Microemulsion

Abstract

To provide a water-in-oil type microemulsion comprising a solubilized oil agent in a solid or semi-solid form.SOLUTION: A water-in-oil type microemulsion comprises the following (A) and (B): (A) polyglyceryl monoisostearate and (B) an oil agent in a solid or semi-solid form at 25°C.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to oil-in-water microemulsions. [Background technology]

[0002] Microemulsions are dispersions of fine micelles, and are known to have unique properties such as being thermodynamically metastable and exhibiting high compatibility with both hydrophilic and lipophilic components. Taking advantage of these properties, microemulsion formulations have been used in the fields of cosmetics and pharmaceuticals.

[0003] As a technique for producing a microemulsion, for example, a technique is known in which a microemulsion can be easily produced without using special equipment by combining multiple nonionic surfactants to adjust the balance between hydrophilicity and hydrophobicity (Patent Document 1).

[0004] Conventionally, various surfactants such as anionic surfactants, cationic surfactants, and amphoteric surfactants have been used to produce emulsions. For example, it has been disclosed that a surfactant such as polyglyceryl isostearate may be contained in an oil-in-water emulsion composition containing N-lauroyl isopropyl sarcosine, a specific active ingredient that is poorly soluble in oil, and an oil phase (Patent Document 2). Thus, a technique for producing an emulsion by solubilizing a liquid oil agent using polyglyceryl monoisostearate is known. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2005-193134 A [Patent Document 2] International Publication No. 2014 / 112194 Summary of the Invention [Problem to be solved by the invention]

[0006] However, no microemulsion in which a solid or semi-solid oil is solubilized with polyglyceryl monoisostearate is known. An object of the present invention is to provide an oil-in-water microemulsion in which a solid or semi-solid oil agent is solubilized. [Means for solving the problem]

[0007] Means of Solving the Problems The present inventors have conducted intensive research to solve the above problems, and as a result have found that the above problems can be solved by using polyglyceryl monoisostearate, thereby completing the present invention.

[0008] That is, the present invention is as follows. [1] An oil-in-water microemulsion comprising the following (A) and (B): (A) Polyglyceryl monoisostearate (B) An oil solution that is solid or semi-solid at 25°C [2] The microemulsion according to [1], wherein the HLB value of (A) is 8 to 15. [3] The microemulsion according to [1] or [2], wherein the average degree of polymerization of the glycerin in (A) is 6 to 13. [4] The microemulsion according to [3], wherein (A) is at least one selected from the group consisting of polyglyceryl-10 monoisostearate and polyglyceryl-6 monoisostearate. [5] The microemulsion according to any one of [1] to [4], wherein the melting point of (B) is 23° C. or higher. [6] The microemulsion according to any one of [1] to [5], wherein the content of (A) is 0.03% by mass to 20.00% by mass based on the total mass of the microemulsion. [7] The microemulsion according to any one of [1] to [6], wherein the content of (B) is 0.01% by mass to 10.00% by mass based on the total mass of the microemulsion. [8] The microemulsion according to any one of [1] to [7], wherein the mass ratio of the content of (A) to the content of (B) is 1:1 to 15:1. [9] The microemulsion according to any one of [1] to [8], further comprising (C) a higher alcohol that is liquid at 25°C.

[10] The microemulsion according to [9], wherein the carbon number of (C) is 10 to 25.

[11] The microemulsion according to [9] or

[10] , wherein (C) is at least one selected from the group consisting of oleyl alcohol and jojoba alcohol.

[12] (C) The microemulsion according to any one of [1] to [8], which is substantially free of a higher alcohol that is liquid at 25°C.

[13] The microemulsion according to any one of [1] to

[12] , further comprising (D) an oil agent that is liquid at 25°C.

[14] The microemulsion according to any one of [1] to

[13] , wherein the average particle size of the oil droplets is 50 nm to 250 nm.

[15] The microemulsion according to any one of [1] to

[14] , which is an external preparation for skin. Effect of the Invention

[0009] The present invention provides a fine microemulsion in which a solid or semi-solid oil agent is solubilized. The present invention also provides a microemulsion that has excellent storage stability, is less sticky on the skin during application, and has an excellent feel when used. Furthermore, the present invention can be easily produced without using a special emulsifying device. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] The microemulsion of the present invention essentially contains components (A) and (B). Each component will be described below.

[0011] Component (A) is polyglyceryl monoisostearate. Component (A) is a type of polyglycerin-based nonionic surfactant, and is a monoester of isostearic acid and polyglycerin. Compared to other polyglycerin surfactants, component (A) is able to solubilize a wide range of oils, including not only liquid oils but also solid and semi-solid oils. The mechanism behind this is unclear, but it is thought to be as follows. In an oil-in-water microemulsion, the surfactant is usually dispersed in water with the hydrophilic group facing outward and the hydrophobic group facing inward, and mainly spherical fine micelles are dispersed. The oil can be solubilized in the vicinity of the hydrophobic group of the surfactant assembled inside the micelle. Here, when the hydrophobic group of the surfactant is a short chain or a straight chain (for example, polyglyceryl laurate or polyglyceryl stearate), the volume required to solubilize the oil is small, so the oil cannot be solubilized. On the other hand, when the hydrophobic group of the surfactant has two or more chains with terminal branching (for example, polyglyceryl diisostearate), the volume is large, but the structure of the hydrophobic group portion makes the mixture bulky, so the particle size of the micelles becomes large and it does not become a microemulsion. On the other hand, in the case of polyglyceryl monoisostearate, the hydrophobic group has a structure with one terminal branching chain, so the mixture does not become bulky and the size of the mixture volume is moderate. Therefore, it is suitable for a wide range of applications, including not only liquid oils but also solid and semi-solid oils. It is believed that a microemulsion in which the oily agent is solubilized can be obtained.

