Oil-in-water emulsion

Abstract

The present invention provides an oil-in-water emulsion comprising: (a) at least one acid selected from the group consisting of an alpha hydroxy acid (AHA), a beta hydroxy acid (BHA) and a polyhydroxyalkanoic acid (PHA); (b) batyl alcohol; (c) at least one thickener selected from the group consisting of cellulose thickeners comprising an alkyl group of 10 to 30 carbon atoms and polysaccharide thickeners comprising glucose, glucuronic acid and rhamnose as constituent monosaccharides of the backbone; and (d) an oil. A cosmetic process for caring for and / or making up keratin materials comprises applying said oil-in-water emulsion to a keratin material, in particular to the skin.

Description

Technical Field

[0001] The present invention relates to oil-in-water emulsions. Background Art

[0002] Polishing serums are peeling serums containing a peeling agent, such as glycolic acid, to remove dead cells from the skin's surface and improve its smoothness. Demand for peeling serums is increasing, particularly in Asia. However, currently available commercial products are problematic because peeling agents can leave a sticky residue on the skin. Therefore, the addition of peeling agents has become problematic, particularly from a texture perspective.

[0003] Technical issues

[0004] On the other hand, oils generally reduce sticky residue on the skin, so emulsified peeling serums can impart smoothness to the skin without leaving a sticky residue. However, because peeling agents act as strong electrolytes, rapidly breaking down emulsions, producing stable emulsions containing peeling agents is difficult. Furthermore, peeling agents typically exhibit their peeling effects at a low pH of 5.5 or lower, and some emulsifiers or thickeners used to stabilize emulsions do not function well at these low pH conditions.

[0005] An example of an emulsified composition is the skin care composition described in WO2015013197A1. This composition is an oil-in-water emulsion having an aqueous phase and an oil phase, the aqueous phase containing greater than about 0.5% of an acid in salt form, and further comprising a gum such that its chemical state or physical homogeneity remains substantially unchanged even when exposed to a temperature of about 50°C for 14 days.

[0006] There is still a need to provide new oil-in-water emulsions containing acids with a peeling effect and having improved properties with regard to texture and stability. Summary of the Invention

[0007] Solution to the problem

[0008] The applicant has demonstrated that the use of the following substances in an oil-in-water emulsion containing an acid and an oil allows the desired effect to be met even at low pH (e.g. 5.5 or lower): (b) batyl alcohol, and (c) at least one thickener chosen from cellulosic thickeners having an alkyl group of 10 to 30 carbon atoms and polysaccharide thickeners containing glucose, glucuronic acid and rhamnose as constituent monosaccharides of the backbone.

[0009] Summary of the Invention

[0010] The present invention therefore relates to an oil-in-water emulsion comprising (a) at least one acid selected from alpha hydroxy acids (AHA), beta hydroxy acids (BHA) and polyhydroxy alkanoic acids (PHA), (b) batyl alcohol, (c) at least one thickener selected from cellulosic thickeners having an alkyl group of 10 to 30 carbon atoms and polysaccharide thickeners comprising glucose, glucuronic acid and rhamnose as constituent monosaccharides of the backbone, and (d) oil.

[0011] In a particular embodiment, component (a) of the oil-in-water emulsion comprises glycolic acid.

[0012] In a particular embodiment, component (a) is present in the oil-in-water emulsion at 0.004 mass % or greater.

[0013] In particular embodiments, the pH of the oil-in-water emulsion is 5.5 or less.

[0014] In certain embodiments, the oil-in-water emulsion further comprises an emulsifier.

[0015] In a particular embodiment, the emulsifier other than component (b) in the oil-in-water emulsion is a nonionic emulsifier.

[0016] In a particular embodiment, the nonionic emulsifier in the oil-in-water emulsion is a polyglycerol fatty acid ester.

[0017] In a particular embodiment, the oil-in-water emulsion further comprises a thickener in addition to component (c).

[0018] In certain embodiments, component (d) in the oil-in-water emulsion further comprises dicaprylylether and / or squalane.

[0019] In certain preferred embodiments, the oil-in-water emulsion is a polishing serum.

[0020] The invention further provides a cosmetic method for caring for keratin materials, which comprises applying the oil-in-water emulsion according to the invention to keratin materials, in particular to the skin.

