JP5670497B2 - Aluminum hydroxide powder and method for producing the same - Google Patents

Description

  The present invention relates to an aluminum hydroxide powder suitable as a raw material for a high-purity alumina molded body and a method for producing the same.

  Conventionally, high-purity alumina compacts used as single crystal materials such as high-strength ceramic tools, clock windows and sapphire for LED substrates are usually formed from high-purity alumina powder raw material with a purity of 99.99% or higher and heated to high temperatures. And is manufactured by sintering.

  Industrial production methods of high-purity alumina raw material powder include aluminum alkoxide hydrolysis (for example, Patent Document 1), ammonium alum pyrolysis (for example, Non-Patent Document 1), ammonium aluminum carbonate Thermal decomposition methods (for example, Non-Patent Document 2), aluminum underwater spark discharge methods (for example, Non-Patent Document 3), and gas phase oxidation methods (for example, Non-Patent Document 4) are known.

At the time of forming the alumina, when forming using only the alumina raw material powder and water, the formability and sinterability are insufficient, and therefore, the alumina raw material powder is usually formed by blending a binder. However, when a binder is added to the alumina raw material powder, there is a problem that the purity of the obtained alumina sintered body is lowered.
Therefore, an alumina powder or an alumina precursor powder that can produce a sintered compact without using any binder is required.

Patent Document 2 discloses a method for obtaining a high-purity alumina sintered granule using, as a raw material, aluminum hydroxide obtained by the Bayer method as an alumina precursor powder. In this method, first, a calcined alumina obtained by calcining aluminum hydroxide at 1250 ° C. or higher is pulverized, granulated by adding water, and further calcined to produce an alumina calcined granule.
However, in this method, since it is necessary to pulverize after calcining aluminum hydroxide to obtain calcined alumina once, the number of steps is increased, and the particle diameter of the calcined alumina particles after pulverization needs to be in a specific range. For example, it was not an industrially suitable production method.

  On the other hand, when obtaining an alumina compact directly from aluminum hydroxide, it is advantageous to form or granulate the aluminum hydroxide powder into a predetermined shape to obtain a molded product, followed by firing, but it was obtained by a conventional manufacturing method. With aluminum hydroxide powder, it is difficult to form or granulate with water alone as described above, and a binder is essential to obtain an aluminum hydroxide molded product having a predetermined shape. Therefore, in this method, there is a problem that impurities due to the binder are mixed and the purity of alumina obtained by firing the aluminum hydroxide molded product is lowered.

JP-A-8-301616 JP 54-16397 A

Kazama Junichi, Ceramics, 17 (9), 764 (1982) Shuzo Kato, Fine Ceramics, 4, 100 (1983). Wataru Ishibashi, Tetsuya Araki, Victory Kishimoto, Haruo Kuno, Ceramics, 6 (6), 461 (1971) Akio Kato, Sanae Kawazoe, Isao Mochida, Materials, 21, 540 (1972).

  Under such circumstances, the present invention is to provide an aluminum hydroxide powder that can be easily formed or granulated by adding only water without using a binder. The aluminum hydroxide here includes alumina monohydrate such as boehmite and pseudoboehmite in addition to alumina trihydrate such as gibbsite and bayerite.

  As a result of intensive studies to solve the above problems, the present inventor has found that aluminum hydroxide powder having specific physical properties is excellent in shape retention even when only water is added, without using a binder, The present invention has been reached.

That is, the present invention relates to the following inventions.
<1> Aluminum hydroxide powder having a cumulative pore volume V measured by a mercury intrusion method in a range where the pore radius R is 0.01 μm or more and 1 μm or less is 1.0 mL / g or more.
<2> In a pore distribution curve measured by a mercury intrusion method and represented by a pore radius R and a logarithmic differential pore volume (dV / dlogR),
The aluminum hydroxide powder according to <1>, wherein dV / dlogR exceeds 0.6 mL / g in all ranges where R is 0.01 μm or more and 1 μm or less.
<3> The light bulk density is 0.10 g / mL or more and 0.25 g / mL or less, and the heavy bulk density is 0.15 g / mL or more and 0.30 g / mL or less, according to <1> or <2> above. Aluminum hydroxide powder.
<4> The water according to any one of <1> to <3>, wherein the contents of Si, Na, Ca, Fe, Cu, and Mg are each 10 ppm by weight or less when converted to impurities in alumina. Aluminum oxide powder.
<5> A method for producing the aluminum hydroxide powder according to any one of <1> to <4>,
Add an aqueous alcohol solution with a water concentration of 5 wt% to 30 wt% to a solution containing aluminum alkoxide so that the water / aluminum alkoxide molar ratio is in the range of 1.5 to 2.0. A first hydrolysis step for hydrolysis,
After the alcohol is separated and recovered from the first hydrolyzed mixed solution, the water or the aqueous alcohol solution has a water / aluminum alkoxide molar ratio in the range of 1.0 or more and less than 6.3 , and the slurry after hydrolysis. A second hydrolysis step of adding and hydrolyzing so that the water concentration in the mixture is less than 10% by weight;
Removing water and alcohol from the mixture after the second hydrolysis to recover aluminum hydroxide powder;
The manufacturing method of the aluminum hydroxide powder containing this.
<6> The method for producing an aluminum hydroxide powder according to <5>, wherein the aluminum alkoxide is aluminum isopropoxide.
<7> The method for producing an aluminum hydroxide powder according to <5> or <6>, wherein the alcohol is isopropyl alcohol.

  ADVANTAGE OF THE INVENTION According to this invention, the aluminum hydroxide powder which can be shape | molded and granulated only with water can be provided, without adding a binder. The alumina molded body obtained by firing or molding the aluminum hydroxide powder is excellent in purity.

2 is an X-ray diffraction pattern of aluminum hydroxide powder of Experimental Example 1. FIG. It is a pore distribution curve of the aluminum hydroxide powder of Experimental Examples 1-5.

  Hereinafter, the present invention will be described in detail.

  The aluminum hydroxide powder of the present invention has a cumulative pore volume V of 1.0 mL / g or more, preferably 1.5 mL, measured in a mercury intrusion method and having a pore radius R in the range of 0.01 μm to 1 μm. / G or more. The cumulative pore volume V is 10 mL / g or less, preferably 3.5 mL / g or less.

  As described above, the aluminum hydroxide powder of the present invention is characterized in that the cumulative pore volume V in the range of the pore radius R in the above range satisfies the above condition in the measurement by the mercury intrusion method. Even when only water is added, the shape retention is good and molding and granulation are easy. Therefore, the alumina molded body obtained by firing the molded body and granulated body of the aluminum hydroxide powder can avoid mixing of impurities derived from the binder, so that high purity can be maintained.

  In the mercury intrusion method, a pressure is applied to allow mercury to enter the pores of the powder sample, a mercury intrusion curve representing the relationship between the pressure applied to the mercury and the amount of mercury intrusion is obtained, and based on the mercury intrusion curve. , Pore distribution curve, pore volume, specific surface area and the like. In addition, the measurement by a mercury intrusion method can be performed with a mercury porosimeter.

  The reason why the aluminum hydroxide powder of the present invention having such a special pore structure has high shape retention by adding only water is not completely clear at this stage, but water is present in pores of various sizes. By being taken in, it is estimated that the shape retention is good.

  Moreover, the aluminum hydroxide powder of the present invention has a pore distribution curve measured by mercury porosimetry and expressed as a pore radius R and a logarithmic differential pore volume (dV / dlogR), and R is 0.01 μm. In the entire range of 1 μm or less, dV / dlogR is preferably more than 0.6 mL / g. Moreover, it is preferable that dV / dlogR is less than 2.0 mL / g in all the ranges where R is 0.01 μm or more and 1 μm or less.

Here, the pore distribution curve measured by the mercury intrusion method in the present invention is also called a logarithmic differential pore volume distribution curve, and the size of the pore radius of the sample and the total pore volume at each pore radius More specifically, the amount of mercury intrusion at each pressure P obtained by measuring the pore distribution by the mercury intrusion method is calculated based on the Washburn equation shown below. This is obtained by plotting the radius (R [μm]) on the horizontal axis and the mercury intrusion amount (dV / dlogR [mL / g]) at each pressure P on the vertical axis.
Washburn formula; pore radius R (m) = − 2γ cos θ / P
P: Pressure (Pa)
γ: surface tension of mercury (482 × 10 ⁻³ N / m)
θ: Contact angle of mercury (140 deg)

Furthermore, the aluminum hydroxide powder of the present invention preferably has a light bulk density of 0.10 to 0.25 g / mL, more preferably 0.14 to 0.18 g / mL.
Further, the heavy bulk density is preferably 0.15 to 0.30 g / mL, and more preferably 0.17 to 0.22 g / mL.

  Here, "light bulk density" refers to the mass of a sample collected by allowing a sample (aluminum hydroxide powder) to fall freely into a container (cylinder) with a known volume that prevents vibration and collects. The density is calculated by dividing the mass by the equivalent volume of water, and can be determined by the method described in JIS R 9301-2-3. The “heavy bulk density” is a density calculated from the volume of the compressed sample after measuring the light bulk density, dropping the cylinder containing the sample 100 times from a predetermined height, and compressing the sample. It is.

Further, in the aluminum hydroxide powder of the present invention, the content of Si, Na, Ca, Fe, Cu and Mg when converted to impurities in alumina is preferably 10 ppm by weight or less, and 5 wt. More preferably, it is ppm or less. In addition, content of these elements can be measured using a solid-state emission analysis method.
When such aluminum hydroxide powder is used as a raw material, not only the impurities derived from the binder but also the amount of impurities derived from the aluminum hydroxide powder is reduced, and an alumina molded body with higher purity can be obtained.

  The aluminum hydroxide powder of the present invention can be easily formed by mixing with water. The weight ratio of water to aluminum hydroxide powder (water / aluminum hydroxide powder) is determined within the range excellent in moldability, and is usually 1.3 to 2.3, preferably 1.4 to 2.0. .

The aluminum hydroxide powder of the present invention having the physical properties as described above is obtained by using a known baking apparatus such as a rotary kiln, instantaneous calcining furnace, filling type baking furnace, fluid type baking furnace, tunnel furnace, vacuum baking furnace, shuttle furnace, etc. By firing at about 700 ° C. to about 1100 ° C., γ, δ, θ type transition alumina is obtained.
Furthermore, when this aluminum hydroxide powder is molded and fired at about 1100 ° C. to about 1400 ° C., an α-alumina molded body is obtained. Such an α-alumina molded body has a low impurity concentration, and thus is suitable for uses such as a single crystal material such as a clock window and a sapphire for an LED substrate.

  Although the manufacturing method of the aluminum hydroxide powder of the present invention is not particularly limited, it is preferable to employ the following manufacturing method because the aluminum hydroxide powder having the above physical properties can be manufactured with good reproducibility.

In the method for producing aluminum hydroxide powder of the present invention, an aqueous alcohol solution having a water concentration of 5 wt% to 30 wt% is added to a solution containing aluminum alkoxide, and the water / aluminum alkoxide molar ratio is 1.5. After the first hydrolysis step of adding and hydrolyzing so as to be in the range of 2.0 or less and separating and recovering alcohol from the mixed solution after the first hydrolysis, water or an aqueous alcohol solution is added to water / Second hydrolysis in which the aluminum alkoxide molar ratio is in the range of 1.0 or more and less than 6.3 , and is hydrolyzed by adding so that the water concentration in the slurry after hydrolysis is less than 10% by weight. Process,
Removing water and alcohol from the mixed solution after the second hydrolysis, and recovering the aluminum hydroxide powder.

  The production method of the present invention is characterized in that the hydrolysis of aluminum alkoxide is carried out in two stages with the water / aluminum alkoxide molar ratio controlled within a certain range. Thus, the aluminum hydroxide powder of the present invention having the above physical properties can be obtained.

  As the aluminum alkoxide used as a raw material, aluminum ethoxide, aluminum n-propoxide, aluminum isopropoxide, aluminum n-butoxide, aluminum sec-butoxide, aluminum tert-butoxide, and the like can be used. Among these, aluminum isopropoxide is preferable.

  Further, an aluminum alkoxide derivative obtained by chemically modifying the above aluminum alkoxide or a mixture of the derivative and aluminum alkoxide may be used as long as the physical properties of the obtained aluminum hydroxide powder are not impaired. .

By using an aqueous alcohol solution for the hydrolysis, the hydrolysis treatment on the aluminum alkoxide can be gradually progressed, and the gradual hydrolysis can be performed without causing a rapid exothermic reaction.
As alcohol used by the manufacturing method of this invention, C1-C8, Preferably C1-C4 monohydric alcohol is mentioned. Specific examples include alcohols represented by the following formula (i). Among these, isopropyl alcohol is particularly preferable.
R ₁ OH (i)
Here, R ₁ is a methyl group, ethyl group, normal propyl group, isopropyl group, normal butyl group, isobutyl group, neobutyl group, normal pentyl group, isopentyl group, neopentyl group, normal hexyl group, isohexyl group, neohexyl group, A normal heptyl group, an isoheptyl group, a neoheptyl group, a normal octyl group, an isooctyl group, and a neooctyl group, one selected from the group consisting of a methyl group having 1 to 4 carbon atoms, an ethyl group, a normal propyl group, and isopropyl Group, normal butyl group, isobutyl group and neobutyl group, more preferably isopropyl group.

  In addition, in the hydrolysis reaction, surfactants such as surface charge regulators such as acids and bases, dispersants, and emulsifiers can be added as long as the physical properties of the resulting aluminum hydroxide powder are not impaired.

  Various physical properties such as the degree of completion of the hydrolysis reaction and the crystal form of aluminum hydroxide in the resulting powder depend on the molar ratio of aluminum alkoxide to water, and the type and amount added when a chemical modifier is included. As described above, the production method of the present invention is characterized in that the hydrolysis is performed in two stages. In the first hydrolysis step, the ratio of aluminum alkoxide and water is limited to perform hydrolysis using an alcohol aqueous solution. The aluminum hydroxide powder of the present invention can be generated by partially stopping the decomposition reaction and further promoting the hydrolysis reaction in the second hydrolysis step.

One of the features of the production method of the present invention is that an aqueous alcohol solution is added instead of water in the first hydrolysis step.
The water concentration in the aqueous alcohol solution to be added is 5 to 30% by weight, preferably 5 to 20% by weight, more preferably 5 to 10% by weight.
If the water concentration in the aqueous alcohol solution is less than 5% by weight, hydrolysis becomes insufficient, and if it exceeds 30% by weight, the reaction proceeds before it can be sufficiently mixed with aluminum alkoxide, resulting in uneven hydrolysis. There is a problem that happens.

In the first hydrolysis step, the molar ratio of aluminum alkoxide to water [water / aluminum alkoxide] is 1.5 to 2.0, preferably 1.6 to 1.8.
If the molar ratio of aluminum alkoxide to water in the first hydrolysis step is out of the above range, the hydrolysis reaction of aluminum alkoxide is incomplete or proceeds too much before the second hydrolysis step. Since the hydrolysis proceeds too much, an aluminum hydroxide powder having the desired physical properties cannot be obtained.

The solution containing aluminum alkoxide as a raw material may be only aluminum alkoxide, but may contain alcohol for the purpose of improving miscibility with the aqueous alcohol solution to be added. As alcohol, the same thing as the alcohol aqueous solution to add is preferable.
The molar ratio of alcohol to aluminum alkoxide [alcohol / aluminum alkoxide] in the solution containing aluminum alkoxide in the case of containing alcohol is within a range that does not adversely affect the hydrolysis reaction in the first hydrolysis step. If there is no particular limitation, it is usually 0 to 1.5.

  The hydrolysis reaction temperature in the first hydrolysis step is not generally limited because the solubility of the aluminum alkoxide in the alcohol differs depending on the type of the aluminum alkoxide and the alcohol used. The temperature is below the boiling point.

Further, in the second hydrolysis step, after alcohol is separated and recovered from the mixed solution after the first hydrolysis, water having a water / aluminum alkoxide molar ratio of 1.0 or more and less than 6.3 is further added. To hydrolyze. The water / aluminum alkoxide molar ratio here is the molar ratio of the water added in the second hydrolysis step and the aluminum alkoxide charged in the first hydrolysis step.
By performing the hydrolysis after separating and recovering the alcohol from the mixed solution after the first hydrolysis, aluminum hydroxide having the desired physical properties is generated.
In addition, you may add the water added as alcohol aqueous solution. In this case, the concentration of the aqueous alcohol solution is not particularly limited as long as the alcohol contained does not adversely affect the hydrolysis reaction in the second hydrolysis step, and is usually 5 to 100% by weight as the water concentration. .

  In the production method of the present invention, the concentration of water contained in the slurry after the completion of the second hydrolysis step is less than 10% by weight, where the total amount of the slurry is 100% by weight.

The method for recovering or removing the alcohol or the aqueous alcohol solution after the first hydrolysis and the second hydrolysis is not particularly limited. For example, the product after hydrolysis is passed through a column packed with an ion exchange resin. And a method of evaporating the solvent by heating the product.
Moreover, what is necessary is just to collect | recover the amount of alcohol separation and collection after a 1st hydrolysis suitably.

  The hydrolysis reaction temperature in the second hydrolysis step is not generally limited because the solubility of the aluminum alkoxide in the alcohol varies depending on the type of the aluminum alkoxide and the alcohol used. The temperature is below the boiling point.

  The mixed solution containing aluminum hydroxide after completion of the second hydrolysis reaction may be subjected to aging treatment. The aging treatment may be carried out by standing at normal temperature to hydrolysis temperature for 30 minutes or longer, usually 1 hour to 1 day.

  Water and alcohol (unreacted alkoxide, if included) are removed from the mixed solution containing the aluminum hydroxide powder produced after the second hydrolysis step, and the aluminum hydroxide powder is recovered. The mixed liquid can obtain aluminum hydroxide as a powder by conventional methods such as filtration and drying.

EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to a following example, unless the summary is changed.
The sample physical properties were evaluated as follows.

(1) Pore volume / pore radius R / pore distribution curve A sample to be measured was dried at 120 ° C. for 4 hours in a dryer, and the weight after drying was precisely weighed to obtain the sample weight. The sample after drying was set in a cell of a pore volume measuring device ("Autopore III9420" manufactured by MICROMERITICS), the inside of the cell system was reduced to 50 µmHg or less, filled with mercury in the system, Pressure was applied stepwise from 007 MPa to 414 MPa, and the mercury intrusion amount at each pressure was measured with a mercury intrusion waiting time of 10 seconds.
The cumulative pore volume (mL / g) was determined by dividing the total mercury intrusion amount (mL) when the pressure was applied from 0.007 MPa to 414 MPa by the sample weight (g).
For the pore radius R (μm), the pore radius R (μm) at each pressure P was calculated from the mercury intrusion amount at each pressure P based on the above-mentioned Washburn equation. Furthermore, the horizontal axis represents the pore radius (R [μm]) at each pressure P calculated based on the Washburn equation, and the vertical axis represents the mercury intrusion amount (dV / dlogR [mL / g]) at each pressure P. The pore distribution curve was obtained by plotting the measurement results.

(2) Bulk density The light bulk density and heavy bulk density were measured by the following methods.
“Lightweight bulk density”
Put a sample of 9 to 10 mL into a 10 mL graduated cylinder, measure the weight (g) of the sample, put the lid on the graduated cylinder, turn it upside down, return it to its original position, and gently drop the sample volume ( mL). Invert and return 3 times to determine the average volume (mL). The value of sample weight ÷ sample average volume is defined as light bulk density (mL / g).
"Heavy bulk density"
After measuring the light bulk density, the graduated cylinder containing the sample is naturally dropped 100 times onto a hard rubber disc from a height of 3 cm, and then the volume (mL) of the sample is measured. The value of sample weight ÷ sample volume is defined as heavy bulk density (mL / g).

(3) Composition analysis (impurity measurement)
The sample was calcined at 1100 ° C. for about 1 hour, mixed with Ultra Carbon powder, ground with acrylic spheres, and the mixed sample was measured by solid-state emission spectrometry (using THERMO Jarrel Ash CID-DCA AURORA). The contents of Si, Na, Ca, Fe, Cu and Mg were determined.

(4) Powder X-ray diffraction measurement RINT-2200 manufactured by Rigaku Corporation was used for the powder X-ray diffraction measurement of the sample. A CuKα radiation source was used as the X-ray radiation source. The sample was filled in a dedicated holder and performed in a diffraction angle range of 2θ = 20 to 70 ° to obtain a powder X-ray diffraction pattern.

1. Example 1 of production of aluminum hydroxide powder
An aqueous alcohol solution of 15.0 parts by weight of water and 165.7 parts by weight of isopropyl alcohol was added to a mixed solution of 100.0 parts by weight of aluminum isopropoxide and 11.1 parts by weight of isopropyl alcohol to cause hydrolysis (water / (Aluminum alkoxide molar ratio = 1.7, water concentration in alcohol aqueous solution 8.3% by weight).
Subsequently, 99.3 parts by weight of isopropyl alcohol was separated and recovered by distillation, and further hydrolyzed by adding an aqueous alcohol solution of 24.9 parts by weight of water and 64.2 parts by weight of isopropyl alcohol (water / aluminum alkoxide mole). Ratio = 2.8). The water concentration in the slurry after completion of the hydrolysis step was 7.8% by weight.
Water and isopropyl alcohol in the suspension containing the obtained aluminum hydroxide, water and isopropyl alcohol were removed to obtain aluminum hydroxide powder of Experimental Example 1. From the powder X-ray diffraction pattern shown in FIG. 1, no crystal phase other than aluminum hydroxide was confirmed.

Experimental example 2
The aluminum hydroxide powder of Experimental Example 2 was obtained in the same manner as in Experimental Example 1, except that the amount of water during the second hydrolysis was 12.5 parts by weight (water / aluminum alkoxide molar ratio = 1.4). . In addition, the water concentration in the slurry after completion | finish of a hydrolysis process was 3.6 weight%. When the evaluation by the X-ray diffraction method was performed, no crystal phase other than aluminum hydroxide was confirmed.

Experimental example 3 (reference example)
The aluminum hydroxide powder of Experimental Example 3 was obtained in the same manner as in Experimental Example 1, except that the amount of water during the second hydrolysis was 55.5 parts by weight (water / aluminum alkoxide molar ratio = 6.3). . In addition, the water concentration in the slurry after completion | finish of a hydrolysis process was 16.9 weight%. When the evaluation by the X-ray diffraction method was performed, no crystal phase other than aluminum hydroxide was confirmed.

Experimental example 4 (reference example)
An aqueous alcohol solution of 15.0 parts by weight of water and 173.0 parts by weight of isopropyl alcohol was added to a mixed solution of 100.0 parts by weight of aluminum isopropoxide and 50.0 parts by weight of isopropyl alcohol to cause hydrolysis (water / Aluminum alkoxide molar ratio = 1.7, water concentration in alcohol aqueous solution 8.0 wt%).
Subsequently, 138.2 parts by weight of isopropyl alcohol was separated and recovered by distillation, and further hydrolyzed by adding an aqueous alcohol solution of 55.5 parts by weight of water and 41.7 parts by weight of isopropyl alcohol (water / aluminum alkoxide mole). Ratio = 6.3). In addition, the water concentration in the slurry after completion | finish of a hydrolysis process was 17.7 weight%.
Water and isopropyl alcohol in the suspension containing the obtained aluminum hydroxide, water and isopropyl alcohol were removed to obtain aluminum hydroxide powder of Experimental Example 4. When the evaluation by the X-ray diffraction method was performed, no crystal phase other than aluminum hydroxide was confirmed.

Experimental Example 5 (Comparative Example)
The same method as in Experimental Example 4 except that the amount of water during the second hydrolysis was 73.2 parts by weight (water / aluminum alkoxide molar ratio = 8.3) and the amount of isopropyl alcohol was 55.1 parts by weight. The aluminum hydroxide powder of Experimental Example 5 was obtained. In addition, the water concentration in the slurry after completion | finish of a hydrolysis process was 21.9 weight%. When the evaluation by the X-ray diffraction method was performed, no crystal phase other than aluminum hydroxide was confirmed.

2. Evaluation (cumulative pore volume)
The cumulative pore volume V ′ in the entire measurement range of Experimental Example 1 was 3.29 mL / g, and the cumulative pore volume V in the range of pore radius R: 0.01 to 1 μm was 1.77 mL / g.
The cumulative pore volume V ′ in the entire measurement range of Experimental Example 2 was 4.08 mL / g, and the cumulative pore volume V in the range of pore radius R: 0.01 to 1 μm was 2.12 mL / g.
The cumulative pore volume V ′ in the entire measurement range of Experimental Example 3 was 2.32 mL / g, and the cumulative pore volume V in the range of pore radius R: 0.01 to 1 μm was 0.86 mL / g. It was.
The cumulative pore volume V ′ in the entire measurement range of Experimental Example 4 is 2.41 mL / g, and the cumulative pore volume V in the range of the pore radius R: 0.01 to 1 μm is 0.64 mL / g. It was.
The cumulative pore volume V ′ in the entire measurement range of Experimental Example 5 was 0.99 mL / g, and the cumulative pore volume V in the range of pore radius R: 0.01 to 1 μm was 0.22 mL / g. It was.

