JPH0123432B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for producing a green body for producing a ceramic sintered body for producing a high-density and high-strength ceramic sintered body. A conventional method of manufacturing a ceramic sintered body is a method in which a powder raw material is molded into a product having a desired shape and then sintered. Various means are known for molding the powder raw material into a product having a desired shape. For example, methods such as slurry casting, extrusion, potter's wheel molding, rocking molding, and dry pressure molding are known. The above-mentioned molding means can be roughly classified into wet molding means and dry molding means depending on the liquid content during molding. Among these methods, wet molding means require sufficient drying of the formed body after molding, and shrinkage due to drying must be taken into consideration.
Defects such as warping and cracking are likely to occur during drying. On the other hand, dry molding means has excellent dimensional accuracy and is a relatively advantageous molding method, but when using fine powder, the fluidity of the powder is poor, so it cannot be uniformly filled into the mold and processed. It is difficult to press, resulting in variations in the bulk density of the formed body or pressure distribution during molding, and defects due to bridging are likely to occur in the formed body. These defects during molding remain in the sintered body even after sintering, causing a significant decrease in the physical properties, especially the mechanical strength, of the sintered body. When molding, it is used after being granulated in advance to improve fluidity. Incidentally, from the viewpoint of handling such as fluidity, it is preferable that the granules have a high bulk density and are hard. It is extremely important that the individual granules are completely crushed during compression molding to obtain an integrated product, and soft granules with relatively low bulk density are usually required. This is because if the bulk density of the granules is high and hard, the granules become difficult to crush, requiring extremely high molding pressure during molding, and furthermore, voids tend to remain in the formed body, making it difficult to obtain a high-strength sintered body. This is because it becomes difficult. However, granules with too low bulk density are easily broken and re-powdered during handling, and compression during molding becomes significantly large, resulting in lamination caused by air trapped in the mold and long molding times. This method has the disadvantage that it is time consuming and difficult to efficiently produce a green body. In order to improve the above-mentioned drawbacks, molding aids such as lubricants and binders are usually added to the granules in order to improve the transmission of molding pressure and improve moldability. Known examples of the lubricant include cellulose acetate, diglycol stearate, stearic acid, magnesium stearate, zinc stearate, barium stearate, aluminum stearate, a mixture of mineral oil and fat, glycerin, polyethylene glycol, and the like. Examples of binders include starch, dextrin, gum arabic, casein, molasses, Na-carboxymethyl cellulose,
Methyl cellulose, polyvinyl alcohol, polyvinyl methyl ether, polyacrylic acid amide,
Tannic acid, liquid paraffin, wax emulsion, ethyl cellulose, polyvinyl acetate, phenol resin, cellulose acetate, glycerin, polyethylene glycol, and the like are known. By the way, relatively coarse foreign matter may be mixed into the sintered raw material for producing normal ceramic sintered bodies during the manufacturing process or during handling.
