Surface-modified zinc oxide, method for producing surface-modified zinc oxide, dispersion liquid, composition, and cosmetic

Abstract

To provide surface-modified zinc oxide capable of sufficiently suppressing generation of active oxygen and having excellent dispersibility, and to provide a method for producing the same.SOLUTION: A surface-modified zinc oxide of the present invention is a surface-modified zinc oxide in which the surfaces of zinc oxide particles are treated with a surface treatment agent and which has a color difference ΔE before and after a vitamin E mixing test of 5.0 or less. A method for producing the surface-modified zinc oxide comprises: bringing the zinc oxide particles and the surface treatment agent into contact in a container in the presence of supercritical carbon dioxide; recovering a mixture of zinc oxide particles and the surface treatment agent by decompressing the inside of the container to remove carbon dioxide; and making the zinc oxide particles and the surface treatment agent react by heating the mixture.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a surface-modified zinc oxide, a method for producing the surface-modified zinc oxide, a dispersion, a composition, and a cosmetic. [Background technology]

[0002] Pigment powders used in sunscreens and the like are sometimes subjected to surface treatment to suppress the generation of active oxygen (for example, Patent Document 1). There are two methods for obtaining surface-treated pigment powder: a dry method and a wet method. In the dry method, the surface treatment agent and the pigment powder are directly brought into contact with each other and mixed. In the wet method, the surface treatment agent is dissolved or suspended in a medium, and then mixed with the pigment powder, after which the medium is removed. After the medium is removed, pulverization is carried out as necessary. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-1867 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the dry method, the surface treatment agent cannot be brought into contact with the inside of the fine zinc oxide particles sufficiently. In this case, untreated zinc oxide particles remain, and the generation of active oxygen cannot be sufficiently suppressed. In the wet method, the powder is likely to aggregate when the medium is removed. It is not easy to finely grind the aggregated powder.

[0005] An object of the present invention is to provide a surface-modified zinc oxide which can sufficiently suppress the generation of active oxygen and has excellent dispersibility, and a method for producing the same. [Means for solving the problem]

[0006] The present invention has the following aspects. [1] Zinc oxide particles are surface-modified zinc oxide particles in which the surface is treated with a surface treatment agent. Surface-modified zinc oxide, with a color difference ΔE of 5 or less before and after a vitamin E mixing test. [2] The surface-modified zinc oxide according to [1], wherein the surface treatment agent contains a silicon compound. [3] The surface-modified zinc oxide according to [2], wherein the silicon compound is at least one selected from the group consisting of silane compounds, silicone compounds and silane coupling agents. [4] Contacting zinc oxide particles and a surface treatment agent in a container in the presence of supercritical carbon dioxide; reducing the pressure inside the container to remove carbon dioxide and recover the mixture of the zinc oxide particles and the surface treatment agent; and heating the mixture to react the zinc oxide particles and the surface treatment agent; A method for producing surface-modified zinc oxide comprising the steps of: [5] The method according to [4], wherein the surface treatment agent contains a silicon compound. [6] The method according to [5], wherein the silicon compound is at least one selected from the group consisting of silane compounds, silicone compounds and silane coupling agents. [7] A dispersion comprising the surface-modified zinc oxide according to any one of [1] to [3] and a dispersion medium. [8] A composition comprising the surface-modified zinc oxide according to any one of [1] to [3], a dispersion medium, and a resin. [9] A cosmetic comprising the surface-modified zinc oxide according to any one of [1] to [3] and a cosmetic base raw material. Effect of the Invention

[0007] According to the present invention, it is possible to provide a surface-modified zinc oxide that can sufficiently suppress the generation of active oxygen and has excellent dispersibility, and a method for producing the same. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] <Surface modified zinc oxide> The surface-modified zinc oxide of the present invention is a surface-modified zinc oxide in which the surfaces of zinc oxide particles are treated with a surface treatment agent. "Treated with a surface treatment agent" means that the surface treatment agent comes into contact with or bonds to the zinc oxide particles due to an interaction between the surface treatment agent and the zinc oxide particles. The contact referred to here may be, for example, physical adsorption. The bond may be, for example, an ionic bond, a hydrogen bond, or a covalent bond. The zinc oxide particles and the surface treatment agent will be described later.

[0009] (Color difference ΔE of surface-modified zinc oxide) The color difference ΔE of the surface-modified zinc oxide of the present invention before and after the vitamin E mixing test is 5 or less. The color difference ΔE before and after the vitamin E mixing test is the difference in the L of the surface-modified zinc oxide before and after mixing with vitamin E. * a * b * This is the color difference in the color space chromaticity diagram. Since the color difference ΔE is 5 or less, the generation of active oxygen is sufficiently suppressed in the surface-modified zinc oxide.

[0010] "L * " is a correlation value of lightness defined in JIS Z 8781-4:2013 "Colorimetry - Part 4: CIE 1976 L*a*b* color space" (corresponding international standard ISO 11664-4:2008). * " and "b * " is a color coordinate defined in JIS Z 8781-4:2013 "Colorimetry - Part 4: CIE 1976 L*a*b* color space" (corresponding international standard ISO 11664-4:2008). The method for measuring the color difference ΔE before and after the vitamin E mixing test is as follows.

[0011] The surface modified zinc oxide before mixing with vitamin E is subjected to measurements as follows. A blank solution is prepared by mixing 3 g of the powder containing the surface-modified zinc oxide and 5 g of cyclopentasiloxane. Next, the 0.1 mm optical path length quartz cell containing the blank solution is set in an ultraviolet-visible-near infrared spectrophotometer (Hitachi High-Tech Science Corporation, model number: UH4150). After measuring the diffuse reflectance spectrum of the mixed solution using an integrating sphere, the L1 * , a1 * , b1 * Calculate.

