FR2906137A1 - Cosmetic use of a water soluble thermogelling copolymer constituted by units resulting from polymerization of a monomer and ethylenic monomeric units as hydrating agent for keratinous matter, particularly for skin - Google Patents

Abstract

Cosmetic use of a water soluble thermogelling copolymer constituted by units (I) resulting from polymerization of a monomer (Ia) and ethylenic monomeric units as hydrating agent for keratinous matter, preferably for skin. Cosmetic use of a water soluble thermogelling copolymer constituted by units (I) resulting from polymerization of a monomer (Ia) of formula (CH2=CRCOX) and monomeric units of formula (-CH2-CH2-(CO-X1-A)) as hydrating agent for keratinous matter, preferably for skin. R : H, -CH3, -CH2H5 or -C3H7; X, X1O or NH; and A : a statistical or block copolymer of ethylene oxide and propylene oxide having a lower critical solution temperature (LCST) of which cloud point in water at a concentration of 1% is 5-40[deg] C, or its salts.

Description

1 USE OF THERMOGELIFYING COPOLYMERS AS MOISTURIZING AGENTS

  The present application relates to the cosmetic use of thermogelling copolymers as hydrating agents for keratin materials and more particularly the skin, the use of a composition containing these polymers and a cosmetic treatment process.

  The Stratum Corneum is the thin stratum corneum that forms the interface between the body and the drying environment. It is formed of the upper epithelial tissue: the epidermis, and connective tissue located below: the dermis. The Stratum Corneum, about 10 to 15 m thick, consists of vertically stacked corneocytes surrounded by a matrix of lipid-enriched membranes. Thus, it is a two-compartment system that can be compared to a brick wall, consisting of anucleate cells (bricks) and intercellular lamellar membranes (cement).

  One of the functions of the Stratum Corneum is to regulate the flow of water into and out of the skin and thus to delay the excessive loss of water from the deeper layers of the epidermis. The Stratum Corneum also protects against mechanical aggression and the passage of chemicals and foreign microorganisms. It is also the first defense against UV radiation. In general, a moisturizing agent is defined as a substance that decreases the feeling of dry skin by affecting the water content of the skin by addition or retention.

  Generally, corneometry is the method used to measure the hydration provided by humectants such as glycerol, urea and its derivatives. But this method can not be used to highlight the moisturizing properties of polymers, it was therefore necessary to develop a suitable method to highlight the moisturizing properties of polymers. Various methods based on spectroscopic techniques (infrared, Raman, NMR, etc.) have been developed in recent years with the aim of improving the knowledge of the skin, in particular in the medical field. These techniques have the advantage of not requiring any particular sample preparation and are non-invasive and non-destructive. These methods are especially described in: 1. K. Wichrowski, G. Sore, and A. Khaiat, "Use of infrared spectroscopy for in vivo measurement of stratum corneum moisturization after application of cosmetic preparations," Int. J. Cos. Sci. 17, 1-11 (1995). 2. Querleux B, Richard S, Bittoun J, Jolivet O, Idy-perettii I, Bazin R, Lévêque JL: In vivo hydration profile in skin layers by highresolution magnetic resonance imaging. Skin Pharmacol 1994; 7: 210-216. 3. B. Schrader, B. Dippel, S. Fendel, S. Keller, T. Lochte, M. Riedl, R. Schulte, and E. Tatsch, "NIR FT Raman Spectroscopy, New Tool in Medical Diagnosis," J. Mol. Struct. 408/409, 23-31 (1997). In the context of the present application, the method adopted for measuring the amount of water supplied by 1% weight polymer solutions is laser confocal microscopy associated with Raman spectroscopy. Raman spectroscopy provides information on the molecular composition and structure of the test sample. Associated with confocal microscopy, it offers the advantage of providing information on the Stratum Corneum from the surface of the skin to a depth of a few hundred microns. In addition, the method used in this application has the advantage of being non-invasive and non-destructive.

