JP5033064B2 - Ceramic body - Google Patents

Description

The present invention relates to a ceramic body of porous.

  As a method for producing a porous ceramic body, it is known to fire a molded body of clay containing burnt-out particles (see, for example, Patent Documents 1 and 2). Examples of burnout particles include pulp, pulp sludge, natural fibers, chemical fibers, grass, rice husk, sawdust, resin particles, foamed plastic particles, and coal particles.

However, in the method of manufacturing a porous ceramic body using these burnable particles, if the mixing ratio of burnable particles is increased, the molded product of the clay is cracked, resulting in a problem in moldability. It was difficult to obtain a lightweight ceramic body having a small specific gravity and high strength.
JP 2007-297259 A JP 2007-63104 A

An object of the present invention is to provide a lightweight heat-resistant ceramic body having a small apparent specific gravity and a high strength.

It is an aspect of the present invention, a clay mainly composed of bentonite or gairome clay, bulk specific gravity is by firing a green body comprising a chaff smoked charcoal from 0.11 to 0.17, and the clay the The weight ratio of the rice husk and charcoal is 100: 300 to 400, and the ceramic body includes silica particles in which the shell shape of the rice husk is maintained and has a cavity derived from the shell shape .

  The substrate may be formed by press-molding a kneaded material containing the clay and the rice husk charcoal at 1 to 10 MPa.

According to the present invention, a lightweight and heat-resistant ceramic body having a small apparent specific gravity and high strength is provided.

  The ceramic body of the present invention is a ceramic body formed by firing a base material containing clay and rice husk firewood obtained by firing rice husk into firewood. Rice husk charcoal is fired while maintaining the shape of the rice husk in the firing process of this base, and the carbon component is burned down to become silica particles that maintain the shell shape of the rice husk, and the silica particles and clay that maintain this shell shape are sintered. In addition, the silica particles maintaining the shell shape are sintered through the sintered clay to obtain a porous ceramic structure. According to the present invention, a lightweight and high-strength porous ceramic body is obtained from this shell shape.

  Furthermore, in the present invention, the shell-shaped silica particles can maintain the cavity derived from the shape of the rice husk in the sintered body even after sintering.

  The ceramic body of the present invention having such a structure has excellent heat resistance and strength because the silica particles and clay are sintered, and the carbon components are burned down by firing and the silica particles maintain the shell shape. By being present in the ceramic body in a state, it becomes very bulky, and a lightweight ceramic body having a small apparent specific gravity and high strength can be obtained.

  In the present invention, the blending ratio of clay and rice husk charcoal can be 100: 300 to 560 in weight ratio. If rice husk charcoal goes around this range with respect to clay, the heat resistance of the ceramic body will be lowered. If the amount of rice husk charcoal exceeds this range, the green body before firing tends to collapse during handling, which hinders the smooth execution of the manufacturing process. In particular, when the blending ratio is 100: 300 to 400, a ceramic body having an apparent specific gravity as extremely low as 0.4 or less, a high strength, light weight and heat resistance is preferable.

  In addition, when clay and rice husk (raw rice husk) are blended in such a ratio, when the blend is compressed at the stage of molding into a base, the molded body expands due to elastic recovery of the rice husks when dewetting after compression. As a result, the molded body cracks or collapses, and a molded body having a predetermined shape cannot be obtained, and molding by the friction molding method is difficult. If this compression is not performed sufficiently, the density of the substrate becomes too low, and the fired ceramic body cannot obtain sufficient strength.

  Furthermore, even if the ratio of rice husk to clay is lowered, for example, 10 to 40 parts by weight of rice husk is blended with 100% by weight of clay, rice husk causes water retention and expansion when water is added. After pressing, the molded product is swollen, and when this molded product is dried, damage and separation phenomenon occur and the shape collapses. Furthermore, when the dried molded body is fired, the molded body tends to fall apart due to burning of rice husks. Even if the ceramic body is obtained by firing, it has a higher specific gravity than the ceramic body of the present invention and is inferior in heat resistance.

