WO2013190465A2

WO2013190465A2 - Cosmetic process for forming a coating on the surface of a nail or false nail

Info

Publication number: WO2013190465A2
Application number: PCT/IB2013/055000
Authority: WO
Inventors: Henri Samain
Original assignee: LOreal SA
Current assignee: LOreal SA
Priority date: 2012-06-19
Filing date: 2013-06-18
Publication date: 2013-12-27
Anticipated expiration: 2014-12-19
Also published as: WO2013190465A3

Description

"Cosmetic process for forming a coating on the surface of a nail or false nail"

The present invention relates to a process for forming a thick, long-lasting coating on the surface of the nails or false nails.

In general, nail varnish users wish to obtain a thick varnish. This has the advantage of reinforcing the natural relief of the nail and, in aesthetic terms, of giving it a smooth surface appearance, which is little influenced by the natural irregularities of the nail.

In the field of nail varnishes, two main techniques exist for forming a coating on the surface of a nail: the first is that of liquid nail varnishes, which are generally solutions based on nitrocellulose and solvent. The second uses photo-polymerizable and/or photo-crosslinkable polymers, such as acrylate polymers, which, under the action of irradiation, especially with UV rays, lead to polymer networks.

Unfortunately, the first nail varnish technique does not make it possible to exceed 100 μιη in terms of the thickness of the coating formed on the surface of the nail. This is due to the fact that the application of these nail varnish solutions requires an intermediate drying step between each applied coat of varnish, in order to allow evaporation of the solvent for the formation of the varnish film. Once the solvent has evaporated off, a second coat can be applied, and so on. In theory, it should be able to produce substantial thicknesses via the application of successive coats. However, in reality, when the second coat is applied, a large proportion of solvent remains. If two or three superposed coats are applied, the solvent will end up by evaporating off. However, if the number of coats is multiplied, the solvent can no longer pass through the thickness formed and evaporate off. The properties of the varnish produced, in particular in terms of durability, are then thereby affected.

As regards the second category of nail varnish, it is possible to produce with these photo-polymerizable and/or photo-crosslinkable varnishes thicker coatings, of up to 500 μιη, in about three applications. On the other hand, it is not possible to produce, in a single application, a thick coating. In addition, on account of the complexity, it is difficult to multiply the coats applied beyond three or four. Specifically, this technique requires the use of a UV lamp, which must illuminate the coating for several minutes. The superposition of coats demands illumination for each of the coats applied, which considerably lengthens the time for varnishing the nails.

Consequently, there is still a need for a method for varnishing the nails that makes it possible to form, quickly and easily, a thick, long-lasting coating.

The present invention is precisely directed towards satisfying this need.

As emerges from the examples presented below, the inventors have discovered that it is possible to satisfy the abovementioned expectations by forming a coating in the form of a set foam via the use of specific photo-crosslinkable compounds.

Thus, according to a first of its aspects, the present invention relates to a cosmetic process for forming a coating on the surface of a nail or false nail, comprising at least the steps consisting in:

(i) forming, on all or part of a nail or false nail, an aerated coat of a composition (M) comprising, in a physiologically acceptable medium, at least one photo- crosslinkable compound, the said compound comprising at least one activated photo- dimerizable group bearing at least one activated double bond; and

(ii) exposing all or part of the surface of the said coat formed in step (i) to conditions favourable for crosslinking the said photo-crosslinkable compound.

The term "physiologically acceptable medium" means a toxicity-free medium that is compatible with application to human keratin materials, in particular the nails.

In the text hereinbelow, the term "nail(s)" will denote the nail(s) or false nail(s) onto which it is desired to form a coating.

The coating formed according to the invention may be more particularly intended for making up and/or caring for the nails.

Preferably, the process of the invention is a process for making up the nails. The term "aerated" composition means a composition comprising a gaseous phase (for example air) in the form of bubbles. It is also referred to as a composition "in foam form".

Structures of foam type have already been proposed for cosmetic applications, especially for giving a volume effect. For example, patent applications US 2004/126 345, WO 04/060 292 and WO 04/060 334 disclose the application, to the skin, the lips or keratin fibres such as the hair, of a composition which forms a foam after application, which will be stabilized via the film formation of a film- forming polymer. However, to the inventors' knowledge, no process has ever been proposed for forming a coating on the nails according to the process of the invention, in particular using an aerated composition comprising at least one photo-crosslinkable compound as defined previously.

The process of the invention proves to be advantageous in several respects.

Firstly, it makes it possible, quickly and easily, to produce thick, smooth nail coatings. In particular, the coating, formed according to the invention in a single application to the nail, has a thickness greater than that which may be obtained via the application of one coat, or even of several successive coats, of standard nail varnish compositions.

Thus, the coating formed on the surface of the nail according to the process of the invention may have, after a single application of aerated composition, a thickness of greater than or equal to 50 μιη, in particular ranging from 50 μιη to 5 mm and more particularly from 100 μι ίο 2 mm.

Moreover, the coating thus formed is stable and long-lasting, in particular for at least 4 days and more particularly up to 7 days. It does not collapse or break down over time. It also shows good resistance to rubbing.

As developed in the text hereinbelow, the aerated coat of step (i) of the process of the invention may be formed according to various embodiments.

Preferably, it is formed in situ on the nail via the application of a composition with delayed expansion.

According to another of its aspects, the present invention is thus directed towards such a cosmetic composition with delayed expansion comprising, in a physiologically acceptable medium:

- at least one photo-crosslinkable compound as defined previously; and

- at least one self- foaming compound.

The term "self-foaming compound" is intended to denote a compound that is capable of giving the composition containing it the form of a foam with an acceptable degree of aeration. The self-foaming compounds that may be used according to the invention will be described more precisely in the text hereinbelow.

Alternatively, the said aerated coat may be formed, simultaneously with its application to the nail, with the aid of an aerated-composition dispenser. According to yet another of its aspects, the present invention thus relates to a product for forming an aerated cosmetic composition, comprising:

(a) a base composition comprising, in a physiologically acceptable medium, at least one photo-crosslinkable compound as defined previously; and

(b) an aerated-composition dispenser for dispensing the said base composition in the form of an aerated composition.

According to yet another of its aspects, the present invention relates to a cosmetic kit, in particular for making up and/or caring for the nails, comprising at least:

- a composition or a product as defined previously; and

- a lighting system capable of photo-crosslinking the said compound.

Other characteristics, variants and applications of the process, composition, product and kit according to the invention will emerge more clearly on reading the description and the examples that follow, which are given as non-limiting illustrations.

Unless otherwise indicated, the term "containing/comprising one" should be understood as meaning "containing/comprising at least one".

STEP (i): AERATED COAT

As mentioned previously, the process of the invention comprises the formation, on all or part of the nail, of an aerated coat of a composition, referred to hereinbelow as (M), comprising at least one photo-crosslinkable compound.

PHOTO-CROSSLINKABLE COMPOUND

The photo-crosslinkable compounds under consideration according to the invention comprise at least one activated photo -dimerizable group bearing at least one activated double bond.

According to a particular embodiment, the said photo-crosslinkable compound(s) may be present in the composition (M) in a proportion of from 1% to 50% by weight and in particular from 3% to 20% by weight relative to the total weight of the said composition.

The mean number of activated double bonds per molecule of compound is preferably greater than 1, in particular greater than 2 and better still greater than 3. For the purposes of the present invention, the term "photo-dimerizable group" means a chemical group that leads to photo-dimerization reactions under irradiation.

For the purposes of the present invention, the term "photo-dimerization" means a chemical reaction between two double bonds (of 2+2 type) or two pairs of double bonds (of 4+4 type), and more particularly between two double bonds (of 2+2 type).

Thus, the double bond under consideration according to the invention, when it is photo-stimulated or, in other words, subjected to a specific radiation, generally UV, proves to be capable of reacting with another double bond by cyclization.

As detailed hereinbelow, the interacting double bonds are preferably ethylenic functions, i.e. of the type CH₂=CH₂.

For the purposes of the invention, the double bond under consideration is said to be activated. This characterization means that the double bond is spontaneously photo- dimerizable in response to a photo -stimulus, without requiring the mandatory presence of a photoinitiator or of a chemical initiator.

Consequently, a composition according to the invention is advantageously free of photoinitiator and/or of chemical initiator.

The activation of the double bond intended to become dimerized is commonly induced by the presence close thereto, generally in the alpha position, of an electron- withdrawing group, for instance an aromatic nucleus such as a phenyl.

The case of a reaction between two double bonds may be represented schematically in the following manner:

+ _^ ^ I

These photo-dimerization reactions are defined in the book Advanced Organic Chemistry, J. March, 4th edition, Wiley Interscience, NY 1992, p. 855.

The materials bearing photo-dimerizable groups according to the invention have the advantage of being stable towards oxygen, moisture and heat, and of leading to reversible crosslinking.

In addition, the photo-dimerizable groups according to the invention are highly photosensitive. Consequently, irradiation even of low energy leads to rapid and efficient crosslinking of the material, which, in the case of a cosmetic application, induces irradiation of short duration and of low energy, which does not cause any degradation of the keratin materials.

The activated photo-dimerizable groups that may be used according to the invention are chosen from:

a) photo-dimerizable groups bearing a stylbazolium function of formula (la) or

(lb):

in which

- R represents a hydrogen atom or a C₁-C₄ alkyl or C₁-C₄ hydroxyalkyl group, preferably R represents a hydrogen atom, a methyl group, an ethyl group or a hydroxyethyl group, and preferentially R is a methyl group;

- R' represents a hydrogen atom or a C₁-C₄ alkyl group and preferably R' represents a hydrogen atom; and

- X^" denotes an ion chosen from chloride, bromide, iodide, perchlorate, tetrafluoroborate, methyl sulfate, phosphate, sulfate, methanesulfonate and p- toluenesulfonate ions, preferably X^" is an ion chosen from chloride and methyl sulfate ions, and preferentially X is a methyl sulfate ion.

in which

- R" denotes an alkylene radical (divalent) containing from 2 to 8 carbon atoms, and preferably R" denotes an alkylene radical (divalent) containing from 2 to 4 carbon atoms;

- R' represents a hydrogen atom or a C₁-C₄ alkyl group, preferably with R' representing a hydrogen atom; and

- X^" having the same meaning as that described for the preceding formula

(la),

b) photo-dimerizable groups bearing a styrylazolium function of formula (II):

in which:

- Ri denotes a hydrogen atom or a C₁-C₄ alkyl or C₁-C₄ hydroxyalkyl group;

- A denotes a sulfur atom, an oxygen atom or a group NR' or C(R')₂, R'; with R' representing a hydrogen atom or a C₁-C₄ alkyl group, R preferably representing a hydrogen atom; and

- X^" having the same meaning as that described for the preceding formula

(la).

Such chemical groups bear activated double bonds, and as such the photo- dimerization of these double bonds is triggered spontaneously in the UVA range, without requiring a photoinitiator.

According to a preferred embodiment, the photo-dimerizable groups that may be used according to the invention bear a stylbazolium function of formula (la):

in which

- R represents a hydrogen atom or a C₁-C₄ alkyl or C₁-C₄ hydroxyalkyl group,

- R' represents a hydrogen atom or a C₁-C₄ alkyl group, and

- X^" denotes an ion chosen from chloride, bromide, iodide, perchlorate, tetrafluoroborate, methyl sulfate, phosphate, sulfate, methanesulfonate and p- toluenesulfonate ions.

The photo-crosslinkable compound is derived from the functionalization of a natural backbone, which is preferably polymeric, with at least one photo-dimerizable group.

This functionalization falls within the competence of a person skilled in the art.

Advantageously, in the compositions of the invention, the compound comprising at least one photo-dimerizable group is a hydrocarbon-based polymer chosen from polyvinyl alcohol, partially or totally hydrolysed polyvinyl acetate and polysaccharides chosen from chondroitin sulfate, keratan, keratan sulfate, heparin, heparin sulfate, xanthan, carrageenan, chitosan, cellulose and derivatives thereof, alginate, starch, dextran, pullulan and galactomannan, and biologically acceptable salts thereof.

According to a particularly preferred embodiment of the invention, the photo- crosslinkable compound according to the invention may bear one or more functions that can be cyclized via a 2/2 reaction, which are sensitive to light irradiation, in particular in the absence of photoinitiator and/or of chemical initiator.

Preferably, a photo-crosslinkable compound comprises at least one photo- dimerizable unit bearing a photo -dimerizable activated double bond, borne by a polymer of partially or totally hydro lysed polyvinyl acetate type, a polysaccharide or a polyvinyl alcohol.

As regards the compounds containing photo-dimerizable groups bearing a stylbazolium function, they are obtained by reacting the polymer under consideration with a chemical species comprising a group of formula (la) or (lb).

Preferably, the chemical species comprising a group (la) bears a reactive group

W of aldehyde or acetyl type.

In other words, this chemical species corresponds to the general formula W-A, with A denoting the group (la).

As chemical species that may be used for grafting groups of styrylpyridinium type, mention may be made especially of quaternary salts of 2-(4- formylstyryl)pyridinium, 4-(4-formylstyryl)pyridinium, 2-(3-formylstyryl)pyridinium, N- methyl-2-(4-formylstyryl)pyridinium, N-methyl-3 -(4-formylstyryl)pyridinium, N-methyl- 2-(3 -formylstyryl)pyridinium, N-methyl-2-(2-formylstyryl)pyridinium, N-ethyl-2-(4- formylstyryl)pyridinium, N-(2-hydroxyethyl)-2-(4-formylstyryl)pyridinium, N-(2- hydroxyethyl)-4-(4-formylstyryl)pyridinium, N-methyl-4-(4-formylstyryl)pyridinium or N- methyl-4-(3-formylstyryl)pyridinium.

The quaternary pyridinium salts may be chloride, bromide, iodide, perchlorate, tetrafluoroborate, methosulfate, phosphate, sulfate, methanesulfonate or p-toluenesulfonate salts. Such chemical species are described in GB-A-2 030 575.

Examples of species that may be mentioned include 4-(4- formylphenylethenyl)- 1 -methylpyridiunium methosulfate, 1 -(3 -ethoxycarbonylmethyl)-4- [2-(4-formylphenyl)ethenyl]pyridinium bromide and l-(methoxycarbonylpropyl)-4-[2-(4- formylphenyl)ethenyl]pyridinium bromide. Such species are described in US 2007/0 112 094.

Use is preferably made of n-methyl-4-(4-formylstyryl)pyridinium methyl sulfate (RN= 74401-04-0), sold especially by the company Wako.

Advantageously, the chemical species of formula W-A react with a polymer of polyvinyl alcohol or polyvinyl acetal type as described in the documents mentioned previously.

For example, a polyvinyl alcohol-grafted polymer comprising units having the following structure is thus obtained:

Polyvinyl alcohol polymers grafted with styrylpyridinium groups are especially described in the publication Ichimura K et al, Preparation and characteristics of photo- crosslinkable poly( vinyl alcohol), Journal of Polymer Science, polymer chemistry edition, Vol 20, 1419-1432 (1982).

The polymers may be obtained by reaction of polyvinyl alcohol or partially hydro lysed polyvinyl acetate with styrylpyridinium salts bearing a formyl or acetal group as described in GB-A-2 030 575, WO 96/29312, US 5 061 603, GB-A-2 076 826 and EP- A-092 901.

Cellulose polymers grafted with styrylpyridinium groups are especially described in US 2007/0 112 094.

Preferably, the chemical species bearing a group (la) bears a reactive group which is a chlorine atom.

In this variant, the chemical species corresponds to a general formula Cl-A', with A' denoting the group (la).

As chemical species of the type Cl-A', use is preferably made of that of formula:

corresponding to the chloro compound (1) described in the preparation examples hereinbelow.

