Scaly boehmite aggregate and method for producing the same

Abstract

To provide a scaly boehmite aggregate of a microsize having a bulky card house structure in which highly crystalline scaly boehmite crystals are aggregated and a manufacturing method thereof.SOLUTION: A scaly boehmite aggregate of the present invention is a scaly boehmite aggregate having a bulky card house structure in which crystals of scaly boehmite aggregate with each other, wherein the oil absorption amount of refined linseed oil measured according to pure linseed oil method of JIS K5101-13-1 (2004) is 190 g / 100 g or more, and the cumulative pore volume at a pore diameter of 0.05 to 2.00 μm is 0.40 mL / g or more, as measured by a mercury porosimeter. In the method for manufacturing scaly boehmite aggregates of the present invention, hydrothermal treatment is applied while stirring a water suspension containing any one additive of aluminum hydroxide having an average particle size (based on volume) of 4 to 20 μm measured by laser diffraction / scattering method, sodium carbonate or sodium aluminate.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a micro-sized scaly boehmite aggregate having a bulky house-of-card structure formed by aggregation of scaly boehmite crystals, and a method for producing the same. [Background technology]

[0002] Boehmite, an alumina monohydrate (AlOOH), is highly versatile and is used as a filler, reinforcing material, flame retardant, luminescent material, fireproof material, thickener, etc. It is also used as a catalyst support, an electrically conductive filler base material, a refractory material, a raw material for high-purity alumina, a raw material for sinterable alumina, a raw material for fluorescent materials, etc. Boehmite can be produced with controlled morphology, and boehmite crystals come in a variety of shapes, including cubic, plate, hexagonal plate, disc, needle, and scale. Depending on the production method, boehmite can sometimes produce agglomerates of boehmite crystals, and these agglomerates can be used for a variety of applications, just like boehmite particles in which boehmite crystals are dispersed.

[0003] There has been a report on boehmite aggregates (Non-Patent Document 1). That is, Non-Patent Document 1 discloses that flower-like boehmite aggregates can be obtained by adding glucose, a surfactant, to a sodium aluminate solution (Bayer solution) and stirring it at 70°C for 60 minutes (aging), and then neutralizing the pH from 11.9 to 9.5 using 1M sulfuric acid (Abstract, page 168, right column, bottom). [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Processing and Application of Ceramics 14〔2〕(2020)168-172 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the flower-like aggregates of boehmite disclosed in the above-mentioned Non-Patent Document 1 have a size of about 100 nm to 200 nm (left column on page 170) and a specific surface area of ​​293.6 to 331.5 m 2 / g, pore diameter 3.5 to 3.9 nm, and pore volume 0.258 to 0.308 m 3 / g (Table 2 on page 171), and is a nano-sized aggregate of boehmite with low crystallinity. Therefore, the flower-like aggregate of boehmite has problems of low thermal conductivity, high hygroscopicity, and a lower dehydration temperature than boehmite with high crystallinity, making it unsuitable for use as a flame retardant. Furthermore, Non-Patent Document 1 does not state or suggest that the flower-like aggregate of boehmite has a bulky house-of-card structure.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a micro-sized scaly boehmite aggregate having a bulky card-house structure in which highly crystalline scaly boehmite crystals are aggregated together, and a method for producing the same. [Means for solving the problem]

[0007] In order to solve the above problems, the inventors of the present invention have conducted extensive research and have come up with the present invention. That is, the invention described in claim 1 relates to a scaly boehmite aggregate having a bulky card-house structure in which scaly boehmite crystals are aggregated together, characterized in that the refined linseed oil absorption measured in accordance with the refined linseed oil method of JIS K5101-13-1 (2004) is 190 g / 100 g or more, and the cumulative pore volume at pore diameters of 0.05 to 2.00 μm measured with a mercury porosimeter is 0.40 mL / g or more.

