Oil-in-water emulsion composition, and method for improving the water resistance and / or adhesion of a coating film of the oil-in-water emulsion composition.

Abstract

To provide an oil-in-water emulsion composition that has excellent adhesion to the skin and is water-resistant. [Solution] An oil-in-water emulsion composition characterized by containing cellulose nanofibers and fatty acids or salts thereof as emulsifiers.

Description

Technical Field

[0001] The present invention relates to an oil-in-water type emulsion composition containing specific cellulose nanofibers and a fatty acid or its salt as an emulsifier, and a method for improving the water resistance and / or adhesion of a coating film of the oil-in-water type emulsion composition.

Background Art

[0002] A dosage form emulsified by adsorbing amphiphilic solid particles onto the interface has been conventionally known as a Pickering emulsion, and its utilization has been proposed in cosmetics. The present applicant has proposed a technique for improving the dispersion state of powder adsorbed on an emulsification interface by including an acrylic polymer (Patent Document 1). In addition, the present applicant has proposed a sunscreen cosmetic that is a Pickering emulsion having resistance to physical rubbing by including a hydrophilic film-forming polymer (Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, the Pickering emulsion conventionally proposed by the present applicant is a Pickering emulsion using fine particle metal oxides, particularly silica fine particles, as an emulsifying powder. Silica fine particles have high emulsification stability and a wide variety of oil agents that can be used. However, the Pickering emulsion using silica fine particles feels squeaky during application, and there is room for improvement in the usability.

[0005] Based on the above challenges, the inventors conducted research and succeeded in obtaining a Pickering emulsion with excellent usability using cellulose nanofibers as an emulsifier. However, when cellulose nanofibers were used as an emulsifier, the resulting Pickering emulsion had problems with water resistance and adhesion to the skin, such as being susceptible to sweat and friction.

[0006] Therefore, the object of the present invention is to provide an oil-in-water emulsion composition that has excellent adhesion to the skin and is water-resistant. [Means for solving the problem]

[0007] The inventors of the present invention discovered that the above problems can be solved by adding fatty acids or salts thereof together with cellulose nanofibers, and thus arrived at the present invention.

[0008] The present invention and its preferred embodiments for solving the above problems are as follows. [1] An oil-in-water emulsion composition characterized by comprising cellulose nanofibers and a fatty acid or a salt thereof as an emulsifier. The oil-in-water emulsion composition of the present invention exhibits excellent water resistance and adhesion to the skin.

[0009] [2] The oil-in-water emulsion composition according to [1], wherein the cellulose nanofibers are adsorbed onto the emulsion interface to form a Pickering emulsion.

[0010] [3] The oil-in-water emulsion composition according to [1] or [2], wherein the content of the cellulose nanofibers is 0.05 to 1.5% by mass. By adopting the above configuration, the water resistance and adhesion to the skin of the oil-in-water emulsion composition can be improved.

[0011] [4] The oil-in-water emulsion composition according to any one of [1] to [3], wherein the content of the fatty acid or salt thereof is 0.1 to 1.5% by mass. By adopting the above configuration, the emulsification of the composition can be stabilized, improving water resistance and adhesion to the skin.

[0012] [5] The oil-in-water emulsion composition according to any one of [1] to [4], wherein the content of the cellulose nanofiber is 0.1 to 1% by mass, and the content of the fatty acid or salt thereof is 0.1 to 0.7% by mass. By adopting the above configuration, the water resistance of the oil-in-water emulsion composition can be further improved, resulting in an oil-in-water emulsion composition with an even more refreshing feel.

[0013] [6] The oil-in-water emulsion composition according to any one of [1] to [5], wherein the fatty acid or salt thereof is a fatty acid having 12 to 22 carbon atoms or a salt thereof.

[0014] [7] An oil-in-water emulsion composition for external use on the skin, as described in any one of [1] to [6].

[0015] [8] An oil-in-water emulsion composition according to any one of [1] to [7], which is a sunscreen cosmetic containing an ultraviolet absorber.

[0016] The present invention also relates to the following methods. [9] A method for improving the water resistance and / or adhesion of a coating film of an oil-in-water emulsion composition containing cellulose nanofibers as an emulsifier, characterized in that a fatty acid or a salt thereof is used as an auxiliary emulsifier when preparing the oil-in-water emulsion composition.

