Method for manufacturing sintered products from three-dimensionally fabricated objects.

Abstract

To provide a method for manufacturing a sintered product from a three-dimensional molded article, suppressing formation of defects such as breakage or strain.SOLUTION: A method for manufacturing a sintered product from a three-dimensional molded article is assembled with a preparation step S11, degreasing step S12, and a sintering step S13. In the preparation step S11, an ink involving an inorganic particle and an organic material is laminated to prepare a three-dimensional molded article. The degreasing step S12 includes a first degreasing step of degreasing the organic material by heating the three-dimensional molded article at a first average degreasing temperature under an inert gaseous atmosphere for a first prescribed time, and a second degreasing step of degreasing the organic material by heating the three-dimensional molded article after degreasing in the first degreasing step at a second average degreasing temperature which is higher than the first average degreasing temperature under an inert gaseous atmosphere for a second prescribed time. In the sintering step S13, the three-dimensional molded article after degreasing in the second degreasing step is sintered at an average sintering temperature which is higher than the second average degreasing temperature to obtain a sintered product.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a sintered product from a three-dimensional shaped object.

Background Art

[0002] Ceramic products are manufactured through a process that involves mixing a mixture of raw material powder of ceramics and an organic binder, shaping the mixture by injection molding, extrusion molding, casting molding, etc., and then subjecting it to a debinding process and a sintering process (Non-Patent Document 1).

[0003] As an organic binder, for example, Patent Document 1 discloses a copolymer having a segment derived from a (meth)acrylic acid alkyl ester monomer and a specific polyalkylene oxide segment.

[0004] On the other hand, as a 3D (three-dimensional) shaping method, a 3D printing shaping method is known in which a liquid curable ink is discharged to form an ink layer, and this is repeated to form a cured layer to create a three-dimensional shape.

[0005] In the production of ceramic products as well, a method for manufacturing ceramic products using the 3D printing shaping method for shaping has been attempted (Non-Patent Document 2).

[0006] For example, Patent Document 2 discloses a method including a step of 3D printing a desired three-dimensional object using a suspension containing 50 to 95% by weight (w / w) of a ceramic material and a polymer material, etc. as a feedstock, and a step of sintering.

Prior Art Documents

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Patent Documents

[0008] [Patent Document 1] Japanese Patent Publication No. 2006-282978 [Patent Document 2] Special Publication No. 2018-536556 [Overview of the project] [Problems that the invention aims to solve]

[0009] Conventionally, when manufacturing sintered products by degreasing and sintering a three-dimensional object, the degreasing process involves rapidly heating the object to a desired degreasing temperature (for example, at a heating rate of 10°C / min), and then heating it at a constant degreasing temperature until most of the organic matter in the three-dimensional object is removed.

[0010] However, when degreasing three-dimensional objects with a high resin content using conventional degreasing processes, there was a problem in that defects such as cracks and distortions were likely to occur.

[0011] In view of the above, the present invention aims to provide a method for manufacturing sintered products from three-dimensionally molded objects that suppresses the occurrence of defects such as cracks and distortions. [Means for solving the problem]

[0012] A method for manufacturing a sintered product from a three-dimensionally molded object according to a first aspect of the present invention is: A process of preparing a three-dimensional object by layering ink containing inorganic particles and organic materials, A first degreasing step involves heating the three-dimensional object in an inert gas atmosphere at a first average degreasing temperature for a first predetermined time to degrease the organic material, A second degreasing step is performed in which the three-dimensional molded object, after degreasing in the first degreasing step, is heated in an inert gas atmosphere at a second average degreasing temperature higher than the first average degreasing temperature for a second predetermined time to degrease the organic material, A sintering step to obtain a sintered product by sintering the three-dimensional molded object after degreasing in the second degreasing step at an average sintering temperature higher than the average degreasing temperature of the second step, It is equipped with.

[0013] With the above configuration, degreasing is performed in stages, which helps to suppress the occurrence of defects such as cracks and distortions.

