JPH06340467A - Production of ceramic molded body - Google Patents

Abstract

PURPOSE:To provide a method for producing a ceramic molded body fit to produce a core for precision casting, etc. CONSTITUTION:Powdery ceramic stock is blended with resol and kneaded to prepare slurry. An acid catalyst is added to the slurry and this slurry is molded by pouring into a mold and hardened. The resulting molded body is taken out of the mold, dried and fired. By this method, molding time can be shortened while adopting molding by pouring and a large-sized or thick product is easily molded without requiring a gypsum mold.

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 a ceramic molded body which does not require a gypsum mold and can be molded in a short time.

[0002]

2. Description of the Related Art Ceramic molding (shape imparting) methods include die pressing, slurry casting (slip casting), cold isostatic pressing plus machining, injection molding, and doctor blade ( There is a method for forming ultra-thin plates, etc.,
Various molding methods are adopted depending on the product shape, production amount, required functions, and the like. Among them, the slurry casting method in which a plaster mold is cast into a plaster mold to absorb water or a solvent such as alcohol, and the ingot is molded, a relatively complicated shaped product can be molded, and the mold is easy and inexpensive to manufacture. It has advantages such as that it does not require specially large size and expensive equipment, and is used for manufacturing many products. On the other hand, on the other hand, it takes a long time to form a thick product because the plaster mold absorbs the solvent and hardens and molds. It requires a large amount of molds and is not suitable for mass production. In addition, the product is prone to cracking, especially in thick-walled products, which is prone to cracking, the life of the gypsum mold is short, and there is a problem in dimensional accuracy.

[0003]

[Problems to be Solved by the Invention] Sludge casting method in which ceramic slurry is poured into a plaster mold (slip casting method)
Has a technical problem as described above, though it can relatively easily mold and manufacture a product having a complicated shape. Although the present invention is a casting method, it is possible to shorten the molding time.
It is intended to provide a ceramic molding method which does not require a gypsum mold and can easily mold a large-sized or thick-walled product.

[0004]

According to the present invention, a ceramic raw material powder is mixed with a resol, kneaded to form a slurry, an acid catalyst is added to the obtained slurry, and the mixture is poured into a mold to be molded. In the method for producing a ceramic molded body, the molded body is taken out, dried and fired. Here, as the acid catalyst, it is preferable to use 20 to 35 parts by weight of an organic acid ester per 100 parts by weight of the resole. Further, by adding 5 parts by weight or less of azodicarbonamide to 100 parts by weight of the total amount of the resole and the organic acid ester, cracking during drying can be prevented.

The most significant feature of the method of the present invention is that a resol (alkali phenol) is used as a solvent and a binder for slurrying the ceramic. When an acid catalyst is added to the resole, it is hardened (gelled) in a short time due to a chemical reaction, so that it can be easily taken out of the mold. It is known that when an acid catalyst such as an organic acid ester is added to a resole, it is cured (gelled) by a condensation reaction,
Used as a binder for casting molds. However,
In the case of a casting mold, it is not necessary to make the molding sand into a slurry, and the amount of the binder added is a small amount of a few% or less relative to the molding sand, and a large amount such that the raw material powder becomes a slurry like the method of the present invention. There is no example of blending the resol.

Next, the method of the present invention will be described in the order of steps thereof. First, a ceramic raw material powder is mixed with a resol and kneaded to form a slurry. The resol used here usually has a structure represented by the general formula (Formula 1), and when an acid catalyst is added, it cures (gels) in a short time of about 10 minutes due to a condensation reaction.

[0007]

[Chemical 1]

The amount of resole to be mixed with the ceramic raw material powder is determined by the fluidity of the slurry when poured,
The amount may be such that the obtained slurry has fluidity such that it can be poured into a mold. This amount varies depending on the type and density of the ceramic raw material powder, physical properties such as shape, and the shape and thickness of the product.

After adding 20 to 35 parts by weight of an acid catalyst to 100 parts by weight of the resole and mixing the resulting slurry,
Pour into the mold to cure. As the acid catalyst to be used, organic acid esters such as various organic carboxylic acid esters and organic sulfonic acid esters are preferable. If the amount of the acid catalyst used is less than 20 parts by weight, the curing time will be too long, and the strength of the molded product after curing will be low. On the other hand, the amount of acid catalyst is 3
If it exceeds 5% by weight, the absolute amount of resole will be insufficient.
It is not preferable because the green strength after molding becomes small.
A mold is generally used as a mold for molding, but the mold for casting is not particularly limited, and a plastic mold, a wooden mold, or the like may be used if necessary.

Since the slurry poured into the mold is hardened in a short time (usually about 10 minutes), it can be taken out from the mold, dried, and then heated to remove the binder and fire to obtain a ceramic molded body. Resol, organic acid ester as an acid catalyst and azodicarbonamide described below are 4
Since they are decomposed and vaporized at 00 to 600 ° C., these binders are completely removed during firing and do not remain in the ceramic molded body after firing to impair the characteristics of the ceramic.

By adding a foaming agent such as azodicarbonamide to the slurry, the air permeability in the molded body is increased, and the gas generated by the vaporization of the binder during drying easily goes out of the molded body. Particularly for thick-walled products, it is possible to prevent cracking in the molded body during drying. When using azodicarbonamide as a foaming agent,
By adding azodicarbonamide in an amount of 5 parts by weight or less to 100 parts by weight of the total amount of the resole and the organic acid ester, the azodicarbonamide is heated to about 13 parts by weight when dried.
It foams at around 0 to 140 ° C and exhibits the above-mentioned effects. When the amount of azodicarbonamide added exceeds 5 parts by weight, the amount of foaming increases, and cracking occurs, which is not preferable.

The method of the present invention does not require a gypsum mold and is capable of molding ceramics in a short time. It can be used for molding various ceramic molded products, ceramic cores for precision casting, etc., especially large size or thick wall. It is an effective method for producing the ceramic molded body.

[0013]

EXAMPLES The method of the present invention will be described in more detail with reference to the following examples. Example 1 A fused silica having an average particle size of 12 μm has a particle size of 44
To 100 parts by weight of the ceramic raw material powder in which the zircon powder having a particle size of less than or equal to μm is mixed in the ratio shown in Table 1, 35 parts by weight of resole (corresponding to m of about 2 and n of about 1 in Chemical formula 1) is mixed. Then, 9.8 parts by weight of ethylene glycol diacetate was added and kneaded for about 30 seconds, and then the mixture was cast into a mold having a shape of 20 × 20 × 100 mm. After 10 minutes, the molded body was taken out of the mold, air-dried in a room for 24 hours, then dried by heating under the temperature conditions shown in FIG. 1, and then the binder was removed and fired under the conditions shown in FIG. No cracks were observed in the ceramic molded body after firing, and the three-point bending strength at room temperature was as shown in Table 1. 100 kgf, which is the strength generally required for precision casting cores for all samples
/ Cm ² was satisfied, and it could be sufficiently used as a core for precision casting.

[0014]

[Table 1]

Example 2 100 parts by weight of the same ceramic raw material powder as used in Example 1 was mixed with 3 parts of resole.
5 parts by weight were mixed and kneaded, and then 9.8 parts by weight of ethylene glycol diacetate and 1.
After adding 3 parts by weight and kneading for about 30 seconds, 30 × 30 ×
It was cast into a mold having a shape of 100 mm.
After 10 minutes, the molded body was taken out of the mold, air-dried in a room for 24 hours, and then heat-dried under the temperature conditions shown in FIG. 3, and then the binder was removed and fired under the conditions shown in FIG. Under the conditions of Example 1 in which no azodicarbonamide was added, the shape of the molded body was 30 × 30 × 100 mm, and as the thickness increased, fine cracks occurred during drying, but in this Example, the ceramic molded body after firing was formed. No cracks were observed, and the three-point bending strength at room temperature was at the same level as shown in Table 1.

[0016]

The method of the present invention has the following effects. First, since the ceramic slurry (sol) is cured (gelled) in a short time of about 10 minutes, molding can be performed in a short time. Therefore, the number of casting molds is small and mass production is possible. Further, since the plaster mold is not required, the mold can be repeatedly used, and maintenance such as drying of the mold is unnecessary. Furthermore, by adding a very small amount of azodicarbonamide, it is possible to prevent cracking during drying, and it has become possible to manufacture large thick products with high efficiency.

[Brief description of drawings]

FIG. 1 is a graph showing a drying temperature condition in Example 1.

FIG. 2 is a graph showing temperature conditions of drying, binder removal and firing in Examples 1 and 2.

FIG. 3 is a graph showing a drying temperature condition in Example 2.

Claims (3)

[Claims] 1. A ceramic raw material powder is mixed with resol,
A method for producing a ceramic molded body, which comprises kneading to form a slurry, adding an acid catalyst to the obtained slurry, casting the mixture into a mold, molding the molded body, and removing the molded body from the mold after curing, drying and firing. . 2. A ceramic raw material powder is mixed with resole,
Knead to make a slurry, and add 100 parts of resole to the obtained slurry.
A method for producing a ceramic molded body, comprising adding 20 to 35 parts by weight of an organic acid ester per part by weight, pouring the mixture into a mold for molding, taking out the molded body from the mold after curing, drying and firing. 3. Resol is mixed with ceramic raw material powder,
Knead to make a slurry, and add 100 parts of resole to the obtained slurry.
20 to 35 parts by weight per 100 parts by weight of organic ester and 5 parts by weight or less of azodicarbonamide are added to 100 parts by weight of the total amount of resole and organic acid ester, and then the mixture is poured into a mold to be molded, and after curing, in the mold. A method for producing a ceramic molded body, which comprises taking out a molded body from the product, drying and firing it.