This method made it possible to establish that the polymers used in accordance with the present application are such that a solution containing 1% by weight of these polymers makes it possible to supply a quantity of water at least equal to that provided by a solution. to 7% by weight of glycerol.

To implement this method, Stratum Corneum isolated, compacted Stratum Corneum dander pellets, artificial skin (Episkin, Matek, Skinethic ...) of the skin resulting from cosmetic surgery can be used as support for Evaluation. These examples are not limiting, all the skin modeling media can be used. In the context of the present application, compacted dander pellets, weighing from 80 to 100mg, with a thickness of more than 100m and a surface area of about 1cm 2 are used as a model of Stratum Corneum; 5 measurements are made on each plantar pellet and 5 pellets are used for each polymer solution, ie 25 measurements for each polymer solution. The amount of polymer solution applied to each pellet is about 500. A Raman laser confocal laser LabRam type (Jobin Yvon to Horiba) equipped with a He: Ne laser (k = 633 nm power approximately 8.4 mW) and a CCD detector is used to perform the measurements. The laser beam is focused in the skin with an X50 lens and the Raman spectra are recorded using a point-to-point mode, from the sample surface, to the depth. The spectral acquisition parameters are: hole and slit: 200 m, acquisition time: 30 s at a frequency of 2800 to 4000 cm -1. a technical modification essential for the measurement of water, with the incorporation of an enclosure making it possible to control the temperature and the humidity during the acquisitions: the parameters are 25 ° C. and 50% relative humidity. the water is determined by the ratio of the 4 OH bands of the water / CH3 bands of the proteins, in Raman spectrography, as described in: 1 Chrit L, Hadjur C, Morel S, Sockalingum GD, Lebourdon G, Leroy F , Manfait M: In vivo chemical investigation of Human skin using a confocal Raman Optic microprobe J. Biomed Opt 2005.

2 Caspers PJ, Lucassen GW, EA Carter, Bruining HA, GJ Puppels: In vivo confocal Raman microspectroscopy of the skin: noninvasive determination of molecular concentration profiles. Journal of Investigative Dermatology 2001; 116 (3): 434-442.

The water / protein ratios in the Stratum Corneum were determined in Raman spectrography, by calculating the ratio between the intensity of the OH bands of the water (area under the curve) integrated between 3350 cm -1 and 3550 cm -1 and the intensity of protein CH3 bands (area under the curve) integrated between 2910cm-1 and 2965 cm-1.

The quantification of the water is calculated from the following equations: W / P = (m, / mp) R Water content (%): mW, (m ,,, + mp) = 100% (W / P) ) / (W / (P + R)) mol, and mp respectively being the water and protein masses in the volume of the tested sample W being the intensity of the Raman signal of the integrated water (OH bands integrated water (area under the curve); Where P is the intensity of the Raman signal of integrated proteins (integrated CH3 bands of protein (area under the curve)); R is a proportionality constant expressing the ratio between the Raman signals of water and proteins in a 50% solution. The water content is expressed in gram of water per 100 g of wet tissue. These features are integrated into the LabSpec software of 30 Jobin-Yvon Horiba. To evaluate the moisturizing performance, the measurements are made at T = 0, before the treatment and at T + 1 hour after the treatment, the surface at 20 m depth. The problem posed by the present application was to propose families of compounds that can be used as moisturizing agents for keratin materials and more particularly for the skin.

The inventors of the present application have shown that this problem can be solved by means of special thermogelling copolymers. The present application therefore relates to the cosmetic use as moisturizing agent of keratin materials and more particularly of the skin of at least one water-soluble thermogelling copolymer comprising units (or repeating units) (I) originating from the polymerizing a monomer of formula (Ia): CH2 = CRCOX (Ia) wherein R is H, -CH3, -C2H5, -C3H7; X represents -OH or -NH2, and units (or repeating units) of formula (II): -CH2-CH2- (CO-X'-A) (II) in which: X 'denotes an atom of oxygen or a group -NH- (preferably a group -NH-); A denotes a random copolymer or block (preferably random) of ethylene oxide and propylene oxide having a LCST (Lower Critical Solution Tem.perature or lower critical temperature of demixing) type whose cloud point in water (or demixing temperature) at a concentration of 1% is between 5 C and 40 C, or one of its salts.

