Alumina particles, and slurry composition and resin composite composition containing same

Abstract

Provided are novel alumina particles, particularly alumina particles in which the ratio (alpha / beta) of the peak area (alpha) of 4-coordinated Al to the peak area (beta) of 6-coordinated Al as measured in 27Al solid NMR is within a specific range, and a slurry composition and a resin composite composition containing the same. An alumina particle in which the ratio (alpha / beta) of the peak area (alpha) of 4-coordinated Al to the peak area (beta) of 6-coordinated Al as measured in 27Al solid NMR is 0.20 or more, and a slurry composition and a resin composite composition containing the alumina particle.

Description

Technical Field

[0001] This invention relates to alumina particles, and more particularly to alumina particles. 27 Alumina particles whose peak area α of 4-coordinated Al and peak area β of 6-coordinated Al are within a specific range as determined by Al solid-state NMR, and slurry compositions and resin composite compositions containing such alumina particles. Background Technology

[0002] Alumina is an oxide of aluminum with a wide variety of uses. As examples of its applications, besides being used as an aluminum material in molten salt electrolysis, it is also added to ceramic materials such as pottery. Furthermore, it is widely used in fields requiring high strength, high toughness, and thermal shock resistance, such as grinding materials or abrasive blasting devices; as a catalyst carrier for catalysts such as automotive exhaust purification catalysts; and in dental treatments (restorative materials such as inlays, crowns, and fillings). It can also be used as an abrasive in industrial sandblasting equipment. Additionally, it can be used as a raw material in medical applications or cosmetic compositions.

[0003] According to Non-Patent Literature 1, aluminum oxide is used as a material in cosmetic compositions for purposes such as imparting luster or surface modification, and is widely used in cosmetic products, nail products, cosmetic base products, concealer products, etc.

[0004] Patent Document 1, relating to cosmetic compositions, discloses the use of highly crystalline plate-shaped alumina particles to achieve a soft-focus effect and good brightness. Furthermore, the so-called soft-focus effect is defined as the effect of using light-diffusing particles such as alumina to scatter light across the skin surface, making shadows on the skin less noticeable and thus minimizing the appearance of skin imperfections.

[0005] Patent Document 2, also related to cosmetic compositions, discloses a soft-focus cosmetic composition comprising approximately 3 wt% or more pyrolytic alumina particles to enhance the soft-focus effect. Furthermore, the term "pyrolytic alumina particles" refers to alumina morphology substantially composed of spherical primary particles, defined as aggregated particles that have fused or agglomerated to form relatively large, irregularly shaped aggregated particles.

[0006] Prior art literature

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2021-59531

[0009] Patent Document 2: Japanese Patent Publication No. 2007-507550

[0010] Non-patent literature

[0011] Non-Patent Literature 1: Cosmetic Ingredient Report, Cosmetic Ingredients Online, Basic Information, Combination Purpose, and Safety of Alumina, [online], Publication Date: November 4, 2022, Search Date: September 11, 2023, Internet, (https: / / cosmetic-ingredients.org / pearlizing-agents / 86 / ) Summary of the Invention

[0012] The technical problem that the invention aims to solve

[0013] As mentioned above, alumina particles are widely used in cosmetic products, etc. (Non-Patent Document 1). To achieve a soft-focus effect, highly crystalline plate-shaped alumina particles or pyrolytic alumina particles (agglomerated particles) are used. (Patent Documents 1, 2)

[0014] However, further requirements for compositions to enhance the soft-focus effect in cosmetics persist. Furthermore, one embodiment of the present invention is not limited to cosmetic applications and can be applied to a wide range of design or identification uses.

[0015] Technical means for solving technical problems

[0016] The inventors of this invention conducted a detailed study on alumina particles and discovered that, through... 27 Al solid-state NMR can resolve the local structure surrounding aluminum atoms and the presence of 4-coordinated and / or 6-coordinated aluminum in alumina. Depending on this ratio (presence ratio), the crystallinity of alumina changes, affecting its diffuse reflectance (or light scattering effect). While not expected to be limited to a specific theory, it is believed that as the presence ratio of 4-coordinated aluminum to 6-coordinated aluminum increases, the crystal structure of alumina tends to become more disordered, leading to increased light scattering. Furthermore, unless otherwise specified in this specification, aluminum and Al have the same meaning and are sometimes referred to as Al.

[0017] The present invention is intended to solve the aforementioned technical problems based on the above insights, and its purpose is to protect the following contents recorded within the scope of protection.

[0018] [1] Alumina particles, characterized in that,

[0019] exist 27 The ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al measured in Al solid NMR is greater than 0.20.

[0020] [2] Alumina particles as described in [1],

[0021] The luminance (L*) measured by a whiteness meter is above 94.5%.

[0022] [3] Alumina particles as described in [1] or [2],

[0023] The diffuse reflectance, as measured by a UV-Vis-NIR spectrophotometer, is above 90.0%.

[0024] [4] Alumina particles as described in any of [1] to [3],

[0025] The luminance (L*) measured by a whiteness meter is above 95.0%.

[0026] [5] Alumina particles as described in any of [1] to [4],

[0027] The colorimetry (C*) measured by the whiteness meter is below 0.50%.

[0028] [6] Alumina particles as described in any of [1] to [5],

[0029] The roundness is 0.85 or higher.

[0030] [7] Alumina particles as described in any of [1] to [6],

[0031] The average particle size is 0.5–10.0 μm.

[0032] [8] A slurry composition, characterized in that,

[0033] Contains alumina particles as described in any one of [1] to [7].

[0034] [9] The slurry composition as described in [8],

[0035] It further contains at least one inorganic filler selected from amorphous spherical alumina particles, non-spherical alumina particles, silica particles, titanium dioxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, alkaline earth alkaline carbonates (calcium carbonate, magnesium carbonate, etc.).

[0036]

[10] A resin composite composition, characterized in that,

[0037] Contains alumina particles as described in any one of [1] to [7].

[0038]

[11] The resin composite composition as described in

[10] ,

[0039] It further contains at least one inorganic filler selected from amorphous spherical alumina particles, non-spherical alumina particles, silica particles, titanium dioxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, alkaline earth alkaline carbonates (calcium carbonate, magnesium carbonate, etc.).

[0040] Invention Effects

[0041] exist 27 Alumina particles in which the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al measured in Al solid NMR falls within a specific range can achieve a certain or higher diffuse reflectance, thus resulting in excellent soft-focus effects.

[0042] Furthermore, the alumina particles can achieve a certain level of whiteness, thereby obtaining excellent gloss.

