JP2024083481A - Pickering emulsion containing acrylic polymer - Google Patents

Abstract

To provide a technique to improve emulsion stability of a Pickering emulsion.SOLUTION: The present invention provides a Pickering emulsion in which powder is adsorbed on an emulsification interface and which contains an acrylic polymer.SELECTED DRAWING: Figure 1

Description

Application for application of Article 30, Paragraph 2 of the Patent Law filed May 23, 2018 Released at Orbis the Shop Ikebukuro Marui store and other stores nationwide

Application for application of Article 30, Paragraph 2 of the Patent Law filed. Released for online sale on May 23, 2018.

Application for application of Article 30, Paragraph 2 of the Patent Law submitted. Published online on May 23, 2018.

Application for application of Article 30, Paragraph 2 of the Patent Law filed. Published via online press release on May 16, 2018.

The present invention relates to Pickering emulsions.

Formulations in which amphiphilic solid particles are adsorbed to the interface to form an emulsion are conventionally known as Pickering emulsions, and their use in cosmetics has also been proposed. For example, titanium dioxide, zinc oxide, etc. have been proposed as the solid particles, and it has been proposed that these solid particles with hydrophobic surfaces be used to prepare Pickering emulsions (Patent Document 1). In addition, oil-in-water emulsions using partially hydrophobic silica have also been proposed, and are considered to be excellent in terms of non-stickiness, freshness, and high-temperature emulsion stability (Patent Document 2).

JP 2001-518111 A JP 2013-129626 A

With Pickering emulsions, there are limitations to the type and amount of oil that can be emulsified, and there was a problem in that the emulsified state deteriorated if the limits were exceeded.
The problem to be solved by the present invention is to provide a technique for improving the emulsion stability of Pickering emulsions, particularly a technique for improving the emulsion stability of Pickering emulsions that can be applied to emulsions containing a polar oil as an oil phase component.

Through the inventor's diligent research efforts, it was discovered that the addition of an acrylic acid polymer can improve the dispersion state of the powder adsorbed to the emulsion interface, and it is possible to prepare a Pickering emulsion with fine emulsion particle size and excellent stability. Based on this knowledge, the present invention was completed.

The present invention, which solves the above-mentioned problems, provides a Pickering emulsion, characterized in that a powder is adsorbed to the emulsion interface and that the emulsion contains an acrylic polymer.
The emulsion composition of the present invention has excellent emulsion stability.

In a preferred embodiment of the present invention, the acrylic polymer is a copolymer containing structural units derived from an alkyl (meth)acrylate.

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

In a preferred embodiment of the present invention, the oil phase component contains a polar oil.
Conventionally, when a polar oil is included as an oil phase component, it has been difficult to prepare a stable Pickering emulsion. By applying the present invention, it is possible to improve the stability of a Pickering emulsion containing a polar oil as an oil phase component.

In a preferred embodiment of the present invention, the polar oil includes a highly polar oil having an IOB value of 0.1 or more.
Conventionally, Pickering emulsions containing such highly polar oils have been poor in stability. According to the present invention, a stable Pickering emulsion can be provided even when such highly polar oils are contained.

In a preferred embodiment of the present invention, the ratio of polar oil to the oil agent contained in the Pickering emulsion is 60 mass % or more.
In the conventional technology, it was difficult to stably prepare a Pickering emulsion in which the ratio of polar oil in the oil agent was 60 mass% or more. According to the present invention, it is possible to provide a Pickering emulsion having excellent emulsion stability even in a form containing such a high content of polar oil.

In a preferred embodiment of the present invention, the polar oil contains an ultraviolet absorber.
According to the present invention, it is possible to improve the emulsion stability of a Pickering emulsion containing an ultraviolet absorber.

In a preferred embodiment of the present invention, the ratio of the ultraviolet absorber to the oil agent contained in the Pickering emulsion is 30 mass % or more.
According to the present invention, it is possible to provide such a Pickering emulsion having a high content of an ultraviolet absorber.

In a preferred embodiment of the present invention, the average emulsion particle size is 15 μm or less.
A Pickering emulsion in this form has excellent emulsion stability.

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 emulsion stability.

The present invention makes it possible to provide a Pickering emulsion with excellent emulsion stability.

1 shows microscopic images of Pickering emulsions of Example 1 and Comparative Example 2.

