Aluminum hydroxide powder and method for producing the same

Abstract

The present invention provides an aluminum hydroxide powder capable of sufficiently suppressing an increase in viscosity when added to a resin, and a method for producing the same. An aluminum hydroxide powder having a density of 1.59 to 2.00 g / cm 3 when molded at 10 MPa, and a ratio of a diffraction intensity of a (002) plane to a diffraction intensity of a (110) plane in an XRD pattern thereof is 2.0 to 7.5.

Description

Technical Field

[0001] This invention relates to aluminum hydroxide powder and its manufacturing method. Background Technology

[0002] The demand for aluminum hydroxide powder as a filler in resin molded materials (sealing materials, thermal interface materials, artificial marble, etc.) is increasing.

[0003] For example, Patent Document 1 discloses a method for manufacturing aluminum hydroxide for use as a filler material, characterized by utilizing a compression capacity of 5 to 500 kgf / cm. 2 The screw-type kneader pulverizes the raw material aluminum hydroxide.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2001-322813 Summary of the Invention

[0007] The problem that the invention aims to solve

[0008] However, it is known that in the prior art disclosed in Patent Document 1, the addition of aluminum hydroxide powder to the resin may easily lead to thickening.

[0009] The present invention was made in view of the following circumstances, and one of its objectives is to provide an aluminum hydroxide powder that can sufficiently suppress viscosity increase when added to a resin, and a method for manufacturing the same.

[0010] Methods for solving problems

[0011] Method 1 of the present invention is an aluminum hydroxide powder.

[0012] Its density when molded at 10 MPa is 1.59–2.00 g / cm³. 3 ,and,

[0013] The ratio of the diffraction intensity of the (002) plane to the diffraction intensity of the (110) plane in its XRD pattern is 2.0 to 7.5.

[0014] Method 2 of the present invention is the aluminum hydroxide powder according to Method 1, wherein,

[0015] 90% by mass of particle size (D90) is less than 100 μm.

[0016] Method 3 of the present invention is aluminum hydroxide powder according to method 1 or 2, wherein,

[0017] In the mass-based particle size distribution, there are one or two peaks in the particle size range of 1 to 200 μm. When there is one peak, the frequency of the peak is greater than 4.0% by mass. When there are two peaks, the frequency of one peak is greater than 4.0% by mass, and the frequency of the other peak is greater than 0% by mass but less than 4.0% by mass.

[0018] Embodiment 4 of the present invention is a method for manufacturing aluminum hydroxide powder, which includes the following steps:

[0019] Aluminum hydroxide powder with a particle size (D50) of 10–200 μm and a cumulative pore volume of 0.01–1 mL / g of 0.05–1 μm radius was pulverized under a pressure of 49.0–294.0 MPa and then crushed at an impact velocity of less than 92 m / s.

[0020] Invention Effects

[0021] According to embodiments of the present invention, it is possible to provide aluminum hydroxide powder that can sufficiently suppress viscosity increase when added to a resin, and a method for manufacturing the same. Detailed Implementation

[0022] In order to achieve an aluminum hydroxide powder that can sufficiently suppress the increase in viscosity (hereinafter also referred to as "resin viscosity") when added to a resin, the inventors conducted research from various perspectives. The results showed that by controlling the density when molded at 10 MPa (hereinafter also referred to as "molding density") and the ratio of the diffraction intensity of the (002) plane to the diffraction intensity of the (110) plane in the XRD pattern (hereinafter also referred to as "(002) / (110) diffraction intensity ratio") within a specified range, the increase in resin viscosity can be sufficiently suppressed.

[0023] It was found that in order to control the molding density and the (002) / (110) diffraction intensity ratio within the specified range, it is important to control the particle size and pore volume of the raw material aluminum hydroxide powder within the specified range, and to apply a higher pressure (500-3000 kgf / cm²) than in the prior art. 2 The material is crushed at a pressure of 49.0 to 294.0 MPa and further broken down at a relatively weak impact velocity of less than 92 m / s.

