JP2003128477A - Method of manufacturing porous layered ceramic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing porous layered ceramics having a multiple pore size distribution, where its strength does not deteriorate by peeling of the layer is. SOLUTION: Slurries containing pores with different pore size distributions are prepared by mixing a ceramic powder, a solvent, a dispersant, a surfactant, and a thermosetting resin as a binder. Then, the slurries are cast into a mold in order of the pore size distributions from a small to a large, heated with the mold, dried and fired.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a porous ceramic laminate, and more specifically,
The present invention relates to a method for producing a porous ceramic in which layers having different porosities are laminated using a precursor containing pores. Examples of applications of the laminated body composed of such a porous ceramics layer include a fluid filter, a catalyst carrier and an electrode material for a solid electrode fuel cell.

[0002]

2. Description of the Related Art Conventionally, as a method for producing porous ceramics, a method of controlling the pores of a compact produced by pressure molding or the like by low-temperature sintering, or adding an organic substance which is the basis of the pores into a ceramic slurry, Methods such as degreasing to remove organic matter to form pores, and a method of impregnating a ceramic slurry with a sponge made of organic matter having open pores have been proposed. It is produced by forming a compact having a narrow pore size distribution, and partially sintering the compact to give a network structure in which pores are formed between interconnected grains.

[0003]

However, in the above-mentioned prior art, it is difficult to control the shape and size of the pores, and the porosity can be obtained only in a limited range. Further, in the method of controlling porosity by low temperature sintering,
Since the sintered body is not dense, there is a problem that bending strength and breaking strength are low. Further, the method for producing a porous ceramics laminate using an organic substance as a porous precursor has a problem that a large amount of the organic substance is removed by degreasing, which often causes deformation or destruction.

In order to solve such a problem, Patent Document 2
No. 802196 proposes a method of laminating and extruding two types of kneaded materials in which raw materials and blends are adjusted so as to finally produce porous bodies having different porosities. However, in such a laminated body, a discontinuous surface is generated, so that there is a problem that the strength is lowered due to peeling or the like.

The present invention has been made in view of the above circumstances and provides a porous ceramics laminate having a high flexural strength, a high breaking strength, etc., the strength does not decrease due to peeling and the like, and has a multi-stage pore size distribution. It is intended to provide a manufacturing method.

[0006]

The above-mentioned object is a method for producing a porous ceramics laminated body which is composed entirely of homogeneous ceramics, and is thermosetting as a ceramics powder, a solvent, a dispersant, a surfactant and a binder. Of a bubble-containing slurry by mixing and stirring a water-soluble resin and one or more bubble-containing slurries having different pore size distributions from the slurry by controlling the type and addition amount of the surfactant. A step of injecting the above-mentioned two or more air-containing slurries into a mold that does not absorb a solvent in the ascending order of pore size distribution, a step of heating and curing each mold, and a step of drying the obtained cured body, And a step of firing the porous ceramics laminate.

Another object of the present invention is to provide a ceramic powder of a bubble-containing slurry, wherein the content of the ceramic powder in the bubble-containing slurry is 30% by volume to 60% by volume and the pore size distribution is different from that of the slurry. It can also be achieved by a method for producing a porous ceramics laminate having a content substantially equal to the content.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below. In the present invention, as the raw material ceramic powder, in addition to oxides such as alumina, zirconia and yttria, non-oxides such as silicon nitride, sialon and silicon carbide can be used. The solvent is not particularly limited as long as it dissolves the thermosetting resin, but does not require environmental safety and health considerations, and does not require a device such as an organic solvent recovery device. Water is preferred. Any dispersant may be used, such as an alkaline dispersant such as ammonium polycarboxylate or an acidic dispersant such as acetic acid, as long as it is used according to the adaptability of the binder used. Next, as the surfactant, dioctylsulfosuccinate or alkylsulfate salt as anions and alkylphenol or the like as nonions can be used depending on the desired pore size distribution or porosity.

The thermosetting resin used as the binder may be any kind of thermosetting polymer such as an epoxy resin, an acrylic resin, a phenol resin, a urea resin and a melamine resin. Also, these monomers may be used. Further, a composite of a combination of high molecular weight polymers, a composite of a combination of monomers, or a composite of a combination of high molecular weight polymers and monomers may be used. Here, as a further preferred embodiment, one or more high molecular polymers or their monomers may be used.

The mold may be made of any material as long as it does not absorb the solvent in the slurry. However, depending on the kind of binder used as the binder, it reacts with oxygen in the air to form an uncured layer. Therefore, metals such as stainless steel that does not allow air to pass through, or fluorine-based resins having high chemical stability are preferable.

Next, the production method of the present invention will be described in more detail. To the ceramic powder, a solvent, a dispersant, and a surfactant are added, and a thermosetting resin such as an epoxy resin is added as a binder. If any, a reaction initiator or a curing agent that aids in curing is added thereto and mixed to prepare a slurry having a ceramic powder content of 30 to 60% by volume. Here, the content of the ceramic powder is 30% by volume.
The reason for using the above-mentioned slurry is that if the content of the ceramic powder is less than 30% by volume, the molded body during shrinking may greatly contract and drying cracks may occur, which is not preferable. On the other hand, if the content of the ceramic powder exceeds 60% by volume, the viscosity of the slurry is remarkably increased, it is difficult to adjust the slurry, and it is not possible to uniformly generate bubbles in the slurry, which is not preferable.

Further, when producing the laminated body, it is necessary to make the content of the ceramic powder in each of the air-containing slurries equal. This is because a stress is generated at the interface of the laminate due to the difference in drying shrinkage at the time of drying, so that the cured body is peeled off and damaged, which is not preferable.

As described above, the prepared slurry is vacuum-degassed and stirred by stirring blades to generate bubbles in the slurry to obtain the bubble-containing slurry used in the present invention.

The procedure for producing the laminate of the present invention will be specifically described below with reference to schematic diagrams and examples. Preparation of Aerated Slurry 100 parts by weight of alumina powder, 15 parts by weight of water as a solvent, 1 part by weight of a polycarboxylic acid-based dispersant, 6 parts by weight of a methacrylamide binder and 1 part by weight of a curing agent. 0.05 parts by weight of ammonium sulfate and
Dioctyl sulfosuccinate, which is an on-type surfactant, was added and blended, mixed at 25 ° C. for 16 hours in a pot mill, and then stirred in a vacuum with a stirring blade to contain 52% by volume of alumina powder. A bubble-containing slurry having a pore size distribution of 60 to 180 mm was prepared.

Preparation of aerated slurries having different pore size distributions In the same manner as described above, a nonionic surfactant, alkylphenol, was added to obtain a pore size distribution of 60 to 480 m.
An aerated slurry having a diameter of m was prepared.

(3) Casting of Air-Containing Slurry into Molding Mold As shown in FIG. 1, a slurry containing an anionic surfactant is used to obtain a molded product of 70 × 100 × 40 mm, which is made of stainless steel. After injecting into the mold 1 to form the layer 2, the slurry containing the nonionic surfactant was slowly injected into the mold to form the layer 3. Next, 50 ml of edible oil that suppresses evaporation of water in the slurry was poured.

(4) Curing, demolding, drying, and sintering The mold was heated at 70 ° C. for 2 hours to cure the slurry. After demolding the obtained cured product, it was dried at room temperature for 4 days, heated at 10 ° C./h, held at 450 ° C. for 3 hours to degrease, and held at 1600 ° C. for 3 hours to be baked. To produce a porous ceramics laminate. In this embodiment, the case where the number of laminated layers is 2 has been described, but the number of laminated layers is not limited, and it is possible to manufacture a laminated cured body having many layers.

(5) Evaluation The obtained fired body was cut, and the dispersed state of the pores on the cut surface was examined by an optical microscope. As a result, the pore size distribution obtained from the slurry to which the anionic surfactant was added was 50 to 150.
mm-layer (hereinafter abbreviated as layer A) and a slurry obtained by adding a nonionic surfactant to 50 to 400.
The mm layer (hereinafter abbreviated as layer B) was in a smoothly joined state, and the pores of each layer were uniformly dispersed. Next, as a result of evaluating each layer of the obtained fired body by the Archimedes method, the bulk specific gravity of the layer A is 1.80, the porosity is 70%, the bulk specific gravity of the layer B is 1.80, and the porosity is Was 55%. Further, the firing shrinkage was 16 to 17%, which was almost the same as the shrinkage rate of the dense body. Next, the bending strengths of the layer A and the layer B were measured again. As a result, the layer A was 34 MPa and the layer B was 1
The strength was as high as 8 MPa.

[0019]

As described above, according to the manufacturing method of the present invention, the bending strength and the breaking strength are high, the strength does not decrease due to peeling and the like, and the porous ceramic laminate has a multi-stage pore size distribution. Has come to be obtained. By this, the porous ceramics laminated body can be easily manufactured at a low cost and has an effect.

[Brief description of drawings]

FIG. 1 is a schematic diagram of a method for manufacturing a porous ceramics laminate according to an example of the present invention.

[Explanation of symbols]

1 Mold 2 Slurry layer formed by adding anionic surfactant 3 Slurry layer formed by adding nonionic surfactant

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Tatsuya Shiogai             2-4-2 Daisaku Sakura City, Chiba Prefecture Pacific Semé             Central Research Institute

Claims (2)

[Claims] 1. A method for producing a porous ceramics laminate, which is composed entirely of homogeneous ceramics, wherein ceramics powder, a solvent, a dispersant, a surfactant, and a thermosetting resin as a binder are mixed and stirred. And a step of adjusting one or more bubble-containing slurries having a pore size distribution different from that of the slurry by controlling the kind and the addition amount of the surfactant, and the two or more bubble-containing slurries. It is characterized by including a step of injecting the slurry into a molding die that does not absorb the solvent in the order of its pore size distribution being small, a step of heating and curing the whole die, a step of drying the obtained cured body, and a step of firing. And a method for producing a porous ceramics laminate. 2. The content of the ceramic powder in the bubble-containing slurry according to claim 1 is 30 to 60% by volume, and the content of the ceramic powder in the bubble-containing slurry having a pore size distribution different from that of the slurry. The method for producing a porous ceramic laminate according to claim 1, wherein the methods are substantially the same.