Polysiloxane-coated metal oxide particles, dispersion liquid, composition, cosmetic, and method for producing polysiloxane-coated metal oxide particles

Abstract

The purpose of the present invention is to provide metal oxide particles which have excellent hydrophobicity and are coated with dimethyl polysiloxane. Another object of the present invention is to provide a dispersion, a composition and a cosmetic containing metal oxide particles coated with the dimethyl polysiloxane. Another object of the invention is to provide a method for producing such metal oxide particles coated with dimethyl polysiloxane. The present invention relates to polysiloxane-coated metal oxide particles, the surfaces of which are coated with dimethyl polysiloxane, and the detection rate of hydroxyl groups is 10% or less. The present invention relates to a polysiloxane-coated metal oxide particle, and a method for preparing the polysiloxane-coated metal oxide particle, the method comprising: a surface treatment step of mixing a metal oxide particle with a dimethyl polysiloxane having a kinematic viscosity at 25 DEG C of 500 mm2 / s or more and 4000 mm2 / s or less without using a solvent to coat the surface of the metal oxide particle with the dimethyl polysiloxane; and a step for heat-treating the metal oxide particles coated with dimethyl polysiloxane at 250 DEG C or more and 380 DEG C or less.

Description

Technical Field

[0001] The present invention relates to a polysiloxane-coated metal oxide particle, a dispersion, a composition, a cosmetic, and a method for producing the polysiloxane-coated metal oxide particle.

[0002] This application claims priority based on Japanese Patent Application No. 2022-164568 filed in Japan on October 13, 2022, and the contents thereof are incorporated herein by reference. Background Art

[0003] Metal oxide particles such as titanium oxide, zinc oxide, and zirconium oxide have various properties. For example, optical properties, mechanical properties, thermal properties, electrical properties, etc.

[0004] Hydroxyl groups exist on the surface of the metal oxide particles. Therefore, it is difficult to directly mix the metal oxide particles with hydrophobic materials.

[0005] Therefore, the metal oxide particles are surface-treated with a hydrophobic surface treatment agent and then mixed into oil-based cosmetics, paints containing organic solvents, and compositions containing hydrophobic resins for use.

[0006] For example, zinc oxide particles are used in cosmetics such as sunscreen and foundation. When applying zinc oxide particles to cosmetics, the surface treatment of the zinc oxide particles is performed to make the surface state of the zinc oxide particles conform to the properties of the cosmetics. As one of such surface treatment agents for zinc oxide particles, silicone oils such as dimethylpolysiloxane or methylhydrogenpolysiloxane are used (for example, refer to Patent Document 1).

[0007] For example, Patent Document 2 proposes a fingerprint collection powder obtained by surface-treating pigments such as titanium oxide, aluminum oxide, and zinc oxide with dimethylpolysiloxane or the like.

[0008] Prior Art Documents

[0009] Patent Documents

[0010] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-12679

[0011] Patent Document 2: Japanese Unexamined Patent Application Publication No. 10-155774 Summary of the Invention

[0012] Problems to be Solved by the Invention

[0013] However, the hydrophobicity of the metal oxide particles coated with dimethylpolysiloxane on the surface is insufficient. Therefore, it is difficult to mix the metal oxide particles coated with dimethylpolysiloxane on the surface with materials such as highly hydrophobic oil-based materials or resins. Therefore, metal oxide particles coated with dimethylpolysiloxane having higher hydrophobicity are required.

[0014] The present invention has been completed in view of the above circumstances, and an object thereof is to provide metal oxide particles having excellent hydrophobicity and coated with dimethylpolysiloxane. Another object thereof is to provide a dispersion, a composition, and a cosmetic containing the metal oxide particles coated with dimethylpolysiloxane. Still another object thereof is to provide a method for producing the metal oxide particles coated with dimethylpolysiloxane.

[0015] Means for Solving the Problems

[0016] The present invention has the following aspects.

[0017] [1] A polysiloxane-coated metal oxide particle, wherein the surface of the metal oxide particle is coated with dimethylpolysiloxane, and

[0018] the hydroxyl group detection rate calculated based on the adsorption amount of a red pigment adsorbed on the hydroxyl groups present on the surface of the metal oxide particle before being coated with the dimethylpolysiloxane and the adsorption amount of the red pigment adsorbed on the hydroxyl groups present on the surface of the metal oxide particle after being coated with the dimethylpolysiloxane is 10% or less.

[0019] [2] The polysiloxane-coated metal oxide particle according to [1], wherein

[0020] the content of the metal oxide particle is 80% by mass or more and 99% by mass or less.

[0021] [3] A dispersion containing the polysiloxane-coated metal oxide particle according to [1] or [2] and a dispersion medium.

[0022] [4] A composition containing the dispersion according to [3] and a resin.

[0023] [5] A cosmetic containing the polysiloxane-coated metal oxide particle according to [1] or [2].

[0024] [6] A cosmetic containing the dispersion according to [3].

[0025] [7] A method for producing a polysiloxane-coated metal oxide particle, which is a method for producing the polysiloxane-coated metal oxide particle according to [1] or [2], and has:

[0026] a surface treatment step of mixing the metal oxide particle and dimethylpolysiloxane having a kinematic viscosity at 25°C of 500 mm 2 / s or more and 4000 mm 2 / s or less without using a solvent, and coating the surface of the metal oxide particle with the dimethylpolysiloxane; and

[0027] A step of heat-treating the metal oxide particles coated with the dimethylpolysiloxane under the condition of higher than 100°C and lower than 380°C.

[0028] [8] A method for manufacturing polysiloxane-coated metal oxide particles, which is the method for manufacturing polysiloxane-coated metal oxide particles described in [1] or [2], and has:

[0029] A surface treatment step of heating and mixing metal oxide particles and dimethylpolysiloxane having a kinematic viscosity at 25°C of 500 mm 2 / s or more and 4000 mm 2 / s or less without using a solvent, and coating the surface of the metal oxide particles with the dimethylpolysiloxane.

[0030] The temperature of the heating and mixing in the surface treatment step is higher than 100°C and lower than 380°C.

[0031] [9] The method for manufacturing polysiloxane-coated metal oxide particles according to [7] or [8], which further has the following steps:

[0032] Prepare the following solutions: solution C1 in which a red pigment is dissolved in toluene, solution A1 obtained by removing the particles after mixing the metal oxide particles before coating and solution C1, and solution B1 obtained by removing the particles after mixing the coated metal oxide particles obtained by the heat treatment or heating and mixing and solution C1;

[0033] Measure the absorbance of the three solutions at a wavelength of 545 nm respectively; according to the three measured absorbances, calculate the adsorption amounts of the red pigment on the metal oxide particles before and after coating respectively; according to the calculated adsorption amounts of the red pigment, calculate the hydroxyl detection rate of the coated metal oxide particles;

[0034] Determine whether the calculated hydroxyl detection rate is 10% or less; and

[0035] In the case where it is determined that the hydroxyl detection rate is 10% or less, determine the coated metal oxide particles as qualified products.

[0036]

[10] The polysiloxane-coated metal oxide particles according to [1] or [2], wherein

[0037] The metal oxide particles are at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, iron oxide particles, and cerium oxide particles.

[0038]

[11] The polysiloxane-coated metal oxide particles according to [1] or [2], wherein,

[0039] the metal oxide particles are dry particles containing zinc oxide particles as the metal oxide particles.

[0040]

[12] The polysiloxane-coated metal oxide particles according to [1] or [2], wherein,

[0041] the dimethylpolysiloxane has a kinematic viscosity at 25 °C of 500 mm 2 / s or more and 4000 mm 2 / s or less and is the dimethylpolysiloxane represented by the following general formula (6).

[0042] [Chemical formula 1]

[0043]

[0044]

[13] The polysiloxane-coated metal oxide particles according to [1] or [2], wherein,

[0045] the hydroxyl detection rate is obtained as follows:

[0046] Prepare the following solutions: a solution C1 in which 250 nmol of a red pigment represented by the following general formula (1) is dissolved in 5 ml of toluene, a solution A1 obtained by removing the particles after mixing the metal oxide particles before being coated with the dimethylpolysiloxane and the solution C1, and a solution B1 obtained by removing the particles after mixing the metal oxide particles after being coated with the dimethylpolysiloxane and the solution C1;

[0047] Measure the absorbances of the three solutions at a wavelength of 545 nm, respectively;

[0048] According to the three measured absorbances, respectively calculate the adsorption amounts A3 and B3 of the red pigment on the metal oxide particles before and after coating from the following formula,

[0049] Adsorption amount = ((Absorbance of solution C1 - Absorbance of solution A1 or B1) / Absorbance of solution C1) × 250 × 10 -9 (mol) / Amount of the metal oxide particles (g); and

[0050] According to the obtained adsorption amounts A3 and B3, calculate the hydroxyl detection rate through the calculation based on the following formula.

[0051] Detection rate of hydroxyl (%) = (B3 / A3) × 100

[0052] [Chemical formula 2]

[0053]

[0054] Effect of the Invention

[0055] According to the present invention, it is possible to provide metal oxide particles coated with polysiloxane having excellent hydrophobicity. Further, according to the present invention, it is possible to provide a dispersion, a composition, and a cosmetic containing such metal oxide particles coated with polysiloxane. Further, according to the present invention, it is possible to provide a method for producing such metal oxide particles coated with polysiloxane. Detailed Description of the Invention

[0056] Embodiments of the metal oxide particles coated with polysiloxane, the dispersion, the composition, the cosmetic, and the method for producing the metal oxide particles coated with polysiloxane of the present invention will be described.

[0057] In addition, the present embodiment is specifically described for better understanding the gist of the invention, and the present invention is not limited unless otherwise specifically specified. For example, unless otherwise particularly limited, conditions such as materials, amounts, types, quantities, sizes, ratios, temperatures, etc. can be changed, added, and omitted as needed. Between the embodiments described below, preferred examples can be replaced or shared with each other.

