JPH03215343A - Molding of fine ceramic and molding device - Google Patents

Abstract

PURPOSE:To carry out uniaxial press, to shorten lead time and to reduce cost by kneading fine ceramic powder with a specific plasticity imparting agent to give kneaded soil and press molding the kneaded soil by porous molds. CONSTITUTION:Fine ceramic powder is kneaded with 0.1-10wt.% plasticity imparting agent selected from an organic binder (e.g. paramylon) of polysaccharides produced by microorganisms and a methyl cellulose-based binder and water by Dalton mixer and a vacuum soil kneader to give kneaded soil 1. Then the kneaded soil is set at the center of a porous bottom force 2 made of synthetic resin, provided with a bottom layer with coarse communicating holes having 50-200mum and a molding face layer having <=10mum particle diameters. A top force 3 made of the same mold material is laid and the kneaded soil is press molded while sucking the top force 3 and the bottom force 2 in vacuum to give a molded article 4. Then, vacuum suction of the bottom force 2 is stopped, the top force 3 is raised while sending air to the molding face of the bottom force, released, vacuum suction of the top force 3 is suspended, compressed air is sent to the mold, the molded article 4 is released, dried and sintered.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a method and apparatus for molding fine ceramics.

BACKGROUND OF THE INVENTION Conventionally, ceramics, tableware, etc. have been molded using the plasticity of clay in industrial production.

Ceramic powder exhibits plasticity because it contains clay. As for molds, plaster molds have mainly been used.

When stones or molds are used to mold fine ceramics, impurities tend to get mixed into the molded product.

On the other hand, methods for forming fine ceramics include uniaxial press forming using spray dryer powder and CIP.
Molding, slip casting, injection molding, extrusion, etc. have been employed.

Problems to be Solved by the Invention Furthermore, the conventional fine ceramic molding method as described above has the following problems.

1) Uniaxial press forming Although it is effective for mass production of single shapes, it is currently limited to simple shapes.

When using spray dryer powder for and <<, if there is a large difference in wall thickness within the product, it is difficult to make the filling rate uniform, and a uniform molded body cannot be obtained.

Furthermore, when a non-porous material is used for the mold material, it is difficult to release the mold from wet clay, the molded body becomes distorted, and a product with a predetermined shape cannot be obtained.

2) CIP molding A comparatively uniform molded body can be obtained, but since processing of the molded body is required, the yield is poor and production costs increase.

3) Slip casting molding A molded body with good homogeneity can be obtained, but when a plaster mold is used, the strength of the mold is low, making it difficult to handle with automation, and it is not suitable for mass production.

4) Injection molding Although suitable for mass production of relatively complex shapes, there is a problem with degreasing after molding. When producing large shapes, there are also problems such as the equipment being large-scale and expensive.

5) Extrusion molding Mass production is possible, but the shape is limited to pipes, honeycombs, and plates.

OBJECTS OF THE INVENTION An object of the present invention is to provide a method and apparatus for molding fine ceramics that can be uniaxially pressed, ensure high production efficiency, and can be applied even to complex shapes.

SUMMARY OF THE INVENTION In order to achieve the above-mentioned object, the present invention provides a method and apparatus for molding phiceramics according to claims 1 and 2.

Means for Solving the Problems If the clay used in the present invention is not imparted with sufficient plasticity, it may be difficult to carry out the molding method of the present invention.

Therefore, the plasticizer used is one that can impart plasticity to the non-plastic inorganic powder and provide a clay having sufficient formability suitable for press molding.

Examples include organic binders of polysaccharides produced by microorganisms and organic binders based on methylcellulose.

The organic binder of polysaccharides produced by microorganisms is one that mainly contains polysaccharides produced by microorganisms as a binder component, and the methylcellulose-based organic binder is one that mainly contains methylcellulose.

Specifically, microorganism-produced polysaccharides include dextran, dulan gum, xanthan gum, pullulan, paramylon, curdlan, screnoglucan, and the like.

Among these, glucan-based polysaccharides are preferred, and β-1,3-glucans having β-1,3-glycosides such as paramylon, curdlan, and screnoglucan are more preferred from the viewpoint of water retention and plasticity.

Further, the organic binder of the microorganism-produced polysaccharide can also be used in combination with other components.

For example, it may contain a cellulose compound, a polyhydric hydroxy compound, a polyvinyl polymer, or the like.

Examples of cellulose-based compounds include methylcellulose, ethylcellulose, carboxymethylcellulose, sodium carboxymethylcellulose, and hydroxypropylcellulose.

Examples of the polyhydric hydroxy compound include alkylene glycols such as glycerin and ethylene glycol, and polyoxyalkylene glycols such as polyethylene glycol.

Examples of the polyvinyl polymer include polyvinyl alcohol, polyvinylpyrrolidone, polyacrylic acid resin, and the like.

Preferably, the amount of other components mixed is not more than 50% by weight of the total weight of the binder.

When used as a mixture in this way, especially β-1,3
- Mixtures of glucans, cellulosic compounds and polyoxyalkylene glycols are suitable for the molding method of the invention.

Similarly, the methylcellulose-based organic binder is also used as a mixture containing the above-mentioned components in addition to methylcellulose.

Such plasticizers have a 0.0% plasticity imparting agent for ceramic powder.
It is blended in a proportion of 1 to 10% by weight, preferably 0.5 to 5% by weight.

Various methods can be used to knead the organic binder of the microbially produced polysaccharide and the fine ceramic powder, but preferably a two-stage kneading method using a Dalton mixer and a vacuum kneader is used.

The best results can be obtained by setting the packing density to 60% when performing two-stage cross-mixing using a Dalton mixer and a vacuum clay kneader.

Press molding is performed using a porous mold. A well-known porous mold is the gypsum mold, which has traditionally been used for wet molding of ceramics and tableware, but because the gypsum mold has low mechanical strength, it has problems with durability and contamination of the molded product. There are problems such as formation (gypsum mold material etc. mixed into the molded product as impurities). Therefore, it is preferable to use a porous type that has high mechanical strength, excellent abrasion resistance, and high air permeability. One example is a mold made of synthetic resin.

In general, synthetic resin molds have strength about 10 times or more than plaster molds, and their wear resistance is 50 to 100 times as long as the number of times they can be used.

In addition, if the two-layer structure is made of a lower surface layer having coarse communication holes of 50 to 200 .mu.m and a molding surface layer having fine pores of 10 .mu.m or less, the pressure loss will be reduced.

The benefits of having a porous mold material include dehydrating the clay by vacuum reduction and efficiently releasing the molded body by compressed air.

EXAMPLE An experiment was conducted using the plastic molding process shown in FIG. The material used in the experiment was Al203-ZrO2. First, Al203 and ZrO2 were weighed at a predetermined ratio,
Mixing treatment was performed for 18 hours using a pot made of AA'203 and a ball made of A1203. At that time, drink 25vj of water.
%, and 0.3 wj% of polycarboxylic acid ammonium salt was added as a dispersant. Regarding the amount of addition and water content,
The highest viscosity within the range that allows efficient mixing was adopted. Regarding the amount of dispersant added, the point at which the apparent viscosity was the lowest was adopted. After that, the raw material is dried and crushed to give 0.5
The particles were sized to a size of mm or less. A binder and water were added to this raw material, and primary kneading was performed using a Dalton mixer. Thereafter, secondary kneading was performed using a vacuum clay kneading machine to obtain kneaded clay.

The above-mentioned clay was press-molded as shown in FIGS. 2-5.

First, as shown in FIG. 2, clay 1 is set in the center of the molding surface of a porous lower mold 2 made of the aforementioned mold material. Then,
A porous upper mold 3 made of the same mold material is set. Upper mold 3
While applying vacuum suction to the lower mold 2, pressure molding is performed on these molding surfaces as shown in FIG. 3 to produce a molded body 4. After molding,
The vacuum suction of the lower mold 2 is stopped, and as shown in FIG. 4, the upper mold 3 is raised while sending compressed air to the molding surface of the lower mold 2, and the molded product 4 is released from the molding surface of the lower mold 2. . after that,
The vacuum suction of the upper mold 3 is stopped, and as shown in FIG. let Thereafter, the molded body 4 is sufficiently dried at 40°C to 100°C. Then, calcination is carried out at 1600° C. for 2 hours.

The effect of adding water, water retention, plasticity, and shape retention after molding were evaluated for the samples of the molded bodies obtained in the above experiment.

Water retention was calculated by drying at room temperature, 40° C., and 100° C. until a constant weight was reached, and measuring the weight loss.

Regarding plasticity, a sample with a diameter of 50 mm and a length of 60 mm was prepared, and an autograph was used to determine the length deformation ratio of 2.
The evaluation was made based on the maximum load within the range showing the value of . 1st
The table shows the test results and a comparison between the characteristic values of the samples made by the molding method of the present invention and other molding methods. The density of the sintered compact of the sample produced by the molding method of the present invention is equivalent to or higher than that of the conventional slip casting molding method or CIP molding method, and is considered to be useful.

Effects of the Invention 1) Since the present invention uses an organic binder of polysaccharides produced by microorganisms for molding fine ceramics, it is possible to obtain kneaded clay with sufficient plasticity at low pressure.

2) By using the molding method of the present invention, it is possible to significantly shorten lead time and reduce costs compared to conventional molding methods for fine ceramics.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing an example of a preferred molding process of the method of the present invention, and FIGS. 2 to 5 are explanatory diagrams showing a series of steps for producing a molded article by the method of the present invention. 1... Kneading Soil 2... Lower Mold 3... Upper Mold 4... Molded body 5.・・・・・・・・・Top plate Fig. 1 Procedural amendment (voluntary)

Claims (2)

[Claims] 1. Molding of fine ceramics characterized by adding an organic binder of microbially produced polysaccharide or a methyl cellulose binder as a plasticizer to fine ceramic powder, kneading it to make kneaded clay, and press-molding the kneaded clay using a porous mold. Method. 2. In a molding device that combines an upper mold and a lower mold and presses between the molding surface of the upper mold and the molding surface of the lower mold to mold fine ceramics clay into a fine ceramic molded body, The upper and lower molds are made of porous mold material, and the molding surface is vacuum depressurized through the mold material to remove moisture from the kneaded soil from the molding surface, or compressed air is sent to the molding surface through the mold material to remove water from the molding surface. A fine ceramics molding device configured to release the molded body from the mold.