Method for molding ceramics using a 3D printer

Abstract

To provide a method and 3D printer for directly forming complex-shaped ceramic products in a space-saving, low-cost manner, without using plaster molds, resin molds, or metal molds. [Solution] A method for molding ceramics using a 3D printer is provided, characterized in that a raw material slurry in a raw material tank is transferred from a tube pump to a screw pump-equipped printer head via a resin tube, and molding is performed by material extrusion while discharging from the screw pump-equipped printer head, and the raw material slurry is molded by utilizing thixotropy which occurs when cellulose nanofibers are contained in the raw material powder at a solid content concentration of 0.05% to 3.0%. A 3D printer having the most preferred and suitable configuration for carrying out the above molding method is also provided.

Description

Technical Field

[0001] The present invention relates to a method for forming ceramics using a 3D printer and a 3D printer that enables direct extrusion and forming of materials for ceramic tableware, ceramic filters, honeycombs, etc., which have been conventionally formed using plaster molds, resin molds, metal molds, etc., without using those molds.

Background Art

[0002] Although many forming methods using 3D printers have been reported so far, most of them extrude the raw material slurry placed in the raw material tank while applying pressure with a compressor or a screw-type electric device. Also, methods for solidifying after forming include a method of solidifying with light or heat below 100°C after discharging from the nozzle (see Patent Document 1), a method of heating and curing the pedestal at 30°C to 80°C (see Patent Document 2), and further, a method of adding a photocurable resin to the raw material and curing with light (see Patent Document 3), etc. are disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the conventional technologies described above still have problems such as the need for large-scale equipment and complicated work, and the cost of adding expensive additives to the raw materials. First, when the raw material slurry is sent out with a compressor, a large compressor is required. Also, when the raw material is pushed out while pressurizing with a screw-type electric device, not only is a pressurizing device required, but when adding raw material slurry, the device must be stopped and the pressure in the raw material tank returned to atmospheric pressure. Furthermore, the method of solidification after molding, such as the method in Patent Document 1, requires additives that solidify with light or heat, or a heating device. Also, the method in Patent Document 2 is complicated, as it requires heating the base to 30°C to 80°C and injecting oil around the laminate. The method in Patent Document 3 requires expensive photocurable resin, and also requires the installation of ultraviolet light or lasers. For the reasons described above, if the raw material can be extruded using a simple method and then maintained and solidified after molding, it will be possible to obtain excellent ceramic products without the disadvantages described in the above-mentioned patent document. [Means for solving the problem]

[0005] Therefore, in this invention, to introduce the raw material slurry from the raw material tank to the final printer head with a screw pump, a tube pump is connected to the outlet of the raw material tank. By utilizing the powerful suction force of the tube pump, stable introduction of the raw material slurry becomes possible. As a result, the compressor and pressurizing device that were conventionally required are not used, and related special high-pressure tanks, tubes, printer heads, etc. are not needed, making it possible to use inexpensive commercially available tanks and tubes. In addition, since the inside of the raw material tank is always at atmospheric pressure, there is the advantage that raw material slurry can be continuously added without interrupting molding, and it becomes possible to mold large products that were previously limited by the capacity of the raw material tank. Furthermore, the tube pump has a strong force for pushing out the raw material slurry, and after introducing the raw material slurry with strong suction, it can be stably transferred through the long resin tube to the screw pump-equipped printer head. On the other hand, the screw pump-equipped printer head is unsuitable for pushing out raw material slurry over long distances because it is prone to backflow, but if it is only for direct discharge, the discharge is stable without pulsation, and the response of raw material discharge to power ON and OFF is also good. Furthermore, regarding the raw material slurry, by adding cellulose nanofibers at a solid content concentration of 0.05% to 3% to the raw material powder, in addition to water and a dispersant, thixotropy is achieved. This results in fluidity during transport within the tube and maintains shape retention after extrusion, enabling the transport, extrusion, and layering of the raw material slurry necessary for 3D printing. Therefore, expensive photocuring agents or cements and other additives for post-extrusion hardening are unnecessary, and heating of the base or other components is also not required. Furthermore, in conventional extrusion molding of ceramics and the like, the tip of the printer head was pressed against the lower layer of material during molding to ensure stable lamination. In contrast, when using the raw material slurry of the present invention, due to its thixotropic properties, it is fluid during transfer within the resin tube, but the pressure is released simultaneously with discharge from the screw pump-equipped printer head, resulting in shape retention. This allows the slurry to solidify in its discharged shape without pressing the tip of the printer head against the lower layer of material, making it possible to produce a stable molded body even when laminated. The appropriate moisture content varies depending on the raw material, but if the moisture content is less than 10%, the fluidity of the raw material slurry decreases, making it prone to clogging in the resin tube. Conversely, if the moisture content exceeds 30%, the viscosity of the raw material slurry decreases, making lamination difficult during molding.

