Method for modifying the surface of powder particles

Abstract

The present invention aims to provide a simple method for modifying the surfaces of powder particles, and also to provide a Pickering emulsion using surface-modified particles, or a method for producing the same. [Solution] A method for modifying the surface of powder particles, comprising immersing the powder particles in an oil solution having oxygen in its molecular structure.

Description

[Technical Field]

[0001] The present invention relates to a method for modifying the surface of powder particles, a Pickering emulsion using surface-modified particles, and a method for producing a Pickering emulsion. [Background technology]

[0002] An emulsion is a mixture of two or more immiscible liquids, one of which is dispersed within the other. Known emulsions include oil-in-water (O / W) emulsions, in which oil droplets are dispersed in water, and water-in-oil (W / O) emulsions, in which water droplets are dispersed in oil. These emulsions are used in cosmetics and other topical skin preparations.

[0003] To form such emulsions, amphiphilic substances called emulsifiers are usually used, which can stabilize the emulsion by adsorbing to the interface between the two phases, reducing the interfacial tension and increasing steric hindrance or electrostatic repulsion.

[0004] However, most emulsifiers used are surfactants, which irritate the skin, so emulsion-form topical skin preparations that do not contain surfactants are desirable.

[0005] A microparticle-stabilized emulsion (Pickering emulsion) is known as an emulsion that does not contain an emulsifier. A Pickering emulsion is an emulsion stabilized by the adsorption of finely dispersed solid particles at the interface between two phases.

[0006] It has been proposed to use solid particles whose surfaces have been treated to be hydrophobic in the preparation of Pickering emulsions (Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Special Publication No. 2007-530721 [Patent Document 2] Special Publication No. 2010-527332 Summary of the Invention [Problem to be solved by the invention]

[0008] However, the method of hydrophobizing the surfaces of solid particles requires changing the surface treatment agent depending on the target emulsion form and emulsified particle size, and it is sometimes difficult to prepare the desired emulsion, which requires a lot of time and effort.

[0009] Therefore, the first object of the present invention is to provide a method for easily modifying the surface of particles, and the second object of the present invention is to enable the preparation of Pickering emulsions in a variety of emulsified states, preferably to provide a novel Pickering emulsion. [Means for solving the problem]

[0010] As a result of extensive research, the inventors discovered that the surface of powder particles can be easily modified by immersing the particles in a specific oil and changing the immersion time, and thus completed the present invention. That is, the present invention, which solves the first problem, is a method for modifying the surface of powder particles, which is characterized by immersing the powder particles in an oil agent having oxygen atoms in the molecular structure. In the prior art, in order to obtain powder particles with the desired surface characteristics in order to obtain an emulsion with a desired emulsification state, it was necessary to first select a surface treatment agent and then react the particles with it, which was a cumbersome process. However, according to the method for modifying powder particle surfaces of the present invention, the powder particle surfaces can be easily modified without undergoing such complicated steps.

[0011] The modification method of the present invention is preferably applied to powder particles having hydroxyl groups on the surface thereof. Powder particles having hydroxyl groups on the surface thereof are particularly likely to interact with oils having oxygen atoms in the molecular structure, and therefore the surface of the powder particles is particularly likely to be modified.

[0012] The modification method of the present invention is preferably applied to powder particles having silanol groups on the surface thereof. Powder particles having silanol groups on the surface thereof are particularly likely to interact with oils having oxygen atoms in the molecular structure, and therefore the surface of the powder particles is particularly likely to be modified.

[0013] The modification method of the present invention is preferably applied to powder particles containing metal oxides. By modifying the surfaces of powder particles containing metal oxides according to the present invention, it becomes possible to obtain Pickering emulsions stabilized by metal oxides, which are usually difficult to prepare.

[0014] The modification method of the present invention is preferably applied to powder particles containing titanium oxide. By modifying the surfaces of powder particles containing titanium oxide according to the present invention, it is possible to obtain a stable Pickering emulsion that has ultraviolet protection properties.

[0015] In a preferred embodiment of the present invention, the oil is a silicone oil. By immersing the powder particles in silicone oil, the surface of the particles can be modified more easily.

[0016] In a preferred embodiment of the present invention, the oil is a cyclic silicone oil. Cyclic silicone oil is generally used as an oil agent in external skin preparations such as sunscreens, etc. Therefore, by immersing powder particles in cyclic silicone oil, it is possible to provide powder particles that can be used in external skin preparations.

[0017] In a preferred embodiment of the present invention, the step of immersing the powder particles in the oil agent is carried out at room temperature or above. By carrying out the immersion step at room temperature or higher, the immersion time required to modify the surfaces of the powder particles can be shortened.

[0018] Furthermore, the present invention, which solves the second problem above, is a method for adjusting the emulsified state of a Pickering emulsion, comprising the steps of modifying the surface of the powder particles using the method for modifying the surface of the powder particles, and adjusting the ratio of the oil phase to the water phase. According to the method for adjusting the emulsified state of the present invention, the emulsified state of an emulsion can be easily adjusted.

[0019] Furthermore, the present invention, which solves the second problem, is a method for producing a Pickering emulsion, which includes a step of modifying the surface of particles using the above-mentioned method for modifying the powder particle surface, and a step of emulsifying the surface-modified particles. According to the method for producing a Pickering emulsion of the present invention, emulsions in various forms can be easily produced. [Effects of the Invention]

[0020] According to the method for modifying the powder particle surface of the present invention, the surface of the powder particle can be easily modified. Also, according to the method for producing a Pickering emulsion of the present invention, Pickering emulsions in various emulsified states can be produced. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 1 is a flowchart of a method for adjusting the emulsification state. [Figure 2] FIG. 2 is a photograph showing emulsified particles of a Pickering emulsion. DETAILED DESCRIPTION OF THE INVENTION

[0022] <1> Powder particles The method for modifying the powder particle surface of the present invention can be applied to both organic and inorganic powder particles. Examples of inorganic powders include metals, metal salts, metal oxides, metal hydroxides, and minerals. An example of the organic powder is an organic polymer powder.

[0023] The method for modifying the powder particle surface of the present invention can also be applied to composite particles that combine two or more of these powders.

[0024] It can also be applied to powder particles whose surfaces are entirely or partially coated with a surface treatment agent. Here, "the powder particle surfaces are completely or partially coated" refers not only to a state in which the surfaces of the powder particles are coated by physically adhering a surface treatment agent, but also to a state in which a compound is covalently bonded to a functional group exposed on the surface of the powder particles.

[0025] Examples of surface treatment agents that can be used include plating treatment agents, hydrophobic treatment agents, and hydrophilic treatment agents, and examples of such agents include titanium oxide, iron oxide, zinc oxide, aluminum oxide, lead oxide, tin oxide, organosilicon compounds, silicone, hydrocarbon oils, fatty acids, fatty acid amides, fatty acid esters, higher alcohols, polyoxyalkylene compounds, polyethylene glycol, polyvinyl alcohol, polyacrylic acid, polyphosphoric acid, metaphosphoric acid, hyaluronic acid, alginic acid, and salts thereof.

[0026] The method for modifying the powder particle surface of the present invention is preferably applied to powder particles having hydroxyl groups on the surface thereof. Examples of "powder particles having hydroxyl groups on the surface" include powders having surface hydroxyl groups such as metal oxides and silica, and powders made of molecules having hydroxyl groups in their structural formula, such as water-soluble polymers.

[0027] Furthermore, powders coated with a surface treatment agent having hydroxyl groups are also included in the "powder particles having hydroxyl groups on the surface of the powder particles."

[0028] Furthermore, composite particles of the above-mentioned "powder particles having hydroxyl groups on the surface" and other powder particles are also included in the "powder particles having hydroxyl groups on the surface".

[0029] The method for modifying the powder particle surface of the present invention is preferably applied to powder particles having silanol groups on the surface thereof. Here, the silanol group includes any silanol group such as an isolated silanol group, a vicinal silanol group, and a geminal silanol group.

[0030] Examples of powder particles having hydroxyl groups or silanol groups on the surface thereof include silica particles alone and composite particles in which the surface of the powder particles is entirely or partially covered with silica particles. The particle surface of such composite particles can be easily modified by the modification method of the present invention. Furthermore, silica particles are commonly used as an emulsified powder for Pickering emulsions, and are preferred because they can form highly stable Pickering emulsions. Furthermore, since silica particles are non-toxic to the human body, Pickering emulsions produced using silica particles can be used in cosmetics, foods, medicines, etc.

[0031] As the silica particles, for example, 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. Examples of dry silica powders that can be used include the Aerosil series (Nippon Aerosil Co., Ltd.), CAB-O-SIL series (Cabot Corporation), and HDK series (Wacker Asahi Kasei Silicone Co., Ltd.), and examples of wet silica powders that can be used include commercially available products such as the Nipsil series (Tosoh Silica Corporation) and HI-SIL series (PPG).

[0032] The method for modifying the surface of powder particles of the present invention is preferably applied to composite particles containing a metal oxide. Preferred examples of metal oxides include titanium oxide, iron oxide, zinc oxide, aluminum oxide, lead oxide, and tin oxide, with titanium oxide being more preferred. Generally, powder particles containing metal oxides are rarely used as powder particles for producing Pickering emulsions, but by applying the method for modifying the powder particle surface of the present invention, powder particles containing metal oxides can be easily used in Pickering emulsions.

[0033] The present invention is particularly preferably applied to composite particles containing a metal oxide as a main component. Furthermore, the present invention is preferably applied to composite particles containing a metal oxide as a main component and silica particles as a secondary component. In this case, the content of silica particles in the entire composite particle is not particularly limited, but from the viewpoint of shortening the time required for surface modification of the powder particles, the lower limit is preferably set to 7 mass% or more, more preferably 12 mass% or more, even more preferably 15 mass% or more, and even more preferably 18 mass% or more.

[0034] Furthermore, from the viewpoint of shortening the time required for modifying the surface of the powder particles, the upper limit of the content of silica particles in the entire composite particle containing a metal oxide as the main component is preferably 45% by mass or less, more preferably 40% by mass or less, even more preferably 35% by mass or less, and even more preferably 30% by mass or less.

[0035] The present invention is preferably applied to composite particles containing aluminum oxide particles (Al2O3) as a minor component and other metal oxides as a major component. In this case, the content of aluminum oxide particles in the entire composite particle is not particularly limited, but from the viewpoint of shortening the time required for surface modification of the powder particles, the lower limit is preferably 0.1 mass% or more, more preferably 1 mass% or more, even more preferably 2 mass% or more, and even more preferably 3 mass% or more. On the other hand, the upper limit of the content of aluminum oxide particles in the entire composite particle is not particularly limited, and can be set as a guideline of preferably 20% by mass or less, more preferably 10% by mass or less.

[0036] Here, "contained as a major component" means "contained in an amount of 50% by mass or more of the total," while "contained as a minor component" means "contained in an amount of less than 50% by mass of the total."

[0037] The composite particles can be produced by mixing the constituent powders using a mixer such as an automatic mortar, a ball mill, a Henschel mixer, a Nauta mixer, a Loedige mixer, a V-type mixer, a hammer mill, or a pin mill.

[0038] <2> Oils with oxygen atoms in the molecular structure Examples of oils having an oxygen atom in the molecular structure used in the method for modifying the powder particle surface of the present invention include oils having a functional group such as a hydroxy group, an aldehyde group, a carbonyl group, a carboxy group, a nitro group, or a sulfo group in the molecular structure, or oils having a bond such as a siloxane bond, an ether bond, or an ester bond.

[0039] Examples of oils having an oxygen atom in the molecular structure include liquid oils, solid oils, waxes, higher fatty acids, higher alcohols, ester oils, and silicone oils.

[0040] Examples of liquid oils and fats 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, camellia oil, castor oil, linseed oil, safflower oil, cottonseed oil, perilla oil, meadowfoam oil, soybean oil, peanut oil, tea seed oil, Japanese kaya oil, rice bran oil, Chinese tung oil, Japanese tung oil, jojoba oil, germ oil, triglycerin, glycerin trioctanoate, and glycerin triisopalmitate.

[0041] Examples of solid fats and oils include cacao butter, coconut oil, horse fat, hardened coconut oil, palm oil, beef tallow, mutton tallow, hardened beef tallow, palm kernel oil, lard, beef bone fat, Japan wax kernel oil, hardened oil, beef trotter fat, Japan wax, and hardened castor oil.

[0042] Examples of waxes include beeswax, candelilla wax, cotton wax, carnauba wax, bayberry wax, Ibota 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, and POE hydrogenated lanolin alcohol ether.

[0043] Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, behenic acid, 12-hydroxystearic acid, undecylenic acid, and tall acid.

[0044] Examples of higher alcohols include cetyl alcohol, stearyl alcohol, behenyl alcohol, batyl alcohol, myristyl alcohol, and cetostearyl alcohol.

[0045] 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-ethylhexanoate, 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, adipyl Examples of the alkyl acrylate include diisobutyl phosphate, 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, and triethyl citrate.

[0046] Examples of silicone oils include chain silicone oils such as dimethylpolysiloxane, methylphenylpolysiloxane, methylhydrogenpolysiloxane, and diphenylsiloxyphenyltrimethicone, and cyclic silicone oils such as pentasiloxane, decamethylpolysiloxane, dodecamethylpolysiloxane, and tetramethyltetrahydrogenpolysiloxane.

[0047] In the method for modifying powder particle surfaces of the present invention, it is more preferable to use silicone oil, and even more preferable to use cyclic silicone oil, as the oil agent having oxygen atoms in its molecular structure. By using silicone oil, the surface of the powder particles can be modified more easily. Cyclic silicone oils are commonly used as oils in sunscreens. By using cyclic silicone oils as the oil in the method for modifying powder particle surfaces of the present invention, application to external skin preparations such as cosmetics becomes easier.

[0048] <3> Method for modifying the surface of powder particles According to the method for modifying powder particle surfaces of the present invention, the surfaces of powder particles can be modified, more specifically, the degree of hydrophobicity of the surfaces of powder particles can be improved, by immersing the powder particles in an oil having an oxygen atom in its molecular structure. Here, "immersing powder particles in an oil having an oxygen atom in its molecular structure" means bringing the entire surfaces of the powder particles into contact with the oil.

[0049] By using the method for modifying the powder particle surface, particles with hydrophilic wettability can be modified to become lipophilic particles, and particles with lipophilic wettability can be modified to become more lipophilic particles.

[0050] When preparing a Pickering emulsion using powder particles, the emulsification state of the Pickering emulsion (whether it is water-in-oil or oil-in-water, emulsion particle size, emulsion stability, etc.) depends on the wettability of the powder particle surface. In other words, if the modification method of the present invention is applied to certain powder particles and a Pickering emulsion is prepared using the powder particles after the method has been applied, the resulting emulsion will have a different emulsified state from that of a Pickering emulsion prepared using the same powder particles before the method has been applied.

