Acrylic polymer-containing Pickering emulsion

Abstract

Provided is a technology for improving the emulsion stability of Pickering emulsions. [Solution] The powder is adsorbed to the emulsion interface and contains an acrylic polymer. the acrylic polymer is a copolymer containing structural units derived from an alkyl (meth)acrylate, A Pickering emulsion characterized in that the content of the acrylic polymer is 0.1% by mass or more.

Description

Technical Field

[0002]

[0001] The present invention relates to Pickering emulsions.

Background Art

[0002] An agent form emulsified by adsorbing amphiphilic solid particles on the interface has been conventionally known as a Pickering emulsion, and its utilization has also been proposed in cosmetics. For example, as the solid particles, titanium dioxide, zinc oxide, etc. have been proposed, and it has been proposed to use solid particles obtained by hydrophobizing the surfaces thereof for the preparation of Pickering emulsions (Patent Document 1). Further, an oil-in-water emulsion using partially hydrophobized silica has also been proposed, and it is said to be good in stickiness, freshness, and high-temperature emulsion stability (Patent Document 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] In Pickering emulsions, there is a problem that the types and amounts of oil agents that can be emulsified are limited, and if the limit is exceeded, the emulsified state deteriorates. The problem to be solved by the present invention is to provide a technique for improving the emulsion stability of Pickering emulsions. In particular, it is an object to provide a technique for improving the emulsion stability of Pickering emulsions applicable also to a form containing a polar oil agent as an oil phase component.

Means for Solving the Problems

[0005] Through the diligent research efforts of the inventors, it has been discovered that by adding an acrylic acid polymer, the dispersion state of the powder adsorbed at the emulsion interface is improved, and a Pickering emulsion with fine emulsion particle size and excellent stability can be prepared. Based on this finding, the present invention was completed.

[0006] The present invention, which solves the above problems, is a Pickering emulsion characterized in that the powder is adsorbed at the emulsion interface and contains an acrylic polymer. The emulsifying composition of the present invention exhibits excellent emulsification stability.

[0007] In a preferred embodiment of the present invention, the acrylic polymer is a copolymer comprising structural units derived from alkyl (meth)acrylate.

[0008] In a preferred embodiment of the present invention, the acrylic polymer is an acrylates copolymer.

[0009] In a preferred embodiment of the present invention, the oil phase component includes a polar oil. Conventionally, it has been difficult to prepare a stable Pickering emulsion when a polar oil is included as an oil phase component. By applying the present invention, the stability of a Pickering emulsion containing a polar oil as an oil phase component can be improved.

[0010] In a preferred embodiment of the present invention, the polar oil includes a highly polar oil with an IOB value of 0.1 or higher. Conventionally, Pickering emulsions containing such highly polar oils have been unstable. According to the present invention, a stable Pickering emulsion can be provided even in a form containing such highly polar oils.

[0011] In a preferred embodiment of the present invention, the proportion of polar oil in the oily component of the Pickering emulsion is 60% by mass or more. In conventional technology, it was difficult to stably prepare Pickering emulsions in which the proportion of polar oil in the oil formulation was 60% by mass or more. According to the present invention, it is possible to provide a Pickering emulsion with excellent emulsification stability even in a form containing a high content of such polar oil.

[0012] In a preferred embodiment of the present invention, the polar oil includes an ultraviolet absorber. According to the present invention, the emulsification stability of Pickering emulsions in a form containing an ultraviolet absorber can be improved.

[0013] In a preferred embodiment of the present invention, the proportion of the ultraviolet absorber in the oil component of the Pickering emulsion is 30% by mass or more. According to the present invention, it is possible to provide a Pickering emulsion with a high content of such ultraviolet absorbers.

[0014] In a preferred embodiment of the present invention, the average emulsion particle size is 15 μm or less. Pickering emulsions of this form exhibit excellent emulsification stability.

[0015] In a preferred embodiment of the present invention, the content of surfactants other than the powder is 0.1% by mass or less. Even in a surfactant-free form, the Pickering emulsion of the present invention exhibits excellent emulsification stability. [Effects of the Invention]

[0016] According to the present invention, a Pickering emulsion with excellent emulsification stability can be provided. [Brief explanation of the drawing]

[0017] [Figure 1] These are microscopic images of the Pickering emulsions from Example 1 and Comparative Example 2. [Modes for carrying out the invention]

[0018] <1>Acrylic polymer The pickering emulsion of the present invention contains an acrylic polymer as an essential component. The acrylic polymer includes a polymer or copolymer having a (meth)acrylic monomer selected from (meth)acrylic acid and its amide and ester as a constituent monomer. In the present invention, it is preferable to use an acrylic copolymer which is a random copolymer, an alternating copolymer or a block copolymer.

[0019] As an ester of (meth)acrylic acid, an alkyl (meth)acrylate can be preferably exemplified. The carbon number of the alkyl group in the alkyl (meth)acrylate is not particularly limited, and preferably 1 to 20, more preferably 1 to 10, and still more preferably 1 to 4 can be exemplified.

[0020] When a (meth)acrylic amide or ester is used as a constituent monomer, the amide residue or ester residue may have a substituent. The substituent may be a substituent derived from a biological constituent such as a sugar residue, an amino acid residue, or phosphorylcholine.