  In the present invention, clay and rice husk charcoal are prepared as a mixture with water added and kneaded, and then pressed to form a molded body at a predetermined pressure to form a molded body. A ceramic body is obtained.

  Baking can be performed at 800-1100 degreeC. It is preferable that it is 800-900 degreeC. The firing time is preferably about 8 hours. The rate of temperature increase until reaching the firing temperature is preferably about 100 ° C./hour. By such firing, the carbon component in the central part of the molded body can be completely burned, and the central part can be oxidized to the ultimate.

  In the present invention, since no spalling occurs after the molded body is fired, the cooling rate can be made relatively short and the process time can be shortened.

  The pressure in the pressure molding is preferably 1 to 10 MPa in order to obtain a ceramic body having a small specific gravity and high strength. This pressure is smaller than the pressure molding pressure required for obtaining a practically sufficient strength when the ceramic body is sintered, but in the present invention, the silica particles maintained the shell shape. Since it exists in the ceramic body in a state, the ceramic body can obtain a practically sufficient strength even with such low pressure molding, and a lightweight ceramic body can be obtained due to the low pressure molding pressure. When the pressure of this pressure molding exceeds 10 MPa, the shell structure of rice husk and coal is crushed, and silica particles present in the ceramic body are reduced in a state where the shell shape is maintained. When the pressure of the pressure molding is 1 MPa, the ceramic body becomes brittle. There is no limitation on the method of pressurization, but it is preferable to obtain a molded body having a small specific gravity and high strength by repeatedly pressing using a friction molding method. Further, since the press molding method does not require a six-sided cut, the molding process can be shortened.

  In the present invention, due to the low pressure molding pressure and the shell structure of rice husk and charcoal, the moisture content of the molded product after pressure molding and before drying is higher than in the case of a normal ceramic making process. The moisture content of the molded product after pressure molding in normal dry molding and before drying (weight% of moisture relative to the total weight of the molded product) is about 7 to 8% by weight, and after drying after pressure molding in normal wet molding In the present invention, the moisture content of the molded product after pressure molding and before drying is as high as 30 to 50% by weight. Moisture is removed by drying of the molded product to obtain a bulky substrate, and the substrate is fired to obtain a bulky ceramic body.

  In addition, a fired body obtained by firing a base material in which clay and rice husk ash are mixed has almost no shell-shaped silica particles in the fired body, and a low specific gravity ceramic body as in the present invention cannot be obtained.

  The chaff husk charcoal used in the present invention is obtained by burning the chaff. The carbonization temperature in smoldering is, for example, 650 to 700 ° C. Rice husk charcoal has a silica content in the range of about 30 to about 50% by weight, and a carbon content in the range of about 30 to about 40% by weight.

  The chaff husk charcoal used in the present invention can be used as long as it partially maintains the shell shape of the chaff, but preferably contains 40 to 70% by weight of carbon. Moreover, it is preferable that the bulk specific gravity as an aggregate of rice husk charcoal is 0.10-0.25. More preferably, it is 0.11-0.17. It is more preferable to obtain a lightweight and high-strength ceramic body from 0.10 to 0.125.

  Rice husk charcoal has a bulk specific gravity that varies depending on the degree of firing, and in the present invention, a bulk specific gravity of 0.10 to 0.22 is preferably used. Among these, those having a bulk specific gravity of 0.10 to 0.12 are preferable because a ceramic body having a high porosity can be obtained.

  The clay used in the present invention is not particularly limited. However, in terms of moldability and heat resistance of the kneaded material (kneaded clay), cocoon clay or bentonite is preferable. In the case of using the clay, the firing temperature in the firing step is preferably 880 to 950 ° C. in terms of pressure strength, heat resistance, and wear resistance. In the case of using bentonite, the firing temperature in the firing step is preferably 780 to 850 ° C. in terms of pressure strength, heat resistance, and wear resistance. Further, when bentonite is used, it is preferable that the clay contains bentonite of 280 mesh pass or more within 30% by weight in order to obtain good moldability. When the particle size of bentonite is less than 360 mesh pass, it cannot be said that the dispersibility of rice husk and charcoal is good, and the compact may not be hardened by press molding.

