EP2211826A2

EP2211826A2 - Method for obtaining a cosmetic composition containing dha, cosmetic compositions obtained according to said method and uses thereof

Info

Publication number: EP2211826A2
Application number: EP08857224A
Authority: EP
Inventors: Véronique GUYOT-FERREOL; Jean-François TRANCHANT
Original assignee: LVMH Recherche GIE
Current assignee: LVMH Recherche GIE
Priority date: 2007-11-29
Filing date: 2008-11-28
Publication date: 2010-08-04
Also published as: WO2009071861A2; WO2009071861A3

Abstract

The invention relates to a method for preparing a cosmetic composition in a solid form that comprises lipidic capsules containing dihydroxyacetone (DHA), wherein said method comprises the following steps: a) hot-preparing of a double emulsion of the water-in-oil-in-water type having an aqueous continuous outer phase and a dispersed phase made of a lipidic continuous phase at the molten state, having a composition corresponding to that of said lipidic capsules and in which is dispersed an inner aqueous phase consisting of an aqueous DHA solution; b) cooling said double emulsion; c) optionally adding at least one solid in a powdery state; d) dehydrating said double emulsion, leading to the production of a lipidic capsule powder; and e) optionally integrating said lipidic capsule powder into a cosmetically acceptable carrier. The invention also relates to solid-form cosmetic compositions including lipidic capsules containing the DHA. The invention further relates to a cosmetic method for dyeing the skin using said compositions.

Description

Process for preparing a cosmetic composition containing DHA, compositions obtained according to this process, and their uses

The invention relates to the field of cosmetic compositions in solid form comprising dihydroxyacetone or 1,3-dihydroxy-2-propanone (hereinafter DHA) as self-tanning active ingredient. It relates more particularly to a process for preparing such a cosmetic composition. It also relates to the use of the compositions obtained according to this process for coloring the skin.

STATE OF THE ART

Self-tanning cosmetic compositions comprising DHA are well known and are regularly the subject of further developments.

DHA is, as those skilled in the art well know, a particularly unstable compound and therefore difficult to use. Indeed, the latter is particularly sensitive to variations in pH and temperature, oxidation, especially by oxygen in the air, the presence of certain compounds such as water, iron oxides, certain amino acids or more generally molecules with primary and / or secondary amino groups.

It appears from the state of the art that such compositions must firstly overcome at least a double technical problem which consists on the one hand, to be able to apply the DHA satisfactorily in order to obtain an effective coloration and if possible uniformity of the skin and on the other hand, to maintain the stability of the DHA until its application in order to avoid a loss of self-tanning active agent which generates, as is now well known, problems of odor and browning of the product during storage.

The document US Pat. No. 5,750,092 (Meyer), such as the document US Pat. No. 2,070,009,452 (Golz-Berner), published recently, illustrates this dual technical difficulty by seeking, on the one hand, to prevent the DHA from reacting with other compounds. before application, and, secondly, to obtain a composition comprising DHA in sufficiently fluid to be applied correctly to the skin, these fluid forms may be in the form of ointments or dispersions, such as creams and lotions, gels or solutions.

Document EP-0 513 103 B1 discloses a process for protecting and stabilizing DHA, as well as cosmetic products containing it. This process consists in producing a watertight composition in order to maintain the dimer DHA in crystallized form until it is applied. The watertight composition protects the DHA from water and oxidation and constitutes an envelope providing a certain thermal insulation. This watertightness is obtained by using a mixture of water-insoluble polymers as the first protective layer, in particular ethylcellulose.

WO 93/16683 (Richardson-Vicks) also discloses stabilized self-tanning compositions in emulsion form. The oily phase contains at least one fatty acid or a derivative thereof and the aqueous phase contains at least one alkylhydroxyalkylcellulose or a derivative thereof, both of which are present in a precise ratio as essential compounds.

EP 0 691 839 (L'Oréal) also discloses fluid compositions based on DHA in the form of a single or multiple emulsion in which the fatty phase comprises a number of particular emulsifiers to provide stability to the emulsion, in particular preferably using solvents, fatty substances and adjuvants having no primary or secondary amine groups, or oxidizing groups capable of reacting with DHA.

Thus, it is apparent from the prior art that the self-tanning products comprising as self-tanning active agent of DHA do not allow optimum application while preserving DHA, provided that it is in sufficiently fluid form, in particular as a single or multiple emulsion. Such emulsions may also contain DHA encapsulated in a liposome-like lamellar structure to stabilize it as described in US 6,007,796 (Nenzel) and US-2007-0009452 (Golz-Berner). Reference may also be made to WO 96-31190 (Henkel), as describing self-tanning compositions in which DHA is encapsulated in liposomes. Other documents such as documents US 4,772,471, FR 2,492,829 and FR 2,597,367 (LOréal) disclose compositions comprising lipid vesicle dispersions encapsulating various active principles.