<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, as a constituent monomer, a (meth)acrylic monomer selected from (meth)acrylic acid and its amides and esters.
In the present invention, it is preferable to use an acrylic copolymer which is a random copolymer, an alternating copolymer or a block copolymer.

A suitable example of the ester of (meth)acrylic acid is an alkyl (meth)acrylate.
The number of carbon atoms in the alkyl group in the (meth)acrylic acid alkyl ester is not particularly limited, and is preferably 1 to 20, more preferably 1 to 10, and further preferably 1 to 4, for example.

When an amide or ester of (meth)acrylic acid 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 component such as a sugar residue, an amino acid residue, or phosphorylcholine.

Such monomers can be prepared by known methods. For example, in the case of sugar residues, 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 is then esterified with acrylic acid or methacrylic acid to produce the desired monomer.

In the case of amino acid residues, the desired amide-type monomer can be obtained by converting acrylic acid or methacrylic acid into an acid chloride using thionyl chloride or the like, and then condensing it with the amino acid in the presence of an alkali to form an acid amide bond.

Phospholipid-like structures such as phosphorylcholine can be obtained by condensing phosphorylcholine with chloroethanol in the presence of an alkali to give hydroxyethylphosphorylcholine. The desired monomer can be obtained by condensing this with acrylic acid chloride or methacrylic acid chloride in the presence of an alkali.

Specific 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, palmityl (meth)acrylate, heptadecyl (meth)acrylate, stearyl (meth)acrylate, isostearyl (meth)acrylate, oleyl (meth)acrylate, behenyl (meth)acrylate, (meth)acrylic acid esters having a linear, branched or alicyclic hydrocarbon group; acrylnitrile; (meth)acrylamides such as acrylamide, diacetone acrylamide, N,N-dimethylacrylamide, N-t-butylacrylamide, N-octylacrylamide, and N-t-octylacrylamide; sulfonic acid group-containing (meth)acrylamides such as 2-(meth)acrylamido-2-methylpropanesulfonic 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)acrylates such as dimethylaminoethyl (meth)acrylamide and diethylaminoethyl (meth)acrylamide. p) Methacrylamide; 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; methacryloyloxyalkyl phosphate monoesters, such as (meth)acryloyloxyethyl phosphate; glyceryl (meth)acrylate, 2-methacryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl phthalate, β -Carboxyethyl acrylate, acryloyloxyethyl succinate, 2-(meth)acryloyloxyethyl tetrahydrophthalic acid, 2-(meth)acryloyloxyethyl hexahydrophthalic acid; 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, methylene bisacrylamide, 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 tricaprolactonate tri(meth)acrylate, trimethylolhexane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, diglycerin tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, ditrimethylolpropane tetracaprolactonate tetra(meth)acrylate Examples of the ethylenically unsaturated double bond include (meth)acrylates having two or more ethylenically unsaturated double bonds, such as dipentaerythritol tetra(meth)acrylate, ditrimethylolethane tetra(meth)acrylate, ditrimethylolbutane tetra(meth)acrylate, ditrimethylolhexane tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, tripentaerythritol hexa(meth)acrylate, tripentaerythritol hepta(meth)acrylate, and tripentaerythritol octa(meth)acrylate.

As the acrylic polymer, a copolymer obtained by copolymerizing a (meth)acrylic monomer with a constituent monomer 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 maleates, monoalkyl fumarate esters, and monoalkyl itaconic acid esters; examples of sulfonic acid group-containing monomers include alkene sulfonic acids such as vinyl sulfonic acid and (meth)allyl sulfonic acid; aromatic vinyl group-containing sulfonic acids such as α-methylstyrene sulfonic 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, diisopropylbenzene, 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, and vinylpyrrolidone.

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, there may be mentioned compounds referred to as "ACRYLATES COPOLYMER" in the INCI name (International Cosmetic Ingredient Dictionary and Handbook, 14th Edition, Vol. 1, CTFA, 2012, pp. 60-61).

The acrylic polymer can be obtained by polymerizing the above-mentioned constituent monomers.
The polymerization may be carried out in the presence of a polymerization initiator such as azobisbutyronitrile according to a conventional method.

From the viewpoint of reducing the emulsion particle size of the Pickering emulsion or improving the emulsion stability, the content of the acrylic polymer 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.

The upper limit of the amount of acrylic polymer in the entire Pickering emulsion is not particularly limited, but 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.

<2> Powder In the Pickering emulsion of the present invention, a powder is adsorbed to the emulsion interface. As the powder, any powder having the emulsifying ability generally used in Pickering emulsions can be used without any particular limitation.

