Method for manufacturing ceramic structures

Abstract

This invention provides a method for producing ceramic structures of various types without high-temperature firing, and is suitable for mass production. [Solution] A method for manufacturing a ceramic structure, comprising the steps of: obtaining activated ceramic powder by mechanochemical treatment of ceramic powder; obtaining clay by mixing and kneading the activated ceramic powder, an organic binder, and water; obtaining a ceramic molded body by extrusion molding of the clay; immersing the ceramic molded body in water or an alkaline liquid; and curing and drying the ceramic molded body after immersion.

Description

[Technical Field]

[0001] The present invention relates to a method for producing a ceramic structure. [Background Art]

[0002] As a method for producing a ceramic structure, Patent Document 1 discloses a method comprising: a grinding step of dry-grinding ceramics having at least a surface formed of silicic acid and / or silicate to obtain activated ceramic powder whose surface is mechanochemically amorphized; and an alkali treatment step of treating the activated ceramic powder with an alkaline aqueous solution containing an alkali metal hydroxide to dissolve and reprecipitate the surface of the activated ceramic powder, thereby obtaining a solidified ceramic body having a bending strength of 10 MPa or more. According to this production method, a high-strength ceramic structure can be obtained without performing high-temperature firing. [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Patent No. 5055550 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] In the production method described in Patent Document 1, a ceramic structure having a predetermined structure can be obtained by molding activated ceramic powder treated with an alkaline aqueous solution. However, in the production method described in Patent Document 1, solidification starts to progress as the activated ceramic powder is treated with the alkaline aqueous solution, which limits the structures of ceramic structures that can be produced, and is also unsuitable for mass production of ceramic structures.

[0005] This invention was made to solve the above-mentioned problems, and aims to provide a method for manufacturing ceramic structures that can be obtained without high-temperature firing and are suitable for mass production. [Means for solving the problem]

[0006] The present inventors have diligently researched methods for manufacturing ceramic structures and have found that the above problems can be solved by extruding a clay mixture containing activated ceramic powder, an organic binder, and water to form a ceramic molded body, and then curing and drying it by immersing it in an alkaline liquid. This led to the completion of the present invention. Specifically, the present invention is illustrated as follows.

[0007] <1> A process to obtain activated ceramic powder by mechanochemical treatment of ceramic powder, The process involves mixing the activated ceramic powder, organic binder, and water, and kneading them to obtain a clay material. The process of obtaining a ceramic molded body by extruding the aforementioned clay, A step of immersing the ceramic molded body in water or an alkaline liquid, The process involves curing and drying the ceramic molded body after immersion. A method for manufacturing ceramic structures, including [the specified element].

[0008] <2> The ceramic molded body has a honeycomb shape, <1> A method for manufacturing the ceramic structure described above.

[0009] <3> The alkaline liquid is alkaline water, or an alkaline aqueous solution containing alkali metal hydroxides and / or alkaline earth metal hydroxides. <1> or <2> A method for manufacturing the ceramic structure described above.

[0010] <4> The organic binder is at least one selected from methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, starch, and polyvinyl alcohol. <1> ~ <3> A method for manufacturing a ceramic structure as described in any one of the following.

[0011] <5> The ceramic powder has at least a surface containing silica and / or alumina. <1> ~ <4> A method for manufacturing a ceramic structure as described in any one of the following.

[0012] <6> The average particle size of the ceramic powder is 0.1 to 1000 μm. <1> ~ <5> A method for manufacturing a ceramic structure as described in any one of the following.

[0013] <7> The pH of the aforementioned alkaline liquid is 8 to 13. <1> ~ <6> A method for manufacturing a ceramic structure as described in any one of the following.

[0014] <8> The curing process is carried out under conditions of maintaining a temperature of 20 to 120°C for 0.5 to 48 hours. <1> ~ <7> A method for manufacturing a ceramic structure as described in any one of the following.