  In the present invention, an additive may be contained in the kneaded material (kneaded material) for molding. Examples of the additive include a paste, a binder, a release agent, a peptizer, and the like, but the additive is not limited thereto, and may be an additive used for ordinary baking. Examples of the binder include sodium silicate, phosphoric acid, sodium phosphate, aluminum phosphate, alumina sol, and wax (oil).

  Clay and paste can be uniformly coated on the surface of rice husk and charcoal by appropriately blending paste into the kneaded product (kneaded clay) before molding. As a result, dehydration due to the molding pressure during press molding is prevented, and a uniform molded body can be obtained with a very large water retention amount of 30% by weight or more with respect to the total weight of the molded body. A high-strength ceramic body can be obtained. The content of the paste is preferably 1 to 2 parts by weight when the amount of rice husk and charcoal contained in the kneaded material (molded clay) for molding is 100 parts by weight.

  Furthermore, when a kneaded material (kneaded material) before molding contains a wax-based binder, the molding pressure can be reduced even at a low pressure, so that the molding pressure can be lowered, and dehydration due to the molding pressure during press molding can be further reduced. Dehydration due to molding pressure at the time of molding is reduced, and a uniform molded body can be obtained with an extremely large water retention amount of 40% by weight or more with respect to the weight of the entire molded body. Can be obtained. As a result, it is possible to obtain a ceramic body that is bulkier or has a higher strength. Examples of the wax-based binder include a binder (trade name: Selna WF-610) manufactured by Chukyo Yushi Co., Ltd., P-222 having the same system as Selna WF-610 and a high content of wax-based components. . The content of the wax-based binder is preferably 0.5 to 3 parts by weight when the amount of rice husk and charcoal contained in the kneaded material for molding (kneaded clay) is 100 parts by weight.

  The ceramic body of the present invention has low specific gravity and high heat resistance, excellent heat insulation, and can be suitably used as a furnace material for a high temperature furnace.

The compressive strength in Examples and Reference Examples was measured according to JIS R2615. The bending strength was measured according to JIS R2619. The bulk specific gravity of the ceramic body was measured according to JIS R2614.

The sizes of the molded bodies in the examples, reference examples, experimental examples, and comparative examples were set to 230 × 115 × 65 (mm) in accordance with the JIS parallel dimensions.

[Comparative Example 1]
40 parts by weight of water was mixed and kneaded with 30 parts by weight of rice husk (raw husk), 70 parts by weight of water-cracked clay (through 250 mesh) and 1 part by weight of chemical glue (CMC) to obtain a clay. This clay was subjected to friction press molding at 4 MPa. After the press molding, the molded body was cracked by repulsion of rice husk.

[Comparative Example 2]
20 parts by weight of rice husk, 80 parts by weight of water-cracked clay (through 250 mesh), 1 part by weight of chemical glue and 60 parts by weight of water were mixed and kneaded to obtain a clay. This clay was subjected to friction press molding at 4 MPa. After the press molding, the molded body was cracked by repulsion of rice husk.

[Comparative Example 3]
10 parts by weight of rice husk, 90 parts by weight of water-cracked clay (through 250 mesh), 1 part by weight of chemical glue and 60 parts by weight of water were mixed and kneaded to obtain a clay. This clay was subjected to friction press molding at 4 MPa. After the press molding, the molded body was cracked by repulsion of rice husk.

[Comparative Example 4]
30 parts by weight of rice husk, 70 parts by weight of water husk clay (through 250 mesh), 1 part by weight of chemical glue, 40 parts by weight of water are prepared, and after immersing the rice husk in water for 12 hours, After kneading together with chemical glue, friction press molding was performed at 4 MPa. When this molded body was left to dry indoors for one week, moisture retained in the rice husks oozed out and cracked in the molded body during drying.

[Comparative Example 5]
50 parts by weight of water are prepared in 20 parts by weight of rice husk, 80 parts by weight of water husk clay (250 mesh), 1 part by weight of chemical glue, and after immersing the rice husk in water for 12 hours, After kneading together with chemical glue, friction press molding was performed at 4 MPa. When this molded body was left to dry indoors for one week, moisture retained in the rice husks oozed out and cracked in the molded body during drying.

