FR2825631A1 - System for topical application, useful for imparting fresh feel to skin, includes a hydrogel containing microspheres of crystalline material with high enthalpy of melting - Google Patents

Abstract

Providing a system (A) for topical application. System (A) for topical application comprises an insoluble support (C) carrying a deposit of hydrogel (H) that contains microspheres (M) which include at least one crystalline, encapsulated compound (I) with enthalpy of melting ( DELTA Hf), as measured by differential scanning calorimetry, 75-330 kJ/kg. An Independent claim is also included for a method for preparing (A).

Description

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Hydrogels containing thermostabilizing microcapsules
The present application relates to the field of hydrogels.

More particularly, it relates to a topical application system comprising an insoluble support on which is deposited a hydrogel containing microcapsules containing a phase change material. The present application also relates to a process for the preparation of such a system for topical application.

 Hydrogels are gels with a high water content, they are known in the prior art for their use as a system for topical application in order, in particular, to retain the moisture of the skin and to give it a feeling of freshness. Generally these hydrogels are concentrated aqueous solutions of semi-solid and weakly adhesive macromolecules, they are, in general, cast on a support which facilitates their use but they can also be without support.

 In general, to meet the needs of users, hydrogels must meet several criteria. Of course, they must sufficiently hydrate the area of the desired skin. They must also have improved mechanical properties that is to say an elasticity and adhesion strength allowing them to adhere properly and sufficiently to the skin, be comfortable to wear and can be removed without embarrassment or difficulty. These hydrogels must not be too wet or too sticky, they must indeed be easily manipulated and easy to apply on the skin.

 The patent application EP 993 936 describes a cosmetic composition comprising a hydrogel deposited on a support, said hydrogel being obtained by crosslinking a water-soluble polymer preferably containing a carboxyvinyl group with polyvalent metal salts such as aluminum salts. .

 Furthermore, the application WO 01/13915 describes a cataplasm containing a support and a crosslinked gel, this crosslinking being obtained

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 by the presence of at least two compounds selected from magnesium aluminate metasilicate, dry aluminum hydroxide and aluminum chloride.

 In addition, the applications WO 01 22999 and WO 01 01950 describe the use of polysaccharides for obtaining hydrogels.

In these demands, the goal is the limitation of water syneresis.

 The main interest of supported hydrogels is their freshness in contact with the skin as mentioned in WO 00 32154, US 6,224, 899 and US 6,039,971. This cool effect is responsible for their decongestion efficiency, smoothing fine lines, reduction of redness and lowering of skin temperature. The fresh effect provided by the hydrogel masks results from the lowering of their temperature occurring during the evaporation of the water contained in the hydrogel. US Pat. No. 6,039,971 indicates that this cool effect will be all the more important as the hydrogel will contain a significant amount of water. However, it is not possible to increase the quantity of water indefinitely because, in return, the proportion of macromolecules decreases and it quickly becomes impossible to obtain a hydrogel having a cohesion and a viscosity sufficient to allow its coating on the surface. support. On the other hand by increasing the amount of water, we encounter problems of syneresis.

 US Patent 6,162,458 discloses the introduction of assets providing a fresh effect. The disadvantage is that such active ingredients as menthol, for example, can cause local irritation of the skin. As a result, for all the hydrogels described in the preceding documents, the supply of freshness tends to decrease during the exposure time.

 There therefore remains the need to increase and especially to prolong the freshness effect while avoiding the disadvantages of the prior art.

 Advantageously and surprisingly, the Applicant has discovered that it is possible to prolong the supply of freshness conferred by topical-hydrogel-based systems by introducing microcapsules into said hydrogel.

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 thermostabilizers containing encapsulated crystalline compounds such that these crystalline compounds have a phase change temperature close to the cutaneous temperature.

 These thermostabilizing microcapsules have improved absorption and heat recovery capabilities. Thus another advantage of these microcapsules is that they substantially improve the thermal stability of the hydrogels that contain them.

 The microcapsules used in the present invention contain, in a tight and impermeable envelope to the crystalline compound in the molten state, partially or completely crystalline compounds which, when they are heated to a temperature close to their melting temperature, absorb a substantial amount of amount of heat, called latent heat of fusion. The absorption of this latent heat of fusion results in a stability of the temperature of the compound despite the contribution of thermal energy. This effect is similar to a "buffer" effect and makes it possible to thermostate, for a certain time and in a temperature range close to the melting temperature of the compound, the direct environment of the microcapsules despite a variation in the outside temperature.

