Oil-in-water emulsion sunscreen cosmetics

Abstract

The present invention provides an oil-in-water emulsion sunscreen composition which is capable of achieving high SPF by blending a large amount of a hydrophobized ultraviolet scattering agent into the oil phase, while having excellent emulsion stability and excellent feeling of use at the same time. A cosmetic composition according to the present invention is characterized by being an oil-in-water emulsion sunscreen composition which contains (A) from 0.05% by mass to 1% by mass of a water-soluble alkyl substituted polysaccharide derivative, (B) a hydrophobized ultraviolet scattering agent and (C) an ionic surfactant, wherein the hydrophobized ultraviolet scattering agent (B) is dispersed in the oil phase.

Description

[Technical Field]

[0001] The present invention relates to an oil-in-water emulsion sunscreen cosmetic. More specifically, the present invention relates to an oil-in-water emulsion sunscreen cosmetic containing a hydrophobically treated UV scattering agent, which can incorporate a high amount of the UV scattering agent into the internal phase (oil phase) while maintaining the fresh feel that is characteristic of oil-in-water emulsions. [Background technology]

[0002] Oil-in-water emulsion sunscreen cosmetics, in which UV scattering agents are dispersed in the internal phase (oil phase), are useful as formulation systems that can achieve both a refreshing feel when used and UV protection effects, but when attempting to incorporate a large amount of UV scattering agent to increase UV protection performance (hereinafter simply referred to as "SPF"), a large amount of surfactant (emulsifier) ​​may also be required. Since the incorporation of a large amount of surfactant can cause stickiness, various measures have been taken to improve the feel when used.

[0003] Patent Document 1 describes that in an oil-in-water emulsion cosmetic containing a hydrophobically treated powder, by incorporating an alkyl cellulose that has been hydrophobically modified with an alkyl group having 14 to 22 carbon atoms as an emulsifier, the cosmetic exhibits a fresh feel when used and can stably emulsify the oil phase containing the powder, even without substantially incorporating a hydrophilic surfactant. However, when attempting to incorporate a larger amount of UV scattering agent into the internal phase in order to achieve a higher SPF, it has been difficult to maintain emulsion stability and usability. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-199453 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in view of the above circumstances, and aims to provide an oil-in-water emulsion sunscreen cosmetic that can achieve a high SPF by incorporating a hydrophobically treated UV scattering agent in a high proportion in the oil phase, while also exhibiting excellent emulsion stability and a pleasant feel when used. [Means for solving the problem]

[0006] In order to solve the above problems, the present inventors conducted extensive research and found that by incorporating a water-soluble alkyl-substituted polysaccharide derivative in combination with an ionic surfactant in an oil-in-water emulsion cosmetic, it is possible to stably incorporate a high amount of a hydrophobized UV scattering agent in the oil phase without impairing the fresh feel of the oil-in-water emulsion, thereby completing the present invention.

[0007] That is, the present invention provides: (A) a water-soluble alkyl-substituted polysaccharide derivative, (B) a hydrophobic treated ultraviolet scattering agent, (C) an ionic surfactant, The present invention provides an oil-in-water emulsion sunscreen cosmetic, characterized in that the (B) ultraviolet scattering agent is dispersed in an oil phase. [Effects of the Invention]

[0008] By adopting the above-described configuration, the oil-in-water emulsion sunscreen cosmetic of the present invention can uniformly and stably incorporate a high amount of the hydrophobized UV scattering agent into the oil phase without impairing the fresh feeling of use of the oil-in-water emulsion.

[0009] Furthermore, in the oil-in-water emulsion sunscreen cosmetic of the present invention, the feel during use can be improved by incorporating an aqueous phase thickener in addition to the components (A) to (C). According to the present invention, a high amount of UV scattering agent can be incorporated, making it possible to achieve a high SPF without incorporating an UV absorber, thereby realizing a sunscreen cosmetic that is "UV absorber-free" or "non-chemical formula." DETAILED DESCRIPTION OF THE INVENTION

[0010] The oil-in-water emulsion sunscreen cosmetic of the present invention (hereinafter simply referred to as "cosmetic") is characterized by containing, as essential ingredients, (A) a water-soluble alkyl-substituted polysaccharide derivative, (B) a hydrophobized UV scattering agent, and (C) an ionic surfactant. Each of the components constituting the cosmetic of the present invention is described in detail below.

[0011] <(A) Water-soluble alkyl-substituted polysaccharide derivative> The water-soluble alkyl-substituted polysaccharide derivative (A) (hereinafter simply referred to as "component (A)") used in the cosmetic of the present invention is not particularly limited, but examples include hydrophobically modified alkyl cellulose and hydrophobically modified sulfonated polysaccharide derivatives.

[0012] The hydrophobically modified alkyl cellulose is preferably an alkyl cellulose hydrophobically modified with an alkyl group having 14 to 22 carbon atoms. More specifically, it is a compound in which a long-chain alkyl group, which is a hydrophobic group, is introduced into a water-soluble cellulose ether derivative, and is preferably represented by the following general formula (I): [ka] [In the formula, R may be the same or different and is a hydrogen atom, an alkyl group having 1 to 4 carbon atoms, a group -[CH2CH(CH3)O] m A is one or more groups selected from -H (wherein m is an integer of 1 to 5, preferably 1 to 3), -CH2CH2OH, and -CH2CH(OH)CH2OR' (wherein R' is an alkyl group having 14 to 22 carbon atoms), but must include the -CH2CH(OH)CH2OR' group. q -(q is an integer of 1 to 3, preferably 1), and n is an integer of 100 to 10,000, preferably 500 to 5,000.]

[0013] The method for producing the hydrophobically modified alkyl cellulose of the formula (I) generally involves the step of: 1) preparing a base water-soluble cellulose ether derivative, specifically, methyl cellulose (wherein R is a hydrogen atom or a methyl group), ethyl cellulose (wherein R is a hydrogen atom or an ethyl group), propyl cellulose (wherein R is a hydrogen atom or a propyl group), butyl cellulose (wherein R is a hydrogen atom or a butyl group), hydroxypropyl cellulose (wherein R is a hydrogen atom or a hydroxypropyl group (group -[CHCH(CH)O] m -H (wherein m is an integer of 1 to 5, preferably 1 to 3))], hydroxypropyl methylcellulose (wherein R is a hydrogen atom, a methyl group, or a hydroxypropyl group (group -[CHCH(CH)O] m -H (wherein m is an integer of 1 to 5, preferably 1 to 3)) or the like, with a compound for introducing a long-chain alkyl group having 14 to 22 carbon atoms, specifically, a long-chain alkyl glycidyl ether of the following formula (II), in the presence of an alkali catalyst, to obtain the compound. [ka] [R' is an alkyl group having 14 to 22 carbon atoms.]

[0014] The content of the -CH2CH(OH)CH2OR' group introduced into the hydrophobically modified alkyl cellulose of the present invention is preferably about 0.1 to 5.0% by mass based on the total mass of the hydrophobically modified alkyl cellulose. To achieve this content, the molar ratio of the water-soluble cellulose ester derivative and the long-chain alkyl glycidyl ether during the reaction, the reaction time, the type of alkali catalyst, and other factors may be appropriately selected. After the reaction, the reaction product may be subjected to purification steps such as neutralization, filtration, washing, drying, and sieving.

[0015] Among the above water-soluble cellulose ether derivatives, it is particularly preferable to select hydroxypropylmethylcellulose (wherein R in formula (I) is a hydrogen atom, a methyl group, a -[CH2CH(CH3)O] group, m H, and the group -CH2CH(OH)CH2OR', and q of the group A is 1, and A is a methylene group). Furthermore, R' in the long-chain alkyl glycidyl ether of formula (II) is an alkyl group having 14 to 22 carbon atoms, preferably an alkyl group having 14 to 20 carbon atoms, and more preferably a stearyl group having 18 carbon atoms (-C 18 H 37 If the alkyl group R' has less than 14 carbon atoms or 23 or more carbon atoms, the emulsion stability of the obtained hydrophobically modified alkyl cellulose may become insufficient.

[0016] The weight average molecular weight of the hydrophobically modified alkyl cellulose is preferably 100,000 to 1,000,000, more preferably 300,000 to 800,000, and even more preferably 550,000 to 750,000.

