Zinc oxide powder, dispersion, paint, cosmetics

Abstract

Provided is zinc oxide powder in which the BET specific surface area is 8 m2 / g to 65 m2 / g, the apparent specific volume measured by a loose packing method is 1.0 mL / g to 7.5 mL / g, and the value obtained by dividing the apparent specific volume (mL / g) measured by the loose packing method by the apparent specific volume (mL / g) measured by a tapping method (apparent specific volume measured by loose packing method / apparent specific volume measured by tapping method) is 1.50 to 2.50.

Description

[Technical Field]

[0001] This invention relates to zinc oxide powder, dispersions, paints, and cosmetics. This application claims priority based on Japanese Patent Application No. 2020-198864, filed in Japan on November 30, 2020, and the contents of that application are incorporated herein by reference. [Background technology]

[0002] Zinc oxide powder possesses ultraviolet shielding and gas permeation suppression properties, as well as high transparency. Therefore, it is used in applications requiring both ultraviolet shielding and transparency, such as ultraviolet shielding films, ultraviolet shielding glass, gas barrier films, and cosmetics. One method for achieving transparency is to reduce the primary particle size of zinc oxide particles to the nanoscale level. Various methods for producing zinc oxide nanoparticles, such as thermal decomposition and gas-phase methods, are being investigated.

[0003] For example, Patent Document 1 states the following: Because of their fine particle size, zinc oxide particles tend to aggregate easily, resulting in low particle independence and high oil absorption. When zinc oxide particles with high oil absorption are incorporated into cosmetics, the zinc oxide particles absorb a large amount of oil components contained in the cosmetics, increasing the viscosity of the cosmetics. Furthermore, when zinc oxide particles aggregate and their dispersibility decreases, their transparency decreases. Therefore, aggregated zinc oxide particles have the disadvantage of appearing unnaturally white when incorporated into cosmetics (when applied to the skin). There is a need for zinc oxide particles that can improve UV shielding while reducing oil absorption and powder volume.

[0004] Patent Document 1 describes a method to solve the viscosity and transparency problems caused by aggregation, where the primary particle diameter is less than 0.1 μm, the aspect ratio is less than 2.5, and the oil absorption / BET specific surface area is 1.5 mL / 100 m 2 The following describes the provision of zinc oxide particles.

[0005] On the other hand, Patent Document 2 describes an organic-inorganic composite pigment in which a highly oil-absorbing inorganic pigment is subjected to a specific surface treatment in order to make the appearance color more vivid when incorporated into cosmetics and to improve durability.

[0006] Patent Document 3 describes a cosmetic composition containing a liquid perfluoroorganic compound, a cyclic silicone or a chain-like silicone with a specific volatilization rate, and a highly oil-absorbing powder capable of absorbing 1.5 times or more of its own weight in squalane. This cosmetic composition has a refreshing feel and can prevent makeup from breaking down over time, such as becoming shiny. [Prior art documents] [Patent Documents]

[0007] [Patent Document 1] International Publication No. 2012 / 147888 [Patent Document 2] Japanese Patent Application Publication No. 11-181329 [Patent Document 3] Japanese Patent Publication No. 2019-099510 [Overview of the project] [Problems that the invention aims to solve]

[0008] Inorganic powders with high oil absorption capacity had the advantage of preventing problems such as the feel of cosmetics and makeup breakdown, including shine, over time. However, conventional inorganic powders with high oil absorption had the drawback of increasing the viscosity of cosmetics and other products over time when incorporated into them. There was a need to develop a superior zinc oxide powder that possessed the above advantages while overcoming the above disadvantages.

[0009] In view of the above circumstances, the present invention has been made, and an object of the present invention is to provide a zinc oxide powder which can suppress an increase in viscosity over time when blended into a dispersion or the like and has a suitably high oil absorption, as well as a dispersion, a coating material and a cosmetic containing the zinc oxide powder. Another object of the present invention is to provide the zinc oxide powder with transparency and other properties equivalent to those of conventional products. Means for Solving the Problem

[0010] That is, the zinc oxide powder according to the first aspect of the present invention has a BET specific surface area of 8 m 2 / g or more and 65 m 2 / g or less, an apparent specific volume by a static method of 1.0 mL / g or more and 7.5 mL / g or less, and a value obtained by dividing the apparent specific volume (mL / g) by the static method by the apparent specific volume (mL / g) by a tap method (apparent specific volume by static method / apparent specific volume by tap method) of 1.50 or more and 2.50 or less. The zinc oxide powder according to the first aspect of the present invention may be further surface-treated. Non-surface-treated zinc oxide powder and surface-treated surface-treated zinc oxide powder may be used in combination.

