JP7759312B2 - Oil-in-water emulsion composition - Google Patents

Description

Related Applications

This invention is based on the priority of Japanese Patent Application No. 2020-033915 (filed February 28, 2020), the entire contents of which are incorporated herein by reference.

The present invention relates to an oil-in-water emulsion composition and a sheet-type topical skin preparation in which said composition is impregnated into a sheet-type substrate, and in particular to improving the skin's moisturizing effect and firmness, and the plump feeling of skin that is firm from the inside.

In recent years, many formulations have been developed that can make the skin feel firmer, as well as formulations that have the effect of smoothing wrinkles (for example, Patent No. 3920797). Many of these formulations contain water-soluble or oil-soluble film-forming agents, but these cosmetics can become sticky and uncomfortable to use when the solvent evaporates and the polymer forms a film on the skin. Furthermore, even if a firming sensation like a film is felt on the outside, it is difficult to feel a plump, firm feeling from within.

Patent No. 3920797

The present invention has been made in consideration of the problems of the prior art, and its purpose is to provide an oil-in-water emulsion composition that does not cause stickiness, provides a feeling of firmness from within the skin, and is effective in improving skin conditions such as wrinkles with long-term use, as well as a sheet-like topical skin preparation in which the composition is impregnated into a sheet-like substrate.

As a result of intensive research conducted by the present inventors to achieve the above-mentioned object, it was found that by combining a specific film-forming agent and blending a polyhydric alcohol as a moisturizing agent with an oil-soluble drug, it is possible to obtain an oil-in-water emulsion composition that has low viscosity but provides a plump, firm feeling from both the inside and outside of the skin and also has an excellent wrinkle-reducing effect, and this has led to the completion of the present invention.
That is, the oil-in-water emulsion composition of the present invention is
polyvinyl alcohol,
Vinyl acetate/vinylpyrrolidone copolymer,
polyhydric alcohols,
Oil-soluble drugs,
Contains oil,
The viscosity is 2000 mPa s or less,
The emulsion is characterized by having an emulsified particle size of 5 μm or less.
In the oil-in-water emulsion composition, the blending ratio of polyvinyl alcohol to vinyl acetate-vinylpyrrolidone copolymer is within the range of 1:2 to 2:1.
The oil-in-water emulsion composition has a mass ratio of (total of polyvinyl alcohol and vinyl acetate-vinylpyrrolidone copolymer):(polyhydric alcohol) of 1:50 to 1:110, and contains 0.05 to 1.0 mass% of polyvinyl alcohol and 0.05 to 1.0 mass% of vinyl acetate-vinylpyrrolidone copolymer.
It is also preferable to prepare a sheet-type external skin preparation by impregnating a sheet-type substrate with the oil-in-water emulsion composition.
Furthermore, the oil-soluble drug contained in the oil-in-water emulsion composition is preferably retinol.

According to the present invention, by combining a specific combination of film-forming agents with a polyhydric alcohol and an oil-soluble drug, it is possible to obtain an emulsion composition that gives the skin a plump, firm feeling from both the inside and outside without causing stickiness, and that can also be expected to have a wrinkle-reducing effect.

(a) Polyvinyl alcohol The polyvinyl alcohol used in the emulsion composition of the present invention is not particularly limited by molecular weight, etc. Polyvinyl alcohol is obtained by hydrolyzing polyvinyl acetate and is a linear polymer of vinyl alcohol. The polyvinyl alcohol used in the present invention preferably has a degree of saponification (mol%) of about 85 to 90.

Examples of polyvinyl alcohols commercially available as cosmetic raw materials include Kuraray Poval (manufactured by Kuraray Co., Ltd.), Denka Poval (manufactured by Denka Co., Ltd.), Poval (manufactured by Japan Vinyl Acetate & Poval Co., Ltd.), and Gohsenol ^™ (manufactured by Mitsubishi Chemical Corporation).

In this invention, polyvinyl alcohol can form a firm film and is expected to be highly effective in improving skin firmness. Furthermore, together with the vinyl acetate-vinylpyrrolidone copolymer, it can provide sufficient film strength and a comfortable fit to the skin.

The amount of polyvinyl alcohol blended in the emulsion composition of the present invention is 0.05 to 1.0% by mass of the total amount of the composition. It is preferably 0.1 to 0.5% by mass, and more preferably 0.3 to 0.5% by mass. If the amount of polyvinyl alcohol blended is less than 0.05% by mass, the coating-forming effect may not be achieved, and if it exceeds 1.0% by mass, usability tends to deteriorate.