[0021] Such monomers can be prepared by known methods. For example, in the case of a sugar residue, a sugar and a halide of a polyhydric alcohol such as chloroethanol are condensed with an alkali in the presence of a catalyst such as silver oxide to introduce a hydroxyethyl group into the anomer, and this hydroxy group and acrylic acid or methacrylic acid are esterified to lead to the desired monomer.

[0022] In the case of an amino acid residue, acrylic acid or methacrylic acid is led to an acid chloride by thionyl chloride or the like, and condensed with an amino acid in the presence of an alkali to construct an acid amide bond, thereby obtaining the desired amide-type monomer.

[0023] Phospholipid-like structures such as phosphorylcholine can be obtained by condensing phosphorylcholine and chloroethanol in the presence of an alkali to form hydroxyethylphosphorylcholine. By condensing this with acrylate chloride or methacrylate chloride in the presence of an alkali, the desired monomer can be obtained.

[0024] Examples of such (meth)acrylic monomers include n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, cyclohexyl (meth)acrylate, decyl (meth)acrylate, undecyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, myristyl (meth)acrylate, pentadecyl (meth)acrylate, and palmite (meth)acrylate. (meth)acrylamide, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, oleyl (meth)acrylate, behenyl (meth)acrylate, (meth)acrylate esters having linear, branched or alicyclic hydrocarbon groups; acrylonitrile; (meth)acrylamides such as acrylamide, diacetone acrylamide, N,N-dimethylacrylamide, Nt-butylacrylamide, N-octylacrylamide, Nt-octylacrylamide; 2-(meth)acrylamide-2-methylpropane (Meth)acrylamides containing sulfonic acid groups such as sulfonic acid; alkylaminoalkyl (meth)acrylates such as aminoethyl (meth)acrylate, t-butylaminoethyl methacrylate, and methylaminoethyl (meth)acrylate; dialkylaminoalkyl (meth)acrylates such as dimethylaminoethyl (meth)acrylate and diethylaminoethyl (meth)acrylate; dialkylaminoalkyl (meth)methacrylamides such as dimethylaminoethyl (meth)acrylamide and diethylaminoethyl (meth)acrylamide; esters of cyclic compounds and meth)acrylic acid such as tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, and glycidyl (meth)acrylate; alkoxyalkyl (meth)acrylate esters such as ethoxyethyl (meth)acrylate and methoxyethyl (meth)acrylate; monoesters of polyalkylene glycols and (meth)acrylic acid such as polyethylene glycol mono(meth)acrylate and polypropylene glycol mono(meth)acrylate; sulfonic acid group-containing (meth)acrylic esters;(meth)acryloyloxyethyl phosphate and other methacryloyloxyalkyl phosphate monoesters; (meth)glyceryl acrylate, 2-methacryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, β-carboxyethyl acrylate, acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl tetrahydrophthalate, 2-(meth)acryloyloxyethyl hexahydrophthalate;1,4-Butanediol di(meth)acrylate, 1,6-Hexanediol di(meth)acrylate, Ethylene glycol di(meth)acrylate, Polyethylene (n=2~50) glycol di(meth)acrylate, Propylene glycol di(meth)acrylate, Polypropylene (n=2~50) glycol di(meth)acrylate, Butylene glycol di(meth)acrylate, Dipentyl glycol di(meth)acrylate, Neopentyl glycol di(meth)acrylate, Trimethylolpropane di(meth)acrylate, Methylenebisacrylamide, Bisphenol F EO-modified (n=2~50) di(meth)acrylate, Bisphenol A EO-modified (n=2~50) di(meth)acrylate, Bisphenol S EO-modified (n=2~50) di(meth)acrylate, trimethylolethane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane tricaprolactone tri(meth)acrylate, trimethylolhexane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, diglycerin tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ditrimethylolpropane tetracaprolactone tetra(meth)acrylate Examples include (meth)acrylates having two or more ethylenically unsaturated double bonds, such as (t)acrylate, ditrimethylolethanetetra(meth)acrylate, ditrimethylolbutanetetra(meth)acrylate, ditrimethylolhexanetetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, and tripentaerythritol octa(meth)acrylate.

[0025] As the acrylic polymer, a copolymer obtained by copolymerizing a (meth)acrylic monomer with constituent monomers other than the (meth)acrylic monomer may be used. Examples of such constituent monomers include unsaturated monocarboxylic acids such as crotonic acid; aromatic vinyl compounds such as styrene; unsaturated dicarboxylic acids such as itaconic acid, maleic acid, fumaric acid, maleic anhydride, and citraconic acid; monoalkyl esters of unsaturated dicarboxylic acids such as monoalkyl maleic acid, monoalkyl fumaric acid, and monoalkyl itaconic acid; sulfonic acid group-containing monomers include, for example, alkenesulfonic acids such as vinylsulfonic acid and (meth)allylsulfonic acid; aromatic vinyl group-containing sulfonic acids such as α-methylstyrenesulfonic acid; unsaturated compounds containing primary to tertiary amino groups such as (meth)allylamine; amino group-containing aromatic vinyl compounds such as N,N-dimethylaminostyrene; compounds having two or more ethylenically unsaturated double bonds such as divinylbenzene, diisopropylphenylbenzene, and trivinylbenzene; urethane oligomers having two or more ethylenically unsaturated double bonds; silicone compounds having two or more ethylenically unsaturated double bonds; vinyl acetate, vinyl chloride, vinylpyrrolidone, etc.

[0026] The acrylic polymer is preferably a copolymer of two or more constituent monomers selected from the group consisting of acrylic acid, methacrylic acid, acrylic acid (C1-C4) alkylate, and methacrylic acid (C1-C4) acrylate. Specifically, this includes compounds that are listed under the INCI name "ACRYLATES COPOLYMER" (International Cosmetic Ingredient Dictionary and Handbook, 14th edition, Vol. 1, CTFA, 2012, pp. 60-61).

[0027] Acrylic polymers can be obtained by polymerizing the constituent monomers described above. Polymerization can be carried out according to conventional methods in the presence of a polymerization initiator such as azobisbutyronitrile.

[0028] The acrylic polymer content is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.1% by mass or more, even more preferably 0.15% by mass or more, and even more preferably 0.2% by mass or more, from the viewpoint of reducing the emulsion particle size of the Pickering emulsion or improving emulsion stability.

[0029] Furthermore, while there is no particular upper limit to the content of acrylic polymers in the entire Pickering emulsion, it is preferably 5% by mass or less, more preferably 2% by mass or less, even more preferably 1% by mass or less, and even more preferably 0.5% by mass or less.

[0030] <2> powder In the Pickering emulsion of the present invention, the powder is adsorbed at the emulsion interface. This powder can be any powder with emulsifying ability typically used in Pickering emulsions, without any particular limitations.

[0031] Either organic or inorganic powders can be used as the powder. In particular, in this invention, it is preferable to use metal oxide powder. The term "metal oxide" here also includes oxides of metalloids such as silicon. Examples of metal oxide powders include silica, titanium dioxide, zinc oxide, iron oxide, zirconium oxide, and cerium oxide.

[0032] When silica powder is used as the metal oxide powder, either so-called dry silica powder, which is produced by vapor phase oxidation of silicon halides, or so-called wet silica powder, which is manufactured from water glass or the like, may be used. Commercially available dry silica powders include, for example, the Aerosil series (Nippon Aerosil Co., Ltd.), the CAB-O-SIL series (Cabot Corporation), and the HDK series (Asahi Kasei Wacker Silicone Co., Ltd.). Commercially available wet silica powders include, for example, the Nipsil series (Tosoh Silica Co., Ltd.) and the HI-SIL series (PPG).

[0033] Many other metal oxide powders are also commercially available, so you can use commercially available products as they are. Specifically, such commercially available products include fine-particle titanium dioxide such as "MTY-110M3S" (manufactured by Teika Co., Ltd.), "MTY-02" (manufactured by Teika Co., Ltd.), "MT-100TV" (manufactured by Teika Co., Ltd.), "MT-500HSA" (manufactured by Teika Co., Ltd.), "MT-100T" (manufactured by Teika Co., Ltd.), "MT-01" (manufactured by Teika Co., Ltd.), "MT-10EX" (manufactured by Teika Co., Ltd.), "MT-05" (manufactured by Teika Co., Ltd.), "MT-100Z" (manufactured by Teika Co., Ltd.), "MT-150EX" (manufactured by Teika Co., Ltd.), "MT-100AQ" (manufactured by Teika Co., Ltd.), "MT-100WP" (manufactured by Teika Co., Ltd.), Examples include "MT-100SA" (manufactured by Teika Co., Ltd.), "MT-500B" (manufactured by Teika Co., Ltd.), "MT-500SA" (manufactured by Teika Co., Ltd.), "MT-600B" (manufactured by Teika Co., Ltd.), "MT-500SAS" (manufactured by Teika Co., Ltd.), "Typeque CR-50" (manufactured by Ishihara Sangyo Co., Ltd.), "Typeque TTO-M-1" (manufactured by Ishihara Sangyo Co., Ltd.), "Typeque TTO-V4" (manufactured by Ishihara Sangyo Co., Ltd.), "ST-455" (manufactured by Titanium Industry Co., Ltd.), "STT-65C-S" (manufactured by Titanium Industry Co., Ltd.), "STT-30EHS" (manufactured by Titanium Industry Co., Ltd.), and "Bayer Titanium R-KB-1" (manufactured by Bayer AG).

[0034] Other examples of fine-particle zinc oxide include "MZ-300" (manufactured by Teika Co., Ltd.), "MZY-303S" (manufactured by Teika Co., Ltd.), "MZ-306X" (manufactured by Teika Co., Ltd.), "MZ-500" (manufactured by Teika Co., Ltd.), "MZY-505S" (manufactured by Teika Co., Ltd.), "MZ-506X" (manufactured by Teika Co., Ltd.), "MZ-510HPSX" (manufactured by Teika Co., Ltd.), "WSX-MZ-700" (manufactured by Teika Co., Ltd.), "SANT-UFZO-450" (manufactured by Miyoshi Kasei Co., Ltd.), "SANT-UFZO-500" (manufactured by Miyoshi Kasei Co., Ltd.), "FZO-50" (manufactured by Ishihara Sangyo Co., Ltd.), "Maxlight ZS-032" (manufactured by Showa Denko K.K.), and "Maxlight ZS-032D" (manufactured by Showa Denko K.K.).

[0035] It is preferable that the surface of the metal oxide powder be hydrophobized. Hydrophobized metal oxide powder can be prepared by reacting the metal oxide powder with a hydrophobic treatment agent to covalently attach hydrophobic groups to the hydroxyl groups present on the surface of the powder, or by physically coating the surface of the metal oxide powder with a hydrophobic treatment agent.

[0036] Hydrophobic treatment is a method of treating metal oxide powders with hydrophobic agents such as organosilicon compounds, silicones, hydrocarbon oils, fatty acids, fatty acid amides, fatty acid esters, higher alcohols, and polyoxyalkylene compounds. Particularly preferred is the treatment of the metal oxide powder with an organosilicon compound or silicone as a hydrophobic treatment agent.

[0037] Examples of organosilicon compounds include hexamethyldisilazane, monomethylsilane, dimethylsilane, trimethylsilane, trimethylethoxysilane, isobutyltrimethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, and palmitylsilane. These are used individually or in mixtures of two or more.

[0038] In preferred embodiments of the present invention, a hydrophobized metal oxide powder is used, which is obtained by treating a metal oxide powder with trimethylsilane to which trimethylsilyl groups are added to the surface. Particularly preferred is a partially hydrophobized silica obtained by treating a silica powder with trimethylsilane to which trimethylsilyl groups are added to the surface.

[0039] Examples of silicones used as hydrophobic agents include dimethyl silicone, methylphenyl silicone, α-methylstyrene-modified silicone, chlorophenyl silicone, and fluorine-modified silicone.

[0040] The average primary particle size of the metal oxide powder is not particularly limited. For example, it can be approximately 1 to 1000 nm, preferably 3 to 100 nm, and more preferably 5 to 30 nm.

[0041] Furthermore, the average secondary particle size of the metal oxide powder is not particularly limited. Preferably, it can be 1 μm or less, more preferably 500 nm or less, more preferably 200 nm or less, and even more preferably 50 nm or less.

[0042] Here, the average primary particle diameter and average secondary particle diameter can be determined by measuring the maximum diameter of 2500 or more particles on a scanning electron microscope image and calculating the average of their numbers. Furthermore, the average secondary particle size can be adjusted by the stress applied during the preparation of the topical composition.

[0043] The lower limit of the powder content is not particularly limited, but it is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, and even more preferably 0.1% by mass or more. Furthermore, while there is no particular upper limit to the powder content, it is preferably 10% or less, more preferably 5% by mass or less, even more preferably 3% by mass or less, and even more preferably 2% by mass or less.

[0044] <3> Oil phase components

[0045] The oily agent contained in the oil phase of the Pickering emulsion of the present invention is not particularly limited and may include liquid oils and fats, solid oils and fats, waxes, hydrocarbon oils, higher fatty acids, higher alcohols, ester oils, silicone oils, and the like.

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

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

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

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

[0050] Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, 12-hydroxystearic acid, undecylenic acid, and tallic acid.

[0051] Examples of higher alcohols include cetyl alcohol, stearyl alcohol, behenyl alcohol, batyl alcohol, myristyl alcohol, and cetostearyl alcohol.

[0052] Ester oils include 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, sucrose stearate, sucrose oleate, cholesteryl 12-hydroxystearylate, ethylene glycol di-2-ethylhexylate, dipentaerythritol fatty acid ester, N-alkyl glycol monoisostearate, neopentyl glycol dicaprate, diisostearyl malate, glyceryl di-2-heptylundecanoate, trimethylolpropane tri-2-ethylhexylate, trimethylolpropane triisostearate, pentane tetra-2-ethylhexylate Lithritol, Glyceryl Tri-2-Ethylhexylate, Trimethylolpropane Triisostearate, Cetyl 2-Ethylhexanoate, 2-Ethylhexyl Palmitate, Glyceryl Trimyristate, Glyceride Tri-2-Heptyl Undecanoate, Methyl Castor Oil, Oleic Acid Oil, Cetostearyl Alcohol, Acetoglyceride, 2-Heptyl Undecyl Palmitate, Cetyl Palmitate, Adipi Examples include diisobutyl acetate, N-lauroyl-L-glutamic acid-2-octyldodecyl ester, di-2-heptylundecyl adipate, ethyl laurate, di-2-ethylhexyl sebatate, 2-hexyldecyl myristate, 2-hexyldecyl palmitate, 2-hexyldecyl adipate, diisopropyl sebatate, 2-ethylhexyl succinate, ethyl acetate, butyl acetate, amyl acetate, triethyl citrate, and the like.

[0053] Examples of silicone oils include linear polysiloxanes such as dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, and diphenylsiloxyphenyl trimethicone, as well as cyclic polysiloxanes such as pentasiloxane, decamethylpolysiloxane, dodecamethylpolysiloxane, and tetramethyltetrahydrogenpolysiloxane.

[0054] Among these, silicone oils, ester oils, liquid oils and fats, solid oils and fats, and waxes are preferably used, with diphenylpolysiloxane and cetyl ethylhexanoate being particularly preferred. One or more types of oils may be used.

[0055] Since the Pickering emulsion of the present invention has excellent emulsification stability, a polar oil can be used as the oil agent. Examples of polar oils that are particularly preferred include vegetable oils such as camellia oil, corn oil, mink oil, olive oil, avocado oil, sasanqua oil, castor oil, jojoba oil, sunflower oil, rapeseed oil, sesame oil, and soybean oil; monoester oils such as cetyl 2-ethylhexanoate, isopropyl myristate, cetyl octanoate, octyl palmitate, isocetyl stearate, isopropyl isostearate, octyl isopalmitate, and isopropyl sebacate; diester oils such as diethyl sebacate, diisopropyl sebacate, di-2-ethylhexyl sebacate, and diisopropyl phthalate; and triester oils such as glyceryl tri-2-ethylhexanoate and tri(caprylic / capric acid)glycerin.

[0056] Furthermore, it is preferable to use a highly polar oil with an IOB value of 0.1 or higher, more preferably 0.2 or higher. When using such a highly polar oil, it has been difficult to prepare a stable Pickering emulsion using conventional methods. According to the present invention, a Pickering emulsion with excellent emulsification stability can be prepared even when using a highly polar oil.

[0057] Furthermore, UV absorbers generally have high polarity, making it difficult to prepare stable Pickering emulsions using them. According to the present invention, it is possible to prepare a Pickering emulsion with excellent emulsification stability even when using UV absorbers.

[0058] As UV absorbers, any UV absorbers used in the field of topical skin preparations such as cosmetics can be used without any particular limitations, including benzoic acid derivatives such as para-aminobenzoic acid, para-aminobenzoic acid monoglycerin ester, N,N-dipropoxypara-aminobenzoate ethyl ester, N,N-diethoxypara-aminobenzoate ethyl ester, N,N-dimethylpara-aminobenzoate ethyl ester, N,N-dimethylpara-aminobenzoate butyl ester, N,N-dimethylpara-aminobenzoate ethyl ester, diethylaminohydroxybenzoyl hexyl benzoate; anthranilic acid derivatives such as homomenthyl-N-acetylanthranilate; salicylic acid and its sodium salts, amyl salicylate, menthyl salicylate, homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, p-isopropanolphenyl salicylate, etc. Salicylic acid derivatives; octyl cinnamate, ethyl-4-isopropyl cinnamate, methyl-2,5-diisopropyl cinnamate, ethyl-2,4-diisopropyl cinnamate, methyl-2,4-diisopropyl cinnamate, propyl-p-methoxy cinnamate, isopropyl-p-methoxy cinnamate, isoamyl-p-methoxy cinnamate, 2-ethylhexyl p-methoxy cinnamate (methoxycinnamate) Cinnamic acid derivatives such as cinnamic acid derivatives including tylhexyl (octyl paramethoxycinnamate), 2-ethoxyethyl-p-methoxycinnamate (cinoxate), cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenyl cinnamate, 2-ethylhexyl 2-cyano-3,3-diphenyl acrylate (octocrylene), glyceryl mono-2-ethylhexanoyl-diparamethoxycinnamate, ferulic acid and its derivatives;2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone (oxybenzone-3), 2-hydroxy-4-methoxy-4'-methylbenzophenone, 2-hydroxy-4-methoxybenzophenone-5-sulfonate, 4-phenylbenzophenone, 2-ethylhexyl-4'-phenyl Benzophenone derivatives such as benzophenone-2-carboxylate, 2-hydroxy-4-n-octoxybenzophenone, and 4-hydroxy-3-carboxybenzophenone; 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 '-methylphenylbenzotriazole; dibenzarazine; dianisioylmethane; 5-(3,3-dimethyl-2-norbornylidene)-3-pentan-2-one; dibenzoylmethane derivatives such as 4-t-butylmethoxydibenzoylmethane; octyltriazone; urocanic acid derivatives such as urocanic acid and ethyl urocanic acid; 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 1-(3,4-dimethoxyphenyl)-4,4-dimethyl-1,3-pentanedione, dimethoxyb Hydantoin derivatives such as 2-ethylhexyl didilidene dioxoimidazolidine propionate; phenylbenzimidazazole sulfonic acid, terephthalylidene dicamphor sulfonic acid, drometrizole trisiloxane, methyl anthranilate, bis-ethylhexyloxyphenol methoxyphenyl triazine, rutin and its derivatives, oryzanol and its derivatives; and silicone-based UV absorbers such as dimethicone diethyl benzalmalonate (polysilicone-15) are preferred.

[0059] The Pickering emulsion of the present invention is particularly useful as an ultraviolet absorber, in a form that includes a UVA absorber, especially one selected from benzophenone derivatives, dibenzoylmethane derivatives, and hydantoin derivatives. This is because the aforementioned UVA absorber has low solubility in oils, and problems such as precipitation occur, especially at low temperatures. According to the present invention, the UVA absorber can be stably incorporated.

[0060] Furthermore, in the Pickering emulsion of the present invention, combining a UVA absorber and a UVB absorber as ultraviolet absorbers is also preferable from the viewpoint of ultraviolet absorption capacity. In particular, using ethylhexyl methoxycinnamate as the UVB absorber is especially preferable from the viewpoint of improving the stability of the system and the feel of use.

[0061] The proportion of oil in the overall Pickering emulsion is not particularly limited, but in the case of an oil-in-water type Pickering emulsion, it is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and even more preferably 30% by mass or more. Furthermore, when using an oil-in-water type formulation, the proportion of the oil in the total can preferably be 50% by mass or less, more preferably 40% by mass or less.

[0062] When an oil-in-water type is used, the content of polar oil in the entire Pickering emulsion can preferably be 5% by mass or more, more preferably 10% by mass or more, even more preferably 20% by mass or more, and even more preferably 25% by mass or more.