[Comparative Example 6]
60 parts by weight of water is prepared in 10 parts by weight of rice husk, 90 parts by weight of water husk clay (250 mesh), 1 part by weight of chemical glue, and after immersing the rice husk in water for 12 hours, After kneading together with chemical glue, friction press molding was performed at 4 MPa. When this molded body was left to dry indoors for one week, moisture retained in the rice husks oozed out and cracked in the molded body during drying.

[Comparative Example 7]
60 parts by weight of water was mixed with 30 parts by weight of rice husk (raw rice husk), 70 parts by weight of water-cracked clay (through 250 mesh) and 1 part by weight of chemical glue to obtain a clay. This clay was subjected to friction press molding at 4 MPa. Ginger husks caused water retention and swelling when water was added. Further, it was elastic and the molded product after pressing could not be molded into a predetermined shape.

[Comparative Example 8]
40 parts by weight of water was mixed with 10 parts by weight of raw rice husk, 90 parts by weight of water-cracked clay (through 250 mesh) and 1 part by weight of chemical glue to obtain a clay. This clay was subjected to friction press molding at 4 MPa. Ginger husks caused water retention and swelling when water was added. Further, there was elasticity, and the molded product was swollen after pressing, but it could be molded into a predetermined shape. However, when the molded body was left to dry indoors for one week, it was damaged and separated, and its shape collapsed. Further, when the dried molded body was baked at 800 ° C. for 2 hours, the molded body was separated by burning of rice husks.

[Experimental Example 1]
A kneaded mixture was obtained by mixing 50 parts by weight of rice husk charcoal (bulk specific gravity 0.11), 50 parts by weight of water clay (250 mesh) and 1 part by weight of chemical glue and mixing 70 parts by weight of water. . This clay was subjected to friction press molding at 4 MPa to obtain a molded body. The molded body was left to dry in a room for one week and then dried at 150 ° C. for 24 hours to obtain a dry molded body free from cracks.

[Experiment 2]
Rice bran charcoal (bulk specific gravity 0.11) 60 parts by weight, water goblet clay (through 250 mesh) 40 parts by weight, chemical glue 1 part by weight, 95 parts by weight of water are kneaded and then subjected to friction press molding at 4 MPa. Got. This molded body was dried in the same manner as in Experimental Example 1 to obtain a dry molded body without cracks.

[Experiment 3]
100 parts by weight of water is kneaded with 65 parts by weight of rice husk charcoal (bulk specific gravity 0.11), 30 parts by weight of water clay (250 mesh) and 1 part by weight of chemical glue, and then subjected to friction press molding at 4 MPa. Got. This molded body was dried in the same manner as in Experimental Example 1 to obtain a dry molded body without cracks.

[Experimental Example 4]
100 parts by weight of water is mixed with 80 parts by weight of rice husk charcoal (bulk specific gravity of 0.11), 20 parts by weight of water clay (250 mesh) and 1 part by weight of chemical glue, and then subjected to friction press molding at 4 MPa. Got. This molded body was dried in the same manner as in Experimental Example 1 to obtain a dry molded body without cracks.

[Experimental Example 5]
100 parts by weight of water was kneaded with 90 parts by weight of rice husk charcoal (bulk specific gravity 0.11), 30 parts by weight of water clay (250 mesh) and 1 part by weight of chemical glue, and then subjected to friction press molding at 4 MPa. The shape of the body collapsed. This molded body was dried in the same manner as in Experimental Example 1, but cracked.

  Table 1 shows the composition (parts by weight) of the clay and the moldability of the molded bodies in Comparative Examples 1 to 6 and Experimental Examples 1 to 5.