[0051] When the powder particles are immersed in an oil having oxygen atoms in its molecular structure, the temperature of the oil is preferably room temperature or higher, more preferably 50°C or higher, even more preferably 60°C or higher, and particularly preferably 70°C or higher. By setting the temperature within the above range, the surface of the particles can be modified in a short immersion time.

[0052] The time for immersing the powder particles in the oil having oxygen atoms in its molecular structure is not particularly limited. Although it varies depending on the type and composition of the powder particles, if it is desired to obtain an effect such that the oil phase and the water phase are reversed in a Pickering emulsion prepared using the powder particles before and after application of the modification method of the present invention, the time for immersing the powder particles in the oil can be set to 6 hours or more at room temperature or 30 minutes or more at 80°C.

[0053] The degree of surface modification of powder particles can be confirmed by measuring the contact angle according to a conventional method, or by emulsifying the particles to produce a Pickering emulsion.

[0054] The properties of Pickering emulsions, such as emulsion stability and emulsion particle size, depend on the surface properties of the powder particles. Therefore, by adjusting the surface properties of the powder particles using the modification method of the present invention, Pickering emulsions with any desired properties can be obtained.

[0055] Powder particles having modified surfaces can be obtained by immersing the powder particles in the oil for a certain period of time and then separating the powder particles from the oil.

[0056] <4> How to adjust the emulsion state The present invention also relates to a method for adjusting an emulsified state, which comprises the steps of modifying the surfaces of powder particles using the above-described method for modifying the surfaces of powder particles, and adjusting the ratio of oil to water. According to the method for adjusting the emulsified state of the present invention, the Pickering emulsion can be adjusted to various emulsified states by adjusting the immersion time of the particles and the ratio of the water phase to the oil phase.

[0057] Conventionally, in order to obtain a Pickering emulsion in a desired emulsified state, it has been common to coat the surfaces of powder particles with an appropriate surface treatment agent to optimize the surface properties of the powder particles. According to the method for adjusting the emulsified state of the present invention, the emulsified state of a Pickering emulsion can be adjusted without the need for the troublesome task of selecting and coating an appropriate surface treatment agent.

[0058] 1 is a flow chart showing a method for adjusting an emulsified state, which will be referred to in detail below.

[0059] First, in step S1, a Pickering emulsion is produced using any powder particles, and the emulsified state is evaluated. Evaluation items include the type of emulsion (e.g., W / O type or O / W type), the emulsion particle size, and the stability of the emulsified state. The evaluation in step S1 makes it possible to estimate how to adjust the powder particles to obtain a Pickering emulsion with a desired emulsified state.

[0060] Specifically, for water-in-oil Pickering emulsions, the longer the immersion time of powder particles in an oil agent having oxygen atoms in the molecular structure, the larger the emulsified particle size of the Pickering emulsion prepared using the same.

[0061] Furthermore, for oil-in-water Pickering emulsions, the longer the immersion time of the powder particles in the oil agent, the smaller the emulsified particle size of the Pickering emulsion prepared using the same can be, and if the immersion time is further extended, a water-in-oil Pickering emulsion can be obtained.

[0062] In step S2, in order to adjust the emulsification state of the Pickering emulsion, a step of modifying the powder particle surface (step S3), a step of adjusting the ratio of the water phase to the oil phase (step S4), or a step of simultaneously performing these two steps are selected. Regarding step S3, <3> The method for modifying the powder particle surface described in 2. is used. In step S4, the ratio of the water phase to the oil phase is adjusted by a conventional method.

[0063] A Pickering emulsion is prepared using the powder particles whose surfaces have been modified in step S3 and the ratio of the water phase to the oil phase adjusted in step S4, and this Pickering emulsion is evaluated in step S5. The evaluation items are the same as those in step S1.

[0064] Then, in step S6, if the prepared Pickering emulsion is in a desired emulsified state, the preparation is terminated. If the prepared Pickering emulsion is not in a desired emulsified state, the process returns to step S2.

[0065] The powder particles used in the preparation method of the present invention include: <1> can be used. Although not shown, a step of selecting powder particles may be performed after step S2 in parallel with steps S3 and S4. More specifically, when composite particles are used to prepare a Pickering emulsion, a step of adjusting the ratio of powder particles constituting the composite particles may be performed.

[0066] In the method for adjusting the emulsified state of the present invention, either water or an aqueous solution is used as the aqueous phase. In addition, the oil phase can be <2> In addition to the oils mentioned above, hydrocarbon oils etc. can also be used. This can be done.

[0067] <5> Pickering emulsion manufacturing method According to the method for producing a Pickering emulsion of the present invention, <3> By modifying the surface of the particles using the powder particle surface modification method described above and then emulsifying the surface-modified particles, Pickering emulsions of various shapes and particle sizes can be obtained.

[0068] The oil phase of a Pickering emulsion is <2> In addition to the oils mentioned above, hydrocarbon oils and the like can also be used.

