JPH02217347A - Production of ceramic raw material, ceramic raw material obtained by same production and molded article thereof - Google Patents

Abstract

PURPOSE:To obtain a ceramic raw material having excellent characteristics in terms of both quality and safety without admixture of impurities and requiring a binder for granulation by grinding a calcined ceramic raw material by using a specific pulverizer. CONSTITUTION:A calcined ceramic powdery or granular raw material is pressed against the inner peripheral face of a high-speed rotating casing 4 by centrifugal force. The raw material is strongly ground down by relatively revolving grinding pieces 9a on the raw material layer wherein movement of the raw material is limited by centrifugal force. The raw material layer is stirred and blended by raking pieces 9b relatively rotating on the raw material layer so that the pulverized raw material is sufficiently mixed and dispersed. Consequently, pulverization, uniform stirring and blending of the raw material are efficiently carried out in a short time as a whole.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for calcining a ceramic raw material and then pulverizing it to obtain a finely powdered ceramic raw material, and a ceramic raw material obtained thereby. The present invention relates to a raw material and a ceramic molded body manufactured using this ceramic raw material.

(Prior art) Conventionally, in order to grind calcined ceramic raw materials into fine powder, a ball mill as shown in FIG. The powder was pulverized using a grinding ball (31).

Another method is to sufficiently pulverize the material using another pulverizer capable of pulverizing it, and then granulate it into an appropriate size.

(Problem B to be solved by the invention) However, the fine powder raw material obtained by ball milling has a wide particle size distribution, and it is difficult to uniformly disperse it during filling during molding. It was insufficient to produce a ceramic molded body having the following properties.

In addition, when using powder that has been sufficiently pulverized with another pulverizer and then granulated, a separate process for granulation is required, and the pulverization process cannot be carried out using conventional high-performance methods. Most of the pulverizers are made of materials other than ceramics, that is, metals such as iron and stainless steel. Therefore, in the pulverization process using these pulverizers, part of the pulverizing member is scraped off by collision with raw material particles or friction. This may become mixed into ceramic products, creating another new problem. In addition, many of these pulverizers are equipped with a classification mechanism in addition to the pulverizing mechanism, and it would be very expensive to make the entire device including this from a ceramic material. Furthermore, the binder added for granulation takes time to completely evaporate during firing, and in some cases it may remain in the ceramic even after firing, so it cannot be treated simply as an impurity in the raw materials. However, depending on the use, it may be inconvenient as a harmful substance.

An object of the present invention is to produce a ceramic molded body that is free from these problems and fears, has components uniformly dispersed, is dense, and has excellent strength, and a ceramic raw material for realizing it.

(Means for Solving the Problems) The characteristic means of the present invention is that when pulverizing the calcined ceramic raw material, the casing is driven to rotate at high speed and the raw material is pressed against the inner peripheral surface of the casing by centrifugal force. , A grinding piece and a scraping piece that rotate relative to the casing are applied to the raw material layer formed by the pressing, and the granular raw material is finely pulverized by the compressive force and shear force of the grinding piece, and is stirred by the scraping piece. Uniform dispersion is achieved by mixing, and the synergistic action of these grinding pieces and scraping pieces causes the particles in the fine powder raw material to fuse with each other to obtain a composite fine powder. The functions and effects are as follows.

(Operation) In other words, the granular raw material is pressed by centrifugal force against the inner peripheral surface of the casing that rotates at high speed, and the grinding pieces are rotated relative to the raw material layer where the movement of the raw material is restricted by centrifugal force. By applying this action, it is possible to grind the raw material with the grinding pieces powerfully, reliably, and efficiently.

In addition, the raw material layer is stirred and mixed with a scraping piece that rotates relative to it, ensuring the mixing and dispersion of fine powder raw materials.
And it can be realized with sufficient efficiency. As a whole, it has become possible to pulverize the raw materials and uniformly stir and mix them in a short time, reliably, and sufficiently uniformly.

Moreover, the fine powder produced in this way causes fusion of particles or smaller particles on the surface of each powder particle by compression and shearing by the grinding pieces and stirring and mixing by the scraping pieces. , a composite powder is obtained in which fine particles are almost uniformly combined. This composite powder has a uniform particle size and can be filled into a mold evenly and well, thereby making it possible to produce a molded body with a dense structure in which the components are uniformly dispersed.

In addition, the corners of each particle are shaved off during grinding and mixing, or the particles become roundless due to the bonding of microparticles.
Internal stress generated due to shrinkage during compression molding or firing is less likely to be concentrated in one part, and a ceramic molded body with excellent strength can be manufactured.

(Effects of the Invention) As a result, it has become possible to produce molded bodies of high quality as ceramics and extremely stable in terms of strength. Furthermore, it is possible to mix ceramic materials with different components in the same apparatus, and it is possible to produce ceramic raw materials and ceramic molded bodies having new compositions. Moreover, since the mixing and granulation operation is performed in the same apparatus, a ceramic raw material for molded bodies can be produced at low cost without requiring a separate granulation process. Furthermore, by composing the powder contact parts such as the inner surface of the casing, the crushed pieces, and the scraped pieces with ceramics, the contamination of impurities is eliminated, and there is no need for a binder for granulation, which is good in terms of both quality and safety. It is now possible to provide ceramic raw materials with specific characteristics.

(Example) Next, examples will be shown.

As shown in FIG. 1, the calcined ceramic raw material is weighed, and the weighed raw material is pulverized and mixed in a dry grinding mixer to produce a finely powdered ceramic raw material. and,
This fine powder raw material is filled into a mold, compressed, and fired to produce a ceramic molded body.

The above-described grinding and mixing apparatus will now be described in detail with reference to FIGS. 2 and 3.

A bottomed cylindrical casing (4) forming a processing chamber (3) is attached concentrically to the upper end of a vertical rotating shaft (2) attached to a machine base (1), and an electric motor (5a) and a transmission (5b
) etc. is interlocked with the lower end of the rotating shaft (2), and the granular raw material inside the casing (4) is pressed against the inner circumferential surface (4a) of the casing (4) by centrifugal force. The casing (4) is configured to rotate at high speed, and the rotational speed of the casing (4) can be adjusted to obtain an appropriate centrifugal force depending on the properties of the raw material.

The casing (4) is surrounded by a cover (7), a fan (12) is connected to the bottom of the casing (4), and the cover (7) is surrounded by a fan (12).
) is configured to suck outside air through an intake port formed in the casing (4) and cool the casing (4) with the sucked outside air. In addition, a conveyance channel (lO
) is configured to be used as air for conveying fine powder raw materials. In addition, the fine powder raw material is transferred from the processing chamber (3) to the cover (7).
), the upper center of the casing (4) is opened to form an overflow outlet (11) for the raw material.

A support (8b) having a conical portion (8c) formed at the upper center thereof is provided on the casing (4), and is fixed to the upper end of the rotation shaft (8a), which is the same as the rotation shaft (2).