As the powder, either an organic powder or an inorganic powder can be used, but in the present invention, it is particularly preferable to use a metal oxide powder.
The metal oxides referred to here also include oxides of semi-metals such as silicon.
Examples of the metal oxide powder include silica, titanium dioxide, zinc oxide, iron oxide, zirconium oxide, and cerium oxide.

When silica powder is used as the metal oxide powder, either so-called dry silica powder produced by vapor phase oxidation of silicon halide, or so-called wet silica powder produced from water glass or the like may be used.
As the dry silica powder, for example, the Aerosil series (Nippon Aerosil Co., Ltd.), the CAB-O-SIL series (Cabot Corporation), and the HDK series (Wacker Asahi Kasei Silicone Co., Ltd.) can be used. As the wet silica powder, for example, the Nipsil series (Tosoh Silica Corporation), the HI-SIL series (PPG), and other commercially available products can be used.

As for other metal oxide powders, many commercially available products are also available, and commercially available products can be used as they are. Specific examples of such commercially available products include fine titanium dioxide particles such as "MTY-110M3S" (manufactured by Teika Corporation), "MTY-02" (manufactured by Teika Corporation), "MT-100TV" (manufactured by Teika Corporation), "MT-500HSA" (manufactured by Teika Corporation), "MT-100T" (manufactured by Teika Corporation), "MT-01" (manufactured by Teika Corporation), "MT-10EX" (manufactured by Teika Corporation), "MT-05" (manufactured by Teika Corporation), "MT-100Z" (manufactured by Teika Corporation), "MT-150EX" (manufactured by Teika Corporation), "MT-100AQ" (manufactured by Teika Corporation), "MT-100WP" (manufactured by Teika Corporation), and " Examples include MT-100SA (manufactured by Teika Corporation), MT-500B (manufactured by Teika Corporation), MT-500SA (manufactured by Teika Corporation), MT-600B (manufactured by Teika Corporation), MT-500SAS (manufactured by Teika Corporation), TYPAQUE CR-50 (manufactured by Ishihara Sangyo Kaisha), TYPAQUE TTO-M-1 (manufactured by Ishihara Sangyo Kaisha), TYPAQUE TTO-V4 (manufactured by Ishihara Sangyo Kaisha), ST-455 (manufactured by Titanium Kogyo Co., Ltd.), STT-65C-S (manufactured by Titanium Kogyo Co., Ltd.), STT-30EHS (manufactured by Titanium Kogyo Co., Ltd.), and Bayer Titanium R-KB-1 (manufactured by Bayer).

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

It is preferable that the surface of the metal oxide powder is hydrophobized. The hydrophobized metal oxide powder can be prepared by reacting the metal oxide powder with a hydrophobizing agent to add hydrophobic groups to the hydroxyl groups present on the surface of the powder through covalent bonds, or by coating the surface of the metal oxide powder by physically attaching the hydrophobizing agent to it.

The hydrophobic treatment may be carried out by treating the metal oxide powder with a hydrophobic treatment agent such as an organosilicon compound, silicone, hydrocarbon oil, fatty acid, fatty acid amide, fatty acid ester, higher alcohol, or polyoxyalkylene compound.
It is particularly preferable to treat the metal oxide powder with an organosilicon compound or silicone as a hydrophobic treatment agent.

Organosilicon compounds include hexamethyldisilazane, monomethylsilane, dimethylsilane, trimethylsilane, trimethylethoxysilane, isobutyltrimethoxysilane, trimethylchlorosilane, dimethyldichlorosilane, methyltrichlorosilane, dimethylethoxysilane, dimethyldimethoxysilane, diphenyldiethoxysilane, hexamethyldisiloxane, palmitylsilane, etc. These may be used alone or in a mixture of two or more.

In a preferred embodiment of the present invention, a hydrophobic metal oxide powder is used in which a metal oxide powder is treated with trimethylsilane and trimethylsilyl groups are added to the surface, and it is particularly preferred to use partially hydrophobic silica in which a silica powder is treated with trimethylsilane and trimethylsilyl groups are added to the surface.

When silicone is used as a hydrophobic treatment agent, examples include dimethyl silicone, methylphenyl silicone, α-methylstyrene modified silicone, chlorophenyl silicone, and fluorine modified silicone.