[0011] The dispersion according to the second aspect of the present invention is characterized by containing the zinc oxide powder according to the first aspect of the present invention and a dispersion medium.

[0012] The coating material according to the third aspect of the present invention is characterized by containing the zinc oxide powder according to the first aspect of the present invention, a resin, and a dispersion medium.

[0013] The cosmetic according to the fourth aspect of the present invention is characterized by containing at least one selected from the group consisting of the zinc oxide powder according to the first aspect of the present invention and the dispersion according to the second aspect of the present invention. The surface-treated zinc oxide powder according to the fifth aspect of the present invention is characterized in that it is a surface-treated zinc oxide powder obtained by surface-treating the zinc oxide powder according to the first aspect of the present invention with at least one of an inorganic component and an organic component. Effect of the Invention

[0014] According to the zinc oxide powder of the present invention, the BET specific surface area is 8 m². 2 / g or more 65m 2 Because the viscosity is less than or equal to / g, the apparent specific volume obtained by the static method is 1.0 mL / g or more and 7.5 mL / g or less, and the value obtained by dividing the apparent specific volume (mL / g) obtained by the static method by the tap method (mL / g) is 1.50 or more and 2.50 or less, it is possible to suppress the increase in viscosity over time when it is blended into a dispersion or the like. Furthermore, the zinc oxide powder of the present invention can maintain an appropriate oil absorption capacity and can maintain excellent transparency when blended into dispersions, etc. The aforementioned excellent effects can also be obtained when the zinc oxide powder is surface-treated.

[0015] The dispersion of the present invention contains either or both of the zinc oxide powder of the present invention and the surface-treated zinc oxide powder of the present invention, along with a dispersion medium, thereby suppressing the increase in viscosity of the dispersion over time.

[0016] The paint of the present invention contains either or both of the zinc oxide powder of the present invention and the surface-treated zinc oxide powder of the present invention, along with a resin and a dispersion medium, thereby suppressing the increase in the viscosity of the paint over time.

[0017] The cosmetic composition 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 of the present invention, and therefore the increase in viscosity of the cosmetic composition over time can be suppressed. [Modes for carrying out the invention]

[0018] This section describes preferred embodiments of the zinc oxide powder, dispersion, paint, and cosmetic materials of the present invention. This embodiment is provided to give a better understanding of the spirit of the invention and does not limit the present invention unless otherwise specified. Omissions, additions, substitutions, and other modifications are possible without departing from the spirit of the present invention.

[0019] [Zinc oxide powder] The zinc oxide powder of this embodiment has a BET specific surface area of ​​8 m². 2 / g or more 65m 2 The apparent specific volume is less than or equal to / g, the apparent specific volume by the standing method is 1.0 mL / g or more and 7.5 mL / g or less, and the value obtained by dividing the apparent specific volume by the standing method (mL / g) by the apparent specific volume by the tap method (mL / g) (apparent specific volume by standing method / apparent specific volume by tap method) is 1.50 or more and 2.50 or less. In this specification, the apparent specific volume by the standing method can be replaced with the standing volume. Similarly, the apparent specific volume by the tap method can be replaced with the tap volume. The zinc oxide powder of this 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 may consist only of zinc oxide, but may also contain trace amounts of impurities that do not affect the effect. Furthermore, the zinc oxide powder of this 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.

[0020] (Methods for measuring the properties of zinc oxide powder or surface-treated zinc oxide powder) The BET specific surface area of ​​the zinc oxide powder in this embodiment 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.).

[0021] The apparent specific volume (mL / g) of the zinc oxide powder in this embodiment, 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.

[0022] 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.

[0023] In this embodiment, the dry particle size D98 of the zinc oxide powder may refer to the value when the cumulative volume percentage is 98% when the volume particle size distribution of the zinc oxide powder is measured dry using a laser diffraction particle size distribution analyzer, for example, using a laser diffraction particle size distribution analyzer (model: Mastersizer 3000, manufactured by Malvern). Hereinafter, the dry particle size D98 may be abbreviated as "D98".

[0024] In this embodiment, the crystallite size of the zinc oxide powder may refer 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, an X-ray diffractometer (product name: AERIS, manufactured by PANalytical). Under the measurement conditions for powder X-ray diffraction using the above apparatus, the radiation source shall be CuKα radiation, with an output of 40 kV and 15 mA. Furthermore, the measurement data obtained by X-ray diffraction measurement can be analyzed using data processing software AERIS (manufactured by PANalytical), whereby the Scherrer diameter can be calculated.