[0017] The hydrophobically modified sulfonated polysaccharide derivative preferably has a polysaccharide or a derivative thereof as a basic skeleton in which some or all of the hydrogen atoms of the hydroxyl groups have been substituted with the following substituents (a) and (b). The substituent (a) is preferably a glyceryl ether group having a hydrophobic moiety selected from an alkyl glyceryl ether group having a linear or branched alkyl group with 10 to 40 carbon atoms and an alkenyl glyceryl ether group having a linear or branched alkenyl group with 10 to 40 carbon atoms. The substituent (b) is preferably a sulfoalkyl group having 1 to 5 carbon atoms, which may be substituted with a hydroxyl group, or a salt thereof. Here, "water-soluble" refers to a compound that dissolves in water at 25°C at a concentration of 0.001% by mass or more.

[0018] Specific examples of the substituent (a) include, but are not limited to, a 2-hydroxy-3-alkoxypropyl group, a 2-alkoxy-1-(hydroxymethyl)ethyl group, a 2-hydroxy-3-alkenyloxypropyl group, and a 2-alkenyloxy-1-(hydroxymethyl)ethyl group. The alkyl or alkenyl group having 10 to 40 carbon atoms substituting these glyceryl ether groups is preferably a linear or branched alkyl or alkenyl group having 12 to 36 carbon atoms, more preferably 16 to 24 carbon atoms, and among these, an alkyl group is preferred, and a linear alkyl group is more preferred.

[0019] Specific examples of the substituent (b) include, but are not limited to, a 2-sulfoethyl group, a 3-sulfopropyl group, a 3-sulfo-2-hydroxypropyl group, a 2-sulfo-1-(hydroxymethyl)ethyl group, and the like, all or a part of which may be a salt with an alkali metal such as Na or K, an alkaline earth metal such as Ca or Mg, an organic cation group such as an amine, an ammonium ion, or the like.

[0020] The degree of substitution with the substituent (a) is preferably 0.001 to 1 per constituent monosaccharide residue, more preferably 0.002 to 0.5, and even more preferably 0.003 to 0.1. The degree of substitution with the substituent (b) is preferably 0.01 to 2.5 per constituent monosaccharide residue, more preferably 0.02 to 2, and even more preferably 0.1 to 1.5. The ratio of the number of the substituents (a) to the number of the substituents (b) is preferably 1:1,000 to 100:1, more preferably 1:500 to 10:1, and even more preferably 1:300 to 10:1.

[0021] The polysaccharide or its derivative that serves as the basic skeleton of the hydrophobically modified sulfonated polysaccharide derivative is not particularly limited, and examples thereof include cellulose, hydroxyethyl cellulose, methyl cellulose, ethyl cellulose, and hydroxypropyl cellulose. The weight-average molecular weight of these polysaccharides or their derivatives is preferably 10,000 to 10,000,000, more preferably 100,000 to 5,000,000, and even more preferably 300,000 to 2,000,000.

[0022] Component (A) used in the cosmetic preparation of the present invention is not particularly limited, but examples include hydrophobically modified alkylcelluloses such as stearoxy hydroxypropyl methylcellulose and laureth-13PG hydroxyethyl cellulose; and hydrophobically modified sulfonated polysaccharide derivatives such as stearoxy PG hydroxyethyl cellulose sulfonate. Among these, stearoxy hydroxypropyl methylcellulose and stearoxy PG hydroxyethyl cellulose sulfonate are more preferred.

[0023] In the present invention, commercially available products can also be used as component (A). For example, examples of stearoxy hydroxypropyl methylcellulose include Sangelose 60L (manufactured by Daido Chemical Industry Co., Ltd.) and Sangelose 90L (manufactured by Daido Chemical Industry Co., Ltd.), and examples of stearoxy PG hydroxyethyl cellulose sulfonate include Poise 310 (manufactured by Kao Corporation).

[0024] The amount of component (A) in the cosmetic of the present invention is 0.05 to 1 mass % of the total amount of the cosmetic, preferably 0.1 to 0.5 mass %, and more preferably 0.1 to 0.3 mass %. If it is less than 0.05 mass %, sufficient emulsion stability cannot be obtained, and if it is added in excess of 1 mass %, it is difficult to obtain further enhancement of the effect.

