JPH0891957A - Method for processing porous ceramic and product therefrom - Google Patents

Abstract

PURPOSE: To obtain the subject product improved in mechanical strength, the accuracy during processing therefor and surface accuracy, by filling or impregnating a porous ceramic with a thermosetting resin followed by curing the resin and then abrading the resultant surface with a specific whetstone. CONSTITUTION: Firstly, a porous ceramic essentially having open cells each 1-1000μm in diameter is filled or impregnated with a thermosetting resin such as phenolic resin, epoxy resin or xylene resin, in combination with a curing agent or regulation of the resin viscosity with a diluent, if needed. The thermosetting resin is a 100% organic material, being <=1wt.% in ash content. For the filling or impregnation, the ceramic is immersed in the liquid resin the system as a whole is subjected to reduced pressure by a vacuum defoaming machine. The resin is completely cured by heat or the curing agent, the resultant ceramic surface is abraded e.g. with a combination of a double side grinder and abrasive material. For the whetstone or abrasive grains, cermet, diamond, silicon carbide, boron nitride, alumina corundum, etc., is used; after abrasion, the resultant ceramic is heated to the decomposition temperature of the resin or higher under controlled temperature raising speed to restore the porosity of the original ceramic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a processing method for finishing a surface of a porous ceramic with high accuracy. The obtained ceramic porous body is used as a filter for setters, shelves or water treatment in the ceramic industry, and for food production.

[0002]

2. Description of the Related Art In the past, when a porous ceramic flat plate was ground, a double-sided grinder was used or a polishing material was used in combination as a low cost method. However, since the object to be ground is originally porous, the abrasive and the grinding powder enter pores to reduce the porosity, and the abrasive and the grinding powder become impurities, which has been a problem. Also,
As a method other than that, a surface grinder may be used, but since it is processed without using an abrasive together, the processing speed becomes slower and the cost further increases, making industrial production impossible. Also, in the case of a shaped object, the strength of the porous ceramic is weak, so that cracking occurs due to chucking and accuracy is poor. The abrasive used herein is a fine abrasive particle contained in the grinding liquid used for improving the cooling efficiency and the efficiency of the cooling supplied between the grindstone and the object to be polished at the time of polishing.

[Problems to be Solved by the Invention]

[0003] A general porous ceramic is one in which ceramics having a large particle diameter are combined to utilize the interstices of particles, one in which the firing temperature is lowered and the firing is not performed densely,
Alternatively, there are three methods in which a urethane foam is used as a matrix and a slurry of a ceramic having a small particle diameter is impregnated and fired to burn off the urethane resin to make it porous. However, in any case, the mechanical strength was lower than that of dense ceramics, and cracking, chipping, chipping, etc. occurred due to chucking during processing, and the product was not accurate.

Particularly in a ceramic which is made porous by particles having a size of 50 μm or more, the bonding strength between particles is weak. Therefore, when the conventional method is used, a part of the particles is not ground and flattened. The surface was inaccurate because of the shedding that occurred.

[0005]

According to the present invention, the pore portion of a porous ceramic having poor surface accuracy is
The means is to fill or impregnate the thermosetting resin, harden the resin, polish the surface with a grindstone, and raise the temperature to the decomposition temperature of the thermosetting resin used.
In short, the pores of the porous ceramic are filled with a resin, the ceramic particles are polished while preventing the particles from falling off, and then the filled resin is thermally decomposed to obtain a porous body. At the time of polishing, the use of a conventional grinding liquid or abrasive does not cause any inconvenience.

The porous ceramics before and after processing in the present invention basically have a pore diameter of 1 μm to 1000 μm.
m having a continuous vent hole. Needless to say, even for a porous ceramic having independent pores, the method of the present invention can be used to obtain a porous body having good surface accuracy.
In the case of using a ceramic porous body, a method of processing a porous ceramic having continuous ventilation holes will be mainly described since the use of the continuous ventilation holes is more frequently used when compared with that of continuous ventilation holes and independent pores.

