JPH0891941A - Optical molding method for ceramic - Google Patents

Abstract

PURPOSE: To provide a method for molding ceramic capable of molding ceramic into a desired shape without requiring a fixed mold and minimizing post processing after molding. CONSTITUTION: This optical molding method for ceramic comprises (a) a process for preparing a slurry comprising ceramic powder, a binder having thermosetting properties and optionally a solvent, (b) a process for forming a ceramic slurry layer in fixed thickness by using the slurry, irradiating the slurry layer with infrared light in a fixed shape and hardening the slurry layer to form a ceramic hardened layer and (c) a process for continuously carrying out operations similar to those of the process (b) fixed times on or under the ceramic hardened layer obtained by the process (b) to successively laminate the ceramic hardened layers in the fixed shape and to mold a solid molded article of ceramic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for molding ceramics having excellent properties such as heat resistance, chemical resistance, and oxidation resistance. More specifically, thermosetting ceramics that undergo thermal polymerization or thermal crosslinking reaction. The present invention relates to an optical thermal molding method for ceramics, which uses a powder slurry to obtain a ceramics molded body having a predetermined shape by utilizing thermosetting by infrared irradiation.

[0002]

2. Description of the Related Art The manufacturing process of ceramics includes a molding process of ceramic powder which has an important influence on the characteristics of a sintered body. Conventionally, as a method of molding a three-dimensional ceramics-shaped body using ceramics powder, a method of using a molding die having a predetermined shape is generally used. For example, dry pressure molding of a dry powder using a mold, slip cast molding of a slurry containing a powder using a water-absorbing mold such as a gypsum mold, and also a gel molding method or the like is filled in a specific mold with a reactive slurry, A method of solidifying and molding by a reaction such as polymerization, crosslinking and aggregation is known.

[0003]

However, as described above, in all of the conventional methods for forming a three-dimensional ceramic body, the shape that can be formed is limited because a specific mold is used. That is, a molded product having a complicated special shape is difficult to mold, and even if it is molded, there is a problem in homogeneity, and defects such as cracks and cracks are likely to occur, resulting in a low molding yield. It was Further, generally, a mold such as a metal mold is expensive, and it is worn out for a long period of time, so that it is necessary to periodically replace the mold, which is one of the causes of increasing the cost of the ceramic product. The inventors
In view of the problem of ceramics molding by the above-mentioned conventional method, a three-dimensional ceramics molded body, especially a molded body having a complicated shape or a special shape can be easily molded with a good yield without using an expensive molding die, and the obtained molded body is homogeneous. For the purpose of providing a molding method, the present invention thoroughly reviewed the molding method and various ceramic technologies such as ceramic molding materials, and further studied various molding technologies in different technical fields. In particular, we reexamined the plastics field, which has made remarkable progress in molding technology. For example, JP-A-56-144478, JP-B-63-40650, and JP-A-2-252.
There are Japanese Patent Laid-Open No. 765 and Japanese Patent Laid-Open No. 3-104626, and the techniques proposed therein are those in which three-dimensional molding is performed by stereolithography using a plastic composition having optical and thermal reactivity. is there.

However, these are all related to the molding of plastics, and it is not possible to obtain a practical molded product having excellent mechanical properties which can be used for structural members such as various mechanical devices. In addition, Japanese Examined Japanese Patent Publication Sho 63-40650
Although Japanese Patent Laid-Open Publications and the like disclose mixing of ceramic powder as a modifying material, a method of molding ceramics using a ceramic powder as a main component and an optical method has not been studied yet. In particular, since the ceramic product is normally sintered at a high temperature of about 800 ° C. or higher, the influence of the added optical reaction component is unknown. Therefore, the present inventors have completed various aspects of the present invention as a result of various studies to apply the above plastic molding technique to ceramics molding.

[0005]

According to the present invention, (a)
A step of preparing a ceramic slurry containing a ceramic powder, a thermosetting binder and, if necessary, a solvent, (b) forming a ceramic slurry layer of a predetermined thickness using the slurry, and forming infrared rays into a predetermined shape. Irradiate
The step of curing the slurry layer to form a ceramic hardened layer, and (c) the same operation as the step (b) above or below the ceramic hardened layer obtained in the step (b) are continuously performed a predetermined number of times. There is provided an optical molding method for ceramics, which is characterized by comprising repeated steps, wherein the hardened ceramic layers are sequentially laminated in a predetermined shape to form a three-dimensionally shaped ceramic body.

Further, (1) a step of holding a ceramic slurry containing a ceramic powder and a thermosetting binder, and optionally a solvent, in a container, (2) a ceramic held in the container A step of setting the support table at a predetermined depth from the surface of the ceramic slurry during the rally, (3) irradiating the surface of the ceramic slurry in the container with infrared rays in a predetermined shape, and making a part of the surface of the slurry at a predetermined depth. And (4) the ceramic hardened layer formed in the step (3) is lowered to a predetermined depth from the surface of the ceramic slurry by lowering the supporting base to form a ceramic on the hardened layer surface. And a ceramic hardened layer sequentially laminated in a predetermined shape by repeating the steps (3) and (4). Optical molding method of the ceramic, which comprises molding a three-dimensional shape is provided.

[0007]

The present invention is constructed as described above, and a predetermined amount of a thermosetting binder and optionally a solvent are added to ceramic powder to prepare a predetermined ceramic powder slurry, and the ceramic slurry is used. Thus, it is possible to form a ceramic hardened layer by irradiating the ceramic slurry layer with infrared rays in a desired shape to heat-harden the slurry layer without using a molding die such as a mold. Further, it is possible to repeatedly form a ceramic slurry layer, infrared irradiation, curing and formation of a ceramic hardened layer again on or under the ceramic hardened layer obtained by infrared thermosetting to successively laminate the ceramic hardened layer. It is possible to obtain a desired three-dimensionally shaped ceramic molded body without using. Therefore, it is possible to mold a molded body having a complicated shape or the like, which cannot be molded by the conventional molding method using a mold. Further, when the molded product shrinks due to drying or the like, unlike the conventional method, it can be freely shrunk without a shrinkage failure due to the mold, so that the occurrence of cracks can be suppressed. Further, at the same time that the entire molded body becomes homogeneous, a desired molded body designed in advance can be obtained, and near net molding is possible.

The present invention will be described in detail below. The ceramic powder used in the present invention includes oxides such as alumina, zirconia, silica, mullite and cordierite,
Carbides such as zirconium carbide, silicon carbide and titanium carbide,
Various ceramics such as nitrides such as aluminum nitride, silicon nitride and titanium nitride, or a mixture thereof can be used. The ceramic powder may be surface-treated with a silane compound such as an alkoxysila compound, chlorosilane, or silazane. Ceramic powder surface-treated with a silane compound is preferable because of its high dispersibility. The particle size of the ceramic powder of the present invention is 1
It is not more than 00 μm, preferably not more than 50 μm. This is because of the dispersion stability of the ceramic slurry.

The thermosetting binder used in the present invention is a so-called thermosetting synthetic resin which is polymerized or crosslinked and cured by heat, such as melamine resin, phenol resin and epoxy resin. Generally, when ceramic powder is added to these resins, the viscosity of the slurry becomes high and molding becomes difficult. Therefore, in the present invention, a resin having a low viscosity that makes the prepared slurry relatively flowable is appropriately used. It is preferable to select. The thermosetting synthetic resin can be cured by irradiation of infrared rays alone, but the curing rate can be increased by adding a catalyst. Examples of the catalyst include acids, Lewis acids, bases, photoproton generators and the like. Generally, in a light irradiation molding method such as infrared irradiation, a resin stability for a relatively long time is often required, and thus a catalyst having a very high activity is not preferable. The addition amount of the thermosetting binder is 5 to 100 parts by weight, preferably 10 to 60 parts by weight, based on 100 parts by weight of the ceramics. If the amount of the binder added is less than 5 parts by weight, the shape-maintaining force of the molded body is weak and the molded body is easily broken after curing. On the other hand, when the amount of the binder exceeds 60 parts by weight, the time required for the degreasing step after molding becomes long. Further, after degreasing, the proportion of voids in the degreased body increases, and as a result, the shrinkage rate increases during sintering, making it difficult to densify, and difficult to set dimensions.
In the present invention, the infrared thermosetting binder alone has sufficient strength for maintaining the shape of the molded body, but if necessary, the binder used in ordinary ceramics molding may be added and used in combination. You can also

When the thermosetting synthetic resin has a high viscosity,
If necessary, a solvent can be added to adjust the viscosity of the slurry. As the solvent, a solvent having high compatibility, low volatility, and low viscosity without reacting with other constituent components and ceramic particles is preferable. For example, n-
Examples are alcohols such as pentanol and n-hexanol, and esters such as diethyl oxalate, dibutyl oxalate and 2- (2-ethoxyethoxy) ethyl acetate. A polymerizable compound, that is, a polymerizable diluent, can be used as long as it has low volatility and low viscosity. For example, octylene oxide, dodecene oxide, butyl glycidyl ether, phenyl glycidyl ether, alkylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether and the like. The content of the solvent in the ceramic slurry can be appropriately selected depending on the characteristics of the ceramic particles and the thermosetting binder used. That is, when the viscosity of the binder is low and the particle size of the ceramic powder used is relatively large, the viscosity of the slurry is relatively low, and it is not necessary to add a solvent. However, since the viscosity of the thermosetting binder is generally high as described above, it is preferable from the viewpoint of workability of stereolithography to appropriately add a solvent to reduce the viscosity of the slurry. Usually 5 to 60% by weight based on the amount of ceramic powder
Added.

In the present invention, the necessity of addition of the dispersant can be selected depending on the kind of the binder used in the ceramic slurry. Usually, it is added in order to stably disperse the ceramic particles in the slurry for a long time. The type of dispersant has good compatibility with the binder to be used, and ordinary dispersants can be used. For example, a surfactant or the like can be used.

In the present invention, a thermosetting ceramic slurry prepared by stirring and mixing the above-mentioned components is irradiated with infrared rays in a predetermined shape to form a ceramic hardened layer, and the hardened layer is laminated, It is possible to obtain a ceramic molded body having a desired three-dimensional shape. Molding may be carried out by forming a slurry layer for each infrared irradiation operation and laminating a hardened ceramic layer obtained by hardening, or by holding a predetermined amount of the ceramic slurry in a predetermined container and appropriately supporting a plate. Introduce the slurry to a predetermined thickness on the body and irradiate the slurry on the plate-shaped support in a desired shape with infrared rays to cure the slurry to form a hardened ceramic layer. It is also possible to stack the ceramic hardened layer by repeating the operation of introducing into the above and irradiating. On the contrary, the first ceramic hardened layer may be fixed upward, the plate-like support may be similarly lowered, and the ceramic hardened layer may be continuously formed under the ceramic hardened layer with a predetermined thickness. Various methods of irradiating the thermosetting ceramic slurry with infrared rays, curing the slurry, forming a laminated ceramic hardened layer, and molding into a predetermined shape can be appropriately selected according to respective molding conditions.

In the present invention, an infrared lamp or an infrared laser can be used for infrared rays in order to thermally harden the slurry to form a ceramic hardened layer. When an infrared lamp is used, a method of irradiating through a mask having a predetermined shape is preferably used, and when an infrared laser beam or the like is used, a predetermined slurry surface is scanned with a laser beam while performing XY axis control or the like. Etc. can be applied. In addition, the intensity of irradiation light, irradiation time or scanning speed, and scanning interval are determined by the type of ceramic powder, particle size distribution, type of thermosetting binder, type and amount of catalyst, concentration of ceramic slurry, and single irradiation. It can be appropriately selected depending on the thickness of the hardened ceramic layer to be hardened.

[0014]

Embodiments of the present invention will be described in more detail with reference to the drawings. However, the present invention is not limited to the following examples. FIG. 1 is a conceptual explanatory view of an apparatus for forming a ceramic by hardening and laminating a ceramic slurry of the present invention. In FIG. 1, a predetermined ceramic slurry 4 is supplied to and held in a slurry container 3, and an infrared laser is provided.
X on the surface of the ceramic slurry 4 with a predetermined beam diameter.
Irradiation into a predetermined shape by a method such as Y control. The support base 2 is previously installed in a predetermined position in the ceramic slurry 4.
The ceramic slurry is hardened by infrared rays on the support base 2 to form a hardened ceramic layer 5. The depth from the surface of the ceramic slurry 4 to the upper surface of the support 2 is preset by the thickness of the hardened ceramic layer formed as described above, the curability and irradiation intensity of the ceramic slurry 4, the time or the scanning speed. Then, the Z-axis precision position control device (not shown) is used to lower the support base 2 to lower the ceramic hardened layer 5 formed on the support base 2 in the ceramic slurry 4 for a predetermined distance, and the ceramic hardened layer 5 The surrounding ceramic slurry 4 is introduced on top of. FIG. 2 is an explanatory view showing a state in which the second ceramic hardened layer is formed on the first ceramic hardened layer by the second infrared irradiation. That is, it is the same as FIG. 1 except that the second ceramic hardened layer 6 is formed on the first ceramic hardened layer 5 in FIG. The above-mentioned operation is repeated to infrared-cure the ceramic slurry layer to form a ceramic hardened layer and stack it to obtain a three-dimensional ceramic molded body.

Example 1 (Preparation of Solution Containing Thermosetting Binder) 160 g of a commercially available epoxy type thermosetting binder containing an onium salt type thermopolymerization initiator was added to polyoxyethylene sorbitan monostea as a dispersant. A rate of 6 g was added and mixed.

(Preparation of Ceramic Slurry) 270 g of silicon carbide (SiC) powder having an average particle size of 1.0 μm treated with γ-glycidoxypropyltrimethoxysilane and 30 g of aluminum oxide (Al ₂ O ₃ ) similarly surface-treated.
Was added to the thermosetting binder containing the dispersant prepared as described above, and the mixture was stirred and mixed at room temperature for 24 hours using a nylon ball and a light-shielded polyethylene pot. The obtained ceramic slurry was transferred to a container and defoamed under reduced pressure.

(Infrared Thermosetting Lamination Molding of Ceramic Slurry) Slurry container 3 of an apparatus similar to that shown in FIG.
To 150 g of the defoamed ceramic slurry obtained above.
In addition, the support base 2 is set to 300 μm below the surface of the ceramic slurry.
Position, and using a carbon dioxide gas laser (maximum output 12 W, wavelength 10.6 μm) while maintaining a nitrogen atmosphere,
The position is set to 100mm from the slurry surface, and the scanning speed is 3mm on the surface of width 10mm and length 30mm by XY control.
/ Sec, irradiation was performed at a scanning interval of 0.2 mm. After the irradiation, the support base 2 is lowered by the Z-axis precision position control device to lower the ceramic hardened layer 5 formed on the support base 2 by 400 μm, and at the same time, the slurry is introduced onto the hardened layer, and similarly the infrared laser is again used. −
Was similarly irradiated, and the ceramic hardened layer 6 was formed and laminated on the ceramic hardened layer 5. Thereafter, the support base 2 was further lowered by 400 μm, the ceramic hardened layer 6 was further lowered by 400 μm, and infrared rays were similarly irradiated. Repeat the above operation 5
Repeated 0 times. A plate-shaped molded body is taken out from the ceramic slurry, the molded body is washed with ethanol to remove the uncured slurry, and then dried in an air atmosphere to obtain a plate having a thickness of about 10 mm, a width of about 20 mm and a length of 30 mm. A silicon carbide compact having the shape of a circle was obtained. The bulk density of the obtained silicon carbide molded body was measured and found to be 1.8 g / cm ³ .

(Sintering) The silicon carbide molded body obtained as described above was degreased by heating in a nitrogen atmosphere to 600 ° C. over 20 hours, and further sintered at 1900 ° C. in an argon atmosphere. The bulk density of the obtained sintered body was 3.0 g / cm ³ (relative density 94%).

Example 2 A slurry obtained in the same manner as in Example 1 was used in the same apparatus as in Example 1 under the same irradiation conditions to obtain internal dimensions of 20 × 20 m.
m, outer dimensions 26 × 26 mm, and height 20 mm were obtained. The obtained compact was sintered in the same manner as in Example 1 to obtain a bulk density of 3.
A prismatic silicon carbide sintered body of 0 g / cm ³ (relative density 94%) was obtained.

Example 3 To 100 g of the same commercially available epoxy binder as in Example 1, 6 g of polyoxyethylene sorbitan monostearate as a dispersant and 40 g of neopentyl glycol diglycidyl ether as a diluent were added, and a solution containing the binder was added. Prepared. To this solution, 300 g of alumina (Al ₂ O ₃ powder having an average particle diameter of 1.5 μm, which was surface-treated in the same manner as in Example 1) was added, and stirred for 24 hours using the same pot mill as in Example 1 to prepare a ceramic slurry. 1 from this slurry
50 g was collected and irradiated with infrared rays in the same manner as in Example 1 to obtain a plate-shaped alumina molded body having a thickness of about 10 mm, a width of about 20 mm and a length of 30 mm. As a result of measuring the bulk density of the obtained alumina molded body, it was 2.0 g / cm ³ . The dried molded body was heated and degreased in an air atmosphere up to 600 ° C. over 20 hours, and thereafter heated at a temperature rising rate of 100 ° C./hour to 1600 ° C.
It hold | maintained at 0 degreeC for 2 hours, and sintered. As a result of measuring the bulk density of the obtained sintered body, 3.4 g / cm ³ (relative density 85.8) was obtained.
%)Met.

