Zinc oxide powder, dispersion, coatings and cosmetics

Abstract

This invention provides a zinc oxide powder, wherein the BET specific surface area is 8 m². 2 / g or more and 65m 2 The apparent specific volume based on the standing method is 1.0 mL / g or more and 7.5 mL / g or less, and the apparent specific volume based on the standing method (mL / g) divided by the apparent specific volume based on the tapping method (mL / g) is, i.e., the apparent specific volume based on the standing method / the apparent specific volume based on the tapping method is 1.50 or more and 2.50 or less.

Description

Technical Field

[0001] This invention relates to zinc oxide powder, dispersion, coating, and cosmetic.

[0002] This application claims priority based on Japanese Patent Application No. 2020-198864 filed on November 30, 2020, the contents of which are incorporated herein by reference. Background Technology

[0003] Zinc oxide powder possesses ultraviolet (UV) shielding and gas permeation suppression properties, and also exhibits high transparency. Therefore, it is used in applications requiring both UV shielding and transparency, such as UV-shielding films, UV-shielding glass, gas-barrier films, and cosmetics.

[0004] One method for achieving transparency is reducing the primary particle size of zinc oxide particles to the nanoscale. Various methods, including thermal decomposition and gas-phase methods, have been investigated for the manufacture of zinc oxide microparticles.

[0005] For example, Patent Document 1 describes the following: Since particulate zinc oxide is a microparticle, it easily aggregates with each other, reducing particle independence and increasing oil absorption. When this high-oil-absorption particulate zinc oxide is incorporated into cosmetics, it absorbs a large amount of oil components contained in the cosmetic, thereby increasing the viscosity of the cosmetic. Furthermore, if the particulate zinc oxide aggregates and its dispersibility decreases, its transparency decreases. Therefore, aggregated particulate zinc oxide also has the disadvantage of producing an unnatural whitening effect when used in cosmetics (applied to the skin). There is a need for particulate zinc oxide to improve UV shielding while reducing oil absorption or powder volume.

[0006] Patent Document 1 describes a zinc oxide particle with a primary particle size of less than 0.1 μm, an aspect ratio of less than 2.5, and an oil absorption / BET specific surface area of ​​1.5 mL / 100 m², provided to address the viscosity or transparency issues caused by the aforementioned agglomeration. 2 the following.

[0007] On the other hand, Patent Document 2 describes an organic-inorganic composite pigment, in which a specific surface treatment is applied to a highly oil-absorbent inorganic pigment in order to make the appearance color bright and improve the durability when it is incorporated into cosmetics.

[0008] Patent document 3 describes a cosmetic product containing a liquid perfluorinated organic compound, cyclic silicones or chain silicones with a specific evaporation rate, and an oil-absorbing powder with a high oil absorption capacity, capable of absorbing more than 1.5 times its own weight in squalane. This cosmetic product has a refreshing feel and can prevent makeup from fading or becoming oily over time.

[0009] Existing technical documents

[0010] Patent documents

[0011] Patent Document 1: International Publication No. 2012 / 147888

[0012] Patent Document 2: Japanese Patent Application Publication No. 11-181329

[0013] Patent Document 3: Japanese Patent Application Publication No. 2019-099510 Summary of the Invention

[0014] The problem the invention aims to solve

[0015] Inorganic powders with high oil absorption have the advantage of preventing makeup from feeling rough or becoming oily and smudged over time.

[0016] However, existing inorganic powders with high oil absorption capacity have the disadvantage of causing the viscosity of cosmetics to increase over time when incorporated into them.

[0017] The requirement is to develop a superior zinc oxide powder that possesses the aforementioned advantages while addressing the aforementioned disadvantages.

[0018] The present invention was made in view of the above circumstances, and its object is to provide a zinc oxide powder that, when incorporated into a dispersion or the like, can suppress the increase in viscosity over time and has an preferably high oil absorption capacity, as well as a dispersion, coating, and cosmetic containing the zinc oxide powder. Furthermore, another object is to impart the zinc oxide powder with the same transparency and other properties as existing materials.

[0019] Solution for solving the problem

[0020] That is, the zinc oxide powder of the first embodiment of the present invention is characterized in that its BET specific surface area is 8m². 2 / g or more and 65m 2 The apparent specific volume based on the standing method is 1.0 mL / g or more and 7.5 mL / g or less, and the value of the apparent specific volume based on the standing method (mL / g) divided by the apparent specific volume based on the tapping method (apparent specific volume based on the standing method / apparent specific volume based on the tapping method) is 1.50 or more and 2.50 or less.

[0021] The zinc oxide powder of the first embodiment of the present invention can be further subjected to surface treatment.

[0022] Untreated zinc oxide powder and surface-treated zinc oxide powder can be used in combination.

[0023] The dispersion of the second aspect of the present invention is characterized in that it contains zinc oxide powder and a dispersion medium of the first aspect of the present invention.

[0024] The third-party coating of the present invention is characterized in that it contains zinc oxide powder, resin and dispersion medium of the first embodiment of the present invention.

[0025] The cosmetic of the fourth aspect of the present invention is characterized in that it is made by containing at least one selected from the group consisting of zinc oxide powder selected from the first aspect of the present invention and dispersion selected from the second aspect of the present invention.

[0026] The surface-treated zinc oxide powder of the fifth aspect of the present invention is characterized in that the zinc oxide powder of the first aspect of the present invention is a surface-treated zinc oxide powder that has undergone surface treatment with at least one of inorganic and organic components.

[0027] The effects of the invention

[0028] The zinc oxide powder according to the present invention has a BET specific surface area of ​​8m². 2 / g or more and 65m 2 The apparent specific volume based on the standing method is 1.0 mL / g or more and 7.5 mL / g or less, and the value of the apparent specific volume based on the standing method (mL / g) divided by the apparent specific volume based on the tapping method (mL / g) (apparent specific volume based on the standing method / apparent specific volume based on the tapping method) is 1.50 or more and 2.50 or less. Therefore, when formulated into dispersions, viscosity increase over time can be suppressed.

[0029] Furthermore, the zinc oxide powder of the present invention can maintain an appropriate oil absorption capacity and, when incorporated into dispersions, maintains excellent transparency. Moreover, these excellent effects are also provided when the zinc oxide powder has undergone surface treatment.

[0030] The dispersion according to the present invention, having contained one or both of the zinc oxide powder of the present invention, the surface-treated zinc oxide powder of the present invention, and the dispersion medium, can suppress the increase in viscosity of the dispersion over time.

[0031] The coating according to the present invention, having contained one or both of the zinc oxide powder of the present invention, the surface-treated zinc oxide powder of the present invention, a resin, and a dispersion medium, is able to suppress the increase in coating viscosity over time.

[0032] The cosmetic according to the present invention, having contained at least one selected from the group consisting of zinc oxide powder and dispersion of the present invention, is able to suppress the increase in viscosity of the cosmetic over time. Detailed Implementation

[0033] Preferred embodiments of the zinc oxide powder, dispersion, coating, and cosmetic of the present invention will be described.

[0034] Furthermore, this embodiment has been specifically described to better understand the spirit of the invention, and unless otherwise specifically specified, it is not intended to limit the invention. Omissions, additions, substitutions, and other modifications may be made without departing from the spirit of the invention.

[0035] Zinc oxide powder

[0036] The BET specific surface area of ​​the zinc oxide powder in this embodiment is 8m². 2 / g or more and 65m 2 The apparent specific volume based on the standing method is 1.0 mL / g or less and 7.5 mL / g or less, and the value of the apparent specific volume based on the standing method (mL / g) divided by the apparent specific volume based on the tapped method (apparent specific volume based on the standing method / apparent specific volume based on the tapped method) is 1.50 or more and 2.50 or less. Furthermore, in this specification, the apparent specific volume based on the standing method can be referred to as the standing volume. And, the apparent specific volume based on the tapped method can be referred to as the tapped volume.

