JPH02283660A - Production of sintered non-oxide ceramics - Google Patents

Abstract

PURPOSE:To readily obtain the title sintered product of high accuracy by mixing a non-oxide ceramic powder, a sintering aid. a specific thermoplastic resin, a lubricant, and a plasticizer, the mixture is injection-molded to give a green product, defatting the green with heat, and firing the green product. CONSTITUTION:(A) A non-oxide ceramic powder such as silicon nitride powder, (B) a sintering aid, (C) a thermoplastic resin selected from the polymers of acrylic acid, methacrylic acid and their derivatives, (D) a lubricant which decomposes at a lower temperature than the vaporization and decomposition point of component (C) such as stearic acid or wax and (E) a plasticizer which decomposes at a lower temperature than the vaporization and decomposition point of component (D) such as diethyl phthalate are homogeneously mixed with heat so that the amount of component (C) becomes 10 to 45wt.% based on 100 pts.wt. of the total amount of components (A) and (B). The resultant mixture is injection molded into a desired shape, the molded products are heated to vaporize and decompose components (D) and (E), then fired to give the subject sintered non-oxide ceramic products.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is directed to a non-oxide ceramic sintered body that is suitable for injection molding and can easily and accurately produce a sintered body having an extremely complicated shape. The present invention relates to a method of manufacturing a body.

Recently, in fields such as electronic industry, atomic crab industry, and high temperature industry, demands for materials are becoming higher and higher with the development of industrial technology. In response to such demands, interest in non-oxide ceramics, which are other than oxides and have excellent mechanical, thermal, electrical, chemical properties, etc., has increased in the ceramics field.

The main applications expected for such non-oxide ceramics are high-temperature structural materials used under harsh conditions such as gas turbine parts and high-temperature heat exchangers, chemical pump parts, engine parts, and mechanical seals. Examples include corrosion-resistant and wear-resistant materials that are used under conditions of severe corrosion and wear, but all of them are required to have complex shapes and excellent dimensional accuracy.

[Conventional technology]

As a method for manufacturing a non-oxide ceramic sintered body with a complex shape and excellent dimensional accuracy as described above, it is advantageous to sinter a preformed green body, that is, an atmospheric pressure sintering method or a reaction sintering method. It is. Known methods for molding the formed body include injection molding, transfer molding, slip casting, dry or wet pressure pressing, rubber pressing, extrusion molding, and the like.

Among these methods, the injection molding method is extremely complex, and is extremely advantageous in that it can rapidly and repeatedly manufacture products with excellent dimensional accuracy in large quantities, and it hardly requires machining as a finishing process. Various methods for producing ceramic sintered bodies using injection molding have been reported.

For example, in Japanese Patent Publication No. 51-29170, 5 to 20 parts of attack polypropylene, which is a thermoplastic resin, and 5 parts or less of each of a lubricant and a plasticizer are added as organic additives to 100 parts of ceramic raw materials, and injection molding is carried out. Discloses an injection molding composition that is used as a material for use.

[Problem to be solved by the invention]

However, the thermoplastic resin (attack polypropylene) used in this known invention has a relatively high volatile decomposition temperature. Therefore, when applying this to non-oxide ceramics for which it is inappropriate to perform degreasing in an oxidizing atmosphere, degreasing must be performed at a relatively high temperature, and the time required for degreasing is extremely long. There was a drawback.

For example, U.S. Pat. No. 4,233,256 discloses a method of manufacturing a sintered body by molding carbide ceramic powder by injection molding. , a method using styrene derivatives.

Moreover, the injection pressure during molding is approximately 4,500 to 900
0psi (approximately 697.5 to 1395 kg/c+a”)
This method requires relatively high pressure. However,
Molding the formed body under such high pressure not only causes significant wear of the injection molding machine and the mold, shortens its life, but also has drawbacks such as the contamination of the sintered body with impurities.

As a method to eliminate the above-mentioned defects, thermoplastic resin,
One possible method is to increase the amount of organic materials such as lubricants or plasticizers to improve the moldability of ceramic compositions. However, increasing the amount of the organic material added not only increases the cost required for the organic material (but also significantly increases the time required for degreasing, and furthermore, the density of the formed bodies after degreasing decreases, resulting in a high-density product). It is difficult to obtain a sintered body and is not practical.

