Zinc oxide powder, dispersion, paint, cosmetics

Abstract

A zinc oxide powder which has a BET specific surface area (X) of 1.5 m2 / g to 65 m2 / g, inclusive, also has a value determined from the formula: [apparent specific volume (mL / g) determined by a layering method] / [apparent specific volume (mL / g) determined by a tap method] is 1.5 to 2.5, inclusive, and satisfies the below-shown formulae (1) and (2). (1): A1 / E2=aX+0.06 (2): (M2-M1) / E2≧0.02

Description

Technical Field

[0001] The present invention relates to zinc oxide powder, a dispersion, a paint, and a cosmetic. This application claims priority based on Japanese Patent Application No. 2020-198905 filed in Japan on November 30, 2020, and incorporates its content herein.

Background Art

[0002] Zinc oxide has functions such as an ultraviolet ray shielding function and a gas permeation suppression function, and also has high transparency. Therefore, it is used in applications that require transparency, such as ultraviolet ray shielding films, ultraviolet ray shielding glasses, cosmetics, and gas barrier films.

[0003] Zinc oxide powder to be incorporated into paints and cosmetics is generally required to have a high whiteness. This is because when zinc oxide powder with a low whiteness is incorporated into paints and cosmetics, it causes coloring and affects the appearance. For example, in Patent Document 1, in order to suppress the coloring of zinc oxide, zinc oxide having a loss on ignition of 1.0 mass% or less and a whiteness W of 95 or more has been proposed.

Prior Art Documents

Patent Documents

[0004] [

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, even with zinc oxide powder having a high whiteness, when energy is applied to incorporate it into paints and cosmetics, there is a problem that the zinc oxide powder is colored yellow or the like, damaging the appearance of the paints and cosmetics. It has been required to control the coloring of zinc oxide powder such as yellow. [

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a zinc oxide powder in which coloring is suppressed even when energy is applied, and a dispersion liquid, a paint, and a cosmetic containing the zinc oxide powder.

Means for Solving the Problems

[0007] That is, the zinc oxide powder of the first aspect of the present invention has a BET specific surface area (X) of 1.5 m 2 / g or more and 65 m 2 / g or less, and the value obtained from the formula of apparent specific volume (mL / g) by the static method / apparent specific volume (mL / g) by the tap method is 1.5 or more and 2.5 or less, and satisfies the following formula (1) and the following formula (2). A1 / E2 = aX + 0.06 (1) (M2 - M1) / E2 ≥ 0.02 (2) Here, X is the specific surface area of the zinc oxide powder (unit: m 2 / g), A1 is the spectral value of the peak existing in the vicinity of 580 cm -1 of the Raman spectrum of the zinc oxide powder obtained by Raman spectroscopy, E2 is the spectral value of the peak existing in the vicinity of 437 cm -1 [[ID=I23]]of the Raman spectrum, a is a value of 0.001 or more and 0.02S or less, M2 is the maximum value of the spectrum in the range of 1091 cm -1 to 1170 cm -1 of the Raman spectrum, and M1 is the maximum value of the spectrum in the range of 1020 cm -1 to 1090 cm -1 of the Raman spectrum.

[0008] The dispersion liquid of the second aspect of the present invention contains the zinc oxide powder of the present invention and a dispersion medium.

[0009] The paint of the third aspect of the present invention contains the zinc oxide powder of the present invention, a resin, and a dispersion medium.

[0010] The cosmetic of the fourth aspect of the present invention contains at least one selected from the group consisting of the zinc oxide powder of the present invention and the dispersion liquid of the present invention. [Effects of the Invention]

[0011] According to the zinc oxide powder of the present invention, the BET specific surface area (X) is 1.5 m². 2 / g or more 65m 2 A zinc oxide powder can be provided in which discoloration is suppressed even when energy is applied, as long as the value obtained from the formula of apparent specific volume (mL / g) by the standing method / apparent specific volume (mL / g) by the tapping method is 1.5 or more and 2.5 or less, and the above formulas (1) and (2) are satisfied.

[0012] According to the dispersion of the present invention, because it contains the zinc oxide powder of the present invention, discoloration is suppressed even when dispersed at high energy, and a highly transparent dispersion with suppressed discoloration can be obtained.

[0013] According to the paint of the present invention, because it contains the zinc oxide powder of the present invention, a paint with high transparency and suppressed discoloration can be obtained.

[0014] According to the present invention, since the cosmetic composition contains at least one selected from the group consisting of the zinc oxide powder and the dispersion of the present invention, it is possible to obtain a cosmetic composition that is highly transparent and has suppressed discoloration. [Modes for carrying out the invention]

[0015] This section describes preferred embodiments of the zinc oxide powder, dispersion, paint, and cosmetic materials of the present invention. These embodiments are provided specifically to better illustrate the spirit of the invention and do not limit the invention unless otherwise specified. Omissions, additions, substitutions, and other modifications are permitted without departing from the spirit of the invention.

[0016] [Zinc oxide powder] The zinc oxide powder of this embodiment has a BET specific surface area (X) of 1.5 m². 2 / g or more 65m 2The value obtained from the formula (Apparent specific volume by static method (mL / g) / Apparent specific volume by tap method (mL / g)) is between 1.5 and 2.5, and satisfies the following equations (1) and (2). A1 / E2 = aX + 0.06 (1) (M2-M1) / E2≧0.02 (2) Here, X is the specific surface area of ​​the zinc oxide powder (unit: m²). 2 ( / g), A1 is the 580 cm⁻¹ of the Raman spectrum of zinc oxide powder obtained by Raman spectroscopy. -1 This is the spectral value of the peak present in the vicinity, where E2 is the 437 cm⁻¹ value of the aforementioned Raman spectrum. -1 This is the spectral value of a nearby peak, where a is between 0.001 and 0.025, and M2 is the 1091 cm⁻¹ value of the Raman spectrum. -1 ~1170cm -1 This is the maximum value of the spectrum in the range, where M1 is the 1020 cm⁻¹ of the Raman spectrum. -1 ~1090cm -1 This is the maximum value of the spectrum within that range. Note that the peak spectral value refers to the value at the peak's highest point (maximum value of the peak). -1 "Nearby" means, for example, the range of 560-600, preferably 570-590, more preferably 572-588, and 437 cm -1 "Nearby" may mean, for example, the range of 427 to 447, preferably 432 to 442. In this specification, apparent specific volume calculated by the static method can be replaced with static volume. Similarly, apparent specific volume calculated by the tap method can be replaced with tap volume. The zinc oxide powder (particles) of the embodiment preferably contains 99.5% by mass or more of zinc oxide, more preferably 99.7% by mass or more, and even more preferably 100% by mass. The zinc oxide powder of the embodiment may also consist only of zinc oxide particles. The zinc oxide content in the zinc oxide powder of this embodiment refers to the value measured by the following method. This measurement method is in accordance with the "Quantitative Method for Zinc Oxide" described in the Quasi-Drug Raw Materials Standards 2006 (External Standards). Place the zinc oxide powder in a muffle furnace and heat strongly at 500°C until constant weight is reached (the mass does not change). Then, allow the zinc oxide powder to cool to room temperature in a glass desiccator containing silica gel. Accurately weigh 1.5 g of the cooled zinc oxide powder, add 50 mL of water and 20 mL of dilute hydrochloric acid, and heat to dissolve the zinc oxide powder. If any impurities remain, add 3 drops of nitric acid to completely dissolve them. Cool the solution to room temperature and add water to make a total volume of 250 mL. Add 10 mL of acetate / ammonium acetate buffer adjusted to pH 5.0 to 25 mL of this solution, and add diluted ammonia water to adjust the pH to 5-5.5. Then, add water to make a total volume of 250 mL, add 0.5 mL of xylenol orange reagent as an indicator, and titrate with 0.05 mol / L disodium edetate solution until yellow. Since 1 mL of 0.05 mol / L disodium edetate solution is equivalent to 4.069 mg of zinc oxide, the amount of zinc oxide content in the zinc oxide powder can be quantified by the amount of 0.05 mol / L disodium edetate solution required for titration. If a value exceeding 100% by mass is calculated using this measurement method, the zinc oxide content should be considered as 100% by mass.

