JPH03208870A - Production of porous ceramic body - Google Patents

Abstract

PURPOSE:To enhance porosity, pore diameter and distribution control thereof by kneading powder consisting of graphite, carbon or a carbon precursor, the raw material powder of ceramic, a binder and water and thereafter molding the kneaded material, drying and calcining the molded body. CONSTITUTION:A mixture is regulated to 100% by mixing 15-70wt.% (hereinafter shown in %) powder such as graphite, carbon or a carbon precursor like synthetic resin beads which has <=3 aspect ratio and is regulated to 1-250mum particle diameter, 20-70% raw material powder of ceramic such as Al2O3 which has 2 aspect ratio and 10-40% binder which is independently an inorganic binder such as clay or used in combination with an organic binder such as acacia. Water is added to the mixture so as to be regulated to 10-30% and kneaded. Furthermore as necessity, a fluidity imparter, carbonate such as Na2CO3 and carbon fiber, etc., may be added. After this kneaded material is molded and the molded body is dried, it is slowly raised in temp. in an oxidative atmosphere and fired at a comparatively low temp. Then it is fired at a high temp. in a nonoxidative atmosphere and thereby a porous ceramic body excellent in air-permeability and durability is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to porous ceramic bodies used as catalyst carriers, bioreactors, gas permeable bodies such as filter media, liquid permeable bodies, solid lubricants, solid abrasives, etc. This relates to the manufacturing method.

[Prior art 1] Conventionally, this type of porous ceramic body has been produced industrially by a method in which ceramic raw material powder is kneaded with a caking material, molded by injection molding, etc., and then dried, degreased, heated, and sintered. had been adopted.

[Problem to be Solved by the Invention 1] Such a porous ceramic body is required to have continuous pores uniformly distributed throughout the ceramic body, regardless of its use, and the porosity and porosity may vary depending on the use. It is desirable that the pore size and its distribution be adjustable.

However, porous ceramic bodies manufactured by the above-mentioned conventional methods do not necessarily fully satisfy this requirement, and in particular, it has been difficult to control the pore diameter and pore distribution.

In addition, in the method for manufacturing a porous ceramic body, glycerin, polyethylene, CMC
A large amount of homoviscous organic matter may be used as a fluidity-imparting agent, and during baking and degreasing following molding, the fluidity-imparting agent gasifies and stagnates, easily causing fatal defects such as cracks or expansion. There was a problem.

Porous ceramic bodies are normally used for applications such as bioreactors, carriers, filtration media, solid abrasive materials, and solid lubricants, but in order to fully demonstrate their functions and maintain their performance for a long period of time, Regardless of the application, pore size and pore distribution are extremely important physical properties. Furthermore, depending on the purpose of use, raw materials to be used must be selected in consideration of wettability with gases, liquids, etc. that come into contact with the porous ceramic body.

As a result of intensive studies to solve the above-mentioned problems, the inventors of the present invention uniformly contained powder and granules made of graphite, carbon, or a carbon precursor in a kneaded material of raw materials, and burned out the powder and granules by firing. As a result, the burnt remains of the powder become pores while maintaining the shape of the powder, and the pores form continuous pores, resulting in a porous ceramic body with excellent air permeability and suitable for various uses. The present invention was achieved based on the discovery that the following can be obtained.

That is, an object of the present invention is to industrially advantageously produce a porous ceramic body with excellent air permeability and durability, in which continuous pores are uniformly distributed throughout the ceramic body.

[Means for Solving the Problems 1] However, the object of the present invention is to form a kneaded material containing powder or granules made of graphite, carbon or a carbon precursor, ceramic raw material powder, a caking agent, and water, and then dry it. , easily achieved by firing.

[Action J The present invention will be explained in detail below.

The method for producing a porous ceramic body according to the present invention is characterized in that a granular material made of graphite, carbon, or a carbon precursor is contained in a molded body of a raw material kneaded product. The powder and granules are easily burnt out as carbon dioxide gas by firing, and after being burnt out, pores having almost the same shape as the powder and granules are formed, and when the powder and granules are burnt out as carbon dioxide gas, The pores are connected to each other to form continuous pores. Note that the carbon precursor herein refers to materials that are easily carbonized by firing, such as wood flour, synthetic resin beads, CMC, or starch granules. Graphite or carbon includes graphite, coke, charcoal,
Examples include carbon black and activated carbon.

As the powder or granule made of graphite, carbon or carbon precursor, powder or granule with as close to a spherical shape as possible, that is, an aspect ratio (major axis l minor axis) of 3 or less, more preferably 2 or less, is used. When used, the pores of the resulting porous ceramic body become nearly spherical, and various properties such as air permeability and durability are further improved, which is preferable. In order to obtain powder particles as close to spherical as possible, for example,
10. Use a powder or granule that is initially approximately spherical, such as synthetic resin beads; knead organic powder or granule such as 2゜0MC1 starch with water and granulate it into a roughly spherical shape; 3. There are methods such as using a raw material that has been pulverized by a method such as grinding that yields approximately spherical granules.

In the case of 2°0, it is preferable to heat and harden the granulated organic powder until just before carbonization and then use it as a raw material.

These powders made of graphite, carbon or carbon precursors are
It is preferable to use particles whose particle size has been adjusted and adjust the amount used, since the pore diameter and porosity of the porous ceramic body to be produced can be easily adjusted.

Depending on the desired pore size, the powder or granule has a particle size slightly larger than the pore size, preferably within the range of 1 to 250 pm, taking into account shrinkage during firing. It is recommended to select. Furthermore, by using powder with relatively uniform particle sizes, products with excellent properties such as air permeability and durability can be obtained. That is, it is preferable to use powder or granules with uniform particle sizes such that substantially all of the particles in the powder or granules are contained within a range of 1100 pm or less, more preferably 80 pm or less in terms of particle size difference.

On the other hand, ceramic raw material powders include alumina, silica, zirconia, talc, mica, verminiquirite, mullite, shirasu, perlite, feldspar, seed stone, and kaolin-based and montmorillonite-based clays and clays. Any commonly used ceramic raw material powder such as clay powder can be used, but unless clay is used without granulation, selecting a ceramic raw material powder from the viewpoints detailed below will result in better air permeability and durability. A high quality porous ceramic body is obtained, which is preferable. That is, as a ceramic raw material powder, a raw material powder with a small aspect ratio, that is, an aspect ratio of less than or equal to 1.5, more preferably 1.5 or less, and most preferably 1.
It is preferable to use raw material powder with a particle diameter of 3 or less, such as silica, alumina, etc., which originally has a small aspect ratio, and is more preferably ground by a grinding method such as grinding that produces a roughly spherical pulverized product. or by kneading originally flat powder or clay such as talc or mica with water or an organic binder to obtain the desired particle size, and then firing or sintering. It is recommended to use it as If an organic binder is used during the granulation, it will foam during firing and a porous ceramic raw material powder can be obtained. In addition, there is a method of using ceramic raw materials that expand in volume during sintering and form a spherical shape, such as pearlite, shirasu, and obsidian.

As these ceramic raw material powders, it is preferable to select a type of powder that matches the properties of the product to be manufactured. In addition, unless the clay is used without granulation, depending on the desired pore size, it is advisable to select a powder with a slightly larger particle size than the pore size, preferably within the range of 2 to 250 pm. . Furthermore, if a powder with as uniform a particle size as possible is used as the ceramic raw material powder, not only will the pore size of the product be uniform, but also the phenomenon of cracks caused by rapid expansion of the fluidity imparting agent during firing can be suppressed. be able to. Specifically, the difference in particle size is 1
It is preferable to adjust the particle size so that substantially all of the particles in the powder are contained within a range of 100 pm, more preferably 80 pm or less.

The caking materials used as raw materials in the present invention include clay, aluminum phosphate, water glass, inorganic caking materials such as highly basic aluminum chloride, gums such as taracanthogum, gum arabic, CMC1 starch, PVA, and various other materials. Organic binders such as synthetic resins can also be used, but they are easy to dry, knead, mold, etc.
Clay is preferred because it is easy to handle and does not damage the device. Among these, when used for adsorption of substances, when kaolin clay is used as a raw material, a porous ceramic body with a large specific surface area and particularly excellent adsorption performance can be produced.On the other hand, when montmorillonite clay is used, Although the specific surface area is relatively small, it is possible to produce a porous ceramic body that is suitable for applications such as filter media that allow fluids to pass through without being adsorbed. However, organic binders are effective in making the pores in the product continuous by being burned away during firing, so even if an inorganic binder such as clay is used as the main binder,
An organic binder may be used in combination, and CMC or starch is preferably used especially for the purpose of forming continuous pores.

In this specification, clay has been described as a material included in both the ceramic raw material powder and the caking agent, but in fact, clay is usually treated as the ceramic raw material powder, and is hardened by firing to provide strength to the entire ceramic body. While it has the effect of imparting clay, it also has a sufficient effect as a caking agent, and when clay is used as a raw material in the present invention, it is not necessarily necessary to use other ceramic raw material powders or caking agents together.

In the production of ceramic bodies, when kneading each raw material,
The particle size of the raw material is small and it is necessary to add a large amount of water to the product using a large amount of organic raw material, but in the case of the present invention, water evaporates during baking and the pores in the product become continuous pores. Therefore, the amount of water added should be adjusted within a range of 10 to 30% by weight in the kneaded material immediately before molding, taking into account the type and particle size of the raw materials as well as the desired porosity. is preferred.