A grinding piece (9a) that compresses and shears the raw material in cooperation with the inner circumferential surface (4a) of the casing (4), and a scraping piece (9b) that stirs, mixes, and disperses the raw material are rotated in the rotation direction of the casing (4). They are arranged in the processing chamber (3) and attached to the tip of the support (8a) in a state where they are lined up at appropriate intervals. Crushed piece (9a)
has an inclined surface formed so that the gap with the casing (4) becomes narrower on the rotational direction side of the casing (4), and on the other hand, the scraping piece (9b) has an inclined surface formed so that the gap with the casing (4) becomes narrower on the side in the direction of rotation of the casing (4). 4) The rotation direction side is wide, and the working surface is formed into a wedge shape or a comb tooth shape so that the width gradually becomes wider. Note that the grinding piece (9a) and the scraping piece (9b) of this device have at least the surface portion made of ceramics to eliminate the problem of foreign matter contamination, but the casing (4) is also completely covered in the same way. Alternatively, the inner circumferential surface (4a) may be partially made of ceramics, or may be made of a material other than ceramics, for example, a metal such as iron or stainless steel. In other words, regarding the inner circumferential surface (4a), since the raw material layer is formed along the inner circumferential surface (4a),
Friction that occurs when the raw material directly collides with the inner circumferential surface (4a) or between the raw material and the crushed pieces (9a) is caused by the inner circumferential surface (4a).
), the inner circumferential surface (4a) is rarely scraped or worn. Therefore, the entire casing (4) including the inner circumferential surface (4a) may be made of a material other than ceramics, unless there is a severe restriction on the ingress of foreign matter.

The rotating shaft (8a) is interlocked with the drive device (5), and the grinding piece (9a) and the scraping piece (9b) are rotated relative to the casing (4) at a constant speed difference, and the grinding piece (9a) The structure is such that fine pulverization and stirring and mixing by the scraping piece (9b) are performed.

A passage (27) is formed through which a heating or cooling medium flows into the rotating shaft (8a), the support (8b), the grinding piece (9a), and the scraping piece (9b), and the rotary joint (24
) connects the channel (27) to the medium storage tank (26).

At the center of the cover (7) there is a conical part (
A path (6) for supplying the raw material from the feeder (19) downward toward the feeder (19) is formed by attaching a pipe (14) to convey an appropriate amount of heated or cooled air, inert gas, etc. as necessary. Air blower (18
) is connected to the path (6), and a jacket (25) is provided around the cover (7) to allow heating or cooling medium from the tank (26) to pass therethrough.

The collector (15) and the exhaust air i (16) are connected to the flow path (1) in that order.
0), and a rotary feeder (17) is provided at the outlet of the collector (15) to collect the fine powder raw material.

In short, the casing (4) is rotated at high speed to press the powdery raw material from the feeder (19) against the inner circumferential surface (4a) of the casing (4) by centrifugal force, and the raw material layer formed by the pressing is coated with the casing ( 4), the grinding piece (9a) and the scraping piece (9b) that rotate relative to each other act on the grinding piece (9a).
In addition to finely pulverizing the raw material in step a), the scraping piece (9b) mixes the raw material sufficiently finely and uniformly, and the fine particles are fused and bonded to the surface of larger particles to form a new material. Create composite particles.

The resulting fine powder particles are conveyed by airflow from the discharge port (11) and collected by the collector (15).

[Experiment example] Next, an experimental example will be shown.

As a raw material, silica alumina coarsely pulverized to a particle size of 1 mm or less is placed in the above-mentioned grinding mixer, and the temperature inside the machine is set to 100-1 mm.
It was operated at 50° C. for about 1 hour to obtain powder with an average particle size of about 5 μm. When this powder was examined, it was found that each particle had a roughly spherical shape with rounded corners, the particle size was uniform, and the gravity fluidity was also very good.

In addition, when a molded body was made using this powder, it was found that the filling during molding was very good, the composition was uniform, and the molded body was of good quality with sufficient strength. .

(Another example) Next, another example will be described.

Raw materials can be appropriately selected in terms of type, mixing ratio, particle size, etc. For example, it is possible to manufacture ceramics for superconductors, which are sufficiently fine and have a dense composition structure due to uniform dispersion, have high strength, and have a high current density due to high molding density. A high-quality superconductor with excellent superconducting properties such as strong effects can be obtained.

In that case, it is known that repeating the calcination and pulverization processes increases the purity of the superconductor's constituent substances and promotes crystallization, making it possible to produce products of significantly higher quality. By using the grinding and mixing device of the embodiment, the same effect as the conventional method can be achieved with a significantly reduced number of repetitions.

In addition, in the case of ceramics other than superconductors, it is possible to repeat the conventional calcination treatment and pulverization process several times in one time, and in some cases, it is also possible to omit the calcination process and perform only the pulverization process. This results in significant time savings and manufacturing cost reductions.

The specific configuration of the dry grinding and mixing device can be changed as appropriate, for example, the rotation axis of the casing (4) may be tilted or turned sideways, or the grinding pieces (9a) and scraping pieces (9b) may be placed in the casing (4). Apply pressure with fluid pressure or a spring within a range that does not contact the sides, stop the rotation of the grinding piece (9a) and scraping piece (9b), or fix the grinding piece (9a) and scraping piece (9b). It is also possible to have a configuration in which the In addition, the shape, material, number of installed pieces, etc. of the grinding pieces (9a) and scraping pieces (9b) can be changed appropriately, and fine powder can be reduced and supplied from the collector (15) to the casing (4) for patch processing. It is possible to configure it so that

How to set the temperature conditions in the heat treatment can be appropriately selected depending on the raw material, and the method, equipment, shape, etc. for supplying the manufactured ceramic raw material to the molding and firing equipment can be selected as appropriate.

Further, the use of the ceramic raw material and the molded body manufactured using the ceramic raw material is not limited.

Note that although reference numerals are written in the claims section for convenient comparison with the drawings, the present invention is not limited to the structure 7 shown in the attached drawings by the reference numerals.

[Brief explanation of the drawing]

1 to 3 show embodiments of the present invention, FIG. 1 is a flow sheet, FIG. 2 is a conceptual diagram of a grinding and mixing device, and FIG. 3 is a sectional view taken along line A-A in FIG. 2. FIG. 4 shows a conventional example. In the figure, (2)...rotation axis, (3)...
...Processing chamber, (4) ...Casing, (4a
)...Inner peripheral surface, (9a)...Friction piece,
(9b) It is a scraping piece. Applicant: Hosokawa Micron Co., Ltd. Figure 4

Claims (3)

[Claims] (1) A method for producing a ceramic raw material obtained by calcining and pulverizing a ceramic raw material, wherein in the pulverizing process, a casing (4) is rotated at high speed to transport the raw material into the casing (4). The grinding pieces (9a) and scraping pieces (9b), which rotate relative to the casing (4), are pressed against the peripheral surface (4a) by centrifugal force, and the grinding pieces (9a) and scraping pieces (9b), which rotate relative to the casing (4), are applied to the raw material layer formed by the pressing. The raw material is finely pulverized by the compression force and shearing force of 9a), and the scraping piece (9a) is
A method for producing ceramic raw materials in which fine powder raw materials are stirred and mixed by the action of b). (2) A ceramic raw material obtained by calcining and pulverizing a ceramic raw material, wherein in the pulverizing process, the casing (4) is rotated at high speed and the raw material is transferred to the inner peripheral surface of the casing (4). (4a) by centrifugal force,
The casing (4) is attached to the raw material layer formed by the pressing.
The grinding piece (9a) and the scraping piece (9b) rotate relative to each other.
), the raw material is finely pulverized by the compressive force and shearing force of the grinding piece (9a), and the finely powdered raw material is stirred and mixed by the action of the scraping piece (9b). (3) A ceramic molded body obtained by calcining a ceramic raw material and molding and firing a fine powder raw material obtained by pulverizing the raw material, in which the casing (4) is rotated at high speed during the pulverizing treatment. is pressed against the inner circumferential surface (4a) of the casing (4) by centrifugal force, and the raw material layer formed by the pressing is coated with grinding pieces (9a) and scraping pieces (9b) that rotate relative to the casing (4). A ceramic molded body produced by pulverizing the raw material with the compressive force and shearing force of the grinding piece (9a), and stirring and mixing the fine powder raw material with the action of the scraping piece (9b).