Method of manufacturing ceramic fired body, and composition for molding

Abstract

To provide a composition for molding and a method of manufacturing a ceramic fired body, which can obtain a sound degreased body free from cells, swellings, and cracks in its inside.SOLUTION: A method uses a composition for molding that includes 30-70 vol.% of a ceramic powder with an average particle diameter of 1.0 μm or under and 30-70 vol.% of an organic binder, wherein the organic binder includes 15-50 vol.% of a thermoplastic resin (A) that does not melt or swell in an organic solvent, 5-40 vol.% of a thermoplastic resin (B) bearing polar groups, and 30-75 vol.% of an organic compound (C) that is soluble in an organic solvent and has a melting point of 70°C or under, wherein the method includes steps of: obtaining a molding by using an injection molder or extruder from the composition for molding; a step of extracting and degreasing, by using a solvent, the organic compound (C) contained in the composition for molding in an amount corresponding to 30 vol.% or more of the organic binder, at a temperature of 40°C or over and 80°C or under; heating the molding after extracting and degreasing for degreasing the residual organic binder; and firing the ceramic molding.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to an extrusion molding composition, an injection molding composition, and a debinding method for use in a method of manufacturing a molded body using ceramic powder having an average particle size of 1 μm or less that can be fired by injection molding and extrusion molding, and manufacturing a fired body product from this molded body.

Background Art

[0002] When injection molding and extrusion molding of ceramics, it is necessary to add an organic binder to process into a desired shape. The organic binder is necessary for imparting a shape during molding, and it is necessary to remove the added organic binder by heating. The conventional injection molding and extrusion molding processes are shown in FIG. 1. In recent years, there has been a strong demand for ceramic products with as high a firing density as possible in order to improve the strength, heat resistance, thermal conductivity, etc. of ceramics. In order to increase the firing density, it is necessary to use powder with as fine an average particle size as possible of 1 μm or less. Depending on the organic binder, residual carbon may remain unless the binder is removed in an inert gas. Further, when the particle size of the powder becomes 1 μm or less, the heat debinding time exceeds 24 hours. In the case of a molded body having a wall thickness exceeding 10 mm, cracks and swelling often occur during heat debinding even when the heat debinding time is 100 hours or more. In order to solve the above problems, an extraction debinding method is known, and Patent Document 1 and Patent Document 2 disclose a debinding method using water.

[0003] When water is used as the solvent to be extracted, it is necessary to use a water-soluble binder. However, when storing and regenerating the molding material and the molded body, the moisture absorption rate increases, which may lead to a decrease in the fluidity and strength of the molded body. In addition, when the molding material contains moisture, it becomes difficult to regenerate the material due to the occurrence of mold and the like. Further, when water is used as the extraction solvent, the boiling point is 100 °C. Among general non-aqueous organic solvents such as ketone-based organic solvents, aromatic-based organic solvents, and chlorine-based organic solvents, the boiling point is 100 °C or lower, and the vapor pressure is also smaller than that of water in many cases. Therefore, in extraction degreasing using water, the drying time becomes longer compared to extraction degreasing using an organic solvent.

[0004] In addition, Patent Documents 3 and 4 and Non-Patent Documents 1 and 2 describe a method of performing extraction degreasing of an injection molded body obtained by adding an organic binder to metal powder with an organic solvent. However, when this method is applied to ceramic powder to create a molded body and extraction degreasing is performed with an organic solvent, swelling occurs in the molded body in the extraction degreasing process, and it is difficult to obtain a sound degreased body after extraction degreasing. The powder used in the metal powder injection molding method has an average particle size of about 5 to 10 μm. Compared with the average particle size in ceramic powder molding of about 0.1 to 1 μm, the particle size is about 10 to 100 times larger. Therefore, even if the resin component in the binder used does not dissolve in the organic solvent, it is possible to soundly extract and degrease the metal powder molded body to the extent of swelling. On the other hand, in injection molding and extrusion molding using ceramic powder with a smaller particle size than metal powder, it becomes difficult for the organic solvent to easily escape from the molded body due to the small powder particle size, and swelling and cracks occur in the extraction degreasing process.

[0005] In addition, Patent Document 5 describes a method of performing extraction debinding using ceramic powder, polyethylene, polypropylene, or polyacetal as an organic binder, and a ketone-based organic solvent, halogen-based organic solvent, hydrocarbon-based organic solvent, or aromatic-based organic solvent as an extraction solvent. Also in Patent Document 5, when powder with a particle size of 0.1 μm or less is used and the wall thickness becomes 3 mm or more, cracks are likely to occur during extraction debinding. Further, although a halogen-based solvent is used in the examples, restrictions are imposed not only on the use of chlorine-based organic solvents but also on the use of bromine-based organic solvents from the perspective of environmental issues, so it is necessary to pay attention to the restrictions on the solvents to be used. Moreover, there is also a problem that cracks are likely to occur when a molded body with a complex shape is created. Recently, it has been confirmed in many technical documents that firing at a low temperature is often possible by using powder with a fine average particle size of 0.1 μm or less (Non-Patent Document 3). However, when powder with an average particle size of 0.1 μm or less is used, it is not easy to prevent cracks from occurring in the above conventional extraction debinding method, and it is very difficult to obtain a sound fired body.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Non-Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, the present invention provides a method for manufacturing a ceramic fired body, which can produce a molded body with a complex shape in injection molding and extrusion molding of ceramic powder, and can perform the extraction and debinding process in a short time using an organic solvent such as acetone or alcohol, and can prevent the swelling and generation of bubbles in the ceramic fired body in the debinding process and the firing process of the ceramic molded body, as well as a molding composition used in the manufacturing method.

Means for Solving the Problems

[0009] One embodiment of the present invention is a method for manufacturing a ceramic fired body using a molding composition containing 30-70% by volume of ceramic powder with an average particle size of 1.0 μm or less that can be fired and 30-70% by volume of an organic binder, wherein the organic binder comprises: A thermoplastic resin (A) that does not melt or swell in an organic solvent; A thermoplastic resin (B) having a polar group; An organic compound (C) having a melting point of 70 or less that is soluble in an organic solvent; and an organic binder, and comprises The thermoplastic resin (A) is contained in an amount such that the proportion thereof in the total organic binder is 15-50% by volume, The thermoplastic resin (B) is contained in an amount such that the proportion thereof in the total organic binder is 5-40% by volume, The organic compound (C) is contained in an amount such that the proportion thereof in the total organic binder is 30-65% by volume. The method for manufacturing a ceramic fired body comprises the following steps: Obtaining a molded body from the molding composition using an injection molding machine or an extrusion molding machine; Using a solvent capable of eluting the organic compound (C) in the obtained molded article, extracting and defatting an amount of the organic compound (C) corresponding to 30% by volume or more of all the organic binders in the molding composition at a temperature of 40°C or higher and 80°C or lower; Heating the molded article after extraction and defatting to defat the organic binder remaining in the molded article to obtain a ceramic molded article; Firing the ceramic molded article to obtain a ceramic fired body; A method for producing a ceramic fired body, comprising: Furthermore, a second embodiment of the present invention is a molding composition comprising 30-70% by volume of a ceramic powder having an average particle size of 1.0 μm or less that can be fired and 30-70% by volume of an organic binder, wherein the organic binder comprises: A thermoplastic resin (A) that does not melt or swell in an organic solvent; A thermoplastic resin (B) having a polar group; An organic compound (C) having a melting point of 40°C to 60°C that is soluble in an organic solvent; and The thermoplastic resin (A) is contained in an amount such that the proportion in the total organic binder is 15-50% by volume, The thermoplastic resin (B) is contained in an amount such that the proportion in the total organic binder is 5-40% by volume, The organic compound (C) is contained in an amount such that the proportion in the total organic binder is 30-70% by volume. The molding composition is as described above.

Advantages of the Invention

[0010] By using the molding composition and the defatting method according to the present invention, in injection molding and extrusion molding using a ceramic powder with a particle size of 1 μm or less, for a molded article with a complex shape, by using a solvent such as acetone or alcohol and performing the extraction defatting process and the heating defatting process in a short time, the obtained defatted body is also a defatted body without defects such as swelling and cracking. As a result, a sound fired body can be obtained in a short time.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Mode for Carrying Out the Invention

[0012] One embodiment relates to a manufacturing method for obtaining a ceramic fired body by, for example, the scheme shown in FIG. 2. Specifically, a mixture of ceramic powder and an organic binder is used as a raw material (molding composition), and a molded body is obtained by a molding method such as an injection molding method or an extrusion molding method using, for example, an injection molding machine or an extrusion molding machine. Then, this molded body is degreased and fired to obtain a ceramic fired body which is the target product. Here, a molding composition containing ceramic powder, a resin component that does not swell in an organic solvent, a thermoplastic resin having polarity, and an organic binder containing an organic compound soluble in an organic solvent can be used. From the molding composition, a molded body can be obtained, for example, in the temperature range of 140°C to 200°C by a molding method such as an injection molding method or an extrusion molding method. Next, for the molded body, first extraction degreasing is performed using an organic solvent containing acetone, alcohols, etc., and then degreasing by heating is performed. The extraction degreasing of the molded body can be carried out, for example, using the extraction degreasing apparatus shown in FIG. 5, using an organic solvent containing an organic compound (C) and acetone or an alcohol-based solvent, and performing extraction degreasing at a temperature of 50°C to 80°C for 1 to 12 hours. In the extraction degreasing step, as shown in FIG. 5, the molded body is immersed in the extraction solvent to extract the organic compound (C). More than 30% by volume of the total organic binder can be removed in the extraction degreasing step, and a ceramic molded body can be obtained after extraction degreasing. Any organic solvent that can elute the organic compound (C) can be used here, but it preferably contains acetone or an alcohol-based solvent such as methanol, ethanol, isopropyl alcohol, etc., and an organic solvent obtained by mixing acetone and an alcohol-based solvent can also be used as the extraction solvent. Such a degreasing method results in the production of a ceramic molded body with a complex shape, shortens the time for degreasing, and enables the production of a ceramic molded body without cracks or swelling as compared with the prior art.

[0013] The thus obtained molded body after extraction and defatting can produce a defect-free ceramic molded body even at a rapid heating rate such as 50°C / hr in the subsequent defatting process by heating. After the completion of the extraction and defatting process, heating defatting is carried out by heating in air or nitrogen to a temperature in the range of 500°C to 800°C at a heating rate of 2 to 20 hours and holding at the maximum temperature for 0.5 to 2 hours. In the heating defatting process, when the heating time is less than 2 hours, the defatted molded body is likely to crack or swell. Heating can be carried out using, for example, an electric heater, an oven, superheated steam, etc. The obtained defatted molded body is fired in an atmosphere and at a temperature suitable for the ceramic powder used (for example, a temperature in the range of 900°C to 2300°C) to obtain a ceramic fired body.

[0014] The second embodiment of the present invention is a molding composition. The molding composition of the second embodiment is preferably used in the manufacturing method of the first embodiment. The molding composition of the second embodiment contains 30 - 70% by volume of a ceramic powder having an average particle size of 1.0 μm or less that can be fired and 30 - 70% by volume of an organic binder. Here, the organic binder includes a thermoplastic resin (A) that does not melt or swell in an organic solvent, a thermoplastic resin (B) having a polar group, and an organic compound (C) having a melting point of 40°C to 60°C that dissolves in an organic solvent; and is characterized by including the organic binder.

[0015] In particular, the addition amounts of the organic binder are formulated such that the thermoplastic resin (A) is 15 - 50% by volume based on the volume of the organic binder, the thermoplastic resin (B) is 5 - 40% by volume based on the volume of the organic binder, and the organic compound (C) is 30 - 75% by volume based on the volume of the organic binder. Such an organic binder and a ceramic powder that can be fired are preferably mixed so as to have a volume ratio of 30:70 to 70:30. As the ceramic powder used in the molding composition of the second embodiment, oxide ceramics such as alumina, zirconia, magnesia, and titania, nitride ceramics such as aluminum nitride and silicon nitride, and carbide ceramics such as silicon carbide and boron carbide can be mentioned. The average particle size of the ceramic powder used in the manufacturing method of one embodiment is preferably 0.01 μm or more and 1 μm or less. When the particle size is less than 0.01 μm, the amount of the organic binder required for molding increases, so defects such as deformation, cracking, and swelling are likely to occur in the ceramic molded body during extraction degreasing or heat degreasing. When the average particle size of the ceramic powder is larger than 1 μm, firing does not proceed sufficiently in the firing process of the ceramic molded body, and it becomes difficult to obtain a high-strength ceramic fired body with high density. Here, in this specification, the average particle size means the average diameter at 50% weight cumulative measured using a particle size distribution measuring device using the laser diffraction / scattering method. As the particle size distribution measuring device, SALD-2000 type manufactured by Shimadzu Corporation can be used.

[0016] The thermoplastic resin (A) that does not melt or swell with respect to the organic solvent and is used in the molding composition of the second embodiment is a non-polar thermoplastic resin. For example, one or a mixture of two or more selected from the group consisting of high-density polyethylene, polypropylene homopolymer, polypropylene block copolymer, and polyacetal can be mentioned. The thermoplastic resin (A) that does not melt or swell with respect to the organic solvent is contained in the organic binder at 15 to 50% by volume, preferably 20 to 45% by volume, and more preferably 25 to 35% by volume. When the content of the thermoplastic resin (A) in the organic binder is less than 15% by volume, the molded body formed from the molding composition may become brittle. In addition, swelling and cracking may occur in the ceramic molded body obtained by degreasing the molded body. When the content of the thermoplastic resin (A) in the organic binder is more than 50% by volume, the viscosity during molding becomes high, and it becomes difficult to mold a molded body with a complex shape.

[0017] The thermoplastic resin (B) having a polar group, which is used in the molding composition of the second embodiment, may be, for example, one or a mixture of plural kinds selected from the group consisting of ethylene vinyl acetate resin, ethylene glycidyl methacrylate copolymer, low density polyethylene, and polypropylene random copolymer. The thermoplastic resin (B) having a polar group is contained in the organic binder in an amount of 5 to 40% by volume, preferably 8 to 35% by volume, and more preferably 10 to 30% by volume. When the content of the thermoplastic resin (B) in the organic binder is less than 5% by volume, the molded body formed from the molding composition may become brittle. Further, when the content of the thermoplastic resin (B) in the organic binder is more than 40% by volume, swelling and cracks may occur in the molded body formed from the molding composition.

[0018] The organic compound (C) having a melting point of 70°C or lower used in the molding composition of the second embodiment can be, for example, one or a mixture of plural kinds selected from the group consisting of paraffin wax and microcrystalline wax having a melting point of 40°C to 70°C. When the content of the organic compound (C) in the organic binder is less than 30% by volume, the fluidity during molding of the molding composition deteriorates, and cracks and fractures are likely to occur in the formed molded body. Also, during extraction and degreasing of the molded body, the organic compound (C) may not be eluted smoothly. Further, when the content of the organic compound (C) in the organic binder exceeds 75% by volume, burrs are likely to occur in the molded body during molding of the molding composition, and the strength of the molded body may decrease. The content of the organic compound (C) in the organic binder is preferably 30 to 75% by volume, more preferably 40 to 70% by volume, and still more preferably 50 to 65% by volume. When the melting point of the organic compound (C) is lower than 40°C, the organic compound (C) is likely to separate from the molded body and the moldability deteriorates. Further, when the melting point of the organic compound (C) is higher than 59°C, the extraction rate of the organic compound (C) in the extraction and degreasing process significantly decreases, and swelling or cracks may occur in the ceramic molded body in the subsequent heat degreasing process. In the method for producing the commercially available liquid, for the purpose of improving the moldability of the molding composition, fatty acid esters, polyethylene wax, polypropylene wax, and ester waxes such as carnauba wax and montan wax may be added to the molding composition as additives. Also, in order to maintain the stability of the molding composition against heat, additives such as antioxidants can be used. The above-mentioned ceramic powder and the organic binder can be kneaded, for example, at a temperature in the range of 120 to 190°C. The molding composition obtained by heat kneading results in a molded body through various known molding methods such as injection molding or extrusion molding. The obtained molded body is extracted at a temperature of 40°C or higher and 80°C or lower using an organic solvent containing acetone or alcohols, etc., to extract an amount of organic compound (C) corresponding to 30% by volume or more of the organic binder in the molding composition, and extraction degreasing is performed to obtain a ceramic molded body after extraction degreasing. At this time, the temperature for extraction degreasing is preferably 40°C to 80°C. When the temperature for extraction degreasing is 40°C or lower, the extraction rate of the organic compound (C) significantly decreases, and when the extraction degreasing temperature exceeds 80°C, the molded body is likely to swell and crack. The organic solvent used for extraction is evaporated from the ceramic molded body after extraction degreasing. Next, the molded body after extraction degreasing is heated and degreased by heating in air or nitrogen so that the maximum temperature is in the range of 500°C to 800°C, with a heating-up time of 2 to 20 hours and held at the maximum temperature for 0.5 to 2 hours. In the heating degreasing process, when the heating-up time is less than 2 hours, the degreased molded body is likely to crack and swell. Heating can be performed using, for example, an electric heater, an oven, superheated steam, etc. The obtained degreased molded body can be fired in an atmosphere and at a temperature suitable for the ceramic powder used (for example, a temperature in the range of 900°C to 2300°C) to obtain a ceramic fired body.

[0019] When obtaining the molding composition of the second embodiment, together with the sinterable ceramic powder, a thermoplastic resin (A) that does not melt or swell with respect to the organic solvent, a thermoplastic resin (B) having polarity, and an organic binder containing an organic compound (C) with a melting point of 70°C or lower are kneaded using a batch-type or continuous-type kneader, preferably at a temperature in the range of 140°C to 180°C for about 1 to 3 hours, and this is pulverized to a size of several millimeters to obtain the molding composition of the second embodiment.

[0020] In the second embodiment, when the organic binder (total of the thermoplastic resin (A), thermoplastic resin (B), and organic compound (C)) is less than 30% by volume based on the total volume of the molding composition (total of the ceramic powder and the organic binder), the viscosity of the molding composition increases, making it difficult to mold the molded body, and the resulting molded body tends to be brittle. Further, when the organic binder (total of the thermoplastic resin (A), thermoplastic resin (B), and organic compound (C)) exceeds 70% by volume based on the total volume of the molding composition (total of the ceramic powder and the organic binder), defects such as deformation, swelling, and cracking are likely to occur in the ceramic molded body during the solvent extraction debinding and heat debinding processes.

[0021] By using the molding composition of the second embodiment and performing the manufacturing method of the first embodiment, a ceramic fired body without defects such as deformation, swelling, and cracking can be obtained even after firing.

[0022] Hereinafter, the invention will be further described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

[0023] [Example 1] As the thermoplastic resin (A), high-density polyethylene (HDPE, Asahi Kasei Suntech J300) was used. As the thermoplastic resin (B), ethylene-vinyl acetate copolymer (EVA633, Tosoh EVA633) was used, and as the organic compound (C), paraffin wax (melting point 46°C) and stearic acid were used. These were put into a batch kneader and melted uniformly. Next, yttria partially stabilized zirconia powder (Tosoh TZ-3YE, primary particle size: 0.01 μm) was added and kneaded at 180°C for 60 minutes. The kneaded product was taken out from the batch kneader and pulverized to obtain a molding composition.