The present invention solves the above-mentioned problems of the conventional method of molding a composition mainly consisting of a non-oxide ceramic powder, a sintering aid, and a thermoplastic resin into a formed body by injection molding. The object of the present invention is to develop a method for advantageously producing a non-oxide ceramic sintered body by improving the plastic resin to overcome the above-mentioned drawbacks.

[Means to solve the problem]

For the purpose of the upper finger, the present invention consists of the following matters: non-oxide ceramic powder, sintering aid, thermoplastic resin,
A lubricant that decomposes at a temperature lower than the volatile decomposition temperature of this thermoplastic resin and a plasticizer that decomposes at a temperature lower than the volatile decomposition temperature of this lubricant are mixed while heating to form a uniform composition. The composition is molded to create a green body with a desired shape, the green body is heated to volatilize and decompose the lubricant and the plasticizer, and degreased to obtain a defatted green body. When producing a sintered body by firing, the thermoplastic resin is made of at least one polymer selected from acrylic acid, methacrylic acid, and their derivatives, and is combined with non-oxide ceramic powder. A ceramic sintered body characterized in that 10 to 45 parts by weight are blended with respect to 100 parts by weight in total with a sintering aid, and injection molding means is used to mold the formed body using the composition. We propose a manufacturing method.

The thermoplastic resin includes at least one of acrylic acid and methacrylic acid in a proportion of 1 to 5 parts by weight, 30 to 85 parts by weight of acrylic ester, and 10 to 69 parts by weight of methacrylic ester. A material mainly composed of polymerized material is used.

[For production]

The present inventors have conducted various studies on non-oxide ceramic compositions used in manufacturing non-oxide ceramic sintered bodies suitable for injection molding, and have found the following facts. I found out.

Now, in the above-mentioned injection molding, 1) the ceramic powder particles in the injection-molded body are bonded to each other to maintain the shape of the body strictly; 2) the surface of the ceramic powder is coated and the injection-molded body is Thermoplastic resin is mainly used to protect the surfaces of the molding machine and mold from wear caused by ceramic powder.

Incidentally, many of the non-oxide ceramic powders used in the present invention are generally difficult to sinter. Therefore,
Sintering powder is used to improve sintering properties.
-A material that is finer and has a larger specific surface area than that used in the C-type injection molding method is required.

However, in the case of conventional thermoplastic resins, it has been difficult to sufficiently coat the surface of fine non-oxide ceramics with a relatively small amount added.

Therefore, some of the powder was not coated with the thermoplastic resin, so that it was not effective in improving fluidity during injection molding.

Based on this knowledge, the present inventors further conducted research to obtain a composition suitable for injection molding. As a result, the present inventors found that the coating property for the non-oxide ceramic powder was extremely good, and a relatively small amount of the composition was found to be suitable for injection molding. We have discovered a new thermoplastic resin that can achieve extremely good moldability that was previously unimaginable, regardless of the amount of compounding. Furthermore, by using such a thermoplastic resin, we have discovered a thermoplastic resin that is extremely difficult to obtain in the past. They found that it was possible to easily obtain a high-density sintered body, and completed the present invention.

According to the present invention, as the thermoplastic resin, at least one polymer mainly selected from acrylic acid, methacrylic acid, and derivatives thereof is used.

In particular, the acrylic acid derivatives are preferably acrylic esters, such as methyl acrylate, ethyl acrylate, n-propyl acrylate, and acrylic acid.
1so-propyl, n-butyl acrylate, 1so-butyl acrylate, 5ec-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, 1so-amyl acrylate, 3eC acrylate −
Using amyl, tert-7 mil acrylate, hexyl acrylate, cyclohexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, furfuryl acrylate, glycidyl acrylate, 2-ethylhexyl acrylate Among them, ethyl acrylate, n-acrylate
Propyl, 1so-propyl acrylate, n-butyl acrylate, and 2-ethylhexyl acrylate are most suitable.

Furthermore, the four HFs of methacrylic acid are preferably methacrylic esters, such as methyl methacrylate, ethyl methacrylate, n-propyl methacrylate,
1so-propyl methacrylate, n-methacrylate
Butyl, methacrylic acid-is.