Advantageously, the photo-crosslinkable compound comprising the groups (lb) is advantageously obtained by reaction of the species CI- A' with the polysaccharide chosen from those defined previously, in the presence of water.

For their part, the compounds containing photo-dimerizable groups bearing a styrylazolium function are obtained by reaction of the polymer with a chemical species comprising a group of formula (II).

Preferably, the chemical species comprising a group (II) bears a reactive group W of aldehyde or acetal type.

In other words, the chemical species corresponds to a general formula W-B, with B denoting the group (II).

As chemical species that may be used for grafting groups of styrylazolium type, mention may be made of those described in EP-A-313 220.

Advantageously, these chemical species of formula W-B react with a polymer of polyvinyl alcohol or polyvinyl acetal type as described in the documents mentioned previously.

A polyvinyl alcohol-grafted polymer comprising units having the following structure is thus obtained:

Polyvinyl alcohol polymers grafted with a styrylazolium group are especially described in EP-A-313 220. In this document, these polymers may be obtained by reaction of polyvinyl alcohol or partially hydrolysed polyvinyl acetate with styrylazolium salts bearing an aldehyde or acetal group. Preferably, the polymer bearing photo-dimerizable group(s) is in the form of particles, in particular dispersed particles.

Thus, in the latter case, the polymer particles are very preferentially polyvinyl alcohol particles.

Thus, according to one embodiment variant, the photo-crosslinkable compound is a polyvinyl alcohol (PVA) partly functionalized with one or more hydroxyl functions and one or more functions of formula III):

The degree of polymerization of the polyvinyl alcohol may be between 100 and 5000.

Advantageously, the polymer has a degree of substitution, as a percentage of functions of formula (la), (lb) or (II) as defined above, which may be between 0.1 and 25.

The following scheme represents a variant in which the polymer is PVA-SbQ (polymer of polyvinyl alcohol PVA type bearing a few hydro lysed functions and a few functions grafted with stylbazolium species), which is capable of crosslinking under the effect of light, as illustrated below.

These materials are particularly appreciated since they do not require photoinitiator and react toward visible light or toward radiation which may comprise both UV light and visible light, in particular a low dose of UV.

By way of example, mention may be made of PVA-SbQ (poly(vinyl alcohol) with N-methylstyrylpyridinium side groups in the form of the methyl sulfate salt), sold under the reference MQ2012 by the company Murakami, especially in the form of a dispersion at 13.3% by weight in water, for example of CAS No: 107845-59-0.

According to another embodiment variant, the photo-crosslinkable compound is featured by a polysaccharide that is functionalized with photo-dimerizable groups.

It may especially be a polysaccharide that may be chosen especially from chondroitin sulfate, keratan, keratan sulfate, heparin, heparin sulfate, xanthan, carrageenan, chitosan, cellulose and derivatives thereof, alginate, starch, dextran, pullulan and galactomannan, and biologically acceptable salts thereof.

The degree of functionalization is obviously adjusted so as to be able to impart the required degree of crosslinking during step (ii) of the process of the invention.

According to the invention, the degree of functionalization with photo- dimerizable units is at least 0.1%, or even at least 0.5%, or even at least 2%.

As stated previously, in a composition according to the invention, the photo- dimerizable groups are preferably borne by a polymer of polyvinyl lactate type, a polyvinyl alcohol or a polysaccharide.

Preferably, in a composition according to the invention, the photo-dimerizable groups are borne by a polyvinyl alcohol.

The photo-crosslinkable compound may be conveyed in a physiologically acceptable medium and in particular an aqueous medium or even pure water. The photo-crosslinkable compound may have a number-average molecular weight ranging from 2000 to 100 000 and preferably ranging from 2000 to 20 000.

According to another particular embodiment, the photo-crosslinkable compound may be chosen from polyurethane and/or polyurea polymers or oligomers bearing (meth)acrylate groups, in particular polyurethane (meth)acrylate oligomers.

Such polyurethanes/polyureas bearing acrylate groups are sold, for example, under the name Ebecryl® by the company Cytec (Ebecryl® 210: molar mass 1500, 2 acrylate functions per molecule, Ebecryl® 230: molar mass 5000, 2 acrylate functions per molecule, Ebecryl® 270: molar mass 1500, 2 acrylate functions per molecule, Ebecryl® 8402: molar mass 1000, 2 acrylate functions per molecule, Ebecryl® 8804: molar mass 1300, 2 acrylate functions per molecule, Ebecryl® 220: molar mass 1000, 6 acrylate functions per molecule, Ebecryl® 1290: molar mass 1000).

Mention may also be made of the water-soluble aliphatic acrylate polyurethanes sold under the names Ucecoat® 6558 and Ucecoat® 6569, and the acrylate polyurethanes in aqueous dispersion sold under the trade names Ucecoat® 7571 , Ucecoat® 7578, Ucecoat® 7655, Ucecoat® 7674, Ucecoat® 7689 and Ucecoat® 7699 by the company Cytec.

These compounds are capable of crosslinking when they are subjected to radiation comprising at least UV light.

An example that may be mentioned is diurethane methacrylate (INCI: Di-

HEMA trimethylhexyl dicarbamate).

The composition may contain a single photo-crosslinkable polymer bearing functions of identical or different nature.

It is also possible to use a mixture of photo-crosslinkable polymers bearing different functions.

Consequently, the reactions may be performed between two photo-dimerizable groups of identical or different chemical nature.

The activated double bonds may react with another double bond of the same chemical nature or react with another double bond of different chemical nature.

Preferably, the photo-crosslinkable compound under consideration according to the invention is chosen from polymers that are capable of photo-crosslinking via a 2+2 cycloaddition reaction, in particular polymers bearing stylbazolium functions. Characteristics of the aerated coat

According to a particular embodiment, the said aerated coat formed in step (i) has a degree of aeration of greater than or equal to 10% and preferably less than 1000%.

The degree of aeration may range, for example, from 10% to 500% and preferably from 20% to 200%.

The degree of aeration corresponds to the amount of gas incorporated into the composition.

The degree of aeration is measured according to the following protocol: prior to the measurement, a quantity Q of composition to be characterized is placed in a transparent container bearing graduations indicating the volume, before aeration, and the volume Vbefore aeration (in cm³) is measured (in practice, the quantity is such that Vbefore aeration is of the order of 10 cm³) at a room temperature of 23°C and at atmospheric pressure. In practice also, provision is made, in order to measure the volume, to tap the quantity Q in the bottom of the container, gently enough so as not to cause appreciable expansion of the product. The quantity Q of composition is then left alone for about 10 minutes in order for it to aerate by itself, naturally. The new volume Vf_oam of the composition in foam form is then measured. If need be, the top of the foam is levelled off somewhat in order to give it a flat surface. In this way, it is easier to evaluate the volume.

As detailed hereinbelow, the aeration may result from expansion of the composition with delayed expansion or may be created via an aerated-composition distributor.

The degree of aeration is then calculated with the aid of the following formula: degree Of aeration = [(Vf_oam-V before aeration) V before aeration] ^X 100

FORMATION OF THE AERATED COAT

According to a first variant of the process of the invention, the composition in foam form is created in situ on the nail, after application of a composition with delayed expansion (E).

A composition with delayed expansion is a system comprising a "self-foaming" agent which is capable of enabling expansion of the said composition to give it the form of a foam, generally by release or formation of a volatile agent in the composition after it has been applied to the nail.

Thus, according to a particular embodiment, the said aerated coat is formed via at least the steps consisting in:

(a) applying to all or part of the nail at least one coat of a composition with delayed expansion, denoted (E), comprising at least one photo-crosslinkable compound as defined previously and at least one self- foaming compound, and

(b) exposing all or part of the said coat from step (a) to conditions that are favourable for expanding the said composition.

In this embodiment, the second crosslinking step is delayed until the transformation of the coat with delayed expansion into an aerated coat.

The term "self-foaming agent" means a compound that is capable of imparting to a composition the form of a foam with an acceptable degree of aeration.