[0008] The invention described in claim 2 may be the invention described in claim 1, wherein the coefficient of variation CV calculated using the following formula is 35% or less. Standard deviation SD=(D84-D16) / 2 (Formula 1) Coefficient of variation CV = (standard deviation SD / D50) × 100 (Equation 2)

[0009] The invention described in claim 3 may be the invention described in claim 1 or claim 2, wherein the 1% weight loss temperature, which is the temperature at which a weight loss of 1 wt% is confirmed when heated at a temperature increase rate of 30°C / min, with the weight loss rate at 100°C set to 0 wt% in thermogravimetric analysis, is 420°C or higher.

[0010] The invention described in claim 4 relates to a method for producing the scaly boehmite aggregate described in any one of claims 1 to 3, characterized in that an aqueous suspension containing aluminum hydroxide having an average particle size (volume basis) of 4 to 20 μm as measured by a laser diffraction / scattering method and one additive of either sodium carbonate or sodium aluminate is subjected to hydrothermal treatment while stirring.

[0011] The invention described in claim 5 is the invention described in claim 4, wherein the concentration of aluminum hydroxide in water may be 1 to 20 wt %, the concentration of the additive in water may be 0.05 to 2.00 mol / L, and the constant temperature of the hydrothermal treatment may be 150 to 250°C. [Effects of the Invention]

[0012] The scaly boehmite aggregate of the present invention has a bulky card-house structure, which allows it to impart high viscosity when filled into a filler such as a resin. In addition, because of its bulky card-house structure, it is porous and is useful as a raw material for catalyst supports and porous ceramics.

[0013] The scaly boehmite aggregate of the present invention has little variation in particle size and is uniform in particle size, so that it can suppress variations in the properties of the final product caused by variations in particle size. For example, when used as a filler, it is possible to reduce variations in the properties of the filled material such as resin, when used as a paint, it is possible to reduce variations in the properties of the coating liquid, and further, when used as a raw material for ceramics, it is possible to prevent variations in properties caused by poor sintering due to non-uniform particle size.

[0014] The method for producing a scaly boehmite aggregate of the present invention directly synthesizes the scaly boehmite aggregate without using an organic binder, and therefore no organic binder remains in the aggregate. A problem with general organic binders is that they do not have high weather resistance and deteriorate, which may prevent the aggregate from being maintained for a long period of time. However, the present invention makes it possible to produce an aggregate made of scaly boehmite with high weather resistance. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is an SEM photograph of the scaly boehmite aggregate of Example 1. [Figure 2] 1 is an SEM photograph of scaly boehmite particles of Comparative Example 1. [Figure 3] 1 is an SEM photograph of a scaly boehmite aggregate of Example 2. [Figure 4] 1 is an SEM photograph of scaly boehmite particles of Comparative Example 2. [Figure 5] 1 is an SEM photograph of a scaly boehmite aggregate of Example 3. [Figure 6] 1 is an SEM photograph of the scaly boehmite aggregate of Example 4. [Figure 7] 1 is an SEM photograph of a scaly boehmite aggregate of Comparative Example 3. [Figure 8] 1 is an SEM photograph showing a cross section of a scaly boehmite aggregate of Example 4. [Figure 9] 1 is an SEM photograph showing a cross section of a scaly boehmite aggregate of Comparative Example 3. DETAILED DESCRIPTION OF THE INVENTION

[0016] The scaly boehmite aggregate of the present invention has a bulky card-house structure in which scaly boehmite crystals are aggregated together, and the oil absorption of the refined linseed oil, which reflects the volume of the voids in the card-house structure and is measured in accordance with the refined linseed oil method of JIS K5101-13-1 (2004), is preferably 190 g / 100 g or more, more preferably 200 g / 100 g or more. The upper limit of the oil absorption of the refined linseed oil may be preferably 300 g / 100 g, more preferably 290 g / 100 g.

[0017] The scaly boehmite aggregate of the present invention has a bulky card-house structure and a large void volume, and therefore the oil absorption is higher than that of scaly boehmite particles in which scaly boehmite crystals are dispersed and which have few voids, and is also higher than that of scaly boehmite aggregates having a dense card-house structure in which scaly boehmite crystals are aggregated together.