[0012] In addition, polyglyceryl monoisostearate can form a thermodynamically stable microemulsion because the volume required to solubilize the oil is adequate and the volume is not too large. Therefore, emulsification can be easily performed by simply mixing and stirring without using a special device such as a high-pressure emulsifier. Furthermore, generally, when an emulsion contains a large amount of surfactant relative to the oil, the emulsion tends to be sticky on the skin. However, by using polyglyceryl monoisostearate, the amount of surfactant can be reduced, thereby preventing stickiness on the skin. Furthermore, since polyglycerin-based surfactants such as polyglyceryl monoisostearate do not have a cloud point, they are not affected by temperature even when stored at high temperatures and have excellent storage stability.

[0013] The HLB value of component (A) is preferably 8 to 15, and more preferably 10 to 13. The average degree of polymerization of glycerin in component (A) is preferably 6 to 13, and more preferably 6 to 10. Specifically, component (A) is preferably one or more selected from the group consisting of polyglyceryl-6 monoisostearate, polyglyceryl-7 monoisostearate, polyglyceryl-8 monoisostearate, polyglyceryl-9 monoisostearate, polyglyceryl-10 monoisostearate, polyglyceryl-11 monoisostearate, polyglyceryl-12 monoisostearate, and polyglyceryl-13 monoisostearate, more preferably one or more selected from the group consisting of polyglyceryl-6 monoisostearate, polyglyceryl-7 monoisostearate, polyglyceryl-8 monoisostearate, polyglyceryl-9 monoisostearate, and polyglyceryl-10 monoisostearate, and even more preferably one or more selected from the group consisting of polyglyceryl-10 monoisostearate and polyglyceryl-6 monoisostearate. The component (A) may be used alone or in combination of two or more kinds.

[0014] The content of component (A) in the microemulsion of the present invention is preferably 0.03 mass% to 20.00 mass%, more preferably 0.50 mass% to 15.00 mass%, even more preferably 1.00 mass% to 12.00 mass%, and even more preferably 2.00 mass% to 5.00 mass%, based on the total mass of the microemulsion.

[0015] Component (B) is a solid or semi-solid oil at 25° C. Specifically, component (B) is a solid or semi-solid oil at room temperature (25° C.) and normal pressure (1 atm). However, in the present invention, component (B) does not fall under component (C) described below. Component (B) can be solubilized by component (A) to form the oil phase of a microemulsion. In addition, a solid state refers to a state that has no fluidity at 25°C, and a semi-solid state refers to a state that shows almost no deformation in a stress-free environment at 20°C under atmospheric pressure, but shows a tendency to deform when subjected to slight stress (10 to 100 g / cm 2 This refers to something that deforms when subjected to a force (such as a degree of deformation). The melting point of component (B) is preferably 23° C. or higher, more preferably 25° C. or higher, and even more preferably 35° C. or higher. Also, the melting point is preferably 100° C. or lower, more preferably 80° C. or lower, and even more preferably 70° C. or lower. In the present invention, the oil agent specifically refers to a component that undergoes phase separation from water after being suspended in water at 25 to 65° C. and left to stand for 1 hour.

[0016] The solid oil at 25° C. is not particularly limited, but examples thereof include hydrocarbon-based solid oils, ester-based solid oils, higher alcohol-based solid oils, silicone-based solid oils, and the like. Examples of solid oils that can be used include paraffin wax, ceresin wax, microcrystalline wax, polyethylene wax, ethylene-propylene copolymer, montan wax, and Fischer-Tropsch wax; solid oils that can be used include ester-based solid oils such as hydrogenated jojoba oil, hydrogenated rapeseed oil, beeswax, carnauba wax, candelilla wax, rice wax, Theobroma grandiflorum seed oil, (eicosene / vinylpyrrolidone) copolymer, α-olefin-vinylpyrrolidone copolymer, glyceryl tribehenate, and cetyl palmitate; stearyl alcohol, Examples of solid oil agents based on higher alcohols, such as cetanol, lauryl alcohol, and behenyl alcohol; and solid oil agents based on silicones, such as trimethylsiloxysilicate, polysilsesquioxane, (acrylates / dimethicone) copolymer, (acrylates / behenyl acrylate / dimethicone methacrylate) copolymer, (acrylates / stearyl acrylate / dimethicone methacrylate) copolymer, alkyl (C30-45) methicone, stearyl dimethicone, stearoxytrimethylsilane, and alkyl (C30-45) dimethylsilyl polypropylsilsesquioxane.

[0017] The semi-solid oil at 25°C is not particularly limited, and examples thereof include hydrocarbon-based semi-solid oil, ester-based semi-solid oil, ether-based semi-solid oil, silicone-based semi-solid oil, and the like. For example, hydrocarbon-based semi-solid oil such as petrolatum; dipentaerythrityl hexa(hydroxystearate / stearic acid / rosin acid), dipentaerythrityl (hydroxystearate / stearic acid / rosin acid), dipentaerythrityl hexahydroxystearate, dipentaerythrityl tetra(hydroxystearate / isostearate), dipentaerythrityl (hydroxystearate / isostearate), tri(caprylic acid / capric acid / myristic acid / stearic acid), bisdiglyceryl polyacyladipate-2, hydrogenated castor oil stearate, hydrogenated castor oil isostearate, hydrogenated castor oil hyd. Examples of the oils include ester-based semi-solid oils such as hydrogenated castor oil with roxystearic acid, hydrogenated palm oil, hydrogenated coconut oil, cholesteryl hydroxystearate, phytosteryl oleate, phytosteryl macadamiate, phytosteryl sunflower seed oil, phytosteryl isostearate, dimer dilinoleate (phytosteryl / isostearyl / cetyl / stearyl / behenyl), dimer dilinoleyl bis(behenyl / isostearyl / phytosteryl) dimer dilinoleate, sucrose pentahydroxystearate, di(octyldodecyl / phytosteryl / behenyl) lauroyl glutamate, and shea butter; ether-based semi-solid oils such as hydroxyalkyl dimer silinoleyl ether; and silicone-based semi-solid oils such as dimethicone crosspolymer and (dimethicone / vinyl dimethicone) crosspolymer.