It therefore seems that there is a prejudice in the art to the satisfactory resolution of the aforementioned double technical problem with other types of formulations, such as a solid formulation, typically in the form of a compacted powder or no, as opposed to creams, gels, and lotions.

Therefore, the resolution of this double technical problem with a stable solid composition would satisfy a real need by providing a form of vectorization of DHA compatible with other types of formulations very widely used in cosmetics such as solid formulations, typically in the form of a free powder, cast or compacted. However, it is known from US Pat. No. 6,623,725 (Golz-Berner) compositions in the form of compact powder or powder cream comprising DHA in a water-in-oil emulsion in combination with at least one other self-tanning active agent chosen from extracts of Mahakanni (Eclipta alba) and tulip. It should be noted that the compositions described in this document are limited to 5% of DHA, moreover always used in combination with at least one other self-tanning agent which can be incorporated up to 10% and in particular does not have the disadvantages. already mentioned relating to the stability of DHA. In addition, the method described for preparing the emulsions suggests, contrary to what is said, that the DHA present in the aqueous or aqueous-alcoholic phase is not stable in the long term because in direct contact with known compounds for their harmful effects, in particular iron oxides (see examples 1 to 3) and the oxygen present. Thus, the obtaining of a self-tanning composition comprising DHA in the form of compact powder or cream-powder is here essentially due to the systematic use in association of a large quantity of at least one other agent. spray tan.

It is also known from EP 1 151 741 (L'Oréal) compositions comprising microcapsules having an aqueous core, with a polymeric and / or waxy envelope, which can contain a large number of active ingredients among which DHA is found. It should be noted here that the microencapsulation method proposed here, comprising an evaporation operation of an organic-type solvent used to produce the primary emulsion involved in the microencapsulation process, does not make it possible to obtain microcapsules at the core. non-aqueous, that is to say in totally dry form, where the DHA is in crystallized form inside the microcapsules.

GOAL OF INVENΗON

The main purpose of the invention is to provide a new method for vectorization of DHA for the preparation of solid formulations, typically in powder form, compacted or otherwise, as opposed to well-known fluid formulations such as creams, gels, and the like. the lotions, which can satisfactorily solve the double technical problem of providing a composition for topical application, which stabilizes the DHA to keep it in undegraded form until it is applied, while allowing a subsequent effective application of it on the skin. This double technical problem is solved for the first time for cosmetic compositions preferably in solid form, by the present invention in a simple, inexpensive way, usable on an industrial and commercial scale, and in particular on the cosmetic scale.

The invention thus makes it possible to use DHA as an effective self-tanning agent in solid compositions, typically powders. This family of cosmetics is very widespread because it covers free powders, cast or compacted.

More specifically, the invention provides a novel means for vectorizing dihydroxyacetone (DHA) in solid form, incorporating it into lipid capsules.

Thus, according to a first aspect, the invention relates to a process for preparing a cosmetic composition in solid form, comprising lipid capsules containing DHA. According to a second aspect, the invention relates to cosmetic compositions in solid form, comprising capsules lipids containing DHA. These compositions are in particular likely to be obtained by the preparation process forming the subject of the first aspect of the invention.

Finally, according to a last aspect, the invention relates to a cosmetic method for coloring the skin by applying to predetermined areas of the skin to be colored with an effective amount of a composition that is the subject of the second aspect of the invention. .

More specifically, in its first aspect, the present invention relates to a method for preparing a cosmetic composition in solid form comprising lipid capsules containing dihydroxyacetone (DHA), characterized in that it comprises the following steps: a) the hot preparation of a double water-in-oil-in-water emulsion having an aqueous continuous continuous phase and a dispersed phase consisting of a continuous lipid phase, in the molten state, whose composition corresponds to that of said lipid capsules, to the interior of which is dispersed an internal aqueous phase consisting of an aqueous solution of dihydroxyacetone (DHA), b) the cooling of said double emulsion, c) the possible incorporation of at least one solid in powder form, d dehydration of said double emulsion, leading to the production of a lipid capsule powder, and e) the possible incorporation of said powder of lipid capsules in at least one cosmetically acceptable excipient.

First of all, details are given below to better define what is meant by lipids (or lipid capsule).

For the purposes of the invention, the term "lipid" means a chemical compound comprising at least one linear, branched or cyclic hydrocarbon-based chain of at least 8 carbon atoms, which is soluble or miscible in organic solvents and insoluble in water in the water. temperature range 0 ⁰ C and 100 ⁰ C.

Thus, a lipid in the sense of the invention is a fatty alcohol, a fatty acid, as well as the esters of these acids and alcohols and the ethers of these alcohols, soluble or miscible in organic solvents and insoluble in water in the water. temperature range between 0 ⁰ C and 100 ⁰ C. More particularly, the term "lipid" means the products of the esterification reaction between a saturated or unsaturated fatty acid and an alcohol. The fatty acids considered are organic acids having at least 8 carbon atoms. This family of derivatives comprises, on the one hand, so-called simple lipids consisting solely of carbon, hydrogen and oxygen atoms, and on the other hand so-called complex lipids which furthermore comprise other categories of atoms, in particular nitrogen, sulfur or phosphorus atoms, among which mention will be made of phospholipids, sphingolipids and glycerophospholipids.