This variant is particularly advantageous insofar as it does not require, unlike compositions conditioned in foam form, the spreading of a foam in order to form the aerated coat, which may often prove to be difficult for forming a uniform coating.

According to another of its aspects, the present invention relates to a cosmetic composition with delayed expansion comprising, in a physiologically acceptable medium,

- at least one photo-crosslinkable compound as defined previously; and - at least one self- foaming compound.

The composition with delayed expansion may be applied to the surface of the nail via any applicator usually used for the application of a cosmetic composition.

The composition with delayed expansion may be dispensed, for example, on the surface of the nail in the form of a gel.

The said composition may be conditioned in a standard aerosol device, with a separation such as a piston or a flexible bag to separate the self-foaming compound from the propellant required for expelling the composition. It may also be a flexible tube, a pump bottle or a bottle with a deformable wall.

These devices are well known to those skilled in the art. Examples 1 and 2 describe an example of a dispenser for compositions with delayed expansion in accordance with the invention. Needless to say, it falls within the knowledge of a person skilled in the art to adapt the characteristics of the dispenser with regard especially to the nature of the self- foaming compound used.

The dispenser may be equipped, for example, with a dispensing control device specially adapted for the dispensing of a self-foaming product, as described, for example, in patent application EP 0 547 925.

The said self-foaming compound(s) may be chosen from the agents known to those skilled in the art, provided that they are capable of giving the composition the form of a foam with an acceptable degree of aeration, and of doing so under conditions that are compatible with application to the nails.

These self- foaming compounds may be chosen, for example, from:

- slow-expanding systems.

The self-foaming agent may be chosen, for example, from volatile hydrocarbons and volatile halogenated hydrocarbons with a boiling point low enough to enable them to evaporate and to foam the composition after application to the nail, and a boiling point that is high enough to prevent premature foaming.

The boiling point of the self- foaming agent preferably ranges from -20 to 40°C. The self-foaming agent is preferably chosen from linear or branched C4-C6 aliphatic hydrocarbons.

Preferably, it is chosen from n-pentane, isopentane, neopentane, n-butane, isobutane and isohexane, and mixtures thereof; and more preferentially isopentane.

- gas-releasing systems

These may be systems that release C0₂ by acidification of a carbonate, as described, for example, in patent application EP 1 133 983; or of aqueous hydrogen peroxide solution made unstable by basification or addition of a compound which promotes the dismutation of water.

- heat-foaming or heat-expandable systems

These may be "heat-expandable" particles, which are capable of expanding under the action of a temperature of greater than or equal to 45°C. They are preferably thermoplastic particles, which are capable of deforming under the action of heat and of conserving their new shape, including after cooling, especially to room temperature.

Examples that may be mentioned are the particles sold under the name Expancel® by the company Akzo Nobel.

According to a particular embodiment, the said self-foaming compound is chosen from slow-expanding systems, in particular as described previously.

According to a particularly preferred embodiment, it is isopentane, or alternatively an isopentane/isobutane mixture especially in a weight ratio ranging from 1/1 to 3/1.

The said composition advantageously has a degree of expansion ranging from

10% to 5000%.

The term "degree of expansion" means the ratio between the volume occupied by the composition measured 15 minutes after its application, divided by the volume occupied by the composition measured immediately after its application.

A person skilled in the art is capable of using the said self- foaming agent(s) in an adequate amount for obtaining the desired degree of expansion.

In particular, the said self-foaming agent(s) may be present in the composition with delayed expansion in a content ranging from 0.1% to 40% by weight relative to the total weight of the said composition.

A person skilled in the art is capable of using the conditions of exposure of the said coat formed in step (a) to obtain the desired expansion of the said composition.

Depending on the nature of the self-foaming agent used, the aerated composition may be obtained, for example, after exposure to atmospheric pressure and/or to shearing and/or to a temperature above room temperature.

In particular, in the context of using a self-foaming compound of volatile hydrocarbon type as described previously, step (b) may consist simply in leaving the said coat formed in step (a) to expand in the ambient atmosphere, especially for a time ranging from 10 seconds to 5 minutes.

According to a particular embodiment, the process of the invention also comprises the application, prior to, simultaneously with or subsequent to the application in step (a) of the said composition with delayed expansion (E) and prior to step (b), of at least one conventional nail varnish composition. Preferably, the said compositions are mixed on the nail surface itself, so as to create partial or total homogenization.

Such a variant makes it possible to obtain a volume effect via the expansion of the composition, while at the same time maintaining good smoothing.

According to yet another particular embodiment, a mould may be applied, simultaneously with the expansion (b) of the said composition, the mould being such that it makes it possible to define a specific volume above the nail surface.

The mould may be made, for example, of plastic, for instance of polyethylene, polystyrene or of fluorinated material, for example of polytetrafluoroethylene (PTFE).

The application of a mould advantageously makes it possible to control the expansion of the composition, in particular the volume and shape of the aerated coat that will be formed on the surface of the nail, and thus makes it possible to obtain a very smooth coating with very good homogeneity.

According to a second variant of the process of the invention, the foam appearance is generated at the time of dispensing the composition onto the nail.

More particularly, the said aerated coat of step (i) of the process of the invention may be formed, simultaneously with its application to the surface of the nail, using a non-aerated base composition comprising the said photo-crosslinkable compound, and with the aid of an aerated-composition dispenser that can dispense the base composition in the form of an aerated composition.

As mentioned previously, according to one of its aspects, the invention relates to a product for forming an aerated cosmetic composition, comprising:

(a) a non-aerated base composition comprising, in a physiologically acceptable medium, at least one photo-crosslinkable compound as defined previously; and

The aerated composition may be formed from the base composition and air or an inert gas.

The base composition which serves to obtain the aerated composition has a similar composition to the aerated composition except for its higher density insofar as it is free of air or inert gas.

These aerated-composition dispensers are well known in the cosmetics field. Such a dispenser comprises at least:

- a reservoir containing the base composition, and

- a dispensing head for dispensing the aerated composition.

This dispenser may be an aerosol, comprising, besides the base composition, a propellant gas.

The propellant gas that may be used may be chosen from carbon dioxide, nitrogen, nitrous oxide, volatile hydrocarbons such as butane, isobutane, propane, ethane, pentane, isododecane or isohexadecane, and mixtures thereof.

Alternatively, the dispenser may contain no propellant gas. In this case, the base composition may be in an aerated-composition dispenser comprising a dispensing head for dispensing the aerated composition, a pump and a dip tube for transferring the composition from the container into the head to dispense the aerated composition. The aerated composition is formed by forcing the base composition to pass through a material comprising a porous substance such as a sintered material, a plastic or metal filtering grille, or similar structures .

PHYSIOLOGICALLY ACCEPTABLE MEDIUM

The composition may comprise a physiologically acceptable aqueous or nonaqueous medium.

The composition may comprise a physiologically acceptable solvent or mixture of solvents.

As aqueous or non-aqueous media that are suitable for use in the invention, examples that may be mentioned include water, alcohols, polyols, polyol ethers, and mixtures thereof. As isotonic agents that are suitable for preparing a composition that is suitable for use in the invention, mention may be made of sugars and sodium chloride.

The alcohols may be chosen from Ci-C₆ lower alkanols and preferably chosen from ethanol, propanol and isopropanol.

The polyols may be chosen from glycerol, propylene glycol, polyethylene glycol, hexylene glycol, glycerol and pentanediol.

These polyols will have the effect of plasticizing the crosslinked polymer and of modifying its final mechanical properties. The polymer/polyol ratio ranges from 100/0 to 1/10. Thus, a composition according to the invention is generally used in the form of an aqueous or non-aqueous isotonic solution or in the form of a dispersion, suspension or emulsion.

The aqueous or non-aqueous medium may represent from 0.1% to 99% by weight, preferably from 30% to 99% by weight or even from 50% to 99% by weight relative to the total weight of the composition.

