JPH11291215A - Method for molding ceramic powder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate such troubles as the generation cracks and deformation in a molding of high water content which was dried naturally. SOLUTION: In a method for molding ceramic powder in which slurry prepared by adding a solvent, a dispersant, and a binder into the ceramic powder and mixing the mixture is cast into a molding mold and molded, and the molding is demolded and dried, in the drying method, the demolded molding is placed in a box having vent holes in the upper and lower surfaces, and the box is allowed to stand in a room for drying.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming ceramic powder, and more particularly to a method for forming ceramic powder with emphasis on drying.

[0002]

2. Description of the Related Art A molded article formed by gel casting (self-curing) or the like contains a large amount of moisture and, when shrunk upon drying, has a large degree of shrinkage.
In order to prevent this, it is necessary to suppress the drying speed. Usually, drying is performed while maintaining the atmosphere at a high humidity in a chamber where the temperature and humidity can be controlled.

[0003] However, since this drying requires a constant temperature and humidity chamber, there is a problem that the cost is high and even if the tank is installed, the productivity is limited due to the capacity in the tank. Was. Therefore, drying is also performed by leaving the demolded compact in a room and allowing it to dry naturally.

[0004]

However, in the natural drying, since the humidity is not controlled even at a low temperature, it is rapidly dried in a normal room, and the moisture in the molded product is high. There is a problem that cracks and deformations occur in the dried molded body when the size of the molded body is large.

[0005] The present invention has been made in view of the problems of the above-described method for forming a ceramic powder, and has as its object to provide a ceramic powder which does not crack or deform in a dried molded product even if it is naturally dried. To provide a molding method.

[0006]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, put the molded product removed from the mold into a box having ventilation holes on the upper and lower surfaces, and put the box in a room. The present invention was found to be free from cracks and deformation in the dried molded article if left to dry naturally and dried, thereby completing the present invention.

That is, according to the present invention, (1) a solvent, a dispersant, and a binder are added to a ceramic powder, and a slurry prepared by mixing is poured into a molding die, molded, and then the molded product is demolded. In the method for forming a ceramic powder to be dried, the drying method is a method in which the demolded molded body is placed in a box having ventilation holes on upper and lower surfaces, and the box is dried by leaving it in a room. And (2) the binder is a thermosetting resin, the molding die is a water-absorbing die, and the molded body is at least 30 vol%. 2. A method for molding ceramic powder according to claim 1, wherein the molding is a molded body containing moisture. (3) The ventilation hole on the upper surface of the box is a ventilation hole whose hole area can be adjusted. Yes,
And the drying speed of the molded body is 0.2 to 1.0 wt.
The gist of the invention is to provide a method for molding ceramic powder according to claim 1 or 2, wherein the area is adjusted to be% / day. This will be described in more detail below.

As described above, the method for molding the ceramic powder is as follows. The method for drying the molded body is to put the molded body in a box having vent holes on the upper and lower surfaces and leave the box indoors. (Claim 1). The molded body is dried in a box having ventilation holes on the upper and lower surfaces as shown in FIGS. 1 and 2, and the box is naturally dried, so that cracks and deformation due to drying do not occur.

[0009] The reason is that the humidity of the air in the box is increased by water vapor evaporating from the compact placed in the box, and the drying speed of the compact is suppressed. Then, the humidity of the air inside the box is increased by the water vapor evaporated from the molded body, but since the water vapor is lighter than the air, the humid air rises and scatters from the ventilation holes on the upper surface of the box, and instead, the low humidity outside the box has a lower humidity. When the air enters through the ventilation holes on the lower surface of the box, the air is exchanged and dried, and the drying proceeds.

[0010] As the molded article to be dried, a thermosetting resin is used as a binder to be used, and a molded article containing 30 vol% or more of water is molded as a mold that does not absorb water (claim 2). The drying described above can be performed on any formed body made of ceramic powder,
Although the same effect is obtained, the molded article formed by the self-curing is particularly effective because it has a high water content, and is more effective when the water content is 30 vol% or more.

The ventilation hole on the upper surface of the box into which the molded article is to be placed is a ventilation hole whose hole area can be adjusted, and the area is adjusted to an area where the drying speed of the molded article is 0.2 to 1.0 wt% / day. It was adjusted (claim 3). The effect on the drying speed is much larger at the top of the box than at the bottom of the box, so adjust the area of the holes at the top of the box to adjust the amount of air that comes out of the humid air. By
The drying speed can be controlled, and it is possible to cope with changes in the moisture and size of the molded body, or changes in room temperature and humidity. The adjustment can be made by preparing several vinyl tapes having different hole diameters and attaching or peeling the tapes to or from the holes. The hole area to be adjusted is preferably an area where the drying rate of the molded body is 0.2 to 1.0 wt% / day, and if the drying rate is slower than 0.2 wt%, it takes too much time for drying. If the area is faster than 1.0 wt%, cracks and deformation may occur in the molded body.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The molding method of the present invention will be described in more detail. First, as a ceramic powder, not only oxides such as alumina and zirconia but also non-oxides such as silicon nitride, sialon and silicon carbide may be used. Prepare these powders. An appropriate sintering aid may be appropriately added to these powders.