Among the lipids, according to the invention, are also included fatty acids having a linear, branched or cyclic, saturated or unsaturated alkyl chain comprising at least 10 carbon atoms, the fatty alcohols having a linear, branched or cyclic alkyl chain, saturated or unsaturated compound comprising at least 14 carbon atoms, as well as the esters of these acids and alcohols and the ethers of these alcohols.

For so-called simple lipids, the alcohols are chosen in particular from glycerol, sterols and fatty alcohols having a linear or branched alkyl chain comprising at least 14 carbon atoms. For the implementation of the invention, the glycerol esters, for example, are chosen from mono-, di- or triglycerides of fatty acids of natural or synthetic origin, preferably those having an alkyl chain. linear or branched comprising from 8 to 24 carbon atoms, in particular glycerol trimyristate, glycerol tripalmitate, glycerol monostearate and glycerol cetylpalmitate.

The lipid esters of the invention may also be chosen from waxes, which are esters of fatty acids and of fatty alcohols, namely mainly monoesters of carboxylic acids having an alkyl chain comprising 14 to 30 carbon atoms and of alcohols having an alkyl chain, preferably linear and saturated, comprising from 14 to 36 carbon atoms.

According to an advantageous variant, said lipids are such that said lipid capsules have a melting temperature of between 45 ° C. and 65 ^° C. According to another advantageous variant of the invention, the lipids are chosen from fatty acid esters and of alcohols selected from glycerol, sterols or alcohols having a linear or branched alkyl chain comprising at least 14 carbon atoms, natural or synthetic fatty acids comprising at least 10 carbon atoms and their esters, and fatty alcohols comprising at least 14 carbon atoms and their esters and ethers.

According to another advantageous variant of the invention, the lipids are advantageously chosen from mono-, di- or triesters of glycerol and of fatty acids having a linear or branched hydrocarbon chain comprising from 8 to 24 carbon atoms, preferably in the group consisting of glycerol trimyristate, glycerol tripalmitate, glycerol monostearate and glycerol cetylpalmitate.

Such lipids are commercially available and in particular under the following trade names: Suppocire® DM and AM from Gattefossé; Dynasan® 114 and 118 from Sasol Company; and Crodamol GTS from Croda Chemicals.

According to the method of the invention, in a first step a), a double emulsion of water-in-oil-in-water type having an aqueous external continuous phase and a dispersed phase consisting of a continuous lipid phase is prepared hot. melt, the composition of which corresponds to that of said lipid capsules, inside which is dispersed an internal aqueous phase consisting of an aqueous solution of dihydroxyacetone (DHA).

According to one particular embodiment of the invention, the concentration of DHA in the solution used to prepare said double emulsion is between 0.5% and 90% by weight, advantageously between 5% and 70% by weight.

In a second step b) of the process according to the invention, said double emulsion is allowed to cool under conventionally appropriate conditions. In a third optional step c) of the process according to

(Invention, at least one solid in the pulverulent state is optionally incorporated in the said double emulsion.) This step can also be carried out after step d) described below, but to allow a better homogenization of the composition. it is preferable to implement step c) before step d). Indeed, one of the problems Well known powder formulations are the isotropic distribution of the active ingredients, here the DHA, within the powder.

In particular, said solid may consist of organic and / or inorganic fillers in variable proportions, for example oxides of titanium, zinc or zirconium, silica, polyamides and polyesters.

In a fourth step d) of the process according to the invention, said double emulsion is subjected to a dehydration operation leading to the production of a powder of said lipid capsules. According to a first variant, the dehydration may be partial, the DHA being found partially or totally incorporated in an aqueous phase internal to said lipid capsules.

In fact, incomplete dehydration can lead to the production of lipid capsules, the internal part of which comprises at least partly or even totally of the DHA solubilized in the internal aqueous phase of said lipid capsules. The DHA may also be partly in the crystallized state, since the DHA precipitates in solid form if dehydration is continued once saturation of the internal aqueous phase of said lipid capsules has been reached. According to a second variant, the dehydration can be complete, the DHA being found crystallized inside said lipid capsules. According to a particular embodiment of the invention, the step of dehydrating said continuous phase of said double water in oil-in-water emulsion is obtained by freeze-drying or flash-type atomization, preferably by lyophilization.

According to this preferred embodiment of the invention, the dehydration operation is preceded, preferably, by the addition of a cryoprotectant in the aqueous continuous continuous phase of said double emulsion. As cryoprotective agent, it is possible to use at least one polyol, sodium chloride or a solution of at least one salt capable of lowering the melting point of water, and mixtures thereof.