[0024] The following details the requirements specified in the embodiments of the present invention.

[0025] <1. Aluminum hydroxide powder>

[0026] The aluminum hydroxide powder of the present invention has a density of 1.59–2.00 g / cm³ when molded at 10 MPa. 3Furthermore, the ratio of the diffraction intensity of the (002) plane to the diffraction intensity of the (110) plane in its XRD pattern is 2.0 to 7.5. Therefore, the increase in resin viscosity can be effectively suppressed.

[0027] If the molding density is less than 1.59 g / cm³ 3 The resin viscosity increases. There is no specific upper limit for the molding density; for example, to exceed 2.00 g / cm³... 3 More detailed manufacturing conditions need to be set; if productivity is taken into consideration, it is preferable to pre-set them to 2.00 g / cm³. 3 the following.

[0028] It should be noted that the molding density is calculated as follows.

[0029] 3.00 g of aluminum hydroxide powder was placed into a cylindrical uniaxial forming mold with an inner diameter of 20.0 mm. Using a universal testing machine (e.g., A&D Corporation, TENSILON RTG-1310), the aluminum hydroxide powder was compressed to a pressure of 10 MPa at a compression rate of 1 mm / min. The weight / volume ratio was used as the molding density.

[0030] If the (002) / (110) diffraction intensity ratio exceeds 7.5, the aluminum hydroxide powder can typically be in a near-spherical shape, resulting in a strained shape similar to a plate, and the resin viscosity increases. Preferably, the (002) / (110) diffraction intensity ratio is 6.0 or less. There is no particular limitation on the lower limit of the (002) / (110) diffraction intensity ratio. In order to make the (002) / (110) diffraction intensity ratio less than 2.0, more detailed manufacturing conditions need to be set. If productivity is taken into consideration, it is preferable to set it to 2.0 or more in advance.

[0031] It should be noted that the diffraction intensity of (002) / (110) is calculated as follows.

[0032] After compacting and filling the glass sample cell for measurement, aluminum hydroxide powder was used to determine the XRD pattern using a powder X-ray diffraction apparatus (e.g., Rigaku RINT-2000) with a step size of 0.02 degrees, a scan rate of 0.04 degrees / sec, an accelerating voltage of 40 kV, and an accelerating current of 30 mA. Cu-Kα was used as the X-ray source. In the obtained XRD pattern, the peak appearing at 2θ = 18.3° was designated as the peak of the (002) plane, and the peak appearing at 2θ = 20.3° was designated as the peak of the (110) plane. The ratio of the diffraction intensity (peak height) of the (002) plane peak to the diffraction intensity (peak height) of the (110) plane peak was taken as the (002) / (110) diffraction intensity ratio.

[0033] The aluminum hydroxide powder of the embodiments of the present invention preferably has a 90% mass particle size (i.e., the particle size at which the cumulative frequency from the microparticle side in the mass-based particle size distribution reaches 90% by mass, also referred to as D90) of less than 100 μm. This sufficiently suppresses appearance defects when aluminum hydroxide powder is filled into a resin molded article, and easily ensures sufficient strength of the resin molded article. Preferably, D90 is 90 μm or less, more preferably 65 μm or less, and even more preferably 45 μm or less.

[0034] In embodiments of the present invention, the aluminum hydroxide powder preferably has a D90 of 20 μm or more. This allows for the suppression of poor dispersion when the aluminum hydroxide powder is dispersed in a liquid.

[0035] The aluminum hydroxide powder of the embodiments of the present invention preferably has one or two peaks in the particle size range of 1 to 200 μm in the mass-based particle size distribution. This suppresses appearance defects when aluminum hydroxide powder is filled into a resin molded article, and also suppresses poor dispersion when aluminum hydroxide powder is dispersed in a liquid. When there is one peak, the frequency of that peak can be 4.0% by mass or more. When there are two peaks, the frequency of one peak can be 4.0% by mass or more, and the frequency of the other peak can be greater than 0% by mass and less than 4.0% by mass. In this case, it is preferable to have only one peak in the particle size range of 1 to 200 μm in the mass-based particle size distribution. This further suppresses appearance defects and poor dispersion of the aforementioned resin molded article.

