Oil-in-water emulsion cosmetic

Abstract

Provided is an oil-in-water emulsion cosmetic that has high water resistance and ultraviolet protection power even with no ultraviolet scattering agent blended therein, and that demonstrates excellent usability and emulsion stability. An oil-in-water emulsion cosmetic according to the present invention is characterized by containing: (A) a fatty acid that is solid at 25°C and has 16 or more carbon atoms; (B) a basic compound that forms a fatty acid soap by pairing with a carboxylic acid anion of the fatty acid (A); and (C) a polar oil. Said cosmetic is also characterized in that: the polar oil (C) contains (C1) an ultraviolet absorber; the content of a surfactant other than the fatty acid soap composed of the fatty acid (A) and the basic compound (B) is less than 0.1 mass%; and the content of an ultraviolet scattering agent is less than 1 mass%.

Description

Oil-in-water emulsified cosmetic

[0001] The present invention relates to an oil-in-water emulsified cosmetic. More specifically, the present invention relates to an oil-in-water emulsified cosmetic that has high water resistance and ultraviolet protection without blending an ultraviolet scattering agent, and is also excellent in usability and emulsion stability.

[0002] Oil-in-water emulsified cosmetics are widely used in external skin preparations such as skin care and body care that are directly applied to the skin, because they provide a refreshing and fresh feeling when applied to the skin. In recent years, since protection of the skin from ultraviolet rays has become a common practice, the importance of UV care has been increasing also in oil-in-water emulsified cosmetics.

[0003] When an ultraviolet scattering agent is blended into an oil-in-water emulsified cosmetic, it is a common practice to subject the surface of inorganic powder such as fine particulate titanium oxide or zinc oxide to hydrophobic treatment, and disperse the treated powder into the internal oil phase of the oil-in-water emulsified cosmetic, in order to achieve excellent freshness and a refreshing use feel. For example, a dispersion is prepared by adding the hydrophobized inorganic powder and various dispersants to an oil phase component, and treating the mixture with a medium stirring mill having high crushing force such as a bead mill, then the dispersion is mixed with an aqueous phase and treated with a homomixer (Patent Documents 1 to 4).

[0004] In addition, since the ultraviolet scattering agent has water-repellent performance after its surface is subjected to hydrophobic treatment, it has the advantage that water resistance can be imparted to the coating film formed when the cosmetic is applied to the skin. Due to the excellent water resistance of the coating film, functional degradation over time can be suppressed even when sweating or bathing in places such as swimming pools and the sea, and the ultraviolet protection ability can be maintained for a longer period of time.

[0005] However, when UV scattering agents are incorporated, they tend to aggregate over time, reducing the stability of the cosmetic product. Furthermore, when applied to the skin, they often cause a squeaky or white cast characteristic of inorganic powders. Additionally, achieving high UV protection requires the inclusion of large amounts of UV scattering agents, which compromises the refreshing and moisturizing feel characteristic of oil-in-water emulsion cosmetics. Therefore, although UV scattering agents are excellent ingredients for UV protection and water resistance, their use must be limited due to concerns about cosmetic stability and usability. Consequently, efforts are being made to achieve both high UV protection and water resistance without relying on UV scattering agents.

[0006] Japanese Patent Publication No. 2004-210698, Japanese Patent Publication No. 2005-247722, Japanese Patent Publication No. 2009-209123, International Publication No. 2012 / 157694

[0007] The present invention aims to provide an oil-in-water emulsion cosmetic that has high water resistance and UV protection without the need for UV scattering agents, and also exhibits excellent usability and emulsion stability.

[0008] The inventors of the present invention have conducted extensive research to solve the aforementioned problems and have found that by forming a fatty acid soap by combining a specific fatty acid with a basic compound, and by emulsifying a polar oil containing an ultraviolet absorber with the fatty acid soap alone without substantially adding any surfactants other than the fatty acid soap, it is possible to obtain an oil-in-water emulsion cosmetic that achieves high water resistance and ultraviolet protection even without containing an ultraviolet scattering agent, and furthermore, has excellent usability and emulsification stability, thus completing the present invention.

[0009] In other words, the present invention provides an oil-in-water emulsion cosmetic comprising (A) a fatty acid that is solid at 25°C and has 16 or more carbon atoms, (B) a basic compound that pairs with the carboxylic acid anion of the fatty acid (A) to form a fatty acid soap, and (C) a polar oil, wherein the polar oil (C) contains (C1) an ultraviolet absorber, the amount of surfactants other than the fatty acid soap composed of (A) the fatty acid and (B) the basic compound is less than 0.1% by mass, and the amount of ultraviolet scattering agent is less than 1% by mass.

[0010] The oil-in-water emulsion cosmetic of the present invention contains (A) a fatty acid and (B) a basic compound, and the fatty acid soap generated from these allows for the stable and large-scale emulsification of a polar oil containing (C) an ultraviolet absorber. Therefore, high ultraviolet protection can be achieved without the inclusion of ultraviolet scattering agents, and problems such as squeaking and white cast caused by ultraviolet scattering agents do not occur.

[0011] Furthermore, conventional methods for improving water resistance in oil-in-water emulsion cosmetics include incorporating film-forming agents, ultraviolet scattering agents, or core-corona type microgels (for example, the core-corona type microgel disclosed in International Publication No. 2018 / 180179) to improve the strength and water repellency of the applied film. However, even with the incorporation of these components, sufficient water resistance may not be obtained, or the moisturizing effect may be compromised. The oil-in-water emulsion cosmetic of the present invention exhibits high water resistance when applied to the skin, as a fatty acid soap consisting of (A) a fatty acid and (B) a basic compound uniformly covers the surface of the applied film.

[0012] The oil-in-water emulsion cosmetic composition of the present invention (hereinafter sometimes referred to as "cosmetic composition") contains (A) fatty acids, (B) basic compounds, and (C) polar oils in specific amounts, and is substantially free of surfactants other than fatty acid soaps produced from (A) fatty acids and (B) basic compounds, and is also substantially free of ultraviolet scattering agents. The components constituting the oil-in-water emulsion cosmetic composition of the present invention will be described in detail below.

[0013] <(A) Fatty Acids> The (A) fatty acids incorporated into the cosmetic composition of the present invention are fatty acids that are solid at 25°C and have 16 or more carbon atoms. Here, "solid at 25°C" means having no fluidity at 25°C, and includes being solid or semi-solid (paste-like, etc.) at 25°C. The number of carbon atoms in (A) fatty acids is 16 or more. There is no particular upper limit to the number of carbon atoms, but for example, 28 or less is preferred, 24 or less is more preferred, and 22 or less is even more preferred.

[0014] Examples of fatty acids (A) include palmitic acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, and montanic acid. Among these, it is preferable that one or more selected from palmitic acid, stearic acid, arachidic acid, and behenic acid be (A). Lauric acid and myristic acid, which are solid at 25°C but have fewer than 16 carbon atoms, or isostearic acid, which is liquid at 25°C but has 16 or more carbon atoms, do not fall under the category of fatty acids (A).

[0015] In the oil-in-water emulsion cosmetic composition of the present invention, the preferred lower limit for the amount of (A) fatty acid is 0.05% by mass or more, 0.15% by mass or more, or 0.25% by mass or more, relative to the total amount of the cosmetic composition, and the preferred upper limit is 10% by mass or less, 4% by mass or less, or 2% by mass or less. Therefore, the blending amount range can be 0.05 to 10% by mass, 0.15 to 4% by mass, 0.25 to 2% by mass, etc.

[0016] <(B) Basic Compounds> The (B) basic compounds incorporated into the cosmetic composition of the present invention are components that pair with the carboxylic acid anion of the (A) fatty acid to form a fatty acid soap. The (B) basic compounds are compounds that exhibit basicity in aqueous solution and include inorganic bases and organic bases having a basic amino group. Typical inorganic bases include sodium hydroxide, potassium hydroxide, calcium hydroxide, and lithium hydroxide. Examples of organic bases include amines such as 2-amino-2-methyl-1,3-propanediol (AMPD), monoethanolamine, diethanolamine, triethanolamine, triisopropanolamine, and tetrahydroxypropylethylenediamine, as well as basic amino acids such as arginine, lysine, and histidine, and amino acid derivatives such as sodium methyltaurate.

[0017] Among these, it is preferable that one or more selected from sodium hydroxide, potassium hydroxide, 2-amino-2-methyl-1,3-propanediol, triethanolamine, sodium methyltaurate, arginine, and tetrahydroxypropylethylenediamine be used.

[0018] In the oil-in-water emulsion cosmetic composition of the present invention, the amount of (B) basic compound can be preferably lowered to 0.01% by mass or more, 0.05% by mass or more, or 0.1% by mass or more, relative to the total amount of the cosmetic composition, and preferably uppered to 5% by mass or less, 2% by mass or less, or 1% by mass or less. Therefore, the blending amount range can be 0.01 to 5% by mass, 0.05 to 2% by mass, 0.1 to 1% by mass, etc.

[0019] <(C) Polar Oil> The (C) polar oil incorporated into the cosmetic composition of the present invention refers to an oil that has a hydrophilic (polar) functional group in its molecule and is commonly used in cosmetics. The IOB of the (C) polar oil is preferably 0.01 or higher, and more preferably 0.1 or higher. Here, IOB is an abbreviation for Inorganic / Organic Balance, which is a value that represents the ratio of the inorganic value to the organic value and serves as an indicator of the degree of polarity of the organic compound. Specifically, the IOB value is expressed as IOB value = inorganic value / organic value. For each of the "inorganic value" and "organic value," for example, an "organic value" of 20 is assigned to one carbon atom in a molecule, and an "inorganic value" of 100 is assigned to one hydroxyl group. The "inorganic value" and "organic value" are set according to the type of atom or functional group, and the IOB value of an organic compound can be calculated by summing the "inorganic value" and "organic value" of all atoms and functional groups in the organic compound (see, for example, Yoshio Koda, "Organic Concept Diagram - Fundamentals and Applications," pp. 11-17, Sankyo Publishing, 1984). (C) Polar oils must contain ultraviolet absorbers as part or all of them. In the following, (C) polar oils will be explained in detail by dividing them into "(c1) ultraviolet absorbers" and "(c2) polar oils other than ultraviolet absorbers."

[0020] (c1) UV absorber The cosmetic composition of the present invention is based on the premise that it is substantially free of UV scattering agents, and in order to achieve a sufficient UV protection effect, it is essential to include (c1) a UV absorber as part or all of (C) polar oil.

[0021] (c1) The ultraviolet absorber is not particularly limited as long as it is commonly used in cosmetics, and examples include benzoic acid derivatives, salicylic acid derivatives, cinnamic acid derivatives, dibenzoylmethane derivatives, β,β-diphenyl acrylate derivatives, benzophenone derivatives, benzylidene camphor derivatives, phenylbenzimidazole derivatives, triazine derivatives, phenylbenzotriazole derivatives, anthranyl derivatives, imidazoline derivatives, benzalmalonate derivatives, and 4,4-diarylbutadiene derivatives.

[0022] Examples of benzoic acid derivatives include ethyl para-aminobenzoate (PABA), ethyl-dihydroxypropyl PABA, ethylhexyl-dimethyl PABA, glyceryl PABA, and diethylaminohydroxybenzoyl hexyl benzoate.

[0023] Examples of salicylic acid derivatives include homosalate, ethylhexyl salicylate, and dipropylene glycol salicylate.

[0024] Examples of cinnamic acid derivatives include ethylhexyl methoxycinnamate, cresyl methoxycinnamate, 2-methylphenyl-4-methoxycinnamate, isopropyl methoxycinnamate, isoamyl methoxycinnamate, and diisopropyl methylcinnamate.

[0025] Examples of dibenzoylmethane derivatives include t-butylmethoxydibenzoylmethane.

[0026] Examples of β,β-diphenyl acrylate derivatives include octocrylene.

