Cosmetic composition in the form of a water-in-water emulsion

Abstract

The present invention relates to a cosmetic composition in the form of a water-in-water emulsion, comprising an internal aqueous phase in the form of droplets in suspension in a continuous external aqueous phase, the aqueous phases comprising: a) at least one first anionic polymer selected from crosslinked polymers of hyaluronic acid, optionally mixed with a second anionic polymer selected from chitosan derivatives modified by at least one carboxyalkyl group in which the carboxyalkyl group is preferably a C2-C6 carboxyalkyl group, hyaluronic acid and its salts, and mixtures thereof, b) at least one cationic polymer selected from C1-C6 hydroxyalkyl quaternary ammonium salts of guar gum, chitosan, polyquaterniums, and mixtures thereof, the total weight % of anionic polymer a) representing at least 0.25% by weight, relative to the total weight of the cosmetic composition, and the composition further comprising at least one hydrophilic gelling agent, at least one weak acid, and at least one weak base. The present invention also relates to a method for preparing a cosmetic composition according to the invention, and to a skin-care and / or hair-care method comprising a step of applying a cosmetic composition according to the invention to at least part of the body and / or the face and / or the hair.

Description

Description Title of the invention: Cosmetic composition in the form of a water-in-water emulsion Technical Field The present invention relates to the cosmetic field, and more particularly to a cosmetic composition in the form of a water-in-water emulsion comprising an internal aqueous phase in the form of droplets, also called "micro-droplets" or "coacervates," suspended in a continuous external aqueous phase, said aqueous phases comprising a combination of specific anionic polymer(s) and cationic polymer(s). The present invention also relates to a method for preparing a cosmetic composition according to the invention, as well as a method for skin and / or hair care comprising a step of applying a cosmetic composition according to the invention to at least one part of the body and / or face and / or hair.

[0002] Mixing an anionic polymer and a cationic polymer in aqueous solution generally results in segregative phase separation, leading to the formation of two distinct phases, each enriched in one of the polymers. This phase separation arises from the incompatibility between the two polymers and becomes more pronounced as the concentrations or molar masses of the polymers increase.

[0003] The inventors have surprisingly observed that the combination of specific anionic and cationic cosmetic polymers, normally incompatible due to their thermodynamic instability, allows the creation of a stable water-in-water emulsion system composed of microscopic coacervate droplets that remain stable over time. The resulting water-in-water emulsion is available as a fast-absorbing lotion or serum, providing a refreshing effect and a unique sensory experience, with a soft, luminous finish and a "second skin" effect upon application. The cosmetic composition in the form of a water-in-water emulsion... The water-in-water emulsion of the invention offers improved efficacy in terms of hydration and skin-smoothing / tightening effect. It also leads to a reduction in transepidermal water loss (TEWL), which corresponds to the amount of water vapor that naturally escapes through the skin barrier. Thus, TEWL is an indicator of the skin's ability to retain moisture and therefore its capacity to maintain good hydration. Furthermore, the water-in-water emulsion cosmetic composition of the invention can incorporate active ingredients that are sometimes difficult to implement because they are poorly soluble in conventional formulations, such as positively or negatively charged hydrophilic actives, for targeted and prolonged release at the epidermal level. Brief description of the drawings

[0004] The attached drawings are schematic and are primarily intended to illustrate the principles of the invention.

[0005] [Fig. 1] Figure 1 represents a colloidal system according to the invention comprising two incompatible water-soluble polymer solutions.

[0006] [Fig. 2] Figure 2 is a diagram representing the formation of a water-in-water emulsion according to the invention, by an aggregative phase separation mechanism.

[0007] [Fig. 3] Figure 3 shows optical microscope photographs of: a water-in-water emulsion according to the invention (a) in dark field, (b) in differential interference contrast, and (c) in confocal microscopy associated with a FITC-DEAE-Dextran type fluorophore. Description of the invention

[0008] The present invention relates to a cosmetic composition in the form of a water-in-water emulsion comprising an internal aqueous phase in the form of droplets suspended in a continuous external aqueous phase, comprising: a) at least one first anionic polymer selected from cross-linked hyaluronic acid polymers, optionally in a mixture with a second anionic polymer selected from chitosan derivatives modified by at least one carboxyalkyl group in which said carboxyalkyl group is preferably C2-CO, hyaluronic acid and its salts, and mixtures thereof; b) at least one cationic polymer selected from Ci-Ce hydroxyalky quaternary ammonium salts of guar gum, chitosan, polyquaterniums, and mixtures thereof; and the total weight % of anionic polymer a) representing at least 0.25% by weight, relative to the total weight of the cosmetic composition, and the composition further comprising at least one hydrophilic gelling agent.at least one weak acid, and at least one weak base.

[0009] In this cosmetic composition in the form of a water-in-water emulsion, the % by weight of anionic polymer a) and cationic polymer b) is advantageously higher in the internal aqueous phase in the form of drops than in the continuous external aqueous phase. The use of chitosan- and hyaluronic acid-based nanoparticles has already been described in the literature, particularly in the medical and food sectors. For example, the publication by LE Puluhulawa et al., Polymers, 2022, 14, 3410, describes chitosan nanoparticles onto which hyaluronic acid molecules are grafted for cancer treatment. H. Van Le et al. also developed complex hyaluronic acid-based polyelectrolytes for messenger RNA delivery (Small 2022, 18, 2204283). None of these documents describes the association of an anionic polymer a) and a cationic polymer b), in the presence of a weak acid and a weak base and a hydrophilic gelling agent, as defined according to the invention, for the preparation of a cosmetic composition in the form of a water-in-water emulsion. [001 The invention consists of bringing one or more cationic polymer(s) a) into contact with one or more anionic polymer(s) b) so as to form microscopic droplets, also called "micro-droplets" or "coacervates," rich in polymers of opposite charges, and kept in suspension in a medium with a low concentration of these same polymers, as shown in Figure 1. It is therefore a colloidal system composed of at least two solutions of incompatible and thermodynamically unstable water-soluble polymers. The cosmetic composition in the form of a water-in-water emulsion of the invention is formed and stabilized by an aggregative phase separation mechanism, as shown in Figure 2.

[0012] In the context of the invention, the anionic polymer comprises at least one first anionic polymer selected from crosslinked hyaluronic acid polymers, preferably sodium hyaluronate crosspolymer. The anionic polymer may also comprise a second anionic polymer selected from chitosan derivatives modified by at least one carboxyalkyl group, in which said carboxyalkyl group is preferably C2-CO, and more preferably selected from carboxymethyl chitosan, succinyl chitosan, and mixtures thereof. This second anionic polymer may also be selected from hyaluronic acid, its salts, and mixtures thereof, and more preferably sodium hyaluronate.

[0013] In a preferred embodiment, the first anionic polymer a) is sodium hyaluronate crosspolymer, optionally in a mixture with a second anionic polymer a) selected from carboxymethyl chitosan, succinyl chitosan, sodium hyaluronate, and mixtures thereof. In an advantageous embodiment, the anionic polymer a) consists of a mixture of sodium hyaluronate crosspolymer and sodium hyaluronate. More particularly, it may be a mixture of sodium hyaluronate crosspolymer having a molecular weight ranging from 1.10 6 at 2.10 6 kg. mol 1 and SODIUM HYALURONATE having a molecular weight of 20,000 to 50,000 kg.mol 1 .

[0014] In another preferred embodiment, the anionic polymer a) consists of a mixture of SODIUM HYALURONATE CROSSPOLYMER and CARBOXYMETHYL CHITOSAN.

[0015] The cationic polymer b) can advantageously be chosen from GUAR HYDROXYPROPYLTRIMONIUM CHLORIDE, CHITOSAN, POLYQUATERNIUM-6, POLYQUATERNIUM-7, POLYQUATERNIUM-22, POLYQUATERNIUM-47, and mixtures thereof.

[0016] In a particular embodiment: - the anionic polymer a) is a mixture of SODIUM HYALURONATE and SODIUM HYALURONATE CROSSPOLYMER, and - the cationic polymer b) is GUAR HYDROXYPROPYLTRIMONIUM CHLORIDE.

[0017] In another particular embodiment: - the anionic polymer a) is SUCCINYL CHITOSAN, and - the cationic polymer b) is GUAR HYDROXYPROPYLTRIMONIUM CHLORIDE.

[0018] In another particular embodiment: - the anionic polymer a) is a mixture of CARBOXYMETHYL CHITOSAN and SODIUM HYALURONATE CROSSPOLYMER, and - the cationic polymer b) is GUAR HYDROXYPROPYLTRIMONIUM CHLORIDE.

[0019] In another particular embodiment: - the anionic polymer a) is SODIUM HYALURONATE CROSSPOLYMER, and - the cationic polymer b) is CHITOSAN.

[0020] In another particular embodiment: - the anionic polymer a) is a mixture of SODIUM HYALURONATE and SODIUM HYALURONATE CROSSPOLYMER, and - the cationic polymer b) is chosen from POLYQUATERNIUM-6, POLYQUATERNIUM-7, POLYQUATERNIUM-22, POLYQUATERNIUM-47, and their mixtures, and preferably POLYQUATERNIUM-6.

[0021] The cosmetic composition of the invention also comprises at least one hydrophilic gelling agent, preferably in its continuous outer aqueous phase. This hydrophilic gelling agent is advantageously a gelling agent with suspending properties, preferably selected from natural or synthetic polysaccharides. The suspending properties of the gelling agent can be evaluated by adding pearlescent pigments to an aqueous solution gelled with a hydrophilic gelling agent, for example, by adding the pearlescent pigments at a weight of 0.5% relative to the total weight of the gelled aqueous solution, and then visually observing whether the pearlescent pigments remain suspended in the gelled aqueous solution at room temperature and after oven curing at temperatures of 4°C, 45°C, and 50°C for one week.Preferably, the hydrophilic gelling agent is selected from agar-agar, sclerotium gum, gellan gum, xanthan gum, carrageenans, cellulose and its derivatives (such as hydroxyethylcellulose and hydroxypropylcellulose), corn starch, cellulose carboxymethyl ethers, Sphingomonas ferment extract, and mixtures thereof. Even more preferably, the hydrophilic gelling agent is selected from agar-agar, sclerotium gum, Sphingomonas ferment extract, and mixtures thereof.