[0014] In the first degreasing step and the second degreasing step, the heating rate when heating to the average degreasing temperature of the first and the average degreasing temperature of the second is less than 10°C / min. It is desirable.

[0015] With the above configuration, the low heating rate further reduces the likelihood of defects occurring.

[0016] The second average degreasing temperature is the temperature at which, when the object made of the organic material is heated in an inert gas atmosphere for 30 minutes at that temperature, 80% or more by mass of the organic material in the object before heating is degreased. It is desirable.

[0017] With the above configuration, most of the organic material is degreased from the three-dimensional object before firing. Therefore, the total amount of organic material released from the three-dimensional object during sintering is reduced, further decreasing the possibility of defects occurring during the sintering process.

[0018] The process further includes one or more additional degreasing steps between the first degreasing step and the second degreasing step, in which the three-dimensional molded object is heated and degreased in an inert atmosphere at an average degreasing temperature higher than the average degreasing temperature of the first step and lower than the average degreasing temperature of the second step. If there are two or more of the above-mentioned additional degreasing steps, the average degreasing temperature of the above-mentioned additional degreasing steps is increased in stages. It is desirable.

[0019] With the above configuration, degreasing is performed in a further stepwise manner, thus further reducing the possibility of defects occurring. [Effects of the Invention]

[0020] According to the present invention, sintered products can be manufactured from three-dimensionally molded objects while suppressing the occurrence of defects such as cracks and distortions. [Brief explanation of the drawing]

[0021] [Figure 1] Flowchart of a manufacturing method for a sintered product according to one embodiment of the present invention. [Figure 2] Schematic diagram of the TGA curve when a three-dimensional object is heated in a nitrogen atmosphere at a heating rate of 10°C / min. [Figure 3] A diagram showing the degreasing conditions in the example. [Modes for carrying out the invention]

[0022] (Method of manufacturing sintered products) A method for manufacturing a sintered product according to one embodiment of the present invention will be described. In this manufacturing method, as shown in Figure 1, a three-dimensional object is prepared (step S11), the three-dimensional object is degreased in at least two stages at different temperatures (step S12), and finally, the degreased three-dimensional object is sintered to obtain a sintered product (step S13).

[0023] (Step S11) In step S11, the three-dimensional object is prepared.

[0024] Three-dimensional objects are formed from a mixture of inorganic particles and organic materials. While it is preferable that the inorganic particles and organic materials be in solid form, other states, such as gels, are also acceptable.

[0025] The ratio of inorganic particles used for molding to organic materials used for molding in a three-dimensional molded object may be 0.5 to 2.0, 0.5 to 1.5, or especially 0.5 to 1.0, as the value obtained by dividing the mass of the inorganic particles used for molding by the mass of the organic materials used for molding.

[0026] (Inorganic particles for modeling) The inorganic particles used for molding can be any inorganic particles that, after sintering in step S13 described below, become one with each other and constitute the sintered product.

[0027] The particle size of the inorganic particles used for molding is arbitrary, as long as a sintered product can be formed after sintering in step S13.

[0028] For example, the components of the inorganic particles for molding include ceramic materials, metallic materials, carbon materials, or mixtures thereof. Each particle of the inorganic particles for molding may be composed of a single material or a mixture of multiple materials. Furthermore, the inorganic particles for molding may be composed of a mixture of particles made of multiple different materials.

[0029] Ceramic materials are inorganic nonmetallic materials made from compounds composed of metallic and nonmetallic elements. Examples of ceramic materials include TCP (tricalcium phosphate), MCP (monocalcium phosphate), DCP (dicalcium phosphate), tetracalcium phosphate, hydroxyapatite, α-TCP, β-TCP, titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), yttrium oxide (yttria), yttria-stabilized zirconia, indium oxide, indium tin oxide, boron nitride, silicon carbide, boron carbide, tungsten carbide, beryllium oxide, zeolite, cerium oxide (ceria), tungsten disilicate, sodium silicide, platinum silicide, zirconium nitride, tungsten nitride, vanadium nitride, tantalum nitride, niobium nitride, silicon boride, clay, soil, cement, Portland cement, silica, barium titanate, and lead zirconate titanate. Examples include titanium, zinc oxide, potassium niobate, lithium niobate, sodium tungstate, glass, geopolymers, sodium chloride, sodium nitrate, potassium nitrate, potassium chloride, magnesium chloride, calcium chloride, calcium nitrate, magnesium nitrate, strontium oxide, strontium phosphate, calcium sulfate, barium sulfate, calcium carbonate, sodium carbonate, sodium fluoride, and mixtures thereof.