[0025] <(B) Hydrophobic treated UV scattering agent> The base material for the hydrophobized UV scattering agent (B) (hereinafter also referred to simply as "component (B)") used in the cosmetic of the present invention is not particularly limited as long as it is a powder having a UV scattering effect that is commonly used in sunscreen cosmetics, etc. In the cosmetic of the present invention, zinc oxide or titanium oxide powder is preferably used. The zinc oxide and titanium oxide powders are not particularly limited and can be appropriately selected from those commonly used in cosmetics.

[0026] Component (B) used in the cosmetic of the present invention is an ultraviolet scattering agent having a hydrophobic surface obtained by subjecting the surface of a substrate such as zinc oxide or titanium oxide to hydrophobic treatment. The method of surface hydrophobic treatment is not particularly limited, but examples thereof include silicone treatment with methylhydrogenpolysiloxane, methylpolysiloxane, or the like; fluorine treatment with perfluoroalkyl phosphate ester, perfluoroalcohol, or the like; amino acid treatment with N-acylglutamic acid, or the like; lecithin treatment; metal soap treatment; fatty acid treatment; alkyl phosphate ester treatment, and the like.

[0027] As the component (B) of the present invention, one or a combination of two or more types can be used.

[0028] The amount of component (B) in the cosmetic of the present invention is preferably 10 to 40% by mass, and more preferably 12 to 30% by mass, based on the total amount of the cosmetic. If it is less than 10% by mass, the UV protection effect will be insufficient, and if it exceeds 40% by mass, emulsion stability will tend to deteriorate.

[0029] Conventionally, because ionic surfactants can be irritating to the skin, nonionic surfactants have been used predominantly in leave-on cosmetics such as skin care cosmetics (see JP 2018-138600 A). Contrary to this common technical knowledge, the present invention has discovered that by combining an ionic surfactant with a water-soluble alkyl-substituted polysaccharide derivative, it is possible to stably and uniformly blend a hydrophobized UV scattering agent into the internal phase (oil phase), and also to obtain a cosmetic that is pleasant to use.

[0030] <(C) Ionic Surfactant> The ionic surfactant (C) used in the cosmetic of the present invention (hereinafter simply referred to as "component (C)") is one that is commonly used in cosmetics and can be selected from anionic surfactants, cationic surfactants, or amphoteric surfactants, and can be used alone or in combination of two or more. Furthermore, their molecular weight is not particularly limited, but is preferably 600 or less.

[0031] The anionic surfactant is not particularly limited, but examples thereof include fatty acid soaps such as sodium laurate and sodium palmitate; salts of higher alkyl sulfates such as sodium lauryl sulfate and potassium lauryl sulfate; salts of polyoxyethylene lauryl sulfate and triethanolamine; salts of alkyl ether sulfates such as sodium polyoxyethylene lauryl sulfate; N-acyl sarcosinates such as sodium lauroyl sarcosinate; sulfonates of higher fatty acid amides such as sodium N-myristoyl-N-methyl taurate, sodium stearoyl methyl taurate, sodium coconut oil fatty acid methyl tauride, and sodium lauryl methyl tauride; phosphate ester salts such as sodium polyoxyethylene oleyl ether phosphate and sodium polyoxyethylene stearyl ether phosphate; sodium di-2-ethylhexyl sulfosuccinate and monolauroyl monoethanolamine. alkylbenzenesulfonates such as sodium dodecylbenzenesulfonate and triethanolamine dodecylbenzenesulfonate; N-acylglutamic acids such as monosodium N-lauroylglutamate and sodium N-stearoyl-L-glutamate; salts of sulfate esters of higher fatty acids such as sodium hydrogenated coconut oil fatty acid glycerin sulfate; carboxylates of polyoxyethylene alkyl ethers, α-olefin sulfonates, sulfonates of higher fatty acid esters, salts of secondary alcohol sulfates, salts of sulfate esters of higher fatty acid alkylolamides, sodium lauroyl monoethanolamide succinate, ditriethanolamine N-palmitoyl aspartate, and alkali salts of coconut oil fatty acid collagen hydrolysate.

[0032] The cationic surfactant is not particularly limited, but examples thereof include alkyltrimethylammonium salts such as stearyltrimethylammonium chloride and lauryltrimethylammonium chloride; dialkyldimethylammonium salts such as distearyldimethylammonium chloride; alkylpyridinium salts such as poly(N,N'-dimethyl-3,5-methylenepiperidinium) chloride and cetylpyridinium chloride; alkyl quaternary ammonium salts, alkyldimethylbenzylammonium salts, alkylisoquinolinium salts, dialkylmorphonium salts, polyoxyethylene alkylamines, alkylamine salts, fatty acid derivatives of polyamines, fatty acid derivatives of amyl alcohol, benzalkonium chloride, benzethonium chloride, cationic polymers, β-N,N-dimethyl-N-ethylammonioethyl acrylate vinylpyrrolidone chloride copolymers, and the like.

[0033] The amphoteric surfactant is not particularly limited, but examples thereof include imidazoline-based amphoteric surfactants such as 2-undecyl-N,N,N-tris(hydroxyethylcarboxymethyl)-2-imidazoline sodium and 2-cocoyl-2-imidazolinium hydroxide-1-carboxyethyloxydisodium; betaine-based amphoteric surfactants such as 2-heptadecyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, lauryldimethylaminoacetic acid betaine, coconut oil fatty acid amidopropyl betaine, alkyl betaine, amidobetaine, and sulfobetaine; lecithin, hydrogenated soybean phospholipid, and the like.

[0034] The amount of component (C) in the cosmetic of the present invention is preferably 0.01 to 3 mass % and more preferably 0.04 to 1 mass % based on the total amount of the cosmetic. If the amount of component (C) is outside the above range, emulsion stability may decrease.

[0035] In the cosmetic of the present invention, the feeling upon use can be improved by further blending an aqueous phase thickener other than (A) the water-soluble alkyl-substituted polysaccharide derivative. The aqueous phase thickener used in the present invention is not particularly limited, but examples thereof include plant-based polymers such as gum arabic, tragacanth gum, galactan, guar gum, carrageenan, pectin, quince seed extract, and brown algae powder; microbial polymers such as xanthan gum, dextran, pullulan, and succinoglycan; animal-based polymers such as collagen, casein, albumin, and gelatin; starches such as carboxymethyl starch and methylhydroxystarch; polyvinyl alcohol, polyvinyl acetate, polyvinyl methyl ether, polyvinyl pyrrolidone, and vinyl pyrrolidone and vinyl acetate. vinyl polymers such as acrylate copolymers and carboxyvinyl polymers; acrylic polymers such as sodium polyacrylate, polyethyl acrylate, polyacrylic alkanolamine, alkyl methacrylate and dimethylaminoethyl methacrylate copolymers, poly2-acrylamido-2-methylpropanesulfonic acid, polymethacryloyloxytrimethylammonium, (acryloyldimethyltaurate ammonium / VP) copolymer, and (dimethylacrylamide / sodium acryloyldimethyltaurate) crosspolymer; and glycyrrhizic acid, alginic acid and its salts. Also included are inorganic thickeners such as bentonite, laponite, hectorite, aluminum magnesium silicate, and silicic anhydride.

[0036] In the cosmetic of the present invention, among the aqueous phase thickeners, if a thickener with low salt tolerance that causes a decrease in viscosity in the presence of electrolytes at concentrations in the range generally used in cosmetics (hereinafter also referred to as a "thickener that causes a decrease in viscosity due to an increase in electrolyte concentration") is used, a uniquely moist and refreshing feel can be obtained when the cosmetic is applied to the skin.

[0037] In the present invention, the "unique, fresh feeling when used" means that when the cosmetic is applied to the skin with the fingers or the like, the viscosity suddenly decreases and the cosmetic feels as if it is breaking down, and at the same time, the cosmetic gives an extremely fresh feeling as it spreads over the skin.

[0038] Examples of thickeners that cause a decrease in viscosity due to an increase in electrolyte concentration include, but are not limited to, vinyl polymers such as polyvinyl alcohol, polyvinyl acetate, polyvinyl methyl ether, polyvinylpyrrolidone, vinylpyrrolidone and vinyl acetate copolymers, and carboxyvinyl polymers; and acrylic polymers such as sodium polyacrylate, polyethyl acrylate, alkanolamine polyacrylate, alkyl methacrylate and dimethylaminoethyl methacrylate copolymers, poly2-acrylamido-2-methylpropanesulfonic acid, polymethacryloyloxytrimethylammonium, (ammonium acryloyldimethyltaurate / VP) copolymer, and (dimethylacrylamide / Na acryloyldimethyltaurate) crosspolymer.