[0022] The hydrophilic gelling agent may represent from 0.05 to 5% by weight, preferably from 0.1 to 3% by weight, and more preferably from 0.2 to 2% by weight, relative to the total weight of the cosmetic composition.

[0023] The anionic polymer a) may represent from 0.05 to 4% by weight, preferably from 0.1 to 3.5% by weight, and more preferably from 0.2 to 3% by weight, relative to the total weight of the cosmetic composition.

[0024] The cationic polymer b) can represent from 0.01 to 3% by weight, preferably from 0.02 to 2.5% by weight, and more preferably from 0.05 to 2% by weight, relative to the total weight of the cosmetic composition.

[0025] The total of anionic polymer a) and cationic polymer b) may represent at least 0.5% by weight, preferably from 0.5 to 8% by weight, and more preferably from 0.5 to 4% by weight, relative to the total weight of the cosmetic composition.

[0026] The ratio of cationic polymer b) to anionic polymer a) advantageously varies from 1 / 1 to 1 / 6, and preferably from 1 / 2 to 1 / 5.

[0027] The cosmetic composition of the invention further comprises at least one weak acid, preferably selected from citric acid, lactic acid, sodium phosphate, disodium phosphate, sodium bisulfite, and mixtures thereof, and more preferably from citric acid, lactic acid, and mixtures thereof. The cosmetic composition of the invention further comprises at least one weak base, preferably selected from citrate salts, lactate salts, acetates such as tris-(hydroxymethyl)aminomethane acetate, and mixtures thereof, more preferably selected from citrate salts, lactate salts, and mixtures thereof, and even more preferably selected from citrate salts and mixtures thereof.

[0028] The mixture of weak acid and weak base can represent 1 to 3% by weight, relative to the total weight of the cosmetic composition.

[0029] The cosmetic composition of the invention advantageously has a pH between 5 and 6.5.

[0030] When its pH is between 5 and 6.5, the cosmetic composition of the invention advantageously exhibits a zeta potential between -100 and -20 mV. The zeta potential measures the intensity of the electrostatic repulsion / attraction between particles. It can be measured using a Zetasizer Pro device, marketed by Malvern Panalytical. [003 l]The cosmetic composition of the invention advantageously has a viscosity ranging from 60 to 3,800 mPa.s at 20°C, and preferably from 100 to 2,000 mPa.s at 20°C.

[0032] In the cosmetic composition of the invention, droplets of the internal aqueous phase are observed suspended in the external aqueous phase, said droplets having a size less than or equal to 20 pm, and advantageously varying from 15 nm to 10 pm. The droplet size can be determined by Dynamic Light Scattering (DLS).

[0033] In one embodiment, the cosmetic composition of the invention may further comprise an oily phase dispersed within said aqueous phases. This oily phase may be a cosmetic active ingredient, preferably selected from a moisturizing agent, an anti-wrinkle agent, a sebum-regulating agent, an antioxidant, a free radical scavenging agent, an agent that repairs the destructive effects of ultraviolet rays, a complexion-perfecting agent, a slimming agent, a fragrance, or mixtures thereof, and more preferably a fragrance. Advantageously, the oily phase represents from 0.01 to 5% by weight, relative to the total weight of the cosmetic composition.

[0034] In one embodiment, the cosmetic composition in the form of a water-in-water emulsion of the invention is in the form of a lotion or a serum.

[0035] The cosmetic composition in the form of a water-in-water emulsion of the invention can be a hair product.

[0036] Another object of the invention relates to a method for preparing a cosmetic composition in the form of a water-in-water emulsion according to the invention, as described above.

[0037] The process for preparing the cosmetic composition in the form of a water-in-water emulsion of the invention comprises the following steps: (i) under stirring, preparation of an aqueous anionic polymer gel a) by mixing water with a first anionic polymer selected from crosslinked hyaluronic acid polymers, optionally mixed with a second anionic polymer selected from chitosan derivatives modified by at least one carboxyalkyl group in which said carboxyalkyl group is preferably C2-C6, hyaluronic acid and its salts, and mixtures thereof, preferably at a temperature between 50 and 90°C, said aqueous anionic polymer gel a) further comprising at least one hydrophilic gelling agent, at least one weak acid and at least one weak base if the aqueous cationic polymer gel b) prepared in step (ii) is free of them, (ii) under stirring, preparation of an aqueous cationic polymer gel b) by mixing water with a cationic polymer selected from the salts of quaternary ammonium hydroxyalkylated in Ci-Ce of guar gum, chitosan, polyquaterniums, and mixtures thereof, preferably at a temperature between 50 and 90°C, said aqueous cationic polymer gel b) further comprising at least one hydrophilic gelling agent, at least one weak acid and at least one weak base if the aqueous anionic polymer gel a) prepared in step (i) is free of them, (iii) coacervation in situ ar mixing of the aqueous anionic polymer gel a) formed in step (i) with the aqueous cationic polymer gel b) formed in step (ii), to form a water-in-water emulsion comprising an internal aqueous phase in the form of droplets suspended in a continuous external aqueous phase.

[0038] The anionic polymer a), the cationic polymer b), the hydrophilic gelling agent, the weak acid and the weak base, used in the process of preparing the cosmetic composition of the invention are as defined above.