[0037] The zinc oxide powder of the embodiment preferably contains 99.5% by mass or more, more preferably 99.7% by mass or more, and even more preferably 100% by mass. The zinc oxide powder may consist solely of zinc oxide, but may also contain trace amounts of impurities that do not affect the efficacy. Furthermore, the zinc oxide powder of the embodiment is preferably composed solely of zinc oxide particles. The zinc oxide content in the zinc oxide powder of this embodiment refers to the value determined by the following method. This determination method is based on the "Quantitative Method for Zinc Oxide" described in Quasi-Pharmaceutical Raw Material Specification 2006 (Quasi-Pharmaceutical Raw Material Specification).

[0038] Zinc oxide powder was added to a muffle furnace and ignited at 500°C until a constant mass was reached. The zinc oxide powder was then cooled to room temperature in a glass desiccator with silica gel. 1.5 g of the cooled zinc oxide powder was accurately weighed and added to 50 mL of water and 20 mL of dilute hydrochloric acid. The mixture was heated to dissolve the zinc oxide powder. If any unwanted substances remained, 3 drops of nitric acid were added to completely dissolve them. The solution was cooled to room temperature, and water was added to bring the total volume to 250 mL. 10 mL of an acetate-ammonium acetate buffer solution (adjusted to pH 5.0) was added to 25 mL of this solution, and dilute ammonia was added to adjust the pH to 5–5.5. Water was then added to bring the total volume to 250 mL. 0.5 mL of xylenol orange reagent was added as an indicator, and the solution was titrated with 0.05 mol / L disodium ethylenediaminetetraacetate solution until a yellow color was obtained. Since 1 mL of 0.05 mol / L disodium ethylenediaminetetraacetate solution is equivalent to 4.069 mg of zinc oxide, the zinc oxide content in the zinc oxide powder can be quantified by the amount of 0.05 mol / L disodium ethylenediaminetetraacetate solution required for titration. In cases where the calculated value exceeds 100% by mass using this method, the zinc oxide content is set as 100% by mass.

[0039] (Methods for determining various properties of zinc oxide powder or surface-treated zinc oxide powder)

[0040] The BET specific surface area in the zinc oxide powder of the embodiment can refer to the value measured by the BET method using a specific surface area measuring device, for example, using a fully automatic specific surface area measuring device (trade name: Macsorb HM Model-1201, manufactured by MOUNTECH Co., Ltd.).

[0041] In this embodiment, the apparent specific volume (mL / g) of the zinc oxide powder based on the standing method refers to the value determined according to JIS K5101-12-1 "Test Methods for Pigments - Part 12: Apparent Density or Apparent Specific Volume - Section 1: Standing Method". Furthermore, for the apparent specific volume based on the standing method, 50 tapping cycles are not performed.

[0042] The apparent specific volume (mL / g) of the zinc oxide powder in this embodiment, based on the tapping method, can be measured using a bulk density meter. For example, a dense-packed bulk density meter (trade name: TVP-1 type, manufactured by TSUTSUISCIENTIFIC INSTRUMENTS CO.,LTD.) will be used. The specific measurement method will be described below.

[0043] The mass (A) of a 150 mL graduated cylinder (inner diameter: 31 mm, manufactured by TSUTSUI SCIENTIFIC INSTRUMENT SCO., LTD.) was measured using an electronic balance. At least 100 mL of zinc oxide powder was placed on a sieve with a mesh size of 500 μm. The zinc oxide powder was then sieved by brushing it. Approximately 100 mL of the sieved zinc oxide powder was added to the 150 mL graduated cylinder. The mass (B) of the graduated cylinder was measured using an electronic balance. The graduated cylinder was then fixed to a dense-packed bulk density measuring device. A black rubber stopper was placed on the graduated cylinder to prevent powder from scattering during compaction. The volume (V) of the zinc oxide powder after 50 compactions using the dense-packed bulk density measuring device was read from the graduated cylinder. The apparent specific volume was then calculated as V / (BA). The compaction width could be set to 20 mm, and the compaction speed could be set to 30 times / minute. Thus, the tapping method is a method of measuring powder by repeatedly tapping the container into which the powder is added.

[0044] In this embodiment, the dry particle size D98 of the zinc oxide powder can refer to the value when the cumulative volume percentage of the volume particle size distribution of the zinc oxide powder is 98% when measured dry using a laser diffraction particle size distribution measuring device, for example, a laser diffraction particle size distribution measuring device (model: Mastersizer 3000, manufactured by Malvern). Hereinafter, the dry particle size D98 will sometimes be abbreviated as "D98".

[0045] The crystallite diameter in the zinc oxide powder of this embodiment can refer to the Scherrer diameter calculated by using an X-ray diffraction apparatus, for example, an X-ray diffraction apparatus (trade name: AERIS, manufactured by PANalytical), using the half-width of the diffraction peaks on the (101) plane of the measured powder X-ray diffraction pattern and the diffraction angle (2θ), and the Scherrer formula.

[0046] In the X-ray diffraction measurement conditions of the powder using the above-described apparatus, the radiation source was set to CuKα rays, and the output was set to 40 kV and 15 mA. Furthermore, the measurement data obtained by X-ray diffraction measurement can be analyzed using the data processing software AERIS (manufactured by PANalytical), thereby enabling the calculation of the Scherer diameter.

[0047] The oil absorption of zinc oxide powder in this embodiment refers to the value measured according to JIS K5101-13-1 (Picture Test Methods - Part 13: Oil Absorption - Section 1: Refined Linseed Oil Method).

[0048] (BET specific surface area)

[0049] The BET specific surface area of ​​the zinc oxide powder in this embodiment is 8m². 2 / g or more and 65m 2 / g or less, preferably 15m 2 / g or more and 60m 2 / g or less, preferably 20m 2 / g or more and 50m 2 / g or less, more preferably 25m 2 / g or more and 45m 2 / g or less.

[0050] By adjusting the BET specific surface area of ​​zinc oxide powder to the above-mentioned range, the transparency of dispersions, coatings, cosmetics, etc. containing zinc oxide powder can be improved, and the viscosity can also be maintained within the preferred range.

[0051] If the specific surface area of ​​BET is less than 8m² 2 If the concentration of zinc oxide powder is high (e.g., the transparency of the dispersion tends to decrease, which is undesirable). On the other hand, if the BET specific surface area exceeds 65 m² / g... 2 If the concentration is / g, the viscosity of the dispersion tends to increase when the zinc oxide powder is in a high concentration, making it difficult to obtain a uniform and highly fluid dispersion, which is therefore not preferred.

[0052] The method for adjusting the BET specific surface area of ​​zinc oxide powder to the above-mentioned range is not particularly limited. For example, a method can be given to adjust the average primary particle size (BET equivalent particle size) converted from the BET specific surface area to be 15 nm or more and 110 nm or less. Generally, if the primary particle size increases, the BET specific surface area decreases, and if the primary particle size decreases, the BET specific surface area increases.

[0053] Furthermore, the BET specific surface area of ​​zinc oxide powder can be adjusted by changing the particle shape or by setting fine pores in the particles.

[0054] The zinc oxide powder of this embodiment is typically composed of secondary particles, but may also contain primary particles. When primary particles are present, the ratio of secondary to primary zinc oxide particles in the zinc oxide powder can be arbitrarily selected. For example, the proportion of secondary particles may be 70% by mass or more, or 80% by mass or more, 90% by mass or more, 95% by mass or more, 98% by mass or more, or 100% by mass.

[0055] (Apparent specific volume based on the static method)

[0056] The apparent specific volume of the zinc oxide powder in this embodiment, based on 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.