[10] A method for improving the water resistance and / or adhesion of a coating film of an oil-in-water emulsion composition containing a fatty acid or a salt thereof as an emulsifier, characterized in that cellulose nanofibers are used when preparing the oil-in-water emulsion composition. [Effects of the Invention]

[0017] According to the present invention, it is possible to provide an oil-in-water emulsion composition that has excellent adhesion to the skin and is water-resistant. [Brief explanation of the drawing]

[0018] [Figure 1]It is a microscopic photograph for confirming the emulsified state of the sunscreen cosmetic according to the present invention in Test Example 2. The scale bar is 10 μm.

Embodiments for Carrying Out the Invention

[0019] <Oil-in-water Emulsion Composition> The oil-in-water composition of the present invention contains cellulose nanofibers (hereinafter referred to as CNF) and a fatty acid or its salt as an emulsifier. Hereinafter, each component will be described in detail.

[0020] (1) CNF The CNF used in the present invention is cellulose fibers refined to the nanosize. The origin of CNF is not particularly limited, and plant raw materials such as wood, straw (e.g., wheat, rice, etc.), stems (e.g., corn, cotton, etc.), sugarcane, bagasse, reed, bamboo, etc., and seaweeds can be used. In the present invention, it is preferable to use CNF derived from bamboo or seaweed, and more preferably to use CNF derived from bamboo.

[0021] The fiber width of CNF is not particularly limited as long as it is generally in the nanosize (1000 nm or less). The fiber width of CNF can be, for example, within the range of 0.1 to 1000 nm. In one embodiment, the average fiber width (average fiber diameter) of CNF is preferably 1 to 1000 nm, more preferably 1 to 500 nm, and even more preferably 2 to 200 nm. In one embodiment, the average fiber length of CNF is preferably 200 nm or more, more preferably 500 nm or more. In one embodiment, the aspect ratio (average fiber length / average fiber diameter) of CNF is preferably 10 or more, more preferably 30 or more, and even more preferably 50 or more. The fiber width and fiber length can be measured based on an electron microscope image.

[0022] As the CNF in the present invention, those obtained by chemically or mechanically treating and defibrating the raw material can be used. Chemical methods for defibrillation include the introduction of carboxyl groups, phosphate groups, sulfonic acid groups, etc., hydrolysis, and enzymatic decomposition. Mechanical methods for defibrillation include underwater counter-impacting, hydraulic penetration micronization, water jet method, high-pressure homogenizer treatment, microfluidizer method, ball mill pulverization, and grinder method. In particular, the CNF used in this invention is preferably CNF produced by the underwater counter-impact method.

[0023] In the oil-in-water emulsion composition of the present invention, CNF functions as an emulsifier (emulsifying powder). That is, CNF adsorbs to the interface between the aqueous phase and the oil phase to form an emulsion interface.

[0024] In this invention, it is preferable that the CNF used is unmodified CNF. Oil-in-water emulsions containing unmodified CNF exhibit superior emulsification stability and feel compared to oil-in-water emulsions containing chemically modified CNF. Furthermore, oil-in-water emulsions containing unmodified CNF are less prone to film distortion when rubbed after application to the skin, compared to oil-in-water emulsions containing chemically modified CNF.

[0025] As the CNF used in this invention, water-dispersible CNF is preferred.

[0026] Commercially available CNF can be used in this invention. An example of a commercially available product is nanoforest-S (manufactured by Chuetsu Pulp & Paper Co., Ltd.).

[0027] The CNF content relative to the total amount of the aqueous emulsion composition is preferably 0.05% by mass or more, more preferably 0.1% by mass or more, more preferably 0.2% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, and particularly preferably 0.5% by mass or more. By adopting this form, the water resistance of the oil-in-water emulsion composition can be improved.

[0028] The CNF content relative to the total amount of the aqueous emulsion composition is preferably 1.5% by mass or less, more preferably 1.3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.8% by mass or less. By adopting this form, an oil-in-water emulsion composition with excellent water resistance and adhesion to the skin can be obtained.

[0029] The CNF content relative to the total amount of the aqueous emulsion composition is preferably 0.05 to 1.5% by mass, more preferably 0.1 to 1.3% by mass, more preferably 0.1 to 1% by mass, more preferably 0.2 to 1% by mass, more preferably 0.3 to 1% by mass, even more preferably 0.4 to 1% by mass, and particularly preferably 0.5 to 0.8% by mass. This configuration improves the water resistance and skin adhesion of the oil-in-water emulsion composition.