[0012] The surface modified zinc oxide after mixing with vitamin E is subjected to measurements as follows: Vitamin E and cyclopentasiloxane are mixed to prepare a cyclopentasiloxane mixed solvent having a vitamin E concentration of 2% by mass. A sample solution containing vitamin E is prepared by mixing 3 g of powder containing surface-modified zinc oxide and 5 g of cyclopentasiloxane mixed solvent. After measuring the diffuse reflectance spectrum of the sample solution using the method described above, the L2 * , a2 * , b2 * Calculate.

[0013] From the above results, the color difference ΔE = ((L2 * -L1 * ) 2 +(a2 * -a1 * ) 2 +(b2 * -b1 * ) 2 ) 1 / 2 Calculate L1 * , a1 * , b1 * , L2 * , a2 * , b2 * L * a * b * Indicates the value in the color space chromaticity diagram.

[0014] It is unclear why the dispersibility of the surface-modified zinc oxide improves when the color difference ΔE before and after the vitamin E mixing test is 5 or less. It is speculated that the reason why the color difference ΔE becomes small is because the generation of active oxygen is suppressed. However, there is no method to directly measure how the surface treatment agent modifies the surface of zinc oxide particles. Therefore, the details of the action of the surface treatment agent to modify the surface of zinc oxide particles to reduce the color difference ΔE are unclear. It is speculated that this is because the surface treatment agent is uniformly and densely present on the surface of zinc oxide particles, but it is also assumed that this alone cannot explain the phenomenon.

[0015] It is presumed that the effect of sufficiently suppressing the generation of active oxygen and improving dispersibility by making the color difference ΔE 5 or less is manifested by a complex intertwining of multiple factors. For example, one of the factors may be the manufacturing conditions in which the surface treatment agent is dissolved in supercritical carbon dioxide and then mixed with zinc oxide particles. It is presumed that the surface treatment agent has better compatibility with non-polar molecular solvents than zinc oxide particles, and therefore may contribute to improving dispersibility. However, it is believed to be virtually impossible to directly describe or identify the characteristics of surface-modified zinc oxide based on the surface state that emerges when the surface treatment agent is dissolved in supercritical carbon dioxide beforehand and then surface-modified.

[0016] As a result of various investigations, the present inventors have focused on the color difference ΔE and found that by dissolving a surface treatment agent in supercritical carbon dioxide in advance and then performing surface treatment, the color difference ΔE can be reduced to 5 or less. Surface-modified zinc oxide with a color difference ΔE of 5 or less has excellent dispersibility and can sufficiently suppress the generation of active oxygen. When ΔE is 3 or less, no difference can be seen visually, but when ΔE is 2 or less, the surface treatment is strong and is very excellent for cosmetic applications. From the above viewpoints, the color difference ΔE is preferably 4.5 or less, more preferably 3 or less, and even more preferably 2 or less.

[0017] (Properties of Surface-Modified Zinc Oxide According to a Preferred Embodiment) The D90 of the surface-modified zinc oxide is preferably 1 μm or less, more preferably 0.5 μm or less, even more preferably 0.4 μm or less, and particularly preferably 0.3 μm or less. Surface-modified zinc oxide having a D90 of 1 μm or less is useful for use in cosmetics. The lower limit of D90 may be 0.05 μm or 0.1 μm. The upper and lower limits of D90 of the surface-modified zinc oxide can be arbitrarily combined. D90 of the surface-modified zinc oxide is the particle size when the cumulative volume percentage of the particle size distribution is 90%.

[0018] The specific surface area of ​​the surface-modified zinc oxide is not particularly limited, but is preferably 1.5 m 2 / g or more, and 10.0m 2 / g or more is more preferable, and 30.0m 2 It is more preferable that the molecular weight is 1 / g or more. The specific surface area of ​​surface-modified zinc oxide is, for example, 300 m 2 / g or less, and 2 / g or less, and 2 More preferably, the specific surface area of ​​the surface-modified zinc oxide is 80 m 2 / g or less, and 2 / g or less, and 2 The upper and lower limits of the specific surface area of ​​the surface-modified zinc oxide may be combined in any desired manner. The specific surface area of ​​surface-modified zinc oxide is 1.5 to 300 m 2 / g, light scattering and reflection of ultraviolet light are likely to occur.

[0019] The specific surface area of ​​surface-modified zinc oxide (unit: m 2 / g) refers to the BET specific surface area determined by the BET method. The specific surface area of ​​the surface-modified zinc oxide can be measured, for example, by the BET method using a fully automatic specific surface area measuring device (product name: Macsorb HM Model-1201, manufactured by Mountec Co., Ltd.).

[0020] (Zinc oxide particles) The specific surface area of ​​the zinc oxide particles before being treated with the surface treatment agent is not particularly limited, but is preferably 1.5 m 2 / g or more, and 10.0m 2 / g or more is more preferable, and 30.0m 2 More preferably, the specific surface area is 300 m 2 / g or less, and 2 More preferably, the specific surface area is 100 m / g or less. 2 / g or less, 2 / g or less, and 2 / g or less.

[0021] The specific surface area of ​​zinc oxide particles before treatment and the specific surface area of ​​surface-modified zinc oxide vary somewhat depending on how the surface treatment agent is attached, but do not change significantly. Therefore, in order to obtain surface-modified zinc oxide with a desired specific surface area, zinc oxide particles having a desired specific surface area may be used. Therefore, the details and preferred aspects of the specific surface area of ​​the surface-modified zinc oxide can be the same as those of the specific surface area of ​​zinc oxide particles.