[0018] The scaly boehmite aggregate of the present invention preferably has an integrated pore volume of 0.40 mL / g or more, more preferably 0.45 mL / g or more, at pore diameters of 0.05 to 2.00 μm, as measured by a mercury porosimeter. The scaly boehmite aggregate of the present invention is a micro-sized aggregate in which the majority of the pores are macropores.

[0019] The scaly boehmite aggregate of the present invention preferably has a coefficient of variation CV calculated using the following formula of 35% or less, more preferably 33% or less. Standard deviation SD=(D84-D16) / 2 (Formula 1) Coefficient of variation CV = (standard deviation SD / D50) × 100 (Equation 2) The scaly boehmite aggregates of the present invention are particles with little variation in particle size, or in other words, "uniform particles." Furthermore, the scaly boehmite aggregates of the present invention are particles with little variation in particle size compared to scaly boehmite particles in which scaly boehmite crystals are dispersed.

[0020] The scaly boehmite constituting the scaly boehmite aggregate of the present invention has a specific surface area of ​​several m 2 / g and is a highly crystalline micro-sized boehmite.

[0021] The 1% weight loss temperature of the scaly boehmite aggregate of the present invention is preferably 420° C. or higher. Here, the 1% weight loss temperature is defined as the temperature at which a weight loss of 1 wt % is confirmed when heated at a heating rate of 30° C. / min in thermogravimetric analysis, with the weight loss rate at 100° C. being 0 wt %. When heated, boehmite undergoes a dehydration reaction, transforming into γ-alumina, a crystalline phase. When using boehmite as a flame retardant, the higher the onset temperature of the dehydration reaction, the better. This tends to decrease with finer boehmite particles or lower crystallinity, resulting in a lower 1% weight loss temperature. Nano-sized boehmite has a 1% weight loss temperature of approximately 300°C, which is too low for boehmite to be used in plastic materials, which require high temperatures for molding, a primary application of boehmite as a flame retardant. Furthermore, the method for producing scaly boehmite aggregates described below does not involve forming aggregates using an organic binder such as polyvinyl alcohol, but rather directly synthesizes the scaly boehmite aggregates. Using an organic binder, the organic binder remaining in the product decomposes during thermal analysis, resulting in a weight loss and a lower 1% weight loss temperature. As described above, the scaly boehmite aggregates of the present invention are micro-sized and highly crystalline, and since no organic binder is used in their production, they can ensure a 1% weight loss temperature of 420°C or higher.

[0022] The scaly boehmite aggregate of the present invention has a tap density of 0.16 g / cm 3 More than 0.18 g / cm is preferable. 3 The tap density of the scaly boehmite aggregate of the present invention is higher than that of scaly boehmite particles in which scaly boehmite crystals are dispersed, and therefore, while scaly boehmite particles in which scaly boehmite crystals are dispersed and have a low tap density, tend to scatter, the scaly boehmite aggregate of the present invention is less likely to scatter and has excellent handleability.

[0023] Next, a method for producing the scaly boehmite aggregate of the present invention will be described. The scaly boehmite aggregate of the present invention can be obtained by subjecting an aqueous suspension containing aluminum hydroxide as a raw material and an additive to hydrothermal treatment while stirring.

[0024] The aluminum hydroxide raw material preferably has an average particle size (volume basis) of 4 to 20 μm, more preferably 5 to 15 μm, as measured by laser diffraction / scattering. If the average particle size of the aluminum hydroxide is less than 4 μm, the scaly boehmite crystals cannot aggregate to form a bulky house-of-card structure. If the average particle size of the aluminum hydroxide is greater than 20 μm, sedimentation is likely to occur during the reaction, and the reaction product may clog the piping, potentially damaging the hydrothermal treatment device. The concentration of aluminum hydroxide in water is preferably 1 to 20 wt%, more preferably 2 to 17 wt%. If it is less than 1 wt%, the amount of boehmite produced is small, which is uneconomical, and if it is more than 20 wt%, the viscosity increases during synthesis, which makes poor stirring more likely to occur.

[0025] Furthermore, it is preferable that the particle size of the aluminum hydroxide used as the raw material is highly uniform. That is, it is preferable that the shape of the particle size distribution of the aluminum hydroxide be a normal distribution or a unimodal distribution close to a normal distribution. This is because the more uniform the particle size of the aluminum hydroxide, the more reliably it is possible to obtain scaly boehmite aggregates having a bulky house-of-card structure and little variation in particle size. Furthermore, the raw material aluminum hydroxide preferably has primary particles having an average length of 2 to 8 μm as measured from an SEM image, and is in the form of secondary particles formed by aggregation of these particles. If the average size of the primary particles is smaller than 2 μm, it is difficult to form a house-of-cards structure in which the scaly boehmite crystals aggregate together, and if it is larger than 8 μm, the center of the house-of-cards structure becomes hollow, making the aggregates brittle.

[0026] The additive is preferably either sodium carbonate or sodium aluminate, but potassium carbonate can also be used. The concentration of the additive in water is preferably 0.05 to 2.00 mol / L, more preferably 0.10 to 1.00 mol / L. If the concentration is less than 0.05 mol / L, the thickness of the scaly boehmite particles increases and they do not become bulky, while if the concentration is more than 2.00 mol / L, the pH becomes high and the produced boehmite dissolves, reducing the amount that can be recovered.

[0027] The water used to prepare the suspension may be hard water or soft water, but soft water, which is less affected by magnesium ions and calcium ions, is preferred.

[0028] The constant temperature for the hydrothermal treatment is preferably 150 to 250°C, more preferably 160 to 230°C. This is because the reaction from aluminum hydroxide to boehmite does not proceed smoothly below 150°C, and expensive equipment that can withstand high pressures is required above 250°C. The reaction time is preferably in the range of 3 to 24 hours. If it is less than 3 hours, scaly boehmite aggregates may not be obtained. If it exceeds 24 hours, no particular effect is obtained and it is uneconomical in terms of energy. Furthermore, the rate of temperature rise to a constant temperature is preferably 100°C / hour or less. If the rate is not 100°C / hour or less, the temperature inside the reaction vessel is likely to vary, making it difficult for the reaction to proceed uniformly. The pressure for the hydrothermal treatment is preferably the pressure that occurs naturally at a constant temperature, and no special pressure is required.

[0029] The stirring impeller tip speed (circumferential speed) in the hydrothermal treatment is preferably 0.4 to 4.0 m / sec, more preferably 0.5 to 3.0 m / sec. If it is less than 0.4 m / sec, the raw materials are likely to settle, making it difficult for the reaction to proceed uniformly, while if it is more than 4.0 m / sec, an expensive motor capable of high-speed stirring is required. The blade tip speed (circumferential speed) can be calculated using the following formula. V = π × D × N / 60 (Equation 3) (V: blade tip speed (m / s), π: Pi, D: blade diameter (m), N: rotation speed (rpm)) [Example]

[0030] Next, the present invention will be described with reference to examples, but the present invention is not limited to the following examples.

[0031] Example 1 86 g of sodium carbonate (Tokuyama Corporation) was added to 3,000 g of soft water and stirred until a transparent solution was obtained. 300 g of aluminum hydroxide (grade: BF083, average particle size (laser diffraction / scattering method): 10 μm, average primary particle size (measured at 30 points in a SEM image): 6.5 μm, Nippon Light Metal Co., Ltd.) was added and stirred thoroughly to prepare an aqueous suspension. This aqueous suspension was placed in a stirring autoclave (volume: 5 L) and hydrothermally treated at 180 °C for 10 hours while stirring at 1.71 m / sec (impeller diameter: 0.142 m, rotation speed: 230 rpm). The temperature was raised from room temperature (25 °C) to 180 °C over a 2-hour period. The hydrothermally treated slurry was dehydrated, washed with water, and dried to obtain a sample.