[0015] <9> The drying is carried out under conditions of holding at a temperature of 40 to 200°C for 0.5 to 48 hours. <1> ~ <8> A method for manufacturing a ceramic structure as described in any one of the following. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a method for manufacturing ceramic structures that can be obtained without high-temperature firing and are suitable for mass production. [Modes for carrying out the invention]

[0017] A method for producing a ceramic structure according to the present invention comprises: a step of mechanochemically treating ceramic powder to obtain activated ceramic powder; a step of mixing and kneading the activated ceramic powder, an organic binder and water to obtain kneaded clay; a step of extruding the kneaded clay to obtain a ceramic molded body; a step of immersing the ceramic molded body in water or an alkaline liquid; and a step of curing and drying the ceramic molded body after immersion. In the method for producing a ceramic structure according to the present invention, before bringing the activated ceramic powder into contact with an alkaline liquid, the kneaded clay containing the activated ceramic powder is prepared and molded, whereby solidification during molding can be suppressed, and molding into various shapes is facilitated. Further, in the method for producing a ceramic structure according to the present invention, since the ceramic molded body containing the activated ceramic powder is immersed in water or an alkaline liquid for curing and drying, the ceramic structure can be solidified to increase strength without performing high-temperature firing.

[0018] Hereinafter, embodiments of the present invention will be specifically described. The present invention is not limited to the following embodiments, and it should be understood that modifications and improvements appropriately made to the following embodiments based on the ordinary knowledge of those skilled in the art without departing from the spirit of the present invention also fall within the scope of the present invention.

[0019] A method for producing a ceramic structure according to an embodiment of the present invention comprises a mechanochemical treatment step, a kneaded clay preparation step, an extrusion molding step, an immersion step, and a curing and drying step.

[0020] (Mechanochemical Treatment Step) The mechanochemical treatment step is a step of mechanochemically treating ceramic powder to obtain activated ceramic powder. Here, the term "mechanochemical treatment" refers to a treatment that applies mechanical energy to a target substance to change the chemical bonds and electron density distribution of the target substance, thereby inducing mechanochemical phenomena in which various chemical reactions via charge transfer occur locally. By performing mechanochemical treatment on ceramic powder, the surface of the ceramic powder is amorphized, and activated ceramic powder can be obtained in a state that is easily eroded by alkaline liquid (in particular, a state that can be solidified without high-temperature firing to increase strength in the dipping step and the curing / drying step described later).

[0021] The mechanochemical treatment is not particularly limited as long as it is a method capable of applying mechanical energy to ceramic powder, but a method that can compositely exert various forces such as impact, friction, compression and shearing force is preferable. Examples of devices capable of imparting such effects include mixing devices such as ball mills, vibration mills, planetary mills and media agitation mills; ball media mills, roller mills, and pulverizers such as mortars. In addition, jet mills that can mainly apply forces such as impact and attrition to ceramic powder can also be used. By pulverizing with a jet mill, compressive force, shearing force, impact force and the like can be applied, thereby amorphizing the surface of the ceramic powder and obtaining activated ceramic powder.

[0022] The conditions of mechanochemical treatment (rotation speed, temperature, time, etc.) may be appropriately adjusted according to the type of ceramic powder used, and are not particularly limited, but it is preferable to perform the treatment until the particle size distribution no longer changes over time. Performing the treatment until the particle size distribution no longer changes over time means that the ceramic powder has reached the limit of fineness achievable by mechanochemical treatment, and the amorphization of the surface of the ceramic powder is in the most advanced state. Activated ceramic powder in this state is more prone to dissolution by alkaline liquid, so the resulting ceramic structure is dense and has high mechanical strength.

[0023] The ceramic powder is not particularly limited as long as it can be activated by mechanochemical treatment. For example, ceramic powders that contain silica and / or alumina on at least their surface can be used. By using such ceramic powder, it is possible to solidify the material without high-temperature firing and obtain a ceramic structure with high strength.

[0024] Specific examples of ceramic powders include clay minerals such as bentonite, kaolinite, metakaolin, and montmorillonite; SiO2-Al2O3 inorganic powders such as quartz and mullite; waste materials such as fly ash, kila, glass, paper sludge, and aluminum dross; silica; amorphous silica; silicon nitride; silicon carbide; alumina; sialon (SiAlON); silicon oxynitride (SiON); and silicon oxycarbide (SiOC). These can be used individually or in combination of two or more. Furthermore, aggregate may be used in combination with the ceramic powder. The aggregate, like the ceramic powder, preferably contains silica and / or alumina on its surface. Examples of such aggregates include sand, crushed sand, gravel, crushed stone, silica sand, silica powder, fly ash, mica, diatomaceous earth, mica, rock powder (shirasu, volcanic rock, etc.), basalt, feldspar, wollastonite, clay, and sepiolite. These can be used individually or in combination of two or more.

[0025] The average particle size of the ceramic powder is not particularly limited, but is preferably 0.1 to 1000 μm, more preferably 0.1 to 500 μm, even more preferably 0.2 to 300 μm, and most preferably 0.2 to 200 μm. If the ceramic powder has such an average particle size, activated ceramic powder can be easily obtained by mechanochemical treatment. Herein, in this specification, "average particle size" means the particle size at 50% of the integrated value of the particle size distribution obtained by the laser diffraction-scattering method (D50).

[0026] (Clay preparation process) The clay preparation process involves mixing activated ceramic powder, an organic binder, and water, and then kneading the mixture to obtain the clay. The organic binder is not particularly limited, and known organic binders can be used. Examples of organic binders include methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, starch, and polyvinyl alcohol. These can be used individually or in combination of two or more. By using such organic binders, a ceramic molded body having a desired structure can be obtained in the extrusion molding process described later.

[0027] The amount of organic binder added is not particularly limited, but is preferably 1 to 20 parts by mass, and more preferably 2 to 5 parts by mass, per 100 parts by mass of activated ceramic powder. The amount of water added is not particularly limited, but it is preferably 20 to 100 parts by mass, and more preferably 20 to 60 parts by mass, per 100 parts by mass of activated ceramic powder. In addition to the above components, known components such as surfactants and pore-forming agents may be added to the clay, to the extent that they do not hinder the effects of the present invention.

[0028] The clay can be prepared by mixing and kneading the above-mentioned components. The kneading method is not particularly limited, but it can be carried out using known equipment such as a kneader or a vacuum clay mixer.

[0029] (Extrusion molding process) The extrusion molding process is a process in which clay is extruded to obtain a ceramic molded body. The shape of the ceramic molded body is not particularly limited and can be of various shapes. For example, the ceramic molded body can have a honeycomb shape. In conventional methods of molding activated ceramic powder treated with an alkaline aqueous solution, it is difficult to obtain ceramic molded bodies with complex shapes such as a honeycomb shape. However, by using the method of the present invention, it is possible to obtain ceramic molded bodies having such shapes. Herein, the term "honeycomb shape" as used herein refers to a shape having an outer perimeter wall and a partition wall disposed inside the outer perimeter wall that divides a plurality of cells extending from a first end face to a second end face, or a shape having an outer perimeter wall, an inner perimeter wall, and a partition wall disposed between the outer perimeter wall and the inner perimeter wall that divides a plurality of cells extending from a first end face to a second end face.

[0030] Extrusion molding is performed using an extrusion machine equipped with a die that corresponds to the shape of the ceramic molded body to be produced. For example, when producing a honeycomb-shaped ceramic molded body, the shape and density of the cells, the shape and thickness of the outer wall, inner wall, and partitions can be controlled by selecting a die of the appropriate shape.

[0031] (Soaking process) The immersion process involves immersing a ceramic molded body in water or an alkaline liquid. Through this process, the surface (amorphous layer) of the activated ceramic powder contained within the ceramic molded body dissolves and undergoes dehydration and condensation, forming a precipitated layer. This precipitated layer acts as an adhesive, promoting solidification and increasing strength.

[0032] The alkaline liquid is not particularly limited, but alkaline water or an alkaline aqueous solution containing alkali metal hydroxides and / or alkaline earth metal hydroxides can be used. Examples of alkaline water include electrolyzed water obtained by electrolyzing water, and ammonia water. Examples of alkali metal hydroxides used in alkaline aqueous solutions include potassium hydroxide, sodium hydroxide, and lithium hydroxide. Examples of alkaline earth metal hydroxides used in alkaline aqueous solutions include calcium hydroxide and barium hydroxide.

[0033] The pH of the alkaline liquid is not particularly limited, but is preferably 8 to 13, more preferably 9 to 12. By controlling the pH within this range, the dissolution and dehydration condensation of the surface (amorphous layer) of the activated ceramic powder can be carried out stably.

[0034] Water or an alkaline liquid may be used at room temperature or heated. Using heated water or an alkaline liquid allows for rapid dissolution and dehydration condensation of the surface (amorphous layer) of the activated ceramic powder. The temperature of the water or alkaline liquid can be adjusted as appropriate depending on the type of activated ceramic powder and alkaline liquid, but is generally room temperature to 90°C, preferably room temperature to 60°C.

[0035] The immersion time for ceramic molded bodies in water or alkaline liquid should be adjusted as appropriate depending on the shape and size of the ceramic molded body, but it is generally between 1 and 60 minutes. In practice, an immersion time of 1 to 2 minutes is sufficient, and there is a risk that the ceramic molded body may disintegrate if the immersion time is too long.

[0036] (Curing / drying process) The curing and drying process involves curing and drying the ceramic molded body after immersion. By curing the ceramic body, the alkaline liquid penetrates sufficiently into the interior of the ceramic molded body. As a result, the surface (amorphous layer) of the activated ceramic powder inside the ceramic molded body dissolves, undergoes dehydration condensation, and forms a precipitate layer. The curing conditions can be adjusted as appropriate depending on the shape and size of the ceramic molded body, but it is preferable to maintain the temperature at 20-120°C for 0.5-48 hours. By curing under these conditions, the above effects can be reliably obtained.

[0037] By drying after curing, the moisture content in the ceramic molded body is reduced, resulting in a ceramic structure that is solidified throughout. The drying conditions can be adjusted as appropriate depending on the shape and size of the ceramic molded body, but it is preferable to carry out the drying under conditions of holding the body at a temperature of 40 to 200°C for 0.5 to 48 hours. By drying under these conditions, the above effects can be reliably obtained. [Examples]

[0038] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0039] (Example 1) Silica (average particle size 80 μm) and amorphous silica (average particle size 0.2 μm) were used as ceramic powders. The ceramic powders were placed in a magnetic pot, zirconia balls (diameter 10φ) were added, and the mixture was rotated in a ball mill for 12 hours to perform mechanochemical treatment and obtain activated ceramic powders. Next, activated ceramic powder, methylcellulose (organic binder), and water were mixed and kneaded to produce a clay body, which was then extruded into a rectangular ceramic molded body. The amount of methylcellulose added was 3 parts by mass per 100 parts by mass of activated ceramic powder, and the amount of water added was 35 parts by mass per 100 parts by mass of activated ceramic powder. The rectangular ceramic molded body was set to a size of 15 mm × 10 mm × 60 mm. Next, the ceramic molded body was immersed in an alkaline aqueous solution (pH 12) containing potassium hydroxide for 1 minute, and then cured and dried to obtain a ceramic structure. Curing was performed at a temperature of 60°C for 1 hour, and drying was performed at 60°C for 24 hours, followed by drying at 80°C for 24 hours. Visual inspection of the obtained ceramic structure revealed no deformation or other defects, and its strength was also good.

[0040] (Example 2) Amorphous silica (average particle size 0.2 μm) was used as the ceramic powder. The ceramic powder was placed in a magnetic pot, zirconia balls (diameter 10φ) were added, and the mixture was rotated in a ball mill for 12 hours to perform mechanochemical treatment and obtain activated ceramic powder. Next, activated ceramic powder, methylcellulose (organic binder), and water were mixed and kneaded to produce a clay body, which was then extruded into a honeycomb-shaped ceramic molded body. The amount of methylcellulose added was 3 parts by mass per 100 parts by mass of activated ceramic powder, and the amount of water added was 39 parts by mass per 100 parts by mass of activated ceramic powder. The honeycomb-shaped ceramic molded body had a cross-section perpendicular to the direction in which the cells extended, measuring 39 mm x 39 mm, a length of 40 mm in the direction in which the cells extend, a thickness of 1 mm for the outer wall, a thickness of 0.3 mm for the partition wall, and a cell density of 46.5 cells / cm³. 2 I set it up so that it would be like this. Next, the ceramic molded body was immersed in an alkaline aqueous solution (pH 12) containing potassium hydroxide for 1 minute, and then cured and dried to obtain a ceramic structure. Curing was performed at a temperature of 60°C for 1 hour, and drying was performed at 60°C for 24 hours, followed by drying at 80°C for 24 hours. Visual inspection of the obtained ceramic structure revealed no deformation or other defects, and its strength was also good.

[0041] (Example 3) Alumina (average particle size 20 μm) was used as the ceramic powder. The ceramic powder was placed in a magnetic pot, zirconia balls (diameter 10φ) were added, and the mixture was rotated in a ball mill for 12 hours to perform mechanochemical treatment and obtain activated ceramic powder. Next, activated ceramic powder, methylcellulose (organic binder), and water were mixed and kneaded to produce a clay body, which was then extruded into a honeycomb-shaped ceramic molded body. The amount of methylcellulose added was 3 parts by mass per 100 parts by mass of activated ceramic powder, and the amount of water added was 99 parts by mass per 100 parts by mass of activated ceramic powder. The honeycomb-shaped ceramic molded body had a cross-section perpendicular to the direction in which the cells extended, a length in the direction in which the cells extended, a thickness of 1 mm for the outer wall, a thickness of 0.3 mm for the partition wall, and a cell density of 46.5 cells / cm³. 2 I set it up so that it would be like this. Next, the ceramic molded body was immersed in an alkaline aqueous solution (pH 12) containing potassium hydroxide for 1 minute, and then cured and dried to obtain a ceramic structure. Curing was performed at 60°C for 24 hours, and drying was performed at 110°C for 24 hours. Visual inspection of the obtained ceramic structure revealed no deformation or other defects, and its strength was also good.

[0042] (Comparative Example 1) Amorphous silica (average particle size 0.2 μm), methylcellulose (organic binder), and water were mixed and kneaded to prepare a clay body, which was then extruded into a honeycomb-shaped ceramic molded body. The amount of methylcellulose added was 3 parts by mass per 100 parts by mass of amorphous silica, and the amount of water added was 39 parts by mass per 100 parts by mass of amorphous silica. The honeycomb-shaped ceramic molded body had a cross-section of 39 mm × 39 mm perpendicular to the direction in which the cells extended, an outer wall thickness of 1 mm, a partition wall thickness of 0.3 mm, and a cell density of 46.5 cells / cm³. 2 The settings were configured to achieve this, but the molding process stopped midway. Observation revealed that the ceramic molded body during the molding process had separated into solid and water components.

[0043] As can be seen from the above results, the present invention provides a method for manufacturing ceramic structures that can be obtained without high-temperature firing and is suitable for mass production.

Claims

1. A process to obtain activated ceramic powder by mechanochemical treatment of ceramic powder, The process involves mixing the activated ceramic powder, organic binder, and water, and kneading them to obtain a clay material. The process of obtaining a ceramic molded body by extruding the aforementioned clay, A step of immersing the ceramic molded body in water or an alkaline liquid, The process involves curing and drying the ceramic molded body after immersion. A method for manufacturing ceramic structures, including [the specified element].

2. The method for manufacturing a ceramic structure according to claim 1, wherein the ceramic molded body has a honeycomb shape.

3. The method for producing a ceramic structure according to claim 1 or 2, wherein the alkaline liquid is alkaline water or an alkaline aqueous solution containing alkali metal hydroxides and / or alkaline earth metal hydroxides.

4. The method for producing a ceramic structure according to claim 1 or 2, wherein the organic binder is at least one selected from methylcellulose, hydroxypropylmethylcellulose, carboxymethylcellulose, starch, and polyvinyl alcohol.

5. The method for producing a ceramic structure according to claim 1 or 2, wherein the ceramic powder comprises at least a surface containing silica and / or alumina.

6. A method for producing a ceramic structure according to claim 1 or 2, wherein the average particle size of the ceramic powder is 0.1 to 1000 μm.

7. The method for producing a ceramic structure according to claim 1 or 2, wherein the pH of the alkaline liquid is 8 to 13.

8. The method for manufacturing a ceramic structure according to claim 1 or 2, wherein the curing is carried out under conditions of holding at a temperature of 20 to 120°C for 0.5 to 48 hours.

9. The method for manufacturing a ceramic structure according to claim 1 or 2, wherein the drying is carried out under conditions of holding at a temperature of 40 to 200°C for 0.5 to 48 hours.