[0022] The BET average particle diameter of the zinc oxide particles before treatment with the surface treatment agent is preferably 3 to 200 nm, more preferably 5 to 100 nm, and even more preferably 10 to 100 nm. When the BET average particle diameter is equal to or greater than the lower limit of the above-mentioned numerical range, it is easy to obtain a surface-modified zinc oxide that can more sufficiently suppress the generation of active oxygen. When the BET average particle diameter is equal to or less than the upper limit of the above-mentioned numerical range, it is easy to obtain a surface-modified zinc oxide with even more excellent dispersibility. The upper and lower limits of the BET average particle diameter of the zinc oxide particles before being treated with a surface treatment agent can be arbitrarily combined. The BET average particle diameter of the zinc oxide particles before being treated with a surface treatment agent is defined as the specific surface area S (m 2 / g) and zinc oxide particle density (g / cm 3) using the formula average particle size (nm) = 6000 / (S × density).

[0023] (Surface treatment agent) The surface treatment agent is not particularly limited as long as it is hydrolyzable. Here, "hydrolyzable" includes not only hydrolysis of alkoxy groups, but also dealkalization of metal soaps and dehydrogenation of SiH of silicone.

[0024] Examples of the surface treatment agent include silicon compounds, fatty acids, fatty acid soaps, fatty acid esters, organic titanate compounds, aluminum compounds, and surfactants. The surface treatment agents may be used alone or in combination of two or more.

[0025] Examples of fatty acids include palmitic acid, isostearic acid, stearic acid, lauric acid, myristic acid, behenic acid, oleic acid, rosin acid, and 12-hydroxystearic acid. Examples of fatty acid soaps include magnesium stearate, zinc stearate, aluminum stearate, calcium stearate, magnesium myristate, zinc myristate, aluminum distearate, aluminum dimyristate, and aluminum 12-hydroxystearate. Examples of fatty acid esters include dextrin fatty acid esters, cholesterol fatty acid esters, sucrose fatty acid esters, and starch fatty acid esters.

[0026] Examples of organic titanate compounds include isopropyl triisostearoyl titanate, isopropyl dimethacryl isostearoyl titanate, isopropyl tri(dodecyl)benzenesulfonyl titanate, neopentyl(diallyl)oxy-tri(dioctyl)phosphate titanate, and neopentyl(diallyl)oxy-trineododecanoyl titanate. Examples of the aluminum compound include organoaluminum compounds and aluminum hydroxide. Examples of the organoaluminum compound include an aluminate coupling agent and an aluminum complex.

[0027] Examples of the silicon compound include a silane compound, a silicone compound, and a silane coupling agent. The silicon compounds may be used alone or in combination of two or more.

[0028] Examples of the silane compound include alkylsilanes and fluoroalkylsilanes. Examples of alkylsilanes include methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, and octyltriethoxysilane. Examples of fluoroalkylsilanes include trifluoromethylethyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane. The silane compound is preferably an alkylsilane, and particularly preferably octyltriethoxysilane. The silane compound may be used alone or in combination of two or more kinds.

[0029] Examples of silicone compounds include silicone oil, methicone, dimethicone, hydrogen dimethicone, triethoxysilylethyl polydimethylsiloxyethyl dimethicone, triethoxysilylethyl polydimethylsiloxyethylhexyl dimethicone, (acrylates / tridecyl acrylate / triethoxysilylpropyl methacrylate / dimethicone methacrylate) copolymer, and triethoxycaprylylsilane. Examples of silicone oils include methylhydrogenpolysiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane. The silicone compound may be used alone or in combination of two or more kinds. A copolymer of these silicone compounds may also be used as the silicone compound.

[0030] An example of the silane coupling agent is a silane coupling agent having an alkoxy group represented by the following formula (1).

[0031] R 1 Si(OR 2 )3···(1) In formula (1), R 1 is an alkyl group having 1 to 18 carbon atoms, a fluoroalkyl group, or a phenyl group, and R 2 is an alkyl group having 1 to 4 carbon atoms.

[0032] The silane coupling agents may be used alone or in combination of two or more kinds. As the silane coupling agent, alkylalkoxysilane, allylalkoxysilane, polysiloxane having an alkyl group on the side chain, and polysiloxane having an allyl group on the side chain are preferred.

[0033] Examples of alkylalkoxysilanes include tetramethoxyorthosilane, tetraethoxyorthosilane, tetrapropoxyorthosilane, tetrabutoxyorthosilane, methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, diphenyldimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, and diphenyldiethoxysilane. The alkylalkoxysilanes may be used alone or in combination of two or more kinds.

[0034] As the silane coupling agent, a polymer type silane coupling agent having a siloxane skeleton as the main chain and an alkoxy group and an acrylic group in the molecular structure may be used. Examples of the polymer type silane coupling agent include dimethoxydiphenylsilane-triethoxycaprylylsilane crosspolymer, triethoxysilylethyl polydimethylsiloxyethyl dimethicone, and triethoxysilylethyl polydimethylsiloxyethylhexyl dimethicone.

[0035] As the silane coupling agent, a fluoroalkylalkoxysilane may be used, for example, trifluoropropyltrimethoxysilane, perfluorooctyltriethoxysilane, or tridecafluorooctyltriethoxysilane.

[0036] As the silane coupling agent, the silane coupling agent having an octyl group in the molecule is preferred.The silane coupling agent that can be applied to a wide range of polar oil phases from natural oil, ester oil to silicone oil is more preferred.As the silane coupling agent, at least one selected from the group consisting of n-octyltriethoxysilane, n-octyltrimethoxysilane and dimethoxydiphenylsilane-triethoxycaprylylsilane crosspolymer is particularly preferred.

[0037] When the surface-modified zinc oxide is applied to cosmetics, preferred silicon compounds include, for example, methicone, dimethicone, hydrogen dimethicone, octyltrimethoxysilane, octyltriethoxysilane, and triethoxycaprylylsilane.