[0006] In view of the above, the main configuration of the present invention is as follows: [1] A method for molding ceramics using a 3D printer, characterized in that a raw material slurry in a raw material tank is transferred from a tube pump to a screw pump-equipped printer head via a resin tube, and the material is molded by extrusion while being discharged from the screw pump-equipped printer head, The raw material slurry is characterized by being molded using thixotropy, which occurs when cellulose nanofibers are present in the raw material powder at a solid content concentration of 0.05% to 3.0%. A method for molding ceramics using a 3D printer. [2] The above tube pump utilizes the suction force at the inlet caused by rotation to introduce raw material slurry from the raw material tank into the tube pump, and / or, A method for molding ceramics using a 3D printer as described in [1], characterized in that the force of the tube pump, which pushes the raw material slurry out of the outlet due to rotation, stably transfers the raw material slurry through a resin tube to a printer head with a screw pump. [3] A raw material tank for containing the raw material slurry, A tube pump connected to a raw material tank by a resin tube, It has a printer head with a screw pump for discharging raw material slurry, connected to a tube pump by a resin tube. 3D printer. [Effects of the Invention]

[0007] As described above, by connecting the raw material tank, tube pump, and screw pump-equipped printer head with a resin tube to transfer the raw material slurry, stable discharge of the raw material slurry became possible without using a compressor or other equipment. Furthermore, by adding an appropriate amount of cellulose nanofiber to the raw material slurry, thixotropy is activated, and by utilizing the fact that it remains fluid during transfer within the tube and maintains its shape after discharge, stable material extrusion molding using a 3D printer becomes possible. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram of the 3D printer of the present invention (hereinafter also simply referred to as "this molding apparatus"). [Figure 2] Figure 2 is a photograph of ceramic characters with an instant noodle-like structure formed by the molding method of the present invention. [Figure 3] Figure 3 is a photograph of an alumina sintered body with a lattice structure formed by the molding method of the present invention. [Modes for carrying out the invention]

[0009] This invention relates to a method for molding ceramics using a 3D printer. In this specification, ceramics refers to inorganic compound materials, and typical examples include pottery, alumina, zirconia, glass, and cement.

[0010] The molding method of the present invention is characterized by transferring a raw material slurry in a raw material tank from a tube pump to a screw pump-equipped printer head using a resin tube, and performing molding by material extrusion while discharging from the screw pump-equipped printer head.

[0011] The raw material tanks used herein are not particularly limited as long as they can accommodate the following raw material slurries. Examples of raw material tank capacities in this specification include 0.1L to 10L.