[0017] (Estimated mechanism of color suppression) Here, we will explain the estimated mechanism by which the zinc oxide powder of this embodiment suppresses discoloration even when energy is applied. The inventors have obtained the following new findings by conducting various studies in detail across a wide range of areas. When high energy is applied to ordinary zinc oxide powder, which is an aggregate of nanometer-sized zinc oxide particles, the zinc oxide powder turns yellow or other colors. This discoloration is thought to depend on oxygen vacancies in the zinc oxide powder. Nanometer-sized zinc oxide particles tend to aggregate with each other. Therefore, during the manufacturing process of zinc oxide powder, the zinc oxide particles tend to aggregate, and as a result, oxygen vacancies tend to form inside the zinc oxide powder. When strong energy is applied to the zinc oxide powder, the aggregation of zinc oxide particles is broken up, and the oxygen vacancies that were present inside the aggregate are exposed to the surface. As a result, the zinc oxide powder turns yellow or other colors due to the oxygen vacancies. Therefore, in order to suppress the discoloration of zinc oxide powder, it is necessary to reduce the oxygen vacancies on the outside and inside of the zinc oxide powder. To reduce oxygen vacancies on the exterior and interior of zinc oxide powder, the generation of oxygen vacancies can be suppressed by supplying a sufficient amount of oxygen during the zinc oxide powder manufacturing process and by controlling the apparent specific volume obtained by the static method / apparent specific volume obtained by the tapping method to fall within the above range.

[0018] The amount of oxygen vacancies in zinc oxide powder can be evaluated by Raman spectroscopy. In Raman spectroscopy, the amount of oxygen vacancies is 437 cm⁻¹. -1 The nearby peak (E2) is a peak originating from the wurtzite-type hexagonal crystal structure of ZnO. Also, 580cm -1 The nearby peak (A1) is a peak originating from crystal strain such as oxygen vacancies. Therefore, a smaller A1 / E2 ratio indicates fewer oxygen vacancies in the zinc oxide powder. The peak intensity of A1 is affected by the ease with which the crystal is deformed. The peak intensity of A1 is affected by the size of the zinc oxide particles, i.e., the size of the BET specific surface area of ​​the zinc oxide powder. Generally, the larger the BET specific surface area of ​​the zinc oxide powder, the more easily the zinc oxide particles' crystals are deformed, and as a result, peaks originating from crystal distortion such as oxygen vacancies become larger, and A1 / E2 becomes larger. Therefore, it is preferable that A1 / E2 be within a predetermined range that takes the BET specific surface area into consideration. The inventors have found that zinc oxide powder satisfying the above formula (1) has fewer oxygen vacancies that contribute to discoloration, and that discoloration can be suppressed when it is incorporated into cosmetics.

[0019] Furthermore, the inventors have found that if the zinc oxide powder satisfies both formula (1) and formula (2) above, discoloration is suppressed even when dispersed at high energy.

[0020] 1020cm -1 ~1170cm -1 The M2 and M1 peaks observed within this range are presumed to originate from impurities contained in the zinc oxide powder, respectively. Note that these impurities and zinc oxide are different substances. In zinc oxide powder, generally, 1091 cm³ -1 ~1170cm -1 The maximum value of the peak spectrum observed within this range is 1020 cm⁻¹. -1 ~1090cm -1 It is greater than or equal to the maximum value of the peak spectrum observed within the range. However, the inventors 1091cm -1 ~1170cm -1 The maximum value of the peaks observed within this range 1020cm -1 ~1090cm -1 We found that if the value obtained by dividing the peak spectrum observed within the range by the spectral value of E2 is greater than a predetermined value, then, although the mechanism is unknown, the discoloration of zinc oxide powder when high energy is applied can be suppressed.

[0021] To obtain zinc oxide powder that satisfies equation (2) above, the amount of transition metals from groups 5 to 11 of the fourth period of the periodic table in the zinc oxide powder should be reduced. Specifically, the sum of the amounts of vanadium, chromium, manganese, iron, cobalt, nickel, and copper should be reduced. Methods for reducing the amount of transition metals include using high-purity raw materials, using raw materials from which the transition metals have been removed, or preventing the contamination of the transition metals during the manufacturing process. By satisfying equation (2) above, discoloration caused by impurities can be prevented.

[0022] The amount of the transition metal is preferably 0.5 ppm or more and 20 ppm or less, more preferably 0.5 ppm or more and 15 ppm or less, and even more preferably 1 ppm or more and 10 ppm or less. For reasons unknown, when zinc oxide powder is incorporated into cosmetics, cosmetics with a natural color are obtained because the amount of the transition metal is between 0.5 ppm and 20 ppm. In this invention, the total content of each element from groups 5 to 11 of the fourth period of the periodic table refers to the value measured by ICP emission spectroscopy.

[0023] If the zinc oxide powder satisfies formulas (1) and (2) above, discoloration of the zinc oxide powder will be suppressed even when dispersed at high energy. The upper limit of (M2-M1) / E2 is not particularly limited. If the value of M2 is too large, the amount of impurities contained in the powder is large, which may affect the quality stability. Therefore, the upper limit of (M2-M1) / E2 is preferably 1.0 or less, more preferably 0.50 or less, even more preferably 0.20 or less, and particularly preferably 0.10 or less. The value shown by (M2-M1) / E2 may be, as needed, for example, 0.02 to 0.16, or 0.03 to 0.14, 0.04 to 0.12, 0.05 to 0.10, or 0.06 to 0.08.

[0024] The zinc oxide powder of this embodiment has an apparent specific volume within the above range, determined by the static method and the tapping method. Because it is manufactured to have these characteristics, the amount of oxygen vacancies remaining in the zinc oxide powder can be reduced, and the appropriate amount of oxygen vacancies and impurities to be reduced to suppress discoloration can be determined according to the BET specific surface area of ​​the zinc oxide powder. In other words, by controlling the apparent specific volume using the static method and the apparent specific volume using the tapping method, it is possible to control the amount of zinc oxide particles with undesirable structures or states as much as possible. As a result, the amount of oxygen vacancies remaining inside the zinc oxide powder can be controlled to an even more favorable degree.

[0025] A1 / E2, which indicates the amount of oxygen vacancies, is preferably small. Since the amount of oxygen vacancies is affected by the particle size, the specific surface area (X) is also included in the above equation (1).

[0026] (Methods for measuring the various properties of zinc oxide powder) In this embodiment, the BET specific surface area of ​​the zinc oxide powder may refer to the value measured by the BET method using a specific surface area measuring device, for example, a fully automatic specific surface area measuring device (product name: Macsorb HM Model-1201, manufactured by Mountec Co., Ltd.).

[0027] In this embodiment, the apparent specific volume (mL / g) of zinc oxide powder obtained by the static method refers to the value measured in accordance with JIS K5101-12-1 "Pigment Test Methods - Part 12: Apparent Density or Apparent Specific Volume - Section 1: Static Method". Note that 50 tapping cycles were not performed when determining the apparent specific volume by the static method.

[0028] The apparent specific volume (mL / g) of the zinc oxide powder in this embodiment, obtained by the tapping method, can be measured using a bulk density meter, specifically, a densely packed bulk density meter (product name: TVP-1, manufactured by Tsutsui Rikagakukikai Co., Ltd.). The specific measurement method will now be described. The mass (A) of a 150 mL graduated cylinder (inner diameter: 31 mm, manufactured by Tsutsui Rikagakukikai Co., Ltd.) is measured using an electronic balance. 100 mL or more of zinc oxide powder is placed on a sieve with a mesh size of 500 μm. Next, the zinc oxide powder is wiped with a brush and passed through the sieve. Approximately 100 mL of the zinc oxide powder that has passed through the sieve is placed into the 150 mL graduated cylinder. The mass (B) of this graduated cylinder is measured using an electronic balance. This graduated cylinder is fixed to a densely packed bulk density measuring device. A black rubber stopper is placed in the graduated cylinder to prevent powder from scattering during tapping. The volume (V) of the zinc oxide powder after 50 taps with the densely packed bulk density measuring device is read from the graduated cylinder. Next, the apparent specific volume is calculated as V / (BA). The tapping width can be 20 mm and the tapping speed can be 30 taps / min. In this way, the tapping method is a method of filling a container with powder by tapping it multiple times, and then performing measurements.