[0030] (2) Fatty acids or salts thereof In the present invention, the fatty acid or salt thereof preferably has 12 to 22 carbon atoms, and more preferably 16 to 18 carbon atoms.

[0031] In the present invention, the fatty acids or salts thereof can include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, and 12-hydroxystearic acid, as well as unsaturated fatty acids such as oleic acid and undecylenic acid. In the oil-in-water emulsion composition of the present invention, saturated fatty acids or salts thereof are preferably used, and in particular, it is preferable to include one or more selected from palmitic acid, stearic acid, 12-hydroxystearic acid, and salts thereof. By including fatty acids or salts thereof, the emulsification of oil-in-water emulsion compositions can be stabilized, and the adhesion of the composition to the skin can be improved.

[0032] The oil-in-water emulsion composition of the present invention may be in a form that includes a mixture of fatty acids and fatty acid salts as a fatty acid or a salt thereof, or in a form that includes only fatty acid salts. In one embodiment, it is preferable that the oil-in-water emulsion composition is in a form that includes at least a fatty acid salt as an emulsifier.

[0033] The fatty acid salt may be obtained by neutralization or by saponification. In one embodiment, a fatty acid salt may be generated by a neutralization reaction during the emulsification process of the oil-in-water emulsion composition. A specific example of this embodiment is a method in which a fatty acid salt is generated in the composition by stirring and mixing an oil phase containing fatty acids with an aqueous phase containing a strong base such as potassium hydroxide.

[0034] The content of fatty acids or their salts relative to the total amount of the oil-in-water emulsion composition is preferably 0.1% by mass or more, more preferably 0.2% by mass or more, even more preferably 0.3% by mass or more, and particularly preferably 0.4% by mass or more. This configuration improves the adhesion of the oil-in-water emulsion composition to the skin.

[0035] The content of fatty acids or their salts relative to the total amount of the oil-in-water emulsion composition is preferably 1.5% by mass or less, more preferably 1% by mass or less, even more preferably 0.8% by mass or less, and particularly preferably 0.7% by mass or less. By adopting this form, an oil-in-water emulsion composition with excellent water resistance and adhesion to the skin can be obtained.

[0036] The content of fatty acids or their salts relative to the total amount of the oil-in-water emulsion composition is preferably 0.1 to 1.5% by mass, more preferably 0.2 to 1.5% by mass, even more preferably 0.3 to 1.5% by mass, and particularly preferably 0.4 to 1% by mass. Alternatively, the content of fatty acids or their salts relative to the total amount of the oil-in-water emulsion composition may be preferably 0.1 to 1% by mass, more preferably 0.1 to 0.8% by mass, and even more preferably 0.1 to 0.7% by mass. This form stabilizes the emulsification of the composition, improving its water resistance and adhesion to the skin.

[0037] The concentration of fatty acids or their salts in the oil-in-water emulsion composition is preferably 8 mmol / kg or more, more preferably 10 mmol / kg or more, even more preferably 15 mmol / kg or more, and particularly preferably 17 mmol / kg or more. This configuration improves the adhesion of the oil-in-water emulsion composition to the skin.

[0038] The concentration of fatty acids or their salts in the oil-in-water emulsion composition is preferably 40 mmol / kg or less, more preferably 35 mmol / kg or less, even more preferably 30 mmol / kg or less, even more preferably 25 mmol / kg or less, and particularly preferably 20 mmol / kg or less. By adopting this form, an oil-in-water emulsion composition with excellent water resistance and adhesion to the skin can be obtained.

[0039] The concentration of fatty acids or their salts in the oil-in-water emulsion composition is preferably 8 to 40 mmol / kg, more preferably 10 to 35 mmol / kg, even more preferably 10 to 30 mmol / kg, even more preferably 15 to 25 mmol / kg, and particularly preferably 17 to 20 mmol / kg. This form stabilizes the emulsification of the composition, improving its water resistance and adhesion to the skin.

[0040] In the case where fatty acids and fatty acid salts are mixed, the above content and concentration should be such that the total of the fatty acids and fatty acid salts falls within the above numerical range.

[0041] Furthermore, the type of fatty acid or salt thereof contained in the oil-in-water emulsion composition of the present invention may be one type or two or more types. Furthermore, if the product contains two or more fatty acids or their salts, it is preferable that the total value of the fatty acids and their salts falls within the above-mentioned range of content and concentration.

[0042] The content of fatty acids or their salts relative to the CNF content (1x) is preferably 0.3 times or more by mass, more preferably 0.4 times or more, even more preferably 0.5 times or more, and particularly preferably 0.8 times or more. The content of fatty acids or their salts relative to the CNF content (1x) is preferably 3 times or less by mass, more preferably 2.5 times or less, even more preferably 2 times or less, and particularly preferably 1.5 times or less. The ratio of fatty acids or their salts to the CNF content (1x) is preferably 0.3 to 3 times, more preferably 0.4 to 2.5 times, even more preferably 0.5 to 2 times, even more preferably 0.5 to 1.5 times, and particularly preferably 0.8 to 1.5 times, on a mass basis. By adopting this form, an oil-in-water emulsion composition with excellent water resistance and skin adhesion can be obtained.

[0043] In one embodiment, the oil-in-water emulsion composition of the present invention comprises stearic acid or a salt thereof, and palmitic acid or a salt thereof, as emulsifiers.

[0044] (3) Form of oil-in-water emulsion composition and other components In one embodiment, the oil-in-water emulsion composition of the present invention is preferably a Pickering emulsion in which CNF is adsorbed at the emulsion interface. A Pickering emulsion refers to an emulsified composition stabilized using particles. Even if it contains other surfactants, any emulsified composition in which particles contribute to its emulsifying stability is considered a Pickering emulsion.

[0045] The oily components contained in the oil phase of the oil-in-water emulsion composition of the present invention are not particularly limited and may include liquid oils and fats, solid oils and fats, waxes, hydrocarbon oils, higher alcohols, ester oils, silicone oils, ultraviolet absorbers, and the like. The oil-in-water emulsion composition of the present invention preferably contains one or more selected from the group consisting of fatty acid esters, glycerin esters, silicone oils, hydrocarbon oils, and ultraviolet absorbers. In this case, the ultraviolet absorber is preferably a liquid ultraviolet absorber.

[0046] Examples of liquid oils include avocado oil, camellia oil, turtle oil, macadamia nut oil, corn oil, mink oil, olive oil, rapeseed oil, egg yolk oil, sesame oil, peach oil, wheat germ oil, sasanqua oil, castor oil, linseed oil, safflower oil, cottonseed oil, elm oil, meadowfoam oil, soybean oil, peanut oil, tea seed oil, kaya oil, rice bran oil, cinnamon oil, Japanese tung oil, jojoba oil, wheat germ oil, triglycerin, glyceryl trioctanoate, and glyceryl triisopalmitate.

[0047] Examples of solid fats include cocoa butter, coconut oil, horse fat, hydrogenated coconut oil, palm oil, beef tallow, sheep fat, hydrogenated beef tallow, palm kernel oil, pork fat, beef bone fat, Japanese wax kernel oil, hydrogenated oil, beef tallow, Japanese wax, and hydrogenated castor oil.

[0048] Examples of waxes include beeswax, candelilla wax, cotton wax, carnauba wax, bayberry wax, privet wax, whale wax, montan wax, rice bran wax, lanolin, kapok wax, lanolin acetate, liquid lanolin, sugarcane wax, isopropyl lanolin fatty acid, hexyl laurate, reduced lanolin, jojoba wax, hard lanolin, shellac wax, POE lanolin alcohol ether, POE lanolin alcohol acetate, POE cholesterol ether, lanolin fatty acid polyethylene glycol, and POE hydrogenated lanolin alcohol ether.

[0049] Examples of hydrocarbon oils include liquid paraffin, ozokerite, pristane, paraffin, ceresin, squalene, petrolatum, and microcrystalline wax.

[0050] Examples of higher alcohols include cetyl alcohol, stearyl alcohol, behenyl alcohol, batyl alcohol, myristyl alcohol, and cetostearyl alcohol.