[Example 1]
100 parts by weight of water was kneaded with 70 parts by weight of rice husk charcoal (bulk specific gravity of 0.11), 30 parts by weight of water clay (250 mesh) and 1 part by weight of chemical glue to obtain a clay. This clay was subjected to friction press molding at 4 MPa to obtain a molded body. The molded body was left to dry in a room for one week and then dried at 150 ° C. for 24 hours to obtain a dry molded body free from cracks. The dried molded body was fired at 800 ° C. in an oxidizing atmosphere for 8 hours to obtain a ceramic body.

[Example 2]
A ceramic body was obtained in the same manner as in Example 1 except that rice husk coal with a specific gravity of 0.13 was used as rice husk coal. There were no cracks in the dried molded body.

[Example 3]
A ceramic body was obtained in the same manner as in Example 1 except that rice husk coal with a specific gravity of 0.16 was used as rice husk coal. There were no cracks in the dried molded body.

  Table 2 shows the bulk specific gravity of rice husk and charcoal in Examples 1 to 3, the moldability of the molded body, and the bulk specific gravity of the ceramic body.

[Example 4]
A ceramic body was obtained in the same manner as in Example 1 except that bentonite (300 mesh pass) was used as the clay. There were no cracks in the dried molded body.

[ Reference Example 1 ]
A ceramic body was obtained in the same manner as in Example 1 except that New Zealand kaolin was used as the clay.

[ Reference Example 2 ]
A ceramic body was obtained in the same manner as in Example 1 except that Vietnamese kaolin was used as the clay.

[ Reference Example 3 ]
A ceramic body was obtained in the same manner as in Example 1 except that Chinese kaolin was used as the clay.

Table 3 shows the formability (formability to the substrate and the characteristics of the dry molded body), the pressure resistance strength and the wear resistance of the ceramic bodies in Examples 1 and 4 and Reference Examples 1 to 3. The moldability was good in Examples 1 and 4 and Reference Examples 1 to 3, and no cracks were observed. Examples 1 and 4 were particularly excellent in pressure resistance. Example 4 was particularly excellent in abrasion resistance. Overall, Example 4 was particularly excellent.

[Example 5 ]
A ceramic body was obtained in the same manner as in Example 1 except that the firing temperature and time of the dried molded body were set to 3 cases of 900 ° C. and 8 hours, 1000 ° C. and 8 hours, 1100 ° C. and 8 hours. The rate of temperature rise until reaching these temperatures was 100 ° C./hour. The ceramic body with a firing temperature of 900 ° C. had a bulk specific gravity of 0.5, and had a compressive strength equivalent to that of Example 1. The ceramic bodies with the firing temperatures of 1000 ° C. and 1100 ° C. had higher pressure resistance than the ceramic bodies with the firing temperature of 900 ° C., but the heat resistance was lowered. In addition, the ceramic bodies with the firing temperatures of 1000 ° C. and 1100 ° C. caused considerable shrinkage due to firing.

[Experiment 2]
A ceramic body was obtained in the same manner as in Example 4 except that the firing temperature and time of the dried molded body were set to 3 cases of 900 ° C. and 8 hours, 1000 ° C. and 8 hours, 1100 ° C. and 8 hours. The rate of temperature rise until reaching these temperatures was 100 ° C./hour. Although the ceramic bodies having the firing temperatures of 900 ° C. and 1000 ° C. had higher pressure strength than that of Example 4, satisfactory heat resistance was not obtained. The ceramic body with a firing temperature of 900 ° C. had a bulk specific gravity of 0.4 and a light weight, but a shape change due to heat was observed during firing. The ceramic body with a firing temperature of 1000 ° C. was melted during firing, and the ceramic body with a firing temperature of 1100 ° C. was significantly deformed by melting.

[ Reference Example 4 ]
A ceramic body was obtained in the same manner as in Reference Example 1 except that the firing temperature and time of the dried molded body were set to 3 cases of 900 ° C. and 8 hours, 1000 ° C. and 8 hours, 1100 ° C. and 8 hours. The rate of temperature rise until reaching these temperatures was 100 ° C./hour. The ceramic body with a firing temperature of 900 ° C. had a higher pressure resistance than that of Reference Example 1 , and the heat resistance was equivalent. The ceramic bodies with the firing temperatures of 1000 ° C. and 1100 ° C. had higher pressure resistance than the ceramic bodies with the firing temperature of 900 ° C., but the heat resistance was lowered. In addition, the ceramic bodies with the firing temperatures of 1000 ° C. and 1100 ° C. caused considerable shrinkage due to firing.