There are no particular limitations on the average primary particle size of the metal oxide powder. For example, it can be 1 to 1000 nm, preferably 3 to 100 nm, and more preferably 5 to 30 nm.

The average secondary particle diameter of the metal oxide powder is also not particularly limited. It is preferably 1 μm or less, more preferably 500 nm or less, and even more preferably 200 nm or less.
More preferably, it is 50 nm or less.

Here, the average primary particle size and the average secondary particle size can be determined by measuring the maximum diameters of 2,500 or more particles on a scanning electron microscope image and calculating the number average.
The average secondary particle size can be adjusted by the stress applied during preparation of the topical composition.

The lower limit of the powder content is not particularly limited, but is preferably 0.01 mass % or more, more preferably 0.05 mass % or more, and even more preferably 0.1 mass % or more.
Furthermore, the upper limit of the powder content is not particularly limited, but is preferably 10 mass % or less, more preferably 5 mass % or less, even more preferably 3 mass % or less, and even more preferably 2 mass % or less.

<3> Oil phase components

The oil contained in the oil phase of the Pickering emulsion of the present invention is not particularly limited, and may contain liquid oils and fats, solid oils and fats, wax, hydrocarbon oils, higher fatty acids, higher alcohols, ester oils, silicone oils, etc.

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, persic oil, wheat germ oil, sasanqua oil, castor oil, linseed oil, safflower oil, cottonseed oil, perilla oil, meadowfoam oil, soybean oil, peanut oil, tea seed oil, kaya oil, rice bran oil, Chinese tung oil, Japanese tung oil, jojoba oil, germ oil, triglycerin, glycerin trioctanoate, glycerin triisopalmitate, etc.

Examples of solid fats and oils include cacao butter, coconut oil, horse tallow, hardened coconut oil, palm oil, beef tallow, mutton tallow, hardened beef tallow, palm kernel oil, lard, beef bone fat, Japan Rice Kernel Oil, hardened oil, beef foot fat, Japan Rice, and hardened castor oil.

Examples of waxes include beeswax, candelilla wax, cotton wax, carnauba wax, bayberry wax, ivory wax, whale wax, montan wax, bran wax, lanolin, kapok wax, lanolin acetate, liquid lanolin, sugarcane wax, lanolin fatty acid isopropyl, 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, POE hydrogenated lanolin alcohol ether, etc.

Hydrocarbon oils include liquid paraffin, ozokerite, pristane, paraffin, ceresin, squalene, petrolatum, microcrystalline wax, etc.

Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, 12-hydroxystearic acid, undecylenic acid, tall acid, etc.

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

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-hydroxystearate, ethylene glycol di-2-ethylhexylate, dipentaerythritol fatty acid ester, N-alkyl glycol monoisostearate, neopentyl glycol dicaprate, diisostearyl malate, glycerin di-2-heptylundecanoate, trimethylolpropane tri-2-ethylhexylate, trimethylolpropane triisostearate, pentane tetra-2-ethylhexylate, Lithritol, glycerin tri-2-ethylhexyl acid, trimethylolpropane triisostearate, cetyl 2-ethylhexanoate, 2-ethylhexyl palmitate, glycerin trimyristate, tri-2-heptylundecanoic acid glyceride, castor oil fatty acid methyl ester, oleic acid oil, cetostearyl alcohol, acetoglyceride, 2-heptylundecyl palmitate, cetyl palmitate, adipine diisobutyl acetate, 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, ethyl acetate, butyl acetate, amyl acetate, triethyl citrate, etc.

Examples of silicone oils include linear polysiloxanes such as dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, and diphenylsiloxyphenyltrimethicone, and cyclic polysiloxanes such as pentasiloxane, decamethylpolysiloxane, dodecamethylpolysiloxane, and tetramethyltetrahydrogenpolysiloxane.

Among these, silicone oils, ester oils, liquid oils, solid oils and waxes are preferably used, and diphenylpolysiloxane, cetyl ethylhexanoate, etc. are particularly preferably used. One or more types of oils can be used.

Since the Pickering emulsion of the present invention has excellent emulsion stability, a polar oil can be used as the oil.
Particularly preferred examples of polar oils 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.

It is also preferable to use a highly polar oil agent with an IOB value of 0.1 or more, more preferably 0.2 or more. When such highly polar oil agents are used, it has been difficult to prepare a stable Pickering emulsion using conventional methods. According to the present invention, a Pickering emulsion with excellent emulsion stability can be prepared even when a highly polar oil agent is used.