Butyl, 5ec-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate, 1so-amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, dodecyl methacrylate, furfuryl methacrylate, Preference is given to using glycidyl methacrylate, 2-hydroxyethyl methacrylate, ethylene glycol dimethacrylate, β-methoxyethyl methacrylate, in particular -n-butyl methacrylate, -1so methacrylate.
-Butyl is most suitable.

According to the present invention, the thermoplastic resin contains 1 to 5 parts by weight of at least one of acrylic acid and methacrylic acid, 30 to 85 parts by weight of acrylic ester, and 10 to 69 parts by weight of methacrylic ester. It is most desirable that the main component is a copolymerized one.

By the way, when the copolymers made of acrylic acid, methacrylic acid, and their derivatives are compared with other conventionally widely used organic resins, such as polystyrene, polypropylene, polyethylene, etc., in terms of glass transition temperature and decomposition temperature, It is as shown in Table 1 below.

As shown in Table 1 above, except for polystyrene, conventional resins and the copolymer of the present invention are glass-based.

Low temperature transition and good fluidity. On the other hand, although polystyrene has a thermal decomposition temperature similar to that of the copolymer of the present invention, the other two types have a disadvantage that their volatile decomposition temperatures are significantly higher and that degreasing takes a long time.

Therefore, it can be seen that the copolymer used in the present invention is the most suitable thermoplastic resin in terms of glass transition temperature and volatile decomposition temperature when mixed with non-oxide ceramic powder.

Below, the reason why the above polymer is extremely suitable as a thermoplastic resin used when injection molding non-oxide ceramic powder will be explained in more detail.

Such a polymer has extremely good compatibility with non-oxide ceramic powder compared to other conventional thermoplastic resins used in fishing boats, and forms a composition in which the powder is sufficiently free from agglomeration. Since it can be rapidly volatile and decomposed in a non-oxidizing atmosphere at a relatively low temperature, it has the effect of easily degreasing the non-oxide ceramic powder without oxidizing it.

In the present invention, polystyrene, polymethyl methacrylate, polyethylene, polypropylene, and ethylene/vinyl acetate copolymer can be added to the thermoplastic resin as an auxiliary addition to the above polymers. However, if the amount added exceeds 50% by weight, it becomes difficult to sufficiently cover the non-oxide ceramic powder with a relatively small amount of thermoplastic resin, and the properties of the polymer are impaired. Advantageously, the amount added is less than 50% by weight. Furthermore, it is advantageous to use a thermoplastic resin that evaporates and decomposes within the range of 200 to 400°C.

In the present invention, the blending amount of the thermoplastic resin is 10 to 45 parts by weight based on 100 parts by weight of the non-oxide ceramic powder and the sintering aid. The reason for such a blending amount is that if the blending amount is less than 10 parts by weight, cracking, blistering, deformation, etc. will easily occur in the formed body, whereas if it is more than 45 parts by weight, the density of the formed body after degreasing will decrease. This is because it becomes difficult to obtain a high-density sintered body because the Among these, a range of 15 to 40 parts by weight is more suitable.

In the present invention, the composition contains a lubricant.

This lubricant has the effect of improving the fluidity of the composition during injection molding and of easily releasing the molded product from the mold. The blending amount is 2 to 2 to 100 parts by weight of the non-oxide ceramic powder and sintering aid.
The amount is preferably 12 parts by weight. Examples of the lubricant include those commonly used during injection molding, such as stearic acid, stearate, defatted acid, fatty acid-1 alcohol,
It is advantageous to use at least one selected from fatty acid esters and hydrocarbon waxes. Further, the lubricant is preferably one that volatilizes and decomposes at a temperature lower than the volatilization and decomposition temperature of the thermoplastic resin, and it is particularly advantageous to use one that volatilizes and decomposes within a temperature range of 160 to 180°C.

In the present invention, the composition contains a plasticizer. This plasticizer has good compatibility with the thermoplastic resin, has the effect of softening the resin, and has the effect of imparting fluidity to the composition and improving moldability. The total amount of the non-oxide ceramic powder and sintering aid is 10
It is preferable to use 1 to 8 parts by weight relative to 0 parts by weight.

