Oil-in-water emulsion composition

Abstract

The present invention provides an oil-in-water emulsion composition that has an excellent ultraviolet light protection effect and that imparts a good sensation when applied.　The present invention relates to an oil-in-water emulsion composition comprising a component (A), which is an ionic surfactant, a component (B), which is a hydrophobic amphiphilic substance, a component (C), which is an oil other than the component (B) and which is liquid at 25°C, a component (D), which is an inorganic powder, and a component (E), which is water, wherein the content of the component (C) in the composition is 17-50 mass%, the content of the component (D) in the composition is not less than 1.5 mass%, the content of an oil-soluble ultraviolet absorber in the composition is less than 5 mass%, and the average particle size of emulsion particles in the composition is 0.1-0.8 μm.

Description

Oil-in-water emulsion composition

[0001] The present invention relates to an oil-in-water emulsion composition.

[0002] Sunburn caused by ultraviolet rays causes problems such as browning of the skin, loss of skin elasticity, and the development of wrinkles. To prevent these problems, cosmetics containing ultraviolet absorbers have generally been developed (see, for example, Patent Document 1). However, among ultraviolet absorbers, oil-soluble ultraviolet absorbers, although having excellent ultraviolet absorbing effects, can cause skin irritation in some people.

[0003] Therefore, UV protective cosmetics using inorganic powders as UV scattering agents instead of oil-soluble UV absorbers have been developed (e.g., Patent Document 2). Cosmetics using inorganic powders and oil-soluble UV absorbers in combination are also known (e.g., Patent Document 3).

[0004] (Patent Document 1) International Publication No. 2018 / 105040 (Patent Document 2) Japanese Patent Application Laid-Open No. 10-182344 (Patent Document 3) Japanese Patent Application Laid-Open No. 2009-102236

[0005] The present invention relates to an oil-in-water emulsion composition comprising component (A): an ionic surfactant, component (B): a hydrophobic amphiphilic substance, component (C): an oil agent that is liquid at 25°C other than component (B), component (D): an inorganic powder, and component (E): water, wherein the content of component (C) in the composition is 17% by mass or more and 50% by mass or less, the content of component (D) in the composition is 1.5% by mass or more, the content of an oil-soluble ultraviolet absorber in the composition is less than 5% by mass, and the average particle size of emulsified particles in the composition is 0.1 μm or more and 0.8 μm or less.

[0006] 1 is a scanning electron microscope (SEM) image of the cross section of an emulsified particle in the oil-in-water emulsion composition obtained in Example 1. Detailed Description of the Invention

[0007] Cosmetics using UV scattering agents such as inorganic powders as UV protection agents have long been available in cream form using oily ingredients as the main base, but these have had the problem of being sticky when applied to the skin and having an unpleasant feel. Some oil-in-water cosmetics have been formulated with inorganic powders to improve the feel when applied to the skin (Patent Document 2, etc.), but this has the problem of not fully demonstrating the UV protection effect. Therefore, the current mainstream technology is the use of inorganic powders in combination with oil-soluble UV absorbers, as in Patent Document 3. However, there is a demand for products that have high UV protection effect even when the amount of oil-soluble UV absorbers is reduced or not used at all.

[0008] The present invention relates to providing an oil-in-water emulsion composition that has an excellent ultraviolet protection effect and is pleasant to use.

[0009]

[0003] The present inventors have conducted studies and found that an oil-in-water emulsion composition containing an inorganic powder as a UV protection agent does not provide sufficient UV protection effect due to aggregation of the inorganic powder within the composition or after application of the composition to the skin. Furthermore, the present inventors have found that the above-mentioned problem can be solved by controlling the contents of the oil and inorganic powder that are liquid at 25°C in the composition within predetermined ranges and further controlling the average particle size of the emulsified particles in the composition within predetermined ranges in an oil-in-water emulsion composition containing an ionic surfactant, a hydrophobic amphiphilic substance, an oil that is liquid at 25°C, an inorganic powder, and water, and having an oil-soluble UV absorber in an amount less than a predetermined amount.

[0010] The oil-in-water emulsion composition of the present invention has excellent ultraviolet protection effect and a good feeling when used, and is therefore useful as various cosmetics such as sunscreen cosmetics.

[0011] [Oil-in-water emulsion composition] The oil-in-water emulsion composition of the present invention (hereinafter also referred to simply as "the composition of the present invention") contains component (A): an ionic surfactant, component (B): a hydrophobic amphiphilic substance, component (C): an oil agent that is liquid at 25°C other than component (B), component (D): an inorganic powder, and component (E): water, wherein the content of component (C) in the composition is 17% by mass or more and 50% by mass or less, the content of component (D) in the composition is 1.5% by mass or more, the content of an oil-soluble UV absorber in the composition is less than 5% by mass, and the average particle size of the emulsified particles in the composition is 0.1 μm or more and 0.8 μm or less. By having the above-mentioned configuration, the composition of the present invention has excellent UV protection effect and a good feel in use.

[0012] The reason why the composition of the present invention exhibits the above-mentioned effects is unclear, but is thought to be as follows. The composition of the present invention is an oil-in-water emulsion composition, resulting in a composition with an excellent feel when used. Furthermore, even when the content of the oil-soluble UV absorber is less than 5% by mass, the composition exhibits excellent UV protection. The (D) inorganic powder functions as a UV protection agent, and excellent UV protection effects can be obtained by adjusting the content of component (D) in the composition to a predetermined amount or more. However, if component (D) aggregates in the composition or after application to skin, the coating uniformity decreases, and the UV protection effect also tends to decrease. In the composition of the present invention, (A) an ionic surfactant, (B) a hydrophobic amphiphilic substance, and (C) an oil agent other than component (B) that is liquid at 25°C are present together with component (D), and the composition is emulsified and dispersed in water to form a composition. This is thought to result in the formation of emulsion particles (hereinafter also referred to as "α-gel particles") having an α-gel structure in which components (C) and (D) are encapsulated in components (A) and (B). Because α-gel particles have excellent robustness and emulsion stability in water, it is believed that aggregation of component (D) can be suppressed both in the composition and after application to an object, resulting in excellent UV protection. Furthermore, it is believed that component (D) encapsulated in components (A) and (B) is dispersed in component (C). Therefore, it is believed that when the content of component (C) in the composition is 17% by mass or more, component (D) is finely dispersed, thereby improving the UV protection effect. Furthermore, when the content of component (C) in the composition is 50% by mass or less, an oil-in-water composition can be stably obtained. Furthermore, when the average particle size of the emulsified particles in the composition is within a predetermined range, it is believed that an oil-in-water emulsion composition with excellent UV protection effect can be obtained even when the content of the oil-soluble UV absorber is less than 5% by mass.

[0013] <Component (A): Ionic Surfactant> The oil-in-water emulsion composition of the present invention contains an ionic surfactant as component (A). It is believed that the inclusion of component (A) in the composition of the present invention enables components (B) to (D) to be stably emulsified and dispersed in water, thereby forming the emulsion particles.