[0039] Advantageously, step (i) is carried out, under stirring, at a temperature ranging from 50 to 90°C, preferably for a duration ranging from 15 minutes to 1 hour. The mixture obtained at the end of step (i) is cooled to a temperature of 40°C if the aqueous anionic polymer gel a) prepared in step (i) comprises lactic acid as a weak acid.

[0040] Advantageously, step (ii) is carried out, under stirring, at a temperature of 50 to 90°C, preferably for a period of 15 to 30 minutes. The mixture obtained at the end of step (ii) is cooled to a temperature of 40°C if the aqueous cationic polymer gel (b) prepared in step (ii) includes lactic acid as a weak acid.

[0041] The mixture obtained at the end of step (iii) is cooled to a temperature of 40°C if the aqueous anionic polymer gel a) prepared in step (i) and the aqueous cationic polymer gel b) prepared in step (ii) do not include lactic acid as a weak acid.

[0042] In an advantageous embodiment, the size of the drops obtained at the end of step (iii) is less than or equal to 20 pm, and advantageously between 15 nm and 10 pm.

[0043] An oily phase may optionally be added at the end of the process, in a subsequent step. This oily phase may be a cosmetic active ingredient, preferably chosen from among a moisturizing agent, an anti-wrinkle agent, a sebum-regulating agent, an antioxidant, a free radical scavenger, an agent that repairs the damaging effects of ultraviolet rays, a complexion-perfecting agent, a slimming agent, a fragrance, or mixtures thereof, and most preferably a fragrance. This oily phase is incorporated into the internal aqueous phase in the form of droplets, which thus stabilize the oily phase.

[0044] Finally, a last object of the invention relates to a skin and / or hair care process comprising a step of applying a cosmetic composition in the form of a water-in-water emulsion as defined according to the invention, to at least one part of the body and / or face and / or hair.

[0045] In addition to the foregoing provisions, the invention includes further provisions which will become apparent from the following supplementary description, which relates to the preparation of cosmetic compositions in the form of water-in-water emulsions according to the invention and comparative cosmetic compositions. Examples:

[0046] In the examples that follow, and unless otherwise indicated, all percentages are given as mass percentages, ingredients are designated by their INCI name, and the temperature is given in degrees Celsius.

[0047] The characterization methods used in the examples are as follows:

[0048] Viscosity measurement: Viscosity was measured using a Rhéolab® rotational rheometer with a CC27 coaxial cylindrical spindle.

[0049] Measurement of zeta potential: Zeta potential measurement uses a Zetasizer Pro device, marketed by the company Malvern Panalytical: The zeta potential of cosmetic compositions in the form of water-in-water emulsions was measured, as a function of pH. The zeta potential allows the charge of the overall system to be determined (when anionic and cationic polymers are brought into contact). The charge of the compositions of the invention is preferably negative, and advantageously ranges between -100 mV and -20 mV.

[0050] Determination of the size and particle size distribution of suspended droplets: The size and particle size distribution, by number and volume, of the suspended droplets were analyzed by dynamic light scattering (DLS) using a Zetasizer. Population peaks are shown in the tables below; several values ​​indicate a heterogeneous particle size population.

[0051] Analysis by optical microscopy: To ensure proper droplet formation and monitor their evolution over time, the compositions of the samples were observed using an optical microscope. This analytical method allows for the identification of the droplet micrometer population and the observation of their size and shape.

[0052] Evaluation of the stability of the compositions: The stability of the compositions was evaluated after oven drying at temperatures of 4°C, 45°C and 50°C, after two weeks or two months. The stability of the compositions was also evaluated at room temperature by placing the samples in daylight for one month. The overall stability of each composition was categorized as follows: ++: very good stability (homogeneous formula and stability of viscosity and pH parameters), + : good stability (slight reversible phase shift), x : not stable (irreversible phase shift and variation of viscosity and pH parameters).

[0053] Hydration level measurement: Hydration levels were measured by corneometry using a Corneometer® CM825 device provided by Courage & Khazaka. The method for measuring stratum corneum hydration relies on creating an electric field at the skin surface and detecting, using electrodes, the variations in the dielectric constant induced by the hydration status of the uppermost layer of the epidermis. The composition was applied to the forearm of a volunteer. The quantity applied corresponds to 2 pL. 2 of composition on the skin. The test was carried out on a panel of 11 subjects. The application area was then protected from friction by placing a metal ring around the application area, fixed to the forearm with adhesive tape. Hydration levels were measured on the application area before (T0) application of the cosmetic composition, and then again 6 hours after application (T6h), with a 15-minute stabilization period following removal of the anti-friction barrier before each measurement. The change in hydration between the measurements at T0 and T6h was calculated as a percentage.

[0054] Measurement of Insensible Water Loss (IWL): The skin barrier strengthening properties were assessed by measuring Insensible Water Loss (IWL) using a vaporometer. The composition was applied to the forearm of a volunteer. The quantity applied corresponded to 2 pL.cnr 2 of composition on the skin. The test was carried out on a panel of 11 subjects. The application area was then protected from friction by placing a metal ring around the application area, fixed to the forearm with adhesive tape. A PIE measurement was taken on the application area before (TO) application of the cosmetic composition, and then 6 hours after application (T6h), allowing a 15-minute stabilization period after removal of the anti-friction protection before taking the measurement. The change in PIE between the measurements at TO and T6h was calculated as a percentage.

[0055] Evaluation of the smoothing / tightening effect: The smoothing and tightening effects were measured before application of the cosmetic composition (TO), and then after application of 2 pL.cnr 2 of cosmetic composition on a defined area of ​​an individual's skin. The smoothing effect was measured by video imaging using a MONADERM® wrinkle detection system (total length, total area). Images were captured on the area at the corner of the eye, known as "crow's feet," where the product had been applied. The smoothing effect is expressed as a percentage and corresponds to the difference between one of these parameters (total length, total area) measured at time T0 on the untreated area and measured 1 hour after application on the treated area (Tlh). The tensor effect was measured using a ballistometer (Dia-Stron) that measures the elastic properties of the skin. The device is equipped with a probe (25 cm long) fitted with a hammer and a sensor that rests on the area of ​​skin being studied (forearm). The measured parameter corresponds to the amplitude of penetration and rebound of the hammer on the skin surface. The result is expressed as a percentage change in this amplitude between 0°C and 15 minutes. after applying the cosmetic composition to an individual's forearm. Example 1:

[0056] A cosmetic composition according to the invention and a comparative composition were prepared and evaluated, to show the effect of weak acid and weak base on the stability of the compositions.

[0057] [Table 1]

[0058] The compositions in Table 1 were prepared according to the following protocol: - Phase A: The ingredients CHLOPHENESIN, HYDROXYACETOPHENONE, CITRIC ACID, and SODIUM CITRATE of phase A were dissolved in water, heated in a water bath to 80°C, and stirred under a deflocculator at 400 rpm. SODIUM HYALURONATE CROSSPOLYMER was incorporated, and the mixture was then stirred under a deflocculator at 500 rpm for 20 minutes and under an emulsifier at 800 rpm for 5 minutes. CARBOXYMETHYL CHITOSAN was pre-mixed with the glycols and then incorporated into the mixture under a deflocculator at 500 rpm for 10 minutes. - Phase B: The water was heated to 80°C under a deflocculator at 400 rpm for 5 minutes. Guar hydroxypropyltrimonium chloride was added and allowed to homogenize for 20 minutes. Phase B was added to phase A under deflocculation at 500 rpm, then cooled to 40°C under deflocculation at 500 rpm.

[0059] The composition of the invention exhibits a turbid appearance characteristic of the presence of droplets dispersed in the continuous aqueous phase. The presence of droplets has been confirmed by optical microscopy. Figure 3 shows optical microscopy photographs of the composition of the invention (a) in dark fields, (b) in differential interference contrast, and (c) in confocal microscopy associated with a FITC-DEAE-Dextran fluorophore.

[0060] Oven stability was improved for the composition of the invention which comprises a weak acid and a weak base, compared to the comparative (control) composition which separated in the bottle.

[0061] The hydration rate and PIE of the cosmetic composition of the invention were measured on a panel of 10 volunteers according to the methods described above. The measured change in hydration between T0 and T6h is +38%, meaning that the composition of the invention provides significant hydration to the skin. It also shows a decrease in PIE of -49%, reflecting a strengthening of the skin barrier due to the application of the composition of the invention to the skin. Example 2:

[0062] A cosmetic composition according to the invention and a comparative composition were prepared and evaluated, to show the effect of the hydrophilic gelling agent on the stability of the compositions after oven curing and exposure to light.

[0063] [Table 2]

[0064] The compositions in Table 2 were prepared according to the following protocol: - Phase A: The ingredients CHLOPHENESIN, HYDROXYACETOPHENONE, CITRIC ACID, and SODIUM CITRATE of phase A were dissolved in water, heated in a water bath to 80°C, and stirred under a deflocculator at 400 rpm. SODIUM HYALURONATE CROSSPOLYMER and the hydrophilic gelling agent (SPHINGOMONAS FERMENT EXTRACT) were incorporated, and the mixture was then stirred under a deflocculator at 500 rpm for 20 minutes and under an emulsifier at 800 rpm for 5 minutes. The SODIUM HYALURONATE was pre-mixed with the glycols and then incorporated into the mixture under a deflocculator at 500 rpm for 10 minutes. - Phase B: The water was heated to 80°C under a deflocculator at 400 rpm for 5 minutes. Guar hydroxypropyltrimonium chloride was added and allowed to homogenize for 20 minutes. Phase B was added to phase A under deflocculation at 500 rpm, then cooled to 40°C under deflocculation at 500 rpm.

[0065] The composition of the invention has a turbid appearance characteristic of the presence of drops dispersed in the continuous aqueous phase, while the comparative (control) composition does not form drops (transparency). Observation by optical microscope confirms the absence of drops in the comparative composition (control).

[0066] Oven stability was improved for the composition of the invention, which includes a hydrophilic gelling agent (SPHINGOMONAS FERMENT EXTRACT), compared to the comparative (control) composition, which separated in the bottle. A loss of viscosity was also observed in the comparative (control) composition under light exposure, compared to the composition of the invention. Example 3:

[0067] A cosmetic composition according to the invention and a comparative composition were prepared and evaluated, to show the effect of the hydrophilic gelling agent on the stability of the compositions after oven curing for 2 months.