This plasticizer is one that is normally used during injection molding, such as phthalate ester, adipate ester,
It is advantageous to use at least one selected from higher fatty acid esters, mineral oils, vegetable oils, and animal oils. The plasticizer is preferably one that volatilizes and decomposes at a temperature lower than the volatilization and decomposition temperature of the lubricant, and it is particularly advantageous to use one that volatilizes and decomposes within a temperature range of 80 to 160°C.

In the present invention, the total amount of the thermoplastic resin, lubricant, and plasticizer is within the range of 15 to 50 parts by weight based on 100 parts by weight of the non-oxide ceramic powder and sintering aid. It is preferable that there be. The reason for this is that if the total amount is less than 15 parts by weight, the moldability of the composition will be markedly deteriorated, and defects such as cracking, blistering, deformation, etc. This is because the subsequent density of the formed body becomes extremely low, making it extremely difficult to produce a high-density sintered body. The best results can be obtained when the amount is 25 to 40 parts by weight.

Examples of the non-oxide ceramics used in the present invention include silicon carbide, boron carbide, aluminum carbide,
It is preferably at least one type of carbide selected from tungsten carbide, titanium carbide, tantalum carbide, and zirconium carbide, and for example, when using silicon carbide powder, it should have a specific surface area of 8 to 50 m''/g. is preferred.

In particular, the silicon carbide powder may be one or two selected from α-type crystal, β-type crystal, and amorphous.
Silicon carbide powder consisting of more than one species can be used.

In order to produce particularly high-strength silicon carbide pressureless sintered bodies using injection molding means, it is advantageous to use silicon carbide powder containing mainly β-type crystals, and in particular, β-type crystals are
Silicon carbide powder containing 4% or more by weight is more suitable.

Examples of the non-oxide ceramics used in the present invention include silicon nitride, boron nitride, aluminum nitride,
It is preferable to use at least one kind of nitride selected from titanium nitride, tantalum nitride, and zirconium nitride. For example, when using silicon nitride powder, it is 1 to 50 m"/g.
It is preferable that it has a specific surface area of .

Note that as the non-oxide ceramic, a powder mixture of at least two or more selected from the group of carbides and nitrides can also be used.

The thermoplastic resin of the present invention can also be used for injection molding of sialon powder or metal silicon powder in addition to the carbides and nitrides that are the non-oxide ceramics.

The sintering aid used in the present invention is selected depending on the type of non-oxide ceramic and the sintering method. For example, when carbide ceramic powder is used as the non-oxide ceramic and is sintered under pressure, the sintering aid added is usually a densification aid or a carbonaceous additive, whichever is smaller (both are less). In addition, when using silicon carbide powder as the densification aid as a carbide ceramic powder, it is advantageous to mainly use a boron-containing additive.In addition, it is advantageous to use a boron-containing additive as a carbide ceramic powder. Additives can also be used as densification aids, especially boron-containing additives.
For example, it is advantageous to add at least one selected from boron and boron carbide in an amount of 0.1 to 3.0 parts by weight in terms of boron content per 100 parts by weight of silicon carbide powder.

The carbonaceous additive can be used as long as it exists in a carbon state at the start of sintering, such as phenol resin, lignin sulfonate, polyvinyl alcohol, corn starch, molasses, coal tar pitch, and alginate. , polyphenylene, polymethylphenylene, or pyrolytic carbon such as carbon black or acetylene black. Particularly when sintering silicon carbide powder, it is advantageous to add 0.3 to 4.0 parts by weight in terms of fixed carbon content per 100 parts by weight of silicon carbide powder.

The sintering aid added when reaction sintering is performed using carbide ceramic powder as the non-oxide ceramic is the uncarburized element of the target carbide or the carbonaceous additive, whichever is smaller (both are 1 type). As the carbonaceous additive, the same substances as those used in the above-mentioned pressureless sintering and various carbon materials can be used.

When nitride ceramic powder is used as the non-oxide ceramic and is sintered under pressure, a densification aid is usually used as the sintering aid.

For example, when silicon nitride powder is used as the nitride ceramic powder, at least one selected from magnesium oxide, calcium oxide, yttrium oxide, or aluminum oxide is used, and when aluminum nitride powder is used, a seed It is advantageous to use at least one selected from indium oxide and silicon dioxide as the densification aid.

The sintering aid added when reaction sintering is performed using nitride ceramic powder as the non-oxide ceramic is a non-nitrided element of the target nitride, for example, when silicon nitride is used as the nitride ceramic. In this case, metallic silicon is used as a sintering aid.

