JP4290404B2 - Pseudo boehmite humidity control material and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a pseudo boehmite humidity control material and a method for producing the same.
[0002]
[Prior art]
In recent years, there has been a problem that indoors become highly humid due to high heat insulation and high airtightness of houses. In order to solve this problem, humidity control materials having moisture absorption / release properties have been used as building materials, and various humidity control materials have been developed. For example, Patent Document 1 listed below discloses that a humidity control material having good moisture absorption / release performance can be obtained by heat-treating aluminum hydroxide powder in a reduced pressure atmosphere. In Patent Document 2, an acid or alkali aqueous solution is added to a metal salt aqueous solution, or an aqueous solution containing S ² -ion is added to precipitate amorphous particles of metal hydroxide or metal sulfide. It is disclosed that a porous oxide having moisture absorption / release performance can be obtained by drying or heat treatment.
[0003]
[Patent Document 1]
JP 11-11939 A (Claims)
[Patent Document 2]
JP 2000-189744 A (Claims)
[0004]
[Problems to be solved by the invention]
In the conventional method for producing a humidity control material as described above, a sufficient moisture absorption and desorption capability cannot be obtained unless heat treatment is performed at a high temperature. Therefore, a high temperature heat treatment must be performed in the production process, which increases the cost. There was a problem.
Accordingly, an object of the present invention is to provide a humidity control material that does not have such a problem and is excellent in moisture absorption and desorption characteristics.
Furthermore, an object of the present invention is to provide a method capable of producing a humidity conditioning material having excellent moisture absorption and desorption characteristics at a low cost without performing a high-temperature heat treatment that is essential for conventional humidity conditioning materials. .
[0005]
[Means for Solving the Problems]
In order to achieve the object, according to the present invention, a product obtained by neutralization reaction between an aqueous alkali aluminate solution and an aqueous aluminum salt solution (acidic aluminum) is dried at a drying temperature of 20 to 150 ° C. is the, Ri Do from pseudo-boehmite powder pore radius of 30nm or less, the water vapor moisture absorption of 45% or more in the range of RH relative humidity 0% to 90%, water vapor desorption amount in the range of RH 5 to 90% relative humidity Pseudoboehmite humidity control material having moisture absorption / release characteristics of 40% or more, and having a moisture absorption / release characteristic in which the rapid rise of the water vapor adsorption isotherm is in the range of 40 to 90% RH but Ru is provided.
Furthermore, according to the present invention, there is also provided a method for producing such a pseudo-boehmite humidity-controlling material, in which an alkali aluminate aqueous solution and an aluminum salt aqueous solution (acidic aluminum) are subjected to a neutralization reaction at pH 7 to 10 to obtain the resulting product by drying objects at a drying temperature 20 to 150 ° C., it is characterized by obtaining a pseudoboehmite humidity material as described above.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
The present invention provides a humidity control material using pseudo boehmite that has never been used as a humidity control material.
That is, the present inventors have obtained a product obtained by neutralizing an alkali aluminate aqueous solution and an aluminum salt aqueous solution (acidic aluminum) at a pH of 7 to 10, which is pseudoboehmite. A porous powder having a pore radius of 30 nm or less, preferably 10 nm or less, becomes a humidity-controlling material powder having excellent moisture absorption and desorption characteristics, and, in terms of production, high temperature that is indispensable for conventional humidity-controlling materials Since it is not necessary to perform heat treatment, it has been found that production at a low cost is possible, and the present invention has been completed.
[0007]
Pseudoboehmite powder of the present invention can be produced by the neutralization reaction with both both an alkaline aqueous solution and an acidic aqueous solution containing aluminum ions, A Rumin alkali aqueous solution and aqueous aluminum salt solution (acidic aluminum). Any alkali aluminate such as sodium aluminate or potassium aluminate can be used as the alkali aluminate. Of these, sodium aluminate is preferred because it is readily available and inexpensive. Alkali aluminates may be used alone or in combination of two or more. As the aluminum salt, various arbitrary aluminum salts such as aluminum sulfate, aluminum chloride, and aluminum nitrate can be used. Of these, aluminum sulfate and aluminum chloride are preferable because they are inexpensive. The aluminum salt may also be used alone or in combination of two or more. In addition, use waste such as sludge (sludge) containing aluminum hydroxide generated from the alkali etching process and water washing process in aluminum or aluminum alloy alumite treatment, and acidic aluminum sludge containing aluminum sulfate etc. generated from the anodizing process. This makes it possible to produce pseudo boehmite powder at a lower cost.