Example 4 To 100 g of a commercially available epoxy-based binder similar to that used in Example 1, 6 g of polyoxyethylene sorbitan monostearate as a dispersant and 40 g of neopentyl glycol diglycidyl ether as a diluent were added and a solution containing the binder was added. Prepared. To this solution, 300 g of silicon carbide (SiC) powder having an average particle size of 1.0 μm and 1.2 g of boron carbide which had been surface-treated in the same manner as in Example 1 were added, and the mixture was stirred for 24 hours using the same pot mill as in Example 1. A ceramic slurry was prepared. 150 g of this slurry was sampled and irradiated with infrared rays under the same apparatus and irradiation conditions as in Example 1 to obtain an internal size of 20 × 2.
A prism having a size of 0 mm, an outer dimension of 26 × 26 mm, and a height of 20 mm was obtained. The obtained molded body was heated to 600 ° C. in a nitrogen atmosphere for 20 hours to carbonize the resin. This heat-treated body was placed in a graphite container and placed under an argon atmosphere for 21
Sintered at 50 ° C. As a result of measuring the bulk density of the obtained sintered body, it was 3.0 g / cm ³ (relative density 94%).

[0022]

INDUSTRIAL APPLICABILITY The present invention prepares a ceramic slurry containing a ceramic powder, a thermosetting binder, and optionally a solvent, and irradiates a specific surface of the obtained ceramic slurry with infrared rays to form a slurry. A method of forming ceramic particles into a predetermined three-dimensional shape by continuously performing an operation of forming a ceramic hardened layer by hardening and laminating a hardened layer having a cross section of a specific shape hardened by infrared irradiation to form a continuous body. Is. Therefore, polishing,
Post-processing such as grinding is not required, which simplifies work. Further, as a matter of course, since a mold is not required, it is not necessary to manufacture a mold for each specific molded body, so that
The cost can be reduced and it is extremely useful industrially. The effects of the present invention can be summarized as follows. (1) Since it is not necessary to use a mold for absorbing water and a solvent such as a plaster mold, there is no restriction on the mold at the time of molding, and it is possible to mold a complicated shape easily and easily. (2) Molding as designed in advance is possible, and near net molding is possible. (3) Since there is no need for post-processing after molding, the raw material ceramic powder and the like can be reduced. (4) Since molds such as molds and gypsum are not required, mold manufacturing time is not required, and a predetermined shape can be molded in a short time, and mold manufacturing cost can be reduced. Moreover, it does not require excessive work for handling large molds, plaster molds, and the like.

[Brief description of drawings]

FIG. 1 is a conceptual explanatory view of an apparatus for forming a ceramic by hardening and laminating a ceramic slurry of the present invention.

FIG. 2 is an explanatory view showing a state in which a second ceramic hardened layer is formed on the first ceramic hardened layer.

[Explanation of symbols]

 1 Infrared Laser 2 Support 3 Slurry Container 4 Slurry 5 Ceramic Hardening Layer (First) 6 Ceramic Hardening Layer (Second)

Claims (2)

[Claims] 1. A step of preparing a ceramic slurry containing (a) a ceramic powder, a thermosetting binder, and optionally a solvent, and (b) a ceramic slurry layer having a predetermined thickness using the slurry. And irradiating infrared rays in a predetermined shape to cure the slurry layer into a ceramic hardened layer, and (c) above or below the ceramic hardened layer obtained in step (b) above. A ceramic having a step of continuously repeating the same operation as the step b) for a predetermined number of times, wherein the hardened ceramic layers are sequentially laminated in a predetermined shape to form a three-dimensional ceramic body. Optical molding method. 2. (1) A step of holding a ceramic slurry containing a ceramic powder, a thermosetting binder, and optionally a solvent in a container, and (2) a ceramic held in the container. A step of setting the support table at a predetermined depth from the surface of the ceramic slurry during the rally, (3) irradiating the surface of the ceramic slurry in the container with infrared rays in a predetermined shape, and making a part of the surface of the slurry at a predetermined depth. And (4) the ceramic hardened layer formed in the step (3) is lowered to a predetermined depth from the surface of the ceramic slurry by lowering the supporting base to form a ceramic slurry on the surface of the hardened layer. And the steps (3) and (4).
An optical molding method for ceramics, characterized in that a ceramic three-dimensional body is molded by repeatedly laminating a hardened ceramic layer in a predetermined shape in sequence.