[0058] First, before describing the present invention in detail, the conceptions of the present inventors for completing the present invention will be described.

[0059] As described in Patent Document 1, in the case of surface-treating metal oxide particles with dimethylpolysiloxane, a method of mixing dimethylpolysiloxane dissolved in a solvent such as isopropyl alcohol and zinc oxide particles and performing heat treatment is generally used. Further, in order to sufficiently coat the surface of the metal oxide particles, dimethylpolysiloxane having a kinematic viscosity at 25°C of 50 mm 2 / s to 500 mm 2 / s is generally used.

[0060] In order to improve the hydrophobicity of the metal oxide particles, for example, dimethylpolysiloxane having a high kinematic viscosity can be considered. However, if dimethylpolysiloxane having a high kinematic viscosity is used, it is difficult to sufficiently coat the surface of the metal oxide particles by the conventional method.

[0061] As a result of various studies conducted by the present inventors, it has been found that by treating at a high temperature with dimethylpolysiloxane having a high hybrid viscosity without using a solvent, the surface of the metal oxide particles is sufficiently coated with dimethylpolysiloxane. That is, it has been found that dimethylpolysiloxane-coated metal oxide particles having high hydrophobicity can be obtained. In addition, by performing coating and heating, on the surface of the dimethylpolysiloxane-coated metal oxide particles, the methyl groups of the dimethylpolysiloxane are present in a state facing outward on the surface of the metal oxide particles, and thus the hydrophobicity of the metal oxide particles can be improved. In the present specification, the metal oxide particles coated with dimethylpolysiloxane are sometimes simply referred to as polysiloxane-coated metal oxide particles, rather than dimethylpolysiloxane-coated metal oxide particles.

[0062] More specifically, the present inventors have conducted various studies and found the following. As the kinematic viscosity of dimethylpolysiloxane increases, it becomes difficult to uniformly mix with a solvent. In addition, if a highly hydrophobic solvent is used, the above-mentioned dimethylpolysiloxane can be dissolved. However, such a highly hydrophobic solvent easily remains in the polysiloxane-coated metal oxide particles and is difficult to use in applications such as cosmetics.

[0063] And dimethylpolysiloxane having a low kinematic viscosity, for example, dimethylpolysiloxane having a kinematic viscosity of about 100 mm 2 / s at 25°C is likely to volatilize and is difficult to process at a high temperature.

[0064] Therefore, then, the present inventors studied the following: In order to uniformly and sufficiently coat the particle surface, without using a solvent that was previously considered essential, and coat the metal oxide particles with dimethylpolysiloxane having a high kinematic viscosity. As a result, it has been found that by mixing dimethylpolysiloxane having a kinematic viscosity within a specified range without using a solvent and performing heat treatment at a high temperature, the hydroxyl groups on the surface of the metal oxide particles can be sufficiently coated, and thus the present invention has been completed.

[0065] [Polysiloxane-coated metal oxide particles]

[0066] The polysiloxane-coated metal oxide particles of the present embodiment are metal oxide particles whose surface is coated with dimethylpolysiloxane, and the hydroxyl group detection rate calculated based on the adsorption amount of the red pigment adsorbed on the hydroxyl groups present on the surface of the metal oxide particles before being coated with the dimethylpolysiloxane and the adsorption amount of the red pigment adsorbed on the hydroxyl groups present on the surface of the metal oxide particles after being coated with the dimethylpolysiloxane is 10% or less. The polysiloxane-coated metal oxide particles can be dry particles.

[0067] A hydroxyl group detection rate of 10% or less may mean that no hydroxyl groups are detected on the surface of the metal oxide particles, that is, the surface of the metal oxide particles is sufficiently coated with dimethylpolysiloxane. Therefore, the polysiloxane-coated metal oxide particles of the present embodiment have excellent hydrophobicity.

[0068] The method for measuring the hydroxyl group detection rate of the present embodiment will be described.

[0069] In this specification, the "hydroxyl group detection rate" refers to a value measured using a red pigment that absorbs light near a wavelength of 545 nm represented by the following general formula (1).

[0070] [Chemical formula 3]

[0071]

[0072] The red pigment represented by the general formula (1) can be produced, for example, by the following method.

[0073] 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.

[0074] Next, the mixed solution is stirred at 70 °C for 3 hours to carry out a dehydration reaction, and diphenyltin oxide is coordinated with 2,2'-dihydroxyazobenzene.

[0075] The mixed solution after the dehydration reaction is filtered to recover the filtrate, and the solvent is distilled off from the filtrate, whereby the above red pigment can be obtained.

[0076] The above red pigment selectively adsorbs to the hydroxyl groups present on the surface of the metal oxide particles and does not react with hydroxyl groups such as water or alcohol. Also, the above red pigment does not react with dimethylpolysiloxane. Therefore, the above red pigment can qualitatively and quantitatively evaluate the amount of metal hydroxyl groups present on the surface of the metal oxide particles or the polysiloxane-coated metal oxide particles without being affected by moisture.

[0077] Hydroxyl groups exist on the surface of the metal oxide particles. Therefore, the red pigment is adsorbed on the metal oxide particles before being coated with dimethylpolysiloxane. On the other hand, the hydroxyl groups at the coated part of the metal oxide particles coated with dimethylpolysiloxane are not exposed on the surface of the polysiloxane-coated metal oxide particles. Therefore, the more the surface of the metal oxide particles is coated with dimethylpolysiloxane, the smaller the hydroxyl detection rate obtained by the following formula. Therefore, by investigating the adsorption amount of the above red pigment on the metal oxide particles before coating and the adsorption amount of the above red pigment on the coated metal oxide particles (polysiloxane-coated metal oxide particles), the coating degree of dimethylpolysiloxane on the metal oxide particles can be investigated. That is, it means that the smaller the hydroxyl detection rate, the more the surface of the metal oxide particles is hydrophobized by being coated with dimethylpolysiloxane.

[0078] The hydroxyl detection rate is preferably 8.0% or less, more preferably 7.5% or less, and further preferably 7.0% or less. The lower limit of the hydroxyl detection rate is 0%, and it can be 0.1%, 0.5%, or 1.0%. The hydroxyl detection rate can be 0.3% - 9.0%, 1.5% - 8.5%, 2.0 - 6.0%, 3.0 - 5.0%, etc. as required.

[0079] The hydroxyl detection rate in this embodiment is calculated based on the adsorption amounts of the above red pigment before and after coating.

[0080] That is, when the adsorption amount before coating based on the above red pigment is set as A and the adsorption amount after coating based on the above red pigment is set as B, the hydroxyl detection rate of the polysiloxane-coated metal oxide particles in this embodiment is calculated by the formula shown by (B / A)×100.

[0081] Specifically, the hydroxyl detection rate (%) based on the above red pigment can be measured by the following method, for example.

[0082] By dissolving 250 nmol (0.12 mg) of the above red pigment in toluene to make 5 mL, an evaluation solution C1 of 5×10 -5 mol / L is obtained. The absorbance C2 of the solution C1 is measured at a wavelength of 545 nm. The absorbance can be measured using a spectrophotometer (model: V-770, manufactured by JASCO Corporation), for example. The unit of the absorbance can be Abs.

[0083] xg of the metal oxide particles before coating is 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 metal oxide particles are removed from this mixed solution by centrifugation or filtration, etc., to obtain an evaluation mixed solution A1 (the mixed solution A1 after mixing). The absorbance A2 of this mixed solution A1 is measured at a wavelength of 545 nm.

[0084] Add yg of the polysiloxane-coated metal oxide particles to be measured to the evaluation solution C1, and stir and mix at 60 °C for 4 hours to prepare a mixed solution. Remove the polysiloxane-coated metal oxide particles from the mixed solution by centrifugation or filtration, etc., to obtain the evaluation mixed solution B1 (the mixed solution B1 after mixing). Measure the absorbance B2 of the mixed solution B1 at a wavelength of 545 nm.

[0085] In addition, x and y can be adjusted according to the BET specific surface area of the metal oxide particles. For example, x and y are 1 to 50 mg. When the BET specific surface area is 40 m 2 / g, x and y are preferably about 4 × 10 -3 g. When the BET specific surface area is 5 m 2 / g, x and y are preferably about 32 × 10 -3 g. x and y are preferably the same value.

[0086] The adsorption amount (mol / g) of the above red pigment on the metal oxide particles before coating is calculated by the following general formula (2).

[0087] Adsorption amount A3 = ((C2 - A2) / C2) × 250 × 10 -9 (mol) / x (g)......(2)

[0088] The adsorption amount (mol / g) of the above red pigment on the polysiloxane-coated metal oxide particles is calculated by the following general formula (3).

[0089] Adsorption amount B3 = ((C2 - B2) / C2) × 250 × 10 -9 (mol) / y (g)......(3)

[0090] In the general formulas (2) and (3), the decrease in absorbance means that the pigment is adsorbed. Therefore, the adsorption amount of the above red pigment is calculated based on the idea that the reduction rate convertible to absorbance = the adsorption rate of the pigment. In addition, the general formula (2) or (3) can be expressed as adsorption amount = ((absorbance of solution C1 - absorbance of solution A1 or B1) / absorbance of solution C1) × 250 × 10 -9 (mol) / the amount (g) of the metal oxide particles.

[0091] The detection rate of hydroxyl groups can be calculated by the following general formula (4).

[0092] Detection rate of hydroxyl groups (%) = (B3 / A3) × 100......(4)

[0093] The hydroxyl group detection rate of the polysiloxane-coated metal oxide particles of the present embodiment is 10% or less. When the hydroxyl group detection rate is 10% or less, the surface of the metal oxide particles is sufficiently coated with dimethylpolysiloxane. Therefore, the polysiloxane-coated metal oxide particles of the present embodiment have excellent hydrophobicity.