If a sintered body is manufactured using a sintered material containing such coarse foreign matter, the coarse foreign matter may cause relatively large defects such as pores and inclusions in the sintered body, causing the sintered body to deteriorate. It is important that the sintering raw material does not contain coarse foreign matter, especially when trying to obtain a sintered body with high strength and reliability, as this can cause a significant deterioration of the physical properties, especially the bending strength. can be,
The present inventors previously proposed an invention relating to a method for removing coarse foreign matter from a sintering raw material in Japanese Patent Application No. 57-48957 entitled "Method for producing high strength silicon carbide sintered body". The present invention aims to further improve the invention for which the present inventors previously applied for a patent, and has conducted various studies to produce a sintering raw material that does not contain coarse foreign matter and has an excellent molded body. As a result, the addition has the surprising effect of not having a negative effect on the dispersibility of ceramic fine powder during sieving, but rather improving the dispersibility, making sieving easier, and improving the formability of granules. This is a newly discovered and perfected agent. According to the present invention, a mixture containing ceramic fine powder as a main component consisting of one or more components is put into a dispersion medium to form a suspension, this suspension is sieved, and then any desired In a method for producing a green body for producing a ceramic sintered body which is molded into a shape, the mixture and the carboxylic acid ester are put into a dispersion medium to form a suspension, and the ceramics occupying in the suspension during the sieving process are The volume ratio of the solid content of the fine powder is within the range of 5 to 50%, and a pressure difference is provided to overcome the stagnation of the sieving action due to the pressure loss that occurs between the sieve front side and the sieve rear side of the suspension. hand,
By passing through a sieve having a mesh size of 65 μm or less, a green body for producing a ceramic sintered body with few pores and inclusions can be produced. Next, the present invention will be explained in detail. According to the present invention, by incorporating a carboxylic acid ester into a mixture mainly composed of ceramic fine powder made of one or more components, the agglomeration of the ceramic fine powder in the suspension is loosened and a uniform dispersion state is achieved. and significantly lowers the viscosity of the suspension, allowing it to easily pass through a sieve with a mesh size of 65 μm or less, and the carboxylic acid ester remains in the mixture even after drying and does not form into a pressure-molded product. It can be made into an extremely excellent sintering raw material. The carboxylic acid ester is preferably an ester made of at least one polymer selected from acrylic acid, methacrylic acid, and derivatives thereof (hereinafter referred to as polyacrylic ester). The derivatives of acrylic acid are preferably acrylic esters, such as methyl acrylate,
Ethyl acrylate, n-propyl acrylate,
Acrylic acid-iso-propyl, acrylic acid-n-
Butyl, iso-butyl acrylate, sec-butyl acrylate, tert-butyl acrylate, n-amyl acrylate, iso-amyl acrylate, sec-amyl acrylate, acrylate
tert-amyl, hexyne acrylate, cyclohexyl acrylate, octyl acrylate, nonyl acrylate, decyl acrylate, dodecyl acrylate, furfuryl acrylate, glycidyl acrylate, 2-ethylhexyl acrylate can be used, among which But ethyl acrylate, n-propyl acrylate, iso-propyl acrylate,
It has been found that n-butyl acrylate and 2-ethylexyl acrylate are optimal. The derivatives of methacrylic acid are preferably methacrylic esters, for example methyl methacrylate, ethyl methacrylate, n-methacrylate.
Propyl, iso-propyl methacrylate, n-butyl methacrylate, iso-butyl methacrylate, sec-butyl methacrylate, tert-butyl methacrylate, n-amyl methacrylate,
-iso-amyl methacrylate, hexyl methacrylate, cyclohexyl methacrylate, octyl methacrylate, dodecyl methacrylate, furfuryl methacrylate, glycidyl methacrylate, 2-hydroxyethyl methacrylate, ethylene glycol dimethacrylate, β-methoxyethyl methacrylate Among them, n-butyl methacrylate and iso-butyl methacrylate were found to be most suitable. According to the present invention, the polyacrylic ester contains 1 to 5 parts by weight of at least one of acrylic acid and methacrylic acid, and 30 parts by weight of an acrylic ester.
~85 parts by weight and 10 to 69 parts of methacrylic acid ester
Advantageously, they are copolymerized in parts by weight. The polyacrylic ester preferably has a glass transition temperature of -52 to 38.5°C and a volatile decomposition temperature of 250 to 550°C in an inert gas at 1 atmosphere. According to the present invention, the mixture contains 0.1 to 100 parts by weight of a carboxylic acid ester based on 100 parts by weight of ceramic fine powder.
It is preferable to contain 30 parts by weight. The reason is,
If the content of the carboxylic acid ester is less than 0.1 part by weight, it will be difficult to loosen the agglomeration of the ceramic fine powder in the suspension and achieve a uniform dispersion state, and furthermore, the viscosity of the suspension will be reduced by that much. On the other hand, if the amount is more than 30 parts by weight, it is not only uneconomical because more carboxylic acid ester is added than necessary.
