JPH06190809A - Mold for slip casting - Google Patents

Abstract

(57) [Summary] [Objective] To provide a mold for slip casting in which the water absorption speed of the molding die is increased and the inking speed is increased without performing operations such as pressurization and vacuuming. [Structure] Aggregate of ceramic powder such as silicon nitride powder,
A mold made of a water-soluble polymer such as polyolefin glycol that is easily wettable by water and has excellent water permeability at the adhesion interface between the inking layer and the mold.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slip casting mold and, more particularly, to a slip casting mold having improved water absorption and a high inking rate.

[0002]

2. Description of the Related Art The slip casting method is a typical method for producing a ceramic molded body. In this slip casting molding method, a mold made of a water-absorbing material such as gypsum is usually used, and moisture is absorbed from the slip (suspension of ceramic powder) injected into the cavity of this mold to solidify the slip. It is done by doing. The molded body obtained above is degreased and then fired to obtain a final ceramic member. This method is generally suitable for producing a comparatively thin molded product or a molded product having a complicated shape.

Since this slip casting method can relatively easily produce a homogenous molded body without distortion, it is a molded body (green) for ceramic products, for which high shape and dimension accuracy is required, such as an automobile. Has been attempted to be applied to the manufacture of turbine rotors and the like.

By the way, in this slip casting molding method, it is usual to fill the cavity of the mold with slip under atmospheric pressure, and to perform dehydration of the slip by natural absorption of water by the mold, but it is relatively thick. When manufacturing a molded body, there is a problem that it takes a long time to dehydrate the slip in the cavity.

Therefore, there is a method of forcibly dehydrating the slip by applying pressure to the slip in the cavity or drawing a vacuum. In such a method, a relatively fragile molding made of gypsum or the like is used. Problems such as mold breakage and mold cracking occur.

Therefore, an object of the present invention is to provide a slip casting mold in which the speed of water absorption from the molded body during inking to the mold is increased and the inking speed is increased without performing operations such as pressurization and vacuuming. Is to provide.

[0007]

In view of the above object, the inventors of the present invention have diligently studied the factors that influence the slip infiltration rate, and as a result, the slip infiltration progresses as water is absorbed into the mold. Its water absorption is the wettability of the mold itself,
It was found that it was influenced by two factors of water permeability to the solidified layer, especially the water permeability factor to the layer. Further, the inventors of the present invention have found that as a mold that is easily wetted by water and has excellent water permeability at the adhesion interface between the inking layer and the mold, an aggregate of ceramic powder such as silicon nitride powder and polyolefin glycol. It has been found that a template composed of a water-soluble polymer such as The present invention has been made based on the above findings.

That is, the slip casting mold of the present invention is characterized by comprising an aggregate made of ceramic powder and a water-soluble polymer.

The present invention will be described in detail below. First, each component forming the slip casting mold of the present invention will be described.

[1] Aggregate Examples of the aggregate used in the present invention include ceramic powders such as silicon nitride, zircon, alumina, silica, and silicon carbide. In particular, if a ceramic powder of the same quality as the ceramic to be molded is used, it is possible to prevent the molded body from being contaminated by the mold material.

The average particle diameter of the above aggregate is 10 μm or less, and particularly, 0.
It is preferably 1 to 2 μm. Average particle size of aggregate is 10μ
When it exceeds m, it is not preferable because effective pores are not formed in the mold.

[2] Water-soluble polymer Examples of the water-soluble polymer used in the present invention include polyolefin glycol, polyvinyl alcohol, methyl cellulose, starch and the like. As the above-mentioned polyolefin glycol, polyethylene glycol,
Examples thereof include polypropylene glycol and polybutylene glycol. Of these, polyethylene glycol is particularly preferable.

When polyethylene glycol is used, it is preferable to use one having a molecular weight of 1,000 to 20,000, particularly 3,000 to 5,000. When the molecular weight of polyethylene glycol is less than 1,000, the state is liquid, while when polyethylene glycol having a molecular weight of more than 20,000 is used, it is dissolved when water is absorbed by the mold, resulting in a high viscosity state in the mold capillary, which is not preferable. .

[3] Blending ratio The blending ratio of the aggregate and the water-soluble polymer is 70% by weight or more of the aggregate, particularly 85 to 95% by weight, and 30% by weight of the water-soluble polymer.
It is particularly preferable that the amount is 5 to 15% by weight. If the content of the water-soluble polymer exceeds 30% by weight (the content of aggregate is less than 70% by weight), the rate of inking is rather lowered, which is not preferable.
Especially when the water-soluble polymer is less than 5% by weight (95% by weight of aggregate)
When the water-soluble polymer exceeds 15% by weight (when the aggregate is less than 85% by weight), the effect of increasing the infiltration rate is insufficient. It is not preferable because it cannot be obtained.

[4] Manufacturing Method The slip casting mold of the present invention is prepared by mixing the above-mentioned aggregate and a water-soluble polymer in water as a medium to prepare a uniform slip, and then obtaining a desired water-absorbing material. It can be manufactured by injecting it into a mold having a shaped cavity (usually using a gypsum mold), leaving it for a predetermined time to dry, and then releasing it.

Alternatively, in the slip casting mold of the present invention, an aggregate and a water-soluble polymer are mixed, and the mixture is subjected to 200 to 2,000 kg / cm ² by a CIP molding machine.
It can also be produced by cold isostatic pressing at a pressure of.

The slip casting mold of the present invention thus obtained can be applied to slip casting of various ceramics. The ceramic raw material to be molded is not particularly limited, and nitride-based, oxide-based, boride-based, and carbide-based materials can be used. In particular, in order to prevent contamination by the molding mold during slip cast molding, it is preferable to form the slip casting mold by using the same ceramic material as the ceramic material to be molded as described above.
Further, the slip casting mold of the present invention has an advantage that it can be repeatedly used depending on the shape of the mold and the like.

[0018]

Since the mold for slip casting of the present invention is composed of an aggregate such as silicon nitride ceramics and a water-soluble polymer such as polyolefin glycol, it can be worn under atmospheric pressure as compared with a conventional mold such as a gypsum mold. The flesh speed has increased significantly. The reason why such an effect is obtained is not necessarily clear, but in the present invention, the aggregate of the mold is made into a ceramic powder, and since it is adhered with a water-soluble polymer, it has a water wettability and It is considered that this is because the water permeability at the adhesion interface of the inking layer was remarkably improved.

[0019]

The present invention will be described in more detail with reference to the following specific examples. Examples 1 to 9 and Comparative Examples 1 and 2 α-Si ₃ N ₄ powder having an average particle size of 0.8 μm and polyethylene glycol (PEG, molecular weight 4000) were weighed at the ratio shown in Table 1, and these were mixed with water 100 50 parts by weight with respect to parts by weight were blended and mixed for 1 hour with a resin ball mill.

The slip thus obtained was poured into a gypsum mold, allowed to stand for 12 hours to dry, and then released to obtain a mold for slip casting having a flat plate-shaped cavity.

On the other hand, 2.5% by weight of Y ₂ O _{3 having} an average particle diameter of 5 μm, 1% by weight of Al ₂ O ₃ powder having an average particle diameter of 1 μm, and the balance α-Si ₃ N ₄ powder having an average particle diameter of 0.8 μm. To 100 parts by weight of the ceramic mixture, 42 parts by weight of water and 0.1 part by weight of a dispersant (ammonia water) were added and mixed for 40 hours with a resin ball mill.

The slip thus obtained was subjected to slip casting using the above-mentioned slip casting mold, and the inking rate was measured. Was calculated. The results are also shown in Table 1.

For comparison, in the case of a mold prepared in the same manner as in the example except that polyethylene glycol was not added (Comparative Example 2), the inking rate was similarly measured. The results are shown in Table 1.

Table 1 Composition (parts by weight) Example 1 Example 2 Example 3 Example 4 Example 5 Si ₃ N ₄ 95 93 92 91 90 PEG 5 7 8 9 10 Inking rate ratio ⁽¹⁾ 110 180 180 340 340

Table 1 (continued)Composition (parts by weight) Example 6 Example 7 Example 8 Example 9 Comparative example 2 Si₃N_Four 89 88 87 70 100 PEG 11 12 13 30 0 Inking speed ratio ⁽¹⁾  270 190 120 30 100 (1) Inking rate: (Inking rate of each Example / Inking of Comparative Example 1)
Calculated by (meat speed) x 100 (%).

As is clear from Table 1, by using the slip casting mold of the present invention, it is possible to significantly increase the inking rate under atmospheric pressure as compared with the gypsum mold.

Example 10 Examples 1 to 9 were prepared by using α-Si ₃ N ₄ powder having an average particle size of 0.8 μm and polyethylene glycol (PEG, molecular weight 4000).
Blended in various ratios similar to the above, using a CIP device, 500
Cold isostatic pressing was performed at kg / cm ² to obtain a slip casting mold having a flat plate-shaped cavity.

Using these slip casting molds, the Y ₂ O ₃ / Al ₂ O ₃ / Si used in Example 1 was used.
_When a slip of ₃ N ₄ ceramic was slip-cast and the inking speed was measured, it was found to have the same effect as the mold produced by the slip-cast method.

[0029]

As described above in detail, since the slip casting mold of the present invention is composed of an aggregate such as silicon nitride ceramics and a water-soluble polymer such as polyolefin glycol, it is under atmospheric pressure as compared with the gypsum mold. The inking speed at is greatly improved. Such a slip casting mold of the present invention is suitable for molding a relatively thick molded body.

Claims (3)

[Claims] 1. A mold for slip casting comprising an aggregate made of ceramic powder and a water-soluble polymer. 2. The slip casting mold according to claim 1, wherein the aggregate is 70% by weight or more and the water-soluble polymer is less than 30% by weight. 3. The slip casting mold according to claim 1, wherein the aggregate is silicon nitride powder having an average particle size of 10 μm or less, and the water-soluble polymer is polyolefin glycol. Mold for slip casting.