JP2912719B2 - Transparent inorganic porous material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic porous material having transparency to visible light and the like and excellent heat insulation.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a light-permeable porous body, a method in which a gel compound obtained by condensation polymerization of a metal hydroxide is dried at a critical point or above (USP2, 093,454). Further, as a method using alkoxysilane, a method of drying in a supercritical state using tetramethyl orthosilicate (TMOS) (see US Pat. No. 4,327,065; US Pat. No. 4,432,956), or a method of using a supercritical state using tetraethyl orthosilicate (See USP 4,610,863).

[0003]

Since the light-transmitting porous body obtained as described above has very fine voids, it has a very low thermal conductivity and has a very low thermal conductivity. Excellent in infrared radiation (especially wavelengths of 3,000 to 5,000)
nm), so that the transmission of heat due to radiation could not be blocked.

In view of such circumstances, the present invention provides a transparent inorganic porous material which is an inorganic porous material which transmits visible light and which is excellent in visible light transmittance but excellent in heat insulating property for reflecting infrared rays. The task is to

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a supercritical dry product of a wet gel obtained by hydrolyzing and polycondensing alkoxysilane (also referred to as silicon alkoxide, alkyl silicate, etc.). Provided is a transparent inorganic porous body carrying a metal. In the present invention, supporting of the metal to the supercritical drying of the wet gel body alkoxysilane is carried out in two ways in the two techniques. One is to disperse (including dissolve) a metal ion source compound such as a metal acid in a sol of alkoxysilane and complete gelation in a state where the compound is adsorbed on a silica fine particle structure generated by condensation polymerization. The other is a method of supercritical drying, and the other is a supercritical drying product of a wet gel of alkoxysilane.
To, any one of vacuum deposition, sputtering, chemical vapor deposition
This is a method of directly supporting a metal by the means . In the first method, firing may be performed after supercritical drying, if necessary, in order to remove excess adsorbed components and the like .

In the present invention, the supported metal is
For example, gold, platinum, aluminum and the like can be mentioned, and there is no particular limitation as long as the metal has an infrared shielding effect (for example, has an infrared reflection characteristic). The state of the supported metal is various, for example, in the form of fine particles or a thin film, and is not particularly limited. Carrying refers to, for example, a state of being contained inside and / or on the surface of a porous body, and more specifically,
These include physical adsorption, chemical adsorption, and adhesion.

The amount of metal carried is not particularly limited, and may be set as appropriate. If the amount of the metal carried is too small, the effect of blocking infrared rays tends not to be seen, and if it is too large, the transparency,
Since the heat insulating property tends to deteriorate, the amount of metal carried can be set in consideration of, for example, those tendencies. In the present invention, for example, at least one of the alkoxysilanes represented by the following general formulas (I), (II) and (III) is used as the alkoxysilane. The use ratio of these is not particularly limited, and may be appropriately set.

[0008]

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[0009]

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[0010]

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Since these polyfunctional (difunctional or more) alkoxysilanes can be polycondensed, they are preferable to monofunctional alkoxysilanes which are not polycondensed. The bifunctional, trifunctional and tetrafunctional alkoxysilanes represented by the general formulas (I), (II) and (III) used in the present invention are not particularly limited. Specific examples thereof include bifunctional alkoxysilanes, for example, dimethyldimethoxysilane, dimethyldiethoxysilane, diphenyldiethoxysilane, diphenyldimethoxysilane, methylphenyldiethoxysilane, methylphenyldimethoxysilane, diethyldimethoxysilane, Diethyldiethoxysilane or the like is used. As the trifunctional alkoxysilane, for example, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, phenyltriethoxysilane, phenyltrimethoxysilane and the like are used. As the tetrafunctional alkoxysilane, for example, tetraethoxysilane, tetramethoxysilane and the like are used.