Next, a method for manufacturing a ceramic sintered body using a ceramic composition suitable for injection molding as described above will be described.

Non-oxide ceramic powder, sintering aid, thermoplastic resin,
The lubricant and desiccant material are mixed in a mixer capable of heating the inside of the container at a temperature of about 150 to 200. A ceramic composition is prepared by thoroughly mixing the mixture while heating it to a temperature of 0.5C to form a homogeneous mixture, and then cooling and solidifying the mixture, followed by crushing and sizing.

As a mixer capable of heating the inside of the container, for example, a Labo Plastomill mixer can be advantageously used.

Note that it is advantageous to uniformly mix the non-oxide ceramic powder and a sintering aid added if necessary in advance.

The composition is then formed into a product shape of the desired shape. This formed body can be molded using a conventionally known injection molding method. According to this injection molding method, a composition heated to about 160 to 210°C is sprued by a hydraulic plunger or a reciprocating screw device.
It is injected through a runner and a gate into a mold maintained at a temperature of about 20-30°C at a pressure of about 700-1400 kg/cm.However, in the present invention,
Advantageously, the temperature of the mold is maintained within the range of about 20-70°C, with the most favorable results being obtained within the range of 25-35°C. Further, according to the present invention, the pressure for injecting into the mold is about 500 to 700 kg/
c+a'', which is lower than the normally used pressure.

As a method for molding the composition, in addition to the injection molding method described above, a transfer molding method that includes injection molding means can also be used.

The composition injected into the mold as described above is left in the mold for about 1 to 60 seconds to form a hardened product, which is then removed.

The green body is then heated, and the thermoplastic resin, lubricant, and plasticizer in the green body are removed by volatile decomposition, resulting in a defatted green body. The degreasing treatment is usually advantageously carried out in a non-oxidizing atmosphere, for example argon,
Good results can be obtained when carried out in a gas atmosphere such as helium or nitrogen.

According to the present invention, the temperature increase schedule during the degreasing treatment of the green body depends on the size and volume of the green body, and particularly on the thickness of the green body, but from room temperature to molding temperature it is approximately 30°C/hr. Alternatively, it is advantageous to raise the temperature at a rate slightly higher than the molding temperature, at a rate of about 5 to 20°C/hr above the molding temperature, and finally to about 400 to 600°C for degreasing. be.

If the temperature increase rate in the degreasing treatment is too high, cracks, cracks, blisters, cave-ins, etc. may occur in the formed body, so it is advantageous to carry out the temperature increase slowly over as long as possible, and if necessary, the temperature increase schedule may be changed from the above-mentioned temperature increase schedule. You can also do it slowly.

According to the present invention, the degreased shaped body is charged into a sintering furnace and sintered. As the sintering method, various methods can be applied, and among them, either the pressureless sintering method or the reaction sintering method can be advantageously applied.

Note that the sintering step in the degreasing step can be carried out using a common furnace, but the rate of temperature increase in the former degreasing step is quite slow, and the maximum temperature used is also around 400°C. Although the temperature range is relatively low at ~600℃, the temperature increase rate in the latter sintering process does not need to be as slow as in the former degreasing process, and the sintering temperature varies depending on the sintering method. Although it is different, the temperature range is usually extremely high, 1500° C. or higher, and atmosphere control is extremely important and high airtightness is required. Therefore, it is advantageous for the degreasing process and the sintering process to use separate furnaces for each purpose.

〔Example〕

The present invention will be described below with reference to Examples.

As a non-oxide ceramic powder on dead coal,
A silicon carbide fine powder produced by the method for producing silicon carbide mainly composed of β-type crystals described in Japanese Patent No. 527 and further refined and classified for particle size was used. This silicon carbide fine powder consists of 96.2% by weight of β-type crystals, 0.38% by weight of free carbon,
It contains 0.18% by weight of oxygen and has a specific surface area of 14.2m"7g.

As the sintering aid, boron carbide powder prepared by crushing and classifying commercially available 200 mesh boron carbide grains to have a specific surface area of 21.4 m"7 g, and a boron carbide powder with an average particle size of 210 m and a specific surface area of 125 m"7 g. I used oil furnace black.

