JPH04160075A - Production of porous ceramic body - Google Patents

Abstract

PURPOSE:To allow the sintering of aggregate and the solidification of a binder with one time of calcination and to obtain the porous ceramic body which hardly generates the collapse of the aggregate and has high merchandise value by adding a flux and shape retaining agent to uncalcined ceramic granules coated with an oily moisture absorption preventive agent on the surface, molding the mixture and calcining the molding. CONSTITUTION:The films (5 to 10 pts.wt. per 100 pts. granules) of the moisture absorption preventive agent consisting of petroleum, etc., such as 'A' oil (boiler fuel or bunker fuel) are formed on the surfaces of the uncalcined ceramic granules (<=3% moisture) granulated to spherical or circular cylindrical shapes of about 0.6 to 4mm diameter. The glassy flux (5 to 20 pts.wt. per 100 pts. granules) and the shape retaining agent, for example, starchy dextrin are added at 2 to 3 pts. to these granules and the granules are press-molded (0.2 to 5kg/cm<2>) by using metallic molds laid with buffer sheets. The molding is calcined and the porous ceramic body useful for a water permeable pavement plate, etc., is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing porous ceramic bodies that can be used, for example, as water-permeable pavement plates at low cost, and particularly relates to The present invention relates to a method for manufacturing a ceramic porous body without constriction of grains on the surface.

(Conventional technology) Conventionally, in order to manufacture porous ceramic bodies used for water-permeable pavement boards, etc., glass such as water glass or glaze is added to ceramic aggregate, which is a fired product, or Cerben, which is crushed and sieved ceramics. Adding quality flux and a shape preservative such as methyl cellulose or polyvinyl alcohol as a temporary binder,
The method used was to press-form the material and then fire it again to make the product.

However, such conventional manufacturing methods have a problem in that the firing cost is high because firing is performed twice: firing the aggregate forming the ceramic porous body and firing the molded product.

Therefore, the present inventors attempted to form the aggregate into a porous shape without firing it, and to obtain a finished product by sintering the aggregate and solidifying it with a binder in one firing. repeated. However, unfired aggregate has low mechanical strength and is easily crushed, so if it is compression-molded into a porous shape as it is, the porosity of the porous body will decrease due to crushing, and the appearance of the product will be poor due to the crushing of the grains on the surface. The drawback was that the product value was lost. In particular, when producing a porous body using granulated aggregate with high hygroscopicity, it is difficult to obtain a porous body with a predetermined porosity because when the granulated aggregate absorbs moisture, its mechanical strength further decreases. The aggregate on the surface of the porous body also easily comes into contact with the porous body, making it difficult to compression mold the porous body into a shape having a predetermined porosity with little crushing of surface particles.

(Problems to be Solved by the Invention) The present invention solves these conventional problems and manufactures a ceramic porous body by sintering the aggregate and solidifying the binder (flux) in one firing. The present invention has been completed in order to provide a method for manufacturing a ceramic porous body which can significantly increase the commercial value without causing collapse of the aggregate.

(Means for solving the problem) The above problem was solved by adding and mixing flux and a shape-retaining agent to unfired ceramic granules coated with an oily moisture absorption inhibitor on the surface, and filling the mixture into a mold and forming it. This problem can be solved by a method of manufacturing a ceramic porous body characterized by firing.

In addition, the above problem was solved by adding and mixing flux and a shape-retaining agent to unfired ceramic granules, and then using a mold with a buffer sheet spread on at least one surface of the mold to prevent the grains from collapsing. This problem can be solved by a method of manufacturing a ceramic porous body, which is characterized by filling, molding, and firing.

Furthermore, the above problem was solved by adding and mixing flux and a shape-retaining agent to unfired ceramic granules whose surface was coated with a moisture absorption prevention material, and then a buffer sheet was placed on the bottom to prevent the granules from collapsing. This problem can be solved by a method for manufacturing a porous ceramic body, which is characterized by filling the inside of a mold, press-molding it, and firing it.

Thus, in the present invention, the diameter is preferably 0.6
A ceramic granule granulated into a spherical or cylindrical shape of about 4 m is dried until the moisture content is 3% or less, and a petroleum such as A heavy oil is applied to the surface of the unfired ceramic granule. Forms a film of moisture absorption preventive agent such as If the water content exceeds 3%, the green strength of the ceramic granules decreases, which is not preferable. The purpose of this film of petroleum, etc., which is an anti-moisture absorption agent, is to prevent the ceramic granules from drying out and decreasing their dry strength, and also to improve the surface slippage and moldability, which also enables low-pressure molding. This prevents the grains from collapsing. When the moisture absorption inhibitor is heavy oil A, the amount thereof may be 5 to 10 parts by weight based on 100 parts by weight of the granules.

The moisture absorption inhibitor coated on the surface of the ceramic granules is decomposed and scattered during firing, and does not remain on the product surface.

The graph in Figure 1 shows the relationship between molding pressure and product dry bulk density depending on the moisture absorption inhibitor, and shows that when heavy oil A is used as the moisture absorption inhibitor, a high product dry bulk density can be obtained with a low molding pressure. It is shown. Furthermore, FIG. 2 shows the relationship between the coating amount and the dry bulk density of the product depending on the moisture absorption inhibitor.

Next, preferably a vitreous flux and a shape retaining agent are added to the ceramic granules whose surfaces are coated with a moisture absorption preventive agent. Flux is granulated 80-95
Add 5 to 20 parts by weight of powder as a powder.

In addition, as a shape retaining agent, for example, starchy dextrin
It is sufficient to add 3 parts by weight.

Ceramic granules to which flux and shape-preserving agents have been added are press-molded inside a mold, but when press-molded normally, a coating with a moisture absorption preventive agent is applied as described above. In addition, as shown in FIG. 4B, it is inevitable that the ceramic granules in the part that comes into contact with the mold are crushed.Therefore, in the present invention, as shown in FIG. Ceramic granules are filled into a mold (2) covered with a buffer sheet (1) and press-molded. Here, as the buffer sheet (1), a sheet made of rubber or synthetic resin material and having a large number of closed cells and having a thickness of about 1 to 4 cm is suitable. For example, from 0.2 to 5.0 g/
By press-forming at a pressure of cj, it is possible to significantly reduce the sagging of grains on the surface of the product in contact with the buffer sheet (1), as shown in FIG. 4A. Note that if vibration is applied together with pressing, the molding and filling properties can be further improved.

Next, examples of the present invention will be shown.

(Example) SiO□60-70%, A]zOi 20-24%, K
ZO+NazO3,5-5.5%, Fezes O,2
% or less, Ti0z 1.0% or less, CaOO, 5% or less, Mgo 0.5% or less, Igloss 5.5 to 9.5
% of ceramic raw materials by adding 5% or less metal oxide pigment,
After adding 4 to 16% water and kneading, the mixture was extruded from a perforated plate of a granulator into a noodle shape with a diameter of about 0.6 to 4.0 mm.

Next, this was sized using a sizing machine so that 95% or more of the total particle size fell within ±50% of the average particle size. The spherical ceramic granules thus granulated were dried until the water content became 3% or less, and the surface of the ceramic granules was coated with heavy oil A as a moisture absorption inhibitor. It is preferable to use A heavy oil in an amount of 5 to 10 parts by weight based on 100 parts by weight of the ceramic granules, and the molding and filling properties can be improved more than when paraffin or the like is used.

In addition, when A heavy oil is coated on the surface of the ceramic granules, the coating layer of A heavy oil is extremely thin, and it seems that it is slightly impregnated inside the surface layer of the ceramic granules. However, when a highly viscous paraffin is coated on the surface of the ceramic granules, the coat layer, that is, the coating layer, is considered to be considerably thicker than when using heavy oil A.

