WO2005042402A1

WO2005042402A1 - Inorganic porous material containing dispersed particles

Info

Publication number: WO2005042402A1
Application number: PCT/JP2003/014023
Authority: WO
Inventors: Naohiro Soga; Kazuki Nakanishi; Shigeru Hanzawa; Yousuke Sato
Original assignee: Ngk Insulators, Ltd.
Priority date: 2003-10-31
Filing date: 2003-10-31
Publication date: 2005-05-12
Also published as: AU2003280697A1

Abstract

An inorganic porous composite material which comprises an inorganic porous skeleton having open pores and dispersed particles being exposed on the wall of open pores of the porous skeleton, wherein the porous skeleton is formed by the sol-gel transformation accompanied by phase transition. The inorganic porous composite material has allowed an inorganic porous material having an inorganic porous skeleton as a main component to carry various types of particles on the wall of open pores of the material in a uniformly dispersed state.

Description

Specification

TECHNICAL FIELD The technical field to which the present invention pertains

The present invention relates to an inorganic porous body containing dispersed particles.

Background art

In general, an inorganic porous material represented by ceramics is produced by sintering a compact formed of raw material particles bound by a resin component called a binder or a pore forming agent with burning of a binder. ing. The pores are formed by burning out the binder and leaving the occupied space between the sintered particles.

Disclosure of the invention

However, it is difficult to disperse and adhere various types of particles to the walls of the pores of the sintered body. For example, when the dispersed particles are mixed with the raw material particles for sintering, the particles are aggregated and mixed into the sintered body, and it is difficult for the particles to adhere to the wall surfaces of the pores. It is also conceivable to inject a liquid containing dispersed particles into the pores of the sintered body after the sintered body is manufactured, and to cure the liquid. However, the sintered body has a non-uniform pore shape, many necks, and a wide pore size distribution. Further, it is difficult to increase the pore diameter to a certain degree or more. For this reason, it is difficult to uniformly adhere and support another type of particles inside the pores of the sintered body. Also, it is difficult to disperse dispersed particles larger than a certain size in the pores of the sintered body.

On the other hand, it is known that, for example, a porous silica material is produced with good reproducibility by a sol-gel method utilizing phase separation (Japanese Patent No. 2123708, Japanese Patent Application Laid-Open No. 3-285833, etc.). In this method, the pore shape and its size distribution are extremely uniform. It also forms relatively large diameter pores. Is possible. However, this porous body is entirely homogeneous, for example, of silica. For this reason, it is difficult for the porous body to retain various functions, and the use of the porous body is limited.

An object of the present invention is to provide a new inorganic porous material mainly composed of an inorganic porous skeleton, which can uniformly support various particles on the porous skeleton without roughening the walls of the open pores. An object of the present invention is to provide an inorganic porous composite _(the present invention includes an inorganic porous skeleton provided with open pores, and dispersed particles exposed on a wall surface facing the open pores of the porous skeleton. Further, the present invention relates to an inorganic porous material, wherein the porous skeleton is generated by a sol-gel transition accompanied by a phase transition.

According to the present invention, the dispersed particles are exposed on the wall surface facing the open pores of the porous skeleton generated by the sol-gel transition accompanied by the phase transition. Such a porous skeleton can control or enlarge the pore diameter of the open pores, has almost no neck portion, and has high uniformity of the pore diameter of the open pores. In addition, it is possible to uniformly disperse the dispersed particles on the wall surfaces of the open pores, and it is relatively easy to control the amount of the dispersed particles to be dispersed. This makes it possible to exhibit various functions of the dispersed particles in the porous body with high efficiency that cannot be obtained by the conventional porous sintered body. In the porous body of the present invention, each dispersed particle is exposed from the open pore wall surface of the porous body. At this time, preferably, at least 1 vol.%, More preferably at least 5 vol.% Of the volume of each dispersed particle is raised from the wall surface of the open pores of the porous skeleton. Brief Description of Drawings

FIG. 1 is a scanning electron micrograph (magnification: 500 ×) showing a cross section of the inorganic porous composite having an addition amount of dispersed particles of 0.0 g in the examples. W

Three

FIG. 2 is a scanning electron micrograph (magnification: 20000) showing a cross section of the inorganic porous composite in which the amount of dispersed particles added was 0.5 g in Examples. FIG. 3 is a scanning electron microscope photograph (magnification: 500,000) showing a cross section of the inorganic porous composite having an added amount of dispersed particles of 1.0 g in the examples.

5 FIG. 4 is a scanning electron micrograph (magnification: 20000) showing a cross section of the inorganic porous composite having an added amount of dispersed particles of 1.0 g in the example. FIG. 5 is a scanning electron micrograph (magnification: 500 ×) showing a cross section of the inorganic porous composite having an added amount of dispersed particles of 2.0 g in the example.

FIG. 6 is a scanning electron micrograph (magnification: 20000 times) showing a cross section of an inorganic porous composite 0 body having an added amount of dispersed particles of 2.0 g in the example.

BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in more detail.

In the present invention, the porous skeleton is formed by a V-Rugel transition accompanied by a phase transition. In order to cause this reaction, a solution containing a precursor of the network-forming component is prepared, and the precursor is reacted in the solution, for example, a hydrolysis reaction is performed to form a sol, and the sol is gelled. (Solidification). This is called a sol-gel transition. During the sol-gel transition, a phase is separated into a phase rich in a network-forming component causing gel formation (gel phase) and a phase rich in a solvent component not causing gel formation (solvent phase). As a result, since this gel forms a network structure, a porous body having open pores can be obtained by drying the solvent phase and removing the solvent.

In the present invention, after obtaining the porous body, It is also possible to expose the dispersed particles to the open pores of the porous body by filling the slurry containing the dispersed particles through the open pores of the porous body and then heat-treating the porous body.

However, in a preferred embodiment, the sol-gel reaction solution The dispersed particles are allowed to coexist in advance. After the sol-gel reaction proceeds, a large number of these dispersed particles are exposed on the wall surface of the open pores of the network structure. In this case, the dispersed particles can be more uniformly dispersed on the walls of the open pores of the porous body.

Hereinafter, a more specific description will be given.

In a preferred embodiment, dispersed particles are allowed to coexist in the sol-gel reaction solution to cause a sol-gel transition accompanied by a phase transition, thereby forming a porous skeleton including open pores and dispersing on the wall surfaces of the open pores. Exposure of particles.

In this sol-gel reaction system, as time elapses, phase separation into a phase rich in a network-forming component causing gel formation (gel phase) and a phase rich in a solvent component not causing gel formation (solvent phase) is performed. Happens. In the formation of each phase region, the diffusion of each component against the concentration gradient occurs using the difference in chemical potential as a driving force until each phase region reaches the equilibrium composition under the given temperature and pressure. , Mass transfer continues. At this time, conditions are selected so that the dispersed particles coexist in the starting composition and that the dispersed particles do not significantly affect the phase separation-sol-gel reaction.

A specific production method will be exemplified.

(1) Add dispersed particles to a solvent, disperse by stirring and sonication. Next, the precursor of the network-forming component is dissolved in the solvent to cause a reaction for generating the network-forming component, and the sol-gel transition and the phase separation reaction to proceed.

(2) Dissolve the network-forming component in the solvent. A dispersion of the dispersed particles is added to this solution, followed by stirring and ultrasonic treatment. Then, a formation reaction of a network-forming component is caused, and a sol-gel transition and a phase separation reaction proceed.

After the steps (1) and (2), wash the wet gel or remove the solvent. After the treatment, the solvent is removed to obtain an inorganic porous composite. If necessary, the inorganic porous composite can be heat-treated at an appropriate temperature.

The pore diameter of the open pores of the porous skeleton is preferably 100 nm or more, more preferably 200 nm or more, from the viewpoint of improving the air permeability of the open pores. Such macropores are formed as regions occupied by the solvent phase generated during phase separation. When the solvent phase and the gel phase are entangled with each other to form a continuous so-called interconnected structure, an extremely sharp size distribution can be obtained.

There is no particular upper limit on the pore diameter (diameter) of the open pores. However, from the viewpoint of easiness of manufacture, it is preferably at most 1000 nm.

The inorganic substance constituting the porous skeleton is not particularly limited. However, metal oxides are particularly preferred. Examples of the metal oxide include silicon oxide, titanium oxide, zirconium oxide, and alumina. Two or more kinds of metal oxidized products may be used.

Currently, industrially produced and commercially available dispersed particles are mainly composed of organic polymers, metal oxides or metals, and their particle diameters (average diameter) are extremely wide from about 5 nm to about 100 m. Range. It is known that the chemical affinity between these fine particles and the network-forming component that causes gel formation can be freely controlled in many cases by chemical modification of the particle surface ₍ accordingly, aggregation during the sol-gel reaction). Particles satisfying conditions that do not cause sedimentation or sedimentation can be applied to the present production method regardless of the chemical composition.

Therefore, in the present invention, as the dispersed particles, metal oxides, metals, organic high molecules, and composites thereof can be used. Specifically, transition metal oxides, silicon oxide, titanium oxide, zirconium oxide, aluminum oxide, calcium oxide, magnesium oxide, iron oxide, transition metal oxides, yttrium oxide, lanthanum oxide, rare earth oxides, and the like are preferable. . Further reaction Carbonates, nitrates, sulfates, phosphates, halides, inorganic salts, and the like that are stable in the liquid can also be used. Organic salts, complexes, protected metal colloids, polymer latexes, and even finely divided organic polymers can be used to produce the inorganic porous composite of the present invention by controlling the dispersibility in the reaction solution. Can be.

The average diameter of the dispersed particles is not particularly limited. Since the dispersed particles must be sized to fit within the open pores of the porous skeleton, the average diameter of the dispersed particles must be smaller than the pore diameter (diameter) of the open pores of the porous skeleton. In particular, from the viewpoint of exerting some function in the open pores, it is preferable that the average diameter of the dispersed particles is somewhat smaller than the diameter of the open pores. From this viewpoint, the diameter of the dispersed particles is preferably 500 nm or less.

The average diameter of the dispersed particles is preferably 5 nm or more from the viewpoint of suppressing aggregation during dispersion. Also, if the average diameter of the dispersed particles is too small compared to the diameter of the open pores, the fluid passing through the open pores will be less likely to come into contact with the dispersed particles, and the function may not be exerted. . Therefore, if the material that forms the basis of the present application is specified, the diameter d of the porous open pores without the addition of dispersed particles DZ The diameter d of the dispersed particles is preferably 600 or less, and 100 or less. More preferably, it is.

In addition, when the dispersed particles are elongated, irregularities are likely to occur on the inner wall surface of the open pores due to a change in the state around the dispersed particles during the phase transition. From the viewpoint of preventing this, the average aspect ratio (major axis / minor axis) of the dispersed particles is preferably set to 1.5 or less.

The weight ratio of the dispersed particles is preferably not more than 90% by weight, more preferably not more than 80% by weight, based on the whole inorganic porous composite material. Further, from the viewpoint of exerting the function of the dispersed particles, the weight ratio of the dispersed particles is preferably 0.01% by weight or more based on the whole inorganic porous composite, and more preferably 0.1% by weight. More preferably, it is at least 1% by weight. The effect of supporting the dispersed particles in the open pores is not particularly limited. <For example, a surface roughness forming function that increases the surface roughness of the open pores and increases the contact area between the fluid and the inner wall surface of the porous skeleton. Good. Further, it may have a catalytic function of a chemical reaction.

Examples of the precursor of the network-forming component that causes gel formation used in the sol-gel reaction include the following.

(1) Metal alkoxides, metal complexes, metal salts, organically modified metal alkoxides, organic crosslinked metal alkoxides, alkyl-substituted organometallic alkoxides

(2) Partial hydrolysis products of metal alkoxides, metal complexes, metal salts, organically modified metal alkoxides, organic crosslinked metal alkoxides, or alkyl group-substituted organometallic alkoxides

(3) Multimers that are partial polymerization products of metal alkoxides, metal complexes, metal salts, organically modified metal alkoxides, organic cross-linked metal alkoxides or alkyl-substituted organic metal alkoxides

(4) Sol-gel transition by changing pH of water glass and silicate aqueous solution

In a more specific production method, a water-soluble polymer is dissolved in an acidic aqueous solution, dispersed particles are added thereto, and the mixture is dispersed by stirring and sonication. The precursor, particularly preferably a hydrolyzable functional group The hydrolysis reaction is performed by adding a metal compound having the following formula. The precursor of the network-forming component gradually increases its degree of polymerization, and the compatibility with the solvent phase mainly composed of water or the solvent phase mainly composed of the water-soluble polymer decreases. At this time, spinodal decomposition occurs in the solution, and at the same time gelation occurs due to hydrolysis and polymerization of the network-forming components. Occur. The product is then dried and heated.

Here, the water-soluble polymer is a water-soluble organic polymer that can be converted into an aqueous solution having an appropriate concentration, and is uniformly dissolved in a reaction system containing an alcohol generated by a metal compound having a hydrolyzable functional group. Anything can be obtained. Specifically, sodium or potassium salts of polystyrene snorenoic acid, which is a polymer metal salt, polyacrylic acid, which is a polymer acid and dissociates into a polyanion, and a polymer base, which is a polycation in an aqueous solution. Suitable are polyallylamine and polyethyleneimine, which produce the above, polyethylene oxide which is a neutral polymer and has an ether bond in the main chain, or polyvinylpyrrolidone. Formamides, polyhydric alcohols and surfactants may be used in place of the organic polymer, in which case glycerin is the most suitable polyhydric alcohol, and polyoxyethylene alkyl ethers are the best surfactants. It is.

As the metal compound having a hydrolyzable functional group, ；; a metal alkoxide or an oligomer thereof can be used. For example, those having a small number of carbon atoms such as a methoxy group, an ethoxy group, and a propoxy group are preferable. No. As the metal, a metal of an oxide to be finally formed, for example, Si, Ti, Zr, or A1 is used. The metal may be one kind or two or more kinds. On the other hand, it is only necessary that the polysaccharide is uniformly dissolved and dispersed in alcohol, and specifically, up to about 10-mers can be used. Alkoxyalkoxysilanes, in which some of the alkoxy groups of these silicon alkoxides are substituted with alkyl groups, and oligomers up to about 10-mers thereof are preferably used. Alkyl-substituted metal alkoxides in which the central metal element is replaced with titanium, zirconium, aluminum or the like instead of silicon can also be used.

As the acidic aqueous solution, a mineral acid such as hydrochloric acid, nitric acid, etc. The above or organic acids such as formic acid, acetic acid and the like having a value of 0.01N or more are preferred.

The hydrolysis and polymerization can be achieved by storing the solution at room temperature of 40 to 80 ° 0 for 0.5 to 5 hours. During this process, gelation and phase separation proceed. Example

(Example 1)

0.9 g of polyethylene oxide (manufactured by Aldrich), which is a water-soluble polymer, was dissolved in 11.3 ml of 0.01 mol / L acetic acid aqueous solution and uniformly dissolved to obtain a solution. To this solution was added silicide particles (dispersed particles: "SO-C2" manufactured by Admatik: average particle diameter 0.4 to 0.6 βπι), and the mixture was stirred for 5 minutes and then dispersed by applying ultrasonic waves for another 10 minutes. Thereafter, the mixture was stirred for 10 minutes under ice-cooling, and 5.7 ml of tetramethoxysilane (a precursor of a network-forming component: manufactured by Shin-Etsu Silicone) was added under stirring to carry out a hydrolysis reaction. The resulting clear solution was sealed and kept in a 40 ° C constant temperature bath where it solidified. The obtained gel was aged at the same temperature for about 24 hours, and then dried at 60 ° C to obtain a bulk porous composite.

Here, the weight of the silica particles (dispersed particles) was changed to 0.1 g, 0.5 g, 1.0 g, and 2.0 g. The weight ratios of the dispersed particles to the entire inorganic porous composite are 4.13, 17.7, 30.1, and 46.3% by weight, respectively. In each case, a porous body having communication holes was obtained. Scanning electron micrographs of the polished surface of the inorganic-porous composite of each example were taken (magnification: 500,000, 200,000). The following drawings are presented among these. (Figure 1) Dispersed particles 0.0 g Magnification 500 000 times

(Figure 2) Dispersed particles 0.5 g Magnification 200 000 (Figure 3) Dispersed particles 1.0 g Magnification 500 000 times

(Figure 4) Dispersed particles 1.0 g Magnification 200 000

(Figure 5) Dispersed particles 2.0 g Magnification 500 000 times

(Figure 6) Dispersed particles 2.0 g Magnification 200 000 times

As shown in FIG. 1, when the dispersed particles were not added, the open pores of the porous skeleton were connected, and the wall facing the open pores was smooth. As shown in FIG. 2, when 0.5 g of the dispersed particles is added, round dispersed particles are exposed on the wall surface facing the open pores. As shown in FIGS. 3 and 4, it can be seen that when 1.0 g of the dispersed particles is added, a larger amount of the dispersed particles is exposed on the wall surface facing the open pores. Furthermore, as shown in Figs. 5 and 6, when 2.0 g of the dispersed particles is added, not only the dispersed particles are exposed on the wall surface facing the open pores, but also the amount of the dispersed particles and the number of the exposed particles are significantly increased. The pore diameter of the pores (diameter) has also been reduced.

In this example, (the diameter D of the open pores of the porous body without added dispersed particles / the average diameter d of the dispersed particles) is 2.5, and the average aspect ratio of the dispersed particles is 1.1. The average aspect ratio of the dispersed particles was calculated by selecting 50 pieces from the SEM photograph.

(Example 2)

An inorganic porous composite was produced in the same manner as in Example 1. However, in Example 1, silica particles “SO_C1” (average particle size: 0.2 to 0.3 jum) manufactured by Admatech Co., Ltd. were used as dispersed particles. The added amount of the dispersed particles was changed to 0.0 g, 0.5 g, 1.0 g, and 2.0 g. A cross section of each of the obtained inorganic porous composites was observed with a scanning electron microscope (magnifications: 500,000 and 20,000). As a result, almost the same observation results as in Example 1 were obtained. In this example, (the diameter of the porous open pores without the addition of the dispersed particles DZ, the average diameter d of the dispersed particles) is 3, and the average aspect ratio of the dispersed particles is 1.1. The The average aspect ratio of the dispersed particles was calculated by selecting 50% from the SEM photograph.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, a novel inorganic porous material mainly comprising an inorganic porous skeleton, in which various particles are uniformly carried on the wall surfaces of the open pores, is provided. A complex can be provided.

Claims

The scope of the claims

1. An inorganic porous skeleton provided with open pores, and dispersed particles exposed on a wall surface of the porous skeleton facing the open pores, wherein the porous skeleton has a phase transition accompanied by a phase transition. An inorganic porous material characterized by being produced by Rugel transition.

The inorganic porous body according to claim 1, wherein the diameter of the open pores is 100 nm or more.

3. The inorganic porous material according to claim 1, wherein the dispersed particles are made of at least one material selected from the group consisting of metal oxides, metals, organic polymers, and composites thereof. Body.

4. The inorganic porous body according to any one of claims 1 to 3, wherein an average diameter of the dispersed particles is 5 nm or more and 100 mm or less.

5. The inorganic porous body according to any one of claims 1 to 4, wherein the inorganic substance is a metal oxide.

6. The inorganic porous material according to any one of claims 1 to 5, wherein an average aspect ratio of the dispersed particles is 1.5 or less.