[0051] As for ester oils, there is isononyl isononanoate, isopropyl risitate, 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, castor oil fatty acid methyl ester, oleic acid oil, cetostearyl alcohol, acetoglyceride, 2-heptylundecyl palmitate, cetyl palmitate, diisobutyl adipate, N-lauroyl-L-glutamic acid-2-octyldodecyl ester, di-2-heptylundecyl adipate, ethyl laurate, di-sebate Examples include fatty acid esters such as 2-ethylhexyl, 2-hexyldecyl myristate, 2-hexyldecyl palmitate, 2-hexyldecyl adipicate, diisopropyl sebatate, 2-ethylhexyl succinate, ethyl acetate, butyl acetate, amyl acetate, triethyl citrate, trimethylolpropane triisostearate, cetyl 2-ethylhexanoate, 2-ethylhexyl palmitate, and diisostearyl malate; sucrose fatty acid esters such as sucrose stearate and sucrose oleate; glycerin esters (glycerin fatty acid esters) such as tri(caprylic / capric acid) glyceryl, glyceryl tri-2-ethylhexanoate, glyceryl di-2-heptylundecanoate, and glyceryl trimyristate.

[0052] Examples of silicone oils include linear polysiloxanes such as dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, and diphenylsiloxyphenyl trimethicone, as well as cyclic polysiloxanes such as pentasiloxane, decamethylpolysiloxane, dodecamethylpolysiloxane, and tetramethyltetrahydrogenpolysiloxane.

[0053] As liquid UV absorbers, UV absorbers that are liquid at room temperature can be used, and examples include cinnamic acid derivatives such as polysilicone-15, ethylhexyl methoxycinnamate (2-ethylhexyl paramethoxycinnamate), 2-ethoxyethyl paramethoxycinnamate, isopropyl paramethoxycinnamate / diisopropyl cinnamic acid ester mixture, methylbis(trimethylsiloxy)silylisopentyl trimethoxycinnamate, benzoic acid derivatives such as amyl paradimethylaminobutyric acid benzoate and 2-ethylhexyl paradimethylaminobutyric acid benzoate, salicylic acid derivatives such as ethylene glycol salicylate, 2-ethylhexyl salicylate, benzyl salicylate, homomentyl salicylate, and octocrylene.

[0054] The oil-in-water emulsion composition of the present invention may contain ultraviolet absorbers other than the above-mentioned ultraviolet absorbers as oily components. For example, para-aminobenzoic acid, para-aminobenzoic acid monoglycerol ester, N,N-dipropoxypara-aminobenzoate ethyl ester, N,N-diethoxypara-aminobenzoate ethyl ester, diethylaminohydroxybenzoyl hexyl benzoate, homomenthyl-N-acetylantranilate, 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, Benzophenone derivatives such as 2-hydroxy-4-methoxybenzophenone (oxybenzone-3), 2-hydroxy-4-methoxy-4'-methylbenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonate, 4-phenylbenzophenone, 2-ethylhexyl-4'-phenylbenzophenone-2-carboxylate, 2-hydroxy-4-n-octoxybenzophenone, 4-hydroxy-3-carboxybenzophenone; 3-(4'-methylbenzylidene)-d,l-camphor, 3-benzylidene Den-d,l-camphor; 2-phenyl-5-methylbenzoxazole; 2,2'-hydroxy-5-methylphenylbenzotriazole; 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole; 2-(2'-hydroxy-5'-methylphenylbenzotriazole); dibenzarazine; dianisioylmethane; 5-(3,3-dimethyl-2-norbornylidene)-3-pentan-2-one; 4-t-butyl methoxydibenzoylmethane, octyltriazone; urocanic acid and ethyl urocanic acid, 2 Examples include -(2'-hydroxy-5-methylphenyl)benzotriazole, 1-(3,4-dimethoxyphenyl)-4,4-dimethyl-1,3-pentanedione, 2-ethylhexyl dimethoxybenzylidene dioxoimidazolidinepropionate, phenylbenzimidazol sulfonic acid, terephthalylidene dicamphor sulfonic acid, drometrizole trisiloxane, methyl anthranilate, bis-ethylhexyloxyphenol methoxyphenyl triazine, rutin and its derivatives, oryzanol and its derivatives.

[0055] The oil phase content relative to the total amount of the oil-in-water emulsion composition is preferably 5 to 40% by mass, more preferably 10 to 35% by mass, even more preferably 15 to 30% by mass, even more preferably 20 to 30% by mass, and particularly preferably 22 to 25% by mass.