[ Reference Example 5 ]
A ceramic body was obtained in the same manner as in Reference Example 2 except that the firing temperature and time of the dried molded body were 3 cases of 900 ° C. and 8 hours, 1000 ° C. and 8 hours, 1100 ° C. and 8 hours. The rate of temperature rise until reaching these temperatures was 100 ° C./hour. The ceramic body with a firing temperature of 900 ° C. had a higher pressure resistance than that of Reference Example 2 , and the heat resistance was equivalent. The ceramic bodies with the firing temperatures of 1000 ° C. and 1100 ° C. had higher pressure resistance than the ceramic bodies with the firing temperature of 900 ° C., but the heat resistance was lowered. In addition, the ceramic bodies with the firing temperatures of 1000 ° C. and 1100 ° C. caused considerable shrinkage due to firing.

[ Reference Example 6 ]
A ceramic body was obtained in the same manner as in Reference Example 3 , except that the firing temperature and time of the dried molded body were set to 3 cases of 900 ° C. and 8 hours, 1000 ° C. and 8 hours, 1100 ° C. and 8 hours. The rate of temperature rise until reaching these temperatures was 100 ° C./hour. The ceramic body with a firing temperature of 900 ° C. had a higher pressure resistance than that of Reference Example 3 , and the heat resistance was equivalent. The ceramic bodies with the firing temperatures of 1000 ° C. and 1100 ° C. had higher pressure resistance than the ceramic bodies with the firing temperature of 900 ° C., but the heat resistance was lowered. In addition, the ceramic bodies with the firing temperatures of 1000 ° C. and 1100 ° C. caused considerable shrinkage due to firing.
Table 4 shows the results of Example 5 , Experimental Example 2, and Reference Examples 4 to 6 .

From Example 5 , Experimental Example 2 , and Reference Examples 4 to 6 , it was found that the use of the clay clay is particularly excellent in the case where the firing temperature is 900 ° C.

[Example 6 ]
100 parts by weight of water was kneaded with 75 parts by weight of rice husk charcoal (bulk specific gravity 0.11), 25 parts by weight of bentonite, and 1 part by weight of chemical paste to obtain clay. This clay was subjected to friction press molding at 4 MPa to obtain a molded body. The water content of this molded body was 40% by weight based on the total amount of the molded body. The molded body was left to dry in a room for one week and then dried at 150 ° C. for 24 hours to obtain a dry molded body free from cracks. The dried molded body was fired at 900 ° C. in an oxidizing atmosphere for 8 hours to obtain a good ceramic body having the strength required for handling. The rate of temperature increase until reaching 900 ° C. was 100 ° C./hour.

[Example 7 ]
A ceramic body was obtained in the same manner as in Example 6 except that 80 parts by weight of rice husk charcoal (bulk specific gravity 0.122) and 20 parts by weight of bentonite were used. This ceramic body had very good wear resistance and good pressure strength.

[Comparative Example 9]
A compact was obtained by friction press molding at 4 MPa in the same manner as in Example 6 except that 85 parts by weight of rice husk charcoal (bulk specific gravity 0.122) and 15 parts by weight of bentonite were used. This molded body was insufficient in strength to move and could not be put on the next step.

[Example 8 ]
A good ceramic body having the strength necessary for handling was obtained in the same manner as in Example 6 except that hydrangea clay (passing 250 mesh) was used instead of bentonite.