[0057] By adjusting the apparent specific volume of zinc oxide powder based on the static method to the above range, the viscosity increase of the dispersion over time when zinc oxide powder is mixed in the dispersion medium can be suppressed. That is, even over time, it is difficult for the viscosity of the dispersion to increase.

[0058] If the apparent specific volume based on the settling method is less than 1.0 mL / g, the transparency of the dispersion containing zinc oxide powder tends to decrease, which is therefore undesirable. On the other hand, if the apparent specific volume based on the settling 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 contributing to a higher apparent specific volume based on the settling method include, for example, small particle size, but this is not the only one.

[0059] The method for controlling the apparent specific volume of zinc oxide powder within the aforementioned range based on the settling method is not particularly limited. For example, when producing zinc oxide powder by the thermal decomposition method described in Japanese Patent Application Publication No. 60-255620, the apparent specific volume of zinc oxide powder based on the settling method can be controlled within the aforementioned range by adjusting the apparent specific volume of zinc oxalate, zinc hydroxide, zinc carbonate, basic zinc carbonate, etc., which are used as raw materials, or by adjusting the thermal decomposition temperature, etc.

[0060] For example, when producing zinc oxide by the gas-phase method described in Japanese Patent Application Publication No. 63-288914, the apparent specific volume of zinc oxide powder based on the static method can be controlled within the above-mentioned range by appropriately adjusting the temperature during the production process.

[0061] (Apparent specific volume based on static method / Apparent specific volume based on vibration method)

[0062] There are still many unexplained aspects regarding the apparent specific volume characteristics and effects of powders. However, the results of studying the apparent specific volume characteristics of zinc oxide powder based on the static method and the tapping method can provide excellent zinc oxide powders that maintain oil absorption while preventing viscosity increase.

[0063] In this embodiment, the apparent specific volume (mL / g) of the zinc oxide powder based on the standing method divided by the apparent specific volume (mL / g) based on the tapping method (apparent specific volume based on the standing method / apparent specific volume based on the tapping method) is 1.50 or more and 2.50 or less. The ratio of "apparent specific volume based on the standing method / apparent specific volume based on the tapping method" is preferably 1.55 or more and 2.30 or less, more preferably 1.60 or more and 2.00 or less.

[0064] By ensuring that the ratio of apparent specific volume based on the settling method to apparent specific volume based on the tapping method is between 1.50 and 2.50, the viscosity increase over time in dispersions containing zinc oxide powder can be suppressed. On the other hand, when the ratio of apparent specific volume based on the settling method to apparent specific volume based on the tapping method is outside the aforementioned range, it is difficult to suppress the viscosity increase over time.

[0065] The mechanism by which the apparent specific volume based on the static method / apparent specific volume based on the tapping method can be controlled within the above range to suppress the viscosity increase of the dispersion containing zinc oxide powder over time is not yet clear. However, it is speculated to be as follows.

[0066] Apparent specific volume based on the settling method is the volume per unit mass of powder measured with air between the particles. In contrast, apparent specific volume based on the tapping method is the volume per unit mass of powder measured after some air has been removed between the powder particles through tapping. Therefore, the apparent specific volume of powder based on the settling method is generally greater than that based on the tapping method. Furthermore, generally, the smaller the powder particles, the greater the amount of air between the particles, and the larger the apparent specific volume based on the settling method.

[0067] When the zinc oxide particles constituting zinc oxide powder are dense and coarse, it is difficult for excess air to be contained between the particles. In the determination of apparent specific volume based on the static method, because these particles are unlikely to contain air, the apparent specific volume value based on the static method is smaller, and the apparent specific volume based on the tapping method also shows almost no change; the ratio of "apparent specific volume based on static method / apparent specific volume based on tapping method" is close to 1. Zinc oxide powder containing coarse zinc oxide particles has poor transparency due to its large aggregate particle size.

[0068] Furthermore, in cases where zinc oxide particles have numerous voids within them, or in cases where agglomerated particles exhibit significant branching structures due to their fusion with each other (agglomerated particle fusion), the apparent specific volume based on the static method is greater than that of the aforementioned coarse zinc oxide particles. In the apparent specific volume determination method based on the tapping method, where vibration is applied to these particles, air within or between the particles does not escape, and the apparent specific volume of the powder hardly changes. That is, the apparent specific volume based on the tapping method remains large, and the ratio of "apparent specific volume based on static method / apparent specific volume based on tapping method" becomes close to 1. On the other hand, when using particles or agglomerated particles with this structure, the structure of the zinc oxide particles is disrupted by the applied force, etc. As a result, micropowder is produced, or the active surface of the zinc oxide particles is exposed, and the dispersion thickens.

[0069] Therefore, in order to improve transparency and suppress the increase in viscosity of the dispersion, the apparent specific volume based on the settling method / apparent specific volume based on the tapping method needs to be above 1.50.

[0070] On the other hand, an apparent specific volume ratio (based on the standing method / based on the tapped method) exceeding 2.50 indicates that the zinc oxide powder contains a large number of fine zinc oxide particles. If very fine zinc oxide particles are mixed into the zinc oxide powder, they will cause the particles to re-aggregate in the dispersion even after being dispersed in a solvent. Therefore, over time, the viscosity of the dispersion tends to increase, and the transparency of the dispersion tends to decrease. Therefore, the apparent specific volume ratio (based on the standing method / based on the tapped method) needs to be below 2.50.

[0071] By controlling the apparent specific volume based on the settling method / apparent specific volume based on the 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 based on the settling method / apparent specific volume based on the tapping method in the zinc oxide powder of this embodiment can capture the microscopic movements or structures of each zinc oxide particle macroscopically, resulting in excellent zinc oxide powder free of particles with undesirable structures. Therefore, these are superior parameters.

[0072] Therefore, by measuring the apparent specific volume based on the settling method / apparent specific volume based on the tapping method, and controlling the size or structure of the zinc oxide particles constituting the zinc oxide powder to ensure that the apparent specific volume based on the settling method / apparent specific volume based on the tapping method is 1.50 or more and 2.50 or less, excellent zinc oxide powder and an excellent dispersion with excellent dispersion stability and suppressed viscosity increase over time can be obtained. Preferably, the manufacturing conditions or materials are appropriately selected so that the apparent specific volume based on the settling method / apparent specific volume based on the tapping method is within a preferred range.

[0073] (D98 / BET converted particle size)

[0074] In this embodiment, the value of the dry particle size D98 (μm) of the zinc oxide powder divided by the BET equivalent particle size (nm) (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 4.0 or less, and even more preferably 0.01 or more and 3.0 or less. Depending on the requirements, it can 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 particle size" is within the above range, it is preferable in terms of suppressing the roughness of the zinc oxide powder.

[0075] In addition, the surface-treated zinc oxide powder (D98 (μm) / BET equivalent particle size (nm)) of the zinc oxide powder of this embodiment described later may also have the above-mentioned range.

[0076] (BET particle size conversion)

[0077] In this specification, "BET converted particle size (nm)" refers to the BET specific surface area (m²) of zinc oxide powder calculated using the following general formula (1). 2 Particle size converted to g).

[0078] BET particle size conversion (nm) = 6000 / (BET specific surface area (m²) 2 / g)×ρ(g / cm 3 (1)

[0079] In formula (1), ρ is the density of zinc oxide, which is 5.61 g / cm³ in this embodiment. 3 The BET equivalent particle size (nm) of the zinc oxide powder can be arbitrarily selected. For example, the particle size can be 15–110 nm or 15–100 nm. Depending on the requirements, it can be 15–80 nm, 20–50 nm, 25–45 nm, 30–35 nm, etc.