 At the user level, the absorption of this latent heat of fusion results in a sensation of freshness. This sensation of freshness will last during the entire period during which the encapsulated compounds in the microcapsules are still at least partly in the crystalline state (they have not yet become totally amorphous), that is to say during the whole period during which the "buffer" effect described above occurs.

 Microcapsules capable of absorbing heat and able to stabilize the temperature of their near environment will be called thereafter "thermostabilizing microcapsules" or more simply "microcapsules".

 The present invention relates to a system for topical application comprising an insoluble support on which is deposited a

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 hydrogel such as this hydrogel contains microcapsules containing at least one encapsulated crystalline compound having an enthalpy of fusion (AHf), measured by differential scanning calorimetry, of between 75 and 330 kJ / kg, and a process for the preparation of such a topical application system and the use of such a system for topical application to give the skin a contribution of prolonged freshness.

 Here is meant by "topical", an external application on the skin of the face or more generally of the body.

 The term "crystalline compound" as used herein includes partially or fully crystalline compounds. The degree of crystallinity of the compounds used is not critical in that the compound has the crystalline enthalpy of fusion required for use in cooling the skin.

 The heat absorption capacity of the microcapsules used is directly proportional to the enthalpy of fusion of the encapsulated crystalline compound. This enthalpy of fusion is measured by Differential Scanning Calorimetry (Differential Scanning Calorimetry).

 The enthalpy of fusion of a compound is the amount of energy required to transform a partially or totally crystalline sample into a totally amorphous sample. The thermogram ACp = f (T), in which ACp represents the difference in heat capacity of the sample with respect to a reference sample not undergoing any thermal transition in the studied domain, therefore has an endothermic signal whose area is proportional. the melting enthalpy (AHf) of the sample.

As indicated, the microcapsules used in the cosmetic compositions of the present invention contain crystalline compounds having a melting enthalpy of between 75 and 330 kJ / kg. This enthalpy of fusion is preferably between 100 and 300 kJ / kg, and ideally between 150 and 280 kJ / kg.

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 In addition to the heat capacity of the crystalline compounds enclosed in the thermostabilizing microcapsules of hydrogels, the melting point of these compounds is an essential parameter determining the mode of action, the range of application and the effectiveness of said hydrogels.

 To bring a feeling of freshness to the skin, the melting temperature of the encapsulated crystalline compound must be slightly lower than the temperature of the human skin. By slightly lower, it is meant that the temperature of the skin must be lower by 5 C, preferably by 3 C.

 The temperature of the human skin is of the order of 32 C, depending on the outside temperature, it can increase by a few degrees.

 Preferably, the fusion of the encapsulated crystalline compound should take place at a temperature between about 25 ° C and 40 ° C.

 Thus, at the storage temperature of these hydrogels, the crystalline compound encapsulated in the microcapsules is in the crystalline state. After application to the skin, it melts by drawing from the immediate skin environment the heat necessary for this fusion, thus creating a local sensation of freshness in the user.

 Without wishing to be bound by any theory, it appears that the microcapsules do not provide any cool effect at the beginning of the application of the mask on the skin, that is to say during the first 5 minutes. The temperature of the topical application system is then too low to allow the phase change of the encapsulated crystalline compounds.

After this period of start of application, the temperature of the topical application system becomes close to skin temperature, the phase change of the crystalline compounds occurs, causing the absorption of a quantity of energy corresponding to the latent heat of fusion . This energy absorption results in a stabilization of the temperature of the topically applied system, the effect felt by

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 the user will be an extension of the duration of the sensation of freshness.

 This freshness effect is comparable to that of menthol, but unlike the latter, the use of crystalline compounds encapsulated according to the invention, to the extent that there is no direct contact with the skin, excludes any risk irritation.

In general, it is quite possible to dispense with the use of alcohols to prepare the hydrogel used in the present application.

 Topically applied systems comprising a "thermostatic" hydrogel according to the present invention will be useful in all applications where it is a question of bringing or locally evacuating heat or of locally stabilizing the temperature of the surfaces (face, body, ...) on which they are applied.

 These topical systems can be used at any time of the day by a user who wishes to arrange a break to relax. They can also be used during periods or in places where the temperature is high or to calm the heat sensation due to shock for example in children.

 The crystalline compounds are preferably encapsulated in a sealed envelope. This encapsulation is an essential condition for the reversibility of the fusion / crystallization processes.

Indeed, the encapsulated molten compound will not be able to diffuse into the hydrogel and will crystallize again when the outside temperature becomes lower than its melting point.

 The tightness of the casing is of interest especially when the topical application system is liable to be exposed to numerous thermal variations in the melting range of the crystalline compound, which can occur during its storage.

In addition, in the context of the present invention, it is possible to introduce into the hydrogel, in encapsulated form,

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 that it would not be possible to introduce as such. It will be, for example, hydrophobic compounds.

 It is thus possible to introduce any type of compound into the topical application system according to the invention. Hydrophilic compounds will be dissolved directly in water and glycols. The lipophilic compounds will be dissolved via a solubilizer such as esters of oxyethylenated polyols or not. As glycol, glycerol will be preferred.

 Examples of encapsulated crystalline compounds suitable for the present invention are: C 10 -C 40 aliphatic hydrocarbons, that is containing 10 to 40 carbon atoms, - aromatic hydrocarbons, - acids C8-40 fatty acids such as stearic acid and lauric acid, - Coo fatty alcohols such as stearyl alcohol and lauryl alcohol, - esters of C10-40 fatty acids such as stearic acid stearate. methyl and methyl cinnamate, - mineral salts containing a large fraction of water of crystallization, such as calcium chloride hexahydrate, sodium sulfate decahydrate, sodium hydrogen phosphate dodecahydrate, thiosulphate pentahydrate of sodium and nickel nitrate hexahydrate, - triglycerides of fatty acids in C1O-40, - silicone waxes such as polydimethylsiloxanes end groups behenoxy or stearoxy (INCI behenoxydimethicone and stearoxydimethico ne), polymethylstearyloxydimethylsiloxanes (INCI: stearic ester dimethicone), polymethylstearyl dimethylsiloxanes (IN CI stearyl dimethicone), copolymers with methacrylate units

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 stearyl with polydimethylsiloxane grafts, polymethyltrifluoromethylalkyl dimethylsiloxane (INCI: trifluoromethyl (Cl-4) alkyl dimethicone), the fatty chains of all these compounds being preferably linear and / or saturated.

 These compounds can be used alone or as a mixture of two or more of them.

 It is also possible to mention at least partially crystalline thermofusible polymers having a crystalline melting point in the temperature zone indicated above.

 Such polymers are, for example, olefinic homopolymers and copolymers, including polyolefin waxes, such as homopolymers of ethylene, copolymers of ethylene and propylene, copolymers of ethylene and octene, copolymers of ethylene. and butene and copolymers of ethylene and vinyl acetate.

 Mention may also be made of poly (alkylene oxide), alkyl polyesters, poly (ε-caprolactones), polyamides, in particular those resulting from the polycondensation of fatty acid dimer, as well as copolymers of fluorinated olefins. .

 Another group of usable crystalline polymers is formed by the crystallizable side chain polymers described in J. Polymer Sci. : Macromol. Rev. 8: 117-253 (1974). These are vinyl and / or acrylic polymers or copolymers containing a large fraction, generally at least 50% by weight, of copolymerized units comprising long crystallizable linear aliphatic side chains, or fluorinated or perfluorinated crystallizable side chains. US Patent 5,156,911 describes the use of such crystallizable side chain polymers in adhesive assemblies whose adhesive properties vary with temperature.

 Preferred encapsulated crystalline compounds for the present invention are linear chain aliphatic hydrocarbons containing from 10 to 40, preferably from 13 to 28 and most preferably from 16 to 28.

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 23 carbon atoms. Indeed, the melting temperature of the compounds of this series of homologous hydrocarbons increases perfectly predictably with the number of carbon atoms (-5.5 C for n-tridecane (C13) at 61.4 C for n-octacosane (C28)) in the temperature range concerned by the cosmetic applications described above. There may be mentioned, for example, octadecane with a melting point of 28 C.

 Crystalline compounds having a melting enthalpy (AHf) of 75 to 330 kJ / kg are preferably encapsulated in a sealed envelope.

 The material forming the wall of the microcapsules can be chosen from all the materials conventionally used in the field of microencapsulation.

 This material can be amorphous, crystalline or semi-crystalline.

When crystalline or semi-crystalline, it must have a higher melting point than encapsulated crystalline compounds. Moreover, this material must be sufficiently elastic to withstand the variations in volume of the crystalline compound during the phase transition and to withstand the shear forces during the application of the composition containing them. In addition, it must be inert with respect to the encapsulated substances and the compounds of the cosmetic or pharmaceutical formulation with which it will be in contact.

 According to the method chosen, it will be possible to use as the material forming the envelope of the microcapsules, polymers such as polyamides, polyurethanes, polyureas, polyesters, polycyanoacrylates, urea-formaldehyde or melamine-formaldehyde resins, and gelatin / gum systems arabic and silica.

 The microcapsules can be prepared according to well known methods described for example in the book entitled "Microencapsulation, Methods and Industrial Applications", Director of the publication S. Benita, Marcel Dekker (1996). Examples that may be mentioned include interfacial polymerization or polycondensation, coacervation, atomization, centrifugal extrusion or microencapsulation on rotating disks.

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The thermostabilizing microcapsules are known and sold for example under the name Thermasorbe by the company Frisby Technologies Inc. or under the references 9850K and 9850Q by the company 3M.

 These microcapsules are in the form of a fine, fluid and non-film-forming powder. Their use is known for example in the field of isothermal clothing and shoes, in cooling systems in microelectronics and in the field of packaging.

 The compound constituting the wall of the microparticles may also be a non-polymeric material. It is possible to use, for example, microcapsules based on precipitated silica, amorphous, hydrated or rendered hydrophobic, proposed by the company PHASE CHANGE LABORATORIES under the name AcuTemp.

 The upper size of the microcapsules is preferably limited, for obvious reasons of visibility, to a few tens or hundreds of micrometers. It is generally preferred to use microcapsules having an average diameter of from 0.01 to 100 microns, more preferably from 0.05 to 50 microns.

 The hydrogels used in the present invention contain water in a significant proportion: from 30 to 90% by weight, and preferably from 40% to 85% by weight, relative to the total weight of the hydrogel, as well as one or more polymers in a proportion of between 1 and 25% by weight, and preferably between 3 and 20% by weight, relative to the total weight of the hydrogel.

 These polymers used in the composition of the hydrogel are preferably chosen from the group consisting of xanthan gum, gum arabic, gelatin, gum tragacanth, glucomannan, gellan gum, cellulose gum, polymers carboxyvinyls, polyacrylic acid, sodium polyacrylate, polyvinyl alcohols, polyvinylpyrrolidones, sodium carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxypropylcellulose, maleic anhydride / methylvinylether copolymers, ethylene vinyl acetate, oxides of

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 polyethylene, polyoxyethylene / polyoxypropylene block copolymers, sodium alginates.

According to a preferred variant, the topical application system according to the invention comprises a hydrogel containing at least one polymer crosslinked with trivalent ions, such as, for example, trivalent aluminum salts such as aluminum hydroxide.
In a preferred embodiment, the polyacrylic acid crosslinked with anhydrous aluminum hydroxide with or without sodium polyacrylate or gelatin will be chosen.

 The hydrogels used in the present invention generally contain from 0.1% to 90%, preferably from 0.5% to 80% and most preferably from 1 to 70% by weight of thermostabilizing microcapsules, based on the final hydrogel.

 The hydrogels used in the present invention may further contain at least one cosmetic active ingredient and / or at least one adjuvant suitable for bringing freshness to the skin. These cosmetic and adjuvant active ingredients may be introduced into the hydrogel directly or in encapsulated form.

 These cosmetic active principles or adjuvants are preferably present in the hydrogels used in the present invention in an amount of between 0.1 and 60%, preferably between 0.5 and 50% and better still between 1 and 40% by weight relative to to the weight of the total hydrogel.

 Examples of the active cosmetic ingredients that may be mentioned include anti-free radical agents, moisturizing agents, vitamins, proteins, enzymes, ceramides, α-hydroxy acids, bhydroxy acids, retinoids, sunscreens, surfactants, matting agents, antiperspirants, fats and silicones.

 Adjuvants are, for example, solvents, pH-regulating agents, antioxidants, sequestering agents, preserving agents, fillers, emollients, antifoam agents, fatty substances such as oils, waxes and body oils. pasty fat, dispersants, silicones such as oils

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 volatile or not, gums, waxes or pasty silicones, perfumes, surfactants, plasticizers, thickening or gelling polymers, and film-forming, soluble or dispersible polymers.

 The hydrogel will be deposited on the support at a rate of 300 to 1500 g / m2. The support on which the hydrogel is placed may be occlusive or non-occlusive.

 As a non-occlusive support, woven or non-woven supports are generally used.

 As an occlusive or partially occlusive support, plastics such as polyurethanes, polyethylenes and polypropylenes are conventionally used.

The method of preparing the topically applied system according to the present invention comprises the following steps:
A) preparing the hydrogel by mixing water, at least one polymer and optionally at least one cosmetic active compound and / or at least one optional adjuvant;
B) introducing crystalline compounds encapsulated in said hydrogel and mixing;
C) Coating the hydrogel obtained on the support.

 This step of coating the hydrogel on the support may be a conventional scraping or calendering step; at the end of this step the hydrogel will be deposited on the support at a rate of 300 to 1500 g / m2.

 It may also be provided to heat the hydrogel to allow better dissolution of the compounds that constitute it. Nevertheless, the heating temperature should be chosen so as not to damage the compounds constituting the hydrogel.

 Generally, the preparation of the hydrogel is carried out at a temperature between 25 and 65 C.

 The examples which follow illustrate the invention without limiting the part thereof.

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Examples of composition Example 1

<Tb>
<tb> - <SEP> polyacrylate <SEP> of <SEP> sodium <SEP> 7,00%
<tb> - <SEP> carboxymethyl <SEP> cellulose <SEP> of <SEP> sodium <SEP> 2.00%
<tb> - <SEP> glycerin <SEP> 18%
<tb> - <SEP> acid <SEP> citric <SEP> 0,45%
<tb> - <SEP> EDTA <SEP> 0.05%
<tb> - <SEP> mono-isostearate <SEP> of <SEP> sorbitan <SEP> 0.05%
<tb> - <SEP> propylene <SEP> glycol <SEP> 2,2%
<tb> - <SEP> hydroxide <SEP> aluminum <SEP> 0.25%
<tb> - <SEP> preservatives <SEP> (parabens) <SEP> 0,15%
<tb> - <SEP> microcapsules <SEP> thermostabilizers <SEP> containing
<tb> of <SEP> octadecane <SEP> (at <SEP> 77%) <SEP> 10%
<tb> - <SEP> palmitate <SEP> of <SEP> tocopheryl <SEP> (active) <SEP> 0.5%
<tb> - <SEP> water <SEP> qsp <SEP> 100
<Tb>
Example 2

<Tb>
<tb> - <SEP> gelatin <SEP> 6,00%
<tb> - <SEP> carboxymethyl <SEP> cellulose <SEP> of <SEP> sodium <SEP> 2.00%
<tb> - <SEP> glycerin <SEP> 23%
<tb> - <SEP> acid <SEP> citric <SEP> 0,45%
<tb> - <SEP> EDTA <SEP> 0, <SEP> 1%
<tb> - <SEP> preservatives <SEP> (parabens) <SEP> 0,15%
<tb> - <SEP> microcapsules <SEP> thermostabilizers <SEP> containing
<tb> of <SEP> octadecane <SEP> (at <SEP> 77%) <SEP> 10%
<tb> - <SEP> ascorbyl <SEP> glucoside <SEP> (active) <SEP> 0.5%
<tb> - <SEP> water <SEP> qsp <SEP> 100
<Tb>

The gel is prepared using conventional stirring techniques, and is then deposited by coating, at a rate of 800 g / m 2

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 a nonwoven fibrous support of 55 g / m 2 composed of viscose and polyester fibers in the proportion 65/35.

Claims (16)

1. topically applied system comprising an insoluble support on which a hydrogel is deposited, characterized in that this hydrogel contains microcapsules containing at least one encapsulated crystalline compound having an enthalpy of fusion (AHf), measured by differential scanning calorimetry, between 75 and 330 kJ / kg.  2. Topical application system according to claim 1, wherein the melting enthalpy of the crystalline compound is between 100 and 300 kJ / kg, preferably 150 and 280 kJ / kg.  3. topically applied system according to one of the preceding claims such that the melting temperature of the crystalline compound is between 25 C and 40 C.  4. topically applied system according to one of the preceding claims, such that the encapsulated crystalline compound has a melting temperature between 25 C and 400C and is selected from: aliphatic hydrocarbons CIO-40, - aromatic hydrocarbons, - Ces-40 fatty acids, - CS-40 fatty alcohols, - C10-40 fatty acid esters, - mineral salts containing a large fraction of water of crystallization, - CIO-fatty acid triglycerides 40, - silicone waxes, - thermofusible polymers at least partially crystalline. <Desc / Clms Page number 16>  5. Topical application system according to the preceding claim, such that the crystalline compound is a linear chain aliphatic hydrocarbon containing from 10 to 40 carbon atoms, preferably from 13 to 28 carbon atoms, and more preferably from 16 to 23 carbon atoms. carbon.  6. Topical application system according to one of the preceding claims, such that the material forming the envelope of the microcapsules is chosen from polyamides, polyurethanes, polyureas, polyesters, polycyanoacrylates, urea-formaldehyde or melamine-formaldehyde resins. , and gelatin / gum arabic systems and silica.  7. Topical application system according to one of the preceding claims such that the microcapsules have an average diameter of between 0.01 and 100 microns, more preferably between 0.05 and 50 microns.  8. topically applied system according to one of the preceding claims such that the microcapsules are from 0.1 to 90% by weight, preferably from 0.5 to 80% by weight relative to the total weight of the final hydrogel.  9. topically applied system according to one of the preceding claims such that the hydrogel contains 30 to 90% water, and 1 to 25% of a polymer by weight relative to the total weight of the final hydrogel .  10. Topical application system according to the preceding claim such that the polymer is selected from the group consisting of xanthan gum, gum arabic, gelatin, gum tragacanth, glucomannan, gellan gum, cellulose gum, carboxyvinyl polymers, polyacrylic acid, sodium polyacrylate, polyvinyl alcohols, polyvinylpyrrolidones, sodium carboxymethylcellulose, methylcellulose, ethylcellulose, hydroxypropylcellulose, maleic anhydride / methylvinylether copolymers, ethylene vinyl <Desc / Clms Page number 17>  acetate, polyethylene oxides, polyoxyethylene / polyoxypropylene block copolymers, sodium alginates.  He. Topical application system according to one of claims 9 or 10 such that the polymer is crosslinked by trivalent ions.  12. Topical application system according to one of claims 9 to 11 such that the polymer is a polyacrylic acid crosslinked with anhydrous aluminum hydroxide with or without sodium polyacrylate or gelatin.  13. topically applied system according to one of the preceding claims such that the hydrogel contains at least one cosmetic active ingredient and / or at least one adjuvant, these compounds may be introduced into the hydrogel directly or in encapsulated form.  14. System for topical application according to one of the preceding claims such that these active ingredients and cosmetics adjuvants are present in the hydrogel in an amount of between 0.1 and 60% by weight, and preferably between 0.5 and 50 % by weight relative to the weight of the total hydrogel.  15. Topical application system according to one of the preceding claims, such that the active ingredient is selected from the group consisting of anti-free radical agents, moisturizers, vitamins, proteins, enzymes, ceramides, α-hydroxyacids, β-hydroxyacids, retinoids, sunscreens, surfactants, matting agents, antiperspirants, fats and silicones.  16. Topical application system according to one of the preceding claims, such that the adjuvants are chosen from the group formed by solvents, pH-regulating agents, antioxidants, sequestering agents, preserving agents, fillers, emollients, anti-foam agents, fatty substances such as oils, waxes and pasty fatty substances, dispersing agents, <Desc / Clms Page number 18>  silicones, such as volatile or non-volatile oils, gums, waxes or pasty silicones, perfumes, surfactants, plasticizers, thickening or gelling polymers, and film-forming, soluble or dispersible polymers.  17. A method of preparing a topical application system according to one of the preceding claims characterized in that the following steps are carried out: A) preparing the hydrogel by mixing water, at least one polymer and optionally at least one cosmetic active compound and / or at least one optional adjuvant, B) the introduction of crystalline compounds encapsulated in said hydrogel and mixture; C) Coating the hydrogel obtained on the support.  18. Use of a topical application system according to one of claims 1 to 16 to give the skin a contribution of prolonged freshness.