Oil-in-water emulsion cosmetic

Abstract

The purpose of the present invention is to provide an oil-in-water emulsion cosmetic which stably contains large-particle-diameter zinc oxide having an average particle diameter of 0.5-5 [mu] m in an inner oil phase. An oil-in-water type emulsion cosmetic according to the present invention is characterized by containing: (A) zinc oxide having an average particle diameter of 0.5-5 [mu] m, which has been hydrophobized; and (B) hydrophobized particulate zinc oxide, the content of the hydrophobized particulate zinc oxide (B) being 5 mass% or more with respect to the total amount of the cosmetic.

Description

Technical Field

[0001] The present invention relates to an oil-in-water emulsified cosmetic that stably contains zinc oxide having a large particle size with an average particle size of 0.5 to 5 μm in an inner oil phase. Background Art

[0002] Protecting the skin from the damage of ultraviolet rays is one of the important issues in skin care and body care. In order to minimize the adverse effects of ultraviolet rays on the skin, various UV protection cosmetics have been developed. UV protection cosmetics generally cover the skin with a coating film containing an ultraviolet absorber and an ultraviolet scattering agent, so as to absorb or scatter UVA and UVB, thereby suppressing the amount of ultraviolet rays reaching the skin and protecting the skin from the damage of ultraviolet rays (Non-Patent Document 1).

[0003] In recent years, sunscreen ingredients called "ultraviolet wavelength conversion substances" or "phosphors", which respond to ultraviolet rays based on a mechanism different from that of ultraviolet absorbers and ultraviolet scattering agents, have attracted much attention.

[0004] An ultraviolet wavelength conversion substance is a substance that converts the wavelength of ultraviolet rays (peak wavelength: 200 nm to 400 nm) contained in incident light and emits emitted light having a wavelength longer than that of ultraviolet rays (peak wavelength: 500 nm to 700 nm). As described in Patent Document 1, various ultraviolet wavelength conversion substances are known, whether they are organic compounds or inorganic compounds.

[0005] Since the ultraviolet wavelength conversion substance absorbs ultraviolet rays without scattering them and converts the wavelength into visible light, it has the advantage of being able to present a natural skin color compared with the conventional ultraviolet scattering agents such as titanium dioxide and zinc oxide. In addition, the ultraviolet wavelength conversion substance also has the function of effectively utilizing ultraviolet rays to activate skin cells, and has effects such as prevention / improvement of wrinkles, spots, skin aging, photoaging, etc.

[0006] In order to apply the above-mentioned unique effects of the ultraviolet wavelength conversion substance to cosmetics, various attempts have been made so far. For example, Patent Document 1 proposes a skin composition containing: (A) an ultraviolet wavelength conversion substance, (B) a hydrocarbon oil and / or a linear silicone oil with a total content of 10% by weight or more, and (C) a powder with a total content of 0 to 65% by weight. In addition, Patent Document 2 proposes an emulsified composition containing: (A) an ultraviolet wavelength conversion substance and (B) an organic oil phase thickener.

[0007] However, zinc oxide (hereinafter referred to as "zinc oxide phosphor" according to Patent Document 1, etc.), which is widely used as an ultraviolet wavelength-converting substance of an inorganic compound system, has an average particle size as large as 1 to 4 μm. Therefore, it is difficult to stably incorporate it into a base, and aggregation, sedimentation, etc. are likely to occur. Therefore, the zinc oxide phosphor is usually incorporated into a water-in-oil type emulsified cosmetic that can incorporate a relatively large amount of oil, as in Example 5 of Patent Document 1 and Example 5 of Comparative Document 2. However, since the external phase of a water-in-oil type emulsified cosmetic is composed of an oil component, it is difficult to achieve a refreshing use feeling like that of a water-in-oil type emulsified cosmetic when applied to the skin.

[0008] On the other hand, a water-in-oil type emulsified cosmetic can provide a refreshing and moist feeling when applied to the skin. Therefore, it is widely used as a base for skin cosmetics and other topical skin agents directly applied to the skin. In skin care and body care, operations to protect the skin from ultraviolet damage are sometimes carried out daily. The importance of water-in-oil type emulsified cosmetics as a base for such UV protection cosmetics is increasing day by day.

[0009] Patent Document 3 proposes a water-in-oil type emulsified composition containing an ultraviolet wavelength-converting substance, and also discloses an example (Example 4) of using a zinc oxide phosphor as the ultraviolet wavelength-converting substance. However, the amount of the zinc oxide phosphor incorporated is slightly suppressed, and the stability is sometimes insufficient.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2021-172607

[0013] Patent Document 2: International Publication No. 2020 / 204196

[0014] Patent Document 3: International Publication No. 2020 / 204189

[0015] Non-Patent Documents

[0016] Non-Patent Document 1: "New Cosmetology", 2nd Edition, edited by Takeo Mitsui, 2001, published by Nansando Publishing Co., Ltd., pp. 497 - 504 Summary of the Invention

[0017] Problems to be Solved by the Invention

[0018] An object of the present invention is to provide a water-in-oil type emulsified cosmetic that stably contains zinc oxide having a large particle size with an average particle size of 0.5 to 5 μm in the internal oil phase.

[0019] Means for Solving the Problems

[0020] The inventors of the present invention have conducted extensive and in - depth research to solve the above - mentioned problems. As a result, it has been found that even for zinc oxide with a large particle size, by subjecting its surface to a hydrophobization treatment and using it in combination with a specified amount of hydrophobized particulate zinc oxide, it can be stably incorporated into the internal oil phase of an oil - in - water emulsified cosmetic. Thus, the present invention has been completed.

[0021] That is, the present invention provides an oil - in - water emulsified cosmetic, which contains:

[0022] (A) Zinc oxide with an average particle size of 0.5 to 5 μm that has been subjected to a hydrophobization treatment (hereinafter sometimes referred to as "hydrophobized zinc oxide"); and,

[0023] (B) Hydrophobized particulate zinc oxide,

[0024] (B) The content of the hydrophobized particulate zinc oxide is 5% by mass or more relative to the total amount of the cosmetic.

[0025] Effects of the Invention

[0026] By forming the above - mentioned configuration, the present invention can stably incorporate zinc oxide with a large particle size in the form of hydrophobized zinc oxide into the internal oil phase of an oil - in - water emulsified cosmetic. Therefore, it is possible to achieve the refreshing feel of use unique to oil - in - water emulsified cosmetics.

[0027] In addition, if zinc oxide with an ultraviolet wavelength conversion function is used as the zinc oxide with a large particle size, it can protect against ultraviolet rays while presenting a natural skin color, and can also exert a cell - activating effect. Detailed Description of the Preferred Embodiments

[0028] The oil - in - water emulsified cosmetic of the present invention is characterized by containing (A) hydrophobized zinc oxide and (B) hydrophobized particulate zinc oxide under specified conditions. Hereinafter, each component constituting the oil - in - water emulsified cosmetic of the present invention will be described in detail.

[0029] <(A) Hydrophobized Zinc Oxide>

[0030] The (A) hydrophobized zinc oxide incorporated in the present invention is obtained by subjecting the surface of zinc oxide with a large particle size having an average particle size of 0.5 to 5 μm to a hydrophobization treatment.

[0031] The zinc oxide with a large particle size constituting (A) hydrophobized zinc oxide is not particularly limited as long as its average particle size is in the range of 0.5 to 5 μm, preferably in the range of 0.7 to 4.5 μm, and more preferably in the range of 1 to 4 μm.

[0032] It should be noted that in this specification, the "average particle size" refers to the particle size at the cumulative value of 50% in the particle size distribution determined by the laser diffraction / scattering method.

[0033] The average particle diameter of the zinc oxide that constitutes (A) hydrophobized zinc oxide is as large as 0.5 to 5 μm. Therefore, it is possible to use highly functional zinc oxides such as those having an ultraviolet wavelength conversion effect. If zinc oxide having an ultraviolet wavelength conversion effect is used, it is possible to impart an ultraviolet protection effect and a cell activation effect to cosmetics, so it is preferred.