[0018] Among these, component (B) is preferably one or more selected from the group consisting of ester-based solid oils, hydrocarbon-based semi-solid oils, and ester-based semi-solid oils, and more preferably one or more selected from hydrogenated rapeseed oil, Theobroma grandiflorum seed butter, cetyl palmitate, petrolatum, phytosteryl macadamiate, dimer dilinoleic acid (phytosteryl / isostearyl / cetyl / stearyl / behenyl), and shea butter. The component (B) may be used alone or in combination of two or more kinds.

[0019] The content of component (B) in the microemulsion of the present invention is preferably 0.01 to 10.00% by mass, more preferably 0.02 to 5.00% by mass, and even more preferably 0.10 to 1.00% by mass, based on the total mass of the microemulsion.

[0020] In the microemulsion of the present invention, the mass ratio of the content of component (A) to the content of component (B) is preferably 1:1 to 15:1, more preferably 2:1 to 14:1, even more preferably 3:1 to 13:1, even more preferably 5:1 to 11:1, and particularly preferably The ratio is 6:1 to 10:1.

[0021] The microemulsion of the present invention may contain component (C), a higher alcohol that is liquid at 25°C. In the present invention, higher alcohol refers to one having 6 or more carbon atoms, and the number of carbon atoms in component (C) is preferably 10 to 25, more preferably 12 to 24, even more preferably 14 to 23, and even more preferably 16 to 22. Component (C) may be linear or branched, saturated or unsaturated.

[0022] Component (C) is not particularly limited, but examples thereof include oleyl alcohol, jojoba alcohol, lauryl alcohol, myristyl alcohol, isostearyl alcohol, octyldodecyl alcohol, 2-hexyldecanol, and 2-decyltetradecanol. Among these, one or more selected from the group consisting of oleyl alcohol and jojoba alcohol are preferred. Jojoba alcohol is an unsaturated higher alcohol obtained by reducing jojoba oil obtained from dried jojoba seeds, and contains about 90% eicosenol having 20 carbon atoms and docosenol having 22 carbon atoms. There are no particular limitations on the type of alcohol used as long as it is suitable for use in cosmetics. For example, commercially available products such as jojoba alcohol (manufactured by Koei Kogyo Co., Ltd.) and NIKKOL jojoba alcohol (manufactured by Nikko Chemicals Co., Ltd.) can be used. The component (C) may be used alone or in combination of two or more kinds.

[0023] The content of component (C) in the microemulsion of the present invention is preferably 0.03 mass % to 5.00 mass %, more preferably 0.10 mass % to 3.00 mass %, and even more preferably 0.20 mass % to 1.50 mass %, based on the total mass of the microemulsion.

[0024] In the microemulsion of the present invention, the mass ratio of the content of component (A) to the content of component (C) is preferably 1:5 to 50:1, more preferably 1:3 to 40:1, even more preferably 1:1 to 25:1, still more preferably 4:1 to 18:1, and particularly preferably 9:1 to 13:1.

[0025] In the microemulsion of the present invention, the mass ratio of the content of component (B) to the content of component (C) is preferably 1:13 to 10:1, more preferably 1:5 to 8:1, even more preferably 1:1 to 6:1, and even more preferably 1:1 to 2:1.

[0026] The microemulsion of the present invention may be substantially free of component (C), a higher alcohol that is liquid at 25° C. Component (C) is generally used as an auxiliary surfactant that assists in solubilizing an oil in the field of microemulsions, but according to the present invention, a microemulsion in which an oil is stably solubilized can be formed even if it is substantially free of component (C).

[0027] In the present invention, "substantially free of component (C)" means that component (C) is not intentionally added to the microemulsion of the present invention, and may contain a small amount of component (C) that is inevitably mixed in during the production of the microemulsion of the present invention. For example, component (C) that is associated with the blended components and is contained in the microemulsion of the present invention in an amount less than that at which the effect of the component (C) is exerted (so-called carry-over component) may be contained. For example, the content of component (C) in the microemulsion of the present invention is 0.01% by mass or less, preferably 0.001% by mass or less, and more preferably 0% by mass.

[0028] The microemulsion of the present invention contains component (D), an oil that is liquid at 25°C. However, in the present invention, component (D) does not fall under the category of component (C). Component (D) can be solubilized by component (A) to form the oil phase of the microemulsion.

[0029] Component (D) is not particularly limited, but examples thereof include hydrocarbon oils, ester oils, fatty acids, silicone oils, fluorine-based oils, etc. Specific examples thereof include hydrocarbon oils such as liquid paraffin, squalane, polybutene, polyisobutylene, α-olefin oligomers, isododecane, and light isoparaffin;Diisobutyl adipate, 2-hexyldecyl adipate, di-2-heptylundecyl adipate, cetyl 2-ethylhexanoate, stearyl 2-ethylhexanoate, isostearyl 2-ethylhexanoate, caprylic / capric triglyceride, neopentyl glycol dicaprate, propylene glycol dicaprate, glyceryl tri-2-ethylhexanoate, pentaerythrityl tetraethylhexanoate, polyglyceryl-10 deca-2-ethylhexanoate, isotridecyl isononanoate, isononanoic acid iso Sononil, diisopropyl sebacate, di-2-ethylhexyl sebacate, isopropyl myristate, octyldodecyl myristate, isostearyl myristate, myristyl myristate, isopropyl palmitate, cetyl palmitate, 2-ethylhexyl palmitate, 2-ethylhexyl stearate, octyldodecyl isostearate, isostearyl isostearate, 2-ethylhexyl isostearate, isopropyl isostearate, trimethylolpropane triisostearate , Ethylhexyl methoxycinnamate, Octyldodecyl stearoyl stearate, Polyglyceryl-2 isostearate, Polyglyceryl-2 diisostearate, Polyglyceryl-2 triisostearate, Polyglyceryl-2 tetraisostearate, Dipentaerythrityl tetraisostearate, Polyglyceryl-10 decaisostearate, Oleyl oleate, Octyldodecyl oleate, Decyl oleate, Triethyl citrate, Di-2-ethylhexyl succinate, Diisostearyl malate, Tri Tridecyl mellitic acid, coconut oil, olive oil, palm oil, macadamia nut oil, meadowfoam oil, jojoba oil, rapeseed oil, rice bran oil, castor oil, mink oil, ester oils such as dimer dilinoleyl bisisostearyl dimer dilinoleate, dimer dilinoleyl diisostearate, di(isostearyl / phytosteryl) dimer dilinoleate, dihydrogenated rosinder madilinoleyl, and di(phytosteryl-2-octyldodecyl) N-lauroyl-L-glutamate; fatty acids such as isostearic acid and oleic acid;Examples of such oils include silicone oils such as dimethylpolysiloxane (dynamic viscosity 1 to 1000CS), cyclomethicone, caprylyl methicone, dimethiconol, methylphenylpolysiloxane, and diphenylpolysiloxane; fluorine-based oils such as perfluorodecane, perfluorooctane, and perfluoropolyether; essential oils, oil-based fragrances, and the like. Among these, hydrocarbon oils are preferred, and squalane is more preferred. The component (D) may be used alone or in combination of two or more kinds.

[0030] The content of component (D) in the microemulsion of the present invention is preferably 0.03 mass% to 20.00 mass%, more preferably 0.50 mass% to 15.00 mass%, even more preferably 1.00 mass% to 7.00 mass%, and still more preferably 2.00 mass% to 4.00 mass%, based on the total mass of the microemulsion.

[0031] In the microemulsion of the present invention, the mass ratio of the content of component (A) to the content of component (D) is preferably 1:5 to 5:1, more preferably 1:4 to 3:1, even more preferably 1:3 to 2:1, and even more preferably 1:2 to 3:2.

[0032] In the microemulsion of the present invention, the mass ratio of the content of component (B) to the content of component (D) is preferably 1:1 to 1:20, more preferably 1:2 to 1:15, even more preferably 1:3 to 1:12, and even more preferably 1:5 to 1:9.

[0033] In the microemulsion of the present invention, the mass ratio of the content of component (C) to the content of component (D) is preferably 2:1 to 1:60, more preferably 1:1 to 1:30, even more preferably 1:2 to 1:20, even more preferably 1:8 to 1:13, and even more preferably 1:9 to 1:11.

[0034] The content of the oily component in the microemulsion of the present invention, either alone or in combination, is preferably 0.01% by mass to 30.00% by mass, more preferably 0.10% by mass to 20.00% by mass, even more preferably 0.50% by mass to 10.00% by mass, even more preferably 1.00% by mass to 5.00% by mass, and particularly preferably 2.00% by mass to 4.00% by mass. In the present invention, the oily component specifically refers to a component (usually excluding surfactants) that is suspended in water at 25 to 65°C and phase-separated from water after being left to stand for 1 hour. The oily component also includes components (B), (C), and (D).

[0035] In the microemulsion of the present invention, the mass ratio of the content of component (A) to the total content of oily components is preferably 3:1 to 1:4, more preferably 2:1 to 1:3, and even more preferably 2:3 to 3:2.

[0036] In the microemulsion of the present invention, the mass ratio of the total content of surfactants to the total content of oily components is preferably 3:1 to 1:4, more preferably 2:1 to 1:3, and even more preferably 2:3 to 3:2. Within the above range, stickiness on the skin is less likely to occur. The surfactant includes component (A) and other surfactants described later.

[0037] The total content of polar oil in the microemulsion of the present invention may be 0.01% by mass to 10.00% by mass, for example, 0.03% by mass to 7.00% by mass, or 0.05% by mass to 5.00% by mass. Generally, when a large amount of polar oil is contained as an oily component in an emulsion, stickiness on the skin occurs, but since component (A) is easy to solubilize polar oil, stickiness on the skin can be suppressed even when a large amount of polar oil is contained in the oily component.

[0038] In the present invention, the polar oil is a polar oil having an IOB value of 0.10 or more among components corresponding to component (B), component (C), or component (D). For example, the IOB value can be 0.15 or more, 0.20 or more, or 0.30 or more, and is 0.70 or less, 0.60 or less, or 0.50 or less.

[0039] Here, the IOB value is the Inorganic / Organic Balance. IOB is an abbreviation for Inorganic / Organic Ratio, which is a value that represents the ratio of inorganic value to organic value, and is an index that indicates the degree of polarity of an organic compound. Specifically, the IOB value is expressed as IOB value = inorganic value / organic value. For each of the "inorganic value" and "organic value", "inorganic value" is set according to various atoms or functional groups, for example, the "organic value" is 20 for one carbon atom in a molecule, and the "inorganic value" is 100 for one hydroxyl group, and the "inorganic value" and "organic value" of each atom and functional group in an organic compound are added up, and the IOB value of the organic compound can be calculated by accumulating the "inorganic value" and "organic value" of all atoms and functional groups in the organic compound (for example, see "Organic Conceptual Diagram - Basics and Applications" by Yoshio Koda, pp. 11-17, Sankyo Publishing, 1984).