[0014] Examples of ionic surfactants include anionic surfactants, cationic surfactants, and amphoteric surfactants. From the viewpoints of emulsification performance, suppressing stickiness to improve the feel during use, and improving storage stability, component (A) preferably contains an anionic surfactant, and is more preferably an anionic surfactant. From the viewpoints of emulsification performance and forming the above-mentioned α-gel particles, the anionic surfactant preferably contains a long-chain N-acyl glutamate. The long-chain N-acyl glutamate is preferably an N-acyl glutamate having an acyl group having 12 to 24 carbon atoms, more preferably one or more selected from the group consisting of sodium N-lauroyl-L-glutamate, sodium N-stearoyl-L-glutamate, arginine N-stearoyl-L-glutamate, sodium N-myristoyl-L-glutamate, and sodium dilauroyl glutamate, even more preferably one or more selected from the group consisting of sodium N-stearoyl-L-glutamate and arginine N-stearoyl-L-glutamate, and even more preferably arginine N-stearoyl-L-glutamate.

[0015] Examples of anionic surfactants other than long-chain N-acyl glutamates include polyoxyethylene alkyl ether sulfates, alkylbenzene sulfonates, alkyl or alkenyl sulfates, alkyl sulfonates, saturated or unsaturated fatty acid salts, alkyl or alkenyl ether carboxylates, α-sulfofatty acid salts, N-acylamino acid salts other than long-chain N-acyl glutamates, mono- or diester phosphate salts, and sulfosuccinate salts, and one or more of these may be used.

[0016] From the viewpoint of emulsifying performance and the formation of the above-mentioned α-gel particles, the content of long-chain N-acyl glutamate in the anionic surfactant is preferably 50% by mass or more, more preferably 60% by mass or more, even more preferably 70% by mass or more, still more preferably 80% by mass or more, and even more preferably 90% by mass or more, and may be 100% by mass. Note that, in this specification, the content of long-chain N-acyl glutamate refers to the content (% by mass) of long-chain N-acyl glutamic acid.

[0017] The component (A) can be used alone or in combination of two or more.

[0018] <Component (B): Hydrophobic Amphiphilic Substance> The oil-in-water emulsion composition of the present invention contains a hydrophobic amphiphilic substance as component (B). It is believed that the inclusion of component (B) in the composition of the present invention enables the formation of the emulsified particles in water together with components (A), (C), and (D), thereby enabling the production of an oil-in-water emulsion composition with excellent UV protection effect.

[0019] Examples of hydrophobic amphiphilic substances include ceramides, alcohols having from 10 to 24 carbon atoms, linear saturated fatty acids having from 10 to 24 carbon atoms, fatty acid monoglycerin esters having from 10 to 24 carbon atoms in the acyl group, monoalkyl glyceryl ethers having from 10 to 24 carbon atoms in the alkyl group, fatty acid sorbitan esters having from 10 to 24 carbon atoms in the acyl group, and fatty acid monosorbite esters having from 10 to 24 carbon atoms in the acyl group. In this specification, the number of carbon atoms in the acyl group and the number of carbon atoms in the alkyl group refer to the number of carbon atoms in one acyl group or alkyl group, and in the case of a two-chain compound, refer to the number of carbon atoms in each chain (the same applies hereinafter). Furthermore, from the viewpoint of the stability of the resulting emulsified particles, it is preferable that the HLB (hydrophilic-lipophilic balance) of component (B) is less than 5. HLB is a value indicating the affinity of a compound for water and oil and can be calculated using the Griffin method using the following formula: HLB=20×[(molecular weight of hydrophilic group contained in compound) / (molecular weight of compound)] Examples of the hydrophilic group include a hydroxy group and an ethyleneoxy group.

[0020] [Ceramides] As the ceramides, one or more types selected from the group consisting of natural ceramides and pseudo-ceramides can be used. From the viewpoint of improving UV protection effect, the ceramides described in JP 2013-53146 A are preferred. Specific examples of natural ceramides include ceramide Types 1 to 7 in which sphingosine, dihydrosphingosine, phytosphingosine, or sphingadienine is amidated (e.g., porcine and human ceramides described in Figure 2 of J. Lipid Res., 24:759 (1983) and Figure 4 of J. Lipid. Res., 35:2069 (1994)). Furthermore, N-alkyl forms (e.g., N-methyl forms) of these ceramides are also included. These ceramides can be used in the form of optically active natural (D(-) form), optically active non-natural (L(+) form), or mixtures thereof. There is no particular limitation on the relative configuration of these compounds. Particularly preferred are the compounds CERAMIDE 1, CERAMIDE 2, CERAMIDE 3, CERAMIDE 5, and CERAMIDE 6II (all of which are INCI, 8th Edition) and those represented by the following formula:

[0021]

[0022] Commercially available natural ceramides include Ceramide I, Ceramide III, Ceramide IIIA, Ceramide IIIB, Ceramide IIIC, and Ceramide VI (all manufactured by Cosmopharm Co., Ltd.), Ceramide TIC-001 (manufactured by Takasago International Corporation), CERAMIDE II (manufactured by Quest International), DS-Ceramide VI, DS-CLA-Phytoceramide, C6-Phytoceramide, DS-ceramide Y3S (manufactured by DOOSAN Co., Ltd.), and CERAMIDE2 (manufactured by Sederma Co., Ltd.).

[0023]

[0024] As the pseudo-type ceramide, a pseudo-type ceramide represented by the following general formula (1) is preferred from the viewpoint of improving the ultraviolet protection effect.

[0025]

[0026] In formula (1), R １ represents a linear, branched or cyclic saturated or unsaturated hydrocarbon group having from 10 to 22 carbon atoms which may have a hydroxy group, or a hydrogen atom. １ represents a hydrogen atom, an acetyl group, or a glyceryl group. ２ R represents a linear, branched or cyclic saturated or unsaturated hydrocarbon group having from 5 to 22 carbon atoms, which may have a hydroxy group or an amino group, or a hydrocarbon group to which a linear or branched, saturated or unsaturated fatty acid having from 8 to 22 carbon atoms, which may have a hydroxy group, is ester-bonded to the ω-terminus of the hydrocarbon group. ３ represents a hydrogen atom or an alkyl group having a total of 1 to 30 carbon atoms which may have a hydroxy group, a hydroxyalkoxy group, an alkoxy group, or an acetoxy group.

[0027] Among pseudo-type ceramides, pseudo-type ceramides represented by the following formula are preferred from the viewpoint of improving the ultraviolet protection effect.

[0028]

[0029]

[0030] [Alcohols Having 10 to 24 Carbon Atoms] Examples of alcohols having 10 to 24 carbon atoms include those having a linear or branched alkyl or alkenyl group having 10 to 24 carbon atoms. From the viewpoint of improving the UV protection effect, the number of carbon atoms is preferably 12 to 24, more preferably 14 to 22, and even more preferably 16 to 18. Examples of such alcohols include lauryl alcohol, myristyl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, and oleyl alcohol. Of these, those having a linear alkyl group are preferred, and one or more selected from the group consisting of cetyl alcohol and stearyl alcohol are more preferred, with cetyl alcohol being even more preferred.

[0031] [Straight-chain saturated fatty acids having from 10 to 24 carbon atoms] Examples of straight-chain saturated fatty acids having from 10 to 24 carbon atoms include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, etc. Of these, from the viewpoint of improving the UV protection effect, the number of carbon atoms in the straight-chain saturated fatty acid is preferably from 12 to 24, more preferably from 14 to 22, and even more preferably from 16 to 18, and one or more selected from the group consisting of palmitic acid and stearic acid are preferred.