Film-forming polymer

A composition according to the invention may also comprise one or more film- forming polymers, other than the (photo)crosslinkable polymers under consideration according to the invention and described previously.

For the purposes of the present invention, the term "film-forming polymer" denotes a polymer that is capable of forming, by itself or in the presence of an auxiliary film-forming agent, an isolable film, which is especially continuous and adherent, on a support, especially on the nails.

This film-forming polymer may be chosen from the group consisting of synthetic polymers, of radical type or of poly condensate type, and polymers of natural origin, and mixtures thereof.

A film- forming polymer that is suitable for use in the invention may be chosen in particular from:

- polysaccharide derivatives, such as cellulose or guar gum derivatives. A polysaccharide derivative that is suitable for use in the invention may be a polysaccharide ester or alkyl ether.

The term "polysaccharide ester or alkyl ether" denotes a polysaccharide formed from repeating units comprising at least two identical or different rings having a degree of substitution per saccharide unit of between 1.9 and 3, preferably between 2.2 and 2.9 and more particularly between 2.4 and 2.8. The term "substitution" denotes the functionalization of the hydroxyl groups into ester and/or alkyl ether functions, and/or the functionalization the carboxylic groups into ester functions.

In other words, it may be a polysaccharide that is partially or totally substituted with ester and/or alkyl ether groups. Preferably, the hydroxyl groups may be substituted with ester and/or C2-C4 alkyl ether functions. Mention may be made in particular of cellulose esters, such as cellulose acetate cellulose acetobutyrates or cellulose acetopropionates; cellulose alkyl ethers such as ethylcelluloses, and ethyl guars;

- synthetic polymers such as polyurethanes, acrylic polymers, vinyl polymers, polyvinyl butyrals, alkyd resins and ketone/aldehyde resins, resins derived from aldehyde condensation products, such as arylsulfonamide-formaldehyde resins, for instance toluenesulfonamide-formaldehyde resin, arylsulfonamide-epoxy resins or ethyl tosylamide resins;

- polymers of natural origin, such as plant resins, such as dammar resins, elemi gums, copal resins, and benzoin; gums such as shellac, sandarac gum and gum mastic.

According to a particular embodiment, the composition under consideration according to the invention comprises a total content of film- forming polymer of between 1% and 60% by weight, especially between 2% and 30% by weight and in particular between 5% and 15% by weight relative to the total weight of the said composition.

Preferably, it is an aqueous dispersion of particles of at least one film-forming polymer. These solid particles may be of anionic, cationic or neutral nature.

A dispersion that is suitable for use in the invention may comprise one or more types of particle, these particles possibly varying in their size, their structure and/or their chemical nature.

The size of the polymer particles in aqueous dispersion may range from 5 to 500 nm and is in particular from 10 to 150 nm. However, particles with a size ranging up to 1 micron may be used.

The size of the particles may be measured, for example, with a machine of the Brookhaven BI-90 type via the light scattering technique, or with a particle size analyser of the Malvern Mastersizer 2000 type, or alternatively by electron microscopy.

According to a particular embodiment, the composition used according to the invention may comprise one or more resins, in particular chosen from (meth)acrylate (co)polymers.

(Meth)acrylate monomers that may especially be mentioned include alkyl (meth)acrylates, in particular of a C1-C20 and preferably Ci-Cs alkyl, aryl methacrylates, in particular of a C₆-Cio aryl, and hydroxyalkyl (meth)acrylates, in particular of a C2-C6 hydroxyalkyl. These (co)polymers are generally soluble in the solvent or in dispersion but coalescable.

Auxiliary film-forming agent

The composition may also comprise an auxiliary film- forming agent.

Such an auxiliary film-forming agent may be chosen from any compound known to those skilled in the art as being capable of satisfying the desired function, and may be chosen especially from plasticizers and coalescers for the film- forming polymer(s).

Thus, the composition may also comprise at least one plasticizer and/or one coalescer. In particular, mention may be made, alone or as a mixture, of common plasticizers and coalescers, such as:

- glycols and derivatives thereof, such as diethylene glycol ethyl ether, diethylene glycol methyl ether, diethylene glycol butyl ether or diethylene glycol hexyl ether, and ethylene glycol ethyl ether, ethylene glycol butyl ether or ethylene glycol hexyl ether;

- glycol esters;

- propylene glycol derivatives and in particular propylene glycol phenyl ether, propylene glycol diacetate, dipropylene glycol ethyl ether, tripropylene glycol methyl ether, diethylene glycol methyl ether and propylene glycol butyl ether;

- acid esters and especially carboxylic acid esters, such as citrates, phthalates, adipates, carbonates, tartrates, phosphates and sebacates;

- oxyethylenated derivatives, such as oxyethylenated oils, especially plant oils such as castor oil;

- oils of natural origin, in particular non-siccative oils, chosen from oils comprising at least one fatty acid chosen from caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, ricinoleic acid, linoleic acid, linolenic acid, arachidic acid, gadoleic acid, behenic acid, erucic acid, brassidic acid, cetoleic acid, lignoceric acid and nervonic acid. In particular, these oils are chosen from triglycerides consisting of fatty acid esters of glycerol, the fatty acids of which may have varied chain lengths from C₄ to C₂₄, these chains possibly being linear or branched, and saturated or unsaturated. These oils are especially heptanoic or octanoic triglycerides, groundnut oil, babassu oil, coconut oil, grapeseed oil, cotton seed oil, corn oil, corn germ oil, mustard seed oil, palm oil, rapeseed oil, sesame seed oil, soybean oil, sunflower oil, wheatgerm oil, canola oil, apricot oil, mango oil, castor oil, shea oil, avocado oil, olive oil, sweet almond oil, almond oil, peach oil, walnut oil, hazelnut oil, macadamia oil, jojoba oil, alfalfa oil, poppy seed oil, pumpkin oil, marrow oil, blackcurrant oil, evening primrose oil, millet oil, barley oil, quinoa oil, rye oil, safflower oil, candlenut oil, passion-flower oil, musk rose oil, shea butter oil, or caprylic/capric acid triglycerides, and

- mixtures thereof.

The type and amount of plasticizer and/or coalescer may be chosen by a person skilled in the art on the basis of his general knowledge.

For example, the content of plasticizer(s) and/or coalescer(s) may range from 0.01% to 20% and in particular from 0.5% to 10% by weight relative to the total weight of the composition.

Gelling agent

The composition according to the invention may also comprise a gelling agent. This gelling agent may be chosen in particular from: hydrophobic silicas, such as those described in the document EP-A-0 898 960, for example sold under the references Aerosil R812^® by the company Degussa, Cab-O-Sil TS-530^®, Cab-O-Sil TS-610^® and Cab-O-Sil TS-720^® by the company Cabot and Aerosil R972^® and Aerosil R974^® by the company Degussa; clays, such as montmorillonite, or modified clays, such as bentones, for example, stearalkonium hectorite or stearalkonium bentonite, polysaccharide alkyl ethers (in particular in which the alkyl group comprises from 1 to 24, preferably from 1 to 10, better still from 1 to 6 and more especially from 1 to 3 carbon atoms) such as those described in document EP-A-0 898 958.

The total proportion of gelling agent(s) in the compositions according to the invention may range from 0.01% to 15% by weight, relative to the total weight of the composition, preferably from 0.5% to 15% by weight and better still from 0.5% to 10% by weight.

Particulate phase

Preferably, the composition under consideration according to the invention comprises at least one particulate phase. The particulate phase may represent a content ranging from 0.01% to 30%, especially from 0.01% to 15%, in particular from 0.02% to 10% and better still from 0.05% to 10% by weight relative to the total weight of the said composition. It may be at least one dyestuff, especially a pigment and/or at least one nacre and/or at least glitter flakes and/or at least one filler used in cosmetic compositions.

The term "pigments" should be understood as meaning white or coloured, mineral or organic particles of any shape, which are insoluble in the physiological medium, and which are intended to colour the composition.

The term "nacres" should be understood as meaning iridescent particles of any shape, especially produced by certain molluscs in their shell or, alternatively, synthesized.

The pigments may be white or coloured, and mineral and/or organic. Among the mineral pigments that may be mentioned are titanium dioxide, optionally surface- treated, zirconium oxide or cerium oxide, and also zinc oxide, iron oxide (black, yellow or red) or chromium oxide, manganese violet, ultramarine blue, chromium hydrate and ferric blue, and metallic powders such as aluminium powder or copper powder.

Among the organic pigments that may be mentioned are carbon black, pigments of D&C type and lakes based on cochineal carmine or on barium, strontium, calcium or aluminium.

Mention may also be made of pigments with an effect such as particles comprising a natural or synthetic, organic or mineral substrate, for example glass, acrylic resins, polyester, polyurethane, polyethylene terephthalate, ceramics or aluminas and optionally coated with metallic substances such as aluminium, gold, copper or bronze, or with metal oxides such as titanium dioxide, iron oxide or chromium oxide, and mineral or organic pigments, and mixtures thereof.

The nacreous pigments may be chosen from white nacreous pigments such as mica coated with titanium or with bismuth oxychloride, coloured nacreous pigments such as titanium mica covered with iron oxides, titanium mica covered with, in particular, ferric blue or chromium oxide, titanium mica covered with an organic pigment of the abovementioned type, and nacreous pigments based on bismuth oxychloride.

Use may also be made of pigments with gonio chromatic properties, especially liquid-crystal or multilayer pigments. The dyes are, for example, Sudan Red, DC Red 17, DC Green 6, β-carotene, soybean oil, Sudan Brown, DC Yellow 1 1, DC Violet 2, DC Orange 5 and quinoline yellow.

The dyestuff may also be chosen from optical brighteners.

And the composition may also comprise fibres optionally coated with optical brighteners.

The term "fillers" should be understood as meaning colourless or white, mineral or synthetic particles of any shape, which are insoluble in the medium of the composition, irrespective of the temperature at which the composition is manufactured. These fillers serve especially to modify the rheology or the texture of the composition.

The fillers may be mineral or organic and of any shape, platelet-shaped, spherical or oblong, irrespective of the crystallo graphic form (for example lamellar, cubic, hexagonal, orthorhombic, etc.). Mention may be made of talc, mica, silica, kaolin, polyamide (Nylon^®) powder (Orgasol^® from Atochem), poly- -alanine powder and polyethylene powder, tetrafluoroethylene polymer (Teflon^®) powders, lauroyllysine, starch, boron nitride, hollow polymer microspheres such as those of polyvinylidene chloride/acrylonitrile, for instance Expancel^® (Nobel Industrie) or of acrylic acid copolymers (Polytrap^® from the company Dow Corning) and silicone resin microbeads (for example Tospearls^® from Toshiba), elastomeric polyorganosiloxane particles, precipitated calcium carbonate, magnesium carbonate, magnesium hydrogen carbonate, hydroxyapatite, hollow silica microspheres (Silica Beads^® from Maprecos), glass or ceramic microcapsules, and metal soaps derived from organic carboxylic acids containing from 8 to 22 carbon atoms and preferably from 12 to 18 carbon atoms, for example zinc stearate, magnesium stearate or lithium stearate, zinc laurate or magnesium myristate.

Thickener

The composition of the invention may also comprise a thickener. The thickener may be chosen from:

- organomodified clays, which are clays treated with compounds chosen especially from quaternary amines and tertiary amines. Organomodified clays that may be mentioned include organomodified bentonites such as those sold under the name Bentone 34 by the company Rheox, and organomodified hectorites such as those sold under the names Bentone 27 and Bentone 38 by the company Rheox;

- hydrophobic fumed silica. Such silicas are sold, for example, under the references Aerosil R812^® by the company Degussa, Cab-O-Sil TS-530^® by the company Cabot and under the references Aerosil R972^® and Aerosil R974^® by the company Degussa and Cab-O-Sil TS-610^® and Cab-O-Sil TS-720^® by the company Cabot.

The thickener may be present in a content ranging from 0.1% to 20% by weight and better still from 0.4% to 10% by weight relative to the total weight of the composition. Surfactant

The composition may comprise one or more surfactants, in particular chosen from amphoteric, anionic, cationic and nonionic surfactants, preferably nonionic surfactants. Mention may be made especially, alone or as a mixture, of:

a) nonionic surfactants with an HLB of less than 8 at 25°C, optionally combined with one or more nonionic surfactants with an HLB of greater than 8 at 25°C, as mentioned below, for instance:

- saccharide esters and ethers such as sucrose stearates, sucrose cocoate and sorbitan stearate, and mixtures thereof;

- fatty acid esters, especially of C8-C24 and preferably of C16-C22, and of polyol, especially of glycerol or sorbitol, such as glyceryl stearate, glyceryl laurate, polyglyceryl-2 stearate, sorbitan tristearate and glyceryl ricinoleate;

- lecithins, such as soybean lecithins;

- oxyethylenated and/or oxypropylenated ethers (which may comprise 1 to 150 oxyethylene and/or oxypropylene groups) of fatty alcohols (especially of C8-C24 and preferably C₁₂-C₁₈ alcohols) such as stearyl alcohol oxyethylene ether containing two oxyethylene units (CTFA name: Steareth-2);

- silicone surfactants, for instance dimethicone copolyols and alkyldimethicone copolyols, for example the mixture of cyclomethicone/dimethicone copolyol especially sold under the name Q2-3225C^® by the company Dow Corning;

b) nonionic surfactants with an HLB of greater than or equal to 8 at 25°C, for instance: - saccharide esters and ethers such as the mixture of cetylstearyl glucoside and of cetyl and stearyl alcohols, for instance Montanov 68 from SEPPIC;

- oxyethylenated and/or oxypropylenated glycerol ethers, which may comprise 1 to 150 oxyethylene and/or oxypropylene units;

- oxyethylenated and/or oxypropylenated ethers (which may comprise from 1 to 150 oxyethylene and/or oxypropylene units) of fatty alcohols, especially of C8-C24 and preferably of C₁₂-C₁₈, such as stearyl alcohol oxyethylene ether containing 20 oxyethylene units (CTFA name: Steareth-20), cetearyl alcohol oxyethylene ether containing 30 oxyethylene units (Ceteareth-30) and the oxyethylene ether of the mixture of C₁₂-C₁₅ fatty alcohols comprising seven oxyethylene units (C_12-15 Pareth-7);

- esters of a fatty acid, especially of C8-C24 and preferably of C16-C22, and of polyethylene glycol (or PEG) (which may comprise 1 to 150 oxyethylene units), such as PEG-50 stearate and PEG-40 monostearate;

- esters of a fatty acid, especially of C8-C24 and preferably of C16-C22, and of oxyethylenated and/or oxypropylenated glycerol ethers (which may comprise from 1 to

150 oxyethylene and/or oxypropylene units), for instance glyceryl monostearate polyoxyethylenated with 200 oxyethylene units; glyceryl stearate polyoxyethylenated with 30 oxyethylene units, glyceryl oleate polyoxyethylenated with 30 oxyethylene units, glyceryl cocoate polyoxyethylenated with 30 oxyethylene units, glyceryl isostearate polyoxyethylenated with 30 oxyethylene units and glyceryl laurate polyoxyethylenated with 30 oxyethylene units;

- esters of a fatty acid, especially of C8-C24 and preferably of C16-C22, and of oxyethylenated and/or oxypropylenated sorbitol ethers (which may comprise from 1 to 150 oxyethylene and/or oxypropylene units), for instance polysorbate 20 and polysorbate 60;

- dimethicone copolyol, especially the product sold under the name Q2-5220^® from Dow Corning;

- dimethicone copolyol benzoate, such as the products sold under the names Finsolv SLB 101^® and 201^® from Finetex;