Furthermore, the risk of solidification and peeling increases.

Next, the ceramic granules 80 coated with this moisture absorption preventive agent
~95 parts by weight of powdered vitreous flank 15-20
parts by weight and 2 to 3 parts by weight of a shape retaining agent are added and kneaded, and the mixture is filled into a mold lined with a polyethylene buffer sheet with closed cells and a thickness of 3 mm on the bottom, and then molded using a press molding machine. by 5
It was molded into a flat plate at a pressure of kg/c+1.

When this molded product was fired in a furnace at a temperature of 1280±20'C using a conventional method, the sintering and solidification of the entire molded product was completed at the same time as the granules were fired, and the grains on the surface of the product were hardly crushed. A ceramic porous body with no porosity was obtained by one firing.

The obtained ceramic porous body had a bending strength of 100 kg/cii or more, and the water permeation time specified in JIS^5403 was 5 to 60 seconds, showing excellent water permeability. Note that the same effect can be obtained even if the above-mentioned buffer sheet is provided on the upper and lower surfaces of the object to be molded, or only on the upper surface and press-molded.

(Effects of the Invention) As explained above, the first and third inventions increase the green strength of the ceramic granules by coating the surface of the unfired ceramic granules with a moisture absorption prevention material, thereby increasing the strength of the granules. By preventing crushing, it is possible to produce a ceramic porous body with excellent appearance and high commercial value. Further, according to the second and third inventions, ceramic granules are filled inside a mold with a cushioning sheet spread on the bottom surface to prevent the particles from collapsing, and press-molded. Since crushing is prevented, a ceramic porous body with excellent appearance and high commercial value can be manufactured. Furthermore, according to the present invention, a ceramic porous body can be obtained by simultaneously sintering the ceramic granules and solidifying them on the bonding side in one firing, thereby reducing manufacturing costs and making it easier to handle the ceramic granules. Since this makes it easier to perform the process, it is possible to improve workability in the manufacturing process. Moreover, the ceramic porous body produced by the present invention has the same porosity and water permeability as those produced by the conventional method, and is suitable for use in water-permeable pavement boards and the like.

Therefore, the present invention greatly contributes to the development of industry as a method for manufacturing porous ceramic bodies that eliminates the problems of the conventional methods.

[Brief explanation of the drawing]

Figure 1 is a graph showing the relationship between molding pressure and dry bulk density of the product due to different moisture absorption inhibitors in the present invention, and Figure 2 is a graph showing the relationship between the coating amount and product dry bulk density due to different moisture absorption inhibitors in the present invention. A graph showing the relationship, FIG. 3 is a cross-sectional view showing the press molding process of the present invention, and FIG. It is a quality item. (1) II receipt (2): Mold. Patent applicant: Nippon Insulators Co., Ltd. Akechi Insulators Co., Ltd. Agent Name: Akira Shima Buma
Tatsu Yuoka Watanuki
Fumi Yamamoto Large box Figure 1 Molding pressure (KQ/crn') Figure 2 Coating amount (Koto) Figure 3 Figure 4

Claims (1)

[Claims] 1. Flux and a shape-retaining agent are added and mixed to an unfired ceramic granule whose surface is coated with an oily moisture absorption inhibitor, and the mixture is filled into a mold, shaped, and fired. A method for manufacturing porous ceramic bodies. 2. Add and mix flux and a shape-retaining agent to unfired ceramic granules, then fill and mold into a mold with a buffer sheet placed on at least one surface of the mold to prevent crushing of the grains. A method for producing a porous ceramic body, which comprises firing the porous ceramic body. 3. Add and mix flux and a shape-retaining agent to unfired ceramic granules whose surface is coated with a moisture absorption prevention material, and then create a mold with a cushioning sheet placed on the bottom to prevent the granules from collapsing. A method for producing a porous ceramic body, which is characterized by filling the inside, press-forming, and firing.