EP2282713A2

EP2282713A2 - Mesoporous vector containing at least one organic uv filter

Info

Publication number: EP2282713A2
Application number: EP09745845A
Authority: EP
Inventors: Philippe Guarilloff; Bénédicte LEBEAU; Joël Patarin; Raphaël BONGUR; Claire Marichal-Westrich
Original assignee: Centre National de la Recherche Scientifique CNRS; Chanel Parfums Beaute SAS
Current assignee: Centre National de la Recherche Scientifique CNRS; Chanel Parfums Beaute SAS
Priority date: 2008-05-16
Filing date: 2009-05-18
Publication date: 2011-02-16
Also published as: WO2009138513A2; WO2009138513A3; FR2931067B1; FR2931067A1

Abstract

The present invention relates to a method for the preparation of a mesoporous vector containing at least one organic UV filter, as well as the vector capable of being thus obtained. It also relates to a composition containing this mesoporous vector in a physiologically acceptable, and preferably a cosmetically acceptable, medium, as well as a cosmetic method for the care and/or make-up of the skin, comprising the topical application to the latter of this composition. It finally relates to the cosmetic use of this mesoporous vector for preventing or combating cutaneous photo-ageing, and for the production of a composition intended to protect the skin against the effects of UV and in particular to prevent cutaneous erythema.

Description

Mesoporous vector containing at least one organic UV filter

The present invention relates to a method for the preparation of a mesoporous vector containing at least one organic UV filter, as well as the vector thus obtained, the cosmetic compositions containing them and uses thereof.

It is known to incorporate in cosmetic compositions for skin care or makeup, agents interacting with light, in particular with UV or visible light, in order to obtain different optical effects such as UV absorption, which are useful in the photoprotection of the skin, or fluorescence, photochromy or interference effects of making it possible to modify the appearance of the skin and in particular to mask surface inhomogeneities and to make the complexion more radiant.

These compounds with an optical effect however have several drawbacks, both in the formulations containing them and on the surface of the skin, which are capable of limiting their use at high concentration.

Thus, certain organic UV filters have a tendency to degrade in the presence of UVA and consequently to produce free radicals which are harmful to the skin, as is the case for certain dibenzoylmethane derivatives. Other organic sun filters, bearing sulphonic acid functions, have a tendency to break the viscosity of gels obtained from acrylic polymers and are poorly compatible with the aqueous-phase gelling agents used in a standard fashion in sun-protection or skincare compositions. It is therefore understood that the encapsulation of these organic filters would make it possible to avoid these phenomena. Moreover, their inclusion in vector systems of a sufficient size to allow them to stay on the surface of the skin would also have a significant advantage from the safety point of view.

Among the solutions proposed up to now for encapsulating cosmetic molecules such as sun filters, several use porous silica or silicate particles. The documents WO 2005/011622 and EP 0 679 382 can therefore be cited in particular. These solutions, using in particular particles obtained by the sol-gel route, are not however completely satisfactory, in particular, due to the fact that the vectors thus obtained do not sufficiently prevent leakage of compound encapsulated in the cosmetic composition conveying them or in contact with perspiration on the skin.

A need therefore remains to have novel vector systems of a size greater than 100 nm, which allow the stable encapsulation of high concentrations of organic UV filters whilst being easy to formulate, in particular in cosmetic compositions, without substantially affecting the stability of these compositions. The stability of the encapsulation should be able to lead to a loss of less than 10% by weight, or even of less than 1% by weight, of the encapsulated compound after storing the vector system for 2 months at 45⁰C in a UV filter solvent.

It is to the inventors' credit to have developed such vector systems, which trap the UV filters that they contain throughout the shelf life of the compositions into which they are introduced, as well as throughout the period of time when they are present on the skin, without producing any substantial leakage of the trapped filters and without loss of photoprotective effectiveness of these filters. These vector systems moreover allow the formulation of compositions having good cosmetic properties, as regards their colour and feel in particular. Finally, the encapsulation of the UV filters is carried out under mild chemical conditions which do not risk damaging them and which make it possible to encapsulate both hydrophilic and lipophilic UV filters.

These vector systems are capable of being obtained by mixing a silica precursor with a micellar solution of a surfactant and the UV filter (s) to be encapsulated, followed by the condensation of the silica precursor in order to form mesoporous vectors.

Vector systems of this type, qualified as mesoporous materials organized for MTS (for "micelle-templated silica") have already been described by J. S. BECK et al . ,

J. Am. Chem. Soc, 1992, 114, 10834. They result from the polycondensation of inorganic species, such as silicates, around an organic phase constituted by micelles of a surfactant, followed by the elimination of the surfactant by calcination or chemical extraction. It is thus possible in particular to obtain mesoporous materials with a hexagonal structure (MCM-41) or with a cubic structure (MCM-48) according to the surfactant/silica ratio used. According to the IUPAC nomenclature, the mesoporous materials have a pore diameter ranging from 20 to 500 A. Uses of these systems in the field of heterogeneous catalysis, photocatalysis or trapping of heavy metals for environment purposes have already been described.

On the other hand, it has never been suggested, to the applicant's knowledge, to propose cosmetic compositions encapsulating UV filters in such systems.

A subject of the present invention is therefore a method for the preparation of a mesoporous vector containing at least one organic UV filter, comprising the following stages:

1- mixing a micellar solution of at least one surfactant in a solvent, with said organic UV filter and a silica precursor, in basic medium,

2- condensation of the silica precursor in order to form a mesoporous vector encapsulating said organic UV filter, and

3- optionally, the drying of said vector.

A subject is also the mesoporous vector capable of being obtained according to this method.

In the remainder of this description, the term "loaded mesoporous vector" denotes the mesoporous vector obtained according to the method described above, encapsulating the organic UV filter.

The first stage of the method according to the invention comprises the formation of a micellar solution of at least one surfactant in a solvent. Micelles are aggregates formed spontaneously by surfactants when they are present in a concentration greater than their critical micellar concentration (CMC) . A person skilled in the art will therefore know how to adjust this concentration in order to obtain a micellar solution .

The surfactants can be chosen from the anionic, non- ionic or cationic surfactants, including the amphiphilic block polymers, or mixtures thereof, the cationic surfactants being preferred for a use in the present invention. The surfactants can in particular be chosen from those mentioned in the work "Emulsifiers and Detergents" by McCUTCHEON.

Examples of cationic surfactants include the quaternary ammonium salts of formula (I) :

(I)

in which:

- the Ri to R₄ radicals, which can be identical or different, represent a linear or branched aliphatic radical comprising 1 to 30 carbon atoms, or an aromatic radical such as aryl or alkylaryl. The aliphatic radicals can comprise heteroatoms such as in particular oxygen, nitrogen, sulphur, halogens. The aliphatic radicals are for example chosen from the alkyl, alkoxy, (C2- Cζ) polyoxyalkylene, alkylamide, (C12-C22) alkylamido (C2- CβJalkyl, (C12-C22) alkyl acetate, hydroxyalkyl radicals, comprising 1 to 30 carbon atoms;

- X is an anion chosen from the group of the halides, phosphates, acetates, lactates, (C2- Ce) alkylsulphates, alkyl- or alkylarylsulphonates .

They also include the quaternary ammonium salts of imidazolinium, such as for example that of formula (II) below :

(ii;

in which R₅ represents an alkenyl or alkyl radical comprising 8 to 30 carbon atoms for example derived from the fatty acids of tallow, R₆ represents a hydrogen atom, a Ci-C₄ alkyl radical or an alkenyl or alkyl radical comprising 8 to 30 carbon atoms, R₇ represents a Ci-C₄ alkyl radical, R₈ represents a hydrogen atom or a Ci-C₄ alkyl radical, X is an anion chosen from the group of the halides, phosphates, acetates, lactates, alkylsulphates, alkyl- or alkylarylsulphonates. Preferably, R₅ and R₆ denote a mixture of alkenyl or alkyl radicals comprising 12 to 21 carbon atoms for example derivatives of the fatty acids of tallow, R₇ denotes methyl, R₈ denotes hydrogen. Such a product is for example marketed under the name REWOQUAT W 75 by REWO. Other examples of cationic surfactants are the quaternary diammonium salts of formula (III) :

2X

(in:

in which R₉ denotes an aliphatic radical comprising approximately 16 to 30 carbon atoms, Ri₀, Rn, R12, R13 and Ri₄, identical or different are chosen from hydrogen or an alkyl radical comprising 1 to 4 carbon atoms, and X is an anion chosen from the group of the halides, acetates, phosphates, nitrates and methylsulphates . Such quaternary diammonium salts comprise in particular diammonium propane tallow dichloride. Further examples of cationic surfactants are the quaternary ammonium salts containing at least one ester function.

The quaternary ammonium salts containing at least one ester function which can be used according to the invention are for example those of formula (IV) below:

(IV) in which: Ri5 is chosen from the C₁-C₆ alkyl radicals and the C₁-C₆ hydroxyalkyl or dihydroxyalkyl radicals; Ri6 is chosen from: the R19-CO- radical, - the saturated or unsaturated, linear or branched

C₁-C₂2 hydrocarbon radicals, the hydrogen atom, R₁8 is chosen from: - the R_2I-CO- radical, - the saturated or unsaturated, linear or branched

C₁-Ce hydrocarbon radicals, the hydrogen atom,

Ri₇, Ri₉ and R₂i, identical or different, are chosen from the saturated or unsaturated, linear or branched C₇- C₂₁ hydrocarbon radicals; n, p and r, identical or different, are integers from 2 to 6; y is an integer from 1 to 10; x and z, identical or different, are integers from 0 to 10;

X^" is an organic or inorganic, simple or complex anion; provided that the sum x + y + z equals 1 to 15, that when x equals 0 then R₁₆ denotes R20 and that when z equals 0 then R₁S denotes R22 •

The alkyl radicals R₁₅ can be linear or branched and more particularly linear. Preferably R₁₅ denotes a methyl, ethyl, hydroxyethyl or dihydroxypropyl radical and more particularly a methyl or ethyl radical.

Advantageously, the sum x + y + z equals 1 to 10. When R₁₆ is a hydrocarbon radical, it can be long and have 12 to 22 carbon atoms or short and have 1 to 3 carbon atoms .

When R₁₈ is a hydrocarbon radical, it preferably has 1 to 3 carbon atoms. Advantageously, R₁₇, R₁₉ and R₂₁, identical or different, are chosen from the saturated or unsaturated, linear or branched, C₁₁-C₂₁ hydrocarbon radicals, and more particularly from the saturated or unsaturated, linear or branched C₁₁-C₂₁ alkyl and alkenyl radicals. Preferably, x and z, identical or different, equal 0 or 1.

Advantageously, y is equal to 1. Preferably, n, p and r, identical or different, equal 2 or 3 and still more particularly are equal to 2.

The anion is preferably a halide (chloride, bromide or iodide) or an alkylsulphate, more particularly methylsulphate . It is however possible to use methanesulphonate, phosphate, nitrate, tosylate, an anion derived from organic acid such as acetate or lactate or any other anion compatible with the ammonium with an ester function. The anion X^" is still more particularly chloride or methylsulphate.

The ammonium salts of formula (IV) are more particularly used, in which:

Ri5 denotes a methyl or ethyl radical; x and y are equal to 1 ; z is equal to 0 or 1; n, p and r are equal to 2 ; Ri6 is chosen from: the Ri₉-CO- radical, the methyl, ethyl or C14-C22 hydrocarbon radicals, the hydrogen atom; R18 is chosen from: - the R_2I-CO- radical, the hydrogen atom;

Ri₇, Ri₉ and R₂i, identical or different, are chosen from the saturated or unsaturated, linear or branched C₁₃-C₁₇ hydrocarbon radicals, and preferably from the saturated or unsaturated, linear or branched Ci₃-Ci₇ alkyl and alkenyl radicals. Advantageously, the hydrocarbon radicals are linear.

