Surface-treated UV-shielding particles, dispersion, cosmetic, and method for producing surface-treated UV-shielding particles

Abstract

Provided are surface-treated UV-shielding particles surface-treated with a metal soap, wherein the metal soap is at least one selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate, and the hydrophobicity of the UV-shielding particles after mixing with ethanol at 50°C is 25% or more.

Description

Surface-treated ultraviolet-shielding particles, dispersion, cosmetic, and method for producing surface-treated ultraviolet-shielding particles

[0001] The present invention relates to surface-treated ultraviolet-shielding particles, dispersions, compositions, cosmetics, and methods for producing surface-treated ultraviolet-shielding particles. This application claims priority to Japanese Patent Application No. 2024-055499, filed March 29, 2024, the contents of which are incorporated herein by reference.

[0002] UV-shielding particles such as zinc oxide and titanium oxide, which have UV-shielding properties, are used in cosmetics such as sunscreens, foundations, etc. When these UV-shielding particles are used in cosmetics, the surface of the UV-shielding particles is treated with a surface treatment agent to match the surface condition of the UV-shielding particles to the properties of the cosmetic product and to suppress the catalytic activity of the UV-shielding particles.

[0003] Examples of surface treatment agents for such ultraviolet-shielding particles include metal soaps such as magnesium stearate, silicone oils such as dimethicone and hydrogen dimethicone, and silane coupling agents having an alkoxy group such as octyltriethoxysilane (see, for example, Patent Documents 1 and 2).

[0004] Furthermore, Patent Document 3 proposes a cosmetic product in which a metal oxide powder and an extender pigment are both surface-treated with a metal soap, thereby improving the ultraviolet protection effect.

[0005] JP 2002-362925 A JP 2001-181136 A WO 2023 / 063387 A

[0006] However, the ultraviolet-shielding particles surface-treated with metal soap have a problem of low alcohol resistance.

[0007] The present invention has been made in view of the above circumstances, and aims to provide surface-treated ultraviolet-shielding particles that have excellent alcohol resistance and are surface-treated with a metal soap. It also aims to provide a dispersion containing the surface-treated ultraviolet-shielding particles that have been surface-treated with a metal soap, and a cosmetic. It also aims to provide a method for producing such surface-treated ultraviolet-shielding particles that have been surface-treated with a metal soap.

[0008] The present invention has the following aspects. [1] Ultraviolet-shielding particles surface-treated with a metal soap, wherein the metal soap is at least one selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate, and the hydrophobicity of the ultraviolet-shielding particles after mixing with ethanol at 50°C is 25% or more. [2] The surface-treated ultraviolet-shielding particles according to [1], wherein the ultraviolet-shielding particles are at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, cerium oxide particles, and iron oxide particles. [3] A BET specific surface area of ​​1.5 m ２ / g or more 65m ２ / g or less. [4] The surface-treated ultraviolet-shielding particles according to any one of [1] to [3], wherein the hydroxyl group treatment rate after mixing with ethanol at 50°C is 90% or more. [5] A dispersion containing the surface-treated ultraviolet-shielding particles according to any one of [1] to [4] and a dispersion medium. [6] A cosmetic comprising at least one of the surface-treated ultraviolet-shielding particles according to any one of [1] to [4] and the dispersion according to [5]. [7] A cosmetic comprising the surface-treated ultraviolet-shielding particles according to any one of [1] to [4]. [8] A cosmetic comprising the dispersion according to [5]. [9] A method for producing surface-treated ultraviolet-shielding particles according to any one of [1] to [4], comprising the steps of heating and mixing ultraviolet-shielding particles with a metal soap and surface-treating the ultraviolet-shielding particles with the molten metal soap, wherein the metal soap is at least one selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate.

[10] The method according to [9], wherein in the surface-treating step, only the ultraviolet-shielding particles and the metal soap are mixed, and the heating temperature during the heating and mixing is equal to or higher than the melting point of the metal soap and lower than the boiling point.

[11] The method according to [9] or

[10] , wherein the heating temperature during the heating and mixing is equal to or higher than 100°C and equal to or lower than 250°C, and the ultraviolet-shielding particles are at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, cerium oxide particles, and iron oxide particles.

[0009] According to the present invention, it is possible to provide surface-treated ultraviolet-shielding particles having excellent alcohol resistance. According to the present invention, it is possible to provide a dispersion containing such surface-treated ultraviolet-shielding particles and a cosmetic. According to the present invention, it is possible to provide a method for producing such surface-treated ultraviolet-shielding particles.

[0010] The following describes embodiments of the surface-treated UV-shielding particles, dispersion, cosmetic, and method for producing surface-treated UV-shielding particles of the present invention. Note that these embodiments are specifically described to provide a better understanding of the gist of the invention, and do not limit the present invention unless otherwise specified. For example, unless otherwise specified, conditions such as materials, amounts, types, numbers, sizes, ratios, and temperatures may be changed, added, or omitted as necessary. Preferred examples may be exchanged or shared among the embodiments described below.

[0011] First, before describing the present invention in detail, the idea behind the present inventors' approach to the present invention will be described.

[0012] As described in Patent Document 3, when a metal oxide powder or an extender pigment is surface-treated with a metal soap, the metal soap can be dissolved in a volatile solvent, mixed with a base powder, and then the volatile solvent can be evaporated to perform the surface treatment. Alternatively, the base powder can be surface-treated with the metal soap simply by mixing the base powder with the metal soap. In order to improve the alcohol resistance of UV-shielding particles surface-treated with a metal soap, the present inventors attempted surface treatment with magnesium stearate, which is considered to have excellent alcohol resistance among metal soaps.

[0013] Magnesium stearate is insoluble in solvents such as water and alcohol. Therefore, in order to uniformly surface-treat the surfaces of ultraviolet-shielding particles with magnesium stearate, it has been common to dissolve soluble sodium stearate in hot water to obtain a solution, mix this solution with ultraviolet-shielding particles, and adsorb sodium stearate onto the surfaces of the ultraviolet-shielding particles to perform a sodium-magnesium substitution treatment. However, in the surface-treated ultraviolet-shielding particles obtained by conventional manufacturing methods, unreacted sodium stearate added in the above treatment remains on the surface of the ultraviolet-shielding particles. Therefore, when these surface-treated ultraviolet-shielding particles are mixed with alcohol, sodium stearate is liberated, resulting in a problem of poor alcohol resistance. Therefore, conventional manufacturing methods have made it difficult to obtain ultraviolet-shielding particles surface-treated with metal soap that have excellent alcohol resistance.

[0014] As a result of various investigations, the present inventors have found that by melting a metal soap having excellent alcohol resistance and mixing the molten metal soap with ultraviolet-shielding particles at a predetermined energy level or higher without using a solvent, the ultraviolet-shielding particles can be surface-treated with the metal soap having excellent alcohol resistance. This production method makes it possible to surface-treat the ultraviolet-shielding particles using only the metal soap having excellent alcohol resistance, and therefore it has been found that ultraviolet-shielding particles surface-treated with the metal soap having excellent alcohol resistance can be obtained.

[0015] [Surface-treated UV-shielding particles] The surface-treated UV-shielding particles of this embodiment are UV-shielding particles that have been surface-treated with a metal soap, wherein the metal soap is at least one selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate, and the hydrophobicity of the UV-shielding particles after mixing with ethanol at 50°C is 25% or more. In other words, the surface-treated UV-shielding particles of this embodiment are UV-shielding particles whose surfaces are coated with the metal soap. The hydrophobicity of the UV-shielding particles being 25% or more after mixing with ethanol at 50°C means that the surfaces of the UV-shielding particles that have been surface-treated with the metal soap remain hydrophobic even after mixing with high-temperature alcohol. In other words, the hydrophobicity of the UV-shielding particles being 25% or more after mixing with ethanol at 50°C means that the metal soap remains attached to the surfaces of the UV-shielding particles even after mixing with alcohol, resulting in excellent alcohol resistance. Since it is extremely difficult to confirm the degree of surface treatment of particles, this confirmation was carried out after various investigations.