Then, 800 g of acetone was added to a mixture of 500 g of the silicon carbide powder, 6.5 g of the boron carbide powder, and 10 g of the oil furnace black, and ball milling was performed for 2 hours. The ball milled mixture slurry was dried to obtain a homogeneous mixture.

To the homogeneous mixture, 50.0 g of a resin having a molecular weight of about 20,000, which is a copolymer of 48 parts by weight of 1so-butyl methacrylate, 50 parts by weight of n-butyl acrylate, and 2 parts by weight of acrylic acid, and polystyrene were added. 33.3g and ethylene/vinyl acetate copolymer (vinyl acetate content 28% by weight) 1
6.7 g of stearic acid, 24.0 g of diethyl phthalate, and 12.0 g of diethyl phthalate were added thereto, and the mixture was heated and mixed for about 30 minutes in a laboplasto mill maintained at 180°C.

The mixture was then cooled, crushed, granulated, and passed through a 6-mesh sieve to obtain a ceramic composition for injection molding.

Molding was performed using a plunger type injection molding machine. The temperature of the heating cylinder is approximately 180℃, the temperature of the mold is 30℃,
Injection molding was carried out under the conditions that the injection time was 2 seconds and the injection pressure was 620 kg/cm''.The formed body was held in the mold for about 3 to 5 seconds and then taken out.The total weight of the formed body was 15
．． It was 2g.

The resulting product is a plate-like product with four steps as shown in Figure 1, with uniform filling properties at each step, no defects such as cavities, cracks, and cracks, and excellent surface quality. Ta.

The green body was placed in a degreasing furnace, and the temperature was raised from room temperature to 400° C. at a rate of 15° C./hr in an argon gas stream to perform a degreasing treatment to obtain a defatted green body.

Next, the degreased green body was placed in a Tammann type sintering furnace and sintered in an argon gas stream. Sintered.

was maintained at a maximum temperature of 2100°C for 30 minutes.

The obtained sintered body had a density of 3.10 g/am3.

2, +11 Ceramic compositions for injection molding were obtained using the same formulation as in Example 1, but varying the blending amounts of the thermoplastic resin, lubricant, and stabilizer as shown in Table 2.

Using this ceramic composition for injection molding, Example 1
A green body was prepared in the same manner as above and degreased.

Next, a sintered body was obtained in the same manner as in Example 1.

The results are shown in Table 2.

As can be seen from the results shown in Table 2, Comparative Example 1-10
When the blending amount of the thermoplastic resin is large, the density of the degreased formed body is low and the shrinkability during sintering is poor, making it impossible to obtain a high-density sintered body.

In addition, when the blending amount of the thermoplastic resin in Comparative Example 1-2 is small, the injection properties are extremely poor, uneven flow occurs in the mold, and the part where the composition is not filled becomes the thinnest step of the step. occured. Furthermore, when comparing Comparative Example 1-3 with Comparative Example 1-2, the injection properties were improved by increasing the amount of lubricant and plasticizer added, and the resulting shape was deformed during degreasing, causing distortion. Ta.

50 skin 1 The same formulation as shown in Example 1, but as a thermoplastic resin, a copolymer of 69 parts by weight of 1so-butyl methacrylate, 26 parts by weight of ethyl acrylate, and 5 parts by weight of methacrylic acid. So, 52.0 g of resin with a molecular weight of about 30,000 and 33.0 g of polystyrene were added. Using Og and 14.0 g of ethylene/vinyl acetate copolymer (vinyl acetate content: 40% by weight), 1
．． 17.1 g of stearic acid and 3.1 g of wax (melting point 66-68 DEG C.) were used as lubricants, and further 5.8 g of dimethyl phthalate was used as a plasticizer.

A green body was produced in the same manner as in Example 1.

The resulting product had a pincushion shape as shown in FIG. 2, had no defects such as cavities, cracks, and cracks, and had excellent surface properties.

The total weight of the formed body was 12.3 g.

The formed body was charged into a degreasing furnace, and the temperature was increased at a rate of about 70°C/hr from room temperature to 160°C in an argon gas flow, and further at a rate of about 15°C/hr from 160°C to 450°C.
Degreasing treatment was carried out by raising the temperature at a rate of r to obtain a defatted product.

