Oil-in-water photoprotective emulsions containing gemini surfactants and associative polymers

Abstract

The invention relates to a photoprotective composition containing as liquid phase, an oil-in-water emulsion, emulsified with at least one dimeric surfactant comprising two surfactant units, which may be identical or different, each consisting of a hydrophilic head and a hydrophobic tail and connected to each other, via the hydrophilic heads, by means of a spacer group, at least one photoprotective system capable of screening out UV rays, containing at least one mineral nanopigment based on metal oxide, and optionally at least one organic, preferably hydrosoluble or liposoluble UV-A and/or UV-B screening agent, and at least one associative polymer comprising at least one C 8-40 fatty chain, and also to a process for preparing such a photoprotective composition.

1 . A photoprotective composition for protecting the skin and/or the hair against UV radiation, comprising:
 as liquid phase, an oil-in-water emulsion, emulsified with at least one dimeric surfactant comprising two surfactant units, which are identical or different, each comprising a hydrophilic head and a hydrophobic tail and connected to each other, via the hydrophilic heads, by means of a spacer group, said dimeric surfactant being an anionic dimeric surfactant of formula (I):   
       
         
           
           
               
               
           
         
         in which
 R 1  and R 3  each represent a linear or branched C 5 -C 25  alkyl group, which is saturated or having up to two non-vicinal unsaturations, 
 R 2  represents a C 1-12  alkylene group, 
 X and Y each represent a group (C 2 H 4 O) x (C 3 H 6 O) y —RF with x=0-15, y=0-10, x+y≧1, and RF═—SO 3 M, —CH 2 —CO 2 M, —P(O)(OM) 2 , H, —C 3 H 6 SO 3 M or a —CH 2 (CHOH) 4 CH 2 OH group when x+y=0, and 
 M represents an alkali metal ion, (alkyl)ammonium, alkanolammonium, H or a ½ alkaline-earth metal ion, the concentration of the dimeric surfactant(s) being between 0.01% and 4% by weight relative to the total weight of the photoprotective composition,
 a photoprotective system which screens out UV rays, comprising at least one mineral nanopigment based on metal oxide, and 
 at least one associative polymer comprising at least one C 8-40  fatty chain, which is an anionic, cationic or amphoteric polymer or a non-ionic polymer selected from the group consisting of hydroxypropyl guars modified with groups comprising at least one fatty chain, copolymers of vinylpyrrolidone and of fatty-chain hydrophobic monomers, copolymers of C 1 -C 6  alkyl methacrylates or acrylates and of amphiphilic monomers comprising at least one fatty chain, copolymers of hydrophilic methacrylates or acrylates and of hydrophobic monomers comprising at least one fatty chain, and copolymers of PEG-180, of tetramethoxymethylglycouril and of laureth-50 or octoxynol-40, 
 
 
         the concentration of the associative polymer(s) being between 0.01% and 10% by weight relative to the total weight of the photoprotective composition. 
       
     
     
         2 . The photoprotective composition according to  claim 1 , wherein the dimeric surfactant is a surfactant of formula (I): 
       
         
           
           
               
               
           
         
         in which: 
         R 1  and R 3  are identical and each represent a linear C 8-16  alkyl group, R 2  represents a C 2-8  alkylene group, X and Y each represent a group (C 2 H 4 O) x —RF with x=10-15 and RF═—SO 3 M, in which M represents an alkali metal ion. 
       
     
     
         3 . The photoprotective composition according to  claim 2 , wherein the dimeric surfactant is sodium dicocoylethylenediamine PEG-15 sulfate (INCI name) corresponding to the following formula: 
       
         
           
           
               
               
           
         
       
     
     
         4 . The photoprotective composition according to  claim 1 , wherein the concentration of the dimeric surfactant(s) is between 0.05% and 3% by weight relative to the total weight of the photoprotective composition. 
     
     
         5 . The photoprotective composition according to  claim 1 , wherein the associative polymers comprising at least one C 8-40  fatty chain are anionic or nonionic polymers. 
     