In addition, UV absorbers are generally highly polar, making it difficult to prepare a stable Pickering emulsion using them. According to the present invention, it is possible to prepare a Pickering emulsion with excellent emulsion stability even when a UV absorber is used.

As the ultraviolet absorbing agent, any ultraviolet absorbing agent used in the field of skin external preparations such as cosmetics can be used without any particular limitation, and examples thereof include benzoic acid derivatives such as para-aminobenzoic acid, para-aminobenzoic acid monoglycerin ester, N,N-dipropoxy para-aminobenzoic acid ethyl ester, N,N-diethoxy para-aminobenzoic acid ethyl ester, N,N-dimethyl para-aminobenzoic acid ethyl ester, N,N-dimethyl para-aminobenzoic acid butyl ester, N,N-dimethyl para-aminobenzoic acid ethyl ester, and diethylaminohydroxybenzoyl hexyl benzoate; anthranilic acid derivatives such as homomenthyl-N-acetylanthranilate; salicylic acid and its sodium salt, salicylic acid derivatives such as amyl salicylate, menthyl salicylate, homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, and p-isopropanol phenyl salicylate; octyl cinnamate, ethyl-4-isopropyl p-methoxycinnamate, ethyl 2,4-diisopropyl cinnamate, methyl 2,4-diisopropyl cinnamate, propyl p-methoxycinnamate, isopropyl p-methoxycinnamate, isoamyl p-methoxycinnamate, 2-ethylhexyl p-methoxycinnamate (ethylhexyl methoxycinnamate, octyl p-methoxycinnamate), 2-ethoxyethyl p-methoxycinnamate (cyano) noxate), cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenylcinnamate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (octocrylene), glyceryl mono-2-ethylhexanoyl-di-para-methoxycinnamate, cinnamic acid derivatives such as ferulic acid and its derivatives; 2,4-dihydroxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, benzophenone derivatives such as 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-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; dibenzalazine; dianisoyl dibenzoylmethane derivatives such as 4-t-butylmethoxydibenzoylmethane; octyl triazone; urocanic acid derivatives such as urocanic acid and ethyl urocanate; 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 1-(3,4-dimethoxyphenyl)-4,4-dimethyl-1,3-pentanedione, dimethoxybenzylidene dioxoimidazolidine Preferred examples include hydantoin derivatives such as 2-ethylhexyl propionate; phenylbenzimidazol sulfonic acid, terephthalidenedicamphor sulfonic acid, drometrizole trisiloxane, methyl anthranilate, bisethylhexyloxyphenol methoxyphenyl triazine, rutin and its derivatives, oryzanol and its derivatives; and silicone-based UV absorbers such as dimethicodimethyi benzalmalonate (polysilicone-15).

The Pickering emulsion of the present invention is particularly useful in a form that contains a UVA absorber as an ultraviolet absorbing agent, in particular a UVA absorber selected from benzophenone derivatives, dibenzoylmethane derivatives, and hydantoin derivatives.
This is because the UVA absorbent has low solubility in oils and therefore poses problems such as precipitation, particularly at low temperatures. According to the present invention, the UVA absorbent can be stably incorporated.

In addition, in the Pickering emulsion of the present invention, it is also preferable to combine a UVA absorber and a UVB absorber as an ultraviolet absorber from the viewpoint of ultraviolet absorbing ability. Here, it is particularly preferable to use ethylhexyl methoxycinnamate as the UVB absorber from the viewpoint of improving the stability of the system and the feeling of use.

The proportion of the oil in the entire Pickering emulsion is not particularly limited, but in the case of an oil-in-water Pickering emulsion, the proportion is preferably 5 mass% or more, more preferably 10 mass% or more, even more preferably 20 mass% or more, and even more preferably 30 mass% or more.
In the case of an oil-in-water type composition, the proportion of the oil in the total composition can be preferably 50% by mass or less, and more preferably 40% by mass or less.

When the emulsion is in the form of an oil-in-water type, the polar oil content of the entire Pickering emulsion can be 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 25% by mass or more.

When the emulsion is in the form of an oil-in-water type, the content of the UV 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 UV absorption function.

The content of polar oil in the entire 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.

From the viewpoint of improving the ultraviolet absorbing function, the lower limit of the content of the ultraviolet absorbing agent in the entire 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, even more preferably 40% by mass or more.

The upper limit of the content of the ultraviolet absorber in the entire 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.