[0032] [Fatty Acid Monoglycerol Esters Having an Acyl Group with from 10 to 24 Carbon Atoms] A fatty acid monoglycerol ester having an acyl group with from 10 to 24 carbon atoms refers to a monoester of a fatty acid with from 10 to 24 carbon atoms and glycerin, and from the viewpoint of improving the UV protection effect, the number of carbon atoms in the fatty acid is preferably from 12 to 24, more preferably from 14 to 22, and even more preferably from 16 to 22. Examples of the monoglycerol ester include glycerol monolaurate, glycerol monomyristate, glycerol monopalmitate, glycerol monostearate, glycerol monobehenate, glycerol monooleate, and glycerol monoisostearate. Among these, one or more selected from the group consisting of glycerol monopalmitate, glycerol monostearate, and glycerol monobehenate are preferred, with glycerol monobehenate being more preferred.

[0033] [Monoalkyl glyceryl ethers having an alkyl group with from 10 to 24 carbon atoms] Examples of monoalkyl glyceryl ethers having an alkyl group with from 10 to 24 carbon atoms include monodecyl glyceryl ether, monolauryl glyceryl ether, monomyristyl glyceryl ether, monocetyl glyceryl ether, monostearyl glyceryl ether, monobehenyl glyceryl ether, etc. From the viewpoint of improving the UV protection effect, the number of carbon atoms in the alkyl group is preferably from 12 to 24, more preferably from 14 to 22, and even more preferably from 16 to 22, and one or more selected from the group consisting of monocetyl glyceryl ether, monostearyl glyceryl ether, and monobehenyl glyceryl ether are preferred.

[0034] [Fatty Acid Sorbitan Esters Having an Acyl Group with 10 to 24 Carbon Atoms] A sorbitan ester of a fatty acid having an acyl group with 10 to 24 carbon atoms refers to an ester of a fatty acid with 10 to 24 carbon atoms and sorbitan. From the viewpoint of improving UV protection effect, a monoester or diester of the fatty acid is preferred, and a diester is more preferred. As the fatty acid having 10 to 24 carbon atoms, a linear saturated fatty acid is preferred, and examples thereof include lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. From the viewpoint of improving UV protection effect, the number of carbon atoms of the fatty acid is preferably 14 to 24, more preferably 16 to 24, and even more preferably 18 to 22. Examples of fatty acid sorbitan esters having an acyl group having from 10 to 24 carbon atoms include monoesters such as sorbitan monolaurate, sorbitan monomyristate, sorbitan monopalmitate, sorbitan monostearate, and sorbitan monobehenate; and diesters such as sorbitan dilaurate, sorbitan dimyristate, sorbitan dipalmitate, sorbitan distearate, and sorbitan dibehenate. Among these, one or more selected from the group consisting of sorbitan monostearate, sorbitan monobehenate, sorbitan dimyristate, sorbitan dipalmitate, sorbitan distearate, and sorbitan dibehenate are preferred, one or more selected from the group consisting of sorbitan dimyristate, sorbitan dipalmitate, sorbitan distearate, and sorbitan dibehenate are more preferred, and one or more selected from the group consisting of sorbitan dipalmitate and sorbitan distearate are even more preferred.

[0035] [Fatty Acid Monosorbite Esters Having an Acyl Group with from 10 to 24 Carbon Atoms] Fatty acid monosorbite esters having an acyl group with from 10 to 24 carbon atoms refer to monoesters of sorbitol and a fatty acid with from 10 to 24 carbon atoms. Fatty acids having from 10 to 24 carbon atoms are preferred, and examples of such fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, and behenic acid. From the viewpoint of improving the UV protection effect, the number of carbon atoms in the fatty acid is preferably from 16 to 24, more preferably from 18 to 22.

[0036] One or more types of component (B) can be used. From the viewpoint of improving the UV protection effect, component (B) preferably contains one or more types selected from the group consisting of alcohols having from 14 to 22 carbon atoms, fatty acid monoglycerin esters having from 14 to 22 carbon atoms in the acyl group, and fatty acid sorbitan esters having from 14 to 22 carbon atoms in the acyl group, more preferably contains an alcohol having from 14 to 22 carbon atoms, fatty acid monoglycerin esters having from 14 to 22 carbon atoms in the acyl group, and fatty acid sorbitan esters having from 14 to 22 carbon atoms in the acyl group, even more preferably contains cetyl alcohol, glycerin monobehenate, and sorbitan distearate, and even more preferably component (B) consists of cetyl alcohol, glycerin monobehenate, and sorbitan distearate.

[0037] <Component (C): Oil that is Liquid at 25°C> The oil-in-water emulsion composition of the present invention contains, as component (C), an oil that is liquid at 25°C other than component (B) (hereinafter, also simply referred to as "liquid oil"). As used herein, "liquid" means that the oil has fluidity at 25°C and normal pressure, and is determined to be liquid in the liquid / solid determination test according to the American Society for Testing and Materials standard "ASTM D 4359-90: Standard Test Method for Determining Whether a Material is a Liquid or Solid." By including component (C) in the composition of the present invention, it is believed that component (D) can be finely dispersed, and further, together with components (A) and (B), the emulsified particles can be formed in water, thereby obtaining an oil-in-water emulsion composition with excellent UV protection effect.

[0038] Component (C) is not particularly limited as long as it is a liquid oil used in ordinary cosmetics, and may be either a synthetic oil or a natural oil. Examples of synthetic oils include linear or branched hydrocarbon oils such as liquid paraffin, light liquid isoparaffin, squalane, and squalene; fatty acid monoesters composed of fatty acids and monohydric alcohols, such as cetyl 2-ethylhexanoate, isopropyl myristate, isopropyl palmitate, 2-ethylhexyl palmitate, 2-octyldodecyl myristate, and 2-ethylhexyl stearate; aromatic carboxylic acid monoesters composed of aromatic carboxylic acids and monohydric alcohols, such as alkyl benzoates (for example, alkyl benzoate (C12-15) "Finsorb TN" manufactured by Innospec Active Chemicals LLC); and polyhydric alcohol fatty acid esters composed of fatty acids and polyhydric alcohols, such as neopentyl glycol dicaprate and pentaerythritol tetra-2-ethylhexanoate; Examples of the natural oil include: silicone oils such as dimethylpolysiloxane, dimethylcyclopolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, and higher alcohol-modified silicone oil; fluorine-based oils such as fluoropolyether and perfluoroalkyl ether silicone; and natural oils such as vegetable oils such as jojoba oil and olive oil; and animal oils such as liquid lanolin.