     
         6 . The photoprotective composition according to  claim 5 , wherein the anionic associative polymers are selected from the group consisting of copolymers of (meth)acrylic acid and of allylic ethers of C 8-30  fatty alcohols, copolymers of unsaturated carboxylic acids and of unsaturated C 10-30  alkyl carboxylates, terpolymers of maleic anhydride/C 30-38  α-olefin/alkyl maleate, acrylic terpolymers of an αβ-unsaturated carboxylic acid, of a non-surfactant α,β-unsaturated monomer other than this acid and of a nonionic surfactant monomer obtained by reacting an ethylenically unsaturated monoisocyanate and a monohydric surfactant, and copolymers of α,β-unsaturated carboxylic acids and of oxyalkylenated fatty alkyl carboxylates. 
     
     
         7 . The photoprotective composition according to  claim 6 , comprising as anionic associative polymer, an acrylic terpolymer of an α,β-unsaturated carboxylic acid, of a non-surfactant α,β-unsaturated monomer other than the acid and of a nonionic surfactant monomer obtained by reaction of an ethylenically unsaturated monoisocyanate and of a monohydric surfactant. 
     
     
         8 . The photoprotective composition according to  claim 1 , wherein the concentration of the associative polymer(s) is between 0.1% and 5% by weight relative to the total weight of the photoprotective composition. 
     
     
         9 . The photoprotective composition according to  claim 1 , wherein the metal oxide-based nanopigment(s) is (are) selected from the group consisting of titanium oxide, iron oxide, zinc oxide, zirconium oxide and cerium oxide, which are optionally coated. 
     
     
         10 . The photoprotective composition according to  claim 9 , wherein the metal oxide-based nanopigments are nanopigments based on amorphous or crystalline titanium dioxide. 
     
     
         11 . The photoprotective composition according to  claim 1 , wherein the nanopigment concentration is between 0.5% and 10% by weight relative to the total weight of the photoprotective composition. 
     
     
         12 . The photoprotective composition according to  claim 1 , wherein the photoprotective system capable of screening out UV rays also contains at least one organic UV-A and/or UV-B screening agent. 
     
     
         13 . The photoprotective composition according to  claim 12 , wherein the organic UV-A and/or UV-B screening agent(s) is (are) selected from the group consisting of cinnamic derivatives, dibenzoylmethane derivatives, salicylic derivatives, benzylidenecamphor derivatives, triazine derivatives, benzophenone derivatives, β,β′-diphenylacrylate derivatives, benzotriazole derivatives, benzalmalonate derivatives, 4,4-diarylbutadienes, bis-benzoxazolyl derivatives, methylenebis(hydroxyphenylbenzotriazole) derivatives, phenylbenzimidazole derivatives, anthranilic derivatives, imidazoline derivatives, p-aminobenzoic acid derivatives, screening hydrocarbon-based polymers and screening silicones, α-alkylstyrene-based dimers, and mixtures of these screening agents. 
     
     
         14 . The photoprotective composition according to  claim 13 , wherein the concentration of UV-A and/or UV-B screening agents is between 0.1% and 30% by weight relative to the total weight of the photoprotective composition. 
     
     
         15 . The photoprotective composition according to  claim 1 , further comprising agents for artificially tanning and/or browning the skin. 
     
     
         16 . The photoprotective composition according to  claim 1 , having a viscosity, measured at 25° C. using a Brookfield viscometer with a No. 7 needle, of less than 200 mPa·s. 
     
     
         17 . The photoprotective composition according to  claim 16 , having a viscosity, measured at 25° C. using a Brookfield viscometer with a No. 7 needle, between 10 and 180 mPa·s. 
     
     
         18 . A process for preparing a photoprotective composition according to  claim 1 , comprising homogenizing, at a temperature of between 40 and 70° C. and using a mixer or a homogenizer of rotor-stator type, an oil phase optionally comprising:
 (a)(1) said at least one dimeric surfactant, 
 (a)(2) one or more organic UV-screening agents, and 
 (a)(3) said at least one nanopigment; and an aqueous phase optionally comprising: 
 (b)(1) said at least one dimeric surfactant, 
 (b)(2) one or more organic UV-screening agents, and 
 (b)(3) said at least one nanopigment; 
 wherein (1) at least one of the phases comprises one or more of said at least one dimeric surfactant, and (2) said at least one associative polymer is incorporated either into the aqueous phase or into the oil phase before homogenization, or into a fine emulsion obtained, after homogenizing and cooling to a temperature of between 30 and 40° C. 
 
     
     
         19 . The process according to  claim 18 , wherein one or more nanopigments are incorporated in pulverulent form into the water-in-oil emulsion, via a second step of homogenization of the composition.