[Example 9 ]
A ceramic body was obtained in the same manner as in Example 7 except that hydrangea clay (through 250 mesh) was used instead of bentonite. By setting the heat treatment temperature to 900 ° C., the oxidation of the carbon component in the molded body was promoted, and there was almost no residual carbon after firing, which was effective in keeping the bulk specific gravity small. When the ceramic body was reheated, the shrinkage rate was -0.23% at 800 ° C, the bulk specific gravity was 0.36, the compressive strength was 0.180 MPa, and the thermal conductivity (600 ° C) was 0. .16 W / m · k (0.138 kcal / m · h · ° C.). According to a micrograph (10 times) of this ceramic body shown in FIG. 1, this ceramic body is composed of silica particles (B) composed of silica components remaining after carbon components are dissipated by oxidation from rice husks, and calcined clay. In addition, it was confirmed that the silica particles and clay were sintered, and that the silica particles maintained the shell shape of the rice husk and had cavities (A) derived from the shell shape.

  The reheating shrinkage rate was measured according to JIS R2613 (1988) using a high-temperature electric furnace SHV-353GI manufactured by Motoyama. The heating conditions are from room temperature to 750 ° C. at 5 ° C./min, from 750 ° C. to 800 ° C. at 1 ° C./min, and the holding time at 800 ° C. is 12 hours.

  The thermal conductivity was measured by the unsteady hot wire method of JIS R2616 using a thermal conductivity measuring device TC-51 manufactured by Kyoto Electronics Industry.

[Comparative Example 10]
A compact was obtained by friction press molding at 4 MPa in the same manner as in Comparative Example 9, except that hydrangea clay (through 250 mesh) was used instead of bentonite. This molded body was insufficient in strength to move and could not be put on the next step.

Table 5 shows the blending (parts by weight) of the clay and the moldability of the molded bodies in Examples 1, 4, 6 to 8 and Comparative Examples 9 and 10.

[Example 10 ]
A ceramic body was obtained in the same manner as in Example 7 except that the firing temperature and time were set to 800 ° C. and 8 hours. The rate of temperature increase until reaching 800 ° C. was 100 ° C./hour. The ceramic body had extremely good pressure strength and heat resistance and good wear resistance. When the ceramic body is reheated, the shrinkage rate is -0.22% at 800 ° C, the bulk specific gravity is 0.42, the compressive strength is 0.21 MPa, the bending strength is 0.19 MPa, The rate (600 ° C.) was 0.19 W / m · k (0.16 kcal / m · h · ° C.).

[Example 11 ]
A ceramic body was obtained in the same manner as in Example 7 except that the firing temperature and time were 850 ° C. and 8 hours. The rate of temperature increase until reaching 850 ° C. was 100 ° C./hour.

[Example 12 ]
A ceramic body was obtained in the same manner as in Example 7 except that the firing temperature and time were 950 ° C. and 8 hours. The rate of temperature increase until reaching 950 ° C. was 100 ° C./hour.

[Example 13 ]
A ceramic body was obtained in the same manner as in Example 9 except that the firing temperature and time were set to 800 ° C. and 8 hours. The rate of temperature increase until reaching 800 ° C. was 100 ° C./hour.

[Example 14 ]
A ceramic body was obtained in the same manner as in Example 9 except that the firing temperature and time were 850 ° C. and 8 hours. The rate of temperature increase until reaching 850 ° C. was 100 ° C./hour.

[Example 15 ]
A ceramic body was obtained in the same manner as in Example 9 except that the firing temperature and time were 950 ° C. and 8 hours. The rate of temperature increase until reaching 950 ° C. was 100 ° C./hour.

Table 6 shows the relationship between the firing temperature, heat resistance, wear resistance, and pressure resistance in Examples 7 and 10-15 .
Heat resistance: Evaluated by the state of shrinkage or warping when the ceramic body is reheated at the firing temperature. A: Almost no shrinkage or warping. ○: There is little shrinkage and warping, and there is no practical problem as a heat insulation furnace material. Δ: Shrinkage or warping occurs but is practically acceptable as a heat insulating furnace material. X: Shrinkage and warping are practical problems as a heat insulating furnace material.
Abrasion resistance: Evaluated by the state of wear when the ceramic body is rubbed by hand. A: Almost no wear. ○: There is little wear and there is no practical problem as a heat insulation furnace material. Δ: Wear occurs but is practically acceptable as a heat insulating furnace material. X: Wear is a practical problem as a heat insulating furnace material.
Compressive strength: Evaluated in the state of dent when the ceramic body is pushed by hand. A: Almost no dent. ○: There is little dent and there is no practical problem as a heat insulation furnace material. Δ: Dent is generated, but is practically acceptable as a heat insulating furnace material. X: A dent is a practical problem as a heat insulation furnace material.

[Example 16 ]
After kneading 80 parts by weight of rice husk charcoal (bulk specific gravity 0.11), 20 parts by weight of water goblet clay (through 250 mesh), 1 part by weight of chemical glue, 100 parts by weight of water, and 1 part by weight of tertiary aluminum phosphate Friction press molding was performed at 4 MPa to obtain a molded body. The water content of this molded body was 45% by weight with respect to the total amount of the molded body. The molded body was left to dry in a room for one week, and then dried at 150 ° C. for 24 hours. The dried molded body was fired at 900 ° C. in an oxidizing atmosphere for 8 hours to obtain a ceramic body. The rate of temperature increase until reaching 900 ° C. was 100 ° C./hour.
The ceramic body had good heat resistance and wear resistance, and the pressure strength was extremely good. When this ceramic body is reheated, the shrinkage rate is -0.11% at 800 ° C, the bulk specific gravity is 0.36, the compressive strength is 0.2 MPa, the bending strength is 0.13 MPa, The rate (600 ° C.) was 0.17 W / m · k (0.146 kcal / m · h · ° C.).

[Example 17 ]
A ceramic body was obtained in the same manner as in Example 16 except that the amount of tertiary aluminum phosphate was changed to 2 parts by weight. The bulk specific gravity of this ceramic body was 0.45, and the thermal conductivity was higher than that of the ceramic body obtained in Example 16 . The heat resistance and wear resistance were good, and the pressure strength was extremely good. ,

[Experimental Examples 6 and 7]
A clay was obtained in the same manner as in Example 4 except that two cases of bentonite (250 mesh pass) and bentonite (200 mesh pass) were used as clay. This clay was subjected to friction press at 4 MPa for molding. Table 7 shows the molding results.

[Example 18 ]
80 parts by weight of rice husk charcoal (bulk specific gravity 0.122), 20 parts by weight water clay (250 mesh), 1 part by weight of chemical glue, 100 parts by weight of water, 1 part by weight of tribasic aluminum phosphate, wax system 10 parts by weight of a binder (manufactured by Chukyo Yushi Co., Ltd .: type P222 (solid content 20 wt%)) was kneaded and then subjected to friction press molding at 3.5 MPa to obtain a molded body. The water content of this molded body was 50% by weight with respect to the total amount of the molded body. The molded body was left to dry in a room for one week, and then dried at 150 ° C. for 24 hours. The dried molded body was fired at 900 ° C. in an oxidizing atmosphere for 8 hours to obtain a ceramic body. The rate of temperature increase until reaching 900 ° C. was 100 ° C./hour. The ceramic body had good heat resistance and wear resistance, and the pressure strength was extremely good. When the ceramic body is reheated, the shrinkage rate is -0.17% at 800 ° C, the bulk specific gravity is 0.33, the compressive strength is 0.13 MPa, the bending strength is 0.08 MPa, The rate (600 ° C.) was 0.16 W / m · k.

  In addition, the present invention can be carried out in a mode in which various improvements, modifications, and changes are added based on the knowledge of those skilled in the art without departing from the spirit of the present invention.

It is a microscope picture which shows the structure of the ceramic body of this invention.

Claims (2)

It is obtained by firing a base material containing clay mainly composed of bentonite or cocoon clay and rice husk husk charcoal having a bulk specific gravity of 0.11 to 0.17, and the ratio of the clay to the husk husk charcoal is a weight ratio. 100: 300-400, a ceramic body including silica particles in which the shell shape of the rice husk is maintained and having a cavity derived from the shell shape . 2. The ceramic body according to claim 1, wherein the substrate is formed by press-molding a kneaded material containing the clay and the rice husk charcoal at 1 to 10 MPa.

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