[0016] In this specification, "ultraviolet-shielding particles surface-treated with a metal soap after mixing with 50°C ethanol (surface-treated ultraviolet-shielding particles)", i.e., "surface-treated ultraviolet-shielding particles after mixing with 50°C ethanol", may refer to surface-treated ultraviolet-shielding particles obtained by mixing 5 g of the surface-treated ultraviolet-shielding particles of this embodiment with 45 g of ethanol, heating the mixture to 50°C, stirring the mixture at 2000 rpm for 10 minutes with a disper, subjecting the mixture to solid-liquid separation, and drying the recovered solid at 40°C for 5 hours.

[0017] In this embodiment, "hydrophobicity" is measured by the limit ethanol method. The limit ethanol method is a method in which a sample is added to a mixed solution of water and ethanol, and whether or not the sample precipitates is observed. The limit ethanol method is a method in which the ethanol ratio required for the sample to precipitate is increased if the sample does not precipitate, and increased if the sample precipitates, thereby evaluating the hydrophobicity of the surface of the ultraviolet-shielding particles. This can also be considered as the ethanol ratio at the timing when the sample starts to precipitate. Specifically, the ethanol ratio (%) contained in the mixed solution when 10 or more surface-treated ultraviolet-shielding particles have precipitated is taken as the hydrophobicity of the surface-treated ultraviolet-shielding particles. A higher ethanol ratio indicates a more hydrophobic surface of the ultraviolet-shielding particles.

[0018] The hydrophobicity of the surface-treated ultraviolet shielding particles of this embodiment after mixing with ethanol at 50°C is 25% or more. The hydrophobicity may be 30% or more, 35% or more, or 40% or more. The upper limit of the hydrophobicity may be 70% or less, 60% or less, or 50% or less. The hydrophobicity may be adjusted depending on the hydrophobicity of the substance into which the surface-treated ultraviolet shielding particles are to be mixed, for example, a cosmetic product. If the hydrophobicity is 25% or more, the surface-treated ultraviolet shielding particles have excellent alcohol resistance.

[0019] The hydrophobicity of the surface-treated ultraviolet shielding particles of this embodiment before mixing with 50°C ethanol may be 25% or more, 30% or more, 35% or more, or 40% or more. The upper limit of the hydrophobicity may be 70% or less, 60% or less, or 50% or less. The hydrophobicity may be adjusted depending on the hydrophobicity of the substance to be mixed with the surface-treated ultraviolet shielding particles, for example, a cosmetic. If the hydrophobicity is 25% or more, the surface-treated ultraviolet shielding particles have excellent alcohol resistance.

[0020] The change in hydrophobicity of the surface-treated ultraviolet-shielding particles of this embodiment between before and after mixing with 50° C. ethanol ((hydrophobicity before mixing−hydrophobicity after mixing) / hydrophobicity before mixing×100) is preferably 20% or less, more preferably 10% or less, even more preferably 8% or less, and particularly preferably 5% or less. When the change in hydrophobicity is within the above range, the change in the surface state of the surface-treated ultraviolet-shielding particles is suppressed even when the surface-treated ultraviolet-shielding particles are exposed to high-temperature ethanol, and therefore the surface-treated ultraviolet-shielding particles can be said to have excellent alcohol resistance.

[0021] The surface-treated ultraviolet-shielding particles of this embodiment preferably have a hydroxyl group treatment rate of 95% or more, as measured by the following method. The hydroxyl group treatment rate may be 96% or more, 97% or more, or even 98% or more. The upper limit of the hydroxyl group treatment rate is 100%. A high hydroxyl group treatment rate means that the degree to which the hydroxyl groups on the surface of the ultraviolet-shielding particles have been treated is high. In other words, the higher the treatment rate of hydroxyl groups on the surface of the ultraviolet-shielding particles, the more the hydroxyl groups present on the surface of the ultraviolet-shielding particles have been treated and made hydrophobic. In other words, a high treatment rate can be considered to mean that the hydroxyl groups present on the surface of the ultraviolet-shielding particles have been treated more extensively with metal soap.

[0022] A method for measuring the hydroxyl group treatment rate according to this embodiment will now be described. In this specification, the term "hydroxyl group treatment rate" refers to a value measured using a red dye that absorbs light at a wavelength of about 545 nm and is represented by the following general formula (1):

[0023]

[0024] The red dye represented by the general formula (1) can be produced, for example, by the following production method. A mixed solution is prepared by mixing 1 mmol of 2,2'-dihydroxyazobenzene, 1 mmol of diphenyltin(IV) oxide as a metal source, and 30 mL of acetone. Next, this mixed solution is stirred at 70°C for 3 hours to carry out a dehydration reaction, and diphenyltin oxide is coordinated to 2,2'-dihydroxyazobenzene. After the dehydration reaction, the mixed solution is filtered to recover the filtrate, and the solvent is distilled off from the filtrate to obtain the red dye.

[0025] The red dye selectively adsorbs to hydroxyl groups present on the surface of the ultraviolet-shielding particles and does not react with hydroxyl groups of water, alcohol, or the like. Furthermore, the red dye does not react with dimethylpolysiloxane. Therefore, the amount of metal hydroxyl groups present on the surface of ultraviolet-shielding particles and the surface of surface-treated ultraviolet-shielding particles can be qualitatively and quantitatively evaluated without being affected by moisture. Hydroxyl groups are present on the surface of the ultraviolet-shielding particles in this embodiment. Therefore, the red dye adsorbs to the ultraviolet-shielding particles before they are coated with the metal soap. On the other hand, in the surface-treated ultraviolet-shielding particles coated with the metal soap, the hydroxyl groups at the coated locations are not exposed on the surface of the surface-treated ultraviolet-shielding particles. Therefore, the greater the area of ​​the ultraviolet-shielding particle surface that is coated with the metal soap, the greater the hydroxyl group treatment rate calculated by the formula described below. Therefore, the degree of coverage of the ultraviolet-shielding particles with the metal soap can be determined by examining the amount of red dye adsorbed on the ultraviolet-shielding particles before coating and the amount of red dye adsorbed on the ultraviolet-shielding particles after coating (surface-treated ultraviolet-shielding particles). The greater the adsorption amount of the red dye, the greater the number of hydroxyl groups present on the surface. In other words, the greater the hydroxyl group treatment rate, the greater the degree to which the surfaces of the ultraviolet-shielding particles are coated with the metal soap and made hydrophobic.

[0026] The hydroxyl group treatment rate in this embodiment is calculated from the adsorption amount of the red dye before and after coating. That is, the hydroxyl group treatment rate of the surface-treated ultraviolet-shielding particles in this embodiment is calculated by the formula 100-(B / A×100)(%), where A is the adsorption amount before coating with the red dye and B is the adsorption amount after coating with the red dye. Note that the greater the degree of coating, the smaller the adsorption amount.

[0027] Specifically, the hydroxyl group treatment rate by the red dye can be measured, for example, by the following method: 250 nmol (0.12 mg) of the red dye is dissolved in toluene to make 5 mL, and 5 × 10 －５ A solution C1 for evaluation of mol / L is obtained. The absorbance C2 of the solution C1 at a wavelength of 545 nm is measured. The absorbance C2 is greater than the absorbance A2 and absorbance B2 described below. The absorbance can be measured using, for example, a spectrophotometer (model number: V-770, manufactured by JASCO Corporation). The unit of absorbance may be Abs.

