Zinc oxide powder, oil-dispersible cosmetic composition, and cosmetic

Abstract

The present invention provides a zinc oxide powder, an oil-dispersible cosmetic composition containing the zinc oxide powder, and a cosmetic, wherein the zinc oxide powder can be used for preparing a cosmetic which can exhibit excellent visible light permeability and ultraviolet shielding performance when applied to the skin. This zinc oxide powder is characterized by having a number distribution D50 of 100-200 nm as determined from a transmission electron microscope image, an aspect ratio of 1.1-1.4, and a crystal grain size of 70-200 nm as determined from an X-ray diffraction spectrum. Furthermore, the oil-dispersible cosmetic composition according to the present invention is characterized in that the zinc oxide powder according to the present invention is dispersed in an oil. A water-in-oil type emulsified cosmetic according to the present invention and an oil-in-water type emulsified cosmetic according to the present invention are characterized in that the composition for oil-dispersible cosmetics according to the present invention or the zinc oxide powder according to the present invention is compounded. The powder cosmetic of the present invention is characterized by being compounded with the zinc oxide powder of the present invention.

Description

Technical Field

[0001] This invention relates to a zinc oxide powder, an oil-dispersible cosmetic composition using the zinc oxide powder, and a cosmetic, wherein the zinc oxide powder can be used to prepare a cosmetic that exhibits excellent visible light transmittance and ultraviolet shielding properties when applied to the skin. Background Technology

[0002] In various cosmetics applied to the skin, such as sunscreen, inorganic powders such as zinc oxide are sometimes added.

[0003] Furthermore, in recent years, when applying cosmetics containing small-particle zinc oxide powder, there is a risk of the fine zinc oxide powder penetrating into the skin. Therefore, the industry tends to require the use of so-called non-nano zinc oxide with a particle size of 100nm or larger (Patent Document 1, etc.), and has also conducted research on the preparation method of large-particle zinc oxide powder (Patent Document 2, etc.).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 2019-517514

[0007] Patent Document 2: International Publication No. 2012 / 169611 Summary of the Invention

[0008] The problem the invention aims to solve

[0009] However, the UV-blocking performance of zinc oxide powder typically increases with decreasing particle size. When using zinc oxide powder with a particle size known as non-nano zinc oxide, it is difficult to produce cosmetics with excellent UV-blocking performance. For example, the sunscreen composition described in Patent Document 1 combines bis-ethylhexyloxyphenol methoxyphenyl triazine, which has UV-blocking properties, with non-nano zinc oxide to compensate for the lack of UV-blocking performance that non-nano zinc oxide alone lacks.

[0010] In addition, zinc oxide powder has the following problems: the increased particle size will reduce the visible light transmittance of the compounded cosmetics when applied to the skin, such as causing whitening.

[0011] Therefore, there is an urgent need to develop technologies for zinc oxide powders of non-nano zinc oxide size that can be compounded into cosmetics and applied to the skin to ensure excellent visible light transmittance and ultraviolet shielding performance.

[0012] The present invention was made based on the above circumstances, and its object is to provide a zinc oxide powder, an oil-dispersible cosmetic composition compounded with the zinc oxide powder, and a cosmetic, wherein the zinc oxide powder can be used to prepare a cosmetic that exhibits excellent visible light transmittance and ultraviolet shielding properties when applied to the skin.

[0013] Solution for solving the problem

[0014] The zinc oxide powder of the present invention is characterized by the D in the number distribution obtained from transmission electron microscopy images. 50 The size ranges from 100 to 200 nm, with an aspect ratio of 1.1 to 1.4. The grain size, determined by X-ray diffraction spectroscopy, is 70 to 200 nm.

[0015] Furthermore, the oil-dispersible cosmetic composition of the present invention is characterized in that the zinc oxide powder of the present invention is dispersed in oil.

[0016] Furthermore, the water-in-oil emulsified cosmetic of the present invention is characterized by being formulated with the oil-dispersible cosmetic composition of the present invention, or with the zinc oxide powder of the present invention.

[0017] Furthermore, the water-in-oil emulsified cosmetic of the present invention is characterized by being formulated with the oil-dispersible cosmetic composition of the present invention, or with the zinc oxide powder of the present invention.

[0018] Furthermore, the powder cosmetic of the present invention is characterized by being formulated with the zinc oxide powder of the present invention.

[0019] Invention Effects

[0020] According to the present invention, a zinc oxide powder, an oil-dispersible cosmetic composition formulated with said zinc oxide powder, and a cosmetic (water-in-oil emulsion cosmetic, oil-in-water emulsion cosmetic, and powder cosmetic) can be provided, wherein the zinc oxide powder can be used to prepare a cosmetic that exhibits excellent visible light transmittance and ultraviolet shielding properties when applied to the skin.

[0021] The oil-in-water emulsion cosmetic and water-in-oil emulsion cosmetic of the present invention can improve transparency. Furthermore, when applied to the skin, they can suppress whitening and provide excellent UV protection. Further, the powder cosmetic of the present invention, when applied to the skin, can suppress whitening and provide excellent UV protection. Detailed Implementation

[0022] <Zinc Oxide Powder>

[0023] The number distribution of zinc oxide powder of the present invention, obtained from transmission electron microscopy (TEM) images, shows the D... 50(The particle size corresponding to 50% of the cumulative frequency based on the number of particles. This will sometimes be abbreviated as "D" below.) 50 The size of the grain is 100nm to 200nm, the aspect ratio is 1.1 to 1.4, and the grain size obtained by X-ray diffraction spectroscopy (hereinafter sometimes simply referred to as "grain size") is 70nm to 200nm.

[0024] The zinc oxide powder of this invention belongs to the so-called non-nano zinc oxide category, specifically D. 50 Powder with a particle size greater than 100 nm. That is, "non-nano zinc oxide" as described in this specification refers to D... 50 The zinc oxide powder is larger than 100 nm. As mentioned above, zinc oxide of this size has poorer UV shielding performance compared to smaller zinc oxide, and it will reduce the visible light transmittance when compounded into cosmetics. For example, when the cosmetic is applied to the skin, it is prone to causing whitening.

[0025] D is defined in the zinc oxide powder of the present invention. 50 The upper limit of the aspect ratio and grain size is kept within a specific range. Thus, when it is compounded into cosmetics, for example, the visible light transmittance and ultraviolet shielding performance of the cosmetics can be improved when applied to the skin.

[0026] As mentioned above, the D of zinc oxide powder 50 It is above 100nm. But if D 50 If the concentration is too high, the visible light transmittance of the resulting cosmetic compound will decrease when applied to the skin, and the UV shielding performance will also be reduced. Therefore, from the perspective of preparing cosmetics that can exhibit excellent visible light transmittance and UV shielding performance when applied to the skin, the D of zinc oxide powder is crucial. 50 Preferably, it is below 200nm, more preferably below 195nm, and even more preferably below 190nm.

[0027] Furthermore, for zinc oxide powder, the number distribution in D obtained from TEM images 10 (The particle size corresponding to 10% of the cumulative frequency based on the number of particles. This will sometimes be abbreviated as "D" below.) 10 The preferred wavelength is 100nm or more and 200nm or less, more preferably 100nm or more and 160nm or less, and even more preferably 100nm or more and 135nm or less.

[0028] Furthermore, for zinc oxide powder, from the perspective of ensuring excellent UV shielding performance and optimizing the balance between the UV shielding performance and the visible light transmittance when the compounded cosmetic is applied to the skin, the aspect ratio is preferably 1.4 or less and 1.1 or more, more preferably 1.2 or more.

[0029] Furthermore, for zinc oxide powder, if the grain size is too small, for example, the visible light transmittance of the formulated cosmetic when applied to the skin will decrease. Therefore, from the perspective of improving the visible light transmittance of the formulated cosmetic when applied to the skin and optimizing the balance between visible light transmittance and ultraviolet (UV) shielding performance, the grain size of zinc oxide powder is 70 nm or more. However, if the grain size of zinc oxide powder is too large, the UV shielding performance will decrease. Therefore, from the perspective of ensuring excellent UV shielding performance and optimizing the balance between UV shielding performance and visible light transmittance of the formulated cosmetic when applied to the skin, the grain size of zinc oxide powder is preferably 200 nm or less, more preferably 180 nm or less, and even more preferably 160 nm.

[0030] The zinc oxide powder described in this specification has D 50 D 10 The aspect ratio is obtained using the following method. Using images of zinc oxide powder taken with a TEM (number of particles (primary particles): 100), the particle size (primary particle size), major diameter (major diameter), minor diameter (minor diameter), and aspect ratio of each powder particle are calculated using image analysis particle size distribution measurement software. The particle size is calculated using the Helwood diameter (projected area equivalent diameter). Furthermore, the major diameter refers to the length of the longer side of the rectangle whose area is minimized when it is circumscribed by the selected particle, and the minor diameter refers to the length of the shorter side of the rectangle whose area is minimized when it is circumscribed by the selected particle. Based on the obtained particle size of each particle, D is calculated using the aforementioned software. 50 With D 10 In addition, the aspect ratio is the average of the aspect ratio of each particle, calculated by the software according to (major diameter / minor diameter), across all (100) particles.

[0031] Furthermore, the values ​​described in the following examples were obtained using a JEM-1230 TEM (Junior Electronics Equipment Inc.) and a Mac-View image analysis software (Manufactured by Montage Corporation) to determine the particle size distribution. Additionally, the D0 value of the zinc oxide powder in the following examples was determined. 90 (The particle size corresponding to 90% of the cumulative frequency based on the number of particles, hereinafter referred to as "D") 90 ") also for the adoption of D 50 The value is obtained using the same method.