[0038] <Method for manufacturing surface-modified zinc oxide> The surface-modified zinc oxide can be produced by a production method including the following (i), (ii) and (iii). (i): Contacting zinc oxide particles and a surface treatment agent in a container in the presence of supercritical carbon dioxide. (ii): Reducing the pressure inside the container to remove carbon dioxide and recover a mixture of zinc oxide particles and a surface treatment agent. (iii): Heating the mixture to react the zinc oxide particles and the surface treatment agent. Here, the details and preferred embodiments of the zinc oxide particles and the surface treatment agent are the same as those described above.

[0039] Carbon dioxide has a critical temperature (Tc) of 31°C and a critical pressure (Pc) of 7.4MPa. Supercritical carbon dioxide is carbon dioxide that is at or above its critical temperature (Tc) and critical pressure (Pc). Supercritical carbon dioxide has the following characteristics: high diffusivity close to that of a gas, dissolving power close to that of a liquid, no surface tension, and instantaneous gasification. Supercritical carbon dioxide also has the property that its density changes suddenly with a slight change in pressure. When the pressure of supercritical carbon dioxide is further increased beyond the critical pressure (Pc) and critical temperature (Tc), the density of supercritical carbon dioxide increases rapidly. Therefore, in the region above the critical pressure, the solubility of solutes in carbon dioxide increases rapidly. Conversely, when the pressure of supercritical carbon dioxide is reduced, the solubility of solutes in carbon dioxide can be rapidly reduced. Therefore, it is possible to separate the solutes from the supercritical carbon dioxide simply by reducing the pressure.

[0040] According to the production method including the above (i), (ii), and (iii), the surface treatment agent can be dissolved in supercritical carbon dioxide. By contacting zinc oxide particles with the surface treatment agent in the presence of supercritical carbon dioxide, the surface treatment agent can be uniformly and efficiently adsorbed onto the surfaces of the zinc oxide particles. In addition, after the zinc oxide particles and the surface treatment agent are brought into contact with each other, the supercritical carbon dioxide can be instantly converted to gaseous carbon dioxide by adjusting the pressure and temperature in the system. Since the gaseous carbon dioxide can be instantly removed from the system by drying it, the mixture of the zinc oxide particles and the surface treatment agent can be efficiently recovered while suppressing aggregation during drying.

[0041] In the recovered mixture, there are composite particles in which the surface treatment agent is uniformly and densely adsorbed on the surfaces of zinc oxide particles. Therefore, by heating the zinc oxide particles and the surface treatment agent mixed in the presence of supercritical carbon dioxide, the surfaces of the zinc oxide particles can be efficiently and densely treated with the surface treatment agent. As a result, it is believed that the generation of active oxygen can be sufficiently suppressed and a surface-modified zinc oxide with excellent dispersibility can be obtained.

[0042] In the above (i), the temperature and pressure conditions in the container when the zinc oxide particles and the surface treatment agent are brought into contact with each other in the presence of supercritical carbon dioxide can be appropriately set by a person skilled in the art in consideration of the above-mentioned properties of supercritical carbon dioxide.The temperature and pressure conditions in the container when carbon dioxide is removed in the above (ii) can also be appropriately set by a person skilled in the art in consideration of the above-mentioned properties of supercritical carbon dioxide.

[0043] In the above (iii), the conditions for reacting the zinc oxide particles with the surface treatment agent are not particularly limited and can be appropriately set by a person skilled in the art depending on the properties of the zinc oxide particles and the surface treatment agent.

[0044] The mixing ratio of zinc oxide particles and surface treatment agent during production is not particularly limited. For example, the ratio of the surface treatment agent is preferably 1 to 100 parts by mass, more preferably 2 to 50 parts by mass, and even more preferably 2 to 30 parts by mass, relative to 100 parts by mass of zinc oxide particles. When the ratio of the surface treatment agent is equal to or greater than the lower limit of the above-mentioned numerical range, the treatment reaction is likely to proceed, and the surface of the zinc oxide particles is likely to be sufficiently modified. As a result, it is easy to obtain surface-modified zinc oxide that can further sufficiently suppress the generation of active oxygen. When the ratio of the surface treatment agent is equal to or less than the upper limit of the above-mentioned numerical range, the surface treatment agent is unlikely to be liberated by itself. Therefore, the treatment time can be shortened.

[0045] The mixing ratio of zinc oxide particles and surface treatment agent during production is somewhat different from the mass ratio of zinc oxide particles and chemical structure derived from surface treatment agent in the obtained surface-modified zinc oxide powder, but does not change significantly.Therefore, in order to obtain a surface-modified zinc oxide powder with a desired mass ratio, the mixing ratio of zinc oxide particles and surface treatment agent during production should be set to a desired value.Therefore, the details and preferred aspects of the mass ratio of zinc oxide particles and chemical structure derived from surface treatment agent in surface-modified zinc oxide can be the same as the mixing ratio of zinc oxide particles and surface treatment agent during production.

[0046] <Applications of surface-modified zinc oxide> The following describes some examples of uses of the surface-modified zinc oxide. The following descriptions are representative examples of uses, and are not intended to limit the scope of the invention.

[0047] (Dispersion liquid) The dispersion includes surface-modified zinc oxide and a dispersion medium. The dispersion may include a paste-like dispersion having a high viscosity. The dispersion medium is not particularly limited as long as it can disperse the surface-modified zinc oxide. For example, when the surface-modified zinc oxide is used for a cosmetic application, a dispersion medium that can be formulated in a cosmetic may be used.

