JP3793809B2 - Porous material comprising hollow fiber aluminum silicate and method for producing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an inorganic porous material having excellent water absorption ability under high humidity conditions, and more specifically, specific mesopore pores exhibiting excellent water absorption behavior under high humidity of 90% or higher relative humidity. The present invention relates to a porous material made of a hollow fiber-like aluminum silicate having the above, its production method, and various uses utilizing its water absorption.
[0002]
[Prior art]
In recent years, buildings related to residences in Japan have been promoted to have high thermal insulation and high airtightness with the progress of quality improvement, such as the occurrence of internal dew condensation and associated wall wetting and stains, mold and mites. Problems such as breeding have occurred. With such changes in living space, the importance of anti-condensation countermeasure technology is increasing. Conventionally, measures have been taken to prevent the occurrence of condensation by using quick lime (calcium oxide) or silica gel as a desiccant, or by operating air conditioning equipment such as a dehumidifier or an air conditioner.
[0003]
However, each of the above desiccants has a problem that the moisture absorption capacity is strong and it is difficult to control the dehumidification capacity. There is a drawback of being short. Furthermore, since it is not easy to separate the moisture once absorbed and restore the hygroscopic ability, it is difficult to reuse it repeatedly. On the other hand, dehumidification by the operation of air conditioning equipment such as a dehumidifier and an air conditioner is not preferable from the viewpoint of economy, such as energy consumption and installation and management of equipment.
[0004]
Under such circumstances, the present inventors previously found that a hollow fibrous aluminum silicate having specific mesopore pores exhibits excellent water absorption behavior under high humidity conditions, and applied for a patent. was performed (JP 200 2 -52 337). However, although this hollow fiber aluminum silicate has pores having a size effective for conditioning under high humidity conditions in the voids, the pores are formed by aggregation of the hollow fiber aluminum silicates. There was a problem that the water-absorbing ability could not be fully exhibited due to being crushed.
[0005]
[Problems to be solved by the invention]
The present invention has been made to solve the above-described problems of the prior art. That is, an object of the present invention is to provide a novel porous material having a sufficient water-absorbing ability and having excellent durability for retaining pores that are effectively used for the expression of humidity control under high humidity conditions and for a long period of time. It is to provide a simple manufacturing method. Another object of the present invention is to provide a good humidity control material, a dew condensation preventing agent and a dew condensation prevention method using a porous material that can be used repeatedly.
[0006]
[Means for Solving the Problems]
The present inventors have solved the problems in conventional hygroscopic materials, and as a result of intensive research toward the development of inorganic porous materials having high water absorption, hollow fiber aluminum having specific mesopore pores During the process of drying the silicate gel, the pores remain unbroken because they do not agglomerate between the resulting hollow fiber aluminum silicates when dried using certain methods. As a result, it was found that a porous material having an excellent water absorption ability was obtained, and the present invention was completed.
[0007]
That is, the porous material of the present invention is made of a hollow fibrous aluminum silicate having mesopore pores having a pore radius of less than 1.5 nm and having pores having a diameter of 6 nm or more held in the gaps between the fibers. It is characterized by. This hollow fibrous aluminum silicate exhibits excellent water absorption behavior under high humidity conditions.
Further, the method for producing a porous material of the present invention is a hollow fiber aluminum silicate gel obtained by synthesizing aluminum silicate from a mixed solution of a silicon compound and an aluminum compound and then treating the mixture under mildly acidic conditions. The hollow product has mesopore pores having a pore radius of less than 1.5 nm, and pores having a diameter of 6 nm or more are retained in the voids between the fibers by freeze drying or supercritical drying of the product. It consists of aluminum silicate.
[0008]
The humidity control material of the present invention has a porous structure composed of hollow fibrous aluminum silicate having mesopore pores with a pore radius of less than 1.5 nm and having pores with a diameter of 6 nm or more held in the gaps between the fibers. It is characterized by containing a quality material.
[0009]
The anti-condensation agent of the present invention has a porous structure composed of hollow fibrous aluminum silicate having mesopore pores with a pore radius of less than 1.5 nm and having pores with a diameter of 6 nm or more held in the gaps between the fibers. It is characterized by containing a quality material.
Further, the dew condensation prevention method of the present invention is a hollow having mesopore pores having a pore radius of less than 1.5 nm as described above in a high-humidity space, and pores having a diameter of 6 nm or more being held in voids between fibers. It is characterized by using a porous material made of fibrous aluminum silicate.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The porous material of the present invention is made of hollow fibrous aluminum silicate having mesopore pores, and pores are formed in voids between the fibers, and the pore radius of the mesopores is 1.5 nm. The pore diameter formed in the voids between the fibers corresponds to a size of 6 nm or more, preferably 6 to 1000 nm. To do. This porous material is made of a hollow fiber tubular aluminum silicate that has a sufficient water absorption capacity and is particularly excellent in water absorption under high humidity conditions. Can absorb most of the water vapor of about 200% of its own weight and release most of the water vapor adsorbed under normal humidity conditions of about 90% or less relative humidity. Repeatedly absorbs and adjusts humidity over a long period of time. Because it can be used, it has excellent durability and energy saving.
[0011]
The method for producing a porous material of the present invention is a hollow fiber aluminum silicate gel obtained by treating an aluminum silicate synthesized by mixing a silicon compound solution and an aluminum compound solution under mildly acidic conditions. The fibrous product is freeze-dried or supercritically dried to obtain a hollow fiber-like aluminum silicate having voids between the fibers. In this production method, water existing between the gel-like substances is frozen, and the ice is dried by sublimation. Therefore, there is no aggregation of the hollow fiber-like aluminum silicates, and therefore the hollow fibers in the gel state are not aggregated. Since the pores having a diameter of 6 nm or more formed in the voids are dried without being crushed, a hollow fiber-like aluminum silicate exhibiting sufficient water absorption capability is obtained. This is because, in the conventional method, the pores formed in the voids of the hollow fiber-like aluminum silicate are gelated under weak alkaline conditions and then dried between the aluminum silicates. This means that the shape is different from the conventional hollow fiber aluminum silicate which is crushed by aggregation.
[0012]
In the production method of the present invention, a silicon compound and an aluminum compound are used as raw materials. The reagent used as the silicon source may be monosilicates, specifically, sodium orthosilicate, sodium metasilicate, amorphous. Colloidal silicon dioxide (aerosil, etc.) is preferred. Also, the aluminum source to be bonded to the silicic acid molecule is not particularly limited as long as it has aluminum ions. Specifically, aluminum compounds such as aluminum chloride, aluminum nitrate, and aluminum perchlorate are preferable. It is done. These silicon sources and aluminum sources are not limited to the compounds described above, and can be used in the same manner as long as they have the same effect.
[0013]
These raw materials are dissolved in an appropriate aqueous solution to prepare a silicon compound solution and an aluminum compound solution having predetermined concentrations, respectively. Even if these solutions are mixed at an arbitrary ratio, there is no particular problem for the formation of the precursor, but it is preferably mixed so that the silicon / aluminum ratio is 0.5 to 1.0. The silicon compound concentration in the solution is 1 to 1000 mmol / l, and the aluminum compound concentration is 1 to 2000 mmol / l. Preferred concentrations are 1 to 500 mmol / l silicon compound solution and 1 to 1000 mmol / l. It is preferable to mix the aluminum compound solution. After mixing a silicon compound solution with this aluminum compound solution, an alkaline solution is dropped, and the pH is adjusted from weakly acidic to near neutral to form a precursor. Examples of the alkaline solution necessary for the neutralization reaction in the precursor generation process include sodium hydroxide, potassium hydroxide, and ammonia.
[0014]
After the precursor is formed in this manner, treatments such as centrifugation, filtration and membrane separation are performed to remove coexisting ions in the solution, and then the recovered precursor is dispersed in pure water. Then, in order to suppress the production | generation of a by-product, an acid is added to the dispersion liquid, and it adjusts to the weakly acidic solution whose pH is 3-6, Preferably the pH is 3.5-4.5. . Moreover, as an acid used in that case, hydrochloric acid, nitric acid, perchloric acid etc. are mentioned, for example.
[0015]
The precursor dispersed in the weakly acidic aqueous solution is subjected to heat treatment for 2 days. The heating method and conditions may be, for example, heating using a mantle heater or autoclave so that water does not evaporate. The temperature range is 50 to 120 ° C., preferably around 100 ° C. . After the heating, the aqueous solution containing the product is evaporated at 100 ° C. for about 1 day, and the gel product is recovered.
[0016]
Moreover, you may aggregate a product as a gel-like substance by adding alkaline aqueous solution to the aqueous solution containing a product after heating, and making pH into about 8-12 alkaline aqueous solution. Examples of the alkali used at this time include ammonia, sodium hydroxide, potassium hydroxide, and the like. Further, the gel-like product can be recovered by removing excess water by centrifugation.
[0017]
Next, it is necessary to dry the recovered gel product by freeze drying or supercritical drying. By adopting this drying method, it is possible to preserve the unique three-dimensional shape of the formed hollow fiber aluminum silicate as it is. As the lyophilization, dehydration can be performed using a known lyophilization apparatus under the conditions of −50 to −30 ° C. and 100 to 500 Pa, for example. Moreover, as supercritical drying, dehydration can be performed, for example, at normal supercritical conditions of 10 to 30 ° C. and 5 to 8 MPa.