[0025] The oil absorption amount of the zinc oxide powder of the present embodiment means a value measured in accordance with JIS K5101-13-1 (Pigment test methods—Part 13: Oil absorption—Section 1: Refined linseed oil method).

[0026] (BET specific surface area) The BET specific surface area of the zinc oxide powder of the present embodiment is 8 m 2 / g or more and 65 m 2 / g or less, preferably 15 m 2 / g or more and 60 m 2 / g or less, more preferably 20 m 2 / g or more and 50 m 2 / g or less, even more preferably 25 m 2 / g or more and 45 m 2 / g or less. By adjusting the BET specific surface area of the zinc oxide powder to fall within the above range, the transparency of dispersions, coatings, cosmetics and the like containing the zinc oxide powder can be increased, and the viscosity can also be maintained within a favorable range. When the BET specific surface area is less than 8 m 2 / g, this is not preferred because when the zinc oxide powder is contained at a high concentration, the transparency of the dispersion tends to decrease. On the other hand, when the BET specific surface area exceeds 65 m 2 / g, this is not preferred because when the zinc oxide powder is contained at a high concentration, the viscosity of the dispersion tends to easily increase, and it tends to become difficult to obtain a uniform dispersion with high fluidity.

[0027] 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 110 nm. Generally, as the primary particle diameter increases, the BET specific surface area decreases, and as the primary particle diameter decreases, the BET 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.

[0028] (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 1.0 mL / g or more and 7.5 mL / g or less, preferably 3.0 mL / g or more and 7.5 mL / g or less, more preferably 4.0 mL / g or more and 7.5 mL / g or less, and even more preferably 5.0 mL / g or more and 7.5 mL / g or less. By adjusting the apparent specific volume of zinc oxide powder, determined by the static setting method, to within the above range, it is possible to suppress the increase in viscosity of the dispersion over time when zinc oxide powder is mixed into the dispersion medium. In other words, even as time passes, an increase in viscosity of the dispersion is less likely to occur. If the apparent specific volume obtained by the static method is less than 1.0 mL / g, the transparency of the dispersion containing zinc oxide powder tends to decrease, which is undesirable. On the other hand, if the apparent specific volume obtained by the static method exceeds 7.5 mL / g, the viscosity of the dispersion containing zinc oxide powder tends to increase over time, which is also undesirable. Examples of factors that increase the apparent specific volume obtained by the static method include, but are not limited to, small particle size.

[0029] 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.

[0030] (Apparent specific volume by static method / Apparent specific volume by tap method) Many aspects of the apparent specific volume characteristics of powders and their effects remained unclear. However, by focusing on the apparent specific volume characteristics of zinc oxide powder obtained by the standing method and the tapping method, we were able to provide an excellent zinc oxide powder that maintains oil absorption while preventing viscosity increase. The zinc oxide powder of this embodiment has a ratio of 1.50 to 2.50 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, and more preferably 1.60 to 2.00. If the ratio of "apparent specific volume by static testing / apparent specific volume by tapping" is between 1.50 and 2.50, the increase in viscosity over time of the dispersion containing zinc oxide powder can be suppressed. On the other hand, if the ratio of "apparent specific volume by static testing / apparent specific volume by tapping" is outside the above range, it is difficult to suppress the increase in viscosity over time.

[0031] The mechanism by which controlling the "apparent specific volume by the static method / apparent specific volume by the tapping method" within the above range can suppress the increase in viscosity of a dispersion containing zinc oxide powder over time is unknown. However, the following can be inferred. 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 particles of a powder, the greater the amount of air trapped between the particles, and the larger the apparent specific volume measured by the static method.

[0032] When zinc oxide particles constituting zinc oxide powder are dense and coarse, they are less likely to contain excess air between particles. In measurements of apparent specific volume by the static method, such particles are less likely to contain air between particles, resulting in a smaller apparent specific volume value by the static method. Furthermore, the apparent specific volume measured by the tap method does not change much, and the value of "apparent specific volume by static method / apparent specific volume by tap method" approaches 1. Zinc oxide powder containing coarse zinc oxide particles has poor transparency due to the large aggregate particle size. Furthermore, in cases where zinc oxide particles have many voids inside, or where steric hindrance (aggregated particle fusion) has occurred, such as when branching structures are significantly formed due to the fusion of zinc oxide particles, the apparent specific volume value obtained by the static method will be larger than that of the coarse zinc oxide particles mentioned above. In such particles, the tap method, which applies vibration by tapping, does not remove air from within or between the particles, and the apparent specific volume of the powder does not change much. That is, the apparent specific volume value obtained by the tap method remains large, and the value of "apparent specific volume by static method / apparent specific volume by tap method" approaches 1. On the other hand, when particles with such structures or aggregated particles are used, the structure of the zinc oxide particles is broken by the applied force when dispersing zinc oxide powder or surface-treated zinc oxide powder in a solvent. As a result, fine powder is generated, or the active surface of the zinc oxide particles is exposed, causing the dispersion to thicken. 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 1.50 or higher.