[0032] The grain size of the zinc oxide powder described in this specification is obtained by the following method. Using an X-ray diffraction apparatus with Cu-Kα rays, and setting the X-ray output to 45 kV and 40 mA, the X-ray diffraction pattern of the zinc oxide powder was obtained. The full width at half maximum (FWHM) of the peak near 36° (the peak at 36.0 ± 0.5°) in the obtained X-ray diffraction pattern was measured, and the grain size of the zinc oxide was calculated using the Scherrer formula based on this FWHM.

[0033] Furthermore, the values ​​described in the following examples were obtained using an Xpert-PRO manufactured by PANalytical Co., Ltd. as an X-ray diffraction apparatus.

[0034] In the zinc oxide powder of the present invention, the ratio Tt550 (transmittance of light with a wavelength of 550 nm) to Tt370 (transmittance of light with a wavelength of 370 nm), obtained from the spectral transmittance curve of a membrane formed together with nitrocellulose (a membrane formed of zinc oxide powder and nitrocellulose), can be set to 3.5 or higher. Light with a wavelength of 370 nm belongs to the ultraviolet (UV) range, while light with a wavelength of 550 nm is in the visible light region. Therefore, Tt550 / Tt370 is an indicator of the balance between UV shielding performance and visible light transmittance in cosmetics containing zinc oxide powder. When this value is 3.5 or higher, the balance between UV shielding performance and visible light transmittance in cosmetics containing zinc oxide powder is more excellent. There is no particular upper limit to the Tt550 / Tt370 value in the zinc oxide powder, but it is typically 8.0. If Tt550 / Tt370 exceeds 8.0, the possibility that it is not non-nano zinc oxide increases.

[0035] Furthermore, by setting the transmittance Tt370 of light at a wavelength of 370 nm, obtained from the spectral transmittance curve of a membrane formed from zinc oxide powder and nitrocellulose, to 24 or less, preferably 23 or less, and even more preferably 22 or less, superior UV protection performance can be ensured, for example, in cosmetics formulated with zinc oxide powder. The lower limit of Tt370 is not specifically limited and is typically 10. When Tt370 is 10, setting the amount of the compound in the sunscreen to the international upper limit of 25% by mass can achieve an SPF (Sun Protection Factor) of 50.

[0036] Furthermore, the transmittance Tt550 of light at a wavelength of 550 nm, obtained from the spectral transmittance curve of a membrane formed from zinc oxide powder and nitrocellulose, can be set to 80 or higher, preferably 82 or higher. Thus, for example, in cosmetics containing zinc oxide powder, transparency can be improved by increasing visible light transmittance, further suppressing whitening when the cosmetic is applied to the skin. The upper limit of Tt550 is not specifically limited, and is typically 92. When Tt550 exceeds 92, the likelihood of it not being non-nano zinc oxide increases.

[0037] The Tt370 and Tt550 mentioned in this specification are values ​​obtained by the following method.

[0038] The membrane used in the assay was prepared as follows: 100.0 g nitrocellulose, 140.0 g ethyl acetate, 210.0 g n-butyl acetate, 70.0 g ethylene glycol mono-n-butyl ether, and 180.0 g toluene were placed in a 1000 mL sealed container and mixed using a shaker at 100 rpm for 12 hours to obtain a nitrocellulose solution. 40.0 g of this nitrocellulose solution, 1.0 g zinc oxide powder, and 50.0 g glass beads with a diameter of 1.5 mm were placed in a 100 mL sealed container and dispersed using a test disperser at 1725 rpm for 1 hour to obtain a zinc oxide powder dispersion.

[0039] The dispersion of the zinc oxide powder was coated onto a polypropylene film and dried to obtain a film formed from zinc oxide and nitrocellulose. The total light transmittance of the film was measured using a spectrophotometer to obtain a spectral transmittance curve. The transmittance at 370 nm and 550 nm wavelengths were read from the spectral transmittance curve to determine Tt370 and Tt550.

[0040] In addition, the values ​​described in the following embodiments were obtained using the following materials and under the following conditions.

[0041] • Nitrocellulose: Nitrocellulose (H1 / 2) manufactured by Kishida Chemical Co., Ltd.

[0042] • Ethyl acetate, n-butyl acetate, ethylene glycol mono-n-butyl ether, toluene: Manufactured by Sigma-Aldrich Corporation

[0043] • Sealed container: "J-type round wide-mouth bottle, 1000mL" manufactured by Nikon Hansen Co., Ltd.

[0044] "J-type round wide-mouth bottle, 100mL" manufactured by Nihon Hansen Co., Ltd.

[0045] • Shaking machine: "Thermostatic Shaking Machine Z-1" manufactured by Sermonix Co., Ltd.