<4> Pickering Emulsion The Pickering emulsion of the present invention may be of the water-in-oil type or the oil-in-water type, and is preferably of the oil-in-water type.

When an oil-in-water type is used, the weight ratio of the water phase to the oil phase is not particularly limited, but 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.

In addition, in the present invention, the mass ratio of the powder to the 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.

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 above range, the emulsion stability of the Pickering emulsion can be improved.

The aqueous phase in the Pickering emulsion of the present invention may contain any component typically used in cosmetics without any particular limitation, but it is preferable that it contains, for example, the following components:
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, and among these, glycerin, 1,3-butylene glycol, and sorbitol are preferred. The content of these is preferably 0.5 to 20% by mass, more preferably 3 to 10% by mass, of the entire Pickering emulsion. The content of these 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 contain a thickener. Examples of the thickener 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 of the surfactant include keratosulfuric acid, locust bean gum, succinoglucan, caronic acid, chitin, chitosan, carboxymethylchitin, agar, polyvinyl alcohol, polyvinylpyrrolidone, carboxyvinyl polymer, sodium polyacrylate, polyethylene glycol, sodium acrylate grafted starch, stearoxy hydroxypropyl methylcellulose, and bentonite. More preferred are water-soluble polysaccharides such as xanthan gum and guar gum, agar, sodium acrylate grafted starch, and stearoxy hydroxypropyl methylcellulose. More preferred are water-soluble polysaccharides such as xanthan gum and guar gum, and agar. The content of these is preferably 0.05 to 5% by mass, more preferably 0.1 to 1% by mass, of the entire Pickering emulsion. The content of these is preferably 0.1 to 3% by mass, more preferably 0.3 to 1% by mass, of the aqueous phase.

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, based on the total mass.
The water content is preferably 70 to 90% by mass, more preferably 75 to 85% by mass, based on the water phase.

The average emulsion particle size in the Pickering emulsion of the present invention is, from the viewpoint of emulsion stability, 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 size can be determined by observing with an optical microscope at 20° C. and calculating the number average of the maximum diameters of 10 randomly selected emulsion particles.

In the present invention, the average emulsion particle size is preferably within the above-mentioned range as an absolute value when the emulsion is allowed to stand at 40° C. for 2 weeks or more, preferably for 1 month.
As a relative value, the average emulsion particle size after standing at 40°C for 2 weeks or more, preferably for 1 month, is preferably 2 times or less, more preferably 1.2 times or less, of the average emulsion particle size immediately after preparation.

In addition to the above-mentioned components, the Pickering emulsion of the present invention may contain optional components that are normally used in cosmetics, provided that the effects of the invention are not impaired. Examples of such optional components include fatty acid soaps (sodium laurate, sodium palmitate, etc.), potassium lauryl sulfate, anionic surfactants such as alkylsulfate triethanolamine ether, cationic surfactants such as stearyltrimethylammonium chloride, benzalkonium chloride, laurylamine oxide, etc., imidazoline-based amphoteric surfactants (2-cocoyl-2-imidazolinium hydroxide-1-carboxyethyloxy disodium salt, etc.), betaine-based surfactants (alkyl betaines, amido betaines, sulfo betaines, etc.), amphoteric surfactants such as acyl methyl taurine, sorbitan fatty acid esters (sorbitan monostearate, sorbitan sesquioleate, etc.), glycerin fatty acids (glycerin monostearate, etc.), propylene glycol fatty acid esculents, and the like. 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 sorbit fatty acid esters (POE-sorbitan 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 alkyl phenyl ethers (POE nonylphenyl ether, etc.), Pluronic (registered trademark) types, POE/POP alkyl ethers (POE/POP 2-decyltetradecyl ether, etc.), Tetronic nonionic surfactants such as 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, etc., powders such as mica, talc, kaolin, synthetic mica, calcium carbonate, magnesium carbonate, anhydrous silicic acid (silica), aluminum oxide, barium sulfate, etc. which may be surface-treated, inorganic pigments such as cobalt oxide, ultramarine, Prussian blue, zinc oxide, etc. which may be surface-treated, composite pigments such as iron oxide titanium dioxide sintered body, etc., pearling agents such as titanium mica, fish phosphorus foil, bismuth oxychloride, etc. which may be surface-treated, Red No. 202, Red No. 228, Red No. 226, Yellow No. 4, Blue No. 404, Yellow No. 5, Red No. 505, Red Preferred examples include organic dyes such as Color No. 230, Red No. 223, Orange No. 201, Red No. 213, Yellow No. 204, Yellow No. 203, Blue No. 1, Green No. 201, Purple No. 201, and Red No. 204; organic powders such as polyethylene powder, polymethylmethacrylate, nylon powder, and organopolysiloxane elastomer; lower alcohols such as ethanol and isopropanol; vitamin A or a derivative thereof; vitamin B such as vitamin B6 hydrochloride, vitamin B6 tripalmitate, vitamin B6 dioctanoate, vitamin B2 or a derivative thereof, vitamin B12, and vitamin B15 or a derivative thereof; vitamin E such as α-tocopherol, β-tocopherol, γ-tocopherol, and vitamin E acetate; vitamin D, vitamin H, pantothenic acid, pantethine, and pyrroloquinoline quinone.

The Pickering emulsion of the present invention may contain a surfactant, but it is preferable to keep the content 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.

The Pickering emulsion of the present invention can be produced by dispersing a powder in an aqueous phase at room temperature, adding an oil phase, and emulsifying the mixture.

The Pickering emulsion of the present invention is suitable for use as an external preparation for the skin, and is particularly preferably used as a sunscreen external preparation for the skin by taking advantage of the function of the ultraviolet absorbing agent.
Among these, it is preferable to use it in cosmetics, such as a makeup base or foundation.

Among the components shown in Table 1, silylated silica was dispersed in a mixture of the aqueous phase components, and an oil agent was added thereto with stirring to emulsify, thereby producing the Pickering emulsions of the examples and comparative examples.
The silylated silica used in Test Example 1 was obtained by mixing silica fine particles (manufactured by AEROSIL, average primary particle diameter 12 nm (measurement method as described above)) with mono-, di-, and trimethylsilyl hydrophobizing agents.

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

(Average emulsion particle size)
The Pickering emulsions of the Examples and Comparative Examples were observed under an optical microscope, and the average emulsion particle size was measured by the above-mentioned method. The results are shown in Table 1. Furthermore, the microscopic images of the Pickering emulsions of Example 1 and Comparative Example 1 are shown in Figure 1.

(UV protection power)
The Pickering emulsions of the Examples and Comparative Examples were applied to a surgical tape (Transpore, manufactured by 3M Healthcare Co., Ltd.) in an amount of 2 mg/cm2 over an area of 6.4 cm x 6.4 cm, and the SPF value was calculated from the average protection spectrum obtained by measuring 10 times using a UV-2000S SPF analyzer manufactured by Labsphere Co., Ltd. The evaluation results are shown in Table 1, with SPF of 50 or more being rated as ⊚, SPF of 30 or more but less than 50 being ◯, SPF of 15 or more but less than 30 being △, and SPF of less than 15 being ×.

As shown in Table 1 and Figure 1, the Pickering emulsion of Example 1, which contained an acrylates copolymer, had a significantly smaller average emulsion particle size and better emulsion stability than the Pickering emulsion of Comparative Example 1, which did not contain the acrylates copolymer.

In addition, the results of Examples 1 to 3 shown in Table 1 show that the average emulsion particle size decreases and emulsion stability improves depending on the content of the acrylates copolymer.

These results indicate that the emulsion stability can be significantly improved by adding an acrylic polymer to a Pickering emulsion.
This effect is believed to be due to the improved dispersibility of the powder adsorbed to the emulsion interface by the acrylic polymer.

Furthermore, as shown in Table 1, although the oil phase compositions of Examples 4 to 6 are different from that of Example 1, all of them have excellent emulsion stability.
In the prior art, the type and composition of the oil phase that can produce a stable Pickering emulsion are limited (Comparative Example 1). However, the results shown in Table 1 show that the application of the present invention can greatly improve the degree of freedom.

Furthermore, the Pickering emulsions of Examples 1 to 3 show excellent emulsion stability, although about half of the oil phase is occupied by the UV absorber.
In the prior art, it was difficult to prepare a Pickering emulsion containing a large amount of UV absorber (e.g., Comparative Example 1). However, the results shown in Table 1 show that the addition of an acrylic polymer can significantly improve the emulsion stability of a Pickering emulsion containing a large amount of UV absorber.

The present invention is suitable for use as a sunscreen for external use on the skin.

Claims (1)

A Pickering emulsion characterized in that the powder is adsorbed to the emulsion interface and contains an acrylic polymer.