[0080] (Manufacturing method of zinc oxide powder and method for adjusting apparent specific volume)

[0081] The method for manufacturing zinc oxide powder in this embodiment is not particularly limited. For example, as described in Japanese Patent Application Publication No. 60-255620, there are methods for manufacturing zinc oxide powder that produce zinc oxalate, zinc hydroxide, zinc carbonate, and basic zinc carbonate as raw materials through thermal decomposition. Furthermore, there is, for example, a gas-phase method for producing zinc oxide powder by oxidizing and burning metallic zinc vapor as described in Japanese Patent Application Publication No. 63-288014.

[0082] To manufacture the zinc oxide powder of this embodiment, for example, a method can be used that allows the addition of materials that increase the apparent specific volume based on the settling method, or a device that increases the apparent specific volume based on the settling method, during the manufacture of zinc oxide powder. Increasing the apparent specific volume based on the settling method results in increased transparency. The apparent specific volume of the powder can be controlled by combining the methods described below or methods used in the prior art to obtain a predetermined value. However, the superior effect of controlling the apparent specific volume of the powder within a predetermined range has not been known or anticipated until now.

[0083] To increase the apparent specific volume of zinc oxide powder based on the static method, for example, when using the thermal decomposition method, a method can be adopted to mix a foaming agent in a small, arbitrarily chosen amount, such as about 1% by mass, into the raw materials for producing zinc oxide powder. 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 borohydride, azo compounds such as azobisisobutyronitrile, hydrazine compounds such as diphenyl sulfone-3,3'-disulfonylhydrazine, aminourea compounds, triazole compounds, and N-nitroso compounds are preferred.

[0084] Examples of devices for increasing the apparent specific volume of zinc oxide powder based on the settling method include, for example, fluidized bed calciners that can calcine while air is being supplied.

[0085] By adjusting the amount of foaming agent or the calcination temperature, the apparent specific volume based on the static method and the "apparent specific volume based on the static method / apparent specific volume based on the vibration method" can be adjusted to the desired range.

[0086] As a method for manufacturing zinc oxide powder according to this embodiment, for example, one method is to add 1% by mass of ammonium carbonate as a foaming agent to zinc carbonate with an apparent specific volume of 1.0 mL / g to 7.5 mL / g based on the static method, and carry out thermal decomposition in a fluidized bed calciner at 300°C to 700°C, preferably at 400°C to 600°C.

[0087] The method for adjusting D98 is not particularly limited; for example, it can be adjusted by crushing the zinc oxide powder under preferred conditions. As for the crushing process, any method capable of crushing individual particles (agglomerated particles and / or aggregates of particles, etc.) in the zinc oxide powder to obtain the desired D98 is acceptable and is not particularly limited. Examples of crushing processes include methods using a crusher to crush individual particles. Examples of crushers include, for instance, roller mills, hammer mills, cage mills, pin mills, decomposers, pulverizers, atomizers, turbine mills, ultramicron mills, fine rice mills, rolling ball mills, vibrating ball mills, planetary mills, tower mills, grinding mills, water mills, basket mills, CF mills, sand mills, dyno-mills, super-viscous colloid mills, co-ball mills, swirling jet mills, fluidized bed jet mills, nano-mills, shear mills, colloid mills, etc.

[0088] As described below, the D98 adjustment method described above can be performed after the zinc oxide powder of this embodiment has undergone surface treatment. That is, the surface-treated zinc oxide powder can be crushed under preferred conditions to obtain the desired D98.

[0089] (Crystal diameter)

[0090] In this embodiment, the crystallite diameter of the zinc oxide powder is preferably 15 nm or more and 26 nm or less. Depending on the requirements, it can be 15 nm or more and 20 nm or less, 15 nm or more and 18 nm or less, 19 nm or more and 23 nm or less, etc.

[0091] (Crystal diameter (nm) / BET converted particle size (nm))

[0092] In this embodiment, the value of the zinc oxide powder crystallite diameter (nm) divided by the BET equivalent particle size (nm) obtained from the BET specific surface area is preferably 0.1 or more and 1.0 or less, more preferably 0.4 or more and 1.0 or less, even more preferably 0.5 or more and 1.0 or less, and even more preferably 0.6 or more and 1.0 or less. Depending on the need, it can be 0.2 or more and 0.9 or less, 0.3 or more and 0.8 or less, etc.

[0093] BET has a specific surface area of ​​8m² 2 / g or more and 65m 2 Zinc oxide powder with a density of less than 1 g and a crystallite diameter of 15 nm to 26 nm has sufficient crystallinity to achieve high transparency and high UV shielding.

[0094] To improve the crystallinity of zinc oxide powder, one can simply raise the temperature during the zinc oxide powder production process to a level that prevents excessive particle growth.

[0095] (oil absorption)

[0096] The zinc oxide powder of this embodiment can have any preferred oil absorption capacity. For example, it can be 80-150 mL / 100g or 85-145 mL / 100g. Depending on the need, it can be 90-140 mL / 100g, 95-135 mL / 100g, 100-130 mL / 100g, 110-120 mL / 100g, etc.

[0097] [Surface-treated zinc oxide powder]

[0098] The zinc oxide powder of this embodiment has at least a portion of its surface treated with at least one of inorganic and organic components. Thus, the zinc oxide powder treated with at least one of inorganic and organic components is referred to as surface-treated zinc oxide powder.

[0099] The inorganic and organic components are selected appropriately according to the intended use of the zinc oxide powder.

[0100] In the case where the surface-treated zinc oxide powder of this embodiment is used in cosmetics, it is not particularly limited as an inorganic or organic component, if it is a surface treatment agent commonly used in cosmetics.

[0101] Examples of inorganic components include silicon dioxide and aluminum oxide.

[0102] Examples of organic ingredients include at least one from the group consisting of silane compounds, silicone compounds, fatty acids, fatty acid soaps, fatty acid esters, and organotitanate compounds.

[0103] Furthermore, surfactants can be used as inorganic or organic components.

[0104] When zinc oxide powder is surface-treated with at least one of the inorganic and organic components, the surface activity of the zinc oxide powder can be suppressed, or the dispersibility of the zinc oxide powder to the dispersion medium can be improved.

[0105] Examples of silane compounds used for 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.

[0106] These silane compounds can be used alone or in combination of two or more.

[0107] Examples of silicone compounds used for surface treatment include methyl hydrogenated polysiloxane, dimethyl polysiloxane, methylphenyl polysiloxane, and other silicone oils; methyl silicone oil, dimethyl silicone oil, hydrogenated dimethyl silicone oil, triethoxysilyl ethyl polydimethylsiloxy ethyl dimethyl silicone oil, triethoxysilyl ethyl polydimethylsiloxy ethylhexyl dimethyl silicone oil, (acrylate / tridecyl acrylate / triethoxysilyl propyl methacrylate / dimethyl methacrylate) copolymers, and triethoxydecyl silane. These silicone compounds can be used alone or in combination of two or more. Furthermore, copolymers of these silicone compounds can be used as silicone compounds.

[0108] Examples of fatty acids include palmitic acid, isostearic acid, stearic acid, lauric acid, myristic acid, benzyl acid, oleic acid, rosin acid, and 12-hydroxystearic acid.

[0109] Examples of fatty acid soaps include aluminum stearate, calcium stearate, and aluminum 12-hydroxystearate.

[0110] Examples of fatty acid esters include dextrin fatty acid esters, cholesterol fatty acid esters, sucrose fatty acid esters, and starch fatty acid esters.

[0111] Examples of organotitanate compounds include isopropyltriisostearoyl titanate, isopropyl dimethacrylate isostearoyl titanate, isopropyltris(dodecyl)benzenesulfonyl titanate, neopentyl(diallyl)oxy-tris(dioctyl)phosphate titanate, and neopentyl(diallyl)oxy-trinedodecanoyl titanate.

[0112] When the surface-treated zinc oxide powder of this embodiment is used in industrial applications such as ultraviolet shielding films or gas barrier films, in addition to inorganic or 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.

[0113] This surface treatment can suppress the surface activity of zinc oxide powder or improve the dispersibility of zinc oxide powder in the dispersion medium.

[0114] In the surface-treated zinc oxide powder of this embodiment, the value of the dry particle size D98 (μm) of the surface-treated zinc oxide powder divided 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, further preferably 0.01 or more and 4.0 or less, and even more preferably 0.01 or more and 3.0 or less. Depending on the requirements, the value can 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 that 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.

[0115] The BET equivalent particle size (nm) of the surface-treated zinc oxide powder can be arbitrarily selected. For example, it can be in the range of 15-110nm, or 15-100nm, or, as needed, 15-80nm, 20-50nm, 25-45nm, 30-35nm, etc.

[0116] In addition, the BET specific surface area of ​​surface-treated zinc oxide powder can be obtained by the same method as that of zinc oxide powder.

[0117] The method for manufacturing the surface-treated zinc oxide powder in this embodiment is not particularly limited; it can be carried out appropriately by known methods, depending on the composition used for surface treatment.

[0118] Furthermore, the surface-treated zinc oxide powder can be crushed to adjust the "D98 / BET equivalent particle size" of the surface-treated zinc oxide to be above 0.01 and below 5. The same crusher as described above can be used in the crushing process.

[0119] In addition, the surface-treated zinc oxide powder in the embodiment preferably contains 80 to 99% by mass of zinc oxide, more preferably 82 to 97% by mass.

[0120] For example, the following methods can be cited as examples of surface treatment methods.

[0121] The zinc oxide powder of the present invention, which has not undergone surface treatment, at least one of the inorganic and organic components for surface treatment, and one or more solvents selected as needed, such as pure water and isopropanol, are mixed by any chosen method or apparatus. Aqueous solvents are preferred examples. The total amount of the mixed inorganic and / or organic components may be, for example, 1 to 25 parts by mass relative to 100 parts by mass of zinc oxide particles, preferably 3 to 22 parts by mass. The amount of solvent can be chosen arbitrarily. After mixing, the mixture may be dried at any chosen temperature to remove at least a portion of the solvent. The drying temperature can be chosen arbitrarily, for example 50 to 200°C, more preferably 60 to 150°C, and even more preferably 70 to 120°C. Furthermore, heat treatment may be performed for further surface treatment reaction. The heat treatment temperature can be chosen arbitrarily, for example 200 to 800°C, more preferably 200 to 700°C, and even more preferably 200 to 600°C. The resulting dried or heat-treated product (surface-treated zinc oxide powder) can be crushed to a D98 of 500 μm or less under any chosen method, apparatus, or conditions. The crushed product can be further dried. The drying temperature can be chosen arbitrarily, for example, 50–200 °C, more preferably 60–150 °C, and even more preferably 70–120 °C. In the surface-treated zinc oxide powder of this embodiment, by controlling the manufacturing conditions, the value of the dry particle size D98 (μm) divided by the BET equivalent particle size (nm) can be controlled to be 0.01 or more and 5 or less.

[0122] [Dispersion]

[0123] The dispersion of this embodiment contains the zinc oxide powder and the dispersion medium of this embodiment. Additionally, in this example of the dispersion, a high-viscosity paste-like dispersion is also included.

[0124] The content of zinc oxide powder in the dispersion of this embodiment is not particularly limited and can be arbitrarily selected. 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, the preferred characteristics of zinc oxide powder can be obtained, and the viscosity increase of the dispersion over time can be suppressed.

[0125] The dispersion medium is appropriately selected according to the intended use of the dispersion. Suitable dispersion media are illustrated below, but the dispersion media used in this embodiment are not limited to these. The dispersion media described below can be used alone or in combination from the examples below.

[0126] Examples of dispersion media include alcohols such as water, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, octanol, and glycerol; 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 preferred. One of these dispersion media may be used alone, or two or more may be used in combination.

[0127] Furthermore, examples of other 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-dimethylacetylacetamide, and N-methylpyrrolidone; and chain polysiloxanes such as dimethylpolysiloxane, methylphenylpolysiloxane, and diphenylpolysiloxane. These are preferred. Only one of these dispersion media may be used, or two or more may be used in combination.

[0128] Furthermore, cyclic polysiloxanes such as octamethylcyclotetrasiloxane, cyclopentasiloxane, and dodecylcyclohexasiloxane are preferred as other dispersion media; modified polysiloxanes such as amino-modified polysiloxanes, polyether-modified polysiloxanes, alkyl-modified polysiloxanes, and fluorine-modified polysiloxanes are also preferred. These dispersion media can be used individually or in combination of two or more.

[0129] Furthermore, as examples of other dispersion media different from those mentioned above, hydrophobic dispersion media such as flowing paraffin, squalane, isoparaffin, branched chain light paraffin, petrolatum, ceresin and other hydrocarbon oils, isopropyl myristate, hexadecyl isooctanoate, glyceryl trioctanoate and other ester oils, cyclopentasiloxane, dimethyl polysiloxane, methylphenyl polysiloxane and other silicone oils, lauric acid, myristic acid, palmitic acid, stearic acid and other higher fatty acids, lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyldodecyl alcohol, isostearyl alcohol and other higher alcohols can be used alone or in combination of two or more.

[0130] The dispersion of this embodiment may contain commonly used additives without impairing its properties. Examples of additives include dispersants, stabilizers, water-soluble binders, thickeners, oil-soluble preservatives, ultraviolet absorbers, oil-soluble pharmaceuticals, oil-soluble pigments, oil-soluble proteins, vegetable oils, and animal oils. These additives may be contained in any amount chosen.

[0131] The method for manufacturing the dispersion in this embodiment is not particularly limited. For example, a method for mechanically dispersing the zinc oxide powder and the dispersion medium of this embodiment using a known dispersion device can be cited.

[0132] Examples of dispersing devices include mixers, self-rotating mixers, homogenizers, ultrasonic homogenizers, sand mills, ball mills, and roller mills.

[0133] In addition to cosmetics, the dispersion of this embodiment can also be preferably used in coatings and the like, which have functions such as ultraviolet shielding or gas permeation suppression.

[0134] [coating]

[0135] The coating of this embodiment contains zinc oxide powder, resin and dispersion medium of this embodiment.

[0136] The content of zinc oxide powder in the coating of this embodiment can be adjusted appropriately according to the desired characteristics. 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.

[0137] By ensuring that the content of zinc oxide powder in the coating is within the above-mentioned range, the properties of zinc oxide powder can be obtained, and the viscosity of the coating can be suppressed over time.

[0138] As a dispersion medium, if it is a dispersion medium commonly used in industrial applications, it is not particularly limited. Examples include alcohols such as water, methanol, ethanol, and propanol, and organic solvents such as methyl acetate, ethyl acetate, toluene, methyl ethyl ketone, and methyl isobutyl ketone.

[0139] The content of the dispersion medium in the coating of this embodiment is not particularly limited, and can be appropriately adjusted according to the characteristics of the target coating.

[0140] As a resin, if it is a resin commonly used in industrial applications, it is not particularly limited. Examples include acrylic resins, epoxy resins, urethane resins, polyester resins, and silicone resins.

[0141] The resin content in the coating of this embodiment is not particularly limited, but can be appropriately adjusted according to the characteristics of the target coating.

[0142] The coating of this embodiment may contain commonly used additives without impairing its properties. Examples of additives include polymerization initiators, dispersants, and preservatives.

[0143] The method for manufacturing the coating in this embodiment is not particularly limited. For example, a method for mechanically mixing the zinc oxide powder, resin, and dispersion medium of this embodiment using a known mixing device can be cited. Furthermore, a method for mechanically mixing the aforementioned dispersion and resin using a known mixing device can also be cited.

[0144] Examples of mixing devices include mixers, self-rotating mixers, homogenizers, and ultrasonic homogenizers.

[0145] The coating of this embodiment is applied to a plastic substrate such as a polyester film using conventional coating methods such as roller coating, flow coating, spray coating, screen printing, brush coating, and dip coating, thereby forming a coating film. These coating films can be used as ultraviolet shielding films or gas barrier films.

[0146] [cosmetic]

[0147] A cosmetic product according to one embodiment of this invention is made by containing at least one selected from the group consisting of zinc oxide powder and dispersion of this embodiment. That is, the cosmetic product may contain one or both of the zinc oxide powder and the dispersion. A cosmetic product according to another embodiment is made by containing a base agent and at least one selected from the group consisting of zinc oxide powder and dispersion of this embodiment dispersed in the base agent. That is, the cosmetic product may contain one or both of the zinc oxide powder and the dispersion, as well as the base agent. The cosmetic product of this embodiment is obtained, for example, by incorporating the dispersion of this embodiment into a base agent such as an emulsion, cream, foundation, lipstick, blush, or eyeshadow in a conventional manner.

[0148] Furthermore, after the zinc oxide powder of this embodiment is incorporated into the oil phase or aqueous phase to form an O / W or W / O type emulsion, it can be formulated with a base agent.

[0149] The base agent is not particularly limited if it is a base agent that can be used in cosmetics.

[0150] The following is a detailed explanation of sunscreen cosmetics.

[0151] The content of zinc oxide powder in sunscreen cosmetics can be chosen arbitrarily, but in order to effectively block ultraviolet rays, especially long-wavelength ultraviolet rays (UVA), it is preferably 1% or more and 30% or less by mass, more preferably 3% or more and 20% or less by mass, and even more preferably 5% or more and 15% or less by mass.

[0152] Depending on the requirements, sunscreen cosmetics may contain hydrophobic dispersion media, inorganic microparticles or inorganic pigments other than zinc oxide powder, hydrophilic dispersion media, oils, surfactants, moisturizers, thickeners, pH adjusters, nutrients, antioxidants, fragrances, etc.

[0153] Examples of aqueous dispersion media include flowing paraffin, squalane, isoparaffin, branched chain light paraffin, petrolatum, ceresin and other hydrocarbon oils, isopropyl myristate, hexadecyl isooctanoate, glyceryl trioctanoate and other ester oils, cyclopentadiene siloxane, dimethyl polysiloxane, methylphenyl polysiloxane and other silicone oils, lauric acid, myristic acid, palmitic acid, stearic acid and other higher fatty acids, lauryl alcohol, cetyl alcohol, stearyl alcohol, hexyldodecyl alcohol, isostearyl alcohol and other higher alcohols.

[0154] Examples of inorganic microparticles or inorganic pigments other than zinc oxide powder include calcium carbonate, calcium phosphate (apatite), magnesium carbonate, calcium silicate, magnesium silicate, aluminum silicate, kaolin, talc, titanium oxide, aluminum oxide, yellow iron oxide, γ-iron oxide, cobalt titanate, cobalt violet, and silicon oxide.

[0155] Sunscreen cosmetics may also contain at least one organic UV absorber. The content of the organic UV absorber can be adjusted appropriately to achieve the desired UV shielding properties. For organic UV absorbers whose amounts in sunscreen cosmetics are restricted, the upper limit can be adjusted appropriately according to the regulations of each country. For example, the content of organic UV absorbers can be less than 20% by mass, less than 15% by mass, less than 12% by mass, less than 10% by mass, less than 9% by mass, less than 8% by mass, less than 6% by mass, less than 4% by mass, or less than 3% by mass.

[0156] Examples of organic ultraviolet absorbers include benzotriazole ultraviolet absorbers, benzoylmethane ultraviolet absorbers, benzoic acid ultraviolet absorbers, aminoanilic acid ultraviolet absorbers, salicylic acid ultraviolet absorbers, cinnamic acid ultraviolet absorbers, silicone ultraviolet absorbers, triazine ultraviolet absorbers, imidazole ultraviolet absorbers, camphor ultraviolet absorbers, benzophenone ultraviolet absorbers, and other organic ultraviolet absorbers.

[0157] Examples of benzotriazole-based ultraviolet absorbers include 2-(2'-hydroxy-5'-tert-octylphenyl)benzotriazole and 2-(2'-hydroxy-5'-methylphenyl)benzotriazole.

[0158] Examples of benzoylmethane-based ultraviolet absorbers include dibenzoxazine, dianiloylmethane, 4-tert-butyl-4'-methoxydibenzoylmethane, 1-(4'-isopropylphenyl)-3-phenylpropane-1,3-dione, and 5-(3,3'-dimethyl-2-norbornene)-3-pentane-2-one.

[0159] Examples of benzoic acid-based ultraviolet absorbers include p-aminobenzoic acid (PABA), PABA monoglyceride, 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 ester, and dimethyl PABA pentyl ester.

[0160] Examples of the aforementioned aminoanisic acid-based ultraviolet absorbers include, for example, mormonyl-N-acetyl-o-aminobenzoic acid ester.

[0161] Examples of salicylic acid-based ultraviolet absorbers include pentyl salicylate, menthyl salicylate, morundyl salicylate, octyl salicylate, phenyl salicylate, benzyl salicylate, p-2-propanol phenyl salicylate, and ethylhexyl salicylate.

[0162] Examples of cinnamic acid-based ultraviolet absorbers include octyl methoxycinnamate, glyceryl di-2-ethylhexanoate, octyl cinnamate, ethyl 4-isopropylcinnamate, methyl diisopropylcinnamate, ethyl 2,4-diisopropylcinnamate, methyl 2,4-diisopropylcinnamate, propyl p-methoxycinnamate, isopropyl p-methoxycinnamate, isoamyl p-methoxycinnamate, and p-methoxycinnamate. Octyl methoxycinnamate (2-ethylhexyl p-methoxycinnamate), 2-ethoxyethyl p-methoxycinnamate, cyclohexyl p-methoxycinnamate, ethyl α-cyano-β-phenylcinnamate, 2-ethylhexyl α-cyano-β-phenylcinnamate, glyceryl mono-2-ethylhexanoyl-di-p-methoxycinnamate, ferric acid, cinnoxalate, methyl bis(trimethylsiloxy)silyl isoamyl trimethoxycinnamate, isopropyl p-methoxycinnamate, etc.

[0163] Examples of silicone-based ultraviolet absorbers include, for instance, [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, polysiloxane-15, and cresoltrazolium trisiloxane.

[0164] Examples of triazine-based ultraviolet absorbers include, for example, diethylhexyloxyphenol methoxyphenyl triazine, ethylhexyl triazine, methylene bisbenzotriazolyl tetramethylbutylphenol, triphenyl triazine, diethylhexylbutyramide triazine, etc.

[0165] Examples of the imidazole-based ultraviolet absorbers include disodium phenyl dibenzimidazole tetrasulfonate, phenyl benzimidazole sulfonic acid, and ethylhexyl dimethoxybenzyl dioxoimidazoline propionate.

[0166] Examples of camphor-based ultraviolet absorbers include 3-(4'-methylbenzyl)-d,l-camphor, 3-benzyl-d,l-camphor, terephthalimide dicamphor sulfonic acid, camphor benzalkonium sulfate methyl ester, benzyl camphor sulfonic acid, polyacrylamide methylbenzyl camphor, etc.

[0167] Examples of benzophenone-based ultraviolet absorbers include oxybenzone-1, oxybenzone-2, oxybenzone-3, oxybenzone-4, oxybenzone-5, oxybenzone-6, oxybenzone-7, oxybenzone-8, oxybenzone-9, and 4-(2-β-pyranoseluresiloxy)propoxy-2-hydroxybenzophenone.