In the present invention, in order to efficiently hydrolyze the above-mentioned alkoxysilane and perform condensation polymerization, it is preferable to add a catalyst to a reaction system containing the alkoxysilane in advance. Such a catalyst is not particularly limited, and examples thereof include an acid catalyst and a base catalyst. Specifically, as the acid catalyst, hydrochloric acid, citric acid, nitric acid, sulfuric acid, ammonium fluoride and the like are used, and as the base catalyst, ammonia, piperidine and the like are used,
It is not limited to them.

[0013] The medium used for supercritical drying in the present invention is not particularly limited. For example, a single system of carbon dioxide, ethanol, methanol, water, dichlorodifluoromethane or the like, or a mixed system of two or more types may be used. Can be mentioned. The method for producing a transparent inorganic porous material according to the present invention is not particularly limited, for example,
This is performed as follows.

First, a mixture of alcohol, water and the catalyst is added to the alkoxysilane and mixed.
The alkoxysilane is hydrolyzed and polycondensed. In addition,
At this time, the alcohol is used as a solvent because, for example, the alkoxysilane and water are hardly mixed, or used to prevent a partial hydrolysis or polymerization reaction from occurring. The alcohol may be, for example, methanol, ethanol, isopropanol, butanol and the like, and is not particularly limited.

When the polycondensation reaction proceeds sufficiently, the reaction mixture gels. The usage ratio of the alkoxysilane, water, catalyst, alcohol, and the like may be appropriately set so that a gel is formed, and is not particularly limited. Next, supercritical drying of the wet gel body is performed. If necessary, the gel is heated in a state in which alcohol is added to the gelled material, that is, aging is performed, followed by supercritical drying.

The method for performing the supercritical drying is not particularly limited. For example, the gelled product of the alkoxysilane obtained as described above is immersed in liquefied carbon dioxide (about 50 to 60 atm), and then carbon dioxide is added. In a supercritical state, or a method in which the alcohol used as a solvent is dried in a supercritical state. In the present invention, the supercritical drying includes drying at a critical point.

By performing such supercritical drying and removing the contained fluid from the gelled product, a supercritical dried product (light-transmitting inorganic porous material) is obtained.

[0018]

When the gelled product obtained by hydrolyzing the alkoxysilane and subjecting it to polycondensation is subjected to supercritical drying, the solvent changes from a liquid to a gas and is removed from the structure of the gelled product. The resulting surface tension of the solvent is weakened, and the destruction and agglomeration of the structure are prevented, so that the resulting porous body has light transmittance.

Further, since the metal is carried on the porous body by the above-described means , infrared rays can be blocked. Since the porous body obtained by the supercritical drying as described above has fine voids, the porous body has low thermal conductivity and excellent heat insulation.

[0020]

EXAMPLES Specific examples and comparative examples of the present invention will be shown below, but the present invention is not limited to the following examples. -Example 1- Tetramethoxysilane (methyl silicate 39, manufactured by Colcoat Co., Ltd.), ethanol and 0.01 mol / l aqueous ammonia are converted to tetramethoxysilane: ethanol: aqueous ammonia = 1: 5: 4 (molar ratio). Was mixed as follows. This mixed solution was allowed to stand at room temperature for 24 hours to gelate to obtain a wet gel. After adding ethanol to the wet gel, the mixture is heated to 50 ° C., and exchanged for 6 hours.
Time so-called aging was performed. Thereafter, the wet gel was taken out, placed in carbon dioxide at 18 ° C. and 55 atm, and an operation of replacing ethanol in the gel with carbon dioxide was performed for 2 to 3 hours. Thereafter, the inside of the system is brought to 40 ° C. and 80 atm, which are the supercritical conditions of carbon dioxide, and supercritical drying is performed for about 24 hours to obtain a supercritical dried product (this is also a porous body, but is not a target porous body). The same applies hereinafter). Aluminum was adsorbed on the obtained dried product by a vacuum evaporation method to obtain a target porous body. The amount of aluminum deposited was 50: 1 in weight ratio to the porous body (the airgel body excluding the supported metal).