[0094] In the total mass of the polysiloxane-coated metal oxide particles of the present embodiment, the metal oxide particles preferably contain 80% by mass or more and 99% by mass or less, more preferably 85% by mass or more and 99% by mass or less, still more preferably 90% by mass or more and 99% by mass or less, and particularly preferably 95% by mass or more and 99% by mass or less. By the content of the metal oxide particles being within the above range, in order to exhibit the inherent properties of the metal oxide particles, the amount added to cosmetics and the like can be reduced. Therefore, the degree of freedom in formulating cosmetics and the like can be increased.

[0095] The polysiloxane-coated metal oxide particles of the present embodiment may consist only of dimethylpolysiloxane and metal oxide particles, in addition to unavoidably contained impurities. Alternatively, as long as it does not interfere with the object of the present invention, the polysiloxane-coated metal oxide particles of the present embodiment may contain a surface treatment agent other than dimethylpolysiloxane.

[0096] The BET specific surface area of the polysiloxane-coated metal oxide particles of the present embodiment can be adjusted according to the use and is not particularly limited. For example, when used in cosmetic applications, the BET specific surface area is preferably 1.5 m 2 / g or more and 65 m 2 / g or less.

[0097] In this specification, "BET specific surface area" 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 MOUNTECH Co., Ltd.).

[0098] (BET specific surface area of polysiloxane-coated metal oxide particles)

[0099] The preferred BET specific surface area of the polysiloxane-coated metal oxide particles when used in cosmetic applications will be described.

[0100] The BET specific surface area of the polysiloxane-coated metal oxide particles can be arbitrarily selected, but is preferably 1.5 m 2 / g or more, more preferably 2.5 m 2 / g or more, still more preferably 3.5 m 2 / g or more. Further, the BET specific surface area of the polysiloxane-coated metal oxide particles is preferably 65 m 2 / g or less, more preferably 60 m 2 / g or less. For example, it may be 40 m 2 / g or less, 30 m 2 / g or less, 20 m 2 / g or less, 10 m 2 / g or less. As needed, the BET specific surface area of the polysiloxane-coated metal oxide particles may be 8 m 2 / g or less, or may be 6.0 m 2 / g or less. The above upper and lower limit values of the BET specific surface area of the polysiloxane-coated metal oxide particles can be arbitrarily combined.

[0101] When the BET specific surface area of the polysiloxane-coated metal oxide particles is 1.5 m 2 / g or more and 65 m 2 / g or less, it is excellent in transparency and ultraviolet shielding property when incorporated into cosmetics.

[0102] When the BET specific surface area of the polysiloxane-coated metal oxide particles is 1.5 m 2 / g or more and 8 m 2 / g or less, the hydrophobicity is more excellent.

[0103] In addition, the value change of the BET specific surface area of the metal oxide particles before being coated with dimethylpolysiloxane and the BET specific surface area of the metal oxide particles after being coated with dimethylpolysiloxane (polysiloxane-coated metal oxide particles) is not significant.

[0104] (Average primary particle diameter of polysiloxane-coated metal oxide particles)

[0105] The average primary particle diameter of the polysiloxane-coated metal oxide particles of the present embodiment is preferably 15 nm or more, more preferably 20 nm or more. It may also be 50 nm or more, 80 nm or more, 100 nm or more. From the viewpoint of improving the hydrophobicity of the polysiloxane-coated zinc oxide particles, the average primary particle diameter is preferably 130 nm or more, more preferably 150 nm or more, and further preferably 200 nm or more. Further, the average primary particle diameter of the polysiloxane-coated metal oxide particles of the present embodiment is preferably 300 nm or less, more preferably 270 nm or less, and further preferably 250 nm or less.

[0106] When the average primary particle diameter of the polysiloxane-coated metal oxide particles is 15 nm or more and 300 nm or less, it is excellent in transparency and ultraviolet shielding property when incorporated into cosmetics.

[0107] The average primary particle diameter of the above-mentioned polysiloxane-coated metal oxide particles can be calculated using the BET specific surface area of the above-mentioned polysiloxane-coated metal oxide particles and by the following general formula (5).

[0108] Average primary particle diameter (nm) = 6000 / (BET specific surface area (m 2 / g) × ρ (g / cm 3 ))... (5)

[0109] (In the formula, ρ is set to the density of the metal oxide particles, 5.61 g / cm 3 .)

[0110] Alternatively, the average primary particle diameter of the above-mentioned polysiloxane-coated metal oxide particles can also be obtained by the following method. That is, when observing the above-mentioned dimethyl polysiloxane-coated metal oxide particles using a transmission electron microscope (TEM) or the like, a specified number (for example, 200 or 100) of polysiloxane-coated metal oxide particles are selected. Then, the longest straight-line part (maximum major axis) of each of these polysiloxane-coated metal oxide particles is measured, and the arithmetic mean of these measured values is taken.

[0111] In addition, when the polysiloxane-coated metal oxide particles are aggregated with each other, the aggregated particle diameter of the aggregate is not measured. A specified number of polysiloxane-coated metal oxide particles (primary particles) constituting the aggregate are measured and set as the average primary particle diameter.

[0112] (Metal oxide particles)

[0113] The metal oxide particles in this embodiment are not particularly limited. When the polysiloxane-coated metal oxide particles in this embodiment are used as a refractive index regulator, for example, it is preferably used to contain at least one selected from the group consisting of zinc oxide particles, titanium oxide particles, iron oxide particles, cerium oxide particles, zirconium oxide particles, aluminum oxide particles, copper oxide particles, tin oxide particles, tantalum oxide particles, niobium oxide particles, tungsten oxide particles, europium oxide particles, yttrium oxide particles, molybdenum oxide particles, indium oxide particles, antimony oxide particles, germanium oxide particles, bismuth oxide particles, hafnium oxide particles, and potassium titanate particles, barium titanate particles, strontium titanate particles, potassium niobate particles, lithium niobate particles, calcium tungstate particles, antimony-doped tin oxide particles, and indium-doped tin oxide particles.

[0114] When the polysiloxane-coated metal oxide particles in this embodiment are used as an ultraviolet shielding material such as cosmetics, zinc oxide particles, titanium oxide particles, iron oxide particles, and cerium oxide particles having ultraviolet shielding properties can be used. From the viewpoint of a wide ultraviolet wavelength region that can be shielded, zinc oxide particles are preferably used.

[0115] (Zinc oxide particles)

[0116] The BET specific surface area of the zinc oxide particles in the present embodiment is preferably 1.5 m 2 / g or more and 65 m 2 / g or less. The BET specific surface area is more preferably 2.5 m 2 / g or more, and further preferably 4 m 2 / g or more. Also, the BET specific surface area of the zinc oxide particles can be, for example, 60 m 2 / g or less, can be 55 m 2 / g or less, can be 50 m 2 / g or less, can be 45 m 2 / g or less. As needed, the BET specific surface area of the zinc oxide particles can be 40 m 2 / g or less, can be 30 m 2 / g or less, can be 10 m 2 / g or less. The above upper and lower limit values of the BET specific surface area of the zinc oxide particles can be arbitrarily combined. If the BET specific surface area of the zinc oxide particles is less than the lower limit value, the transparency will decrease when compounded in cosmetics, so it is not preferred. If the BET specific surface area of the zinc oxide particles exceeds the upper limit value, when zinc oxide particles coated with dimethylpolysiloxane (hereinafter referred to as "polysiloxane-coated zinc oxide particles") are contained at a high concentration in cosmetics, the particles sometimes tend to aggregate, so it is not preferred.

[0117] From the viewpoint of improving the hydrophobicity of the polysiloxane-coated zinc oxide particles, the BET specific surface area of the zinc oxide particles is preferably 10.0 m 2 / g or less, more preferably 8.2 m 2 / g or less, further preferably 7.1 m 2 / g or less, and even more preferably 6.0 m 2 / g or less.

[0118] The smaller the BET specific surface area of the zinc oxide particles, the more the aggregation of the particles is suppressed, and the less the uncoated part is, so the alcohol resistance is excellent.

[0119] The BET specific surface area of the zinc oxide particles in the present embodiment means the value measured by the BET method using a fully automatic specific surface area measuring device (trade name: Macsorb HM Model-1201, manufactured by MOUNTECH Co., Ltd.).

[0120] In the present embodiment, the average primary particle diameter of the zinc oxide particles is preferably 15 nm or more, more preferably 20 nm or more. From the viewpoint of improving the hydrophobicity of the polysiloxane-coated zinc oxide particles, it is preferably 130 nm or more, more preferably 150 nm or more, and further preferably 200 nm or more. Further, the average primary particle diameter of the zinc oxide particles in the present embodiment is preferably 300 nm or less, more preferably 270 nm or less, and further preferably 250 nm or less.

[0121] When the average primary particle diameter of the above zinc oxide particles is 15 nm or more and 300 nm or less, the transparency and ultraviolet shielding properties are excellent when compounded in cosmetics.

[0122] When the average primary particle diameter of the above zinc oxide particles is 130 nm or more and 300 nm or less, polysiloxane-coated zinc oxide particles with excellent alcohol resistance can be obtained.

[0123] Similar to the BET-converted particle diameter of the above polysiloxane-coated metal oxide particles, the average primary particle diameter of the above zinc oxide particles can be calculated using the BET specific surface area of the above zinc oxide particles and the above general formula (5).

[0124] Further, similar to the average primary particle diameter of the above polysiloxane-coated metal oxide particles, the average primary particle diameter of the above zinc oxide particles can be measured using a transmission electron microscope.

[0125] The hydrophobicity of the polysiloxane-coated metal oxide particles of the present embodiment based on the critical ethanol method is preferably 16% or more, more preferably 19% or more, further preferably 22% or more, and still more preferably 35% or more.

[0126] Further, the hydrophobicity of the polysiloxane-coated metal oxide particles after mixing with ethanol at 50 °C based on the critical ethanol method is preferably 16% or more, more preferably 19% or more, further preferably 22% or more, and still more preferably 35% or more.

[0127] Since the hydroxyl detection rate of the polysiloxane-coated metal oxide particles of the present embodiment is 10% or less, the hydrophobicity based on the critical ethanol method can be made 16% or more, and high hydrophobicity can be maintained even after mixing with ethanol at 50 °C.