[0048] Examples of the dispersion medium include chain polysiloxanes such as dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane; Cyclic polysiloxanes such as octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, and dodecamethylcyclohexasiloxane; Modified polysiloxanes such as amino-modified polysiloxanes, polyether-modified polysiloxanes, alkyl-modified polysiloxanes, and fluorine-modified polysiloxanes; Hydrocarbon oils such as liquid paraffin, squalane, isoparaffin, branched light paraffin, vaseline, ceresin, dodecane, isododecane, tridecane, tetradecane, hexadecane, isohexadecane, and octadecane; Ester oils such as isopropyl myristate, cetyl isooctanoate, glyceryl trioctanoate, tri(caprylic / capric)glyceryl, alkyl benzoate (C12-15); Higher fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid; Examples of the hydrophobic dispersion medium include higher alcohols such as lauryl alcohol, cetyl alcohol, stearyl alcohol, octyldodecanol, and isostearyl alcohol.

[0049] In addition to hydrophobic dispersion media, examples of the dispersion media include alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, octanol, and glycerin; Esters such as ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and gamma-butyrolactone; Ethers such as diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether; Aromatic hydrocarbons such as benzene, toluene, ethylbenzene, 1-phenylpropane, isopropylbenzene, n-butylbenzene, tert-butylbenzene, sec-butylbenzene, o-, m- or p-xylene, 2-, 3- or 4-ethyltoluene; Ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; Amides such as dimethylformamide, N,N-dimethylacetoacetamide, and N-methylpyrrolidone; nitriles such as acetonitrile; Examples of natural oils include oleic acid, jojoba oil, olive oil, coconut oil, grapeseed oil, castor oil, rice bran oil, horse oil, and mink oil. The dispersion medium may be used alone or in combination of two or more kinds.

[0050] When the surface-modified zinc oxide is used for cosmetic applications, the dispersion medium is preferably a chain polysiloxane, a cyclic polysiloxane, a modified polysiloxane, a hydrocarbon oil, an ester oil, a higher fatty acid, a higher alcohol, a natural oil, ethanol, or glycerin.

[0051] The dispersion may further contain commonly used additives, such as preservatives, dispersants, dispersion aids, stabilizers, water-soluble binders, thickeners, oil-soluble drugs, oil-soluble dyes, oil-soluble proteins, and UV absorbers, provided that the properties of the dispersion are not impaired.

[0052] The particle size (D50) when the cumulative volume percentage of the particle size distribution in the dispersion is 50% is not particularly limited, but is preferably 300 nm or less, more preferably 250 nm or less, and even more preferably 200 nm or less. The upper limit of D50 may be 150 nm or less, or 100 nm or less. The lower limit of D50 is not particularly limited, and may be, for example, 20 nm or more, 40 nm or more, or 60 nm or more. The upper limit and lower limit of D50 can be combined arbitrarily.

[0053] The particle size (D90) when the cumulative volume percentage of the particle size distribution in the dispersion is 90% is preferably 350 nm or less, more preferably 300 nm or less, and even more preferably 250 nm or less. The lower limit of D90 is not particularly limited, and may be, for example, 60 nm or more, 80 nm or more, or 100 nm or more. The upper and lower limits of D90 can be combined in any manner.

[0054] When the D50 of the dispersion is 300 nm or less, the surface-modified zinc oxide is easily distributed uniformly when a cosmetic prepared using the dispersion is applied to the skin, and the ultraviolet shielding effect is improved, which is preferable.When the D90 of the dispersion is 350 nm or less, the transparency of the dispersion is high, which is preferable.

[0055] The cumulative volume percentage of the particle size distribution in the dispersion may be measured, for example, by using a dynamic light scattering particle size distribution measuring device (manufactured by Microtrack Bell, model number: NANOTRAC WAVE).

[0056] The content of the surface-modified zinc oxide in the dispersion is appropriately adjusted depending on the desired properties of the dispersion. When the dispersion is used in a cosmetic preparation, the content of the surface-modified zinc oxide in the dispersion is preferably 30% by mass or more, more preferably 40% by mass or more, and even more preferably 50% by mass or more, and preferably 90% by mass or less, more preferably 85% by mass or less, and even more preferably 80% by mass or less. The upper and lower limits for the content of the surface-modified zinc oxide in the dispersion may be combined in any desired manner.

[0057] When the content of the surface-modified zinc oxide in the dispersion is within the above range, the surface-modified zinc oxide tends to be at a sufficiently high concentration in the dispersion, which tends to improve the degree of freedom in the formulation of the cosmetic preparation, and the viscosity of the dispersion is easily adjusted to a range that is easy to handle.

[0058] When the content of surface-modified zinc oxide is 37.5% by mass, the viscosity of the dispersion at 20°C is preferably 5000 mPa·s or less, more preferably 3000 mPa·s or less, and even more preferably 1000 mPa·s or less. If the viscosity is equal to or less than the upper limit, the dispersion can be said to have excellent dispersibility. The lower limit of the viscosity of the dispersion is not particularly limited, but may be, for example, 10 mPa·s, 100 mPa·s, or 300 mPa·s. The viscosity of the dispersion at 20°C is measured using a tuning fork vibration viscometer (A&D Co., Ltd., Model No. SV-10). The measured value is taken 5 minutes after the start of sample measurement.

[0059] The method for producing the dispersion is not particularly limited, and may be, for example, a method in which the surface-modified zinc oxide is mechanically dispersed in a dispersion medium using a dispersing device. The dispersion device is not particularly limited, and examples thereof include a stirrer, a planetary mixer, a homomixer, an ultrasonic homogenizer, a sand mill, a ball mill, and a roll mill.

[0060] (composition) The composition includes surface-modified zinc oxide, a dispersing medium, and a resin. The content of the surface-modified zinc oxide in the composition is appropriately adjusted according to the desired properties of the composition. The content of the surface-modified zinc oxide in the composition is, for example, preferably 10 to 40 mass %, more preferably 20 to 40 mass %.

[0061] When the content of the surface-modified zinc oxide in the composition is within the above range, the surface-modified zinc oxide tends to be concentrated in the composition, so that the properties of the surface-modified zinc oxide can be fully obtained and a composition in which the surface-modified zinc oxide is uniformly dispersed can be obtained.

[0062] The dispersion medium of the composition is not particularly limited as long as it is one that is generally used in industrial applications. Examples of the dispersion medium include alcohols such as methanol, ethanol, and propanol; Methyl acetate, ethyl acetate, toluene, methyl ethyl ketone, methyl isobutyl ketone, and the like. The content of the dispersion medium in the composition is not particularly limited and is appropriately adjusted depending on the desired properties of the composition.

[0063] The resin is not particularly limited as long as it is one that is generally used in industrial applications, and examples of the resin include acrylic resin, epoxy resin, urethane resin, polyester resin, and silicone resin. The content of the resin in the composition is not particularly limited and is appropriately adjusted depending on the desired properties of the composition.

[0064] The composition may contain commonly used additives to the extent that the properties of the composition are not impaired. Examples of the additives include a polymerization initiator, a dispersant, and a preservative.

[0065] The method for producing the composition is not particularly limited. For example, a method of mechanically mixing the surface-modified zinc oxide, the resin and the dispersion medium with a mixing device can be mentioned. The composition may be prepared by mechanically mixing the above-mentioned dispersion liquid and the resin with a mixing device. Examples of the mixing device include a stirrer, a planetary mixer, a homomixer, and an ultrasonic homogenizer.

[0066] The use of the composition is not particularly limited. For example, a coating film can be formed by applying the composition to a plastic substrate such as a polyester film by a common coating method such as roll coating, flow coating, spray coating, screen printing, brush coating, or immersion.

[0067] (Cosmetics) The cosmetic contains surface-modified zinc oxide and a cosmetic base raw material. In addition to the surface-modified zinc oxide and the cosmetic base raw material, the cosmetic may further contain a dispersion medium. A cosmetic base raw material is a raw material that can be the main component of a cosmetic product. Examples of cosmetic base raw materials include oil-based raw materials, water-based raw materials, surfactants, and powder raw materials.

[0068] Examples of oil-based raw materials include fats and oils, higher fatty acids, higher alcohols, and ester oils. Examples of aqueous ingredients include purified water, alcohol, and thickeners. Examples of powdered raw materials include colored pigments, white pigments, pearlescent agents, and extender pigments.

[0069] The cosmetic base raw material may be used alone or in combination of two or more. As the cosmetic base raw material, the use of an oil-based raw material alone, the use of a powder raw material alone, or the use of an oil-based raw material and a powder raw material in combination is preferable, and the use of an oil-based raw material alone is more preferable.

[0070] In cosmetics, the surface-modified zinc oxide is preferably contained in an oil component or oil phase. The oil component used in the oil-based cosmetic or oil phase of the emulsion is not particularly limited as long as it is one that is commonly used in cosmetics, such as silicone oil, oils and fats, higher fatty acids, higher alcohols, ester oils, and natural oils.

[0071] The content of the surface-modified zinc oxide in the cosmetic is appropriately adjusted according to the properties of the cosmetic to be produced. For example, the lower limit of the content of the surface-modified zinc oxide may be 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more. The upper limit of the content of the surface-modified zinc oxide may be 50% by mass or less, 40% by mass or less, or 30% by mass or less. The upper and lower limits of the content of the surface-modified zinc oxide in the cosmetic can be combined in any manner.

[0072] The cosmetic may be an oil-based cosmetic, or an emulsion-type cosmetic containing surface-modified zinc oxide in the oil phase, or may be a cosmetic in which the surface-modified zinc oxide is contained in an oil component (oil phase) during the production process or in the final form, such as a powdered solid cosmetic produced by mixing surface-modified zinc oxide with an oil and then removing the oil to form a molded product. The emulsion-type cosmetic preparation may be an O / W type emulsion or a W / O type emulsion.

[0073] Cosmetics can be obtained by blending the surface-modified zinc oxide or the above-mentioned dispersion with a cosmetic base such as milky lotion, cream, sunscreen, foundation, lipstick, blusher, eyeshadow, or the like. The cosmetic preparation can be obtained, for example, by blending the surface-modified zinc oxide or the above-mentioned dispersion liquid into an oil phase to form an O / W or W / O type emulsion, and then blending the emulsion with the cosmetic preparation raw materials.

[0074] A sunscreen cosmetic will be described in detail below as an example of the cosmetic. In order to effectively block ultraviolet rays, particularly long-wavelength ultraviolet rays (UVA), and obtain a good feeling of use with little powderiness or squeaking, the lower limit of the content of surface-modified zinc oxide in the sunscreen cosmetic is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and even more preferably 1% by mass or more. The upper limit of the content of surface-modified zinc oxide in the sunscreen cosmetic may be 50% by mass or less, 40% by mass or less, or 30% by mass or less. The upper and lower limits of the content of surface-modified zinc oxide in the sunscreen cosmetic can be combined in any manner.

[0075] The sunscreen cosmetic may further contain, as necessary, a hydrophobic dispersion medium, inorganic fine particles or inorganic pigments other than surface-modified zinc oxide, a hydrophilic dispersion medium, oils and fats, surfactants, moisturizers, thickeners, pH adjusters, nutrients, antioxidants, fragrances, etc.

[0076] Examples of hydrophobic dispersion media include hydrocarbon oils such as liquid paraffin, squalane, isoparaffin, branched light paraffin, vaseline, and ceresin; Ester oils such as isopropyl myristate, cetyl isooctanoate, and glyceryl trioctanoate; Silicone oils such as decamethylcyclopentasiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane; Higher fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid; Higher alcohols such as lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyldodecanol, and isostearyl alcohol.