[0040] Examples of polar oils include higher fatty acids such as oleic acid and isostearic acid; isopropyl myristate, octyl palmitate, isopropyl palmitate, butyl stearate, hexyl laurate, myristyl myristate, decyl oleate, isononyl isononanoate, isotridecyl isononanoate, cetyl ethylhexanoate, tetraethylhexanoate, and the like. Pentaerythrityl phosphate, diethylhexyl succinate, glycol distearate, glyceryl diisostearate, neopentyl glycol dicaprate, diisostearyl malate, trimethylolpropane triisostearate, glyceryl tri-2-ethylhexanoate (triethylhexanoin), trimethylolpropane trioctanoate, trimethylolpropane triisostearate, diisobutyl adipate, N-lauroyl-L-glutamic acid-2-octyldodecyl ester, 2-hexyldecyl adipate, diisopropyl sebacate Examples of suitable oils include ester oils such as ethylhexyl methoxycinnamate, octyl methoxycinnamate (sometimes referred to as "ethylhexyl methoxycinnamate"), 2-ethylhexyl palmitate, 2-ethylhexyl ethylhexanoate, triisostearin, tripropylene glycol dipivalate (sometimes referred to as "PPG-3 dipivalate"), octyl salicylate, and tri(caprylic / capric acid)glyceryl; vegetable oils such as olive oil and castor oil (IOB value = 0.43); higher alcohols such as decyl tetradecanol, octyldodecanol, and oleyl alcohol; and the like.

[0041] The content of the aqueous component in the microemulsion of the present invention is preferably 60.00 mass% to 99.99 mass%, more preferably 70.00 mass% to 99.80 mass%, even more preferably 80.00 mass% to 97.00 mass%, and even more preferably 90.00 mass% to 95.00 mass%, based on the total mass of the microemulsion. In the present invention, the aqueous component specifically refers to a component (usually not including a surfactant) that does not undergo phase separation from water after being suspended in water at 25 to 65° C. and left to stand for 1 hour.

[0042] The microemulsions of the present invention are of the oil-in-water type. Components (B), (C), and (D) may constitute the oil phase of the microemulsion.

[0043] The particle size of the oil droplets in a microemulsion is generally known to be slightly larger than that of a micelle and smaller than that of an emulsion, with a size of several nm to about 250 nm or less. The microemulsion of the present invention preferably has an average particle size of the oil droplets of 250 nm or less, more preferably 200 nm or less, and even more preferably 180 nm or less. If it is 250 nm or less, it is less susceptible to the effect of the difference in specific gravity between the aqueous phase and the oil phase, and the oil droplets are less likely to settle or float, so that the storage stability is easily improved. In addition, the average particle size of the oil droplets is preferably 50 nm or more, more preferably 100 nm or more, and even more preferably 150 nm or more. Here, the average particle size is the average particle size calculated by cumulant analysis using a dynamic light scattering device, for example, a dynamic light scattering particle size distribution analyzer (ELSZ-2000Z, manufactured by Otsuka Electronics Co., Ltd.) at 20°C, in a PP disposable cell, and measuring 75 times in total, and is the average particle size in the microemulsion of the present invention immediately after preparation.

[0044] The microemulsion of the present invention can be produced by a conventional method. That is, the mixing order is not particularly limited, and the components can be mixed and solubilized in any order and by any method. In addition, the mixture can be stirred by applying a high shear force by a machine, or a fine microemulsion can be easily formed by manual stirring.

[0045] The microemulsion of the present invention has excellent storage stability. In addition, the microemulsion of the present invention has excellent usability because it is less sticky on the skin during application. Therefore, the microemulsion of the present invention is preferably used as an external preparation for skin, specifically, as a cosmetic, a quasi-drug, or a pharmaceutical.

[0046] The microemulsion of the present invention may contain any other components as long as the effects of the present invention are not impaired. Such optional ingredients may be any ingredients that are commonly used in skin care products such as cosmetics. Examples of such additives include other alcohols, powders, moisturizers, other surfactants, sequestering agents, pearlescent agents, amino acids, organic amines, pH adjusters, vitamins, antioxidants, preservatives, water-soluble polymers, and various active ingredients.

[0047] Examples of other alcohols other than component (C) include monohydric lower alcohols such as ethanol; and dihydric alcohols such as ethylene glycol, 1,3-butylene glycol, trimethylene glycol, 1,2-butylene glycol, propylene glycol, propanediol, 1,2-pentanediol, 3-methyl-1,3-butanediol, tetramethylene glycol, 2,3-butylene glycol, pentamethylene glycol, and 2-butene-1,4-diol.

[0048] The powder may be spherical, needle-like, plate-like, or the like, and its shape is not particularly limited. Examples of the powder include inorganic powders (e.g., talc, kaolin, mica, sericite, white mica, gold mica, synthetic mica, red mica, black mica, vermiculite, magnesium carbonate, calcium carbonate, aluminum silicate, barium silicate, calcium silicate, magnesium silicate, strontium silicate, tungstate metal salts, magnesium, silica, alumina, zeolite, barium sulfate, calcined calcium sulfate (calcined gypsum), calcium phosphate, fluorapatite, hydroxyapatite, ceramic powder, boron nitride, etc.); organic powders (e.g., polyamide resin powder (nylon powder), polyethylene powder, polymethyl (meth)acrylate powder, polystyrene powder, styrene and acrylic acid copolymer resin powder, silicone resin powder, benzoguanamine resin powder, polytetrafluoroethylene powder, cellulose powder, etc.); metal soaps (e.g., methyl methacrylate powder, polymethyl methacrylate powder, cellulose powder, etc.); Zinc stearate, calcium palmitate, aluminum stearate); inorganic white pigment (e.g., titanium dioxide, zinc oxide, etc.); inorganic red pigments (e.g., iron oxide (red oxide), iron titanate, etc.); inorganic brown pigments (e.g., gamma-iron oxide, etc.); inorganic yellow pigments (e.g., yellow iron oxide, ocher, etc.); inorganic black pigments (e.g., black iron oxide, low-order titanium oxide, etc.); inorganic purple pigments (e.g., mango violet, cobalt violet, etc.); inorganic green pigments (e.g., chromium oxide, chromium hydroxide, cobalt titanate, etc.); inorganic blue pigments (e.g., ultramarine, Prussian blue, etc.); pearl pigments (e.g., titanium oxide coated mica, titanium oxide coated bismuth oxychloride, titanium oxide coated talc, colored titanium oxide coated mica, bismuth oxychloride, fish scales, foil, etc.); metal powder pigments (e.g., aluminum powder, copper powder, etc.); organic pigments such as zirconium, barium or aluminum lake (e.g., organic pigments such as Red 201, Red 202, Red 204, Red 205, Red 220, Red 226, Red 228, Red 405, Orange 203, Orange 204, Yellow 205, Yellow 401, and Blue 404, Red 3, Red 104, Red 106, Red 227, Red 230, Red 401, Red 505, Orange 205, Yellow 4, Yellow 5, Yellow 202, Yellow 203, Green 3, and Blue 1, etc.); natural pigments (e.g., chlorophyll, β-carotene, etc.), etc.

[0049] Examples of moisturizing agents include chondroitin sulfate, hyaluronic acid, mucoitin sulfate, caronic acid, atelocollagen, cholesteryl-12-hydroxystearate, sodium lactate, dl-pyrrolidone carboxylate, short-chain soluble collagen, diglycerin (EO)PO adduct, Rosa rugosa extract, Achillea millefolium extract, and Melilot extract.

[0050] The other surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and nonionic surfactants other than component (A).

[0051] Examples of anionic surfactants include fatty acid soaps (e.g., sodium laurate, sodium palmitate, etc.); higher alkyl sulfates (e.g., sodium lauryl sulfate, potassium lauryl sulfate, etc.); alkyl ether sulfates (e.g., POE triethanolamine lauryl sulfate, POE sodium lauryl sulfate, etc.; N-acyl sarcosinic acid (e.g., sodium lauroyl sarcosinate, etc.); higher fatty acid amide sulfonate (e.g., sodium N-myristoyl-N-methyl taurate, sodium coconut oil fatty acid methyl tauride, sodium lauryl methyl tauride, etc.); phosphate salts (sodium POE oleyl ether phosphate, POE stearyl ether phosphate, etc.); sulfosuccinates (e.g., sodium di-2-ethylhexyl sulfosuccinate, sodium monolauroyl monoethanolamide polyoxyethylene sulfosuccinate, sodium lauryl polypropylene glycol sulfosuccinate, etc.); alkylbenzene sulfonate (e.g., sodium linear dodecyl benzene sulfonate, sodium linear dodecyl benzene sulfonate, sodium lauryl methyl tauride, etc.); triethanolamine benzenesulfonate, linear dodecylbenzenesulfonic acid, etc.); higher fatty acid ester sulfate salts (e.g., sodium hydrogenated coconut oil fatty acid glycerin sulfate, etc.); N-acyl glutamates (e.g., monosodium N-lauroyl glutamate, disodium N-stearoyl glutamate, monosodium N-myristoyl-L-glutamate, etc.); sulfated oils (e.g., turmeric oil, etc.); POE alkyl ether carboxylic acids; POE alkyl allyl ether carboxylates; α-olefin sulfonates; higher fatty acid ester sulfonates; secondary alcohol sulfate salts; higher fatty acid alkylolamide sulfate salts; sodium lauroyl monoethanolamide succinate; ditriethanolamine N-palmitoyl aspartate; sodium caseinate, etc.

[0052] Examples of the cationic surfactant include alkyl trimethyl ammonium salts (e.g., stearyl trimethyl ammonium chloride, lauryl trimethyl ammonium chloride, etc.); alkyl pyridinium salts (e.g., cetyl pyridinium chloride, etc.); distearyl dimethyl ammonium chloride, dialkyl dimethyl ammonium salts; poly(N,N'-dimethyl- 3,5-Methylenepiperidinium;Alkyl quaternary ammonium salts;Alkyl dimethyl benzyl Examples of the alkylaminoethyl ammonium salt include benzyl ammonium salts; alkyl isoquinolinium salts; dialkyl morphonium salts; POE alkyl amines; alkyl amine salts; polyamine fatty acid derivatives; amyl alcohol fatty acid derivatives; benzalkonium chloride; and benzethonium chloride.

[0053] Examples of amphoteric surfactants include imidazoline-based amphoteric surfactants (e.g., 2-undecyl-N,N,N-(hydroxyethylcarboxymethyl)-2-imidazoline sodium, 2-cocoyl-2-imidazolinium hydroxide-1-carboxyethyloxy disodium salt, etc.); betaine-based surfactants (e.g., 2-heptadecyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, lauryl dimethylaminoacetic acid betaine, alkyl betaine, amido betaine, sulfobetaine, etc.).

[0054] Examples of nonionic surfactants other than component (A) include polyether-modified silicones (e.g., polyethylene glycol-10 dimethicone, polyethylene glycol-12 dimethicone, etc.); polyglycerin-modified silicones (e.g., polyglyceryl-3 disiloxane dimethicone, polyglyceryl-3 polydimethylsiloxyethyl dimethicone, etc.); sorbitan fatty acid esters (e.g., sorbitan monooleate, sorbitan monostearate, sorbitan monoisostearate, sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan sesquioleate, sorbitan non-hydrophilic nonionic surfactants such as diglycerol sorbitan penta-2-ethylhexyl, diglycerol sorbitan tetra-2-ethylhexyl, etc.; glycerin fatty acids (e.g., glyceryl monocottonseed oil fatty acid, glyceryl monoerucate, glyceryl sesquioleate, glyceryl monostearate, glyceryl α,α'-oleate pyroglutamate, glyceryl (monostearate / malate), etc.); propylene glycol fatty acid esters (e.g., propylene glycol monostearate, etc.); POE·POP alkyl ethers; and glycerin alkyl ethers. Also included are non-hydrophilic nonionic surfactants such as polyglyceryl monooleate, polyglyceryl monostearate, etc. lyceryl, etc.); POE sorbitan fatty acid esters (e.g., POE sorbitan monooleate, POE sorbitan monostearate, POE sorbitan tetraoleate, etc.); POE sorbit fatty acid esters (e.g., POE sorbitan monolaurate, POE sorbitan monooleate, POE sorbitan pentaoleate, POE sorbit monostearate, etc.); POE glycerin fatty acid esters (e.g., POE glycerin monostearate, POE glycerin monoisostearate, POE glycerin triisostearate, etc. POE monooleates, etc.; POE fatty acid esters (e.g., POE distearate, POE monodioleate, ethylene glycol distearate, etc.); POE alkyl ethers (e.g., POE lauryl ether, POE oleyl ether, POE stearyl ether, POE-behenyl ether, POE-2-octyldodecyl ether, POE cholestanol ether, etc.); POE alkyl phenyl ethers (e.g., POE nonyl phenyl ether, etc.); Pluronic types (e.g., Pluronic (registered trademark), etc.); tetra-POE·tetra-POP ethylenediamine condensates (e.g., tetraisopropyl ether ... hydrophilic nonionic surfactants such as POE beeswax and lanolin derivatives (e.g., POE sorbitol beeswax, etc.); alkanolamides (e.g., coconut oil fatty acid diethanolamide, lauric acid monoethanolamide, fatty acid isopropanolamide, etc.); POE propylene glycol fatty acid esters; POE alkylamines; POE fatty acid amides; sucrose fatty acid esters; alkyl glucosides; alkyl ethoxydimethylamine oxides; and trioleyl phosphate.

[0055] The microemulsion of the present invention may be substantially free of surfactants other than component (A). Incidentally, "substantially free of surfactants other than component (A)" means that no surfactants other than component (A) are intentionally added to the microemulsion of the present invention, and may contain a small amount of the surfactant that is inevitably mixed in during the production of the microemulsion of the present invention. For example, the surfactant may be contained in the microemulsion of the present invention in an amount smaller than that at which the effect of the surfactant is exerted (so-called carry-over component) that is associated with the blended components. For example, the content of the surfactant other than component (A) in the microemulsion of the present invention is 0.1% by mass or less, preferably 0.05% by mass or less, more preferably 0.01% by mass or less, even more preferably 0.001% by mass or less, and particularly preferably 0% by mass.

[0056] Examples of sequestering agents include 1-hydroxyethane-1,1-diphosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid tetrasodium salt, disodium edetate, trisodium edetate, tetrasodium edetate, sodium citrate, sodium polyphosphate, sodium metaphosphate, gluconic acid, phosphoric acid, citric acid, ascorbic acid, succinic acid, edetic acid, and trisodium ethylenediaminehydroxyethyltriacetate.

[0057] Examples of pearlescent agents include glycol distearate and titanium mica.

[0058] Examples of the amino acid include neutral amino acids (e.g., threonine, cysteine, etc.), basic amino acids (e.g., hydroxylysine, etc.), etc. Examples of the amino acid derivatives include sodium acyl sarcosine (sodium lauroyl sarcosine), acyl glutamate, sodium acyl β-alanine, glutathione, pyrrolidone carboxylic acid, etc.

[0059] Examples of organic amines include monoethanolamine, diethanolamine, triethanolamine, and Examples of the amines that can be used include isopropanolamine, morpholine, triisopropanolamine, 2-amino-2-methyl-1,3-propanediol, and 2-amino-2-methyl-1-propanol.

[0060] Examples of pH adjusters include buffers such as lactic acid-sodium lactate, citric acid-sodium citrate, and succinic acid-sodium succinate.

[0061] Vitamins include, for example, vitamins A, B1, B2, B6, C, E and their derivatives. , pantothenic acid and its derivatives, biotin, etc.

[0062] Examples of antioxidants include tocopherols, dibutylhydroxytoluene (BHT), butylhydroxyanisole, pyrosulfite, gallic acid esters, phosphoric acid, citric acid, ascorbic acid, maleic acid, malonic acid, succinic acid, fumaric acid, cephalin, hexametaphosphate, phytic acid, and ethylenediaminetetraacetic acid.

[0063] Examples of preservatives include parabens and phenoxyethanol.

[0064] Examples of water-soluble polymers include plant-based polymers (e.g., carrageenan, starch (co (corn, potato, wheat), glycyrrhizic acid); microbial polymers (e.g. natural water-soluble polymers such as animal polymers (e.g., collagen, casein, albumin, gelatin, etc.); Starch-based polymers (e.g., carboxymethyl starch, methylhydroxypropyl starch, etc.); cellulose-based polymers (hydroxypropylmethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, methylcellulose, ethylcellulose, hydroxypropylmethylcellulose stearoxy ether, sodium cellulose sulfate, carboxymethylcellulose, sodium carboxymethylcellulose, crystalline cellulose, cellulose powder, etc.); Examples of the water-soluble polymer include synthetic water-soluble polymers such as vinyl polymers (e.g., polyvinyl alcohol, polyvinyl methyl ether, polyvinylpyrrolidone, carboxyvinyl polymer, etc.); polyoxyethylene polymers (e.g., polyethylene glycol 20,000, 40,000, 60,000, etc.); acrylic polymers (e.g., sodium polyacrylate, polyethyl acrylate, polyacrylamide, etc.); polyethyleneimine; and cationic polymers.

[0065] Examples of the various active ingredients include anti-inflammatory agents (e.g., glycyrrhizinic acid derivatives, glycyrrhetinic acid derivatives, salicylic acid derivatives, hinokitiol, zinc oxide, allantoin, etc.); whitening agents (e.g., placenta extract, saxifrage extract, arbutin, etc.); various extracts (e.g., Phellodendron bark, Coptis japonica, Lithospermum root, Peony root, Swertia japonica, Birch, Sage, Loquat, Carrot, Aloe, Mallow, Iris, Grape, Coix seed, Loofah, Lily, Saffron, Cnidium rhizome, Angelica acutiloba, Hypericum perforatum, Ononis, Garlic, Capsicum annuum, Citrus chinensis, Angelica acutiloba, Seaweed, etc.), activators (e.g., Royal jelly, , photosensitizers, cholesterol derivatives, etc.); blood circulation promoters (e.g., nonylic acid valenylamide, nicotinic acid benzyl ester, nicotinic acid β-butoxyethyl ester, capsaicin, zingerone, cantharides tincture, ichthammol, tannic acid, α-borneol, tocopherol nicotinate, inositol hexanicotinate, cyclandelate, cinnarizine, tolazoline, acetylcholine, verapamil, cepharanthine, γ-oryzanol, etc.); antiseborrheic agents (e.g., sulfur, thianthol, etc.); anti-inflammatory agents (e.g., tranexamic acid, thiotaurine, hypotaurine, etc.), etc. EXAMPLES

[0066] The present invention will be described in more detail below with reference to examples, but the present invention does not exceed the gist of the present invention. However, the present invention is not limited to the following examples.

[0067] An oil-in-water microemulsion composition was prepared based on Table 1. Specifically, the components in Table 1 except for water were mixed and dissolved by heating to 60°C, and then water heated to 60°C was gradually added while stirring and mixing at 60°C and 120 rpm. The mixture was then cooled to 25°C. Each of the obtained microemulsion compositions was evaluated for the following items. The results are shown in Table 1.

[0068] [Table 1]

[0069] <Particle size and storage stability> The composition was stored at 40° C. for one month, and then the appearance was visually inspected. The average particle size of the composition before and after storage was calculated by dynamic light scattering. Measurement was performed using ELSZ-2000Z (manufactured by Otsuka Electronics Co., Ltd.) at 20°C, in a PP disposable cell, and cumulant analysis was performed. For each composition, the average particle size after storage was subtracted from the average particle size before storage (hereinafter also referred to as the difference between the average particle size before and after storage), and the storage stability was evaluated according to the following criteria. ◎: The difference in average particle size before and after storage is 0 nm or more and less than 50 nm ◯: The difference in average particle size before and after storage is 50 nm or more and less than 100 nm △: The difference in average particle size before and after storage is 100 nm or more and less than 175 nm ×: The difference in average particle size before and after storage is 175 nm or more, or there is obvious separation or creaming. is occurring.

[0070] <Non-sticky> Ten expert evaluation panelists evaluated the stickiness of the composition when it was directly applied to the inside of the forearm, and rated it according to the following criteria based on the number of panelists who evaluated it as sticky. ◎: No stickiness on skin during application (2 or fewer panelists rated the product as sticky) ◯: Almost no stickiness on the skin during application (3 to 5 panelists rated the product as sticky) △: Sticky feeling on skin during application (6 to 8 panelists rated the product as sticky) ×: Skin feels quite sticky during application (9 or more panelists rated the product as sticky) [Industrial Applicability]

[0071] The present invention provides a fine microemulsion having excellent storage stability and excellent usability. The microemulsion of the present invention is expected to be applied to skin external preparations that are comfortable to use, and is therefore extremely useful industrially.

Claims

1. An oil-in-water microemulsion comprising the following (A) and (B): (A) Polyglyceryl monoisostearate (B) An oil solution that is solid or semi-solid at 25°C

2. The microemulsion according to claim 1, wherein the HLB value of (A) is 8 to 15.

3. 2. The microemulsion according to claim 1, wherein the average degree of polymerization of the glycerin in (A) is 6 to 13.

4. The microemulsion according to claim 3, wherein (A) is at least one selected from the group consisting of polyglyceryl-10 monoisostearate and polyglyceryl-6 monoisostearate.

5. 2. The microemulsion according to claim 1, wherein the melting point of (B) is 23° C. or higher.

6. The microemulsion according to claim 1, wherein the content of (A) is 0.03% by mass to 20.00% by mass based on the total mass of the microemulsion.

7. The microemulsion according to claim 1, wherein the content of (B) is 0.01% by mass to 10.00% by mass based on the total mass of the microemulsion.

8. 2. The microemulsion according to claim 1, wherein the mass ratio of the content of (A) to the content of (B) is 1:1 to 15:

1.

9. The microemulsion according to claim 1, further comprising (C) a higher alcohol that is liquid at 25°C.

10. The microemulsion according to claim 9, wherein the carbon number of (C) is 10 to 25.

11. The microemulsion according to claim 9, wherein (C) is at least one selected from the group consisting of oleyl alcohol and jojoba alcohol.

12. The microemulsion according to claim 1, which is substantially free of (C) a higher alcohol that is liquid at 25°C.

13. The microemulsion according to claim 1, further comprising (D) an oil that is liquid at 25°C.

14. 2. The microemulsion according to claim 1, wherein the average particle size of the oil droplets is from 50 nm to 250 nm.

15. The microemulsion according to any one of claims 1 to 14, which is an external preparation for skin.

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