Examples of polyols that may be used include glycerin, mannitol, sorbitol, polyethylene glycol or sugar such as mannose, glucose, fructose, xylose, trehalose and mixtures thereof. As salt capable of lowering the melting point of water, sodium chloride is preferably used.

Finally, in an optional fifth step e) of the process according to the invention, said lipid capsule powder is optionally incorporated into a cosmetically acceptable excipient.

This cosmetically acceptable excipient may for example consist of at least one solid in the pulverulent state as in optional step c), in particular for free powder formulations, or at least one binder, ie a fatty substance, especially for compact powder type formulations.

From said lipid capsule powder, all kinds of self-tanning cosmetic compositions can be prepared in solid form, in particular in the form of a powder.

In the case of a powder, the process is conventionally carried out by mixing fillers and pigments that have been ground beforehand with the aid of a coffee grinder, for example with solid lipid capsules and compounds that do not require grinding, such as nacre. It is also possible to add other well-known cosmetically acceptable agents such as fatty substances, preservatives, sunscreens, perfumes. If it is desired to make a compact powder, use a binder, that is to say a fatty substance and sieving the final composition before compacting it in buckets.

In general, among the fats well known in cosmetics, it will be possible to use an oil or a wax or their mixtures, a fatty acid, a fatty alcohol, a fatty acid ester.

The oils may be chosen from animal, vegetable, mineral or synthetic oils and in particular from liquid petroleum jelly, paraffin oil, silicone oils, volatile or not, isoparaffins, polyolefins, fluorinated oils and the like. perfluorinated. Similarly, the waxes can be chosen from animal, fossil, vegetable, mineral or synthetic waxes known per se.

Among the waxes that can be used in the context of the present invention, mention may be made, for example, of beeswax, candelilla wax, wax of

Carnabua, Ouricoury wax, Japan wax, paraffin waxes, microcrystalline waxes, silicone waxes. The double emulsion obtained at the end of step a) according to the process of the invention may, if appropriate, also comprise one or more active ingredients that the skilled person will be able to incorporate according to their lipophilic nature. or hydrophilic. Those skilled in the art will choose from among the known surfactants that which is suitable for the emulsion which it wishes to prepare.

According to one embodiment of the invention, on the one hand, said lipid capsules may additionally contain a pH adjusting agent, in order to maintain the pH of the inner aqueous phase of said capsules between 3 and 6, preferably between 3 and 6. 4, such as a buffer composition comprising a mixture of sodium bisulfite and lactic acid.

In particular, it is possible to use as a buffer composition a mixture of sodium bisulfite and lactic acid, for example in a ratio of 1: 2.5, for example. According to one embodiment of the invention, on the other hand, said lipid capsules may further contain at least one antioxidant stabilizing DHA, preferably selected from sodium mono- or bisulfite, ascorbic acid hydroquinone.

According to one embodiment of the invention, finally, said lipid capsules further contain a DHA stabilizing agent, in particular at a concentration of between 0.1% and 5% by weight relative to the total weight of the aqueous solution.

As a stabilizing agent for DHA, an alkylhydroxyalkylcellulose in which the alkyl group comprises from 8 to 30 carbon atoms and the hydroxyalkyl group comprises 1 to 4 carbon atoms, preferably ethylhydroxyethylcellulose, a hydroxyalkylcellulose with alkyl chain comprising 1 to 4 carbon atoms, preferably hydroxyethylcellulose, and methylcellulose, or a mixture thereof. Of course, the presence of pH adjusting agents, antioxidant, or stabilizing DHA in the internal phase of said lipid capsules results from the addition of said agent or agents during the preparation of the double emulsion in step a) of process according to the invention.

According to a particularly advantageous variant, the method according to the invention comprises the following steps: i) a first water-in-oil emulsion is prepared by incorporating under hot shear, preferably in the presence of a surfactant having an HLB value of less than or equal to 10, a first aqueous phase consisting of an aqueous solution of DHA, which preferably contains at least one pH adjusting agent and / or at least one DHA stabilizing agent, in a melted lipid phase, the composition of which is that of the wall of said lipid capsules, ii) then, is incorporated under shearing heat-treating said first emulsion in a previously heated aqueous second phase, preferably in the presence of a surfactant having an HLB value greater than or equal to 10, to form said double emulsion comprising said second aqueous phase as an aqueous continuous continuous phase, iii ) it is allowed to cool to a temperature below 30 ^° C., iv) said double emulsion obtained is dehydrated, preferably by an ope lyophilization ration, to obtain said lipid capsules in the form of a powder, v) finally, said powder is optionally incorporated in at least one cosmetically acceptable excipient.

According to the invention, the solid-form composition obtained by the process can be in the form of a free powder or a compacted powder.

Those skilled in the art will be able to determine the proportions of the various constituents of the double emulsion prepared in the process of the invention, in order to obtain in particular a cosmetic composition having a DHA concentration of between 0.5 and 90% by weight. advantageously between 5 and 70% by weight, relative to the total weight of the content of said lipid capsules.

On the other hand, likewise, those skilled in the art will be able to determine the proportions of the various constituents of the cosmetic composition obtained by the process according to the invention, so as to obtain in particular a cosmetic composition having from 0.1% to 10% by weight. %, preferably from 1% to 6% by weight of DHA encapsulated in said capsules relative to the total weight of said cosmetic composition.

The method of the invention makes it possible to obtain novel cosmetic compositions, in the case where the dehydration carried out in stage d) is total, and where the internal phase of said lipid capsules is completely crystallized, all the water initially present having been evaporated. These compositions have the particular advantage of being completely anhydrous and thus of having improved stability.

Thus, according to its second aspect, the invention also relates to cosmetic compositions, in particular capable of being obtained by the process according to the invention, in solid form and containing lipid capsules containing dihydroxyacetone (DHA) as the active ingredient bronzer, characterized in that:

said lipid capsules comprise, as essential constituent, a lipid having a melting point of greater than or equal to 30 ^° C. or a mixture of lipids having a melting temperature greater than or equal to 30 ^° C., said lipids optionally containing surfactants and / or or organic and / or inorganic fillers and / or liposoluble compounds and being present in an amount sufficient for said lipid capsules to have a melting point of between 30 ^° C. and 75 ° C., and

the DHA is found crystallized inside said lipid capsules.

The expression "essential constituent" means that the lipid capsule may also contain a generally very small amount of surfactant solubilized inherently during the preparation of the emulsions necessary for the manufacture of said lipid capsules (see method exposed upper).

The person skilled in the art will know and will be able, if he wishes, to add liposoluble compounds in variable proportions, so that the melting temperature of the capsule remains between 30 and 75 ^° C.

By way of example, it is possible to use, among the fat-soluble compounds, sunscreens, antioxidants and dyes.

The person skilled in the art may also, during the preparation of the first oil-in-water emulsion, disperse organic and / or mineral fillers in a variable proportion such that the melting temperature of the capsule remains between 30 and 75 ° C.

By way of example, it is possible to use oxides of titanium, zinc or zirconium, silica, polyamides and polyesters. According to a particular embodiment of the cosmetic composition according to the invention, the concentration of DHA is between 0.5 and 90% by weight, advantageously between 5 and 70% by weight, relative to the total weight of the content of said lipid capsules.

On the other hand, the cosmetic composition according to the invention may comprise from 0.1% to 10%, preferably from 1% to 6% by weight of DHA encapsulated in said capsules relative to the total weight of said cosmetic composition.

According to the invention, it may be a composition in the form of a free powder or a compacted powder.

According to a particular embodiment, the cosmetic composition may further comprise a moisturizing active agent, preferably chosen from glycerine, trimethylglycine or hyaluronic acid.

All variants of cosmetic compositions according to the invention, or obtainable by the method according to the invention, can be used alone or in combination. In general, it is possible to produce solid lipid capsules, which may or may not be sized. In this case, the general method of preparation of the capsules remains unchanged but the emulsification techniques change depending on whether it is desired to obtain a calibrated emulsion (monodisperse) or not (polydisperse) emulsion. Such emulsification techniques are known. For example, reference may be made to the techniques described in documents WO2001 / 85319 or WO9738787.

Moreover, the size of the lipid capsules according to the invention depends on the average diameter of the dispersed phase in the aqueous continuous phase during the preparation of the double emulsion. Indeed, the average diameter of the dispersed phase, whose composition is that of said lipid capsules, prefigures the size of the future lipid capsules that will solidify during cooling. The size of the lipid capsules according to the invention may thus vary between 1 and 100 μm, preferably between 5 and 25 μm.

The inventors of the present invention have unexpectedly found that the encapsulated DHA as indicated above or obtained according to the method described above is particularly stable over time with respect to temperature, pH and temperature variations. oxidation, in particular that resulting from the ambient air. According to a last aspect, the present invention also relates to a cosmetic method for coloring the skin, characterized in that, on predetermined areas of the skin to be colored by a person, an effective amount of a composition in the form of solid as defined above, or obtainable by the method as defined above, to obtain the desired coloration.

Other objects, features and advantages of the invention will become apparent in the light of the explanatory description which follows, with reference to several embodiments of the invention given merely by way of illustration and which in no way limit the scope of the invention.

In the examples, all the percentages are by weight, the temperature is in ⁰ C, the pressure is the atmospheric pressure, unless otherwise indicated.

Example 1

I. Preparation of lyophilized lipid capsules containing DHA

La: Preparation of lyophilized lipid capsules containing a high level of DHA from a double emulsion, water in oil in water, uncalibrated

An internal aqueous phase and an external fatty phase are prepared in a conventional manner. For this, an aqueous solution is used as an internal phase composed of: 49.97% of DHA, 0.05% of sodium disulphite, 0.12% of lactic acid,

1.0% hydroxyethyl cellulose (sold under the name Natrosol® 250 M),

2.34% sodium chloride, 46.52% water.