[0056] The aqueous components contained in the aqueous phase of the oil-in-water emulsion composition of the present invention may include, without particular limitation, components commonly used in cosmetics. Examples include water and polyols such as polyethylene glycol, glycerin, 1,3-butylene glycol, erythritol, sorbitol, xylitol, maltitol, propylene glycol, dipropylene glycol, diglycerin, isoprene glycol, 1,2-pentanediol, 2,4-hexylene glycol, 1,2-hexanediol, and 1,2-octanediol, with 1,3-butylene glycol being particularly preferred.

[0057] In the present invention, it is preferable that the aqueous component includes a thickening agent. The thickeners included in the oil-in-water emulsion composition are not particularly limited, but may include xanthan gum, gellan gum, guar gum, quince seed, carrageenan, galactan, gum arabic, pectin, mannan, starch, curdlan, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylhydroxypropylcellulose, chondroitin sulfate, dermatan sulfate, glycogen, heparan sulfate, hyaluronic acid, sodium hyaluronate, tragacanth gum, keratan sulfate, chondroitin, mucoitin sulfate, and hydroxyethyl guar gum. Examples include carboxymethyl guar gum, dextran, keratosulfate, locust bean gum, succinoglycan, carotenoid acid, chitin, chitosan, carboxymethyl chitin, agar, polyvinyl alcohol, polyvinylpyrrolidone, polyethylene glycol, sodium acrylate graft starch, stearoxyhydroxypropyl methylcellulose, bentonite, polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, carbomer, (acrylates / alkyl acrylate (C10-30)) crosspolymer, polyacrylamide, etc. In particular, the thickening agents preferably include polysaccharides such as xanthan gum, gellan gum, guar gum, quince seed, carrageenan, galactan, gum arabic, pectin, mannan, starch, curdlan, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, and methylhydroxypropylcellulose, and / or acrylic acid-based thickening agents such as polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, carbomer, (acrylates / alkyl acrylate (C10-30)) crosspolymer, and polyacrylamide, and more preferably xanthan gum and / or carbomer.

[0058] The amount of thickener relative to the total amount of the oil-in-water emulsion composition is preferably 0.001 to 10% by mass, more preferably 0.01 to 5% by mass, even more preferably 0.01 to 1% by mass, and particularly preferably 0.05 to 0.5% by mass.

[0059] In the present invention, the thickening agent preferably includes polysaccharides and acrylic acid-based thickening agents, and more preferably includes xanthan gum and carbomer. By including these thickening agents, an oil-in-water emulsion composition with excellent emulsification stability and a refreshing feel can be obtained.

[0060] When a thickening polysaccharide such as xanthan gum is included as a thickening agent, the content of the thickening polysaccharide relative to the total amount of the oil-in-water emulsion composition is preferably 0.01 to 1% by mass, more preferably 0.05 to 0.5% by mass, even more preferably 0.05 to 0.3% by mass, and particularly preferably 0.1 to 0.25% by mass.

[0061] When an acrylic acid-based thickener such as carbomer is included as a thickening agent, the content of the acrylic acid-based thickener relative to the total amount of the oil-in-water emulsion composition is preferably 0.001 to 1% by mass, more preferably 0.005 to 0.5% by mass, even more preferably 0.01 to 0.3% by mass, and particularly preferably 0.01 to 0.2% by mass.

[0062] The content of the aqueous phase relative to the total amount of the oil-in-water emulsion composition is preferably 60 to 95% by mass, more preferably 65 to 90% by mass, even more preferably 70 to 85% by mass, even more preferably 70 to 80% by mass, and particularly preferably 75 to 78% by mass.

[0063] Furthermore, in the oil-in-water emulsion composition of the present invention, optional components commonly used in cosmetics may be included in addition to the above-mentioned components, as long as they do not impair the effects of the invention.

[0064] The oil-in-water emulsion composition of the present invention can be produced by dispersing CNF in an aqueous phase and fatty acids in an oil phase at room temperature, and then adding the oil phase to the aqueous phase and emulsifying them.

[0065] The oil-in-water emulsion composition of the present invention is suitable for topical skin preparations. In particular, it is preferably used in cosmetics, such as makeup bases, foundations, and sunscreens.