[0021] Advantageous Effects of the Invention

[0022] According to the present invention, a stable oil-in-water emulsion that exhibits a skin-resurfacing effect even at a low pH (eg, 5.5 or lower) can be provided. DETAILED DESCRIPTION

[0023] Preferred embodiments of the present invention will now be described in detail. However, the present invention is not limited to the described embodiments.

[0024] The oil-in-water emulsion of this embodiment comprises (a) at least one acid selected from alpha hydroxy acid (AHA), beta hydroxy acid (BHA) and polyhydroxyalkanoic acid (PHA), (b) batyl alcohol, (c) at least one thickener selected from cellulosic thickeners having an alkyl group of 10 to 30 carbon atoms and polysaccharide thickeners comprising glucose, glucuronic acid and rhamnose as constituent monosaccharides of the backbone, and (d) oil.

[0025] The oil-in-water emulsion of the embodiment has a skin surface smoothing effect (skin-removing effect) due to the inclusion of component (a), has excellent stability even at a low pH (e.g., 5.5 or lower) due to the inclusion of components (b) and (c), and has an excellent feeling during use without leaving a sticky residue on the skin due to the inclusion of oil (component (d)).

[0026] <Component (a)>

[0027] The oil-in-water emulsion of the present invention comprises at least one acid selected from alpha hydroxy acid (AHA), beta hydroxy acid (BHA), polyhydroxyalkanoic acid (PHA) and mixtures thereof as component (a). Component (a) in the oil-in-water emulsion of an embodiment is used as a skin peeling agent.

[0028] Examples of alpha hydroxy acids (AHAs) include glycolic acid, lactic acid, mandelic acid, malic acid, tartaric acid, citric acid, and mixtures thereof. Examples of beta hydroxy acids (BHAs) include salicylic acid and carnitine. Examples of polyhydroxyalkanoic acids (PHAs) include gluconolactone and lactobionic acid.

[0029] AHAs, BHAs, and PHAs are all weak acids known for their chemical peeling properties (skin exfoliation). AHAs are water-soluble and remove old keratin from the skin's surface, promoting skin renewal. BHAs are water-soluble and gently remove sebum and old skin cells, making them effective against acne and sunburn damage. PHAs are less irritating than AHAs or BHAs, have high moisturizing properties, and are effective for dry skin or sensitive skin with acne, acne scars, rough skin, and atopy.

[0030] The acid used in component (a) of the oil-in-water emulsion of the present invention may be a single type or a combination of two or more types. Component (a) is preferably glycolic acid, lactic acid, salicylic acid or a combination thereof, with glycolic acid being particularly preferred.

[0031] In a specific embodiment, for example, the total content of component (a) in the oil-in-water emulsion of the present invention is 0.004% by mass or more, 0.01% by mass or more, 0.05% by mass or more, 0.1% by mass or more, or 0.5% by mass or more, and is 10% by mass or less, 9% by mass or less, 8% by mass or less, 7% by mass or less, 6% by mass or less, or 5% by mass or less, relative to the total amount of the oil-in-water emulsion. In a preferred embodiment, the total content of component (a) is in the range of 0.1% by mass to 10% by mass, particularly 0.5% by mass to 8% by mass or 1% by mass to 5% by mass, relative to the total amount of the oil-in-water emulsion.

[0032] In a specific embodiment, the total content of component (a) in the oil-in-water emulsion of the present invention is such that the pH of the oil-in-water emulsion is less than 7.0, for example, 6.5 or less, 6.0 or less, 5.5 or less, 5.0 or less or 4.5 or less, more preferably such that the pH of the oil-in-water emulsion is 5.5 or less, even more preferably such that the pH of the oil-in-water emulsion is from 3.5 to 5.5.

[0033] <Component (b)>

[0034] The oil-in-water emulsion of the present invention comprises batyl alcohol as component (b). Component (b) in the oil-in-water emulsion of the present invention serves as a co-emulsifier and also as a moisturizer.

[0035] In a specific embodiment, for example, the content of component (b) in the oil-in-water emulsion of the embodiment is 0.01% by mass or more, 0.03% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.15% by mass or more, 0.2% by mass or more, or 0.25% by mass or more, and is 3.0% by mass or less, 2.5% by mass or less, 2.2% by mass or less, 2.0% by mass or less, 1.5% by mass or less, 1.0% by mass or less, or 0.5% by mass or less, relative to the total amount of the oil-in-water emulsion. The total content of component (b) is particularly in the range of 0.05% by mass to 3.0% by mass, particularly 0.1% by mass to 2.0% by mass or 0.2% by mass to 1.0% by mass, relative to the total amount of the oil-in-water emulsion.

[0036] <Component (c)>

[0037] The oil-in-water emulsion of the present invention contains at least one thickener selected from a cellulose thickener having an alkyl group of 10 to 30 carbon atoms and a polysaccharide thickener as component (c). The cellulose thickener has an alkyl group of 10 to 30 carbon atoms, and the polysaccharide thickener contains glucose, glucuronic acid, and rhamnose as constituent monosaccharides of the backbone. Component (c) in the oil-in-water emulsion of the present invention acts as a thickener and also works together with component (b) to stabilize the oil-in-water emulsion.

[0038] In a particular embodiment, the cellulose thickener having an alkyl group with 10 to 30 carbon atoms is a hydrophobically modified alkyl cellulose having the structural formula (1)

[0039]

[0040] where R 1 、R 2 and R 3 are the same or different and are hydrogen atoms, lower alkyl groups, -[CH2CH 2-k (CH3) k O] m H group or -CH2CH(OH)CH2OC j H 2j+1 group; n is an integer from 100 to 10,000; k is an integer from 0 or 1; m is an integer from 1 to 10; j is an integer from 6 to 26; the hydrophobically modified alkyl cellulose must contain -CH2CH(OH)CH2OC j H 2j+1 A group wherein the lower alkyl group is methyl or ethyl, as described, for example, in WO2011-162421A.

[0041] In a specific embodiment, the cellulose thickener having an alkyl group of 10 to 30 carbon atoms is preferably a cellulose thickener derived from hydroxypropyl methylcellulose, such as hydroxypropyl methylcellulose stearyloxy ether obtained by reacting stearyl glycidyl ether with hydroxypropyl methylcellulose (e.g., SANGELOSE 90L from Daido Chemical Corp.). In this case, the hydrophobic group introduced into the hydrophobized modified alkylcellulose is a stearyl (-C 18 H 37 ; Carbon number: 18). The reaction can also be carried out using hexadecyl glycidyl ether and decyl glycidyl ether instead of stearyl glycidyl ether.

[0042] In a specific embodiment, the polysaccharide thickener comprising glucose, glucuronic acid and rhamnose as the main chain of the constituent monosaccharides has a main chain in which the structural units comprise glucose, glucuronic acid, glucose and rhamnose (they are linearly bound in this order). The polysaccharide thickener of component (c) may also have side chains as part of the polysaccharide structure, or may not have side chains. In a specific embodiment, the side chains have one or more selected from rhamnose, fucose, glucose and mannose as the side chain constituent monosaccharides. The polysaccharide thickener may have a main chain in which the structural units comprise glucose, glucuronic acid, glucose and rhamnose (they are linearly bound in this order), and has rhamnose as a side chain. The polysaccharide thickener may have a main chain in which the structural units comprise glucose, glucuronic acid, glucose and rhamnose (they are linearly bound in this order), and has fucose as a side chain. The polysaccharide thickener may be obtained from microorganisms such as bacteria. According to a specific embodiment, the polysaccharide thickener includes at least one selected from diutan gum, welan gum, gellan gum and a combination thereof. Preferably, the polysaccharide thickener is ditetary gum. Ditetary gum (INCI: Sphingomonas ferment extract) is a polysaccharide obtained by aerobic fermentation of corn syrup starting material using microorganisms of the genus Alcaligenes.

[0043] The component (c) in the oil-in-water emulsion of the embodiment can be a single type, or a combination of multiple different types. In a specific embodiment, for example, the total content of component (c) is 0.01% by mass or more, 0.02% by mass or more, 0.03% by mass or more, 0.05% by mass or more, 0.06% by mass or more, 0.07% by mass or more, or 0.1% by mass or more, and is 1.0% by mass or less, 0.8% by mass or less, 0.6% by mass or less, 0.5% by mass or less, 0.4% by mass or less, 0.3% by mass or less, or 0.2% by mass or less. The total content of component (c) is preferably in the range of 0.01% by mass to 1.0% by mass, especially in the range of 0.05% by mass to 0.5% by mass, relative to the total amount of the oil-in-water emulsion.