[0034] As the zinc oxide having an ultraviolet wavelength conversion effect, those obtained by doping zinc oxide with a sulfur-containing compound are known. For example, they can be produced according to the methods described in International Publication No. 2018 / 004006, Japanese Patent Application Laid-Open No. 2018-131422, and Japanese Patent Application Laid-Open No. 5-117127.

[0035] Examples of the hydrophobization treatment of (A) hydrophobized zinc oxide include silane compound treatment (such as triethoxy octylsilane), silicone compound treatment, fluorine-modified silicone compound treatment, fluorine compound treatment, higher fatty acid treatment (such as stearic acid), higher alcohol treatment, fatty acid ester treatment, metal soap treatment, amino acid treatment, alkyl phosphate treatment, etc. Among them, stearic acid treatment is particularly preferred.

[0036] The blending amount of (A) hydrophobized zinc oxide is preferably 0.01% by mass or more, more preferably 1% by mass or more, and preferably 10% by mass or less, more preferably 7% by mass or less, based on the total amount of the oil-in-water type emulsified cosmetic. Thus, as the blending amount range, 0.01 to 10% by mass, 1 to 7% by mass, etc. can be cited.

[0037] <(B) Hydrophobized fine zinc oxide>

[0038] The (B) hydrophobized fine zinc oxide blended in the present invention is particulate zinc oxide that has been conventionally used as an ultraviolet scatterer and whose surface has been hydrophobized.

[0039] The average particle diameter of (B) hydrophobized fine zinc oxide is in the range of 2 to 300 nm, preferably in the range of 5 to 100 nm. If the average particle diameter is within this range, (A) hydrophobized zinc oxide can be stably blended in the internal oil phase of the oil-in-water type emulsified cosmetic.

[0040] The method for surface treatment of (B) hydrophobized fine zinc oxide is not particularly limited, and examples include silicone compound treatment such as methylhydrogenpolysiloxane and methylpolysiloxane; fluorine compound treatment based on perfluoroalkyl phosphate, perfluoroalcohol, etc.; amino acid treatment based on N-acylglutamic acid, etc.; silane compound treatment such as triethoxy octylsilane; and lecithin treatment; metal soap treatment; fatty acid treatment; alkyl phosphate treatment, etc. Among them, silicone compound treatment is particularly preferred.

[0041] Examples of the silicone compound used in the treatment of silicone compounds include various silicone oils such as methylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, methylcyclopolysiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, octamethyltrisiloxane, tetradecamethylhexasiloxane, dimethylsiloxane / methyl(polyoxyethylene)siloxane / methyl(polyoxypropylene)siloxane copolymer, dimethylsiloxane / methyl(polyoxyethylene)siloxane copolymer, dimethylsiloxane / methyl(polyoxypropylene)siloxane copolymer, dimethylsiloxane / methylhexadecyloxysiloxane copolymer, dimethylsiloxane / methylstearoxysiloxane copolymer, etc. Methylhydrogenpolysiloxane and methylpolysiloxane are preferred.

[0042] (B) The compounding amount of the hydrophobized particulate zinc oxide is 5% by mass or more, more preferably 7% by mass or more, based on the total amount of the oil-in-water type emulsified cosmetic. If the compounding amount is 5% by mass or more, (A) hydrophobized zinc oxide can be stably compounded in the internal oil phase of the oil-in-water type emulsified cosmetic. On the other hand, the upper limit of the compounding amount is not particularly limited, and even if it is compounded in excess, no corresponding improvement in stability can be expected. Therefore, it is preferably set to 15% by mass or less. Thus, as the range of the compounding amount, examples include 5 - 15% by mass, 7 - 15% by mass, etc., based on the total amount of the cosmetic.

[0043] <Optional Compounding Ingredients>

[0044] In the oil-in-water type emulsified cosmetic of the present invention, in addition to the above components (A) and (B), components commonly used in oil-in-water type emulsified cosmetics can be compounded within the range that does not hinder the effects of the present invention. For example, in addition to oil components, aqueous solvents, and ultraviolet absorbers, surfactants, hydrophilic thickeners, moisturizers, pharmaceuticals, antioxidants, chelating agents, preservatives, powders, edible flavors (materials), coloring materials, pigments, etc. can be appropriately compounded as needed.