[0039] The cosmetic of the present invention provides adequate emulsion stability due to the water-soluble alkyl-substituted polysaccharide derivative (A), and is a system in which components contained in the internal phase are easily released when stimulated by application of the cosmetic. Therefore, if the cosmetic of the present invention contains a thickener other than the water-soluble alkyl-substituted polysaccharide derivative (A) as an aqueous phase thickener that causes a decrease in viscosity due to an increase in electrolyte concentration, when the cosmetic is applied to the skin, the electrolyte, such as an ultraviolet scattering agent, will leak out of the internal phase and come into contact with the thickener in the aqueous phase, resulting in a sudden decrease in viscosity of the cosmetic. It is believed that this viscosity change is responsible for the unique, refreshing, melting sensation that the cosmetic of the present invention provides when applied to the skin.

[0040] In the cosmetic of the present invention, when an anionic polymer is used as an aqueous phase thickener, it tends to interact with the cationic surfactant, slightly reducing emulsion stability. Therefore, when an aqueous phase thickener is incorporated in the cosmetic of the present invention, it is more preferable to use an anionic surfactant or an amphoteric surfactant as the ionic surfactant (C).

[0041] The amount of aqueous phase thickener in the cosmetic of the present invention is preferably 0.05 to 3% by mass, more preferably 0.1 to 2% by mass, and even more preferably 0.15 to 1% by mass, based on the total amount of the cosmetic. If the amount is less than 0.05% by mass, the thickener's function (viscosity adjustment and emulsion stabilization) is not fully exerted. If the amount is more than 3% by mass, stickiness and sliminess may occur.

[0042] The oil component constituting the oil phase of the cosmetic of the present invention is not particularly limited and can be one or more oil components selected from oil components commonly used in cosmetics. The blending amount of the oil component is preferably 5 to 40% by mass, more preferably 10 to 40% by mass, and even more preferably 20 to 35% by mass, based on the total amount of the cosmetic.

[0043] In the cosmetic of the present invention, emulsion stability can be further improved by using polar oil in an amount of 55% by mass or more, preferably 70% by mass or more, and more preferably 80% by mass or more of the oil content. There is no upper limit on the proportion of polar oil in the oil content, and for example, 100% of the oil content may be polar oil.

[0044] The "polar oil" in the present invention is not particularly limited as long as it is an oil with a high polarity among oils commonly used in cosmetics, but for example, an oil with a relative dielectric constant of about 5 or more, preferably about 10 or more, is used. Typical examples of polar oils in the cosmetic of the present invention include ester oils.

[0045] Suitable ester oils for use in the cosmetic composition of the present invention are not particularly limited, but include tripropylene glycol dineopentanoate, isononyl isononanoate, isopropyl myristate, cetyl octanoate, octyldodecyl myristate, isopropyl palmitate, butyl stearate, hexyl laurate, myristyl myristate, decyl oleate, hexyldecyl dimethyloctanoate, cetyl lactate, myristyl lactate, lanolin acetate, isocetyl stearate, isocetyl isostearate, cholesteryl 12-hydroxystearate, cetyl ethylhexanoate, ethylene glycol di-2-ethylhexanoate, dipentaerythritol fatty acid esters, N-alkyl glycol monoisostearate, neopentyl glycol dicaprate, diisostearyl malate, glycerin di-2-heptylundecanoate, trimethylolpropane tri-2-ethylhexanoate, triisostearyl ester ... Trimethylolpropane acrylate, pentaerythrityl tetra-2-ethylhexanoate, triethylhexanoin (glyceryl tri-2-ethylhexanoate), glycerin trioctanoate, glycerin triisopalmitate, cetyl 2-ethylhexanoate, 2-ethylhexyl palmitate, glycerin trimyristate, tri-2-heptylundecanoic acid glyceride, castor oil fatty acid methyl ester, oleyl oleate, acetoglycerin amide, 2-heptylundecyl palmitate, diisobutyl adipate, N-lauroyl-L-glutamic acid-2-octyldodecyl ester, di-2-heptylundecyl adipate, ethyl laurate, di-2-ethylhexyl sebacate, 2-hexyldecyl myristate, 2-hexyldecyl palmitate, 2-hexyldecyl adipate, diisopropyl sebacate, 2-ethylhexyl succinate, triethyl citrate, and the like.