[0028] Uncoated ultraviolet-shielding particles and surface-treated ultraviolet-shielding particles coated with a metal soap are prepared. x g of the uncoated ultraviolet-shielding particles are added to the evaluation solution C1, and the mixture is stirred and mixed at 60°C for 4 hours to prepare a mixed solution. The ultraviolet-shielding particles are removed from this mixture by centrifugation, filtration, or the like to obtain an evaluation mixed solution A1 (mixed solution A1). The absorbance A2 of this mixed solution A1 at a wavelength of 545 nm is measured. y g of the surface-treated ultraviolet-shielding particles to be measured are added to the evaluation solution C1, and the mixture is stirred and mixed at 60°C for 4 hours to prepare a mixed solution. The surface-treated ultraviolet-shielding particles are removed from this mixture by centrifugation, filtration, or the like to obtain an evaluation mixed solution B1 (mixed solution B1). The absorbance B2 of this mixed solution B1 at a wavelength of 545 nm is measured. The absorbance B2 is greater than the absorbance A2. Note that x and y can be adjusted based on the BET specific surface area of ​​the ultraviolet-shielding particles. For example, x and y are 1 mg to 50 mg. ２ / g, x and y are approximately 4 × 10 －３ It is preferable that the BET specific surface area is 5 m ２ / g, x and y are approximately 32 × 10 －３Preferably, x and y have the same value.

[0029] The amount (mol / g) of the red dye adsorbed to the ultraviolet-shielding particles before coating is calculated using the following formula (2): Adsorption amount A3=((C2-A2) / C2)×250×10 －９ (mol) / x(g) (2) The amount (mol / g) of the red dye adsorbed to the surface-treated ultraviolet-shielding particles is calculated using the following formula (3): Adsorption amount B3=((C2-B2) / C2)×250×10 －９ (mol) / y(g) ... (3) In the above formulas (2) and (3), a decrease in absorbance means that the dye is adsorbed, so the adsorption amount of the red dye is calculated based on the idea that the rate of decrease in absorbance can be converted to the rate of adsorption of the dye. Note that the above formulas (2) and (3) are calculated based on the following equation: adsorption amount = ((absorbance of solution C1 - absorbance of solution A1 or B1) / absorbance of solution C1) × 250 × 10 －９ It can be expressed as (mol) / amount (g) of ultraviolet-shielding particles.

[0030] The hydroxyl group treatment rate can be calculated by the following formula (4): Hydroxyl group treatment rate (%) = 100 - ((B3 / A3) x 100) (4)

[0031] The surface-treated ultraviolet-shielding particles of this embodiment preferably have a hydroxyl group treatment rate of 90% or more after mixing with ethanol at 50°C. The surface-treated ultraviolet-shielding particles of this embodiment may have a hydroxyl group treatment rate of 92% or more, 95% or more, or even 96% or more after mixing with ethanol at 50°C. The upper limit of the hydroxyl group treatment rate after mixing with ethanol at 50°C is 100%. A hydroxyl group treatment rate of 90% or more means that the surface of the ultraviolet-shielding particles surface-treated with the metal soap remains hydrophobic even after mixing with high-temperature alcohol. In other words, a hydroxyl group treatment rate of 90% or more of the ultraviolet-shielding particles after mixing with ethanol at 50°C means that the metal soap remains attached to the surface of the ultraviolet-shielding particles even after mixing with alcohol, resulting in excellent alcohol resistance.

[0032] The change in the hydroxyl group treatment rate, calculated by the above formula, before and after mixing with ethanol at 50° C., i.e., the difference in the hydroxyl group treatment rate, of the surface-treated ultraviolet-shielding particles of this embodiment is preferably 6% or less, more preferably 4% or less, and even more preferably 2% or less. When the change in the hydroxyl group treatment rate is within the above range, the change in the surface state of the surface-treated ultraviolet-shielding particles is suppressed even when the surface-treated ultraviolet-shielding particles are exposed to high-temperature ethanol, and therefore the surface-treated ultraviolet-shielding particles can be said to have excellent alcohol resistance.

[0033] The BET specific surface area of ​​the surface-treated ultraviolet shielding particles of this embodiment may be adjusted depending on the intended use and is not particularly limited. For example, when used in cosmetics, the BET specific surface area is 1.5 m ２ / g or more 65m ２ / g or less, and 1.5m ２ / g or more 8m ２ It is more preferable that the SiO2 content is 1 / g or less.

[0034] In this specification, the term "BET specific surface area" refers to a value measured by the BET method using a fully automatic specific surface area measuring device (trade name: Macsorb HM Model-1201, manufactured by Mountec Co., Ltd.).

[0035] (BET Specific Surface Area of ​​Surface-Treated UV-Shielding Particles) A ​​preferred BET specific surface area of ​​the surface-treated UV-shielding particles for use in cosmetics will be described. The BET specific surface area of ​​the surface-treated UV-shielding particles can be selected arbitrarily, but is preferably 1.5 m ２ / g or more, and 2.5m ２ / g or more, and 3.5m ２ The BET specific surface area of ​​the surface-treated ultraviolet shielding particles is more preferably 65 m / g or more. ２ / g or less, and ２ / g or less is more preferable. For example, ２ / g or less, 30m ２ / g or less, 20m ２ / g or less, 10m ２If necessary, the BET specific surface area of ​​the surface-treated ultraviolet-shielding particles may be 8 m / g or less. ２ / g or less, and ２ The upper and lower limits of the BET specific surface area of ​​the surface-treated ultraviolet-shielding particles can be arbitrarily combined. ２ / g or more 65m ２ When the BET specific surface area of ​​the surface-treated ultraviolet-shielding particles is 1.5 m / g or less, the particles have excellent transparency and ultraviolet-shielding properties when blended in a cosmetic. ２ / g or more 8m ２ / g or less, the hydrophobicity is superior. Note that there is not much difference between the BET specific surface area of ​​the ultraviolet-shielding particles before being coated with the metal soap and the BET specific surface area of ​​the ultraviolet-shielding particles after being coated with the metal soap (surface-treated ultraviolet-shielding particles).

[0036] (Average primary particle diameter of surface-treated ultraviolet-shielding particles) The average primary particle diameter of the surface-treated ultraviolet-shielding particles of this embodiment is preferably 15 nm or more, and more preferably 20 nm or more. It may be 50 nm or more, 80 nm or more, or 100 nm or more. From the viewpoint of increasing the hydrophobicity of the surface-treated ultraviolet-shielding particles, the average primary particle diameter is preferably 130 nm or more, more preferably 150 nm or more, and even more preferably 200 nm or more. Furthermore, the average primary particle diameter of the surface-treated ultraviolet-shielding particles of this embodiment is preferably 300 nm or less, more preferably 270 nm or less, and even more preferably 250 nm or less. When the average primary particle diameter of the surface-treated ultraviolet-shielding particles is 15 nm or more and 300 nm or less, the surface-treated ultraviolet-shielding particles have excellent transparency and ultraviolet-shielding properties when incorporated into cosmetics.

[0037] The average primary particle size of the surface-treated ultraviolet-shielding particles can be calculated by the following formula (5) using the BET specific surface area of ​​the surface-treated ultraviolet-shielding particles: average primary particle size (nm) = 6000 / (BET specific surface area (m ２ / g) × ρ (g / cm ３)) (5) (wherein ρ is the density of the ultraviolet-shielding particles. ρ of zinc oxide particles is 5.61 g / cm ３ The average primary particle diameter of the surface-treated ultraviolet-shielding particles may also be determined by the following method. That is, when the surface-treated ultraviolet-shielding particles are observed using a transmission electron microscope (TEM) or the like, a predetermined number of surface-treated ultraviolet-shielding particles, for example, 200 or 100 particles, are selected. The longest linear portion (maximum major axis) of each of these surface-treated ultraviolet-shielding particles is then measured, and these measured values ​​are arithmetically averaged. Note that when the surface-treated ultraviolet-shielding particles are aggregated together, the aggregate particle diameter of the aggregate is not measured. A predetermined number of surface-treated ultraviolet-shielding particles (primary particles) constituting the aggregate are measured, and the average primary particle diameter is determined.