[0063] When in the form of an oil-in-water type, the amount of ultraviolet absorber in the entire Pickering emulsion can be preferably 2% by mass or more, more preferably 5% by mass or more, even more preferably 10% by mass or more, and even more preferably 15% by mass or more, from the viewpoint of ultraviolet absorption function.

[0064] Furthermore, the content of polar oil in the total oil phase is preferably 40% by mass or more, more preferably 50% by mass or more, even more preferably 60% by mass or more, and even more preferably 70% by mass or more.

[0065] From the viewpoint of improving the ultraviolet absorption function, the lower limit of the content of ultraviolet absorbers in the total oil phase is preferably 5% by mass or more, more preferably 10% by mass or more, even more preferably 15% by mass or more, even more preferably 20% by mass or more, even more preferably 25% by mass or more, even more preferably 30% by mass or more, even more preferably 35% by mass or more, and even more preferably 40% by mass or more.

[0066] The upper limit of the amount of ultraviolet absorber in the total oil phase is not particularly limited, but is preferably 90% by mass or less, more preferably 80% by mass or less, even more preferably 70% by mass or less, even more preferably 60% by mass or less, and even more preferably 50% by mass or less.

[0067] <4> Pickering Emulsion The Pickering emulsion of the present invention may be a water-in-oil type or an oil-in-water type. Preferably, it is an oil-in-water type.

[0068] In the case of an oil-in-water type, the mass ratio of the aqueous phase to the oil phase is not particularly limited, but it is preferably 4:6 to 9:1, more preferably 5:5 to 8:2, even more preferably 5.5:4.5 to 7:3, and even more preferably 6:4 to 6.5:3.5.

[0069] Furthermore, in the present invention, the mass ratio of powder to oil phase is preferably 1:120 to 3:10, more preferably 1:60 to 1:5, and even more preferably 1:30 to 1:10.

[0070] Furthermore, in the present invention, the mass ratio of the acrylic polymer to the powder is preferably 1:0.5 to 1:100, more preferably 1:1 to 1:50, even more preferably 1:1.5 to 1:20, even more preferably 1:2 to 1:15, even more preferably 1:3 to 1:10, and even more preferably 1:3 to 1:8. By setting the mass ratio of the acrylic polymer to the powder within the aforementioned range, the emulsification stability of the Pickering emulsion can be improved.

[0071] The aqueous phase in the Pickering emulsion of the present invention may contain any ingredients commonly used in cosmetics without particular limitations, but it is preferable to contain, for example, the following ingredients. Examples of polyols include polyethylene glycol, glycerin, 1,3-butylene glycol, erythritol, sorbitol, xylitol, maltitol, propylene glycol, dipropylene glycol, diglycerin, isoprene glycol, 1,2-pentanediol, 2,4-hexylene glycol, 1,2-hexanediol, and 1,2-octanediol, with glycerin, 1,3-butylene glycol, and sorbitol being particularly preferred. The content of these polyols is preferably 0.5 to 20% by mass, more preferably 3 to 10% by mass, of the entire Pickering emulsion. Furthermore, the content of these polyols is preferably 3 to 15% by mass, and even more preferably 5 to 10% by mass, of the aqueous phase. It is also preferable to include a thickening agent. Examples of thickening agents include xanthan gum, gellan gum, guar gum, quince seed, carrageenan, galactan, gum arabic, pectin, mannan, starch, curdlan, methylcellulose, hydroxyethylcellulose, carboxymethylcellulose, methylhydroxypropylcellulose, chondroitin sulfate, dermatan sulfate, glycogen, heparan sulfate, hyaluronic acid, sodium hyaluronate, tragacanth gum, keratan sulfate, chondroitin, mucoitin sulfate, hydroxyethyl guar gum, carboxymethyl guar gum, dextran, Examples include keratosulfate, locust bean gum, succinoglucan, carotenic acid, chitin, chitosan, carboxymethyl chitin, agar, polyvinyl alcohol, polyvinylpyrrolidone, carboxyvinyl polymer, sodium polyacrylate, polyethylene glycol, sodium acrylate grafted starch, stearoxyl hydroxypropyl methylcellulose, bentonite, etc. More preferably, water-soluble polysaccharides such as xanthan gum and guar gum, agar, sodium acrylate grafted starch, and stearoxyl hydroxypropyl methylcellulose. Even more preferably, water-soluble polysaccharides such as xanthan gum and guar gum, and agar are mentioned. The content of these is preferably 0.05 to 5% by mass of the entire Pickering emulsion, more preferably 0.1 to 1% by mass. Also, the content of these is preferably 0.1 to 3% by mass of the aqueous phase, more preferably 0.3 to 1% by mass.

[0072] Furthermore, the water content in the Pickering emulsion of the present invention is preferably 30 to 80% by mass, more preferably 40 to 70% by mass, and particularly preferably 45 to 65% by mass, relative to the total. Furthermore, the water content is preferably 70-90% by mass, more preferably 75-85% by mass, relative to the aqueous phase.

[0073] From the viewpoint of emulsification stability, the average emulsified particle size in the Pickering emulsion of the present invention is preferably less than 20 μm, more preferably 15 μm or less, even more preferably 10 μm or less, even more preferably 8 μm or less, even more preferably 6 μm or less, even more preferably 5 μm or less, and even more preferably 4 μm or less. The average emulsion particle diameter can be determined by observing the emulsion under an optical microscope at 20°C and calculating the average number of the largest diameter particles among 10 randomly selected emulsion particles.

