JPH04149079A - Production of ceramics porous body - Google Patents

Abstract

PURPOSE:To produce a ceramics porous body which has communicated fine pores and is enhanced in porosity by blending emulsion of liquid organic substance with a raw material for ceramics incorporating inorganic powder and curing type resin, and shaping this slurry and burning the shaped body. CONSTITUTION:Emulsion (C) of liquid organic substance (e.g. liquid paraffin) (a) having <=50mum mean particle diameter is obtained by forcedly emulsifying the component (a) into a dispersion solvent (b) in the presence of an emulsifying agent (c). Slurry is obtained by blending the emulsion component C and (D) a dispersion medium (e.g. water) with a raw material for ceramics incorporating both (A) inorganic powder (e.g. aluminum oxide) having <=10mum particle diameter and (B) 1-35wt.% curing type resin (e.g. epoxy resin causing cross-linking reaction in an alkaline region) based on the component A. Then, this slurry is shaped into a prescribed shape and a green body is obtained by curing the component B. Successively this green body is dried to remove the component D and the dispersion solvent (b) and heated at 500-600 deg.C at 10-200 deg.C/hr temp. rise rate to remove the component (a) and the component B, and thereafter burned at 1200-1800 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing a ceramic porous body having a high porosity and fine continuous pores suitable for filters, lightweight refractories, bioreactors, etc.

(Prior Art) Ceramic porous bodies having communicating pores are useful for filters, lightweight refractories, bioreactors, etc., and many have already been put into practical use.

Methods for manufacturing these porous ceramic bodies include impregnating urethane foam with ceramic slurry, drying and heat treating to burn out the urethane foam and sintering the ceramic at the same time, and molding a mixture of ceramic powder and combustible material. A method of subsequently firing the molded body is known.

However, although these methods can produce porous ceramic bodies with relatively large pores of 10 μm or more, it is difficult to produce porous bodies with smaller pores.

On the other hand, in order to create fine pores, a method is known in which ceramic raw material particles having a particle size composition are used and voids between the raw material particles remain even after firing. However, in this method, the pores are determined by the voids between the raw material particles, which is difficult to control, and the porosity is about 40% at most, making it impossible to obtain a material with a high porosity.

As another method for producing a ceramic porous body with fine pores, a method has been proposed in which ceramic Zhao fine powder is used and α-olefin oligomer or liquid paraffin is added as an additive (for example, Japanese Patent Application Laid-open No. 1172283), L. However, since this method uses ultrafine powder as a ceramic raw material, it is expensive, and it also requires pressure molding, making it difficult to mold into complicated shapes, and is not a practical method.

(Problems to be Solved by the Invention) The present invention has been achieved as a result of repeated research to overcome the drawbacks of the existing methods of manufacturing porous ceramic bodies as described above, and its purpose is to Another object of the present invention is to provide a method for producing a porous ceramic body having high porosity and fine continuous pores.

(Means for Solving the Problems) The above object is to use an emulsion of a liquid organic substance as a pore-forming material when manufacturing a ceramic porous body having continuous pores using a ceramic raw material containing an inorganic powder and a hardening resin. This is achieved by a method for producing a ceramic porous body characterized by the following.

The slurry in the present invention is prepared using an inorganic powder, a curable resin that increases the strength of the green body through a curing action, a dispersion of a liquid organic substance in an emulsion state, and a dispersion medium.

Inorganic powders used in the present invention include, for example, alumina, zirconia, zircon, cordierite, murai [
・Oxides such as titania, silica, aluminum titanate, and magnesia; non-oxide powders such as silicon nitride, aluminum nitride, silicon carbide, and sialon; and the like. Furthermore, metal silicon powder, metal aluminum powder, carbon powder, etc. may be used for the purpose of producing silicon nitride, aluminum nitride, and silicon carbide by reaction sintering. The inorganic powder that can be applied to the present invention is not limited to these, but the type of inorganic powder and its properties are determined depending on the intended use, such as heat resistance, thermal shock resistance, corrosion resistance, acid resistance, and oxidation resistance. The blending amount can be selected as appropriate.