[0043] Furthermore, the alumina particles can be spherical, which can reduce wear or improve lubricity (flowability), thereby resulting in an excellent user experience (texture).

[0044] It should be noted that the above-mentioned effects are particularly useful when the alumina particles are used as a cosmetic composition. Detailed Implementation

[0045] (exist 27 In Al solid-state NMR, the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al is greater than 0.20.

[0046] The alumina particles provided by one embodiment of the present invention are characterized in that,

[0047] exist 27 The ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al measured in Al solid NMR is greater than 0.20.

[0048] use 27When performing solid-state NMR measurements on alumina particles, the local structure surrounding aluminum (Al) atoms can be resolved. Specifically, the coordination number of aluminum present in alumina can be determined. Through this resolution, the inventors of this invention recognized that in alumina, in addition to the electronically stable 6-coordinate Al, there also exists 4-coordinate Al, and that the crystal structure of alumina varies according to its presence ratio (the ratio of the peak area α of 4-coordinate Al to the peak area β of 6-coordinate Al (α / β)), affecting the diffuse reflectance (or light scattering effect). While not wishing to be limited to a specific theory, it is believed that as the ratio of the peak area α of 4-coordinate Al to the peak area β of 6-coordinate Al (α / β) increases, the crystal structure of alumina is more prone to disorder, resulting in improved light scattering.

[0049] It is known that alumina can exist as a crystal. As typical crystalline phases, besides the α phase, we know of the θ, δ, η, γ, and ρ phases. The α phase consists only of 6-coordinated Al, and its crystal structure is trigonal. θ-alumina and δ-alumina contain 4-coordinated Al in addition to 6-coordinated Al, and their respective crystal structures are monoclinic and histogrammatic, respectively. Details will be discussed later. However, if the proportion of 4-coordinated Al in alumina is increased through rapid quenching or other treatments, and the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al is controlled above 0.20, then, in addition to the α phase, crystalline structures containing 4-coordinated Al, such as the θ, δ, η, γ, and ρ phases, will coexist. Therefore, the overall crystalline structure of alumina, besides the trigonal α phase alone, also includes a complex crystalline structure with multiple crystal phases such as θ, δ, η, γ, and ρ, resulting in improved diffuse reflectance (or light scattering effect). In general, the larger the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al, the more complex the crystal structure and the higher the diffuse reflectance (or light scattering effect). Therefore, the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al can be adjusted according to the desired diffuse reflectance (or light scattering effect). However, when the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al is too large, the diffuse reflectance (or light scattering effect) may sometimes decrease. Therefore, the upper limit of the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al can be set to 0.55.

[0050] Furthermore, crystallinity information, such as the proportion of crystalline phases present in inorganic materials, is usually evaluated based on results from XRD analysis, etc. However, for the evaluation of the crystallinity of alumina particles, especially the evaluation of diffuse reflectance (or light scattering effect), the ratio of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al (α / β) is set as the index, and thus, based on previous XRD analysis, a well-accurate analytical result is obtained.

[0051] [based on 27Determination of the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al in solid-state NMR.

[0052] based on 27 The ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al in solid-state NMR was determined in the following order.

[0053] Using a JEOL RESONANCE JNM-ECA400R / S1 device (static magnetic field strength 9.4T), solid-state... 27 Al NMR analysis. Each sample was filled into a φ3.2 mm solid NMR sample tube and rotated at 20 kHz under magic angle conditions at 23 °C. The spectra were obtained by single-pulse measurement.

[0054] When the peak value of 1M AlCl3 aqueous solution is set to 0ppm, the peak value detected in the range of -30 to 30ppm is estimated to be the peak value of 6-coordinated aluminum, and the peak value detected in the range of 40 to 100ppm is estimated to be the peak value of 4-coordinated aluminum. The coordination number ratio (the ratio of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al (α / β)) is calculated based on the ratio of the integral values ​​of each peak value.

[0055] The conditions for single-pulse measurement are as follows.

[0056] • Pulse hysteresis time: 50 seconds

[0057] • Pulse width: 30-degree pulse of 6-coordinated aluminum

[0058] • Total number of attempts: 8

[0059] [Control of the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al in alumina]

[0060] The ratio (α / β) of the peak area of ​​4-coordinated Al to the peak area of ​​6-coordinated Al in alumina can be adjusted according to the manufacturing conditions of the alumina. Details will be described later. Alumina particles can be manufactured by melt-blowing, where raw materials (alumina, boehmite, or aluminum hydroxide, etc.) are melted in a flame and then cooled. In summary, the crystalline morphology of alumina varies depending on the cooling conditions. Specifically, the greater the cooling rate, i.e., the more rapid the cooling, the greater the ratio (α / β) of the peak area of ​​4-coordinated Al to the peak area of ​​6-coordinated Al. Therefore, by setting the temperature difference between the flame temperature (melting zone) and the furnace temperature (cooling zone) to a certain level, the desired ratio (α / β) of the peak area of ​​4-coordinated Al to the peak area of ​​6-coordinated Al can be obtained.

[0061] Furthermore, in the melt-blowing method, the sphericity and volumetric density of the resulting alumina particles can be adjusted by changing the amount of raw material or the type of fuel gas introduced into the flame per unit time. Additionally, the particle size of the melt-blown alumina particles can be adjusted by changing the particle size of the raw material used.

[0062] (The brightness (L*) measured by a whiteness meter is above 94.5%)

[0063] In one embodiment of the present invention, the alumina particles preferably have a brightness (L*) of 94.5% or higher as measured by a whiteness meter. In another embodiment of the present invention, the alumina particles may also have a brightness (L*) of 95.0% or higher as measured by a whiteness meter. Furthermore, since single crystals of alumina are originally colorless and transparent, the chromaticity of alumina is generally low. Therefore, in one embodiment of the present invention, the alumina particles may also have a chromaticity (C*) of 0.50% or less as measured by a whiteness meter.

[0064] Here, the values ​​of luminance (L*) and chromaticity (C*) are obtained according to JIS Z 8729. The L* and C* values ​​are indicators used to represent the color of the measured object based on the L*a*b* color system (CIE 1976). In this color system, the L* value represents luminance, the C* value represents chromaticity, and the chromaticity, representing hue and chromaticity, is expressed using the a* and b* values ​​(a...). 2 +b 2 ) 1 / 2 express.

[0065] The a* and b* values ​​are called colorimetric indices, indicating the direction of color. The a* value is set to 0 as a reference; a negative value indicates an increase in greenness within the hue of the measured substance, while a positive value indicates an increase in redness. Similarly, the b* value is set to 0 as a reference; a negative value indicates an increase in blueness within the hue of the measured substance, while a positive value indicates an increase in yellowness. Furthermore, when both a* and b* values ​​are 0, it represents an achromatic color with no odor. The C* value represents chromaticity, expressed by the formula (a...). 2 +b 2 ) 1 / 2 express.

[0066] The luminance (L*) value indicates that as its value increases, the whiteness of the measured substance increases, and as its value decreases, the blackness increases. The chromaticity (C*) value indicates that the larger the value, the more vivid the color of the measured substance. On the other hand, a smaller C* value indicates that it is closer to a colorless and odorless achromatic color.

[0067] In one embodiment of the present invention, the alumina particles preferably have a brightness (L*) of 94.5% or higher. Alumina particles with high brightness (L*) can be incorporated into cosmetic compositions to obtain cosmetic compositions with high whiteness and excellent gloss. In general, higher brightness (L*) is preferred as it corresponds to higher whiteness or gloss. The upper limit of brightness (L*) can be 98.0%. On the other hand, the lower limit of brightness (L*) can also be 95.0%. Furthermore, the alumina particles in one embodiment of the present invention may also have a chromaticity (C*) of 0.50% or lower. Because of the low chromaticity (C*), it is possible to obtain an effect that does not interfere with the color and aroma of the coloring pigments contained in the cosmetic composition. In this respect, the lower the chromaticity (C*), the more preferred. The lower limit of chromaticity (C*) can also be 0%.

[0068] [Methods for measuring luminance (L*) and chromaticity (C*)]

[0069] Luminance (L*) and chromaticity (C*) were measured using a whiteness meter (Nippon Denshoku, NW-12). Specifically, the luminance (L*) value, a* value, and b* value were measured, and the whiteness was measured using (a... 2 +b 2 ) 1 / 2 Calculate the chromaticity (C*).

[0070] (The diffuse reflectance measured by a UV-Vis-NIR spectrophotometer is above 90.0%)

[0071] In one embodiment of the present invention, the alumina particles exhibit a complex crystalline structure due to the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al falling within a specific range, thus resulting in improved diffuse reflectance (or light scattering effect). Furthermore, the alumina particles of one embodiment of the present invention have a high whiteness (L*) measured by a whiteness meter, which is considered to contribute to improved diffuse reflectance (or light scattering effect). Therefore, in one embodiment of the present invention, the alumina particles may also have a diffuse reflectance of 90.0% or higher as measured by a UV-Vis-NIR spectrophotometer.

[0072] Diffuse reflectance is the proportion of incident light of a specific wavelength that is diffusely reflected as scattered light; it includes a component of reflected light that exhibits specular reflection. Therefore, diffuse reflectance can be considered a parameter that influences the color perception or detection of a color. By incorporating alumina particles with high diffuse reflectance into cosmetic compositions, light is scattered across the skin surface, making skin shadows less visible, thereby improving the effect of minimizing skin imperfections and enhancing the so-called soft-focus effect. In one embodiment of the present invention, the alumina particles have a diffuse reflectance of 90.0% or higher, resulting in an excellent soft-focus effect. In general, a higher diffuse reflectance is preferred for a better soft-focus effect. An upper limit for diffuse reflectance can also be 96.0%.

[0073] Methods for measuring diffuse reflectance

[0074] The reflectance is the diffuse reflectance including positive reflectance according to JIS Z 8722:2009, and the reflected light of alumina particles is determined using an integrating sphere.

[0075] More specifically, using a UV-Vis-NIR spectrophotometer (Shimadzu Corporation, Solid Spec-3700), the reflectance of alumina particles was measured using an integrating sphere containing both reflected and reflected light from the alumina particles. The average reflectance at measurement points from 400 nm to 700 nm was obtained.

[0076] (Spherical shape)

[0077] Alumina particles according to one embodiment of the present invention can be manufactured by melt-blowing. In melt-blowing, the shape of the resulting alumina particles can be adjusted by the amount of raw material or the type of fuel gas fed into the flame per unit time, thereby obtaining spherical alumina particles.

[0078] The term "spherical" includes not only particles that are perfectly spherical, but also those that are approximately spherical. Specifically, the determination of spherical shape is as follows: First, photograph the particle as a two-dimensional image. Observe the shape of the two-dimensional image (i.e., circular or approximately circular), and measure its roundness (circumference of the equivalent circle / circumference of the particle's projected image). For more than 50 particles, measure the roundness and calculate the average value. Particles with an average roundness value of 0.85 or higher are considered spherical.

[0079] The spherical alumina particles have a roundness of 0.85 or higher.

[0080] The higher the sphericity of the alumina particles, the more likely the composition containing these particles is to reduce abrasion in cosmetic compositions, or improve lubricity (flowability), thereby achieving a superior user experience (texture). Circularity can be 0.90 or higher, or 0.91 or higher, or 0.92 or higher, or 0.93 or higher, or 0.94 or higher, or 0.95 or higher. Theoretically, the upper limit for sphericity is 1.0, but from a manufacturing management perspective, it can be set to 0.98 or lower, or 0.97 or lower.

[0081] [Methods for determining roundness]

[0082] Circularity can be determined using an electron microscope or an optical microscope along with image analysis software or devices. For example, images taken with an electron microscope can be analyzed using a Mac-View (Mountech) or an automated flow particle image analysis device such as an FPIA (Sysmex). After obtaining a two-dimensional image of the particle using these methods, the circularity (circumference of the equivalent circle / circumference of the particle's projected image) is measured against this image. Circularity is measured for 50 or more particles, and the average value is taken as the circularity of that particle.

[0083] (Average particle size is 0.5 to 10.0 μm)

[0084] In one embodiment of the present invention, the alumina particles have an average particle size of 0.5 to 10.0 μm. When the average particle size is less than 0.5 μm, the particle agglomeration increases, and the lubricity (flowability) of the composition containing such alumina particles, typically in cosmetic compositions, may sometimes decrease, which is not preferred. When the average particle size exceeds 10.0 μm, the miscibility of the composition containing such alumina particles, typically in cosmetic compositions, with other ingredients may sometimes decrease. The average particle size of the alumina particles can be appropriately adjusted according to the desired use or properties in the composition containing them. Therefore, the lower limit of the average particle size can be 1.0 μm or 3.0 μm. Furthermore, the upper limit of the average particle size can be 7.0 μm or 5.0 μm. In addition, the alumina particles in one embodiment of the present invention can be manufactured according to the melt-blowing method. In the melt-blowing method, the particle size of the melt-blown alumina particles can be adjusted by adjusting the particle size of the raw material used.

[0085] Here, the term "average particle size" refers to the average particle size (D50), which is the median particle size D50 of the cumulative volume in a volume-based particle size distribution determined by laser diffraction scattering particle size distribution measurement method. Furthermore, the laser diffraction scattering particle size distribution measurement method involves irradiating a dispersion of spherical alumina particles with a laser and determining the particle size distribution based on the intensity distribution pattern of the diffracted and scattered light emitted from the dispersion. In one embodiment of the present invention, a laser diffraction scattering particle size distribution measurement device, "Master sizer 3000" (manufactured by Malvern), is used. Moreover, the average particle size can also be determined similarly for the raw material of the alumina particles.

[0086] (Slurry composition containing alumina particles)

[0087] According to one embodiment of the present invention, a slurry composition containing alumina particles is provided. The slurry composition can be obtained using a composition comprising alumina particles and a dispersion medium. The slurry composition can be used in resin composite compositions, cosmetic compositions, etc., as described later. The slurry composition of one embodiment of the present invention, especially the cosmetic composition, can achieve excellent soft-focus effects based on the diffuse reflectance of the contained alumina particles. Furthermore, this slurry composition, especially the cosmetic composition, can achieve excellent gloss due to the whiteness of the alumina particles, and further, when the alumina particles are spherical, can reduce abrasion or improve lubricity (flowability), thereby also achieving excellent user experience (texture). In addition, a resin composite composition with excellent flowability can be obtained.

[0088] The dispersion medium in the slurry composition can be adjusted appropriately, using water or a known organic solvent, depending on the intended use of the slurry composition. Multiple dispersion media can also be used in combination. Typically, the dispersion medium is a liquid, such as water or an organic solvent. Examples of organic solvents include alkane solvents such as hexane, heptane, octane, and decane; alcohol solvents such as methanol, ethanol, and propanol; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; and aromatic solvents such as benzene, toluene, ethylbenzene, and xylene. Ketone solvents such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone are preferred.

[0089] In the manufacture of the slurry composition, in addition to alumina particles and dispersion media, known dispersants, pigments, fragrances, preservatives, purified water, surfactants, etc., may be added as needed, and compounded by known methods such as mixing.

[0090] The dispersant in the slurry composition may be adjusted appropriately with water or a known organic solvent, depending on the intended use of the slurry composition. Multiple dispersants may also be used in combination.

[0091] Dispersants include, for example, dispersants comprising at least one selected from nonionic and cationic dispersants.

[0092] As a nonionic dispersant, there are no particular limitations, and known dispersants can be used. Examples include polymers having polyoxyethylene chains. Examples of polymers having polyoxyethylene chains include alkyl polyoxyethylene ethers, alkyl polyoxyethylene polyoxypropylene ethers, alkyl polyoxypropylene polyoxyethylene ethers, polyoxyethylene polyoxypropylene ethers (polyoxyethylene oxypropylene block copolymers), fatty acid polyoxyethylene esters, fatty acid polyoxyethylene dehydrated sorbitan esters, fatty acid polyoxyethylene sorbitan esters, polyoxyethylene dehydrated sorbitan monoalkyl ethers, polyoxyethylene alkyl ether sulfates, polyoxyethylene castor oil (hydrogenated castor oil), and ethynylene glycol ethylene oxide adducts. Examples of alkyl polyoxyethylene ethers include polyoxyethylene lauryl ether, polyoxyethylene stearyl ether, polyoxyethylene oil-based ether, polyoxyethylene octyl ether, polyoxyethylene cetyl ether, polyoxyethylene octylphenyl ether, and polyoxyethylene nonylphenyl ether. Examples of fatty acid polyoxyethylene dehydrated sorbitan esters include, for example, polyoxyethylene dehydrated sorbitan monolaurate.

[0093] The cationic dispersant is not particularly limited, and known dispersants can be used. Examples include alkylamine salts, acylamine salts, quaternary ammonium salts, ammonium salts having amide, ester, or ether bonds, imidazoline, imidazoline salts, and amine derivatives. The cationic dispersant can be a low-molecular-weight compound or a high-molecular-weight compound, but from the viewpoint of the dispersibility of alumina particles, a high-molecular-weight compound is preferred. Examples of such high-molecular-weight dispersants include polyethyleneimine, aminoalkyl (meth)acrylate copolymers, polyvinylimidazoline, polyvinylpyridine derivatives, polyoxyethylene alkylamines, and polyoxyethylene alkylamides. Examples of polyvinylpyridine derivatives include copolymers of vinylpyridine and (meth)acrylic acid, and copolymers of vinylpyridine with (meth)acrylic acid and oxygen-containing vinyl polymers. Examples of copolymers of vinylpyridine with (meth)acrylic acid and oxygen-containing vinyl polymers include copolymers of vinylpyridine with (meth)acrylic acid and polyoxyethylene. Among these, from the viewpoint of the dispersibility of alumina particles, amine-type high-molecular-weight dispersants are preferred.

[0094] Furthermore, known surface treatment agents are cited as dispersants. By containing surface treatment agents, the dispersibility of alumina particles and dispersion media in slurry compositions, the dispersibility or affinity with resins in resin composite compositions, and the dispersibility of alumina particles in cosmetic compositions are improved.

[0095] Examples include compounds having at least one functional group selected from alkyl groups such as methyl, ethyl, propyl, and butyl; alkenyl groups such as vinyl and propenyl; phenyl, amino, phenylamino, acryloyl, methacryloyl, epoxy, and styryl; silane coupling agents; and silazanes. More preferably, silane coupling agents having SiH, SiOH, or SiOR (where R is a hydrocarbon group) and silazanes such as hexamethyldisilazane.

[0096] Examples of silane coupling agents include vinyltrimethoxysilane, vinyltriethoxysilane, 3-epoxypropoxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-epoxypropoxypropyltriethoxysilane, 3-methacryloyloxypropyltrimethoxysilane, and N-phenyl-3-aminopropyltrimethoxysilane. Examples of alkoxysilane compounds include hexyltrimethoxysilane, octyltriethoxysilane, and phenyltriethoxysilane. Examples of silazane compounds include hexamethyldisilazane and trimethylsilane. From the viewpoint of excellent reactivity, silazane compounds are more preferred. Hexamethyldisilazane and trimethylsilane are more preferred.

[0097] The content of alumina particles in the slurry composition (including, in the case of "inorganic fillers" or "other fillers" described later, the sum of their contents) can be appropriately adjusted according to the intended use of the slurry composition. Typically, from the viewpoint of demonstrating the effect of alumina particles according to an embodiment of the present invention, it is 50 to 95 wt%. More preferably, the lower limit is 55 wt%, more preferably 60 wt%, more preferably 65 wt%, and more preferably 70 wt%. More preferably, the upper limit is 93 wt%, more preferably 90 wt%, and more preferably 85 wt%.

[0098] (Inorganic packing)

[0099] Furthermore, in the manufacture of the slurry composition and the resin composite composition described later, in addition to the alumina particles of one embodiment of the present invention, other inorganic fillers may be incorporated as the inorganic fillers, including amorphous spherical alumina particles, non-spherical alumina particles, silica particles (amorphous spherical silica particles, crystalline spherical silica particles, broken silica particles (amorphous or crystalline), etc.), titanium oxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, alkaline earth alkaline carbonates (calcium carbonate, magnesium carbonate, etc.). The proportion of the inorganic fillers can be appropriately adjusted according to the intended use of the slurry composition or resin composite composition. Typically, from the viewpoint of maximizing the effect of the alumina particles of one embodiment of the present invention, the ratio of (weight of alumina particles) to (weight of other inorganic fillers) can be 5:95 to 90:10.

[0100] Furthermore, when used in cosmetic compositions, these inorganic fillers can replace or be used in combination with organic fillers such as polymethyl methacrylate crosspolymer, nylon particles, melamine resin, or hydroxides of aluminum, magnesium, calcium, and zinc (collectively referred to as "other fillers"). The proportion of these other fillers can be adjusted appropriately according to the intended use of the slurry composition or resin composite composition. Typically, based on the viewpoint of demonstrating the effect of alumina particles according to one embodiment of the present invention, the ratio can be (weight of alumina particles): (weight of other fillers) = 5:95 to 90:10.

[0101] (Other ingredients)

[0102] When used as a cosmetic composition, in addition to the inorganic fillers mentioned above, it may contain various ingredients commonly found in cosmetics. Examples include colorants, carriers (substrates), surfactants, active ingredients, thickeners, curing agents, binders, spraying agents, moisturizers, and anti-aging agents, but it is not limited to these.

[0103] <Coloring agent>

[0104] As a coloring agent, it can be used simultaneously with coloring pigments and extender pigments that are not part of the aforementioned alumina particles. As a coloring pigment, known pigments can be used appropriately according to the desired hue. Examples include inorganic pigments such as titanium dioxide, chromium oxide, iron oxide, lead yellow, zinc yellow, ultramarine, Prussian blue, and carbon black, or organic pigments such as isoindolineone, isoindoline, azomethyl, anthraquinone, anthrone, xanthones, diketopyrrole, perylene, quinacridone, indigo, dioxazine, phthalocyanine, and azo pigments.

[0105] <Carrier>

[0106] Examples of suitable carriers include water, aliphatic alcohols, hydrocarbons, higher fatty acids, oils, esters, and silicone oils. These can be used individually or in combination of two or more. Furthermore, the substrate can be water-based, oil-based, or an emulsion.

[0107] Examples of hydrocarbons include chain saturated hydrocarbons with 15 or more carbon atoms. Examples include petrolatum, paraffin, and isoeicosane.

[0108] As higher fatty acids, examples include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, and behenic acid, as well as unsaturated fatty acids such as palmitoleic acid, oleic acid, transoleic acid, ricinoleic acid, linoleic acid, gamma-linolenic acid, and alpha-linolenic acid.

[0109] Examples of silicone oils include linear silicone oils such as polydimethylsiloxane and trisiloxane; cyclic silicone oils such as cyclopentane, cyclohexane, and cyclopolydimethylsiloxane; phenyl-substituted silicone oils such as diphenylpolydimethylsiloxane, phenylpolytrimethylsiloxane, and diphenylsiloxyphenyltrimethylpolysiloxane; alkyl-modified silicone oils such as stearyl polydimethylsiloxane, cetyl polydimethylsiloxane, and octyl polymethylsiloxane; and amino-modified silicone oils such as amino-terminated polydimethylsiloxane, aminopropyl polydimethylsiloxane, diaminopropyl polydimethylsiloxane, and dicetistayl amino-terminated polydimethylsiloxane.

[0110] <surfactants>

[0111] As a surfactant, it can be amphoteric, nonionic, anionic, or cationic.

[0112] <Active Ingredients>

[0113] Examples of active ingredients include UV blockers, moisturizers, anti-aging active ingredients, vitamins, and sunscreens.

[0114] (Resin composite composition containing alumina particles)

[0115] According to one embodiment of the present invention, a resin composite composition containing alumina particles is provided. Using a composition comprising alumina particles and resin, a resin composite composition can be obtained.

[0116] For example, alumina particles are not limited to cosmetic compositions; resin composite compositions such as semiconductor sealing materials (especially solid sealing materials) and interlayer insulating films can be obtained. Furthermore, by curing these resin composite compositions, resin composites such as sealing materials (cured bodies) and semiconductor packaging substrates can be obtained. In applications other than cosmetic compositions such as semiconductor sealing materials, interlayer insulating films, heat sinks, and thermal greases, the alumina particles of one embodiment of the present invention enable the production of resin composite compositions with excellent visibility, and therefore are preferred for use.

[0117] In manufacturing the aforementioned resin composite composition, for example, in addition to alumina particles and resin, curing agents, curing accelerators, flame retardants, silane coupling agents, etc., are added as needed, and the composite is compounded by known methods such as mixing. Furthermore, it is shaped into granules, films, etc., depending on the application.

[0118] Furthermore, in manufacturing the aforementioned resin composite composition, in addition to alumina particles and resin, the aforementioned inorganic fillers may also be incorporated. The inorganic fillers incorporated into the resin composite composition (or slurry composition) may include amorphous spherical alumina particles, non-spherical alumina particles, silica particles (amorphous spherical silica particles, crystalline spherical silica particles, broken silica particles (amorphous or crystalline), etc.), titanium oxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, and carbon fibers. The proportion of the inorganic fillers can be appropriately adjusted according to the intended use of the resin composite composition. From the viewpoint of maximizing the effect of spherical alumina particles according to one embodiment of the present invention, it is preferable that (weight of spherical alumina particles): (weight of other inorganic fillers) = 95:5 to 60:40.

[0119] Furthermore, in the case of manufacturing a resin composite by curing the resin composite composition, for example, the resin composite composition is heated to melt it, processed into a shape corresponding to the application, and then subjected to a higher heat than when it is melted to completely cure it. In this case, known methods such as transfer molding can be used.

[0120] For example, in the manufacture of cosmetic compositions, known resins can be used as the resin composite composition, but melamine resin and silicone resin are examples. Furthermore, in the manufacture of semiconductor-related materials such as encapsulation substrates or interlayer insulating films, known resins can be used as the resin composite composition, but epoxy resin is preferred. The epoxy resin is not particularly limited, but examples include bisphenol A type epoxy resin, bisphenol F type epoxy resin, biphenyl type epoxy resin, phenolic varnish type epoxy resin, cresol varnish type epoxy resin, naphthalene type epoxy resin, phenoxy type epoxy resin, etc. One of these can be used alone, or two or more with different molecular weights can be used together. Among them, from the viewpoint of curability, heat resistance, etc., epoxy resins having two or more epoxy groups in one molecule are preferred. Specifically, examples include biphenyl-type epoxy resins, phenolic varnish-type epoxy resins, o-cresol varnish-type epoxy resins, substances obtained by epoxidizing phenolic and aldehyde varnish resins, glycidyl ethers such as bisphenol A, bisphenol F, and bisphenol S, glycidyl ester epoxy resins obtained by reacting polybasic acids such as phthalic acid or dimer acids with epichlorohydrin, linear aliphatic epoxy resins, alicyclic epoxy resins, heterocyclic epoxy resins, alkyl-modified polyfunctional epoxy resins, β-naphthol varnish-type epoxy resins, 1,6-dihydroxynaphthyl type epoxy resins, 2,7-dihydroxynaphthyl type epoxy resins, dihydroxybiphenyl type epoxy resins, and epoxy resins further incorporating halogens such as bromine to impart flame retardancy. Among these epoxy resins having two or more epoxy groups per molecule, bisphenol A type epoxy resins are particularly preferred.

[0121] In addition to composite materials used in semiconductor sealing materials, resins used in resin composite compositions such as prepregs for printed circuit boards and various engineering plastics can also be applied, including resins other than epoxy resins. Specifically, in addition to epoxy resins, examples include silicone resins, phenolic resins, melamine resins, urea-formaldehyde resins, unsaturated polyesters, fluoropolymers, polyimides, polyamide-imides, polyether-imides, and other polyamides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyesters, polysulfones, liquid crystal polymers, polyethersulfones, polycarbonates, maleimide-modified resins, ABS resins, AAS (acrylonitrile-acrylic rubber-styrene) resins, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resins.

[0122] As a curing agent used in the resin composite composition, a known curing agent can be used to cure the resin, such as a phenolic curing agent. As a phenolic curing agent, phenolic varnish resin, aminophenolic varnish resin, polyvinylphenol, etc., can be used alone or in combination of two or more.

[0123] The preferred ratio of the phenolic curing agent to the epoxy resin (phenolic hydroxyl equivalent / epoxy group equivalent) is 0.1 or more and less than 1.0. This ensures no unreacted phenolic curing agent remains, improving moisture absorption and heat resistance.

[0124] In one embodiment of the present invention, the amount of spherical alumina particles added to the resin composite composition is preferably higher from the viewpoint of heat resistance and thermal expansion rate, but is generally 70% by mass or more and 95% by mass or less, preferably 80% by mass or more and 95% by mass or less, and more preferably 85% by mass or more and 95% by mass or less. This is because if the amount of spherical alumina particles is too small, it is difficult to obtain effects such as improving the strength of the sealing material or suppressing thermal expansion; conversely, if the amount is too large, regardless of the surface treatment of the spherical alumina particles, it is easy to cause segregation due to the agglomeration of spherical alumina particles in the composite material, and the viscosity of the composite material becomes too high, making it difficult to use as a sealing material. Furthermore, when using the aforementioned "other fillers", the preferred amount added to the resin composite composition is the combined amount of spherical alumina particles and "other fillers".

[0125] In addition to resin, additives such as silane coupling agents, curing agents, colorants, and curing delay materials can be used.

[0126] Furthermore, regarding silane coupling agents, known coupling agents can be used, but those with epoxy functional groups are preferred.

[0127] In addition, heat sinks, thermal greases, etc. can be obtained by using resin composite compositions.

[0128] In obtaining the heat sink, alumina particles, in addition to resin and appropriate additives, are compounded using known methods such as mixing. The resulting composite is then shaped into a sheet using known methods.

[0129] For example, in the manufacture of heat sinks, the resin used as the resin composite composition can be any known resin, specifically including silicone resin, phenolic resin, melamine resin, urea-formaldehyde resin, unsaturated polyester, fluoropolymer, polyimide, polyamide-imide, polyetherimide, and other polyamides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide-modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, and AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin. Silicone resin is preferred. The silicone resin is not particularly limited, but peroxide-cured, additional-cured, condensation-cured, and UV-cured types can be used, for example.

[0130] In addition to resins, additives such as silane coupling agents, curing agents, colorants, and curing delay materials can be used.

[0131] In obtaining the aforementioned thermal grease, spherical alumina particles are compounded with appropriate additives in addition to the resin, and then compounded using known methods such as mixing. Here, the resin used in the thermal grease is also referred to as a base oil.

[0132] For example, in the manufacture of thermal grease, the resin used as the resin composite composition can be a known resin, but specifically, examples include silicone resin, phenolic resin, melamine resin, urea-formaldehyde resin, unsaturated polyester, fluoropolymer, polyimide, polyamide-imide, polyetherimide and other polyamides; polyesters such as polybutylene terephthalate and polyethylene terephthalate; polyphenylene sulfide, aromatic polyester, polysulfone, liquid crystal polymer, polyethersulfone, polycarbonate, maleimide modified resin, ABS resin, AAS (acrylonitrile-acrylic rubber-styrene) resin, AES (acrylonitrile-ethylene-propylene-diene rubber-styrene) resin, mineral oil, synthetic hydrocarbon oil, ester oil, polyethylene glycol oil, silicone oil, and fluoropolymer oil.

[0133] In addition to resins, additives such as silane coupling agents, colorants, and thickeners can be used. Thickeners can be well-known substances such as calcium soaps, lithium soaps, aluminum soaps, calcium complexes, aluminum complexes, lithium complexes, barium complexes, bentonite, urea, PTFE, sodium paraformylbenzoate, silica gel, and organoformed bentonite.

[0134] [Method for manufacturing alumina particles]

[0135] The alumina particles of one embodiment of the present invention are not particularly limited in their manufacturing method and can be manufactured by the following method. This manufacturing method is suitable for manufacturing the above-mentioned alumina particles and can include the following steps.

[0136] (1) A process of producing alumina particles by melting at least one of alumina, boehmite, or aluminum hydroxide in a flame and then cooling it, and

[0137] (2) A process of classifying the alumina particles using a sieve or the like after the manufacturing process.

[0138] (1) The process of manufacturing alumina particles involves immersing the raw material for alumina particles (hereinafter also referred to as "raw material") in a flame to melt it, followed by cooling. These raw materials can be immersed in the flame while suspended in a carrier gas. Air, oxygen, propane, etc., can be used as the carrier gas.

[0139] The flame is preferably formed inside a heat-resistant furnace. Preferably, the flame is formed in the upper part of the heat-resistant furnace, into which raw materials are supplied. The molten alumina particles settle due to gravity and are recovered from the bottom of the furnace. By setting the flame so that it does not form below the raw materials in the heat-resistant furnace, the alumina particles settling below cool and become spherical.

[0140] The area in the upper part of the heat-resistant furnace where the raw materials are supplied and melted by the flame is called the melting zone, and the area in the lower part of the heat-resistant furnace where the molten alumina particles are cooled is called the cooling zone.

[0141] The method of flame formation is not particularly limited, but it can involve supplying fuel (known fuels such as propane, LPG, LNG, hydrogen, and amines) and combustion-supporting gas (air or oxygen) separately to the molten zone through a burner, or supplying a mixture of fuel and combustion-supporting gas to the molten zone through a burner, or supplying a mixture of raw materials, fuel, and combustion-supporting gas to the molten zone through a burner to form a flame. In particular, from the viewpoint of increasing the maximum temperature of the flame and increasing the temperature gradient within the heat-resistant furnace, a method of flame formation that supplies a mixture of fuel and combustion-supporting gas or a mixture of raw materials, fuel, and combustion-supporting gas to the molten zone is preferred.

[0142] When molten alumina is rapidly cooled in the cooling zone, Al atoms with an electronically unstable 4-coordinate structure are more readily generated compared to 6-coordinate structures. As a result, this promotes the formation of crystalline phases containing 4-coordinate Al, such as the θ, δ, η, γ, and ρ phases. On the other hand, at slower cooling rates, the formation of electronically stable 6-coordinate Al is promoted.

[0143] As a method for controlling the ratio (α / β) of the peak area α of 4-coordinated Al and the peak area β of 6-coordinated Al, an example is setting the temperature difference between the molten region and the cooling region to a certain level or higher. For example, the temperature difference is 1500°C or higher, preferably 1600°C or higher, more preferably 1800°C or higher, and more preferably 2000°C or higher, thereby increasing the cooling rate during the cooling process after melting. As a result, the ratio of 4-coordinated Al increases. On the other hand, when the cooling rate is lower, the ratio of 6-coordinated Al, which is more electron-stable, increases. Furthermore, the temperature difference between the molten region and the cooling region can be appropriately adjusted according to the particle size and composition of the target spherical alumina particles. Additionally, the temperature of the molten region can be adjusted by the flame temperature.

[0144] Furthermore, if sufficient melting heat can be applied to the raw material particles in the molten zone, the amount of non-spherical irregularly shaped particles can be reduced. This allows for adjustment of the bulk density of the alumina particles. Additionally, the sphericity and bulk density can be adjusted by changing the amount of fuel gas introduced into the flame per unit time or by adjusting the type of fuel gas. Alternatively, the particle size of the melt-blown alumina particles can be adjusted by changing the particle size of the raw material powder used.

[0145] The raw materials for alumina particles can be at least one of alumina, boehmite, or aluminum hydroxide. When these raw materials are introduced into a flame, the alumina remains in its alumina state, while the boehmite or aluminum hydroxide forms alumina through oxidation or dehydration reactions.

[0146] In the cooling zone, refrigerants can also be used. While there are no particular restrictions on the refrigerant, from the viewpoint of not reducing the purity of the alumina particles, air, or distilled water or ion-exchanged water that does not contain sodium or chloride ions as impurities, is preferred.

[0147] In the grading process of (2), the alumina particles obtained in the alumina particle manufacturing process are appropriately graded using a sieve with a specified mesh size. Pre-treatment or post-treatment, such as separating coarse and fine particles using a cyclone separator, may also be added as needed. Through this process, desired particle size, particle size distribution, specific surface area, and volumetric density can be obtained.

[0148] Example

[0149] The following examples and comparative examples illustrate one embodiment of the present invention. However, this embodiment of the present invention is not limited to the following examples and is not intended to be construed as such.

[0150] Alumina particles are fed into a flame formed by LPG and oxygen, i.e., alumina particles are manufactured by melt-blowing. By controlling the particle size of the fed alumina particles, the average particle size of the alumina particles is adjusted. Further adjustments are made to flame formation conditions, particle size of the raw material, raw material supply rate, and grading conditions to produce spherical alumina particles with the physical properties shown in Table 1. Table 1 shows the physical properties of the obtained alumina particles.

[0151] [Table 1]

[0152]

[0153] The methods for determining each physical property value are described below.

[0154] [Average Particle Size]

[0155] The average particle size (D50) was measured using a laser diffraction and scattering particle size distribution measuring device, "Master sizer 3000" (manufactured by Malvern).

[0156] [based on 27 Determination of the ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al in solid-state NMR.

[0157] Determine based on the following order 27 The ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al in solid-state NMR.

[0158] Using a JNM-ECA400R / S1 device (static magnetic field strength 9.4T) manufactured by JEOL RESONANCE, solid-state... 27 Al NMR analysis. Each sample was packed into a φ3.2 mm solid-state NMR sample tube and rotated at 20 kHz under magic angle conditions at 23 °C. Spectra were obtained by single-pulse measurement. The measurement conditions are shown below.

[0159] • Pulse hysteresis time: 50 seconds

[0160] • Pulse width: 30-degree pulse of 6-coordinated aluminum

[0161] • Total number of attempts: 8

[0162] When the peak value of 1M AlCl3 aqueous solution is set to 0ppm, the peak value detected in the range of -30 to 30ppm is estimated to be the peak value of 6-coordinated aluminum, and the peak value detected in the range of 40 to 100ppm is estimated to be the peak value of 4-coordinated aluminum. The coordination number ratio (the ratio of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al (α / β)) is calculated based on the ratio of the integral values ​​of each peak value.

[0163] Methods for measuring diffuse reflectance

[0164] The reflectance is based on diffuse reflectance including positive reflectance according to JIS Z 8722:2009, and the reflected light of alumina particles is determined using an integrating sphere.

[0165] Specifically, a UV-Vis-NIR spectrophotometer (Shimadzu Corporation, Solid Spec-3700) was used to measure the reflectance of alumina particles using an integrating sphere containing both reflected and reflected light from the alumina particles. The average reflectance at measurement points with wavelengths from 400 nm to 700 nm was obtained.

[0166] More specifically, a 15g sample is weighed and placed into a 60mm quartz glass chamber. The chamber is tapped 20 times to fill it with powder, and the reflectance is measured. The diffuse reflectance is calculated based on the average relative reflectance against a white standard reflector plate (99%) for the spectrometer.

[0167] [Methods for measuring luminance (L*) and chromaticity (C*)]

[0168] Luminance (L*) and chromaticity (C*) were measured using a whiteness meter (Nippon Denshoku Kogyo, NW-12). Specifically, the luminance (L*) value, a* value, and b* value were measured, and the chromaticity (C*) was measured using a whiteness meter (a*). 2 +b 2 ) 1 / 2 calculate.

[0169] More specifically, according to JIS Z 8722:2009. As the testing container, weigh 15g of sample and place it into a φ100mm circular chamber. Tap the chamber 20 times to fill it with powder. Set the chamber to a whiteness meter and measure the powder's brightness (L*), a*, and b* values. Calculate c* based on the a* and b* values.

[0170] [Circularity]

[0171] The roundness of the samples in this embodiment and the comparative example was measured using images taken with an electric field emission scanning electron microscope and image analysis software manufactured by Mountech Mac-View Version 5. Regarding the electron microscope images, since particles with an average diameter of less than 5 μm tend to aggregate, the particles were dispersed in ethanol, and the dispersion was dropped onto flat carbon black and allowed to dry naturally before being photographed. In Mac-View analysis, the electron microscope images were read, the substrate setting tool was used to specify areas not identified as particles, and the particles were selected using the automatic extraction tool. The automatic extraction conditions were set as follows: acquisition mode "spherical", detection sensitivity "40 [minimum]", edge correction "10%", detection accuracy "standard (0.7)", and "particle smoothing". The roundness of more than 50 particles selected under these conditions was analyzed, and the average value was taken as the roundness of the powder.

[0172] Within the scope of one embodiment of the present invention, a good diffuse reflectance of 90.0% or more was confirmed in the alumina particles. Furthermore, the alumina particles within the scope of one embodiment of the present invention were confirmed to have a good whiteness with a luminance (L*) of 95% or more or a chromaticity (C*) of 0.50% or less. Further, the alumina particles within the scope of one embodiment of the present invention were confirmed to have a sphericity of 0.85 or more. Furthermore, the alumina particles within the scope of one embodiment of the present invention were also confirmed to have an average particle size of 0.5 to 10.0 μm or less. Further, as shown in Examples 7 and 8 below, a resin composite composition containing alumina particles within the scope of one embodiment of the present invention was also confirmed, and various inorganic fillers could be incorporated into this resin composition.

[0173] (Example 7)

[0174] The alumina particles obtained in Example 1 were mixed with aluminum nitride particles (D50 = 30 μm) at a ratio of (weight of alumina particles): (weight of aluminum nitride particles) = 90:10 to prepare alumina particle mixture A. Further, alumina particle mixture A was mixed with Dow Toray's silicone resin CY52-276A liquid at an addition amount of 90% by mass in the resin composite composition, and vacuum-mixed in a THINKY-manufactured vacuum mixer ("defoaming mixer") to obtain a resin composite composition. The mixing conditions were 15 seconds of pre-mixing and 90 seconds of vacuum mixing. 10g of the obtained resin composite composition was placed on a smooth iron plate. The iron plate was tilted 60° relative to the horizontal direction to check the flowability of the resin composite composition. It was confirmed that after tilting for 5 hours, the flow was more than 15cm, indicating good flowability.

[0175] (Example 8)

[0176] The alumina particles obtained in Example 2 were mixed with boron nitride particles (D50 = 20 μm) at a ratio of (weight of alumina particles): (weight of boron nitride particles) = 90:10 to prepare alumina particle mixture B. Alumina particle mixture B was then mixed with Dow Toray's silicone resin CY52-276A liquid at a 90% by mass level in a THINKY vacuum mixer "defoaming mixer" to obtain a resin composite composition. The mixing conditions were 15 seconds of pre-mixing followed by 90 seconds of vacuum mixing. 10 g of the obtained resin composite composition was placed on a smooth iron plate. The iron plate was tilted 60° relative to the horizontal direction to check the flowability of the resin composite composition. It was confirmed that after tilting for 5 hours, the flow was more than 15 cm, indicating good flowability.

[0177] Industrial availability

[0178] The alumina particles of one embodiment of the present invention have good diffuse reflectance and can further have good whiteness, spherical shape, and particle size. These alumina particles can be used in various applications such as cosmetic compositions. In another embodiment of the present invention, a resin composite composition comprising alumina particles is also provided, which, based on the properties of the alumina particles (good diffuse reflectance, etc.), can achieve excellent soft-focus effects and other benefits.

Claims

1. An alumina particle, characterized in that, exist 27 The ratio (α / β) of the peak area α of 4-coordinated Al to the peak area β of 6-coordinated Al measured in Al solid NMR is greater than 0.

20.

2. The alumina particles according to claim 1, The luminance (L*) measured by a whiteness meter is above 94.5%.

3. The alumina particles according to claim 1, The diffuse reflectance, as measured by a UV-Vis-NIR spectrophotometer, is above 90.0%.

4. The alumina particles according to claim 1, The luminance (L*) measured by a whiteness meter is above 95.0%.

5. The alumina particles according to claim 1, The colorimetry (C*) measured by the whiteness meter is below 0.50%.

6. The alumina particles according to claim 1, The roundness is 0.85 or higher.

7. The alumina particles according to claim 1, The average particle size is 0.5–10.0 μm.

8. A slurry composition, characterized in that, It contains alumina particles as described in any one of claims 1 to 7.

9. The slurry composition according to claim 8, It also includes at least one inorganic filler selected from amorphous spherical alumina particles, non-spherical alumina particles, silica particles, titanium dioxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, and alkaline earth carbonates (calcium carbonate, magnesium carbonate).

10. A resin composite composition, characterized in that, It contains alumina particles as described in any one of claims 1 to 7.

11. The resin composite composition according to claim 10, It also includes at least one inorganic filler selected from amorphous spherical alumina particles, non-spherical alumina particles, silica particles, titanium dioxide particles, magnesium oxide particles, aluminum nitride particles, boron nitride particles, barium titanate particles, calcium titanate particles, carbon fiber, talc, mica, kaolin, calcium oxide, zinc oxide, barium sulfate, calcium sulfate, and alkaline earth carbonates (calcium carbonate, magnesium carbonate).

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