[0066] <Method for improving the water resistance and / or adhesion of a coating film of an oil-in-water emulsion composition> The present invention also relates to a method for improving the water resistance and / or adhesion of a coating film of an oil-in-water emulsion composition (hereinafter also referred to as a method for improving the water resistance and / or adhesion of a coating film).

[0067] In one embodiment, a method for improving the water resistance and / or adhesion of a coated film is a method for improving the water resistance and / or adhesion of a coated film of an oil-in-water emulsion composition containing cellulose nanofibers as an emulsifier, characterized in that a fatty acid or a salt thereof is used as an auxiliary emulsifier when preparing the oil-in-water emulsion composition. The preferred form of the fatty acid or its salt used is as described above.

[0068] In one embodiment, a method for improving the water resistance and / or adhesion of a coating film of an oil-in-water emulsion composition containing a fatty acid or a salt thereof as an emulsifier, characterized in that cellulose nanofibers are used when preparing the oil-in-water emulsion composition. The preferred form of cellulose nanofiber to be used is as described above. [Examples]

[0069] <Test Example 1> A sunscreen cosmetic according to the present invention was prepared using the formulation shown in Table 1 below. Specifically, an aqueous phase component containing CNF and an oil phase component containing fatty acids were mixed separately, and the oil phase was stirred and mixed while adding the oil phase to the aqueous phase to obtain an oil-in-water sunscreen cosmetic. Furthermore, the CNF used was derived from bamboo.

[0070] Each sunscreen cosmetic obtained was evaluated based on four criteria: water resistance, adhesion to the skin, texture, and duration of protection when sweating, according to the evaluation criteria below.

[0071] [Evaluation Criteria] (1)Water resistance The resulting sunscreen cosmetic was placed on a PMMA plate (Helios Plate HD6) at a concentration of 0.2 mg / cm². 2 The material was applied in the specified manner, and the SPF was measured immediately afterward. Next, the PMMA plate was immersed in water for 80 minutes, and the SPF was measured again. The retention rate of the SPF measurement after 80 minutes of immersion compared to the measurement immediately after application was calculated. Based on this retention rate, the evaluation was performed according to the evaluation criteria below. ○: SPF maintenance rate of 80% or more after 80 minutes of swimming. △: SPF maintenance rate after 80-minute bath is between 50% and 80%. ×: SPF maintenance rate after 80 minutes of bathing is less than 50% In the evaluation, a rating of △ or higher was considered to indicate water resistance.

[0072] (2) Adhesion to the skin The resulting sunscreen cosmetic was applied to artificial leather at a rate of 0.2 mg / cm². 2 The surface was applied in the manner described, and the SPF was measured immediately afterward. Next, a certain amount of friction was applied to the applied area, and the SPF was measured again. The retention rate of the SPF measurement after friction was calculated compared to the measurement immediately after application. Based on this retention rate, the evaluation was performed according to the evaluation criteria below. ○: SPF retention rate after friction application is 80% or higher. △: SPF retention rate after friction application is 50% or more but less than 80% ×: SPF retention rate after friction application is less than 50% In the evaluation, a score of △ or higher was considered to indicate good adhesion to the skin.

[0073] (3) Texture Ten sensory evaluators, highly knowledgeable in cosmetic evaluation, applied 0.2g of the obtained sunscreen cosmetic to their palms, arms, etc., and judged whether the sunscreen cosmetic had a refreshing feel upon application. Based on the results of their judgment, each example was evaluated according to the following criteria. ○: Over 80% of sensory evaluators rated it as having a fresh, juicy texture. △: Between 50% and 80% of sensory evaluators rated the product as having a fresh, juicy texture. ×: Less than 50% of sensory evaluators rated the product as having a fresh, juicy texture. In the evaluation, a rating of △ or higher indicated that the product had a fresh, juicy texture.