There can be mentioned as examples of compounds of formula (IV) the salts (chloride or methylsulphate in particular) of diacyloxyethyl dimethyl ammonium, diacyloxyethyl hydroxyethyl methyl ammonium, monoacyloxyethyl dihydroxyethyl methyl ammonium, triacyloxyethyl methyl ammonium, monoacyloxyethyl hydroxyethyl dimethyl ammonium and mixtures thereof. The acyl radicals preferably have 14 to 18 carbon atoms and originate more particularly from a vegetable oil such as palm or sunflower oil.

When the compound contains several acyl radicals, the latter can be identical or different.

These products are obtained for example by direct esterification of triethanolamine, triisopropanolamine, alkyldiethanolamine or alkyldiisopropanolamine optionally oxyalkylenated on fatty acids or on mixtures of fatty acids of vegetable or animal origin or by transesterification of their methyl esters. This esterification is followed by quaternization using an alkylating agent such as an alkyl halide (methyl or ethyl preferably) , a dialkylsulphate (methyl or ethyl preferably) , methyl methanesulphonate, methyl paratoluenesulphonate, glycol or glycerol chlorhydrin.

Such compounds are for example marketed under the names DEHYQUART by HENKEL, STEPANQUAT by STEPAN, NOXAMIUM by CECA, REWOQUAT WE 18 by REWOWITCO.

Among the cationic surfactants, on the one hand, the tetraalkylammonium chlorides such as for example dialkyldimethylammonium or alkyltrimethylammonium chlorides are preferred, in which the alkyl radical comprises 8 to 22 carbon atoms, in particular behenyltrimethylammonium, distearyldimethylammonium, cetyltrimethylammonium, benzyl dimethyl stearyl ammonium chlorides or also, on the other hand, stearamidopropyldimethyl (myristyl acetate) ammonium chloride marketed in particular under the name CERAPHYL 70 by VAN DYK.

It has been demonstrated in particular that alkyltrimethylammonium chlorides and bromides the alkyl chain of which contains 12 to 16 carbon atoms, such as hexadecyltrimethylammonium and dodecyltrimethylammonium chlorides and bromides, are the quaternary ammonium salts which are more particularly preferred according to the invention, in the case of hydrophilic organic UV filters, to the extent that they make it possible to reach a higher encapsulation level of these molecules. In the case of lipophilic UV organic filters, it is preferable to use according to the invention alkyltrimethylammonium chlorides and bromides the alkyl chain of which contains 8 to 16, preferably 12 to 16 carbon atoms.

The solvent used in the formation of the micellar solution can be water or an oil. It is preferably water.

As indicated previously, this micellar solution is mixed with at least one organic UV filter intended to be encapsulated in the mesoporous vectors according to the invention.

The organic UV filter utilized according to the invention can be of a hydrophilic or hydrophobic nature. According to its polarity, it will rather be oriented towards the polar heads of the surfactant molecules or towards the interior of the micelles, in the first stage of the method according to the invention.

Examples of lipophilic or hydrophobic UV organic filters are in particular chosen from the anthranilates; cinnamic derivatives; dibenzoylmethane derivatives; salicylic derivatives, camphor derivatives; triazine derivatives such as those described in the patent applications US 4 367 390, EP 863 145, EP 517 104, EP 570 838, EP 796 851, EP 775 698, EP 878 469, EP 933 376, EP

507 691, EP 507 692, EP 790 243 and EP 944 624; benzophenone derivatives; β, β ' -diphenylacrylate derivatives; benzotriazole derivatives; benzalmalonate derivatives; benzimidazole derivatives; imidazolines; bis-benzoazolyl derivatives as described in the patents

EP 669 323 and US 2,463,264; the p-aminobenzoic acid

(PABA) derivatives; methylene bis- (hydroxyphenyl benzotriazole) derivatives as described in the applications US 5,237,071, US 5,166,355, GB 2 303 549, DE 197 26 184 and EP 893 119; the filter polymers and filter silicones such as those described in particular in the application WO-93/04665; the dimers derived from CC- alkylstyrene such as those described in the patent application DE 19 855 649; 4, 4-diarylbutadienes as described in the applications EP 0 967 200, DE 19 746 654, DE 19 755 649, EP-A-I 008 586, EP 1 133 980 and EP 133 981; and mixtures thereof.

As examples of hydrophobic organic filters, there can be mentioned those designated below by their INCI name :

- Para-aminobenzoic acid derivatives: Ethyl PABA, Ethyl Dihydroxypropyl PABA, Ethylhexyl Dimethyl PABA sold in particular under the name "ESCALOL 507" by ISP,

- Salicylic derivatives: Homosalate sold under the name "Eusolex HMS" by Rona/EM Industries, Ethylhexyl Salicylate sold under the name "NEO HELIOPAN OS" by DSM, - Dibenzoylmethane derivatives: Butyl

Methoxydibenzoylmethane sold in particular under the trade name "PARSOL 1789" by SYMRISE, Isopropyl Dibenzoylmethane,

- Cinnamic derivatives: Ethylhexyl Methoxycinnamate sold in particular under the trade name "PARSOL MCX" by

SYMRISE, Isopropyl Methoxy cinnamate, Isoamyl Methoxy cinnamate sold under the trade name "NEO HELIOPAN E 1000" by DSM, Diisopropyl Methylcinnamate,

- β, β ' -diphenylacrylate derivatives: Octocrylene, sold in particular under the trade name "UVINUL N539" by

BASF, Etocrylene, sold in particular under the trade name "UVINUL N35" by BASF, - Benzophenone derivatives: Benzophenone-1 sold under the trade name "UVINUL 400" by BASF, Benzophenone-2 sold under the trade name "UVINUL D50" by BASF, Benzophenone-3 or Oxybenzone, sold under the trade name "UVINUL M40" by BASF, Benzophenone-6 sold under the trade name "Helisorb 11" by Norquay, Benzophenone-8 sold under the trade name "Spectra-Sorb UV-24" by American Cyanamid, Benzophenone-10, Benzophenone-11, Benzophenone-12, Diethylamino Hydroxy-benzoyl Hexyl Benzoate sold under the trade name "UVINUL A PLUS" by BASF,