[0168] Examples of organic ultraviolet absorbers other than those mentioned above include uric acid, ethyl uric acid, 2-phenyl-5-methylbenzoxazole, 5-(3,3'-dimethyl-2-norbornene)-3-pentane-2-one, diethylaminohydroxybenzoylbenzoate, octocrylene, silicone-modified ultraviolet absorbers, and fluorine-modified ultraviolet absorbers.

[0169] As explained above, the zinc oxide powder according to this embodiment has its BET specific surface area, apparent specific volume based on the standing method, and the ratio of apparent specific volume based on the standing method to apparent specific volume based on the tapping method adjusted within a specified range. Therefore, the viscosity increase over time in dispersions containing this zinc oxide powder can be suppressed. Furthermore, using this zinc oxide powder can yield dispersions or cosmetics with high transparency and excellent UV shielding properties. These characteristics are highly superior effects.

[0170] According to 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 one of an inorganic component and an organic component. Therefore, the surface activity of the zinc oxide powder can be suppressed, and its dispersibility in the dispersion medium can be improved. Furthermore, the viscosity increase over time in dispersions containing this surface-treated zinc oxide powder can be suppressed. Moreover, the same high transparency effect as conventional methods can be obtained.

[0171] The dispersion of this embodiment contains zinc oxide powder or surface-treated zinc oxide powder as described in this embodiment. Therefore, it is possible to suppress the increase in viscosity of the dispersion over time.

[0172] The coating of this embodiment contains zinc oxide powder or surface-treated zinc oxide powder as described in this embodiment. Therefore, it is possible to suppress the increase in viscosity of the coating over time.

[0173] The cosmetic product 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 product over time.

[0174] Example

[0175] The present invention will now be described in more detail with reference to embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0176] [Manufacturing of Zinc Oxide Powder]

[0177] [Example 1]

[0178] "Preparation of Surface-Treated Zinc Oxide Powder"

[0179] Zinc oxide powder A1 (BET specific surface area 39.6 m²) was prepared. 2 / g, apparent specific volume based on static method 7.31mL / g, apparent specific volume based on tapping method 3.85mL / g, crystallite diameter 17nm, oil absorption 140mL / 100g). The characteristics, crystallite diameter, BET equivalent particle size, and crystallite diameter (nm) / BET equivalent particle size (nm) of zinc oxide powder A1 are shown in Table 1.

[0180] A mixture containing 6 parts by weight of octyltriethoxysilane (trade name: KBE-3083, manufactured by Shin-Etsu Chemical Co., Ltd.), 100 parts by weight of zinc oxide powder A1, 0.6 parts by weight of pure water, and 34.1 parts by weight of isopropanol was mixed in a Henschel mixer.

[0181] Next, the mixture was dried at 80°C until the isopropanol was removed. The resulting dried material was then crushed using a hammer mill at 16,000 rpm until the D98 was below 500 μm. The crushed powder was then dried at 120°C for 3 hours to obtain the surface-treated zinc oxide powder B1 of Example 1. The D98 (μm) of the surface-treated zinc oxide powder B1 is shown in Table 1. Regarding D98, the volumetric particle size distribution of zinc oxide powder B1 was determined using a laser diffraction particle size distribution measuring device (model: Mastersizer 3000, manufactured by Malvern Corporation), and the value at a cumulative volume percentage of 98% was taken as D98.

[0182] Preparation of dispersion

[0183] 50 parts by weight of surface-treated zinc oxide powder B1 from Example 1, 10 parts by weight of PEG-9 polydimethylsiloxane ethyl dimethyl silicone oil (trade name: KF-6028, manufactured by Shin-Etsu Chemical Co., Ltd.), and 40 parts by weight of cyclopentasiloxane (trade name: SH245 Fluid, manufactured by Dow Corning Toray Co., Ltd.) were mixed and dispersed using a bead mill to obtain dispersion C1 of Example 1.

[0184] Evaluation of the viscosity and long-term stability of the dispersion

[0185] The viscosity of dispersion C1 of Example 1 was determined using a rheometer (trade name: Modular Compact Rheometer MCR102, manufactured by Anton Paar Japan K.K.) under the following conditions. The results are shown in Table 1.

[0186] Measurement temperature: 25℃

[0187] Fixture: Conical plate CP25-2

[0188] Shear rate: 1 / sec.

[0189] The 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.

[0190] Evaluation of transparency and UV shielding properties

[0191] In the dispersion of Example 1, the solution was diluted with cyclopentasiloxane to make the content of surface-treated zinc oxide powder 0.005% by mass. The linear transmittance of the diluted solution at 308 nm and 555 nm was determined using a UV-Vis-NIR spectrophotometer (JASCO Corporation, model V-770). The results are shown in Table 1.

[0192] Low transmittance at 308nm indicates high UV shielding. Therefore, low linear transmittance at 308nm is preferred.

[0193] High transmittance at 555nm indicates high transparency. Therefore, high transmittance at 555nm is preferred.

[0194] [Example 2]

[0195] In addition to replacing zinc oxide powder A1, zinc oxide powder A2 (BET specific surface area 40.4 m²) was used. 2Except for the following properties (6.43 mL / g based on the static method, 3.81 mL / g based on the tapping method, 17 nm crystallite diameter, and 126 mL / 100 g oil absorption), surface-treated zinc oxide powder B2 and dispersion C2 containing surface-treated zinc oxide powder B2 were obtained in the same manner as in Example 1.

[0196] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0197] [Example 3]

[0198] In addition to replacing zinc oxide powder A1, zinc oxide powder A3 (BET specific surface area 39.8 m²) was used. 2 Except for the following properties (apparent specific volume based on static method 5.21 mL / g, apparent specific volume based on tapping method 2.90 mL / g, crystallite diameter 16 nm, oil absorption 116 mL / 100 g), the surface-treated zinc oxide powder B3 and the dispersion C3 containing the surface-treated zinc oxide powder B3 of Example 3 were obtained in exactly the same manner as in Example 1.

[0199] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0200] [Example 4]

[0201] In addition to replacing zinc oxide powder A1, zinc oxide powder A4 (BET specific surface area 34.1 m²) was used. 2 Except for the following properties (apparent specific volume based on static method 1.60 mL / g, apparent specific volume based on tapping method 1.05 mL / g, crystallite diameter 15 nm, oil absorption 94 mL / 100 g), the surface-treated zinc oxide powder B4 and the dispersion C4 containing the surface-treated zinc oxide powder B4 of Example 4 were obtained in the same manner as in Example 1.

[0202] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0203] [Example 5]

[0204] In addition to replacing zinc oxide powder A1, zinc oxide powder A5 (BET specific surface area 10.5 m²) was used. 2 Except for the following properties (apparent specific volume based on static method 1.64 mL / g, apparent specific volume based on tapping method 1.07 mL / g, crystallite diameter 25 nm, oil absorption 92 mL / 100 g), the surface-treated zinc oxide powder B5 and the dispersion C5 containing the surface-treated zinc oxide powder B5 of Example 5 were obtained in exactly the same manner as in Example 1.

[0205] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0206] [Example 6]

[0207] In addition to replacing zinc oxide powder A1, zinc oxide powder A6 (BET specific surface area 37.2 m²) was used. 2 Except for the following properties (apparent specific volume based on static method 3.30 mL / g, apparent specific volume based on tapping method 1.95 mL / g, crystallite diameter 16 nm, oil absorption 108 mL / 100 g), the surface-treated zinc oxide powder B6 and the dispersion C6 containing the surface-treated zinc oxide powder B6 of Example 6 were obtained in exactly the same manner as in Example 1.

[0208] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0209] [Example 7]

[0210] In addition to replacing zinc oxide powder A1, zinc oxide powder A7 (BET specific surface area 34.6 m²) was used. 2 Except for the following properties (6.36 mL / g based on the static method, 2.93 mL / g based on the tapping method, 18 nm crystallite diameter, and 93 mL / 100 g oil absorption), the surface-treated zinc oxide powder B7 and the dispersion C7 containing the surface-treated zinc oxide powder B7 of Example 7 were obtained in the same manner as in Example 1.