[0024] Composition for molding Yttria partially stabilized zirconia powder: 47% by volume Organic binder: 53% by volume (Ratio of organic binder addition) High-density polyethylene (thermoplastic resin (A)): 25% by volume Vinyl acetate ethylene (Thermoplastic resin (B)): 20% by volume Paraffin wax (Organic compound (C)): 55% by volume In addition, for improving moldability, 5% by volume of stearic acid was added to the organic binder.

[0025] Using the obtained molding composition, injection molding was performed under the condition of a molding temperature of 180°C to obtain a molded body having the shape described in FIG. 3 (thickness 6 mm, width 6 mm, length 20 mm). The obtained molded body was immersed in acetone at a temperature of 52°C in the extraction and debinding furnace shown in FIG. 5 and extracted and debound for 8 hours to obtain a post-extraction and debinding ceramic molded body. Next, in the heating and debinding furnace shown in FIG. 6, the temperature was raised from room temperature to 500°C over 12 hours, and then the furnace was cooled to perform debinding to obtain a ceramic molded body. The obtained ceramic molded body was held in a firing furnace at 1350°C in the atmosphere for 2 hours, and then the furnace was cooled to obtain a ceramic fired body. The obtained ceramic fired body was sound without defects such as cracks and swelling, and the firing density was 6.05 g / cm 3 (Relative density 100%).

[0026] [Example 2] As the thermoplastic resin (A), polypropylene homopolymer (PP, Prime Polymer J107G) was used. As the thermoplastic resin (B), ethylene glycidyl methacrylate (EGMA, Sumitomo Chemical Bondfast 7B), and as the organic compound (C), paraffin wax (melting point 53°C), carnauba wax, and stearic acid were put into a batch kneader and uniformly melted, and then alumina powder (Daming Chemical Industry TM-DAR average particle size: 0.12 μm) was put in and kneaded at 180°C in the batch kneader for 60 minutes. The kneaded product was taken out and pulverized to obtain a molding composition.

[0027] Composition for molding Alumina powder: 50% by volume Organic binder addition amount: 50% by volume (Organic binder addition ratio) Polypropylene homopolymer (Thermoplastic resin (A)): 25% by volume Ethylene Glycidyl Methacrylate (Thermoplastic Resin (B)): 25% by volume Paraffin Wax (Organic Compound (C)): 50% by volume In addition, for improving the moldability, 5% by volume of carnauba wax and 5% by volume of stearic acid were added to the organic binder.

[0028] Using the obtained molding material, extrusion molding was carried out under the condition of a molding temperature of 180 °C to obtain a molded body having the shape described in Fig. 4 (rod shape with a diameter of 5 mm and a length of 60 mm). The obtained molded body was immersed in ethanol at a temperature of 65 °C in the extraction and debinding furnace shown in Fig. 5 and extracted and debound for 8 hours to obtain a ceramic molded body after extraction and debinding. Next, in a superheated steam debinding furnace, the temperature was raised from 200 °C to 500 °C over 2 hours, and then the furnace was cooled to obtain a ceramic molded body. The obtained ceramic molded body was held in a firing furnace at 1600 °C for 2 hours in the atmosphere, and then the furnace was cooled to obtain a ceramic fired body. The obtained ceramic fired body was sound without defects such as cracks and swelling, and the firing density was 3.98 g / cm 3 (Relative density 99.5%).

[0029] [Example 3] As the thermoplastic resin (A), polyacetal (POM, Polyplastics M90 - 44) and polypropylene homopolymer (PP - HM, Prime Polymer J107G), as the organic compound (B), ethylene - vinyl acetate copolymer and low - density polyethylene, and as the organic compound (C), paraffin wax (melting point 53 °C) were put into a batch kneader and uniformly melted. Then, alumina powder (Daming Chemical Industry TM - DAR, average particle size: 0.12 μm) was put in and kneaded in a batch kneader at 180 °C for 60 minutes. The kneaded product was taken out and pulverized to obtain a composition for molding.

[0030] Composition for molding Alumina powder: 50% by volume Amount of organic binder added: 50% by volume (Ratio of organic binder added) Polyacetal (Thermoplastic Resin (A)): 10% by volume Polypropylene homopolymer (thermoplastic resin (A)): 10% by volume Ethylene vinyl acetate copolymer (thermoplastic resin (B)): 15% by volume Low density polyethylene (thermoplastic resin (B)): 10% by volume Paraffin wax: (organic compound (C): 55% by volume In addition, for improving moldability, 5% by volume each of carnauba wax and stearic acid was added to the organic binder.

[0031] Using the obtained molding material, injection molding was carried out under the condition of a molding temperature of 180 °C to obtain a molded body having the shape (thickness 6 mm, width 6 mm, length 20 mm) described in FIG. 3. The obtained molded body was immersed in isopropyl alcohol at a temperature of 70 °C in the extraction and debinding furnace shown in FIG. 5 and extracted and debound for 8 hours to obtain a ceramic molded body after extraction and debinding. Next, in a heating debinding furnace, the temperature was raised from 200 °C to 500 °C over 5 hours, and then the furnace was cooled to obtain a ceramic molded body. The obtained ceramic molded body was held in a firing furnace at 1600 °C in the air for 2 hours, and then the furnace was cooled to obtain a ceramic fired body. The obtained ceramic fired body was sound without defects such as cracks and swelling, and the firing density was 3.95 g / cm 3 (relative density 99.5%).

