare SC96 from BASF)

Lactic acid 2.5 Sodium hydroxide (10% aqueous solution) 7

Bisamino PEG/PPG-41 -3 aminoethyl PG-propyl dimethicone at

30% AM in dipropylene glycol (Silsoft A 843 from Momentive 2

Performance Materials)

Water Qs

^* pH 2.2 ± 0.2

The above composition is applied to a lock of hair having a substantial level of curliness. After a leave-on time of 20 minutes on the hair, the lock is blow-dried with a hairdryer and is then straightened with a straightening iron. The evolution of fumes during the use of the iron is low.

The lock is then washed and dried with a hairdryer. A straight lock of hair free of curliness is thus obtained. Comparative example:

Compositions A and B were prepared with the following compositions :

2.7g hair locks of curl type IV bleached hair were washed with a shampoo and blow dried. Then 2.7g of composition A was applied to one of the hair lock and 2.7g of composition B was applied to another hair lock. After a leave-on time of 20 minutes on the hair, the locks were blow-dried with a hairdryer (brushing with 15 passes of a brush) and were then straightened with a straightening iron (10 passes). The locks were then washed with a shampoo and let air dried (spontaneous).

Qualities of use and conditioning performances were improved by using composition A.

In particular, the flat iron was easily applied on the hair lock treated with composition A. Hair was smoother and silkier after being treated by composition A. The hair lock treated with composition A was easier to comb than the hair lock treated with composition B on humid and dry hair.

Then, the hair locks were washed again with a second shampoo and then let air dried (spontaneous). Better lasting curl reduction was observed on the hair lock treated with composition A.