[0029] In this embodiment, the crystallite size of the zinc oxide powder refers to the Scherrer diameter calculated using Scherrer's formula, using the full width at half maximum of the diffraction peak of the (10¹) plane and the diffraction angle (2θ) of the powder X-ray diffraction pattern measured by an X-ray diffractometer, for example, using an X-ray diffractometer (product name: AERIS, manufactured by PANalytical). In the X-ray diffraction measurement conditions for powder using the above apparatus, the radiation source is set to CuKα rays, with an output of 40kV and 15mA. Furthermore, the measurement data obtained from the X-ray diffraction measurement can be analyzed using the data processing software AERIS (manufactured by PANalytical). This allows for the calculation of the Scherrer diameter. The Raman spectrum obtained by Raman spectroscopy in the zinc oxide powder of this embodiment may refer to the value obtained using a Raman spectrometer, specifically a Raman spectrometer (model: XploRA PLUS, manufactured by Horiba, Ltd.). Measurement conditions when using the above apparatus include, for example, objective lens: 10x, laser wavelength: 532nm, grating: 1200nm, slit: 100μm, confocal hole: 300μm, neutral density filter: 10%, spectrometer: 1671.63, and measurement wavelength range: 300cm².-1 ~2000cm -1 Alternatively, the exposure time may be 10 seconds, and the number of integrations may be 2. In this embodiment, the zinc oxide powder may be crushed until the D98 is 500 μm or less in order to confirm the degree of coloration. For example, the zinc oxide powder may be crushed under predetermined conditions, for example, crushed at 16,000 rpm in a hammer mill, and the color difference may be measured using a colorimeter, specifically a spectrophotometer, L * a * , b * You may also measure the following: For zinc oxide powder before and after grinding, W * =100-((100-L * ) 2 +(a * ) 2 +(b * ) 2 ) 1 / 2 (3) Calculate the W before and after crushing. * The difference (ΔW) * ) may be obtained. ΔW * The value is selected according to the conditions, but for example, it may be between 0.1 and 1.2, or it may be between 0.2 and 1.0, or between 0.3 and 0.8.

[0030] (BET specific surface area) The BET specific surface area of ​​the zinc oxide powder in this embodiment is 1.5 m². 2 / g or more 65m 2 / g or less, 2.0m 2 / g or more 60m 2 It is preferable that the amount be less than or equal to 2.5m 2 / g or more 50m 2 It is more preferable that it be less than or equal to / g, and 3.0m 2 / g or more 45m 2 It is even more preferable that the amount be less than or equal to / g. By adjusting the BET specific surface area of ​​the zinc oxide powder to within the above range, the transparency of dispersions, paints, cosmetics, etc., containing this zinc oxide powder can be increased. BET specific surface area is 1.5m 2If the amount is less than / g, it is undesirable because the transparency of the dispersion tends to decrease when zinc oxide powder is present at a high concentration. On the other hand, if the BET specific surface area is 65m² 2 If the amount exceeds / g, the viscosity of the dispersion tends to increase when zinc oxide powder is present at a high concentration, making it difficult to obtain a uniform and highly fluid dispersion, which is undesirable.

[0031] There are no particular limitations on the method for adjusting the BET specific surface area of ​​zinc oxide powder to the above range, but one example is to adjust the average primary particle diameter (BET equivalent particle diameter) calculated from the BET specific surface area to between 15 nm and 715 nm. Generally, as the primary particle diameter increases, the specific surface area decreases, and as the primary particle diameter decreases, the specific surface area increases. Furthermore, the BET specific surface area of ​​zinc oxide powder can also be adjusted by adjusting the particle shape or by creating pores in the particles. The zinc oxide powder of this embodiment usually consists of secondary particles, but may also contain primary particles. If primary particles are included, the ratio of zinc oxide secondary particles to zinc oxide primary particles in the zinc oxide powder can be arbitrarily selected. For example, the proportion of secondary particles may be 70% by mass or more, 80% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, or 100% by mass.

[0032] (Apparent specific volume by static observation method) The apparent specific volume of the zinc oxide powder in this embodiment obtained by the standing method is preferably 1.0 mL / g or more and 7.5 mL / g or less, more preferably 3.0 mL / g or more and 7.5 mL / g or less, even more preferably 4.0 mL / g or more and 7.5 mL / g or less, and particularly preferably 5.0 mL / g or more and 7.5 mL / g or less. By adjusting the apparent specific volume of zinc oxide powder by the static setting method to within the above range, it is possible to suppress the increase in viscosity of the dispersion liquid over time when zinc oxide powder is mixed into the dispersion medium. A dispersion containing zinc oxide powder is preferable if the apparent specific volume determined by the static method is 1.0 mL / g or higher, as this improves its transparency. On the other hand, a dispersion containing zinc oxide powder is preferable if the apparent specific volume determined by the static method is 7.5 mL / g or lower, as this suppresses the increase in viscosity of the dispersion over time.

[0033] The method for controlling the apparent specific volume of zinc oxide powder by the static decomposition method within the above range is not particularly limited. For example, when producing zinc oxide powder by a thermal decomposition method as described in Japanese Patent Publication No. 60-255620, the apparent specific volume of zinc oxide powder by the static decomposition method can be controlled within the above range by adjusting the apparent specific volume of the raw materials such as zinc oxalate, zinc hydroxide, zinc carbonate, and basic zinc carbonate by the static decomposition method, or by adjusting the thermal decomposition temperature. For example, when producing zinc oxide by a gas-phase method as described in Japanese Patent Publication No. 63-288914, the apparent specific volume of zinc oxide powder obtained by the standing method can be controlled to be within the above range by appropriately adjusting the temperature during the production process.

[0034] (Apparent specific volume by static method / Apparent specific volume by tap method) The zinc oxide powder of this embodiment has a ratio of 1.5 to 2.5 when the apparent specific volume (mL / g) obtained by the static method is divided by the apparent specific volume (mL / g) obtained by the tap method (apparent specific volume by static method / apparent specific volume by tap method). Preferably, the ratio of "apparent specific volume by static method / apparent specific volume by tap method" is 1.55 to 2.30, more preferably 1.60 to 2.00, and even more preferably 1.70 to 2.00. If the ratio of "apparent specific volume by static setting method / apparent specific volume by tapping method" is between 1.5 and 2.5, the increase in viscosity over time of a dispersion containing zinc oxide powder can be suppressed. On the other hand, if the ratio of "apparent specific volume by static setting method / apparent specific volume by tapping method" is outside the above range, it is difficult to suppress the increase in viscosity over time.

[0035] The mechanism by which the increase in viscosity over time can be suppressed in a dispersion containing zinc oxide powder where the "apparent specific volume by the static method / apparent specific volume by the tapping method" is within the above range is unknown, but it is speculated to be as follows. The apparent specific volume measured by the static method is the volume per unit mass of powder measured with air trapped between the particles. In contrast, the apparent specific volume measured by the tapping method is the volume per unit mass of powder measured after some of the air trapped between the particles has been removed by tapping. Therefore, the apparent specific volume measured by the static method is usually larger than that measured by the tapping method. Also, generally speaking, the smaller the powder particles, the greater the amount of air trapped between the particles, and the larger the apparent specific volume measured by the static method.

[0036] However, if the zinc oxide particles constituting the zinc oxide powder are coarse, the apparent specific volume measured by the static method will be small because it is difficult to capture air between the particles, and the value of "apparent specific volume by static method / apparent specific volume by tapping method" will be close to 1. In this case, the transparency will be poor because the aggregated particle size of the zinc oxide powder is large. Furthermore, if there are many voids inside the zinc oxide particles, or if steric hindrance occurs due to significant branching structures formed by the fusion of zinc oxide particles, the air between particles cannot be removed even when measuring apparent specific volume by the tap method. As a result, the apparent specific volume value obtained by the tap method increases, and the value of "apparent specific volume by static method / apparent specific volume by tap method" approaches 1. In this case, when dispersing zinc oxide powder or surface-treated zinc oxide powder in a solvent, the structure of the zinc oxide particles breaks down, the active surface of the zinc oxide particles is exposed, and the dispersion becomes thicker. Therefore, in order to achieve high transparency and suppress the increase in viscosity of the dispersion, the ratio of "apparent specific volume by static method / apparent specific volume by tapping method" must be 1.5 or higher.