[0027] Examples of benzophenone derivatives include benzophenone-1, benzophenone-2, benzophenone-3 or oxybenzone, benzophenone-4, benzophenone-5, benzophenone-6, benzophenone-8, benzophenone-9, and benzophenone-12.

[0028] Examples of benzylidene camphor derivatives include 3-benzylidene camphor, 4-methylbenzylidene camphor, benzylidene camphor sulfonic acid, terephthalylidene dicamphor sulfonic acid, and polyacrylamide methylbenzylidene camphor.

[0029] Examples of phenylbenzimidazole derivatives include phenylbenzimidazole sulfonic acid and phenyldibenzimidazole tetrasulfonate disodium.

[0030] Examples of triazine derivatives include bisethylhexyloxyphenol methoxyphenyl triazine, ethylhexyl triazone, diethylhexylbutamide triazone, 2,4,6-tris(diisobutyl-4'-aminobenzalmalonate)-s-triazine, and 2,4,6-tris[4-(2-ethylhexyloxycarbonyl)anilino]-1,3,5-triazine.

[0031] Examples of phenylbenzotriazole derivatives include drometrizole trisiloxane and methylenebisbenzotriazolyltetramethylbutylphenol.

[0032] Examples of anthranil derivatives include methyl anthranilate.

[0033] Examples of imidazoline derivatives include ethylhexyl dimethoxybenzylidene dioxoimidazolidine propionate.

[0034] Examples of benzalmalonate derivatives include organopolysiloxanes having benzalmalonate functional groups (e.g., polysilicone-15).

[0035] Examples of 4,4-diarylbutadiene derivatives include 1,1-dicarboxy(2,2'-dimethylpropyl)-4,4-diphenylbutadiene.

[0036] Particularly preferred (c1) UV absorbers include one or more selected from ethylhexyl salicylate, octocrylene, ethylhexyl methoxycinnamate, cresyl methoxycinnamate, ethylhexyl triazone, t-butyl methoxydibenzoylmethane, polysilicone-15, bis-ethylhexyloxyphenol methoxyphenyl triazine, diethylamino hydroxybenzoyl hexyl benzoate, 2-methylphenyl-4-methoxycinnamate, and drometrizole trisiloxane.

[0037] In the oil-in-water emulsion cosmetic composition of the present invention, the amount of (c1) ultraviolet absorber can be preferably lowered to 1% by mass or more, 5% by mass or more, or 10% by mass or more, relative to the total amount of the cosmetic composition, and preferably uppered to 50% by mass or less, 30% by mass or less, or 20% by mass or less. Therefore, the range of the amount can be 1 to 50% by mass, 5 to 30% by mass, 10 to 20% by mass, etc.

[0038] (c2) Polar oils other than UV absorbers Examples of polar oils other than UV absorbers include butyloctyl salicylate, diisopropyl sebacate, pentaerythrityl tetraethylhexanoate, cetyl ethylhexanoate, jojoba oil, phytosteryl / octyldodecyl lauroyl glutamate, triisostearin, glyceryl diisostearate, triethylhexanoin, phytosteryl / behenyl dimer dilinoleate, phytosteryl / isostearyl / cetyl / stearyl / behenyl dimer dilinoleate, isopropyl palmitate, phytosteryl macadamia nut fatty acid, pentaerythrityl tetra(behenate / benzoate / ethylhexanoate), ethylhexyl palmitate, myristyl myristate, isopropyl myristate, tripropylene glycol dipivalate, isodecyl neopentanoate, alkyl benzoate and phenethyl benzoate. Among these, it is preferable that one or more selected from butyloctyl salicylate, isopropyl myristate, alkyl benzoate, and phenethyl benzoate be used.

[0039] In the oil-in-water emulsion cosmetic composition of the present invention, the amount of polar oil other than the ultraviolet absorber (c2) is preferably 1% by mass or more, 3% by mass or more, or 5% by mass or more relative to the total amount of the cosmetic composition as a lower limit, and preferably 70% by mass or less, 50% by mass or less, or 30% by mass or less as a upper limit. Therefore, the blending range can be 1 to 70% by mass, 3 to 50% by mass, 5 to 30% by mass, etc.