[0044] <Component (d)>

[0045] The oil-in-water emulsion of the present invention comprises oil as component (d). In a specific embodiment, for example, the oil of component (d) is in the form of a liquid oil or a pasty oil, but is preferably a liquid oil. The liquid oil can be a non-polar liquid oil or a polar liquid oil.

[0046] Liquid oil is a non-volatile oil component that is liquid at normal temperature (within the range of 15°C to 25°C) and normal pressure (1 atmosphere). Liquid oil includes non-volatile hydrocarbon oil, higher alcohol, ester oil, ether oil and vegetable oil.

[0047] Examples of the non-volatile hydrocarbon oil include squalane, liquid paraffin, petrolatum, polybutene, polyisobutene, hydrogenated polyisobutene, hydrogenated polydecene, olefin oligomers, and mixtures thereof.

[0048] The higher alcohol is an aliphatic monohydric alcohol having 6 or more carbon atoms, preferably an aliphatic monohydric alcohol having 12 to 28 carbon atoms. Examples of the higher alcohol include octanol, dodecanol, oleyl alcohol, octyldodecanol, hexyldecanol, isostearyl alcohol, decyltetradecyl alcohol, and mixtures thereof.

[0049] The ester oil is a carboxylic acid ester that is liquid and does not vaporize in an environment of normal temperature and normal pressure (e.g., 25° C., 1 atmosphere), preferably a carboxylic acid alkyl ester, wherein the carboxylic acid or alcohol of the ester has 8 to 18 carbon atoms. Examples of the ester include propylene glycol fatty acid esters such as propylene glycol dicaprylate and propylene glycol dicaprate; fatty acid alkyl esters such as isoamyl laurate, hexyl laurate, ethylhexyl palmitate, isopropyl myristate, 2-octyldodecyl tetradecanoate, hexadecyl 2-ethylhexanoate, isononyl isononanoate, and isotridecyl isononanoate; carbonates such as dicaprylyl carbonate; tri or greater fatty acid esters of polyglycerol (tri or greater fatty acid esters); esters), such as polyglyceryl-2 triisostearate, polyglyceryl-2 tetraisostearate, and polyglyceryl-10 decisostearate; fatty acid triglycerides (also known as triglyceride oils), such as tri-2-ethylhexanoin, tribehenin, tri(caprylic / capric)glyceryl, and triheptanoin; benzoic acid derivatives, such as diisostearyl malate and alkyl (C12-15) benzoate; salicylic acid derivatives, such as homosalate and ethylhexyl salicylate; alkyl esters, such as coconut oil. Cinnamic acid derivatives such as octyl methoxycinnamate, isopropyl methoxycinnamate, isoamyl methoxycinnamate, cinnoxate, DEA methoxycinnamate, diisopropyl methylcinnamate, glyceryl-ethylhexanoate-dimethoxycinnamate and di-(2-ethylhexyl)-4'-methoxybenzylidenemalonate; β,β-diphenylacrylate derivatives such as octocrylene, and mixtures thereof.

[0050] Dioctyl ether is an example of an ether oil.

[0051] Examples of vegetable oils include meadowfoam seed oil, olive fruit oil, jojoba seed oil, camellia oil, coconut oil, macadamia nut oil, rosehip oil, avocado oil, sunflower seed oil, rice bran oil, castor oil, almond oil, and mixtures thereof.

[0052] Component (d) in the oil-in-water emulsion of the embodiment may be a single type or a combination of a plurality of different types. Component (d) preferably comprises dicaprylyl ether and / or squalane.

[0053] In a specific embodiment, for example, the total content of component (d) is 1% by mass or more, 2% by mass or more, 3% by mass or more, 4% by mass or more, 5% by mass or more, 6% by mass or more, or 7% by mass or more, and is 15% by mass or less, 14% by mass or less, 13% by mass or less, 12% by mass or less, 11% by mass or less, 10% by mass or less, 9% by mass or less, or 8% by mass or less, relative to the total amount of the oil-in-water emulsion. The total content of component (d) is preferably in the range of 1% by mass to 15% by mass, particularly 2% by mass to 10% by mass, relative to the total amount of the oil-in-water emulsion.