[0037] On the other hand, if the ratio of "apparent specific volume by static method / apparent specific volume by tapping method" exceeds 2.5, it means that the zinc oxide powder contains very fine zinc oxide particles. When very fine zinc oxide particles are mixed into zinc oxide powder, they can cause the zinc oxide particles to re-aggregate in the dispersion even after being dispersed in the solvent. As a result, the viscosity of the dispersion increases over time, and the transparency of the dispersion decreases. Therefore, the ratio of "apparent specific volume by static method / apparent specific volume by tapping method" must be 2.5 or less.

[0038] By appropriately adjusting the structure and size of the zinc oxide particles, the transparency and dispersion stability of the dispersion are maintained. In other words, the "apparent specific volume by the static method / apparent specific volume by the tapping method" in the zinc oxide powder of this embodiment is an excellent parameter that can capture the microscopic behavior of each individual zinc oxide particle at a macroscopic level. Therefore, by measuring the "apparent specific volume by static method / apparent specific volume by tapping method" and controlling the size and structure of the zinc oxide particles constituting the zinc oxide powder so that the apparent specific volume by static method / apparent specific volume by tapping method is between 1.5 and 2.5, it is possible to obtain a dispersion with excellent dispersion stability in which the increase in viscosity over time is suppressed.

[0039] (crystallite size) The zinc oxide powder of this embodiment preferably has a crystallite size of 15 nm to 60 nm. If necessary, it may also have a crystallite size of 15 nm to 50 nm, 15 nm to 40 nm, 15 nm to 35 nm, 15 nm to 30 nm, 20 nm to 25 nm, etc. (Crystallite diameter (nm) / BET equivalent particle diameter (nm)) In this embodiment, the zinc oxide powder preferably has a value obtained by dividing the crystallite size (nm) by the BET-equivalent particle size (nm) obtained from the BET specific surface area that is between 0.1 and 1.0, more preferably between 0.4 and 1.0, even more preferably between 0.5 and 1.0, and still more preferably between 0.6 and 1.0. If necessary, it may also be between 0.2 and 0.9, or between 0.3 and 0.8, etc.

[0040] BET specific surface area is 1.5m 2 / g or more 65m 2 Zinc oxide powder having a density of less than / g and a crystallite size of 15 nm to 60 nm has sufficient crystallinity to obtain high transparency and high UV shielding properties. To improve the crystallinity of zinc oxide powder, for example, the temperature during the production process of zinc oxide powder can be raised to a level that does not cause excessive grain growth.

[0041] (Method for producing zinc oxide powder, and method for adjusting its apparent specific volume) The method for producing zinc oxide powder in this embodiment is not particularly limited. For example, one method for producing zinc oxide powder is to use a thermal decomposition method to produce it from raw materials such as zinc oxalate, zinc hydroxide, zinc carbonate, and basic zinc carbonate, as described in Japanese Patent Publication No. 60-255620. Another method is to produce zinc oxide powder using a gas phase method in which metallic zinc vapor is oxidized and burned, as described in Japanese Patent Publication No. 63-288014. To produce the zinc oxide powder of this embodiment, methods include adding materials that increase the apparent specific volume by the static method during production, using equipment that can increase the apparent specific volume by the static method, or producing the powder while supplying an excess amount of oxygen. Zinc oxide powder with a high apparent specific volume by the static method has suppressed aggregation of particles, thus reducing oxygen vacancies within the zinc oxide powder. The desired value can be obtained by controlling the apparent specific volume of the powder by the static method by combining the methods described below or methods used in the prior art. However, the excellent effects obtained by controlling the apparent specific volume of the powder within a predetermined range have not been known or anticipated until now.

[0042] To increase the apparent specific volume of zinc oxide powder by the static decomposition method, when using the thermal decomposition method, for example, a small amount of a foaming agent, arbitrarily selected, can be mixed with the raw materials for producing zinc oxide powder, for example, in an amount of about 1% by mass. As foaming agents, inorganic foaming agents such as ammonium carbonate, ammonium bicarbonate, ammonium nitrite, sodium borohydride, calcium azide, sodium bicarbonate, ammonium bicarbonate, ammonium carbonate, ammonium nitrite, neutral magnesium carbonate, ferrous oxalate, ammonium persulfate, and sodium boron hydride can be preferably used, as well as organic foaming agents such as azo compounds such as azobisisobutyronitrile, hydrazine compounds such as diphenylsulfone-3,3'-disulfohydrazine, semicarbazide compounds, triazole compounds, and N-nitroso compounds.

[0043] Examples of apparatus for increasing the apparent specific volume of zinc oxide powder by the static setting method include, for example, a fluidized bed type firing furnace that can perform firing while supplying air. By adjusting the amount of foaming agent and the firing temperature, the apparent specific volume obtained by the static method and the "apparent specific volume obtained by the static method / apparent specific volume obtained by the tapping method" can be adjusted to a desired range. One example of a method for producing zinc oxide powder in this embodiment is to add 1% by mass of ammonium carbonate, which is a foaming agent, to zinc carbonate having an apparent specific volume of 1.0 mL / g to 7.5 mL / g using a static method, and then thermally decompose it in a fluidized bed furnace at 300°C to 700°C, preferably 400°C to 600°C.

[0044] [Surface-treated zinc oxide powder] The zinc oxide powder of this embodiment may have at least a portion of its surface treated with at least one of the inorganic and organic components. Zinc oxide powder that has been surface-treated with at least one of the inorganic and organic components in this manner is called surface-treated zinc oxide powder. The inorganic and organic components are selected as appropriate depending on the application of the zinc oxide powder.

[0045] When the surface-treated zinc oxide powder of this embodiment is used in cosmetics, the inorganic and organic components are not particularly limited as long as they are surface treatment agents commonly used in cosmetics. Examples of inorganic components include silica and alumina. Examples of organic components include, for instance, at least one selected from the group consisting of silane compounds, silicone compounds, fatty acids, fatty acid soaps, fatty acid esters, and organic titanate compounds. Furthermore, surfactants may be used as the inorganic or organic components. When zinc oxide powder is surface-treated with at least one of such inorganic and organic components, it is possible to suppress the surface activity of the zinc oxide powder or improve its dispersibility in the dispersion medium.

[0046] Examples of silane compounds used in surface treatment include alkylsilanes and fluoroalkylsilanes. Examples of alkylsilanes include methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, and octyltriethoxysilane. Examples of fluoroalkylsilanes include trifluoromethylethyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane. Among these silane compounds, alkylsilanes are preferred, and octyltriethoxysilanes are particularly preferred. These silane compounds may be used individually or in combination of two or more.

[0047] Examples of silicone compounds used in surface treatment include silicone oil, methicone, dimethicone, hydrogen dimethicone, triethoxysilylethyl polydimethylsiloxyethyl dimethicone, triethoxysilylethyl polydimethylsiloxyethyl hexyl dimethicone, (acrylates / tridecyl acrylate / triethoxysilylpropyl methacrylate / dimethicone methacrylate) copolymer, and triethoxycaprylylsilane. Examples of silicone oils include methylhydrogenpolysiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane. These silicone compounds may be used individually or in combination of two or more. Copolymers of these silicone compounds may also be used as the silicone compounds themselves.

[0048] Examples of fatty acids include palmitic acid, isostearic acid, stearic acid, lauric acid, myristic acid, behenic acid, oleic acid, rosinic acid, and 12-hydroxystearic acid. Examples of fatty acid soaps include aluminum stearate, calcium stearate, and aluminum 12-hydroxystearate. Examples of fatty acid esters include dextrin fatty acid esters, cholesterol fatty acid esters, sucrose fatty acid esters, and starch fatty acid esters.

[0049] Examples of organic titanate compounds include isopropyl triisostearoyl titanate, isopropyl dimethacrylate isostearoyl titanate, isopropyl tri(dodecyl)benzenesulfonyl titanate, neopentyl(diallyl)oxytri(dioctyl)phosphate titanate, and neopentyl(diallyl)oxytrineododecanoyl titanate.

[0050] When the surface-treated zinc oxide powder of this embodiment is used in industrial applications such as UV-shielding films and gas barrier films, in addition to inorganic and organic components used in cosmetics, general dispersants used to disperse particles, such as anionic dispersants, cationic dispersants, nonionic dispersants, silane coupling agents, and wetting dispersants, can also be appropriately selected and used as surface treatment agents. Such surface treatment can suppress the surface activity of zinc oxide powder or improve its dispersibility in the dispersion medium.