[0046] • Experimental disperser: RedDevil Paint Mixer 1400

[0047] • Polypropylene film: "Plain Color OPP Film #40" manufactured by Mitsui Chemicals Higashi Cellulose Co., Ltd.

[0048] • Spectrophotometer: "U-4100" (equipped with an integrating sphere) manufactured by Hitachi High Technology Co., Ltd.

[0049] • Spectrophotometer measurement conditions

[0050] Scanning speed: 300nm / minute

[0051] Sampling interval: 2nm

[0052] Measurement wavelength: 250–700 nm

[0053] Furthermore, the transmittance of light with a wavelength of 320 nm is also described in the following embodiments: Tt320, which is a value obtained using the same method as Tt370, etc.

[0054] If it is the zinc oxide powder described above, then Tt370, Tt550, and Tt550 / Tt370 can be set to the values ​​described above.

[0055] Zinc oxide powder can be manufactured, for example, by mixing an aqueous solution of zinc chloride with an aqueous solution of sodium carbonate to prepare a slurry containing basic zinc carbonate, extracting the basic zinc carbonate from the slurry and calcining it.

[0056] Furthermore, the zinc chloride aqueous solution and sodium carbonate aqueous solution used in preparing the slurry containing basic zinc carbonate preferably have low impurity content (components other than zinc chloride and water in the zinc chloride aqueous solution, and components other than sodium carbonate and water in the sodium carbonate aqueous solution), thereby facilitating the D of the final zinc oxide powder. 50 and D 10 Then, the aspect ratio and grain size are adjusted to the values ​​mentioned above.

[0057] Furthermore, the concentration of zinc chloride in the aqueous zinc chloride solution used to prepare the slurry containing basic zinc carbonate is, for example, 1 to 30% by mass. Additionally, the concentration of sodium carbonate in the aqueous sodium carbonate solution used to prepare the slurry containing basic zinc carbonate is, for example, 1 to 20% by mass.

[0058] Furthermore, as conditions for calcining the basic zinc carbonate extracted from the above slurry, for example, the calcination temperature can be set to 500–650°C and the calcination time can be set to 2–12 hours.

[0059] Zinc oxide powder can be surface-treated. As a surface treatment agent for surface treatment of zinc oxide powder, at least one material (hydrophobic modifier) ​​selected from the group consisting of silicone oil, fatty acids, and alkylsilanes can be listed. Zinc oxide powder is hydrophilic, but by surface treatment using the aforementioned surface treatment agent acting as a hydrophobic modifier, the hydrophobicity of the zinc oxide powder surface can be improved, for example, its dispersibility in cosmetic oils can be enhanced, and the loss of zinc oxide powder from the skin due to moisture such as sweat can be prevented when cosmetics are applied to the skin.

[0060] As silicone oils, examples include so-called linear silicone oils such as dimethyl silicone oil (dimethyl polysiloxane), phenyl dimethyl polysiloxane (methyl phenyl polysiloxane), and hydrogenated dimethyl polysiloxane (polymethyl hydrosiloxane); and so-called branched silicone oils such as trimethylsiloxysilicic acid and triethoxysilyl ethyl polydimethylsiloxane ethylhexyl dimethyl polysiloxane.

[0061] Examples of fatty acids include lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, and behenic acid.

[0062] Examples of alkylsilanes include methyltrimethoxysilane, dimethyldimethoxysilane, phenyltrimethoxysilane, methyltriethoxysilane, dimethyldiethoxysilane, phenyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltriethoxysilane, decyltrimethoxysilane, and other alkoxysilanes; hexamethyldisilazane and other silazanes; and so on.

[0063] From the perspective of ensuring stable improvement in water resistance and hydrophobicity (improved dispersibility in oil) resulting from its use, the content of the aforementioned surface treatment agent in the zinc oxide powder is preferably 0.5 parts by mass or more, more preferably 1 part by mass or more, based on 100 parts by mass of zinc oxide component in the powder. Furthermore, if the amount of surface treatment agent in the zinc oxide powder is too high, for example, the amount of zinc oxide component itself in the powder may become too low, and there is a risk that the effect of its use may be weakened. Therefore, based on 100 parts by mass of zinc oxide component in the powder, the content of the surface treatment agent in the zinc oxide powder is preferably 30 parts by mass or less, more preferably 25 parts by mass or less.

[0064] Surface treatment using the above-mentioned surface treatment agent can be performed by directly contacting zinc oxide powder with the above-mentioned surface treatment agent through mixing, or by mixing zinc oxide powder with a solution obtained by dissolving the above-mentioned surface treatment agent in an organic solvent (such as toluene).

[0065] <Oil-dispersible cosmetic compositions>

[0066] The oil-dispersible cosmetic composition of the present invention is a composition for use in cosmetics, compounded with zinc oxide powder of the present invention and oil (oil fraction), wherein the zinc oxide powder is dispersed in the oil.