[0030] Examples of metallic materials include copper, zinc, aluminum, iron, silver, gold, palladium, platinum, tin, antimony, bismuth, lead, nickel, cobalt, vanadium, manganese, chromium, titanium, tantalum, tungsten, neodymium, lithium, sodium, osmium, iridium, uranium, thorium, plutonium, yttrium, zirconium, niobium, molybdenum, rhodium, cadmium, hafnium, rhenium, mercury, gallium, indium, thallium, lanthanum, cerium, praseodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, potassium, calcium, magnesium, strontium, barium, germanium, arsenic, and astatine, as well as their alloys and hydrides.

[0031] Examples of carbon materials include graphite, graphene, and carbon allotropes such as carbon nanotubes.

[0032] (Organic materials for modeling) The organic material for molding is any organic material that is mixed with inorganic particles for molding in a three-dimensional object and provides sufficient strength to maintain the three-dimensional shape of the object during the degreasing and sintering stages.

[0033] Although most of the organic material used for molding is degreased in step S12 described below, any remaining organic material can help maintain the three-dimensional shape of the molded object throughout steps S12 and S13.

[0034] Examples of organic materials used for molding include polymer materials.

[0035] Polymer materials include polylactic acid (PLA), polycaprolactone (PCL), polyglycolic acid (PGA), polystyrene (PS), polyethylene (PE), polypropylene (PP), polycarbonate (PC), poly(methyl methacrylate) (PMMA), poly(1,4-phenylene sulfide) (PPS), poly(2,6-dimethyl-1,4-phenylene oxide) (PPO), polyamide (PA), polybutylene terephthalate (PBT), polyether ether ketone (PEEK), polyether ketone (PEK), polyethylene terephthalate (PET), polyimide (PI), polyoxymethylene (POM), polysulfone (PSU), polyurethane (PU), polybutadiene (PB), polytetrafluoroethylene (PTFE), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polychlorotrifluoroethylene (PCTFE), and perfluoroalkoxy polymer (PFA). Examples include fluoroethylene-propylene (FEP), polyethylene tetrafluoroethylene (ETFE), polyethylene chlorotrifluoroethylene (ECTFE), polyethylene glycol (PEG), polyhydroxyalkanoic acid (PHA), polyhydroxyvaleric acid (PHV), polyhydroxybutyric acid (PHB), liquid crystal polymers, polyacrylates, polyacetals, polyamide-imides (PAI), polybutylene (PB), polyvinyl chloride (PVC), acrylonitrile butadiene styrene (ABS), polyphenylsulfone (PPSU), polymethylpentane (PMP), arginate, chitin, chitosan, acrylic acid, hyaluronic acid, starch, amylose, amylopectin, pectin, dextran, pullulan, acacia gum, xanthan gum, pullulan, cellulose, elastin, collagen, gelatin, fibronectin, silk, polysaccharides, proteins, nucleic acids, rubber, silicones, and copolymers thereof.

[0036] (Other ingredients) Three-dimensional molded objects may contain components such as pigments, monomers, oligomers, polymerization initiators, dispersants, antioxidants, surfactants, and solvents. Of these components, those that satisfy the above-mentioned definition of inorganic particles for molding are counted as inorganic particles for molding, and those that satisfy the above-mentioned definition of organic materials for molding are counted as organic materials for molding. Of these components, those that do not satisfy the above-mentioned definitions of inorganic particles and organic materials for molding are called other components.

[0037] The three-dimensional object may contain other components to an extent that does not affect the shape of the three-dimensional object after degreasing in step S12 or sintering in step S13. For example, the three-dimensional object may contain other components in an amount of 33.3 to 66.7% by mass, 40 to 66.7% by mass, or 50 to 66.7% by mass relative to the mass of the three-dimensional object.

[0038] (Method of manufacturing three-dimensional objects) The above-mentioned method for manufacturing three-dimensional objects is not particularly limited, but additive manufacturing methods, especially additive manufacturing methods using material injection, are preferable. For example, a manufacturing method that forms a three-dimensional object by layering three-dimensional ink using an inkjet method or a dispenser method is preferable.

[0039] In this method of manufacturing three-dimensional objects, three-dimensional printing ink is printed layer by layer to create a stack, and the stack is cured by external stimuli such as radiation (e.g., ultraviolet irradiation) or heating to produce a three-dimensional object with a desired three-dimensional shape.

[0040] This three-dimensional printing ink contains inorganic particles for printing and a fluid capable of forming the aforementioned polymer material, which is an organic material for printing.

[0041] The particle size of the inorganic particles for molding can be any size as long as it can be ejected from the nozzle of the inkjet nozzle or dispenser. For example, it is preferably 1 μm or less, 500 nm or less, 400 nm or less, or 300 nm or less, and preferably 10 nm or more, 50 nm or more, 100 nm or more, or 200 nm or more, and particularly preferably 200 nm to 500 nm.

[0042] A fluid capable of forming a polymer material includes a polymerizable compound (e.g., a monomer or a polymer with a lower degree of polymerization than the aforementioned polymer material) that serves as a raw material for the aforementioned polymer material, and is any fluid (e.g., liquid, gel, etc.) that can be dispensed from an inkjet nozzle or dispenser nozzle, including, for example, a fluid of the aforementioned polymerizable compound, a solution in which the polymerizable compound is dissolved, a dispersion in which the fluid or solid particles of the polymerizable compound are dispersed, or a gel of these solutions or dispersions.

[0043] Depending on the ink dispensing method and the ink curing method, the ink may contain any additional components, such as solvents, dispersants, surface tension modifiers, polymerization initiators, polymerization inhibitors, etc.

[0044] Furthermore, in some additive manufacturing methods (for example, the inkjet method for manufacturing three-dimensional objects described above), a support composition is sometimes used to surround the uncured three-dimensional object in order to maintain its shape.

[0045] If such support composition is deposited around the three-dimensional object, it is preferable to remove this support composition before proceeding to step S12. For example, if the support composition is washable (e.g., a water-soluble support composition that can be washed with water), the support composition is washed and removed between step S11 and step S12.

[0046] Also, if the support composition is naturally removed by heating in step S12 or step S13, there is no need to remove the support composition before moving to step S12. For example, when the support composition is the polymer material described above, most of such a support composition is removed in steps S12 and S13 together with the organic material for shaping the three-dimensional object, so there is no need to provide a separate removal step for the support composition. Also, when washing and removing the support composition that still remains after steps S12 and S13, since the amount of the support composition to be removed is significantly reduced, less energy consumption is required.

[0047] (Step S12) In step S12, debinding is performed by heating the three-dimensional object in at least two stages at different temperatures under an inert gas atmosphere such as a nitrogen atmosphere.

[0048] Specifically, step S12 includes steps SD1 to SD n which are n (n is an integer of 2 or more) inert gas atmosphere debinding steps. In each step SD k (k = 1 to n), the three-dimensional object is heated at temperature T k for time P k under the same or different inert gas atmospheres.

[0049] (Heating temperature) The heating temperature T k of each step SD k is set such that T k < T k+1 '. The heating temperature T1 of the first step SD1 may be higher than 25°C, for example, it may be 100°C or higher.

[0050]

[0051] The heating temperature T n of the last step SD n is preferably determined based on the relationship between the temperature and the limiting debinding rate described below from the ratio of the organic matter to be debound.

[0052] (Maximum degreasing rate) Generally, when degreasing an object by heating it at a certain temperature T, if heated for a sufficiently long time, it is not possible to remove more than R mass% of organic matter from the object, based on the organic matter content in the object before degreasing. In this specification, this R is referred to as the limiting degreasing rate at temperature T.

[0053] The critical degreasing rate can be determined, for example, by measuring the density of an object before and after degreasing and finding the degreasing rate at which no substantial change in density occurs.

[0054] The critical degreasing rate increases monotonically as the temperature increases. Therefore, there is a one-to-one correspondence between the critical degreasing rate and temperature. Thus, the heating temperature in the degreasing process can be determined from the proportion of organic matter to be degreased in the degreasing process. It is also considered that the critical degreasing rate corresponds to approximately the same temperature even when degreasing under different inert gas atmospheres.

[0055] If, in step S12, it is necessary to remove organic matter (especially the organic material used for fabrication) from the three-dimensional object to a mass percentage of the initial amount, but not beyond that, then in the final step SD n Heating temperature T n It is desirable to set the temperature to one that corresponds to the limiting degreasing rate W by mass.

[0056] For example, the final step SD n Heating temperature T n This temperature may be such that, when an object made of a molding organic material is heated in an inert gas atmosphere at that temperature for 30 minutes, 80% or more of the molding organic material in the object before heating is degreased.

[0057] If the degreasing rate is increased, for example, if more than 80% of the organic material used for molding is degreased before heating, most of the organic material will be degreased from the three-dimensional object before firing. As a result, the total amount of organic material released from the three-dimensional object during sintering is reduced, further lowering the possibility of defects occurring during the sintering process.

[0058] (Heating time) The final step SD n Heating time P n The corresponding heating temperature T n It is desirable to set the length to one that can achieve a limit degreasing rate of 70%, 80%, 90%, 99%, or 100%.

[0059] The final step SD n Each step SD excluding k Heating time P k The corresponding heating temperature T k The length may be set to achieve 50%, 60%, 70%, 80%, 90%, 99%, or 100% of the limiting degreasing rate.

[0060] (Step SD1~SD n (Implementation) Step SD1~SD n This may be performed continuously within the same degreasing apparatus, or it may be performed within different degreasing apparatuses. In either case, steps SD1 to SD n In between, the degreased 3D printed object may be removed and temporarily stored in a storage location outside the degreasing apparatus at a lower temperature than inside the apparatus (for example, 25°C).

[0061] Furthermore, the 3D printed objects stored outside the degreasing equipment were stepped to the SD k When applying this, for example, when performing the first step SD1, or when transferring a 3D printed object that has been temporarily stored outside the degreasing device as described above, to step SD k When applying this process, the three-dimensional object may be preheated at a preheating temperature lower than the degreasing temperature of the step.

[0062] Step SD within the same degreasing device k and the next step SD k+1 When this process is performed continuously, the heating rate should preferably be such that no defects occur in the three-dimensional object, for example, less than 10°C / min. The same applies to the heating rate when performing the preheating described above.

[0063] Step SD1~SD n This can be carried out by a degreasing method under any suitable inert gas atmosphere. An electric furnace or similar device can be used as the degreasing apparatus.

[0064] (Degreasing rate) In step S12, the majority of the organic matter in the three-dimensional object is ultimately removed. For example, at least 70% by mass, 75% by mass, 80% by mass, 85% by mass, 90% by mass, 95% by mass, or 99% by mass of the total amount of organic matter in the three-dimensional object prepared in step S11 may be removed through step S12. Alternatively, for example, at least 70% by mass, 75% by mass, 80% by mass, 85% by mass, 90% by mass, 95% by mass, or 99% by mass of the total amount of organic material for molding in the three-dimensional object prepared in step S11 may be removed through step S12.

[0065] Furthermore, as described above, the organic material used for molding that remains in the three-dimensional object during and / or after degreasing may help maintain the three-dimensional shape of the object throughout steps S12 and S13. For example, at least 1% by mass, 5% by mass, 10% by mass, 15% by mass, 20% by mass, 25% by mass, or 30% by mass of the total amount of organic material used for molding in the three-dimensional object prepared in step S11 may remain in the object after step S12.

[0066] (Degreasing under an oxygen atmosphere) Furthermore, optionally, after degreasing in the inert gas atmosphere described above, the three-dimensional object may be further heated and degreased in an oxygen atmosphere such as air. In this case, it is desirable that, for example, 80% of the degreasing rate described above be achieved by degreasing in the inert gas atmosphere and the remaining 20% ​​by degreasing in an oxygen atmosphere. Degreasing in an oxygen atmosphere can be carried out by any appropriate degreasing method.

[0067] (Step S13) In step S13, the three-dimensional object that was degreased in step S12 is sintered to obtain a sintered product.

[0068] The sintering temperature is arbitrary as long as it is higher than the degreasing temperature mentioned above and the inorganic particles for molding become one with each other after sintering to form a sintered product. For example, if the material of the inorganic particles for molding is alumina, the sintering temperature is preferably 1500°C to 1700°C.

[0069] Sintering can be carried out using any suitable sintering method. An electric furnace or similar device can be used as the sintering apparatus.

[0070] (Effects of this manufacturing method) Conventionally, when manufacturing sintered products by degreasing and sintering a three-dimensional object, the degreasing process involves rapidly heating the object to a desired degreasing temperature (for example, at a heating rate of 10°C / min), and then heating it at a constant degreasing temperature until most of the organic matter in the three-dimensional object is removed.

[0071] However, when degreasing three-dimensional objects with a high resin content using conventional degreasing processes, there was a problem in that defects such as cracks and distortions were likely to occur.

[0072] While we do not wish to limit ourselves to these, the following are possible reasons why this problem occurs. Generally, due to differences in thermal conductivity between parts of a three-dimensional object, some parts may heat up more easily than others during the degreasing process. Therefore, when degreasing a three-dimensional object with a high resin content using conventional degreasing processes, the degree of heating differs between adjacent parts, resulting in different release rates of degreasing components released as gas from those parts. This makes it more likely for defects such as cracks and distortions to occur at the boundaries of these parts.

[0073] Furthermore, due to the increasing demand for highly aesthetically pleasing three-dimensional objects, there is a desire to create three-dimensional objects with complex designs using inkjet printers, and then degrease and sinter them to produce fired products. However, three-dimensional objects formed with inkjet printers have a high resin content, and in the case of three-dimensional objects with complex designs, uneven heating in different parts is particularly pronounced, making the possibility of defects like those described above even higher.

[0074] On the one hand, according to this manufacturing method, since degreasing is performed step by step, the occurrence of defects such as cracks and distortions can be suppressed.

[0075] As its principle, although it is not desired to be limited to this, the following can be considered. When degreasing on the high-temperature side, the total amount of gas of the organic material released from the three-dimensional shaped object is reduced. Therefore, even if there is a heating bias in adjacent parts within the three-dimensional shaped object, the influence of the gas released from those parts is small, and the possibility of defects occurring at the boundaries of those parts is reduced. Thereby, the occurrence of defects such as cracks and distortions can be suppressed, and a sintered product can be manufactured from the three-dimensional shaped object.

[0076] (Variant example) When the three-dimensional shaped object contains a plurality of organic components with different degreasing temperatures, each step SD k heating temperature T k may be set according to the degreasing temperature of each. For example, when the temperature at which those organic components start to be degreased (hereinafter referred to as the degreasing start temperature) is TD1 to TD m (m is an integer of 2 or more), the heating temperature T l+k of m consecutive steps SD l+k may be equal to TD k , or may be approximately the same as TD k (for example, within ±10% of TD k ), or may be in the range of TD k - 20°C to TD k - 10°C.