[0051] In the surface-treated zinc oxide powder of this embodiment, the value obtained by dividing the dry particle size D98 (μm) of the surface-treated zinc oxide powder by the BET-equivalent particle size (nm) of the surface-treated zinc oxide powder (D98 (μm) / BET-equivalent particle size (nm)) is preferably 0.01 or more and 5.0 or less, more preferably 0.01 or more and 4.5 or less, even more preferably 0.01 or more and 4.0 or less, and particularly preferably 0.01 or more and 3.0 or less. If necessary, the above value may be 0.01 or more and 1.0 or less, 0.15 or more and 0.80 or less, or 0.20 or more and 0.60 or less. The BET-equivalent particle size of the surface-treated zinc oxide powder can be calculated by applying the BET specific surface area of ​​the surface-treated zinc oxide powder to the following formula (5). BET equivalent particle diameter (nm) = 6000 / (BET specific surface area (m 2 (g) × ρ(g / cm²) 3 ) (5) In formula (5), ρ is the density of zinc oxide, and in this embodiment, ρ is 5.61 g / cm³. 3 It uses this. The BET-equivalent particle size (nm) of the zinc oxide powder can be arbitrarily selected. For example, the size may be between 15 and 715 nm, or between 15 and 550 nm. If necessary, it may also be between 15 and 250 nm, 15 and 200 nm, 20 and 100 nm, 20 and 50 nm, 25 and 40 nm, 30 and 35 nm, etc. If the "D98 / BET equivalent particle size" of the surface-treated zinc oxide powder is within the above range, the rough texture of the surface-treated zinc oxide powder can be suppressed. Dry particle size D98 refers to the value obtained when the cumulative volume percentage reaches 98% when the volume particle size distribution of zinc oxide powder is measured dry using a laser diffraction particle size distribution analyzer (model: Mastersizer 3000, manufactured by Malvern).

[0052] The method for producing the surface-treated zinc oxide powder of this embodiment is not particularly limited and may be carried out appropriately by known methods depending on the components used for surface treatment. Alternatively, the zinc oxide powder after surface treatment may be subjected to crushing treatment. The surface-treated zinc oxide powder in the embodiment preferably contains 80 to 99% by mass of zinc oxide, and more preferably contains 82 to 97% by mass. For example, the following methods can be used as surface treatment methods. The zinc oxide powder of the present invention, which has not undergone surface treatment, is mixed with at least one inorganic component and / or organic component used for surface treatment, and one or more optionally selected solvents such as pure water or isopropyl alcohol, using an optionally selected method or apparatus. Aqueous solvents are preferred examples of the solvent. The total amount of the inorganic and / or organic components mixed may be 1 to 25 parts by mass, and preferably 3 to 22 parts by mass, per 100 parts by mass of zinc oxide particles. The amount of solvent can be optionally selected. After mixing, the mixture obtained may be dried at an optionally selected temperature to remove at least one part of the solvent. The drying temperature can be optionally selected, but examples include 50 to 200°C, more preferably 60 to 150°C, and even more preferably 70 to 120°C. Furthermore, heat treatment may be performed to further advance the surface treatment reaction. The heat treatment temperature can be optionally selected, but examples include 200 to 800°C, more preferably 200 to 700°C, and even more preferably 200 to 600°C. The resulting dried or heat-treated material (surface-treated zinc oxide powder) may be crushed using any method, apparatus, or conditions selected, for example, until the D98 is 500 μm or less. The crushed material may be further dried. The drying temperature can be selected arbitrarily, but examples include 50 to 200°C, with 60 to 150°C being more preferable, and 70 to 120°C being even more preferable. In this embodiment, the surface-treated zinc oxide powder may be controlled by controlling the manufacturing conditions so that the value obtained by dividing the dry particle size D98 (μm) by the BET-equivalent particle size (nm) is between 0.01 and 5.

[0053] [Dispersion] The dispersion of this embodiment contains the zinc oxide powder of this embodiment and a dispersion medium. The dispersion of this embodiment also includes a paste-like dispersion with high viscosity.

[0054] The zinc oxide powder content in the dispersion of this embodiment is not particularly limited and can be arbitrarily selected, but for example, it is preferably 10% by mass or more and 90% by mass or less, more preferably 20% by mass or more and 85% by mass or less, and even more preferably 30% by mass or more and 80% by mass or less, based on the total amount of the dispersion. When the zinc oxide powder content in the dispersion is within the above range, desirable properties of the zinc oxide powder can be obtained, and the increase in viscosity of the dispersion over time can be suppressed.

[0055] The dispersion medium is selected appropriately depending on the application of the dispersion. Suitable dispersion mediums are exemplified below, but the dispersion medium in this embodiment is not limited to these. The dispersion mediums listed below may be used individually or in combination from the examples below. Examples of suitable dispersion media include, for example, water, alcohols, esters, ethers, and the like. Examples of alcohols include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, octanol, and glycerin. Examples of esters include ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone. Examples of ethers include diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether. These dispersion media may be used individually or in combination of two or more types.

[0056] Other suitable dispersion media include ketones, aromatic hydrocarbons, cyclic hydrocarbons, amides, and linear polysiloxanes. Examples of ketones include acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, and cyclohexanone. Examples of aromatic hydrocarbons include benzene, toluene, xylene, and ethylbenzene. Examples of cyclic hydrocarbons include cyclohexane. Examples of amides include dimethylformamide, N,N-dimethylacetacetamide, and N-methylpyrrolidone. Examples of linear polysiloxanes include dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane. These dispersion media may be used individually or in combination of two or more types.

[0057] Furthermore, cyclic polysiloxanes and modified polysiloxanes are also suitably used as other dispersion media. Examples of cyclic polysiloxanes include octamethylcyclotetrasiloxane, cyclopentasiloxane, and dodecamethylcyclohexasiloxane. Examples of modified polysiloxanes include amino-modified polysiloxanes, polyether-modified polysiloxanes, alkyl-modified polysiloxanes, and fluorine-modified polysiloxanes. These dispersion media may be used individually or in combination of two or more types.

[0058] In addition, hydrophobic dispersion media such as liquid paraffin, squalane, isoparaffin, branched light paraffin, petrolatum, ceresin, and other hydrocarbon oils, ester oils such as isopropyl myristate, cetyl isooctanoate, and glyceryl trioctanoate, silicone oils such as cyclopentasiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane, higher fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid, and higher alcohols such as lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyldodecanol, and isostearyl alcohol may be used as other dispersion media.

[0059] The dispersion of this embodiment may contain commonly used additives, to the extent that it does not impair its properties. Examples of additives include dispersants, stabilizers, water-soluble binders, thickeners, oil-soluble preservatives, UV absorbers, oil-soluble drugs, oil-soluble dyes, oil-soluble proteins, vegetable oils, animal oils, and the like. These additives may be included in amounts that can be selected at will.

[0060] The method for producing the dispersion of this embodiment is not particularly limited, but one example is to mechanically disperse the zinc oxide powder of this embodiment and a dispersion medium using a known dispersion apparatus. Examples of dispersion devices include agitators, orbital mixers, homomixers, ultrasonic homogenizers, sand mills, ball mills, and roll mills.

[0061] The dispersion of this embodiment can be preferably used in cosmetics, as well as in paints and other materials that have functions such as ultraviolet shielding and gas permeation suppression.

[0062] [paint] The paint of this embodiment contains the zinc oxide powder of this embodiment, a resin, and a dispersion medium.

[0063] The zinc oxide powder content in the paint of this embodiment can be adjusted as appropriate to suit the desired properties. The zinc oxide powder content in the paint of this embodiment is preferably 10% to 40% by mass, more preferably 15% to 35% by mass, and even more preferably 20% to 30% by mass, based on the total amount of paint. By keeping the zinc oxide powder content in the paint within the above range, the properties of zinc oxide powder can be obtained, and the increase in the viscosity of the paint over time can be suppressed.

[0064] The dispersion medium is not particularly limited as long as it is commonly used in industrial applications, but examples include organic solvents such as water, alcohols, methyl acetate, ethyl acetate, toluene, methyl ethyl ketone, and methyl isobutyl ketone. The content of the dispersion medium in the paint of this embodiment is not particularly limited and can be adjusted as appropriate according to the desired properties of the paint.