Next, the degreased formed body was sintered in the same manner as in Example 1,
A sintered body was obtained.

The obtained sintered body had a density of 3.11 g/cm', and no defects such as cracks, cracks, or blisters were observed.

Raw material 11 (same formulation as shown in Example 1, but commercially available α-type silicon carbide powder (G C
#6000) is further ground, refined, and classified for particle size, and contains 0.42 wt. free carbon, 0.42 wt.
Using silicon carbide powder containing 14% by weight of oxygen and having a specific surface area of 7g of 15.4, 60 parts by weight of n-butyl methacrylate, 36 parts by weight of ethyl acrylate and 4 parts by weight of methacrylic acid were used. A ceramic composition for injection molding was obtained using 130 g of a copolymer resin having a molecular weight of about 25,000, 26.0 g of stearic acid, and 10.0 g of dimethyl adipate.

Next, a green body was produced in the same manner as in Example 1.

The formed body had the shape shown in FIG. 2, had no defects such as cavities, cracks, and cracks, and had excellent surface properties.

The total weight of the formed body was 12.5 g.

Next, the formed body was degreased in the same manner as in Example 3, and further in the same manner as in Example 1, but at a maximum temperature of 23.
The temperature was changed to 00°C to obtain a sintered body.

The obtained sintered body had a density of 3.09 g/cm3, and no defects such as cracks, cracks, or blisters were observed.

methacrylic acid was added to a homogeneous mixture of 200 g of silicon nitride powder with a purity of 98.2% by weight and a specific surface area of 7.3 m''/g and 6.0 g of yttrium oxide with an average particle size of 0.8 μm. A copolymer of 50 parts by weight of -1so-butyl, 48 parts by weight of -phthyl acrylate, and 2 parts by weight of methacrylic acid,
20.0 g of resin with a molecular weight of approximately 20,000 and 12.0 g of polystyrene.
0 g, 6.0 g of ethylene/vinyl acetate copolymer (vinyl acetate content: 28% by weight), 6.0 g of paraffin wax (melting point 66-68°C), 6.0 g of stearic acid, and 4.0 g of diethyl phthalate. A ceramic composition for injection molding was obtained in the same manner as in Example 1.

Using this ceramic composition for injection molding, Example 1
A green body was prepared in the same manner as above and degreased.

Next, the degreased shaped body was placed in a sintering furnace and sintered in a nitrogen gas stream. Sintering was maintained at a maximum temperature of 1650° C. for 4 hours.

The obtained sintered body had a density of 3.10 g/cm', and no defects such as cracks, cracks, or blisters were observed.

〔Effect of the invention〕

As explained above, according to the present invention, since a thermoplastic resin, which has not been used conventionally, is used, a non-oxide ceramic composition can be injection molded, and therefore, excellent properties can be obtained. A non-oxide ceramic sintered body having the following structure can be easily manufactured.

[Brief explanation of drawings]

FIG. 1 and FIG. 2 are perspective views of a product having a four-step shape and a product having a pincushion shape, respectively, manufactured according to the present invention and a comparative example.

Claims (2)

[Claims] 1. Non-oxide ceramic powder, sintering aid, thermoplastic resin, lubricant that decomposes at a temperature lower than the volatile decomposition temperature of this thermoplastic resin, and plasticizer that decomposes at a temperature lower than the volatile decomposition temperature of this lubricant. are mixed while heating to form a uniform composition, this composition is molded to create a formed body of a desired shape, and this formed body is heated to volatilize and decompose the lubricant and the plasticizer. When a defatted shaped body is obtained by degreasing and then the defatted shaped body is fired to produce a sintered body, the thermoplastic resin is at least one selected from acrylic acid, methacrylic acid, and derivatives thereof. When blending 10 to 45 parts by weight of a seed polymer with respect to a total of 100 parts by weight of non-oxide ceramic powder and sintering aid, and molding a formed body using the composition, A method for manufacturing a ceramic sintered body, characterized by using injection molding means. 2. The thermoplastic resin is copolymerized with at least one of acrylic acid and methacrylic acid in a proportion of 1 to 5 parts by weight, 30 to 85 parts by weight of acrylic ester, and 10 to 69 parts by weight of methacrylic ester. The manufacturing method according to claim 1, which mainly comprises: