JP4116691B2 - Ceramic molding method - Google Patents

Description

[0001]
[Industrial application fields]
The present invention belongs to a complex-shaped ceramic molding technique and can be used for small-scale production that does not require a large-scale initial investment. It can also be used for mass production.
[0002]
[Prior art]
Ceramics are currently applied in various industrial fields. There are various application forms, and there are molding methods according to it. There is a pressure molding method as the simplest method. A manufacturing apparatus used for the pressure molding method is generally automated, and a molded body having controlled characteristics can be obtained. Many electronic ceramics and structural ceramics are manufactured by pressure molding. For parts that require mass production, high-speed molding of about 5000 pieces / min is possible. However, this molding method is extremely difficult to produce a complicated shape, and an apparatus for high-speed molding requires enormous capital investment. The casting method does not require a special mechanical device, and a molded body can be easily obtained if there is a mold. For this reason, it is used for experimental products and small-scale production. Although this method can produce a complicated shape, there are limitations on the particle size and type of the ceramic powder to be used, and the application range is limited. Casting includes pressure casting, freeze casting, centrifugal casting, ultrasonic casting and the like.
Freeze-casting is a method conceived for casting raw materials containing coarse particles, which is difficult with ordinary casting. In this method, after molding using a rubber mold, it is frozen and freeze-dried to obtain a molded body. In this method, since the rubber mold as a mold is frozen, the molded product expands and expands when frozen. Moreover, when producing in large quantities, a lot of molds are required.
Injection molding is a widely used method for plastic molding, but it has also been active in the ceramics field in recent years. It is suitable for the manufacture of products that require complex and high precision, and can be mass-produced. This method requires about 15 to 50% of resin relative to the non-plastic raw material, and there are ceramics that cannot be used depending on the case. Also, injection molding machines are expensive and require a large initial investment. The forming method of the multilayer structure ceramics can be performed by a pressure forming method. In this method, two or more powders are put into a mold and pressure is applied. According to this method, it is possible to form a composite ceramic having two or more layers. However, since each layer can be clearly confirmed at the interface between the layers, it smoothly changes to the next layer. Not suitable for products that are required to follow.
[0003]
[Problems to be solved by the invention]
With the conventional technology, it is difficult to obtain a ceramic molded body having a complicated shape with a small initial investment. The only possible method is the casting method. However, mass production and multi-layer structure are difficult with this method.
[0004]
[Means for Solving the Problems]
In view of the above, the present invention provides a molding method capable of obtaining a ceramic molded body having a complicated shape with a small initial investment. Moreover, it is easy to automate the apparatus, and it is possible to deal with mass production and multi-layer structure.
[0005]
According to the present invention, first, water or a binder and an aqueous solution suitable for it are kneaded with ceramics as a raw material to form a slurry.
[0006]
The ceramic used as a raw material is not particularly defined, and may be various metal oxides such as general alumina, stabilized zirconia or partially stabilized zirconia, compounds thereof, and mixtures thereof. Preferred examples include alumina, stabilized zirconia, partially stabilized zirconia, calcium phosphate, feldspar and the like.
[0007]
Examples of the binder include polyvinyl alcohol, polyethylene oxide, starch, methyl cellulose, sodium alginate, hydroxyethyl cellulose and the like.
[0008]
When injecting the above-mentioned slurry into a cooled mold, it is sufficient to separately inject different ceramics. However, the use of the injection means shown in FIG. An injection mode for obtaining a composite layer that is appropriately bonded will be described. Note that FIG. 1 is merely an example, and the shape, structure, material, and the like are not particularly limited as long as they have a suction and extrusion structure.
First, the obtained slurry is filled into an injector.
Although the filling method is not particularly defined, when a multilayer structure molded body is manufactured, after the first type of slurry is sucked from the discharge port, the second and subsequent types of slurry are continuously sucked in the injector. It is possible to inject in a properly mixed state. It inject | pours into a casting_mold | template using the injection machine with which these 1 type and 2 or more types of slurry is filled.
The injector has a sliding body 2 that alternately slides in the longitudinal direction inside the cylindrical shape, and an input / output port 3 that is in close contact with one end of the sliding body 2 and performs external input / output at the other end. It has a syringe-like structure and operation as formed in the reservoir 1.
That is, when the sliding body 2 slides in one direction, the input / output port 3 generates a suction force to increase the volume of the internal reservoir 1 and suck and store a liquid such as an external ceramic slurry. In order to squeeze the storage part 1 having an enlarged volume when sliding in the opposite direction, the operation of discharging the liquid in the storage part 1 from the input / output port 3 to the outside is performed. Is performed automatically or manually. In the case of using a single ceramic slurry from the size that can form a single molded body, the size of the injector is large enough to store an amount that allows multiple molded bodies to be formed. Preferably, it is appropriately adjusted depending on the size of the molded body.
[0009]
The mold is made of a metal that is resistant to corrosion, preferably various stainless alloys, titanium, titanium alloys, etc., and the mold itself is preliminarily cryogenic with a liquid refrigerant such as liquid nitrogen or an electrical cooling device such as a refrigerator or other cooling means. It is preferably cooled at -20 ° C or lower. A wide inlet for slurry injection is opened above the mold.
[0010]
When the slurry is quickly poured into the mold cooled to this cryogenic temperature, it is possible to obtain a frozen material in accordance with the mold within one minute.
Therefore, it is not always necessary to further cool the mold after the injection, and the cooling state of the mold may be canceled as it is, but the cooling by the refrigerant or the refrigeration apparatus may be continued.
When two or more types of slurry are mixed in the injector, the slurry that has been sucked into the injector at the end is sequentially injected into the mold. As a result, since it is cooled to a very low temperature, freezing is started simultaneously with the injection, and it is possible to obtain a multilayer structure frozen body in accordance with the injection order.
In this way, the quick freezing operation of the ceramics performed by cooling the mold in advance can reduce the molding time, and the molded body can be easily removed from the mold, thereby shortening the time for the next drying process. Become.
At the same time, since the slurry is properly mixed in the injector, the layers of the frozen bodies are smoothly connected.
[0011]
Next, the obtained molded body is sublimated at a temperature adjusted to room temperature or higher, preferably under a reduced pressure of 20 Pa or less, preferably for 24 to 48 hours, to obtain a desired molded body. Note that such pressure, temperature, and time ranges are appropriately adjusted depending on the objective molded body, binder, and ceramics, and are not limited to the values described above.
For this step, a general freeze-drying step can be used.
[0012]
As described above, in the present invention, it is possible to produce a molded body by mixing a plurality of ceramic raw materials in an injector. When a plurality of ceramic raw materials (slurry) are placed in this injector, the raw material is injected into the injector and then poured into the mold without vibration to form a layer toward the center in the reverse order of the injection. Is possible.
It is also possible to form a random layer by injecting the raw material into the injector and then pouring the injector into a mold after appropriate motion such as vibration and rotation.
Furthermore, taking advantage of the raw material ceramics in a slurry state, it is possible to uniformly mix the strength reinforcing material and the porous material. By mixing the strength reinforcing material, the strength of the ceramic molded body can be expected to be increased by firing the ceramic molded body. As the strength reinforcing material, carbon fiber, glass fiber, ceramic fiber or the like is preferably used. “Porosification” means that the fired ceramic product has appropriate porosity due to burning of the porous material when the ceramic molded body is fired. As the porous material, styrene, latex, and various polymer materials are preferably used. The same effect can be expected even if various foaming agents are mixed in place of the porous material.
The molded body is fired as desired. The firing is appropriately performed depending on the purpose of the molded body. However, when molding a biomaterial, it is preferably a firing range of 850 to 1500 ° C. in the air atmosphere, for example, 1 to 30 minutes for feldspar, and calcium phosphate. However, it is not limited to these values, furnace atmosphere, and furnace pressure, and the values, furnace atmosphere, and furnace pressure are the raw materials. It is appropriately set depending on the kind of the molded body, the size of the molded body, the intended use of the fired body, and the like.
[0013]
【Example】
Example 1
A feldspar as a ceramic raw material and an aqueous starch solution as a binder were appropriately kneaded to prepare a slurry. Then, 30 cc of raw material slurry was quickly poured into a stainless alloy mold that had been cooled by a refrigeration system at about -80 ° C. in advance to obtain a frozen body conforming to the mold. The frozen body was dehydrated for 24 hours under a reduced pressure of about 10 Pa and dried to obtain a molded body shown in FIG.
[0014]
Example 2
When the same operation was carried out using calcium phosphate as the ceramic raw material of Example 1 and polyvinyl alcohol as the binder, a good molded article could be obtained.
[0015]
Example 3
As a ceramic raw material A, feldspar added with metal so that it becomes milky white when vacuum fired, as a ceramic raw material B, feldspar added with metal so that it becomes skin color when vacuum fired, and an aqueous starch solution as a binder are appropriately kneaded, and two types of slurry Was made. After the raw material B was sucked into the injector, the raw material A was continuously sucked and two kinds of slurry were filled in the injector. Then, the raw slurry was rapidly injected without vibration into a titanium alloy mold that had been cooled with liquid nitrogen in advance, thereby obtaining 10 10 g frozen bodies according to the mold. This frozen body is separated into two layers as shown in FIG. 3, and the raw material B appears in layers to cover the raw material B inside. This frozen body was then dehydrated and dried under a reduced pressure of 10 Pa for 24 hours to obtain a multilayer structure molded body.
[0016]
【The invention's effect】
As described above, the present invention can basically obtain a ceramic molded body having a complicated shape without using a special mechanical device. Moreover, it is easy to make these molded bodies into a multi-layer structure, and application in various fields can be examined. And it can respond to mass production by automating apparatuses, such as an injection machine, a mold cooling device, and a freeze dryer.
[Brief description of the drawings]
FIG. 1 shows an example of an injector.
FIG. 2 is a view showing an example of a molded body produced according to the present invention.
FIG. 3 is a view showing another example of a molded body produced in the present invention.
[Explanation of symbols]
1 Storage part 2 Sliding part 3 Input / output port

Claims (3)

After filling the plurality of slurry reservoir body Nde write successively taken up in the reservoir body a plurality of raw ceramic slurry reservoir having input and output ports for performing suction and discharge of the raw material ceramic, a previously cryogenic cooling The ceramic slurry is discharged from the input / output port of the storage body into the mold, and the frozen material is produced by instant freezing in the mold, and the layered compact is produced by sublimating moisture under reduced pressure. A method for producing a ceramic molded body.   The method for producing a ceramic molded body according to claim 1, wherein the raw ceramic material according to claim 1 is a metal oxide and a compound thereof, or a mixture of two or more of these. The storage body includes a cylindrical storage portion connected to the input / output port, and a sliding body that slides within the storage portion, and the sliding body moves within the storage portion, so that the raw material ceramics from the input / output port. The manufacturing method of the ceramic molded body of Claim 1 which takes in or outputs a slurry .

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