JP2003201188A - Inorganic porous body and production method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a fine structure which effectively provides a reaction field by three-dimensionally forming coarse pores with the burn out traces of fibrous polymers utilizes, and further forming pores with a shape different from the same, and to obtain a porous body which has no occurrence of fractures and cracks caused by degreasing and burning even if a large, thick product is produced. <P>SOLUTION: Gel casting slurry in which fibrous polymers are dispersed as pore forming materials is poured into a frame mold. The slurry is hardened under heating, and is thereafter dried to obtain a molding. This molding is degreased, and is burned to produce the inorganic porous body having pores communicating with each other. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inorganic porous body and a method for producing the same, more specifically, an inorganic porous body used as a fluid filter, a catalyst carrier, a diaphragm reactor, an electrode material for a fuel cell, and the same. The present invention relates to a manufacturing method.

[0002]

2. Description of the Related Art An inorganic porous material having continuous pores according to the present invention is one in which individual pores distributed in the structure are connected to each other, and individual pores represented by a heat insulating material are independent pores. Distinguished from the body. As the application of this continuous pore porous body, fluid passes from one surface of the member to the other surface,
Examples thereof include fluid filters, catalyst carriers and fuel cell electrode materials.

Here, as a method of producing an inorganic porous material having continuous pores, a method of utilizing gel casting has been conventionally known. Gel casting is a method in which a slurry containing a component that forms a dispersion medium-containing gel as a binder upon heat stimulation or the like is poured into a molding frame that does not absorb the dispersion medium to cure it. Here, if a component such as starch particles or carbon particles that burns and burns in the air is contained in the slurry as a pore-forming material, the molded product obtained by drying after curing can be burned as a whole. A porous body with uniformly distributed pores is obtained.

[0004]

Here, in order to reduce the fluid permeation resistance in the porous material, it is preferable that the porous material has a simple shape with a large pore diameter and small bending and unevenness. However, on the other hand, in the case of causing some interaction between the porous material and the components in the fluid, such as a reforming reaction, the macroscopic fluid permeation resistance is small, but the microscopic fluid permeation resistance is small. It is desired to provide a reaction field that grows.

However, in the porous body obtained by using the above-mentioned burned particles, the spherical pores form continuous pores by sharing the openings in their contact areas, but the diameter of the openings is spherical. It is smaller than the diameter of the holes. This means that, for example, when the reaction is substantially completed in each spherical hole existing near the inlet of the fluid, the fluid permeation resistance is simply large in the subsequent passage regions and does not contribute to the progress of the reaction. There was a problem.

In order to solve the above problems, it is necessary to have a fine structure in which the pores contact and communicate with each other. Therefore, the conventional method using burned particles contains a large amount of pore-forming material. As a result, when producing a thick product or a large product, there was a problem that during degreasing, the gas and heat generated by the combustion of the pore-forming material cause degreasing cracks and firing cracks. .

That is, in the present invention. The present invention has been made in view of the above problems, by forming coarse air holes three-dimensionally using burnout marks of fibrous polymer, or further, by forming pores of a different shape from this, It is intended to obtain a microstructure that effectively provides a reaction field and to obtain a porous body that does not cause cracks or cracks due to degreasing or firing even when a large-sized thick product is manufactured.

[0008]

The above-mentioned object is achieved by an inorganic porous material characterized by having open pores formed by fibrous polymer burnout marks. Further, an object of the present invention is to cast a gel-casting slurry in which a fibrous polymer is dispersed, heat-cure and dry the resulting molded body to degrease it, and then calcine it. It is also achieved by the manufacturing method of. Further, the object of the present invention is to
A method for producing an inorganic porous material, which comprises impregnating a gel-casting slurry into a fibrous polymer forming a bulk shape, degreasing a molded body obtained by drying after heating and curing, and baking the molded body. . Further, it is achieved by a method for producing an inorganic porous body, characterized in that the content of the fibrous polymer in the molded body is 1 to 70% by volume. Further, an object of the present invention is to cast a gel casting slurry into a gap of a fibrous polymer molded body, degreasing the molded body obtained by drying after heating and curing, and then firing the inorganic material. It is also achieved by the method for producing a porous body. Further, the content of the fibrous polymer in the molded body is 1
It is also achieved by a method for producing an inorganic porous body, which is characterized by being -95% by volume.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The slurry used in the gel casting according to the present invention is obtained by mixing a predetermined ceramic material or metal material as an inorganic skeleton with a dispersion medium and a predetermined gelling agent, dispersant or the like. Can be done. Here, the inorganic ceramic material and the metal material are not particularly limited, and any material that can be cast can be used.

Here, gel casting is used in the preparation of the inorganic porous material of the present invention. It is possible to obtain a molded article by pouring the slurry into the cavity, curing it in that state, and then drying it. It depends on what you can do. This has the advantage that the various pore-forming materials are uniformly dispersed as in the slurry. In addition, since it is possible to mold by drying after curing in a state where the slurry is separately impregnated into the structure, there is an advantage that the width of the microstructure that can be realized is wide.

Next, the fibrous polymer according to the present invention acts as a pore-forming material by firing, and as a result, an inorganic porous material having continuous pores composed of burn marks of the fibrous polymer can be obtained. it can. Here, it is desirable that the fibrous polymer decomposes and burns out at a lower temperature than the binder component,
The reason is that it is possible to dissipate the gas generated by the decomposition and burning of the binder component and other pore-forming materials through the continuous pores formed as burn marks.

Specifically, as the fibrous polymer, it is preferable to use amylose, cellulose, polyurethane, polyacetal, polyester, or acetate, which is a polymer containing oxygen in the structural main chain. Alternatively, it is preferable to use polyacrylonitrile, polyvinyl alcohol, polyethylene, or polypropylene, which is a polymer having a main chain with a simple linear structure.

Next, the present invention proposes a method for producing an inorganic porous body in which the content of the fibrous polymer in the molded body is 1 to 70% by volume. The reason is that if the content of the fibrous polymer in the molded body is less than 1% by volume, an inorganic porous body having open pores cannot be obtained. Further, if the content of the fibrous polymer in the molded product is more than 70% by volume, the strength of the inorganic porous material obtained after firing is reduced, which is not preferable in practical use. In yet another invention, the content of the fibrous polymer in the molded body is 1 to 95% by volume, although it depends on the shape of the desired molded body and the type and shape of the fibers used. A method for manufacturing a porous body is proposed. The reason is that if the content of the fibrous polymer in the molded product is less than 1% by volume, an inorganic porous material having open pores cannot be obtained, and the content of the fibrous polymer in the molded product is 95% by volume. This is because if it is more than%, the strength of the inorganic porous material obtained after firing is reduced, which is not preferable in practical use. In the present invention, since the fibrous polymer is used by imparting a shape in a state of being in contact with each other in advance, as a result, the contact cross-sectional area of the gel casting slurry-derived portion obtained by solidifying after impregnation in the voids becomes large, It becomes possible to increase the content of the fibrous polymer in the molded body.

Here, the fibrous polymer is used as the pore-forming material by introducing coarse pores having a relatively small gas permeation resistance into the obtained porous material so that the fluid can be quickly introduced into the porous material. This is for supplying inside. The diameter of the pores thus obtained depends on the diameter of the fiber to be used, and the shape can be variously bent according to the rigidity of the fiber. The continuous voids due to the burnt marks of this fiber,
By combining with the pores formed by the burnout marks of the spherical pores, it becomes possible to rapidly supply the target fluid into the inside of the porous body and at the same time to develop chemical or physical interactions everywhere.

Further, the fibrous polymer can be used in the form of being dispersed in the slurry or in the form of bulk. Short fibers can be used as the former example, and nonwoven fabrics and cloths can be used as the latter example. Further, the fibrous polymer is used as a molded body by preliminarily dispersing the fibrous polymer in a slurry, casting this into a cavity having a desired shape, removing the dispersion medium. Examples of the method for removing the dispersion medium include incorporating the dispersion medium into the cavity itself capable of absorbing the dispersion medium, and evaporating the dispersion medium by a method such as heating in the cavity that cannot absorb the dispersion medium. The fibrous polymer that is usually used has a diameter of several microns to several tens of microns and a length of several hundreds of microns to several millimeters. The polymers can be entangled with each other and maintain their shape even when taken out from the cavity. This is particularly remarkable in a polymer containing a large number of functional groups forming hydrogen bonds, and specific examples thereof include cellulose having a hydroxyl group and chitosan having an amino group. Alternatively, if the slurry in which the fibrous polymer is dispersed contains a binder component, the shape can be kept stable regardless of the properties of the polymer.

As the binder component of the slurry, that is, as the gelling agent, for example, a water-soluble epoxy resin can be used. However, considering the handling property of the slurry and the molded product, a component that constitutes a polymer by reactive crosslinking is used. It is desirable to use. This is because the viscosity of the slurry becomes high when a component that constitutes a polymer from the beginning such as agar or polyvinyl alcohol is used, and it is necessary to increase the dispersion medium in order to ensure sufficient handleability. This is because there is a problem that it is low and cracks are likely to occur during degreasing and firing. Therefore, it is desirable to add it as a monomer or a low polymer in the slurry, and to cross-link it by a heat or other stimulus in the mold to obtain a polymer. In addition to the epoxy resin, an acrylic resin, Urea-amide resin,
Phenol resins and the like can be mentioned, but most of them have excellent heat resistance and relatively high decomposition and burning temperatures. Thus, as a substantially continuous and / or dispersed fibrous polymeric pore-forming material in contact with each other,
As described above, a polymer containing oxygen in the structure main chain, particularly amylose, cellulose, polyurethane, polyacetal, polyester, acetate, or a dispersed fibrous polymer pore-forming material, a simple linear structure main If a chain-containing polymer, especially polyacrylonitrile, polyvinyl alcohol, polyethylene, polypropylene, etc., is used, the decomposition and burning temperatures of these are relatively low, so they are first burned from the molded body, and the binder passes through the traces. It becomes easy to dissipate the gas generated by burning out the components and other pore-forming materials, and it is possible to obtain a porous body without cracks.

In order to make a portion where the dispersed fibrous polymer pore-forming material does not exist as a porous body, or with the pores derived from the dispersed fibrous polymer pore-forming material. In order to introduce pores having different diameters and shapes, in addition to the above, a pore-forming material that forms pores by burning can be separately used. Examples of such a pore-forming material include synthetic resin beads such as polyethylene and polystyrene, and particulate organic substances such as starch and carbon. Also, fine pores can be formed by adding a binder component in a larger amount than that required for molding and utilizing the disappearance mark of the binder component. Of course, without using such a pore-forming material, only the independent pores may be present in a portion where the fibrous polymer pore-forming material is not present, or the pores may be dense.

The mold for gel casting is
Use a material that does not absorb the dispersion medium in the gel casting slurry. However, since the gel casting slurry is completely solidified by, for example, leaving it standing or heating it to a predetermined temperature, the mold does not need to be absorbent.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to the examples. (Example 1) 100 parts by weight of zirconia powder, 40 parts by weight of gelling agent (water-soluble epoxy resin), carbon beads (average particle size)
25 parts by weight of 60 μm), 2 parts by weight of cellulose fibers, and 160 parts by weight of ion-exchanged water were mixed in a ball mill to prepare a gel casting slurry. White vaseline was applied inside the styrene mold. The gel casting slurry was cast into the styrene cavity and sealed. This is heated to 80 ° C to make a 100 × 70 × 30 mm hardened body, which is taken out of the mold and frozen at -25 ° C, then 1 To
A molded body was obtained by vacuum degassing and drying so as to maintain rr or less. Here, the content of the fibrous polymer in the molded body was 3% by volume. After degreasing this in air at 500 ° C, 150
A porous body was obtained by firing at 0 ° C. The open porosity of the obtained fired porous body was 70% as determined by the Archimedes method in water, but no cracks or blisters were observed, and fibrous pores and spherical pores dispersed around them were found. It was a microstructure with and.

Example 2 100 parts by weight of zirconia powder,
Gelling agent (water-soluble epoxy resin) 40 parts by weight deionized water
230 parts by weight were mixed in a ball mill to prepare a gel casting slurry. White vaseline was applied inside the styrene mold. After the cellulose nonwoven fabric was placed in the polystyrene cavity, the gel casting slurry was cast and sealed. Heat it to 80 ° C and
A cured product of 0 × 70 × 30 mm was taken out from the mold, frozen at −25 ° C., and then vacuum deaerated so as to maintain 1 Torr or less and dried to obtain a molded product. Here, the content of the fibrous polymer in the molded body was 15% by volume. This was degreased in air at 500 ° C and then calcined at 1500 ° C to obtain a porous body. The open porosity of the obtained fired porous body was 77% when determined by the underwater Archimedes method, but cracks and swelling were not observed, and fibrous pores and spherical pores dispersed around them were found. It was a microstructure with and.

Comparative Example 1 A molded body was obtained in the same manner as in Example 1 except that cellulose fiber was not used.
The open porosity of the porous body obtained by degreasing the obtained molded body and then firing was 64%, but swelling occurred in the central portion and voids were formed.

Example 3 100 parts by weight of acrylic short fiber,
100 parts by weight of ion-exchanged water and 1 part by weight of water-soluble phenol resin were slurried using a mixer. A space was formed by press-bonding two acrylic plates of 200 × 250 × 5 mm, which were coated with white petrolatum on the portion in contact with the slurry, with a silicone resin having a thickness of 5 mm, using a clamp. After the slurry was cast into the mold, it was frozen at -25 ° C, the mold was removed, and the ion-exchanged water was removed in a reduced pressure container kept at 1 Torr or less. On the other hand, 100 parts by weight of alumina powder, gelling agent
45 parts by weight of (water-soluble epoxy resin), 15 parts by weight of carbon beads (average diameter 50 μm), and 190 parts by weight of ion-exchanged water were mixed in a ball mill to form a gel casting slurry.
The above-mentioned fiber molding is placed in a mold having a cavity of 180 W × 225 H × 4 Tmm, and with this standing, the gel casting slurry is cast from the bottom to the top in the gap of the fiber molding, and flowed. Sealed with paraffin. 80 ° C
It is heated to 200 x 250 x 3 mm to obtain a cured product, which is taken out of the mold, frozen at -25 ° C, and then vacuum degassed to keep it at 1 Torr or less and dried to obtain a molded product. It was
Here, the content of the fibrous polymer in the molded body is 50% by volume.
Met. This was degreased in air at 500 ° C and then calcined at 1400 ° C to obtain a porous body. The open porosity of the obtained fired porous body was 35% as determined by the underwater Archimedes method, but no cracks or swelling was observed, and the microstructure had fibrous pores.

Example 4 100 parts by weight of cellulose fiber,
150 parts by weight of ion-exchanged water and 1 part by weight of water-soluble phenol resin were slurried using a mixer. This slurry was cast into a 100 × 70 × 30 mm styrene frame coated with white petrolatum, and then heated to 60 ° C. in a decompression container kept at 1 Torr or less to remove ion-exchanged water. On the other hand, 100 parts by weight of zirconia powder, 30 parts by weight of gelling agent (water-soluble epoxy resin), and 130 parts by weight of ion-exchanged water were mixed in a ball mill to prepare a gel casting slurry. The gel casting was cast into the slurry styrene cavity and sealed with liquid paraffin. By heating this to 80 ℃ to make a 100 × 70 × 30 mm hardened body, taking it out of the mold, freezing it at -25 ° C., and then vacuum degassing to keep it at 1 Torr or less and drying it. A molded body was obtained. here,
The content of the fibrous polymer in the molded body was 90% by volume. This was degreased in air at 500 ° C and then calcined at 1500 ° C to obtain a porous body. The open porosity of the obtained fired porous body was 85% as determined by the Archimedes method in water, but cracks and swelling were not observed, and it was a fine structure having fibrous pores.

(Comparative Example 2) 15 parts by weight of acrylic short fibers, 100 parts by weight of alumina powder, 40 parts by weight of gelling agent (water-soluble epoxy resin), 15 parts by weight of carbon beads (average diameter 50 μm), ion-exchanged water 210 Parts by weight were mixed with a ball mill to prepare a gel casting slurry. 200W x 250H x 5Tmm
The gel casting slurry was cast from the bottom to the top in a state where the inside of the mold having the cavities was erected. The slurry could be cast without pressure at a height of about 100 mm, but pressure was required before that. The gel casting slurry was pushed in with compressed air adjusted to 1.2 atm using a pressure reducing valve, but the casting proceeds from a height of about 180 mm, when the pressure of the compressed air is further increased, the air suddenly enters the cavity. It could not be molded because it penetrated.

From the above results, the porous body produced by the production method of the present invention has three-dimensionally continuous coarse pores derived from the fibrous polymer pore-forming material, which is different from other pore-forming materials. It was confirmed that cracking and swelling did not occur while having a large open porosity by suppressing the dissipation of gas accompanying the burning.

[0026]

As described above, according to the present invention,
A microstructure capable of effectively providing a reaction field can be obtained by forming coarse air holes three-dimensionally by utilizing burnout marks of fibers or by forming pores having a different shape. Furthermore, even if a large-sized thick product is manufactured, there is an effect that cracks and cracks caused by degreasing and firing do not occur.

Claims (6)

[Claims] 1. An inorganic porous material having open pores composed of fibrous polymer burn marks. 2. A molded body obtained by casting a gel casting slurry in which a fibrous polymer is dispersed, heating and curing it, and degreasing and firing the molded body.
A method for producing the inorganic porous body described. 3. The molded product obtained by impregnating a gel-casting slurry into a fibrous polymer forming a bulk shape, heating and curing and then degreasing and firing the molded product. Method for producing inorganic porous body. 4. The method for producing an inorganic porous body according to claim 2 or 3, wherein the content of the fibrous polymer in the molded body is 1 to 70% by volume. 5. A slurry in which a fibrous polymer is dispersed is cast into a cavity of a desired shape, the dispersion medium is removed, and then a gel casting slurry is cast into the gap of the polymer molded body, The method for producing an inorganic porous body according to claim 1, wherein a molded body obtained by heating and curing the dried body is degreased and then fired. 6. The method for producing an inorganic porous body according to claim 5, wherein the content of the fibrous polymer in the molded body is 1 to 95% by volume.