[0013] A solvent and a dispersant are added to the prepared powder, and a thermosetting resin such as an acrylic resin is added as a binder and mixed to prepare a slurry. The solvent is not particularly limited as long as it dissolves the thermosetting resin,
Water that does not require environmental safety and health considerations and does not require equipment such as an organic solvent recovery device is desirable.
After vacuum defoaming the slurry, the slurry is poured into a mold from which a molded body that does not absorb the solvent is obtained. The slurry is self-cured by heating the mold together with the mold to a temperature at which the resin is cured, and the cured body is released. The drying rate of the obtained molded body is 0.
It is placed in a box having ventilation holes adjusted to a hole area of 2 to 1.0 wt% / day, and the box is left indoors and dried. The position of the hole may be anywhere on the upper and lower surfaces.
The box may be made of any material having no air permeability, such as polyvinyl chloride, polyethylene, polypropylene, aluminum, and wood. The obtained molded body is degreased by a conventional method, and sintered in a predetermined atmosphere, firing temperature and firing time.

If the ceramic powder is formed by the above-described method, the powder can be formed without any problem even when it is naturally dried.

[0015]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples of the present invention and Comparative Examples.

(Examples 1 to 4) (1) Molding of Ceramic Powder Alumina powder having a purity of 99.99% and an average particle diameter of 0.2 μm was mixed with 10 vol of acrylic acid ester as a binder.
%, 2 vol% of polycarboxylic acid as a dispersant and 3
After adding 8 vol% and mixing with a pot mill for 24 hours,
A slurry was prepared by vacuum degassing. After the obtained slurry was poured into an acrylic resin mold from which a molded article having the size shown in Table 1 was obtained, the mold was heated together with the mold at 70 ° C. for 3 hours to allow the slurry to self-cure. After the obtained molded body was released from the mold, it was provided with one vent hole having the hole diameter shown in Table 1 at the center of the lower surface of the box, and the drying speed was set to approximately 0.4 wt% / day at the four corners of the upper surface of the box. It is made of vinyl chloride and has a size of 500 × 500 × 300 m having four ventilation holes having the hole diameters shown in Table 1 and adjusted as follows.
m, as shown in FIG. 1, and the box was left indoors at the temperature and humidity shown in Table 1 and dried for the number of days shown in Table 1. The drying speed was determined by measuring the weight of the entire box and determining the weight loss.

(2) Evaluation The obtained molded product was visually observed to check for cracks. Further, the molded body was placed on a surface plate shown in FIG. 3, and the height of the lower surface end of the molded body that was lifted was measured to determine the magnitude of the warpage. Table 1 shows the results.

(Examples 5 to 8) The use of alumina powder having a purity of 99.5% and an average particle diameter of 0.6 μm, and the alumina content, water content, size and drying rate of the molded product were approximately 0.
A ceramic powder was molded and evaluated in the same manner as in Example 1 except that the diameter of the vent hole was set to be 6 wt% / day, as shown in Table 1. Table 1 shows the results.

(Comparative Examples 1 to 8) For comparison, Comparative Example 1
In Comparative Examples 5 to 4, in the same manner as in Example 1, except that the demolded molded body was left in a room without being put in a box and dried.
In Nos. To 8, ceramic powder was molded in the same manner as in Example 5,
evaluated. Table 1 shows the results.

[0020]

[Table 1]

As is clear from Table 1, no cracks occurred in any of the examples, and the deformation was 0.9 m.
m or less. This indicates that even if the molded body has a high moisture content and the size of the molded body is large, the drying is slow, but it can be naturally dried without any problem.

On the other hand, in Comparative Examples 1 to 8, cracks all occurred, and the warpage was large, and there was a problem in drying.

[0023]

As described above, according to the molding method of the present invention, even if the molded body contains high moisture and the size of the molded body is large, it can be naturally dried without any problem in drying. You can now. As a result, the production efficiency can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a view showing a box used for drying.

FIG. 2 is a view showing ventilation holes on the upper and lower surfaces of the box.

FIG. 3 is a diagram for measuring the magnitude of warpage.

Claims (3)

[Claims] 1. A ceramic powder formed by adding a solvent, a dispersant, and a binder to a ceramic powder, mixing a slurry prepared by injection into a molding die, molding the molded body, removing the molded body, and drying the molded body. The method of forming a ceramic powder, wherein the drying method is a method in which the demolded compact is placed in a box having vent holes on upper and lower surfaces, and the box is dried by leaving the box indoors. Method. 2. The binder is a thermosetting resin, the mold is a mold that does not absorb water, and the molded body is 30 vol%.
2. The method for molding ceramic powder according to claim 1, wherein the molded article contains the above-mentioned water. 3. The ventilation hole on the top surface of the box is a ventilation hole whose hole area can be adjusted, and the area is adjusted to an area where the drying rate of the molded body is 0.2 to 1.0 wt% / day. The method for forming a ceramic powder according to claim 1 or 2, wherein: