JPH04202071A - Production of ceramic porous body - Google Patents

Abstract

PURPOSE:To enhance strength by dispersing or dissolving ceramic powder and a specified org. substance in a solvent, adding a cross-linking agent to the resulting ceramic slurry, foaming the slurry by stirring, molding and hardening the foamed slurry, drying and sintering the molded body. CONSTITUTION:Powder of ceramic such as Al2O3 is mixed with prescribed amts. of water and an org. substance hardenable by cross-linking or polymn., e.g. PVA to prepare a ceramic slurry. A peptizer such as ammonium polyacrylate, a thickener such as methylcellulose, a foam regulating agent such as ammonium stearate and a cross-linking agent such as glutaraldehyde are added to the ceramic slurry and this slurry is foamed by mechanical stirring and poured into a mold. Cross-linking or polymn. is allowed to proceed and the resulting hardened molded body is dried and sintered in the air to obtain a ceramic porous body.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for manufacturing a ceramic porous body used for filters, heat insulating materials, catalyst carriers, heaters, etc.

[Conventional technology]

Conventionally, porous ceramic bodies have been manufactured by the following method.

■A method for manufacturing porous ceramic bodies by filling and sintering particles with controlled particle diameters and turning the filled voids into pores.

(2) A method of manufacturing a ceramic porous body by depositing ceramic slurry on a porous resin (foam) having open pores, drying it, degreasing it, and sintering it.

■A method of manufacturing porous ceramic bodies by mixing ceramics and a foaming agent in a porous resin (foam) prepolymer, curing the foamed state, degreasing, and sintering.

■Ceramic slurry or ceramic fine particles and particles made of a sublimable, combustible or soluble substance with a controlled particle size are mixed and formed, and then the sublimable, combustible or soluble substance is removed, A method of manufacturing porous ceramic bodies by sintering.

■A method of producing a ceramic porous body by foaming a ceramic slurry, dehydrating it to lose its fluidity, drying it, and sintering it.

[Problem to be solved by the invention]

Each of the above-mentioned methods has the following drawbacks.

With method (2), it is not possible to obtain a ceramic porous body with high porosity.

With method (2), it is possible to obtain a ceramic porous body with high porosity. However, the gas generated when the resin is burned out tends to cause cracks in the ceramic skeleton, making it impossible to obtain a high-strength ceramic porous body. Also,
Since it is necessary to impregnate a porous resin with a ceramic slurry and remove excess slurry, the pore diameter of the porous resin is required to be large to some extent, and it is not possible to obtain a ceramic porous body with a small pore diameter.

With method (2), a high-strength ceramic porous body can be obtained. However, the conditions for degreasing a large amount of resin contained in a molded body are limited, and it is particularly difficult to produce a porous ceramic body having closed pores.

With method (2), a ceramic porous body with a uniform pore size distribution can be obtained. However, sublimable, flammable or soluble substances tend to remain as impurities such as ash. For this reason, for example, when a ceramic porous body is used at high temperatures, there is a problem that impurities may cause gas generation. Moreover, using these substances leads to an increase in cost.

In method (2), when the foam slurry is dried and dehydrated to fix the foam structure, the dehydration progresses gradually from the surface, and during this time the internal foam structure grows and the foam diameter increases. A ceramic porous body obtained by sintering has a problem in that the pore diameter tends to vary.

The present invention was made in order to solve the above problems, and it is possible to easily produce a ceramic porous body with a wide range of pore diameters, a uniform pore diameter distribution, and high strength, regardless of whether the pores are closed or open. It is an object of the present invention to provide a method that can be manufactured at low cost.

[Means to solve the problem]

The method for producing a porous ceramic body of the present invention includes the steps of preparing a ceramic slurry in which ceramic powder and an organic substance that can be hardened by crosslinking polymerization are dispersed or dissolved in a solvent, adding a crosslinking agent to the ceramic slurry, This method is characterized by a step of molding and curing the foamed product by stirring, and drying and sintering the molded product.

[For production]

In the method of the present invention, a ceramic slurry is first prepared by dispersing or dissolving a ceramic powder and an organic substance that can be hardened by crosslinking polymerization in a solvent. A binder, a dispersant, a deflocculant, a foam stabilizer, a foam stabilizer, a thickener, etc. may be added to this ceramic slurry. Organic substances that can be cured by crosslinking polymerization include polyfunctional polymers. Multifunctional polymers also function as binders.

Next, a crosslinking agent is added to the obtained ceramic slurry,
The foamed material is mechanically stirred and then molded, and the organic material is gelled and cured by a crosslinking polymerization reaction. A cross-linking agent may be added to ceramic slurry and foamed by mechanical stirring, which may be poured into a mold or molded, or the ceramic slurry may be molded by adding a cross-linking agent to the slurry and forming the foam in a mold with a fixed volume (closed system). The rally may be stirred and shaped. At this time, the bubble diameter of the foamy slurry can be controlled by adjusting the stirring intensity. The bubble diameter of the foamed slurry immediately after foaming is uniform. In this state, the crosslinking polymerization reaction proceeds throughout the foamy slurry and gelation occurs.
The growth of bubbles is suppressed, and the pore size in the cured molded product is uniform. In addition, by controlling the speed of the crosslinking polymerization reaction by adjusting the type and addition rate of the polyfunctional polymer and curing agent, reaction temperature, pH, etc., it is possible to make the pores either closed or open. .

Furthermore, by drying the molded body to remove the solvent, degreasing it, and then sintering it, a ceramic porous body with uniform pore diameter and high strength can be manufactured.

〔Example〕

The present invention will be explained in detail below.

Example 1 100 parts of alumina with an average particle size of 1.0, 4 parts of ion-exchanged water
0 parts of polyvinyl alcohol (PVA) as a crosslinkable polymer, and 1 part of ammonium polyacrylate as a deflocculant were mixed in a pot mill overnight to prepare a slurry. To this slurry were added 1 part of methylcellulose as a thickener and 1.25 parts of glutaraldehyde (25 vi% relative to PVA) as a crosslinking agent, and stirred and foamed using a stirrer. Furthermore, hydrochloric acid was added to this slurry as a crosslinking catalyst so that the pH became 1.2, and after thorough stirring, it was poured into a mold. As a result, crosslinking polymerization progressed, and it became possible to release the mold after about 1 hour. After drying the molded body, it was sintered to obtain a ceramic porous body.

The obtained ceramic porous body had a porosity of 65%, a bulk density of 1-4 g/cm 3 , and an average pore diameter of 200 μm.

In addition, all the pores were closed pores.

Example 2 100 parts of calcia-stabilized zirconia with an average particle size of 1.0, 30 parts of ion-exchanged water, 3 parts of Isopan-110 (manufactured by Kuraray) as a crosslinkable polymer, and 1 part of ammonium polyacrylate as a deflocculant. A slurry was prepared by mixing the two parts in a pot mill overnight.

To this slurry, 1 part of methylcellulose was added as a thickener.
And 1 part of ammonium stearate was added as a foam stabilizer, and the mixture was stirred and foamed using a stirrer. Furthermore, 0.3 parts of B-1 (manufactured by Kuraray) (10 wt % based on isopane-110) was added to this slurry as a crosslinking agent, and after thorough stirring, it was poured into a mold. As a result, crosslinking polymerization progressed, and it became possible to release the mold after about 5 hours. After drying the molded body, it was sintered in air at 1700°C for 2 hours to obtain a ceramic porous body.

The obtained ceramic porous body had a porosity of 87%, a bulk density of 0.8 g/cm 3 , an average pore diameter of 50 mm, a maximum pore diameter of 70 mm, and small variations in pore diameter.

In addition, almost all the pores were open pores.

〔Effect of the invention〕

As detailed above, if the method of the present invention is used, closed pores,
Regardless of open pores, a ceramic porous body with a wide range of pore diameters, a uniform pore diameter distribution, and high strength can be easily and inexpensively produced.

Applicant's agent: Patent attorney Takehiko Suzue

Claims (1)

[Claims] A step of preparing a ceramic slurry in which ceramic powder and an organic substance that can be hardened by crosslinking polymerization is dispersed or dissolved in a solvent, and a step of adding a crosslinking agent to this ceramic slurry, stirring it, foaming it, and then molding and hardening it. and a method for producing a ceramic porous body, which comprises drying and sintering this molded body.