[0032] [Example 4] As the thermoplastic resin (A), high density polyethylene (HDPE, Asahi Kasei Suntech J300), as the thermoplastic resin (B), ethylene vinyl acetate copolymer (EVA633, Tosoh EVA633), as the organic compound (C), paraffin wax (melting point 46 °C) and stearic acid were put into a batch kneader, and after uniformly melting them, aluminum nitride powder (Tokuyama grade E, particle size: 1.0 μm) with 2 mol% yttrium oxide additive was put in, and kneaded at 180 °C in the batch kneader for 60 minutes. The kneaded product was taken out and pulverized to obtain a molding composition.

[0033] Composition for molding Aluminum nitride powder (with 2 mol% yttrium oxide added): 50% by volume Addition amount of organic binder: 50% by volume (Ratio of addition of organic binder) High-density polyethylene (thermoplastic resin (A)): 25% by volume Ethylene vinyl acetate (thermoplastic resin (B)): 20% by volume Paraffin wax (organic compound (C)): 55% by volume In addition, for improving the moldability, 5% by volume of stearic acid was added to the organic binder.

[0034] Using the obtained molding material, injection molding was carried out under the condition of a molding temperature of 180 °C to obtain a molded body having the shape (thickness 6 mm, width 6 mm, length 20 mm) described in FIG. 3. The obtained molded body was immersed in a mixed liquid of acetone and isopropyl alcohol with a weight ratio of 1:1 at a temperature of 52 °C in the extraction and debinding furnace shown in FIG. 5 and extracted and debound for 8 hours to obtain a post-extraction and debinding ceramic molded body. Next, in a heating and debinding furnace, the temperature was raised from room temperature to 500 °C over 12 hours, and then the furnace was cooled to obtain a ceramic molded body. The obtained ceramic molded body was held in a firing furnace at 1850 °C for 2 hours in the atmosphere, and then the furnace was cooled to obtain a ceramic fired body (FIG. 7 is an electron micrograph of the ceramic fired body of Example 4). The obtained ceramic fired body was sound without defects such as cracks and swelling, and the firing density was 3.32 g / cm 3 It was. Also, the thermal conductivity of the ceramic fired body was 180 W / mK, and it was found to have a high thermal conductivity.

[0035] [Comparative Example 1] As the thermoplastic resin (B), an ethylene vinyl acetate copolymer resin (EVA, Evaflex EV250), as the organic compound (C), paraffin wax (melting point 53 °C), carnauba wax, and stearic acid were put into a batch kneader, uniformly melted, and then yttria partially stabilized zirconia powder (Tosoh TZ-3YE, primary particle size: 0.01 μm) was put in and kneaded in a batch kneader at 180 °C for 60 minutes. The kneaded product was taken out and pulverized to obtain a composition for molding.

[0036] Composition for molding Yttria partially stabilized zirconia powder: 50% by volume Amount of organic binder added: 50% by volume (Ratio of organic binder added) Ethylene vinyl acetate copolymer resin, (Thermoplastic resin (B)): 40% by volume Paraffin wax, (Organic compound (C)): 60% by volume In addition, to improve the moldability, 5% by volume of carnauba wax and 5% by volume of stearic acid were added to the organic binder each.

[0037] Using the obtained molding material, injection molding was carried out under the condition of a molding temperature of 180 °C to obtain a molded body having the shape (thickness 6 mm, width 6 mm, length 20 mm) described in FIG. 3. The obtained molded body was immersed in acetone at a temperature of 60 °C in the extraction and debinding furnace shown in FIG. 5 and extracted and debound for 8 hours to obtain a ceramic molded body after extraction and debinding. The obtained ceramic molded body had cracks and bulges as shown in FIG. 8, and subsequent extraction and debinding, heat debinding, and firing could not be carried out.

[0038] [Comparative Example 2] As the thermoplastic resin (A), low-density polyethylene (LDPE, Novatec UJ580) and as the organic compound (C), paraffin wax (melting point 53 °C) were put into a batch kneader and uniformly melted, and then alumina powder (Daming Chemical Industry TM-DAR average particle size: 0.12 μm) was put in and kneaded at 180 °C in the batch kneader for 60 minutes. The kneaded product was taken out and pulverized to obtain a molding composition.

[0039] Composition for molding Alumina powder: 50% by volume Amount of organic binder added: 50% by volume (Ratio of organic binder added) Low-density polyethylene, (Thermoplastic resin (A)): 40% by volume Paraffin wax, (Organic compound (C)): 60% by volume In addition, to improve the moldability, 5% by volume of carnauba wax and 5% by volume of stearic acid were added to the organic binder each.

[0040] Using the obtained molding material, injection molding was carried out under the condition of a molding temperature of 180 °C to obtain a molded body having the shape described in Fig. 3 (thickness 6 mm, width 6 mm, length 20 mm). The obtained molded body was immersed in normal hexane at a temperature of 60 °C in the extraction and debinding furnace shown in Fig. 5 and extracted and debound for 8 hours to obtain a ceramic molded body after extraction and debinding. Cracks and swelling occurred in the obtained ceramic molded body, and subsequent extraction and debinding, heat debinding, and firing could not be carried out.

[0041] [Comparative Example 3] As the thermoplastic resin (A), polyacetal (POM, Polyplastics M90-44) and ethylene vinyl acetate copolymer resin (EVA, Evaflex EV250) were put into a batch kneader together with paraffin wax (melting point 53 °C) as the organic compound (C), and after uniformly melting them, alumina powder (Daming Chemical Industry TM-DAR average particle size: 0.12 μm) was put in and kneaded at 180 °C for 60 minutes in a batch kneader. The kneaded product was taken out and pulverized to obtain a molding composition.

[0042] Composition for molding Alumina powder: 50% by volume Organic binder addition amount: 50% by volume (Organic binder addition ratio) Polyacetal, thermoplastic resin (A): 20% by volume Ethylene vinyl acetate copolymer resin, thermoplastic resin (B): 20% by volume Paraffin wax, organic compound (C): 60% by volume In addition, for improving moldability, 5% by volume of carnauba wax and 5% by volume of stearic acid were added to the organic binder.

[0043] Using the obtained molding material, injection molding was carried out under the condition of a molding temperature of 180 °C to obtain a molded body having the shape described in Fig. 3 (thickness 6 mm, width 6 mm, length 20 mm). The obtained molded body was immersed in 1,1,2,2-tetrafluoroethyl-2,2,2-trifluoroethyl ether at a temperature of 50 °C in the extraction and debinding furnace shown in Fig. 5. After extraction and debinding for 8 hours, a ceramic molded body after extraction and debinding was obtained. Cracks and swelling occurred in the obtained ceramic molded body, and subsequent extraction and debinding, heat debinding, and sintering could not be carried out.

[0044] [Examples 5 to 12, Comparative Examples 4 to 7] Furthermore, experiments were conducted with various changes in the organic binder component. The composition of the organic binder used is shown in Table 1, and the composition and results in injection molding are shown in Table 2. The kneading conditions, debinding conditions, and sintering conditions were carried out according to Example 1. Regarding the wall thickness of the molded body, the molded body described in Fig. 3 was used.

[0045] The notations in Table 1 are as follows. Ceramic powder: (Zirconia, Tosoh TZ-3YE) Organic binder component table (volume%) (Thermoplastic resin (A)) High-density polyethylene (HDPE, Japan Polyethylene HJ560) Polypropylene homopolymer (PP, Prime Polymer J107G) Polyoxymethylene (POM, Polyplastics M90-44) (Thermoplastic resin (B)) Ethylene vinyl acetate copolymer (EVA, Tosoh EVA633) Ethylene glycidyl methacrylate (EGMA, Sumitomo Chemical Bondfast 7B) (Organic compound (C)) Paraffin wax (melting point 48 °C): F-115 Paraffin wax (melting point 53 °C): F-125 (Other additives) Carnauba wax: CWAX Stearic acid: STA Extraction and debinding solvent: Isopropyl alcohol The extraction degreasing temperature is 75 °C

[0046]

Table 1

[0047]

Table 2

[0048] In Table 2, for Examples 5 to 12, an organic binder was compounded within the scope of the present invention (A to K in Table 1), and the organic binder was compounded at a ratio of 55% by volume with respect to 45% by volume of partially stabilized zirconia powder (primary particle diameter 0.01 μm), heated and kneaded at 180 °C, and the obtained molding composition was injection-molded at a molding temperature of 180 °C to obtain a molded body having the shape described in FIG. 3 (thickness 6 mm, width 6 mm, length 20 mm). The obtained molded body was immersed in isopropyl alcohol in a container heated to 50 °C in a heating degreasing furnace shown in FIG. 5 for 8 hours for extraction degreasing, then the temperature was raised from 200 °C to 500 °C over 5 hours, and then the furnace was cooled to obtain a ceramic molded body. Since a sound ceramic molded body could be obtained at this point, the obtained ceramic molded body was fired in a firing furnace at 1600 °C in an argon atmosphere. The obtained fired ceramic body had no cracks, bulges, etc., and in each case, the relative sintering density when the sintering density of partially stabilized zirconia (6.05 g / cm 3 ) was taken as 100% was 99% or more, and a sound fired body could be obtained. The test results are shown in Table 2.