[0038] The particle size D50 of the surface-treated ultraviolet-shielding particles in this embodiment, when the cumulative volume percentage of the dry particle size distribution is 50%, may be 40 μm or less, 30 μm or less, or 20 μm or less. Furthermore, the D50 may be 100 nm or more, 500 nm or more, or 1 μm or more. The particle size D90 of the surface-treated ultraviolet-shielding particles in this embodiment, when the cumulative volume percentage of the dry particle size distribution is 90%, may be 150 μm or less, 130 μm or less, or 100 μm or less. The maximum value D of the dry particle size distribution of the surface-treated ultraviolet-shielding particles in this embodiment ｍａｘ The oil absorption of cyclopentasiloxane in the surface-treated ultraviolet shielding particles of this embodiment may be 30 ml / 100 g or less, 20 ml / 100 g or less, or 18 ml / 100 g or less.

[0039] (Ultraviolet-shielding particles) The ultraviolet-shielding particles in this embodiment are not particularly limited as long as they are metal oxide particles that can shield ultraviolet rays. The ultraviolet-shielding particles in this embodiment are preferably at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, iron oxide particles, and cerium oxide particles. Among these, zinc oxide particles are preferably used as the ultraviolet-shielding particles because they can block a wide range of ultraviolet wavelengths.

[0040] (Zinc oxide particles) The zinc oxide particles in this embodiment have a BET specific surface area of ​​1.5 m ２ / g or more 65m ２ The BET specific surface area is preferably 2.5 m / g or less. ２ / g or more is more preferable, and 4m ２ The BET specific surface area of ​​the zinc oxide particles is preferably 60 m / g or more. ２ / g or less, and ２ / g or less, ２ / g or less, ２ If necessary, the BET specific surface area of ​​the zinc oxide particles may be 40 m / g or less. ２ / g or less, ２ / g or less, ２ / g or less. The upper and lower limits of the BET specific surface area of ​​the zinc oxide particles can be combined in any way. If the BET specific surface area of ​​the zinc oxide particles is less than the lower limit, transparency will decrease when the zinc oxide particles are incorporated into a cosmetic, which is not preferred. If the BET specific surface area of ​​the zinc oxide particles exceeds the upper limit, the zinc oxide particles may be prone to aggregation when the zinc oxide particles surface-treated with the metal soap (hereinafter referred to as "metal soap-coated zinc oxide particles") are contained in a cosmetic at a high concentration, which is not preferred. From the viewpoint of increasing the hydrophobicity of the metal soap-coated zinc oxide particles, the BET specific surface area of ​​the zinc oxide particles is 10.0 m ２ / g or less, and ２ / g or less, and more preferably 7.1m ２ / g or less, and more preferably 6.0m ２The smaller the BET specific surface area of ​​zinc oxide particles, the more the particles are prevented from aggregating and the less the untreated surface area, resulting in better alcohol resistance.

[0041] The BET specific surface area of ​​the zinc oxide particles in this embodiment means a value measured by the BET method using a fully automatic specific surface area measuring device (trade name: Macsorb HM Model-1201, manufactured by Mountec Co., Ltd.).

[0042] The average primary particle diameter of the zinc oxide particles in this embodiment is preferably 15 nm or more, and more preferably 20 nm or more. From the viewpoint of increasing the hydrophobicity of the metal soap-coated zinc oxide particles, the average primary particle diameter of the zinc oxide particles is preferably 130 nm or more, more preferably 150 nm or more, and even more preferably 200 nm or more. Furthermore, the average primary particle diameter of the zinc oxide particles in this embodiment is preferably 300 nm or less, more preferably 270 nm or less, and even more preferably 250 nm or less. When the average primary particle diameter of the zinc oxide particles is 15 nm or more and 300 nm or less, the zinc oxide particles exhibit excellent transparency and ultraviolet shielding properties when incorporated into cosmetics. When the average primary particle diameter of the zinc oxide particles is 130 nm or more and 300 nm or less, the obtained metal soap-coated zinc oxide particles exhibit excellent alcohol resistance.

[0043] The average primary particle diameter of the zinc oxide particles can be calculated using the BET specific surface area of ​​the zinc oxide particles according to the formula (5), similarly to the BET equivalent particle diameter of the surface-treated ultraviolet-shielding particles. The average primary particle diameter of the zinc oxide particles may also be measured using a transmission electron microscope, similarly to the average primary particle diameter of the surface-treated ultraviolet-shielding particles.

[0044] The content of the ultraviolet-shielding particles relative to the total mass of the surface-treated ultraviolet-shielding particles of this embodiment is preferably 80% by mass or more and 98.9% by mass or less, more preferably 85% by mass or more and 98.8% by mass or less, even more preferably 90% by mass or more and 98.7% by mass or less, and particularly preferably 95% by mass or more and 98.6% by mass or less. When the content of the ultraviolet-shielding particles is within the above range, the amount added to cosmetics and the like can be reduced in order to exhibit the performance inherent to the ultraviolet-shielding particles. This increases the degree of freedom in the formulation design of cosmetics and the like.

[0045] The content of at least one metal soap selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate relative to the total mass of the surface-treated ultraviolet-shielding particles of this embodiment is preferably 1.1 mass% or more and 20 mass% or less, more preferably 1.2 mass% or more and 15 mass% or less, even more preferably 1.3 mass% or more and 10 mass% or less, and particularly preferably 1.4 mass% or more and 5 mass% or less. By having the content of the metal soap within the above range, the surface of the ultraviolet-shielding particles can be made hydrophobic. Furthermore, the surface-treated ultraviolet-shielding particles of this embodiment preferably do not have sodium stearate, calcium stearate, zinc stearate, stearic acid, etc. on their surfaces.

[0046] The surface-treated ultraviolet-shielding particles of this embodiment may be composed only of the above-mentioned metal soap and ultraviolet-shielding particles, excluding impurities that are inevitably contained therein. Alternatively, the surface-treated ultraviolet-shielding particles of this embodiment may contain at least one surface treatment agent other than the metal soap selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate, as long as the object of the present invention is not impaired.

[0047] In this embodiment, by coating the surfaces of zinc oxide particles with the metal soap, the BET specific surface area of ​​the metal soap-coated zinc oxide particles tends to be smaller than the BET specific surface area of ​​the zinc oxide particles before coating with the metal soap, but the BET specific surface area of ​​the metal soap-coated zinc oxide particles and the BET specific surface area of ​​the zinc oxide particles before coating are substantially the same. Similarly, by coating zinc oxide particles with the metal soap, the average primary particle diameter of the metal soap-coated zinc oxide particles tends to be larger than the average primary particle diameter of the zinc oxide particles before coating with the metal soap, but the average primary particle diameter of the metal soap-coated zinc oxide particles and the average primary particle diameter of the zinc oxide particles before coating with the metal soap are substantially the same. Here, "substantially the same" means that the difference between the BET specific surface area of ​​the zinc oxide particles and the BET specific surface area of ​​the metal soap-coated zinc oxide particles is 5 m ２ This means that the molecular weight is about 1 / g.

[0048] The zinc oxide particles in this embodiment are preferably high-purity zinc oxide particles from the viewpoint of improving dispersion stability in the cosmetic. In addition, when high-purity zinc oxide particles are used, the whiteness of the surface-treated ultraviolet-shielding particles in this embodiment is increased, which is preferable. ＊ a ＊ b ＊ L in the color space chromaticity diagram ＊ The value is preferably 80 or more. ＊ The value may be 83 or more, or 85 or more. ＊ The value may be 99 or less, 95 or less, 93 or less, or 90 or less. ＊ The value may be -3.0 or greater, -2.0 or greater, or -1.0 or greater. ＊ The upper limit of the value is preferably 0. ＊ The value may be 15 or less, 10 or less, or 8 or less. ＊ The lower limit of the value is preferably 0.

[0049] The surface-treated ultraviolet shielding particles of this embodiment are hydrophobic and have excellent alcohol resistance because the surfaces of the ultraviolet shielding particles are sufficiently coated with the metal soap.

[0050] [Method for Producing Surface-Treated UV-Shielding Particles] The method for producing surface-treated UV-shielding particles of this embodiment is a method for producing surface-treated UV-shielding particles of this embodiment, and includes a step of heat-mixing UV-shielding particles with at least one metal soap selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate, and surface-treating the UV-shielding particles with the molten metal soap (hereinafter referred to as the "surface treatment step"). In the method for producing surface-treated UV-shielding particles of this embodiment, the heat-mixing is preferably performed without using a solvent. Here, "mixing without using a solvent" in the surface treatment step means that a solvent such as water or alcohol, which is added in conventional dry surface treatment methods or wet treatment methods, is not added. It is preferable to heat-mix only the UV-shielding particles and the metal soap. Note that the heat-mixing may be performed after mixing, or the metal soap may be heated and then heat-mixed, or mixing and heating may be performed simultaneously. The UV-shielding particles and the metal soap may be the same as those used in the surface-treated UV-shielding particles of this embodiment.

[0051] The temperature (heating temperature) at which the ultraviolet-shielding particles and the metal soap are heated is not particularly limited as long as it can melt the metal soap. That is, the heating temperature may be equal to or higher than the melting point of the metal soap and lower than the boiling point. The heating temperature may be, for example, 100°C or higher and 250°C or lower, 110°C or higher and 230°C or lower, or 120°C or higher and 200°C or lower. It may also be 130°C or higher and 180°C or lower, or 140°C or higher and 160°C or lower.

[0052] The time (mixing time) for mixing the ultraviolet-shielding particles and the metal soap is preferably such that the hydrophobicity of the surface-treated ultraviolet-shielding particles after mixing with 50°C ethanol is 25% or more. The mixing time may be, for example, 1 hour or more, 2 hours or more, or 3 hours or more. The mixing time may be 24 hours or less, 12 hours or less, or 8 hours or less. Experiments may be repeated multiple times in advance by changing the heating temperature, treatment temperature, stirring conditions, and other conditions to determine the preferred time, temperature, stirring conditions, and other conditions for obtaining the desired surface-treated ultraviolet-shielding particles.

[0053] The surface-treated ultraviolet-shielding particles of this embodiment can be produced by continuously mixing the ultraviolet-shielding particles and the molten metal soap with a stirring force of at least a certain level while maintaining the molten state of the metal soap by heating. The stirring force is not particularly limited as long as the desired hydrophobicity is obtained. Any device for heating and mixing can be selected. When heating and mixing is performed using a Henschel mixer, the peripheral speed may be, for example, 10 m / s or more and 60 m / s or less, or 12 m / s or more and 40 m / s or less.

[0054] According to the method for producing surface-treated ultraviolet-shielding particles of this embodiment, the metal soap is heated and mixed in a molten state at a high peripheral speed for a certain period of time or more without mixing a solvent, so that the surfaces of the ultraviolet-shielding particles can be uniformly and evenly surface-treated with the metal soap. In other words, it is possible to obtain surface-treated ultraviolet-shielding particles that are highly hydrophobic, have a high hydroxyl group treatment rate, and have excellent alcohol resistance.

[0055] The surface-treated ultraviolet-shielding particles after the surface treatment step may be crushed using a crusher. Crushing can suppress the roughness of the surface-treated ultraviolet-shielding particles. The surface-treated ultraviolet-shielding particles can be crushed using, for example, a known crusher. Examples of such crushers include an atomizer, a hammer mill, a jet mill, an impeller mill, and a pin mill. It is also preferable that the surface-treated ultraviolet-shielding particles of this embodiment are dried particles.

[0056] According to the method for producing surface-treated ultraviolet shielding particles of this embodiment, it is possible to obtain surface-treated ultraviolet shielding particles having excellent alcohol resistance.

[0057] [Dispersion] The dispersion of the present embodiment contains the surface-treated ultraviolet-shielding particles of the present embodiment and a dispersion medium. The dispersion of the present embodiment also includes a paste-like dispersion with high viscosity.

[0058] When used in cosmetics, the dispersion medium is not particularly limited as long as it can be formulated into the cosmetic and can disperse the surface-treated UV-shielding particles. Suitable dispersion media include, for example, water, alcohols, esters, ethers, natural oils, ester oils, and silicone oils. Examples of alcohols include methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, octanol, and glycerin. Examples of esters include ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone. Examples of ethers include 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.

[0059] Other dispersing media that can be used include ketones, aromatic hydrocarbons, cyclic hydrocarbons, amides, linear polysiloxanes, cyclic polysiloxanes, modified polysiloxanes, hydrocarbon oils, ester oils, silicone oils, higher fatty acids, and higher alcohols.

[0060] Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, and cyclohexanone. Examples of aromatic hydrocarbons include benzene, toluene, xylene, and ethylbenzene. Examples of cyclic hydrocarbons include cyclohexane. Examples of amides include dimethylformamide, N,N-dimethylacetoacetamide, and N-methylpyrrolidone. Examples of chain polysiloxanes include dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane.

[0061] Examples of cyclic polysiloxanes include octamethylcyclotetrasiloxane, cyclopentasiloxane (decamethylcyclopentasiloxane), dodecamethylcyclohexasiloxane, etc. Examples of modified polysiloxanes include amino-modified polysiloxane, polyether-modified polysiloxane, alkyl-modified polysiloxane, fluorine-modified polysiloxane, etc.

[0062] Examples of hydrocarbon oils include liquid paraffin, squalane, isoparaffin, branched light paraffin, petrolatum, and ceresin. Examples of ester oils include isopropyl myristate, cetyl isooctanoate, and glyceryl trioctanoate. Examples of silicone oils include decamethylcyclopentasiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane. Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, and stearic acid. Examples of higher alcohols include lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyldodecanol, and isostearyl alcohol.

[0063] The dispersion medium may be used alone or in combination of two or more thereof.

[0064] The dispersion of the present embodiment may contain commonly used additives to the extent that the properties of the dispersion are not impaired.

[0065] Suitable additives include, for example, preservatives, dispersants, dispersing aids, stabilizers, water-soluble binders, thickeners, oil-soluble drugs, oil-soluble dyes, oil-soluble proteins, UV absorbers, and the like.

[0066] The particle size (D50) of the surface-treated ultraviolet-shielding particles when the cumulative volume percentage of the particle size distribution in the dispersion of this embodiment is 50% can be selected arbitrarily, but is preferably 50 μm or less, more preferably 30 μm or less, and even more preferably 10 μm or less.

[0067] The lower limit of D50 in the dispersion of this embodiment is not particularly limited, and may be, for example, 130 nm or more, 140 nm or more, or 150 nm or more. The upper and lower limits of D50 can be combined in any manner.

[0068] Furthermore, the particle size (D90) of the surface-treated ultraviolet-shielding particles when the cumulative volume percentage of the particle size distribution in the dispersion of this embodiment is 90% can be selected arbitrarily, but is preferably 60 μm or less, more preferably 40 μm or less, and even more preferably 20 μm or less.

[0069] The lower limit of D90 in the dispersion of this embodiment is not particularly limited and may be, for example, 150 nm or more, 200 nm or more, or 250 nm or more. The upper and lower limit values ​​of D90 can be combined in any manner.

[0070] In the dispersion of this embodiment, D50 is preferably 50 μm or less, because when a cosmetic prepared using this dispersion is applied to the skin, the surface-treated ultraviolet-shielding particles are likely to be uniformly distributed, improving the ultraviolet-shielding effect. In addition, in the dispersion of this embodiment, D90 is preferably 60 μm or less, because the transparency of the dispersion is high, and the transparency of a cosmetic prepared using this dispersion is also high.

[0071] That is, when the D50 and D90 of the dispersion of this embodiment are within the above ranges, a dispersion having excellent transparency and excellent UV-shielding properties can be obtained. Furthermore, a cosmetic product prepared using this dispersion also has excellent transparency and UV-shielding properties.

[0072] The cumulative volume percentage of the particle size distribution in the dispersion can be measured using a wet dispersion unit of a laser diffraction particle size distribution measuring device.

[0073] The content of the surface-treated ultraviolet-shielding particles in the dispersion of this embodiment may be adjusted appropriately according to the desired properties.

[0074] When the dispersion of this embodiment is used in a cosmetic, the content of the surface-treated ultraviolet-shielding particles relative to the total mass of the dispersion can be selected arbitrarily, but is preferably 10% by mass or more, more preferably 20% by mass or more, and even more preferably 30% by mass or more. Furthermore, the content of the surface-treated ultraviolet-shielding particles relative to the total mass of the dispersion is 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 of the content of the surface-treated ultraviolet-shielding particles relative to the total mass of the dispersion can be arbitrarily combined.

[0075] When the content of the surface-treated ultraviolet-shielding particles in the dispersion is within the above range, the surface-treated ultraviolet-shielding particles are contained at a high concentration, which improves the degree of freedom in formulation and allows the viscosity of the dispersion to be at a level that makes it easy to handle.

[0076] The viscosity of the dispersion of this embodiment can be selected arbitrarily, but is preferably 5 Pa·s or more, more preferably 8 Pa·s or more, even more preferably 10 Pa·s or more, and most preferably 15 Pa·s or more. Furthermore, the viscosity of the dispersion is preferably 300 Pa·s or less, more preferably 100 Pa·s or less, even more preferably 80 Pa·s or less, and most preferably 60 Pa·s or less. The upper and lower limit values ​​of the viscosity of the dispersion can be arbitrarily combined.

[0077] When the viscosity of the dispersion is within the above range, it is possible to obtain a dispersion that is easy to handle even if it contains a high concentration of solids (surface-treated ultraviolet-shielding particles).

[0078] The method for producing the dispersion of this embodiment is not particularly limited. Examples of the method for producing the dispersion of this embodiment include a method in which the surface-treated ultraviolet-shielding particles of this embodiment and a dispersion medium are mechanically dispersed using a known dispersion device. The dispersion device can be selected as needed. Examples of the dispersion device include a stirrer, a planetary mixer, a homomixer, an ultrasonic homogenizer, a sand mill, a ball mill, and a roll mill.

[0079] The dispersion of this embodiment can be used in cosmetics as well as paints and the like that have ultraviolet blocking properties, gas permeation inhibiting properties, and the like.

[0080] According to the dispersion of the present embodiment, since the surface-treated ultraviolet-shielding particles of the present embodiment are contained, when the dispersion is blended into a cosmetic, for example, the feeling of roughness is suppressed and the transparency and ultraviolet-shielding properties are excellent.

[0081] [Composition] The composition of the present embodiment contains the dispersion of the present embodiment and a resin.

[0082] The content of the surface-treated ultraviolet-shielding particles relative to the total mass of the composition of this embodiment may be appropriately adjusted according to the desired properties. The content is, for example, preferably 10% by mass or more and 40% by mass or less, and more preferably 20% by mass or more and 30% by mass or less. The dispersion of this embodiment and the resin are mixed so that the content of the surface-treated ultraviolet-shielding particles relative to the total mass of the composition of this embodiment falls within the above-mentioned range.

[0083] When the content of the surface-treated ultraviolet-shielding particles relative to the total mass of the composition is within the above range, the solid content (surface-treated ultraviolet-shielding particles) is contained at a high concentration, so that the properties of the surface-treated ultraviolet-shielding particles can be fully obtained and a composition in which the surface-treated ultraviolet-shielding particles are uniformly dispersed can be obtained.

[0084] The resin is not particularly limited as long as it is one that is commonly used in industrial applications, and examples thereof include acrylic resin, epoxy resin, urethane resin, polyester resin, and silicone resin.

[0085] The content of the resin relative to the total mass of the composition of the present embodiment is not particularly limited and is adjusted appropriately depending on the desired properties of the composition.

[0086] The composition of the present embodiment may contain commonly used additives, such as a polymerization initiator, a dispersant, and a preservative, as long as the additives do not impair the properties of the composition.

[0087] The method for producing the composition of the present embodiment is not particularly limited, but examples thereof include a method in which the surface-treated ultraviolet-shielding particles of the present embodiment, a resin, and a dispersion medium are mechanically mixed using a known mixing device.

[0088] Another method is to mechanically mix the dispersion and the resin using a known mixer.

[0089] Examples of the mixing device include a stirrer, a planetary mixer, a homomixer, and an ultrasonic homogenizer.

[0090] A coating film can be formed by applying the composition of the present embodiment to an arbitrarily selected substrate, for example, 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, dipping, etc. These coating films can be used for arbitrarily selected purposes, for example, as an ultraviolet screening film or a gas barrier film.

[0091] According to the composition of this embodiment, since the surface-treated ultraviolet-shielding particles of this embodiment are contained, it is easy to mix with a resin and can exhibit excellent transparency and ultraviolet-shielding properties.

[0092] [Cosmetic] The cosmetic of the present embodiment contains at least one selected from the group consisting of the surface-treated ultraviolet-shielding particles of the present embodiment and the dispersion of the present embodiment, or the cosmetic of the present embodiment contains at least one selected from the group consisting of the surface-treated ultraviolet-shielding particles of the present embodiment, the dispersion of the present embodiment, and the composition of the present embodiment.

[0093] A cosmetic preparation in another embodiment contains a cosmetic base raw material and at least one selected from the group consisting of the surface-treated ultraviolet-shielding particles of this embodiment and the dispersion of this embodiment. Alternatively, a cosmetic preparation in another embodiment contains a cosmetic base raw material and at least one selected from the group consisting of the surface-treated ultraviolet-shielding particles of this embodiment, the dispersion of this embodiment, and the composition of this embodiment. In the cosmetic preparation, it is preferable to use zinc oxide particles as the ultraviolet-shielding particles.

[0094] Cosmetic base raw materials are the raw materials that form the base material of cosmetics. Examples of cosmetic base raw materials include oil-based raw materials, water-based raw materials, surfactants, powder raw materials, etc. Oil-based raw materials can be selected arbitrarily, and examples include fats and oils, higher fatty acids, higher alcohols, and ester oils.

[0095] The aqueous raw material can be selected arbitrarily, and examples thereof include purified water, alcohol, thickeners, and the like.

[0096] The powder raw material can be selected arbitrarily, and examples thereof include colored pigments, white pigments, pearlescent agents, extender pigments, and the like.

[0097] The cosmetic of this embodiment can be obtained, for example, by blending the dispersion of this embodiment with a cosmetic base material such as emulsion, cream, foundation, lipstick, blush, or eye shadow in a conventional manner.

[0098] The cosmetic of the present embodiment can be obtained, for example, by blending the surface-treated ultraviolet-shielding particles of the present embodiment into an oil phase or an aqueous phase to form an O / W or W / O emulsion, and then blending this with a cosmetic base raw material.

[0099] The content of the surface-treated ultraviolet-shielding particles relative to the total mass of the cosmetic of this embodiment may be adjusted appropriately depending on the desired properties. For example, the lower limit of the content of the surface-treated ultraviolet-shielding particles may be 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more. Furthermore, the upper limit of the content of the surface-treated ultraviolet-shielding particles 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-treated ultraviolet-shielding particles in the cosmetic can be combined in any manner.

[0100] Sunscreen cosmetics are described in detail below. In order to effectively block ultraviolet rays, particularly long-wavelength ultraviolet rays (UVA), and to achieve a pleasant feel when used with a sunscreen cosmetic that is less powdery or squeaky, it is also preferable to adjust the content of surface-treated ultraviolet-shielding particles. For example, the lower limit of the content of the surface-treated ultraviolet-shielding particles relative to the total mass of 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. Furthermore, the upper limit of the content of the surface-treated ultraviolet-shielding particles relative to the total mass of 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 the surface-treated ultraviolet-shielding particles relative to the total mass of the sunscreen cosmetic can be combined in any desired manner. Furthermore, within the above ranges, a preferred range can be selected as desired, such as 5% to 15% by mass or 10% to 20% by mass.

[0101] The sunscreen cosmetic may contain, as necessary, a hydrophobic dispersion medium, inorganic fine particles or inorganic pigments other than surface-treated UV-shielding particles, a hydrophilic dispersion medium, oils and fats, surfactants, moisturizers, thickeners, pH adjusters, nutrients, antioxidants, fragrances, preservatives, dispersants, antifoaming agents, colorants, cosmetic ingredients, polymeric substances, biologically derived ingredients, plant-derived ingredients, antibacterial agents, disinfectants, antifungal agents, aqueous ingredients, oily ingredients, vitamins, emulsifiers, stabilizers, solubilizers, pearlescent agents, refatting substances, and the like.

[0102] Examples of hydrophobic dispersion media include hydrocarbon oils, ester oils, silicone oils, higher fatty acids, and higher alcohols. Examples of hydrocarbon oils include liquid paraffin, squalane, isoparaffin, branched light paraffin, petrolatum, and ceresin. Examples of ester oils include isopropyl myristate, cetyl isooctanoate, and glyceryl trioctanoate. Examples of silicone oils include decamethylcyclopentasiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane. Examples of higher fatty acids include lauric acid, myristic acid, palmitic acid, and stearic acid. Examples of higher alcohols include lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyldodecanol, and isostearyl alcohol.

[0103] Examples of inorganic fine particles and inorganic pigments other than the surface-treated UV-shielding particles 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.

[0104] The sunscreen cosmetic may further contain at least one organic ultraviolet absorber. Cosmetics containing both surface-treated ultraviolet-shielding particles and an organic ultraviolet absorber are preferred because they have a booster effect that broadens the ultraviolet-shielding range and enhances the ultraviolet-shielding properties.

[0105] 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, silicone-based cinnamic acid ultraviolet absorbers, and triazine-based ultraviolet absorbers.

[0106] Examples of benzotriazole-based ultraviolet absorbers include 2,2'-hydroxy-5-methylphenylbenzotriazole, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole, and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole.

[0107] 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.

[0108] 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.

[0109] Examples of anthranilic acid-based ultraviolet absorbers include homomenthyl-N-acetylanthranilate.

[0110] 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.

[0111] Examples of cinnamic acid-based ultraviolet absorbers include octyl methoxycinnamate (ethylhexyl methoxycinnamate), glyceryl di-para-methoxycinnamate-mono-2-ethylhexanoate, 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-methyl Examples of suitable phenyl cinnamates include 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.

[0112] 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. Examples of triazine-based ultraviolet absorbers include bisethylhexyloxyphenol methoxyphenyl triazine, ethylhexyl triazone, methylene bisbenzotriazolyl tetramethylbutylphenol, trisbiphenyl triazine, and diethylhexyl butamido triazone.

[0113] 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, fluorine-modified ultraviolet absorbers, etc. The ultraviolet absorbers may be used alone or in combination of two or more.

[0114] The cosmetic of this embodiment preferably has a critical wavelength of 370 nm or longer. When the cosmetic has a critical wavelength of 370 nm or longer, it can block a wide range of ultraviolet rays, including long-wavelength ultraviolet rays (UVA) and short-wavelength ultraviolet rays (UVB).

[0115] According to the cosmetic of the present embodiment, since it contains at least one selected from the group consisting of the surface-treated ultraviolet-shielding particles of the present embodiment, the dispersion of the present embodiment, and the composition of the present embodiment, it is possible to obtain a cosmetic with excellent quality stability.

[0116] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0117] [Example 1] "Preparation of surface-treated zinc oxide particles" Zinc oxide particles A1 (BET specific surface area: 5 m ２ 97 parts by mass of zinc oxide particles B1 (100% sucrose / g, manufactured by Sumitomo Osaka Cement Co., Ltd.) and 3 parts by mass of magnesium stearate were mixed in a Henschel mixer heated to 130°C at a peripheral speed of 15 m / s for 4 hours to obtain surface-treated zinc oxide particles B1 of Example 1.

[0118] (Evaluation of Hydrophobicity by Limit Ethanol Method) The surface-treated zinc oxide particles B1 of Example 1 were evaluated by the limit ethanol method. As a result, it was confirmed that 10 or more particles settled when the ethanol ratio was 42%. That is, the hydrophobicity of the surface-treated zinc oxide particles of Example 1 was 42%. The results are shown in Table 1.

[0119] (Evaluation of hydrophobicity by limit ethanol method after mixing with ethanol at 50°C) 5 g of the surface-treated zinc oxide particles of Example 1 and 45 g of ethanol were mixed and stirred at 2000 rpm in a disper for 10 minutes while heated to 50°C. The mixed solution after stirring was subjected to solid-liquid separation, and the recovered solid portion (surface-treated zinc oxide particles) was dried at 40°C for 5 hours. The hydrophobicity of the dried surface-treated zinc oxide particles D1 was evaluated by the limit ethanol method, and the result was 42%. The results are shown in Table 1. That is, it was confirmed that there was no change in hydrophobicity even after mixing with ethanol at 50°C.

[0120] (Measurement of Hydroxyl Group Treatment Ratio) "Preparation of Red Dye" A mixed solution was prepared by mixing 1 mmol of 2,2'-dihydroxyazobenzene, 1 mmol of diphenyltin(IV) oxide, and 30 mL of acetone. Next, this mixed solution was stirred at 70°C for 3 hours to carry out a dehydration reaction, and diphenyltin oxide was coordinated to 2,2'-dihydroxyazobenzene. After the dehydration reaction, the mixed solution was filtered to recover the filtrate, and the solvent was distilled off from the filtrate to obtain the red dye represented by the general formula (1) above.

[0121] "Preparation of solution for evaluation" 250 nmol (0.12 mg) of the obtained red pigment was dissolved in toluene to make 5 mL, and 5 × 10 －５ The absorbance C2 of the evaluation solution C1 at 545 nm was measured using a spectrophotometer (model number: V-770, manufactured by JASCO Corporation).