By water-soluble polymer is meant a polymer soluble in water at least 1% by weight at the temperature of 25 C.

For the purposes of the present patent application, the term "thermogelling copolymer" means a copolymer comprising water-soluble or water-dispersible units and units called LCST (Lower Critical Solution Temperature); this polymer has a gelling temperature of between 10 ° C. and 40 ° C., especially at a concentration of 2% by weight of polymer in water. These thermogelling copolymers are, in particular, polymers of acrylic acid, or their salts, grafted with polyethylene oxide / propylene oxide (POE / POP) chains having an LCST type temperature. The POE / POP chains may comprise from 15 to 60 (more preferably 20 to 50) propylene oxide units and from 1 to 40 (more preferably 1 to 20) ethylene oxide units. Advantageously, the mass proportion of the LCST units in the final polymer is preferably between 5% and 70%. especially between 20% and 65%, and particularly between 30% and 60% by weight, relative to the final polymer. Advantageously, the thermogelling polymer has a gelling property such that the viscosity of an aqueous solution at 5% by weight of polymer is at least 5 times higher at a temperature of between 10 ° C. and 40 ° C. than the viscosity of this same polymer. aqueous solution at 5 C.

The salts of the polymers used according to the invention may be of any nature, organic or inorganic, for example chosen from the sodium, magnesium, ammonium and triethanolamine salts, and preferably the sodium salt. The monomer (Ia) is chosen from acrylic acid, especially in the form of sodium salt. These polymers are described in particular in application WO 02/09064.

Among the preferred thermogelling copolymers, mention may be made of polyacrylic acid thermogelling copolymers, sodium salt grafted with a mono-amino-terminated polyethylene oxide / propylene oxide polyoxide copolymer, such as those described in Examples 1, 2a and 2, for example. The characteristics of these copolymers are summarized in the following table: Skeleton Grafting Proportion: Water soluble content (units at LCST) units at LCST grafting (% in polymer mole) final (by weight) Polymer 1 (OE) 6 (OP) polyacrylate 39 statistics 51% 3.9% sodium; MW = 450000 monoamino; MW = 2600 Polymer 2 (EP) polyacrylate 6 (OP) 39 statistic 35% 2% sodium; MW = 450000 monoamino; MW = 2600 Polymer 3 (EO) 6 (OP) polyacrylate 39 statistic 59% 5.3% sodium; MW = 450000 monoamino; PM = 2600 Polymer 1 is particularly preferred. The inventors of the present application have shown that the copolymers used in accordance with the present application are such that a 1% by weight solution of these polymers makes it possible to supply a quantity of water at least equal to that provided by a solution. to 7% by weight of glycerol. In the context of the present application, the thermogelling copolymers described above may be used in compositions in an amount of between 0.01% and 20% by weight, preferably between 0.1% and 10% by weight relative to the weight. total of said composition. The usable compositions then contain a physiologically acceptable medium, that is to say, compatible with cutaneous tissues such as the skin and the scalp. This physiologically acceptable medium may more particularly consist of water and optionally of a physiologically acceptable organic solvent chosen, for example, from lower alcohols having from 1 to 8 carbon atoms and in particular from 1 to 6 carbon atoms, such as ethanol, isopropanol, propanol, butanol; polyethylene glycols having from 6 to 80 ethylene oxide units and polyols such as propylene glycol, isoprene glycol, butylene glycol, glycerine and sorbitol.

The compositions which can be used can be in any of the galenical forms conventionally used for topical application and especially in the form of aqueous, hydroalcoholic, oil-in-water (O / W) or water-in-oil (E / W) solutions. H) or multiple (triple: E / H / E or H / E / H), aqueous gels, or dispersions of a fatty phase in an aqueous phase using spherules, these spherules may be nanoparticles polymers such as nanospheres and nanocapsules or lipid vesicles of ionic and / or nonionic type (liposomes, niosomes, oleosomes). These compositions are prepared according to the usual methods. In addition, the compositions that may be used according to the invention may be more or less fluid and have the appearance of a white or colored cream, an ointment, a milk, a lotion or a serum. a paste or a mousse. They may optionally be applied to the skin in the form of an aerosol. They may also be in solid form, for example in the form of a stick.

When the composition usable according to the invention comprises an oily phase, it preferably contains at least one oil. It may also contain other fatty substances. As oils that can be used in the composition of the invention, mention may be made, for example: hydrocarbon-based oils of animal origin, such as perhydrosqualene; hydrocarbon oils of plant origin, such as liquid triglycerides of fatty acids containing from 4 to 10 carbon atoms, for example triglycerides of heptanoic or octanoic acids, or else, for example, sunflower, corn or soya bean oils. , squash, grape seed, sesame, hazelnut, apricot, macadamia, arara, castor oil, avocado, triglycerides of caprylic / capric acids such as those sold by the company Stearineries Dubois or those sold under the names Miglyol 810, 25 812 and 818 by Dynamit Nobel, jojoba oil, shea butter oil; esters and synthetic ethers, in particular of fatty acids, such as the oils of formulas R 1 COOR 2 and R 1 OR 2 in which R 1 represents the residue of a fatty acid comprising from 8 to 29 carbon atoms, and R 2 represents a hydrocarbon-based chain , branched or unbranched, containing from 3 to 30 carbon atoms, for example purcellin oil, isononyl isononanoate, isopropyl myristate, 2-ethylhexyl palmitate, stearate octyl-2-dodecyl, octyl-2-dodecyl erucate, isostearyl isostearate; hydroxylated esters such as isostearyl lactate, octylhydroxystearate, octyldodecylhydroxystearate, diisostearyl malate, triisocetyl citrate; heptanoates, octanoates, decanoates of fatty alcohols; polyol esters, such as propylene glycol dioctanoate, neopentyl glycol diheptanoate and diethylene glycol diisononanoate; and pentaerythritol esters such as pentaerythrityl tetraisostearate; linear or branched hydrocarbons of mineral or synthetic origin, such as paraffin oils, volatile or not, and their derivatives, petroleum jelly, polydecenes, hydrogenated polyisobutene such as parleam oil; fatty alcohols having from 8 to 26 carbon atoms, such as cetyl alcohol, stearyl alcohol and their mixture (cetylstearyl alcohol), octyldodecanol, 2-butyloctanol, 2-hexyldecanol and 2-undecylpentadecanol; , oleic alcohol or linoleic alcohol; partially fluorinated hydrocarbon oils and / or silicone oils such as those described in document JP-A-2-295912; Silicone oils such as volatile or non-volatile polymethylsiloxanes (PDMS) with a linear or cyclic silicone chain, which are liquid or pasty at room temperature, in particular cyclopolydimethylsiloxanes (cyclomethicones) such as cyclohexasiloxane; polydimethylsiloxanes comprising alkyl, alkoxy or phenyl groups, during or at the end of the silicone chain, groups having from 2 to 24 carbon atoms; phenyl silicones such as phenyltrimethicones, phenyldimethicones, phenyltrimethylsiloxydiphenylsiloxanes, diphenyl-dimethicones, diphenylmethyldiphenyltrisiloxanes, 2-phenylethyltrimethylsiloxysilicates, and polymethylphenylsiloxanes; their mixtures. The term "hydrocarbon-based oil" is used in the list of the oils mentioned above, any oil predominantly comprising carbon and hydrogen atoms, and optionally ester, ether, fluoro, carboxylic acid and / or alcohol groups. The other fatty substances that may be present in the oily phase are, for example, fatty acids containing from 8 to 30 carbon atoms, such as stearic acid, lauric acid, palmitic acid and oleic acid; waxes such as lanolin, beeswax, carnauba or candelilla wax, paraffin waxes, lignite waxes or microcrystalline waxes, ceresin or ozokerite, synthetic waxes such as polyethylene waxes, Fischer-Tropsch waxes; silicone resins such as trifluoromethyl-C 1-4 -alkyldimethicone and trifluoropropyldimethicone; and silicone elastomers such as the products sold under the names KSG by the company Shin-Etsu, under the names Trefil, BY29 or EPSX by the company Dow Corning or under the names Gransil by the company Grant Industries. These fatty substances may be chosen in a varied manner by those skilled in the art in order to prepare a composition having the desired properties, for example of consistency or texture. The emulsions generally contain at least one emulsifier chosen from amphoteric, anionic, cationic or nonionic emulsifiers, used alone or as a mixture, and optionally a co-emulsifier. The emulsifiers are suitably selected depending on the emulsion to be obtained (W / O or O / W). The emulsifier and the co-emulsifier are generally present in the composition, in a proportion ranging from 0.3 to 30% by weight, and preferably from 0.5 to 20% by weight relative to the total weight of the composition.

For the W / O emulsions, examples of emulsifiers that may be mentioned include dimethicone copolyols such as the mixture of cyclomethicone and dimethicone copolyol, sold under the name DC 5225 C by the company Dow Corning, and alkyldimethicone copolyols such as Laurylmethicone copolyol sold under the name Dow Corning 5200 Formulation Aid by Dow Corning and Cetyl dimethicone copolyol sold under the name Abil EM 90 by the company Goldschmidt. It is also possible to use, as surfactant of W / O emulsions, a crosslinked solid elastomeric solid organopolysiloxane comprising at least one oxyalkylene group, such as those obtained according to the procedure of Examples 3, 4 and 8 of US Pat. No. 5,412,004 and US Pat. examples of US-A-5,811,487, including the product of Example 3 (synthetic example) of US-A-5,412,004. and such as that sold under the reference KSG 21 by Shin Etsu. For O / W emulsions, non-ionic emulsifiers such as oxyalkylenated (more particularly polyoxyethylenated) fatty acid and glycerol esters may be exemplified as emulsifiers; oxyalkylenated fatty acid and sorbitan esters; oxyalkylenated fatty acid esters (oxyethylenated and / or oxypropylenated); oxyalkylenated fatty alcohol ethers (oxyethylenated and / or oxypropylenated); sugar esters such as sucrose stearate; and mixtures thereof such as the mixture of glyceryl stearate and PEG-40 stearate. In a known manner, the cosmetic or dermatological composition that may be used may also contain adjuvants which are customary in the cosmetic or dermatological field, such as gelling agents, film-forming polymers, preservatives, solvents, perfumes, fillers, UV filters, bactericides, odor absorbers, dyestuffs, plant extracts and salts. The amounts of these various adjuvants are those conventionally used in the field under consideration, and for example from 0.01 to 20% of the total weight of the composition. These adjuvants, depending on their nature, can be introduced into the fatty phase and / or into the aqueous phase.

In the context of cosmetic compositions, the thermogelling copolymers may be combined with one another, or with other additional skin moisturizing agents and / or with at least one other cosmetic active agent.

As such an additional cosmetic asset, there may be mentioned active agents acting on the barrier function of the skin, the active agents promoting the hydration of the skin and the desquamating agents. In the context of dermatological compositions, the thermogelling copolymers may be combined with one another, or with other additional skin hydrating agents and / or with at least one other active ingredient, this active ingredient may be cosmetic or dermatological. As such an additional asset, there may be mentioned active agents acting on the barrier function of the skin, the active agents promoting the hydration of the skin and desquamating agents. By desquamating agent is meant any compound capable of acting either directly on desquamation by promoting exfoliation, such as 13-hydroxy acids, in particular salicylic acid and its derivatives (including n-octanoyl 5-salicylic acid); α-hydroxy acids, such as glycolic, citric, lactic, tartaric, malic or mandelic acids; urea; gentisic acid; oligofucoses; cinnamic acid; Saphora japonica extract; resveratrol; or on the enzymes involved in the desquamation or degradation of corneodesmosomes, such as glycosidases, Stratum Corneum chymotryptic enzyme (SCCE) or even other proteases (trypsin, chymotrypsin-like). Mention may be made of the chelating agents for mineral salts: EDTA; N-acyl-N, N ', N', ethylene diaminetriacetic acid; aminosulfonic compounds and in particular N- (2-hydroxyethyl) piperazine-N'-2-ethanesulfonic acid (HEPES); 2-oxothiazolidine-4-carboxylic acid derivatives (procysteine); alpha-amino acid derivatives of the glycine type (as described in EP-0 852 949, as well as the sodium methyl glycine diacetate marketed by BASF under the trade name TRILON M); honey ; sugar derivatives such as O-octanoyl-6-D-maltose and N-acetyl glucosamine. Among the active agents acting on the barrier function of the skin, or promoting the hydration of the skin, mention may be made of: - either the compounds acting on the barrier function, with a view to maintaining the hydration of the stratum corneum, or the occlusive compounds , In particular ceramides, sphingoid-based compounds, lecithins, glycosphingolipids, phospholipids, cholesterol and its derivatives, phytosterols (stigmasterol, 13-sitosterol, campesterol), essential fatty acids, 1-2 diacylglycerol 4-chromanone, pentacyclic triterpenes such as ursolic acid, petrolatum and lanolin; or compounds directly increasing the water content of Stratum Corneum, such as thralose and its derivatives, hyaluronic acid and its derivatives, glycerol, pentanediol, sodium pidolate, serine, xylitol, lactate sodium, glycerol polyacrylate, ectoin and its derivatives, chitosan, oligo- and polysaccharides, cyclic carbonates, N-lauroyl pyrrolidone carboxylic acid, and Na-benzoyl-L-arginine; or compounds that activate the sebaceous glands, such as steroid derivatives (including DHEA) and vitamin D and its derivatives.

The compositions can show their effectiveness as a non-therapeutic skin care treatment, that is, as a preventive measure. They can also be used as a non-therapeutic treatment of the skin after a manifestation of disorders of the hydration of the skin.

The composition may be presented as a non-therapeutic care product and / or makeup, and also as a lip balm.

The thermogelling copolymers may also be used in or for the implementation of a cosmetic treatment method for the non-therapeutic care and / or for the make-up of the skin, characterized in that it comprises the application on the skin at least one cosmetic composition according to the present invention comprising at least one thermogelling copolymer as defined above or a mixture thereof in all proportions. Among the makeup-type applications that the cosmetic treatment method makes it possible to envisage, there may be mentioned the foundations, blushers, eyeshadows, concealer and body make-up. The thermogelling copolymers as defined above or a mixture thereof may also be used for the preparation of a dermatological composition intended for the hydration of the skin 15 and more particularly to the treatment of dry skin or the treatment of dry skin . The following examples are given by way of illustration of the present invention, and can not limit the scope thereof. Examples The moisturizing performance of the following solutions was tested. 93% Solution A Distilled water Glycerol 7% Solution B 99% Distilled water 20 Thermolabeling polymer according to Example 1 of WO 02/09064 * 1% (* Sodium polyacrylate of 450,000 g / mol with POE grafts / POP 5 (6/39): grafting rate: 4 mol%) Solution Moisture performance measured according to the method Confocal Laser Confocal Laser Raman A 1 B 1.23 Significantly, the thermogelling copolymer used according to the present invention in solution in the water at 1%, has a moisturizing performance, measured in confocal laser Raman microscopy, higher than that of glycerol at 7% in water. Composition Example The following moisturizing cosmetic composition was carried out: Phase Al: sucrose distearate (marketed by the Company 2.0% "STEARINERIE DUBOIS") Sorbitan stearate oxyethylenated with 4 moles of oxide 1.4% ethylene ( sold under the name "TWEEN 61" by the company ICI) Stearic acid 0.75% Stearyl heptanoate (marketed by the company 5.50% DRAGOCO under the name PCL solid) Vaseline codex 2, 1 % Avocado Oil 4.50% Jojoba Oil 4.10% Volatile Silicone Oil 3.70% Vitamin E Acetate 0.50% Phase A2: Silicone Gum (marketed by the Company 4.00% DOW CORNING under the name "Q2-1403 Fluid") Perfume 0.3% Propylparaben 0.1% 5 Phase B: Methylparaben 0.30% Triethanolamine 0.40% Demineralized water qs 100.00% Phase C: Mixture of carboxyvinyl polymers 0.30% (sold under the name "CARBOPOL 980" by the company GOODRICH) Thermogelling polymer according to Example 1 of WO 2% 02/09064 (sodium polyacrylate of 450,000 g / mol with POE / POP grafts (6/39): grafting rate: 4 mol%) Demineralized water 9.70% The two phases Al and B are brought to 65 C before being associated with 2906137 18 (B in Al) under very vigorous agitation (rotor-stator). After checking for perfect dispersion, it is possible, optionally, to homogenize the dispersion between 20 × 10 6 Pascal and 60 × 10 6 Pascal, to obtain a dispersion whose oil globule size is less than 500 nm. Phase A2 is dispersed at room temperature in the first dispersion, with vigorous stirring. Phase C, previously prepared, is then dispersed in order to gel the suspension. A moisturizing emulsion adapted for dry skin is obtained whose moisturizing action is provided by the thermogelling polymer.