[0039] In addition, component (C) may contain an oil-soluble UV absorber, but from the viewpoint of ensuring the flexibility of formulation, it is preferable that the content of the oil-soluble UV absorber is small. The oil-soluble UV absorber refers to an oil-soluble one among salicylic acid UV absorbers, para-aminobenzoic acid UV absorbers, cinnamic acid UV absorbers, benzophenone UV absorbers, triazine UV absorbers, benzoylmethane UV absorbers, and other organic UV absorbers. In this specification, "oil-soluble" means water-insoluble, and specifically means that the solubility in 100 g of water at a temperature of 25°C is 1 g or less.Specific examples of oil-soluble UV absorbers include salicylic acid-based UV absorbers such as homomenthyl salicylate (homosalate, for example, "Parsol HMS" manufactured by DSM Co., Ltd.) and octyl salicylate (for example, "Parsol EHS" manufactured by DSM Co., Ltd.); paraaminobenzoic acid-based UV absorbers such as paraaminobenzoic acid, ethyldihydroxypropylparaaminobenzoate, glycerylparaaminobenzoate, octyldimethylparaaminobenzoate, amylparadimethylaminobenzoate, and 2-ethylhexylparadimethylaminobenzoate; 2-ethylhexylparamethoxycinnamate (for example, BASF Cinnamic acid-based ultraviolet absorbers such as "Uvinal MC80" manufactured by SE), glyceryl di-paramethoxycinnamate mono-2-ethylhexanoate, methyl 2,5-diisopropylcinnamate, bis(trimethylsiloxy)silylisopentyl methyl trimethoxycinnamate, and a mixture of isopropyl paramethoxycinnamate and diisopropylcinnamate; benzophenone-based ultraviolet absorbers such as 4-(2-β-glucopyranosyloxy)propoxy-2-hydroxybenzophenone, dihydroxydimethoxybenzophenone, sodium dihydroxydimethoxybenzophenone disulfonate, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfuric acid, 2,2'-dihydroxy-4-methoxybenzophenone, 2,4-dihydroxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, and 2-hydroxy-4-N-octoxybenzophenone; 2,4,6-tris[4-(2-ethylhexyloxycarbonyl)anilino]-1,3,5-triazine (hereinafter also referred to as "ethylhexyltriazone")For example, triazine-based ultraviolet absorbers such as "Uvinal T150" manufactured by BASF SE) and bis(ethylhexyloxyphenol)methoxyphenyltriazine (for example, "TINOSORB S" manufactured by BASF SE); benzoylmethane-based ultraviolet absorbers such as 2-phenyl-benzimidazole-5-sulfuric acid, 4-isopropyldibenzoylmethane, and 4-tert-butyl-4'-methoxydibenzoylmethane (for example, "Parsol 1789" manufactured by DSM Co., Ltd.); Examples of the antiperspirant include octocrylene (e.g., "Parsol 340" manufactured by DSM Corporation), 1-(3,4-dimethoxyphenyl)-4,4-dimethyl-1,3-pentanedione, cinoxate, methyl-o-aminobenzoate, 3-(4-methylbenzylidene)camphor, 2-ethylhexyl dimethoxybenzylidene dioxoimidazolidinepropionate (e.g., "Soft Shade DH" manufactured by Ajinomoto Co., Inc.), diethylaminohydroxybenzoylhexyl benzoate (e.g., "Uvinal Aplus Granular" manufactured by BASF SE), and methylenebisbenzotriazolyltetramethylbutylphenol (e.g., "TINOSORB M" manufactured by BASF SE).

[0040] Component (C) may be used singly or in combination with other ingredients. From the viewpoint of improving the feel during use and the UV protection effect, component (C) is preferably one or more synthetic oils selected from the group consisting of linear or branched hydrocarbon oils, ester oils, and silicone oils, more preferably an ester oil, even more preferably one or more selected from the group consisting of fatty acid monoesters and aromatic carboxylic acid monoesters, still more preferably a fatty acid monoester, still more preferably one or more selected from the group consisting of cetyl 2-ethylhexanoate, isopropyl myristate, isopropyl palmitate, 2-ethylhexyl palmitate, 2-octyldodecyl myristate, and 2-ethylhexyl stearate, and still more preferably 2-ethylhexyl palmitate.

[0041] <Component (C'): Oil agent in a solid state at 25°C> The oil-in-water emulsion composition of the present invention preferably further contains, as component (C'), an oil agent in a solid state at 25°C. When the composition of the present invention contains component (C'), it is possible to form more robust α-gel particles in water. In addition, the UV protection effect is further improved. As used herein, "solid" refers to a state with no fluidity at 25°C and normal pressure, and is determined to be solid in the liquid-solid determination test according to the American Society for Testing and Materials standard "ASTM D 4359-90: Standard Test Method for Determining Whether a Material is a Liquid or Solid." Examples of component (C') include solid oils other than component (B) and oil-soluble UV absorbers, such as vegetable waxes like candelilla wax, rice wax, sunflower wax, carnauba wax, and Japan wax; animal waxes like beeswax and spermaceti; mineral waxes like montan wax and ozokerite; petroleum waxes like microcrystalline wax, paraffin, and ceresin; synthetic waxes like hydrogenated castor oil, hydrogenated jojoba oil, 12-hydroxystearic acid, stearic acid amide, silicone wax, and polyethylene wax; hexadecyl myristate, hexadecyl palmitate, etc., and one or more of these may be used. Among the above, from the viewpoint of forming more robust α-gel particles in water, component (C') preferably contains a petroleum wax, and more preferably contains one or more petroleum waxes selected from the group consisting of paraffin and ceresin.

[0042] <Component (D): Inorganic Powder> The oil-in-water emulsion composition of the present invention contains an inorganic powder as component (D). Component (D) functions as an ultraviolet protection agent, and by forming the emulsified particles in water together with components (A), (B), and (C), aggregation is suppressed, thereby making it possible to obtain an oil-in-water emulsion composition with excellent ultraviolet protection effect.

[0043] Component (D) is not limited as long as it is an ultraviolet scattering agent commonly used in cosmetics, and examples thereof include metal oxide powders such as titanium oxide powder, zinc oxide powder, and cerium oxide powder; metal powders such as aluminum powder, etc. From the viewpoint of ultraviolet protection effect, component (D) preferably contains a metal oxide powder, more preferably contains one or more selected from the group consisting of titanium oxide powder and zinc oxide powder, and even more preferably contains titanium oxide powder.

[0044] From the viewpoint of improving UV protection effect, emulsion stability, storage stability, and usability, component (D) is preferably subjected to a conventionally known surface treatment. The surface treatment is preferably a hydrophobic surface treatment, and examples thereof include fluorine compound treatment (perfluoroalkyl phosphate ester treatment, perfluoroalkylsilane treatment, perfluoropolyether treatment, fluorosilicone treatment, fluorinated silicone resin treatment, etc.), silicone treatment (methylhydrogenpolysiloxane treatment, dimethylpolysiloxane treatment, gas-phase method tetramethyltetrahydrogencyclotetrasiloxane treatment, etc.), silicone resin treatment (trimethylsiloxysilicate treatment, etc.), pendant treatment (treatment of adding an alkyl chain or the like after gas-phase method silicone treatment, etc.), silane coupling agent treatment, titanium coupling agent treatment, silane treatment (alkylsilane treatment, alkylsilazane treatment, etc.), oil treatment, N-acylated lysine treatment, polyacrylic acid treatment, metal soap treatment (stearate treatment, isostearate treatment, myristate treatment, etc.), acrylic resin treatment, and metal oxide treatment.

[0045] The surface treatment applied to component (D) may be a combination of two or more of the above surface treatments. For example, a titanium oxide powder whose surface is coated with a metal oxide such as silane or alumina, and then surface-treated with an alkylsilane, a fatty acid, or the like, can be used as component (D). From the viewpoints of improving the UV protection effect, emulsion stability, storage stability, and usability, component (D) is preferably a titanium oxide powder whose surface has been surface-treated with a metal soap such as a stearate, isostearate, or myristate.