[0032] Example 2 175 g of sodium aluminate (Kanto Chemical Co., Inc.) was added to 3500 g of soft water and stirred until a transparent solution was obtained. 350 g of aluminum hydroxide (grade: BF083, average particle size (laser diffraction / scattering method): 10 μm, average primary particle size (measured at 30 points in a SEM image): 6.5 μm, Nippon Light Metal Co., Ltd.) was added and stirred thoroughly to prepare an aqueous suspension. This aqueous suspension was placed in a stirring autoclave (volume: 5 L) and hydrothermally treated at 180 °C for 8 hours while stirring at 1.49 m / sec (impeller diameter: 0.142 m, rotation speed: 200 rpm). The temperature was raised from room temperature (25 °C) to 180 °C over 2 hours. The hydrothermally treated slurry was dehydrated, washed with water, and dried to obtain a sample.

[0033] Example 3 86 g of sodium carbonate (Tokuyama Corporation) was added to 3,000 g of soft water and stirred until a transparent solution was obtained. 300 g of aluminum hydroxide (grade: B103, average particle size (laser diffraction / scattering method): 7 μm, average primary particle size (measured at 30 points in a SEM image): 4 μm, Nippon Light Metal Co., Ltd.) was added and stirred thoroughly to prepare an aqueous suspension. This aqueous suspension was placed in a stirring autoclave (volume: 5 L) and hydrothermally treated at 170 °C for 8 hours while stirring at 1.49 m / sec (impeller diameter: 0.142 m, rotation speed: 200 rpm). The temperature was raised from room temperature (25 °C) to 170 °C over 2 hours. The hydrothermally treated slurry was dehydrated, washed with water, and dried to obtain a sample.

[0034] Example 4 260 g of sodium carbonate (Tokuyama Corporation) was added to 3000 g of soft water and stirred until a transparent solution was obtained. 300 g of aluminum hydroxide (grade: BF083, average particle size (laser diffraction / scattering method): 10 μm, average primary particle size (measured at 30 points in a SEM image): 6.5 μm, Nippon Light Metal Co., Ltd.) was added and stirred thoroughly to prepare an aqueous suspension. This aqueous suspension was placed in a stirring autoclave (volume: 5 L) and hydrothermally treated at 180 °C for 6 hours while stirring at 1.49 m / sec (impeller diameter: 0.142 m, rotation speed: 200 rpm). The temperature was raised from room temperature (25 °C) to 180 °C over 2 hours. The hydrothermally treated slurry was dehydrated, washed with water, and dried to obtain a sample.

[0035] Comparative Example 1 A sample was produced in the same manner as in Example 1, except that the aluminum hydroxide was changed to aluminum hydroxide (grade name: BF013, average particle diameter (laser diffraction / scattering method): 1 μm, average value of primary particles (measured at 30 points in an SEM image): 1 μm, manufactured by Nippon Light Metal Co., Ltd.).

[0036] Comparative Example 2 A sample was produced in the same manner as in Example 2, except that the aluminum hydroxide was changed to aluminum hydroxide (grade name: BF013, average particle diameter (laser diffraction / scattering method): 1 μm, average value of primary particles (measured at 30 points in an SEM image): 1 μm, manufactured by Nippon Light Metal Co., Ltd.).

[0037] Comparative Example 3 25 g of sodium hydroxide (Kanto Chemical Industry Co., Ltd.) was added to 3000 g of soft water and stirred until a transparent solution was obtained. 300 g of aluminum hydroxide (grade: BF083, average particle size (laser diffraction / scattering method): 10 μm, average primary particle size (measured at 30 points in a SEM image): 6.5 μm, Nippon Light Metal Co., Ltd.) was added and stirred thoroughly to prepare an aqueous suspension. This aqueous suspension was placed in a stirring autoclave (volume: 5 L) and hydrothermally treated at 180 °C for 8 hours while stirring at 1.49 m / sec (impeller diameter: 0.142 m, rotation speed: 200 rpm). The temperature was raised from room temperature (25 °C) to 180 °C over 2 hours. The hydrothermally treated slurry was dehydrated, washed with water, and dried to obtain a sample.

[0038] Comparative Example 4 A sample was produced in the same manner as in Example 1, except that the aqueous suspension of sodium carbonate and aluminum hydroxide was left to stand without stirring and then subjected to hydrothermal treatment.