The thermosetting resin used in the present invention includes phenol resin, epoxy resin, xylene resin, granamine resin, vinyl ester resin, unsaturated polyester resin, furan resin, polyurethane resin, melamine resin and urea resin. These resins will react and cure when heated or mixed with a curing agent. When filling or impregnating the porous ceramics with these resins, a curing agent may be used together, or a diluent may be used to adjust the viscosity. This time,
If the solid content is lowered too much by the diluent, for example, 30
If it is less than 100%, the resin may be thinned during curing, a gap may be formed, or the strength may be reduced, and there is a possibility that the particles may shed during polishing and the polishing particles may enter the gaps in the pores.

If the resin used for impregnation is composed of 100% organic matter or the ash content is not less than 1%, impurities in the ceramic will increase and it will not be possible to use it in the fields of semiconductors and filters. Further, if the viscosity of the resin is not low, it takes a long time to impregnate the resin, or the resin having a small pore diameter may not be impregnated. Therefore, it is preferable to select or adjust the resin having 1000 CPS or less.

The filling or impregnation of the thermosetting resin into the porous ceramic can be easily carried out by submerging the ceramic in a liquid resin and placing it under reduced pressure by a vacuum defoaming machine. However, in the case of a closed-cell porous ceramic, impregnation cannot be expected or is difficult, so that only the surface layer portion of the ceramic is filled. Although it is possible to fill only the surface layer portion with a brush or a flow coater, in order to prevent the formation of gaps, it is preferable to depressurize the ceramic and the bubbles in the resin after application so as to remove the bubbles.

After the resin is completely cured by heat or a curing agent, it may be polished by a usual method, for example, by using a double-sided grinder and an abrasive together. According to the method of the present invention, a porous ceramic having a shape other than a flat plate, for example, a cylindrical or cylindrical shape can be polished. Cermet, diamond, silicon carbide, cubic boron nitride, alumina corundum and the like can be exemplified as the abrasive grains which are the main component of the grindstone or the abrasive used in the grinder.

Next, the polished ceramic may be heated to a temperature above the decomposition temperature of the resin used in order to restore its porosity. However, if the temperature rising speed is fast, cracks or breaks will occur due to the pressure of the decomposition gas inside, so it is necessary to adjust the temperature rising speed.

[0012]

By filling the pores with resin, the overall strength of the porous ceramic is temporarily increased, and water absorption is eliminated to prevent the inclusion of abrasive particles. At the time of polishing, the strength of the whole is increased, so that cracking or chipping due to chucking does not occur, and since the ceramic particles are strongly held by the resin, it is possible to obtain good surface accuracy without shedding. Further, the abrasive particles do not enter the pores of the ceramic, and no impurities remain after the resin is burned off.

[0013]

Example 1 In Example 1, the porous ceramic has a pore size of 3
Alumina ceramic porous body at 0 μm, Lepton K-T621 manufactured by Kikusui Chemical Co., Ltd. is used, and the thermosetting resin is phenol resin manufactured by Asahi Organic Materials Co., Ltd. 70%) was mixed with 100 parts by weight of a curing agent composed of an organic acid, and Px-18 (solid content: 55%) manufactured by the same company was mixed at a ratio of 5 parts by weight to impregnate it. The impregnation method was performed by immersing the ceramic porous body in a mixed liquid of a thermosetting resin and a curing agent and placing the ceramic porous body under reduced pressure. The resin-impregnated ceramic is taken out from the resin liquid, and although the resin exudes to some extent, heat is applied as it is to 100
Cured at ° C. The ceramics hardened with phenolic resin were ground by a double-sided grinder to a thickness of 3 mm and a thickness of 2 mm which are desired to be manufactured. At this time, silicon carbide was used as the abrasive grains of the grindstone used for polishing. Further, the polishing accuracy in the state of containing the resin was ± 0.01 mm. Next, the polished ceramic was fired at 1500 ° C. to decompose the resin component that had been impregnated and cured, and a flat polished ceramic porous body was obtained while maintaining the surface accuracy.

In Example 2, the same porous ceramic as in Example 1 was used, and the thermosetting resin was a urea resin manufactured by Aika Kogyo Co., Ltd. under the trade name UN-830 (solid content: 5).
0%) to 100 parts by weight of curing agent, UH-1 manufactured by the same company
0 (main component ammonium chloride) was mixed at a ratio of 2 parts by weight, and this was impregnated. The impregnation method and the subsequent procedure were the same as in Example 1 to obtain a polished porous ceramic.

In Example 3, the same porous ceramic as in Example 1 was used, and the thermosetting resin was an epoxy resin manufactured by Yuka Shell Epoxy Co., Ltd., trade name Epicoat 81.
9 (100% resin content) to 100 parts by weight of reactive diluent, YED-111 (100% resin content) manufactured by the same company as 20%
Parts by weight, and curing agent, Epomate B-002 manufactured by the same company
The (main component amine) was mixed at a ratio of 40 parts by weight to impregnate this. The impregnation method and the subsequent procedure were the same as in Example 1 to obtain a polished porous ceramic.

In Example 4, the same porous ceramic as in Example 1 was used, and the thermosetting resin was a furan resin manufactured by Hitachi Chemical Co., Ltd., trade name Hitafuran VF-901.
(Resin content 95% or more) was mixed with 100 parts by weight of a curing agent composed of an acid anhydride and SH-20 manufactured by the same company at a ratio of 30 parts by weight, and the mixture was impregnated under reduced pressure. After the impregnation, the resin was awaited for curing by the reaction, and after curing, polishing and firing were performed in the same manner as in Example 1. After firing, a polished porous ceramic was obtained.

In Example 5, the same porous ceramic as in Example 1 was used, and as the thermosetting resin, unsaturated polyester resin manufactured by Showa Highpolymer Co., Ltd., trade name Rigolac W-1005BQ (resin) was used. 100 parts by weight of water was added to 100 parts by weight of water and mixed, and this was impregnated under reduced pressure. After the impregnation, the resin was awaited for curing by the reaction, and after curing, polishing and firing were performed in the same manner as in Example 1. After firing, a polished porous ceramic was obtained.

Comparative Example 1 To the resin used in Example 1, Hp-3000L, 200 g of ethanol as a diluent was added, and the same processing as in Example 1 was performed with the resin solid content being 23%. Next, it was fired at 1500 ° C, but since silicon carbide had sunk inside the product,
Appeared as spots on the product.

Comparative Example 2 Sumitomo Chemical Co., Ltd.'s vinyl chloride resin, Summit PX-QHT (100% resin content), which is a thermoplastic resin.
A plasticizer in 00 parts by weight and a dispersion in 60 parts by weight of DOP was used as a slurry for impregnation, and Lepton K-T621 was used.
What was impregnated in was heated at 130 ° C. to gel.
Then, after processing from 3 mm to 2 mm with a double-sided grinder,
The surface accuracy was ± 0.15 mm. Moreover, shedding of particles was also observed.

Comparative Example 3 The porous ceramic of Example 1 was polished without being impregnated with resin.

[0021]

[Table 1] (The surface accuracy represents the dimensional accuracy when a plate with a plate thickness of 3 mm is processed to 2 mm.)

Tata plate having a large degreasing effect using the pores of porous ceramics (Tana plate which facilitates escape of gas decomposed during firing of resin contained in a ceramic product such as a substrate to be fired on a tatami plate) When the substrate was fired in, the scratch was generated on the raw plate due to the coarse particles of the flat plate. Next, when the substrate was fired by using a porous ceramic shelf plate whose surface was polished without using an abrasive, the occurrence of scratches was observed although the number was reduced. However,
No scratches were found on the resin-impregnated and polished by the method of the present invention.

[0023]

According to the present invention, it is possible to obtain a porous ceramic having a smooth surface and no cracking, chipping or shedding of the ceramic particles constituting the porous body with high surface accuracy. For example, a product without defects can be obtained when it is used as a shelf plate for firing a work.

Claims (2)

[Claims] 1. A grindstone having cermet, diamond, silicon carbide, boron nitride, alumina corundum or the like as abrasive grains is used after the porous ceramic is filled with or impregnated with a thermosetting resin to cure the resin. The method for processing a porous ceramic is characterized in that the porous ceramic having a flat surface is manufactured by polishing and polishing, and raising the temperature to the decomposition temperature of the thermosetting resin used. 2. A porous ceramic product obtained by the method of claim 1.