(b) Vinyl Acetate-Vinyl Pyrrolidone Copolymer The vinyl acetate-vinyl pyrrolidone copolymer used in the present invention is a copolymer of vinyl pyrrolidone and vinyl acetate, and is an amphiphilic copolymer having an average molecular weight of 50,000 to 60,000.

Vinyl acetate/vinylpyrrolidone copolymers commercially available as cosmetic ingredients include, for example, PVP/VA S-630 (Ashland Specialty Ingredients) and PVA-6450 Acorn M (Osaka Organic Chemical Industry Co., Ltd.).

In the present invention, the film-forming ability of vinyl acetate-vinylpyrrolidone copolymer is slightly inferior to that of polyvinyl alcohol, but it has high affinity with the skin and can provide a comfortable fit.

The amount of vinyl acetate-vinylpyrrolidone copolymer blended in the emulsion composition of the present invention is 0.05 to 1.0% by mass of the total amount of the composition. It is preferably 0.1 to 0.5% by mass, and more preferably 0.3 to 0.5% by mass. If the amount of vinyl acetate-vinylpyrrolidone copolymer blended is less than 0.05% by mass, it may be difficult to feel a firming sensation from the inside, and if it exceeds 1.0% by mass, it may feel oily.

In the emulsion composition of the present invention, the blending ratio of (a) polyvinyl alcohol to (b) vinyl acetate-vinylpyrrolidone copolymer is preferably 1:2 to 2:1, and more preferably 0.8:1 to 1:0.8.

(c) Moisturizing Agent The humectant used in the emulsion composition of the present invention is preferably a polyhydric alcohol, such as propylene glycol, polyethylene glycol, dipropylene glycol, glycerin, 1,3-butylene glycol, xylitol, sorbitol, maltitol, ethylene glycol, or trimethylolpropane.
One or more of these may be used, and dipropylene glycol, glycerin, and 1,3-butylene glycol are particularly preferred.
The moisturizing agent employed in the present invention gels the film formed on the skin by the vinyl acetate-vinylpyrrolidone copolymer and polyvinyl alcohol, contributing to the formation of a moist, flexible gel-like film.

The amount of the moisturizing agent blended in the emulsion composition of the present invention is 10 to 25% by mass, preferably 10 to 20% by mass, and more preferably 10 to 17% by mass, based on the total amount of the composition.
If the amount of moisturizer is less than 10% by mass, the moisturizer may not be effective, and if it exceeds 25% by mass, resistance may be felt with the fingers when spreading it on the skin, and the product may subjectively feel heavy when spread.

(d) Oil-Soluble Drugs Examples of oil-soluble drugs used in the emulsion composition of the present invention include oil-soluble vitamins, etc. Examples include retinol, retinolate derivatives (retinol acetate, retinol palmitate, etc.), vitamin E, vitamin E derivatives (vitamin E acetate, etc.), vitamin Ds, vitamin K, etc.
Among these, retinol is particularly preferred, as it improves skin firmness and reduces wrinkles. Retinol is an oil-soluble organic compound that is a nutrient, vitamin _A1 , and is approved as an active ingredient in quasi-drugs to reduce wrinkles. Retinol alone is highly unstable and highly vulnerable to heat, light, and oxygen.

The amount of retinol in the emulsion composition of the present invention is 0.01 to 0.1% by mass. Preferably, it is 0.01 to 0.06% by mass. An appropriate amount can be added taking into account drug stability.

In order to improve the pharmaceutical stability of retinol, silicone oil, hydrocarbon oil, ester oil, etc. can be blended as oil components other than retinol.
Specific examples include linear polysiloxanes such as dimethylpolysiloxane and diphenylpolysiloxane; cyclic polysiloxanes such as octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane and dodecamethylcyclohexasiloxane; silicone oils such as various modified polysiloxanes (amino-modified polysiloxane, polyether-modified polysiloxane, alkyl-modified polysiloxane, fluorine-modified polysiloxane, etc.); liquid paraffin, ozokerite, and squalane. Hydrocarbon oils such as pristane, paraffin, ceresin, squalene, petrolatum, and microcrystalline wax; isopropyl myristate, cetyl octanoate, octyldodecyl myristate, isopropyl palmitate, butyl stearate, hexyl laurate, myristyl myristate, decyl oleate, hexyldecyl dimethyloctanoate, cetyl lactate, myristyl lactate, lanolin acetate, isocetyl stearate, isocetyl isostearate, Cholesteryl 12-hydroxystearate, ethylene glycol di-2-ethylhexanoate, dipentaerythritol fatty acid ester, N-alkyl glycol monoisostearate, neopentyl glycol dicaprate, diisostearyl malate, glycerin di-2-heptylundecanoate, trimethylolpropane tri-2-ethylhexanoate, trimethylolpropane triisostearate, glycerin trioctanoate, glycerin triisopalmitate, trimethylolpropane triisostearate, cetyl 2-ethylhexanoate, 2-ethylhexyl palmitate, glycerin trimyristate, tri-2-heptylundecanoate glyceride, castor oil fatty acid methyl ester, oleyl oleate, acetoglyceride, 2-heptylundecyl palmitate, diisostearate Synthetic ester oils such as butyl, N-lauroyl-L-glutamic acid-2-octyldodecyl ester, di-2-heptylundecyl adipate, ethyl laurate, di-2-ethylhexyl sebacate, 2-hexyldecyl myristate, 2-hexyldecyl palmitate, 2-hexyldecyl adipate, diisopropyl sebacate, 2-ethylhexyl succinate, triethyl citrate, etc.; other avocado oils Examples of suitable oils include vegetable oils and fats such as camellia oil, macadamia nut oil, corn oil, olive oil, rapeseed oil, sesame oil, persic oil, wheat germ oil, sasanqua oil, castor oil, linseed oil, safflower oil, cottonseed oil, perilla oil, soybean oil, peanut oil, grapeseed oil, almond oil, tea seed oil, kaya oil, rice bran oil, Chinese tung oil, Japanese tung oil, jojoba oil, and germ oil; and animal oils and fats such as turtle oil, egg yolk oil, and mink oil.
In particular, methylphenyl silicone oil, pentaerythrityl tetra-2-ethylhexanoate (for example, "RA-PE-408" (manufactured by Nippon Fine Chemical Co., Ltd.)) is useful for the pharmaceutical stability of retinol.

Furthermore, the oil-in-water emulsion composition of the present invention contains water as an essential component.

In addition to the essential components described above, the emulsion composition of the present invention can contain other ingredients typically used in emulsion compositions of cosmetics, pharmaceuticals, etc., such as powder components, water-soluble polymers, thickeners, UV absorbers, sequestering agents, sugars, amino acids, organic amines, polymer emulsions, pH adjusters, antioxidants, antioxidant aids, fragrances, etc., within quantitative and qualitative ranges that do not impair the effects of the present invention.

Examples of powder components include inorganic powders (e.g., talc, kaolin, mica, sericite, muscovite, phlogopite, synthetic mica, lepidolite, biotite, vermiculite, magnesium carbonate, calcium carbonate, aluminum silicate, barium silicate, calcium silicate, strontium silicate, metal tungstate, magnesium, silica, zeolite, barium sulfate, calcined calcium sulfate, calcium phosphate, fluorapatite, hydroxyapatite, ceramic powder, metal soaps (e.g., zinc myristate, calcium palmitate, stearic acid, aluminum phosphate, boron nitride, etc.); organic powders (for example, polyamide resin powder (nylon powder), polyethylene powder, polymethyl methacrylate powder, polystyrene powder, styrene-acrylic acid copolymer resin powder, benzoguanamine resin powder, polytetrafluoroethylene powder, cellulose powder, etc.); inorganic white pigments (for example, titanium dioxide, zinc oxide, etc.); inorganic red pigments (for example, iron oxide (red iron oxide), iron titanate, etc.); inorganic brown pigments (for example, γ-iron oxide, etc.); inorganic yellow pigments (for example, yellow iron oxide, yellow ochre, etc.); inorganic black pigments (for example, black 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, iron blue, etc.); pearl pigments (e.g., titanium dioxide coated mica, titanium dioxide coated bismuth oxychloride, titanium dioxide coated talc, colored titanium dioxide coated mica, bismuth oxychloride, fish scale foil, etc.); metal powder pigments (e.g., aluminum powder, copper powder, etc.); zirconium, barium or aluminum Examples of organic pigments include aluminum lakes (e.g., organic pigments such as Red No. 201, Red No. 202, Red No. 204, Red No. 205, Red No. 220, Red No. 226, Red No. 228, Red No. 405, Orange No. 203, Orange No. 204, Yellow No. 205, Yellow No. 401, and Blue No. 404; Red No. 3, Red No. 104, Red No. 106, Red No. 227, Red No. 230, Red No. 401, Red No. 505, Orange No. 205, Yellow No. 4, Yellow No. 5, Yellow No. 202, Yellow No. 203, Green No. 3, and Blue No. 1); and natural pigments (e.g., chlorophyll, β-carotene, etc.).

Natural water-soluble polymers include, for example, plant-derived polymers (e.g., gum arabic, tragacanth gum, galactan, guar gum, carob gum, karaya gum, carrageenan, pectin, agar, quince seed, algae colloid (cassow extract), starch (rice, corn, potato, wheat)); and microbial-derived polymers (e.g., xanthan gum, dextran, succinoglucan, pullulan, etc.).

Semi-synthetic water-soluble polymers include, for example, starch-based polymers (e.g., carboxymethyl starch, methylhydroxypropyl starch, etc.); cellulose-based polymers (methyl cellulose, ethyl cellulose, methylhydroxypropyl cellulose, hydroxyethyl cellulose, sodium cellulose sulfate, hydroxypropyl cellulose, carboxymethyl cellulose, sodium carboxymethyl cellulose, crystalline cellulose, cellulose powder, etc.); and alginate-based polymers (e.g., sodium alginate, propylene glycol alginate, etc.).

Synthetic water-soluble polymers include, for example, vinyl polymers (e.g., polyvinyl alcohol, polyvinylpyrrolidone, carboxyvinyl polymer, etc.); polyoxyethylene polymers (e.g., polyethylene glycol 20,000, 40,000, 60,000, 1,000,000 polyoxyethylene polypropylene copolymers, etc.); acrylic polymers (e.g., sodium polyacrylate, polyethyl acrylate, polyacrylamide, etc.); cationic polymers, etc.

Examples of thickeners include gum arabic, carrageenan, karaya gum, tragacanth gum, carob gum, quince seed, casein, dextrin, gelatin, sodium pectinate, sodium allaginate, methylcellulose, ethylcellulose, sodium carboxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, sodium polyacrylate, carboxyvinyl polymer, alkyl-modified carboxyvinyl polymer, locust bean gum, guar gum, tamarind gum, dialkyldimethylammonium cellulose sulfate, xanthan gum, gellan gum, aluminum magnesium silicate, bentonite, hectorite, AlMg silicate (Bee Gum), Laponite, and silicic anhydride.

Examples of ultraviolet absorbers include benzoic acid-based ultraviolet absorbers (e.g., para-aminobenzoic acid (hereinafter abbreviated as PABA), PABA monoglycerin ester, N,N-dipropoxy PABA ethyl ester, N,N-diethoxy PABA ethyl ester, N,N-dimethyl PABA ethyl ester, N,N-dimethyl PABA butyl ester, N,N-dimethyl PABA ethyl ester, etc.); anthranilic acid-based ultraviolet absorbers (e.g., homomenthyl-N- acetyl anthranilate, etc.); salicylic acid-based ultraviolet absorbers (e.g., amyl salicylate, menthyl salicylate, homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, p-isopropanol phenyl salicylate, etc.); cinnamic acid-based ultraviolet absorbers (e.g., octyl cinnamate, ethyl-4-isopropyl cinnamate, methyl-2,5-diisopropyl cinnamate, ethyl-2,4-diisopropyl cinnamate, methyl-2,4-diisopropyl cinnamate, propyl-p-methoxycinnamate, isopropyl-p-methoxycinnamate, isoamyl-p-methoxycinnamate, octyl-p-methoxycinnamate (2-ethylhexyl-p-methoxycinnamate), 2-ethoxyethyl-p-methoxycinnamate, cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenylcinnamate, 2-ethylhexyl Examples of suitable benzotriazole derivatives include cyclohexyl-α-cyano-β-phenylcinnamate, glyceryl mono-2-ethylhexanoyl-diparamethoxycinnamate, etc.; pyridazine derivatives (dimorpholinopyridazine); 3-(4'-methylbenzylidene)-d,l-camphor, 3-benzylidene-d,l-camphor; 2-phenyl-5-methylbenzoxazole; 2,2'-hydroxy-5-methylphenylbenzotriazole; 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole; 2-(2'-hydroxy-5'-methylphenyl)benzotriazole; dibenzalazine; dianisoylmethane; 4-methoxy-4'-t-butyldibenzoylmethane; 5-(3,3-dimethyl-2-norbornylidene)-3-pentan-2-one, etc.

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.

Amino acids include, for example, neutral amino acids (e.g., threonine, cysteine, etc.); basic amino acids (e.g., hydroxylysine, arginine, etc.); and amino acid derivatives include, for example, sodium acyl sarcosine (sodium lauroyl sarcosine), acyl glutamate, acyltaurate, sodium acyl β-alanine, glutathione, pyrrolidone carboxylic acid, trimethylglycine, etc.

Examples of organic amines include monoethanolamine, diethanolamine, triethanolamine, morpholine, triisopropanolamine, 2-amino-2-methyl-1,3-propanediol, and 2-amino-2-methyl-1-propanol.

Examples of pH adjusters include buffers such as lactic acid-sodium lactate, citric acid-sodium citrate, and succinic acid-sodium succinate. Examples of antioxidants include delta-tocopherol, dibutylhydroxytoluene, butylhydroxyanisole, and gallic acid esters.

Examples of antioxidant aids include phosphoric acid, citric acid, ascorbic acid, maleic acid, malonic acid, succinic acid, fumaric acid, cephalin, hexametaphosphate, phytic acid, ethylenediaminetetraacetic acid, etc.

Other ingredients that can be added include, for example, preservatives (ethylparaben, butylparaben, phenoxyethanol, etc.); water-soluble whitening agents (for example, arbutin, tranexamic acid, potassium 4-methoxysalicylate, ellagic acid, ascorbic acid, ascorbic acid glucoside, acorbic acid derivatives such as magnesium ascorbyl phosphate, nicotinamide, etc.); enhancers (for example, royal jelly, photosensitizers, cholesterol derivatives, etc.); blood circulation promoters (for example, nonyl valerinamide, nicotinic acid benzyl ester, nicotinic acid citric acid β-butoxyethyl ester, capsaicin, zingerone, cantharides tincture, ichthammol, tannic acid, inositol hexanicotinate, cyclandelate, cinnarizine, tolazoline, acetylcholine, verapamil, cepharanthine, etc.; antiseborrheic agents (e.g., sulfur, thianthol, etc.); anti-inflammatory agents (e.g., glycyrrhizinate, salicylic acid derivatives, hinokitiol zinc oxide, allantoin, thiotaurine, hypotaurine, etc.), vitamin B6 tripalmitate, vitamin B6 dioctanoate, vitamin B2, vitamin B2 derivatives, vitamin B12, vitamin B15, vitamin B15 derivatives, etc.

The oil-in-water emulsion composition of the present invention is preferably produced by a method including the following steps (X) and (Y).
(X): A step of adding a hydrophilic nonionic surfactant to a moisturizer, and then adding an oil to the mixture to emulsify it.
(Y): A step of, after step (X), adding water to the emulsion composition, or diluting the emulsion composition by adding the emulsion composition to an aqueous phase, to obtain an oil-in-water emulsion composition.

The emulsification method of the present invention is a method in which, instead of a general oil-water system, a surfactant and oil are added to a moisturizing agent containing glycerin or the like to form liquid crystals, and water is then added to stabilize them.
In this method, (f) a hydrophilic nonionic surfactant is dissolved in an aqueous solvent and then emulsified by adding an oil component. Therefore, the interfacial tension between the oil and aqueous solvent is low, and even hydrophilic nonionic surfactants with low surface activity can be easily adsorbed to the interface with very little stirring force. Furthermore, since there is no need to apply heat, the manufacturing process is simplified and even heat-sensitive oil-soluble drugs (e.g., retinol) can be stably incorporated. Therefore, in this manufacturing method, all steps are preferably carried out at room temperature (5 to 40°C) to stably incorporate the oil-soluble drug (retinol). Furthermore, by adding water later, an extremely stable oil-in-water emulsion composition can be obtained that has low viscosity, a non-sticky, pleasant feel, a small particle size, and good uniformity. This method achieves an average emulsion particle size of 5 μm or less.

The hydrophilic nonionic surfactant (f) added in step (X) is not particularly limited as long as it is a hydrophilic nonionic surfactant typically used in topical skin preparations. However, preferred examples include POE-alkyl ethers such as POE-lauryl ether, POE-oleyl ether, POE-sterial ether, POE-behenyl ether, POE-2-octyldodecyl ether, and POE-cholestanol ether; Pluronic-type surfactants such as Pluronic (registered trademark); and POE-POP-alkyl ethers such as POE-POP-cetyl ether, POE-POP-2-decyltetradecyl ether, POE-POP-monobutyl ether, POE-POP-hydrogenated lanolin, and POE-POP-glycerin ether.

In the present invention, (f) hydrophilic nonionic surfactants can be used singly or in combination of two or more. The amount of surfactant to be added varies depending on the intended efficacy and effect of the topical skin preparation, but is preferably 0.2 to 0.8% by mass, and particularly preferably 0.4 to 0.6% by mass, of the oil-in-water emulsion composition.

Regarding the quantitative relationship of the stable oil-in-water emulsion composition of the present invention, in step (X), the blending ratio of the oil to the water-soluble solvent is preferably 25:12 to 1:3, and the blending ratio of the water-soluble solvent to the hydrophilic nonionic surfactant is preferably 15:1 to 75:1.
In step (Y), the ratio of the emulsified composition in step (X):water is in the range of 3:7 to 3:17.

With conventional emulsification methods, it was difficult to prepare a stable oil-in-water emulsion composition when the oil phase component was high. However, with the method of the present invention, an oil-based emulsion composition is first prepared in a water-soluble solvent, and then water is added to the emulsion composition, making it possible to stably prepare an oil-in-water emulsion composition with a high oil phase component.

Furthermore, in conventional emulsification methods, the viscosity increases and the feel becomes sticky as the oil phase component increases, but the method of the present invention makes it possible to obtain an oil-in-water emulsion composition that has low viscosity, is not sticky, and has a good feel, even when the oil phase component is present in a large amount.

The oil-in-water emulsion composition of the present invention is suitable not only for use in the form of emulsion cosmetics, but also for use as a sheet-type topical skin preparation in which the emulsion composition is impregnated into a sheet-type substrate. In this case, the viscosity of the oil-in-water emulsion composition is preferably 800 to 2000 mPa·s (30°C), more preferably 900 to 1100 mPa·s (30°C). If the viscosity exceeds 2000 mPa·s, the penetration into the substrate will be poor. Conversely, if the viscosity is less than 800 mPa·s, the composition may drip from the substrate during use, or if the content of the composition is reduced to prevent dripping, the effect of the oil-soluble drug may not be fully exerted.
The viscosity was measured at 30° C. using a BL viscometer manufactured by Shibaura Semtec Co., Ltd. under conditions of 12 rpm and 1 minute.

The oil-in-water emulsion composition of the present invention can be impregnated into a sheet-like substrate in sufficient quantity, allowing the oil-soluble drug to fully exert its effects. Furthermore, it has good stability on the substrate, and there are no problems with stability over time. Because the emulsion particles obtained by the emulsification process of the present invention are fine, the oil-soluble drug is uniformly dispersed in the emulsion composition and easily soaks into the sheet-like substrate.

When the oil-in-water emulsion composition of the present invention is used as a sheet-type topical skin preparation, it is essential that the oil-in-water emulsion composition be impregnated into a sheet substrate. The amount of the composition to be impregnated into the sheet substrate varies depending on the material of the sheet substrate, but at least an amount sufficient to wet the entire sheet substrate with the composition is required. Specifically, the amount is 5 to 20 times, and preferably 12 to 16 times, the mass of the sheet substrate.

By impregnating a sheet substrate with the oil-in-water emulsion composition of the present invention, it becomes possible to apply a larger amount per unit area of skin.
Furthermore, when the sheet is impregnated with the oil-soluble drug, the oil-soluble drug is more easily released into the skin when applied to the skin, and the amount absorbed by the skin is increased, so greater effects can be expected.

When using the oil-in-water emulsion composition of the present invention as a sheet-type topical skin preparation, the sheet-type substrate used is not particularly limited as long as it can absorb liquid and retain it between or on its surface, but nonwoven fabric is particularly preferred. Fiber materials that make up nonwoven fabric include cotton, rayon, pulp, hemp, acrylic, nylon, silk, polyamide, polyester, polyurethane, polypropylene, etc., and mixtures thereof. Cotton is particularly preferred because of its high ability to penetrate and retain the composition and its pleasant feel against the skin.

The oil-in-water emulsion composition can be impregnated into a sheet-like substrate by known methods. Examples include the dropping method, spraying method, pressure method, and dipping method. The sheet-like substrate can be used as is or folded, and one or more sheets can be used for impregnation.

The impregnated sheet-like substrate can be immediately sealed in an airtight container to produce a sheet-like topical skin preparation, but by placing it on a polyethylene terephthalate (PET) tray or the like and sealing it in a light-shielding, airtight bag or the like, such as an aluminum laminate package or a package with the inside coated with PET, a sheet-like topical skin preparation with dramatically improved stability of the oil-soluble drug can be produced.
PET is particularly suitable because it has low adsorption of oil-soluble drugs.

Even when packaged in this manner, the sheet-like skin preparation for external use can be impregnated with a large amount of the emulsified composition without dripping, and is therefore extremely easy to handle during the working process.
In addition, when sealing and filling, it is preferable to seal in an inert gas such as argon gas or nitrogen gas to prevent the oil-soluble drug from being oxidized by oxygen. Furthermore, in order to maintain an oxygen-free state, it is also possible to fill the package with an oxygen-absorbing material or use a package made of a material with oxygen-absorbing ability.

The timing for impregnating the sheet-like substrate with the composition can be such that the user impregnates the sheet-like substrate at the time of use, but it is preferable to impregnate the sheet-like substrate with the composition before use by the user, as this ensures the stability of the oil-soluble drug and provides excellent usability and portability.
The sheet-type external preparation for skin impregnated with the emulsion composition of the present invention is applied by adhering it to areas where wrinkles are noticeable, such as under the eyes or around the mouth, leaving it for an appropriate period of time, and then peeling it off.

Next, the present invention will be explained in more detail using test examples as examples, but the technical scope of the present invention is not limited to these examples. Note that all blend amounts are in mass %.

[0043] First, the present inventors investigated the relationship between the type of thickener and usability in order to find a suitable thickener when using the emulsion composition of the present invention as a sheet-type external skin preparation. The results are shown in Table 1.

<Usability evaluation method>
The evaluation method for each usability is as follows.
・Mask falling off (during use)
Seven expert panels evaluated the "slip-down of a mask until it comes off" and classified it as follows based on the number of panelists who answered "it does not slip down": A: 5 or more people B: 3-4 people C: 0-2 people

- Absorption: Seven expert panels evaluated the "absorption of the impregnated liquid remaining on the skin after removing the mask" and classified the results as follows based on the number of panelists who answered "absorption is good": A: 5 or more people B: 3-4 people C: 0-2 people

- Firmness: Seven expert panels evaluated the firmness of the skin after the mask was removed and the impregnated liquid was absorbed into the skin. The results were categorized as follows based on the number of panelists who answered "I feel firmness": A: 5 or more people B: 3-4 people C: 0-2 people

- Plumpness: Seven expert panels evaluated the plumpness of the skin after the mask was removed and the impregnated liquid was absorbed into the skin. The results were categorized as follows based on the number of panelists who answered "I feel plumpness": A: 5 or more people B: 3-4 people C: 0-2 people

*1 RA-PE-408 (manufactured by Nippon Fine Chemical Co., Ltd.)
*2 KF-56A (manufactured by Shin-Etsu Kogyo Co., Ltd.)
*3 PVP/VA S-630 (manufactured by Ashland Specialty Ingredients)
*4 Gozenol ^™ EG-05 (Mitsubishi Chemical Corporation)

As can be seen from Table 1, when the amount of (a) polyvinyl alcohol blended is increased, a certain degree of usability can be obtained with (a) polyvinyl alcohol alone, but when both (b) vinyl acetate-vinylpyrrolidone copolymer and (a) polyvinyl alcohol are added, good usability can be obtained with a lower content.
Therefore, it is preferable that the oil-in-water emulsion composition according to the present invention contains both (a) polyvinyl alcohol and (b) vinyl acetate-vinylpyrrolidone copolymer as thickeners.

Next, the blending amounts of (a) polyvinyl alcohol and (b) vinyl acetate-vinylpyrrolidone copolymer were investigated. The results are shown in Table 2.

*1 RA-PE-408 (manufactured by Nippon Fine Chemical Co., Ltd.)
*2 KF-56A (manufactured by Shin-Etsu Kogyo Co., Ltd.)
*3 PVP/VA S-630 (manufactured by Ashland Specialty Ingredients)
*4 Gozenol ^™ EG-05 (Mitsubishi Chemical Corporation)

As shown in Table 2, cosmetics with good usability were obtained when the blending amounts of (a) polyvinyl alcohol and (b) vinyl acetate/vinylpyrrolidone were each up to 0.5% by mass. Furthermore, no significant changes in usability were observed when the blending amounts of (a) polyvinyl alcohol and (b) vinyl acetate/vinylpyrrolidone were between 0.1 and 0.5% by mass, demonstrating their stability.

The inventors also investigated the amount of (c) moisturizer. The results are shown in Table 3.

*1 RA-PE-408 (manufactured by Nippon Fine Chemical Co., Ltd.)
*2 KF-56A (manufactured by Shin-Etsu Kogyo Co., Ltd.)
*3 PVP/VA S-630 (manufactured by Ashland Specialty Ingredients)
*4 Gozenol ^™ EG-05 (Mitsubishi Chemical Corporation)

As can be seen from Table 3, when the amount of (c) polyhydric alcohol as a humectant exceeds 20% by mass of the total composition, compatibility tends to be somewhat poor. When (c) humectant is contained in an amount of 10% by mass or more, good usability is obtained even with two types of polyhydric alcohol. A mass ratio of (a) polyvinyl alcohol and (b) vinyl acetate-vinylpyrrolidone copolymer: (c) polyhydric alcohol as a humectant) of 1:50 to 1:110 is preferable for usability.