[0008]
The neutralization reaction can be performed either by mixing both the aluminum salt solution and the alkali aluminate solution or by pouring the other into one of the two methods. There is a change in the product. Therefore, in order to always produce a constant-quality pseudoboehmite, it is desirable to add both an aluminum salt solution and an alkali aluminate solution at the same time, and to maintain a constant pH during the formation of a precipitate by neutralization. It is desirable to do.
[0009]
At the time of precipitation formation, it is necessary to adjust so that the neutralization reaction proceeds within the range of pH 7 to 10, preferably 7.5 to 9. When the pH of the reaction solution is less than 7, amorphous aluminum hydroxide is formed, which does not provide moisture absorption and desorption characteristics unless heat treatment is performed at a high temperature. There is no solid. On the other hand, when the pH exceeds 10, pseudo boehmite is generated, but the precipitate is dissolved in the reaction solution, so that there is a problem that the yield is deteriorated.
[0010]
The temperature of the neutralized solution in the reaction vessel (reaction temperature) is desirably adjusted to normal temperature (20 ° C.) to 100 ° C., preferably 40 to 70 ° C., and may be preheated. Or you may heat after neutralization. If the temperature of the neutralized solution is less than room temperature, the precipitated particles are strongly aggregated, and the pore volume of the powder obtained through the aging and drying steps is not preferable. On the other hand, when the temperature of the solution in the reaction vessel exceeds 100 ° C., a phase having a large particle size is folded out, and the specific surface area is decreased, which is not preferable.
In addition, when stirring during the neutralization reaction, if the product is slowly stirred, the product obtained by drying the product tends to become a powder, but if vigorously stirred, it tends to become a solid (solidified body).
[0011]
It is desirable to heat the neutralized solution after precipitation. The crystallinity of pseudo boehmite is improved by this aging process. Although the heat generation time is not particularly limited, it is suitably within 2 hours. If the aging time is too long, pseudoboehmite particles grow too much and the pore volume of pseudoboehmite tends to be small. After completion of aging, pseudo boehmite and liquid are separated by filtration. After the separation, by-products such as sodium sulfate and sodium chloride which are adsorbed on the surface of the pseudo boehmite particles are removed by washing with water, and then dried using a drying apparatus such as a spray dryer. The drying temperature is not particularly limited. However, if the drying temperature is too high, the obtained pseudoboehmite is liable to undergo phase transition to γ-alumina, and is generally in the range of 20 to 150 ° C.
[0012]
The pseudo boehmite powder produced in this way has a pore size distribution with a pore radius of 30 nm or less, preferably 10 nm or less, and is excellent in water vapor absorption and desorption characteristics, so that it is used as a humidity control material in various fields. be able to.
In addition, the powdery humidity control material obtained can be used as it is, mixed with an appropriate binder, reinforcing material, etc., and molded by pressing to form a solid material such as a sheet material, a plate material, It can also be used in any form such as a coating material. For example, it can be suitably used for a building material such as a wall material, a ceiling material, and a floor base material by mixing into a cloth material or a ceramic molded body. Further, it is possible to select and use a humidity control material whose adsorption amount sharply increases in an appropriate humidity range according to the desired humidity. For example, it is possible to keep any space, such as underfloor, close-in, and shoeboxes, which are difficult to ventilate and become highly humid, at any suitable humidity, thereby preventing condensation and mold / mite breeding. It is extremely safe and economical.
[0013]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, it cannot be overemphasized that this invention is not settled to the following Example.
[0014]
Example 1
An aqueous solution of aluminum sulfate and an aqueous solution of sodium aluminate, both heated to 60 ° C., were mixed and neutralized while maintaining pH = 8. After completion of the neutralization reaction, the mixture was held for 30 minutes, and then solid-liquid separation was performed. During the solid-liquid separation, water was further added to remove the neutralized salt. The resulting product was dried at 60 ° C. The powder obtained after drying was identified as a product by X-ray diffraction, and found to be pseudoboehmite. Further, when the water vapor adsorption isotherm of this powder was measured, it was as shown in FIG. 1 and had a moisture absorption / release capacity of 57 wt% in the range of 0 to 90% RH.
Further, the water vapor adsorption isotherm of the powder obtained by heat treatment at 300 ° C. for 3 hours is shown in FIG. 2, and the water vapor adsorption isotherm of the powder heat treated at 600 ° C. for 3 hours is shown in FIG. As is apparent from a comparison between FIG. 1, FIG. 2 and FIG. 3, the moisture absorption / release performance does not change even when heat-treated at a high temperature, and according to the present invention, the moisture absorption / release performance is sufficiently high only by drying the precipitate. It can be seen that
[0015]
Example 2
A normal temperature aluminum sulfate aqueous solution was added to a normal temperature sodium aluminate aqueous solution, and a neutralization reaction was performed while maintaining pH = 8. After completion of the neutralization reaction, the resulting suspension was heated to 60 ° C. and held for 30 minutes. Thereafter, solid-liquid separation was performed. During the solid-liquid separation, water was added to remove the neutralized salt. The resulting product was dried at 60 ° C. The powder obtained after drying was identified as a product by X-ray diffraction, and found to be pseudoboehmite. Further, when the water vapor adsorption isotherm of this powder was measured, it showed a curve similar to that in FIG. 1 and had a moisture absorption / release capacity of 50 wt% in the range of 0 to 90% RH.
[0016]
Example 3
A room temperature sodium sulfate aqueous solution was added to a room temperature aluminum sulfate aqueous solution, and a neutralization reaction was carried out while maintaining pH = 8. After completion of the neutralization reaction, the resulting suspension was heated to 60 ° C. and held for 30 minutes. Thereafter, solid-liquid separation was performed. During the solid-liquid separation, water was added to remove the neutralized salt. The resulting product was dried at 60 ° C. The powder obtained after drying was identified as a product by X-ray diffraction, and found to be pseudoboehmite. Further, when the water vapor adsorption isotherm of this powder was measured, it showed a curve similar to that in FIG. 1 and had a moisture absorption / release capacity of 50 wt% in the range of 0 to 90% RH.
[0017]
Comparative Example 1
A mixture of an aluminum sulfate aqueous solution and a sodium aluminate aqueous solution heated to 60 ° C. was mixed, and neutralized while maintaining the pH = 6. After completion of the neutralization reaction, the mixture was held for 30 minutes, and then solid-liquid separation was performed. During the solid-liquid separation, water was further added to remove the neutralized salt. The resulting product was dried at 60 ° C. When the powder obtained after drying was identified by X-ray diffraction, it was amorphous. Moreover, when the water vapor adsorption isotherm of this powder was measured, it was as shown in FIG. 4, and although the moisture absorption capability was recognized, it was inferior to the moisture release capability.
[0018]
【The invention's effect】
As described above, since the humidity control material of the present invention is made of pseudo-boehmite powder having a pore radius of 30 nm or less, it has excellent water vapor absorption and desorption characteristics. In addition, according to the method of the present invention, it is possible to relatively easily produce a humidity control material composed of such pseudo-boehmite powder having excellent water vapor absorption and desorption characteristics, and high temperature that is indispensable for conventional humidity control materials. Since it is not necessary to perform heat treatment, manufacturing at a low cost is possible.
[Brief description of the drawings]
1 is a graph showing a water vapor adsorption isotherm of pseudoboehmite powder obtained in Example 1. FIG.
2 is a graph showing a water vapor adsorption isotherm of a powder obtained by heat-treating the pseudo-boehmite powder obtained in Example 1 at 300 ° C. FIG.
3 is a graph showing a water vapor adsorption isotherm of a powder obtained by heat-treating the pseudo-boehmite powder obtained in Example 1 at 600 ° C. FIG.
4 is a graph showing a water vapor adsorption isotherm of the amorphous aluminum hydroxide powder obtained in Comparative Example 1. FIG.

Claims (2)

From a pseudo boehmite powder having a pore radius of 30 nm or less , which is produced by drying a product obtained by neutralization reaction between an alkali aluminate aqueous solution and an aluminum salt aqueous solution (acidic aluminum) at a drying temperature of 20 to 150 ° C. Do Ri, steam moisture absorption of 45% or more in the range of RH relative humidity 0% to 90%, water vapor desorption amount has hygroscopic capacity of more than 40% RH range 5 to 90% relative humidity, and water vapor A pseudo-boehmite humidity-controlling material characterized by having a water vapor moisture-absorbing / releasing property in which the rapid rise of the adsorption isotherm is in the range of 40 to 90% RH . The alkali aluminate solution and an aluminum salt solution (acidic aluminum), by neutralization reaction at pH 7-10, by the resulting product is dried at a drying temperature 20 to 150 ° C., pore radius 30nm following pseudo It consists of boehmite powder, has a moisture absorption capacity of 45% or more in the range of relative humidity 0 to 90% RH, and moisture absorption and release capacity of 40% or more in the range of relative humidity 5 to 90% RH, and the method of pseudoboehmite humidity material you characterized by rapid rise of the water vapor adsorption isotherm obtained pseudoboehmite humidity material having a water vapor Hygroscopic properties in the range of RH 40 to 90%.

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