JP2023106702A - Scaly boehmite aggregate and manufacturing method thereof - Google Patents

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 The present invention relates to a micro-sized scaly boehmite aggregate having a bulky card house structure in which scaly boehmite crystals are aggregated together, and a method for producing the same.

Alumina monohydrate (AlOOH) boehmite is highly versatile and is used as a filler for reinforcing materials, flame retardants, luster materials, fireproof materials, thickeners, etc. It is also used as a catalyst carrier and an electrically conductive filler base material. , refractories, raw materials for high-purity alumina, raw materials for easily sinterable alumina, and raw materials for fluorescent materials. Since boehmite can be produced by controlling its shape, boehmite crystals have various shapes such as cubic, plate-like, hexagonal plate-like, disk-like, needle-like, and scale-like. Boehmite crystal aggregates can be obtained depending on the production method, and the boehmite aggregates can be used for various purposes in the same manner as boehmite particles in which boehmite crystals are dispersed.

Conventionally, there is a report on aggregates of boehmite (Non-Patent Document 1). That is, in Non-Patent Document 1, a sodium aluminate solution (Bayer's solution) and glucose as a surfactant were stirred at 70° C. for 60 minutes (aging), and the pH was adjusted to 11.0 using 1M sulfuric acid. It is disclosed that neutralization from 9 to 9.5 yields boehmite flower-like aggregates. (Abstract, page 168, right column, bottom row)

Processing and Application of Ceramics 14〔2〕(2020) 168-172

However, the boehmite flower-like aggregates disclosed in Non-Patent Document 1 have a size of about 100 nm to 200 nm (left column on page 170), a specific surface area of 293.6 to 331.5 m ² /g, and a pore size of 3.5 to 3.9 nm and a pore volume of 0.258 to 0.308 m ³ /g (Table 2 on page 171). Therefore, the flower-like aggregates of boehmite have problems of low thermal conductivity, high hygroscopicity, and a low dehydration temperature compared to boehmite with high crystallinity, resulting in a problem of usability as a flame retardant. In addition, Non-Patent Document 1 does not describe or suggest that the boehmite flower-like aggregates have a bulky card house structure.

The present invention has been made in view of the above circumstances, and aims 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. Make it an issue.

In order to solve the above-described problems, the inventors of the present invention have made intensive studies and arrived at the present invention.
That is, the invention according to claim 1 is a scale-like boehmite aggregate having a bulky card house structure in which crystals of scale-like boehmite are aggregated with each other, and is purified linseed oil according to JIS K5101-13-1 (2004). The refined linseed oil has an oil absorption of 190 g/100 g or more, measured according to the law, and an accumulated pore volume of 0.40 mL/g at a pore diameter of 0.05 to 2.00 μm, measured with a mercury porosimeter. It relates to scale-like boehmite aggregates characterized by the above.

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

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

In the invention according to claim 4, aluminum hydroxide having an average particle size (volume basis) of 4 to 20 μm as measured by a laser diffraction/scattering method, an additive of either sodium carbonate or sodium aluminate, The method for producing scale-like boehmite aggregates according to any one of claims 1 to 3, wherein the aqueous suspension containing is hydrothermally treated while stirring.

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

Since the scale-like boehmite aggregates of the present invention have a bulky card house structure, they can impart high viscosity when filled into a filling material such as a resin. In addition, since it has a bulky card house structure, it is porous and useful as a raw material for catalyst carriers and porous ceramics.

Since the scale-like boehmite aggregates of the present invention have a uniform particle size with little variation in particle size, it is possible to suppress variations in the properties of the final product due to variations in particle size. For example, in the case of filler applications, it is possible to reduce the variation in the properties of the material to be filled, such as resin, and in the case of coating applications, it is possible to reduce the variation in the properties of the coating liquid. , it is possible to prevent variations in properties due to poor sintering due to non-uniform particle sizes.

