JPH101366A - Slurry for casting and method for producing the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To increase the deposition rate of a slurry for ceramic cast molding to which curdlan is added. SOLUTION: Ammonia is added to a ceramic raw material powder, a binder, a dispersant, curdlan and water to obtain a pH.
9 or more and mixing at a temperature lower than 35 ° C. Thereafter, the mixture is heated to a temperature of 35 ° C. or higher to mix while dissolving the curdlan.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a slurry for casting ceramics and a method for producing the slurry, and more particularly to a slurry for cast molding to which curdlan (β-1,3-glucan) is added, and a slurry therefor. It relates to a manufacturing method.

[0002]

2. Description of the Related Art When casting ceramics, a slurry obtained by dispersing ceramic raw material powder in water together with a dispersant and a binder is supplied into a water-absorbing mold such as a gypsum mold, and the solid content in the slurry is reduced. It is attached (that is, inlaid) to the inner surface of the mold.

In some cases, curdlan is added to this slurry as a water-retaining plasticizer (JP-A-7-330438).
No. 8-34674). This curdlan has a property of gelling when it comes into contact with water, and since this gel is contained in the molded article, the moisture of the molded article is prevented from rapidly evaporating. Cracks are prevented.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to increase the deposition speed of a slurry for ceramic cast molding to which this curdlan has been added.

[0005]

The slurry for casting of the present invention is a slurry for casting containing a ceramic raw material powder, a binder, a dispersing agent and curdlan, and has a pH value.
The curdlan is in a dissolved state by making it 9 or more alkaline.

The method for producing a slurry for casting according to the present invention is a method for producing a slurry for casting according to the present invention, wherein a ceramic raw material powder, a binder, a dispersant, curdlan and water are heated at 35 ° C. A first mixing step of mixing at a low temperature, and a second mixing step of mixing while heating to a temperature of 35 ° C. or higher to dissolve the curdlan,
The pH is adjusted to 9 or more by adding an alkali agent to the first mixing step or the second mixing step.

In the casting slurry of the present invention, the ceramic particles are agglomerated by the curdlan in a dissolved state, so that moisture can be quickly absorbed from the inlaid object into the molding die during the inlay. And the inking speed increases.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, the ceramic raw material powder may be any of oxide, nitride, sulfide, silicide and the like. The average particle size of this raw material powder is 5
0 μm or less, especially 0.01 to 10.0 μm, especially 0.1 μm.
1-5 μm is preferred.

The curdlan is made of a ceramic raw material powder 10
It is preferable to add 0.1 to 2 parts by weight, especially 0.2 to 1 part by weight, based on 0 parts by weight (dry weight).

As the binder, saccharides are preferred. The binder is preferably added in an amount of 0.1 to 10.0 parts by weight, especially 0.5 to 3 parts by weight, based on 100 parts by weight (dry weight) of the ceramic raw material powder.

As the dispersant, ammonium polycarboxylate is preferred. The dispersant is ceramic raw material powder 100
It is preferable to add 0.05 to 5.0 parts by weight, especially 0.1 to 1.0 part by weight, based on parts by weight (dry weight).

Water is added to the above ceramic raw material powder,
The volume of the slurry is adjusted to 100 parts by volume (solid content + water). At this time, it is preferable to add 40 to 80 parts by volume of water. In particular, it is preferable to add 45 to 65 parts by volume of water.

When mixing water and ceramic raw material powder, it is preferable to use a stirrer having a medium such as a ball mill.

When stirring with this stirrer, first, at 35 ° C.
Stir and mix at a lower temperature, preferably lower than 30 ° C. (usually room temperature).

In the first mixing step, the curdlan absorbs water and gels. In the stirring device, the ceramic raw material powders are sufficiently mixed with the gel. When two or more kinds of raw material powders are used as the ceramic raw material powder, the raw material powders are also sufficiently mixed in the first mixing step. In the first mixing step, the viscosity of the slurry is not so high because the curdlan is in a gel state.
Therefore, the raw material powder and the curdlan gel are sufficiently mixed.

In the first mixing step, an alkali agent may be added. By making it alkaline, the curdlan is easily dissolved, but since the temperature is lower than 35 ° C., the curdlan hardly dissolves and remains in a gel state.

As the alkaline agent, ammonia which volatilizes or decomposes upon firing is suitable. The amount of the alkali agent added is such that the pH of the slurry is 9 or more, preferably 9 to 12,
More preferably, the amount is 9.5 to 11.

The first mixing step is carried out for 1 hour or more, especially for 3 hours.
It is preferable to carry out for more than an hour.

In the second mixing step after the first mixing step, the slurry temperature is set to 35 ° C. or higher, preferably 35 to 80 ° C.
Heat to 40-70 ° C and mix. The first
When no alkali was added in the mixing step, an alkali was added in the second mixing step to reduce the p of the slurry.
H is 9 or more, preferably 9 to 12, and more preferably 9.
5 to 11.

When the mixing is continued under the conditions of pH 9 or more and the temperature of 35 ° C. or more, the curdlan starts to be gradually dissolved, and by continuing the mixing, almost all of the curdlan is dissolved. The dissolution of curdlan increases the viscosity of the slurry. In addition, the ceramic material particles sufficiently dispersed in the first step are reaggregated by the curd run to form large secondary particles. The secondary particles have a property that water is easily separated in a subsequent inking process.

This second mixing step is carried out preferably for at least 1 hour, preferably for at least 3 hours, using the above-mentioned stirring device.

By this second mixing step, a high viscosity slurry in which curdlan is dissolved can be obtained.

This slurry is supplied to a water absorbing mold,
The molded body is formed by inking. The slurry may be pressurized during the casting.

The curdlan dissolved in water as described above significantly increases the viscosity of the slurry for casting.

This increase in viscosity is caused by the curdlan adsorbed on the ceramics, which is caused by the reagglomeration of the ceramic particles in the slurry. That is, the primary particles of ceramics homogeneously dispersed by the dispersant in the first mixing step are aggregated into secondary particles having an appropriate size in the second mixing step. The agglomerated secondary particles promote the separation and filtration of the solid content and the water on the mold surface during the casting, so that the slurry deposition rate is greatly increased and the molding time is greatly reduced.

Further, the moisture contained between the curdlan and the ceramic particles (gap between the granulated particles) causes
The strength of the molded article when wet is increased, and this also imparts plasticity to the molded article.

As described above, when the casting slurry of the present invention is used, the productivity is improved because the deposition rate is high. Furthermore, since the inking molding time is short and the molding can be performed in a short time, the density distribution inside the molded body is uniform. As a result, cracks during drying and firing are reduced, and productivity (yield) is reduced.
Is improved.

The slurry for cast molding of the present invention is suitable for production of ceramic products, particularly for products having complicated shapes. That is, the plasticity is imparted to the molded body, and the handling strength of the molded body when wet is greatly improved, so that when the mold is released from the mold, cracks, cracks, and chips having a complicated shape are likely to occur with a high yield. Can be molded.

The casting slurry of the present invention is also suitable for the casting of large / thick products. That is, large /
In the case of thick-walled products, it takes a long time to deposit and mold, and there is a difference in the density distribution (center and surface layer) inside the molded body. As a result, dry cracking and cracking during firing are likely to occur. In the case of using the slurry of the present invention, since the deposition speed is high, the deposition molding can be performed in a short time, cracks due to the difference in density of the compact are reduced, and the yield is improved.

Further, the slurry for cast molding of the present invention can be used for producing a porous body having fine and uniform pores. That is, by adjusting the amount of curdlan added and the amount of water, a slurry having a high viscosity and a high moisture content is produced, and the resulting slurry is cast or molded by a filter press and fired, whereby a porous product can be produced. .

[0031]

【Example】

 Examples 1 to 5, Comparative Examples 1 and 2 Sialon was cast-formed according to the following procedure.

1. Manufacture of Slurry for Casting (Sialon) Raw Material Mixing After sintering to 86 parts by weight of silicon nitride (Stark LC-10), sialon of Si _6-Z Al _Z O _Z N _8-Z (Z <4.2) 2.3 parts by weight of AlN (Starck Grade C) and Y ₂ O ₃ (Shin-Etsu Chemical Co., Ltd.)
RU) 7.0 parts by weight, Al ₂ O ₃ (Sumitomo Electric AKP-
30) 4.6 parts by weight were blended to make the total amount of the ceramic raw material powder 100 parts by weight.

This ceramic raw material powder was put into a pot mill (capacity: 10 liters), and curdrun was placed therein.
β-1,3-glucan (Takeda Pharmaceutical Company Biopoly P1
03) with respect to 100 parts by weight of the ceramic solid content,
0.1 to 1.0 part by weight was added.

Further, based on 100 parts by weight of the ceramic raw material powder, 35 parts by weight of water (room temperature, 20 ° C. in this case), 0.2 part by weight of a dispersant (Chukyo Yushi D-305), and 1 part of binder (Kao Sorbitol) 0.0 parts by weight were added. Further, a slight amount of ammonia was added to adjust the pH to 10.

First Mixing Step Alumina balls were added to the pot, and mixed at room temperature for 5 hours by ball milling. Thus, a slurry in which the ceramic raw material powder was homogeneously dispersed was obtained.

Second Mixing Step The pot was externally heated by an electric heater to adjust the slurry temperature to 40 ° C. In this state, ball milling was performed for 5 hours.

Third Mixing Step (Cooling Step) After completion of the second mixing step, the temperature was lowered to room temperature while mixing the slurry to obtain a slurry for casting.

Viscosity Measurement The slurry was in the form of a soft cream. The viscosity of this slurry was measured with a B-type viscometer. If necessary, air bubbles in the slurry were removed by vacuum defoaming, and then subjected to casting.

2. Cast molding Using this slurry, the slurry was pressed into a cylindrical mold having a diameter of 50 × 40 mm at a molding pressure shown in Table 1 with a pressure casting apparatus, and the thickness of the obtained disk-shaped molded body was measured. From the molding time at this time, the inking rate (constant) was examined.

3. Test results The results are shown in Table 1.

[0041]

[Table 1]

Table 1 shows the following.

(1) The viscosity of the slurry to which curdlan was added and heated and mixed was higher than that of the unheated slurry of the same component. Also, increasing the amount of curdlan added increased the viscosity.

(2) In the case of the slurry of Comparative Example 1 where no curdlan was added, the slurry viscosity was significantly lower than those of the slurries of Examples 1 to 5.

(3) Second of curdlan added
The slurry of Comparative Example 2 in which the mixing step was at room temperature increased the viscosity, but the rate of increase was smaller than that of Example 2 in which the mixture was heated and mixed.

(4) In the slurry of Comparative Example 1 in which curdlan was not added, the inking rate was extremely low. Further, the curdlan was added, but the slurry of Comparative Example 2 in which the second mixing step was at room temperature was the same, and the properties were not much different from those of Comparative Example 1. On the other hand, although the slurries of Examples 1 to 5 are in the form of high-viscosity slurries which are unsuitable for general casting, the deposition rate is extremely high.

[0047]

As described above, the slurry for casting ceramics provided by the present invention has a high deposition rate,
The productivity during molding is significantly improved. In addition, since the deposition time is short, the density distribution inside the molded body is uniform, and reduction in cracks during drying and firing can be expected. Further, the strength of the molded article when wet is increased, and the plasticity of the molded article is also improved.

Claims (2)

[Claims] 1. A casting slurry containing a ceramic raw material powder, a binder, a dispersant and a curdlan, wherein the curdlan is in a dissolved state by making it alkaline at pH 9 or more. slurry. 2. The method for producing a slurry for casting according to claim 1, wherein a first mixing step of mixing the ceramic raw material powder, binder, dispersant, curdlan and water at a temperature lower than 35 ° C., A second mixing step of heating the mixture to a temperature of 35 ° C. or higher to mix while dissolving the curdlan, and adding an alkali agent to the first mixing step or the second mixing step to adjust the pH to 9 or higher. A method for producing a slurry for casting molding.