[0068] [Table 3]

[0069] The compositions in Table 3 were prepared according to the following protocol: - Phase A: The ingredients CHLOPHENESIN, HYDROXYACETOPHENONE, PENTYLENE GLYCOL, CITRIC ACID, and SODIUM CITRATE of phase A were dissolved in water, heated in a water bath to 80°C, and stirred under a deflocculator at 400 rpm. SODIUM HYALURONATE CROSSPOLYMER was incorporated, and the mixture was then stirred under a deflocculator at 500 rpm for 20 minutes and under an emulsifier at 800 rpm for 5 minutes. - Phase B: The water was heated to 80°C under a deflocculator at 400 rpm for 5 minutes. The CHITOSAN and the hydrophilic gelling agent (SCLEROTIUM GUM) were added and allowed to homogenize for 20 minutes. Phase B was added to phase A under deflocculation at 500 rpm, then cooled to 40°C under deflocculation at 500 rpm.

[0070] The composition of the invention has a turbid appearance characteristic of the presence of drops dispersed in the continuous aqueous phase, while the comparative (control) composition does not form drops (transparency).

[0071] Oven stability has been improved for the composition of the invention which includes a hydrophilic gelling agent (SCLEROTIUM GUM).

[0072] The hydration level and the smoothing and tightening effects of the cosmetic composition of the invention were measured on a panel of 10 volunteers according to the methods described above. The change in hydration level measured between T0 and T6h is +67%, meaning that the composition of the invention provides particularly significant hydration to the skin. It also exhibits a wrinkle-smoothing effect of -27%, reflecting an apparent reduction in the surface area / length of wrinkles in the studied area, and a skin-tightening effect of +30%, indicating an improvement in the skin's mechanical properties. Example 4:

[0073] Cosmetic compositions according to the invention comprising hydrophilic gelling agents either in the anionic phase or in the cationic phase have been prepared and evaluated.

[0074] [Table 4]

[0075] The compositions in Table 4 were prepared according to the following protocol: - Phase A: The ingredients CHLOPHENESIN, HYDROXYACETOPHENONE, PENTYLENE GLYCOL, LACTIC ACID, CITRIC ACID, SODIUM CITRATE, POLYGLYCERIN-3, and PULULAN, along with the gelling agent (SPHINGOMONAS FERMENT EXTRACT), from phase A were dissolved in water, heated in a water bath to 80°C, and stirred under a deflocculator at 400 rpm. SODIUM HYALURONATE CROSSPOLYMER was incorporated, and the mixture was then stirred under a deflocculator at 500 rpm for 20 minutes and under an emulsifier at 800 rpm for 5 minutes. - Phase B: The water was heated to 80°C under a deflocculator at 400 rpm for 5 minutes. The CHITOSAN and the hydrophilic gelling agent (SCLEROTIUM GUM) were added and allowed to homogenize for 20 minutes. Phase B was added to phase A under deflocculation at 500 rpm, then cooled to 40°C under deflocculation at 500 rpm.

[0076] The compositions of the invention all exhibit a turbid appearance characteristic of the presence of droplets dispersed in the continuous aqueous phase. Furthermore, they all demonstrate very good stability after oven drying and exposure to light. Example 5:

[0077] Other cosmetic compositions according to the invention have been prepared and evaluated.

[0078] [Table 5]

[0079] The compositions in Table 5 were prepared according to the following protocol: - Phase A: The ingredients CHLOPHENESIN, HYDROXYACETOPHENONE, LACTIC ACID, CITRIC ACID, and SODIUM CITRATE of phase A were dissolved in water, heated in a water bath to 80°C, and stirred under a deflocculator at 400 rpm. The SODIUM HYALURONATE CROSSPOLYMER and the gelling agent (SPHINGOMONAS FERMENT EXTRACT) were incorporated, and the mixture was then stirred under a deflocculator at 500 rpm for 20 minutes and under an emulsifier at 800 rpm for 5 minutes. The CARBOXYMETHYL CHITOSAN and SODIUM HYALURONATE, when present, were mixed separately with the glycols and then incorporated into the mixture under a deflocculator at 500 rpm for 10 minutes. - Phase B: The water was heated to 80°C under a deflocculator at 400 rpm for 5 minutes. Guar hydroxypropyltrimonium chloride and the hydrophilic gelling agent (agar) were added and allowed to homogenize for 20 minutes. Phase B was added to phase A under a deflocculator at 500 rpm, then cooled to 40°C under a deflocculator at 500 rpm.

[0080] The compositions of the invention all exhibit a turbid appearance characteristic of the presence of droplets dispersed in the continuous aqueous phase. Furthermore, they all demonstrate very good stability after oven drying and exposure to light. Example 6:

[0081] Other cosmetic compositions according to the invention have been prepared and evaluated.

[0082] [Table 6]

[0083] The compositions in Table 6 were prepared according to the following protocol: - Phase A: the ingredients CHLOPHENESIN, HYDROXYACETOPHENONE and SODIUM CITRATE from phase A was solubilized in water, heated in a water bath to 80°C, and stirred under a deflocculator at 400 rpm. SODIUM HYALURONATE CROSSPOLYMER and the gelling agent (SPHINGOMONAS FERMENT EXTRACT) were incorporated, and the mixture was then stirred under a deflocculator at 500 rpm for 20 minutes and under an emulsifier at 800 rpm for 5 minutes. CARBOXYMETHYL CHITOSAN and SODIUM HYALURONATE, when present, were mixed separately with the glycols and then incorporated into the mixture under a deflocculator at 500 rpm for 10 minutes. - Phase B: Water was heated to 80°C under a deflocculator at 400 rpm for 5 minutes. Guar hydroxypropyltrimonium chloride was added and allowed to homogenize for 20 minutes. Lactic acid was incorporated after the formation of the Phase B gel at a temperature below 40°C. Phase B was added to phase A under deflocculation at 500 rpm, then cooled to 40°C under deflocculation at 500 rpm.

[0084] The compositions of the invention all exhibit a turbid appearance characteristic of the presence of droplets dispersed in the continuous aqueous phase. Furthermore, they all demonstrate very good stability after oven drying and exposure to light. Example 7:

[0085] Other cosmetic compositions according to the invention have been prepared and evaluated.

[0086] [Table 7]

[0087] The compositions in Table 7 were prepared according to the following protocol: - Phase A: The ingredients CHLOPHENESIN, HYDROXYACETOPHENONE, and SODIUM CITRATE of phase A were dissolved in water, heated in a water bath to 80°C, and stirred under a deflocculator at 400 rpm. SODIUM HYALURONATE CROSSPOLYMER was incorporated, and the mixture was then stirred under a deflocculator at 500 rpm for 20 minutes and under an emulsifier at 800 rpm for 5 minutes. The SODIUM HYALURONATE was separately mixed with the glycols and then incorporated into the mixture under a deflocculator at 500 rpm for 10 minutes. - Phase B: The water was heated to 80°C under a deflocculator at 400 rpm for 5 minutes. Polyquaternium and the hydrophilic gelling agent (AGAR) were added and allowed to homogenize for 20 minutes. Phase B was added to phase A under deflocculation at 500 rpm, then cooled to 40°C under deflocculation at 500 rpm.

[0088] The compositions of the invention all exhibit a turbid appearance characteristic of the presence of droplets dispersed in the continuous aqueous phase. Furthermore, they all demonstrate very good stability after oven drying and exposure to light.

[0089] Cosmetic compositions 14, 15, 16 and 17 of the invention are skin care compositions that allow for hydration and provide a Enhanced barrier effect. Applying these cosmetic compositions to the skin produces a tightening effect after application, as well as a significant smoothing effect.

Claims

Demands

1. A cosmetic composition in the form of a water-in-water emulsion comprising an internal aqueous phase in the form of droplets suspended in a continuous external aqueous phase, characterized in that said aqueous phases comprise: a) at least one first anionic polymer selected from cross-linked hyaluronic acid polymers, optionally in a mixture with a second anionic polymer selected from chitosan derivatives modified by at least one carboxyalkyl group in which said carboxyalkyl group is preferably C2-CO, hyaluronic acid and its salts, and mixtures thereof; b) at least one cationic polymer selected from Ci-Ce hydroxyalky quaternary ammonium salts of guar gum, chitosan, polyquaterniums, and mixtures thereof; and in that the total weight % of anionic polymer a) represents at least 0.25% by weight, relative to the total weight of the cosmetic composition; and in that the composition further comprisesat least one hydrophilic gelling agent, at least one weak acid, and at least one weak base.

2. Cosmetic composition according to claim 1, wherein the first anionic polymer a) is SODIUM HYALURONATE CROSSPOLYMER, optionally in mixture with a second anionic polymer a) selected from CARBOXYMETHYL CHITOSAN, SUCCINYL CHITOSAN, SODIUM HYALURONATE, and mixtures thereof.

3. A cosmetic composition according to claim 2, wherein the anionic polymer a) consists of a mixture of SODIUM HYALURONATE CROSSPOLYMER and SODIUM HYALURONATE, and preferably a mixture of SODIUM HYALURONATE CROSSPOLYMER having a molecular weight ranging from 1.10 6 at 2.10 6 kg. mol 1 and SODIUM HYALURONATE having a molecular weight ranging from 20,000 to 50,000 kg.mol 1 .

4. Cosmetic composition according to claim 2, wherein the anionic polymer a) consists of a mixture of SODIUM HYALURONATE CROSSPOLYMER and CARBOXYMETHYL CHITOSAN.

5. Cosmetic composition according to any one of claims 1 to 4, wherein the cationic polymer b) is selected from GUAR HYDROXYPROPYLTRIMONIUM CHLORIDE, CHITOSAN, POLYQUATERNIUM-6, POLYQUATERNIUM-7, POLYQUATERNIUM-22, POLYQUATERNIUM-47, and mixtures thereof.

6. A cosmetic composition according to any one of claims 1 to 5, wherein: - the anionic polymer a) is a mixture of SODIUM HYALURONATE and SODIUM HYALURONATE CROSSPOLYMER, and - the cationic polymer b) is GUAR HYDROXYPROPYLTRIMONIUM CHLORIDE.

7. A cosmetic composition according to any one of claims 1, 2, 4 and 5, wherein: - the anionic polymer a) is a mixture of CARBOXYMETHYL CHITOSAN and SODIUM HYALURONATE CROSSPOLYMER, and - the cationic polymer b) is GUAR HYDROXYPROPYLTRIMONIUM CHLORIDE.

8. A cosmetic composition according to any one of claims 1, 2 and 5, wherein: - the anionic polymer a) is SODIUM HYALURONATE CROSSPOLYMER, and - the cationic polymer b) is CHITOSAN.

9. A cosmetic composition according to any one of claims 1 to 8, wherein the hydrophilic gelling agent is a gelling agent having a suspending power, preferably selected from natural or synthetic polysaccharides, more preferably selected from agar-agar, sclerotium gum, gellan gum, xanthan gum, carrageenans, cellulose and its derivatives, corn starch, cellulose carboxymethyl ethers, Sphingomonas ferment extract, and mixtures thereof, and even more preferably selected from AGAR, SCLEROTIUM GUM, SPHINGOMONAS FERMENT EXTRACT, and mixtures thereof.

10. A cosmetic composition according to any one of claims 1 to 9, wherein said weak acid is selected from citric acid, lactic acid, the sodium phosphate, disodium phosphate, sodium hydrogen sulfite, and mixtures thereof, and preferably citric acid, lactic acid, and mixtures thereof.

11. Cosmetic composition according to any one of claims 1 to 10, wherein the weak base is selected from citrate salts, lactate salts, acetates such as tris-(hydroxymethyl)aminomethane acetate, and mixtures thereof, more preferably selected from citrate salts, lactate salts, and mixtures thereof, and even more preferably selected from citrate salts, and mixtures thereof.

12. A cosmetic composition according to any one of claims 1 to 11, wherein the total of anionic polymer a) and cationic polymer b) represents at least 0.5% by weight, preferably from 0.5 to 8% by weight, and more preferably from 0.5 to 5% by weight, relative to the total weight of the cosmetic composition.

13. Cosmetic composition according to any one of claims 1 to 12, wherein the anionic polymer a) represents from 0.25 to 4% by weight, preferably from 0.25 to 3.5% by weight, and more preferably from 0.25 to 3% by weight, relative to the total weight of the cosmetic composition.

14. Cosmetic composition according to any one of claims 1 to 13, wherein the cationic polymer b) represents from 0.01 to 3% by weight, preferably from 0.02 to 2.5% by weight, and more preferably from 0.05 to 2% by weight, relative to the total weight of the cosmetic composition.

15. Cosmetic composition according to any one of claims 1 to 14, wherein the ratio cationic polymer b) / anionic polymer a) varies from 1 / 1 to 1 / 6, and preferably from 1 / 2 to 1 / 5.

16. Cosmetic composition according to any one of claims 1 to 15, wherein the hydrophilic gelling agent represents from 0.05 to 5% by weight, preferably from 0.1 to 3% by weight, and more preferably from 0.2 to 2% by weight, relative to the total weight of the cosmetic composition.

17. Cosmetic composition according to any one of claims 1 to 16, wherein the weak acid and weak base represent 1 to 3% by weight, relative to the total weight of the cosmetic composition.

18. Cosmetic composition according to any one of claims 1 to 17, characterized in that its viscosity varies from 60 to 3,800 mPa.s at 20°C, and preferably from 100 to 2,000 mPa.s at 20°C.

19. Cosmetic composition according to any one of claims 1 to 18, wherein the droplets of the internal aqueous phase have a size ranging from 15 nm to 10 pm.

20. Cosmetic composition according to any one of claims 1 to 19, characterized in that it is in the form of a lotion or a serum.

21. A method for preparing a cosmetic composition according to any one of claims 1 to 20, characterized in that it comprises the following steps: (i) under stirring, preparation of an aqueous anionic polymer gel a) by mixing water with a first anionic polymer selected from crosslinked hyaluronic acid polymers, optionally mixed with a second anionic polymer selected from chitosan derivatives modified by at least one carboxyalkyl group in which said carboxyalkyl group is preferably C2-C6, hyaluronic acid and its salts, and mixtures thereof, preferably at a temperature between 50 and 90°C, said aqueous anionic polymer gel a) further comprising at least one hydrophilic gelling agent, at least one weak acid and at least one weak base if the aqueous cationic polymer gel b) prepared in step (ii) is free of them, (ii) under stirring, preparation of an aqueous cationic polymer gel b) by mixing water with a cationic polymer selected from the Ci-Ce hydroxyalkylated quaternary ammonium salts of guar gum, chitosan, polyquaterniums, and mixtures thereof, preferably at a temperature between 50 and 90°C, said aqueous cationic polymer gel b) further comprising at least one hydrophilic gelling agent, at least one weak acid and at least one weak base if the aqueous anionic polymer gel a) prepared in step (i) is free of them, (iii) in situ coacervation by mixing the aqueous anionic polymer gel a) formed in step (i) with the aqueous cationic polymer gel b) formed in step (ii), to form a water-in-water emulsion comprising a phase internal aqueous phase in the form of droplets suspended in a continuous external aqueous phase.

22. A method for skin and / or hair care, characterized in that it comprises a step of applying a cosmetic composition as defined according to any one of claims 1 to 20, to at least one part of the body and / or face and / or hair.

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