[0033] On the other hand, a ratio of "apparent specific volume by static method / apparent specific volume by tapping method" exceeding 2.50 means that the zinc oxide powder contains a large number of fine zinc oxide particles. When zinc oxide particles with very fine particle sizes 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 tends to increase over time, and the transparency of the dispersion also tends to decrease. Therefore, it is necessary for the ratio of "apparent specific volume by static method / apparent specific volume by tapping method" to be 2.50 or less.

[0034] By controlling the "apparent specific volume by static method / apparent specific volume by tapping method," the structure and size of zinc oxide particles can be appropriately adjusted, maintaining the transparency and dispersion stability of the dispersion. In other words, the "apparent specific volume by static method / apparent specific volume by tapping method" in the zinc oxide powder of this embodiment allows for macroscopic observation of the microscopic behavior and structure of each individual zinc oxide particle, resulting in a superior zinc oxide powder free from particles with undesirable structures. Thus, it is an excellent parameter. 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 1.50 and 2.50, it is possible to obtain a superior zinc oxide powder and a superior dispersion with excellent dispersion stability and suppressed viscosity increase over time. It is preferable to appropriately select manufacturing conditions and materials so that the "apparent specific volume by static method / apparent specific volume by tapping method" falls within a desirable range.

[0035] (D98 / BET equivalent particle size) In this embodiment, the zinc oxide powder preferably has a dry particle size D98 (μm) divided by the BET equivalent particle size (nm) (D98 (μm) / BET equivalent particle size (nm)) of 0.01 to 5.0, more preferably 0.01 to 4.0, and even more preferably 0.01 to 3.0. If necessary, it may be 0.01 to 3.5, 0.05 to 2.0, 0.10 to 1.00, 0.15 to 0.80, 0.20 to 0.60, etc. If "D98 / equivalent diameter" is within the above range, it is preferable in that the roughness of the zinc oxide powder can be suppressed. Furthermore, the surface-treated zinc oxide powder obtained by surface-treating the zinc oxide powder of this embodiment, as described later, may also have the above-mentioned range for (D98 (μm) / BET equivalent particle size (nm)). (BET equivalent particle size) In this specification, "BET equivalent particle size (nm)" refers to the BET specific surface area (m²) of zinc oxide powder. 2This refers to the particle size converted from ( / g) using the following general formula (1). BET equivalent particle diameter (nm) = 6000 / (BET specific surface area (m 2 (g) × ρ(g / cm²) 3 ) (1) In formula (1), ρ is the density of zinc oxide, and in this embodiment, ρ is 5.61 g / cm³. 3 The BET-equivalent particle size (nm) of the zinc oxide powder is used. The particle size can be arbitrarily selected. For example, the particle size may be 15-110 nm, or 15-100 nm. If necessary, it may also be 15-80 nm, 20-50 nm, 25-45 nm, 30-35 nm, etc.

[0036] (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, for example, one could add a material that increases the apparent specific volume by the static setting method when producing the zinc oxide powder, or use an apparatus that can increase the apparent specific volume by the static setting method. Increasing the apparent specific volume by the static setting method results in improved transparency. The desired value can be obtained by controlling the apparent specific volume of the powder by combining the methods described below or methods used in the prior art. However, the excellent effect obtained by controlling the value of the apparent specific volume of the powder to a predetermined range has not been known or anticipated until now.

[0037] To increase the apparent specific volume of zinc oxide powder by the static decomposition method, for example, when using the thermal decomposition method, a blowing agent can be mixed with the raw materials for producing zinc oxide powder in a small amount of arbitrarily selected ingredients, for example, about 1% by mass. Suitable blowing agents include inorganic blowing 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, as well as organic blowing agents such as azo compounds such as azobisisobutyronitrile, hydrazine compounds such as diphenylsulfone-3,3′-disulfohydrazine, semicarbazide compounds, triazole compounds, and N-nitroso compounds.

[0038] 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 obtained by the static method, and then thermally decompose it in a fluidized bed furnace at 300°C to 700°C, preferably 400°C to 600°C.