- Benzylidene camphor derivatives: 3-Benzylidene camphor, Methylbenzylidene camphor sold under the name "EUSOLEX 6300" by MERCK, Polyacrylamidomethyl Benzylidene camphor, - Triazine derivatives: Bis-Ethylhexyloxyphenol

Methoxyphenyl Triazine sold under the trade name "TINOSORB S" by CIBA GEIGY, Ethylhexyl triazone sold in particular under the trade name "UVINUL T150" by BASF, Diethylhexyl Butamido Triazone sold under the trade name "UVASORB HEB" by SIGMA 3V, 2, 4, β-tris (dineopentyl 4'- amino benzalmalonate) -s-triazine, 2, 4, 6-tris- (diisobutyl 4 ' -amino benzalmalonate) -s-triazine,

- Phenyl benzotriazole derivatives: Drometrizole Trisiloxane sold under the name "Silatrizole" by RHODIA CHIMIE, Methylene bis-Benzotriazolyl Tetramethylbutyl- phenol, sold in solid form under the trade name "MIXXIM BB/100" by FAIRMOUNT CHEMICAL or in micronized form in aqueous dispersion under the trade name "TINOSORB M" by CIBA SPECIALTY CHEMICALS, - Anthranilic derivatives: Menthyl anthranilate sold under the trade name "NEO HELIOPAN MA" by DSM,

- Imidazoline derivatives: Ethylhexyl Dimethoxybenzylidene Dioxoimidazoline Propionate, - Benzalmalonate derivatives: Polyorganosiloxanes with a benzalmalonate function such as the Polysilicone- 15 sold under the trade name "PARSOL SLX" by SYMRISE,

- 4, 4-diarylbutadiene derivatives: 1, 1-dicarboxy (2,2' -dimethyl-propyl) -4, 4-diphenylbutadiene,

- Benzoxazole derivatives: 2,4-bis-[5- 1 (dimethylpropyl) benzoxazol-2-yl-( 4-phenyl) -imino] -6- (2- ethylhexyl) -imino-1, 3, 5-triazine sold under the name Uvasorb K2A by Sigma 3V, - and mixtures thereof.

The preferential hydrophobic organic UV filters are chosen from: Ethylhexyl Salicylate, Homosalate, Ethylhexyl Methoxycinnamate, Butyl Methoxydibenzoyl- methane, Octocrylene, Benzophenone-3, n-hexyl 2- (4- diethylamino-2-hydroxybenzoyl) -benzoate, 4-Methyl- benzylidene camphor, Bis-Ethylhexyloxyphenol Methoxy- phenyl Triazine, Ethylhexyl triazone, Diethylhexyl Butamido Triazone, Methylene bis-Benzotriazolyl Tetramethylbutylphenol, Drometrizole Trisiloxane, Polysilicone-15, 1, 1-dicarboxy (2, 2 ' -dimethyl-propyl) - 4, 4-diphenylbutadiene, 2,4-bis-[5- (dimethylpropyl) benzoxazol-2-yl-( 4-phenyl) -imino] -6- (2-ethylhexyl) -imino- 1, 3, 5-triazine, and mixtures thereof.

Among the hydrophilic organic UV filters which can be used according to the invention, there can be mentioned those referred to above under their INCI name:

(1) p-aminobenzoic (PABA) derivatives such as PABA, Glyceryl PABA, and PEG-25 PABA sold under the name

"UVINUL P25" by BASF;

(2) benzophenone derivatives comprising at least one sulphonic radical such as Benzophenone-4 sold under the trade name "UVINUL MS40" by BASF, Benzophenone-5 and Benzophenone-9 ;

(3) benzylidene camphor derivatives comprising at least one sulphonic radical such as for example: Benzylidene Camphor Sulphonic Acid, Camphor Benzalkonium Methosulphate and Terephthalylidene Dicamphor Sulphonic Acid;

(4) benzimidazole derivatives comprising at least one sulphonic radical such as for example: Phenylbenzimidazole Sulphonic Acid sold in particular under the trade name "EUSOLEX 232" by MERCK or "PARSOL HS" by GIVAUDAN, bis-benzoazolyl derivatives as described in the patents EP 669 323 and US 2,463,264 and more particularly the compound Disodium Phenyl Dibenzimidazole Tetra-sulphonate sold under the trade name "NEO HELIOPAN AP" by DSM;

(5) hydrophilic cinnamate derivatives such as for example DEA Methoxycinnamate; and

(6) mixtures thereof.

Among these hydrophilic filters, the most preferential are chosen from Terephthalylidene Dicamphor

Sulphonic Acid, Benzophenone-4, Phenylbenzimidazole

Sulphonic Acid, Disodium Phenyl Dibenzimidazole Tetra- sulphonate, as well as mixtures thereof.

In the first stage of the method according to the invention, a silica precursor is moreover mixed with the organic UV filter and the micellar solution of surfactant.

This silica precursor is advantageously sodium silicate. As a variant, it may be hydrophobic or fumed silica such as that marketed under the trade name Aerosil^® by DEGUSSA or under the trade name Cab-O-Sil^® by CABOT, or a colloidal silica such as that marketed by GRACE under the trade name Ludox^®. Also as a variant, it may be a tetraalkyl orthosilicate such as tetraethyl orthosilicate (TEOS) or tetramethyl orthosilicate (TMOS), or or silicic acid Si(OH)₄.

The encapsulation of the UV filter in the surfactant micelles may be improved, in certain cases, by the use of ultrasonics .

The mixing of the constituents described previously is carried out in a basic medium, advantageously at a pH of at least 8, which can be adjusted by the addition of a strong base such as sodium hydroxide. This mixture does not generally contain ethanol as solvent, nor lecithin as surfactant .

The condensation of the silica precursor can then be carried out, by optional hydrolysis of the alkoxylated silicates and polycondensation of the silicic species at the interface of the surfactant micelles, for example by adjustment of the pH to an acid pH in the case of sodium silicate or to a basic pH, in the case of TEOS.

The drying of the mesoporous vectors thus obtained can then be carried out by any means known to a person skilled in the art.

The organic UV filter advantageously represents at least 30% by weight, preferably at least 35% by weight, more preferentially at least 40% by weight, or even at least 50% by weight, with respect to the weight of the loaded mesoporous vector. Measurement of the encapsulation level can in particular be carried out by X-ray fluorescence or by a thermogravimetric analysis (making it possible to access the total level of encapsulated molecule + surfactant) coupled with a CHN assay (oxidation then assay of CO₂, NO₂ and H₂O) or X-ray fluorescence or mass spectrometry analysis.

It should be noted that these encapsulation levels can be achieved according to the invention without it being necessary to mix with one of the reagents, in the first stage of the method, a co-solvent such as an alcohol which would be capable of affecting the odour of the loaded vectors obtained and/or of interacting with the support to which these vectors are intended to be applied, for example drying the skin in the case of a cosmetic application.

In the case of the encapsulation of a hydrophilic UV filter, in order to obtain this encapsulation level whilst preserving for the loaded vector a visual appearance compatible with a cosmetic use, it has been determined by the inventors that the weight ratio of the surfactant to the mixture of the surfactant, the silica precursor and the molecule to be encapsulated should preferentially be greater than 25% by weight, more preferentially at least 30% by weight, advantageously comprised between 30 and 50% by weight, for instance between 35 and 45% by weight inclusive. Moreover, it is preferable for the weight ratio of the silica precursor to the three abovementioned constituents to be comprised between 15 and 35% by weight, for instance between 15 and 25% by weight or between 25 and 30% by weight inclusive, and for the weight ratio of the molecule to be encapsulated to the three abovementioned constituents to be comprised between 30 and 60% by weight, for instance between 40 and 50% by weight inclusive.

In the case of a lipophilic UV filter, the weight ratio of the silica precursor to the mixture of the surfactant, the silica precursor and the molecule to be encapsulated is preferably at least 30% by weight, advantageously 30 to 60% by weight, or better, 35 to 45% by weight. Moreover, the weight ratio of the surfactant to the three abovementioned constituents is preferably comprised between 15 and 25% by weight inclusive, more preferentially between 15 and 20% by weight. The weight ratio of the lipophilic molecule to the total of the three abovementioned constituents is for its part advantageously comprised between 35 and 50% by weight, better, between 40 and 50% by weight inclusive.

Moreover, the UV filter is trapped in a sufficiently stable manner within the mesoporous vector for the rate of release of this UV filter in a composition containing one of its solvents to be less than 10% by weight, preferably less than 5% by weight, or better, less than 1% by weight, with respect to the weight of molecule utilized, after 2 months at 45⁰C. The solvent used for carrying out this release test can be any appropriate lipophilic organic solvent, in the case where the UV filter is lipophilic, such as a paraffin oil and/or a silicone oil, or any appropriate hydrophilic organic solvent in the case where the trapped UV filter is hydrophilic, such as water. The inventors have discovered that the release of the UV filter (especially the hydrophilic UV filter) in such a solvent could be reduced by adjusting the molar amounts of the surfactant and the UV filter used, so as to keep the molar ratio of the surfactant to the UV filter between 1 and 1.4 inclusive. They have also realized that using this ratio allowed to encapsulate a higher proportion of UV filter (especially hydrophilic UV filter) within the mesoporous vector of this invention.

In order to avoid their penetrating into the skin whilst being substantially undetectable in cosmetic compositions, it is preferable for the mesoporous vectors according to the invention to have an average size ranging from 200 to 500 nm. These vectors usually are in the form of agglomerates of small spheres. Their size can be adjusted by grinding in the case where their production method leads to vectors of a size greater than 500 nm. It is in any case preferable for the loaded mesoporous vectors according to the invention to have a size not exceeding 5 μm in order not to negatively affect the stability and/or the feel of the composition in which they are intended to be incorporated.

Moreover, it is possible, according to a form of execution of the invention, to provide, in the method for the synthesis of the mesoporous vectors, an additional stage of coating the mesoporous vectors formed, for example using silica, alumina or a polymer such as a polyacrylate or an organopolysiloxane or by grafting functions onto their external surface, for example -Si-R' functions linked by covalent bonds to the oxygen atoms of the silica, using as an R'-SiCl3 or R'-Si(0R)3 reagent. This coating stage makes it possible to obtain coated mesoporous materials which may prove to be easier to formulate or also more impervious, in certain applications.

Moreover, it is preferable for the method according to the invention to be implemented continuously in a single reactor.

The mesoporous vectors according to the invention can be used in different types of industry, for different uses such as the protection of human skin, the protection of synthetic materials against UV and the surface treatment of plastic or metallic materials, without this list being limitative.

They also make it possible to formulate lipophilic UV filters in a hydrophilic vehicle, and thus produce resultly compositions which feel less greasy.

It is preferable for these vectors to be used in the cosmetics industry.

A subject of the present invention is therefore also a composition containing, in a physiologically acceptable, and preferably a cosmetically acceptable, medium at least one vector as described previously.

By "physiologically acceptable", is meant compatible with the skin and optionally with its appendages such as the nails, eyelashes and hair. The expression "cosmetically acceptable" denotes more particularly a medium which does not produce any sensations of discomfort, such as flushing, pain, tingling or tightness, which are unacceptable to the user of cosmetic compositions .

Apart from the mesoporous vectors, the composition according to the invention can also comprise at least one additive chosen from: the oils, which can be chosen in particular from: the volatile or non-volatile, linear or cyclic silicone oils, such as the polydimethylsiloxanes

(dimethicones) , the polyalkylcyclosiloxanes

(cyclomethicones) and the polyalkylphenylsiloxanes

(phenyldimethicones) ; the synthetic oils such as the fluorinated oils, the alkyl benzoates and the branched hydrocarbons such as polyisobutylene; the vegetable oils and in particular soya or jojoba; and the mineral oils such as paraffin oil; the waxes, such as ozokerite, polyethylene wax, beeswax or carnauba wax; the silicone elastomers obtained in particular by reaction, in the presence of a catalyst, of a polysiloxane having at least one reactive group (hydrogen or vinyl, in particular) and bearing at least one terminal and/or side alkyl (in particular methyl) or phenyl group, with an organosilicone such as an organohydrogenpolysiloxane; the surfactants, preferably emulsifying, whether non- ionic, anionic, cationic or amphoteric, and in particular the esters of fatty acids and polyols such as the esters of fatty acids and glycerol, the esters of fatty acids and sorbitan, the esters of fatty acids and polyethyleneglycol and the esters of fatty acids and sucrose; the ethers of fatty alcohols and polyethyleneglycol; the alkylpolyglucosides; the polyether modified polysiloxanes; betaine and its derivatives; the polyquaterniums; the sulphate salts of ethoxylated fatty alcohols; the sulphosuccinates; the sarcosinates; the alkyl- and dialkylphosphates and their salts; and the fatty acid soaps; the co-surfactants such as the linear fatty alcohols and in particular the cetyl and stearyl alcohols; - the thickeners and/or gelling agents, and in particular the hydrophilic or amphiphilic, crosslinked or non-crosslinked homo- and copolymers of acryloylmethylpropane sulphonic acid (AMPS) and/or of acrylamide and/or of acrylic acid and/or the salts or esters of acrylic acid; xanthan or guar gum; cellulose derivatives; and silicone gums (dimethiconol) ; the humectants, such as the polyols, including glycerine, propylene glycol and the sugars, and the glycosaminoglycans such as hyaluronic acid and its salts and esters; the inorganic filters, based on mineral oxides in the form of pigments or nanopigments, coated or uncoated, and in particular based on titanium dioxide or zinc oxide; - the organic filters such as those mentioned previously; colourants; - preservatives; the fillers, and in particular the powders with soft- focus effect, which can be in particular chosen from the polyamides, silica, talc, mica, fibres (in particular of polyamide or cellulose) ; tensors (skin tightening agents), and in particular vegetable proteins, synthetic latex (in particular acrylic) and colloidal dispersions of inorganic fillers; - sequestering agents such as EDTA salts; perfumes; and mixtures thereof, without this list being limitative .

Examples of such adjuvants are mentioned in particular in the CTFA Dictionary (International Cosmetic Ingredient Dictionary and Handbook published by the Cosmetic, Toiletry and Fragrance Association, 9th Edition, 2002) .

The composition according to the invention can also contain at least one active ingredient chosen from: agents stimulating the expression of tensin 1; agents stimulating the expression of FN3K and/or of FN3K RP; agents stimulating the expression of matriptase MT-SPl; agents stimulating the production of growth factors; anti-glycation or deglycating agents; agents increasing the synthesis of collagen or preventing its degradation (anti-collagenase agents, in particular inhibitors of matrix metalloproteinases) ; agents increasing the synthesis of elastin or preventing its degradation (anti- elastase agents); agents increasing the synthesis of glycosaminoglycans or proteoglycans or preventing their degradation (anti-proteoglycanase agents); agents stimulating the synthesis of integrins by the fibroblasts; agents increasing the proliferation or differentiation of the keratinocytes; agents increasing the proliferation of the fibroblasts; depigmenting or anti-pigmenting agents; antioxidant or anti-radical or anti-pollution agents; agents increasing the synthesis of epidermal lipids; and mixtures thereof, without this list being limitative.

A subject of the present invention is also the cosmetic use of the mesoporous vector described previously for preventing or combating cutaneous photo- ageing.

A subject is also the use of this mesoporous vector for the production of a composition intended to protect the skin against the effects of UV and in particular to prevent cutaneous erythema.

A subject is also a cosmetic method for the care and make-up of the skin, comprising the topical application to the latter of the abovementioned composition.

The invention will be better understood in light of the following non-limitative examples, given for the purposes of illustration and which do not have the purpose of reducing the scope of the invention, defined by the attached claims.

EXAMPLES

Example 1 : Preparation of mesoporous vectors incorporating organic UV filters

Mesoporous vectors containing respectively a hydrophobic (or lipophilic) organic filter (octyl methoxycinnamate, PARSOL MCX^® marketed by GIVAUDAN) and a hydrophilic organic filter (phenylbenzimidazole sulphonic acid, PARSOL^® HS marketed by GIVAUDAN) were synthesized.

Example IA. Encapsulation of hydrophilic UV filter

3.5g of sodium hydroxide was dissolved in 222.3 ml of water in a polypropylene flask. 33.33 g of sodium silicate was added, then the mixture was homogenized with a magnetic stirring bar for approximately 30 minutes. 12 g of Parsol HS was then added gradually and the mixture was left under stirring until the filter was completely dissolved, for approximately 1 hour. Still under stirring, 37.1 ml of a 25% hexadecyltrimethyl ammonium chloride solution (hereafter, Ci₆TMACl) in water was added and the reaction mixture was heated so as to liquefy it in case gelification occurred. The stirring was continued for approximately 2 hours. A IN HCl solution was then added dropwise to the mixture under vigorous stirring until a pH of 8.5 was obtained. Gelling and bleaching of the mixture was observed, which was then placed in an oven at 9O⁰C for 24 hours, in a sealed polypropylene flask. The product obtained was then centrifuged at 11,000 rpm (15,557 G) for 20 minutes, washed with 2 x 300 ml of distilled water before being stirred with a magnetic bar for 5 minutes at 1400 rpm and centrifuged at 11,000 rpm (15,557G) for another 20 minutes. It was then dried in an oven at 7O⁰C for 16 hours (one night) .

The appearance of the sample obtained (hereafter, "RBO 115"), under a scanning electron microscope, is in the form of agglomerates of between 5 and 40 μm, consisting of small spheres of a few nanometres. Its encapsulation level was approximately 27% by weight, as measured by thermogravimetry (SETARAM Labsys

Thermoanalyzer, under air flushing with a rise in temperature of 5°C/minute between 25⁰C and 800⁰C) coupled with X-ray fluorescence analysis (PHILIPS Magix on a pellet of 200 mg of the product mixed with 100 mg of boric acid) , whereas the theoretical amount of encapsulated UV filter expected was about 40% (starting from 30% surfactant, 40% UV filter and 30% silica) .

The powder obtained was grinded with a ball mill (MiniMill, PHILIPS), in the presence of three zircon balls and the speed was set at 4 for 10 minutes. A white powder having a pleasant cosmetic feel was obtained.

Example IB. Encapsulation of lipophilic UV filter

A lipophilic UV filter was encapsulated in the mesoporous vectors of this invention, using a weight ratio of silica precursor: UV filter : surfactant of about 39:45:16.

0.22g of sodium hydroxide was dissolved in 68.09 ml of water in a polypropylene flask. 2.62 ml of a 25%

C₁₆TMACI solution in water was added. Stirring was continued for approximately 1 hour. Still under stirring,

1.77 ml of Parsol^® MCX was added. The mixture was subjected to ultrasound for 15 minutes (power 400 W, d=3.2 mm) then stirred again. Under stirring, 5.87 ml of tetraethyl orthosilicate (hereafter, TEOS) was incorporated, then the mixture was again subjected to ultrasound for 15 minutes and stirred for 24 hours at ambient temperature. The product obtained was filtered through a Bϋchner filter then washed with 3 x 70 ml of distilled water before being dried in an oven at 8O⁰C for 16 hours (one night) . Alternatively, the product could be recovered by centrifugation .

The appearance of the sample obtained, under an scanning electron microscope (PHILIPS XL30 FEG) , is in the form of agglomerates of 5-40 μm, consisting of very of small spheres of a few nanometers.

Its encapsulation level was approximately 50%, as measured by thermogravimetry (SETARAM Labsys

Thermoanalyzer , under air flushing with a rise in temperature of 5°C/minute between 25⁰C and 800⁰C) coupled with a CHN assay (ThermoElectron, Flash EA 1112) .

The product appeared as a white powder having a pleasant cosmetic feel.

Example 1C. Encapsulation of hydrophilic UV filter

Parsol® HS was encapsulated according to this invention, following the protocol described in example 1, except that the respective amounts of reactants were changed to a weight ratio of surfactant : Parsol HS : silica of 45:35:20.

To this end, 1.02g of sodium hydroxide was dissolved in 69.60 ml of water in a polypropylene flask. 7.41 g of sodium silicate were added, then the mixture was homogenized with a magnetic stirring bar for approximately 30 minutes. 3.5g of Parsol^® HS was then added gradually and the mixture was left under stirring until the filter was completely dissolved, for approximately 1 hour. Still under stirring, 18.54 ml of a 25% hexadecyltrimethyl ammonium chloride solution (hereafter, Ci₆TMACl) in water was added and the reaction mixture was heated so as to liquefy it in case gelification occurred. The stirring was continued for approximately 2 hours. A IN HCl solution was then added dropwise to the mixture under vigorous stirring until a pH of 8.5 was obtained. Gelling and bleaching of the mixture was observed, which was then placed in an oven at

9O⁰C for 24 hours, in a sealed polypropylene flask. The product obtained was then centrifuged at 11,000 rpm

(15,557G) for 20 minutes, washed with 2 x 80 ml of distilled water before being stirred with a magnetic bar for 5 minutes at 1,400 rpm and centrifuged at 11,000 rpm (15,557G) for another 20 minutes. It was then dried in an oven at 7O⁰C for 16 hours (one night) .

The appearance of the sample obtained (hereafter, "RBO 181"), under a scanning electron microscope, is in the form of agglomerates of between 5 and 40 μm, consisting of small spheres of a few nanometres.

Its encapsulation level was approximately 35% by weight, as measured by thermogravimetry (SETARAM Labsys Thermoanalyzer, under air flushing with a rise in temperature of 5°C/minute between 25⁰C and 800⁰C) coupled with X-ray fluorescence analysis (PHILIPS Magix on a pellet of 200 mg of the product mixed with 100 mg of boric acid) . This amount of UV filter corresponded to the theoretical amount expected. The powder obtained was grinded with a ball mill

(MiniMill, PHILIPS), in the presence of three zircon balls and the speed was set at 4 for 10 minutes. It had the appearance of a white powder having a pleasant cosmetic feel.

Example 2 : Evaluation of the effectiveness of the organic UV filters encapsulated in mesoporous vectors

A UV-visible absorption spectroscopy method was used in order to evaluate the effectiveness of encapsulated UV filters prepared as described in Example 1.

The principle of this method is as follows: a light source composed of a lamp for the visible range (400-800 nm) and another for the UV (< 400 nm) illuminated a quartz cell containing the material in the form of powder. A detector picked up the reflected signal. A curve illustrating the absorbance as a function of the wavelength was then drawn in the wavelength range from

200 to 450 nm. The device used was of the PERKIN-ELMER

Lambda 35 type.

Sample 2A, which corresponded to RBO115 of Example 1, and sample 2B, which was prepared in the same way as sample IB of Example 1 but starting with a silica iParsol® MCX: surfactant weight ratio of

43.75:36.25:20.00 were tested.

The results obtained for the samples 2A and 2B are respectively illustrated in Figures 1 and 2. As shown by these figures, the encapsulated UV filters absorbed the UV radiation, which demonstrates that the encapsulation of these materials retains their effectiveness, the absorbance maximum being 325 nm for the Parsol^® HS and 315 nm for the Parsol^® MCX.

Example 3 : Evaluation of the stability of the encapsulation of organic UV filters in mesoporous vectors

The release in water of encapsulated hydrophilic UV filters according to the invention was evaluated.

In order to do this, standard solutions containing known amounts of UV filter were analyzed by UV spectroscopy. Three maxima of absorption were identified at 207 nm, 240 nm and 302 nm. A calibration line was then drawn, which illustrated the absorbance at 302 nm as a function of the percentage of Parsol® HS present in the solution. From this line, it was then possible to assess the concentrations of Parsol® HS in any test solution.

Samples RBO115 and RBO181 of Example 1 were thus evaluated. To this end, the samples have been suspended for 24 hours and for two weeks in water or in an aqueous medium at pH=7, under static conditions, at 45⁰C. The amount of sample used was calculated so as to provide exactly O.Olg of Parsol® HS in 3Og of aqueous medium.

The amount of Parsol® HS before and after the test was determined by comparing the absorbance measured at 302 nm with the calibration line. It was then possible to assess the amount of Parsol® HS released in the aqueous medium and then to calculate the percentage of release according to the following equation: % of release = 100 x (weight of Parsol® HS after test / weight of Parsol® HS before test)

The following Table 1 summarizes the results thus obtained.

Table 1

These results demonstrate that, after two weeks, the UV filter was stably encapsulated within the mesoporous vectors of this invention and that sample RBO181, which had the highest amount of encapsulated UV filter also led to the lowest release of UV filter in water. The stability after two months at 45⁰C is expected to be similar to that measured in this experiment.

Example 4 : Comparison of the techniques for encapsulation of organic UV filters The stability of the different vectors incorporating organic UV filters, presented in Table 2, was compared vis-a-vis the leakage of these filters in different solvents .

Table 2

This table shows that the standard vectors encapsulate the UV filters in a less stable manner than that tested in Example 3.

Claims

1. Method for the preparation of a mesoporous vector containing at least one organic UV filter, comprising the following stages:

1- mixing a micellar solution of at least one surfactant in a solvent with said organic UV filter and a silica precursor, in basic medium,

3- optionally, the drying of said vector.

2. Method according to claim 1, characterized in that the surfactant is a cationic surfactant.

3. Method according to claim 2, characterized in that the surfactant is chosen from: the tetraalkylammonium chlorides such as for example dialkyldimethylammonium or alkyltrimethylammonium chlorides, in which the alkyl radical comprises 8 to 22 carbon atoms, in particular the behenyltrimethylammonium, distearyldimethylammonium, cetyltrimethylammonium, benzyl dimethyl stearyl ammonium chlorides; and stearamidopropyldimethyl (myristyl acetate) ammonium chloride .

4. Method according to claim 3, characterized in that the UV filter is hydrophilic and the surfactant is chosen from the alkyltrimethylammonium chlorides and bromides the alkyl chain of which contains 12 to 16 carbon atoms, such as the hexadecyltrimethylammonium and dodecyltrimethylammonium chlorides and bromides.

5. Method according to claim 3, characterized in that the UV filter is lipophilic and the surfactant is chosen from the alkyltrimethylammonium chlorides and bromides the alkyl chain of which contains 8 to 16, preferably 8 to 12 carbon atoms, such as the octyltrimethylammonium and dodecyltrimethylammonium chlorides and bromides.

6. Method according to any one of claims 1 to

5, characterized in that the solvent is water.

7. Method according to any one of claims 1 to 3, characterized in that the UV filter is hydrophobic.

8. Method according to claim 7, characterized in that the UV filter is chosen from: the anthranilates; cinnamic derivatives; dibenzoylmethane derivatives; salicylic derivatives, camphor derivatives; triazine derivatives; benzophenone derivatives; β,β'- diphenylacrylate derivatives; benzotriazole derivatives; benzalmalonate derivatives; benzimidazole derivatives; imidazolines; bis-benzoazolyl derivatives; p-aminobenzoic acid (PABA) derivatives; methylene bis- (hydroxyphenyl benzotriazole) derivatives; the filter polymers and filter silicones; the dimers derived from α-alkylstyrene; 4, 4-diarylbutadienes; and mixtures thereof.

9. Method according to any one of claims 1 to 3, characterized in that the UV filter is hydrophilic.

10. Method according to claim 9, characterized in that the UV filter is chosen from: (1) p-aminobenzoic (PABA) derivatives such as PABA, Glyceryl PABA, and PEG-25 PABA;

(2) benzophenone derivatives comprising at least one sulphonic radical such as Benzophenone-4, Benzophenone-5 and Benzophenone-9 ;

(4) benzimidazole derivatives comprising at least one sulphonic radical such as for example: Phenylbenzimidazole Sulphonic Acid, bis-benzoazolyl derivatives and more particularly the compound Disodium Phenyl Dibenzimidazole Tetra-sulphonate;

(6) mixtures thereof.

11. Method according to any one of claims 1 to 10, characterized in that the silica precursor is chosen from: fumed or colloidal silica, tetraalkyl orthosilicate and silicic acid.

12. Method according to any one of claims 1 to 11, characterized in that the organic UV filter represents at least 30% by weight, preferably at least 35% by weight, more preferentially at least 40% by weight, or even at least 50% by weight, with respect to the weight of the loaded mesoporous vector.

13. Method according to claim 9 or 10, characterized in that the weight ratio of the surfactant to the mixture of surfactant, silica precursor and hydrophilic UV filter is greater than 25% by weight, more preferentially at least 30% by weight, advantageously comprised between 30 and 50% by weight inclusive.

14. Method according to claim 9 or 10, characterized in that the weight ratio of the silica precursor to the mixture of surfactant, silica precursor and hydrophilic UV filter is comprised between 15 and 35% by weight, preferentially between 15 and 25% by weight inclusive .

15. Method according to claim 7 or 8, characterized in that the weight ratio of the surfactant to the mixture of surfactant, silica precursor and lipophilic UV filter is comprised between 15 and 25% by weight inclusive, more preferentially between 15 and 20% by weight.

16. Method according to claim 7 or 8, characterized in that the weight ratio of the silica precursor to the mixture of surfactant, silica precursor and lipophilic UV filter is at least 30% by weight, advantageously 30 to 60% by weight, or better, 35 to 45% by weight.

17. Method according to any of claims 1 to 16, characterized in that the molar ratio of the surfactant to the UV filter is between 1 and 1.4 inclusive.

18. Mesoporous vector capable of being obtained by the method according to any one of claims 1 to 17.

19. Mesoporous vector according to claim 18, characterized in that it has an average size ranging from 200 to 500 nm.

20. Composition containing, in a physiologically acceptable, and preferably a cosmetically acceptable medium, at least one mesoporous vector according to claim 18 or 19.

21. Cosmetic use of a mesoporous vector according to claim 17 or 18 for preventing or combating cutaneous photo-ageing .

22. Use of a mesoporous vector according to claim 18 or 19 for the production of a composition intended to protect the skin against the effects of UV and in particular to prevent cutaneous erythema.

23. Cosmetic method for the care and/or make-up of the skin, comprising the topical application to the latter of a composition according to claim 20.