[0046] The shape of component (D) is not particularly limited, and examples thereof include spherical, flaky, plate-like, rod-like, spindle-like, needle-like, and irregular shapes. From the viewpoint of improving UV protection effect, the average particle size of component (D) is preferably 0.02 μm or more, more preferably 0.035 μm or more, and even more preferably 0.05 μm or more. From the viewpoint of improving emulsion stability and storage stability and suppressing white residue upon application to the skin, it is preferably 0.12 μm or less, more preferably 0.1 μm or less, and even more preferably 0.08 μm or less. The average particle size of component (D) can be determined by the same method as the average particle size of emulsified particles. Details will be described later.

[0047] Commercially available surface-treated zinc oxide powders include the FINEX series (manufactured by Sakai Chemical Industry Co., Ltd.), the MZ series, and the MZY series (all manufactured by Teika Corporation). Commercially available surface-treated titanium oxide powders include the STR series (manufactured by Sakai Chemical Industry Co., Ltd.), the TTO-55 series, and the TTO-51 series (all manufactured by Ishihara Sangyo Kaisha, Ltd.), the MT series, and the MTY series (all manufactured by Teika Corporation).

[0048] <Component (E): Water> As component (E), deionized water or distilled water is preferred, but tap water, groundwater, etc. sterilized with hypochlorous acid or the like may also be used as long as the stability of the composition of the present invention is not impaired.

[0049] <Other Components> In addition to the above-mentioned components, the composition of the present invention may appropriately contain cosmetic ingredients, medicinal ingredients, and ingredients commonly used in cosmetics, as long as the purpose of the present invention is not impaired. Examples of such ingredients include surfactants other than component (A), powder dispersants, water-soluble polymers, thickeners, bactericides, moisturizers, humectants, colorants, preservatives, feel-improving agents, powders other than component (D), aqueous media other than component (E), fragrances, anti-inflammatory agents, whitening agents, antiperspirants, antioxidants, pH adjusters, etc. Examples of surfactants other than component (A) include nonionic surfactants such as polyoxyethylene sorbitan fatty acid esters and polyethylene alkyl ethers.

[0050] <Contents> The contents of each component in the oil-in-water emulsion composition of the present invention are preferably as follows, from the viewpoint of providing an oil-in-water emulsion composition that has excellent UV protection effect and is pleasant to use.

[0051] The content of component (A) in the composition is preferably 0.4% by mass or more, more preferably 1% by mass or more, and even more preferably 1.5% by mass or more, from the viewpoint of stably emulsifying and dispersing components (B) to (D) in water; and from the viewpoint of obtaining excellent UV protection effect, it is preferably 10% by mass or less, more preferably 8% by mass or less, even more preferably 5% by mass or less, and even more preferably 3.5% by mass or less. Furthermore, from the viewpoint of stably emulsifying and dispersing components (B) to (D) in water, the content of component (A) in the composition is preferably 0.4% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 8% by mass or less, even more preferably 1.5% by mass or more and 5% by mass or less, and even more preferably 1.5% by mass or more and 3.5% by mass or less. In this specification, when component (A) is an anionic surfactant and a salt of an acid compound, the content of component (A) refers to the content as the acid compound. For example, when component (A) is a long-chain N-acyl glutamic acid salt, the content of component (A) refers to the content (% by mass) of long-chain N-acyl glutamic acid.

[0052] From the viewpoint of improving storage stability and obtaining an excellent ultraviolet protection effect, the content of component (B) in the composition is preferably 1% by mass or more, more preferably 2% by mass or more, even more preferably 3% by mass or more, and preferably 12% by mass or less, more preferably 10% by mass or less, even more preferably 8% by mass or less, and still more preferably 5% by mass or less. Also, from the viewpoint of improving storage stability and obtaining an excellent ultraviolet protection effect, the content of component (B) in the composition is preferably 1% by mass or more and 12% by mass or less, more preferably 2% by mass or more and 10% by mass or less, even more preferably 3% by mass or more and 8% by mass or less, and still more preferably 3% by mass or more and 5% by mass or less.

[0053] The content of component (C) in the composition is 17% by mass or more, preferably 18% by mass or more, more preferably 19% by mass or more, and even more preferably 20% by mass or more, from the viewpoint of finely dispersing component (D) and obtaining an excellent ultraviolet protection effect. Also, from the viewpoint of stably obtaining an oil-in-water emulsion composition, it is 50% by mass or less, preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, even more preferably 30% by mass or less, and even more preferably 25% by mass or less. Also, the content of component (C) in the composition is 17% by mass or more and 50% by mass or less, but from the viewpoint of finely dispersing component (D) and obtaining an excellent ultraviolet protection effect, it is preferably 18% by mass or more and 45% by mass or less, more preferably 19% by mass or more and 40% by mass or less, even more preferably 19% by mass or more and 35% by mass or less, even more preferably 20% by mass or more and 30% by mass or less, and even more preferably 20% by mass or more and 25% by mass or less.

[0054] When the composition of the present invention contains component (C'), the content of component (C') in the composition is preferably 0.5% by mass or more, more preferably 1% by mass or more, and even more preferably 2% by mass or more from the viewpoint of forming more robust α-gel particles in water, and is preferably 10% by mass or less, more preferably 8% by mass or less, and even more preferably 5% by mass or less from the viewpoint of improving the usability. Furthermore, when the composition of the present invention contains component (C'), the content of component (C') in the composition is preferably 0.5% by mass or more and 10% by mass or less, more preferably 1% by mass or more and 8% by mass or less, and even more preferably 2% by mass or less from the viewpoint of forming more robust α-gel particles in water.

[0055] From the viewpoint of obtaining an excellent ultraviolet protection effect, the content of component (D) in the composition is 1.5% by mass or more, preferably 2% by mass or more, more preferably 3% by mass or more, even more preferably 5% by mass or more, even more preferably 8% by mass or more, and even more preferably 10% by mass or more. Also, from the viewpoint of improving emulsion stability and storage stability, it is preferably 25% by mass or less, more preferably 20% by mass or less, and even more preferably 18% by mass or less. Also, from the viewpoint of obtaining an excellent ultraviolet protection effect, the content of component (D) in the composition is 1.5% by mass or more, preferably 1.5% by mass or more and 25% by mass or less, more preferably 3% by mass or more and 20% by mass or less, even more preferably 5% by mass or more and 20% by mass or less, even more preferably 8% by mass or more and 18% by mass or less, and even more preferably 10% by mass or more and 18% by mass or less.

[0056] The content of component (E) in the composition is not particularly limited as long as it is within a range that allows stable formation of an oil-in-water emulsion composition containing components (A) to (D), but from the viewpoint of improving the feel when used, it is preferably 30% by mass or more, more preferably 40% by mass or more, and from the viewpoint of obtaining excellent UV protection effect, it is preferably 80% by mass or less, more preferably 70% by mass or less, even more preferably 60% by mass or less, and even more preferably 50% by mass or less. Furthermore, from the viewpoint of improving the feel when used, the content of component (E) in the composition is preferably 30% by mass or more and 80% by mass or less, more preferably 30% by mass or more and 70% by mass or less, even more preferably 40% by mass or more and 60% by mass or less, and even more preferably 40% by mass or more and 50% by mass or less.

[0057] From the viewpoint of obtaining the effects of the present invention, the total content of components (A) to (E) in the composition is preferably 50% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and still more preferably 85% by mass or more, and may be 100% by mass.

[0058] The mass ratio of component (D) to component (C) in the composition [(D) / (C)] is preferably 0.01 or more, more preferably 0.1 or more, and even more preferably 0.3 or more, from the viewpoint of obtaining an excellent UV protection effect. From the viewpoint of improving the UV protection ability (UV protection efficiency) per component (D) content, it is preferably 1 or less, more preferably 0.9 or less, even more preferably 0.85 or less, and even more preferably 0.8 or less. Furthermore, from the viewpoint of obtaining an excellent UV protection effect, the mass ratio of component (D) to component (C) in the composition [(D) / (C)] is preferably 0.01 or more and 1 or less, more preferably 0.1 or more and 0.9 or less, even more preferably 0.3 or more and 0.85 or less, and even more preferably 0.3 or more and 0.8 or less. Specifically, the UV protection efficiency can be evaluated by the method described in the Examples.

[0059] Furthermore, from the viewpoint of ensuring freedom of formulation, the content of the oil-soluble UV absorber in the composition of the present invention is less than 5% by mass, preferably 3% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and still more preferably 0% by mass.

[0060] <Encapsulation> The emulsion particles in the composition of the present invention are preferably emulsion particles in which components (C) and (D) are encapsulated within components (A) and (B). More preferably, the emulsion particles are emulsion particles having an α-gel structure (α-gel particles) in which components (C) and (D) are encapsulated within components (A) and (B). Because α-gel particles have excellent fastness and emulsion stability in water, it is believed that they can suppress aggregation of component (D) in the composition and after application to the skin, resulting in excellent UV protection effects. Whether the emulsion particles in the composition are emulsion particles in which components (C) and (D) are encapsulated within components (A) and (B) can be confirmed by observing the cross-section of the emulsion particles in the oil-in-water composition with a scanning electron microscope (SEM). Furthermore, whether the emulsion particles in the composition have an α-gel structure can be confirmed by X-ray diffraction (XRD). Specifically, particles that show at least one sharp diffraction peak at a Bragg angle of approximately 21 to 22° in wide-angle X-ray diffraction can be determined to have an α-gel structure.

[0061] Emulsified particles (preferably α-gel particles) in which components (C) and (D) are encapsulated in components (A) and (B) can be produced by the production method described below.

[0062] <Average particle size> From the viewpoint of obtaining an excellent UV protection effect, the average particle size of the emulsified particles in the composition of the present invention is 0.1 μm or more and 0.8 μm or less, preferably 0.1 μm or more and 0.7 μm or less, and more preferably 0.1 μm or more and 0.65 μm or less. In this specification, the average particle size means the volume median diameter (D50). The average particle size is a value measured at 25°C using a dynamic light scattering particle size distribution analyzer, and specifically, can be measured by the method described in the Examples.

[0063] [Method for Producing Oil-in-Water Emulsion Composition] The method for producing the oil-in-water emulsion composition of the present invention preferably comprises the following steps I to III in this order. This method makes it possible to form emulsion particles, preferably α-gel particles, in which components (C) and (D) are encapsulated in components (A) and (B), and to efficiently produce an oil-in-water emulsion composition that exhibits the effects of the present invention. Step I: A step of dispersing component (D): an inorganic powder in component (C): an oil agent that is liquid at 25°C other than component (B) to obtain a dispersion. Step II: A step of mixing the dispersion obtained in step I with component (A): an ionic surfactant and component (B): a hydrophobic amphiphilic substance, and mixing the obtained mixture with component (E): water under heating to obtain an emulsion. Step III: A step of cooling the emulsion obtained in step II at a cooling rate of 1°C / min or more and 300°C / min or less.

[0064] <Step I> In step I, an inorganic powder, which is component (D), is dispersed in a liquid oil, which is component (C), to obtain a dispersion. Step I allows component (D) to be finely dispersed in component (C). Devices used for dispersion in step I include high-pressure emulsifiers, ultrasonic emulsifiers, homogenizers, mills, dispersers, pitched paddles, homomixers, extruders, kneaders, and the like, which are commonly used when wet-dispersing powders in dispersion media. Among these, from the viewpoint of finely dispersing component (D) in component (C), it is preferable to use a high-pressure emulsifier, homogenizer, or mill, and it is more preferable to use a high-pressure emulsifier. This is because when a high-pressure emulsifier is used, the average particle size of the resulting emulsified particles can be easily adjusted to a desired range by adjusting the pressure conditions.

[0065] When a high-pressure emulsifier is used in step I, the pressure conditions can be set, for example, in the range of normal pressure (0 MPa) to 300 MPa. From the viewpoint of adjusting the average particle size of the resulting emulsion particles to a desired range and enhancing the ultraviolet protection effect, the pressure conditions are preferably 0 MPa or more, more preferably 30 MPa or more, even more preferably 50 MPa or more, and still more preferably 100 MPa or more, and are preferably 300 MPa or less, more preferably 250 MPa or less.

[0066] The dispersion in step I is preferably carried out under heating, although this varies depending on the type of component (C). The temperature during dispersion in step I is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of finely dispersing component (D) in component (C), and is preferably 100°C or lower, more preferably 90°C or lower, from the viewpoints of productivity and suppressing decomposition of the blended components.

[0067] <Step II> In step II, the dispersion obtained in step I is mixed with component (A) and component (B), and the resulting mixture is mixed with component (E) under heating to obtain an emulsion. The mixing temperature under heating varies depending on the types of components (B) and (C), but is preferably 60°C or higher, more preferably 70°C or higher, from the viewpoint of emulsion dispersibility and adjusting the average particle size of the resulting emulsion particles to a desired range, and is preferably 120°C or lower, more preferably 100°C or lower, from the viewpoints of productivity and suppressing decomposition of the blended components.

[0068] Examples of the apparatus used in step II include a high-pressure emulsifier, an ultrasonic emulsifier, a homomixer, etc. Among these, from the viewpoint of adjusting the average particle size of the resulting emulsion particles to a desired range, it is preferable to use a high-pressure emulsifier and a homomixer. More specifically, it is more preferable to mix the dispersion obtained in step I with component (A) and component (B) using a homomixer, then mix with component (E) under heating, and then further emulsify and disperse using a high-pressure emulsifier to obtain an emulsion. The pressure conditions and their preferred ranges when using a high-pressure emulsifier are the same as those in step I.

[0069] <Step III> In Step III, the emulsion obtained in Step II is cooled at a cooling rate of 1°C / min or more and 300°C / min or less (cooling step). Through Step III, emulsion particles having an α-gel structure in which components (C) and (D) are encapsulated in components (A) and (B) can be formed. Furthermore, when component (C') is used, component (C') is solidified in Step III, resulting in the formation of more robust emulsion particles. From the viewpoint of forming α-gel particles, the cooling rate is preferably 3°C / min or more, more preferably 5°C / min or more, even more preferably 10°C / min or more, still more preferably 30°C / min or more, even more preferably 50°C / min or more, still more preferably 100°C / min or more, still more preferably 150°C / min or more, and still more preferably 180°C / min or more, and is preferably 250°C / min or less, more preferably 230°C / min or less.

[0070] In the cooling step of Step III, a continuous rapid cooling method using a vibration-type agitation mixer, a scraped-surface heat exchanger (Onlator, manufactured by Sakura Seisakusho), a static mixer (manufactured by Noritake Company Limited), a general plate-type heat exchanger, a double-tube heat exchanger, or the like, or a method of agitation and cooling in a general blending tank can be used. Among these, a method using a vibration-type agitation mixer is preferred. The vibration-type agitation mixer is a vibration-type agitation mixer having a tubular casing, a stirrer consisting of a drive shaft and a stirring blade attached to the drive shaft, and the drive shaft is configured to vibrate in the axial direction, and the stirring blade preferably has one or more openings and / or one or more notches. In the cooling step, the emulsion obtained in Step II is preferably supplied to the vibration-type agitation mixer and continuously cooled while stirring by vibrating the stirring blade. This allows for the production of an oil-in-water emulsion composition in which emulsified particles having an α-gel structure and a desired average particle size are dispersed in water.

[0071] Examples of the high-pressure emulsifier used in Step I and Step II and the vibration-type stirring and mixing device used in the cooling step include those described in JP-A-2017-7969.

[0072] [Oil-in-water emulsion cosmetic] The oil-in-water emulsion composition of the present invention has excellent UV protection effect and is therefore useful as an oil-in-water emulsion cosmetic (hereinafter also simply referred to as "cosmetics"), and is particularly useful as an UV protection cosmetic. Specific examples of the above-mentioned cosmetic are preferably skin cosmetics applied to the skin, such as sunscreens, lotions, emulsions, creams, gels, and serums. Furthermore, the cosmetic can also be used as a sheet-type cosmetic impregnated with or applied to a sheet-type substrate such as a woven fabric or nonwoven fabric. The cosmetic of the present invention can be used by applying it to the skin, preferably the skin excluding the scalp, and more preferably the face, trunk, or limbs.

[0073] In relation to the above-described embodiments, the present invention further discloses the following oil-in-water emulsion compositions, etc.: <1> An oil-in-water emulsion composition comprising: component (A): an ionic surfactant, component (B): a hydrophobic amphiphilic substance, component (C): an oil agent that is liquid at 25°C other than component (B), component (D): an inorganic powder, and component (E): water, wherein the content of component (C) in the composition is 17% by mass or more and 50% by mass or less, the content of component (D) in the composition is 1.5% by mass or more, the content of an oil-soluble ultraviolet absorber in the composition is less than 5% by mass, and the average particle size of emulsified particles in the composition is 0.1 μm or more and 0.8 μm or less.

[0074] <2> The oil-in-water emulsion composition according to <1>, wherein component (A) is an anionic surfactant. <3> The oil-in-water emulsion composition according to <1> or <2>, wherein the mass ratio of component (D) to component (C) [(D) / (C)] is 0.01 or more and 0.8 or less. <4> The oil-in-water emulsion composition according to any one of <1> to <3>, wherein the emulsion particles are emulsion particles in which components (C) and (D) are encapsulated in components (A) and (B). <5> The oil-in-water emulsion composition according to any one of <1> to <4>, further comprising component (C'): an oily agent that is solid at 25°C. <6> The oil-in-water emulsion composition according to <5>, wherein the content of component (C') in the composition is 0.5% by mass or more and 10% by mass or less.

[0075] <7> The oil-in-water emulsion composition according to any one of <1> to <6>, wherein component (D) comprises one or more selected from the group consisting of titanium oxide powder and zinc oxide powder. <8> The oil-in-water emulsion composition according to any one of <1> to <7>, wherein the content of component (A) in the composition is 0.4% by mass or more and 10% by mass or less. <9> The oil-in-water emulsion composition according to any one of <1> to <8>, wherein the content of component (B) in the composition is 1% by mass or more and 12% by mass or less. <10> The oil-in-water emulsion composition according to any one of <1> to <9>, wherein the content of component (D) in the composition is 1.5% by mass or more and 25% by mass or less. <11> The oil-in-water emulsion composition according to any one of <1> to <9>, wherein the content of component (D) in the composition is 10% by mass or more and 18% by mass or less. <12> The oil-in-water emulsion composition according to any one of <1> to <11>, wherein the composition is a cosmetic.

[0076] The present invention will be described below with reference to examples, but the present invention is not limited to the scope of the examples. In the examples, various measurements and evaluations were carried out by the following methods.

[0077] (Average particle size) The average particle size (volume median diameter: D50) was measured using a dynamic light scattering particle size distribution analyzer "LB-500" manufactured by Horiba, Ltd. Three drops of the oil-in-water emulsion composition (cosmetic) of each example were placed in a 1 cm square measurement cell using a 2 mL dropper, and then diluted with approximately 2 mL of ion-exchanged water to prepare a measurement sample, which was used to measure the average particle size at 25°C (N=1). The refractive index of the sample was 1.446 for ethylhexyl palmitate, and the refractive index of the dispersion medium was 1.333 for water.

[0078] (Slurry absorbance) A JASCO V-750 spectrophotometer was used to measure the absorbance of the slurry obtained by diluting the oil-in-water emulsion composition (cosmetic) of each example. The oil-in-water emulsion composition was diluted 100 times with ion-exchanged water, and this was further diluted 80 times with ion-exchanged water to form a slurry, which was then filled approximately 80% into a 1 cm square measurement cell (optical path length 10 mm). The measurement cell was set in a cell holder, and the absorbance was measured in the wavelength range of 250 to 750 nm (N=1). The absorbance value at a wavelength of 315 nm is shown in Table 1. Note that an integrating sphere was not used. A higher slurry absorbance value indicates a higher UV protection effect of the emulsion composition.

[0079] (Slurry absorbance (ultraviolet protection efficiency) per 10 ppm of inorganic powder) The slurry absorbance values ​​obtained by the above method were converted into values ​​per 10 ppm of inorganic powder (component (D)) contained in the slurry, and the converted values ​​are shown in Table 1. A larger value indicates a higher ultraviolet protection ability (ultraviolet protection efficiency) per inorganic powder content in the slurry.

[0080] Example 1 (Production and Evaluation of Oil-in-Water Emulsion Composition (UV Protective Cosmetic)) <Step I> 2-ethylhexyl palmitate (component (C)), titanium oxide (component (D)), and polyhydroxystearic acid (listed in Table 1) were mixed using a disper under heating at 85°C, and then a high-pressure emulsifier ("Starburst Mini HJP-25001" manufactured by Sugino Machine Corporation) was used to obtain a dispersion in which component (D) was finely dispersed in component (C). The number of passes through the high-pressure emulsifier was 1, and the high-pressure emulsification pressure was 200 MPa. <Step II> Next, the dispersion obtained in Step I, component (A), component (B), component (C'), glycerin, 1,3-propanediol, and dextrin palmitate (listed in Table 1) were melt-mixed using a paddle under heating at 85°C to prepare mixture A. Meanwhile, water (component (E)), L-arginine, and phenoxyethanol listed in Table 1 were mixed under heating at 85°C to prepare mixture B. Mixture B was added to mixture A, and the mixture was dispersed using a homomixer. The resulting mixture was then emulsified using the high-pressure emulsifier to obtain an emulsion. The number of passes through the high-pressure emulsifier was one, and the high-pressure emulsification pressure was 200 MPa. <Step III> While maintained at 85°C, the emulsion obtained in step II was supplied to a vibration-type stirring and mixing device ("Vibromixer" manufactured by Reika Kogyo Co., Ltd.) with a transition time of 10 seconds. While stirring the emulsion by vibrating the stirring element up and down within the device, the emulsion was continuously cooled to 40°C or below at a cooling rate of 210°C / min, to obtain an oil-in-water emulsion composition (ultraviolet protection cosmetic). In the vibration-type agitation mixer, the emulsion flow rate was 4 g / sec, and the total flow rate of cooling water circulating through the cooling jacket was 8 g / sec, so that the emulsion was cooled by cooling water at a total flow rate twice the emulsion flow rate. The vibration frequency of the vibration-type agitation mixer was 20 Hz. The obtained cosmetic was evaluated using the above-mentioned method. The results are shown in Table 1. The blending amounts listed in Table 1 are the amount of active ingredient (mass %) of each component.

[0081] Examples 2 to 6, Comparative Examples 1 to 3 UV protective cosmetics were produced and evaluated in the same manner as in Example 1, except that the ingredients of the cosmetic and the emulsification pressure in Step II were changed as shown in Table 1. The results are shown in Table 1.

[0082]

[0083] The ingredients in Table 1 are as follows: *1 N-stearoyl-L-glutamic acid: Amisoft HA-P (Ajinomoto Co., Inc.) *2 Cetyl alcohol: Cetyl alcohol NX (Kyukyu Alcohol Kogyo Co., Ltd.) *3 Sorbitan distearate: Sunsoft No. 63-C (Taiyo Kagaku Co., Ltd.) *4 Glyceryl behenate: Glycerin monobehenate, Sunsoft No. 8100-C (manufactured by Taiyo Kagaku Co., Ltd.) * 5 2-ethylhexyl palmitate: Salacos P-8 (manufactured by Nisshin Oillio Group Co., Ltd.) * 6 Ceresin: Ceresin # 810K (manufactured by Nikko Rica Co., Ltd.), melting point 74 ° C. * 7 Paraffin wax: HNP-9 (manufactured by Nippon Seiro Co., Ltd.), melting point 75 ° C. * 8 Titanium oxide: MT-10EX (manufactured by Teika Co., Ltd.), alkali metal isostearate salt treatment, average particle size: 0.060 μm * 9 86% glycerin (manufactured by Kao Corporation) * 10 1,3-propanediol (manufactured by Glory Co., Ltd.) * 11 Dextrin palmitate: Leopearl KL2 (manufactured by Chiba Flour Milling Co., Ltd.) * 12 L-Arginine (manufactured by Ajinomoto Co., Inc.) * 13 Phenoxyethanol: Highsolve EPH (manufactured by Toho Chemical Industry Co., Ltd.) *14 Polyhydroxystearic acid: contained in titanium oxide MT-10EX dispersion liquid "FLT-12" (manufactured by Teika Co., Ltd.).

[0084] Table 1 shows that UV protective cosmetics comprising the oil-in-water emulsion composition of the present invention have a high UV protective effect even when the content of the oil-soluble UV absorber is less than 5% by mass. On the other hand, the cosmetics of Comparative Example 1, in which the average particle size of the emulsified particles exceeds 0.8 μm, Comparative Example 2, in which the content of component (C) is less than 17% by mass, and Comparative Example 3, in which the content of component (D) is less than 1.5% by mass, all had low UV protective effects.

[0085] FIG. 1 is a scanning electron microscope (SEM) image of the cross section of an emulsion particle in the oil-in-water emulsion composition obtained in Example 1. In FIG. 1, 1 represents α-gel, which is the outer shell of the emulsion particle and is composed of component (A) and component (B), 2 represents component (C) encapsulated in the α-gel of 1, and 3 (white particles in the image) represents component (D) dispersed in component (C) of 2. 4 represents the inner shell composed of component (C') present between 1 and 2. From this SEM image, it was determined that the emulsion particle in the composition of the present invention is an emulsion particle in which component (C) and component (D) are encapsulated in component (A) and component (B). SEM photography was performed using the following method. Specifically, a sample (oil-in-water emulsion composition) was aspirated using a glass capillary, rapidly frozen, and then fractured so that the cross section could be observed. The sample was then subjected to a sublimation treatment at -90°C for 20 minutes to prepare a specimen for observation. The sample for observation was observed and photographed using a cryo-SEM at an accelerating voltage of 1.0 kV and a magnification of 30,000 times.

[0086] Comparative Example 4: A comparison was made in which the ionic surfactant was replaced with a nonionic surfactant. That is, a composition was produced in the same manner as in Example 1, except that the ingredients of the cosmetic preparation in Example 1 were changed as shown in Table 2. However, the resulting composition was a water-in-oil type, and an oil-in-water emulsion composition could not be obtained. Furthermore, when the appearance of the resulting water-in-oil emulsion composition was visually observed, the formation of emulsified particles was not confirmed, and the formation of aggregates was observed.

[0087]

[0088] The oil-in-water emulsion composition of the present invention has excellent ultraviolet protection effect and a good feeling when used, and is therefore useful as various cosmetics such as sunscreen cosmetics.

[0089] 1: α-gel, the outer shell of an emulsion particle composed of components (A) and (B) 2: Component (C) encapsulated in α-gel at 1 ratio 3: Component (D) dispersed in component (C) at 2 ratio (white particles in the image) 4: Inner shell composed of component (C') located between components 1 and 2

Claims

1. An oil-in-water emulsion composition comprising: component (A): an ionic surfactant; component (B): a hydrophobic amphiphilic substance; component (C): an oil agent that is liquid at 25°C other than component (B); component (D): an inorganic powder; and component (E): water, wherein the content of component (C) in the composition is 17% by mass or more and 50% by mass or less; the content of component (D) in the composition is 1.5% by mass or more; the content of an oil-soluble ultraviolet absorber in the composition is less than 5% by mass; and the average particle size of emulsified particles in the composition is 0.1 μm or more and 0.8 μm or less.

2. The oil-in-water emulsion composition according to claim 1, wherein component (A) is an anionic surfactant.

3. The oil-in-water emulsion composition according to claim 1 or 2, wherein the mass ratio of component (D) to component (C) [(D) / (C)] is 0.01 or more and 0.8 or less.

4. The oil-in-water emulsion composition according to any one of claims 1 to 3, wherein the emulsion particles are emulsion particles in which component (C) and component (D) are encapsulated in component (A) and component (B).

5. The oil-in-water emulsion composition according to any one of claims 1 to 4, further comprising component (C'): an oil agent that is solid at 25°C.

6. The oil-in-water emulsion composition according to any one of claims 1 to 5, wherein component (D) comprises at least one member selected from the group consisting of titanium oxide powder and zinc oxide powder.

7. The oil-in-water emulsion composition according to any one of claims 1 to 6, which is a cosmetic.

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