[0069] The method for producing a Pickering emulsion of the present invention can be an embodiment in which a Pickering emulsion is produced by modifying the surface of powder particles and then adding an oil, water, or aqueous solution having an oxygen atom in the molecular structure in which the particles are immersed.

[0070] In another embodiment, after modifying the surfaces of powder particles, the surface-modified powder particles are separated from the oil agent having oxygen atoms in its molecular structure, and the powder particles are used to emulsify a separately prepared oil phase and water phase, thereby producing a Pickering emulsion. The oil agent and the powder particles can be separated by a conventional method, such as centrifugation.

[0071] The emulsification step in the method for producing the Pickering emulsion of the present invention can be carried out using a conventional method.

[0072] Furthermore, according to the method for producing a Pickering emulsion of the present invention, it is possible to produce a Pickering emulsion containing particles of a form that could not be produced by conventional techniques.

[0073] <6> Pickering Emulsion The present invention also relates to a Pickering emulsion produced by the above-mentioned production method. That is, the present invention relates to a method for manufacturing a powder containing powder particles immersed in an oil solution having oxygen atoms in its molecular structure. It is a Pickering emulsion characterized by:

[0074] Regarding oils <2> The matters described in the previous paragraph can be applied as they are. Particularly preferred embodiments of the present invention include powder particles soaked in cyclic silicone oil.

[0075] The present invention also relates to a Pickering emulsion, characterized in that it contains powder particles coated with a cyclic silicone oil.

[0076] Examples of the cyclic silicone oil used in the present invention include pentasiloxane, decamethylpolysiloxane, dodecamethylpolysiloxane, and tetramethyltetrahydrogenpolysiloxane.

[0077] The powder particles are: <1> can be applied as is.

[0078] In addition to the above-mentioned components, the Pickering emulsion of the present invention may contain optional components commonly used in cosmetics to the extent that the effects of the invention are not impaired. Such optional components include anionic surfactants such as fatty acid soaps (sodium laurate, sodium palmitate, etc.), potassium lauryl sulfate, and alkyl sulfate triethanolamine ethers, 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, amido betaine, etc.), and the like. Amphoteric surfactants such as acylmethyl taurine, sorbitan fatty acid esters (sorbitan monostearate, sorbitan sesquioleate, etc.), glycerin fatty acids (glycerin monostearate, etc.), propylene glycol fatty acid esters (propylene glycol monostearate, etc.), hydrogenated castor oil derivatives, glycerin alkyl ether, POE sorbitan fatty acid esters (POE sorbitan monooleate, polyoxyethylene sorbitan monostearate, etc.), POE sorbit 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 alkyl phenyl ethers (POE nonylphenyl ether, etc.), Pluronic (registered trademark) types, POE·POP alkyl ethers (POE·POP 2-decyltetradecyl ether, etc. ), Tetronics, POE castor oil / hydrogenated castor oil derivatives (POE castor oil, POE hydrogenated castor oil, etc.), sucrose fatty acid esters, nonionic surfactants such as alkyl glucosides, moisturizing ingredients such as sodium pyrrolidone carboxylate, lactic acid, sodium lactate, powders such as mica, talc, kaolin, synthetic mica, calcium carbonate, magnesium carbonate, silicic anhydride (silica), aluminum oxide, barium sulfate, etc., which may be surface-treated, inorganic pigments such as cobalt oxide, ultramarine, iron blue, zinc oxide, etc.,Composite pigments such as sintered iron oxide and titanium dioxide, which may be surface-treated; pearling agents such as titanium dioxide, fish phosphate foil, and bismuth oxychloride, which may be surface-treated; organic dyes such as Red No. 202, Red No. 228, Red No. 226, Yellow No. 4, Blue No. 404, Yellow No. 5, Red No. 505, Red 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, which may be laked; polyethylene powder, polymethyl methacrylate, nylon powder, and organopolysiloxane. Organic powders such as polyethylene elastomers, lower alcohols such as ethanol and isopropanol, vitamin A or its derivatives, vitamin B6 hydrochloride, vitamin B6 tripalmitate, vitamin B6 dioctanoate, vitamin B2 or its derivatives, vitamin B12, vitamin B15 or its derivatives, vitamin E such as α-tocopherol, β-tocopherol, γ-tocopherol, vitamin E acetate, vitamin D, vitamin H, vitamins such as pantothenic acid, pantethine, pyrroloquinoline quinone, para-aminobenzoic acid, Benzoic acid derivatives such as N,N-aminobenzoic acid monoglycerin ester, N,N-dipropoxyparaaminobenzoic acid ethyl ester, N,N-diethoxyparaaminobenzoic acid ethyl ester, N,N-dimethylparaaminobenzoic acid ethyl ester, N,N-dimethylparaaminobenzoic acid butyl ester, N,N-dimethylparaaminobenzoic acid ethyl ester, and diethylaminohydroxybenzoylhexylbenzoate; anthranilic acid derivatives such as homomenthyl-N-acetylanthranilate; salicylic acid and its sodium salt, and amyl salicylate Salicylic acid derivatives such as menthyl salicylate, homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, and p-isopropanol phenyl salicylate; 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, and isoamyl p-methoxy cinnamate.Cinnamic acid derivatives such as 2-ethylhexyl p-methoxycinnamate (ethylhexyl methoxycinnamate, octyl p-methoxycinnamate), 2-ethoxyethyl-p-methoxycinnamate (cinoxate), cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenylcinnamate, 2-ethylhexyl 2-cyano-3,3-diphenylacrylate (octocrylene), glyceryl mono-2-ethylhexanoyl-di-paramethoxycinnamate, ferulic acid and its derivatives; 2,4-dihydroxybenzophenone, 2,2'-di Hydroxy-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-2-carboxylate, 2-hydroxy-4-n-octoxybenzophenone, 4-hydroxybenzophenone Benzophenone derivatives such as 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; dianisoylmethane; 5-(3,3-dimethyl-2-norbornylidene)-3-pentan-2-one; Dibenzoylmethane derivatives such as 4-t-butylmethoxydibenzoylmethane; octyl triazone; urocanic acid derivatives such as urocanic acid and ethyl urocanate; hydantoin derivatives such as 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, 1-(3,4-dimethoxyphenyl)-4,4-dimethyl-1,3-pentanedione, and 2-ethylhexyl dimethoxybenzylidene dioxoimidazolidinepropionate; phenylbenzimidazol sulfonic acid, terephthalidene dicamphor sulfonic acid, drometrizole trisiloxane,Examples of such ultraviolet absorbers include methyl anthranilate, bisethylhexyloxyphenol methoxyphenyl triazine, rutin and its derivatives, and oryzanol and its derivatives.

