JP2720123B2 - Method for producing piezoelectric ceramic microspheres for piezoelectric elastomer - 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 producing sintered piezoelectric ceramic microspheres filled in an elastomer as a piezoelectric elastomer having a function of sensing pressure.
In particular, the present invention relates to a method for producing piezoelectric ceramic microspheres such as lead zirconate titanate suitable for a piezoelectric elastomer that can be controlled to a constant particle size.

[0002]

2. Description of the Related Art Piezoelectric elastomers and piezoelectric ceramics generate a voltage in response to an applied stress, or generate a distortion when a voltage is applied. Used in A piezoelectric elastomer is made by uniformly dispersing piezoelectric ceramic powder in silicon rubber, natural rubber, chloroprene rubber, rubber, or the like.

[0003] Conventional piezoelectric ceramic powders are manufactured as follows. That is, as shown in FIG.
After calcination at 0 ° C, sintering is performed at a high temperature of 1100 to 1300 ° C.
For the calcination and sintering, an electric furnace is generally used because automatic temperature control is easily performed. After sintering, the mixture is pulverized by a mechanical method (for example, a hammer mill) to be mixed with the elastomer. Furthermore, since the particle size varies only by pulverization, the sintered ceramic powder pulverized to obtain a constant particle size is adjusted to a constant particle size by using a ball mill, a roll mill, a jet mill or the like by a dry method or a wet method. Prepare and classify this.

[0004]

In order to produce a high quality piezoelectric elastomer, the piezoelectric ceramic powder must be uniformly dispersed.
In addition, it is necessary to perform high filling, and it is expected that uniform high filling improves the polarization efficiency and improves the obtained piezoelectric characteristics. However, mechanically pulverized piezoelectric ceramic powder has the following problems as in the above manufacturing method. That is, sintered piezoelectric ceramics are hard to pulverize because they are inherently hard, and are merely mechanically pulverized, so the particle morphology is irregular and the particle size distribution is extremely wide. . Therefore, not only could it not be uniformly dispersed in the elastomer, but also high filling was difficult. In addition, due to poor dispersibility and difficulty in high filling, there was a large variation in the obtained piezoelectric characteristics.

Further, it is possible to obtain particles having a constant particle size from the pulverized piezoelectric ceramic powder by a classification operation, but the loss of material due to the classification is extremely large due to the wide particle size distribution. Since the piezoelectric ceramic powder has already been sintered, it cannot be reused, and the cost of the product is increased due to the loss due to classification. Thus, it is difficult to uniformly disperse and highly fill the conventional piezoelectric ceramic powder simply mechanically pulverized,
High quality piezoelectric elastomers could not be produced.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for manufacturing piezoelectric ceramic microspheres having a good dispersibility and a uniform size which enables high filling.

[0007]

The present invention has the following configuration to achieve the above object. That is, first, a piezoelectric ceramic such as lead zirconate titanate is calcined, and
Add the binder to the baked powder, mix, and then
Preform the product, extruding the preform from the mesh
After passing through, the sphere diameter was reduced to 20 to 50 by shaking.
Into microspheres of 0 μm, and further dry the microspheres.
Or sintering after dehydration.

The above manufacturing method will be further described in detail based on the manufacturing steps shown in FIG. The calcined powder of the piezoelectric ceramic can be obtained by calcining the raw material powder of the piezoelectric ceramic at 700 to 900 ° C. Next, the raw material powder of the piezoelectric ceramic and the binder are mixed well. As the binder, known starch, PVA, dextrin , wax emulsion, or the like can be used alone or in combination of two or more, as long as it does not contain inorganic substances that disperse and scatter at as low a temperature as possible during sintering and remain. Good. Mixing can be performed by a known means such as a ball mill.

After the calcined powder of the piezoelectric ceramics is mixed with the binder, a process for forming microspheres is started. The molding of the microspheres can be performed, for example, as follows. First,
The mixture of the calcined powder having the plasticity mixed with the binder is preformed into a plate shape, a rod shape or the like by a press, and the preformed product is passed through a mesh of a predetermined mesh. The size of the mesh is selected according to the size of the microsphere to be molded,
For example, a mesh of 20 to 500 μm can be used. The material of the net is not particularly limited, and may be a wire net or a resin net. Although it is extruded into a rod shape when it is looked through, it is cut into several millimeters and forms a short, elliptical prismatic body when viewed from the side. If these prismatic bodies are shaken with a shaking device, microspheres having the same diameter as the size of the mesh that has been seen can be obtained.

As the shaking device, for example, one having a structure as shown in FIGS. 2 and 3 can be used. The shaking device 1 as shown in FIG. 2 is one in which a drive shaft 7 of a shaker 5 is attached to the bottom of a box 3 having an open top, so that the box 3 is shaken vertically or horizontally by the shaker 5. Is configured. The mixture of the piezoelectric ceramic calcined powder and the binder is passed through the box 3 of the shaking device 1 and obtained.
When the prisms placed in the box 3 are shaken, the prisms
Collides with the surface and at the same time the prisms collide with each other
Therefore, the end of the prismatic body is torn off, and has a dimension substantially the same as the diameter in the length direction, and the corner is gradually removed to form a spherical shape. Since the broken end portion is also formed into a spherical shape at the same time, a large number of microspheres smaller than that are formed together with spherical particles having the same diameter as the mesh.

FIG. 3 comprises a shaking device 10, a hopper 12, and a storage box 14. The shaking device 10 has a drive shaft 17 of a shaker 15 attached to the lower surface of a slanted saw 13.
As in the case of the shaker 1, the grinder 13 is configured to be shaken vertically or horizontally by a shaker 15. The prism-shaped body supplied from the hopper 12 to the grates 13 is attached to the inner surface of the grates 13 while falling through the grates 13.
Whether they collide with each other and at the same time
Thus, microspheres are formed in the same manner as in the case of the shaking device 1. The formed microspheres are stored in the storage box 14. In the second method, the broken end is also formed into a spherical shape at the same time, so that a large number of microspheres smaller than the microsphere having the same diameter as the mesh are formed. The microspheres formed as described above are gradually formed into spheres, and are hardened by collision, so that harder microspheres are obtained.

Next, the microspheres are classified into a predetermined size. Classification can be performed by sieving the formed microspheres. By classifying, microspheres having a constant sphere diameter can be obtained. The classified microspheres are dried by oven etc.
Or it is dehydrated and then sintered. The sintering method is not particularly limited, and can be performed by a known method.
Sintering can be performed for up to 3 hours. At the time of sintering, it is preferable to perform sintering at a constant heating rate so that the fine particles of the piezoelectric ceramic grow sufficiently for a certain period of time. When sintering is completed, microspheres of sintered piezoelectric ceramics having a uniform shape and size are obtained.

In the present invention, the classification can be omitted as appropriate, and the classification can be performed before and after drying and dehydration after molding and before sintering. Further, in the present invention, since sintering is performed after forming into microspheres, the microspheres before sintering can be pulverized before sintering or reused without pulverization. Therefore, in the past, it was impossible to reuse because it was already pulverized and classified after sintering. However, in the present invention, classification is performed before sintering. can do. The microsphere in the present invention does not mean only a perfect spherical body, but means a spherical particle formed into a substantially spherical body including an ellipse if all surfaces are formed on a round surface.

[0014]

[Function] Since the microspheres are formed into fine microspheres before sintering, microspheres having a size other than a certain size can be reused, and work to reduce material loss. In addition, since all the surfaces of the microspheres are formed on the radius surface, the dispersion in the elastomer is improved.

[0015]

EXAMPLE A specific example of the present invention will be described. A binder of an 8% PVA aqueous solution was added to calcined lead titanate zirconate powder and mixed well. The mixture of the powder and the binder was pressed by a press molding machine to a diameter of 60 m.
m, and preliminarily formed into a disk having a thickness of 4 mm, and the formed body was pressed through a 250-μm mesh stainless steel wire mesh and passed through. Furthermore, the prismatic body obtained through the above was sufficiently shaken using a shaking device. The shaking apparatus used was a box type shown in FIG. 2 and had a vertical height of 1.5 mm and a frequency of 300 per minute.
By shaking 0 times and shaking for 0.5 hour, the sphere diameter becomes about 25.
0 μm lead zirconate titanate microspheres were obtained. These microspheres were dehydrated in an oven at 100 ° C. × 1 hour, and then classified through a sieve having a mesh of 175 μm, and the classified microspheres were heated in an electric sintering furnace at a rate of 150 ° C./hour. Sintered at ℃ for 2 hours. In this way,
Sintered lead zirconate titanate microspheres having a diameter of 150 to 200 μm were obtained.

FIG. 5 is a photomicrograph of sintered lead zirconate titanate microspheres according to an example, and FIG. 6 is a photomicrograph of sintered lead zirconate titanate powder according to a conventional production method as a comparative example. Comparing the example with the comparative example, it is clear that the example is formed substantially in a spherical body, but the comparative example has sharp corners and is mechanically pulverized.

[0017]

According to the manufacturing method of the present invention, the following effects can be obtained. That is, sintered piezoelectric ceramic microspheres having a uniform size can be obtained, the dispersibility in the elastomer is improved, and high filling is possible. Therefore, the obtained piezoelectric characteristics were constant, and the polarization efficiency was improved. Furthermore, since classification is performed before sintering, microspheres having a sphere diameter outside a certain range can be reused and material loss can be reduced.

[Brief description of the drawings]

FIG. 1 is a process chart showing a manufacturing method of the present invention.

FIG. 2 is an explanatory front view of a shaking device showing an example of molding.

FIG. 3 is an explanatory front view of a shaking device showing another example of molding.

FIG. 4 is a process chart showing a conventional method for producing a piezoelectric ceramic powder.

FIG. 5 is a photomicrograph of sintered lead zirconate titanate microspheres produced according to the present invention.

FIG. 6 is a photomicrograph of a sintered lead zirconate titanate powder manufactured by a conventional manufacturing method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shaking device 3 Box 5 Shaker 10 Shaking device 13 Sawing 15 Shaker 12 Hopper 14 Storage box

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Tomoharu Iwata 1 Nobesawa, Kaisei-cho, Ashigara-gun, Kanagawa Prefecture Inside the Meiji Rubber Chemical Kanagawa Plant (56) References JP-A-2-48031 (JP, A) JP-A-60-175534 (JP, A) JP-A-64-61352 (JP, A) JP-A-3-88758 (JP, A) JP-B 55-22262 (JP, B2) JP-B 56-12028 (JP, A) , B2) Tokiko Sho 60-30248 (JP, B2)

Claims (1)

(57) [Claims] 1. A piezoelectric ceramic such as lead zirconate titanate is calcined, and a binder is added to the calcined powder and mixed.
Then, the mixture is preformed, and the preformed
After pushing out through the mesh and passing through,
And formed into microspheres with a sphere diameter of 20-500 μm.
Sintering after drying or dehydrating the microspheres
A method for producing piezoelectric ceramic microspheres for a piezoelectric elastomer, comprising: