JPS61127301A - Mud casting molding method of ceramics - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a slurry casting method for ceramics.

[Technical background of the invention and its problems]

As ceramic molding techniques, mold press molding methods, rubber press molding methods, hot press molding methods, hot isostatic press molding methods, injection molding methods, slurry casting molding methods 1, etc. are generally well known. Among these, the slurry casting method is an extremely easy process and can mold products with complex shapes, and has been used in ceramics since ancient times.

It is well known as a molding technology for sanitary ware, etc., and has recently been applied to fine ceramics such as alumina (HTlO8).

This slurry casting method includes a step of draining excess slurry to obtain a molded product with a uniform wall thickness, and a slurry casting method that does not include a step of draining the slurry, resulting in uniform or uneven wall thickness. There is a solid cast molding method that can be molded in either case.

The mold material used in this case is one that is small enough to cause a capillary phenomenon that absorbs water in the slurry, and has many pores that communicate with each other. Examples include foams that

Generally, the process of slurry casting is Slime adjustment ↓ cast into mold ↓ The base absorbs water and the powder adheres to it. ↓ Release the molded object from the mold ↓ drying It is.

However, it is known that as the thickness of the molded body increases, the difference in moisture distribution within the molded body increases, and drying breaks are more likely to occur during the drying process.

To deal with this, a drying method called humidity-controlled drying has been adopted, but this method requires a longer time as the thickness of the molded product increases, and is not suitable for mass production.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide a slurry casting method for ceramics that can obtain a molded product without drying out in a short time without requiring a long time-consuming humidity control drying process even if the molded product has a large thickness. The present inventors have found that the reason why the difference in water distribution in the molded body increases as the wall thickness increases is that if water absorption is performed only by capillary force in the plaster mold, it is far greater than that in the plaster mold. In the fleshy skin at a distance, moisture transfer to the mold becomes slower and the survival rate increases.
Therefore, in the process of slurry casting, from the completion of inking to the time of demolding, in addition to the capillary force of the plaster mold, the movement of moisture to the glue in the inking layer causes some kind of forced force. By applying pressure, the residual moisture rate in the molded product is reduced,
I thought it might be possible to prevent dryness.

Therefore, as the above-mentioned forced pressure, moisture transfer can be promoted by vacuum deaeration, which can be done relatively easily, but a preliminary test was conducted by selecting a molded product with a simple shape.

First, for the sludge removal method, a pot-shaped molded article 1 as shown in FIG. 1 was selected. The dimensions of this molded product 1 are height 2QQ
m, maximum diameter 15 Qu, wall thickness approximately 20 Ku.

The hearing aids used in the experiment were conventional plaster mold 2 shown in FIG. 2 for comparison, and molds 3 and 4 shown in FIGS. 3 and 4 for experiment.

The mold 3 shown in FIG. 3 uses the conventional plaster mold shown in FIG. 2, and has a cavity between the mold inner surface 3a and the mold outer surface 3b for vacuum degassing of moisture in the casting slurry. A hollow space 21 is formed therein. This hollow space 21 was formed by digging a hole with a drill or the like. In addition, in the mold 4 shown in FIG. 4, a breathable glass cool pipe 23 is set in advance.
By pouring gypsum slurry and embedding the glass cool pipe 23 in the mold 4, a hollow space 21 in which the glass wool pipe 23 is embedded between the indoor surface 4a and the mold outer surface 4b is created.
′ is formed. In order to prevent air from entering the mold from the outside when vacuuming the mold 3.4, a sealing material 22 is applied to the mold outer surfaces 3b and 4b to seal the plaster mold. .

The nine slurries used in the experiment had an average particle size of 1. oμ, α phase rate 91%
Silicon nitride powder (5tsN, ) Q zlci part e Spinel powder (yxg
hl, o, ) 6 parts by weight and 25 parts by weight of water to form an aqueous slurry! ! 11, and further added 0.15 parts by weight of an acrylic polymer as a peptizer to reduce the viscosity.

Then, the slurry was poured into each mold, and the thickness was 20 mm.
jLil±1. After the Oox is deposited, excess slurry is discharged, and the molds K cast into the experimental molds 3 and 4 are degassed by a vacuum pump through the hollow space 21, 21'. It was demolded.

Table 1 shows the drying method after demolding and the occurrence of dry cracks. The room temperature during the experiment was 26°C.

The relative humidity is 75%.

From the above results, in the conventional method, when the wall thickness increases, it is necessary to adjust the humidity and dry it, but if you vacuum the bottle after draining the mud to speed up the movement of moisture in the body to the bottom, It was confirmed that since the molded body had a small difference in moisture distribution during demolding, no drying breakage occurred, and therefore there was no need for humidity adjustment and drying.

Next, a test was conducted using the solid casting method by selecting a rectangular parallelepiped molded product 5 as shown in FIG.

The dimensions of the molded product are 3QQauc in length and 50cm in height.

It is 50m wide.

The mold used in the experiment was a conventional plaster mold shown in Figure 6 for comparison.
and houses 7 and 8 shown in FIGS. 7 and 8 for experimental purposes. The molding method in Cases 7 and 8, the slurry used and the temperature and humidity conditions during the experiment were the same as in the case of the slurry removal method described above.

The results of the experiment are shown in Table 2.

Based on the above results, even with the conventional solid casting method, when the wall thickness increases, it is necessary to adjust the humidity and dry it. It was confirmed that if this was done, a molded product with a small difference in moisture distribution during de-indigo generation would be obtained, so no drying breakage would occur, and therefore, there would be no need for humidity-controlled drying.

However, the method of providing a hollow hollow space 21 as shown in FIGS. 3 and 7 is easy to break or crack during processing, and processing is difficult if the shape of the molded product is complex. , FIG. 4.

It has been found that it is preferable to provide a hollow space 21' in which a ventilation pipe 23 is embedded as shown in FIG.

[Summary of the invention]

The ceramic slurry casting method of the present invention was obtained as a result of the above-mentioned findings and tests, and its feature is that the mold is formed between the inner surface and the outer surface of the casting pot using a mold material having communicating pores. A hollow space is formed to vacuum degas the moisture in the casting slurry, and after the slurry is poured, the water in the casting slurry is vacuum degassed through the hollow space to perform molding.

The method of the present invention can be applied to both a sludge casting method and a solid casting method.

However, any ceramic can be applied as long as it can be molded by slurry casting.

[Embodiments of the invention]

Examples of desired shape molding are described below.

Example 1 Silicon nitride powder (Si
, N, ) 92 parts by weight, spinel (M
gAL, O,) f3 parts by weight and 25 parts by weight of water were mixed to prepare an aqueous slurry, and 0.15 parts by weight of an acrylic polymer was added as a peptizer to lower the viscosity to obtain a raw material slurry. Ta. The desired shape is a mortar 9 as shown in F, g9, and its dimensions are 300IIJ in diameter at the top! ,height'
A conventional plaster mold 10 shown in FIG. 10 for comparison, and a mold 11 for the present invention shown in FIG. 11. In addition, type 0 11, whose casting method is a sludge removal method, is a plaster mold in which an air-permeable glass cool pipe 23 is embedded between the mold inner surface 11a and the mold outer surface 11b to form a hollow space 21'. oFJ. A sealing material 22 is applied to the outer surface 11b.

Then, the above slurry was poured into each room and the wall thickness was 151 mm.
After filling 1L1, excess slurry was discharged, and the material cast in the mold 11 was degassed by a vacuum pump through the hollow space 21' and then debonded.

Table 3 shows the drying method after de-foxing and the occurrence of dry cracks. The room temperature was 25° C. and the relative humidity was 75° C.

However, it was difficult to process the mold for the mold in which the hollow space 2 was hollow, so it was not carried out.

Example 2 A slurry similar to that in Example 1 was prepared and pestle 1 shown in FIG. 12 was prepared.
2 was molded. The dimensions of the pestle 12 are length 200 rt
tx, diameter of large diameter end 4 Qrun, radius of curvature 5 Qrun, diameter of small diameter end 3Qtrat,
The radius of curvature is 40 mm. The molds used were a conventional plaster mold 13 shown in FIG. 13 for comparison and molds 14 and 15 for the present invention shown in FIGS. 14 and 15. d The casting method is a solid casting method. The mold 14 has a mold inner surface 14a and a mold outer surface 14b.
A hollow hollow space 21 is formed between the two. The mold 15 was formed in the same manner as the mold 11 of the first embodiment. Type 1
4.

The outer surfaces 14b and 15b of 15 are coated with a /-ru material 22. The deaeration, temperature, and humidity conditions after casting are the same as in the first embodiment. The results are shown in Table 4.

Example 3 In order to mold a mortar 9 as shown in Fig. 9, a ceramic molding material (hereinafter referred to as a resin-based molding material) made of a mixture of plaster-free plaster and inorganic aggregate was used as a molding material capable of forming minute conduits from the inner surface. ), the resin mold 10 shown in FIG.
A resin mold 11 in which a glass cool pipe 23 as shown in FIG. 1 was embedded was created. In this case as well, the outer surface 11 of the mold 11
A sealing material was applied to b. A slurry similar to that in Example 1 was prepared thereto to obtain a silicon nitride molded product. The results are shown below.

〔Effect of the invention〕

The slurry casting method of the present invention makes it possible to obtain a molded product without drying out in a short time even if the molded product has a large wall thickness as described above, without requiring a long period of time for humidity adjustment and drying. .

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram of a test molded body, FIG. 2 is a vertical cross-sectional view of a conventional type, FIGS. 3(a), (b), and 4(a). (b) is a vertical cross-sectional view and a bottom view of the different molds used in the test, Figure 5 is an explanatory diagram of the test molded body, and Figure 6 (a)
, (b) is a vertical cross-sectional view and a front view of the conventional type, Figures 7 and 8.
The figures are longitudinal cross-sectional views of different molds used in the tests, Figures 9(a) and (b) are vertical cross-sectional views and plan views of molded bodies for Examples 1 and 3, and Figure 10 is a vertical cross-section of the conventional mold. 11 is a vertical sectional view of the mold for the present invention, FIG. 12 is an explanatory diagram of the molded body for Example 2, FIG. 13 is a vertical sectional view of the conventional type, and FIGS. 14 and 15. are longitudinal sectional views of different molds for use in the present invention.

Claims (1)

[Claims] A hollow space for vacuum degassing of moisture in the casting slurry is formed between the inner surface and the outer surface of a mold using a mold material having communicating pores, and after the slurry is poured, the hollow space is removed. 1. A slurry casting molding method for ceramics, characterized in that water in the casting slurry is vacuum degassed through a process.