[0079] The Pickering emulsion of the present invention may contain a surfactant, but the content thereof is preferably kept as low as possible, 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. By using such a form, it is possible to suppress skin irritation caused by the surfactant, reduce stickiness during use, and improve the durability and stability of the cosmetic.

[0080] The Pickering emulsion of the present invention is suitable for use as an external skin preparation, and is particularly preferably used as an external sunscreen skin preparation. In particular, it is preferably used in cosmetics, such as sunscreens and makeup bases. [Example]

[0081] <Samples and Test Methods> Modification of powder particle surface and production of Pickering emulsion The preparation of powder particles used in Test Examples 1 to 3 described below, the modification of their surfaces, and the production of Pickering emulsions were carried out as described in (1) and (2) below. (1) Preparation of powder particles Powder particles were mixed according to the composition shown in Table 1 to prepare nine particles, particles 1 to 9.

[0082] (2) Surface modification of powder particles The powder particles were immersed in decamethylcyclopentasiloxane contained in a glass bottle at a constant temperature for a certain period of time, with the weight fraction of the powder particles in the decamethylcyclopentasiloxane adjusted to 0.0125.

[0083] (3) Production of Pickering emulsion After immersing the powder particles in an oil solution containing oxygen atoms in its molecular structure for a certain period of time, an appropriate amount of water was added to the oil solution in which the powder particles were immersed, and emulsification was carried out for 5 minutes at 20 kHz using an ultrasonic device (Vibracell VCX130, tip diameter 3 mm, manufactured by Sonics & Material Co., Ltd.). To evaluate the morphology of the emulsion formed, eosin blue was added to the aqueous phase for coloring.

[0084] [Table 1]

[0085] Test Example 1: Morphology of the formed emulsion Particles 3 and 9 were immersed in cyclopentasiloxane at 25°C for 0 minutes to 30 days to produce Pickering emulsions. Water was added so that the weight fraction of water (φw) relative to the total weight of water and oil was 0.10 to 0.80. The produced emulsions were observed and evaluated using an optical microscope. The results for Particles 3 are shown in Table 2 (Example 1), and the results for Particles 9 are shown in Table 3 (Example 2).

[0086] [Table 2]

[0087] [Table 3]

[0088] In Example 1, an o / w Pickering emulsion was formed when the immersion time in the oil solution was 0 to 6 hours and the weight fraction of water was 0.1 to 0.8. Furthermore, when the immersion time in the oil solution exceeded 6 hours, the emulsification state of the emulsion formed changed depending on the weight fraction of water, and a w / o emulsion and an o / w / o or w / o / w double emulsion were formed.

[0089] On the other hand, in Example 2, when φw=0.35 to 0.4, the o / w / o type emulsion However, when the immersion time exceeded 3 to 6 hours, an unemulsified aqueous phase was observed. I can no longer do it. These results show that immersing powder particles in an oil containing oxygen atoms in its molecular structure improves the hydrophobicity of the particles and enables the modification of the powder particle surface. Furthermore, it was found that the emulsification state of the Pickering emulsion can be adjusted by adjusting the immersion time and the weight fraction of water and oil.

[0090] <Test Example 2> Adjustment of emulsion particle size The emulsion particle sizes of Pickering emulsions (Ts: 12 hours to 120 days, φw: 0.2) prepared using Particles 3 (Example 3) and Particles 9 (Example 4) were measured using an optical microscope. The results are shown in Figure 2.

[0091] From the results of Example 3, it was found that the emulsion particle size was approximately 6 μm when the immersion time was 12 hours, but was 30 μm when the immersion time was 120 days. Furthermore, from the results of Example 4, small emulsified particles observed in the emulsion immersed for 0 days (emulsion emulsified without immersion) were not observed in the emulsion immersed for 120 days.

[0092] From these results, it can be seen that the water-in-oil Pickering emulsion is The longer the immersion time in oil containing oxygen atoms in the molecular structure, the larger the emulsion particle size. I found out that...

[0093] Furthermore, looking at the photograph of Example 3 taken 12 hours later, it can be seen that most of the emulsified particles are small and irregular in shape. This is thought to be because the emulsion had just changed from an o / w type to a w / o type Pickering emulsion. These results show that the longer the immersion time in the oil containing oxygen atoms in the molecular structure of the particles used for preparation of the oil-in-water Pickering emulsion, the smaller the emulsion particle size becomes, and that after a certain time, the emulsion changes to a water-in-oil type.

[0094] <Test Example 3> Particles 1 to 8 were immersed in decamethylcyclopentasiloxane at 80°C for a certain period of time. Water was then added so that φw was 0.2 to produce emulsions, and the morphology of each emulsion was observed and evaluated using an optical microscope. The results are shown in Table 4 (Examples 5 to 12).

[0095] [Table 4]

[0096] The results in Table 4 show that, regardless of the type of particles used, an o / w emulsion is formed when the immersion time is short, but an o / w / o or w / o emulsion is formed when the immersion time is long. It was also found that the immersion time differs depending on the composition of the powder particles.

[0097] Furthermore, from the results of Examples 1 and 7 in Tables 2 and 4, it was found that when immersion was carried out at 25°C, a w / o type emulsion was formed after immersion for 6 hours or more, whereas when immersion was carried out at 80°C, a w / o type emulsion was formed after immersion for 1 hour or more. These results indicate that the immersion time required to modify the powder particle surface can be shortened by increasing the temperature when immersing the particles in an oil solution containing oxygen atoms in its molecular structure.

[0098] Furthermore, the emulsified state of the Pickering emulsion prepared above did not change over time after preparation. This result indicates that when powder particles are adsorbed at the interface between the water and oil phases in a Pickering emulsion, the surface properties are not modified even though part of the particles' surface is in contact with the oil phase. [Industrial Applicability]

[0099] The present invention can be applied to external skin preparations in the form of emulsions.

Claims

1. A method for adjusting the emulsified state of a Pickering emulsion in which powder particles containing silica are adsorbed to the interface between an aqueous phase and an oil phase, comprising the steps of: the step of modifying the surfaces of the powder particles by immersing the powder particles in an oil solution having oxygen atoms in its molecular structure so that the entire surfaces of the powder particles come into contact with the oil solution; and the step of adjusting the ratio of an oil phase to a water phase, the powder particles have silanol groups on their surfaces, The oil is selected from 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, camellia 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, solid fats and oils, wax, higher fatty acids, higher alcohols, ester oils, and silicone oils. How to adjust the emulsion state.

2. A method for adjusting the emulsified state of a Pickering emulsion in which powder particles containing silica are adsorbed to the interface between an aqueous phase and an oil phase, comprising the steps of: (1) a step of producing a Pickering emulsion to be prepared using powder particles containing silica; (2) evaluating the type of emulsification and / or emulsion particle size of the Pickering emulsion to be prepared; (3) a step of setting an immersion time for immersing the powder particles in the oil having an oxygen atom in its molecular structure, based on the evaluation result of the step (2), using any one of the following (i) to (iii) as an index; (4) a step of modifying the surfaces of the silica-containing powder particles by immersing the powder particles in an oil having an oxygen atom in its molecular structure so that the entire surfaces of the powder particles come into contact with the oil for the immersion time set in the step (3); (5) producing a Pickering emulsion by using the powder particles modified in the step (4) instead of the powder particles contained in the Pickering emulsion to be adjusted, the powder particles have silanol groups on their surfaces, The oil is selected from 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, camellia 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, solid fats and oils, wax, higher fatty acids, higher alcohols, ester oils, and silicone oils. How to adjust the emulsion state. (i) When the Pickering emulsion to be adjusted is a water-in-oil type, the longer the immersion time of the powder particles in the oil agent, the larger the emulsion particle size of the Pickering emulsion prepared using the immersed powder particles instead of the powder particles contained in the Pickering emulsion to be adjusted. (ii) When the Pickering emulsion to be prepared is an oil-in-water type, the longer the immersion time of the powder particles in the oil agent, the smaller the emulsion particle size of the Pickering emulsion prepared using the immersed powder particles instead of the powder particles contained in the Pickering emulsion to be prepared can be adjusted. (iii) When the Pickering emulsion to be prepared is an oil-in-water type, by immersing the powder particles in the oil agent for a certain period of time, the Pickering emulsion prepared using the immersed powder particles can be adjusted to a water-in-oil type instead of the powder particles contained in the Pickering emulsion to be prepared.