[0040] From the above, particularly preferred polar oils (C) that combine both (c1) UV absorbers and (c2) polar oils other than UV absorbers are one or more selected from ethylhexyl salicylate, butyloctyl salicylate, octocrylene, ethylhexyl methoxycinnamate, cresyl methoxycinnamate, ethylhexyl triazone, t-butyl methoxydibenzoylmethane, polysilicone-15, bis-ethylhexyloxyphenol methoxyphenyl triazine, diethylamino hydroxybenzoyl hexyl benzoate, 2-methylphenyl-4-methoxycinnamate, drometrizole trisiloxane, isopropyl myristate, alkyl benzoate, and phenethyl benzoate.

[0041] In the oil-in-water emulsion cosmetic composition of the present invention, the amount of (C) polar oil blended is preferably 1% by mass or more, 5% by mass or more, or 10% by mass or more, relative to the total amount of the cosmetic composition, and preferably 80% by mass or less, 60% by mass or less, or 40% by mass or less. Therefore, the blending amount range is 1 to 80% by mass, 5 to 60% by mass, 10 to 40% by mass, etc.

[0042] <AC Ratio> In the oil-in-water emulsion cosmetic composition of the present invention, the blending mass ratio of (A) fatty acid to (C) polar oil (hereinafter sometimes referred to as the "AC ratio") is preferably 1:10 to 1:30, more preferably 1:10 to 1:25, and even more preferably 1:10 to 1:20. An AC ratio within this range is preferable because it allows for particularly excellent emulsification stability and usability.

[0043] <Ultraviolet light scattering agent> The cosmetic of the present invention is premised on substantially not containing an ultraviolet light scattering agent. Therefore, the cosmetic of the present invention contains no ultraviolet light scattering agent at all, or contains only a small amount of ultraviolet light scattering agent. When an ultraviolet light scattering agent is contained, the content thereof is less than 1% by mass, preferably less than 0.5% by mass, based on the total mass of the cosmetic.

[0044] In the present specification, the ultraviolet light scattering agent is a fine inorganic powder having an average primary particle diameter of 10 nm to 150 nm that can physically reflect and scatter ultraviolet light, and examples thereof include titanium oxide, zinc oxide, cerium oxide, and the like.

[0045] <Surfactants other than fatty acid soaps> The cosmetic of the present invention substantially does not contain surfactants other than fatty acid soaps (hereinafter referred to as "surfactants other than fatty acid soaps") composed of (A) a fatty acid and (B) a basic compound. This is because when a surfactant other than a fatty acid soap is blended, the fatty acid tends to precipitate, which tends to reduce water resistance. Therefore, it is preferable that the cosmetic of the present invention does not contain any surfactant other than fatty acid soap at all, and even when it is contained, it is desirable that the amount is extremely small. Specifically, the content is less than 0.1% by mass, more preferably less than 0.05% by mass, based on the total mass of the cosmetic.

[0046] In the present specification, surfactants other than fatty acid soaps refer to surfactants generally used in cosmetics, and examples thereof include polyoxyalkylene alkyl ethers (such as beheneth-20), polyalkylene glycol fatty acid esters, POE hydrogenated castor oil derivatives, POE alkyl ethers, POE / POP alkyl ethers, PEG fatty acid esters, polyglycerol fatty acid esters, POE glycerol fatty acid esters, PEG glyceryl isostearates, and silicone-based surfactants. POE, POP, and PEG are abbreviations for polyoxyethylene, polyoxypropylene, and polyethylene glycol, respectively.

[0047] In addition to the above components, the cosmetic of the present invention may contain optional components that can be blended in oil-in-water emulsified cosmetics, as long as the effects of the present invention are not inhibited. Examples of the optional components include higher alcohols, oil components other than (C) polar oil, water, thickeners, various pharmaceutical agents, antioxidants, preservatives, and fragrances.