[0046] Other oils (hereinafter also referred to simply as "non-polar oils") that can be blended together with the polar oil can be one or more types selected from oils with low polarity that are commonly used in cosmetics, for example, oils with a relative dielectric constant of less than about 5.

[0047] The non-polar oil used in the cosmetic of the present invention is not particularly limited, but is preferably selected from volatile or non-volatile silicone oils and hydrocarbon oils. Examples include linear silicone oils such as polydimethylsiloxane, methylphenylpolysiloxane (diphenylsiloxyphenyltrimethicone), and methylhydrogenpolysiloxane; cyclic silicone oils such as octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane; and hydrocarbon oils such as decane, dodecane, isododecane, isohexadecane, liquid paraffin, squalane, squalene, and paraffin.

[0048] UV absorbers may irritate the skin depending on the user's constitution. In addition, UV absorbers such as ethylhexyl methoxycinnamate are known to cause irritation to the eyes if they come into contact with the eyes (see JP 2015-124172 A). In the cosmetic of the present invention, a high content of ultraviolet scattering agents can be incorporated, so that high ultraviolet protection power can be obtained even without incorporating an ultraviolet absorber. Therefore, the cosmetic of the present invention includes an embodiment in which no ultraviolet absorber is incorporated. According to the present invention, it is possible to realize a sunscreen cosmetic that is "free of ultraviolet absorbers" or "non-chemical formula."

[0049] In addition to the above-mentioned components, the cosmetic of the present invention may contain various components typically incorporated into cosmetic preparations to the extent that the effects of the present invention are not impaired. Specific examples include, but are not limited to, glycols such as propylene glycol, dipropylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, diethylene glycol, triethylene glycol, and polyethylene glycol; glycerols such as glycerin, diglycerin, and polyglycerin; sugar alcohols such as sorbitol, mannitol, maltitol, xylitol, and erythritol; sugars such as fructose, glucose, galactose, maltose, lactose, and trehalose; natural pigments such as chlorophyll and β-carotene; vitamins such as magnesium ascorbyl phosphate, ascorbyl glucoside, vitamin B6 hydrochloride, and pantothenyl ethyl ether; pharmaceuticals such as disinfectants, anti-inflammatory agents, preservatives, plant extracts, amino acids, and cooling agents; lower alcohols such as ethanol and isopropyl alcohol; and aromatic alcohols such as phenoxyethanol and benzyl alcohol.

[0050] Lower alcohols such as ethanol may be used to improve powder dispersibility. In the cosmetic of the present invention, since the powder is present in the oil phase, a cosmetic with good powder dispersibility can be obtained without blending lower alcohols. Therefore, even when ethanol is blended, its content is preferably 5% by mass or less, more preferably 3% by mass or less, and even more preferably 1% by mass or less, based on the total amount of the cosmetic. By reducing the amount of ethanol blended, a low-irritation cosmetic can be achieved.

[0051] The cosmetic of the present invention can be prepared according to a method commonly used for oil-in-water emulsion cosmetics, i.e., by separately mixing the aqueous phase component and the oil phase component, and then emulsifying the aqueous phase component by adding the oil phase component while stirring the aqueous phase component.

[0052] The cosmetic of the present invention is not particularly limited, but it is generally preferred that the cosmetic has an internal phase (oil phase) with an average particle size of about 15 μm or less.

[0053] The cosmetic of the present invention can be suitably used in various formulations such as cream, emulsion, liquid, etc. The product form can be a skin care cosmetic having a sunscreen effect, or a makeup cosmetic such as a makeup base or foundation having a sunscreen effect. [Example]

[0054] The present invention will be described in more detail below with reference to specific examples, but the present invention is not limited to these examples. The blending amounts are expressed in mass % unless otherwise specified.

[0055] Oil-in-water emulsion cosmetics were prepared by conventional methods according to the formulations shown in Tables 1 to 3 below, and their properties were evaluated according to the following evaluation methods and criteria. The results are also shown in the tables.