- copolymers of propylene oxide and of ethylene oxide, also known as EO/PO poly condensates, which are copolymers formed from polyethylene glycol and polypropylene glycol blocks, for instance polyethylene glycol/polypropylene gly col/poly ethylene glycol triblock poly condensates. c) anionic surfactants such as:

- salts of C16-C30 fatty acids, especially amine salts, such as triethanolamine stearate or 2-amino-2-methylpropane-l ,3-diol stearate;

- polyoxyethylenated fatty acid salts, especially aminated salts or salts of alkali metals, and mixtures thereof;

- phosphoric esters and salts thereof, such as DEA oleth-10 phosphate (Crodafos N ION from the company Croda) or monopotassium monocetyl phosphate;

- sulfo succinates such as disodium PEG-5 citrate lauryl sulfosuccinate and disodium ricinoleamido ME A sulfosuccinate;

- alkyl ether sulfates such as sodium lauryl ether sulfate;

- isethionates;

- acylglutamates such as Disodium hydrogenated tallow glutamate (Amisoft HS-21 R® from Ajinomoto) and sodium stearoyl glutamate (Amisoft HS-11 PF® from Ajinomoto);

- soybean derivatives, for instance potassium soyate;

- citrates, for instance glyceryl stearate citrate;

- proline derivatives, for instance sodium palmitoyl proline or the mixture of sodium palmitoyl sarcosinate, magnesium palmitoyl glutamate, palmitic acid and palmitoyl proline (Sepifeel One from SEPPIC);

- lactylates, for instance sodium stearoyl lactylate;

- sarcosinates, for instance sodium palmitoyl sarcosinate or the 75/25 mixture of stearoyl sarcosine and myristoyl sarcosine;

- sulfonates, for instance sodium C 14-17 alkyl-sec-sulfonate;

- glycinates, for instance sodium cocoyl glycinate.

d) cationic surfactants such as:

- alkylimidazolidiniums such as isostearylethylimidonium ethosulfate,

- ammonium salts such as (C12-30 alkyl)tri(C_1-4 alkyl)ammonium halides, for instance N,N,N-trimethyl-l-docosanaminium chloride (or behentrimonium chloride);

e) amphoteric surfactants, for instance N-acylamino acids, such as N- alkylaminoacetates and disodium cocoamphodiacetate, and amine oxides such as stearamine oxide. Additives

The composition according to the invention may also contain ingredients commonly used in cosmetics and more especially in the cosmetic and/or nailcare field. They may be chosen especially from vitamins, trace elements, softeners, sequestrants, acidifying agents, basifying agents, spreading agents, wetting agents, dispersants, preserving agents, UV-screening agents, active agents, moisturizers, fragrances, neutralizers, stabilizers and antioxidants, and mixtures thereof.

Thus, when the dispersions according to the invention are more particularly intended for caring for natural nails, they may especially incorporate, as active agents, hardeners for keratin materials, active agents acting on the growth of the nail, for instance methyl sulfonyl methane, and/or active agents for treating various complaints located on the nail, for instance onychomycosis.

The amounts of these various ingredients are those conventionally used in this field, for example from 0.01% to 20% and especially from 0.01% to 10% by weight relative to the total weight of the article.

Needless to say, a person skilled in the art will take care to select this or these optional additional compound(s), and/or the amount thereof, such that the advantageous properties of the composition for the use according to the invention are not, or are not substantially, adversely affected by the envisaged addition.

Preferably, the composition used according to the invention comprises one or more additional compounds chosen from surfactants, thickeners, resins chosen especially from (meth)acrylate (co)polymers, and particles such as fillers and/or dyestuffs.

Preferably, the composition under consideration according to the invention is free of photoinitiator and/or of chemical initiator.

For the purposes of the present invention, the term "photoinitiator" means a compound which initiates the photo-dimerization reaction and releases a radical under irradiation, especially in the UV range.

As representatives of conventional photoinitiators, which are therefore not required according to the invention, mention may be made especially of thioxanthone, rose Bengal, phloxin, eosin, erythrosin, fluorescein, acriflavin, thionine, riboflavin, proflavin, chlorophylls, haematoporphyrin and methylene blue, and mixtures thereof, this list not being limiting. STEP (ii): CROSSLINKING

According to a particular embodiment, step (ii) may be preceded by a step of smoothing the said coat of composition (M). This step may be performed, for example, using a mould to be applied onto the surface of the coat so as to give it a shape, or alternatively via a system for levelling or for removing the surplus foam, by scraping.

Such a step advantageously makes it possible to improve the smooth and uniform appearance of the coating formed.

As mentioned previously, the process of the invention comprises at least one step (ii) of exposing all or part of the surface of the said aerated coat formed in step (i) to conditions suitable for crosslinking the said photo-crosslinkable compound.

It falls to a person skilled in the art to select the adequate exposure conditions, especially with regard to the nature of the photo-crosslinkable compound used in the composition.

Step (ii) may consist in illuminating the surface of the said coat with ambient light or with a source of artificial light.

The ambient or artificial light may emit radiation in the visible and/or UV range. Preferably, it emits at least a proportion of radiation in the UV range, for example a proportion of UV of at least 2% of the total light energy of the ambient light.

According to a particular embodiment, step (ii) comprises, or even consists in, illuminating the surface of the said coat with ambient light, in particular for a time of at least 1 minute.

The time of exposure to the ambient light may more particularly range from 10 seconds to 15 minutes and especially from 5 to 10 minutes.

According to another particular embodiment, step (ii) comprises, or even consists in, illuminating the surface of the said coat with a source of artificial light.

The time of exposure to the said artificial light may range from 10 seconds to 10 minutes and in particular from 30 seconds to 5 minutes.

The lighting system for providing artificial light may consist, for example, of lighting with a lamp, a torch, a laser or LEDs, for example in the form of an LED array.

The artificial light source may emit radiation in the visible range and/or radiation in the UV range. The emitted light may or may not be monochromatic. The wavelength of the emitted light is preferably centred on 365 nm, in particular between 400 nm and 700 nm and better still between 365 nm and 550 nm.

The crosslinking may be initiated by illumination without the need for a photoinitiator.

Preferably, it will be a source of artificial light emitting energy of at least 0.2 mW/cm² and in particular from 0.5 to 20 mW/cm².

The crosslinking may take place with a reduced light intensity, and the lighting system may, for example, produce a light intensity of less than 50 mJ/cm² or even 10 J/cm².

In particular, the light energy in the UV range is preferably less than 10 J/cm².

The twofold characteristic of the absence of photoinitiator and of relatively weak light intensity is particularly advantageous since it makes it possible to limit the harmful effects of aggressive initiators or of prolonged exposure to intense light, in particular in UV wavelengths.

A person skilled in the art will be capable of adapting the illumination characteristics, especially in terms of duration of exposure and of radiation wavelengths, with regard to the nature of the photo-crosslinkable compound used.

Thus, the photo-crosslinking of polyurethanes bearing (meth)acrylate groups will require light emitting at least radiation in the UV range, whereas the photo- crosslinking of polymers of PVA-SbQ type may be performed with radiation in the visible range.

Other variants of the process of the invention, in the case of the use of a composition with delayed expansion, are described below.

Thus, according to a first embodiment variant, step (ii) may be performed, on all or part of the surface of the said coat, before the complete expansion of the composition with delayed expansion (E).

It is thus possible to stop the expansion of the composition when the coat has reached the desired thickness.

According to yet another variant, it is possible to perform heterogeneous illumination on the nail surface. Thus, according to a particular embodiment, the process of the invention may comprise at least one step of illumination, as described previously, of one or more localized zones of the surface of the said coat of composition with delayed expansion (E), before the complete expansion of the said composition (E), or even immediately after its application (a) and prior to its expansion (b).

The said zones may be defined, for example, by means of a cache that is capable of permitting the illumination of only the said zones.

In particular, the process may comprise at least two illumination steps performed for different localized zones of the surface of the said coat of composition with delayed expansion (E), and when the said composition has reached different degrees of aeration.

It is thus possible to obtain on the nail surface varied volume effects, by creating zones of more or less thick coating. For example, it is possible to create roughness effects.