3. a step of modifying the surface of the silica-containing powder particles by immersing the particles in an oil having oxygen atoms in its molecular structure so that the entire surfaces of the particles come into contact with the oil; and performing emulsification using the surface-modified particles, the powder particles have silanol groups on their surfaces, The oil is selected from 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, camellia 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, solid fats and oils, wax, higher fatty acids, higher alcohols, ester oils, and silicone oils. A method for producing a Pickering emulsion in which the powder particles are adsorbed to the interface between the water phase and the oil phase.

4. a modification step of modifying the surface of the silica-containing powder particles by immersing the particles in an oil having oxygen atoms in its molecular structure so that the entire surfaces of the particles come into contact with the oil; an emulsification step of emulsifying the surface-modified powder particles, the powder particles have silanol groups on their surfaces, The oil is selected from 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, camellia 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, solid fats and oils, wax, higher fatty acids, higher alcohols, ester oils, and silicone oils. A method for producing a Pickering emulsion in which the powder particles are adsorbed to the interface between the water phase and the oil phase, in an emulsified state different from that of a Pickering emulsion emulsified using the powder particles before the modification process.

5. a step of evaluating an emulsification state of a Pickering emulsion produced using powder particles containing silica before the powder particles are immersed in an oil having an oxygen atom in its molecular structure so that the entire surfaces of the powder particles containing silica are in contact with the oil; a step of modifying the surface of the powder particles by immersing the particles in an oil having oxygen atoms in its molecular structure so that the entire surface of the particles comes into contact with the oil; and performing emulsification using the surface-modified powder particles, the powder particles have silanol groups on their surfaces, The oil is selected from 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, camellia 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, solid fats and oils, wax, higher fatty acids, higher alcohols, ester oils, and silicone oils. A method for producing a Pickering emulsion in which the powder particles are adsorbed to the interface between the water phase and the oil phase, in an emulsified state different from that evaluated above.

6. A method for producing a Pickering emulsion in which powder particles containing silica are adsorbed to the interface between an aqueous phase and an oil phase, comprising: (1) a step of producing a Pickering emulsion to be prepared using powder particles containing silica; (2) evaluating the type of emulsification and / or emulsion particle size of the Pickering emulsion to be prepared; (3) a step of setting an immersion time for immersing the powder particles in the oil having an oxygen atom in its molecular structure, based on the evaluation result of the step (2), using any one of the following (i) to (iii) as an index; (4) a step of modifying the surfaces of the powder particles by immersing the powder particles in an oil having oxygen atoms in its molecular structure so that the entire surfaces of the powder particles come into contact with the oil for the immersion time set in the step (3); (5) producing a Pickering emulsion by using the powder particles modified in the step (4) instead of the powder particles contained in the Pickering emulsion to be adjusted, the powder particles have silanol groups on their surfaces, The oil is selected from 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, camellia 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, solid fats and oils, wax, higher fatty acids, higher alcohols, ester oils, and silicone oils. Method for producing Pickering emulsions. (i) When the Pickering emulsion to be adjusted is a water-in-oil type, the longer the immersion time of the powder particles in the oil agent, the larger the emulsion particle size of the Pickering emulsion prepared using the immersed powder particles instead of the powder particles contained in the Pickering emulsion to be adjusted. (ii) When the Pickering emulsion to be prepared is an oil-in-water type, the longer the immersion time of the powder particles in the oil agent, the smaller the emulsion particle size of the Pickering emulsion prepared using the immersed powder particles instead of the powder particles contained in the Pickering emulsion to be prepared can be adjusted. (iii) When the Pickering emulsion to be prepared is an oil-in-water type, by immersing the powder particles in the oil agent for a certain period of time, the Pickering emulsion prepared using the immersed powder particles can be adjusted to a water-in-oil type instead of the powder particles contained in the Pickering emulsion to be prepared.

7. a step of modifying the surfaces of powder particles containing silica by immersing the powder particles in an oil having oxygen atoms in its molecular structure so that the entire surfaces of the powder particles come into contact with the oil; adding water or an aqueous solution to the oil agent in which the surface-modified powder particles are immersed to emulsify the oil agent; the powder particles have silanol groups on their surfaces, The oil is selected from 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, camellia 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, solid fats and oils, wax, higher fatty acids, higher alcohols, ester oils, and silicone oils. A method for producing a Pickering emulsion in which the powder is adsorbed to the interface between an aqueous phase containing the water or aqueous solution and an oil phase containing the oil agent.

8. a step of modifying the surfaces of powder particles by immersing the silica-containing powder particles in an oil having oxygen atoms in its molecular structure so that the entire surfaces of the powder particles come into contact with the oil, and separating the surface-modified powder particles from the oil; The method further comprises a step of emulsifying an oil phase and an aqueous phase separately prepared using the powder particles separated from the oil agent, the powder particles have silanol groups on their surfaces, The oil is selected from 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, camellia 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, solid fats and oils, wax, higher fatty acids, higher alcohols, ester oils, and silicone oils. Method for producing Pickering emulsions.

Images