[0056] 1. Emulsion stability: Dispersibility of hydrophobic treated UV scattering agent The condition of the sample immediately after preparation and the condition of the sample filled in a screw tube and observed two weeks later were evaluated visually. <Evaluation criteria> A: Stable emulsification was achieved, and no separation or aggregation was observed over time. B: Stable emulsification was achieved, and slight separation and aggregation were observed over time, but this did not pose any problems in use. C: Stable emulsification was achieved, but separation and aggregation were observed over time. D: Unable to emulsify.

[0057] 2. Evaluation method for "unique, refreshing feel when used" Each sample of the Examples and Comparative Examples was actually used by a panel of five experts, who evaluated the feel of use. Each panelist was asked to rate the feel of use on a scale of one to five according to the following evaluation criteria, and the total score was used to make a judgment based on the following evaluation criteria. <Evaluation criteria> 5: Excellent. 4: Excellent. 3: Normal. 2: Inferior. 1: Very poor. <Evaluation criteria> A: A total score of 20 or more. B: Total score is 15 to 19 points. C: Total score is 14 points or less.

[0058] [Table 1]

[0059] [Table 2]

[0060] [Table 3]

[0061] As shown in Tables 1 to 3 above, when an ionic surfactant (anionic surfactant, cationic surfactant, or amphoteric surfactant) was added (Examples 1 to 18), excellent emulsion stability was exhibited. On the other hand, when no surfactant was added (Comparative Example 1) or a nonionic surfactant was added (Comparative Examples 2 to 4), emulsion stability was poor. Furthermore, when a thickener that reduces viscosity with an increase in electrolyte concentration was added (Examples 1 to 14), a unique, refreshing feeling of melting was obtained when applied to the skin. When a highly salt-tolerant aqueous phase thickener (succinoglycan) was added as a thickener (Examples 15 to 17) or when no aqueous phase thickener was added (Example 18), a refreshing feeling of use was obtained, although the feeling of crumbling was not observed when applied to the skin. Furthermore, it was confirmed that excellent emulsion stability and feel in use were obtained even when the blending amount of the hydrophobic treated UV scattering agent was increased from 12.5 mass % to 17.5, 20, 22.5, or 30 mass % (Examples 11 to 14). When the molecular weight of the ionic surfactant added was 600 or less (Examples 1 to 6, 8, 11 to 18), superior emulsion stability was observed compared to when the molecular weight was greater than 600 (Examples 9 and 10). On the other hand, when the cationic surfactant coexisted with the aqueous phase thickener, which was an anionic acrylic polymer, even when the molecular weight was 600 or less, slight separation and aggregation over time were observed, but sufficient emulsion stability was maintained (Example 7).

Claims

1. (A) 0.05 to 1% by mass of hydrophobic hydroxypropyl methylcellulose relative to the total amount of the cosmetic; (B) 10 to 40% by mass of a hydrophobic treated ultraviolet scattering agent relative to the total amount of the cosmetic, and (C) an ionic surfactant, An oil-in-water emulsion sunscreen cosmetic, characterized in that the hydrophobized UV scattering agent (B) is dispersed in an oil phase.

2. 2. The cosmetic according to claim 1, wherein the blending amount of the ionic surfactant (C) is 0.01 to 3% by mass based on the total amount of the cosmetic.

3. 3. The cosmetic preparation according to claim 1, wherein the molecular weight of the ionic surfactant (C) is 600 or less.

4. The cosmetic preparation according to claim 1 , wherein the ionic surfactant (C) is an anionic surfactant or an amphoteric surfactant.

5. The cosmetic preparation according to claim 1 , further comprising an aqueous phase thickener other than the component (A).

6. The cosmetic preparation according to claim 5, wherein the aqueous phase thickener is a thickener whose viscosity decreases with an increase in electrolyte concentration.

7. The cosmetic preparation according to claim 6, wherein the thickener whose viscosity decreases with an increase in electrolyte concentration is an acrylic polymer or a vinyl polymer.

8. The cosmetic according to claim 1 , wherein the proportion of polar oil in the oil content is 55 mass % or more.

9. The cosmetic preparation according to claim 1 , wherein the blending amount of ethanol is 5% by mass or less.

10. The cosmetic preparation according to claim 1 , which does not contain an ultraviolet absorber.

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