The raw materials used in the present invention have been described in detail above, and preferred examples are listed below in terms of combinations of raw materials in the method of the present invention. However, the present invention is not limited to these.

1. A roughly spherical powder made of graphite, carbon, or a carbon precursor, more preferably a kneaded material containing ground silica or alumina, clay, and an organic binder, is shaped, dried, and fired.

2. Forming a kneaded material containing approximately spherical powder made of graphite, carbon or carbon precursor, ceramic raw material powder that expands in volume during firing such as pearlite, shirasu or obsidian, clay, organic caking agent and water; Dry and bake.

3. A kneaded material containing approximately spherical powder made of graphite, carbon, or a carbon precursor, granulated talc or mica, clay, an organic caking agent, and water is molded, dried, and fired.

4. A kneaded material containing approximately spherical powder made of graphite, carbon, or a carbon precursor, granulated clay, an organic caking agent, and water is shaped, dried, and fired.

5. A kneaded material containing approximately spherical powder made of graphite, carbon, or a carbon precursor, ungranulated talc or mica, clay, an organic caking agent, and water is molded, dried, and fired.

6. A kneaded material containing approximately spherical powder made of graphite, carbon or a carbon precursor, clay, an organic binder and water is molded, dried and fired.

According to each of the above-mentioned methods, a porous ceramic body having excellent various properties such as air permeability and durability can be manufactured with particular industrial advantage.

In addition, when using a ceramic raw material powder with a small aspect ratio or a ceramic raw material powder that expands in volume during firing as in cases 1 to 5 above, it is assumed that a powder consisting of graphite, carbon, or a carbon precursor is not used. However, the gaps between the particles of the ceramic raw material powder form continuous pores, and a porous ceramic body exhibiting relatively good properties can be easily produced. In that case, the particle size, amount, combination with other materials, etc. of the ceramic raw material powder to be used are exactly the same as in the method of the present invention, except that powder consisting of graphite, carbon, or a carbon precursor is not used. It is. Specifically, for example, powder obtained by grinding industrially obtained silica lumps with a continuous grinder or raw material powder obtained by classifying shirasu powder such as Winquit MSB-302 manufactured by Ijichi Kasei Co., Ltd. The porous ceramic body obtained by kneading, molding, drying, and firing with clay, water, and a small amount of organic caking agent if necessary exhibits relatively good properties in terms of breathability, durability, etc. .

In the present invention, in addition to the above-mentioned raw materials, that is, graphite, carbon or carbon precursor powder, ceramic raw material powder, caking agent, and water, fluidity imparting agents, etc., which are normally used in the production of ceramic bodies, are used. There is no problem in using the same materials as well as other materials. Specifically, if a carbonate such as soda carbonate, sodium bicarbonate, or calcium carbonate is included in the raw material kneaded material and foamed during firing, a porous ceramic body with better air permeability can be produced. It is preferable to include carbon fiber in the carbon fiber because it facilitates the formation of continuous pores. When carbonate is used as a raw material, the content of carbonate is preferably 5 to 25 wt% in the raw material excluding water.

The method of the present invention is characterized by adding water to each of the above materials, kneading, molding, drying, and firing. The mixing ratio of each material and the conditions for molding, drying, and firing are not particularly limited, but graphite,
The granular material made of carbon or carbon precursor has a weight of 15 to 70 wt.
%, ceramic raw material powder is 20-70wt%, caking agent is 1
0 to 40wt% (however, the total amount of raw materials other than water amount is 100w)
It is preferable to determine the mixing ratio of each raw material in accordance with the characteristics desired for the product, including the porosity, within a range of

In addition, in the firing, the temperature is first gradually raised in an oxidizing atmosphere to a temperature at which the powder consisting of graphite, carbon, or a carbon precursor is burned out, and then, more preferably, the temperature increase is temporarily stopped to ensure that the powder is sufficiently combusted. If the temperature is raised again after being burnt out, it is possible to prevent the occurrence of cracks and produce products with better air permeability and durability.

After the powder consisting of graphite, carbon, or a carbon precursor is burnt out, firing may be performed in a reducing atmosphere, and is preferably performed by raising the temperature to a temperature at which the ceramic raw material powder is partially sintered.

Furthermore, the ceramic body generally exhibits a color tone such as pale yellow, and various pigments, preferably oxides of metals such as chromium, cobalt, iron, and nickel, and particularly preferably ceramic pigments containing these metal oxides as main components. It is also possible to freely color it by adding appropriately.

When producing a blackish ceramic body, graphite,
Either the carbon or carbon precursor is first fired at a relatively low temperature and for a short time in an oxidizing atmosphere so as not to be completely burnt out, and then fired at a high temperature in a non-oxidizing atmosphere, or the porous ceramic body produced once is fired. After impregnating it with a liquid substance rich in carbon, such as various synthetic resins such as phenolic resin, furan resin, and epoxy resin, liquid paraffin, waxes, molasses, most preferably oils and fats, or solutions containing these,
It is preferable to re-fire by adjusting the temperature, time, l or atmosphere so that the carbon content is not completely burnt out. In either case, graphite or carbonaceous substances remain in the pores, making it possible to easily produce a blackish ceramic body. The porous ceramic body produced by the method of the present invention is characterized by continuous fine pores and is therefore extremely useful as a deodorizing carrier.

The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

[Example 1 Example 1 65 parts by weight of approximately spherical polyethylene beads whose particle size was adjusted to 90 to 1100p, 30 parts by weight of kaolin clay, CM04 by Daicel, parts by weight of polyethylene glycol #4001 by NOF Corporation, and water. 20 parts by weight were added, kneaded, and formed into a cylinder with an outer diameter of 50 mm, a wall thickness of 10 mm, and a length of 100 mm. After drying, the temperature was raised to 500 ° C over 15 hours until carbonization of the polyethylene beads was completed. te10
The material was heated to 00°C and sintered to obtain a porous ceramic body with a porosity of 65% and a concentration of pore diameters of approximately 70 pm.

Example 2 The same polyethylene beads used in Example 1 were
Carbon beads with a particle size of 80 to 95 pm were preliminarily carbonized with C, and 65 parts by weight of these beads, 33 parts of kaolin clay, and 2 parts by weight of Daicel's CM0 were used as raw materials in exactly the same manner as in Example 1. Pore diameter is 75pm
A porous ceramic body with a porosity of 72% concentrated in the vicinity was obtained.

Example 3 43 parts of talc whose particle size was adjusted to 43-74 pm, 18 parts of kaolin clay, 6 parts of wood flour whose particle size was adjusted to 74-149 pm
31 parts of chemical coke powder (trade name TGP, manufactured by Osaka Kasei Co., Ltd.) whose particle size was adjusted to <74 to 149 pm, and 23 parts of water were added to 2 parts of 0M0 and kneaded, and the water content was adjusted to 20 parts.
Extrude into a rod shape using a 7.5 mm die, and
After drying at o'c for 24 hours, from room temperature to 400°C 8
Time, 3 hours from 400'C to 600°C, 600°
Raise the temperature from C to 850°C over 3 hours, and then raise the temperature to 850°C.
It was held for 3 hours. The obtained fired product was impregnated with oil at 180°C and then heated to 1050°C for 10 days in a reducing atmosphere.
The temperature was increased over time and held at 1050°C for 2 hours to sinter, producing a black porous ceramic body.

Example 4 49 parts of mica whose particle size was adjusted to 43-7 ppm, 14 parts of kaolin clay, ground into approximately spherical shape by grinding, 61-11 parts
Add 20 parts of water to 35 parts of graphite powder whose particle size was adjusted to 04p and 2 parts of CMC and knead to adjust the water content to 18 parts.
Extrude into a rod shape using a mm die and heat at 80°C.
After drying for 24 hours at room temperature to 600°C for 8 hours,
The temperature was raised from 600°C to 850°C over 3 hours for firing. The obtained fired product was impregnated with oil at 180°C, then heated to 1050°C over 10 hours in a reducing atmosphere, held at 1050°C for 2 hours, and sintered to form a black porous material. A ceramic body was produced.

Example 5 42 parts of mica whose particle size was adjusted to 43 to 74 pm, 24 parts of montmorillonite clay, crushed into approximately spherical shape by grinding, 6
30 parts of graphite powder with particle size adjusted to 1-1104p, 0M02
20 parts of water was added to 2 parts of a ceramic pigment (-06 manufactured by Saito Shikoku Kogyo Co., Ltd.) whose main components are metal oxides and metal oxides, and kneaded to adjust the water content to 18 parts. Extrusion molded into a rod shape using a die, dried at 80'C for 24 hours, and then heated from room temperature to 600°C for 8 hours, 600'
Raise the temperature from C to 850°C over 3 hours, and then raise the temperature to 850°C.
The mixture was held for 3 hours to produce a silver-colored porous ceramic body.

[Effect of the invention 1] According to the method for producing a porous ceramic body of the present invention, the ceramic body has a high porosity in which continuous pores are uniformly formed throughout the body, and has excellent various properties such as air permeability and durability. Porous ceramic bodies can be produced reliably and easily without cracking, and when the particle size of each raw material, especially graphite, carbon, or a carbon precursor, is adjusted,
Porosity, pore size and their distribution can be easily controlled, providing great industrial benefits.

Claims (1)

[Claims] (1) Powder consisting of graphite, carbon or carbon precursor,
A method for producing a porous ceramic body, which comprises shaping a kneaded material containing ceramic raw material powder, a caking agent, and water, drying it, and firing it.