[0039] The following various tests were carried out on the above Examples 1 to 4 and Comparative Examples 1 to 4.

[0040] 1. Presence or absence of boehmite The crystalline phase was measured using an X-ray diffractometer (D2 Phaser, manufactured by Bluker Corporation). When no unreacted raw materials remained and boehmite crystals were observed, the result was evaluated as ◯, and when unreacted raw materials remained, the result was evaluated as ×. 2. House of cards structure The sample was attached to carbon tape, and the particle surface and shape were observed using a scanning electron microscope (JEOL Ltd. JSM-7500FA). Those in which a house-of-cards structure was observed were rated as ◯, and those in which no or almost no house-of-cards structure was observed were rated as ×. 3. Particle size (D50, D16, D84 (all by volume)) The sample was dispersed in a 0.2% aqueous solution of sodium hexametaphosphate, and the particle size distribution (volume basis) was measured using a laser diffraction / scattering particle size distribution analyzer (MT3000, manufactured by Microtrack Bell Co., Ltd.), and the values ​​of D50, D16, and D84 were read. 4. Standard deviation SD, coefficient of variation CV The standard deviation SD and coefficient of variation CV were calculated using the following formula: Standard deviation SD=(D84-D16) / 2 (Formula 1) Coefficient of variation CV = (standard deviation SD / D50) × 100 (Equation 2) 5.Oil absorption amount Using linseed oil reagent (Kanto Chemical Co., Ltd.), measurements were carried out in accordance with the refined linseed oil method of JIS K5101-13-1 (2004). The measurement procedure is as follows. (1) 2 g of sample was weighed and placed on a glass measuring plate. (2) Linseed oil was gradually added from the dropper, 4 to 5 drops at a time, and the sample was kneaded into the linseed oil with a palette knife. (3) The above procedure (2) was repeated, and the dropping was continued until lumps of linseed oil and sample were formed. (4) After that, add linseed oil drop by drop and knead thoroughly, repeating the process until the paste becomes soft and hard. (5) The oil absorption value was calculated using the following formula: Oil absorption (g / 100g) = (weight of linseed oil used up to the end point (g) / weight of sample (g)) × 100 (Equation 4) 6. Tap density 0.5 g or 1 g of sample was placed in a 10 mL measuring cylinder and dropped from a certain height at a constant speed until the volume stopped changing. The volume after filling was read and the tap density was calculated using the following formula. Tap density (g / cm 3 ) = sample weight (g) / volume after filling (cm 3 ) (Equation 5) 7.Specific surface area Using a fully automatic specific surface area measuring device (Macsorb (registered trademark) HM model-1200 manufactured by Mountec Co., Ltd.), the sample was pretreated by vacuum heating and evacuation at 150°C for 30 minutes before the BET surface area measurement, and then the sample was measured by the BET flow method (single-point method) at a temperature close to the liquid nitrogen temperature (77 K). 8.1% weight loss temperature Measurements were performed using a differential thermal and thermogravimetric simultaneous analyzer (TG-DTA 2000SA, manufactured by Bruker AXS Co., Ltd.). The temperature was increased at a rate of 30°C / min, and the temperature at which the weight loss reached 1.00% was measured, with 100°C as the reference temperature. 9. Cumulative pore volume Measurements were performed using a mercury porosimeter (manufacturer: Anton Paar, model: Poremaster 60). A measurement cell containing approximately 0.2 g of sample was placed in the instrument, and after sufficient vacuum (10 m torr), mercury was introduced. Pressure was gradually increased to approximately 410 MPa. The amount of mercury injected into the sample relative to the pressure applied to the mercury was measured. The pressure applied to the mercury was converted to pore size using the Washburn equation, and the pore size distribution was calculated using the amount of mercury injected. From this pore size distribution, the cumulative pore volumes in the ranges of 0.05 to 0.50 μm, 0.05 to 1.00 μm, and 0.05 to 2.00 μm were derived, respectively.

[0041] Table 1 shows the manufacturing methods of the Examples and Comparative Examples, and Tables 2 and 3 show the results of various tests on the Examples and Comparative Examples.

[0042] [Table 1]

[0043] [Table 2]

[0044] [Table 3]

[0045] 1 to 7 are SEM photographs of Examples 1 to 4 and Comparative Examples 1 to 3. FIG. 8 is an SEM photograph showing a cross section of the scaly boehmite aggregate of Example 4, and FIG. 9 is an SEM photograph showing a cross section of the scaly boehmite aggregate of Comparative Example 3. The lower parts of FIGS. 1 to 7 are SEM photographs that are enlarged portions of the upper parts. With reference to these SEM photographs, the following can be analyzed based on the above results.

[0046] As shown in the SEM photographs in the lower rows of each example, the scaly boehmite aggregates form a bulky house-of-cards structure. Furthermore, as shown in the SEM photographs in the upper rows of each example, the scaly boehmite aggregates have small particle size variations and are composed of particles of uniform size. From the SEM photograph of the cross section of the scaly boehmite aggregate of Example 4 in FIG. 8, it can be seen that the scaly boehmite aggregate of Example 4 forms a bulky house-of-cards structure. Furthermore, from the SEM photograph of the cross section of the scaly boehmite aggregate of Comparative Example 3 in FIG. 9, it can be seen that the scaly boehmite aggregate of Comparative Example 3 forms a dense house-of-cards structure. On the other hand, it is clear that Comparative Examples 1 and 2 are scaly boehmite particles in which scaly boehmite crystals that do not form a house-of-card structure are dispersed. Example 1 and Comparative Example 1 were produced by the same method, except for the difference in the average particle size of the raw material aluminum hydroxide. Example 1 formed a bulky card house structure, resulting in an oil absorption capacity approximately 1.8 times that of Comparative Example 1 and a higher tap density than Comparative Example 1. Comparative Example 1, which has a lower tap density than Example 1 and is prone to scattering, is less prone to scattering than Comparative Example 1 and has excellent handleability. Furthermore, the difference in the coefficient of variation CV indicates that Example 1 has smaller particle size variations than Comparative Example 1 and is a particle of uniform particle size. Furthermore, the cumulative pore volume data indicates that Example 1 is dominated by macropores with pore diameters of 0.05 to 2.00 μm, forming micro-sized aggregates. Furthermore, Example 2 and Comparative Example 2, which were produced by the same method except for the difference in the average particle size of the raw material aluminum hydroxide, can also be analyzed in a manner similar to that described above. Comparative Example 3 was produced in a manner similar to that of Example 1, except that sodium hydroxide was used instead of sodium carbonate as a raw material additive, and the resulting scaly boehmite aggregate had a dense card-house structure in which scaly boehmite crystals aggregated together, as shown in Figure 7. Because Comparative Example 3 had a dense card-house structure, the void volume was small, and the oil absorption was about 40% to 50% of that of each Example. Comparative Example 4 was produced in the same manner as in Example 1, except that the aqueous suspension was allowed to stand. In Comparative Example 4, a molded product was obtained and boehmite formation was confirmed, but other tests could not be carried out satisfactorily. The specific surface area of ​​crystallized boehmite is several m 2 / g~several tens of meters 2 The specific surface area of ​​the scaly boehmite in the examples and comparative examples is several m 2 / g, and it can be seen that the examples and comparative examples are all micro-sized boehmite with high crystallinity. The 1% weight loss temperatures of both the Examples and Comparative Examples exceed 420°C because neither the Examples nor the Comparative Examples used organic binders in their production and because the boehmite has high crystallinity.