[0065] The resin is not particularly limited as long as it is commonly used in industrial applications, but examples include acrylic resin, epoxy resin, urethane resin, polyester resin, and silicone resin. The resin content in the paint of this embodiment is not particularly limited and can be adjusted as appropriate according to the desired properties of the paint.

[0066] The paint of this embodiment may contain commonly used additives, to the extent that they do not impair its properties. Examples of additives include polymerization initiators, dispersants, and preservatives.

[0067] The method for manufacturing the paint of this embodiment is not particularly limited, but for example, one method is to mechanically mix the zinc oxide powder of this embodiment, the resin, and the dispersion medium using a known mixing device. Another method is to mechanically mix the above-mentioned dispersion liquid and the resin using a known mixing device. Examples of mixing devices include agitators, self-rotating mixers, homomixers, and ultrasonic homogenizers.

[0068] The coating of this embodiment can be applied to a plastic substrate such as a polyester film by conventional coating methods such as roll coating, flow coating, spray coating, screen printing, brush coating, or dipping, thereby forming a coating film. These coating films can be used as ultraviolet shielding films or gas barrier films.

[0069] [Cosmetics] A cosmetic composition according to one embodiment of this embodiment contains at least one selected from the group consisting of the zinc oxide powder of this embodiment and the dispersion of this embodiment. That is, the cosmetic composition may contain either or both of the zinc oxide powder and the dispersion. A cosmetic composition of another embodiment comprises a base and at least one selected from the group consisting of the zinc oxide powder of this embodiment and the dispersion of this embodiment, dispersed in the base. That is, the cosmetic composition may include the zinc oxide powder, the dispersion, or both, and the base. The cosmetic composition of this embodiment can be obtained, for example, by blending the dispersion of this embodiment with a base such as an emulsion, cream, foundation, lipstick, blush, or eyeshadow, in the same manner as before. Alternatively, the zinc oxide powder of this embodiment may be blended into an oil or aqueous phase to form an O / W or W / O emulsion, which may then be blended with the base material. The aforementioned base is not particularly limited as long as it can be used as a base for cosmetics. The following provides a detailed explanation of sunscreen cosmetics.

[0070] The zinc oxide powder content in sunscreen cosmetics can be arbitrarily selected, but in order to effectively block ultraviolet rays, especially long-wavelength ultraviolet rays (UVA), it is preferable that the content be 1% to 30% by mass, more preferably 3% to 20% by mass, and even more preferably 5% to 15% by mass, based on the total amount of the cosmetic.

[0071] Sunscreen cosmetics may, as needed, contain hydrophobic dispersion media, inorganic fine particles other than zinc oxide powder, inorganic pigments, hydrophilic dispersion media, oils and fats, surfactants, humectants, thickeners, pH adjusters, nutrients, antioxidants, fragrances, etc. Examples of hydrophobic dispersion media include hydrocarbon oils such as liquid paraffin, squalane, isoparaffin, branched light paraffin, petrolatum, and ceresin; ester oils such as isopropyl myristate, cetyl isooctanoate, and glyceryl trioctanoate; silicone oils such as cyclopentasiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane; higher fatty acids such as lauric acid, myristic acid, palmitic acid, and stearic acid; and higher alcohols such as lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyldodecanol, and isostearyl alcohol.

[0072] Examples of inorganic fine particles and inorganic pigments other than zinc oxide powder include calcium carbonate, calcium phosphate (apatite), magnesium carbonate, calcium silicate, magnesium silicate, aluminum silicate, kaolin, talc, titanium dioxide, aluminum oxide, yellow iron oxide, γ-iron oxide, cobalt titanate, cobalt violet, and silicon dioxide.

[0073] The sunscreen cosmetic may further contain at least one organic UV absorber. The amount of organic UV absorber may be adjusted as appropriate to obtain the desired UV protection. For organic UV absorbers whose amount that can be included in sunscreen cosmetics is regulated, the upper limit may be adjusted as appropriate according to the regulations of each country. For example, the amount of organic UV absorber may be 20% by mass or less, 15% by mass or less, 12% by mass or less, 10% by mass or less, 9% by mass or less, 8% by mass or less, 6% by mass or less, 4% by mass or less, or 3% by mass or less. Examples of organic UV absorbers include benzotriazole-based UV absorbers, benzoylmethane-based UV absorbers, benzoic acid-based UV absorbers, anthranilic acid-based UV absorbers, salicylic acid-based UV absorbers, cinnamic acid-based UV absorbers, silicone-based UV absorbers, triazine-based UV absorbers, imidazole-based UV absorbers, camphor-based UV absorbers, benzophenone-based UV absorbers, and other organic UV absorbers.

[0074] Examples of the aforementioned benzotriazole-based ultraviolet absorbers include, for example, 2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole. Examples of benzoylmethane-based UV absorbers include dibenzarazine, dianisioylmethane, 4-tert-butyl-4'-methoxydibenzoylmethane, 1-(4'-isopropylphenyl)-3-phenylpropane-1,3-dione, and 5-(3,3'-dimethyl-2-norbornylidene)-3-pentan-2-one.

[0075] Examples of the aforementioned benzoic acid-based ultraviolet absorbers include, for example, para-aminobenzoic acid (PABA), PABA monoglycerol ester, N,N-dipropoxy PABA ethyl ester, N,N-diethoxy PABA ethyl ester, N,N-dimethyl PABA ethyl ester, N,N-dimethyl PABA butyl ester, N,N-dimethyl PABA methyl ester, dimethyl PABA ethylhexyl, dimethyl PABA amyl, and the like. Examples of anthranilic acid-based UV absorbers include homomenthyl-N-acetylanthranilate. Examples of the aforementioned salicylic acid-based ultraviolet absorbers include, for example, amyl salicylate, menthyl salicylate, homomenthyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, p-2-propanolphenyl salicylate, and ethylhexyl salicylate.

[0076] Examples of the aforementioned cinnamic acid-based UV absorbers include, for example, octyl methoxycinnamate, glyceryl di-paramethoxycinnamate mono-2-ethylhexanoate, octyl cinnamate, ethyl-4-isopropyl cinnamate, methyl diisopropylcinnamate, ethyl-2,4-diisopropyl cinnamate, methyl-2,4-diisopropyl cinnamate, propyl-p-methoxycinnamate, isopropyl-p-methoxycinnamate, isoamyl-p-methoxycinnamate, and octyl-p-methoxycinnamate. Examples include (2-ethylhexyl-p-methoxycinnamate), 2-ethoxyethyl-p-methoxycinnamate, cyclohexyl-p-methoxycinnamate, ethyl-α-cyano-β-phenyl cinnamate, 2-ethylhexyl-α-cyano-β-phenyl cinnamate, glyceryl mono-2-ethylhexanoyl-diparamethoxycinnamate, ferulic acid, cinoxate, methylbis(trimethylsiloxy)silylisopentyl trimethoxycinnamate, and isopropyl paramethoxycinnamate.

[0077] Examples of the aforementioned silicone-based UV absorbers include, for example, [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, polysilicone-15, drometrizole trisiloxane, and the like.

[0078] Examples of the aforementioned triazine-based ultraviolet absorbers include, for example, bisethylhexyloxyphenol methoxyphenyl triazine, ethylhexyl triazone, methylenebisbenzotriazolyltetramethylbutylphenol, trisbiphenyl triazine, and diethylhexylbutamide triazone. Examples of the imidazole-based ultraviolet absorbers include, for example, disodium phenyldibenzimidazole tetrasulfonic acid, phenylbenzimidazole sulfonic acid, and ethylhexyl dimethoxybenzylidene dioxoimidazolidine propionate.

[0079] Examples of the aforementioned camphor-based UV absorbers include, for example, 3-(4'-methylbenzylidene)-d,l-camphor, 3-benzylidene-d,l-camphor, Examples include terephthalylidene dicamphor sulfonic acid, camphor benzalkonium methosulfate, benzylidene camphor sulfonic acid, and polyacrylamide methylbenzylidene camphor. Examples of the benzophenone-based ultraviolet absorbers include, for example, oxybenzone-1, oxybenzone-2, oxybenzone-3, oxybenzone-4, oxybenzone-5, oxybenzone-6, oxybenzone-7, oxybenzone-8, oxybenzone-9, and 4-(2-β-glucopyranosiloxy)propoxy-2-hydroxybenzophenone.