The method for producing scaly boehmite aggregates of the present invention directly synthesizes scaly boehmite aggregates without using an organic binder, so that no organic binder remains in the aggregates. The problem with general organic binders is that they do not have high weather resistance and deteriorate, and they may not be able to maintain aggregates for a long period of time. Aggregates can be manufactured.

1 is an SEM photograph of scale-like boehmite aggregates of Example 1. FIG. 4 is an SEM photograph of scale-like boehmite particles of Comparative Example 1. FIG. 4 is an SEM photograph of scale-like boehmite aggregates of Example 2. FIG. 4 is an SEM photograph of scale-like boehmite particles of Comparative Example 2. FIG. 4 is a SEM photograph of scale-like boehmite aggregates of Example 3. FIG. 4 is an SEM photograph of scale-like boehmite aggregates of Example 4. FIG. 4 is an SEM photograph of scale-like boehmite aggregates of Comparative Example 3. FIG. 4 is an SEM photograph showing a cross section of the scale-like boehmite aggregates of Example 4. FIG. 4 is an SEM photograph showing a cross section of a scale-like boehmite aggregate of Comparative Example 3. FIG.

The scale-like boehmite aggregates of the present invention have a bulky card house structure in which crystals of scale-like boehmite aggregate with each other, and reflect the volume of voids in the card house structure. The oil absorption of the refined linseed oil measured according to the linseed oil method is preferably 190 g/100 g or more, more preferably 200 g/100 g or more. The upper limit of the oil absorption of refined linseed oil may be preferably 300 g/100 g, more preferably 290 g/100 g.

Since the scaly boehmite aggregates of the present invention have a bulky card house structure and a large void volume, the oil absorption is higher than that of scaly boehmite particles with few voids in which scaly boehmite crystals are dispersed. It is also higher than scale-like boehmite aggregates having a dense card house structure in which crystals of scale-like boehmite are aggregated together.

The scale-like boehmite aggregates of the present invention preferably have a cumulative pore volume of 0.40 mL/g or more, more preferably 0.45 mL/g or more, at a pore diameter of 0.05 to 2.00 μm, as measured by a mercury porosimeter. is more preferred. The scale-like boehmite aggregates of the present invention are micro-sized aggregates that are mostly composed of macropores.

The scale-like boehmite aggregates of the present invention preferably have a coefficient of variation CV of 35% or less, more preferably 33% or less, calculated using the following formula.
Standard deviation SD = (D84-D16) / 2 (Formula 1)
Coefficient of variation CV = (standard deviation SD / D50) × 100 (Formula 2)
The scale-like boehmite aggregates of the present invention are particles with little variation in particle size, so to speak, "uniform" particles. In addition, the scale-like boehmite aggregates of the present invention are particles with less variation in particle size than scale-like boehmite particles in which crystals of scale-like boehmite are dispersed.

The scale-like boehmite constituting the scale-like boehmite aggregate of the present invention is micro-sized boehmite with a specific surface area of several m ² /g and high crystallinity.

The 1% weight loss temperature of the scale-like boehmite aggregates of the present invention is preferably 420° C. or higher. Here, the 1% weight loss temperature is the temperature at which a weight loss of 1 wt% is confirmed when the rate of weight loss at 100° C. is assumed to be 0 wt % and the temperature is heated at a rate of 30° C./min in thermogravimetric analysis. is defined as
Boehmite undergoes a dehydration reaction when heat is applied, and the crystal phase transitions to γ-alumina. When using boehmite as a flame retardant, the higher the temperature at which the dehydration reaction starts, the better, and the finer the particles of boehmite. Or, if the crystallinity is low, it tends to decrease, and the 1% weight loss temperature also decreases. Nano-sized boehmite has a 1% weight loss temperature of about 300°C and a dehydration temperature that is too low. In addition, the method for producing scale-like boehmite aggregates of the present invention, which will be described later, does not use an organic binder such as polyvinyl alcohol to form aggregates, but directly synthesizes scale-like boehmite aggregates. When an organic binder is used, the organic binder remaining in the product is decomposed and the weight is reduced during thermal analysis, resulting in a decrease in the 1% weight loss temperature. Thus, the scale-like boehmite aggregates of the present invention are micro-sized and highly crystalline, and do not use an organic binder for production, so that a 1% weight loss temperature of 420° C. or higher can be ensured.

The scale-like boehmite aggregates of the present invention preferably have a tap density of 0.16 g/cm ³ or more, more preferably 0.18 g/cm ³ or more. Since the tap density of the scaly boehmite aggregates of the present invention is higher than the tap density of the scaly boehmite particles in which the scaly boehmite crystals are dispersed, the scaly boehmite particles in which the scaly boehmite crystals are dispersed have a low tap density. While it is easy to scatter, the scale-like boehmite aggregates of the present invention are difficult to scatter and are excellent in handleability.

Next, the method for producing scale-like boehmite aggregates of the present invention will be described.
The scale-like boehmite aggregates of the present invention can be obtained by hydrothermally treating an aqueous suspension containing aluminum hydroxide as a raw material and an additive while stirring.

Aluminum hydroxide as a raw material preferably has an average particle diameter (volume basis) of 4 to 20 μm, more preferably 5 to 15 μm, as measured by a laser diffraction/scattering method. This is because if the average particle size of aluminum hydroxide is less than 4 μm, a bulky card house structure in which scaly boehmite crystals aggregate together cannot be formed. On the other hand, if it exceeds 20 μm, sedimentation is likely to occur during the reaction, and the reaction product may clog the pipes, resulting in damage to the hydrothermal treatment apparatus.
Further, the concentration of aluminum hydroxide in water is preferably 1 to 20 wt%, more preferably 2 to 17 wt%. If the content is less than 1 wt%, the amount of boehmite produced is small, which is uneconomical.

Moreover, it is preferable that the particle size of aluminum hydroxide as a raw material has high uniformity. That is, the shape of the particle size distribution of aluminum hydroxide preferably exhibits a normal distribution or a unimodal distribution close to the normal distribution. This is because the higher the uniformity of the particle size of aluminum hydroxide, the more reliably obtained is a scaly boehmite aggregate having a bulky card house structure and less variation in particle size.
Further, the raw material aluminum hydroxide preferably has an average primary particle size of 2 to 8 μm as measured by an SEM image, and is agglomerated secondary particles.
If the average value of the primary particles is less than 2 μm, it is difficult to form a card house structure in which scaly boehmite crystals aggregate with each other.

The additive is preferably sodium carbonate or sodium aluminate, but potassium carbonate can also be used. The concentration of the additive to water is preferably 0.05 to 2.00 mol/L, more preferably 0.10 to 1.00 mol/L. If it is less than 0.05 mol/L, the thickness of the scaly boehmite particles increases and the volume does not increase. This is because the

The water used for preparing the suspension may be either hard water or soft water, but soft water that is less affected by magnesium ions and calcium ions is preferred.

The constant temperature of the hydrothermal treatment is preferably 150-250°C, more preferably 160-230°C.
This is because if the temperature is lower than 150°C, the reaction from aluminum hydroxide to boehmite does not easily proceed, and if it exceeds 250°C, expensive equipment that can withstand high pressure is required.
The reaction time is preferably in the range of 3 hours to 24 hours. If it is less than 3 hours, scaly boehmite aggregates may not be obtained. Moreover, even if it exceeds 24 hours, there is no particular effect, and it is uneconomical in terms of energy.
Moreover, the rate of temperature increase to a constant temperature is preferably 100° C./hour or less. This is because if the temperature is not 100° C./hour or less, the temperature in the reaction vessel tends to vary, making it difficult to proceed with a uniform reaction.
The pressure for the hydrothermal treatment is preferably a spontaneously generated pressure at a constant temperature, and no particular pressurization is required.