This is because it remains in the formed body and has an adverse effect on sintering, so it is more preferably within the range of 1 to 20 parts by weight. According to the invention, the mixture contains an optionally added lubricant. The lubricant exhibits a lubricating effect by being blended into the powder and reduces molding defects that occur during molding.
The lubricant is magnesium stearate,
There are barium stearate, aluminum stearate, zinc stearate, stearic acid, cellulose acetate, glycerin, polyethylene glycol, etc., but those with a viscosity of 10 to 150 cP at room temperature and a boiling point of 100°C or higher are advantageous. It is preferable to use at least one of dihydric alcohol, trihydric alcohol, or a polymer thereof, and it has been found that the best effect can be obtained by combining glycerin, polyethylene glycol, etc. with the carboxylic acid ester. did. The amount of the lubricant added is preferably 0.1 to 15 parts by weight, particularly preferably 0.5 to 12 parts by weight, based on 100 parts by weight of the ceramic fine powder. Various types of ceramic fine powder can be used as the ceramic fine powder in the present invention, but among them, it is preferable that the ceramic powder has at least one type selected from carbides, nitrides, oxides, or compounds thereof as a main component. Preferably, carbides include silicon carbide, boron carbide, aluminum carbide,
Tungsten carbide, titanium carbide, tantalum carbide,
Zirconium carbide, nitrides such as silicon nitride, boron nitride, aluminum nitride, titanium nitride, tantalum nitride, zirconium nitride, oxides such as steatite, forsterite,
Alumina, beryllia, zircon, magnesia, mullite, cordierite, aluminum titanate,
Zirconia etc. can be used. In the present invention, the ceramic fine powder preferably has an average particle size of 2 μm or less.
This is because ceramic powder with an average particle size larger than 2 μm has relatively few contact points between particles and has poor sinterability, making it difficult to produce a high-density sintered body. As the ceramic fine powder in the present invention, one whose main components are silicon carbide fine powder having a specific surface area of 5 to 100 m ² /g and a sintering aid added if necessary can be most preferably used. As the silicon carbide fine powder, silicon carbide fine powder consisting of one or more types selected from α-type crystal, β-type crystal, and amorphous can be used. In particular, in order to produce high-strength silicon carbide pressureless sintered bodies, it is advantageous to use silicon carbide fine powder containing mainly β-type crystals, and in particular, silicon carbide fine powder containing 80% by weight of β-type crystals. is more suitable. The sintering aid added as necessary is usually at least one of a densification aid and a carbonaceous additive. It is advantageous to use mainly boron-containing additives as the densification aid, and other additives such as beryllium,
Additives containing aluminum and the like can also be used. As the boron-containing additive, for example, at least one selected from boron and boron carbide is converted into silicon carbide fine powder in terms of boron content.
It is advantageous to add from 0.1 to 3.0 parts by weight per 100 parts by weight. The carbonaceous additive can be used as long as it exists in a carbon state at the start of sintering, such as phenolic resin, coal tar pitch, polyphenylene, polymethylphenylene, carbon black, and acetylene black. At least one of the selected types is converted into fixed carbon content of 0.3 parts by weight per 100 parts by weight of silicon carbide fine powder.
It is advantageous to add up to 4.0 parts by weight. According to the present invention, the volume ratio of the solid content of ceramic fine powder in the suspension during the sieve treatment is within the range of 5 to 50%, and the space between the front side of the sieve and the back side of the suspension is By applying a pressure difference to overcome the stagnation of the sieving action due to the pressure loss that occurs in the suspension, and passing it through a sieve with a sieve mesh of 65 μm or less while applying vibration to the suspension, the strength of the sintered body is significantly increased. The causes of relatively large defects such as pores and inclusions that cause deterioration in the sintered body are eliminated. According to the present invention, a mixture containing ceramic fine powder as a main component is added to a dispersion medium, and the volume ratio of the solid content of ceramic fine powder in the suspension during sieving is controlled to be within the range of 5 to 50%. It is necessary to do something. The reason for this is that if the volume ratio is higher than 50%, it is difficult to uniformly disperse the ceramic fine powder, and the viscosity of the suspension becomes extremely high, making it difficult to pass through the sieve efficiently.
On the other hand, if it is lower than 5%, the uniform dispersion of ceramic fine powder in the suspension will improve, but a large amount of suspension must be sieved, and the actual throughput per unit equipment is small, which is not economical. Among them, suitable results can be obtained within the range of 10 to 40%. According to the present invention, water is mainly used as the dispersion medium used during the sieving process. According to the present invention, a dispersant is added to the suspension if necessary. Examples of the dispersant include tetramethylammonium hydroxide, monoethanolamine, monoethylamine, diethylamine, trimethylamine, propylamine, isobutylamine, monobutylamine, di-n-propylamine, tannic acid, sodium alginate, ammonium alginate, polyacrylic acid. , polyacrylic acid amine, polyacrylic ammonium, sodium lignin sulfonate, ammonium lignin sulfonate, sodium aluminate, ammonium aluminate, water glass, fatty acid salt, alkylbenzene sulfonate, linear alkyl sulfonate, α-
Olefin sulfonate, sulfonate of naphthalene-formalin condensate, polyoxyethylene alkyl phenyl ether, etc. can be used. Note that the dispersion state can also be improved by adjusting the pH value of the suspension with aqueous ammonia or the like. Advantageously, the PH value is in the range from 5.5 to 11. The dispersant has the effect of loosening the agglomeration of ceramic fine powder in the suspension, improving the uniform dispersibility of ceramic fine powder with different specific gravity and particle size, and lowering the viscosity of the suspension so that it can pass through a sieve. It has the effect of making it easier. According to the present invention, a deflocculant or an antifoaming agent can also be added to the suspension. According to the present invention, the suspension is subjected to uniform dispersion treatment in advance in order to efficiently pass through a sieve. The uniform dispersion treatment is carried out using a vibrating mill, an attritor,
This can be advantageously carried out using at least one dispersion device selected from a ball mill, a colloid mill, a Henschel mixer, or a high-speed mixer. According to the present invention, the suspension can be sieved more efficiently and quickly by providing a pressure difference to overcome the stagnation of the sieving action due to the pressure loss occurring between the sieve front side and the sieve back side of the suspension. can be passed through. According to the present invention, it is preferable that the pressure applied to the front side of the suspension to be sieved is varied at a period of 1/400 to 5 seconds. The advantage of varying the pressure applied to the sieve front side of the suspension is that the flow of the suspension in the sieve can be significantly disturbed by pressure fluctuations, further improving the dispersibility of the ceramic fine powder in the sieve. This is because particles can be prevented from aggregating with each other and can be efficiently passed through the sieve. In addition, the period of the pressure fluctuation is set to 1/400 to 5
The reason why it is preferable to set the period within the range of 1/400 seconds is that if the period is shorter than 1/400 seconds, the transmission of pressure fluctuations in the suspension will be significantly deteriorated, which is not efficient, whereas if it is longer than 5 seconds, the sieve This is because the effect of pressure fluctuation is small because the flow of the suspension cannot be disturbed to that extent, especially when the flow is 1/100~
Optimal results are obtained within 2 seconds. According to the present invention, the difference between the maximum and minimum pressures applied to the front side of the suspension is at least 0.3Kg/
^cm2 , and when the pressure applied to the front side of the suspension is maximum, the pressure difference between the front side of the sieve and the back side of the sieve is 0.2
The pressure difference between the front side of the sieve and the back side of the sieve is within the range of ~5Kg/ ^cm2 , and the pressure difference between the front side of the sieve and the backside of the sieve when the pressure applied to the rear side of the sieve is the minimum is -0.5~2Kg/ ^cm2 . Get results. Note that the pressure difference is a value obtained by subtracting the pressure value on the back side of the sieve from the pressure value on the front side of the sieve. Various means can be considered as a means for applying pressure to the suspension, but among them, a means using a pulsating pump is capable of applying pressure to the suspension while applying pressure fluctuations, and at the same time applying vibration. This is extremely advantageous. For example, a diaphragm pump can be used as the pulsating pump. Further, according to the present invention, vibrations are applied to the suspension if necessary. By applying vibration to the suspension, it is possible to prevent the suspended ceramic fine powder from aggregating with each other and maintain a uniformly dispersed state,
Furthermore, by applying vibrations of appropriate strength to the suspension, the viscosity of the suspension can be significantly lowered, allowing it to pass through a sieve easily. The vibration applied to the suspension is preferably within the range of 0.1 to 400 Hz. The reason for this is that if the frequency is lower than 0.1Hz, it is difficult to maintain uniform dispersion of the suspension or reduce the viscosity, while if it is higher than 400Hz, vibrations into the suspension are difficult to maintain. This is because the transmittance deteriorates significantly, making it difficult to maintain uniform dispersion of the suspension or reduce the viscosity, as in the case of low vibration frequencies.
Optimal results are obtained when applying vibrations in the range of 0.5-100Hz. As the vibrations applied to the suspension, at least one selected from, for example, mechanical vibrations, vibrations applied by electromagnetic force, and vibrations applied by a pulsating pump can be advantageously used. According to the present invention, it is necessary that the mesh size of the sieve is 65 μm or less. If the mesh size of the sieve is larger than 65 μm, coarse foreign matter that significantly affects the physical properties of the sintered body cannot be removed, and the object of the present invention is to obtain a sintered body with high strength and high reliability. This is because it becomes difficult to obtain a sintered body with even higher strength and reliability.
It is advantageous that: In addition, the sieving date is
For the purpose of removing foreign substances from the mixture, it is advantageous for the mesh size of the sieve to be as small as possible;
Foreign matter small enough to pass through a 5 μm sieve has little effect on the strength of the sintered compact, and if a sieve with a sieve mesh smaller than 5 μm is used, the time required to pass through the sieve becomes significantly longer. Therefore, it is not practical, and it is advantageous that the sieve mesh is within the range of 5 to 44 μm. According to the present invention, the suspension that has passed through the sieve is dried to remove the dispersion medium, and then a product form is produced in the form of a dry mixture by a dry molding method such as a dry pressure molding method. Ru. According to the invention, the dry mixture can contain a forming aid which has the effect of a binder. Examples of the molding aids include starch, dextrin, gum arabic, casein, molasses, Na
- Carboxymethyl cellulose, methyl cellulose, polyvinyl alcohol, polyvinyl methyl ether, polyacrylic acid amide, tannic acid, liquid paraffin, wax emulsion, ethyl cellulose, polyvinyl acetate, phenol resin, cellulose acetate, glycerin, polyethylene glycol, etc. Type 1 or 2
It is possible to contain more than one species. According to the present invention, the mixture is granulated to improve its fluidity before use. The powder bulk density of the mixture is 5 to 46% of the theoretical density.
Preferably, the granules have a density corresponding to . The reason why the bulk density of the powder is set within the above range is that if the bulk density of the powder is less than 5%, the compression ratio during molding becomes extremely large, making molding difficult. If the size is larger, the particle size distribution of the granules may be relatively wide or the apparent granule density may be high, but in the former case, the fluidity deteriorates, and in the latter case, the crushing strength of the granules is extremely strong. This is because it may remain in the same shape without being crushed during molding, resulting in areas with extremely low density in the sintered body, and a range of 10 to 40% is particularly preferable. The powder bulk density refers to the volume of ceramic fine powder that occupies a certain volume of granules.
In other words, it is the volume of ceramic fine powder that occupies a unit volume including the solid, internal voids, and external voids, and is the apparent granule density.
"density" is the volume of ceramic fine powder that occupies a unit bulk volume, and bulk volume is the volume that includes the ceramic fine powder that occupies the granules and internal voids. Preferably, the mixture is in the form of granules with an average particle size within the range of 0.02 to 0.8 mm. The reason for this is that when the average particle size of the granules is less than 0.02 mm, the fluidity is significantly reduced, causing variations in the bulk density of the formed body and pressure distribution during molding, and defects due to bridging are likely to occur in the formed form. On the other hand, if it is larger than 0.8 mm, it is difficult to mold a small and complex shaped product. As a method for granulating the mixture, any one selected from, for example, a tablet method, a direct granulation method, a granulation method by spray drying, or a granulation method involving spray freezing and then freeze drying can be used. can. According to the invention, it is advantageous for the mixture to be pressed into a shaped body having a density corresponding to at least 45% of the theoretical density. The reason for this is that when the density is lower than 45%, there are relatively few contact points between the ceramic fine powder particles, making it difficult to uniformly progress the firing shrinkage during sintering, and making it difficult to obtain a high-density sintered body. This is because it becomes difficult to obtain a high-strength sintered body due to variations in physical properties such as the density of the sintered body.In particular, when a high-strength sintered body is required, the density should be increased by 50%. It is effective to do the above. In addition, as a method for pressure molding the mixture, it is advantageous to use, for example, a press molding method or a hydrostatic molding method. According to the present invention, a high-density and high-strength ceramic sintered body can be manufactured by charging the green body manufactured as described above into a sintering furnace and sintering it. Next, the present invention will be explained with reference to examples. Example 1 97.3% by weight consists of β-type crystals, contains 0.40% by weight of free carbon, 0.17% by weight of oxygen, 15.6 m ² /
500 g of silicon carbide fine powder with a specific surface area of 22.7 g
6.5 g of boron carbide powder with a specific surface area of m ² /g
and 10 g of carbon black with an average particle size of about 210 Å and a specific surface area of 124 m ² /g.
25 g of polyacrylic ester having a molecular weight of approximately 20,000, which is a copolymer of 50 parts by weight of n-butyl acrylate and 2 parts by weight of acrylic acid, 5 g of polyethylene glycol (300), and 2 g of tetramethylammonium hydroxide. After adding 450 ml of distilled water and carrying out dispersion treatment for 10 hours using a ball mill, the suspension was discharged from the ball mill, and a diaphragm was applied to the suspension while applying 12 Hz vibration to the suspension using an electric vibrator. A pump was used to pressurize the front side of the suspension to pass through the sieve. The sieve used had a sieve mesh of 25 μm and a sieve frame diameter of 200 mmφ, and ultrasonic vibrations of 26 KHz and 600 W were applied to the suspension near the sieve portion on the front side of the sieve. The maximum value of the pressure applied to the suspension is 2.5
Kg/cm ² , the minimum value was 0.2 Kg/cm ² , the fluctuation period was 1 second, and the pressure applied to the suspension on the back side of the sieve was released to the atmosphere. The suspension under the sieve passed through the sieve was heated to -60 to -70℃.
The average particle size is 0.11mm when sprayed into a container maintained at
Frozen granules were obtained. Next, the frozen granules are placed in a container maintained at 0.01 to 20 mmHg and -5 to -10°C, and freeze-dried to determine the bulk density of the powder.
