JPH0940478A - Production of open pore type porous body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method of an open pore type porous body by which the formation of a fine pore layer is uniform and stable on an inclined open pore type porous laminated body, and the arrangement of the particle, etc., optimized. SOLUTION: The open pore type porous body having a fine pore film on the surface of the open pore type porous laminated body inclined such that fine pore diameters become successively small toward the surface or a fine pore layer across a slight depth from the surface is produced with this production method, and the thin film or the surface layer is formed at least with either one method among a vapor chemical reaction method, a vacuum deposition method, an ion plating method or a sputtering method on the surface of the open pore type porous laminated body.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a gas filter,
The present invention relates to a method for producing an open-pore type porous body used as a filter body, a catalyst carrier, and the like.

[0002]

2. Description of the Related Art A porous body has a large number of small holes in its solid structure. The porous body includes an open pore type and a closed pore type. The open-pore type has pores communicating with each other and has air permeability and water permeability as a whole porous body, and is mainly used for gas filters, filter bodies, catalyst carriers and the like. In the closed pore type, pores are surrounded by walls and are independent of each other, and the porous body as a whole has no air permeability or water permeability, and is mainly used as a heat insulating material and a heat exchanger. The present invention particularly refers to the former open-pore type porous body.

In order to eliminate pressure loss during use and to obtain optimum permeation performance and separation performance, the following manufacturing method is adopted for such open-pore type porous material.
In particular, a method of manufacturing a ceramic open-pore type porous body will be described. (1) The ceramic powder is molded by a cast molding method, an extrusion molding method, a doctor blade method, an injection molding method, or the like. (2) Next, a layer having a pore size smaller than that of the ceramic powder is formed on the surface of the ceramic powder compact. A slurry or a plastic material containing ceramic particles having a particle size smaller than that of ceramic powder and having a high concentration is applied, dipped or laminated, dried, and sintered. This formed a two-layer inclined open-pore type porous laminate. (3) When it is desired to further incline, in order to make the pore size smaller than that of the layer formed in (2), a ceramic having a different particle size or composition from the ceramic particles of (2) is used as in (2). A slurry or a plastic material containing particles is applied, dipped or laminated, dried and sintered. (4) A microporous layer having a smaller pore size is formed on the surface of this open-pore type porous laminate. This fine pore layer is formed by applying a sol containing ceramic particles having a particle size or a composition such that a desired pore size and a porosity can be obtained, and gelling,
It is formed by drying and sintering. The application, gelation, drying and sintering of this sol are often repeated.

The microporous layer formed on the surface of the open-pore type porous laminate has a great influence on the permeation performance and separation performance of the open-pore type porous body. The volume of the pores contained in a unit weight of the porous body is called the pore volume, and the ratio of the pore volume to the total volume is called the porosity.

[0005]

However, in the above-mentioned production method, since the concentration of the active ingredient in the sol is low, the amount remaining as a microporous layer when dried and sintered is very small, and the sol It is difficult to uniformly coat the surface of the open-pore type porous laminate with a uniform amount of sol, so that the coating amount of the sol becomes uneven. Therefore, in the process of sintering the sol, pinholes, cracks, peeling, and the like were likely to occur, and the pore size distribution of the micropore layer was uneven.

Further, in order to improve the permeation performance and separation performance of the microporous layer, it is necessary to optimize the arrangement of particles in the microporous layer, but in the conventional manufacturing method, the coating unit of the sol containing particles is used. Only then could the placement of the particles be controlled. Therefore, even if the particle size and composition of the particles contained in the sol are changed or the coating amount of the sol is changed, it is difficult to optimize the arrangement of the particles in the formed microporous layer.

The present invention was created to solve the above problems. That is, a method for producing an open-pore type porous body, which can uniformly and stably form a fine-pore layer in a graded open-pore type porous laminate and can optimize the arrangement of particles thereof The purpose is to do.

[0008]

According to the present invention, a fine pore film or a slight depth from the surface is formed on the surface of an open pore type porous laminate in which the pore diameter is gradually decreased toward the surface. A method for producing an open-pore type porous body having a fine-pore layer across, wherein the surface of the open-pore type porous laminate has any of a vapor phase chemical reaction method, a vacuum deposition method, an ion plating method and a sputtering method. There is provided a method for producing an open-pore type porous body, which comprises forming a thin film or a surface layer by at least one of the methods.

According to a preferred embodiment of the present invention, the thin film or surface layer is made of alumina, zirconia, silica, aluminum silicate, mullite, zeolite, cordierite, porcelain, carbonized. It is formed of at least one component selected from silicon, silicon nitride, and carbon.

Further, according to a preferred embodiment of the present invention, in the case where the thin film is formed of two or more kinds of components, in consideration of use under heating, the open pore type porous laminate and the thin film are formed. The ratio of the composition components is changed so as to reduce the difference in thermal expansion.

As described above, when a thin film or surface layer is formed on the surface of the open-pore type porous laminate by any one of the vapor phase chemical reaction method, the vacuum deposition method, the ion plating method and the sputtering method, Since the pore layer can be formed from a particle unit to an atom unit, it is possible to easily optimize the arrangement of particles and improve the permeation performance and the separation performance thereof. Further, peeling of the thin film can be prevented by changing the composition ratio of the thin film to form the thin film so as to reduce the difference in thermal expansion between the open-pore type porous laminate and the thin film.

[0012]

Embodiments of the present invention will be described below. The method for producing an open-pore type porous body of the present invention, in place of the conventional method of forming a fine pore layer by applying a sol, CVD (Chemi
cal vapor deposition (chemical vapor deposition) method, sputtering method, ion plating method or vacuum deposition method is used to form a thin film that is a fine pore layer, or a graded open pore type porous laminate The surface layer, which is a fine pore layer, is formed by a CVI (Chemical Vapor Infiltration) method over a slight depth from the surface.

The CVD method and the CVI method are generically called a vapor phase chemical reaction method. Since a thin film is formed using gas in this method, it is possible to form a thin film having a uniform film thickness even on an object having a complicated shape, and the degree of freedom in selecting raw materials for forming the thin film is high. Its main feature is that it is extremely large. Further, since the structure of the thin film can be controlled on the order of several atomic layers, the arrangement of the particles can be easily optimized.

The CVD method is a method of forming a thin film by introducing a source gas onto a heated substrate and precipitating a reaction product from the gas phase on the surface thereof. The main feature is that a high-purity thin film can be formed from a metal or inorganic material having a high melting point at a relatively low temperature, and it is particularly used when forming a ceramic thin film. In addition, the CVI method is a method in which a source gas is introduced into the inside of an object, a reaction product is deposited therein, and the inside of the object is filled with the reaction product. According to this method, the reaction product can be filled to a slight depth from the surface of the inclined open-pore type porous laminate to form a surface layer which is a microporous layer.

The vacuum deposition method, the ion plating method and the sputtering method are generally PVD (Physical Vapor).
It is called a Deposition (physical vapor deposition) method and has the following features. (1) The degree of freedom in selecting raw materials for forming a thin film is extremely high, and it is possible to coat metals, alloys, ceramics and organic materials. (2) The film structure can be controlled by changing the temperature of the object on which the thin film is formed. (3) A thin film of the reaction product can be formed by reacting the vaporized substance with the atmospheric gas. (4) It is possible to form a smooth thin film having high purity and good adhesion.

Although it is not possible to control the structure of the thin film on the order of several atomic layers as in the vapor phase chemical reaction method described above, by controlling the film structure, a thin film with excellent porosity and pore size distribution is formed. be able to.

The vacuum deposition method is a method of evaporating a metal in a vacuum at a pressure of 10 ^-5 to 10 ^-6 Torr and depositing the metal into a thin film with the vapor. It is the simplest thin film forming means in the PVD method, and its main feature is that it is easy to electrically control an evaporation source for evaporating a metal.

The ion plating method is a method of forming a thin film by causing a gas discharge in an atmospheric gas and ionizing the vaporized particles to activate them. The main characteristics are that the adhesion of the thin film is extremely strong, that the thin film is formed quickly, that there are very few defects such as pinholes, and that it is easy to obtain a high density.

The sputtering method is a method of irradiating ions in plasma onto a solid surface and causing them to collide at a high speed, exchanging momentum between ions and atoms on the solid surface, and ejecting atoms from the solid surface to form a thin film. is there. The main characteristics are that the adhesion of the thin film is extremely strong, that a thin film of a high melting point substance can be easily formed, that a uniform thin film can be formed over a wide area, and that the composition of the thin film can be easily controlled.

Therefore, by forming a thin film or surface layer on the surface of the graded open-pore type porous laminate by these methods having the above-mentioned characteristics, the arrangement of particles can be optimized, and A uniform and stable microporous layer can be formed.

If the raw material gas components are combined so that the coefficient of thermal expansion of the thin film is close to the coefficient of thermal expansion of the open pore type porous laminate, the difference in thermal expansion between the open pore type porous laminate and the thin film is obtained. It is relaxed and its peeling can be prevented. When a thin film is formed by combining two or more kinds of components, in order to achieve the desired pore diameter, porosity and pore diameter distribution, and to prevent the peeling, the composition of the source gas or the flow rate ratio is By changing it in series, the coefficient of thermal expansion of the portion in close contact with the open-pore type porous laminate is made close to that of the open-pore type porous laminate, and the thermal expansion of the open-pore type porous laminate and the thin film is increased. The difference should be eased.

[0022]

[Examples] Next, Examples 1 and 2 in which an open-pore type porous body was produced by using the production method of the present invention and a comparative example in which an open-pore type porous body was produced by a conventional production method were prepared. Table 1
This will be described with reference to FIG.

[0023]

[Table 1]

In Example 1, first, alumina powder having a particle diameter of 21 μm, a dispersant, a binder, and water were wet-mixed in a ball mill to form a mud, which was then molded by a cast molding method using a gypsum mold. The molded body is sintered at 1500 ° C. for 1 hour to form a base layer (hereinafter referred to as a base layer) of the open pore type porous laminate, and this base layer is bonded with alumina powder having a particle diameter of 0.5 μm, a dispersant, and a binder. A wet-mixed agent and water were wet mixed in a ball mill, and the steps of dipping and drying were repeated 5 times, followed by sintering at 1400 ° C. for 1 hour to obtain a graded open-pore porous laminate. Formed and the surface temperature is 800
℃, pressure 5 × 10 ^-3 Toll, sputtering gas Ar
A thin film (alumina film), which is a fine pore layer, is formed on the surface of the open pore type porous laminate by a sputtering method under the condition of a —O ₂ mixed gas (O ₂ concentration 20%).

In advance, the film thickness is 100 nm and the average pore diameter is 5
When the sputtering method was carried out with 0 nm and a porosity of 75%, a desired microporous layer could be obtained as shown in Table 1. In addition, no defects such as pinholes, cracks, and peeling were observed. The surface temperature is 500 to 1200 ° C and the pressure is 5 × 10 ^{-2 to} 5 × 1.
A thin film could be formed under the conditions of 0 ⁻⁴ Toll and a sputtering gas of Ar—O ₂ mixed gas (O ₂ concentration of 5 to 30%).

In Example 2, first, alumina powder having a particle diameter of 15 μm, a dispersant, a binder, and water were wet mixed in a ball mill to form a mud, which was then molded by a filter press, and the molded body at 1450 ° C. Sintering for 1 hour forms a base layer of the open-pore type porous laminate, and the base layer has a particle size of 0.
4 μm alumina powder, dispersant, binder, and water were wet-mixed in a ball mill to make a mud scoop, and the process of dipping and drying was repeated 5 times, and then the mixture was sintered at 1400 ° C. for 1 hour to be graded. To form an open-pore type porous laminate having a surface temperature of 1100 ° C., a pressure of 4 Torr, a source gas of aluminum alkoxide system and O ₂ system, and a carrier gas of H _2-.
Ar gas (Ar concentration 5%), gas flow rate is 2000cc /
A microporous layer is formed on the surface of the open-pore type porous laminate by repeating the discontinuous CVD method for alternately supplying aluminum alkoxide-based and O ₂ -based source gases under the condition of minutes (25 ° C., 1 atm) for 300 times. It is a thin film (alumina film) formed.

The film thickness is 50 nm and the average pore size is 25 in advance.
When the CVD method was carried out so that the pore size was 45 nm and the porosity was 45%, a desired fine pore layer could be obtained as shown in Table 1. In addition, defects such as pinholes, cracks, and peeling were not found at all as in Example 1. In addition,
Surface temperature is 600 ~ 1300 ℃, pressure is 0.1 ~ 50To
rr, carrier gas is H ₂ -Ar gas (Ar concentration 0-10
%), The gas flow rate is 1500 to 5000 cc / min (25
A thin film could be formed even under the condition of (° C., 1 atm).

In the comparative example, first, alumina powder having a particle diameter of 21 μm, a dispersant, a binder and water were wet mixed in a ball mill to make mud, and then molded by a cast molding method using a gypsum mold, and the molding was performed. The body is sintered at 1500 ° C. for 1 hour to form a base layer of an open-pore type porous laminate, and the base layer is wet-mixed with an alumina powder having a particle size of 0.5 μm, a dispersant, a binder and water in a ball mill. After repeating the process of dipping and drying 5 times in a mud-removed product,
After the time sintering, a graded open-pore type porous laminate is formed, and alumina sol coating, gelling, drying and sintering are performed.
Repeated times to form a microporous layer on the surface of the open-pore type porous laminate.

As shown in the table, a fine pore layer having an average pore diameter of 60 nm and a porosity of 30% was obtained. Moreover, in this microporous layer, pinholes and cracks were generated at several places.

From these results, comparing Example 1 and Example 2 with Comparative Example, the porosity was 70% in Example 1, 45% in Example 2, and 30% in Comparative Example. The Example 2 is far superior to the Comparative Example in the permeation performance and the separation performance. That is, to put it simply, Embodiment 1 and Embodiment 2
This means that the number of pores is larger, and the permeation performance and separation performance are superior. Furthermore, Example 1,
In Example 2, it can be seen that the microhole layer has no defects such as pinholes and cracks, whereas the comparative example has pinholes and cracks.

The present invention is not limited to the above-described embodiments and examples, and it goes without saying that various modifications can be made without departing from the gist of the present invention.

[0032]

According to the above-described method for producing an open-pore type porous body of the present invention, in the formation of the fine pore layer, the arrangement of the particles can be optimized only by changing the conditions for forming the thin film. Therefore, it has an excellent effect such that the porosity can be increased and a fine pore layer having no defects such as pinholes, cracks, and peeling can be formed.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Tadashi Sasa Tadashi, 1-1-15 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Ltd. Technical Research Institute (72) Nobuo Ninomiya 3-1-1, Toyosu, Koto-ku, Tokyo No. Ishikawajima Harima Heavy Industries Co., Ltd. Technical Research Institute (72) Inventor Joji Shinohara 3-1-15-1 Toyosu, Koto-ku, Tokyo Ishikawajima Harima Heavy Industries Co., Ltd. Technical Research Institute

Claims (3)

[Claims] 1. An open pore having a fine pore film or a fine pore layer extending to a slight depth from the surface on the surface of an open pore type porous laminate in which the pore diameter is gradually decreased toward the surface. A method for producing a porous mold body, wherein a gas phase chemical reaction method, a vacuum deposition method,
A method for producing an open-pore type porous body, comprising forming a thin film or a surface layer by at least one of an ion plating method and a sputtering method. 2. The thin film or surface layer is made of alumina, zirconia, silica, aluminum silicate, mullite, zeolite, cordierite, porcelain, silicon carbide, silicon nitride, or carbonaceous material. The method for producing an open-pore type porous body according to claim 1, which is formed of at least one kind of component. 3. When the thin film is formed of two or more kinds of components, the ratio of the composition components is changed so as to reduce the difference in thermal expansion between the open pore type porous laminate and the thin film. Alternatively, the method for producing an open-pore type porous body according to claim 2.