The blade tip speed (peripheral speed) for stirring in the hydrothermal treatment is preferably 0.4 to 4.0 m/sec, more preferably 0.5 to 3.0 m/sec. This is because if the velocity is less than 0.4 m/sec, the raw materials tend to settle and the reaction does not progress uniformly, and if it exceeds 4.0 m/sec, an expensive motor capable of high-speed stirring is required.
The blade tip speed (peripheral speed) can be obtained by the following formula.
V = π × D × N/60 (Formula 3)
(V: blade tip speed (m/s), π: circumference ratio, D: blade diameter (m), N: rotation speed (rpm))

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

[Example 1]
Add 86 g of sodium carbonate (manufactured by Tokuyama Co., Ltd.) to 3000 g of soft water and stir and mix until a clear aqueous solution is formed. Aluminum hydroxide (grade name: BF083, average particle size (laser diffraction/scattering method): 10 μm) , Average value of primary particles (measured at 30 points from SEM image): 6.5 μm, manufactured by Nippon Light Metal Co., Ltd.) 300 g was added and thoroughly stirred 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 (blade diameter: 0.142 m, rotation speed: 230 rpm). The temperature was raised from room temperature (25°C) to 180°C in 2 hours. After the hydrothermal treatment, the slurry was dehydrated, washed with water, and dried to obtain a sample.

[Example 2]
Add 175 g of sodium aluminate (manufactured by Kanto Kagaku Co., Ltd.) to 3500 g of soft water and stir and mix until a clear aqueous solution is formed. Aluminum hydroxide (grade name: BF083, average particle size (laser diffraction/scattering method) : 10 µm, average value of primary particles (measured at 30 points from SEM image): 6.5 µm, manufactured by Nippon Light Metal Co., Ltd.) was added, and 350 g was thoroughly stirred and mixed 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 (blade diameter: 0.142 m, rotation speed: 200 rpm). The temperature was raised from room temperature (25°C) to 180°C in 2 hours. After the hydrothermal treatment, the slurry was dehydrated, washed with water, and dried to obtain a sample.

[Example 3]
Add 86 g of sodium carbonate (manufactured by Tokuyama Co., Ltd.) to 3000 g of soft water and stir and mix until a clear aqueous solution is formed. Aluminum hydroxide (grade name: B103, average particle size (laser diffraction/scattering method): 7 μm) , Average value of primary particles (measured at 30 points from SEM image): 4 µm, manufactured by Nippon Light Metal Co., Ltd.) was added and mixed well with stirring 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 (blade diameter: 0.142 m, rotation speed: 200 rpm). The temperature was raised from room temperature (25°C) to 170°C in 2 hours. After the hydrothermal treatment, the slurry was dehydrated, washed with water, and dried to obtain a sample.

[Example 4]
Add 260 g of sodium carbonate (manufactured by Tokuyama Co., Ltd.) to 3000 g of soft water and stir and mix until a clear aqueous solution is formed. , Average value of primary particles (measured at 30 points from SEM image): 6.5 μm, manufactured by Nippon Light Metal Co., Ltd.) 300 g was added and thoroughly stirred 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 (blade diameter: 0.142 m, rotation speed: 200 rpm). The temperature was raised from room temperature (25°C) to 180°C in 2 hours. After the hydrothermal treatment, the slurry was dehydrated, washed with water, and dried to obtain a sample.

[Comparative Example 1]
Aluminum hydroxide (grade name: BF013, average particle size (laser diffraction/scattering method): 1 μm, average value of primary particles (measured at 30 points from SEM image): 1 μm, manufactured by Nippon Light Metal Co., Ltd.) produced samples in the same manner as in Example 1.

[Comparative Example 2]
Aluminum hydroxide (grade name: BF013, average particle size (laser diffraction/scattering method): 1 μm, average value of primary particles (measured at 30 points from SEM image): 1 μm, manufactured by Nippon Light Metal Co., Ltd.) manufactured samples in a manner similar to that of Example 2.

[Comparative Example 3]
Add 25 g of sodium hydroxide (manufactured by Kanto Kagaku Kogyo Co., Ltd.) to 3000 g of soft water and stir and mix until a clear aqueous solution is formed. ): 10 µm, average value of primary particles (measured at 30 points from SEM image): 6.5 µm, 300 g of Nippon Light Metal Co., Ltd.) was added and thoroughly stirred 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 (blade diameter: 0.142 m, rotation speed: 200 rpm). The temperature was raised from room temperature (25°C) to 180°C in 2 hours. After the hydrothermal treatment, the slurry was dehydrated, washed with water, and dried to obtain a sample.

[Comparative Example 4]
A sample was produced in the same manner as in Example 1, except that the aqueous suspension in which sodium carbonate and aluminum hydroxide were mixed was allowed to stand without being stirred and mixed, and then hydrothermally treated.

The following various tests were performed on Examples 1 to 4 and Comparative Examples 1 to 4 described above.

1. Presence or absence of boehmite formation
The crystal phase was measured with an X-ray diffractometer (D2 Phaser, manufactured by Bluker Co.). When no unreacted starting material remained and boehmite crystals were observed, it was evaluated as ◯, and when unreacted starting material remained, it was evaluated as x.
2. Presence or Absence of Card House Structure A sample was stuck on a carbon tape, and the particle surface and shape were observed using a scanning electron microscope (JSM-7500FA, manufactured by JEOL Ltd.). A sample with a card house structure was evaluated as ◯, and a sample with no card house structure or almost no card house structure was evaluated as x.
3. Particle size (D50, D16, D84 (both based on volume))
The sample is dispersed in 0.2% sodium hexametaphosphate aqueous solution, and the particle size distribution (volume basis) is measured using a laser diffraction/scattering particle size distribution measuring device (MT3000 manufactured by Microtrack Bell Co., Ltd.), D50, D16 , the value of D84 was read.
4. Standard deviation SD, coefficient of variation CV
Standard deviation SD and coefficient of variation CV were calculated using the following formulas.
Standard deviation SD = (D84-D16)/2 (Formula 1)
Coefficient of variation CV = (standard deviation SD/D50) x 100 (Formula 2)
5. Oil Absorption Measured according to the refined linseed oil method of JIS K5101-13-1 (2004) using linseed oil (manufactured by Kanto Kagaku Co., Ltd.) as a reagent. The measurement procedure is as follows.
(1) 2 g of sample was weighed and placed on a glass measuring plate.
(2) 4 to 5 drops of linseed oil were gradually added at a time from a dropper, and the sample was kneaded into the linseed oil with a palette knife.
(3) The above operation (2) was repeated, and dropping was continued until lumps of linseed oil and the sample were formed.
(4) Thereafter, the linseed oil was dropped drop by drop, and the mixture was thoroughly kneaded.
(5) The value of oil absorption was obtained using the following formula.
Oil absorption (g/100g) = (weight of linseed oil used up to the end point (g)/weight of sample (g)) x 100 (Formula 4)
6. tap density
0.5 g or 1 g of the sample was placed in a 10 mL graduated cylinder and filled by dropping from a constant height at a constant speed until the change in volume disappeared. The value of the volume after filling was read, and the tap density value was calculated using the following formula.
Tap density (g/cm ³ ) = sample weight (g)/volume after filling (cm ³ ) (Formula 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.), pretreatment by vacuum heating and exhausting at 150 ° C for 30 minutes before measuring the BET surface area. , was measured by the BET flow method (single-point method) near liquid nitrogen temperature (77K).
8.1% Weight Loss Temperature Measured using a simultaneous differential thermal/thermogravimetric analyzer (TG-DTA 2000SA, manufactured by Bruker AXS Co., Ltd.). The temperature was raised at a rate of 30°C/min, and the temperature at which the temperature decreased by 1.00% by weight from 100°C was read.
9. Accumulated pore volume Measured using a mercury porosimeter (manufacturer: Anton Paar, model: Poremaster 60). A measuring cell containing about 0.2 g of a sample was installed in the apparatus, and after the pressure was sufficiently reduced (10 mtorr), mercury was introduced, and the pressure was gradually increased to about 410 MPa. At this time, the amount of mercury injected into the sample was measured against the pressure applied to the mercury. The pressure applied to mercury was converted to pore size using the Washburn equation, and the pore size distribution was determined using the amount of mercury injected. From this pore size distribution, 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.

Table 1 shows the production methods of Examples and Comparative Examples, and Tables 2 and 3 show the results of various tests of Examples and Comparative Examples.

1 to 7 are SEM photographs of Examples 1 to 4 and Comparative Examples 1 to 3. FIG. 8 is a SEM photograph showing a cross section of the scale-like boehmite aggregate of Example 4, and FIG. 9 is a SEM photograph showing a cross section of the scale-like boehmite aggregate of Comparative Example 3. FIG. 1 to 7 are SEM photographs in which a part of the upper part is enlarged. With reference to these SEM photographs, the following can be analyzed based on the above results.

- As shown in the lower SEM photographs of each example, the scale-like boehmite aggregates form a bulky card house structure. In addition, as shown in the upper SEM photographs of each example, the scaly boehmite aggregates are particles of uniform particle size with little variation in particle size. From the SEM photograph of the cross section of the scale-like boehmite aggregates of Example 4 in FIG. 8, it can be seen that the scale-like boehmite aggregates of Example 4 form a bulky card house structure. Further, from the SEM photograph of the cross section of the scale-like boehmite aggregate of Comparative Example 3 in FIG. 9, it can be seen that the scale-like boehmite aggregate of Comparative Example 3 forms a dense card house structure.
On the other hand, it can be seen that Comparative Examples 1 and 2 are scaly boehmite particles in which scaly boehmite crystals that do not form a card house structure are dispersed.
- Example 1 and Comparative Example 1 were produced by the same method except that the average particle size of aluminum hydroxide as a raw material was different. Since Example 1 forms a bulky card house structure, the oil absorption is approximately 1.8 times that of Comparative Example 1, and the tap density is higher than that of Comparative Example 1. Compared to Example 1, Comparative Example 1, which has a lower tap density, is more likely to scatter, whereas Example 1 is less likely to scatter compared to Comparative Example 1, and is excellent in handleability. Also, from the difference in the coefficient of variation CV, it can be seen that Example 1 has smaller variation in particle size than Comparative Example 1, and the particles have a uniform particle size. Further, from the cumulative pore volume data, it can be seen that Example 1 is mostly composed of macropores with a pore diameter of 0.05 to 2.00 μm, and is a micro-sized aggregate.
Also, Example 2 and Comparative Example 2, which were produced in the same manner except that the average particle size of aluminum hydroxide used as the raw material was different, could be analyzed in substantially the same manner as described above.
・Comparative Example 3 was produced in substantially the same manner as in Example 1, except that sodium hydroxide was used instead of sodium carbonate as the raw material additive. It is a scale-like boehmite aggregate having a dense card house structure in which the particles are aggregated together. Since Comparative Example 3 has a dense card house structure, the void volume is small, and the oil absorption is 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 although boehmite conversion was confirmed, other tests could not be performed sufficiently.
・The specific surface area of boehmite that has advanced crystallization is several m ² /g to several tens of m ² /g. The specific surface area of the scale-like boehmite of Examples and Comparative Examples is several m ² /g, and it can be seen that both of Examples and Comparative Examples are micro-sized boehmite with high crystallinity.
・The reason why the 1% weight loss temperature of both Examples and Comparative Examples exceeds 420°C is that organic binders are not used in the production of Examples and Comparative Examples, and the crystallinity of boehmite is high. caused by.

For Example 1 and Comparative Example 3, the surface thermal conductivity of the resin composition obtained by kneading the sample into the following resin up to the kneading limit was measured.
(1) Type of resin: epoxy resin (bisphenol A type)
(Product name: R140P, manufacturer: Mitsui Chemicals, Inc., viscosity at 25°C: 12,000-15,000 cps)
(2) Preparation method: Put 30 g of epoxy resin in a 205 mL paper cup, gradually mix the sample until the kneading limit is reached, and repeat the process of mixing with a rotation / revolution mixer (Thinky Co., Ltd. ARE-310). rice field. After blending and mixing the sample up to the kneading limit, 0.6 g of 2-ethyl-4-methylimidazole (manufactured by Wako Pure Chemical Industries, Ltd.) was added, thoroughly mixed and defoamed, and heat-cured at 120 ° C for 2 hours. . The resulting cured product was processed into a desired shape to obtain a test piece of the resin composition.
The volumetric filling rate of the kneading limit sample was derived from the following equation.
Sample volume filling rate (vol%) = (Sample volume (cm ³ ) / (Sample volume (cm ³ ) + Epoxy resin volume (cm ³ ))) × 100 (Formula 6)
Sample volume (cm ³ ) = sample weight (g)/sample density (g/cm ³ ) (Formula 7)
Epoxy resin volume (cm ³ ) = Epoxy resin weight (g)/Epoxy resin density (g/cm ³ ) (Formula 8)
Boehmite density: 3.0 g/cm ³ , Epoxy resin density: 1.16 g/cm ³
(3) Measurement method: hot wire method (product name: QTM-500, manufactured by Kyoto Electronics Co., Ltd.)
(4) Shape of test piece of resin composition: disc having 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 on the surface of the resin composition (0.89 W / (m K))
Comparative Example 3: Volume filling rate filled to the kneading limit (34 vol%), thermal conductivity on the surface of the resin composition (1.09 W / (m K))
The reason why the volume filling rate of Example 1 when filled to the kneading limit is lower than that of Comparative Example 3 is that the card house structure is bulky, and the volume filling rate of the resin composition when filled to the kneading limit is low. Conductivity is also lower. In addition, the reason why the volume filling rate of Comparative Example 3 when filled to the kneading limit is higher than that of Example 1 is that the card house structure is dense, and the volume filling rate when filled to the kneading limit is high. The thermal conductivity of the composition is also increased.
Thus, whether the card house structure is bulky or not can be understood from the difference in the volumetric filling rate and the thermal conductivity when the scale-like boehmite aggregates are filled into the resin composition to the kneading limit.

The scale-like boehmite aggregates of the present invention are suitable as fillers such as resins and catalyst carriers.

Claims (5)

Refined linseed oil measured according to the refined linseed oil method of JIS K5101-13-1 (2004), which is a scaly boehmite aggregate having a bulky card house structure in which scaly boehmite crystals aggregate together. An oil absorption of 190 g/100 g or more, and a cumulative pore volume of 0.40 mL/g or more at a pore diameter of 0.05 to 2.00 μm, as measured by a mercury porosimeter. aggregates. 2. The scale-like boehmite aggregates 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 (Formula 2) In thermogravimetric analysis, the 1% weight loss temperature, which is the temperature at which 1 wt% weight loss is confirmed when the weight loss rate at 100 ° C. is 0 wt% and the heating is performed at a heating rate of 30 ° C./min, is 420 ° C. or higher. The scale-like boehmite aggregate according to claim 1 or 2, 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 an additive of either sodium carbonate or sodium aluminate is stirred. 4. The method for producing scale-like boehmite aggregates according to any one of claims 1 to 3, wherein the hydrothermal treatment is performed while heating. A claim 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. Item 5. A method for producing scale-like boehmite aggregates according to item 4.