[0049] On the other hand, for Comparative Examples 4 to 7, an organic binder was blended with the formulations of each component outside the scope of the present invention (a to e in Table 1), a molding composition was obtained under the same conditions as in Examples 5 to 12, and a molded body was obtained under the same conditions as in Examples 5 to 12. Regarding Comparative Example 7, the obtained molded body was very brittle and a sound molded body could not be obtained. Regarding Comparative Examples 4 to 6, extraction and debinding were performed under the same conditions as in Examples 5 to 12. However, as shown in Table 2, the obtained ceramic molded body after extraction and debinding had swelling and cracking and was not a sound ceramic molded body.

[0050] Also, when extraction and debinding were performed using the molded bodies of Examples 1 to 3 such that the extraction rate in the total organic binder was less than 30% by volume, and the debinding conditions in the subsequent heat debinding were a heating rate of 200 °C / hr, cracks and swelling occurred in the obtained ceramic molded body. From this, it was confirmed that it is preferable to perform extraction and debinding such that the extraction rate in the total organic binder is 30% by volume or more.

Industrial Applicability

[0051] Using the molding composition of the present invention, a sound ceramic molded body and a ceramic fired body having no defects and having a complex shape were obtained in a short time. According to the present invention, it is possible to promote the application to medical-related parts, automobile parts, and communication equipment parts that use complex-shaped parts.

Claims

1. A method for manufacturing a ceramic fired body using a molding composition containing 30 - 70% by volume of ceramic powder having an average particle size of 1.0 μm or less that can be fired and 30 - 70% by volume of an organic binder, wherein the organic binder is a thermoplastic resin (A) that does not melt or swell in an organic solvent; a thermoplastic resin (B) having a polar group; an organic compound (C) having a melting point of 70°C or less that dissolves in an organic solvent, and the thermoplastic resin (A) is contained in an amount such that the proportion in the total organic binder is 15 - 50% by volume, the thermoplastic resin (B) is contained in an amount such that the proportion in the total organic binder is 5 - 40% by volume, the organic compound (C) is contained in an amount such that the proportion in the total organic binder is 30 - 75% by volume. The method for manufacturing a ceramic fired body includes the following steps: a step of obtaining a molded body from the molding composition using an injection molding machine or an extrusion molding machine; a step of extracting and degreasing an amount of the organic compound (C) corresponding to 30% by volume or more of the organic binder in the molding composition using a solvent capable of eluting the organic compound (C) in the obtained molded body at a temperature of 40°C or more and 80°C or less; a step of heating the molded body after extraction and degreasing to degrease the organic binder remaining in the molded body to obtain a ceramic molded body; a step of firing the ceramic molded body to obtain a ceramic fired body; A method for manufacturing a ceramic fired body, including these steps.

2. The thermoplastic resin (A) includes one selected from the group consisting of high - density polyethylene, polypropylene homopolymer, polypropylene block copolymer, and polyacetal, or any mixture thereof, The thermoplastic resin (B) includes one selected from the group consisting of ethylene - vinyl acetate copolymer, ethylene - glycidyl methacrylate copolymer, low - density polyethylene, and polypropylene random copolymer, or any mixture thereof, The method for manufacturing a ceramic fired body according to Claim 1, wherein the organic compound (C) includes one selected from the group consisting of paraffin wax and microcrystalline wax, or any mixture thereof.

3. The method for producing a fired ceramic body according to claim 1, wherein the solvent used in the extraction and degreasing step contains one selected from the group consisting of acetone, methanol, ethanol, and isopropyl alcohol, or any mixture thereof.

4. A molding composition comprising 30 - 70% by volume of a ceramic powder having a sinterable average particle size of 1.0 μm or less and 30 - 70% by volume of an organic binder, wherein the organic binder comprises a thermoplastic resin (A) that does not melt or swell in an organic solvent; a thermoplastic resin (B) having a polar group; an organic compound (C) having a melting point of 70°C or less and soluble in an organic solvent, and the thermoplastic resin (A) is contained in an amount such that the proportion in the total organic binder is 15 - 50% by volume, the thermoplastic resin (B) is contained in an amount such that the proportion in the total organic binder is 5 - 40% by volume, the organic compound (C) is contained in an amount such that the proportion in the total organic binder is 30 - 70% by volume.

5. The molding composition according to claim 4, wherein the ceramic is an oxide ceramic selected from the group consisting of alumina, zirconia, magnesia, and titania, a nitride ceramic selected from the group consisting of aluminum nitride and silicon nitride, a carbide ceramic selected from the group consisting of silicon carbide and boron carbide, or a mixture of one or more thereof.

6. The thermoplastic resin (A) contains one selected from the group consisting of high-density polyethylene, polypropylene homopolymer, polypropylene block copolymer, and polyacetal, or any mixture thereof, the thermoplastic resin (B) contains one selected from the group consisting of ethylene vinyl acetate copolymer, ethylene glycidyl methacrylate copolymer, low-density polyethylene, and polypropylene random copolymer, or any mixture thereof, the organic compound (C) contains one selected from the group consisting of paraffin wax and microcrystalline wax, or any mixture thereof.

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