[0128] The evaluation method for the hydrophobicity based on the critical ethanol method of the present embodiment will be described.

[0129] In the present specification, the critical ethanol method refers to a method in which polysiloxane-coated metal oxide particles are added to a solution of water and ethanol, and whether the polysiloxane-coated metal oxide particles precipitate is observed.

[0130] Moreover, the critical ethanol method is as follows: If the polysiloxane-coated metal oxide particles do not precipitate, the ethanol ratio is increased. When the polysiloxane-coated metal oxide particles precipitate, the water ratio is increased. Thus, the degree of hydrophobicity of the surface of the polysiloxane-coated metal oxide particles is evaluated by the ethanol ratio (by mass) required for the precipitation of the polysiloxane-coated metal oxide particles.

[0131] The higher the ethanol ratio, the more the surface of the metal oxide particles is hydrophobized by dimethylpolysiloxane and the higher the hydroxyl treatment rate.

[0132] In this specification, the "polysiloxane-coated metal oxide particles after mixing with ethanol at 50 °C" may mean the polysiloxane-coated metal oxide particles in a state where 5 g of the polysiloxane-coated metal oxide particles of the present embodiment and 45 g of ethanol are mixed, stirred at 2000 revolutions per minute for 10 minutes with a disperser in a state heated to 50 °C, the stirred mixture is subjected to solid-liquid separation, and the recovered solid is dried at 40 °C for 5 hours.

[0133] In the present embodiment, by coating zinc oxide particles with dimethylpolysiloxane, the BET specific surface area of the polysiloxane-coated zinc oxide particles tends to be smaller than that of the zinc oxide particles before being coated with dimethylpolysiloxane, but the BET specific surface area of the polysiloxane-coated zinc oxide particles and the BET specific surface area of the zinc oxide particles before coating are substantially of the same magnitude. Similarly, by coating the zinc oxide particles, the average primary particle size of the polysiloxane-coated zinc oxide particles tends to be larger than that of the zinc oxide particles before being coated with dimethylpolysiloxane, but the average primary particle size of the polysiloxane-coated zinc oxide particles and the average primary particle size of the zinc oxide particles before coating with dimethylpolysiloxane are substantially of the same magnitude. Here, substantially the same magnitude means that the difference in the BET specific surface area between the zinc oxide particles and the polysiloxane-coated zinc oxide particles is about 5 m 2 / g.

[0134] From the viewpoint of improving the dispersion stability in cosmetics, high-purity zinc oxide particles are preferably used for the zinc oxide particles in the present embodiment.

[0135] (dimethylpolysiloxane)

[0136] The dimethylpolysiloxane in the present embodiment is represented by the following general formula (6).

[0137] In addition, the dimethylpolysiloxane of the present embodiment is also known as dimethyl silicone oil.

[0138] [Chemical formula 4]

[0139]

[0140] In the above general formula (6), n may be appropriately selected as long as the hydroxyl group detection rate of the polysiloxane-coated metal oxide particles is 10% or less. For example, n is preferably 220 or more and 570 or less, more preferably 250 or more and 500 or less, and still more preferably 300 or more and 400 or less.

[0141] In the present embodiment, the molecular weight of the dimethylpolysiloxane is preferably 16,000 or more and 42,000 or less, more preferably 20,000 or more and 39,000 or less, still more preferably 22,000 or more and 34,000 or less, and even more preferably 24,000 or more and 30,000 or less.

[0142] In the present embodiment, the kinematic viscosity of the dimethylpolysiloxane at 25 °C is preferably 500 mm 2 / s or more and 4000 mm 2 / s or less, more preferably 700 mm 2 / s or more and 3000 mm 2 / s or less, still more preferably 900 mm 2 / s or more and 2000 mm 2 / s or less. It may also be 600 mm 2 / s or more and 3500 mm 2 / s or less, 800 mm 2 / s or more and 2500 mm 2 / s or less, 1000 mm 2 / s or more and 1500 mm 2 / s or less, etc.

[0143] In the total mass of the polysiloxane-coated metal oxide particles of the present embodiment, the dimethylpolysiloxane of the present embodiment preferably contains 1% by mass or more and 20% by mass or less, and more preferably contains 1% by mass or more and 15% by mass or less. It may also be 2% by mass or more and 10% by mass or less, 3% by mass or more and 8% by mass or less, etc.

[0144] Within the scope that does not impede the object of the present invention, the dimethylpolysiloxane in the present embodiment may contain silicone oils having other functional groups such as hydrogen groups in the side chains or at the ends of the methyl groups. However, if the inevitable impurities are removed, the polysiloxane-coated metal oxide particles of the present embodiment preferably consist only of the dimethylpolysiloxane represented by the above general formula (6) and the metal oxide particles.

[0145] When the polysiloxane-coated metal oxide particles of the present embodiment are used in cosmetics, it is preferable that they are composed only of the dimethylpolysiloxane represented by the above general formula (6) and the metal oxide particles. Since the above dimethylpolysiloxane is widely used as a solvent for cosmetics, the compatibility with cosmetics is improved. Also, it is preferable from the viewpoint of heat resistance.

[0146] In addition, as long as it does not interfere with the object of the present invention, in addition to the above dimethylpolysiloxane, a substance other than the above dimethylpolysiloxane can be used to surface-treat the metal oxide particles.

[0147] As the surface treatment agent other than the above dimethylpolysiloxane, for example, inorganic materials such as silica and alumina, or organic materials such as silane coupling agents, silicone compounds, fatty acids, fatty acid soaps, fatty acid esters, and organic titanate compounds can be used.

[0148] In the polysiloxane-coated metal oxide particles of the present embodiment, since the surface of the metal oxide particles is sufficiently coated with dimethylpolysiloxane, the hydrophobicity is excellent. Also, the alcohol resistance of the metal oxide particles coated with dimethylpolysiloxane having a high molecular weight is excellent.

[0149] [Method for producing polysiloxane-coated metal oxide particles]

[0150] One embodiment of the method for producing the polysiloxane-coated metal oxide particles of the present embodiment is the method for producing the polysiloxane-coated metal oxide particles of the present embodiment, which has: a surface treatment step (hereinafter referred to as the "surface treatment step"), mixing the metal oxide particles and the dimethylpolysiloxane represented by the above general formula (6) having a kinematic viscosity at 25°C of 500 mm 2 / s or more and 4000 mm 2 / s or less without using a solvent, and coating the surface of the metal oxide particles with the dimethylpolysiloxane; and a step of heat-treating the metal oxide particles coated with the dimethylpolysiloxane under the conditions of 100°C or more and 380°C or less (hereinafter referred to as the "heat treatment step"). In addition, in the heat treatment step, mixing may or may not be performed.

[0151] Here, in the surface treatment step, "mixing without using a solvent" means not adding solvents such as alcohol added in the conventional dry surface treatment method.

[0152] The metal oxide particles and the dimethylpolysiloxane can be the same substances as those described above.

[0153] In addition, the surface treatment step and the heat treatment step can be performed simultaneously.

[0154] That is, another embodiment of the method for manufacturing polysiloxane-coated metal oxide particles of the present embodiment is the method for manufacturing polysiloxane-coated metal oxide particles of the present embodiment, which does not use a solvent and has a kinematic viscosity at 25°C of 500 mm 2 / s or more and 4000 mm 2 / s or less of dimethylpolysiloxane represented by the above general formula (6) is heated and mixed, and the surface of the metal oxide particles is coated with the dimethylpolysiloxane. The temperature of the heating and mixing is 100°C or more and 380°C or less. The heating and mixing can be heated after mixing, or mixed after heating, or heating and mixing can be carried out simultaneously. For example, the heating and mixing can be carried out while mixing and heating after starting mixing, or while heating and mixing after starting heating, or heating and mixing can be started simultaneously.

[0155] In the method for manufacturing polysiloxane-coated metal oxide particles of the present embodiment, no organic solvents such as alcohols are added in the surface treatment step.

[0156] In the surface treatment step coated with dimethylpolysiloxane having a high kinematic viscosity, if a solvent such as alcohol is added, the compatibility between the above dimethylpolysiloxane and alcohol is low, so the above dimethylpolysiloxane and alcohol cannot be uniformly mixed. Therefore, in the case of surface treatment with dimethylpolysiloxane having a high kinematic viscosity, the alcohol added to uniformly surface-treat the metal oxide particles cannot fully perform its function, and the surface cannot be fully coated with dimethylpolysiloxane.

[0157] Therefore, in the method for manufacturing polysiloxane-coated metal oxide particles of the present embodiment, by the dry surface treatment method, without adding solvents such as alcohols necessary for uniformly coating the metal oxide particles, after coating the metal oxide particles with dimethylpolysiloxane having a specified kinematic viscosity, heat treatment is performed at a specified temperature, whereby polysiloxane-coated metal oxide particles having high hydrophobicity and excellent alcohol resistance can be manufactured. In addition, "mixing without using a solvent" means not excluding additives, catalysts, and impurities inevitably contained to the extent that they do not affect the effects of the present invention.

[0158] In the above surface treatment step, while stirring the metal oxide particles as a raw material in a mixer such as a Henschel mixer or a super mixer, the above dimethylpolysiloxane is added to the metal oxide particles by droplets or spraying, and then the metal oxide particles and the above dimethylpolysiloxane are stirred at high speed for a certain time.

[0159] The stirring can be carried out at room temperature or at 30°C to 150°C.

[0160] When performing the surface treatment process and the heat treatment process simultaneously, stirring can be carried out at a temperature of 100°C or higher and 380°C or lower. For example, as needed, stirring can be carried out at a temperature of 100°C or higher and 350°C or lower, 110°C or higher and 330°C or lower, 130°C or higher and 300°C or lower, 150°C or higher and 250°C or lower.

[0161] The stirring speed is not particularly limited as long as the metal oxide particles and the above-mentioned dimethylpolysiloxane are mixed and the surface treatment reaction proceeds. For example, it can be carried out at a circumferential speed of 5 m / s to 60 m / s. According to the required conditions, stirring can be carried out at a circumferential speed of 10 m / s to 40 m / s, or a circumferential speed of 20 m / s to 30 m / s.

[0162] The stirring time is not particularly limited as long as the metal oxide particles and dimethylpolysiloxane are mixed and the surface treatment reaction proceeds. For example, stirring can be carried out for 1 minute to 5 hours, and preferably for about 30 minutes to 2 hours.

[0163] The mixing amount of the above-mentioned dimethylpolysiloxane is preferably 1.0 part by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the polysiloxane-coated metal oxide particles. When heating and mixing or heat treatment is carried out at 250°C or higher, the mixing amount of the above-mentioned dimethylpolysiloxane is preferably 1.0 part by mass or more and 10.0 parts by mass or less with respect to 100 parts by mass of the polysiloxane-coated metal oxide particles.

[0164] The mixing amount of the above-mentioned dimethylpolysiloxane is more preferably 1.1 part by mass or more and 8.0 parts by mass or less, further preferably 1.3 part by mass or more and 6.5 parts by mass or less, and even more preferably 1.5 part by mass or more and 5.0 parts by mass or less.

[0165] When heating and mixing or heat treatment is carried out at 100°C or higher and less than 250°C, the mixing amount of the above-mentioned dimethylpolysiloxane is preferably 10.1 parts by mass or more and 20.0 parts by mass or less with respect to 100 parts by mass of the polysiloxane-coated metal oxide particles.

[0166] The mixing amount of the above-mentioned dimethylpolysiloxane is more preferably 10.1 parts by mass or more and 18.0 parts by mass or less, further preferably 10.5 parts by mass or more and 15.0 parts by mass or less, and even more preferably 11.0 parts by mass or more and 13.0 parts by mass or less.

[0167] When the hydroxyl detection rate is high, in order to effectively carry out the surface treatment reaction, the mixing amount of dimethylpolysiloxane can be increased, or the heating temperature can be raised.

[0168] In the above heat treatment process or heat mixing, the surface treatment is carried out at a temperature at which the surface of the metal oxide particles is hydrophobized and lower than the temperature at which the dimethylpolysiloxane is decomposed. That is, the treatment is carried out at a temperature of 100°C to 380°C. The temperature can be 100°C to 350°C, 150°C to 320°C, 200°C to 300°C, 250°C to 280°C, etc. as needed. The heat treatment can be appropriately carried out for a time when the surface is sufficiently hydrophobized. For example, heat treatment can be carried out for 30 minutes to 24 hours. The atmosphere during the heat treatment is not particularly limited as long as it does not interfere with the surface treatment, and can be any one of an air atmosphere, an oxygen atmosphere, an inert atmosphere, a reduced pressure atmosphere, or a vacuum atmosphere.

[0169] The heat treatment process can be carried out while stirring.

[0170] The polysiloxane-coated metal oxide particles after the heat treatment process can be crushed by a crusher. By crushing, the roughness of the polysiloxane-coated metal oxide particles can be suppressed.

[0171] The crushing of the polysiloxane-coated metal oxide particles after the heat treatment can be carried out, for example, using a known crusher. As such a crusher, for example, an atomizer, a hammer mill, a jet mill, an impeller mill, a needle mill, etc. can be cited.

[0172] According to the method for manufacturing polysiloxane-coated metal oxide particles of the present embodiment, polysiloxane-coated metal oxide particles excellent in hydrophobicity and alcohol resistance can be obtained.

[0173] [Dispersion liquid]

[0174] The dispersion liquid of the present embodiment contains the polysiloxane-coated metal oxide particles of the present embodiment and a dispersion medium.

[0175] In addition, the dispersion liquid of the present embodiment further includes a paste-like dispersion with high viscosity.

[0176] When the dispersion medium is used in cosmetics, it can be formulated in cosmetics and is not particularly limited as long as it can disperse the polysiloxane-coated metal oxide particles.

[0177] As the dispersion medium, for example, water, alcohols, esters, ethers, natural oils, ester oils, silicone oils, etc. are preferably used.

[0178] As the alcohols, for example, methanol, ethanol, n-propanol, isopropanol, n-butanol, 2-butanol, octanol, glycerol, etc. can be cited.

[0179] As the esters, for example, ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, γ-butyrolactone, etc. can be cited.

[0180] As ethers, for example, diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, etc. can be cited.

[0181] Furthermore, as other dispersion media, ketones, aromatic hydrocarbons, cyclic hydrocarbons, amides, linear polysiloxanes, cyclic polysiloxanes, modified polysiloxanes, hydrocarbon oils, ester oils, silicone oils, higher fatty acids, higher alcohols, etc. can be used.

[0182] As ketones, for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, cyclohexanone, etc. can be cited.

[0183] As aromatic hydrocarbons, for example, benzene, toluene, xylene, ethylbenzene, etc. can be cited.

[0184] As cyclic hydrocarbons, for example, cyclohexane, etc. can be cited.

[0185] As amides, for example, dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, etc. can be cited.

[0186] As linear polysiloxanes, for example, dimethylpolysiloxane, methylphenylpolysiloxane, diphenylpolysiloxane, etc. can be cited.

[0187] As cyclic polysiloxanes, for example, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, etc. can be cited.

[0188] As modified polysiloxanes, for example, amino-modified polysiloxane, polyether-modified polysiloxane, alkyl-modified polysiloxane, fluorine-modified polysiloxane, etc. can be cited.

[0189] As hydrocarbon oils, for example, liquid paraffin, squalane, isoparaffin, branched light paraffin, petrolatum, ozokerite, etc. can be cited.

[0190] As ester oils, for example, isopropyl myristate, cetyl isooctanoate, glyceryl trioctanoate, etc. can be cited.

[0191] As silicone oils, for example, decamethylcyclopentasiloxane, dimethylpolysiloxane, methylphenylpolysiloxane, etc. can be cited.

[0192] As higher fatty acids, for example, lauric acid, myristic acid, palmitic acid, stearic acid, etc. can be cited.

[0193] As higher alcohols, for example, lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyl dodecanol, isostearyl alcohol, etc. can be cited.

[0194] The above-mentioned dispersion media can be used alone or in combination of two or more.

[0195] The dispersion of the present embodiment may contain commonly used additives within the range that does not impair its properties.

[0196] As additives, for example, preservatives, dispersants, dispersion aids, stabilizers, water-soluble binders, thickeners, oil-soluble agents, oil-soluble pigments, oil-soluble proteins, UV absorbers, etc. are preferably used.

[0197] When the cumulative volume percentage of the particle size distribution in the dispersion of the present embodiment is 50%, the particle diameter (D50) of the polysiloxane-coated metal oxide particles can be arbitrarily selected, preferably 600 nm or less, more preferably 500 nm or less, and further preferably 400 nm or less.

[0198] There is no particular limitation on the lower limit value of D50 in the dispersion of the present embodiment. For example, it can be 130 nm or more, 140 nm or more, or 150 nm or more. The upper limit value and the lower limit value of the above D50 can be arbitrarily combined.

[0199] Furthermore, when the cumulative volume percentage of the particle size distribution in the dispersion of the present embodiment is 90%, the particle diameter (D90) of the polysiloxane-coated metal oxide particles can be arbitrarily selected, preferably 1 μm or less, more preferably 900 nm or less, and further preferably 800 nm or less.

[0200] There is no particular limitation on the lower limit value of D90 in the dispersion of the present embodiment. For example, it can be 150 nm or more, 200 nm or more, or 250 nm or more. The upper limit value and the lower limit value of the above D90 can be arbitrarily combined.

[0201] When D50 in the dispersion of the present embodiment is 600 nm or less, when the cosmetic product made using this dispersion is applied to the skin, the polysiloxane-coated metal oxide particles are likely to be evenly distributed, and the ultraviolet ray shielding effect is improved, so it is preferred. Also, when D90 in the dispersion of the present embodiment is 1 μm or less, the transparency of the dispersion is high, and the transparency of the cosmetic product made using this dispersion is also high, so it is preferred.

[0202] That is, when D50 and D90 in the dispersion of the present embodiment are within the above ranges, a dispersion with excellent transparency and excellent ultraviolet ray shielding property can be obtained. Also, the transparency and ultraviolet ray shielding property of the cosmetic product made using this dispersion are also excellent.

[0203] The cumulative volume percentage of the particle size distribution in the dispersion can be measured using a dynamic light scattering type particle size distribution measuring device.

[0204] The content of the polysiloxane-coated metal oxide particles in the dispersion of the present embodiment can be appropriately adjusted according to the desired properties.

[0205] When the dispersion of the present embodiment is used in cosmetics, the content of the polysiloxane-coated metal oxide particles in the dispersion can be arbitrarily selected, but it is preferably 10% by mass or more, more preferably 20% by mass or more, and further preferably 30% by mass or more. Also, the content of the polysiloxane-coated metal oxide particles in the dispersion is preferably 90% by mass or less, more preferably 85% by mass or less, and further preferably 80% by mass or less. The upper limit value and the lower limit value of the content of the polysiloxane-coated metal oxide particles in the dispersion can be arbitrarily combined.

[0206] By having the content of the polysiloxane-coated metal oxide particles in the dispersion within the above range, the polysiloxane-coated metal oxide particles are contained at a high concentration. Therefore, the degree of freedom of the formulation can be increased, and the viscosity of the dispersion can be set to an easily handleable level.

[0207] The viscosity of the dispersion of the present embodiment can be arbitrarily selected, but it is preferably 5 Pa·s or more, more preferably 8 Pa·s or more, further preferably 10 Pa·s or more, and most preferably 15 Pa·s or more. Also, the viscosity of the dispersion is preferably 300 Pa·s or less, more preferably 100 Pa·s or less, further preferably 80 Pa·s or less, and most preferably 60 Pa·s or less. The upper limit value and the lower limit value of the viscosity of the dispersion can be arbitrarily combined.

[0208] By having the viscosity of the dispersion within the above range, an easily handleable dispersion can be obtained even when the solid content (polysiloxane-coated metal oxide particles) is contained at a high concentration.

[0209] The method for producing the dispersion of the present embodiment is not particularly limited. For example, a method of mechanically dispersing the polysiloxane-coated metal oxide particles and the dispersion medium of the present embodiment using a known dispersion device can be cited.

[0210] The dispersion device can be selected as needed. For example, a stirrer, a rotation-revolution type mixer, a homogenizing mixer, an ultrasonic homogenizer, a sand mill, a ball mill, a roll mill, etc. can be cited.

[0211] In addition to being used in cosmetics, the dispersion of the present embodiment can also be used in coatings having an ultraviolet shielding function or a gas permeation inhibiting function, etc.

[0212] Due to the polysiloxane-coated metal oxide particles of the present embodiment being contained in the dispersion of the present embodiment, when formulated in cosmetics, it suppresses roughness and is excellent in transparency and ultraviolet shielding properties.

[0213] [Composition]

[0214] The composition of this embodiment contains the dispersion liquid and resin of this embodiment.

[0215] The content of the polysiloxane-coated metal oxide particles in the composition of this embodiment can be appropriately adjusted according to the desired properties. The above content is preferably 10% by mass or more and 40% by mass or less, more preferably 20% by mass or more and 30% by mass or less. In addition, the dispersion liquid and resin of this embodiment are mixed so that the content of the polysiloxane-coated metal oxide particles in the composition of this embodiment is within the above range.

[0216] When the content of the polysiloxane-coated metal oxide particles in the composition is within the above range, since the solid components (polysiloxane-coated metal oxide particles) are contained at a high concentration, the properties of the polysiloxane-coated metal oxide particles can be fully obtained, and a composition in which the polysiloxane-coated metal oxide particles are uniformly dispersed can be obtained.

[0217] As the resin, if it is a resin commonly used in industrial applications, there is no particular limitation, and examples thereof include acrylic resins, epoxy resins, urethane resins, polyester resins, silicone resins, etc.

[0218] The content of the resin in the composition of this embodiment is not particularly limited and can be appropriately adjusted according to the properties of the target composition.

[0219] The composition of this embodiment can contain commonly used additives within the range that does not impair its properties.

[0220] As additives, for example, polymerization initiators, dispersants, preservatives, etc. can be cited.

[0221] The manufacturing method of the composition of this embodiment is not particularly limited. For example, a method of mechanically mixing the polysiloxane-coated metal oxide particles, resin, and dispersion medium of this embodiment by a known mixing device can be cited.

[0222] And a method of mechanically mixing the above dispersion liquid and resin by a known mixing device can be cited.

[0223] As the mixing device, for example, a stirrer, a rotary-revolution mixer, a homogenizer, an ultrasonic homogenizer, etc. can be cited.

[0224] By means of common coating methods such as roll coating, flow coating, spray coating, screen printing, brush coating, dipping, etc., the composition of the present embodiment is coated on an arbitrarily selected substrate (such as a plastic substrate like a polyester film), whereby a coating film can be formed. These coating films can be used for arbitrarily selected purposes, such as an ultraviolet shielding film or a gas barrier film.

[0225] Due to containing the polysiloxane-coated metal oxide particles of the present embodiment, the composition of the present embodiment is easily mixed with resins and can exhibit excellent transparency and ultraviolet shielding properties.

[0226] [Cosmetics]

[0227] A cosmetic of one embodiment of the present embodiment contains at least one selected from the group consisting of the polysiloxane-coated metal oxide particles of the present embodiment and the dispersion of the present embodiment. Alternatively, a cosmetic of one embodiment of the present embodiment contains at least one selected from the group consisting of the polysiloxane-coated metal oxide particles of the present embodiment, the dispersion of the present embodiment, and the composition of the present embodiment.

[0228] A cosmetic of another embodiment contains a cosmetic base material raw material and at least one selected from the group consisting of the polysiloxane-coated metal oxide particles of the present embodiment and the dispersion of the present embodiment. Alternatively, a cosmetic of another embodiment contains a cosmetic base material raw material and at least one selected from the group consisting of the polysiloxane-coated metal oxide particles of the present embodiment, the dispersion of the present embodiment, and the composition of the present embodiment.

[0229] In cosmetics, zinc oxide particles are preferably used as the metal oxide particles.

[0230] Cosmetic base material raw materials refer to various raw materials that form the cosmetic base material. As cosmetic base material raw materials, for example, oily raw materials, aqueous raw materials, surfactants, powder raw materials, etc. can be cited.

[0231] As the oily raw materials, they can be arbitrarily selected. For example, oils and fats, higher fatty acids, higher alcohols, ester oils, etc. can be cited.

[0232] As the aqueous raw materials, they can be arbitrarily selected. For example, purified water, alcohols, thickeners, etc. can be cited.

[0233] As the powder raw materials, they can be arbitrarily selected. For example, colored pigments, white pigments, pearlescent agents, extender pigments, etc. can be cited.

[0234] Regarding the cosmetic of the present embodiment, for example, it is obtained by formulating the dispersion of the present embodiment into cosmetic base material raw materials such as emulsions, creams, foundation creams, lipsticks, blushes, eyeshadows, etc. in the conventional manner.

[0235] The cosmetic of the present embodiment is obtained, for example, by formulating the polysiloxane-coated metal oxide particles of the present embodiment into an oil phase or an aqueous phase to form an O / W type or W / O type emulsion, and then formulating with a cosmetic base material.

[0236] The content of the polysiloxane-coated metal oxide particles in the cosmetic of the present embodiment can be appropriately adjusted according to the desired properties. For example, the lower limit of the content of the polysiloxane-coated metal oxide particles can be 0.01% by mass or more, 0.1% by mass or more, or 1% by mass or more. Also, the upper limit of the content of the polysiloxane-coated metal oxide particles can be 50% by mass or less, 40% by mass or less, or 30% by mass or less. The upper limit value and the lower limit value of the content of the polysiloxane-coated metal oxide particles in the cosmetic can be arbitrarily combined.

[0237] Hereinafter, sunscreen cosmetics will be specifically described.

[0238] In sunscreen cosmetics, in order to effectively shield ultraviolet rays, especially long-wavelength ultraviolet rays (UVA), and obtain a good feeling in use with less powdery feeling or dry feeling, it is also preferable to adjust the content of the polysiloxane-coated metal oxide particles. For example, the lower limit of the content of the polysiloxane-coated metal oxide particles in the sunscreen cosmetic is preferably 0.01% by mass or more, more preferably 0.1% by mass or more, and further preferably 1% by mass or more. Also, the upper limit of the content of the polysiloxane-coated metal oxide particles in the sunscreen cosmetic can be 50% by mass or less, 40% by mass or less, or 30% by mass or less. The upper limit value and the lower limit value of the content of the polysiloxane-coated metal oxide particles in the sunscreen cosmetic can be arbitrarily combined. And within the above range, preferred ranges such as 5% to 15% by mass and 10% to 20% by mass can be arbitrarily selected.

[0239] The sunscreen cosmetic may contain, as needed, a hydrophobic dispersion medium, inorganic fine particles or inorganic pigments other than the polysiloxane-coated metal oxide particles, a hydrophilic dispersion medium, oils and fats, surfactants, humectants, thickeners, pH adjusters, nutrients, antioxidants, fragrances, preservatives, dispersants, defoamers, colorants, beauty components, high molecular substances, biogenic components, plant-derived components, antibacterial agents, fungicides, mildew-proof agents, aqueous components, oily components, vitamin agents, emulsifiers, stabilizers, solubilizers, pearlescent agents, fatliquoring substances, etc.

[0240] Examples of the hydrophobic dispersion medium include hydrocarbon oils, ester oils, silicone oils, higher fatty acids, higher alcohols, etc.

[0241] As hydrocarbon oils, for example, liquid paraffin, squalane, isoparaffin, branched light paraffin, petrolatum, ozokerite, etc. can be cited.

[0242] As ester oils, for example, isopropyl myristate, cetyl isooctanoate, glyceryl trioctanoate, etc. can be cited.

[0243] As silicone oils, for example, decamethylcyclopentasiloxane, dimethylpolysiloxane, methylphenylpolysiloxane, etc. can be cited.

[0244] As higher fatty acids, for example, lauric acid, myristic acid, palmitic acid, stearic acid, etc. can be cited.

[0245] As higher alcohols, for example, lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyl dodecanol, isostearyl alcohol, etc. can be cited.

[0246] As inorganic fine particles or inorganic pigments other than polysiloxane-coated metal oxide particles contained in cosmetics, for example, 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, silicon oxide, etc. can be cited.

[0247] The sunscreen cosmetic may further contain at least one organic ultraviolet absorber. A cosmetic containing both polysiloxane-coated metal oxide particles and an organic ultraviolet absorber is preferred because the ultraviolet shielding region becomes wider and the ultraviolet shielding property increases by enhancing the effect.

[0248] As organic ultraviolet absorbers, for example, 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, triazine-based ultraviolet absorbers, etc. can be cited.

[0249] As benzotriazole-based ultraviolet absorbers, for example, 2,2'-hydroxy-5-methylphenylbenzotriazole, 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole, 2-(2'-hydroxy-5'-methylphenyl)benzotriazole, etc. can be cited.

[0250] As benzoylmethane-based ultraviolet absorbers, for example, dibenzoylmethane, bis(4-methoxyphenyl)methane, 4-tert-butyl-4'-methoxydibenzoylmethane, 1-(4'-isopropylphenyl)-3-phenylpropane-1,3-dione, 5-(3,3'-dimethyl-2-norbornene)-3-pentan-2-one, etc. can be cited.

[0251] As benzoic acid-based ultraviolet absorbers, examples include p-aminobenzoic acid (PABA), PABA monoglyceride, N,N-dipropoxyethyl PABA, N,N-diethoxyethyl PABA, N,N-dimethyl ethyl PABA, N,N-dimethyl butyl PABA, N,N-dimethyl methyl PABA, etc.