The particle size of the inorganic powder is preferably 10 μm or less, more preferably 2 μm or less, in view of sinterability and slurry stability.
Most preferably it is 1 μm or less.

In the present invention, the curable resin is present in a slurry containing an inorganic powder and a liquid organic emulsion, and is used to increase the strength of the green body through its curing action. The curable resin is preferably a crosslinking resin that forms a three-dimensional network bond, such as epoxy, phenol,
Examples include soluble or dispersible resins such as urea and melamine. Among these, epoxy resins that cause a crosslinking reaction in the alkaline region where the deflocculant acts particularly effectively are preferred.

In the present invention, the amount of the curable resin added is preferably kept to the minimum necessary amount within the scope of achieving the purpose of the present invention. In other words, the curable resin is burned and removed during the manufacturing process of the ceramic sintered body, and the final product is does not remain, and excessive addition is economically disadvantageous. Furthermore, if the amount of curable resin added increases, cracks tend to occur frequently during the degreasing process, so from this point of view as well, it is better not to add too much.The content of curable resin is preferably 1 to 10% relative to the inorganic powder. It is about 35% by weight, more preferably about 5 to 25% by weight.

The emulsion of liquid organic material in the present invention acts as a pore-forming side and plays an important role in forming a ceramic porous body having fine interconnected pores.

Examples of liquid organic substances include polymer compounds that are liquid at room temperature, such as liquid paraffin and liquid isopropylene.

Further examples include liquid materials in which high molecular weight polymers such as styrene, methacrylate, and acrylate are dissolved in organic solvents, but are not limited thereto. In order to form continuous pores, it is preferable to use a material that is liquid at room temperature. The continuous pores in ceramics are caused by the dispersion of the emulsion being destroyed before or during the curing of the curable resin, and the dispersed particles of the liquid organic substance changing from a free state to a communicating state, and the continuous organic phase is removed during the firing process. Formed by being removed by incineration.

Emulsions can be manufactured by selecting an appropriate method from known methods. For example, a method in which a liquid organic substance is sequentially added dropwise while stirring a dispersion solvent containing an emulsifier using a high-speed shear mixing device such as a homomixer, A common method is a forced emulsification method, typified by a method in which a dispersion medium is sequentially added dropwise to an organic mixture while stirring it with a high-speed shear mixer. The emulsifier used may be an anionic, cationic or nonionic emulsifier, but anionic or nonionic emulsifiers excluding alkali metal salts are preferred in order to maintain dispersion stability of the inorganic powder and avoid residual metal impurities. The emulsion content is an important factor in determining the porosity of the final product, but if the emulsion content is low, the resulting pores will be closed pores instead of open pores. On the other hand, if the content is high, the strength of the ceramic body obtained will be low. The content of the emulsion is usually 20 to 400% by volume, preferably 100 to 300% by volume of the liquid organic substance based on the inorganic powder. The particle size of the emulsion is an important factor determining the pore size of the final product. Considering the storage stability of the emulsion, the average particle size is 5.
It is 0 μm or less, preferably 10 μm or less. The particle size of the emulsion can be appropriately controlled depending on the type and amount of the emulsifier used and the shear rate.

In the present invention, water is usually used as the slurry dispersion.

The slurry in the present invention has a mixed phase mainly composed of the above-mentioned inorganic powder, a hardening resin that increases the strength of the green body, and a liquid in an emulsion state. A deflocculant to effectively and stably disperse the slurry in the dispersion medium, a viscosity adjuster to improve the workability of the slurry, a drying speed adjuster, etc. can be appropriately added to the slurry using a ball mill, attritor, etc. It can be prepared according to a conventional method, such as by uniformly mixing in advance, then adding a liquid resin emulsion and a curable resin to the obtained inorganic powder dispersion and uniformly mixing. The solid content concentration of the slurry is preferably 20-60% by volume, and the viscosity is preferably 10% from the viewpoint of separation due to sedimentation of inorganic powder and ease of handling.
0 to 2000 cps, more preferably 500 to 1000
cps.

The slurry prepared as described above is shaped into a predetermined shape by an appropriate method such as a doctor blade method or a casting method, and the curable resin is cured by standing at room temperature or by heat treatment.
The body should be green and easy to handle. The dispersion solvent is then removed from the green body by air drying or heat drying. Subsequently, in a degreasing step, the liquid organic matter and curable resin of the green body are removed, and then the green body is fired. Degreasing is preferably carried out by raising the temperature at a relatively slow rate of temperature e.g. is preferable and is usually carried out in an air atmosphere, but a nitrogen gas atmosphere or the like may be selected as appropriate depending on the type of ceramic raw material powder.

(Effects of the Invention) The ceramic porous body of the present invention has fine continuous pores and high porosity, and is suitable for filters, lightweight refractories, bioreactors, catalyst carriers, and the like.

Example 1 A dispersion of an inorganic powder and an emulsion of a liquid organic substance having the pure composition shown below were prepared.

Plain aluminum oxide 80% by weight Water 19% by weight Deflocculant 1% by weight Emulsion liquid paraffin 45% by weight Water 50% by weight Emulsifier 5% by weight The inorganic powder mixture was prepared by mixing and dispersing the specified amount in a ball mill for 24 hours. I got it. Aluminum oxide is 0.5% by weight
using particles with an average particle size of 2 μm containing magnesia,
As the deflocculant, Boyze 530 manufactured by Kao was used. The emulsion of the liquid organic substance was prepared by sequentially adding the liquid organic substance dropwise at a rate of 20 CC/min while stirring water at 70° C. to which an emulsifier had been added in advance at a rate of 3000 cps using a homomixer. The emulsifier is Kao's nonionic emulsifier Emulgen 22.
A mixture of Emulgen 910, Emulgen 910 and Emazol in a 1:l:1 weight ratio was used. The particle size of the liquid resin was 15 μm.

The obtained inorganic powder dispersion, liquid organic emulsion, and resin shown in Table 1 were each mixed in a solid content ratio of 63
:23:14 to prepare a slurry. Here, Denacol EX-421 manufactured by Nagase Chemical Industries, Ltd. was used as the water-soluble epoxy. As the amount of epoxy resin, the total amount of water-soluble epoxy and water-soluble amine was converted into solid content. Furthermore, for systems using melamine and phenol, para-toluenesulfonic acid is added to the slurry to adjust its pH to 2 to 2.5.
It was adjusted so that Next, the obtained slurry was poured into a polypropylene container, heat-treated at 80° C. for 12 hours, and after hardening, the green body was removed from the mold and dried. Firing was carried out using an atmospheric electric furnace, and the temperature was raised at a rate of 0.5°C/min up to 400°C and 10°C/min thereafter, held at 1600°C for 1 hour, and then cooled. The results are shown in Table 1.

The appearance of the green body was evaluated based on the following criteria. .

○: No cracks and sufficient strength for handling. △: No cracks, but some difficulty in handling. went.

○: Firing was completed with no cracks. △: Some cracks were generated. As shown in Table 1, it was not possible to produce a satisfactory ceramic body using polyvinyl alcohol, which does not have a hardening property. It can be seen that it is possible to manufacture

Example 2 The second example was carried out in the same manner as in Example 1, except that a liquid emulsion and an aqueous emulsion of liquid amine were used as the curable resin, and the types of nonionic and anionic emulsifiers were appropriately selected when preparing the emulsion of the liquid organic substance. As shown in the table, emulsions of various organic substances were prepared to produce ceramic bodies.The closed porosity was measured by the Archimedes method, and the closed porosity was calculated from the apparent density of the ceramic body and the true specific gravity of the ceramic.

It is clear from Table 2 that continuous pores can be formed by using a liquid organic emulsion.

Example 3 Ceramic bodies were produced in the same manner as in Example 1 except that the amount of liquid organic matter was changed as shown in Table 3 below. However, the firing temperature is 1650℃ and the bending strength is J
A three-point bending test was conducted according to the IS standard (R1601).

As is clear from Table 3, when the amount of liquid organic matter is small, it becomes difficult to form continuous pores, and when it is too large, the strength tends to decrease.

Claims (1)

[Claims] A method for producing a porous ceramic body, which comprises using an emulsion of a liquid organic substance as a pore-forming material when producing a porous ceramic body having continuous pores using a ceramic raw material containing an inorganic powder and a curable resin.