[0047] For Example 1 and Comparative Example 3, the sample was kneaded into the following resin to the kneading limit, and the thermal conductivity on the surface of the resin composition was measured. (1) Resin type: Epoxy resin (bisphenol A type) (Product name: R140P, Manufacturer: Mitsui Chemicals, Inc., Viscosity at 25°C: 12,000-15,000 cps) (2) Preparation method: 30 g of epoxy resin was placed in a 205 mL paper cup, and the sample was gradually mixed in until the kneading limit was reached. This process was repeated using a planetary centrifugal mixer (ARE-310, manufactured by Thinky Corporation). After the sample was mixed and mixed to the kneading limit, 0.6 g of 2-ethyl-4-methylimidazole (manufactured by Wako Pure Chemical Industries, Ltd.) was added, thoroughly mixed and degassed, and then heated and cured at 120°C for 2 hours. The resulting cured product was processed into the desired shape to obtain test pieces of the resin composition. The volume filling rate of the sample at the kneading limit was calculated using the following formula. Volume filling rate of sample (vol%) = (volume of sample (cm 3 ) / (sample volume (cm 3 ) + volume of epoxy resin (cm 3 )))×100 (Equation 6) Sample volume (cm 3 ) = sample weight (g) / sample density (g / cm 3 ) (Equation 7) Epoxy resin volume (cm 3 ) = Weight of epoxy resin (g) / Density of epoxy resin (g / cm 3 ) (Equation 8) Density of boehmite: 3.0 g / cm 3 , Epoxy resin density: 1.16 g / cm 3 (3)Measurement method: Hot ray method (product name: QTM-500, manufactured by Kyoto Denshi Co., Ltd.) (4) Shape of resin composition test piece: disc with a diameter of 5 cm and a thickness of 1.5 cm The results are as follows: Example 1: Volume filling rate (30 vol%) filled to the kneading limit, thermal conductivity of the resin composition on the surface (0.89 W / (m K)) Comparative Example 3: Volume filling rate filled to the kneading limit (34 vol%), thermal conductivity of the resin composition on the surface (1.09 W / (m K)) The volume filling rate filled to the kneading limit in Example 1 is lower than that in Comparative Example 3 because the card house structure is bulky, and the thermal conductivity of the resin composition is also low because the volume filling rate filled to the kneading limit is low. Also, the volume filling rate filled to the kneading limit in Comparative Example 3 is higher than that in Example 1 because the card house structure is dense, and the thermal conductivity of the resin composition is also high because the volume filling rate filled to the kneading limit is high. In this way, whether the house-of-card structure is bulky or dense can be determined from the difference in the volume filling rate, in which the scaly boehmite aggregates are filled into the resin composition up to the kneading limit, and the difference in thermal conductivity. [Industrial Applicability]

[0048] The scaly boehmite aggregate of the present invention is suitable as a filler for resins and the like, or as a catalyst carrier.

Claims

1. The scaly boehmite aggregate has a bulky card-house structure in which scaly boehmite crystals are aggregated together, and is characterized in that the refined linseed oil absorption measured in accordance with the refined linseed oil method of JIS K5101-13-1 (2004) is 190 g / 100 g or more, and the cumulative pore volume measured by a mercury porosimeter in the range of pore diameters of 0.05 to 2.00 μm is 0.40 mL / g or more.

2. 2. The scaly boehmite aggregate according to claim 1, wherein the coefficient of variation CV calculated using the following formula is 35% or less. Standard deviation SD = (D84-D16) / 2 (Formula 1) Coefficient of variation CV=(standard deviation SD / D50)×100 (Equation 2)

3. 3. The scaly boehmite aggregate according to claim 1 or 2, characterized in that in thermogravimetric analysis, the weight loss rate at 100°C is set to 0 wt %, and the 1% weight loss temperature, at which a weight loss of 1 wt % is confirmed when heated at a temperature rising rate of 30°C / min, is 420°C or higher.

4. The method for producing the scaly boehmite aggregate according to any one of claims 1 to 3, characterized in that an aqueous suspension containing aluminum hydroxide having an average particle size (volume basis) of 4 to 20 µm as measured by a laser diffraction / scattering method and one additive selected from sodium carbonate and sodium aluminate is subjected to hydrothermal treatment while being stirred.

5. The method for producing scaly boehmite aggregates according to claim 4, characterized in that the concentration of aluminum hydroxide in water is 1 to 20 wt %, the concentration of the additive in water is 0.05 to 2.00 mol / L, and the constant temperature of the hydrothermal treatment is 150 to 250°C.

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