[0045] The oil component is not particularly limited as long as it is an oil component compounded in the oil-in-water type emulsified cosmetic, and examples include hydrocarbon oils, silicone oils, higher alcohols, ester oils, fatty acids, fats and oils, waxes, etc.

[0046] Examples of hydrocarbon oils include liquid paraffin, isocetane, isododecane, ozokerite, squalane, squalene, pristane, paraffin, isoparaffin, ceresin, petrolatum, microcrystalline wax, hydrogenated polyisobutene, and olefin oligomers.

[0047] Examples of silicone oils include dimethylpolysiloxane, methylphenylpolysiloxane, hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, etc.

[0048] As higher alcohols, for example, linear alcohols such as lauryl alcohol, cetyl alcohol, stearyl alcohol, behenyl alcohol, myristyl alcohol, oleyl alcohol, cetearyl alcohol, etc.; branched-chain alcohols such as monostearin (batyl alcohol), 2-decyltetradecanol, lanolin alcohol, cholesterol, phytosterol, hexyl dodecanol, isostearyl alcohol, octyldodecanol, etc.

[0049] As ester oils, for example, isopropyl myristate, cetyl ethylhexanoate, octyldodecyl myristate, isopropyl palmitate, butyl stearate, hexyl laurate, myristyl myristate, decyl oleate, cetyl dimethyl octanoate, cetyl lactate, myristyl lactate, acetylated lanolin, isocetyl isostearate, isocetyl isostearate, cholesterol 12-hydroxystearate, ethylene glycol bis(2-ethylhexanoate), dipentaerythritol fatty acid ester, N-alkyl ethylene glycol monoisostearate, neopentyl glycol didecanoate, diisostearyl malate, glycerol bis(2-heptylundecanoate), trimethylolpropane tris(2-ethylhexanoate), trimethylolpropane triisostearate, pentaerythritol tetra(ethylhexanoate), glycerol tri(2-ethylhexanoate), cetyl 2-ethylhexanoate, 2-ethylhexyl palmitate, glycerol trimyristate, glycerol tri(2-heptylundecanoate), methyl ricinoleate, oleyl oleate, acetyl glyceride, 2-heptylundecyl palmitate, diisobutyl adipate, bis(heptylundecanol) adipate, ethyl laurate, bis(2-ethylhexyl) sebacate, 2-hexyl decyl myristate, 2-hexyl decyl palmitate, 2-hexyl decyl adipate, diisopropyl sebacate, 2-ethylhexyl succinate, ethyl acetate, butyl acetate, amyl acetate, and triethyl citrate, etc.

[0050] As fatty acids, for example, oleic acid, isostearic acid, linoleic acid, linolenic acid, etc.

[0051] As oils and fats, for example, Toxicodendron succedaneum, cocoa seed butter, hydrogenated castor oil, avocado oil, camellia seed oil, macadamia nut oil, corn oil, olive fruit oil, rapeseed oil, sesame seed oil, peach kernel oil, wheat germ oil, Camellia kissi seed oil, castor oil, linseed oil, safflower oil, cottonseed oil, perilla oil, soybean oil, peanut oil, tea seed oil, torreya nucifera oil, rice bran oil, paulownia oil, Japanese tung oil, jojoba seed oil, germ oil, triglycerol, trioctanoin, and tripalmitolein, etc.

[0052] As waxes, for example, carnauba wax, beeswax, candelilla wax, and jojoba wax, etc.

[0053] As aqueous solvents, for example, water (such as purified water, ion-exchanged water, and tap water, etc.), lower alcohols, or their mixtures.

[0054] Examples of the ultraviolet absorber include 2-ethylhexyl p-methoxycinnamate, benzophenone, butyl methoxydibenzoylmethane, ethylhexyl triazone, bis-ethylhexyloxyphenol methoxyphenyl triazine, dioctyl butamido triazone, diethylamino hydroxybenzoyl hexyl benzoate, isooctyl 2-cyano-3,3-diphenylacrylate, polysiloxane-15, ethylhexyl salicylate, homomenthyl salicylate, and 3-(4-methylbenzylidene)-camphor, etc.

[0055] It should be noted that in the oil-in-water emulsified cosmetic of the present invention, widely known fine titanium dioxide as an ultraviolet scatterer can also be incorporated, but there is a tendency for the stability of the cosmetic to deteriorate. Therefore, it is preferred that fine titanium dioxide is not incorporated at all, or even when fine titanium dioxide is incorporated, it is less than 1% by mass relative to the total amount of the cosmetic. Fine titanium dioxide, like (B) hydrophobized fine zinc oxide, is a component classified as an ultraviolet scatterer, but does not exhibit the stabilizing effect like (B) hydrophobized fine zinc oxide. In the present invention, surprisingly, those skilled in the art could not anticipate at all the stabilizing effect brought about by (B) hydrophobized fine zinc oxide.

[0056] <Usage>

[0057] The form of the oil-in-water emulsified cosmetic of the present invention is not particularly limited, and it can be widely applied in any form such as lotion, milk, cream, gel, essence (beauty liquid), and sunscreen cosmetic, etc. Specific Examples

[0059] Examples are listed below to further elaborate the present invention, but the present invention is not limited by any of these. The blending amount is expressed in mass % relative to the oil-in-water emulsified cosmetic unless otherwise specified. For each example, before specific description, the evaluation method used is described.

[0060] <Stability>

[0061] Each cosmetic (sample) was stored at 50 °C for 4 weeks, and the viscosity and pH were measured. The change rate was calculated from the measured values before storage (initial value) and after storage, and the viscosity stability and pH stability were evaluated according to the following criteria.

[0062] <Evaluation Criteria>

[0063] A: The change rate compared with the initial value is less than 15%

[0064] B: The change rate compared with the initial value is 15% or more and less than 50%

[0065] C: The change rate compared with the initial value is 50% or more

[0066] Oil-in-water emulsified cosmetics of Reference Example 1, Examples 1 to 3, and Comparative Examples 1 to 3 shown in Table 1 below were prepared and evaluated based on the above evaluation methods and evaluation criteria. The evaluation results are also shown.

[0067] [Table 1]

[0068]

[0069] As shown in Table 1, when (A) hydrophobized zinc oxide is not formulated, even if fine titanium dioxide is contained, there are no problems with the viscosity stability and pH stability of the cosmetic (Reference Example 1). However, when (A) hydrophobized zinc oxide coexists with fine titanium dioxide, the result is insufficient viscosity stability and pH stability (Comparative Examples 1 and 2).

[0070] In contrast, when fine hydrophobized zinc oxide (B) is formulated instead of fine titanium dioxide, very excellent viscosity stability and pH stability can be achieved (Examples 1 and 2).

[0071] On the other hand, when a small amount (0.5% by mass) of fine titanium dioxide is formulated in the presence of fine hydrophobized zinc oxide (B), the viscosity stability is slightly reduced, but the viscosity stability and pH stability are not significantly impaired (Example 3). However, it was confirmed that when the formulation amount of fine titanium dioxide is increased to 1% by mass, the viscosity stability and pH stability become insufficient (Comparative Example 3).

Claims

1. An oil-in-water emulsified cosmetic, comprising: (A) Zinc oxide having an average particle size of 0.5 to 5 μm and subjected to hydrophobization treatment; and, (B) Hydrophobized particulate zinc oxide, (B) The content of the hydrophobized particulate zinc oxide is 5% by mass or more based on the total amount of the cosmetic.

2. The oil-in-water emulsified cosmetic according to claim 1, wherein, (A) The hydrophobized zinc oxide is zinc oxide treated with stearic acid.

3. The oil-in-water emulsified cosmetic according to claim 1, wherein (B) The average particle size of the hydrophobized particulate zinc oxide is in the range of 2 to 300 nm.

4. The oil-in-water type emulsified cosmetic according to claim 1, wherein, (B) The content of the hydrophobized particulate zinc oxide is in the range of 5 to 15% by mass based on the total amount of the cosmetic.

5. The oil-in-water emulsified cosmetic according to claim 1, wherein, When the cosmetic contains particulate titanium dioxide, the content of the particulate titanium dioxide is less than 1% by mass based on the total amount of the cosmetic.

Images