[0012] The raw material slurry described herein is prepared by thoroughly mixing the main raw material (forming material), a dispersant, cellulose nanofiber (CNF) as an additive, and water in a stirrer. As the main raw materials of the raw material slurry in this specification, there may be mentioned Amakusa kaolin (selected high-quality Amakusa kaolin or selected medium-quality Amakusa kaolin), alumina powder, zirconia powder, silica powder, etc. From the perspective of high versatility and being a typical material, Amakusa kaolin (selected high-quality Amakusa kaolin or selected medium-quality Amakusa kaolin) or alumina powder is preferred. Among Amakusa kaolins, selected high-quality Amakusa kaolin is preferred from the perspective of high purity. As the dispersant of the raw material slurry in this specification, there may be mentioned sodium silicate, acrylic acid-based dispersant, polycarboxylic acid-based dispersant, etc. The cellulose nanofibers in this specification are obtained by mechanically defibrating plant materials, and are composed of cellulose microfibrils (single nanofibers) consisting of crystalline parts, quasi-crystalline parts, and amorphous parts, or those that are longitudinally torn, entangled, or aggregates having a network structure, and refer to those with a width of 3 to 100 nm, an aspect ratio of 10 or more, and a length of up to 1 μm. Cellulose nanofibers are mainly made from wood, but in addition to wood, they can also be produced from raw materials such as bamboo, rice straw, wheat straw, rice husks, agricultural residues (such as vegetable scraps, tea husks, orange peels, etc.), herbs (such as pampas grass, etc.), and seaweeds. When the raw material slurry in this specification contains cellulose nanofibers, in order to favorably exhibit thixotropy, the solid content concentration thereof with respect to the raw material powder is preferably 0.05% by mass to 3% by mass, more preferably 0.08% by mass to 1.5% by mass, and even more preferably 0.1% by weight to 1% by weight. In addition, the raw material slurry in this specification may contain additives other than cellulose nanofibers, and examples of such additives include iron oxide, zeolite, chromium oxide, magnesium oxide, etc. When the main raw material of the raw material slurry in this specification is Amakusa kaolin, iron oxide or zeolite can be included as an additive in an appropriate amount (for example, 1% by mass to 30% by mass) from the perspectives of functionality and color development effects. When the main raw material of the raw material slurry in this specification is alumina powder, from the viewpoints of functionality and color development effect, an appropriate amount (for example, 0.5% by mass to 5% by mass) of chromium oxide can be included as an additive, and from the viewpoint of suppressing grain growth during firing, an appropriate amount (for example, 0.1% by mass to 1% by mass) of magnesium oxide can be included as an additive. The water content of the raw material slurry in this specification varies depending on the main raw material, but in order to balance the fluidity in the tube and the viscosity after discharge, it is preferably 10% to 30%, and more preferably 14% to 25%. The viscosity of the raw material slurry in this specification varies depending on the main raw material, but is about 60,000 mPa·s to 100,000 mPa·s when measured with a B-type viscometer, for example.

[0013] The resin used for the resin tube in this specification is not particularly limited, and may be a natural resin or a synthetic resin. When the resin is a synthetic resin, it may be a thermosetting resin or a thermoplastic resin, and preferably a fluorine tube, a silicone tube, etc. (specifically, the Alam fluorine tube (transparent fluorine tube) manufactured by Alam Co., Ltd., the Labolan silicone tube (silicone) manufactured by AS ONE Corporation, the Tygon tube (vinyl chloride, platinum-vulcanized silicone, etc.) manufactured by SAINT-GOBAIN, the flexible fluorine tube (fluororesin) manufactured by Hakko Co., Ltd.). The length of the resin tube in this specification may be 10 cm to 50 cm, and the inner diameter may be 1 mm to 10 mm.

[0014] The tube pump in this specification is not particularly limited as long as it conveys liquid through the tube by strongly pressing a rotating roller against a flexible tube in the pump housing. In the tube pump described herein, the flow rate range is 0.5 mL / min to 1 L / min, the suction pressure is -0.01 MPa to -0.1 MPa, the discharge pressure is 0.01 MPa to 1 MPa, the tube inner diameter is 2 mm to 10 mm, and the roller rotation speed is 10 rpm to 300 rpm. However, from the viewpoint of flowing the high-viscosity raw material slurry described herein, a flow rate range of 0.5 mL / min to 400 mL / min is preferred. In the molding method of the present invention, it is preferable to introduce the raw material slurry from the raw material tank into the tube pump by utilizing the suction force at the inlet caused by the rotation of the tube pump. Furthermore, in the method of the present invention, it is preferable to stably transfer the raw material slurry through the long resin tube to the screw pump-equipped printer head using the strong force of the tube pump pushing the raw material slurry out from the outlet due to rotation.

[0015] The screw pump described herein is not particularly limited as long as it is a pump that draws up liquid and transfers it to a discharge port by rotating a screw (a spiral component) inside a stator (a cylindrical component). In the screw pump described herein, the flow rate range is 0.5 mL / min to 0.5 L / min, the suction pressure is -0.01 MPa to -0.1 MPa, the discharge pressure is 0.01 MPa to 0.5 MPa, the discharge port diameter is 0.2 mm to 10 mm, and the screw rotation speed is 10 rpm to 500 rpm. However, from the viewpoint of flowing the high-viscosity raw material slurry described herein, the flow rate range is preferably 0.5 mL / min to 400 mL / min.

[0016] This invention also relates to a 3D printer. The 3D printer of the present invention is A raw material tank for containing the raw material slurry, A tube pump connected to a raw material tank by a resin tube, It has a printer head with a screw pump that is connected to a tube pump by a resin tube and for discharging the raw material slurry. While the 3D printer of the present invention has the most preferred and suitable configuration for carrying out the molding method of the present invention, it may also be used to carry out molding methods other than the molding method of the present invention. Furthermore, the specifications of each component of the 3D printer of the present invention can be appropriately referenced from the description of the molding method of the present invention above.

[0017] Examples, comparative examples, and reference examples of the present invention will be described in detail below, but the present invention is not limited in any way by these examples, comparative examples, and reference examples. [Examples]

[0018] The molding conditions for the 3D printer of this molding apparatus used in the following examples, comparative examples, and reference examples are as follows: Raw material tank: Capacity 0.3L (made from resin using a 3D printer) Resin tube: Fluorine-based, 3mm inner diameter x 330mm length (manufactured by Aram Co., Ltd.) Tube pump: Flow rate 1 mL / min, discharge pressure 0.1 MPa (manufactured by Tsukasa Electric Co., Ltd.) Screw pump: Motor (manufactured by DAPERCI); Screw part (made from resin using a 3D printer); Flow rate 1 mL / min; Outlet diameter 0.5 mm

[0019] Example 1 Example 1 describes a 3D printer using the present molding apparatus, with commercially available Amakusa Selected Ceramic Clay as the main material for the molding process. First, 0.2% by mass of sodium silicate and 0.08% by mass of cellulose nanofiber (derived from wood (pulp), 3-4 nm wide, manufactured by Nippon Paper Industries Co., Ltd.; the same applies to the following examples and comparative examples) were thoroughly mixed with water prepared to a moisture content of 24% relative to the solid content of the Amakusa Selected Ceramic Clay. Then, the Amakusa Selected Ceramic Clay was added and thoroughly mixed with a stirrer to obtain a raw material slurry (0.3 L) for the 3D printer. The raw material slurry was poured into the raw material tank of the molding apparatus shown in Figure 1. Then, the power to the tube pump was turned on and rotated at 60 rpm, and the raw material slurry was introduced into the pump by its suction force. The raw material slurry was transported through the resin tube connecting the tube pump and the screw pump-equipped printer head while pulsating, and after confirming that it had been introduced into the screw pump-equipped printer head, the power to the screw pump was turned on and rotated at 180 rpm, causing the raw material slurry to be discharged from the nozzle at the tip. After confirming that the extrusion was stable, the computer was operated to perform molding by extruding and layering the raw material slurry from the printer head according to the drawing (the hiragana character "あ") that had been prepared in advance on the 3D printer software. After shaping, the material was air-dried and then fired in an electric furnace at 1,300°C to obtain ceramic characters with a structure similar to instant noodles (Figure 2).

[0020] Example 2 In Example 2, the process was the same as in Example 1, except that the solid content concentration of cellulose nanofibers relative to the solid content concentration of Amakusa selected clay was set to 2% by mass. As in Example 1, ceramic characters with an instant noodle-like structure were obtained.

[0021] Example 3 In Example 3, the effect of adding zeolite in addition to cellulose nanofibers will be described using the 3D printer of this molding apparatus, with commercially available Amakusa Selected Ceramic Clay as the main material for the molding. First, 0.2% by mass of sodium silicate relative to the solid content concentration of Amakusa Selected Ceramic Clay will be added, along with 0.2% by mass of cellulose nanofibers and 10% by mass of zeolite powder (manufactured by Shin Tohoku Chemical Industry Co., Ltd.), and water prepared to achieve a moisture content of 23% will be added and thoroughly mixed. After that, Amakusa Selected Ceramic Clay will also be added and mixed with a stirrer to obtain a raw material slurry (0.3 L) for the 3D printer. The raw material slurry was poured into the raw material tank of the molding apparatus shown in Figure 1. Then, it was transferred from the tube pump to the screw pump-equipped printer head, and the raw material slurry was discharged from the nozzle at the tip. Afterward, it was stacked in a circular shape to confirm whether stacking was possible. The test results are shown in Table 1. Furthermore, the porous body obtained by air-drying after molding and firing it in an electric furnace at 800°C exhibited greater effects compared to those of Examples 1 and 2, including adsorption and deodorization of ammonia odor and adsorption of heavy metal ions in wastewater.

[0022] Example 4 Example 4 describes the use of alumina powder as the molding material with the 3D printer of this molding apparatus. First, 0.4% by mass of acrylic acid-based dispersant (A30SL, manufactured by Toagosei Co., Ltd.) and 1.5% by mass of cellulose nanofiber were thoroughly mixed with water prepared to have a moisture content of 12%. Then, the alumina powder was added and mixed with a stirrer to obtain a raw material slurry (0.3 L) for the 3D printer. The raw material slurry was poured into the raw material tank of the molding apparatus shown in Figure 1. Then, the power to the tube pump was turned on and it was rotated at 60 rpm, and the raw material slurry was introduced into the pump by its suction force. The raw material slurry was transported through the resin tube connecting the tube pump and the screw pump while pulsating, and after confirming that it had been introduced into the printer head with the screw pump, the power to the screw pump was turned on and it was rotated at 180 rpm, causing the raw material slurry to be discharged from the discharge port at the tip. After confirming that the extrusion was stable, the computer was operated to perform molding by extruding and layering the raw material slurry from the printer head according to the drawing (lattice structure) prepared in advance on the 3D printer software. After molding, the material was air-dried and then fired in an electric furnace at 1,600°C to obtain a lattice-structured alumina sintered body (Figure 3).

[0023] Example 5 In Example 5, the effect of adding chromium oxide in addition to cellulose nanofibers will be described using the 3D printer of this molding apparatus, with alumina powder as the main raw material for the molding material. First, 0.4% by mass of an acrylic acid-based dispersant (A30SL, manufactured by Toagosei Co., Ltd.) relative to the mass of alumina powder was added, along with cellulose nanofibers with a solid content of 1.5% by mass and chromium oxide with a solid content of 2% by mass (manufactured by Kanto Chemical Co., Ltd.). Water prepared to achieve a moisture content of 14% was added and thoroughly mixed. After that, the alumina powder was also added and mixed with a stirrer to obtain a raw material slurry (0.3 L) for the 3D printer. The raw material slurry was poured into the raw material tank of the molding apparatus shown in Figure 1. Then, it was transferred from the tube pump to the screw pump-equipped printer head, and the raw material slurry was discharged from the nozzle at the tip. Afterward, it was stacked in a circular shape to confirm whether stacking was possible. The test results are shown in Table 1. Furthermore, the alumina sintered body obtained by air-drying after molding and firing in an electric furnace at 1,600°C developed a more beautiful red color compared to that of Example 4.

[0024] Comparative Examples 1-3 and Reference Examples 1 and 2 Comparative Examples 1-3 and Reference Examples 1 and 2 describe the effect of adding cellulose nanofibers, using a 3D printer of this molding apparatus, with commercially available Amakusa clay and alumina powder as the main raw materials. First, 0.2% by mass of sodium silicate relative to the solid content of Amakusa clay was mixed thoroughly with cellulose nanofibers at solid content concentrations of 0.02% by mass (Comparative Example 1) and 3.5% by mass (Comparative Example 2), and water prepared to have a moisture content of 24%. For reference, commercially available CMC (carboxymethylcellulose manufactured by Daicel Corporation) was also added at a solid content concentration of 1% by mass (Reference Example 1) and 0.1% by mass (Reference Example 2) instead of cellulose nanofibers. After that, Amakusa clay was also added and mixed with a stirrer to obtain a raw material slurry (0.3 L) for the 3D printer. The raw material slurry was poured into the raw material tank of the molding apparatus shown in Figure 1. Then, it was transferred from the tube pump to the screw pump-equipped printer head, and the raw material slurry was discharged from the nozzle at the tip. Afterward, it was stacked in a circular shape to confirm whether stacking was possible. Similarly, for alumina, 0.4% by mass of an acrylic acid-based dispersant (A30SL, manufactured by Toagosei Co., Ltd.) was added to alumina powder, along with 3.2% by mass of cellulose nanofibers and water prepared to a moisture content of 12%, and thoroughly mixed. Then, the alumina powder was added and mixed with a stirrer to obtain a raw material slurry (0.3 L) for 3D printing (Comparative Example 3). The raw material slurry was poured into the raw material tank of the manufacturing apparatus shown in Figure 1. Then, it was transferred from the tube pump to a screw pump-equipped printer head, and the raw material slurry was discharged from the nozzle at the tip. Afterward, it was stacked in a circular pattern to confirm whether or not stacking was possible. The results of those tests are shown in Table 1.

[0025] [Table 1]

[0026] Comparative Example 4 In Comparative Example 4, the screw pump-equipped printer head was removed, and instead, a resin straw-shaped nozzle was connected to a resin tube and used as the printer head. Discharge tests were then conducted. Using the same raw material slurry and transfer conditions as in Example 1, the slurry was passed from the tube pump through a 19 cm long resin tube, and the discharge from the resin straw-shaped nozzle was observed. A pulsation at regular intervals, characteristic of tube pumps, was observed. Furthermore, when the power switch of the tube pump was repeatedly turned ON and OFF, it was confirmed that due to residual pressure in the tube, the raw material slurry continued to be discharged for more than 3 seconds after the switch was turned OFF, making it impossible to accurately control the discharge. [Industrial applicability]

[0027] By utilizing 3D printers, it is possible to easily manufacture molded products with complex shapes. In particular, according to this invention, since it can be easily manufactured with low-cost equipment, it is expected that its potential applications will expand not only in the ceramics industry but also in other industries in the future. Furthermore, by processing the shape of the tip of the printer head, it is possible to extrude raw materials in a hollow straw shape, and by stacking these, it is possible to manufacture ceramics with lightweight and heat-retaining functions. In addition, compared to honeycomb for automobile exhaust gases, the three-dimensional mesh structure has a larger surface area, enabling lighter and more compact exhaust gas systems. Furthermore, since it is possible to extrude with a shape other than a circle, such as a star shape, it is possible to create a honeycomb with a significantly larger surface area in the resulting lattice structure, enabling unprecedented high functionality and compactness.

Claims

1. A method for molding ceramics using a 3D printer, characterized in that a raw material slurry in a raw material tank is transferred from a tube pump to a screw pump-equipped printer head via a resin tube, and the material is molded by extrusion while being discharged from the screw pump-equipped printer head, The raw material slurry is characterized by being molded using thixotropy, which occurs when cellulose nanofibers are present in the raw material powder at a solid content concentration of 0.05% to 3.0% by mass. A method for molding ceramics using a 3D printer.

2. The above tube pump utilizes the suction force at the inlet caused by rotation to introduce raw material slurry from the raw material tank into the tube pump, and / or, A method for molding ceramics using a 3D printer according to claim 1, characterized in that the force of the tube pump, which pushes the raw material slurry out from the outlet due to rotation, stably transfers the raw material slurry through a resin tube to a printer head with a screw pump.

3. A raw material tank for containing the raw material slurry, A tube pump connected to a raw material tank by a resin tube, It has a printer head with a screw pump for discharging raw material slurry, connected to a tube pump by a resin tube. 3D printer.

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