[0039] The method for adjusting D98 is not particularly limited, but for example, it can be adjusted by crushing zinc oxide powder under favorable conditions. The crushing treatment can be any method that can crush each particle (aggregated particles and / or aggregates of particles, etc.) in the zinc oxide powder so that the desired D98 is obtained, and is not particularly limited. An example of a crushing treatment is a method of crushing each particle using a crusher. Examples of crushers include roller mills, hammer mills, cage mills, pin mills, disintegrators, pulperizers, atomizers, turbo mills, supermicron mills, finemicron mills, rolling ball mills, vibrating ball mills, planetary mills, tower mills, attritors, aquamizers, basket mills, CF mills, sand grinders, dyno mills, ultravisco mills, coball mills, swirling flow jet mills, fluidized bed jet mills, nanomizers, shear mills, colloid mills, etc. The above-described method for adjusting D98 may be performed after surface treatment of the zinc oxide powder of this embodiment, as will be described later. That is, the surface-treated zinc oxide powder may be subjected to crushing treatment under preferred conditions to obtain the desired D98.

[0040] (crystallite size) The zinc oxide powder of this embodiment preferably has a crystallite size of 15 nm to 26 nm. If necessary, it may also have a crystallite size of 15 nm to 20 nm, 15 nm to 18 nm, 19 nm to 23 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.

[0041] BET specific surface area 8m 2 / g or more 65m 2Zinc oxide powder having a density of less than / g and a crystallite size of 15 nm to 26 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 increased to a degree that does not cause excessive grain growth. (Oil absorption amount) The zinc oxide powder of this embodiment may have a preferred oil absorption amount, which can be optionally selected. For example, it may be 80-150 mL / 100g, or 85-145 mL / 100g. If necessary, it may also be 90-140 mL / 100g, 95-135 mL / 100g, 100-130 mL / 100g, 110-120 mL / 100g, etc.

[0042] [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.

[0043] 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.

[0044] Examples of silane compounds used in surface treatment include alkylsilanes such as methyltrimethoxysilane, ethyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, and octyltriethoxysilane; and fluoroalkylsilanes such as trifluoromethylethyltrimethoxysilane and heptadecafluorodecyltrimethoxysilane. Among these silane compounds, alkylsilanes are preferred, and octyltriethoxysilane is particularly preferred. These silane compounds may be used individually or in combination of two or more.

[0045] Examples of silicone compounds used for surface treatment include silicone oils such as methylhydrogenpolysiloxane, dimethylpolysiloxane, and methylphenylpolysiloxane; methicone, dimethicone, hydrogen dimethicone, triethoxysilylethyl polydimethylsiloxyethyl dimethicone, triethoxysilylethyl polydimethylsiloxyethyl hexyl dimethicone, (acrylates / tridecyl acrylate / triethoxysilylpropyl methacrylate / dimethicone methacrylate) copolymer, and triethoxycaprylylsilane. 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.

[0046] 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.

[0047] 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.

[0048] 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.

[0049] 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 even more 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 obtaining the BET specific surface area of ​​the surface-treated zinc oxide powder and applying this value to the above general formula (1). If the "D98 / BET-equivalent particle size" of the surface-treated zinc oxide powder is within the above range, the roughness of the surface-treated zinc oxide powder can be suppressed. The BET equivalent particle size (nm) of the surface-treated zinc oxide powder can be arbitrarily selected. For example, it may be within the range of 15 to 110 nm, or 15 to 100 nm, or, if necessary, 15 to 80 nm, 20 to 50 nm, 25 to 45 nm, 30 to 35 nm, etc. Furthermore, the BET specific surface area of ​​surface-treated zinc oxide powder can be obtained in the same manner as that of zinc oxide powder.

[0050] 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 crushed to adjust the "D98 / BET equivalent particle size" of the surface-treated zinc oxide to be between 0.01 and 5. The same crusher as described above can be used for the crushing process. The surface-treated zinc oxide powder in the embodiment preferably contains 80 to 99% by mass of zinc oxide, and more preferably 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.

[0051] [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.

[0052] The content of zinc oxide powder 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. When the content of zinc oxide powder in the dispersion is within the above range, desirable properties of zinc oxide powder can be obtained, and the increase in viscosity of the dispersion over time can be suppressed.

[0053] 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 dispersion media include, for example, alcohols such as water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, octanol, and glycerin; esters such as ethyl acetate, butyl acetate, ethyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, and γ-butyrolactone; and ethers such as diethyl ether, ethylene glycol monomethyl ether (methyl cellosolve), ethylene glycol monoethyl ether (ethyl cellosolve), ethylene glycol monobutyl ether (butyl cellosolve), diethylene glycol monomethyl ether, and diethylene glycol monoethyl ether. These are suitably used. These dispersion media may be used individually or in combination of two or more.

[0054] Other examples of dispersion media include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, acetylacetone, and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, xylene, and ethylbenzene; cyclic hydrocarbons such as cyclohexane; amides such as dimethylformamide, N,N-dimethylacetacetamide, and N-methylpyrrolidone; and linear polysiloxanes such as dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane. These are suitably used. These dispersion media may be used individually or in combination of two or more.

[0055] Furthermore, other dispersion media that can be suitably used include cyclic polysiloxanes such as octamethylcyclotetrasiloxane, cyclopentasiloxane, and dodecamethylcyclohexasiloxane; and modified polysiloxanes such as amino-modified polysiloxane, polyether-modified polysiloxane, alkyl-modified polysiloxane, and fluorine-modified polysiloxane. These dispersion media may be used individually or in combination of two or more.

[0056] Furthermore, examples of other dispersion media different from those mentioned above include hydrophobic dispersion media such as liquid paraffin, squalane, isoparaffin, branched light paraffin, hydrocarbon oils such as 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. These may be used individually or in combination of two or more.

[0057] 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.

[0058] 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.

[0059] 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.

[0060] [paint] The paint of this embodiment contains the zinc oxide powder of this embodiment, a resin, and a dispersion medium.

[0061] The zinc oxide powder content in the paint of this embodiment can be adjusted as appropriate to suit the desired properties. For example, it is preferably 10% by mass or more and 40% by mass or less, more preferably 15% by mass or more and 35% by mass or less, and even more preferably 20% by mass or more and 30% by mass or less. 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.

[0062] The dispersion medium is not particularly limited as long as it is commonly used in industrial applications, but examples include water, alcohols such as methanol, ethanol, and propanol, and organic solvents such as 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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.

[0067] [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 of this embodiment. A cosmetic composition according to another embodiment contains 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 contain either or both of the zinc oxide powder and the dispersion of this embodiment and the base. A cosmetic composition according to this embodiment can be obtained, for example, by conventionally blending the dispersion of this embodiment with a base such as an emulsion, cream, foundation, lipstick, blush, or eyeshadow. 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.

[0068] 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 preferably 1% by mass or more and 30% by mass or less, more preferably 3% by mass or more and 20% by mass or less, and even more preferably 5% by mass or more and 15% by mass or less.

[0069] 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.

[0070] 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.

[0071] 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.

[0072] 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 the aforementioned benzoylmethane-based ultraviolet absorbers include, for example, 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.

[0073] 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 the aforementioned anthranilic acid-based ultraviolet absorbers include, for example, 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.

[0074] 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.

[0075] 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.

[0076] 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.

[0077] 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.

[0078] 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.

[0079] As described above, the zinc oxide powder of this embodiment adjusts the BET specific surface area, the apparent specific volume by the static method, and the ratio of the apparent specific volume by the static method to the apparent specific volume by the tapping method to a predetermined range. Therefore, it is possible to suppress the increase in viscosity over time of dispersions containing this zinc oxide powder. Furthermore, using this zinc oxide powder, dispersions and cosmetics with high transparency and excellent UV shielding properties can be obtained. The above characteristics are extremely advantageous.

[0080] 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, the increase in viscosity over time of dispersions containing this surface-treated zinc oxide powder can be suppressed. And the effect of high transparency, as in the conventional method, can be obtained.

[0081] The dispersion of this embodiment contains the zinc oxide powder or surface-treated zinc oxide powder of this embodiment. Therefore, it is possible to suppress the increase in viscosity of the dispersion over time.

[0082] The paint of this embodiment contains the zinc oxide powder or surface-treated zinc oxide powder of this embodiment. Therefore, it is possible to suppress the increase in viscosity of the paint over time.

[0083] The cosmetic composition of this embodiment contains the zinc oxide powder or surface-treated zinc oxide powder of this embodiment. Therefore, it is possible to suppress the increase in viscosity of the cosmetic composition over time. [Examples]

[0084] 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.

[0085] [Manufacturing of zinc oxide powder] [Example 1] "Preparation of surface-treated zinc oxide powder" Zinc oxide powder A1 (BET specific surface area 39.6 m²) 2 A sample was prepared with a specific volume of 7.31 mL / g (apparent specific volume by static method, 3.85 mL / g by tapping method, crystallite size of 17 nm, and oil absorption of 140 mL / 100 g). The characteristics, crystallite size, BET-equivalent particle size, and the ratio of crystallite size (nm) to BET-equivalent particle size (nm) for zinc oxide powder A1 are shown in Table 1. A mixture containing 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 crushed in a hammer mill at 16,000 rpm until the D98 was 500 μm or less. This crushed powder was dried at 120°C for 3 hours to obtain surface-treated zinc oxide powder B1 of Example 1. The D98 (μm) of surface-treated zinc oxide powder B1 is shown in Table 1. D98 was obtained by measuring the volume particle size distribution of zinc oxide powder B1 using a laser diffraction particle size distribution analyzer (model: Mastersizer 3000, manufactured by Malvern), and the value when the cumulative volume percentage was 98% was taken as D98.

[0086] "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 mixed and dispersed using a bead mill to obtain dispersion C1 from Example 1.

[0087] "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.

[0088] "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 (JASCO Corporation, model: V-770). 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.

[0089] [Example 2] Instead of zinc oxide powder A1, use zinc oxide powder A2 (BET specific surface area 40.4 m²). 2 Except for using (6.43 mL / g / g, apparent specific volume by standing method, 3.81 mL / g by tapping method, crystallite size 17 nm, oil absorption 126 mL / 100 g), the 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. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0090] [Example 3] Instead of zinc oxide powder A1, use zinc oxide powder A3 (BET specific surface area 39.8 m²). 2 Except for using (amount: 5.21 mL / g by static method, 2.90 mL / g by tapping method, crystallite size 16 nm, oil absorption 116 mL / 100 g), the 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. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0091] [Example 4] Instead of zinc oxide powder A1, use zinc oxide powder A4 (BET specific surface area 34.1 m²). 2 Except for using (1.60 mL / g by static method, 1.05 mL / g by tapping method, crystallite size 15 nm, oil absorption 94 mL / 100 g), the surface-treated zinc oxide powder B4 of Example 4 and a dispersion C4 containing surface-treated zinc oxide powder B4 were obtained in exactly the same manner as in Example 1. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0092] [Example 5] Instead of zinc oxide powder A1, use zinc oxide powder A5 (BET specific surface area 10.5 m²). 2 Except for using (1.64 mL / g by static method, 1.07 mL / g by tapping method, crystallite size 25 nm, oil absorption 92 mL / 100 g), the surface-treated zinc oxide powder B5 of Example 5 and a dispersion C5 containing surface-treated zinc oxide powder B5 were obtained in exactly the same manner as in Example 1. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0093] [Example 6] Instead of zinc oxide powder A1, use zinc oxide powder A6 (BET specific surface area 37.2 m²). 2 Except for using (amount: 3.30 mL / g by static method, 1.95 mL / g by tapping method, crystallite size 16 nm, oil absorption 108 mL / 100 g), the surface-treated zinc oxide powder B6 of Example 6 and a dispersion C6 containing surface-treated zinc oxide powder B6 were obtained in exactly the same manner as in Example 1. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0094] [Example 7] Instead of zinc oxide powder A1, use zinc oxide powder A7 (BET specific surface area 34.6 m²). 2Except for using (6.36 mL / g by static method, 2.93 mL / g by tapping method, crystallite size 18 nm, oil absorption 93 mL / 100 g), the surface-treated zinc oxide powder B7 of Example 7 and a dispersion C7 containing surface-treated zinc oxide powder B7 were obtained in exactly the same manner as in Example 1. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0095] [Example 8] Instead of zinc oxide powder A1, use zinc oxide powder A8 (BET specific surface area 52.5 m²). 2 Except for using (1.80 mL / g, apparent specific volume by static method, 1.15 mL / g, crystallite size 15 nm, oil absorption 105 mL / 100 g), the surface-treated zinc oxide powder B8 of Example 8 and a dispersion C8 containing surface-treated zinc oxide powder B8 were obtained in exactly the same manner as in Example 1. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1. The zinc oxide powders A1 to A8 used in the examples all had a dry particle size D98 (μm) divided by the BET-equivalent particle size (nm) of 0.01 or more and 5 or less.

[0096] [Comparative Example 1] Instead of zinc oxide powder A1, use commercially available zinc oxide powder A9 (BET specific surface area 44.8 m²). 2 Except for using (amount: 7.99 mL / g by static method, 4.92 mL / g by tapping method, crystallite size 14 nm, oil absorption 163 mL / 100 g), the surface-treated zinc oxide powder B9 of Comparative Example 1 and a dispersion C9 containing surface-treated zinc oxide powder B9 were obtained in exactly the same manner as in Example 1. The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0097] [Comparative Example 2] Instead of zinc oxide powder A1, use commercially available zinc oxide powder A10 (BET specific surface area 36.8 m²). 2A dispersion C10 containing surface-treated zinc oxide powder B10 was obtained in exactly the same manner as in Example 1, except that the following parameters were used: (amount: 5.49 mL / g by static method, 3.73 mL / g by tapping method, crystallite size 18 nm, oil absorption 104 mL / 100 g). The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0098] [Comparative Example 3] Instead of zinc oxide powder A1, use zinc oxide powder A11 (BET specific surface area 55.2 m²). 2 A dispersion C11 containing surface-treated zinc oxide powder B11 was obtained in exactly the same manner as in Example 1, except that the following parameters were used: (amount: 8.18 mL / g by the standing method, apparent specific volume: 3.15 mL / g by the tapping method, crystallite size: 16 nm, oil absorption: 154 mL / 100 g). The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0099] [Comparative Example 4] Instead of zinc oxide powder A1, use zinc oxide powder A12 (BET specific surface area 35.5 m²). 2 A dispersion C12 containing surface-treated zinc oxide powder B12 was obtained in exactly the same manner as in Example 1, except that the following was used: (6.15 mL / g by the standing method, 4.45 mL / g by the tapping method, crystallite size 18 nm, oil absorption 95 mL / 100 g). The results of the evaluation, which was performed in the same manner as in Example 1, are shown in Table 1.

[0100] [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.

[0101] By comparing Examples 1 to 8 with Comparative Examples 1 to 4, the BET specific surface area was found to be 8 m². 2 / g or more 65m 2Dispersions containing zinc oxide particles with a concentration of 1.0 mL / g or less, an apparent specific volume of 1.0 mL / g to 7.5 mL / g by the standing method, and an apparent specific volume of 1.50 to 2.50 by the standing method / tap method were confirmed to suppress viscosity increase over time while maintaining oil absorption within a desirable range. Furthermore, it was confirmed that transparency and UV shielding properties equivalent to those of conventional materials were obtained. These are exceptionally superior effects not seen in conventional materials. Furthermore, surface-treated zinc oxide powder B5 of Example 5 felt rougher to the touch compared to the surface-treated zinc oxide powders of Examples 1 to 4 and Examples 6 to 8. In other words, it was confirmed that surface-treated zinc oxide powders with a D98 / BET equivalent particle size of 0.01 to 3.0 suppressed roughness. The present invention achieved an excellent effect that had not been solved in the past: preventing the viscosity of zinc oxide powder while maintaining oil absorption. [Industrial applicability]

[0102] The zinc oxide powder of the present invention, when dispersed in a dispersion medium to form a dispersion liquid, can suppress the increase in viscosity over time. Therefore, the zinc oxide powder of the present invention exhibits excellent stability when applied to dispersion liquids, paints, and cosmetics, and has great industrial value. The present invention provides zinc oxide powder that has a high oil absorption capacity and can suppress thickening over time when incorporated into dispersions, as well as dispersions, paints, and cosmetics containing zinc oxide powder.

Claims

1. BET specific surface area is 8 m ２ / g or more 65m ２ / g or less, The BET equivalent particle size is 10 to 110 nm. The apparent specific volume obtained by the static method is 1.0 mL / g or more and 7.5 mL / g or less, The value obtained by dividing the apparent specific volume (mL / g) obtained by the static method by the apparent specific volume (mL / g) obtained by the tap method (apparent specific volume by static method / apparent specific volume by tap method) is 1.50 or more and 2.50 or less. 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 tapping method is as follows: the zinc oxide powder is passed through a sieve with a mesh size of 500 μm, and 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, and the graduated cylinder is covered with a lid. The lidded graduated cylinder is fixed to the bulk density measuring device, tapped 50 times, and the volume of the zinc oxide powder after tapping is read. 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. Zinc oxide powder.

2. The zinc oxide powder according to claim 1, wherein the value obtained by dividing the dry particle size D98 (μm) by the BET-equivalent particle size (nm) is 0.01 or more and 5.0 or less.

3. The value obtained from the formula for the zinc oxide powder, which is the crystallite size (nm) / BET-equivalent particle size (nm), is between 0.1 and 1.

0. The zinc oxide powder according to claim 1 or 2.

4. The oil absorption capacity of the zinc oxide powder is 80 to 150 mL / 100 g. The zinc oxide powder according to any one of claims 1 to 3.

5. The zinc oxide powder according to any one of claims 1 to 4, wherein the zinc oxide powder consists only of zinc oxide particles.

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. The zinc oxide powder according to claim 6, wherein the value obtained by dividing the dry particle size D98 (μm) by the BET-equivalent particle size (nm) is 0.01 or more and 5 or less.

8. The zinc oxide powder according to claim 7, wherein the value obtained by dividing the dry particle size D98 (μm) by the BET-equivalent particle size (nm) is 0.01 or more and 3.0 or less.

9. A dispersion containing zinc oxide powder according to any one of claims 1 to 8 and a dispersion medium.

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

11. A cosmetic composition comprising the zinc oxide powder described in any one of claims 1 to 8.

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