JP3266204B2 - Manufacturing method of ceramic sphere - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a fine ceramic sphere.

[0002]

2. Description of the Related Art In recent years, there has been an increasing tendency to pulverize raw material powders in various industrial fields. It is in. 2. Description of the Related Art Conventionally, a rolling granulation method is generally known as a method of forming a ceramic powder into a small-diameter sphere having a diameter of 20 mm or less. Further, as a rolling granulator, a rotary drum type granulator, a rotating dish type granulator, or the like is used to form a small-diameter sphere.

[0003]

In order to obtain a ceramic sintered body close to the theoretical density, it is necessary that the inside of the molded body before sintering is uniformly and sufficiently compacted.
However, the granulating mechanism of the above-mentioned rotary drum type granulator, rotary dish type granulator, etc. compacts and grows by the own weight of the granulated material. Therefore, it is difficult to consolidate, and an insufficiently compacted portion occurs inside the molded body. When such a molded body is sintered, a defect occurs inside the sintered body, and a problem such as insufficient strength of the ceramic sphere occurs. Further, in order to sufficiently consolidate, long rolling is required, resulting in poor productivity. Furthermore, since these granulators have a low rotation speed, there is a problem that the granulator must be increased in size in order to increase the peripheral speed and give a sufficient rolling power to the granulated material. SUMMARY OF THE INVENTION It is an object of the present invention to obtain a ceramic sphere without internal defects by compacting ceramic powder uniformly into a sufficiently compacted small-particle sphere in a relatively compact apparatus in a short time.

[0004]

As a result of various studies, the present inventor has found that a compact can be formed into a sphere and compacted in a short time by rotating the compact at high speed and utilizing the centrifugal force. Reached the present invention. That is, according to the present invention, a stirring granulator is used, the rotation speed of the stirring blade is set to a peripheral speed of 2.5 m / sec or more, and the ceramic powder is first charged and stirred.
While adding a binder, fine
Produce small particle size granules,
Powder and a binder to form the fine particle size granules.
Lengthened to obtain a sphere having a diameter of 2 mm or less, drying the sphere,
A method for producing ceramic spheres, characterized by firing. First, using a stirring granulator, set the rotation speed of the stirring blade to a peripheral speed of 2.5 m / sec or more, and first set the ceramic powder.
Add the binder while stirring and add the binder
Production of granules having a fine particle size of 0.1 mm or less, followed by stirring
Add ceramic powder and binder into the stirring granulator
The microparticles are grown to obtain a sphere having a diameter of 2 mm or less, and the rotational speed of the rotating disk is set to 8 m using a spherical sizing machine.
/ Sec or more, while rolling the sphere, supplying ceramic powder and a binder thereto to grow the sphere,
A method for producing a ceramic sphere, comprising obtaining a sphere having a diameter of 2 to 20 mm, drying and firing the sphere. Further
The production of the ceramic sphere according to claim 1 or 2
In the method, the obtained spheres having a diameter of 2 mm or less are classified.
What is smaller than the intended purpose
Of ceramic spheres characterized by being recycled
The gist is a manufacturing method .

Hereinafter, the present invention will be described in more detail. The rotation speed of the stirring blade of the stirring granulator must be not less than 2.5 m / sec at peripheral speed. If the peripheral speed does not reach 2.5 m / sec, the centrifugal force is small, the consolidation and the rolling speed become insufficient, the shape of the obtained molded sphere is poor, and the particle size distribution is very wide.

First, a small amount of ceramic powder is charged,
Add the binder little by little with high speed stirring. At this point, the ceramic powder becomes a fine particle having a diameter of 0.1 mm or less. Subsequently, the ceramic powder and the binder are added little by little into the agitation granulator to grow the fine-grained granules and form them into spheres having a target size of 2 mm or less in diameter. As the fine particle size granules, those having a smaller particle size than that of the object obtained by classification from the obtained molded spheres described below can be circulated.

The sphere having a small particle diameter obtained in this manner has a good sphericity and is sufficiently compacted by centrifugal force caused by high-speed rotation. For example, when zirconia powder is molded, the ratio of the maximum diameter to the minimum diameter of one sphere is 1.03 or less, and the sphericity is very good, and the density of the small-diameter sphere after drying is 3. A very well consolidated product of 10 g / cm ³ or more is obtained. Incidentally, the density of a compact of zirconia powder obtained by a mechanical press molding method with a press pressure of 1 T / cm ² is about 2.8 g / cm ³ . By sintering a sufficiently compacted compact, a ceramic sphere having no mechanical defects and excellent mechanical properties can be obtained. In order to obtain small-diameter spheres having the same density with an ordinary rotary dish-type granulator, long-term rolling is required because the spheres are compacted only by their own weight.

[0008] The small particle size sphere obtained by the stirring granulator has a wide particle size distribution, and is classified by a sieve or the like to obtain a small particle size sphere of an intended size. The spheres smaller than the target spheres obtained by classification are used as nuclei in the next agitation granulation, so that the granulation operation can be performed more easily than starting from the powder.

As the high-speed stirring granulator, a Henschel mixer manufactured by Mitsui Miike Co. is known. The agitation granulation method is characterized in that a high-speed rotation of the agitation blade imparts shearing, rolling and consolidation effects to obtain heavy, small-diameter spheres in a short time. Since the small spheres are broken by shearing in the granulator, the diameter is 2 mm.
It is not preferable for molding a sphere having a diameter exceeding 100 mm.

The thus obtained spheres having a small particle diameter of 2 mm or less as a nucleus and grown by a spherical sizing machine, the spheres having a good sphericity and having a uniformly compacted diameter 2 are obtained. A small particle size sphere of 〜20 mm is obtained. In order to obtain a compact having better sphericity and better compaction by this spherical sizing machine, the diameter of the sphere having a small particle diameter as the nucleus is preferably 0.5 to 2 mm. Examples of the spherical sizing machine include, for example, a marmulizer manufactured by Fuji Paudal Co., Ltd. which is used for the purpose of spheroidizing the extruded and granulated columnar pellets.

The rotating disk of the spherical sizing machine is rotated at a rotational speed at which the peripheral speed is 8 m / sec or more. If the peripheral speed does not reach 8 m / sec, it takes a long time to grow and consolidate the nuclei. Next, the diameter of 2 mm obtained by the stirring granulator was used.
The following classified small-diameter spheres are charged into the core of a spherical sizing machine, and a ceramic powder and a binder are added little by little into the core to grow the nucleus. Obtain a diameter sphere.

Usually, it takes one to two days for a nucleus having a diameter of 1 mm or less to grow into a sphere having a diameter of about 5 mm using a rotary dish granulator.
The time required to grow the following nuclei to a diameter of about 5 mm is about 2 hours, and is characterized by being able to be formed in a very short time. As with the agitation granulation, the spherical sizing machine gives rolling and consolidation effects by the high-speed rotation of the rotating disk, so that a heavy, small-diameter sphere can be obtained in a short time. In addition, since the nucleus of the spherical sizing machine is classified to a certain size, the particle size distribution of the grown small-sized spheres is narrow, and small-sized spheres of the desired size can be obtained in high yield. It is also a feature.

As the binder for granulation, although it depends on the raw ceramic powder to be used, water or an aqueous solution of carboxymethylcellulose, polyvinyl alcohol, polyethylene glycol or the like is usually preferably used. , Usually around 10 wt%. INDUSTRIAL APPLICABILITY The present invention is suitable for manufacturing ceramic spheres such as zirconia, alumina, and mullite, and is particularly suitable for manufacturing zirconia spheres having a large true specific gravity.

Next, small-diameter spheres having a diameter of 20 mm or less obtained by stirring granulation or a spherical sizing machine are heated to 100 to 200 ° C.
After sintering under conditions such as temperature and time suitable for each ceramic, dense ceramic spheres without defects can be obtained. For example, in the case of a molded body using zirconia powder, if sintered at 1500 ° C. for 2 hours, a dense ceramic sphere having a density of 6.0 g / cm ³ or more can be obtained.

[0015]

According to the present invention, it is possible to form a compact sphere having good sphericity and uniformly compacted in a short time by a compact granulator, Suitable for mass production of spheres.

[0016]

EXAMPLES Example 1 A laboratory-scale stirring granulation apparatus (stirring motor,
Agitating blades 80 mm wide, 14 mm high four blades,
Polyethylene container Upper inner diameter 93mm, Lower inner diameter 85
(with a height of 100 mm) and 50 g of zirconia powder TZ-3YS manufactured by Tosoh Corporation into a container, and water is added little by little as a binder while rotating the stirring blade at 600 rpm (peripheral speed: 2.51 m / sec). The whole powder was made into small granules. Subsequently, a small amount of zirconia powder and water were alternately added into the small granules rotating at a high speed to grow the granules to obtain 415 g of spheres having a diameter of 2 mm or less. The time required for this operation was 30 minutes. The obtained spheres were classified with a sieve and had a diameter of 0.84 to 1.19.
mm spheres were obtained. The measurement results of the particle size distribution at this time are shown in Table 1.
It is shown in FIG.

Next, the spheres having a diameter of 0.84 mm or less after classification were returned to the stirring granulator of FIG. 1 again, and spheres were grown by the same operation as described above. This operation was repeated to obtain 600 g of a sphere having a diameter of 0.84 to 1.19 mm. Next, the obtained sphere having a diameter of 0.84 to 1.19 mm was placed in 12
Dried at 0 ° C. The water content of the molded body was 13% by weight. Next, the dried spheres were sintered at 1500 ° C. for 2 hours to obtain zirconia spheres. Table 2 shows the physical properties of the obtained dried spheres and sintered spheres. As a control, molding was performed by the same operation except that the rotation speed of the stirring blade was set to 300 rpm (peripheral speed: 1.26 m / sec). However, the shape of the molded body was poor and the particle size distribution was very wide. there were.

Example 2 Next, a melmerizer QJ-40 manufactured by Fuji Paudal Co., Ltd.
Using a type 0, a rotating disk with a diameter of 400 mm
m (peripheral speed: 8.38 m / sec), into which the undried sphere 50 having a diameter of 0.84 to 1.19 mm obtained in Example 1 was placed.
Then, an operation of growing nuclei by adding 0 g of the zirconia powder and water alternately little by little was performed. A part of the sphere was taken out during the growing operation and the volume of the whole sphere inside the marmellaizer was adjusted. Finally, 2000 g of a sphere having a diameter of about 10 mm was obtained. The time required for this operation was 3 hours.

Next, the obtained sphere having a diameter of about 10 mm was dried at 120 ° C. The water content of the molded body was 11%. Next, the dried sphere was sintered at 1500 ° C. for 2 hours to obtain a zirconia sphere. Table 2 shows the physical properties of the obtained dried spheres and sintered spheres. As is evident from Table 2, both Examples 1 and 2 are a sufficiently compacted compact with good sphericity and a sufficiently compacted sintered compact. Further, as a result of internal observation of the cut sintered sphere, no defective portion was observed. As a control, molding was performed by the same operation except that the rotating disk was rotated at 300 rpm. However, the compacting and growth took time, and the diameter of the sphere was about 5 mm even after 3 hours from the start of molding. Was.

[0020]Table 2 Physical properties of sphereExample 1 Example 2  * Sphericality 1.03 1.02 Dry sphere density (g / cm³3.30 3.41 Sintered sphere density (g / cm³6.07 6.09 * Sphericality = Maximum diameter / Minimum diameter of the same sphere

[Brief description of the drawings]

FIG. 1 is a perspective view of a stirring granulation apparatus used in Example 1.

[Description of symbols]: Stirring motor: Stirring blade: Polyethylene container

Claims (3)

(57) [Claims] A ceramic powder is first prepared by using a stirring granulator and setting a rotation speed of a stirring blade to a peripheral speed of 2.5 m / sec or more.
And add a binder while stirring, and
Production of granules having a fine particle size of 0.1 mm or less, followed by stirring
Add ceramic powder and binder into the stirring granulator
A method for producing a ceramic sphere, comprising: growing the fine particle size granule to obtain a sphere having a diameter of 2 mm or less, drying and firing the sphere. 2. Using a stirring granulator, the rotating speed of the stirring blade is set to a peripheral speed of 2.5 m / sec or more, and the ceramic powder is first used.
And add a binder while stirring, and
Production of granules having a fine particle size of 0.1 mm or less, followed by stirring
Add ceramic powder and binder into the stirring granulator
The microparticles are grown to obtain a sphere having a diameter of 2 mm or less, and the rotational speed of the rotating disk is set to 8 m using a spherical sizing machine.
/ Sec or more, while rolling the sphere, supplying ceramic powder and a binder thereto to grow the sphere,
A method for producing a ceramic sphere, comprising obtaining a sphere having a diameter of 2 to 20 mm, drying and firing the sphere. 3. The ceramic sphere of claim 1 or claim 2.
In the method of the above, the obtained sphere having a diameter of 2 mm or less
Fine particle size smaller than the intended one
Ceramics characterized by being recycled as granules
A method for manufacturing a sphere.