[0077] Examples of inorganic fine particles and inorganic pigments other than surface-modified zinc oxide contained in cosmetics include calcium carbonate, calcium phosphate (apatite), magnesium carbonate, calcium silicate, magnesium silicate, aluminum silicate, kaolin, talc, titanium oxide, aluminum oxide, yellow iron oxide, γ-iron oxide, cobalt titanate, cobalt violet, and silicon oxide.

[0078] The sunscreen cosmetic may further contain at least one organic ultraviolet absorbing agent. Examples of organic ultraviolet absorbers include benzotriazole-based ultraviolet absorbers, benzoylmethane-based ultraviolet absorbers, benzoic acid-based ultraviolet absorbers, anthranilic acid-based ultraviolet absorbers, salicylic acid-based ultraviolet absorbers, cinnamic acid-based ultraviolet absorbers, and silicone-based cinnamic acid ultraviolet absorbers.

[0079] Examples of the benzotriazole-based ultraviolet absorbers include 2,2'-hydroxy-5-methylphenylbenzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, and 2-(2'-hydroxy-5'-methylphenylbenzotriazole).

[0080] Examples of benzoylmethane ultraviolet absorbers include dibenzalazine, dianisoylmethane, 4-tert-butyl-4'-methoxydibenzoylmethane, 1-(4'-isopropylphenyl)-3-phenylpropane-1,3-dione, and 5-(3,3'-dimethyl-2-norbornylidene)-3-pentan-2-one.

[0081] Examples of benzoic acid-based ultraviolet absorbers include para-aminobenzoic acid (PABA), PABA monoglycerin ester, N,N-dipropoxy PABA ethyl ester, N,N-diethoxy PABA ethyl ester, N,N-dimethyl PABA ethyl ester, N,N-dimethyl PABA butyl ester, and N,N-dimethyl PABA methyl ester.

[0082] An example of an anthranilic acid-based ultraviolet absorber is homomenthyl-N-acetylanthranilate.

[0083] Examples of salicylic acid-based ultraviolet absorbers include amyl salicylate, menthyl salicylate, homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, and p-2-propanol phenyl salicylate.

[0084] Examples of cinnamic acid-based ultraviolet absorbers include octyl methoxycinnamate (ethylhexyl methoxycinnamate), di-paramethoxycinnamate-mono-2-ethylhexanoate glyceryl, octyl cinnamate, ethyl-4-isopropyl cinnamate, methyl-2,5-diisopropyl cinnamate, ethyl-2,4-diisopropyl cinnamate, methyl-2,4-diisopropyl cinnamate, propyl-p-methoxycinnamate, isopropyl-p- Methoxycinnamate, isoamyl-p-methoxycinnamate, octyl-p-methoxycinnamate (2-ethylhexyl-p-methoxycinnamate), 2-ethoxyethyl-p-methoxycinnamate, cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenylcinnamate, 2-ethylhexyl-α-cyano-β-phenylcinnamate, and glyceryl mono-2-ethylhexanoyl-di-para-methoxycinnamate.

[0085] Examples of silicone-based cinnamic acid ultraviolet absorbers include [3-bis(trimethylsiloxy)methylsilyl-1-methylpropyl]-3,4,5-trimethoxycinnamate, [3-bis(trimethylsiloxy)methylsilyl-3-methylpropyl]-3,4,5-trimethoxycinnamate, [3-bis(trimethylsiloxy)methylsilylpropyl]-3,4,5-trimethoxycinnamate, [3-bis(trimethylsiloxy)methylsilylbutyl]-3,4,5-trimethoxycinnamate, [3-tris(trimethylsiloxy)silylbutyl]-3,4,5-trimethoxycinnamate, and [3-tris(trimethylsiloxy)silyl-1-methylpropyl]-3,4-dimethoxycinnamate.

[0086] Examples of organic ultraviolet absorbers other than those mentioned above include 3-(4'-methylbenzylidene)-d,l-camphor, 3-benzylidene-d,l-camphor, urocanic acid, urocanic acid ethyl ester, 2-phenyl-5-methylbenzoxazole, 5-(3,3'-dimethyl-2-norbornylidene)-3-pentan-2-one, silicone-modified ultraviolet absorbers, and fluorine-modified ultraviolet absorbers. EXAMPLES

[0087] The present invention will be described in more detail below using examples, but the present invention is not limited to the description of the following examples.

[0088] <Raw material, abbreviation> (Zinc oxide particles) FZO-50: Zinc oxide fine particle powder with a BET average particle size of 21 nm (Ishihara Sangyo Co., Ltd. product). F-1: Zinc oxide fine particle powder with a BET average particle size of 100 nm (product of Hakusui Tech Co., Ltd.).

[0089] (Surface treatment agent) KF-9901: Hydrogen Dimethicone (Shin-Etsu Chemical Co., Ltd. product) KF-99: Methicone (product of Shin-Etsu Chemical Co., Ltd.) KBE-3083: Octyltriethoxysilane (product of Shin-Etsu Chemical Co., Ltd.)

[0090] <Example 1> 100g of FZO-50 and 5g of KF-9901 were mixed and placed in a pressure-resistant container. Carbon dioxide gas was injected into the pressure-resistant container, and the pressure was increased until the mixture reached a supercritical state, and the temperature was adjusted. After that, FZO-50 and KF-9901 were mixed in the presence of supercritical carbon dioxide, allowing KF-9901 to come into sufficient contact with the surface of FZO-50. Next, the pressure in the pressure-resistant container was reduced to convert the supercritical carbon dioxide into carbon dioxide gas. The carbon dioxide gas was separated to extract the powder of the mixture. The powder was then placed in an oven at 120°C for heat treatment. The heat treatment caused FZO-50 and KF-9901 to react with each other, and the surface-modified zinc oxide powder of Example 1 was obtained.