(Pore distribution curve)
FIG. 2 shows pore distribution curves of the aluminum hydroxide powders of Experimental Examples 1 to 5.
In the pore distribution curves of Experimental Examples 3 to 5, a peak protruding near the pore radius R: 5 to 7 μm in Experimental Examples 3 and 4 and the cumulative pore radius R: near 0.004 μm in Experimental Example 5 was confirmed. It can be seen that dV / dlogR does not exceed 0.6 mL / g in the range of R: 0.01 to 1 μm.
On the other hand, in the pore distribution curves of Experimental Example 1 and Experimental Example 2, pores exist in regions other than the protruding peak confirmed in Experimental Examples 3 to 5, and the pore radius R is 0.01 to 1 μm. In all ranges, dV / dlogR exceeded 0.6 mL / g.

(Bulk density)
The light bulk density of the aluminum hydroxide powder of Experimental Example 1 was 0.14 g / mL, and the heavy bulk density was 0.17 g / mL.
The light bulk density of the aluminum hydroxide powder of Experimental Example 2 was 0.13 g / mL, and the heavy bulk density was 0.15 g / mL.
The light bulk density of Experimental Example 3 was 0.24 g / mL, and the heavy bulk density was 0.30 g / mL.
The light bulk density of Experimental Example 4 was 0.27 g / mL, and the heavy bulk density was 0.35 g / mL.
The light bulk density of Experimental Example 5 was 0.58 g / mL, and the heavy bulk density was 0.76 g / mL.

(Evaluation of impurity concentration)
As a result of measuring the impurity concentration of the aluminum hydroxide powder of Experimental Example 1, it was Si = 3 ppm, Na <5 ppm, Ca <1 ppm, Fe = 4 ppm, Cu <1 ppm, Mg <1 ppm in terms of alumina.

(Evaluation of formability)
The aluminum hydroxide powder of Example 1 and water were mixed at a weight ratio of 1: 1.6 and extruded (using Miyazaki Tekko's MP-100-1 model), φ4 mm x 4 mmL cylindrical molding A body was obtained, and when this molded body was dried and fired, an alumina molded body of φ2 mm × 2 mmL was obtained.
On the other hand, when the aluminum hydroxide powder of Experimental Example 5 and water were mixed at a weight ratio of 1: 1.6, it became a paste and could not be molded. Furthermore, when the aluminum hydroxide powder of Example 5 and water were mixed at a ratio of 1: 1.4 and extrusion molded, a cylindrical molded body of φ4 mm × 4 mmL was obtained, but cracking occurred during drying. .

  The aluminum hydroxide powder of the present invention can be molded or granulated only with water without adding a binder.

Claims (7)

  An aluminum hydroxide powder having a cumulative pore volume V measured by a mercury intrusion method in a range of a pore radius R of 0.01 μm or more and 1 μm or less of 1.0 mL / g or more. In the pore distribution curve when expressed by pore radius R and logarithmic differential pore volume (dV / dlogR) measured by mercury porosimetry,
The aluminum hydroxide powder according to claim 1, wherein dV / dlogR exceeds 0.6 mL / g in the entire range of R from 0.01 µm to 1 µm.   The aluminum hydroxide powder according to claim 1 or 2, wherein the light bulk density is 0.10 g / mL or more and 0.25 g / mL or less, and the heavy bulk density is 0.15 g / mL or more and 0.30 g / mL or less.   The aluminum hydroxide powder according to any one of claims 1 to 3, wherein the contents of Si, Na, Ca, Fe, Cu, and Mg are each 10 ppm by weight or less when converted to impurities in alumina. A method for producing the aluminum hydroxide powder according to any one of claims 1 to 4,
Add an aqueous alcohol solution with a water concentration of 5 wt% to 30 wt% to a solution containing aluminum alkoxide so that the water / aluminum alkoxide molar ratio is in the range of 1.5 to 2.0. A first hydrolysis step for hydrolysis,
After the alcohol is separated and recovered from the first hydrolyzed mixed solution, the water or the aqueous alcohol solution has a water / aluminum alkoxide molar ratio in the range of 1.0 or more and less than 6.3 , and the slurry after hydrolysis. A second hydrolysis step of adding and hydrolyzing so that the water concentration in the mixture is less than 10% by weight;
Removing water and alcohol from the mixture after the second hydrolysis to recover aluminum hydroxide powder;
The manufacturing method of the aluminum hydroxide powder characterized by including.   6. The method for producing aluminum hydroxide powder according to claim 5, wherein the aluminum alkoxide is aluminum isopropoxide.   The method for producing an aluminum hydroxide powder according to claim 5 or 6, wherein the alcohol is isopropyl alcohol.