A granular dry mixture of 0.51 g/cm ³ was obtained. An appropriate amount of the granules was taken and pre-molded using a metal mold at a pressure of 0.15 t/cm ² , and then molded using a hydrostatic press at a pressure of 1.8 t/cm ² . The density of the formed body obtained by the above molding is 1.89 g/
cm ³ was observed. The resulting green body was placed in a Tammann-type firing furnace and sintered in an argon gas stream. The heating rate is from room temperature to
The temperature was raised at a rate of 5°C/min up to 1650°C, and after being held at 1650°C for 45 minutes, the temperature was further raised at a rate of 5°C/min, and the maximum temperature was held at 2100°C for 30 minutes. The density of the obtained sintered body was 3.09 g/cm ³ (corresponding to 96.4% of the theoretical density). This sintered body is
It was processed into a rod shape of ×3 × 30 mm, and finally polished with 2 μm diamond abrasive grains.The three-point bending strength was measured at a span of 20 mm and a crosshead speed of 0.5 mm/min, which was 71.7 Kg/mm at room temperature. It was confirmed that the sintered body had an average strength of ² and a Weibull coefficient of 12, making it extremely dense and highly reliable. Note that the measurement of the three-point bending strength is
The test was carried out on 30 specimens, and the Weibull coefficient was determined using Weibull probability paper. The Weibull coefficient is a value determined from the relationship between fracture stress and survival probability in Weibull statistics, which is used as a statistical representation of ceramic strength, and is used as a measure of reliability of strength. be. Example 2, Comparative Example 1 Same as Example 1, but as shown in Table 1,
A sintered body was obtained by creating a green body by changing the blending amounts of polyacrylic acid ester and polyethylene glycol, sieving conditions, molding conditions, etc. The results were measured in the same manner as in Example 1 and are shown in Table 1.

【table】

[Table] When the amount of polyacrylic ester blended in Comparative Example 1-1 was small, even though the concentration of the suspension was extremely low, dispersion was insufficient and a portion of the mixture remained on the sieve. Ivy. On the other hand, Comparative Example 1-2
When the blending amount of polyacrylic ester was too large, the strength of the sintered body deteriorated. The reason for this is thought to be that some defects occurred in the formed body during degreasing. Further, in Comparative Example 1-3, the viscosity of the suspension was extremely high and sieving could not be performed. Example 3 The formulation and operation were the same as in Example 1, but as silicon carbide fine powder, 96.1% by weight consisted of β-type crystals, contained 0.42% by weight of free carbon, 0.20% by weight of oxygen, and 36.8 m ² Silicon carbide fine powder having a specific surface area of /g, 50 parts by weight of iso-butyl methacrylate, 48 parts by weight of n-butyl acrylate, and 2 parts by weight of methacrylic acid.
A polyacrylic acid ester with a molecular weight of approximately 20,000 parts by weight was used instead of polyethylene glycol, and the molding pressure was changed as shown in Table 2 to create a green body, and sintered. I got a body. The results were measured in the same manner as in Example 1 and are shown in Table 2.

[Table] As shown in Table 2, according to the present invention, a sintered body with extremely high strength and reliability could be produced even at a relatively low molding pressure. Example 4 For ceramic fine powder consisting of 300 g of silicon carbide powder with a purity of 98.2% by weight and a specific surface area of 7.3 m ² /g and 36 g of yttrium oxide with an average particle size of 0.8 μm,
A copolymer of 69 parts by weight of iso-butyl methacrylate, 26 parts by weight of ethyl acrylate, and 5 parts by weight of methacrylic acid, 13 g of polyacrylic acid ester with a molecular weight of approximately 30,000, 10 g of glycerin, and a sulfone of a naphthalene-formalin condensate. After adding 1.5 g of the acid salt and 200 ml of distilled water and carrying out dispersion treatment for 6 hours using a vibration mill, the suspension was discharged from the vibration mill. is 10Hz, the maximum value of the pressure applied to the suspension is 2.0Kg/cm ² , and the minimum value is 0
Kg/cm ² , and the sieving process was performed with a fluctuation period of 1/2 second. The under-sieve suspension passed through the sieve was spray-dried to obtain granules with an average particle diameter of 0.13 mm and a powder bulk density of 0.82 g/cm ³ . An appropriate amount of the granules was collected and subjected to the same procedure as in Example 1 to obtain a product weighing 1.93 g/cm ³ . Next, the green body was placed in a Tammann-type firing furnace and sintered in a nitrogen gas stream. Sintering at 5℃/
The temperature was raised at 1,650° C. for 1 hour. The obtained sintered body had a theoretical density of 3.16 g/cm ³ (98.8
%). In addition, the three-point bending strength measured in the same manner as in Example 1 was 83.3Kg/3 at room temperature.
It had an average strength of mm ² and a Weibull coefficient of 13. Example 5 Calcined α- with a purity of 99.9% by weight and an average particle size of 5 μm
A copolymer of 60 parts by weight of n-butyl methacrylate, 36 parts by weight of ethyl acrylate, and 4 parts by weight of methacrylic acid was added to a fine ceramic powder consisting of 300 g of alumina powder and 6 g of magnesium fluoride with an average particle size of 3 μm. is approximately 25,000 polyacrylic acid ester 6g and polyethylene glycol (300)
After adding 3 g of alkylbenzene sulfonate, 2 g of alkylbenzene sulfonate, and 200 ml of distilled water and performing dispersion treatment for 7 hours using an attritor, the attritor was discharged, and sieving was performed in the same manner as in Example 4 to obtain an average Granules with a particle size of 0.10 mm and a powder bulk density of 1.03 g/cm ³ were obtained. An appropriate amount was taken from the granules and subjected to the same procedure as in Example 1 to obtain a product weighing 2.37 g/cm ³ . Next, the formed body was placed in a Tanmann-type firing furnace and maintained at 1900°C for 1 hour. The obtained sintered body had a theoretical density of 3.92 g/cm ³ (98.6
%). In addition, the three-point bending strength measured in the same manner as in Example 1 was 35.2Kg/35.2Kg at room temperature.
It had an average intensity of mm ² and a Weibull coefficient of 25. As described above, according to the method of the present invention, by mixing a carboxylic acid ester when suspending ceramic fine powder in a dispersion medium, the agglomeration of the ceramic fine powder in the suspension is loosened and a uniform dispersion state is achieved. None, it can be easily sieved, and even after drying, the pressure moldability is extremely good, and the moldability is even better when used in combination with a lubricant such as glycerin or polyethylene glycol. As a result, it is possible to produce a green body with high density and few molding defects even at a relatively low molding pressure.By sintering this green body, it is possible to produce a green body with extremely low defects and high density. It is possible to produce a strong ceramic sintered body and is extremely useful industrially.

Claims (1)

[Scope of Claims] 1. A mixture of one or more components, the main component of which is ceramic fine powder, is put into a dispersion medium to form a suspension, this suspension is sieved, and then optionally In the method for producing a green body for producing a ceramic sintered body, the mixture and the carboxylic acid ester are put into a dispersion medium to form a suspension, and the mixture and the carboxylic acid ester are added to a dispersion medium to form a suspension, and the sieving process comprises the steps of: The volume ratio of the solid content of the ceramic fine powder is within the range of 5 to 50%, and a pressure difference is created to overcome the stagnation of the sieving action due to the pressure loss that occurs between the sieve front side and the sieve back side of the suspension. Giving,
A method for producing a green body for producing a ceramic sintered body with few pores, inclusions, etc., characterized by passing it through a sieve having a sieve size of 65 μm or less. 2. The manufacturing method according to claim 1, wherein the carboxylic acid ester is made of at least one polymer selected from acrylic acid, methacrylic acid, and derivatives thereof. 3 The carboxylic acid ester is contained in an amount of 0.1 to 30 parts by weight based on 100 parts by weight of the ceramic fine powder.
Manufacturing method described in section. 4 The ceramic fine powder contains carbide, nitride,
The manufacturing method according to any one of claims 1 to 3, wherein at least one selected from oxides and compounds thereof is used. 5 The ceramic fine powder has an average particle size of 2 μm.
The manufacturing method according to any one of claims 1 to 4, which is the following fine powder. 6. The silicon carbide fine powder of the ceramic fine powder has a specific surface area of 5 to 100 m ² /g.Claims 1, 3, 4, and 5
The manufacturing method described in section. 7 A patent characterized in that when applying a pressure difference between the front side of the sieve and the back side of the suspension, the pressure difference is varied at a cycle within a range of 1/400 to 5 seconds. The manufacturing method according to any one of claims 1 to 6.