[0067] As for oils that can be used in oil-dispersible cosmetic compositions, the preferred types are those that are conventionally used in cosmetics applied to the skin, such as sunscreens, for example, ester oils (oils that are liquid at 25°C), hydrocarbon oils (oils that are liquid at 25°C), and silicone oils (oils that are liquid at 25°C).

[0068] Examples of ester oils that are liquid at 25°C include isononyl isononanoate, triglycerides (caprylic / capric), ethylhexyl palmitate, ethylhexyl methoxycinnamate, triethylhexyl triethylhexanoate, cetyl ethylhexanoate, methyl heptyl laurate, methyl heptyl myristate, and alkyl benzoate (C12-15).

[0069] Examples of hydrocarbons that are liquid at 25°C include hydrogenated polyisobutylene, isododecane, mineral oil, and squalane.

[0070] Examples of silicone oils that are liquid at 25°C include dimethyl silicone oil, cyclopentasiloxane, cyclopolydimethylsiloxane, and diphenylsiloxyphenyltrimethyl silicone oil.

[0071] There is no particular limitation on the amount of zinc oxide powder in oil-dispersible cosmetic compositions, which is usually 20 to 70% by mass.

[0072] <Oil-in-water emulsion cosmetics and water-in-oil emulsion cosmetics>

[0073] The water-in-oil emulsion cosmetic and the oil-in-water emulsion cosmetic of the present invention are emulsion cosmetics, compounded with the oil-dispersible cosmetic composition of the present invention, or compounded with the zinc oxide powder of the present invention. That is, when preparing the water-in-oil emulsion cosmetic and the oil-in-water emulsion cosmetic, the zinc oxide powder of the present invention can be dispersed in oil to prepare the oil-dispersible cosmetic composition of the present invention, and then the composition can be used to prepare the water-in-oil emulsion cosmetic or the oil-in-water emulsion cosmetic. Alternatively, the dispersion step of zinc oxide powder in oil can be omitted when preparing the water-in-oil emulsion cosmetic or the oil-in-water emulsion cosmetic.

[0074] Furthermore, when using zinc oxide powder that has undergone surface treatment with the aforementioned surface treatment agent (hydrophobic modifier), this type of zinc oxide powder, due to its strong hydrophobicity, typically constitutes a higher proportion in the oil phase of water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics. On the other hand, since untreated zinc oxide powder has a strong hydrophilicity, when using this type of powder, it typically constitutes a higher proportion in the aqueous phase of the aforementioned emulsion cosmetics. To allow it to exist in the oil phase, a surfactant with a lower HLB (Hydrophile-Lipophile Balance) can be used.

[0075] The amount of zinc oxide powder in the blend of water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics can be set according to the required amount based on their intended use, usually 0.1 to 40% by mass.

[0076] Furthermore, both water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics are emulsions, therefore water is added in combination. The amount of water in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics can be determined according to their form (whether they are water-in-oil emulsions or oil-in-water emulsion cosmetics, etc.) and their intended use, and is usually 10-80% by mass.

[0077] Furthermore, since water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics are emulsions, they are compounded with oils. Oils that can be used in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics include, for example, the oils previously exemplified as materials that can be compounded into oil-dispersible cosmetic compositions. The amount of oil compounded in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics can be set according to its form (whether it is a water-in-oil emulsion or an oil-in-water emulsion cosmetic, etc.) and its intended use, and is typically 10 to 80% by mass.

[0078] In addition, surfactants are often compounded into water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics to emulsify water and oil. Regarding surfactants, various types of surfactants commonly used in cosmetics (cationic surfactants, anionic surfactants, nonionic surfactants, and amphoteric surfactants) can be compounded.

[0079] The amount of surfactant in the combination of water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics is, for example, enough to maintain the emulsion state well, usually 1 to 10 by mass.

[0080] Furthermore, in water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics, desired ingredients can be formulated from various ingredients commonly used in conventional cosmetics, depending on their intended use. Examples of such ingredients include, for instance, oils, higher alcohols, waxes, silicone oils, lower alcohols, UV absorbers, skin feel improvers, pigments, clay minerals, film-forming agents, thickeners, moisturizers (polyols, etc.), preservatives, pH adjusters, and fragrances.

[0081] <Powder Cosmetics>

[0082] The powder cosmetic of the present invention is formulated with the zinc oxide powder of the present invention. The amount of zinc oxide powder in the powder cosmetic can be set according to its intended use, etc., and is usually 0.1 to 40% by mass.

[0083] Powder cosmetics can be formulated with ingredients other than zinc oxide powder. Examples of such ingredients include inorganic powders other than zinc oxide powder, organic powders such as polymer powders, surfactant metal salt powders (metal soaps), pigments, fragrances, preservatives, binders, etc.

[0084] Example

[0085] The present invention will now be described in detail with reference to embodiments. However, the following embodiments do not constitute a limitation on the present invention.

[0086] <Preparation of Zinc Oxide Powder>

[0087] Example 1

[0088] 132g of a 47% (w / w) zinc chloride aqueous solution was diluted with 519g of deionized water. Then, 430g of a 10% (w / w) sodium carbonate aqueous solution (prepared by dissolving 43g of sodium carbonate in 387g of deionized water) was added to obtain a white slurry. The slurry was filtered, and the precipitate was collected. The precipitate was then repeatedly washed with deionized water until the conductivity of the filtrate reached below 150 μS / cm. The resulting filter cake was then dried at 130℃ for 12 hours, followed by calcination at 500℃ for 4 hours. The resulting powder was pulverized using a needle mill to obtain zinc oxide powder.

[0089] Example 2

[0090] Except for changing the calcination conditions after drying the filter cake to 500°C and 6 hours, zinc oxide powder was obtained in the same manner as in Example 1.

[0091] Example 3

[0092] Except for changing the calcination conditions after drying the filter cake to 550°C and 6 hours, zinc oxide powder was obtained in the same manner as in Example 1.

[0093] Example 4

[0094] Except for changing the calcination conditions after drying the filter cake to 600°C and 2 hours, zinc oxide powder was obtained in the same manner as in Example 1.

[0095] Comparative Example 1

[0096] Except for changing the calcination conditions after drying the filter cake to 600°C and 6 hours, zinc oxide powder was obtained in the same manner as in Example 1.

[0097] Comparative Example 2

[0098] 132g of a 47% (w / w) zinc chloride aqueous solution was diluted with 396g of deionized water, and 207g of a 10% (w / w) ammonia solution was added to generate zinc oxide nuclei. Then, 352g of a 10% (w / w) sodium hydroxide aqueous solution was added to the slurry to obtain a white slurry. The slurry was then heated to 90°C over 60 minutes while stirring, and further heated and matured at 90°C for 30 minutes while stirring. After maturation, the resulting slurry was filtered, and the precipitate was collected. The precipitate was then repeatedly washed with deionized water until the conductivity of the filtrate reached below 150 μS / cm. The resulting filter cake was then dried at 130°C for 12 hours, followed by calcination at 600°C for 2 hours. The calcined powder was then pulverized using a needle mill to obtain zinc oxide powder.

[0099] Comparative Example 3

[0100] 16.28 g of micronized zinc oxide "MZ-150" (primary particle size: 80 nm) manufactured by Teika Co., Ltd. was dispersed in 500 g of deionized water to obtain a zinc oxide slurry. Furthermore, 20.77 g of hydrogen peroxide aqueous solution (manufactured by Wako Pure Pharmaceutical Co., Ltd.) was diluted with 500 g of deionized water to prepare a hydrogen peroxide aqueous solution. The hydrogen peroxide aqueous solution was then added to the slurry while stirring at 25°C for 6 hours. The resulting liquid was then filtered, and the precipitate was collected and washed with water. The filter cake obtained from this operation was then dried at 110°C for 12 hours, followed by calcination at 600°C for 2 hours. The calcined powder was then pulverized using a needle mill to obtain zinc oxide powder.

[0101] The physical properties of the zinc oxide powder in the examples and comparative examples are shown in Table 1.

[0102] In addition, for the zinc oxide powder in the examples and comparative examples, Tt320, Tt370 and Tt550 were obtained according to the above method, and Tt550 / Tt370 was calculated. These results are shown in Table 2.

[0103] Furthermore, the specific surface area of ​​the zinc oxide powder in the examples and comparative examples was determined by the BET method using a fully automated specific surface area measuring device (Macsorb HMmodel-1208 manufactured by Monttec Co., Ltd.). In addition, the degassing process conditions during the measurement were set to 150°C for 20 minutes. These results are recorded in Table 1.

[0104] [Table 1]

[0105]

[0106] [Table 2]

[0107]

[0108] As shown in Tables 1 and 2, D 50 The zinc oxide powders in Examples 1-4, whose aspect ratio and grain size are all within suitable ranges, have low Tt370 values, high Tt550 values, and high Tt550 / Tt370 values, thus ensuring a high level of balance between UV blocking performance and visible light transmittance (UV blocking performance and visible light transmittance when compounded in cosmetics, etc. The same definition applies to the UV blocking performance and visible light transmittance of zinc oxide powder below). Additionally, D 50 The zinc oxide powder in Example 4, which has a relatively large grain size, has a higher Tt370 value compared to the zinc oxide powders in Examples 1 to 3. Its ultraviolet shielding performance is slightly worse, but it can still ensure a practical level of performance.

[0109] In contrast, D 50 The zinc oxide powder in Comparative Example 1, with its excessively large grain size, has a high Tt370 value, a low Tt550 value, and a low Tt550 / Tt370 ratio, resulting in poor ultraviolet (UV) shielding performance and poor visible light transmittance. Furthermore, the zinc oxide powder in Comparative Example 2, with its excessively large aspect ratio and grain size, has a high Tt370 value and a low Tt550 / Tt370 ratio, resulting in poor UV shielding performance and a poor balance between UV shielding performance and visible light transmittance. Further, the zinc oxide powder in Comparative Example 3, with its excessively small grain size, has a low Tt550 value and poor visible light transmittance.

[0110] As can be seen from the above results, the zinc oxide powder in Examples 1 to 4 can be used to prepare water-in-oil emulsion cosmetics and oil-in-water emulsion cosmetics, which have excellent UV shielding performance, relatively high transparency, and can inhibit whitening when applied to the skin; in addition, powder cosmetics can be prepared, which have excellent UV shielding performance and can inhibit whitening when applied to the skin.

[0111] <Preparation of Cosmetics>

[0112] (Preparation of surface-treated zinc oxide powder)

[0113] Example 5

[0114] The zinc oxide powder in Example 1 was surface-treated by contacting it with octyltriethoxysilane to obtain the surface-treated zinc oxide powder in Example 5.

[0115] Comparative Example 4

[0116] Surface-treated zinc oxide powder was prepared in the same manner as in Example 5, except that zinc oxide powder was used in Comparative Example 1.

[0117] Comparative Example 5

[0118] Except for using the zinc oxide powder in Comparative Example 2, the surface-treated zinc oxide powder was prepared in the same manner as in Example 5.

[0119] Comparative Example 6

[0120] Except for using the zinc oxide powder in Comparative Example 3, the surface-treated zinc oxide powder was prepared in the same manner as in Example 5.

[0121] (Preparation of water-in-oil emulsion cosmetics)

[0122] Examples 6-8 and Comparative Examples 7-9

[0123] By combining the components shown in Table 3 according to the proportions shown in Table 3, the water-in-oil emulsion cosmetics in Examples 6-8 and Comparative Examples 7-9 were prepared (all of these cosmetics were water-in-oil emulsions after preparation).

[0124] The ultraviolet (UV) shielding performance (UV protection effect) of the water-in-oil emulsion cosmetics in Examples 6-8 and Comparative Examples 7-9 was evaluated (in vitro test). The evaluation was based on the SPF determination method (ISO 24443), with the water-in-oil emulsion cosmetics in each example and comparative example measured at 1.3 mg / cm³. 2 An appropriate amount of the sample was applied to an evaluation sample (HELIOPLATE HD6, manufactured by Helioscreen), and dried at room temperature for 30 minutes to obtain the test sample. The SPF and UVAPF (Ultraviolet A Protection Factor) were then measured using an SPF analyzer (UV-2000S, manufactured by Labsphere). Furthermore, the transmittance at 450 nm was determined from the spectral transmittance curve obtained during the SPF measurement, and the transparency of each water-in-oil emulsion cosmetic was also evaluated.

[0125] These results are recorded in Table 3. Furthermore, in Table 3, the percentage of each ingredient is expressed as a percentage (%) with the total amount of each cosmetic product as 100%; all percentages are by mass. The percentage is omitted from this table; only the numerical value representing the total amount is used (the same applies to Tables 4-7 below). Additionally, the “titanium dioxide powder (A)” shown in Table 3 is “MT-N1” manufactured by Teika Co., Ltd., and the “spherical silica powder” is “TMS-T05DCB” manufactured by Teika Co., Ltd. (the same applies to Tables 5-7 below).

[0126] [Table 3]

[0127]

[0128] As shown in Table 3, the water-in-oil emulsion cosmetics in Examples 6-8 have higher SPF and UVAPF values ​​than the cosmetics in Comparative Examples 7-9, exhibiting excellent UV shielding performance. Furthermore, the water-in-oil emulsion cosmetics in Examples 6-8 all show relatively high transmittance at a wavelength of 450 nm and excellent transparency.

[0129] (Preparation of water-in-oil emulsion cosmetics)

[0130] Examples 9-11 and Comparative Examples 10-18

[0131] By compounding the components shown in Tables 4 to 6 according to the proportions shown in Tables 4 to 6, the oil-in-water emulsion cosmetics in Examples 9 to 11 and Comparative Examples 10 to 18 were prepared (all of these cosmetics were oil-in-water emulsions after preparation).

[0132] For the water-in-oil emulsion cosmetics in Examples 9-11 and Comparative Examples 10-18, the UV shielding performance (UV protection effect) and transparency were evaluated in the same manner as the oil-in-water emulsion cosmetics in Example 6. These results are recorded in Tables 4-6.

[0133] [Table 4]

[0134]

[0135] [Table 5]

[0136]

[0137] [Table 6]

[0138]

[0139] As shown in Table 4, the water-in-oil emulsified cosmetic in Example 9 has a higher SPF value and excellent UV shielding performance compared to the cosmetics in Comparative Examples 10-12, which have the same composition except for the zinc oxide powder surface treatment. It also has high transmittance at 450nm wavelength and excellent transparency.

[0140] In addition, as shown in Table 5, the water-in-oil emulsified cosmetic in Example 10 has a higher SPF value and excellent UV shielding performance compared to the cosmetics in Comparative Examples 13-15, which have the same composition except for the zinc oxide powder surface treatment. It also has high transmittance at 450nm wavelength and excellent transparency.

[0141] Furthermore, as shown in Table 6, the water-in-oil emulsified cosmetic in Example 11 has a higher SPF value and excellent UV shielding performance compared to the cosmetics in Comparative Examples 16-18, which have the same composition except for the zinc oxide powder surface treatment. It also has high transmittance at 450nm wavelength and excellent transparency.

[0142] (Preparation of powder cosmetics)

[0143] The powder cosmetics in Example 12 and Comparative Examples 19-21 were prepared by combining the ingredients shown in Table 7 according to the proportions shown in Table 7.

[0144] For the powder cosmetics in Examples 12 and Comparative Examples 19-21, the UV shielding performance (UV protection effect) was evaluated in the same manner as the water-in-oil emulsion cosmetics in Example 6. These results are recorded in Table 7. The "titanium dioxide powder (B)" shown in Table 7 is "MPY-1133M" manufactured by Teika Co., Ltd., and the "titanium dioxide powder (C)" is "MT-100TV" manufactured by Teika Co., Ltd.

[0145] [Table 7]

[0146]

[0147] As shown in Table 7, the powder cosmetic in Example 12 has higher SPF and UVAPF values ​​than the cosmetics in Comparative Examples 19-21, and has excellent UV shielding performance.

[0148] This invention may employ other embodiments besides those described above without departing from its core spirit. The embodiments disclosed in this application are merely illustrative, and the invention is not limited to these embodiments. The scope of this invention should be determined by the appended claims and interpreted in a way that takes precedence over the foregoing description. All modifications within the scope of equivalents to the claims are included within the scope of the claims.

[0149] Industrial availability

[0150] The oil-in-water emulsified cosmetics, water-in-oil emulsified cosmetics, and powder cosmetics of the present invention are applicable to various cosmetics (sunscreens, foundations, lotions, skin creams, etc.) formulated with zinc oxide powder. The zinc oxide powder of the present invention can constitute the oil-dispersible cosmetic composition, oil-in-water emulsified cosmetic, water-in-oil emulsified cosmetic, and powder cosmetic of the present invention. The oil-dispersible cosmetic composition of the present invention can constitute the oil-in-water emulsified cosmetic and water-in-oil emulsified cosmetic of the present invention.

Claims

1. A zinc oxide powder, characterized in that, D in the number distribution obtained from transmission electron microscopy images 50 The size ranges from 100 to 200 nm, with an aspect ratio of 1.1 to 1.

4. The grain size, determined by X-ray diffraction spectroscopy, is 70 to 200 nm.

2. The zinc oxide powder according to claim 1, wherein, D in the number distribution obtained from transmission electron microscopy images 10 The wavelength is 100–200 nm.

3. The zinc oxide powder according to claim 1 or 2, wherein, The ratio of the transmittance Tt550 of light at a wavelength of 550 nm to the transmittance Tt370 of light at a wavelength of 370 nm, obtained from the spectral transmittance curve of the membrane formed with nitrocellulose, is greater than 3.

5.

4. The zinc oxide powder according to claim 3, wherein, Tt370 is below 24.

5. The zinc oxide powder according to claim 3 or 4, wherein, Tt550 is above 80.

6. The zinc oxide powder according to any one of claims 1 to 5, wherein it has undergone surface treatment.

7. The zinc oxide powder according to claim 6, wherein it has been surface treated with at least one surface treatment agent selected from the group consisting of silicone oil, fatty acids and alkylsilanes.

8. An oil-dispersible cosmetic composition, characterized in that, The zinc oxide powder according to any one of claims 1 to 7 is dispersed in oil.

9. A water-in-oil emulsion cosmetic, characterized in that, It is compounded with the oil-dispersible cosmetic composition of claim 8.

10. A water-in-oil emulsion cosmetic, characterized in that, It is compounded with the oil-dispersible cosmetic composition of claim 8.

11. A water-in-oil emulsion cosmetic, characterized in that, It is compounded with zinc oxide powder according to any one of claims 1 to 7.

12. A water-in-oil emulsion cosmetic, characterized in that, It is compounded with zinc oxide powder according to any one of claims 1 to 7.

13. A powder cosmetic, characterized in that, It is compounded with zinc oxide powder according to any one of claims 1 to 7.

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