Example 2 In Example 1, tetraethoxysilane (manufactured by Colcoat, ethyl silicate 28), ethanol and water were used in a molar ratio of tetraethoxysilane: ethanol: water = 1: 1.
5.5 were mixed so as to be 5, NH ₄ F solution was added N
A porous body was obtained in the same manner as in Example 1 except that the concentration of H ₄ F was adjusted to 0.001 mmol / l, and this was allowed to stand for 24 hours to gelate.

Example 3 Instead of using tetramethoxysilane in Example 1, 9: 1 of tetramethoxysilane and methyltrimethoxysilane (manufactured by Toray Dow Corning Silicone Co., Ltd.) was used.
(Molar ratio) A porous body was obtained in the same manner as in Example 1 except that the mixture was used.

Example 4 A porous body was obtained in the same manner as in Example 1 except that the supercritical conditions were set to 80 ° C. and 160 atm and the supercritical drying was performed for 48 hours. Example 5 An aqueous solution of H ₂ PtCl ₆ was added to the solution of tetramethoxysilane (solvent: alcohol and water) in Example 1 and mixed. At this time, the weight ratio of tetramethoxysilane: Pt was 20: 1. After the mixed solution was allowed to stand for 24 hours to gel, the gel was aged in the same manner as in Example 1 and supercritically dried. The supercritical dried product obtained here is 400 ° C.
At 400 ° C. for 1 hour and then under a hydrogen reducing atmosphere for 400 hours.
C. for 1 hour to obtain a porous body sample carrying platinum.

Comparative Example 1 A mixed solution was prepared in the same manner as in Example 1, and after gelation and aging, supercritical drying was performed to obtain a porous body.
No aluminum deposition was performed. -Comparative Example 2- A mixed solution was prepared in the same manner as in Example 2, and after gelation and aging, supercritical drying was performed to obtain a porous body.
No aluminum deposition was performed.

In each of the above Examples and Comparative Examples, the porous sample had a diameter of 50 mm and a thickness of 5 mm. The thermal conductivity and visible light transmittance of the porous bodies finally obtained in the above Examples and Comparative Examples at temperatures of 20 ° C. and 200 ° C. were examined. The light transmittance was obtained by measuring the spectral distribution in the visible light range, and determining the visible light transmittance based on JIS-R3106.

[0026]

[Table 1]

As shown in Table 1, it can be seen that the porous sample of the example maintains a low thermal conductivity even at a high temperature and prevents thermal conduction by radiation.

[0028]

The transparent inorganic porous material of the present invention is obtained by carrying a metal on a supercritical dry product of a wet gel obtained by hydrolyzing and condensation-polymerizing an alkoxysilane by the above-mentioned specific means. Low rate, and it blocks out infrared rays.
For this reason, the transparent inorganic porous body of the present invention has very excellent heat insulating properties, excellent transparency of visible light, and has functional properties specific to porous materials.

This porous body can be used for various applications such as a heat insulating material, an acoustic material, a Cherenkov element, etc., but is not limited thereto. Various applications that require heat retention are conceivable.

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Yuriko Uegaki 1048 Oaza Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works, Ltd. (56) References JP-A-61-46237 (JP, A) JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) C01B 33/12-33/193

Claims (2)

(57) [Claims] 1. A transparent inorganic porous material obtained by supporting a metal on a supercritical dry product of a wet gel obtained by hydrolyzing and polycondensing an alkoxysilane , wherein the metal is contained in a sol of the alkoxysilane. Dispersed gold
Metal ions supplied from the metal ion source compound
Silicon formed by hydrolysis and condensation polymerization of lucoxysilane
Transparent inorganic adsorbed on fine particle structure
Porous body . 2. An alkoxysilane is hydrolyzed and polycondensed.
Metal on a supercritical dry product of
A transparent inorganic porous material, wherein the metal is formed by vacuum deposition, sputtering, or chemical vapor deposition.
Supercritical drying by any one means selected from the group consisting of
A transparent inorganic porous material that is carried by a substance.