In this way, the tube-shaped aluminum silicate having a mesopore pore having a pore radius of less than 1.5 nm and having a unique three-dimensional shape in which pores of 6 nm or more are formed in the voids of the hollow fiber. Aluminum silicate is obtained.
[0018]
The hollow fiber-like aluminum silicate obtained by the above method is composed of an inorganic porous material formed by intricately intertwining the hollow fibers having the pores described above, and has excellent performance in water adsorption and desorption. In addition, it has durability, for example, it can adsorb water vapor of about 200% or more of its own weight under high humidity conditions with a relative humidity of 90% or more, and adsorbs under low humidity conditions. Since it has the property that it can easily release most of the water vapor, it can be used repeatedly to adjust the amount of water, store water and prevent condensation in the space, etc., for humidity conditioning, moisture storage and prevention of condensation It can be used advantageously.
[0019]
In order to use the porous material made of the hollow fiber-like aluminum silicate of the present invention as a humidity control material, it is arranged, for example, as a conventionally known tile-shaped wall material or wallpaper in a room or container that requires humidity adjustment. To do. In addition, since the porous material can adsorb and retain a large amount of moisture, it is conventionally used as a desiccant in the windows and closets of houses where condensation is likely to occur in order to prevent condensation caused by condensation of moisture. It can be performed by arranging in the same manner as quicklime (calcium oxide) and silica gel.
[0020]
【Example】
EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the examples.
Example 1
125 ml of sodium orthosilicate aqueous solution diluted with pure water was adjusted so that the SiO ₂ concentration was 100 mmol / l. Separately, aluminum chloride was dissolved in pure water to prepare 125 ml of an aqueous solution having an Al ₂ O ₃ concentration of 150 mmol / l.
Next, the orthosilicate aqueous solution was mixed with the adjusted aluminum chloride aqueous solution and stirred with a magnetic stirrer to prepare a mixed solution. The silicon / aluminum ratio of this solution was 0.67.
Thereafter, 22 ml of a 1N sodium hydroxide aqueous solution was dropped into this mixed solution, and the solution adjusted to have a pH of about 6 was centrifuged to recover the precursor. Furthermore, this precursor was washed with pure water by centrifugation three times, and then dispersed in 1000 ml of pure water.
[0021]
Next, a solution prepared by adding 1.2 ml of 5N hydrochloric acid to the solution in which the precursor was dispersed and adjusting the pH to about 4 was heated at 100 ° C. for 2 days with a mantle heater. After the heating, the solution was transferred to a beaker and left in a dryer at 100 ° C. for about 1 day to evaporate water. The gel product thus obtained was freeze-dried at 300 Pa and −45 ° C. for 12 hours using a freeze-drying apparatus (trade name: vacuum freeze-dryer FD-5N type, manufactured by Tokyo Rika Kikai Co., Ltd.). By performing, a hollow fiber-like aluminum silicate having a large amount of pores having a pore radius of 0.8 nm and a void diameter of 6 to 20 nm was obtained.
[0022]
【The invention's effect】
According to the present invention, it is possible to easily produce a porous material having a unique three-dimensional structure formed by intricately intertwining hollow inorganic fibers.
This porous material is made of hollow fibrous aluminum silicate, has a large number of pores with a size excellent in moisture adsorption and desorption performance, and also has durability with excellent reproducibility. Therefore, it is useful as a humidity control material capable of preventing dew condensation and using it repeatedly, and can absorb and retain a large amount of water in a high humidity range, so that it can also be used as a moisture storage material.

Claims (6)

A porous material comprising mesoporous pores having a pore radius of less than 1.5 nm, and comprising a hollow fiber-like aluminum silicate in which pores having a diameter of 6 nm or more are held in voids between fibers. The porous material according to claim 1, wherein the hollow fibrous aluminum silicate exhibits excellent water absorption behavior under high humidity conditions. Freeze drying or supercritical drying of a hollow fiber aluminum silicate gel product obtained by synthesizing an aluminum silicate from a mixed solution of a silicon compound and an aluminum compound and then treating under a weakly acidic condition. A method for producing a porous material comprising a hollow fibrous aluminum silicate having mesopore pores having a pore radius of less than 1.5 nm and having pores having a diameter of 6 nm or more held in the gaps between the fibers. A humidity control material comprising the porous material according to claim 1. An anti-condensation agent comprising the porous material according to claim 1. A method for preventing condensation in a high humidity space, wherein the porous material according to claim 1 is used in the high humidity space.