In a container kept at 65 ° C were mixed 5.70 g of PEG-30 dipolyhydroxystearate sold under the name Arlacel P135 ^® as the surfactant and 54.24 g of a glyceride mixture of saturated fatty acids in this Qe sold under the name Suppocire DM ^® . In this fatty phase, 40.06 g of the aqueous solution prepared above, which had been preheated to 65 ° C., were dispersed using a Rayneri-type stirrer. A non-calibrated inverse emulsion is then obtained, the internal phase of which contains the DHA which will now be mixed with an external aqueous phase. For this, in a container maintained at 65 ° C., 15.0 g of the uncalibrated inverse emulsion prepared above is incorporated under shear into 85.0 g of an aqueous solution heated to 65 ° C. and consisting of:

0.4 g of sodium disulphite, 0.10 g of lactic acid, 0.05 g of sodium alginate,

0.80 g of a mixture of mono-, di-, tri-glycerides and mono-, di-, tri-esters of polyethylene glycol and of fatty acids (sold under the name Gelucire 44/14 ^® ), 2.44 g of glucose,

18.45 g of trehalose,

63.12 g of water.

This double water-in-oil emulsion in non-calibrated water containing DHA in the internal phase is then cooled to room temperature, at which temperature the lipid mixture according to the invention, here the wax, is in solid form, thus forming an interface protective lipid surrounding compartments containing the internal aqueous phase containing DHA, dispersed in the external aqueous phase.

The previously prepared non-calibrated double emulsion is then frozen and placed in a freeze-dryer to be dehydrated.

A dry powder consisting of lipid capsules is then recovered within which is found 8.54% by weight of DHA in stabilized form relative to the total weight of capsules. Indeed, after 1 month of aging at 45 ° C. in an oven, the DHA content only decreased by 1.75% and after 3 months at 45 ° C. by 6.51% relative to the total weight of capsules . By way of comparison, the level of free DHA decreases by 8% after 1 month of aging at 45 ^° C.

Lb: Preparation of lyophilized lipid capsules containing DHA from a double-calibrated emulsion In the same general method of preparation described in point La), a solution serving as an internal phase is prepared from: 55.90% of DHA, 0.06% sodium disulphite, 0.13% lactic acid, 2.68% sodium chloride,

41.23% water.

In a container maintained at 70 ⁰ C is mixed 10.13 g of Arlacel P135 ^®, 10.21 g of a mixture of glycerine triesters and myristic acid (sold under the name DYNASAN 114 ^®) and 10, 21 g of Suppocire DM ^® . In order to calibrate the emulsion, 69.45 g of the solution are dispersed in this fatty phase by means of a quilt type device. aqueous solution prepared previously, which has been previously heated to 70 ^° C. This gives a calibrated inverse emulsion whose internal phase contains DHA. This calibrated inverse emulsion is then diluted into: 14.84 g of DM ^® suppocire and 14.84 g of dynasan 114 ^® preheated to 70 ^° C.

In a container maintained at 70 ^° C., 30.00 g of calibrated inverse emulsion prepared above are emulsified by means of a quilt type device with 17.45 g of an aqueous solution heated to 70 ^° C. and constituted 0.01 g of sodium disulphite,

0.02 g of lactic acid,

0.10 g of sodium alginate,

1.61 g of gelatin 44/14,

2.44 g glucose, 13.27 g water.

47.00 g of this double-calibrated emulsion containing DHA in the internal phase is then diluted with 141.10 g of an aqueous solution preheated to 70 ^° C. and containing:

0.07 g of sodium disulphite, 0.17 g of lactic acid,

17.36 g of trehalose,

123.5 g of water.

This double-sized emulsion is then cooled to room temperature, at which temperature the lipid mixture according to the invention, here the wax, is in solid form, thus forming a protective lipid interface surrounding compartments containing the internal aqueous phase containing DHA. dispersed in the external aqueous phase.

The double-calibrated emulsion thus cooled is then frozen and placed in a lyophilizer to be dehydrated. A dry powder is then recovered in the form of solid lipid capsules within which there is 9.13% by weight of stabilized DHA relative to the total weight of the capsules.

It is observed that after 1 month of aging at 45 ° C. in an oven, the DHA content only decreased by 2.57% and after 3 months at 45 ^° C. by 6.52%. Lc: Preparation of freeze-dried lipidic capsules containing a low level of DHA from a non-calibrated double emulsion

In the same general mode of preparation, an internal phase solution composed of: 29.26% DHA is prepared,

0.03% of sodium disulphite,

0.07% lactic acid,

1.37% sodium chloride,

69.27% water. In a container kept at 65 ° C were mixed 5.70 g of Arlacel P135 ^® and 54.24 g of Suppocire DM®. In this fatty phase, 40.06 g of the aqueous solution prepared above, which had been preheated beforehand at 65 ^° C., was dispersed using a Rayneri-type stirrer. An uncalibrated inverse emulsion, the internal phase of which was then obtained, was obtained. contains DHA.