[0077] Also, the steps SD m using the heating temperature T k corresponding to TD1 to TD k do not necessarily have to be continuous. For example, the step SD k using the heating temperature T k corresponding to TD k and the step SD k+1 using the heating temperature T k+1 corresponding to TDk+1 Between, T k ≦T p ≦T k+1 The heating temperature T is the result. p Step SD using p It may exist.

[0078] For example, Figure 2 shows a schematic diagram of the TGA curve when a three-dimensional object of a certain composition is heated in a nitrogen atmosphere under a heating rate of 10°C / min. The horizontal axis represents temperature (°C), and the vertical axis represents the mass loss rate (mass % / min) relative to the initial weight. As indicated by the arrows in the figure, this curve has three peaks, which suggests that the three-dimensional object contains three different organic components that are degreased at different temperatures. Note that the temperatures at which these organic components begin to degrease do not necessarily coincide with the temperatures at which the corresponding peaks in the figure are produced, and are generally considered to be lower than those temperatures, around the peak rise temperatures. In Figure 2, the degreasing start temperature for the organic component corresponding to peak 1 is thought to be around 200°C, the degreasing start temperature for the organic component corresponding to peak 2 is thought to be around 310°C, and the degreasing start temperature for the organic component corresponding to peak 3 is thought to be around 420°C. In this case, the degreasing process may be performed at these temperatures.

[0079] The degreasing start temperature for each organic component in a three-dimensional object can be determined by thermogravimetric analysis.

[0080] Also, each step SD k In this case, a constant heating temperature T k Instead of heating by [this method], the average heating temperature is set to heating temperature T within a predetermined temperature range. k The heating may be carried out in such a way that it results in the following. For example, a certain step SD k In this case, heating temperature T k ±50℃, heating temperature T k ±40℃, heating temperature T k ±30℃, heating temperature T k ±20℃, heating temperature T k ±10℃ or heating temperature T k With a temperature range of ±5℃, the average heating temperature is the heating temperature T kTo achieve this, the temperature may be raised at a constant rate of heating or lowered at a constant rate of cooling. In this case, step SD k The heating rate or cooling rate in steps SD1 to SD k It is desirable that the absolute value be sufficiently smaller than the heating rate between steps SD1 to SD1. k It is preferable that the absolute value is smaller than 50%, 40%, 30%, 20%, 10%, and 5% of the intermediate heating rate. The average heating temperature can be calculated by dividing the cumulative heating temperature during heating by the time required for heating. Similarly, in the sintering process, heating may be performed not at a constant sintering temperature, but over a predetermined temperature range so that the average sintering temperature becomes the aforementioned sintering temperature.

[0081] (Examples) (Example 1) We prepared ink for a 3D inkjet printer and used an inkjet printer (UV-curing inkjet full-color 3D printer, 3DUJ-553, manufactured by Mimaki Engineering Co., Ltd.) to form a rectangular prism measuring 5cm x 5cm x 5cm.

[0082] Ink for 3D inkjet printers is As a ceramic component (pigment), 38.8 parts of small-particle high-purity alumina (Sumitomo Chemical Co., Ltd., AKP-53, median particle size 0.18 μm) are used. As a dispersant, an active polymer dispersant (manufactured by Lubrizol, trade name: SOLSPERSE 36000, pour point: 40°C, boiling point: approximately 200°C, flash point: approximately 200°C, density: 1.05 g / cm³) is used. 3 )0.91 copies, As the binder component oligomer, an aliphatic polyester urethane acrylate oligomer (manufactured by Sartomer, product name: CN968, number of functional groups: 6, density: 1.2 g / cm³) is used. 3 )8.3 parts, The binder components consist of 12.4 parts of benzyl acrylate (BZA) and 32.8 parts of phenoxyethyl acrylate (PEA) as monomers. As photopolymerization initiators, 0.50 parts of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide (manufactured by Ciba Specialty Chemicals, trade name: Irg819) and 4.66 parts of 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide (manufactured by BASF, trade name: Irgacure-TPO) were used. As a thioxanthone-based sensitizer, 1.58 parts of 2,4-diethylthioxanthene-9-one (DETX) were added. As a polymerization inhibitor, 0.04 parts of 2,5-di-tert-butylhydroquinone (manufactured by Seiko Chemical Co., Ltd., product name: Nonflex Alba) As a radiation-curable additive, 0.046 parts of fully crosslinked silicone polyether acrylate (manufactured by Evonik Resource Efficiency GmbH, trade name: TEGO RAD2100, short-chain siloxane skeleton / long-chain organic modified highly crosslinked additive) were mixed in. Prepared.

[0083] A rectangular parallelepiped was degreased and sintered in an electric furnace (Tammann tube atmosphere electric furnace S7T-2025D-SP, manufactured by Motoyama Co., Ltd.) under the following conditions to obtain sintered product E1. The degreasing conditions are also shown in Figure 3. The heating rate between each process was set to 40°C / hour. (1) First degreasing process Atmosphere: Nitrogen Degreasing temperature: 300℃ Degreasing time: 15 minutes (2)Second degreasing process Atmosphere: Nitrogen Degreasing temperature: 310℃ Degreasing time: 15 minutes (3) Third degreasing process Atmosphere: Nitrogen Degreasing temperature: 320℃ Degreasing time: 15 minutes (4) Fourth degreasing process Atmosphere: Nitrogen Degreasing temperature: 330℃ Degreasing time: 15 minutes (5) Fifth degreasing process Atmosphere: Nitrogen Degreasing temperature: 340℃ Degreasing time: 15 minutes (6) Sintering process Atmosphere: Nitrogen Sintering temperature: 1600℃ Sintering time: 6 hours

[0084] No defects were observed in sintered product E1.

Claims

1. A three-dimensional object preparation step, comprising: preparing a three-dimensional object formed from a mixture of inorganic particles and an organic material which is the polymer material, by extruding an ink containing a polymerizable compound and a fluid capable of forming a polymer material and inorganic particles from a nozzle using an inkjet method or a dispenser method to form a laminate, and curing the polymerizable compound in the laminate to form the polymer material; A first degreasing step involves heating the three-dimensional object in an inert gas atmosphere at a first average degreasing temperature for a first predetermined time to degrease the organic material, A second degreasing step is performed in which the three-dimensional molded object, after degreasing in the first degreasing step, is heated in an inert gas atmosphere at a second average degreasing temperature higher than the first average degreasing temperature for a second predetermined time to degrease the organic material, The second degreasing step is a sintering step in which the degreased three-dimensional molded object is heated at an average sintering temperature higher than the second average degreasing temperature and at an average sintering temperature that allows the inorganic particles to become one with each other and form a sintered product after sintering, Equipped with, The fluid can be dispensed from an inkjet nozzle or a dispenser nozzle. The process further includes one or more additional degreasing steps between the first degreasing step and the second degreasing step, in which the three-dimensional molded object is heated and degreased in an inert atmosphere at an average degreasing temperature higher than the average degreasing temperature of the first step and lower than the average degreasing temperature of the second step. If there are two or more of the above-mentioned additional degreasing steps, the average degreasing temperature of the above-mentioned additional degreasing steps is increased in stages. A method for manufacturing sintered products from three-dimensionally molded objects.

2. In the first degreasing step and the second degreasing step, the heating rate when heating to the first average degreasing temperature and the second average degreasing temperature is less than 10°C / min. The method according to claim 1.

3. The second average degreasing temperature is the temperature at which, when the object made of the organic material is heated in an inert gas atmosphere for 30 minutes at that temperature, 80% or more by mass of the organic material in the object before heating is degreased. The method according to claim 1 or 2.

4. The ratio of inorganic particles to organic material in the three-dimensional object prepared in the three-dimensional object preparation step is 0.5 to 2.0, which is the value obtained by dividing the mass of the inorganic particles by the mass of the organic material. The method according to any one of claims 1 to 3.

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