[0048] Among these, higher alcohols function as emulsification aids and can contribute to improving the water resistance and usability of cosmetics, and are therefore preferred. Higher alcohols are not particularly limited as long as they are commonly used in cosmetics, and examples include straight-chain alcohols such as lauryl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, myristyl alcohol, oleyl alcohol, and cetostearyl alcohol; dihydric alcohols such as monostearyl glycerin ether (batyl alcohol); and branched-chain alcohols such as 2-decyltetradecinol, hexyldecanol, isostearyl alcohol, and octyldodecanol. In the present invention, behenyl alcohol and batyl alcohol are particularly preferred.

[0049] The oil-in-water emulsion cosmetic of the present invention may contain a thickening agent, but it is preferable not to include water-swellable clay minerals, as their inclusion may worsen the usability. Specific examples of water-swellable clay minerals include smectite-type hectorite, bentonite, montmorillonite, bydelite, nontronite, and saponite. Preferred thickeners to be incorporated into the oil-in-water emulsion cosmetic of the present invention include, for example, dextrin fatty acid esters such as dextrin palmitate, dextrin oleate, and dextrin stearate; sucrose fatty acid esters such as sucrose caprylic acid, sucrose capric acid, sucrose laurate, and sucrose myristic acid; hydrocarbon oils that are solid or semi-solid at room temperature (25°C) such as petrolatum, hydrogenated palm oil, hydrogenated castor oil, hydrogenated palm kernel oil, and hydrogenated castor oil; and plant-derived thickeners such as gum arabic, tragacanth gum, galactan, carob gum, guar gum, karaya gum, carrageenan, pectin, agar, and quince seed (marmelo). Examples of molecules include: microbial polymers such as dextran, succinoglucan, pullulan, and xanthan gum; cellulosic polymers such as methylcellulose, nitrocellulose, ethylcellulose, methylhydroxypropylcellulose, hydroxyethylcellulose, sodium cellulose sulfate, hydroxypropylcellulose, sodium carboxymethylcellulose, crystalline cellulose, and cellulose powder; alginate polymers such as sodium alginate and propylene glycol alginate; and vinyl polymers such as polyvinyl alcohol, polyvinyl methyl ether, polyvinylpyrrolidone, and carboxyvinyl polymer (carbomer).

[0050] The oil-in-water emulsion cosmetic of the present invention has a refreshing feel characteristic of oil-in-water emulsions, and exhibits excellent UV protection and water resistance. Therefore, the oil-in-water emulsion cosmetic of the present invention can be suitably used in various dosage forms such as cream, lotion, and liquid. In terms of product form, for example, it can be used in skincare cosmetics containing sunscreen cosmetics, or makeup cosmetics such as makeup bases and foundations that have sunscreen effects.

[0051] The present invention will be described in more detail below with specific examples, but the present invention is not limited to the following examples. Furthermore, unless otherwise specified, the amounts used in the following examples are expressed as mass % relative to the total amount of the cosmetic composition.

[0052] <Examples 1-6 and Comparative Examples 1-3> Oil-in-water emulsion cosmetic formulations of Examples 1-6 and Comparative Examples 1-3, as described in Table 1 below, were prepared by conventional methods.

[0053] For each example of cosmetic composition, UV protection, water resistance, usability, and emulsion stability were evaluated. The evaluation methods and criteria are as follows. The evaluation results for each example of cosmetic composition are also shown in Table 1.

[0054] (1) UV protection: Samples of each example were 1.75 mg / cm² ２ The coating was applied to a PMMA substrate, and the absorbance of the formed coating film at a wavelength of 310 nm was measured using a Hitachi U-4100 Spectrophotometer manufactured by Hitachi, Ltd. <Evaluation Criteria> A: Excellent B: Average C: Poor