In a container maintained at 65 ° C, 15.0 g of the previously prepared uncalibrated emulsion is incorporated under shear to 85.0 g of an aqueous solution heated to 65 ° C and consisting of:

0.23 g of sodium disulphite, 0.06 g of lactic acid,

0.03 g of sodium alginate,

0.47 g of gelatin 44/14,

1.43 g of glucose,

10.80 g of trehalose, 71.98 g of water.

This non-calibrated double emulsion containing the DHA in the internal phase is then cooled to room temperature, at which temperature the lipid mixture according to the invention, here the wax, is in solid form thus forming a protective lipid interface surrounding compartments containing the internal aqueous phase containing DHA, dispersed in the external aqueous phase.

The previously prepared non-calibrated double emulsion is then frozen and placed in a freeze-dryer to be dehydrated. A dry powder consisting of lipid capsules is then recovered inside which there is 5.0% by weight of DHA in stabilized form relative to the total weight of capsules.

The lipid capsules described above can be directly used in the context of a cosmetic process for coloring the skin. For this purpose, it is applied to the areas of the skin to be colored by a person in need of solid lipid capsules containing DHA directly. It is found that after a few days the skin has a golden tan and uniform.

Example 2

Self-tanning cosmetic compositions in the form of powders comprising freeze-dried lipid capsules containing DHA

Self-tanning free powder

Lipidic capsules according to Example 1 The 29.5%

Loads (mica, sericite, alumina, silica) 46.9%

Pigments (iron oxides, titanium oxides) 9.0%

EA-209 (*) 12.0% Conservative 2.5%

0.1% perfume concentrate

(*) EA-209 is a copolymer of ethylene and acrylic acid marketed by KOBO Products, Inc.

This composition contains 2.52% of DHA by weight relative to the total weight of the composition.

After one month storage at 45 ° C, the DHA level decreased by only 36.43% by weight and after three months by 55.72% by weight relative to the total weight of the composition.

By way of comparison, the level of DHA present in an identical powder but comprising free DHA drops by 96% by weight relative to the total weight of the composition after 1 month of aging at 45 ^° C. Compact, self-tanning powder foundation

Lipid Capsules Prepared According to Example 1.Lb 41.0%

Loads (mica, sericite, alumina, silica) 22.5%

Pigments (iron oxides, titanium oxides) 10.8% Nacres 7.0%

Mineral solar filter 10.0%

Organic solar filter 7.0%

Conservatives 0.6%

Silicone oil (DC 556 fluid) 1.0% Perfume concentrate 0.1%

Self-tanning care powder

Solid lipidic capsules according to the example l.I.c 40.0%

Polyethylene wax 39.5% Loads (mica, sericite, alumina, silica) 7.5%

Pigments (iron oxides, titanium oxides) 9.0%

KSP-300 (*) 10.0%

Moisturizing active ingredient (glycerin) 2.4%

Preservative 0.5% Perfume Concentrate 0.1%

(*) KSP-300 is a copolymer of diphenyl dimethicone / vinyl dimethicone / silsesquioxane sold by Shin-Etsu Chemicals Co.

The self-tanning cosmetic compositions described above may be used in the context of a cosmetic process for coloring the skin. For this, one applies, on the areas of the skin to be stained by a person in need, a cosmetic composition containing said solid lipid capsules at a rate of once a day for 15 days.

It is found that after a week, the skin has a golden and uniform tan.

During the implementation of this method of staining the skin, the lipid capsules according to the invention open more or less rapidly, thus releasing DHA, by contact with the skin and / or by mechanical shear during application. .

Claims

REVENDICAπQNS

1. A process for preparing a cosmetic composition in solid form comprising lipid capsules containing dihydroxyacetone (DHA), characterized in that it comprises the following steps: a) the hot preparation of a double emulsion of water type in oil in water having an aqueous continuous continuous phase and a dispersed phase consisting of a continuous lipid phase, in the molten state, whose composition corresponds to that of said lipid capsules, inside which is dispersed an internal aqueous phase consisting of an aqueous solution of dihydroxyacetone (DHA), b) the cooling of said double emulsion, c) the possible incorporation of at least one solid in the pulverulent state, d) the dehydration of said double emulsion, leading to the obtaining a lipid capsule powder, and e) optionally incorporating said lipid capsule powder into a cosmetically acceptable excipient.

2. Method according to claim 1, characterized in that the dehydration operation of said double emulsion is freeze drying or flash type atomization.

3. Method according to claim 2, characterized in that the dehydration operation is lyophilization preceded, preferably, the addition of a cryoprotective agent in the external aqueous continuous phase of said double emulsion.

4. Method according to claim 3, characterized in that said cryoprotective agent is selected from polyols, sodium chloride or a solution of at least one salt capable of lowering the melting point of water, and mixtures thereof .

5. Process according to claim 4, characterized in that the said polyols are chosen from glycerine, mannitol and sorbitol, a polyethylene glycol, or a sugar such as mannose, glucose, fructose, xylose, trehalose, and mixtures thereof.

6. Method according to one of claims 1 to 5, characterized in that said lipids are such that said lipid capsules have a melting temperature between 45 ° C and 65 ⁰ C.

7. Method according to one of claims 1 to 6, characterized in that said lipids of said lipid capsules are selected from esters of fatty acids and alcohols selected from glycerol, sterols or alcohols having a linear alkyl chain or branched chain comprising at least 14 carbon atoms, natural or synthetic fatty acids comprising at least 10 carbon atoms and their esters, and fatty alcohols comprising at least 14 carbon atoms and their esters and ethers.

8. Method according to claim 7, characterized in that said lipids of said lipid capsules are chosen from mono-, di- or triesters of glycerol and of fatty acids having a linear or branched hydrocarbon chain comprising from 8 to 24 carbon atoms preferably in the group consisting of glycerol trimyristate, glycerol tripalmitate, glycerol monostearate and glycerol cetylpalmitate.

9. Method according to one of claims 1 to 8, characterized in that said lipid capsules further contain a pH adjusting agent, in order to maintain the pH of said aqueous solution between 3 and 6, preferably between 3 and 4, such as a buffer composition comprising a mixture of sodium bisulfite and lactic acid.

10. Method according to one of claims 1 to 9, characterized in that said lipid capsules further contain at least one antioxidant stabilizing DHA, preferably selected from sodium mono- or bisulfite, ascorbic acid, hydroquinone.

11. Method according to one of claims 1 to 10, characterized in that said lipid capsules further contain a stabilizing agent DHA, such as an alkylhydroxyalkylcellulose in which the alkyl group comprises from 8 to 30 carbon atoms and the hydroxyalkyl group comprises from 1 to 4 carbon atoms, preferably the ethylhydroxyethylcellulose, a hydroxyalkylcellulose having an alkyl chain comprising from 1 to 4 carbon atoms, preferably hydroxyethylcellulose, and methylcellulose, or a mixture thereof.

12. Method according to one of claims 1 to 11, characterized in that it comprises the following steps;

i) a first water-in-oil emulsion is prepared by incorporating under hot shear, preferably in the presence of a surfactant having an HLB value of less than or equal to 10, a first aqueous phase consisting of an aqueous solution of DHA, which preferably contains at least one pH adjusting agent and / or at least one DHA stabilizing agent, in a melted lipid phase, the composition of which is that of the wall of said lipid capsules,

ii) then, said first emulsion is incorporated under hot shear in a previously heated aqueous second phase, preferably in the presence of a surfactant having an HLB value of greater than or equal to 10, to form said double emulsion comprising said second phase; aqueous as external aqueous continuous phase,

iii) allowed to cool to a temperature below 30 ⁰ C

iv) dehydrating said double emulsion obtained, preferably by a lyophilization operation, to obtain said lipid capsules in the form of a powder,

v) finally, said powder is optionally incorporated in at least one cosmetically acceptable excipient.

13. Method according to one of claims 1 to 12, characterized in that the composition is in the form of a loose powder or a compacted powder.

14. Method according to one of claims 1 to 13, characterized in that the dehydration is partial, the DHA being found partially or totally incorporated in an aqueous phase internal to said lipid capsules,

15. Process according to one of Claims 1 to 13, characterized in that the dehydration is complete, the DHA being crystallized inside said lipid capsules.

16. Cosmetic composition, especially obtainable by the method according to claim 15, in solid form and containing lipid capsules containing dihydroxyacetone (DHA), characterized in that: said lipid capsules comprise as essential constituent a lipid having a melting point of greater than or equal to 30 ^° C. or a mixture of lipids having a melting point greater than or equal to 30 ^° C., said lipids optionally containing surfactants and / or organic and / or inorganic fillers and / or liposoluble compounds and being present in an amount sufficient for said lipid capsules to have a melting point of between 30 ^° C. and 75 ° C., and the DHA is crystallized inside said lipid capsules.

17. Cosmetic composition according to claim 16, or obtainable by the method according to one of claims 1 to 16, characterized in that the concentration of DHA is between 0.5 and 90% by weight, advantageously between 5 and 70% by weight, relative to the total weight of the content of said lipid capsules.

18. Cosmetic composition according to claim 16 or 17, or obtainable by the method according to one of claims 1 to 15, characterized in that it comprises from 0.1% to 10%, preferably from 1 to % to 6% by weight of dihydroxyacetone (DHA) encapsulated in said capsules relative to the total weight of said cosmetic composition.

19. A cosmetic method for coloring the skin, characterized in that, on predetermined areas of the skin to be colored by a person, an effective quantity of a composition as defined in any one of the claims is applied. 18, or obtainable by the process according to one of claims 1 to 15, to obtain the desired coloration.