[Formulation Example 1] Sheet-type topical skin preparation
(1) Retinol 0.05
(2) Tocopherol acetate 0.1
(3) Stearyl glycyrrhetinate 0.1
(4) Squalane 0.1
(5) Pentaerythritol tetra-2-ethylhexanoate 10.0
(6) Methylphenylpolysiloxane 10.0
(7) POE (60) hydrogenated castor oil 0.5
(8) Glycerin 5.0
(9) 1,3-butylene glycol 7.0
(10) Dipropylene glycol 5.0
(11) Carboxyvinyl polymer 0.1
(12) Xanthan gum 0.05
(13) Dibutylhydroxytoluene 0.05
(14) EDTA-3Na 0.02
(15) Potassium hydroxide 0.02
(16) Methylparaben (appropriate amount) (17) Phenoxyethanol (appropriate amount) (18) Ethyl alcohol 3.0
(19) Vinyl acetate/vinylpyrrolidone copolymer 0.3
(20) Polyvinyl alcohol 0.3
(21) Angelica keiskei extract 0.1
(22) Olive leaf extract 0.1
(23) Caffeine 0.1
(24) Betaine 5.0
(25) Potassium methoxysalicylate 1.0
(26) Nicotinamide 5.0
(27) Ion-exchanged water Remaining amount (Production method) (7) is added to (8) to (10) and dissolved. (1) to (6) are added to this, and emulsified using a homomixer. A solution of (11) to (27) is added to the resulting emulsion to obtain an oil-in-water emulsion composition. This is impregnated into a cotton nonwoven fabric, placed in a PE pouch, and sealed in the pouch together with argon gas.

[Formulation Example 2] Sheet-type topical skin preparation
(1) Retinol palmitate 0.1
(2) Tocopherol acetate 0.1
(3) Oil-soluble licorice extract 0.1
(4) Squalane 0.1
(5) Glycerin tri-2-ethylhexanoate 10.0
(6) Methylphenylpolysiloxane 5.0
(7) POE (60) hydrogenated castor oil 0.5
(8) Glycerin 5.0
(9) 1,3-butylene glycol 7.0
(10) Dipropylene glycol 8.0
(11) Xylitol 2.0
(12) Alkyl-modified carboxyvinyl polymer 0.2
(13) Xanthan gum 0.05
(14) Dibutylhydroxytoluene 0.05
(15) EDTA-3Na 0.02
(16) Potassium hydroxide 0.02
(17) Methylparaben (appropriate amount) (18) Phenoxyethanol (appropriate amount) (19) Ethanol 2.0
(20) Vinyl acetate/vinylpyrrolidone copolymer 0.05
(21) Polyvinyl alcohol 0.05
(22) Safflower flower extract 0.1
(23) Rose water 0.1
(24) Jujube fruit extract 0.05
(25) PEG/PPG-14/7 dimethyl ether 0.5
(26) Tranexamic acid methylamide hydrochloride 1.0
(27) Nicotinamide 5.0
(28) Ion-exchanged water Remaining amount (Production method) (7) is added to (8) to (10) and dissolved. (1) to (6) are added to this, and emulsified using a homomixer. A solution of (11) to (28) is added to the resulting emulsion to obtain an oil-in-water emulsion composition. A cotton nonwoven fabric is impregnated with this.

Claims (5)

(a) 0.05 to 0.5% by mass of polyvinyl alcohol,
(b) vinyl acetate/vinylpyrrolidone copolymer 0.05 to 0.5% by mass,
(c) 10 to 20% by mass of a polyhydric alcohol, which is two or more selected from dipropylene glycol, glycerin, and 1,3-butylene glycol;
(d) retinol 0.01 to 0.1% by mass,
(e) 13.05 to 20.1% by mass of an oil content which is at least one selected from pentaerythrityl tetraethylhexanoate, diphenylsiloxyphenyl trimethicone, squalane, methylphenylpolysiloxane, and glycerin tri-2-ethylhexanoate,
an external skin preparation comprising an oil-in-water emulsion composition comprising
Its viscosity is 2000 mPa s or less at 30°C,
An external skin preparation comprising an oil-in-water emulsion composition characterized in that the particle size is 5 μm or less. A topical skin preparation comprising the oil-in-water emulsion composition according to claim 1, characterized in that the blending ratio of (a) polyvinyl alcohol to (b) vinyl acetate-vinylpyrrolidone copolymer is 1:2 to 2:1. A topical skin preparation comprising the oil-in-water emulsion composition according to claims 1 and 2, characterized in that the mass ratio of (a) the sum of polyvinyl alcohol and (b) vinyl acetate-vinylpyrrolidone copolymer to (c) the polyhydric alcohol) is 1:50 to 1:110. The topical skin preparation according to any one of claims 1 to 3, wherein (c) the polyhydric alcohol is one of three types: dipropylene glycol, glycerin, and 1,3-butylene glycol. A sheet-like external preparation for skin, comprising a sheet-like substrate impregnated with an external preparation for skin comprising the oil-in-water emulsion composition according to any one of claims 1 to 4.