[0055] (2) Water resistance: Each sample was placed on an S plate (5 x 5 cm V-groove PMMA plate, SPFMASTER-PA01) at a concentration of 2 mg / cm². ２The sample was dropped onto the plate, spread with a finger for 60 seconds, and dried for 15 minutes. The absorbance (400-280 nm) was then measured using a Hitachi U-4100 Spectrophotometer manufactured by Hitachi, Ltd. An uncoated plate was used as a control, and the absorbance (Abs) was calculated using the following formula: Abs = -log(T / To) T: transmittance of the sample, To: transmittance when uncoated. The measured plate was thoroughly immersed in water with a hardness of 50-500 and stirred in the water for 30 minutes (300 rpm with a 3-1 motor). After that, it was dried for about 15-30 minutes until the water droplets on the surface were gone, and the absorbance was measured again. The Abs change rate (using the following formula) was calculated from the cumulative Abs value before and after the water bath as an indicator of water resistance. Change in absorbance before and after bathing (%) = (Summarized absorbance after bathing) / (Summarized absorbance before bathing) × 100 <Evaluation criteria> A: Change in absorbance of 95% or more B: Change in absorbance of 85% or more and less than 95% C: Change in absorbance of less than 85%

[0056] (3) A practical usage test was conducted by a panel of experts in usability, and the user experience was evaluated from the perspective of freshness and non-stickiness according to the following criteria: <Evaluation Criteria> A: Excellent B: Average C: Poor

[0057] (4) Emulsification Stability The emulsion state of each sample was visually observed after being stored at 50°C for 72 hours. <Evaluation Criteria> A: Good B: Average C: Poor

[0058]

[0059] As shown in Table 1, cosmetic compositions containing (A) a fatty acid that is solid at 25°C and has 16 or more carbon atoms, (B) a basic compound, and (C) a polar oil, and that do not contain surfactants other than fatty acid soaps or UV scattering agents, showed excellent results in all evaluation items (Examples 1-6). On the other hand, when lauric acid or myristic acid, which have fewer than 16 carbon atoms, or isostearic acid, which is liquid at 25°C, were used instead of (A) the fatty acid, it was confirmed that the emulsification stability was significantly inferior (Comparative Examples 1-3).

[0060] <Comparative Examples 4-11> The water-in-oil emulsion cosmetics of the formulations of Comparative Examples 4 and 5, as described in Table 2 below, and the oil-in-water emulsion cosmetics of the formulations of Comparative Examples 6-11 were prepared by conventional methods.

[0061] For each example of cosmetic composition, the UV protection, water resistance, usability, and emulsion stability were evaluated using the method described above. The evaluation results for each example of cosmetic composition are shown in Table 2. For comparison, the evaluation results for Example 2 are also included.

[0062]

[0063] As shown in Table 2, in the form of water-in-oil emulsion cosmetics, the outer phase lacked freshness due to its oily components, and its usability was significantly inferior compared to oil-in-water emulsion cosmetics (Comparative Examples 4 and 5). Furthermore, even in the form of oil-in-water emulsion cosmetics, when surfactants other than fatty acid soaps, such as beheneth-20, or core-corona type microgels such as (acrylamide / DMAPA acrylate / methoxyPEG methacrylate) copolymer were incorporated, the results were inferior to Example 2 in at least one evaluation item (Comparative Examples 6 to 11). In particular, even when film-forming agents (triciloxysilicate), ultraviolet scattering agents (hydrophobized fine particle titanium dioxide and fine particle zinc oxide), or core-corona type microgels ((acrylamide / DMAPA acrylate / methoxyPEG methacrylate) copolymer), which are generally considered to contribute to improved water resistance, it was confirmed that sufficient water resistance could not be obtained (Comparative Examples 6, 8, and 11).

[0064] <Examples 7-9 and Comparative Examples 12-15> Oil-in-water emulsion cosmetic formulations of Examples 7-9 and Comparative Examples 12-15, as described in Table 3 below, were prepared by conventional methods.

[0065] For each example of cosmetic composition, the UV protection, water resistance, usability, and emulsification stability were evaluated using the method described above. The evaluation results for each example of cosmetic composition are shown in Table 3. For comparison, the evaluation results for Example 2 are also included.

[0066]

[0067] As shown in Table 3, even when the amount of fatty acid (A) was changed from the formulation of Example 2, excellent results were obtained in all evaluation items of UV protection, water resistance, usability, and emulsification stability (Examples 2 and 7-9). However, it was confirmed that when a surfactant other than fatty acid soap (beheneth-20) was added at 1% by mass, water resistance was impaired, and usability and emulsification stability tended to become insufficient (Comparative Examples 12-15).

[0068] The following are examples of formulations for the oil-in-water emulsion cosmetic of the present invention. It goes without saying that the present invention is not limited in any way by the following formulation examples, but is specified by the claims. All amounts are expressed as mass percent of the total amount of the oil-in-water emulsion cosmetic.

[0069] Formula Example 1: (Ingredient Name) Amount (Mass %) Purified Water Residual Ethanol 7 Octocrylene 5 Butyl Octyl Salicylate 5 Ethylhexyl Salicylate 4.5 Isopropyl Myristate 4 Alkyl (C12-15) Benzoate 3.5 Hydrogenated Polydecene 3 t-Butyl Methoxydibenzoylmethane 2.5 Bis-Ethylhexyloxyphenol Methoxyphenyl Triazine 2.5 Behenic Acid 2 Ethylhexyl Triazone 2 Silica 1.8 Behenyl Alcohol 1 Trehalose 1 Diethylamino Hydroxybenzoyl Hexyl Benzoate 0.8 AMPD 0.3 Xanthan Gum 0.05 Peony Root Extract 0.004 Glutamic Acid 0.003 Tormentilla Root Extract 0.000475 Camellia Sinensis Leaf Extract 0.00025 Sodium Acetylated Hyaluronate 0.0001 Water-soluble collagen 0.00000035 Glycerin 0.5 Dextrin palmitate 0.5 Alkyl (C30-45) methicone 0.27 Olefin (C30-45) 0.23 Batyl alcohol 0.2 Butylene glycol 0.078 Dibutylhydroxytoluene 0.05 Tocopherol 0.00015Chlorphenesin 0.2, Benzoic acid 0.00005, Phenoxyethanol 0.0000001, Fragrance 0.06

Claims

1. An oil-in-water emulsion cosmetic comprising (A) a fatty acid that is solid at 25°C and has 16 or more carbon atoms, (B) a basic compound that pairs with the carboxylic acid anion of the fatty acid (A) to form a fatty acid soap, and (C) a polar oil, wherein the polar oil (C) contains (C1) an ultraviolet absorber, the amount of surfactants other than the fatty acid soap composed of (A) the fatty acid and (B) the basic compound is less than 0.1% by mass, and the amount of ultraviolet scattering agent is less than 1% by mass.

2. (A) The oil-in-water emulsion cosmetic composition according to claim 1, wherein the fatty acid is one or more selected from palmitic acid, stearic acid, arachidic acid, and behenic acid.

3. (C) The oil-in-water emulsion cosmetic according to claim 1, wherein the polar oil is one or more selected from ethylhexyl salicylate, butyloctyl salicylate, octocrylene, ethylhexyl methoxycinnamate, cresyl methoxycinnamate, ethylhexyl triazone, t-butyl methoxydibenzoylmethane, polysilicone-15, bis-ethylhexyloxyphenol methoxyphenyl triazine, diethylamino hydroxybenzoyl hexyl benzoate, 2-methylphenyl-4-methoxycinnamate, drometrizole trisiloxane, isopropyl myristate, alkyl benzoate, and phenethyl benzoate.

4. (B) The oil-in-water emulsion cosmetic composition according to claim 1, wherein the basic compound is one or more selected from sodium hydroxide, potassium hydroxide, 2-amino-2-methyl-1,3-propanediol, triethanolamine, sodium methyltaurate, arginine, and tetrahydroxypropylethylenediamine.

5. The oil-in-water emulsion cosmetic composition according to claim 1, further comprising a higher alcohol.

6. The oil-in-water emulsion cosmetic composition according to claim 1, wherein the blending mass ratio of (A) fatty acid and (C) polar oil is 1:10 to 1:30.

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