[0036] The aluminum hydroxide powder of the embodiments of the present invention may have one or more peaks in one or both of the particle size ranges of less than 1 μm and greater than 200 μm in the mass-based particle size distribution. The frequency of the peaks may be greater than 0% by mass and less than 0.5% by mass, or there may be no peaks in the particle size ranges of less than 1 μm and greater than 200 μm.

[0037] In embodiments of the present invention, the 50% mass particle size of the aluminum hydroxide powder (i.e., the particle size at which the cumulative frequency from the microparticle side in the mass-based particle size distribution reaches 50% mass, also referred to as D50) is preferably 30 μm or less. This allows for the suppression of undesirable appearance when aluminum hydroxide powder is filled into a resin molded article, and easily ensures the strength of the resin molded article.

[0038] In embodiments of the present invention, the aluminum hydroxide powder preferably has a D50 of 7 μm or more. This allows for the suppression of poor dispersion when the aluminum hydroxide powder is dispersed in a liquid.

[0039] It should be noted that the quality reference particle size distribution (including D50 and D90) is calculated as follows.

[0040] Aluminum hydroxide powder was added to a 0.2% (w / w) sodium hexametaphosphate aqueous solution and irradiated with ultrasound at an output power of 25W for 120 seconds to disperse the aluminum hydroxide powder in the aqueous solution. The mass reference particle size distribution (including D50 and D90) was determined using a laser scattering particle size distribution measuring device. This particle size distribution was determined by dividing the particle size range of 0.02 μm to 2000 μm into 132 portions on a logarithmic scale and measuring the mass of aluminum hydroxide with particle sizes in each range. It should be noted that, considering differences between devices and compatibility with this embodiment, a Microtrac MT-3300EXII (manufactured by Nikkiso Corporation) or an equivalent device is preferred as the laser scattering particle size distribution measuring device. Furthermore, the particle size distribution measurement can be performed by appropriately adjusting the concentration of the aluminum hydroxide powder to the measurable concentration of the aforementioned measuring device.

[0041] In embodiments of the present invention, the aluminum hydroxide powder preferably has a BET specific surface area of ​​2.0 m². 2 / g or less. This allows for the suppression of poor dispersion when aluminum hydroxide powder is dispersed in a liquid. It should be noted that the BET specific surface area is determined by nitrogen adsorption using a fully automated specific surface area measuring device (e.g., Mounttech MacsorbHM-1201) according to the method specified in JIS-Z-8830:2013.

[0042] The aluminum hydroxide powder of the embodiments of the present invention may contain Na2O as an impurity. The Na2O content is preferably set to 0.13% by mass or less, for example. This suppresses resin degradation and insulation degradation when filled into a resin molded body. The Na2O content is determined as follows: after preparing an aqueous solution by dissolving the aluminum hydroxide powder in an aqueous solution of an inorganic acid, the Na2O content is determined using an ICP-based spectrophotometer. Specifically, the intensity of sodium at its wavelength (589.592 nm) is measured, converted to Na2O, and the mass of Na2O is calculated. The ratio of this Na2O mass to the mass of the dissolved aluminum hydroxide powder is taken as the Na2O content (by mass%). Furthermore, the aluminum hydroxide powder of the embodiments of the present invention may contain unavoidable impurities in addition to Al(OH)3 and Na2O. As unavoidable impurities, the inclusion of elements introduced due to the condition of raw materials, resources, manufacturing equipment, etc., is permitted.

[0043] The aluminum hydroxide powder of the present invention, when added to resin, can effectively suppress viscosity increase, making it suitable as a filler material for resin molded articles (sealing materials, thermal interface materials, artificial marble, etc.). Examples of applicable resins include thermosetting resins such as unsaturated polyester resins, epoxy resins, phenolic resins, and polyurethane resins; polyolefins, represented by copolymers of polyethylene, polypropylene, ethylene and propylene, and copolymers of ethylene and / or propylene with other α-olefins such as butene-1, pentene-1, hexene-1, heptene-1, octene-1, nonene-1, 4-methylpentene-1, and decene-1; styrene (co)polymers; methyl methacrylate (co)polymers; polyamides; polycarbonates; ethylene-vinyl acetate copolymers; polyacetals; acrylonitrile-butadiene-styrene copolymers; polyphenylene ethers; polyethersulfones; polyarylates; polyetheretherketones; and polymethylpentene, etc. The aluminum hydroxide powder of the present invention is not limited to the above-mentioned resins and can also be used as a filler material for other synthetic resins, natural resins, or paper.

[0044] <2. Method for manufacturing aluminum hydroxide powder>

[0045] The method for manufacturing aluminum hydroxide powder according to embodiments of the present invention includes: (a) a step of preparing 50% by mass of aluminum hydroxide powder with a particle size (D50) of 10 to 200 μm and a cumulative volume of fine pores with a radius of 0.05 to 1 μm of 0.01 to 1 mL / g; (b) a step of pulverizing under a pressure of 49.0 to 294.0 MPa; and (c) a step of crushing at an impact velocity of 92 m / s or less. Each step will be described in detail below.

[0046] [(a) The process of preparing aluminum hydroxide powder]

[0047] First, prepare aluminum hydroxide powder (hereinafter also referred to as "raw aluminum hydroxide powder") as raw material. The raw aluminum hydroxide powder should have a cumulative volume (hereinafter also referred to as "cumulative pore volume") of 50% by mass of fine pores with a particle size (D50) of 10–200 μm and a radius of 0.05–1 μm, of 0.01–1 mL / g. This readily yields the desired molding density. Preferably, the cumulative pore volume is 0.02–1 mL / g. This readily yields the desired D90, and also readily yields aluminum hydroxide powder with the desired mass-based particle size distribution.

[0048] If D50 is less than 10 μm or greater than 200 μm, and / or the cumulative pore volume is less than 0.01 mL / g or greater than 1 mL / g, it is difficult to obtain the desired molding density.

[0049] It should be noted that the cumulative volume of the fine pores is calculated as follows.

[0050] Aluminum hydroxide powder was dried at 120°C for 4 hours to remove adsorbed moisture. Then, approximately 0.5–0.6 g was weighed using a precision balance and filled into a measuring cell with a diameter of 15 mm and a height of 24 mm. This measuring cell was placed in an automatic porosity meter (e.g., Micromeritics Autopore III 9420) and measurements were taken on both a low-pressure side (1–10000 psi) and a high-pressure side (10000–60000 psi). These measurement data were summed to determine the pore volume distribution in the region with a pore radius greater than 0.002 μm and less than 100 μm, and the cumulative volume in the region with a pore radius greater than 0.05 μm and less than 1.0 μm was calculated.

[0051] The crystal structure of the raw material aluminum hydroxide powder is, for example, gibbsite or diaspore, preferably gibbsite.

[0052] Raw aluminum hydroxide powder can be manufactured by adding seed crystals to a supersaturated sodium aluminate solution, hydrolyzing while stirring to precipitate aluminum hydroxide, filtering and washing the resulting aluminum hydroxide, and then drying it. By appropriately adjusting the precipitation conditions (and / or partially dissolving the precipitated material, and / or pulverizing or crushing the precipitated material), raw aluminum hydroxide powder with the aforementioned particle size and cumulative pore volume can be obtained. It should be noted that commercially available aluminum hydroxide powder can also be used as long as the above-mentioned particle size and cumulative pore volume are met.

[0053] [(b) Crushing process at a pressure of 49.0–294.0 MPa]

[0054] Next, the above-mentioned raw material, aluminum hydroxide powder, is pulverized under a pressure of 49.0–294.0 MPa. Here, "pulverization" refers to the operation of applying energy to solid particles (e.g., primary particles) of a certain size, thereby reducing their size to a smaller size.

[0055] If the crushing pressure is less than 49.0 MPa, the desired molding density cannot be obtained. Preferably, it is greater than 49.0 MPa, more preferably 68.6 MPa or higher. There is no particular upper limit to the crushing pressure, but if productivity is taken into account, it is preferable to pre-set it to 294.0 MPa or lower.

[0056] Examples of the pulverizer for performing pulverization under the above pressure include two-way kneaders, open roll mills, self-cleaning kneaders, gear kneaders, single-shaft screw kneaders, and double-shaft screw kneaders. One of these apparatuses may be used alone, or two or more thereof may be used in combination. Further, the pulverizer may be of either batch type or continuous type; from the viewpoint of reducing pulverization energy per unit weight, the continuous type is preferable. When a continuous pulverizer is used, it is not necessary to pulverize the entire raw material aluminum hydroxide in the pulverizer; for example, it is sufficient that the pulverization degree gradually increases along the conveying direction (axial direction) of the raw material aluminum hydroxide. In the case of a screw kneader, the compression capacity is adjusted, for example, according to the shape and length of the screw, the rotation speed, and the rotation speed of a rotor (which functions to convey the raw material to the screw).

[0057] In the pulverizer, the raw material aluminum hydroxide powder exists as a solid phase; in addition, generally, air or the like exists as a gas phase, and water or the like exists as a liquid phase. These states in the pulverizer during pulverization may sometimes affect the physical properties of the aluminum hydroxide powder obtained by pulverization. Therefore, pulverization is preferably carried out under a filling form of solid phase, liquid phase and gas phase that is any one of (i) a dry state where the solid phase and the gas phase are continuous and substantially no liquid phase exists, (ii) a pendular state (Japanese: ペンデユラ一状態) where the solid phase and the gas phase are continuous and the liquid phase is discontinuous, or (iii) a funicular I state (Japanese: フア二キユラ一I状態) where the solid phase, the gas phase and the liquid phase are all continuous. Such a filling form visually constitutes a smooth and dry mixed system.

[0058] Pulverization is preferably carried out after adjusting the liquid content of the raw material aluminum hydroxide powder before pulverization, so as to achieve the dry state, the pendular state or the funicular I state during pulverization. The liquid content may be adjusted, for example, by drying the raw material aluminum hydroxide powder or adding a liquid such as water or alcohol. The preferred liquid content varies depending on the particle size distribution of the raw material aluminum hydroxide and is not unique; for example, it is 30% by weight or less, more preferably 10% by weight or less, and further is 1% by weight or more, more preferably 5% by weight or more. If the liquid content becomes too high, it is difficult to effectively pulverize the raw material aluminum hydroxide.

[0059] When a liquid such as water is added during pulverization, or when raw material aluminum hydroxide powder containing water or the like is pulverized, the pulverized aluminum hydroxide powder is generally subjected to drying. Drying can be carried out, for example, by a method using a known dryer, or a method of heating a part of a continuous pulverizer when performing pulverization with the continuous pulverizer.

[0060] [(c) step of crushing at an impact velocity of 92 m / sec or less]

[0061] After the above step (b), the material is broken down at a collision velocity of 92 m / s or less. Here, "breaking down" refers to the operation of loosening and refining the material obtained by aggregating fine particles into a single mass (e.g., secondary particles) (e.g., making primary particles).

[0062] If the impact velocity during crushing exceeds 92 m / s, the desired (002) / (110) diffraction intensity ratio cannot be obtained. Crushing at the aforementioned impact velocity is possible by using, for example, an impact crusher.

[0063] The method for manufacturing aluminum hydroxide powder according to embodiments of the present invention may include other steps (e.g., surface treatment steps) within the scope of achieving the objectives of the present invention.

[0064]

Example

[0065] The following examples illustrate the implementation of the present invention in more detail. The implementation of the present invention is not limited to the following examples; appropriate modifications may be made to achieve the objectives described above and below, and all such modifications are included within the technical scope of the embodiments of the present invention.

[0066] The raw material, aluminum hydroxide powder (D50: 81μm, cumulative pore volume: 0.09mL / g), was adjusted to a moisture content of 5wt% and continuously fed into a pulverizer (single-shaft screw kneader) for pulverization. The pulverizer pressure was set to 196.0MPa by adjusting the feeding speed. It should be noted that, regarding the pulverizer pressure, the same raw material aluminum hydroxide powder was separately compressed and pulverized using a cold isostatic press. The relationship between the compression pressure and D90 was investigated beforehand, and the pulverizer pressure was easily calculated from the D90 of the pulverized aluminum hydroxide powder.

[0067] The resulting pulverized material was dried at 120°C and then crushed in an impact pulverizer (free pulverizer, Nara Machinery Manufacturing Co., Ltd.) to obtain the aluminum hydroxide powder of Example 1. The impact velocity of the impact pulverizer was set to 46 m / s.

[0068] Furthermore, according to the manufacturing method of Example 1 above, the conditions were changed as shown in Table 1 below to obtain aluminum hydroxide powders of Examples 2 to 4 and Comparative Examples 1 to 2. In addition, commercially available aluminum hydroxide powders were used as Comparative Example 3 (Sumitomo Chemical, CW-308), Comparative Example 4 (Sumitomo Chemical, C-305), and Comparative Example 5 (Sumitomo Chemical, CM-3080).

[0069] Table 1

[0070]

[0071] For the aluminum hydroxide powders of Examples 1-4 and Comparative Examples 1-5, the molding density, (002) / (110) diffraction intensity ratio, mass-based particle size distribution (including D50 and D90), BET specific surface area and Na2O content were determined by the following methods.

[0072] [Molding density]

[0073] 3.00g of aluminum hydroxide powder was placed into a cylindrical uniaxial forming mold with an inner diameter of 20.0mm. Using a universal testing machine (A&D Corporation, TENSILON RTG-1310), the aluminum hydroxide powder was compressed to a pressure of 10MPa at a compression rate of 1mm / min. The weight / volume ratio was used as the molding density.

[0074] [(002) / (110) diffraction intensity ratio]

[0075] After compacting and filling the glass sample cell for measurement, aluminum hydroxide powder was used to measure the XRD pattern using a powder X-ray diffraction apparatus (Rigaku, RINT-2000) with a step size of 0.02 degrees, a scan rate of 0.04 degrees / sec, an accelerating voltage of 40 kV, and an accelerating current of 30 mA. Cu-Kα was used as the X-ray source. In the obtained XRD pattern, the peak appearing at 2θ = 18.3° was taken as the peak of the (002) plane, and the peak appearing at 2θ = 20.3° was taken as the peak of the (110) plane. The ratio of the diffraction intensity (peak height) of the (002) plane peak to the diffraction intensity (peak height) of the (110) plane peak was taken as the (002) / (110) diffraction intensity ratio.

[0076] [Quality reference particle size distribution (including D50 and D90)]

[0077] Aluminum hydroxide powder was added to a 0.2% (w / w) sodium hexametaphosphate aqueous solution and irradiated with ultrasound at an output power of 25W for 120 seconds to disperse the aluminum hydroxide powder in the aqueous solution. The resulting substance was then subjected to a laser scattering particle size distribution assay to determine the mass-based particle size distribution (including D50 and D90). This particle size distribution was determined by dividing the particle size range of 0.02 μm to 2000 μm into 132 portions on a logarithmic scale and measuring the mass of aluminum hydroxide with particle sizes in each range. A Microtrac MT-3300EXII (manufactured by Nikkiso Corporation) was used as the laser scattering particle size distribution assay. Furthermore, during the particle size distribution measurement, the concentration of the aluminum hydroxide powder was appropriately adjusted to the measurable concentration of the assay device before measurement.

[0078] [BET specific surface area]

[0079] The BET specific surface area was determined by nitrogen adsorption using a fully automated specific surface area measuring device (Macsorb HM-1201, manufactured by Mountech) according to the method specified in JIS-Z-8830:2013.

[0080] [Na2O content]

[0081] After preparing an aqueous solution by dissolving aluminum hydroxide powder in an aqueous solution of inorganic acid, the Na2O content was determined using an ICP-based spectrophotometer. Specifically, the intensity of sodium at its wavelength (589.592 nm) was measured, converted to Na2O, and the mass of Na2O was calculated. The ratio of this Na2O mass to the mass of dissolved aluminum hydroxide powder was taken as the Na2O content (mass%).

[0082] In addition, the resin viscosity was determined using the following method.

[0083] 5.59 parts by weight of aluminum hydroxide powder and 1.86 parts by weight of bisphenol A type epoxy resin mixture (AQ010-8140, room temperature curing resin type 53 main agent) were mixed at 1000 rpm for 3 minutes using a planetary mixer (THINKY Corporation, deaerator Rintaro ARV-310) to obtain a composite. The composite was placed on a parallel plate with a diameter of 30 mm mounted on a dynamic viscoelasticity measuring device (Rheosol-G3000). After standing for 10 minutes with a gap of 0.50 mm between the parallel plates and a temperature of 100°C, the shear rate was measured over 40 seconds. -1 The viscosity of the resin is as follows.

[0084] The results are summarized in Table 2 below. It should be noted that in Table 2, a "-" in the "Second Peak" column indicates that a second peak does not exist.

[0085] Table 2

[0086]

[0087] Based on the results in Table 2, the following analysis can be conducted. Examples 1-4 in Table 2 are examples that satisfy all the requirements specified in the embodiments of the present invention, with a resin viscosity of 10 Pa·s or less, which sufficiently suppresses the increase in resin viscosity. Among them, Examples 1-3 have a D90 of less than 100 μm, therefore, considering that they can sufficiently suppress appearance defects when filled into the resin molded body and easily ensure sufficient strength of the resin molded body, they are preferred examples. The aluminum hydroxide powder used in Example 4 has a cumulative pore volume of less than 0.02 mL / g, therefore its D90 is 100 μm or more.

[0088] On the other hand, Comparative Examples 1 to 5 are examples that do not meet the requirements specified in the embodiments of the present invention, and the resin viscosity exceeds 10 Pa·s, which cannot sufficiently suppress the increase in resin viscosity.

[0089] In Comparative Example 1, the (002) / (110) diffraction intensity ratio exceeds 7.5 because the collision velocity during breakage exceeds 92 m / s, and the resin viscosity exceeds 10 Pa·s.

[0090] The crushing pressure in Comparative Example 2 was less than 49.0 MPa, therefore the molding density was less than 1.59 g / cm³. 3 The resin viscosity exceeds 10 Pa·s.

[0091] The molding density of Comparative Examples 3 and 4 is less than 1.59 g / cm³. 3 Therefore, the resin viscosity exceeds 10 Pa·s.

[0092] The (002) / (110) diffraction intensity ratio of Comparative Example 5 exceeds 7.5, therefore the resin viscosity exceeds 10 Pa·s.

Claims

1. An aluminum hydroxide powder, having a density of 1.59–2.00 g / cm³ when molded at 10 MPa. 3 ,and, The ratio of the diffraction intensity of the (002) plane to that of the (110) plane in its XRD pattern is 2.0–7.

5. In the mass-based particle size distribution, there are one or two peaks in the particle size range of 1 μm to 200 μm. When there is only one peak, the frequency of this peak is above 4.0% of mass. When there are two peaks, one peak has a frequency of more than 4.0% mass, and the other peak has a frequency greater than 0% mass but less than 4.0% mass.

2. The aluminum hydroxide powder according to claim 1, wherein, 90% by mass of particle size D90 is less than 100 μm.

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