[0074] (4) Duration of sunscreen effect when sweating Apply 0.2 mg / cm² of sunscreen cosmetic to artificial leather. 2 The material was applied in this manner, dried for 10 minutes, and then immersed in artificial sweat solution (acidic artificial sweat solution, Kishida Chemical Co., Ltd.) for 5 minutes. The surface roughness (Sa value) of the film formed on the artificial leather was measured before and after immersion in the artificial sweat solution under the following measurement conditions. [Measurement conditions] • Equipment used: One-shot 3D shape measuring machine VR-6000 (Keyence) ·Viewing angle: 1mm x 1mm Based on the degree of change in surface roughness before and after immersion in artificial sweat solution, the effect on artificial sweat was evaluated according to the following evaluation criteria. ○: The change in the number before and after immersion is 10 or less. △: The change in the number before and after immersion is greater than 10 and less than or equal to 50. ×: The change in the number before and after immersion exceeds 50. When the film of sunscreen cosmetic peels off from artificial leather, irregularities appear on the surface of the film, causing a change in the surface roughness (Sa value). In the evaluation, a degree of change in surface roughness of △ or higher was judged to indicate that the sunscreen effect is long-lasting.

[0075] [Table 1]

[0076] As shown in Table 1, the sunscreen cosmetics of Examples 1 to 6 exhibited excellent adhesion to the skin and water resistance, demonstrating a good balance between both aspects. In particular, the sunscreen cosmetics of Examples 1 to 4 showed excellent water resistance and adhesion to the skin, as well as a refreshing feel, superior usability, and excellent resistance to sweat.

[0077] On the other hand, Comparative Example 1, which did not contain cellulose nanofibers but contained fatty acids, exhibited inferior water resistance and durability of sunscreen effect when sweating. Furthermore, Comparative Example 2, which contained cellulose nanofibers but did not contain fatty acids, exhibited inferior adhesion to the skin and durability of sunscreen effect when sweating.

[0078] From these results, it was found that an oil-in-water emulsion composition containing cellulose nanofibers and fatty acids or their salts as emulsifiers exhibits superior water resistance and adhesion to the skin compared to compositions containing only cellulose nanofibers or fatty acids or their salts as emulsifiers.

[0079] <Test Example 2> The emulsification state of the sunscreen cosmetics of the above examples was observed using an optical microscope. As a result, it was confirmed that spherical Pickering emulsions were formed in Examples 1 to 4, which contain cellulose nanofibers and fatty acids or their salts. Figure 1 shows the emulsification state of Example 1 as an example. It is believed that the Pickering emulsion in question is formed by the adsorption of cellulose nanofibers to the emulsion interface. Furthermore, referring to the results of Test Example 1, it can be said that Examples 1 to 4, which form the Pickering emulsion, exhibit particularly excellent water resistance and adhesion to the skin. From the above, it has become clear that, in a preferred embodiment, the oil-in-water emulsion composition of the present invention has the form of a Pickering emulsion and exhibits excellent water resistance and adhesion to the skin. [Industrial applicability]

[0080] The oil-in-water composition of the present invention can be applied to pharmaceuticals, cosmetics, and other formulations.

Claims

1. An oil-in-water emulsion composition characterized by containing cellulose nanofibers and a fatty acid or a salt thereof as an emulsifier.

2. The oil-in-water emulsion composition according to claim 1, wherein the cellulose nanofibers are adsorbed at the emulsion interface to form a Pickering emulsion.

3. The oil-in-water emulsion composition according to claim 1, wherein the content of the cellulose nanofibers is 0.05 to 1.5% by mass.

4. The oil-in-water emulsion composition according to claim 1, wherein the content of the fatty acid or salt thereof is 0.1 to 1.5% by mass.

5. The oil-in-water emulsion composition according to claim 1, wherein the content of the cellulose nanofiber is 0.1 to 1% by mass, and the content of the fatty acid or salt thereof is 0.1 to 0.7% by mass.

6. The oil-in-water emulsion composition according to claim 1, wherein the fatty acid or salt thereof is a fatty acid having 12 to 22 carbon atoms or a salt thereof.

7. An oil-in-water emulsion composition according to any one of claims 1 to 6, which is a composition for external use on the skin.

8. The oil-in-water emulsion composition according to claim 7, which is a sunscreen cosmetic containing an ultraviolet absorber.

9. A method for improving the water resistance and / or adhesion of a coated film of an oil-in-water emulsion composition containing cellulose nanofibers as an emulsifier, characterized in that a fatty acid or a salt thereof is used as an auxiliary emulsifier when preparing the oil-in-water emulsion composition.

10. A method for improving the water resistance and / or adhesion of a coating film of an oil-in-water emulsion composition containing a fatty acid or a salt thereof as an emulsifier, characterized in that cellulose nanofibers are used when preparing the oil-in-water emulsion composition.

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