[0211] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0212] [Example 8]

[0213] In addition to replacing zinc oxide powder A1, zinc oxide powder A8 (BET specific surface area 52.5m²) was used. 2 Except for the following properties (apparent specific volume based on static method 1.80 mL / g, apparent specific volume based on tapping method 1.15 mL / g, crystallite diameter 15 nm, oil absorption 105 mL / 100 g), the surface-treated zinc oxide powder B8 and the dispersion C8 containing the surface-treated zinc oxide powder B8 of Example 8 were obtained in the same manner as in Example 1.

[0214] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0215] In addition, the dry particle size D98 (μm) of the zinc oxide powders A1 to A8 used in the examples, divided by the BET equivalent particle size (nm), is 0.01 or more and 5 or less.

[0216] [Comparative Example 1]

[0217] In addition to replacing zinc oxide powder A1, commercially available zinc oxide powder A9 (BET specific surface area 44.8 m²) was used. 2Except for the following properties (approximately 7.99 mL / g based on the static method, 4.92 mL / g based on the tapping method, crystallite diameter 14 nm, and oil absorption 163 mL / 100 g), surface-treated zinc oxide powder B9 and a dispersion C9 containing surface-treated zinc oxide powder B9 of Comparative Example 1 were obtained in exactly the same manner as in Example 1.

[0218] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0219] [Comparative Example 2]

[0220] In addition to replacing zinc oxide powder A1, commercially available zinc oxide powder A10 (BET specific surface area 36.8 m²) was used. 2 Except for the following properties (apparent specific volume based on static method 5.49 mL / g, apparent specific volume based on tapping method 3.73 mL / g, crystallite diameter 18 nm, oil absorption 104 mL / 100 g), surface-treated zinc oxide powder B10 and dispersion C10 containing surface-treated zinc oxide powder B10 of Comparative Example 2 were obtained in exactly the same manner as in Example 1.

[0221] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0222] [Comparative Example 3]

[0223] In addition to replacing zinc oxide powder Al1, zinc oxide powder Al1 (BET specific surface area 55.2 m²) was used. 2 Except for the following properties (approximately 8.18 mL / g based on the static method, 3.15 mL / g based on the tapping method, 16 nm crystallite diameter, and 154 mL / 100 g oil absorption), surface-treated zinc oxide powder B11 and a dispersion C11 containing surface-treated zinc oxide powder B11 were obtained in the same manner as in Example 1.

[0224] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0225] [Comparative Example 4]

[0226] In addition to replacing zinc oxide powder A1, zinc oxide powder A12 (BET specific surface area 35.5 m²) was used. 2 Except for the following properties (6.15 mL / g based on the static method, 4.45 mL / g based on the tapping method, 18 nm crystallite diameter, and 95 mL / 100 g oil absorption), the surface-treated zinc oxide powder B12 and the dispersion C12 containing the surface-treated zinc oxide powder B12 of Comparative Example 4 were obtained in exactly the same manner as in Example 1.

[0227] The results evaluated in the same manner as in Example 1 are shown in Table 1.

[0228] [Table 1]

[0229]

[0230] In Table 1, the settling volume represents the apparent specific volume based on the settling method. The tapped volume represents the apparent specific volume based on the tapped method.

[0231] By comparing Examples 1 to 8 and Comparative Examples 1 to 4, it was confirmed that the specific surface area containing BET was 8m². 2 / g or more and 65m 2 Dispersions of zinc oxide particles with an apparent specific volume of 1.0 mL / g or less (based on the static method) and 7.5 mL / g or less, and an apparent specific volume of 1.50 or more (based on the static method) and 2.50 or less (based on the tapping method), maintained oil absorption within a preferred range while suppressing viscosity increase over time. Furthermore, it was confirmed that the same transparency and UV shielding properties as existing methods were achieved. These are unprecedented and exceptionally superior results.

[0232] Furthermore, compared to the surface-treated zinc oxide powders of Examples 1-4 and Examples 6-8, the surface-treated zinc oxide powder B5 of Example 5 felt very rough to the touch. That is, it was confirmed that the roughness of the surface-treated zinc oxide powder with a D98 / BET equivalent particle size of 0.01 or more and 3.0 or less was suppressed. In this invention, an excellent effect that was previously unresolved—maintaining oil absorption while preventing thickening of the zinc oxide powder—is achieved.

[0233] Industrial availability

[0234] The zinc oxide powder of the present invention, when dispersed in a dispersion medium as a dispersion liquid, can suppress the increase in viscosity over time. Therefore, the zinc oxide powder of the present invention exhibits excellent stability when used in dispersion liquids, coatings, and cosmetics, and has significant industrial value.

[0235] The present invention can provide zinc oxide powder that can inhibit thickening over time when it has high oil absorption and is incorporated into dispersions, as well as dispersions containing zinc oxide powder, coatings and cosmetics.

Claims

1. A zinc oxide powder, wherein, BET has a specific surface area of ​​8m² 2 / g or more and 65m 2 / g or less Based on the static method, the apparent specific volume is above 1.0 mL / g and below 7.5 mL / g, and The apparent specific volume based on the static method divided by the apparent specific volume based on the tapped method, i.e., the ratio of the apparent specific volume based on the static method to the apparent specific volume based on the tapped method is greater than 1.50 and less than 2.50, wherein the unit of the apparent specific volume is mL / g. The dry particle size D98 divided by the BET equivalent particle size has a value of 0.01 or higher and 3.0 or lower, wherein the unit of the dry particle size D98 is μm and the unit of the BET equivalent particle size is nm.

2. The zinc oxide powder according to claim 1, wherein, The apparent specific volume based on the static method is above 5.0 mL / g and below 7.5 mL / g.

3. The zinc oxide powder according to claim 1 or 2, wherein, The BET equivalent particle size of the zinc oxide powder is 10–110 nm.

4. The zinc oxide powder according to claim 1 or 2, wherein, The value of the zinc oxide powder obtained from the expression of crystallite diameter / BET-converted particle size is greater than 0.1 and less than 1.0, wherein the units of the crystallite diameter and the BET-converted particle size are nm.

5. The zinc oxide powder according to claim 1 or 2, wherein, The zinc oxide powder has an oil absorption capacity of 80-150 mL / 100 g.

6. The zinc oxide powder according to claim 1 or 2, wherein, The zinc oxide powder consists only of zinc oxide particles.

7. The zinc oxide powder according to claim 1 or 2, wherein it is a surface-treated powder having undergone surface treatment with at least one of inorganic and organic components.

8. A dispersion comprising zinc oxide powder and a dispersion medium as described in any one of claims 1 to 7.

9. A coating comprising zinc oxide powder, resin, and dispersion medium as described in any one of claims 1 to 7.

10. A cosmetic product comprising zinc oxide powder according to any one of claims 1 to 7.

11. The zinc oxide powder according to any one of claims 1 to 7, wherein, The apparent specific volume based on the static method is a value measured according to JIS K5101-12-1. The apparent specific volume based on the tapping method is a value determined through the following steps: The zinc oxide powder was passed through a sieve with a mesh size of 500 μm. Then, the zinc oxide powder that has passed through the sieve is added to a 150 mL graduated cylinder of known weight to make a volume of 100 mL. The weight of the graduated cylinder containing the zinc oxide powder was measured. Cover the measuring cylinder with a lid. Fix the capped graduated cylinder onto the bulk density measuring device and vibrate it 50 times. Read the volume of the zinc oxide powder after tapping. Divide the volume of the compacted zinc oxide powder by the weight of the zinc oxide powder added to the measuring cylinder. The unit of apparent specific volume is mL / g.

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