The process of the invention may also comprise one or more subsequent steps of superposition, onto the coating formed after step (ii), of one or more additional coats of conventional nail varnish composition(s), such as nitrocellulose-based nail varnish compositions or alternatively UV gels.

The present invention will be understood more clearly by means of the examples that follow.

These examples are given as illustrations of the invention and cannot be interpreted as limiting the scope thereof.

EXAMPLES EXAMPLE 1

Self-foaming nail varnish with a PVA-SbO polymer as photo-crosslinkable material

Preparation of the composition

Phases 1 and 2 described in Table 1 below are mixed together in the following manner.

Phase 1 is placed in a reactor. Phase 2 is then introduced gently and with stirring into the reactor. Stirring is continued for 1 hour. All these operations are performed protected from light.

TABLE 1

A rigid pressurizable bottle made of tin, of about 200 ml, from the company Impress Vendel is used (commercial reference 190-Impress Vendel). A valve from the company Coster (commercial reference C 30605) is attached to a bag. This bag is crimped onto the drum. The bag is then filled with 60 g of formulation.

3 g of isopentane are then introduced into the bag. Next, the whole is shaken. The space outside the bag is then pressurized with 5 g of a propane/butane mixture. A push button is fixed onto the valve mounted on the bag.

Application to the nails

To use the product, the push button is pressed. When the product exits via the push button, it is spread on the nails, at a rate of about 15 mg per nail.

Without touching the nails, the coating is left to expand and photo-crosslink in the ambient light for 10 minutes. Result

A thick coating about 1 mm thick is then obtained.

A nitrocellulose-based varnish or a UV gel, for example from the company Shellac, may optionally be applied over the said coating formed, and photo-crosslinked with a UV lamp for 2 minutes.

A thick coating about 1 mm thick and especially smooth is then obtained.

EXAMPLE 2

Self-foaming nail varnish with a polyurethane bearing acrylate groups as photo-crosslinkable material

Preparation of the composition

TABLE 2

A rigid pressurizable bottle made of tin, of about 200 ml, from the company

Impress Vendel is used (commercial reference 190-Impress Vendel). A valve from the company Coster (commercial reference C 30605) is attached to a bag. This bag is crimped onto the drum. The bag is then filled with 60 g of formulation.

3 g of isopentane are then introduced into the bag. Next, the whole is shaken. The space outside the bag is then pressurized with 5 g of a propane/butane mixture. A push button is fixed onto the valve mounted on the bag. Application to the nails

Without touching the nails, the coating is left to expand for 4 minutes.

The fingers are then placed under a UV lamp for 4 minutes.

Result

A thick coating about 1 mm thick is then obtained.

A thick coating about 1 mm thick and especially smooth is then obtained.

Claims

1. Cosmetic process for forming a coating on the surface of a nail or false nail, comprising at least the steps consisting in:

(i) forming, on all or part of a nail or false nail, an aerated coat of a composition comprising, in a physiologically acceptable medium, at least one photo- crosslinkable compound, the said compound comprising at least one activated photo- dimerizable group bearing at least one activated double bond; and

2. Process according to Claim 1, in which the said photo-crosslinkable compound bears one or more functions that can be cyclized via a 2/2 reaction, which are nsitive to light irradiation in the absence of photoinitiator and/or of chemical initiator.

in which

- R represents a hydrogen atom or a C1-C4 alkyl or C1-C4 hydroxyalkyl group,

- R' represents a hydrogen atom or a C1-C4 alkyl group, and

- X^" denotes an ion chosen from chloride, bromide, iodide, perchlorate, tetrafluoroborate, methyl sulfate, phosphate, sulfate, methanesulfonate and p- toluenesulfonate ions,

in which

- R' ' denotes a divalent alkylene radical containing from 2 to 8 carbon atoms; - R' represents a hydrogen atom or a C₁-C₄ alkyl group; and

- X^" having the same meaning as that described for the preceding formula

(la), and/or

b) photo-dimerizable groups bearing a styrylazolium function of formula (II):

in which:

- A denotes a sulfur atom, an oxygen atom or a group NR' or C(R')₂, R'; with R' representing a hydrogen atom or a C₁-C₄ alkyl group; and

- X^" having the same meaning as that described for the preceding formula

(la).

4. Process according to any one of the preceding claims, in which the photo- dimerizable group is a photo-dimerizable group bearing a stylbazolium function of formula (la):

in which

- R' represents a hydrogen atom or a C₁-C₄ alkyl group, and

5. Process according to any one of the preceding claims, in which the photo-crosslinkable compound is a polyvinyl alcohol partly functionalized with one or more hydroxyl functions and one or more functions of formula (III):

6. Process according to Claim 1, in which the said photo-crosslinkable compound is chosen from polyurethane and/or polyurea polymers or oligomers bearing (meth)acrylate groups, in particular polyurethane (meth)acrylate oligomers.

7. Process according to any one of the preceding claims, in which step (ii) comprises the illumination of the surface of the said coat with ambient light, the said ambient light in particular emitting at least a proportion of radiation in the UV range.

8. Process according to any one of the preceding claims, in which step (ii) comprises the illumination of the surface of the said coat with a source of artificial light, in particular emitting radiation in the UV range.

9. Process according to any one of the preceding claims, in which the said coating obtained after step (ii) has a thickness of greater than or equal to 50 μιη, in particular ranging from 50 μιη to 5 mm and more particularly from 100 μιη to 2 mm.

10. Process according to any one of the preceding claims, in which the said aerated coat is formed via at least the steps consisting in:

(a) applying to all or part of the nail at least one coat of a composition with delayed expansion comprising at least the said photo-crosslinkable compound and at least one self-foaming compound, and

(b) exposing all or part of the said coat from step (a) to conditions favourable for expanding the said composition.

11. Process according to the preceding claim, in which the said self- foaming compound is chosen from slow-expanding systems such as isopentane, gas-releasing systems, such as systems releasing C0₂ by acidification of a carbonate or of aqueous hydrogen peroxide solution made unstable by basification or addition of a compound which promotes the dismutation of water, and heat-foaming or heat-expandable systems.

12. Process according to Claim 10 or 11, in which the said self-foaming compound is a slow-expanding system chosen from volatile hydrocarbons and volatile halogenated hydrocarbons with a boiling point ranging from -20 to 40°C, in particular from linear or branched C4-C6 aliphatic hydrocarbons.

13. Process according to any one of Claims 10 to 12, in which the said self- foaming compound is chosen from n-pentane, isopentane, neopentane, n-butane, isobutane and isohexane, and mixtures thereof; and preferably isopentane.

14. Process according to Claim 12 or 13, in which step (b) is performed in the ambient atmosphere, in particular for a time ranging from 10 seconds to 5 minutes.

15. Process according to any one of Claims 10 to 14, in which step (ii) is performed, on all or part of the surface of the said coat, before the complete expansion of the composition with delayed expansion.

16. Cosmetic composition with delayed expansion, comprising, in a physiologically acceptable medium,

- at least one photo-crosslinkable compound as defined according to any one of Claims 1 to 6; and

- at least one self- foaming compound, in particular as defined in claims 11 to 13.

17. Process according to any one of Claims 1 to 9, in which the said aerated coat is formed, simultaneously with its application to the surface of the nail, using a non- aerated base composition comprising the said photo-crosslinkable compound, and with the aid of an aerated-composition dispenser that can dispense the base composition in the form of an aerated composition.

18. Product for forming an aerated cosmetic composition, comprising:

(a) a non-aerated base composition comprising, in a physiologically acceptable medium, at least one photo-crosslinkable compound as defined according to any one of Claims 1 to 6; and (b) an aerated-composition dispenser for dispensing the said base composition in the form of an aerated composition.

19. Cosmetic kit, in particular for making up and/or caring for the nails, comprising at least:

- a composition as defined in Claim 16 or a product as defined in Claim 18; and

- a lighting system capable of photo-crosslinking the said compound.