[0054] <Emulsifier>

[0055] According to a specific embodiment, the oil-in-water emulsion may further comprise an emulsifier. Examples of emulsifiers include nonionic emulsifiers (nonionic surfactants).

[0056] Examples of the nonionic emulsifier include esters of polyglycerol and fatty acids (polyglycerol fatty acid esters) and esters of glycerol and fatty acids (glycerol fatty acid esters), preferably polyglycerol fatty acid esters.

[0057] According to specific embodiment, polyglycerol fatty acid ester is the polyglycerol ester with 12 to 24 carbon atoms, preferably 16 to 22 carbon atoms, more preferably 18 to 22 carbon atoms, most preferably the fatty acid of 18 or 22 carbon atoms.The example of the fatty acid of composition comprises palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, isostearic acid, arachidic acid, arachidonic acid and behenic acid.Lipid acid can be saturated or unsaturated, but is preferably saturated.The quantity (also referred to as the polymerization degree of glycerol) of the glycerol unit in polyglycerol fatty acid ester can be 2 to 12, preferably 2 to 10, more preferably 2 to 8, for example, especially preferably 2 or 6.

[0058] According to a specific embodiment, the polyglyceryl fatty acid ester is chosen from polyglyceryl-2 stearate, polyglyceryl-2 isostearate, polyglyceryl-2 oleate, polyglyceryl-6 stearate, polyglyceryl-6 behenate and mixtures thereof.

[0059] According to a specific embodiment, the glycerol fatty acid ester is a glycerol ester of a fatty acid having 12 to 24 carbon atoms, preferably 16 to 22 carbon atoms, more preferably 16 to 20 carbon atoms, and most preferably 18 carbon atoms. Examples of fatty acids include palmitic acid, palmitoleic acid, stearic acid, oleic acid, linoleic acid, α-linolenic acid, γ-linolenic acid, arachidic acid, arachidonic acid, and behenic acid. The fatty acid can be saturated or unsaturated, but is preferably saturated. According to a specific embodiment, the glycerol fatty acid ester is selected from glyceryl stearate, glyceryl oleate, glyceryl myristate, glyceryl coconut fatty acid ester, glyceryl undecenoate, and mixtures thereof.

[0060] The emulsifier is preferably solid at room temperature (e.g., 25° C.). According to a particularly preferred embodiment, the emulsifier is preferably selected from polyglycerol esters of fatty acids having 12 to 24 carbon atoms and glycerol esters of fatty acids having 12 to 24 carbon atoms and having 2 to 12 glycerol units, and more preferably selected from polyglycerol esters of fatty acids having 12 to 24 carbon atoms and mixtures thereof. In a specific embodiment, the emulsifier is, for example, polyglyceryl-6 stearate or polyglyceryl-6 behenate. An example of a commercial product comprising a combination of polyglyceryl-6 stearate and polyglyceryl-6 behenate is TEGO CARE PBS 6 (Evonik Operations GmbH).

[0061] According to a specific embodiment, the emulsifier can be a single type, or a combination of multiple different types. In a specific embodiment, the total content of emulsifiers is 0.1% by mass or more, 0.2% by mass or more, 0.5% by mass or more, 0.7% by mass or more, 1.0% by mass or more, or 1.2% by mass or more, and is 10% by mass or less, 8% by mass or less, 6% by mass or less, 5% by mass or less, 4% by mass or less, 3% by mass or less, 2.5% by mass or less, 2.2% by mass or less, or 2% by mass or less, relative to the total amount of the oil-in-water emulsion. The total content of emulsifiers is especially in the range of 0.5% to 10% by mass, in particular 0.5% to 5% by mass, or preferably 1% to 3% by mass, relative to the total amount of the oil-in-water emulsion.

[0062] <Thickener>

[0063] According to a specific embodiment, the oil-in-water emulsion further comprises a thickener other than component (c). Examples of thickeners other than component (c) include cellulose thickeners other than component (c), polysaccharide thickeners other than component (c), alkyl-modified carboxyvinyl polymers (e.g., acrylates / C10-30 alkyl acrylate crosspolymers), acrylic acid polymers (and (meth)acrylic acid (co)polymers), and mixtures thereof, preferably polysaccharide thickeners other than component (c), alkyl-modified carboxyvinyl polymers (e.g., acrylates / C10-30 alkyl acrylate crosspolymers), acrylic acid polymers (and (meth)acrylic acid (co)polymers), and mixtures thereof.

[0064] Examples of the cellulose thickener other than component (c) include ethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl methyl cellulose stearyl ether, cellulose gum, carboxymethyl cellulose, and mixtures thereof.

[0065] Polysaccharide thickeners other than component (c) include, for example, glucomannan, xanthan gum, dehydroxanthan gum, or mixtures of these substances.

[0066] The (meth)acrylic acid polymer may be a polymer obtained by polymerizing one or more monomers selected from (meth)acrylic acid and (meth)acrylic acid ester. There is no particular limitation on the (meth)acrylic acid ester, and it may be an alkyl (meth)acrylate, or an alkyl (meth)acrylate in which the alkyl group of the alkyl (meth)acrylate has been substituted with a substituent such as a hydroxyl group, but is preferably an alkyl (meth)acrylate. The alkyl (meth)acrylate includes alkyl (meth)acrylates having an alkyl group of 10 to 30 carbon atoms and alkyl (meth)acrylates having an alkyl group of 1 to 9 carbon atoms, preferably an alkyl (meth)acrylate having an alkyl group of 10 to 30 carbon atoms. In a specific embodiment, the (meth)acrylic acid polymer is a copolymer of at least one monomer selected from (meth)acrylic acid and alkyl (meth)acrylates having an alkyl group of 1 to 9 carbon atoms and at least one monomer selected from alkyl (meth)acrylates having an alkyl group of 10 to 30 carbon atoms.

[0067] In certain embodiments, the (meth)acrylic acid polymer further comprises carbomer. Commercially available (meth)acrylic acid polymers may be used, examples of which include Lubrizol's Carbopol TM Ultrez30 polymer, Carbopol TM Ultrez 10, Carbopol TM ETD 2020, Carbopol TMUltrez 20 polymer and Pemulen TR-1, Japan Clariant's Aristoflex TM AVC and Seppic SA's Simulgel TM NS MB.

[0068] According to a specific embodiment, the thickener other than component (c) can be a single type, or a combination of two or more different types. In a specific embodiment, for example, the total content of the thickener other than component (c) is 0.01% by mass or more, 0.02% by mass or more, 0.03% by mass or more, 0.05% by mass or more, 0.07% by mass or more, 0.10% by mass or more, or 0.12% by mass or more, and is 1.0% by mass or less, 0.8% by mass or less, 0.5% by mass or less, 0.3% by mass or less, or 0.2% by mass or less, relative to the total amount of the oil-in-water emulsion. The total content of the thickener other than component (c) is preferably in the range of 0.01% by mass to 1.0% by mass.

[0069] In a specific embodiment, for example, the total content of component (c) and thickeners other than component (c) is 0.01% by mass or more, 0.02% by mass or more, 0.03% by mass or more, 0.05% by mass or more, 0.1% by mass or more, 0.2% by mass or more, or 0.3% by mass or more, and is 1.5% by mass or less, 1.0% by mass or less, 0.8% by mass or less, 0.6% by mass or less, 0.5% by mass or less, 0.4% by mass or less, 0.3% by mass or less, 0.2% by mass or less, 0.15% by mass or less, or 0.1% by mass or less, relative to the total amount of the oil-in-water emulsion. The total content of component (c) and thickeners other than component (c) is preferably in the range of 0.01% by mass to 1.5% by mass.

[0070] <Moisturizer>

[0071] According to a specific embodiment, the oil-in-water emulsion further comprises a moisturizer in addition to component (b). By including a moisturizer, in addition to the skin-rejuvenating effect, a high moisturizing effect can also be provided simultaneously. Examples of moisturizers other than component (b) include polyols having 3 to 5 carbon atoms. Examples of polyols include those having 2 or 3 alcoholic hydroxyl groups. Examples of polyols having 3 to 5 carbon atoms include glycerol, 1,3-butylene glycol, pentylene glycol, propylene glycol, and mixtures thereof.

[0072] According to a specific embodiment, the humectant other than component (b) can be a single type, or a combination of two or more different types. In a specific embodiment, the total content of the humectant other than component (b) is 2% by mass or more, 3% by mass or more, 4% by mass or more, 5% by mass or more, 6% by mass or more, 7% by mass or more, 8% by mass or more, or 9% by mass or more, and is 25% by mass or less, 20% by mass or less, 18% by mass or less, 15% by mass or less, 13% by mass or less, 12% by mass or less, or 11% by mass or less. The total content of the humectant other than component (b) is most preferably in the range of 2% to 20% by mass, especially in the range of 4% to 15% by mass, relative to the total amount of the oil-in-water emulsion.

[0073] <Other components>

[0074] According to a specific embodiment, the oil-in-water emulsion further contains additives commonly used in cosmetics, such as pH regulators, fragrances, preservatives, active ingredients, antioxidants, skin whitening agents, pigments, colorants and skin conditioners. According to a specific embodiment, the oil-in-water emulsion contains an active ingredient.

[0075] The oil-in-water emulsion of the present invention further contains water. In specific embodiments, for example, the water content is 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 48% by mass or more, or 50% by mass or more, and is 70% by mass or less, 65% by mass or less, 60% by mass or less, 61% by mass or less, 59% by mass or less, or 57% by mass or less, relative to the total amount of the oil-in-water emulsion. In a preferred embodiment, the total water content is in the range of 30% to 70% by mass, particularly 35% to 65% by mass, relative to the total amount of the oil-in-water emulsion.

[0076] In certain embodiments, the pH of the oil-in-water emulsion of the present invention is below 7.0, and can be, for example, 6.5 or less, 6.0 or less, or 5.5 or less, and 2.0 or more, 2.5 or more, 3.0 or more, or 3.5 or more. The pH of the oil-in-water emulsion of the present invention is most preferably in the range of 3.5 to 5.5.

[0077] According to a specific embodiment, the oil-in-water emulsion has a viscosity of, for example, 300 to 5000 mPa·s, 500 to 3000 mPa·s, or 600 to 2000 mPa·s, measured at 25°C. The viscosity can be measured based on shear viscosity using a rotational viscometer (e.g., Anton Paar's Rheolab QC, spindle: ST-22-4V-40; rotation speed: 100 rpm). The oil-in-water emulsion of the present invention has a relatively low viscosity and a light texture.

[0078] According to a specific embodiment, the oil-in-water emulsion is prepared, for example, by stirring and mixing component (b), component (c), component (d) and other thickeners, emulsifiers, humectants or water while heating at 80° C. to 85° C., emulsifying the mixture, and then cooling it to room temperature, and then mixing it with component (a) and other components.

[0079] According to another specific embodiment, the oil-in-water emulsion of the embodiment is in the form of a cream or a serum. In a specific embodiment, the oil-in-water emulsion of the present invention is especially a polishing serum.

[0080] Oil-in-water emulsified cosmetics according to specific embodiments have excellent long-term storage stability (for example, no phase separation occurs when stored at 50°C for one month). As a rigorous stability test to predict long-term product stability, the condition of samples stored at a constant temperature of 45°C or 50°C for a certain period of time (for example, one or three months) can be evaluated. To more accurately assess stability, samples can be centrifuged (for example, by spinning a centrifuge tube containing 10 mL of emulsion at 4200 rpm for 15 minutes in an EPPENDORF 5702R centrifuge) and evaluated.

[0081] The present invention will now be explained in detail by way of examples. However, the present invention is not limited to these examples.

[0082] Example

[0083] [Preparation of oil-in-water emulsion]

[0084] The oil-in-water emulsions of Examples 1 to 9 and Comparative Examples 1 to 12 were prepared using the ingredients and mixing ratios listed in Tables 1 to 3. The "%" values in Tables 2 and 3 are weight percent values based on the total weight of each oil-in-water emulsion. The ingredients of Phases D, E, H, and K were dissolved at room temperature. The ingredients of Phase A were dissolved at 80°C. A 0.5 to 1.0 kg portion of the oil-in-water emulsion was prepared using a Rayneri mixer. The ingredients of Phase B were added to a container, heated at 80°C, and mixed at 100 to 500 rpm. After most of the components in the container became homogenous, the ingredients of Phase C were added to the container and mixed for 20 minutes until the mixture swelled. The ingredients of Phase A were then gradually added to the container, and the mixture in the container was emulsified using a Rayneri mixer at 80°C for 5 minutes, followed by emulsification using a Turrax homogenizer at 10,000 rpm at room temperature for 1 minute. The mixture was air-cooled to 30°C, and the ingredients of the remaining phases were then added in sequence below 40°C. Oil-in-water emulsions of Examples 1 to 9 and Comparative Examples 1 to 12 were obtained.

[0085] [Table 1]

[0086]

[0087]

[0088]

[0089]

[0090]

[0091]

[0092] The stability of each emulsion obtained was evaluated by the following method: Viscosity was measured as shear viscosity using a viscometer (Rheolab QC (Anton Paar), spindle: ST-22-4V-40; rotation speed: 100 rpm) at 25°C.

[0093] Stability was evaluated by examining the emulsion's state after centrifugation (4200 rpm, 15 minutes) and after storage at 50°C for one month. The results of the stability tests confirmed that SANGELOSE 90L (hydroxypropyl methylcellulose stearyl ether) and NIKKOL Batyl 100 (batyl alcohol) stabilized the emulsion (Examples 1 to 3 and 6 to 9). When other cellulosic thickeners, hydroxyethylcellulose (Comparative Examples 1 and 3) or hydroxypropyl methylcellulose (Comparative Examples 2 and 4), were used in place of hydroxypropyl methylcellulose stearyl ether, or when no cellulosic thickener was used (Comparative Examples 5 to 10), phase separation was observed and the emulsion failed to stabilize. When batyl alcohol was omitted (Comparative Examples 11 and 12), the emulsion also failed to stabilize. Furthermore, when dimethicone was used in place of SANGELOSE 90L, the emulsion was stabilized in the same manner as SANGELOSE 90L (Examples 4 and 5). These results therefore demonstrate that the use of (b) batyl alcohol and (c) at least one thickener selected from cellulosic thickeners having an alkyl group of 10 to 30 carbon atoms and polysaccharide thickeners containing glucose, glucuronic acid and rhamnose as constituent monosaccharides of the backbone enables acid-containing oil-in-water emulsions to be stable even at low pH (5.5 and below).

Claims

1. An oil-in-water emulsion comprising: (a) at least one acid selected from the group consisting of alpha hydroxy acids (AHA), beta hydroxy acids (BHA) and polyhydroxyalkanoic acids (PHA), (b) batyl alcohol, (c) at least one thickener selected from the group consisting of cellulose thickeners having an alkyl group of 10 to 30 carbon atoms and polysaccharide thickeners containing glucose, glucuronic acid and rhamnose as constituent monosaccharides of the backbone, and (d) Oil.

2. The oil-in-water emulsion according to claim 1, wherein Component (a) comprises glycolic acid.

3. The oil-in-water emulsion according to claim 1 or 2, comprising 0.004% by mass or more, preferably in the range of 0.1% by mass to 10% by mass, especially 0.5% by mass to 8% by mass or 1% by mass to 5% by mass of component (a), relative to the total amount of the oil-in-water emulsion.

4. The oil-in-water emulsion according to any one of claims 1 to 3, wherein The pH is 5.5 or lower.

5. The oil-in-water emulsion according to any one of claims 1 to 4, further comprising an emulsifier.

6. The oil-in-water emulsion according to claim 5, wherein The emulsifier is a nonionic emulsifier.

7. The oil-in-water emulsion according to claim 6, wherein The nonionic emulsifier is polyglycerol fatty acid ester.

8. The oil-in-water emulsion according to any one of claims 1 to 7, further comprising a thickener in addition to component (c).

9. The oil-in-water emulsion according to any one of claims 1 to 8, wherein Component (d) comprises dicaprylyl ether and / or squalane.

10. The oil-in-water emulsion according to any one of claims 1 to 9, which is a polishing essence.

11. A cosmetic method for caring for and / or making up keratin materials, comprising applying the oil-in-water emulsion according to any one of claims 1 to 10 to keratin materials, in particular to the skin.

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