Claims (9)

  1. Cosmetic use as moisturizing agent of keratin materials and more particularly of the skin of at least one water-soluble thermogelling copolymer comprising units (I) resulting from the polymerization of a monomer of formula (Ia): CH2 = CRCOX (Ia) wherein: R is H, -CH3, -C2H5, -C3H7; X represents -OH or -NH2, and units of formula (II): -CH2-CH2- (CO-X'-A) (II) wherein: X 'is an oxygen atom or a group -NH-; A denotes a random copolymer or block of ethylene oxide and of propylene oxide having a temperature of LCST type whose cloud point in water at a concentration of 1% is between 5 C and 40 C, or one of its salts.   2. Use according to claim 1, characterized in that the thermogelling copolymers are acrylic acid polymers, or their salts grafted with polyethylene oxide / propylene oxide (POE / POP) chains having an LCST type temperature. .   3. Use according to claim 1 or 2, characterized in that the POE / POP chains comprise from 15 to 60, preferably from 20 to 2906, 50 propylene oxide units and from 1 to 40, preferably from 1 to 20 ethylene oxide units.   4. Use according to any one of claims 1 to 3, characterized in that the mass proportion of LCST units in the final polymer is between 5% and 70%, especially between 20% and 65%, and particularly between 30% and 60% by weight, based on the final polymer. 10   5. Use according to any one of claims 1 to 4, characterized in that the thermogelling polymer has a gelling property such that the viscosity of an aqueous solution at 5% by weight of polymer is at least 5 times higher at a temperature of between 10 ° C. and 40 ° C. than the viscosity of this same aqueous solution at 5 ° C.   6. Use according to any one of claims 1 to 5, characterized in that the salts of the polymers used are selected from sodium, magnesium, ammonium, triethanolamine, and preferably the sodium salt.   7. Use according to any one of claims 1 to 6, characterized in that the monomer (Ia) is selected from acrylic acid, especially in the form of sodium salt. 25   8. Use according to any one of claims 1 to 7, characterized in that the thermogelling copolymers are chosen from polyacrylic acid thermogelling copolymers, grafted sodium salt of a polyethylene oxide copolymer / propylene oxide monoxide terminated monoamine .   9. Use according to any one of claims 1 to 8, characterized in that the thermogelling copolymers are used in compositions in an amount of between 0.01% and 20% by weight, preferably between 0.1% and 10% by weight relative to the total weight of said composition. 5