[0080] Examples of organic UV absorbers other than those mentioned above include urocanic acid, ethyl urocanic acid, 2-phenyl-5-methylbenzoxazole, 5-(3,3'-dimethyl-2-norbornylidene)-3-pentan-2-one, diethylaminohydroxybenzoyl hexyl benzoate, octocrylene, silicone-modified UV absorbers, and fluorine-modified UV absorbers.

[0081] As described above, the zinc oxide powder of this embodiment has a BET specific surface area and a ratio of apparent specific volume by the static method to apparent specific volume by the tapping method that are within the above range, and has been adjusted to satisfy formulas (1) and (2) above. Therefore, when preparing cosmetics, discoloration of the zinc oxide powder can be suppressed even when dispersed at high energy. Furthermore, using this zinc oxide powder, it is possible to obtain dispersions and cosmetics that have high transparency and excellent UV shielding properties. The above characteristics represent extremely excellent effects.

[0082] In the surface-treated zinc oxide powder of this embodiment, at least a portion of the surface of the zinc oxide powder is surface-treated with at least one of the inorganic and organic components. Therefore, the surface activity of the zinc oxide powder can be suppressed, and the dispersibility in the dispersion medium can be improved. Furthermore, when preparing a dispersion containing this surface-treated zinc oxide powder, discoloration of the zinc oxide powder can be suppressed even when dispersed at high energy.

[0083] The dispersion of this embodiment contains the zinc oxide powder or surface-treated zinc oxide powder of this embodiment. Therefore, it can be mixed with high energy when incorporated into cosmetics.

[0084] The paint of this embodiment contains zinc oxide powder or surface-treated zinc oxide powder of this embodiment. Therefore, the discoloration of the zinc oxide powder is suppressed, and a paint with a natural color can be obtained.

[0085] The cosmetic composition of this embodiment contains the zinc oxide powder or surface-treated zinc oxide powder of this embodiment. Therefore, the discoloration of the zinc oxide powder is suppressed, and a cosmetic composition with a natural color can be obtained. [Examples]

[0086] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

[0087] [Raman spectroscopy] Raman spectroscopy was performed using a Raman spectrometer (model: XploRA PLUS, manufactured by Horiba, Ltd.) under the following conditions. The measurement results are shown in Table 1. Objective lens: 10x Laser wavelength: 532nm Grating: 1200nm Slit: 100 μm Confocal hole: 300 μm Neutral density filter: 10% Spectrometer:1671.63 Measurement wavelength range: 300cm -1 ~2000cm -1 Exposure time: 10s Number of times: 2

[0088] [Transition metal content] The amount of transition metals was determined by measuring the amounts of vanadium, chromium, manganese, iron, cobalt, nickel, and copper contained in zinc oxide powder using an ICP emission spectrometer (model: ICP-AES 700-ES, Varian). The sum of these amounts was calculated. A total amount between 0.5 ppm and 20 ppm was evaluated as "○ (acceptable)," and a total amount exceeding 20 ppm was evaluated as "× (unacceptable)." The measurement results are shown in Table 1.

[0089] [Manufacturing of zinc oxide powder] [Example 1] Zinc oxide powder A1 (BET specific surface area 39.8 m²) 2 A sample was prepared with a specific volume of 5.2 mL / g (apparent specific volume by static method) and 2.9 mL / g (apparent specific volume by tapping method), where A1 / E2 in formula (1) is 0.17, a in formula (1) is 0.003, and (M2-M1) / E2 in formula (2) is 0.081, with a crystallite size of 16 nm. The characteristics, crystallite size, BET-equivalent particle size, and transition metal content of the zinc oxide powder A1 are shown in Table 1. Next, for color evaluation, 500g of zinc oxide powder A1 was crushed in a hammer mill at 16,000 rpm until the D98 particle size was 500 μm or less. In other words, high energy was applied to the zinc oxide powder A1. L of zinc oxide powder A1 before and after crushing * a * , b * This was measured using a spectrophotometer (model TC-1800, manufactured by Tokyo Denshoku Co., Ltd.). Furthermore, in order to evaluate the degree of coloration of zinc oxide powder before and after crushing, the coloration W is calculated using the following formula (3). * The result was calculated. W * =100-((100-L * ) 2 +(a * ) 2 +(b * ) 2 ) 1 / 2 (3) Then, the difference in color, ΔW, is calculated using the following equation (4). * ΔW was calculated. * A larger value indicates a greater difference in color before and after grinding. ΔW * =W before crushing * -W after crushing * (4) Furthermore, the amount of transition metals contained in the zinc oxide powder before crushing was measured, and the total amount was calculated. Then, it was checked whether equation (1) was satisfied. The results are shown in Table 1.

[0090] "Preparation of surface-treated zinc oxide powder" A mixture of 6 parts by mass of octyltriethoxysilane (product name: KBE-3083, manufactured by Shin-Etsu Chemical Co., Ltd.), 100 parts by mass of zinc oxide powder A1, 0.6 parts by mass of pure water, and 34.1 parts by mass of isopropyl alcohol was mixed in a Henschel mixer. Next, the mixture was dried at 80°C until the isopropyl alcohol was removed. Then, the resulting dried material was dried at 120°C for 3 hours to obtain surface-treated zinc oxide powder B1 of Example 1.

[0091] "Preparation of dispersion" 50 parts by mass of surface-treated zinc oxide powder B1 from Example 1, 10 parts by mass of PEG-9 polydimethylsiloxyethyl dimethicone (product name: KF-6028, manufactured by Shin-Etsu Chemical Co., Ltd.), and 40 parts by mass of cyclopentasiloxane (product name: SH245 Fluid, manufactured by Toray Dow Corning Co., Ltd.) were dispersed using a bead mill to obtain dispersion C1 from Example 1.

[0092] "Evaluation of viscosity and temporal stability of dispersions" The viscosity of dispersion C1 from Example 1 was measured using a rheometer (product name: Modular Compact Rheometer MCR102, manufactured by Anton Paar Japan) under the following conditions. The results are shown in Table 1. Measurement temperature: 25℃ Jig: Cone plate CP25-2 Shear rate: 1 / sec. This dispersion was stored at 50°C for 28 days, and its viscosity was measured under the same conditions as described above. The results are shown in Table 1.

[0093] "Evaluation of transparency and UV shielding properties" The dispersion from Example 1 was diluted with cyclopentasiloxane so that the surface-treated zinc oxide powder content was 0.005% by mass. The linear transmittance of this diluted solution at 308 nm and 555 nm was measured using a UV-Vis-Near-Infrared spectrophotometer (model: V-770, manufactured by JASCO Corporation). The results are shown in Table 1. A low transmittance at 308 nm indicates high UV shielding. Therefore, a low linear transmittance at 308 nm is preferable. A high transmittance at 555 nm indicates high transparency. Therefore, a high transmittance at 555 nm is desirable.

[0094] [Example 2] Instead of zinc oxide powder A1, use zinc oxide powder A2 (BET specific surface area 29.6 m²). 2A sample was prepared with a specific volume of 5.1 mL / g obtained by the standing method and 2.7 mL / g obtained by the tapping method, where A1 / E2 in formula (1) was 0.16, a in formula (1) was 0.004, and (M2-M1) / E2 in formula (2) was 0.096, with a crystallite size of 21 nm. Surface-treated zinc oxide powder B2 of Example 2 and a dispersion C2 containing surface-treated zinc oxide powder B2 were obtained in exactly the same manner as in Example 1, except that zinc oxide powder A2 was used. The results of the evaluation in the same manner as in Example 1 are shown in Table 1.

[0095] [Example 3] Instead of zinc oxide powder A1, use zinc oxide powder A3 (BET specific surface area 34.6 m²). 2 A sample was prepared with a specific volume of 6.4 mL / g obtained by the standing method and 2.9 mL / g obtained by the tapping method, with A1 / E2 in formula (1) being 0.12, a in formula (1) being 0.002, and (M2-M1) / E2 in formula (2) being 0.093, and a crystallite size of 18 nm. Surface-treated zinc oxide powder B3 of Example 3 and a dispersion C3 containing surface-treated zinc oxide powder B3 were obtained in exactly the same manner as in Example 1, except that zinc oxide powder A3 was used. The results of the evaluation in the same manner as in Example 1 are shown in Table 1.

[0096] [Example 4] Instead of zinc oxide powder A1, use zinc oxide powder A4 (BET specific surface area 36.5 m²). 2 A sample was prepared (amount: 3.7 mL / g by static method, apparent specific volume: 2.2 mL / g by tapping method, A1 / E2 in formula (1) is 0.72, a in formula (1) is 0.018, (M2-M1) / E2 in formula (2) is 0.025, crystallite size: 16 nm). Surface-treated zinc oxide powder B4 of Example 4 and dispersion C4 containing surface-treated zinc oxide powder B4 were obtained in exactly the same manner as in Example 1, except that zinc oxide powder A4 was used. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0097] [Example 5] Instead of zinc oxide powder A1, use zinc oxide powder A5 (BET specific surface area 5.0 m²). 2 / g, apparent specific volume by the static method of 2.0 mL / g, apparent specific volume by the tapping method of 1.0 mL / g, A1 / E2 in the above formula (1) is 0.10, a in the above formula (1) is 0.009, (M2 - M1) / E2 in the above formula (2) is 0.078, and crystallite size of 37 nm) were prepared. Except for using zinc oxide powder A5, in the same manner as in Example 1, surface-treated zinc oxide powder B5 of Example 5 and dispersion liquid C5 containing surface-treated zinc oxide powder B5 were obtained. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0098] [Example 6] Instead of zinc oxide powder A1, zinc oxide powder A6 (BET specific surface area of 51.2 m 2 / g, apparent specific volume by the static method of 5.5 mL / g, apparent specific volume by the tapping method of 3.1 mL / g, A1 / E2 in the above formula (1) is 0.20, a in the above formula (1) is 0.003, (M2 - M1) / E2 in the above formula (2) is 0.084, and crystallite size of 15 nm) were prepared. Except for using zinc oxide powder A6, in the same manner as in Example 1, surface-treated zinc oxide powder B6 of Example 6 and dispersion liquid C6 containing surface-treated zinc oxide powder B6 were obtained. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0099] [Comparative Example 1] Instead of zinc oxide powder A1, zinc oxide powder A7 (BET specific surface area of 34.1 m 2 / g, apparent specific volume by the static method of 1.6 mL / g, apparent specific volume by the tapping method of 1.1 mL / g, A1 / E2 in the above formula (1) is 0.25, a in the above formula (1) is 0.006, (M2 - M1) / E2 in the above formula (2) is 0.015, and crystallite size of 15 nm) were prepared. Except for using zinc oxide powder A7, in the same manner as in Example 1, surface-treated zinc oxide powder B7 of Comparative Example 1 and dispersion liquid C7 containing surface-treated zinc oxide powder B7 were obtained. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0100] [Comparative Example 2] Instead of zinc oxide powder A1, zinc oxide powder A8 (BET specific surface area of 10.5 m 2A sample was prepared with a specific volume of 1.6 mL / g (apparent specific volume by static method, 1.1 mL / g by tapping method, A1 / E2 in formula (1) being 0.23, a in formula (1) being 0.016, (M2-M1) / E2 in formula (2) being 0.014, and a crystallite size of 25 nm). The surface-treated zinc oxide powder B8 of Comparative Example 2 and a dispersion C8 containing surface-treated zinc oxide powder B8 were obtained in exactly the same manner as in Example 1, except that zinc oxide powder A8 was used. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0101] [Comparative Example 3] Instead of zinc oxide powder A1, use zinc oxide powder A9 (BET specific surface area 4.5 m²). 2 A sample was prepared (amount: 1.4 mL / g by static method, apparent specific volume: 0.8 mL / g by tapping method, A1 / E2 in formula (1) is 0.22, a in formula (1) is 0.036, (M2-M1) / E2 in formula (2) is 0.078, crystallite size: 45 nm). Surface-treated zinc oxide powder B9 and dispersion C9 containing surface-treated zinc oxide powder B9 were obtained in exactly the same manner as in Example 1, except that zinc oxide powder A9 was used. The results of evaluation in the same manner as in Example 1 are shown in Table 1.

[0102] [Table 1] In Table 1, static volume represents the apparent specific volume determined by the static method. Tap volume represents the apparent specific volume determined by the tap method.

[0103] By comparing Examples 1 to 6 with Comparative Examples 1 to 3, it was found that the BET specific surface area is 1.5 m². 2 / g or more 65m 2 Zinc oxide powder that is less than or equal to / g, whose value obtained from the formula (apparent specific volume by static method (ml / g) / apparent specific volume by tap method (ml / g) is between 1.5 and 2.5, and satisfies the above formulas (1) and (2), will not exhibit ΔW even when high energy is applied. * It was confirmed that the value was 1 or less, and that the discoloration of the zinc oxide powder was suppressed. [Industrial applicability]

[0104] The zinc oxide powder of the present invention exhibits suppressed discoloration even when dispersed at high energy. Therefore, the zinc oxide powder of the present invention has excellent stability when applied to dispersions, paints, and cosmetics, and its industrial value is significant. The present invention provides zinc oxide powder that can suppress discoloration even when high energy is applied, as well as a dispersion, paint, and cosmetic containing zinc oxide powder.

Claims

1. BET specific surface area (X) is 1.5 m ２ / g or more 65m ２ / g or less, The value obtained from the formula (Apparent specific volume by static method (mL / g) / Apparent specific volume by tapping method (mL / g) is 1.5 or more and 2.5 or less, and satisfies the following formulas (1) and (2). Zinc oxide powder. A1 / E2=aX+0.06 (1) (M2-M1) / E2≧0.02 (2) (X is the BET specific surface area of the zinc oxide powder (unit: m ２ / g); A1 is the spectral value of the peak existing near 580 cm －１ in the Raman spectrum of the zinc oxide powder obtained by Raman spectroscopy; E2 is the spectral value of the peak existing near 437 cm －１ in the Raman spectrum; a is a value of 0.001 or more and 0.025 or less; M2 is the maximum value of the spectrum in the range of 1091 cm －１ to 1170 cm －１ in the Raman spectrum; M1 is the maximum value of the spectrum in the range of 1020 cm －１ to 1090 cm －１ in the Raman spectrum.)

2. The zinc oxide powder according to claim 1, wherein the apparent specific volume (mL / g) obtained by the static setting method is 1.0 mL / g or more and 7.5 mL / g or less.

3. The zinc oxide powder according to claim 1 or 2, wherein the total amount of metals selected from the group consisting of vanadium, chromium, manganese, iron, cobalt, nickel, and copper contained in the zinc oxide powder is 0.5 ppm or more and 20 ppm or less.

4. A zinc oxide powder according to any one of claims 1 to 3, wherein the crystallite size is 15 nm or more and 60 nm or less.

5. The zinc oxide powder is measured using a spectrophotometer, L ＊ a ＊ , b ＊ When measured, W is obtained by the following equation (3). ＊ Regarding the above, the W before and after crushing the zinc oxide powder until the D98 is 500 μm or less. ＊ The zinc oxide powder according to any one of claims 1 to 4, wherein the difference is 0.1 to 1.

2. W ＊ =100-((100-L ＊ ) ２ +(a ＊ ) ２ +(b ＊ ) ２ ) １／２ (3)

6. The zinc oxide powder according to any one of claims 1 to 5, which is a surface-treated powder that has been surface-treated with at least one of an inorganic component and an organic component.

7. A dispersion containing zinc oxide powder according to any one of claims 1 to 6 and a dispersion medium.

8. A paint comprising zinc oxide powder according to any one of claims 1 to 6, a resin, and a dispersion medium.

9. A cosmetic composition containing zinc oxide powder according to any one of claims 1 to 6.

10. The apparent specific volume (mL / g) obtained by the static method was measured in accordance with JIS K5101-12-1. The apparent specific volume (mL / g) obtained by the tap method is: The zinc oxide powder is passed through a sieve with a mesh size of 500 μm. Then, the zinc oxide powder that has passed through the sieve is placed into a 150 mL graduated cylinder of known weight to a volume of 100 mL. The weight of the graduated cylinder containing the zinc oxide powder is measured. Place the lid on the graduated cylinder, The lidded graduated cylinder is fixed to the bulk density measuring device and tapped 50 times. Read the volume of the zinc oxide powder after tapping. This value is obtained by dividing the volume of the zinc oxide powder after tapping by the weight of the zinc oxide powder placed in the graduated cylinder. The zinc oxide powder according to any one of claims 1 to 6.

Images