[0122] 4.0 mg of zinc oxide particles A1 were added to solution C1, and the mixture was stirred and mixed at 60°C for 4 hours to prepare a mixed solution. This mixed solution was filtered through a syringe filter (0.2 µm), and the absorbance A2 of the filtrate at 545 nm was measured. 4.0 mg of surface-treated zinc oxide particles B1 of Example 1 were added to solution C1, and the mixture was stirred and mixed at 60°C for 4 hours to prepare a mixed solution. This mixed solution was filtered through a syringe filter (0.2 µm), and the absorbance B2 of the filtrate at 545 nm was measured.

[0123] The amount of red dye adsorbed to the zinc oxide particles A1 and the amount of red dye adsorbed to the surface-treated zinc oxide particles B1 were calculated using the above formulas (2) and (3). Amount of dye adsorbed to surface-treated zinc oxide particles B1 B3 = ((C2 - B2) / C2) × 250 × 10 －９ (mol) / 4×10 －３ (g) (3) Amount of dye adsorbed to zinc oxide particles A1 A3 = ((C2 - A2) / C2) × 250 × 10 －９ (mol) / 4×10 －３ (g) ... (2)

[0124] The hydroxyl group treatment rate of the surface-treated zinc oxide particles B1 of Example 1 was calculated by the above formula (4). The results are shown in Table 1. Hydroxyl group treatment rate=100−(B3 / A3×100) (4)

[0125] (Measurement of hydroxyl group treatment rate after mixing with ethanol at 50°C) The hydroxyl group treatment rate of surface-treated zinc oxide particles D1 after mixing with ethanol at 50°C was measured in the same manner as above. As a result, the hydroxyl group treatment rate of surface-treated zinc oxide particles D1 was 98.7%. The results are shown in Table 1. That is, it was confirmed that even after mixing with ethanol at 50°C, magnesium stearate was not liberated from the surface of the zinc oxide particles but remained attached to the surface of the zinc oxide particles.

[0126] [Example 2] Surface-treated zinc oxide particles of Example 2 were obtained in the same manner as in Example 1, except that 98 parts by mass of zinc oxide particles A1 and 2 parts by mass of magnesium stearate were used. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0127] [Example 3] Surface-treated zinc oxide particles of Example 3 were obtained in the same manner as in Example 1, except that 98.5 parts by mass of zinc oxide particles A1 and 1.5 parts by mass of magnesium stearate were used. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0128] [Example 4] BET specific surface area: 40 m ２ Surface-treated zinc oxide particles of Example 4 were obtained in the same manner as in Example 1, except that 90 parts by mass of zinc oxide particles having a molecular weight of 1 / g and 10 parts by mass of magnesium stearate were used. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0129] Surface-treated zinc oxide particles of Comparative Example 1 were obtained in the same manner as in Example 1, except that 99 parts by mass of zinc oxide particles A1 and 1 part by mass of magnesium stearate were used. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0130] Comparative Example 2 30 parts by mass of zinc oxide particles A1 and 70 parts by mass of pure water were mixed. 0.6 parts by mass of sodium stearate was added to the resulting mixture, which was then heated to 80° C. and mixed at 300 rpm for 2 hours. Subsequently, 15% by mass of MgCl ２ MgCl aqueous solution ２ The zinc oxide particles were surface-treated with magnesium stearate by adding magnesium stearate to the mixture so that the amount of magnesium stearate was 0.4 parts by mass and mixing was carried out at 80°C for 1 hour to substitute sodium for magnesium. That is, the zinc oxide particles were surface-treated with 2.5 parts by mass of magnesium stearate per 97.5 parts by mass of zinc oxide particles. The mixed liquid after the surface treatment was subjected to solid-liquid separation, and the surface-treated zinc oxide particles were recovered, washed, heat-treated at 130°C for 18 hours, and crushed to obtain surface-treated zinc oxide particles of Comparative Example 2. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0131] [Comparative Example 3] 97 parts by mass of zinc oxide particles A1 and 3 parts by mass of magnesium stearate were mixed in a Henschel mixer at a peripheral speed of 15 m / s for 4 hours at room temperature. The mixed particles were then heat-treated at 130°C for 18 hours and crushed to obtain surface-treated zinc oxide particles of Comparative Example 3. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0132] Surface-treated zinc oxide particles of Comparative Example 4 were obtained in the same manner as in Example 1, except that the peripheral speed during heating and mixing was set to 7 m / s. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0133] Surface-treated zinc oxide particles of Comparative Example 5 were obtained in the same manner as in Example 1, except that the heating and mixing time was changed to 30 minutes. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0134]

[0135] ​By comparing the examples and comparative examples, it was confirmed that zinc oxide particles surface-treated with a metal soap having a hydrophobicity of 25% or more after mixing with ethanol at 50°C can prevent the metal soap from being released from the surface of the zinc oxide particles even when mixed with ethanol at 50°C.

[0136] A comparison between the examples and comparative examples confirmed that the surface-treated ultraviolet-shielding particles of this embodiment can be obtained by mixing a molten metal soap and ultraviolet-shielding particles with a certain level of energy or higher without using a solvent. The surface-treated zinc oxide particles of this embodiment have excellent alcohol resistance. Therefore, they can be easily formulated into oil-based cosmetics and have excellent quality stability after being formulated into cosmetics.

[0137] The present invention provides ultraviolet-shielding particles that have been surface-treated with a specified metal soap and have excellent alcohol resistance. The surface-treated ultraviolet-shielding particles of the present invention are highly hydrophobic and have excellent alcohol resistance. As a result, they are easily mixed with various hydrophobic materials and have excellent quality stability in hydrophobic materials such as cosmetics. Therefore, the surface-treated ultraviolet-shielding particles of the present invention can easily ensure the design quality when applied to dispersions, compositions, paints, and cosmetics, and are of great industrial value.

Claims

1. Surface-treated ultraviolet-shielding particles that have been surface-treated with a metal soap, wherein the metal soap is at least one selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate, and the hydrophobicity of the ultraviolet-shielding particles after mixing with ethanol at 50°C is 25% or more.

2. The surface-treated ultraviolet-shielding particles according to claim 1, wherein the ultraviolet-shielding particles are at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, cerium oxide particles, and iron oxide particles.

3. BET specific surface area is 1.5m ２ / g or more 65m ２ 3. The surface-treated ultraviolet-shielding particles according to claim 1, wherein the surface-treated ultraviolet-shielding particles have a viscosity of 1 / g or less.

4. The surface-treated ultraviolet shielding particles according to any one of claims 1 to 3, wherein the hydroxyl group treatment rate after mixing with ethanol at 50°C is 90% or more.

5. A dispersion liquid containing the surface-treated ultraviolet-shielding particles according to any one of claims 1 to 4 and a dispersion medium.

6. A cosmetic comprising the surface-treated ultraviolet-shielding particles according to any one of claims 1 to 4.

7. A method for producing surface-treated ultraviolet-shielding particles according to claim 1, comprising the steps of heating and mixing ultraviolet-shielding particles with a metal soap and surface-treating the ultraviolet-shielding particles with the molten metal soap, wherein the metal soap is at least one selected from the group consisting of magnesium stearate, aluminum stearate, aluminum dimyristate, and aluminum myristate.

8. The method for producing surface-treated ultraviolet-shielding particles according to claim 7, wherein in the surface-treating step, only the ultraviolet-shielding particles and the metal soap are mixed, and the heating temperature in the heating and mixing is equal to or higher than the melting point temperature of the metal soap and lower than the boiling point.

9. The method for producing surface-treated ultraviolet-shielding particles according to claim 7 or 8, wherein the heating temperature during the heating and mixing is 100°C or higher and 250°C or lower, and the ultraviolet-shielding particles are at least one type selected from the group consisting of zinc oxide particles, titanium oxide particles, cerium oxide particles, and iron oxide particles.

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