JPH08310880A - Ceramic stock composition, ceramic structure and its production - Google Patents

Abstract

PURPOSE: To obtain a ceramic stock compsn. excellent in thermal and mechanical characteristics and to produce a ceramic structure made from the ceramic stock compsn. CONSTITUTION: When a ceramic slurry is blended with water-soluble polysaccharides, the water content of the slurry can be reduced without deteriorating the characteristics of the slurry and ceramic produced from the resultant ceramic compsn. has increased density and gives a ceramic structure excellent in thermal and mechanical characteristics. A ceramic porous structure suitable for use as a filter medium for a molten metal, etc., is produced by impregnating the ceramic slurry into open cell type plastic foam and carrying out drying and firing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic raw material composition for obtaining a ceramic structure having excellent mechanical and thermal properties, a method for producing a ceramic structure from the ceramic raw material composition, and the ceramic composition. A ceramic structure formed from the object.

[0002]

2. Description of the Related Art Conventionally, a ceramic mud film is adhered to a synthetic resin continuous porous body such as a flexible polyurethane foam having a three-dimensional network skeleton structure without a cell membrane, which is dried and fired. The ceramic porous body thus obtained is used as a filtering material for impurities such as metal oxides contained in molten metal. When ceramics are used for such purposes, they must have at least a heat resistance higher than the melting point of the metal to be filtered, and must be able to withstand thermal shock.

On the other hand, as a method for producing ceramic products used for these purposes, ceramic powder has been conventionally used as a mud impregnated with the above-mentioned soft polyurethane foam having a three-dimensional reticulated skeleton structure, etc. There is known a method of removing, drying and firing. At this time, a dispersant, a defoaming agent or the like is generally added to the ceramic mud to prevent clogging and to adhere uniformly. Furthermore, since the water content in the mud affects the drying rate and the thermal and mechanical properties after firing, keep the water content in the mud as low as possible and attach a large amount of effective ceramic. It is desirable to increase the molding density so that the effect is sufficiently exhibited. However, in reality, there was a limit in reducing the water content in order to maintain the mud-reinforcing properties. (Increased mud viscosity etc.)

Further, although the ceramics used for the above-mentioned applications are mainly composed of non-oxide ceramics such as silicon carbide and silicon nitride, which are advantageous in heat resistance, they are oxidized in order to be fired in the atmosphere. The phenomenon that the volume becomes large occurs. For this reason, the powder density was not increased and the characteristics could not be sufficiently obtained. The present invention has been made in view of the above circumstances, and an object thereof is to provide a ceramic raw material composition having excellent thermal and mechanical properties, a ceramic structure made of the ceramic raw material composition, and a method for producing the same. .

[0005]

Means and Actions for Solving the Problems As a result of intensive studies for achieving the above-mentioned object, the present inventors have found that mud-reinforcing properties are improved by adding a water-soluble polysaccharide to a ceramic mud-reinforcing component. It was possible to reduce the water content without impairing it, the ceramic structure obtained from this ceramic composition had a high density, and a ceramic structure excellent in thermal and mechanical properties was obtained. Further, they have found that a ceramic porous body structure suitable as a molten metal filtering material can be produced by impregnating a synthetic resin open-cell body with the above-mentioned ceramic mud, drying and firing. is there.

Therefore, the present invention provides a ceramic raw material composition characterized in that a water-soluble polysaccharide is contained in the ceramic mud as claimed in claim 1, and the ceramic mud as claimed in claim 2. The ceramics therein are metal oxides and / or non-oxides, and as claimed in claims 3 and 4, the ceramics have a particle size of 0.5 to 200 μm and primary particles, and also according to claim 5. As described above, the polysaccharide blended in the mud scum is a polysaccharide obtained by complexing sucrose, saccharose, dextrin or a monosaccharide.

Then, as described in claims 6 to 8, 0.1 parts of polysaccharide is added to 100 parts by weight of the ceramic in the mud.
A skeleton is a ceramic structure composed of a porous body composed of 10 to 10 parts by weight of mud and a method for producing the same. Hereinafter, the present invention will be described in more detail.

The ceramic raw material composition of the present invention contains a water-soluble polysaccharide in a ceramic mud containing water as a dispersion medium as described above. Here, the ceramic is preferably a primary particle in the range of 0.5 to 200 μm and excellent in heat resistance and thermal shock resistance. For example, alumina, zirconia, mullite or the like is suitable as the metal single oxide, and the metal composite is also preferable. As the oxide, cordierite, aluminum titanate, barium titanate, lithium aluminosilicate, etc. are preferably used. Further, examples of non-oxide ceramics include metal carbides, nitrides, borides, and silicides. In this case, as the carbide, SiC, T
Examples are iC, ZrC, WC, HfC and the like. Examples of the nitride include TiN, Si ₃ N ₄ and AlN. Examples of borides include AlB, TiB and WB. Further, as metal silicides, MoSi, TiSi, Z
An example is rSi. Among these, metal carbides and metal nitrides can give excellent effects, especially SiC and Si.
₃ N ₄ is preferably used because it has excellent high temperature characteristics.

The above ceramic must be in the range of 0.5 to 200 μm because if it is 0.5 or less, the porous body will be clogged and the cost will be low, and if it is 200 μm or more, it will settle out and the mud composition tends to change. is there. Moreover, the particle morphology needs to be primary particles, and secondary particles have a small powder surface activity, so they easily settle and do not become mud, and are foamed as a base material in the production of the porous body described later. It does not adhere evenly to the hydrophilic polyurethane, causing uneven adhesion.

Examples of the above water-soluble polysaccharides include sucrose, saccharose, dextrin and the like. Further, a polysaccharide obtained by synthesizing and complexing a monosaccharide represented by fructose as a polysaccharide may be used. Ceramic 100 is added
0.1 to 10 parts by weight is preferable with respect to parts by weight. It is more preferably 0.5 to 8 parts by weight. When the amount is less than 0.1 parts by weight, the effect is small, and when the amount is more than 10 parts by weight, the mud recommended viscosity is increased and the mud recommended characteristic is deteriorated, which may cause clogging of the ceramic porous body described later and the pressure loss may be poor. is there.

The effect of the addition of polysaccharides, which is the point of the present invention, is the reduction of mud viscosity. In general, in addition to a binder and an antifoaming agent, a peptizer is added to the mud to improve the dispersion of ceramic powder. The peptizer has improved dispersibility,
The viscosity of the mud drops, but the addition of polysaccharides further reduces its viscosity. Therefore, in order to maintain the viscosity before adding the polysaccharide, the water content is adjusted by reduction. In other words, since the water content is reduced, the subsequent drying efficiency is improved. Furthermore, since the powder density increases, the density after firing also increases. Since the density correlates with the characteristics, it is desirable to increase the density as much as possible within the range that does not impair the dimensional accuracy. In addition, defoaming agent, peptizer, thickener,
You may add a binder etc. suitably as needed. Further, viscosity, flux, glaze and the like can be added to this composition as a binder.

Here, as a method of constructing a ceramic porous body using the above ceramic raw material composition, a mud cloth made of the above ceramic raw material composition is used as a synthetic resin continuous foam,
Particularly preferably, the soft polyurethane foam having a three-dimensional reticulated skeleton structure with the cell membrane removed is impregnated or adhered, dried and then fired at 600 to 1600 ° C. to burn and remove the foam, and the foam is almost the same as the foam. It is possible to obtain a porous body having the cell structure of. In this case, the firing temperature is determined by the ceramic material used. The structure of the ceramic porous body obtained by the above method has a three-dimensional network structure having an internal communication space, is excellent in thermal and mechanical properties, and is suitably used as a molten metal filter material.

The ceramic porous body structure is not particularly limited, but has a bulk specific gravity of 0.3 to 0.
7, preferably 0.4 to 0.6, and the number of holes is 4 to 30 /
25 mm, preferably 5 to 20 pieces / 25 mm, porosity 70 to 95%, preferably 70 to 90%, and pressure loss of air is 15 to 200 mm in water for passing a thickness of 2 cm at a wind speed of 10 m / sec. It is preferable to form a net-like shape from the viewpoint of excellent air permeability and filterability. That is, if the bulk specific gravity is less than 0.3, the strength may be insufficient, while if it exceeds 0.7, clogging is likely to occur and pressure loss increases. Further, if the number of holes is larger than 30/25 mm, the strength is lowered and the pressure loss is increased. On the other hand, if it is smaller than 4 pieces / 25 mm, the contact with the fluid is insufficient and it may be unsuitable as a filter material. Further, if the porosity is less than 70%, clogging is likely to occur and the pressure loss increases, while if it exceeds 95%, the strength decreases. Also, a pressure loss of more than 200 is not preferable for the purpose of passing a fluid. In addition,
The ceramic structure composed of the above ceramic raw material composition is not limited to the porous body, and it is possible to make a high density structure, and in this case as well, excellent thermal and mechanical properties are exhibited. It is a thing.

[0014]

By using the ceramic raw material composition of the present invention, the water content in the mud can be reduced, and the original ability of the ceramic can be exerted more fully than before, resulting in thermal or mechanical properties. In particular, a porous material is suitable for use as a filter for molten metal.

[0015]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples. Examples 1 to 3 70 parts by weight of silicon carbide having an average particle size of 35 μm, 20 parts by weight of alumina having a particle size of 2 μm, and 10 parts by weight of knotobushi clay having a particle size of 1 μm were added with water, and polyacrylate as a peptizer. 0.1 parts by weight and 18 parts by weight of water were added. Sucrose was added as a polysaccharide in an amount of 1, 2, 5 parts to make a mud. Same Mud Award 5
After dispersion and stirring for an hour, water is added to increase the viscosity to 16
Adjusted around 0 poise. Primary particles were used for all the ceramic powders. Polyurethane foam with a mesh structure of the base material without cell membrane and 18 pores per 25 mm 50 mm x
It was impregnated with 50 mm × 20 mmt and the excess mud was removed with a roll. Then, after drying at 60 ° C. for 6 hours, it was fired at 1250 ° C. to obtain a ceramic porous body structure having a bulk specific gravity of 0.52. Bending strength of each obtained ceramic porous body structure,
The softening temperature and pressure loss were measured. The results are shown in Table 1.

[Comparative Example 1] A ceramic porous body structure was obtained in the same manner as in Example 1 except that sucrose was not added, and the evaluation tests of the same items were conducted.
The results are shown in Table 1.

Although a secondary particle type of alumina was used in the system of Example 5 containing 5 parts of sucrose, uneven adherence to the substrate was caused and clogging was remarkable, and a ceramic porous structure was obtained. I couldn't do it.

[0018]

[Table 1]

From the results shown in Table 1 above, the sucrose-added type has the same viscosity and excellent thermal or mechanical properties as compared with the non-added type even if the water content is small. Further, the shrinkage rate of the example is smaller than that of the comparative example. In other words, this is because the density of the ceramic porous body structure has increased. that's all,
It became clear that the characteristic values obtained in the examples can be suitably used as a filter material for molten metal.

Claims (8)

[Claims] 1. A ceramic raw material composition comprising a ceramic mud containing a water-soluble polysaccharide. 2. The ceramic raw material composition according to claim 1, wherein the ceramic in the ceramic mud is a metal oxide and / or a metal non-oxide. 3. The ceramic contained in the ceramic mud is
The ceramic composition according to claim 1 or 2, wherein the particle size is 0.5 to 200 µm and the particles are primary particles. 4. The water-soluble polysaccharide contained in the ceramic mud is a polysaccharide obtained by complexing sucrose, saccharose, dextrin, or a monosaccharide. The ceramic composition according to Item 1. 5. The ceramic mud admixture, which comprises mud admixture containing 0.1 to 10 parts by weight of polysaccharide with respect to 100 parts by weight of ceramic. The ceramic composition according to any one of 1. 6. A ceramic structure and a method for manufacturing the same, comprising the above-mentioned claims 1 to 5. 7. The ceramic structure according to claim 6, wherein the ceramic structure is a porous body, and a method for manufacturing the same. 8. The porous ceramic structure having a bulk specific gravity of 0.3 to 0.7 and a porosity of 4 to 30 /
The ceramic structure according to claim 7, which has a three-dimensional network structure of 25 mm, a porosity of 70 to 95%, a pressure loss of air of 10 m / sec, and a thickness of 2 cm of 15 to 200 mm in water. The manufacturing method.