[0252] As anthranilic acid-based ultraviolet absorbers, examples include menthyl-N-acetyl anthranilate, etc.

[0253] As salicylic acid-based ultraviolet absorbers, examples include amyl salicylate, menthyl salicylate, homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, p-(2-propylphenyl) salicylate, etc.

[0254] As cinnamic acid-based ultraviolet absorbers, examples include octyl methoxycinnamate (ethylhexyl methoxycinnamate), di-p-methoxycinnamic acid mono-2-ethylhexanoin, octyl cinnamate, ethyl 4-isopropylcinnamate, methyl 2,5-diisopropylcinnamate, ethyl 2,4-diisopropylcinnamate, methyl 2,4-diisopropylcinnamate, propyl p-methoxycinnamate, isopropyl p-methoxycinnamate, isopentyl 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, glycerol mono-2-ethylhexanoyl di-p-methoxycinnamate, etc.

[0255] As silicone-based cinnamic acid ultraviolet absorbers, examples 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, [3-tris(trimethylsiloxy)silyl-1-methylpropyl]-3,4-dimethoxycinnamate, etc.

[0256] As triazine-based ultraviolet absorbers, examples include bis-ethylhexyloxyphenol methoxyphenyl triazine, ethylhexyl triazone, methylene bis-benzotriazolyl tetramethylbutyl phenol, terphenyl triazine, diethylhexyl butyramido triazone, etc.

[0257] As organic ultraviolet absorbers other than those described above, for example, 3-(4'-methylbenzylidene)-d,l-camphor, 3-benzylidene-d,l-camphor, urocanic acid, ethyl urocanate, 2-phenyl-5-methylbenzoxazole, 5-(3,3'-dimethyl-2-norbornene)-3-pentan-2-one, silicone-modified ultraviolet absorbers, fluorine-modified ultraviolet absorbers, etc. can be cited. The above ultraviolet absorbers can be used alone or in combination of two or more.

[0258] The critical wavelength of the cosmetic of the present embodiment is preferably 370 nm or more. By setting the critical wavelength of the cosmetic to 370 nm or more, it is possible to shield a wide range of ultraviolet rays including long-wavelength ultraviolet rays (UVA) and short-wavelength ultraviolet rays (UVB).

[0259] The cosmetic according to the present embodiment contains at least one selected from the group consisting of the polysiloxane-coated metal oxide particles of the present embodiment, the dispersion liquid of the present embodiment, and the composition of the present embodiment. Therefore, a cosmetic having excellent quality stability can be obtained.

[0260] Examples

[0261] Hereinafter, the present invention will be described more specifically with reference to Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[0262] [Example 1]

[0263] "Production of polysiloxane-coated zinc oxide particles"

[0264] In a Henschel mixer heated to 60 °C, 98 parts by mass of zinc oxide particles A1 (BET specific surface area: 40 m 2 / g, manufactured by Sumitomo Osaka Cement Co., Ltd.) and 2 parts by mass of dimethylpolysiloxane (trade name: KF-96-1,000 cs, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed at a circumferential speed of 15 m / s.

[0265] Next, the mixture was heat-treated at 350 °C for 3 hours to obtain the polysiloxane-coated zinc oxide particles B1 of Example 1.

[0266] (Measurement of hydroxyl detection rate)

[0267] "Production of red pigment"

[0268] A mixed solution was prepared by mixing 1 mmol of 2,2'-dihydroxyazobenzene, 1 mmol of diphenyltin(IV) oxide, and 30 mL of acetone.

[0269] Next, the mixture was stirred at 70 °C for 3 hours to carry out a dehydration reaction, causing tin diphenyl oxide to coordinate with 2,2'-dihydroxyazobenzene.

[0270] The mixture after the dehydration reaction was filtered to recover the filtrate, and the solvent was removed by distillation from the filtrate, thereby obtaining the red pigment represented by the above general formula (1).

[0271] "Preparation of the evaluation solution"

[0272] 250 nmol (0.12 mg) of the obtained red pigment was dissolved in toluene to make 5 mL, obtaining the evaluation solution C1 of 5×10 -5 mol / L. The absorbance C2 of this evaluation solution C1 at 545 nm was measured using a spectrophotometer (model: V-770, manufactured by JASCO Corporation).

[0273] 4.0 mg of zinc oxide particles A1 was added to solution C1, and the mixture was stirred and mixed at 60 °C for 4 hours to prepare a mixture. The mixture was filtered using a syringe filter (0.2 μm), and the absorbance A2 of the filtrate at 545 nm was measured.

[0274] 4.0 mg of the polysiloxane-coated zinc oxide particles B1 of Example 1 was added to solution C1, and the mixture was stirred and mixed at 60 °C for 4 hours to prepare a mixture. The mixture was filtered using a syringe filter (0.2 μm), and the absorbance B2 of the filtrate at 545 nm was measured.

[0275] The adsorption amount of the red pigment on the zinc oxide particles and the adsorption amount of the red pigment on the polysiloxane-coated zinc oxide particles were calculated by the above general formula (2) and the above general formula (3).

[0276] The adsorption amount B3 of the pigment on the polysiloxane-coated zinc oxide particles = ((C2 - B2) / C2) × 250×10 -9 (mol) / 4×10 -3 (g)......(3)

[0277] The adsorption amount A3 of the pigment on the zinc oxide particles = ((C2 - A2) / C2) × 250×10 -9 (mol) / 4×10 -3 (g)......(2)

[0278] The hydroxyl group detection rate of the polysiloxane-coated zinc oxide particles B1 of Example 1 was calculated by the above general formula (4). The results are shown in Table 1.

[0279] Hydroxyl group detection rate = (B3 / A3) × 100......(4)

[0280] (Evaluation of hydrophobicity)

[0281] The hydrophobicity of the polysiloxane-coated zinc oxide particles B1 of Example 1 was evaluated by the critical ethanol method.

[0282] As a result, it was confirmed that when the ethanol ratio was 20% by mass, 10 or more particles settled.

[0283] That is, the hydrophobicity of the polysiloxane-coated zinc oxide particles B1 of Example 1 was 20%.

[0284] The results are shown in Table 1.

[0285] 5 g of the polysiloxane-coated zinc oxide particles B1 of Example 1 and 45 g of ethanol were mixed, and the mixture was stirred at 2000 revolutions per minute for 10 minutes with a disperser while being heated to 50 °C.

[0286] The stirred mixture was subjected to solid-liquid separation, and the recovered polysiloxane-coated zinc oxide particles were dried at 40 °C for 5 hours.

[0287] Regarding the dried polysiloxane-coated zinc oxide particles, hydrophobicity evaluation based on the critical ethanol method was performed, and the result was 20% by mass.

[0288] The results are shown in Table 1.

[0289] It was confirmed that the polysiloxane-coated zinc oxide particles of Example 1 had equal hydrophobicity before and after stirring in ethanol at 50 °C and excellent alcohol resistance.

[0290] [Example 2]

[0291] Zinc oxide particles D1 with a specific surface area of 5 m 2 / g were used instead of zinc oxide particles A1 with a BET specific surface area of 40 m 2 / g, and in other respects, polysiloxane-coated zinc oxide particles E1 of Example 2 were obtained in the same manner as in Example 1.

[0292] 32 mg of zinc oxide particles D1 were added to the solution C1 of Example 1, and the mixture was stirred and mixed at 60 °C for 4 hours to prepare a mixed solution. The mixed solution was filtered through a needle filter (0.2 μm), and the absorbance D2 of the filtrate at 545 nm was measured.

[0293] 32 mg of the polysiloxane-coated zinc oxide particles E1 of Example 1 were added to the solution C1, and the mixture was stirred and mixed at 60 °C for 4 hours to prepare a mixed solution. The mixed solution was filtered through a needle filter (0.2 μm), and the absorbance E2 of the filtrate at 545 nm was measured.

[0294] The adsorption amounts of the red pigment on zinc oxide particles and polysiloxane-coated zinc oxide particles are calculated by the above general formula (2) and the above general formula (3).

[0295] The adsorption amount E3 of the pigment on the polysiloxane-coated zinc oxide particles = ((C2 - E2) / C2) × 250 × 10 -9 (mol) / 32 × 10 -3 (g)……(3)

[0296] The adsorption amount D3 of the pigment on the zinc oxide particles = ((C2 - D2) / C2) × 250 × 10 -9 (mol) / 32 × 10 -3 (g)……(2)

[0297] The hydroxyl detection rate of the polysiloxane-coated zinc oxide particles E1 in Example 2 is calculated by the above general formula (4). The results are shown in Table 1.

[0298] Hydroxyl detection rate = E3 / D3 × 100……(4)

[0299] The hydrophobicity was evaluated in the same manner as in Example 1. The results are shown in Table 1.

[0300] [Example 3]

[0301] Dimethylpolysiloxane with a kinematic viscosity of 3000 mm 2 / s was used to replace dimethylpolysiloxane with a kinematic viscosity of 1000 mm 2 / s. Except for this, the polysiloxane-coated zinc oxide particles of Example 3 were obtained in the same manner as in Example 1.

[0302] The hydroxyl detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0303] [Example 4]

[0304] In a Henschel mixer heated to 120 °C, 94 parts by mass of zinc oxide particles A1 (BET specific surface area: 40 m 2 / g, manufactured by Sumitomo Osaka Cement Co., Ltd.) and 6 parts by mass of dimethylpolysiloxane (trade name: KF-96-1,000 cs, manufactured by Shin-Etsu Chemical Co., Ltd.) were mixed for 5 hours to obtain the polysiloxane-coated zinc oxide particles of Example 4.

[0305] The hydroxyl detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0306] [Example 5]

[0307] 88 parts by mass of zinc oxide particles and 12 parts by mass of dimethylpolysiloxane were used. Except for this, the polysiloxane-coated zinc oxide particles of Example 5 were obtained in the same manner as in Example 4.

[0308] The hydroxyl detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0309] [Example 6]

[0310] 96 parts by mass of zinc oxide particles D1 with a specific surface area of 5 m 2 / g and 4 parts by mass of dimethylpolysiloxane were used. Except for this, the polysiloxane-coated zinc oxide particles of Example 5 were obtained in the same manner as in Example 4.

[0311] The hydroxyl detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0312] [Example 7]

[0313] 96 parts by mass of zinc oxide particles and 4 parts by mass of dimethylpolysiloxane were used, and the heating temperature was set to 200 °C. Except for this, the polysiloxane-coated zinc oxide particles of Example 7 were obtained in the same manner as in Example 1.

[0314] The hydroxyl detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0315] [Example 8]

[0316] 94 parts by mass of zinc oxide particles and 6 parts by mass of dimethylpolysiloxane were used, and the heating temperature was set to 200 °C. Except for this, the polysiloxane-coated zinc oxide particles of Example 8 were obtained in the same manner as in Example 1.

[0317] The hydroxyl detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0318] [Example 9]

[0319] 92 parts by mass of zinc oxide particles and 8 parts by mass of dimethylpolysiloxane were used, and the heating temperature was set to 200 °C. Except for this, the polysiloxane-coated zinc oxide particles of Example 9 were obtained in the same manner as in Example 1.

[0320] The hydroxyl detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0321] [Comparative Example 1]

[0322] Using a kinematic viscosity of 5000 mm2 Dimethylpolysiloxane with a kinematic viscosity of 1000 mm 2 / s was replaced with dimethylpolysiloxane. Except for this, polysiloxane-coated zinc oxide particles of Comparative Example 1 were obtained in the same manner as in Example 1.

[0323] The hydroxyl group detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0324] [Comparative Example 2]

[0325] Dimethylpolysiloxane with a kinematic viscosity of 30 mm 2 / s was used to replace dimethylpolysiloxane with a kinematic viscosity of 1000 mm 2 / s. The heating temperature was set at 200 °C. Except for this, polysiloxane-coated zinc oxide particles of Comparative Example 2 were obtained in the same manner as in Example 1.

[0326] The hydroxyl group detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0327] [Comparative Example 3]

[0328] In a Henschel mixer heated to 60 °C, 75.7 parts by mass of zinc oxide particles (specific surface area: 40 m 2 / g, manufactured by Sumitomo Osaka Cement Co., Ltd.), 22.7 parts by mass of isopropyl alcohol, and 1.5 parts by mass of dimethylpolysiloxane with a kinematic viscosity of 30 mm 2 / s were mixed at a circumferential speed of 15 m / s. Then, the mixture was heated at 200 °C for 3 hours to obtain polysiloxane-coated zinc oxide particles of Comparative Example 3.

[0329] The hydroxyl group detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0330] [Comparative Example 4]

[0331] In a Henschel mixer heated to 60 °C, 75.7 parts by mass of zinc oxide particles (specific surface area: 40 m 2 / g, manufactured by Sumitomo Osaka Cement Co., Ltd.), 22.7 parts by mass of isopropyl alcohol, and 1.5 parts by mass of dimethylpolysiloxane with a kinematic viscosity of 1000 mm 2 / s were mixed at a circumferential speed of 15 m / s. Then, the mixture was heated at 350 °C for 3 hours to obtain polysiloxane-coated zinc oxide particles of Comparative Example 4.

[0332] The hydroxyl group detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0333] [Comparative Example 5]

[0334] Heat treatment was carried out at 200 °C instead of at 350 °C. Except for this, polysiloxane-coated zinc oxide particles of Comparative Example 5 were obtained in the same manner as in Example 1.

[0335] The hydroxyl group detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0336] [Comparative Example 6]

[0337] Dimethylpolysiloxane with a kinematic viscosity of 30 mm 2 / s was used instead of dimethylpolysiloxane with a kinematic viscosity of 1000 mm 2 / s. Except for this, polysiloxane-coated zinc oxide particles of Comparative Example 6 were obtained in the same manner as in Example 2.

[0338] The hydroxyl group detection rate and hydrophobicity were measured in the same manner as in Example 1. The results are shown in Table 1.

[0339] [Table 1]

[0340]

[0341] By comparing the Examples with the Comparative Examples, it was confirmed that the hydroxyl group detection rate of the polysiloxane-coated zinc oxide particles obtained by surface-treating zinc oxide particles with dimethylpolysiloxane having a kinematic viscosity of 500 mm 2 / s or more and 4000 mm 2 / s or less without using a solvent at a high temperature was small. And it was confirmed that the hydroxyl group detection rate of the polysiloxane-coated zinc oxide particles obtained by surface-treating zinc oxide particles with dimethylpolysiloxane having a kinematic viscosity of 500 mm 2 / s or more and 4000 mm 2 / s or less in a specified amount or more without using a solvent was small. A small hydroxyl group detection rate indicates that the amount of hydroxyl groups present on the surface of the zinc oxide particles is small. That is, it was confirmed that in the surface-treated zinc oxide particles (polysiloxane-coated zinc oxide particles) of the Examples, the zinc oxide particles were sufficiently coated with dimethylpolysiloxane.

[0342] The higher the kinematic viscosity of dimethylpolysiloxane, the more excellent the hydrophobicity and the more excellent the alcohol resistance. The polysiloxane-coated zinc oxide particles of the examples can sufficiently coat the surface of the zinc oxide particles with dimethylpolysiloxane having a high kinematic viscosity by using the method for producing polysiloxane-coated metal oxide particles of the present embodiment. Therefore, since the hydroxyl groups derived from the zinc oxide particles are not exposed on the surface, the polysiloxane-coated zinc oxide particles of the examples have excellent hydrophobicity.

[0343] Moreover, dimethylpolysiloxane having a high kinematic viscosity has high hydrophobicity and excellent alcohol resistance. Therefore, the polysiloxane-coated zinc oxide particles of the examples have high hydrophobicity and excellent alcohol resistance. Therefore, they can be easily formulated into oil-based cosmetics, and the quality stability after being formulated into cosmetics is excellent.

[0344] Industrial Applicability

[0345] The present invention provides metal oxide particles having excellent hydrophobicity and coated with dimethylpolysiloxane. The polysiloxane-coated metal oxide particles of the present invention have high hydrophobicity and excellent alcohol resistance. Therefore, they can be easily mixed with various hydrophobic materials, and the quality stability in hydrophobic materials such as cosmetics is excellent. Therefore, the polysiloxane-coated metal oxide particles of the present invention can easily ensure the design quality when applied to dispersions, compositions, coatings, and cosmetics, and have great industrial value.

Claims

1. A polysiloxane-coated metal oxide particle, wherein the surface of the metal oxide particle is coated with dimethylpolysiloxane, wherein, the hydroxyl group detection rate calculated based on the adsorption amount of a red pigment adsorbed on the hydroxyl groups present on the surface of the metal oxide particle before being coated with the dimethylpolysiloxane and the adsorption amount of the red pigment adsorbed on the hydroxyl groups present on the surface of the metal oxide particle after being coated with the dimethylpolysiloxane is 10% or less.

2. The polysiloxane-coated metal oxide particle according to claim 1, wherein, the content of the metal oxide particle is 80% by mass or more and 99% by mass or less.

3. A dispersion liquid containing the polysiloxane-coated metal oxide particle according to claim 1 or 2 and a dispersion medium.

4. A composition containing the dispersion liquid according to claim 3 and a resin.

5. A cosmetic containing the polysiloxane-coated metal oxide particle according to claim 1 or 2.

6. A cosmetic containing the dispersion liquid according to claim 3.

7. A method for manufacturing a polysiloxane-coated metal oxide particle, which is a method for manufacturing the polysiloxane-coated metal oxide particle according to claim 1 or 2, and has: A surface treatment process, without using a solvent, mixes metal oxide particles and dimethylpolysiloxane having a kinematic viscosity at 25 °C of 500 mm 2 / s or more and 4000 mm 2 / s or less, and coats the surface of the metal oxide particles with the dimethylpolysiloxane; and a step of heat-treating the metal oxide particle coated with the dimethylpolysiloxane under the condition of 100°C or higher and 380°C or lower.

8. A method for manufacturing a polysiloxane-coated metal oxide particle, which is a method for manufacturing the polysiloxane-coated metal oxide particle according to claim 1 or 2, and has: Surface treatment process, heating and mixing metal oxide particles without using a solvent, and dimethylpolysiloxane having a kinematic viscosity at 25 °C of 500 mm 2 / s or more and 4000 mm 2 / s or less, and coating the surface of the metal oxide particles with the dimethylpolysiloxane the temperature of the heat mixing in the surface treatment step is 100°C or higher and 380°C or lower.

9. The polysiloxane-coated metal oxide particle according to claim 1, wherein, the metal oxide particle is a dry particle containing zinc oxide particles as the metal oxide particle.

10. The polysiloxane-coated metal oxide particle according to claim 1, wherein, the hydroxyl group detection rate is obtained as follows: Prepare the following solutions: solution C1 in which 250 nmol of a red pigment represented by the following general formula (1) is dissolved in 5 ml of toluene, solution A1 obtained by removing the particles after mixing the metal oxide particle before being coated with the dimethylpolysiloxane and solution C1, and solution B1 obtained by removing the particles after mixing the metal oxide particle after being coated with the dimethylpolysiloxane and solution C1; Measure the absorbances of the three solutions at a wavelength of 545 nm respectively; According to the measured absorbances of the three, calculate the adsorption amounts A3 and B3 of the red pigment on the metal oxide particles before and after coating respectively from the following formula, Adsorption amount = ((Absorbance of solution C1 - Absorbance of solution A1 or B1) / Absorbance of solution C1) × 250 × 10 -9 (mol) / amount (g) of the metal oxide particles; and According to the obtained adsorption amounts A3 and B3, calculate the hydroxyl group detection rate through the calculation based on the following formula, Detection rate of hydroxyl group (%) = (B3 / A3) × 100 [Chemical formula 1]

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