[0091] <Examples 2 to 6> Surface-modified zinc oxide powders of each example were obtained by supercritical treatment in the same manner as in Example 1, except that the type of zinc oxide particles, the type of silicon compound in the surface treatment agent, and the mixing ratio of the surface treatment agent to the zinc oxide particles (amount of treatment agent) were changed as shown in Table 1.

[0092] <Comparative Example 1> While FZO-50 was being stirred at high speed with a Henschel mixer, KF-9901 was added dropwise to FZO-50 so that the mixing ratio (amount of treatment agent) was 5 mass%. After stirring for 5 minutes, the powder obtained was heat-treated in an oven at 120°C to obtain the powder of Comparative Example 1.

[0093] <Comparative Examples 2-5 and 7> Powders of each example were obtained by dry processing in the same manner as in Comparative Example 1, except that the type of zinc oxide particles, the type of treating agent, and the amount of treating agent were changed as shown in Table 2.

[0094] <Comparative Example 6> KF-9901 was weighed and dissolved in methyl ethyl ketone so that the concentration was 5% by mass. 100 g of FZO-50 was added to 100 g of this solution, and then ultrasonic irradiation was performed for 5 minutes using an ultrasonic disperser (SMT Corporation's "UH-600S", horn diameter 20 mm, scale 7). Next, methyl ethyl ketone was completely removed using a rotary evaporator, and the obtained powder was heat-treated in an oven at 120°C to obtain the powder of Comparative Example 6.

[0095] <Comparative Example 8> In Comparative Example 8, FZO-50 was directly subjected to the following evaluation without any surface treatment.

[0096] <Measurement and Evaluation> (color difference ΔE) The color difference ΔE before and after the vitamin E mixing test was measured by the method described below. The powder of each example before being mixed with vitamin E was subjected to the following measurements. A blank solution was prepared by mixing 3 g of powder and 5 g of cyclopentasiloxane. Next, a quartz cell with an optical path length of 0.1 mm containing the blank solution was set in an ultraviolet-visible-near infrared spectrophotometer (Hitachi High-Tech Science Corporation, model number: UH4150). After measuring the diffuse reflectance spectrum of the mixed solution using an integrating sphere, the L1 * , a1 * , b1 * was calculated.

[0097] The powders of each example after mixing with vitamin E were subjected to the following measurements. Vitamin E and cyclopentasiloxane were mixed to prepare a cyclopentasiloxane mixed solvent having a vitamin E concentration of 2% by mass. A sample solution containing vitamin E was prepared by mixing 3 g of powder and 5 g of cyclopentasiloxane mixed solvent. The diffuse reflectance spectrum of the sample solution was measured using the method described above, and the L2 * , a2 * , b2 * was calculated.

[0098] From the above results, the color difference ΔE = ((L2 * -L1 * ) 2 +(a2 * -a1 * ) 2 +(b2 * -b1 * ) 2 ) 1 / 2 was calculated.

[0099] (dispersibility) 30 g of powder and 50 g of cyclopentasiloxane were mixed. The viscosity of the resulting dispersion at 20°C was measured using a tuning fork vibration viscometer (A&D Co., Ltd., model number: SV-10). The dispersion state was measured according to the following criteria. A: The viscosity of the dispersion is less than 1000 mPa s. The dispersion state is good. B: The viscosity of the dispersion is 1000 mPa·s or more and less than 5000 mPa·s. The dispersion state is somewhat poor. C: The viscosity of the dispersion is 5000 mPa s or more. The dispersion state is poor.

[0100] <Result> The results of each example are shown in Tables 1 and 2.

[0101] [Table 1]

[0102] [Table 2]

[0103] In Examples 1 to 6, the color difference ΔE was 5 or less. Therefore, the generation of active oxygen was sufficiently suppressed. Furthermore, surface-modified zinc oxide with excellent dispersibility was obtained. In contrast, in Comparative Examples 1 to 8, the dispersibility was poor. In Comparative Examples 1 to 8, where the color difference ΔE exceeded 5, it is considered that the generation of active oxygen cannot be sufficiently suppressed. [Industrial Applicability]

[0104] According to the present invention, it is possible to provide a surface-modified zinc oxide that can sufficiently suppress the generation of active oxygen and has excellent dispersibility, and a method for producing the same.

Claims

1. The zinc oxide particles are surface-modified zinc oxide particles in which the surfaces of the zinc oxide particles are treated with a surface treatment agent, A surface-modified zinc oxide having a color difference ΔE of 5 or less before and after a vitamin E mixing test.

2. 2. The surface modified zinc oxide of claim 1, wherein the surface treatment agent comprises a silicon compound.

3. 3. The surface-modified zinc oxide according to claim 2, wherein the silicon compound is at least one selected from the group consisting of silane compounds, silicone compounds and silane coupling agents.

4. Contacting zinc oxide particles and a surface treatment agent in a container in the presence of supercritical carbon dioxide; reducing the pressure inside the container to remove carbon dioxide and recover the mixture of the zinc oxide particles and the surface treatment agent; and heating the mixture to react the zinc oxide particles and the surface treatment agent; A method for producing surface-modified zinc oxide comprising the steps of:

5. The method according to claim 4 , wherein the surface treatment agent comprises a silicon compound.

6. The method according to claim 5, wherein the silicon compound is at least one selected from the group consisting of a silane compound, a silicone compound, and a silane coupling agent.

7. A dispersion comprising the surface-modified zinc oxide according to any one of claims 1 to 3 and a dispersion medium.

8. A composition comprising the surface-modified zinc oxide according to any one of claims 1 to 3, a dispersion medium, and a resin.

9. A cosmetic comprising the surface-modified zinc oxide according to any one of claims 1 to 3 and a cosmetic base raw material.

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