[0074] In the present invention, the average emulsion particle size is preferably within the aforementioned range in absolute value when it is left standing at 40°C for two weeks or more, preferably one month. Furthermore, as a relative value, it is preferable that the average emulsion particle diameter after standing at 40°C for two weeks or more, preferably one month, is twice or less, and more preferably 1.2 times or less, compared to the average emulsion particle diameter immediately after preparation.

[0075] Furthermore, in the Pickering emulsion of the present invention, optional components commonly used in cosmetics may be included in addition to the above components, to the extent that they do not impair the effects of the invention. Such optional components include, for example, fatty acid soaps (sodium laurate, sodium palmitate, etc.), anionic surfactants such as potassium lauryl sulfate and alkyl sulfate triethanolamine ether, cationic surfactants such as stearyltrimethylammonium chloride, benzalkonium chloride and laurylamine oxide, imidazoline-based amphoteric surfactants (2-cocoyl-2-imidazolinium hydroxide-1-carboxyethyloxy disodium salt, etc.), betaine-based surfactants (alkyl betaine, Amphoteric surfactants such as amide betaine, sulfobetaine, etc., acylmethyl taurine, sorbitan fatty acid esters (sorbitan monostearate, sorbitan sesquioleate, etc.), glycerin fatty acids (glyceryl monostearate, etc.), propylene glycol fatty acid esters (propylene glycol monostearate, etc.), hydrogenated castor oil derivatives, glycerin alkyl ethers, POE sorbitan fatty acid esters (POE sorbitan monooleate, polyoxyethylene sorbitan monostearate, etc.), POE sorbitol fatty acid esters (POE-sorbitol monolaurate, etc.), POE glycerin fatty acid esters (POE-glycerin monoisostearate, etc.), POE fatty acid esters (polyethylene glycol monooleate, POE distearate, etc.), POE alkyl ethers (POE 2-octyldodecyl ether, etc.), POE alkylphenyl ethers (POE nonylphenyl ether, etc.), Pluronic® type, POE·POP alkyl ethers (POE·POP 2-decyl Nonionic surfactants such as trandecyl ether, tetronics, POE castor oil / hydrogenated castor oil derivatives (POE castor oil, POE hydrogenated castor oil, etc.), sucrose fatty acid esters, alkyl glucosides, etc., moisturizing ingredients such as sodium pyrrolidone carboxylate, lactic acid, sodium lactate, powders such as mica, talc, kaolin, synthetic mica, calcium carbonate, magnesium carbonate, anhydrous silicic acid (silica), aluminum oxide, barium sulfate, etc., powders which may be surface-treated, cobalt oxide, ultramarine, Prussian blue, etc.Inorganic pigments such as zinc oxide, composite pigments such as iron oxide titanium dioxide sintered bodies (which may be surface-treated), pearlescent agents such as titanium mica, fish scale foil, and bismuth oxychloride (which may be surface-treated), organic pigments such as Red 202, Red 228, Red 226, Yellow 4, Blue 404, Yellow 5, Red 505, Red 230, Red 223, Orange 201, Red 213, Yellow 204, Yellow 203, Blue 1, Green 201, Violet 201, Red 204 (which may be lake-formed), polyethylene powder, polymethyl methacrylate, nylon powder, organoplasty Organic powders such as risiloxane elastomer, lower alcohols such as ethanol and isopropanol, vitamin A or its derivatives, vitamin B compounds such as vitamin B6 hydrochloride, vitamin B6 tripalmitate, vitamin B6 dioctanoate, vitamin B2 or its derivatives, vitamin B12, vitamin B15 or its derivatives, vitamin E compounds such as α-tocopherol, β-tocopherol, γ-tocopherol, and vitamin E acetate, vitamin D compounds, vitamin H, pantothenic acid, pantethine, pyrroloquinoline quinone, and other vitamins are preferred examples.

[0076] The Pickering emulsion of the present invention may contain a surfactant, but it is preferable to keep the amount as low as possible. The surfactant content is preferably 5% by mass or less, more preferably 1% by mass or less, even more preferably 0.1% by mass or less, and particularly preferably 0% by mass.

[0077] The Pickering emulsion of the present invention can be produced by dispersing powder in an aqueous phase at room temperature and then adding an oil phase to emulsify it.

[0078] The Pickering emulsion of the present invention is suitable for topical skin preparations. In particular, it is preferable to utilize the function of the ultraviolet absorber to create a sunscreen topical skin preparation. In particular, it is preferable to use it in cosmetics, and especially in makeup bases, foundations, and the like. [Examples]

[0079] In the mixture of aqueous phase components shown in Table 1, silylated silica was dispersed, and the oil was added while stirring to emulsify the mixture, thereby producing the Pickering emulsions of the examples and comparative examples. The silylated silica used in Test Example 1 was obtained by mixing silica microparticles (manufactured by AEROSIL, with an average primary particle size of 12 nm (measurement method as described above)) with mono, di, and trimethylsilyl hydrophobic treatment agents.

[0080] [Table 1]

[0081] (Emulsification stability) The Pickering emulsions of the examples and comparative examples were left at 40°C for one month. The average emulsion particle size was measured before and after standing, and the rate of increase in the average emulsion particle size over time was calculated. The emulsion stability was evaluated according to the following criteria. The results are shown in Table 1. ○···100%~120% △···120%~200% ×···200%~

[0082] (Average emulsion particle size) The Pickering emulsions of the examples and comparative examples were observed with an optical microscope, and the average emulsion particle size was measured using the method described above. The results are shown in Table 1. Microscopic images of the Pickering emulsions of Example 1 and Comparative Example 1 are shown in Figure 1.

[0083] (UV protection) The Pickering emulsions of the examples and comparative examples were applied to surgical tape (Transpore 3M Healthcare Co., Ltd.) at a rate of 2 mg / cm² over an area of ​​6.4 cm × 6.4 cm. The SPF value was determined from the average protective spectrum obtained by measuring 10 times using a Labsphere UV-2000S SPF analyzer. Table 1 shows the evaluation results, with ◎ indicating an SPF of 50 or higher, ○ indicating an SPF of 30 or higher but less than 50, △ indicating an SPF of 15 or higher but less than 30, and × indicating an SPF of less than 15.

[0084] As shown in Table 1 and Figure 1, the Pickering emulsion of Example 1, which contained acrylates copolymer, had a significantly smaller average emulsion particle size and superior emulsion stability compared to the Pickering emulsion of Comparative Example 1, which did not contain acrylates copolymer.

[0085] Furthermore, the results from Examples 1 to 3 shown in Table 1 indicate that the average emulsion particle size decreases and emulsion stability improves in a manner dependent on the acrylates copolymer content.

[0086] These results demonstrate that adding an acrylic polymer to Pickering emulsion can significantly improve its emulsion stability. This effect is thought to be due to the improved dispersibility of powders adsorbed at the emulsion interface by the acrylic polymer.

[0087] Furthermore, as shown in Table 1, although Examples 4 to 6 have different oil phase compositions from Example 1, they all exhibit excellent emulsification stability. Conventional techniques have limited the types and compositions of oil phases that can be used to obtain a stable Pickering emulsion (see Comparative Example 1, for example). However, the results shown in Table 1 demonstrate that the application of the present invention significantly improves this degree of flexibility.

[0088] Furthermore, although the Pickering emulsions of Examples 1-3 consist of an ultraviolet absorber making up about half of the oil phase, they exhibit excellent emulsification stability. With conventional techniques, it was difficult to prepare Pickering emulsions containing a large amount of UV absorber (see Comparative Example 1 if necessary). However, the results shown in Table 1 demonstrate that the emulsification stability of Pickering emulsions containing a large amount of UV absorber can be significantly improved by adding an acrylic polymer. [Industrial applicability]

[0089] This invention is suitable for use as a sunscreen for topical skin application.

Claims

1. The powder is adsorbed at the emulsion interface, and the aqueous phase contains an acrylic polymer. The acrylic polymer is a copolymer (excluding crosslinked polymers) whose constituent monomers are (meth)acrylic monomers containing (meth)acrylic acid and its esters. The (meth)acrylic acid ester is an alkyl (meth)acrylic acid ester in which the alkyl group has 1 to 20 carbon atoms. The powder is a metal oxide having emulsifying ability, which has been hydrophobized using an organosilicon compound or silicone as a hydrophobic treatment agent. The content of the acrylic polymer is 0.1% by mass or more. A Pickering emulsion characterized in that the mass ratio of the acrylic polymer to the powder is 1:1.5 to 1:

20.

2. The powder is adsorbed at the emulsion interface, and the aqueous phase contains an acrylic polymer. The acrylic polymer is a copolymer comprising (meth)acrylic monomers containing (meth)acrylic acid and its esters as constituent monomers. The (meth)acrylic acid ester is an alkyl (meth)acrylic acid ester in which the alkyl group has 1 to 20 carbon atoms. The powder is a metal oxide having emulsifying ability, which has been hydrophobized using an organosilicon compound or silicone as a hydrophobic treatment agent. The content of the acrylic polymer is 0.1% by mass or more. The mass ratio of the acrylic polymer to the powder is 1:1.5 to 1:

20. A Pickering emulsion characterized by having an average emulsified particle size of 8 μm or less.

3. The aforementioned acrylic polymer is an acrylates copolymer. The aforementioned powder is silylated silica, The Pickering emulsion according to claim 1 or 2, characterized in that the mass ratio of the acrylic polymer to the powder is 1:1.5 to 1:

20.

4. A Pickering emulsion according to any one of claims 1 to 3, characterized in that it contains a polar oil as an oil phase component.

5. The Pickering emulsion according to claim 4, characterized in that the polar oil contains a highly polar oil with an IOB value of 0.1 or higher.

6. The Pickering emulsion according to claim 4 or 5, characterized in that the proportion of polar oil in the oily component contained in the Pickering emulsion is 60% by mass or more.

7. The Pickering emulsion according to any one of claims 4 to 6, characterized in that the polar oil contains an ultraviolet absorber.

8. The Pickering emulsion according to claim 7, characterized in that the proportion of the ultraviolet absorber in the oil contained in the Pickering emulsion is 30% by mass or more.

9. The Pickering emulsion according to claim 1, characterized in that the average emulsified particle size is 15 μm or less.

10. A Pickering emulsion according to any one of claims 1 to 9, characterized in that the content of surfactants other than the aforementioned powder is 0.1% by mass or less.

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