JPH02223403A - Manufacture of ceramics molding - Google Patents

Abstract

PURPOSE:To improve the property of a sintered body by putting, and then press-molding, plasticity body being mixed and kneaded with non-plasticity, non-oxide ceramics powder, and solvent and organic binder into a mold having three dimensional net-shaped air holes, and then removing the organic binder through a calcining process. CONSTITUTION:Plasticity body consisting of ceramics powder, solvent, deflocculant and organic binder is kneaded by a kneader, after that, it is further kneaded by a vacuum kneader. On the other hand, a gas permeable tube made by knitting glass wool or the like is buried into a gypsum mold so as to mold a working mold, and next, air is supplied thereinto from the glass wool, and mold-release is carried out then. Then body is cut in a required quantity, and mounted on the lower gypsum mold 8 of a wet compression apparatus in order to perform compression mold therefor. The molded body released from a upper mold 5 is subjected to a calcining process at approximate 550 deg.C in order to remove the binder, after that, it is sintered in N2 of approximate 1700 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing a ceramic molded body. More specifically, the present invention relates to a method for manufacturing a ceramic molded body using a wet compression molding method using a mold with improved water absorption efficiency and demolding efficiency.

[Prior Art] One method of molding ceramic products is a wet compression molding method using a plaster mold. This is a method of adding water to ceramic raw materials, kneading them in a vacuum clay kneading machine, extruding them, cutting out the required amount, and inserting them into molds made of plaster to form dishes, bowls, etc. This method is applicable to ceramic raw materials because they contain large amounts of plastic components such as clay and kaolin.

In the case of so-called new ceramic raw materials such as silicon nitride, it is difficult to mold them using such methods because they do not contain plastic components, so ceramic molded bodies are formed using injection molding or slip casting. ing.

[Problems to be Solved] Molding of new ceramics such as silicon nitride by wet compression molding has not been successful in the past due to problems with the plastic component, so-called clay, and the mold.

Among these, in order to obtain plastic clay, in the case of ceramics, kaolin etc. are mixed, and a clay with plasticity is obtained due to the plasticity of kaolin, but with new ceramics such as silicon nitride, appropriate plasticity is obtained. There was no substance and molding was difficult.

Furthermore, a plaster mold is usually used as the mold, and it is often difficult to remove the mold after molding.

An object of the present invention is to provide a method for manufacturing a ceramic molded body by molding a new ceramic powder such as silicon nitride using a wet compression molding method, which can solve the above-mentioned problems. .

[Means for Solving the Problems] The method for manufacturing a ceramic molded body of the present invention provides a non-plastic,
A plastic clay obtained by mixing and kneading non-oxide ceramic powder, a solvent, and an organic binder soluble in the solvent is placed in a mold having a three-dimensional network of ventilation holes, and compression molded. After molding, gas is supplied through the vent hole to remove the mold, and the molded body is dried, degreased, and fired to obtain a ceramic sintered body.

Examples of organic binders soluble in solvents include wax-based binders having binding properties, demolding properties, and plasticity, tragacanth rubber, MC (methyl cellulose), PVA, and PV
B etc. can be used.

[Function] Regarding the production of silicon nitride clay, if kaolin or the like is used to obtain plasticity, inorganic substances such as 5i02 and Na20 will be mixed into the silicon nitride and the properties of the sintered body will deteriorate; By using a binder, the organic binder can be removed during the calcination stage, and problems related to clay can be solved without adversely affecting the properties of the sintered body.

In addition, regarding demolding from the plaster mold, the C of the surface of the plaster mold
It is said that a small amount of a is eluted into the base material, and the plaster mold is removed, so to speak, as if it were to be peeled off. However, for materials with high viscosity and low moisture content, such as clay, demolding by elution is not successful. By supplying gas to lift the base material, it can be easily demolded.

[Example] Preliminary test 1) Regarding silicon nitride clay, water and a wax binder were added to a powder of silicon nitride mixed with a sintering aid, and the mixture was kneaded in a kneader and then kneaded in a vacuum mixer.

The mixed wire was appropriately cut and placed in a plaster mold 1 having four hemisphere parts 1a shown in FIG. 1 to form a spherical object. This is 550℃
After calcining, the binder could be removed.

Thereafter, when the material was sintered at 1700° C. in N2, a sintered body having a theoretical density of 98% could be obtained.

2) About the plaster mold A breathable tube made of woven glass wool (hereinafter referred to as a glass wool pipe) was embedded inside the plaster mold. This is the same as that disclosed in Japanese Patent Application Laid-Open No. 61-127301.

That is, a glass wool pipe fixed to a wire mesh was placed in a case mold made of plaster, and plaster was poured therein. After solidification, the pipe was removed from the case mold and used. After thoroughly drying this, a treatment was applied to prevent air leakage except for the parts that were in contact with the clay. After molding using this mold, the mold could be easily removed by supplying air through glass wool.

Examples of molds other than plaster include molds made by compression molding particles such as ceramics or stainless steel with a diameter of about 10 to 30 μm, which are not affected by water or organic solvents, and adding a few percent of an organic or inorganic adhesive to bond the particles. Any mold in which finely powdered glass is mixed with particles and baked at a high temperature to adhere the particles, that is, a mold in which holes are formed in a three-dimensional network between the particles, can be used.

In addition, controlling the flow rate is important when supplying air during demolding.At first, air is supplied gradually so that the demolding air circulates over the entire molding surface, and then the air pressure is gradually increased to remove the mold. Make a mold. If the air flow rate and pressure are rapid, only one part of the molded body will be demolded and the molded body will be deformed. The air flow rate and pressure must be determined by testing the optimum values based on the surface area and wall thickness of the molded body, the amount of solvent in the molded body, and the molding pressure.

The blending ratio of the plastic clay varies depending on the particle size of the ceramic powder, etc., but when the entire plastic clay is taken as 100% by weight, the proportion of the ceramic powder is 45 to 65% by weight, and the solvent is 1% by weight.
0 to 30% by weight of heavy poison, 0.1 to 1.0% by weight of peptizer, and 15 to 30% by weight of organic binder.

When the blending ratio of ceramic powder decreases, the shrinkage of the obtained ceramic molded body increases, making it difficult to obtain a ceramic molded body with high dimensional accuracy.

On the other hand, if the blending ratio is too high, the viscosity of the plastic clay will become too high, resulting in poor moldability.

Regarding the blending ratio of the organic binder, if it exceeds 30% by weight, the mixability with the ceramic powder tends to deteriorate, making it difficult to obtain a homogeneous plastic clay. On the contrary, 15
If it is less than % by weight, it is difficult to obtain a plastic clay.

Regarding the blending ratio of the solvent, if it is too large, cracks will tend to appear during drying, while if it is too small, the viscosity of the plastic clay will become high and the moldability will deteriorate.

Regarding the injection mouthwash, if the amount is less than 0.1% by weight, the viscosity of the plastic clay will increase and the moldability will deteriorate; The effect becomes significantly higher, the viscosity of the plastic clay increases,
Formability deteriorates.

Further, the pore diameter of the three-dimensional ventilation hole is preferably within the range of 0.5 to 10 μm at the surface portion in contact with the plastic clay.

If the pore size is larger than 10 μm, the particle size of the ceramic powder used is small, and the powder will enter the pores of the mold due to the pressure during molding, making it difficult for the solvent in the molded body to escape, clogging the pores. It becomes difficult to remove the mold using air during demolding. Also,
If the pore diameter is less than 0.5 μm, the transfer of the solvent to the mold becomes difficult and the molding time becomes long.

Example 1 A sintering pot lid 2 (110φ, 10t) shown in FIG. 2 was molded.

Figure 3 shows the case type used. The lower case mold 4 has a convex portion 4b corresponding to the lid 2 formed on a base 4a. The upper case mold 3 is a cylindrical mold placed on the base 4a. A glass wool vibro fixed with a wire mesh was placed inside this case mold, and a cap 7 for air introduction and exhaust was attached.

Then, gypsum was mixed with water and poured to obtain an upper mold 5 shown in FIG. After that, from base 7 to 0. 3kg/
The mold was thoroughly dried by flowing air at a pressure of CD.

Epoxy resin was diluted with a solvent and applied to the parts of Use Type 5 that did not touch the clay to prevent air leakage.

This upper mold made of plaster 5 and the lower mold made of plaster 8 in which a glass wool vibe was embedded in the same manner as the upper mold were assembled into a wet compression apparatus shown in FIG.

Silicon nitride clay contains 92% silicon nitride (average particle size 1 μm).
Parts by weight, 8 parts by weight of spinel (average particle size 1 μm), 0.3 parts by weight of peptizer (Middle East Cerna D735), 29.7 parts by weight of waxy binder (Middle East Cerna WD601)
After measuring 20 parts by weight of water and kneading it in a small kneader,
It was obtained by extrusion using a vacuum clay kneader.

The required amount of this clay was cut out, placed on the lower plaster mold 8 of the wet compression device shown in Fig. 5, and compression molded at a pressure of 20 kg/c4 (the pressure was calculated from the torque meter installed on the shaft of the handle 9). ).

The upper and lower molds were evacuated, and after 10 minutes, the vacuum in the lower mold 8 was stopped, air was flowed through the lower mold at a pressure of 0.7 kg/c, the clay was attached to the upper mold 5, and the upper mold was lifted. Afterwards, the vacuuming of the upper mold 5 was also stopped.

Next, put a support pillar under the upper mold 5, and put 0.7 kg into the upper mold 5.
The mold was demolded by flowing air of /c-. Dry this, 110
A molded body having a diameter of 10t was obtained. The yield to obtain a molded body is 90
%Met. The compacts were sintered at 1'700°C in N2 after removing the binder at 550°C. The density was 98% of the theoretical density.

Example 2 As in Example 1, the sintering pot lid 2 shown in FIG.
was molded.

The usage type in this case is shown in FIG. The upper mold 15 is made of mullite and has a recess 12a having the same dimensions as the lid 2.
It is constructed by mounting an inorganic continuous porous body 12 inside an aluminum container 11. Then, the porous body 12 and the container 11
The space between the two is sealed with an epoxy resin 13, and holes 7a are formed in the porous body 12, so that air is introduced and exhausted from the air introduction lower. On the other hand, the lower mold 18 has the same structure as the upper mold 15 except that the four parts are not formed.

The material and molding method for the molded body are the same as in Example 1. As a result of the molding, a complete molded body could be obtained with a yield of 90% or more. The density after sintering was also 98% of the theoretical density.

Example 3 Using the same ceramic powder as in Example 1, deflocculating agent (
0.5 parts by weight of Middle East Serna E 503) and 24.5 parts of butyral resin binder (Middle East Oil 5E604).
A clay was made using a vacuum clay kneading machine using 25 parts by weight of ethanol, and molded using the same mold as in Example 2.

The molding yield was 85%, a complete molded body could be obtained, and the density of the sintered body was 98% of the theoretical value.

Example 4 Silicon carbide clay contains 9 silicon carbide (average particle size 0.9 μm)
7.5 parts by weight of boron carbide (84C.

0.5 parts by weight of average particle size 1.5 μm), 2 parts by weight of carbon black, 0.3 parts by weight of peptizer (Kao Demol AS), and 16.7 parts by weight of methyl cellulose binder (Daiichi Kogyo Seiyaku Celogen). 20 parts by weight of water were measured, and a SiC molded body was obtained using the same method and apparatus as in Example 1. Both moldability and demoldability were good, and the yield was 93%. 500 molded bodies
After degreasing and removing binder in N2 atmosphere at 2160 °C
Sintered in argon for 1 hour at °C. The density was 98% of the theoretical value.

Comparative Example A lid having the shape shown in Example 1 was molded using a plaster mold without a glass wool pipe. The plaster mold was created by mixing plaster with water and pouring it into a case mold.

The same clay as in Example 1 was used.

Table 1 summarizes the blending ratio of the plastic clay, the handleability of the plastic clay, the demoldability of the molded body, etc. in the above Examples and Comparative Examples.

Comparative examples were tested 10 times, but only 4 could be removed from the mold without any defects, and the other 6 were unsatisfactory as they were broken or had cracks. The two pieces that could be demolded also had severe surface roughness, and did not have the good surface condition as in Example 1.

[Effects of the Invention] The present invention forms a ceramic plastic clay, molds a molded body using a wet compression molding method in a mold having three-dimensional network ventilation holes, and The mold can be easily demolded by supplying gas through the mold, and the use of an organic binder that is removed during degreasing facilitates molding without adversely affecting the product.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a plaster mold for preliminary testing, Fig. 2 is an explanatory diagram of a molded product in an example, and Figs. 3 (a) and (b) are perspective views of an upper case mold and a lower case mold. Figure 4 is a perspective view of the top-use type.
Figure 5 is an explanatory diagram of the wet compression molding apparatus, Figures 6 (a), (
b) is a sectional view of the upper mold and the lower mold of another embodiment. Figure Figure a Figure

Claims (1)

[Claims] A plastic clay obtained by mixing and kneading a non-plastic, non-oxide ceramic powder with a solvent and an organic binder soluble in the solvent is placed in a mold having three-dimensional network ventilation holes and compression molded. A method for manufacturing a ceramic molded body.