JP2571147B2 - Porous ceramic body and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a gas carrier and a liquid passage such as a catalyst carrier, a bioreactor, and a filter material, a wicking evaporator, an aromatic device, an insecticide,
The present invention relates to a porous ceramic body used for a solid lubricant, a solid abrasive, and the like, and a method for manufacturing the same.

[Conventional technology]

In recent years, porous ceramics have been widely used in gas separation, ultrafiltration, microfiltration, bioreactors, wicking evaporators, etc., and have various properties such as heat resistance and chemical resistance, depending on the conditions of use. Is required. In particular, the porosity, pore diameter, and pore distribution are extremely important physical properties for the porous ceramic body to sufficiently exhibit its function and maintain the function for a long time.

However, conventionally, in such a porous ceramic body,
The porosity, pore diameter, and pore distribution in one body were uniform.

Therefore, when trying to obtain a ceramic body having portions having different porosity and pore diameter as one body, several types of ceramic bodies having respective porosity and pore diameter are bonded by an adhesive or the like. And then firing the molded body, or coating one ceramic body with the other ceramic material.

[Problem to be solved by the invention]

However, such a ceramic body has problems in mechanical strength at the bonding surface, heat resistance and chemical resistance of the bonding portion when used, and furthermore, the porosity and the pore diameter change too rapidly, so that the above-mentioned application is not possible. The application was not always favorable, because it did not meet the requirements of In addition, ceramic bodies with different porosity and pore size after heat degreasing or sintering are bonded,
In the case of sintering, since the shrinkage and the like are not performed uniformly, the fluidity imparting agent and the like compounded at the time of degreasing or sintering are gasified and accumulate, causing cracks, and further expanding and contracting. From the balance, there is a problem that fatal defects such as dimensional instability of the finished product are likely to occur.

[Means for solving the problem]

The present inventors have conducted intensive studies in order to solve the above-described problems, and as a result, when firing a molded body obtained by mixing and kneading flammable powders, the temperature or temperature along the length direction or the thickness direction of the molded body. The present inventors have found that when firing is carried out while changing the oxidation conditions, a porous ceramic body having a different porosity such as a porosity and an average pore diameter can be obtained due to a different degree of burnout of the granular material.

That is, an object of the present invention is to provide a porous ceramic body in which at least two portions having different porosity exist along a length direction or a thickness direction in one porous ceramic body, and a method of manufacturing the same. It is in.

Thus, an object of the present invention is to form and dry a kneaded material containing flammable particles, ceramic raw material powder, a binder and a kneading liquid, and to vary along the length direction or the thickness direction of the formed body. This is easily achieved by firing at a temperature or firing one in a non-oxidizing atmosphere and the other in an oxidizing atmosphere along the length or thickness direction.

 Hereinafter, the present invention will be described in detail.

The raw material of the porous ceramic body of the present invention contains flammable particles composed of graphite, carbon, a carbon precursor, etc., and all of the flammable particles are burned by firing and easily burnt down as carbon dioxide gas. Then, pores having substantially the same shape as the powder and granules are formed after burning, and when the powder and granules are burned off as carbon dioxide gas,
The pores are connected to each other to form continuous pores. Incidentally, gums such as polyvinyl alcohols, starches, various types of CMC, gum arabic and the like which effectively act as an organic substance, a synthetic resin and also as a binder are naturally included in the combustible powder.

The use of powder particles as close to spherical as possible as these combustible powder particles makes the pores of the resulting porous ceramic body closer to spherical, and further improves various properties such as air permeability and durability, and is preferable. It becomes a ceramic body. In order to obtain particles as nearly spherical as possible, use spherical particles from the beginning, such as synthetic resin beads, or granulate organic materials such as CMC, starch, etc. with water. There is a method of using a raw material pulverized by a method for obtaining a spherical or a substantially spherical powder. It is also effective to heat and cure the organic spherical granules or use a carbon precursor as a raw material.

If the amount of these flammable powders is adjusted and the amount used is adjusted, the porosity and porosity of the produced porous ceramic body can be easily adjusted, which is preferable. As the granular material, it is preferable to select a granular material having a slightly larger particle diameter than the pore diameter in consideration of shrinkage during firing according to a desired pore diameter. Further, when powders having a uniform particle size are used, a product excellent in various properties such as air permeability and durability can be obtained.

On the other hand, as the ceramic raw material powder, alumina, silica, zirconia, talc, mica, shirasu, pearlite, olivine, furthermore, kaolin-based and montmorillonite-based clays, and powders obtained by granulating clays, etc. Any ceramic raw material powder used can be used,
Also in this case, in order to obtain a porous ceramic body having more excellent air permeability and durability, it is desirable that the raw material powder be as spherical as possible.

When trying to obtain a powder having a more spherical shape such as alumina or silica, use a raw material powder obtained by grinding by a grinding method capable of obtaining a substantially spherical ground product such as grinding, or use talc, mica, or the like. In the case of originally flat powder or clay, it is preferable to knead it with an organic binder to obtain a desired particle size, and then calcinate or sinter to use it. If an organic binder is used at the time of the granulation, it foams at the time of sintering and can itself obtain a porous ceramic powder. There is also a method of using a ceramic raw material that causes volume expansion during sintering and forms a spherical shape, such as pearlite, shirasu, and black stone.

For these ceramic raw material powders, it is desirable to select a type of granule that matches the properties of the target ceramic body, and unless the clay is used without granulation, the powder is selected according to the desired pore size. It is preferable to select a powder having a slightly larger particle diameter than the pore diameter. Further, when powder having a uniform powder diameter is used as the ceramic raw material powder, not only does the pore diameter of the product ceramic body become uniform, but also the fluidity imparting agent expands rapidly during firing, and cracks occur. The resulting phenomenon can be suppressed.

As the binder used as a raw material in the present invention, clay, aluminum phosphate, water glass, and inorganic binders such as basic aluminum chloride, taracant gum, gum arabic, rubber such as kipro rubber, CMC, starch PVA and Any organic binder such as various synthetic resins can be used. However, clay is preferred because it is easy to dry, knead, mold, etc., and is easy to handle without damaging the device. Above all, when the kaolin-based clay is used as a raw material for use in adsorbing a substance, a porous ceramic body having a large specific surface area and particularly excellent in adsorption performance can be produced. On the other hand, when a montmorillonite-based clay is used, a porous ceramic body having a relatively small specific surface area but suitable for use in passing a fluid such as a filter medium without adsorbing a fluid can be manufactured. The organic binder is a main binder since it exhibits properties as a binder, but also has properties as a combustible powder which burns out during firing and makes pores in the product continuous. Even when an inorganic binder such as clay is used, these organic binders may be used in combination, and in particular, for the purpose of forming continuous pores, it is preferable to use CMC or various starches.

In this specification, clay is described as a material contained in both the ceramic raw material powder and the binder, but generally, clays are generally treated as ceramic raw material powder, and are hardened by firing to form the entire ceramic body. Has the effect of imparting strength, but also has a sufficient effect as a binder. When clay is used as a raw material of the present invention, it is not always necessary to use another ceramic raw material powder or binder together.

In the production of the ceramic body, a kneading liquid appropriately selected from water, alcohol, an organic solvent or the like is used according to the properties of the raw materials used when kneading the raw materials. The smaller the particle size of the raw material, the more the organic raw material, the more the kneading liquid needs to be added, but in the case of the present invention, if the kneading liquid used is at least one that evaporates at the time of baking, the product will be contained in the product It is also effective to make the pores continuous pores. Further, it is useful in the case of laminating and molding different kinds of kneaded materials, and the amount of addition is 10 to 45 in the kneaded material immediately before molding in order to form the same kneaded material at the time of lamination molding with a desired porosity. It is preferable to adjust the amount within the range of weight%.

As described above, in the case of using a ceramic material powder having a relatively spherical shape or a lamic material powder that expands in volume during firing, graphite, carbon, a carbon precursor, etc. Even when the powdery material is not used, the pores between the particles of the ceramic raw material powder form continuous pores, so that a porous ceramic body exhibiting relatively good characteristics can be easily manufactured.
In this case, the aspect of the particle size and amount of the ceramic raw material powder used, the combination with other materials, and the like are exactly the same as those of the method of the present invention except that a flammable powder is used. Specifically, for example, a granular material obtained by pulverizing an industrially obtained silica lump with a grinder, or a raw material such as a shirasu balloon, pearlite, and pearlite classified into a certain range, clay, water,
And, if necessary, kneading with a small amount of an organic binder, molding (extrusion, embedding, laminating, slurry casting, etc.), drying, and drying the molded body at different temperatures along the length or thickness direction. It can be obtained by firing or by firing one in a non-oxidizing atmosphere and the other in an oxidizing atmosphere. The porous ceramic body thus obtained is
A ceramic body having different porosity, pore diameter, and the like in the length direction or the thickness direction, and exhibits good properties in terms of air permeability, liquid permeability, durability, and the like.

In the present invention, in addition to the above-mentioned raw materials, other materials such as a material generally used for producing a ceramic body, such as a fluidity imparting agent, may be used in combination. In particular,
When a carbonate or the like such as sodium carbonate, sodium bicarbonate, and calcium carbonate is contained in the kneaded raw material and foamed during firing, a porous ceramic body having more excellent air permeability can be produced. 5 to 30 in raw materials excluding liquid
It is preferably set to wt%. Furthermore, calcium hydroxide, magnesium hydroxide, and hydroxides such as aluminum hydroxide are contained in the raw material kneaded material, and are decomposed at the time of firing to release water and leave pores. An excellent porous ceramic body can be produced, and the content of the hydroxide is preferably 5 to 35% of the raw material excluding the kneading liquid.

The present invention, kneading by adding a kneading liquid to each of the above materials,
Lamination molding in which several types of kneaded materials are stacked according to the purpose,
Formed by methods such as slip casting, mold forming, or extrusion molding, dried, and fired at different temperatures along the length or thickness direction of the molded product, or in the length or thickness direction Is characterized in that one is fired in a non-oxidizing atmosphere and the other is fired in an oxidizing atmosphere, and the mixing ratio of each material is not particularly limited.
20-75wt% ceramic raw material powder, 3-50wt% binder
It is preferable to determine the mixing ratio of each raw material in the range of (the total amount of raw materials other than water is 100 wt%) according to the porosity and the characteristics required for the product.

Incidentally, as described above, when the ceramic raw material powder also serves as a binder, and when the combustible powder also serves as a binder,
It is within the scope of the present invention, and the mixing ratio in that case may be appropriately determined with reference to the respective raw material ratios.

The most characteristic feature of the present invention is a porous ceramic body in which at least two porous porosity portions having different porosity and average pore diameter in a length direction or a thickness direction are present in one body, and a place for producing the same. However, in order to achieve this object, in the case of mixing the above-mentioned powder and granules, in relation to the firing method,
It is also effective to mix two or more kinds of combustible powders having different burning temperatures.

As a method of firing one of the molded bodies in a non-oxidizing atmosphere and the other in an oxidizing atmosphere, for example, one of the molded bodies is buried in graphite powder along a length direction or a thickness direction, and the other is embedded in graphite powder. Can be easily performed by performing a heat treatment in a heating furnace such as an electric furnace in a state where is exposed to the air atmosphere.

Prior to firing, after the combustible powder gradually rises to a temperature at which it burns off on the high temperature side or on the oxidizing atmosphere side, more preferably, the temperature rise is temporarily stopped, and the molding on the high temperature side or on the oxidizing atmosphere side is performed. After the powder in the body is sufficiently burned and burned down, when the temperature is raised again, the occurrence of cracks can be prevented and more air permeability,
A product with excellent durability can be manufactured. The firing after the combustible powder has been burned off may be performed entirely in a reducing atmosphere,
The temperature may be raised to a temperature at which the ceramic raw material partially sinters.

Further, the ceramic body generally exhibits a color tone such as pale yellow, but can be freely colored by appropriately adding various high-temperature pigments, ceramic pigments, metals such as chromium, cobalt, nickel, iron, and copper, or metal compounds. It is also possible.

In order to produce a black-colored ceramic body, in addition to using a pigment as described above, first, in order not to completely burn off flammable particles such as graphite, carbon, carbon precursor, etc. Baking at low temperature and short time, then baking at high temperature under non-oxidizing atmosphere, or once manufacturing porous ceramic body, various synthetic resins such as phenol resin, furan resin, liquid paraffin wax, molasses, various organic substances After the impregnation with the solution in which is dissolved, the temperature, time and / or atmosphere may be adjusted so as not to completely burn off the carbon content. In either case, the graphite or carbonaceous material remains in the pores, and a blackish ceramic body can be easily manufactured.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples unless it exceeds the gist.

〔Example〕

(Example 1) 30 parts by weight of substantially spherical polyethylene beads whose particle size has been adjusted to 20 to 40 µm (hereinafter, “parts” means parts by weight), 43 to
35 parts of mica powder sized to 74μm, kaolin clay
30 parts, 5 parts of CMC manufactured by Daicel, 1 part of polyethylene glycol # 400 manufactured by NOF CORPORATION, and 23 parts of water are added and kneaded to form an outer diameter of 1 part.
Molded into a columnar shape of 0 mm and length of 100 mm, dried at 80 ° C for 24 hours, buried 50 mm in the length direction in graphite powder, and until 450 ° C at which carbonization of polyethylene beads was completed without other lids As a result of raising the temperature over time and then sintering to 1200 ° C., the side buried in the graphite powder had an average pore diameter of 20 μm and a porosity of 61%, and the open side had an average pore diameter of 25 μm and a porosity of 67%. %, A porous ceramic body having portions having different porosity in one body was obtained.

(Example 2) 35 parts of substantially spherical acrylic resin beads having a particle size adjusted to 20 to 40 µm, and ichiwinlite (Shirasu balloon) 30
Parts, 30 parts of kaolin clay, 5 parts of CMC, 1 part of polyethylene glycol # 400 manufactured by NOF Corporation and 25 parts of water, and kneaded.
Formed into a plate having a thickness of 30 mm, a length of 100 mm and a width of 100 mm, dried at 80 ° C. for 48 hours, buried 15 mm in the thickness direction in graphite powder, and the other 15 mm was in a state without a lid. As a result of sintering in the same manner as described above, the side buried in the graphite powder has an average pore diameter
The porosity is 59% at 22 μm and the porosity is 70 μm at the open side with a pore diameter of 28 μm.
%, A porous ceramic body having portions having different porosity in one body was obtained.

(Example 3) 34 parts of raw coke powder whose particle size was adjusted to 43 to 74 µm,
34 parts of mica powder, particle size adjusted to 43 to 74 μm, 26 parts of kaolin clay, 5 parts of CMC, 1 part of polyethylene glycol, 23 parts of water are added and kneaded to form a plate with a thickness of 30 mm, a length of 100 mm and a width of 100 mm. After drying at 80 ° C. for 42 hours, sintering was performed in the same manner as in Example 2. The obtained sintered body was impregnated with oil at 180 ° C., and then heated to 1020 ° C. in a reducing atmosphere for 10 hours. After holding at 1020 ° C. for 2 hours and gradually cooling to room temperature over 10 hours, one had an average pore diameter of 48 μm and a porosity of 55%, and the other had an average pore diameter of 55 μm.
A porous ceramic body having a porosity of 62% and having portions with different porosity in one body was obtained.

(Example 4) 32 parts of graphite powder adjusted to a particle size of 61 to 104 µm, 43 to 74 µm
mica flour 41 parts, kaolin clay 20 parts, CMC5
Parts, 1 part of nickel oxide and 1 part of polyethylene glycol, kneaded with 22 parts of water, extruded into a rod shape of 7.5 mm in diameter and 100 mm in length, dried at 80 ° C. for 24 hours, and then 50 mm in the length direction in silica powder. Buried in 600 ℃ for 15 hours, 600 ℃ to 850 ℃
Temperature from 850 ° C to 1050 ° C over 5 hours,
After the holding, the temperature was gradually cooled to room temperature over 8 hours. One obtained an average pore diameter of 62 μm and a porosity of 56%, and the other obtained an average pore diameter of 70 μm and a black porous ceramic body having a portion having a different porosity in one body having a porosity of 65%.

〔The invention's effect〕

ADVANTAGE OF THE INVENTION According to the porous ceramic body of the present invention and the method for producing the same, a portion having a different porosity such as a porosity and an average pore size is present in one body, and since the pores in the boundary area are continuous pores, ventilation is possible. Since a porous ceramic body having excellent durability, chemical resistance, and mechanical strength can be easily produced without cracking, deformation, etc., since it does not use an adhesive method, the porosity and average Used in various applications such as liquid passing, gas passing, and filtration media that require delicate adjustment of pore size, etc., and also require durability, chemical resistance, and strength, and provide great industrial benefits. Is what you do.

Claims (2)

(57) [Claims] 1. A porous ceramic body comprising at least two porosity portions having different porosity and average pore diameter along a length direction or a thickness direction of the ceramic molded body. 2. A kneaded product containing a combustible powder, a ceramic raw material powder, a binder and a kneading liquid is formed and dried, and is subjected to different temperatures along the length direction or thickness direction of the formed product. A method for producing a porous ceramic body, comprising firing or firing one in a non-oxidizing atmosphere and the other in an oxidizing atmosphere along a length direction or a thickness direction.