Molding liquid and method for manufacturing molded objects

Abstract

To provide a molding fluid which has excellent dischargeability in a binder jetting method, and can increase a glass transition point of a resin in a resulting green body even when a molding fluid containing a binder resin with a low glass transition point is used, and which has excellent strength of the green body and can suppress deformation of the green body.SOLUTION: This invention relates to a molding fluid to be applied to a layer of a powder containing metal particles, containing oligomer having a ring structure with an average molecular weight of 3,000 or less and an organic solvent, and substantially containing no water.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a molding fluid and a method for manufacturing molded objects. [Background technology]

[0002] In recent years, there has been a growing need to produce complex and intricate objects made of metals and other materials. To meet this need, particularly from the perspective of high productivity, there is a method in which a sintered precursor fabricated using the binder jetting method is sintered and densified using powder metallurgy.

[0003] As for metals, a wide variety of metals are being considered, including aluminum alloys. Among these, solvent-based inks are being considered as binder jetting inks suitable for aluminum alloys, from the standpoint of safety and handling for aluminum powder. As for resins, resins containing many hydrophobic functional groups are being considered as binder resins that have high solubility in solvents and good degreasing properties.

[0004] As a composition for 3D printers containing inorganic powder, for example, a composition for 3D printers containing inorganic powder, an organic binder, and an organic compound with a molecular weight or weight-average molecular weight of 2,000 or less has been proposed (see Patent Document 1). [Overview of the project] [Problems that the invention aims to solve]

[0005] The present invention aims to provide a molding fluid that, even when using a molding fluid containing a binder resin with excellent extrusion properties and a low glass transition temperature in a binder jetting method, can increase the glass transition temperature of the resin in the resulting green body, thereby providing a green body with excellent strength and reduced deformation. [Means for solving the problem]

[0006] The molding liquid of the present invention, as a means for solving the aforementioned problems, is a molding liquid applied to a powder layer containing metal particles, and contains an oligomer having a ring structure and a number average molecular weight of 3,000 or less, and an organic solvent, and substantially no water. [Effects of the Invention]

[0007] According to the present invention, even when using a molding fluid containing a binder resin with excellent extrusion properties and a low glass transition temperature in a binder jetting method, it is possible to increase the glass transition temperature of the resin in the resulting green body, thereby providing a molding fluid that has excellent strength and can suppress deformation in the green body. [Brief explanation of the drawing]

[0008] [Figure 1A] Figure 1A is a schematic diagram showing an example of the operation of a three-dimensional object manufacturing apparatus. [Figure 1B] Figure 1B is a schematic diagram showing another example of the operation of a three-dimensional object manufacturing apparatus. [Figure 1C] Figure 1C is a schematic diagram showing another example of the operation of a three-dimensional object manufacturing apparatus. [Figure 1D] Figure 1D is a schematic diagram showing another example of the operation of a three-dimensional object manufacturing apparatus. [Figure 1E] Figure 1E is a schematic diagram showing another example of the operation of a three-dimensional object manufacturing apparatus. [Modes for carrying out the invention]

[0009] (modeling liquid) The molding fluid of the present invention is a molding fluid applied to a layer of powder containing metal particles, It contains an oligomer having a ring structure and a number-average molecular weight of 3,000 or less, and an organic solvent. It contains virtually no water.

[0010] The present invention relates to a problem in the prior art, namely, that as the range of resins for binder jetting methods has diversified, polyvinyl acetate-based resins, which have high solubility in organic solvents and excellent jetting properties, have a relatively low glass transition temperature (Tg). The inventors have found that green bodies solidified with resins with a relatively low Tg are at risk of deformation during long-term storage due to the effects of moisture absorption and storage temperature. Furthermore, the 3D printer composition described in the prior art document Japanese Patent Publication No. 2020-015848 contains an organic binder and an oligomer as a 3D modeling material, but it is not an ink and is used in fused deposition modeling (FDM), which presents a problem as it is not suitable as an ink in the binder jetting method.

[0011] The "molding liquid" of the present invention is a liquid composition used in the manufacture of molded objects and applied to a layer of powder containing metal particles. The molding liquid of the present invention contains an oligomer having a ring structure and an organic solvent, substantially free of water, and optionally contains additives such as resins and surfactants. The manufacturing of the molded object is carried out by a manufacturing method that includes a powder layer formation step of forming a layer of powder containing metal particles, a molding fluid application step of applying molding fluid to the powder layer, and a lamination step of forming a laminate by sequentially repeating the powder layer formation step and the molding fluid application step. Furthermore, it is preferable that the manufacturing of the molded object be carried out by a manufacturing method that includes, in addition to the above-mentioned lamination process, a heating process to form a solid by heating the lamination; an excess powder removal process to obtain a green body by removing excess powder adhering to the solid, a drying process to remove any remaining liquid components from the green body by drying the green body; a degreasing process to obtain a degreased body by heating the green body and removing resin and other substances derived from the applied molding fluid; a sintering process to obtain a sintered body by heating the degreased body; and a post-processing process to perform post-treatment on the sintered body. In the present disclosure, the term "three-dimensional modeled object" is a general term for three-dimensional objects that maintain a fixed three-dimensional shape. For example, it refers to a solidified product or a structure derived from a solidified product, and specifically is a concept encompassing solidified products, green bodies, degreased bodies, and sintered bodies. Note that the modeled object after the heating step may be referred to as a "green body (unsintered body)", the modeled object after the degreasing step may be referred to as a "degreased body", and the modeled object after the sintering step may be referred to as a "sintered body" in some cases.

[0012] <Oligomer Having a Cyclic Structure> The oligomer having a cyclic structure is an oligomer that has a cyclic structure and a number average molecular weight of 3,000 or less. The number average molecular weight of the oligomer having a cyclic structure is 3,000 or less; from the standpoint that the increase in viscosity of the modeling liquid (ink) is moderate and degreasing performance is favorable, the number average molecular weight is preferably 2,500 or less, and more preferably 2,000 or less. The number average molecular weight of the oligomer having a cyclic structure is preferably 500 or more. There are no particular limitations on the method for measuring the number average molecular weight, and it can be appropriately selected according to the purpose. For example, it can be measured by gel permeation chromatography.

[0013] There are no particular limitations on the glass transition temperature (Tg) of the oligomer having a cyclic structure, and it can be appropriately selected according to the purpose, but it is preferably 55°C or higher, more preferably 70°C or higher, and still more preferably 80°C or higher. Further, it is preferably 110°C or lower, more preferably 105°C or lower, and still more preferably 100°C or lower.

[0014] The glass transition temperature (Tg) can be measured, for example, using a DSC system (differential scanning calorimeter) (DSC2500, manufactured by TA Instruments Japan Inc.). Specifically, the glass transition temperature (Tg) of a target sample can be measured by the following procedure. First, 5 mg of the target sample is placed in an alumina sample container, the sample container is placed on a holder unit, and set in an electric furnace. Next, the sample is heated from -30°C to 200°C at a temperature increase rate of 10°C / min under a nitrogen atmosphere. Thereafter, the sample is cooled from 200°C to -30°C at a temperature decrease rate of 10°C / min, further heated to 200°C at a temperature increase rate of 10°C / min, and a DSC curve is measured using a differential scanning calorimeter. From the obtained DSC curve, using the analysis program "Endothermic Shoulder Temperature" in the DSC system, the DSC curve during the first temperature increase is selected, and the glass transition temperature of the target sample during the first temperature increase can be obtained. Further, using the "Endothermic Shoulder Temperature", the DSC curve during the second temperature increase is selected, and the glass transition temperature of the target sample during the second temperature increase can be obtained.

[0015] The softening point of the oligomer having a ring structure is preferably 100°C or higher, more preferably 120°C or higher, and still more preferably 140°C or higher. Further, it is preferably 180°C or lower, more preferably 170°C or lower, and still more preferably 160°C or lower. The softening point can be measured using a micro melting point apparatus (for example, MP-S3, manufactured by Yanaco Instrument Development Research Institute Co., Ltd.). The softening point is measured by increasing the temperature of the target sample at a rate of 2°C / min and observing the state of the target sample.

[0016] Since the oligomer having a ring structure is a hydrocarbon compound having a ring structure, it has a high density and is advantageous in that it has a high Tg relative to its molecular weight. Further, the oligomer having a ring structure has a low number-average molecular weight, and is advantageous in that it has good fluidity in a high temperature region equal to or higher than the softening point, easily wets an adherend, easily exhibits adhesiveness, and exhibits cohesive force when cooled. In addition, the oligomer having a ring structure is advantageous in that it has high compatibility with the hydrophobic portion of the binder resin. Therefore, by containing the oligomer having the ring structure in the molding fluid, the oligomer having the ring structure and a binder resin such as vinyl acetate become compatible, allowing them to wet and bond firmly at the metal particle interface, and after cooling, a binder structure with a high Tg can be formed. Consequently, even when using a molding fluid containing a binder resin with a low glass transition temperature, the glass transition temperature of the resin in the resulting green body can be increased, providing a molding fluid with excellent strength and reduced deformation in the green body.

[0017] The oligomer having the aforementioned ring structure is not particularly limited and can be appropriately selected depending on the purpose. Examples include aromatic oligomers such as copolymers having aromatic rings and copolymers having hydrogenated aromatic rings; terpene resins such as polyterpene resins, hydrogenated terpene resins, aromatically modified terpene resins, and terpene phenol resins; rosin resins such as rosin-modified phenol resins and rosin ester resins; and alkylphenol resins. The oligomer having the aforementioned ring structure preferably has an unsaturated bond in the ring structure, and more preferably includes a thermoplastic oligomer having an unsaturated bond in the ring structure. These may be used individually or in combination of two or more types. Here, "thermoplastic oligomer" refers to an oligomer that has at least one of a glass transition temperature (Tg) and a softening temperature.

[0018] <<Aromatic oligomers>> Examples of the aromatic oligomers include copolymers having aromatic rings and copolymers having hydrogenated aromatic rings. The copolymer having the aromatic ring is a copolymer having repeating structural units having the aromatic ring and other repeating structural units, and may be a block copolymer or a random copolymer. The copolymer having the hydrogenated aromatic ring is a copolymer having repeating structural units having the hydrogenated aromatic ring and other repeating structural units, and may be a block copolymer or a random copolymer. Here, "hydrogenated" or "hydrogenated" refers to a ring structure that has been reduced by adding hydrogen to the unsaturated bonds of an aromatic ring. There are no particular restrictions on the glass transition temperature (Tg) of the aromatic oligomer, and it can be appropriately selected depending on the purpose, but 80°C to 100°C is preferred.

[0019] The aromatic ring and the hydrogenated aromatic ring are not particularly limited and can be appropriately selected depending on the purpose. Examples include aromatic hydrocarbons and condensed rings formed by their condensation, which may have substituents. Among these, aromatic hydrocarbons with five or six membered rings and condensed rings formed by their condensation are preferred, and these may also have substituents. The repeating structural unit having an aromatic ring and the repeating structural unit having a hydrogenated aromatic ring may be a repeating structural unit having a ring structure that constitutes any of the terpene resin, the rosin resin, and the alkylphenol resin. The aforementioned other repeating structural units are not particularly limited and can be appropriately selected depending on the purpose, and examples include allyl compounds and vinyl compounds.

[0020] An example of a copolymer having the aromatic ring is poly(styrene-co-allyl alcohol), which is a copolymer having repeating structural units derived from styrene (number of repeating structural units: x) and repeating structural units derived from allyl alcohol (number of repeating structural units: y), as shown in the following structural formula. [ka]

[0021] The aromatic oligomer may be synthesized or a commercially available product. Examples of the commercially available product include TEGO Vari Plus SK (polystyrene-containing polyol resin, manufactured by Evonik, e.g., number average molecular weight (Mn): 2,500, Tg: 94°C), poly(styrene-co-allyl alcohol) (polymer having an aromatic ring, manufactured by Sigma-Aldrich LLC, e.g., number average molecular weight (Mn): 1,200, Tg: 92°C), and poly(styrene-co-maleic anhydride) (manufactured by Sigma-Aldrich LLC, e.g., number average molecular weight (Mn): 1,900, Tg: 71°C).

[0022] The Tg of the aromatic oligomer is preferably 60°C to 140°C, and more preferably 80°C to 120°C. The aforementioned aromatic oligomers have an advantage in that their aromatic ring skeleton is hydrophobic, making them less susceptible to moisture absorption and less likely to cause a decrease in Tg under high humidity conditions.

[0023] <<Terpene resins>> Examples of the terpene resins include polyterpene resins, hydrogenated terpene resins, aromatically modified terpene resins, and terpene phenol resins. There are no particular restrictions on the terpenes used as raw materials for the aforementioned terpene resins. Depending on the purpose, terpenes having a ring structure can be appropriately selected. Examples include α-pinene, β-pinene, dipentene (limonene), α-terpinene, β-terpinene, terpinolene, camphene, and Δ3-carene, which are represented by the following structural formulas. Among these, α-pinene, β-pinene, and dipentene (limonene) are preferred.

[0024] [ka]

[0025] Examples of the terpene-based resins include, for example, polyterpene resins, hydrogenated terpene resins, aromatically modified terpene resins, and terpene phenol resins, which are represented by the following structural formulas, when the terpene used as a raw material is any of α-pinene, β-pinene, or dipentene (limonene). [ka]

[0026] The terpene resin may be synthesized or a commercially available product. Examples of commercially available products include YS Polystar G150 (terpene phenol resin, manufactured by Yasuhara Chemical Co., Ltd., number average molecular weight (Mn): 700, Tg: 92℃), YS Resin PX1250 (polyterpene resin, manufactured by Yasuhara Chemical Co., Ltd., number average molecular weight (Mn): 1,100, Tg: 69℃), Clearon P125 (hydrogenated terpene resin, manufactured by Yasuhara Chemical Co., Ltd., for example, number average molecular weight (Mn): 700, Tg: 68℃), and YS Resin TO125 (aromatically modified terpene resin, manufactured by Yasuhara Chemical Co., Ltd., for example, number average molecular weight (Mn): 800, Tg: 64℃).

[0027] The Tg of the terpene resin is preferably 55°C to 105°C, and more preferably 60°C to 120°C. The aforementioned terpene resin has the advantage of being less susceptible to moisture absorption and less prone to Tg reduction under high humidity conditions, due to its hydrophobic terpene skeleton.

[0028] <<Rosin-based resin>> Examples of the rosin-based resins include rosin-modified phenolic resins and rosin ester resins. There are no particular restrictions on the rosin used as a raw material for the aforementioned rosin-based resin; rosin can be appropriately selected depending on the purpose, and examples include abietic acid, palastic acid, and isopimal.

[0029] The rosin-based resin may be synthesized or a commercially available product. Examples of commercially available products include Tamanol 135 (rosin-modified phenolic resin, manufactured by Arakawa Chemical Industries, Ltd., e.g., Tg: 70°C to 80°C) and Pencel D-135 (rosin ester resin, manufactured by Arakawa Chemical Industries, Ltd., e.g., Tg: 70°C to 80°C).

[0030] <<Alkylphenol resin>> The alkylphenol resin may be synthesized or a commercially available product. An example of the commercially available product is Tamanol 200N (alkylphenol resin, manufactured by Arakawa Chemical Industries, Ltd., for example, Tg: 70℃~80℃).

[0031] There are no particular restrictions on the content of the oligomer having the ring structure, and it can be appropriately selected according to the purpose, but it is preferably 2% by mass or more and 45% by mass or less, and more preferably 3% by mass or more and 7% by mass or less, relative to the mass of the molding fluid. When the content is 45% by mass or less, the viscosity of the molding fluid can be kept low, and for example, the molding fluid can be appropriately ejected using an inkjet method. When the content is 2% by mass or more, the bending strength of the molded product before sintering, such as the solidified product and the green body derived from the solidified product, is further improved.

[0032] <Resin> The molding fluid preferably further contains a resin having a structural unit represented by the following structural formula (1). Note that "resin" may be referred to as a binder resin. The structural unit represented by the above structural formula (1) is a structural unit of polyvinyl acetate. [ka]

[0033] The resin having the structural unit represented by structural formula (1) is arranged within the powder layer when the molding fluid is applied to the powder layer containing metal particles. Through an appropriate heating process corresponding to the resin's softening point, it functions as a binder that binds the metal particles together in the area where the molding fluid is applied, forming pre-sintered molded objects such as solidified material and green bodies derived from the solidified material. Because these pre-sintered molded objects are formed from a resin having the structural unit represented by structural formula (1) that imparts flexibility, their bending strength is improved.

[0034] Furthermore, the resin having the structural unit represented by the structural formula (1) exhibits excellent thermal decomposition properties, allowing it to be appropriately removed in the degreasing process, thereby improving the density of the sintered body produced through the subsequent sintering process. Therefore, the effects obtained become more pronounced when metal particles, which are materials intended for or preferably sintered, are used as the material for forming the molded object. Specifically, the resin having the structural unit represented by structural formula (1) is preferably thermally decomposed by 95% by mass or more when the temperature is raised from 30°C to 550°C, and more preferably by 97% by mass or more. Here, "thermal decomposition of the resin" means that random decomposition of the main chain or depolymerization at the molecular chain ends occurs, and the resin is removed by vaporization, oxidative decomposition, combustion, etc. Furthermore, thermal decomposition is measured using a TG-DTA (Differential Thermal Analysis-Thermogravimetric Analysis) device. Specifically, the temperature is raised from 30°C to 550°C at a rate of 10°C / min in an air or nitrogen atmosphere, and then the temperature is maintained for 2 hours after reaching 550°C, and the weight loss rate before and after the temperature increase is determined.

[0035] Furthermore, resins having the structural unit represented by structural formula (1) exhibit improved solubility in organic solvents due to the hydrophobicity of the structural unit represented by structural formula (1). Therefore, when the molding fluid contains an organic solvent, the solubility of the resin having the structural unit represented by structural formula (1) is improved, which in turn reduces the viscosity of the molding fluid, allowing for proper ejection of the molding fluid, for example, using an inkjet method. Furthermore, it is preferable that the resin having the structural unit represented by structural formula (1) is soluble in the organic solvent of the molding liquid and insoluble in water.

[0036] The Tg of the resin having the structural unit represented by structural formula (1) is preferably 0°C or higher, more preferably 10°C or higher, and even more preferably 20°C or higher. Furthermore, it is preferably 100°C or lower, more preferably 90°C or lower, and even more preferably 80°C or lower.

[0037] The softening point of the resin having the structural unit represented by structural formula (1) is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher. Furthermore, it is preferably 150°C or lower, more preferably 140°C or lower, and even more preferably 130°C or lower.

[0038] The number-average molecular weight (Mn) of the resin having the structural unit represented by structural formula (1) is preferably 5,000 to 50,000, and more preferably 10,000 to 30,000. Having the number-average molecular weight (Mn) within this range allows for both improved strength and molding accuracy, as well as reduced viscosity of the molding fluid and increased resin concentration in the molding fluid.

[0039] A resin having structural units represented by structural formula (1) may also be a resin having structural units other than those represented by structural formula (1), or it may be a resin consisting only of structural units represented by structural formula (1). Other preferred structural units besides structural formula (1) include, for example, the structural unit represented by structural formula (2) and the structural unit represented by structural formula (3) below. [ka] [ka]

[0040] A resin having structural units represented by structural formula (2) in addition to structural units represented by structural formula (1) improves the flexural strength of pre-sintered molded products such as solidified products and green bodies derived from solidified products. Furthermore, the structural unit represented by structural formula (2) is hydrophobic, just like the structural unit represented by structural formula (1), which improves the solubility of the resin in organic solvents. From these viewpoints, in the resin, the total amount of structural units represented by structural formula (1) and structural units represented by structural formula (2) is preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, even more preferably 75 mol% or more, and particularly preferably 80 mol% or more. The same applies if the resin does not have structural units represented by structural formula (2) or structural formula (3); the above ratio can be calculated by setting the amount of the missing structural units to 0.

[0041] A resin having a structural unit represented by structural formula (3) in addition to the structural unit represented by structural formula (1) improves the affinity with metal particles in the powder layer to which the molding fluid is applied, due to the hydroxyl groups in the structural unit represented by structural formula (3). As a result, the bending strength of the molded product before sintering, such as the solidified product and the green body derived from the solidified product, is further improved, as is the density of the molded product before sintering and the density of the molded product after sintering. From these viewpoints, in the resin, the amount of structural units represented by structural formula (3) is preferably 5 mol% or more, more preferably 15 mol% or more, and even more preferably 25 mol% or more, relative to the total amount of structural units represented by structural formula (1), structural units represented by structural formula (2), and structural units represented by structural formula (3). However, since the structural unit represented by structural formula (3) is hydrophilic, an increase in the proportion of structural units represented by structural formula (3) suppresses the improvement in the solubility of the resin having structural units represented by structural formula (1) when the molding fluid contains an organic solvent, and consequently suppresses the decrease in the viscosity of the molding fluid. From this perspective, in the resin, the amount of structural units represented by structural formula (3) is preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 30 mol% or less, even more preferably 25 mol% or less, and particularly preferably 20 mol% or less, relative to the total amount of structural units represented by structural formula (1), structural units represented by structural formula (2), and structural units represented by structural formula (3). The same applies when the resin does not have structural units represented by structural formula (2); the above ratio can be calculated by setting the amount of the missing structural units to 0.

[0042] Examples of resins having a structural unit represented by structural formula (1) include polyvinyl acetate resin, partially saponified polyvinyl acetate resin, and polyvinyl butyral resin. Among these, polyvinyl acetate resin and a predetermined partially saponified polyvinyl acetate resin are preferred because they can reduce the viscosity of the molding fluid. Here, the specified partially saponified polyvinyl acetate resin refers to a partially saponified polyvinyl acetate resin in which the amount of structural units represented by structural formula (1) is 75 mol% or more of the total amount of structural units represented by structural formula (1) and structural formula (3), and preferably a partially saponified polyvinyl acetate resin in which the amount is 80 mol% or more. These resins may be used individually or in combination of two or more types. Both commercially available and synthetic resins can be used.

[0043] The polyvinyl acetate resin is a resin having structural units represented by structural formula (1) and substantially lacking structural units represented by structural formula (2) and structural formula (3). Partially saponified polyvinyl acetate resin is a resin that has structural units represented by structural formula (1) and structural units represented by structural formula (3), but substantially does not have structural units represented by structural formula (2). Polyvinyl butyral resin is a resin having structural units represented by structural formula (1) and structural units represented by structural formula (2), or a resin having structural units represented by structural formula (1), structural units represented by structural formula (2), and structural units represented by structural formula (3). Partially saponified polyvinyl acetate resin is a resin obtained by partially saponifying polyvinyl acetate resin. Furthermore, in the partially saponified polyvinyl acetate resin in this disclosure, the amount of structural units represented by structural formula (3) is 40 mol% or less, preferably 35 mol% or less, more preferably 30 mol% or less, even more preferably 25 mol% or less, and even more preferably 20 mol% or less, relative to the total amount of structural units represented by structural formula (1) and structural formula (3). In other words, the degree of saponification of the partially saponified polyvinyl acetate resin in this disclosure is 40 or less, preferably 35 or less, more preferably 30 or less, even more preferably 25 or less, and even more preferably 20 or less.

[0044] The content of the resin having the structural unit represented by structural formula (1) is preferably 5.0% by mass or more, more preferably 7.0% by mass or more, even more preferably 10.0% by mass or more, and particularly preferably 11.0% by mass or more, relative to the mass of the molding fluid. Furthermore, it is preferably 30.0% by mass or less, more preferably 25.0% by mass or less, and even more preferably 20.0% by mass or less. When the content is 5.0% by mass or more, the flexural strength of the molded product before sintering, such as the solidified product and the green body derived from the solidified product, is further improved. Furthermore, when the content is 30.0% by mass or less, the viscosity of the molding fluid is further reduced, allowing the molding fluid to be appropriately ejected, for example, by an inkjet method. Furthermore, resins in which the total amount of structural units represented by structural formula (1) and structural formula (2) is 95 mol% or more of the total amount of structural units represented by structural formula (1), structural formula (2), and structural formula (3) have improved solubility in organic solvents and reduced viscosity of the molding fluid, so they can also be included in high mass (for example, 15.0% by mass or more or 20.0% by mass or more relative to the mass of the molding fluid). This further improves the bending strength of molded products before sintering, such as solidified products and green bodies derived from solidified products.

[0045] The amount (mol%) of each structural unit represented by its structural formula in the resin can be determined, for example, by the polyvinyl alcohol test method described in JIS-K6276-1994.

[0046] <Organic solvents> The aforementioned molding fluid contains an organic solvent. The organic solvent is a liquid component used to keep the molding fluid in a liquid state at room temperature. Furthermore, it is preferable that the molding fluid is a non-aqueous type of molding fluid, as it contains an organic solvent. Here, "non-aqueous molding fluid" refers to a molding fluid that contains an organic solvent as a liquid component, and in which the component with the largest mass is the organic solvent. Furthermore, the content of the organic solvent relative to the liquid component content in the molding fluid is preferably 90.0% by mass or more, and more preferably 95.0% by mass or more. Using a non-aqueous molding fluid is advantageous in that it improves solubility, particularly in resins having structural units represented by structural formula (1), and reduces the viscosity of the molding fluid. Furthermore, non-aqueous 3D printing fluids can sometimes be described as 3D printing fluids that are substantially water-free. This allows the 3D printing fluid to be applied even when the materials constituting the metal particles are highly reactive metals, or in other words, water-reactive materials (e.g., aluminum, zinc, and magnesium). For example, aluminum forms an aluminum hydroxide film when it comes into contact with water, so a high water content in the 3D printing fluid can lead to a decrease in the sintering density of the sintered body. However, this problem can be suppressed by using a 3D printing fluid that does not contain water. As another example, aluminum is difficult to handle because it generates hydrogen when it comes into contact with water, but this problem can also be suppressed by using a 3D printing fluid that does not contain water.

[0047] Examples of organic solvents include n-octane, m-xylene, solvent naphtha, diisobutyl ketone, 3-heptanone, 2-octanone, acetylacetone, butyl acetate, amyl acetate, n-hexyl acetate, n-octyl acetate, ethyl butyrate, ethyl valerate, ethyl caprylate, ethyl octanoate, ethyl acetoacetate, ethyl 3-ethoxypropionate, diethyl oxalate, diethyl malonate, diethyl succinate, diethyl adipate, bis-2-ethylhexyl maleate, triacetin, tributyl Examples include phosphorus, propylene glycol monomethyl ether acetate, ethylene glycol monobutyl ether acetate, dibutyl ether, 1,2-dimethoxybenzene, 1,4-dimethoxybenzene, diethylene glycol monobutyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, α-Terpionel, 2-methoxy-1-methylethyl acetate, γ-butyrolactone, propylene carbonate, cyclohexanone, and butyl cellosolve. These may be used individually or in combination of two or more.

[0048] When using a resin having a structural unit represented by structural formula (1), there are no particular restrictions on the organic solvent used in combination, and it can be appropriately selected according to the purpose. However, an organic solvent having at least one structure selected from the group consisting of alkoxy groups, ether bonds, and ester bonds is preferred, an organic solvent having an ether bond is more preferred, and alkylene glycol dialkyl ethers are particularly preferred. When these organic solvents are used, the solubility of the resin having a structural unit represented by structural formula (1) is further improved, and consequently the viscosity of the molding liquid can be further reduced, allowing the molding liquid to be appropriately ejected, for example, by an inkjet method. Here, "alkylene glycol dialkyl ethers" refers to R1-(O-R2) m Represented as -OR3, R1 and R3 are each independently alkyl groups having 1 to 5 carbon atoms, which may be linear or branched, and preferably have 1 or 2 carbon atoms. R2 is an alkylene group having 2 to 5 carbon atoms, which may be linear or branched, and more preferably have 2 or 3 carbon atoms. m represents an integer between 1 and 5, and more preferably 2 or 3. Examples of alkylene glycol dialkyl ethers include diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, and diethylene glycol butyl methyl ether. Among these, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether are preferred, and triethylene glycol dimethyl ether is more preferred.

[0049] There are no particular restrictions on the content of the organic solvent, and it can be appropriately selected according to the purpose, but it is preferably 60.0% to 95.0% by mass, and more preferably 70.0% to 95.0% by mass, relative to the mass of the molding fluid. When the content is 60.0% to 95.0% by mass, the solubility of the resin is further improved, and the viscosity of the molding fluid can be further reduced, allowing the molding fluid to be appropriately ejected, for example, by an inkjet method. In addition, drying of the molding fluid is suppressed in the molding fluid dispensing means, and a molding fluid with excellent ejection stability can be provided.

[0050] The viscosity of the organic solvent is preferably low, specifically, at 25°C, it is preferably 5.0 mPa·s to 50.0 mPa·s, and more preferably 8.0 mPa·s to 30.0 mPa·s. When the viscosity of the organic solvent is within the above range, the viscosity of the molding fluid containing the organic solvent is also easily reduced, which stabilizes the ejection from molding fluid dispensing means such as an inkjet head, and accurate ejection of the molding fluid improves the bending strength of the molded product before sintering, such as solidified material and green material derived from the solidified material, and also improves dimensional accuracy. Viscosity can be measured, for example, in accordance with JIS K7117.

[0051] The boiling point of the organic solvent is preferably high, specifically 150°C or higher, and more preferably 180°C or higher. When the molding liquid is ejected using an inkjet method or the like, a high boiling point of the organic solvent suppresses drying of the molding liquid at or near the nozzle, thereby suppressing nozzle clogging caused by precipitated resin. High-boiling point organic solvents are not particularly limited, but examples include γ-butyrolactone (boiling point: 204°C), propylene carbonate (boiling point: 242°C), cyclohexanone (boiling point: 155.6°C), diethylene glycol dimethyl ether (boiling point: 162°C), triethylene glycol dimethyl ether (boiling point: 216°C), and α-terpionel (boiling point: 217-218°C).

[0052] When the molding liquid contains the resin, the total content of the oligomer having a ring structure and the resin is preferably 2% by mass or more and 45% by mass or less, and more preferably 5% by mass or more and 25% by mass or less. When the total content of oligomers with a ring structure and resin is 25% by mass or less, the viscosity of the molding fluid can be kept low, allowing for proper ejection of the molding fluid, for example, using an inkjet method. When the total content of oligomers with a ring structure and resin is 5% by mass or more, the flexural strength of the molded product before sintering, such as the solidified product and the green body derived from the solidified product, is further improved. Furthermore, if the molding fluid does not contain resin, the increase in viscosity of the molding fluid is suppressed, and if the content of oligomers having a ring structure is 45% by mass or less, the molding fluid can be appropriately ejected using an inkjet method.

[0053] The total amount of organic solvent and ring-structured oligomer is preferably 90.0% by mass or more, more preferably 95.0% by mass or more, even more preferably 99.0% by mass or more, and still more preferably 99.5% by mass or more, relative to the mass of the molding liquid. Furthermore, the product may not contain substantially any components other than organic solvent and ring-structured oligomer. Furthermore, the statement that a molding fluid substantially contains no components other than organic solvents and oligomers having a ring structure means that no components other than organic solvents and oligomers having a ring structure are actively used as materials during the manufacture of the molding fluid, or that the content of components other than organic solvents and oligomers having a ring structure in the molding fluid is below the detection limit when using publicly known and commonly used methods.

[0054] Furthermore, if the molding liquid contains the resin, the total amount is replaced with the sum of the content of the organic solvent, the content of the oligomer having a ring structure, and the content of the resin. When the total amount is 90.0% by mass or more relative to the mass of the molding fluid, the content of oligomers having a ring structure in the molding fluid increases, and the bending strength of the molded product before sintering, such as the solidified product and the green body derived from the solidified product, is further improved. In addition, when the content of components other than organic solvents and oligomers having a ring structure (for example, materials that are insoluble in the molding fluid, such as metal nanoparticles) decreases or is substantially eliminated, the viscosity of the molding fluid decreases, the dispensing stability of the molding fluid improves, and the storage stability of the molding fluid also improves.

[0055] <Additives> The molding fluid is not particularly limited and may contain surfactants, drying inhibitors, viscosity modifiers, penetrants, defoamers, pH adjusters, preservatives, fungicides, colorants, preservatives, stabilizers, etc., as appropriate, depending on the purpose. Conventionally known materials can be used.

[0056] <Other ingredients> <<Wed>> The molding fluid contains substantially no water. Here, "substantially water-free" means that the water content is 10.0% by mass or less relative to the mass of the molding fluid, preferably 5.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably the molding fluid contains no water at all. By substantially free of water in the molding fluid, the solubility of the resin is further improved, and consequently the viscosity of the molding fluid can be further reduced. In addition, the formation of a hydrogel containing a large amount of water around the resin is suppressed, and the resulting increase in the viscosity of the molding fluid is suppressed. For this reason, the molding fluid can be appropriately ejected, for example, using an inkjet method. Furthermore, "the molding fluid is substantially water-free" means that water is not actively used as a material during the manufacture of the molding fluid, or that the water content in the molding fluid is below the detection limit when using publicly known and commonly accepted technical methods. Furthermore, because the molding fluid contains virtually no water, it can be applied even if the materials constituting the metal particles are highly reactive metals, in other words, water-reactive materials (e.g., aluminum, zinc, and magnesium). For example, aluminum forms an aluminum hydroxide film when it comes into contact with water, so a high water content in the molding fluid can lead to a decrease in the sintering density of the sintered body. However, this problem is suppressed because the molding fluid does not contain water. As another example, aluminum is difficult to handle because it generates hydrogen when it comes into contact with water, but this problem is also suppressed because the molding fluid does not contain water.

[0057] [Method for manufacturing molding fluid] There are no particular restrictions on the method for producing the molding fluid, and it can be appropriately selected depending on the purpose. For example, a method of mixing and stirring the aforementioned materials can be used.

[0058] As described above, the viscosity of the molding fluid is preferably low. Specifically, at 25°C, it is preferably 5 mPa·s to 50 mPa·s, more preferably 5 mPa·s to 40 mPa·s, and even more preferably 5 mPa·s to 30 mPa·s. When the viscosity of the molding fluid is within the above range, the ejection from the molding fluid application means, such as an inkjet head, is stabilized, and accurate ejection of the molding fluid further improves the bending strength of the molded product before sintering, such as the solidified product and the green body derived from the solidified product, and also improves dimensional accuracy. Viscosity can be measured, for example, in accordance with JIS K7117.

[0059] The surface tension of the molding fluid is preferably 40 mN / m or less at 25°C, and more preferably 10 mN / m to 30 mN / m. When the surface tension is 40 mN / m or less, the ejection from the molding fluid application means, such as an inkjet head, is stabilized, and accurate ejection of the molding fluid improves the bending strength of the molded product before sintering, such as the solidified material and the green body derived from the solidified material, and also improves dimensional accuracy. Surface tension can be measured, for example, using the DY-300 manufactured by Kyowa Interface Science Co., Ltd.

[0060] <Powder containing metal particles> The aforementioned powder contains metal particles and, if necessary, other components. The metal particles are used as a powder, which is an aggregate containing multiple metal particles, and the molded object is manufactured by applying a molding fluid to a layer of this powder.

[0061] <<Metal particles>> The aforementioned metal particles are used in the manufacture of molded objects and contain metal as a constituent material. The constituent material of the metal particles is not particularly limited as long as it contains metal, and may contain materials other than metal, but it is preferable that the main material is metal. The main material being metal means that the amount of metal contained in the metal particles is 50.0% by mass or more of the total amount of metal particles, preferably 60.0% by mass or more, more preferably 70.0% by mass or more, even more preferably 80.0% by mass or more, and particularly preferably 90.0% by mass or more.

[0062] Examples of metals that make up metal particles include magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), lead (Pd), silver (Ag), indium (In), tin (Sn), tantalum (Ta), tungsten (W), neodymium (Nd), and alloys of these metals. Among these, stainless steel (SUS), iron (Fe), copper (Cu), silver (Ag), titanium (Ti), aluminum (Al), zinc (Zn), magnesium (Mg), and alloys of these metals are preferably used. Examples of aluminum alloys include AlSi 10 Mg, AlSi 12 AlSi7Mg 0.6 , AlSi3Mg, AlSi9Cu3, Scalmalloy, ADC 12 Examples include AlSi3. These may be used individually or in combination of two or more types.

[0063] Metal particles can be manufactured using conventionally known methods. Examples of methods for manufacturing metal particles include pulverization, which involves crushing a solid by applying compression, impact, friction, etc.; atomization, which involves spraying molten metal to obtain rapidly cooled powder; precipitation, which involves precipitating components dissolved in a liquid; and gas-phase reaction, which involves vaporization to crystallize the particles. Among these, atomization is preferred because it yields a spherical shape and has little variation in particle size. Examples of atomization methods include water atomization, gas atomization, centrifugal atomization, and plasma atomization, all of which can be suitably used.

[0064] The metal particles may be commercially available. Examples of commercially available products include AlSi 10 Mg (manufactured by Toyo Aluminum Co., Ltd., Si 10 Examples include MgBB, pure Al (manufactured by Toyo Aluminum Co., Ltd., A1070-30BB), pure Ti (manufactured by Osaka Titanium Technologies Co., Ltd.), SUS316L (manufactured by Sanyo Special Steel Co., Ltd., product name: PSS316L), SiO2 (manufactured by Tokuyama Corporation, product name: Excelica SE-15K), AlO2 (manufactured by Daimyo Chemical Industry Co., Ltd., product name: Tymicron™-5D), and ZrO2 (manufactured by Tosoh Corporation, product name: TZ-B53).

[0065] There are no particular restrictions on the volume-average particle size of the metal particles, and they can be appropriately selected depending on the purpose. However, for example, a size of 2 μm to 100 μm is preferred, and a size of 8 μm to 50 μm is more preferred. When the volume-average particle size of the metal particles is 2 μm or more, aggregation of the metal particles is suppressed, which can prevent a decrease in the manufacturing efficiency of the molded product and a decrease in the handling of the metal particles. Furthermore, when the volume-average particle size of the metal particles is 100 μm or less, a decrease in the contact points between metal particles and an increase in voids can be suppressed, which can prevent a decrease in the strength of the molded product. There are no particular restrictions on the particle size distribution of the metal particles, and they can be appropriately selected according to the purpose, however, a sharper particle size distribution is preferable. The volume-average particle size and particle size distribution of metal particles can be measured using known particle size measuring devices, such as the Microtrac MT3000II series particle size distribution analyzer (manufactured by Microtrac Bell).

[0066] While a conventional method of manufacturing molded objects using metal particles having a metal substrate and a coating resin covering the substrate, and applying a liquid to the metal particles to exert a binder function in the coating resin, in this disclosure, the molding liquid contains a resin having a binder function. Therefore, the metal particles do not need to be surface-coated with resin. By using metal particles whose surfaces are not surface-coated with resin, it is possible to suppress the formation of unintended solidified objects, for example, in areas of powder where no liquid has been applied (in other words, non-molding areas), by preventing the coating resin from binding the metal particles together during the heating process. Here, "surface not coated with resin" means, for example, that the ratio of the surface area of ​​the resin to the surface area of ​​the metal particles (surface coverage rate) is less than 15%, and may be 0%. The surface coverage ratio is determined, for example, by taking a photograph of the metal particles and measuring the ratio (%) of the area of ​​the resin-coated portion to the total surface area of ​​the metal particles within the range captured in the two-dimensional photograph. For determining the resin-coated portion, techniques such as elemental mapping using energy-dispersive X-ray spectroscopy (SEM-EDS) can be used.

[0067] --Other ingredients-- Other components include, for example, fillers, leveling agents, sintering aids, and polymer resin particles. Fillers are effective materials for adhering to the surface of metal particles or filling voids between metal particles. By using fillers, for example, the fluidity of powders can be improved, and the contact points between metal particles can be increased, reducing voids and thereby improving the strength and dimensional accuracy of the fabricated object. Leveling agents are effective materials for controlling the wettability of a powder layer's surface. By using leveling agents, for example, the penetration of the molding fluid into the powder layer can be increased, thereby improving the strength of the molded object. Sintering aids are effective materials for increasing sintering efficiency when sintering molded objects. By using sintering aids, for example, the strength of the molded object can be improved, the sintering temperature can be lowered, and the sintering time can be shortened. Polymer resin particles are effective materials for adhering to the surface of metal particles and are also called organic additives. There are no particular restrictions on the average particle size of polymer resin particles, and they can be appropriately selected depending on the purpose, but a size of 0.1 μm to 10 μm is preferred, and a size of 0.1 μm to 1 μm is more preferred.

[0068] The angle of repose of the powder is preferably 60° or less, more preferably 50° or less, and even more preferably 40° or less. An angle of repose of 60° or less allows the powder to be efficiently and stably placed at the desired location on the support. The angle of repose can be measured, for example, using a powder properties measuring device (Powder Tester PT-N type, manufactured by Hosokawa Micron Corporation).

[0069] (Kit for manufacturing molded objects) The kit for manufacturing a molded object according to the present invention comprises the molding fluid of the present invention and the powder containing the metal particles, and may optionally include other components such as a removal liquid as described later. Furthermore, the kit for manufacturing a molded object does not need to be limited to cases where the molding fluid container and the powder container are integrated, and the molding fluid container containing the molding fluid and the powder container containing the powder are each in an independent state. For example, even if the molding fluid and the powder are each contained in separate containers, the kit is included in cases where it is assumed that the powder and the molding fluid will be used together, or where the combined use of the powder and the molding fluid is substantially encouraged.

[0070] (Method of manufacturing molded objects) The present invention provides a method for manufacturing a molded object comprising a powder layer formation step of forming a layer of powder containing metal particles, A molding liquid application step in which molding liquid is applied to the powder layer, The process includes a lamination step of forming a laminate by sequentially repeating the powder layer formation step and the molding liquid application step, and further includes other steps as necessary. The method for manufacturing the molded object may further include a heating step of forming a solid by heating the laminate, an excess powder removal step of removing excess powder adhering to the solid, which is powder, to obtain a green body, a drying step of drying the green body to remove any remaining liquid components, a degreasing step of heating the green body to remove resin and the like derived from the molded liquid applied, a sintering step of heating the degreasing body to obtain a sintered body, and a post-processing step of performing post-processing on the sintered body.

[0071] <Powder layer formation process> The aforementioned powder layer formation step is a step of forming a layer of powder containing metal particles. The powder layer is formed on the support (on the build stage). There are no particular limitations on the method for forming a thin layer of powder by arranging powder on a support, and can be appropriately selected depending on the purpose. Examples include a method using a known counter rotation mechanism (counter roller) used in the selective laser sintering method described in Japanese Patent Publication No. 3607300, a method of spreading the powder using a brush, roller, blade, or other component, a method of spreading the powder by pressing the surface with a pressing component, and a method using a known additive manufacturing apparatus.

[0072] When forming a powder layer using powder layer forming means such as a counter rotating mechanism (counter roller), brush, blade, or pressing member, it can be carried out, for example, in the following manner. Specifically, powder is placed on a support that is positioned to slide up and down along the inner wall of an outer frame (sometimes called a "mold," "hollow cylinder," or "tubular structure") using a counter-rotating mechanism (counter roller), brush, roller, blade, or pressing member. When a support that can move up and down within the outer frame is used, the support is positioned slightly below the upper opening of the outer frame (in other words, positioned below by the thickness of one layer of powder), and the powder is placed on the support. In this way, a thin layer of powder can be placed on the support.

[0073] There are no particular restrictions on the thickness of the powder layer, and it can be appropriately selected depending on the purpose. However, for example, the average thickness per layer is preferably 30 μm to 500 μm, and more preferably 60 μm to 300 μm. If the average thickness is 30 μm or more, the strength of the solidified product formed by applying the molding fluid to the powder is improved, and deformation that may occur in subsequent processes such as the sintering process can be suppressed. Furthermore, if the average thickness is 500 μm or less, the dimensional accuracy of the molded product derived from the solidified product formed by applying the molding fluid to the powder is improved. The average thickness is not particularly limited and can be measured according to known methods.

[0074] The powder supplied by the powder layer forming means may be contained in a powder containment section. The powder containment section is a container or other component that contains the powder, and examples include storage tanks, bags, cartridges, and tanks.

[0075] <Forming fluid application process> The molding fluid application step is a step of applying molding fluid to the powder layer. The molding fluid contains an oligomer having a ring structure with a number average molecular weight of 3,000 or less, an organic solvent, and is substantially free of water. The molding fluid can be appropriately selected from those described as the molding fluid of the present invention. As a method for applying the molding fluid to the powder layer, a method of dispensing the molding fluid is preferred. There are no particular restrictions on the method of dispensing the molding fluid, and it can be appropriately selected according to the purpose. Examples include a dispenser method, a spray method, and an inkjet method. Among these, the dispenser method is excellent in droplet quantity, but the coating area is small. The spray method can easily form fine ejected material, has a wide coating area and excellent coating performance, but droplet quantity is poor, and the molding fluid scatters due to the spray flow. For this reason, the inkjet method is preferred. Compared to the spray method, the inkjet method has the advantage of better droplet quantity and a wider coating area compared to the dispenser method, and is preferred because it can form complex molded objects accurately and efficiently.

[0076] When using the inkjet method, the means for applying the molding fluid by ejecting it is an inkjet head having a nozzle for ejecting the molding fluid. Suitable inkjet heads can be those from known inkjet printers. Examples of inkjet heads from inkjet printers include the RICOH MH / GH SERIES industrial inkjet printers manufactured by Ricoh Co., Ltd. Examples of inkjet printers include the SG7100, also manufactured by Ricoh Co., Ltd.

[0077] The molding fluid supplied to the molding fluid dispensing means may be contained in a molding fluid storage section. The molding fluid storage section is a container or other component that holds the molding fluid, and examples include a storage tank, bag, cartridge, or tank.

[0078] <Lamination process> The lamination process is a process of forming a laminate by sequentially repeating the powder layer formation process and the molding liquid application process. A "laminate" is a structure formed by stacking multiple layers of powder, each having a region to which a molding fluid has been applied. In this case, the structure may or may not contain any three-dimensional objects that maintain a certain three-dimensional shape internally.

[0079] The lamination process comprises a step of placing powder on a thin layer (powder layer formation step) and a step of applying molding fluid onto the thin layer (molding fluid application step), thereby forming a region of the powder layer to which molding fluid has been applied. Furthermore, the lamination process comprises a step of placing powder on a thin layer (lamination) in the same manner as above (powder layer formation step) and a step of applying molding fluid onto the thin layer (molding fluid application step), thereby forming a region of molding fluid in the newly laminated powder layer. At this time, the region of molding fluid that is formed in the uppermost laminated powder thin layer is continuous with the region of molding fluid that is applied in the powder thin layer below it. As a result, a region of molding fluid with a thickness equivalent to two layers of powder is obtained.

[0080] <Heating process> The manufacturing method for the molded object preferably includes a heating step in which the layered material is heated to form a solidified material. "Solidification" refers to the process of maintaining a certain shape. A "solidified material" is a structure that has a three-dimensional shape that is maintained. Furthermore, a solidified material refers to a material that has not undergone the excess powder removal process, which removes excess powder that does not constitute a three-dimensional object.

[0081] In the heating process, the heating temperature is preferably higher than the softening point of the ring-structured oligomer (or, if resin is present, the softening point of both the ring-structured oligomer and the resin). This promotes the volatilization of residual solvent components that are miscible with the oligomer, thereby enabling the formation of suitable pre-sintered molded products such as solidified material and green bodies derived from the solidified material. On the other hand, if solvent residue remains during the drying process, it can lead to a decrease in the strength of the green body. The heating method is not particularly limited, but for example, a dryer or a constant temperature and humidity chamber can be used.

[0082] <Excess powder removal process> The manufacturing method for the molded object preferably includes an excess powder removal step to remove excess powder, which is powder adhering to the solidified material, in order to obtain a green object. A "green body" refers to a three-dimensional object that maintains a certain three-dimensional shape and has undergone an excess powder removal process to remove excess powder that does not constitute solidified material. Preferably, it refers to a three-dimensional object from which excess powder is substantially absent. The molded object after the heating process may be called a "green body (unsintered body)," the molded object after the degreasing process may be called a "degreased body," and the molded object after the sintering process may be called a "sintered body." Furthermore, the excess powder removal process preferably includes at least one step selected from the steps of removing excess powder from the solidified material by air blowing and removing excess powder from the solidified material by immersing it in a removal liquid, and more preferably both steps.

[0083] After the heating process, the solidified material is embedded in excess powder, which is powder that has not been treated with the molding fluid. When the solidified material is removed from this embedded state, excess powder adheres to its surface and interior, making it difficult to remove easily. Furthermore, it becomes even more difficult if the surface shape of the solidified material is complex or if its internal structure is like a flow channel. Since pre-sintered molded materials created using a general binder jetting method do not have high strength, increasing the pressure of the air blow from the blower may cause the molded material to collapse. On the other hand, since the solidified product formed using the molding liquid of this disclosure is formed from the aforementioned resin, its flexural strength is improved and it has the strength to withstand the pressure of an air blow. In this case, the strength of the solidified material is preferably 4.0 MPa or higher, more preferably 5.0 MPa or higher, and even more preferably 6.0 MPa or higher, based on a three-point bending stress.

[0084] -Removal liquid- The removal solution contains an organic solvent and, if necessary, other components. To distinguish between the organic solvent in the molding fluid and the organic solvent in the removal solution, the organic solvent in the molding fluid may be referred to as the first organic solvent, and the organic solvent in the removal solution as the second organic solvent.

[0085] Examples of organic solvents include ketones, halogens, alcohols, esters, ethers, hydrocarbons, glycols, glycol ethers, glycol esters, pyrrolidones, amides, amines, and carbonate esters.

[0086] Examples of ketones include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, isophorone, acetophenone, and diacetone alcohol.

[0087] Examples of halogens include methylene chloride, trichloroethylene, perchloroethylene, HCFC141-b, HCFC-225, 1-bromopropane, chloroform, and orthodichlorobenzene.

[0088] Examples of alcohols include methanol, ethanol, butanol, isobutanol, isopropyl alcohol, n-propyl alcohol, tertiary butanol, secondary butanol, 1,3-butanediol, 1,4-butanediol, 2-ethylhexanol, and benzyl alcohol.

[0089] Examples of esters include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, secbutyl acetate, methoxybutyl acetate, 3-methoxybutyl acetate, 3-methoxy-3 methylbutyl acetate, ethyl-3-ethoxypropionate, amyl acetate, n-propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, butyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether propionate, ethyl 3-ethoxypropionate, and dibasic acid esters (DBE).

[0090] Examples of ethers include dimethyl ether, ethyl methyl ether, diethyl ether, ethylene oxide, tetrahydrofuran, furan, benzofuran, diisopropyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, 1,4-dioxane, methyl tert-butyl ether (MTBE), ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, and dipropylene glycol monomethyl ether.

[0091] Examples of hydrocarbons include benzene, toluene, xylene, solvent naphtha, n-hexane, isohexane, cyclohexane, ethylcyclohexane, methylcyclohexane, cyclohexene, cycloheptane, cyclopentane, heptane, pentamethylbenzene, pentane, methylcyclopentane, n-heptane, isooctane, n-decane, n-pentane, isopentane, mineral spirits, dimethyl sulfoxide, and linear alkylbenzene.

[0092] Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and dimethoxytetraethylene glycol.

[0093] Examples of glycol esters include ethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate.

[0094] Examples of glycol ethers include methyl carbitol, ethyl carbitol, butyl carbitol, and methyl triglycol.

[0095] Examples of pyrrolidones include 2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0096] Examples of amides include dimethylformamide, dimethylacetamide, and formamide.

[0097] Examples of amines include tetramethylethylenediamine, N,N-diisopropylethylamine, ethylenediamine, triethylamine, diethylamine, aniline, pyrrolidine, piperidine, morpholine, pyrrole, pyridine, pyridazine, oxazole, thiazole, and 1,3-dimethyl-2-imidazolidinone.

[0098] Examples of carbonate esters include diethyl carbonate, dimethyl carbonate, propylene carbonate, and ethylmethyl carbonate.

[0099] Other ingredients may include, as needed, additives such as surfactants, defoamers, preservatives and antifungal agents, pH adjusters, chelating agents, and rust inhibitors.

[0100] <Drying process> The manufacturing method for the molded object preferably includes a drying step in which the green body is dried to remove any remaining liquid components such as removal solution within the green body. The drying process may remove not only liquid components such as removal solutions contained in the green material, but also organic matter. As drying methods, for example, known dryers, constant temperature and humidity chambers, etc., can be used.

[0101] <Degreasing process> The method for manufacturing the molded object preferably includes a degreasing step to obtain a degreased object by heating the green body and removing the oligomer having a ring structure (or, if the resin is included, the oligomer having a ring structure and the resin) etc. which originate from the molding liquid applied. A "defatted body" is a three-dimensional object obtained by degreasing organic components such as the oligomer having the ring structure (or, if the resin is included, the oligomer having the ring structure and the resin) from the green body. The degreasing step involves using a degreasing means to ensure that the temperature of the organic components, such as the oligomer having a ring structure (or, if the resin is included, the oligomer having a ring structure and the resin), is above the thermal decomposition temperature and the melting point or solidus temperature (e.g., AlSi) of the material (metal) constituting the metal particles. 10 If Mg particles are used, the organic components are decomposed and removed by heating the green material at a temperature lower than approximately 570°C for a certain period of time (e.g., 1 to 10 hours). Examples of degreasing methods include known sintering furnaces and electric furnaces. Specifically, the oligomer having the ring structure (or, if the resin is included, the oligomer having the ring structure and the resin) is decomposed at a temperature higher than its thermal decomposition temperature and lower than the melting point or solidus temperature of the metal particles. Depending on the components of the oligomer having the ring structure and the resin used, it is also possible to set multiple temperatures for heating and holding. Alternatively, a degreasing method by solvent extraction is also applicable, in which the oligomer having the ring structure (or, if the resin is included, the oligomer having the ring structure and the resin) is extracted by immersing the green material in a solvent instead of heating.

[0102] <Sintering process> The manufacturing method for the molded object preferably includes a sintering step in which a degreased body is heated to obtain a sintered body. A "sintered body" is a three-dimensional object formed by the integration of metal materials constituting metal particles, and is manufactured by sintering a degreased body. The sintering process uses sintering means to raise the solidus temperature of the metal material constituting the metal particles (for example, AlSi10 When Mg particles are used, the temperature is about 570°C or higher and is lower than the liquidus temperature (for example, AlSi 10 When Mg particles are used, the temperature is about 600°C or lower. The degreased body is heated at this temperature for a certain period of time (for example, 1 to 10 hours), so that the metal materials constituting the metal particles are integrated. As the sintering means, for example, a known sintering furnace can be cited, and it may be the same means as the above degreasing means. Further, the degreasing step and the sintering step may be performed continuously. Specifically, after heating the degreased green body to a temperature between the liquidus temperature and the solidus temperature at a heating rate of 1°C / hour to 200°C / hour (the heating rate can also be changed during the process), the temperature is maintained for about 1 to 10 hours. As a more specific maximum reachable temperature, it is preferably a temperature at which a liquid phase of 10% to 50% of the metal material is generated. These steps can be performed in a vacuum, Ar, H2, N2 atmosphere or the like. After heating and holding, the inside of the furnace is cooled, and the molded product is taken out.

[0103] <Post-treatment Step> The method for manufacturing a shaped article preferably includes a post-treatment step of performing post-treatment on the sintered body. The post-treatment step is not particularly limited and can be appropriately selected according to the purpose. Examples thereof include a surface protection treatment step and a coating step.

[0104] [Embodiment of Method for Manufacturing Shaped Article] An embodiment (shaping flow) of the method for manufacturing a shaped article of the present invention will be described with reference to FIGS. 1A to 1E. FIGS. 1A to 1E are schematic diagrams showing an example of the operation of the apparatus for manufacturing a shaped article.

[0105] First, we will explain the state in which the first layer of powder (the layer to which the molding liquid is applied 30) has been formed on the molding stage of the molding tank. When forming the next layer of powder on the first layer of powder to which the molding liquid is applied 30, the supply stage 23 of the supply tank is raised and the molding stage 24 of the molding tank is lowered, as shown in Figure 1A. At this time, the lowering distance of the molding stage 24 is set so that the distance (layer pitch) between the upper surface of the powder layer in the molding tank 22 and the lower part (lower tangential part) of the flattening roller 12 is Δt1. The distance Δt1 is not particularly limited, but it is preferably about several tens to 100 μm.

[0106] In this disclosure, the flattening roller 12 is positioned such that there is a gap between it and the upper surfaces of the supply tank 21 and the molding tank 22. Therefore, when the powder 20 is transferred and supplied to the molding tank 22 for flattening, the upper surface of the powder layer is higher than the upper surfaces of the supply tank 21 and the molding tank 22. This reliably prevents the flattening roller 12 from coming into contact with the upper surfaces of the supply tank 21 and the molding tank 22, thereby reducing damage to the flattening roller 12. If the surface of the flattening roller 12 is damaged, streaks may appear on the surface of the powder layer 31 (see Figure 1D) supplied to the molding tank 22, making it easier for the flatness to decrease.

[0107] Next, as shown in Figure 1B, the powder 20, which is positioned higher than the upper end surface of the supply tank 21, is transferred and supplied to the build tank 22 by moving the flattening roller 12 toward the build tank 22 while rotating it in the direction of the arrow (powder supply). Furthermore, as shown in Figure 1C, the flattening roller 12 is moved parallel to the stage surface of the build stage 24 of the build tank 22 to form a powder layer 31 of a predetermined thickness Δt1 on the build tank 22 of the build stage 24 (flattening). At this time, any excess powder 20 that was not used to form the powder layer 31 falls into the excess powder receiving tank 29. After the powder layer 31 is formed, the flattening roller 12 is moved toward the supply tank 21 and returned to its initial position (origin position) as shown in Figure 1D (return).

[0108] Here, the flattening roller 12 is designed to move while maintaining a constant distance from the upper end surfaces of the molding tank 22 and the supply tank 21. By moving while maintaining a constant distance, the flattening roller 12 can transport the powder 20 onto the molding tank 22, while simultaneously forming a layer of powder 31 with a uniform thickness h (corresponding to the layer pitch Δt1) on the molding tank 22 or on the already formed molding liquid coated layer 30. In the following explanation, the thickness h of the powder layer 31 and the layer pitch Δt1 may not be distinguished, but unless otherwise specified, they refer to the same thickness and have the same meaning. Alternatively, the thickness h of the powder layer 31 may be determined by actually measuring it, in which case it is preferable to use the average value of multiple locations.

[0109] Subsequently, as shown in Figure 1E, droplets 10 of the molding fluid are discharged from the head 52 of the liquid discharge unit to laminate a molding fluid-coated layer 30 of the desired shape onto the next powder layer 31. Next, the powder layer formation process and the molding fluid application process described above are repeated to form and laminate a new molding fluid-coated layer 30. At this time, the new molding fluid-coated layer 30 and the molding fluid-coated layer 30 below it become one. Thereafter, the powder layer formation process and the molding fluid application process are repeated to complete the laminate. [Examples]

[0110] The present invention will be described more specifically below based on examples, but the present invention is not limited to the following examples.

[0111] (Example 1) <Preparation of molding fluid> The materials shown in Table 1 were mixed and stirred with a magnetic stirrer for 4 hours while being heated at 70°C. After 4 hours of stirring, the heating was stopped and stirring continued until the temperature reached room temperature to prepare the ink of Example 1. Note that the content of each material in Tables 1 and 2 is expressed in mass percent. Furthermore, resins, oligomers with a ring structure, and oligomers without a ring structure are all in powder, pellet, or block form, and the content mentioned above represents the total amount of each material.

[0112] <Powder containing metal particles> As a powder containing metal particles, AlSi 10 Mg powder (manufactured by Toyo Aluminum Co., Ltd., Si 10 Mg-30BB (volume-average particle size: 35 μm, metal particle surface not coated with resin) was used.

[0113] <Shaping of a three-dimensional object (green body)> Using the powder and the molding fluid from Example 1, a three-dimensional object (green body) was manufactured by layering solidified material according to a shape printing pattern of the size (length 40 mm x width 10 mm) as follows.

[0114] 1) First, using a known three-dimensional object manufacturing apparatus as shown in Figures 1A to 1E, powder was transferred from the supply tank to the molding tank, and a thin layer of powder with an average thickness of 100 μm was formed on the molding stage.

[0115] 2) Next, a molding liquid was applied (discharged) onto the surface of the thin layer formed from the powder through the nozzle of a known inkjet ejection head, and the ring-structured oligomer (or ring-structured oligomer and resin if resin is included) contained in the molding liquid arranged the ring-structured oligomer and resin around the metal particles. The molding fluid discharge area was designed as a rectangle measuring 40 mm in length and 10 mm in width.

[0116] 3) Next, the operations described in 1) and 2) above were repeated until a predetermined total average thickness of 3 mm was reached, and thin layers of solidified powder were sequentially stacked to form a laminate. After that, a heating process was carried out using a dryer at at least 140°C to obtain a three-dimensional molded object with solidified material stacked on top of each other.

[0117] 4) After drying, the excess powder was removed from the three-dimensional molded object by air blowing to obtain a green object.

[0118] <Rating> <<Viscosity of molding fluid>> The modeling liquid was measured using a cone-plate rotational viscometer (VISCOMETER TVE-22L, manufactured by Toki Sangyo Co., Ltd.). The temperature inside the measurement container was fixed at 25°C using a high-temperature circulation tank, and a cone rotor (1°34'×R24) was used as the rotor. The results are shown in Table 1.

[0119] <<Measurement of Tg>> 1 g of the modeling liquid was weighed into an aluminum cup and heated at 150°C for 6 hours on a hot stirrer to obtain a dried resin. A portion of the resin was scraped off from the aluminum cup and measured with a differential scanning calorimetry (DSC) apparatus (DSC2500, manufactured by TA Instruments Japan Inc.) using a profile involving a total of four heating and cooling cycles. Specifically, the measurement was carried out in the range from -30°C to 200°C as follows: first heating to 200°C (first cycle), cooling to -30°C (second cycle), heating to 200°C (third cycle), and cooling to -30°C (fourth cycle). Data obtained during the third heating cycle was adopted for Tg, and evaluation was performed based on the following evaluation criteria. The results are shown in Table 1. [Evaluation Criteria] A: Tg is 60°C or higher B: Tg is 50°C or higher and lower than 60°C C: Tg is 45°C or higher and lower than 50°C D: Tg is lower than 45°C

[0120] <<Bending Strength of Green Body>> The bending strength of the green body produced in 4) above was measured, and evaluation was performed based on the following evaluation criteria. For the measurement of bending strength, a universal testing machine (Autograph, model AG-I, manufactured by Shimadzu Corporation) was used, with a 1 kN load cell and a three-point bending jig. The distance between fulcrums was set to 24 mm, the stress obtained when displacing the load point at a speed of 1 mm / min was plotted against strain, and the stress at break was taken as the maximum stress. Evaluation was performed based on the following evaluation criteria. The results are shown in Table 1. [Evaluation Criteria] A: Bending strength is 6.0 MPa or higher B: Bending strength is 5.0 MPa or higher and lower than 6.0 MPa C: Bending strength is 4.0 MPa or higher and lower than 5.0 MPa D: Bending strength is lower than 4.0 MPa

[0121] <<Deformation of the molded object (green body) under high temperature and high humidity conditions>> A green object measuring 100mm in length, 3mm in thickness, and 10mm in width was stored in a small environmental testing machine (SH-222, manufactured by ESPEC Corporation) in a double-supported position, with the support located 5mm from both ends. The amount of deflection was checked by placing a straight stainless steel ruler on top of the green object and confirming whether there was a gap in the center. The small environmental testing chamber was operated under constant conditions of 40°C and 60% humidity. Deflection was checked at arbitrary intervals, such as one day, two weeks, four weeks, and five weeks after storage. [Evaluation Criteria] A: No bending or deformation after more than four weeks. B: No bending or deformation between two and four weeks. C: Deformation within two weeks

[0122] <<Relative density of sintered body>> The resulting green material is subjected to a temperature above which the ring-structured oligomer and resin decompose, and metal particles AlSi 10 A degreased body was obtained by heating at a temperature below the solidus temperature of Mg (approximately 570°C). Furthermore, a sintered body was manufactured by heating the degreased body at a temperature above the solidus temperature (approximately 570°C) and below the liquidus temperature (approximately 600°C) for 1 to 10 hours. The ratio of the density of the sintered body to the density of the metal material constituting the sintered body was calculated and evaluated based on the following evaluation criteria. [Evaluation Criteria] A: Sintered body density ratio of 97% or higher B: Sintered body density ratio is 93% or more but less than 97% C: Sintered body density percentage is less than 93%

[0123] (Examples 2-6 and Comparative Examples 1-2) Except for the material composition being changed as shown in Tables 1 and 2 in Example 1, the molding liquids and three-dimensional molded objects of Examples 2 to 6 and Comparative Examples 1 to 2 were obtained and evaluated in the same manner as in Example 1. The results are shown in Tables 1 and 2.

[0124] [Table 1]

[0125] [Table 2]

[0126] The names of the materials or trade names, and the names of the manufacturers / sellers used in Examples 1-6 and Comparative Examples 1-2 are as follows.

[0127] [Table 3]

[0128] The results from Examples 1-6 showed that including a small amount of oligomer having a ring structure can increase the Tg of the molding solution (dried product), and the resulting green product maintains high strength. Furthermore, because it is a low molecular weight oligomer, the molding solution does not thicken, making it suitable for inkjet printing. On the other hand, in Comparative Examples 1 and 2, it was found that adding a small amount of oligomer without a ring structure did not increase the Tg of the molding solution (dried product), but rather lowered it. Furthermore, a comparison of Examples 2 and 3 revealed that terpene phenol resins containing unsaturated bonds in their ring structure have a greater effect on increasing the Tg of the molded liquid (dried product) than terpene resins that do not contain unsaturated bonds in their ring structure.

[0129] Examples of the present invention are as follows: <1> A molding fluid applied to a layer of powder containing metal particles, It contains an oligomer having a ring structure with a number average molecular weight of 3,000 or less, and an organic solvent. This molding fluid is characterized by containing virtually no water. <2> The oligomer having the ring structure is selected from copolymers having aromatic rings, copolymers having hydrogenated aromatic rings, polyterpene resins, hydrogenated terpene resins, aromatically modified terpene resins, terpene phenol resins, rosin-modified phenol resins, rosin ester resins, and alkylphenol resins. <1> This is the molding fluid described in [the relevant section]. <3> The oligomer having the ring structure includes a thermoplastic oligomer having an unsaturated bond in the ring structure. <1> from <2> It is a molding fluid as described in one of the following. <4> The above further contains a resin having a structural unit represented by the following structural formula (1). <1> from <3> It is a molding fluid as described in one of the following. [ka] <5> The metal particles contain at least one selected from the group consisting of aluminum, zinc, and magnesium. <1> from <4> It is a molding fluid as described in one of the following. <6> The metal particles whose surface is not coated with resin <1> from <5> It is a molding fluid as described in one of the following. <7> The viscosity at 25°C is 5 mPa·s or more and 50 mPa·s or less. <1> from <6> It is a molding fluid as described in one of the following. <8> A powder layer formation process that forms a layer of powder containing metal particles, A process of applying a molding liquid to the powder layer using an inkjet method, The process includes a lamination step of forming a laminate by sequentially repeating the powder layer formation step and the molding liquid application step, The method for producing a molded object is characterized in that the molding liquid contains an oligomer having a ring structure and a number average molecular weight of 3,000 or less, an organic solvent, and substantially no water. <9> The molding fluid application step is a step of ejecting the molding fluid onto the powder layer using an inkjet method. <8> This is a method for manufacturing the molded object described above. <10> A heating step in which the laminate is heated to form a solidified material, The process further includes an excess powder removal step, which involves removing the excess powder adhering to the solidified material to obtain a green material. <8> from <9> This is a method for manufacturing a molded object as described in any of the above. <11> A degreasing step in which the green body is heated to form a degreased body from which the oligomer having the ring structure is removed, The process further comprises a sintering step of heating the degreased body to form a sintered body. <10> This is a method for manufacturing the molded object described above.

[0130] The aforementioned <1> from <7> A molding liquid described in any of the above can solve the aforementioned problems of the conventional method and achieve the objectives of the present invention. The aforementioned <8> from <10> The method for manufacturing a molded object described in any of the above aims to solve the aforementioned problems in the conventional method and achieve the following objectives. Specifically, the method for manufacturing a molded object aims to provide a method for manufacturing a molded object that has excellent strength in molded objects such as green bodies, degreased bodies, and sintered bodies, by increasing the glass transition temperature of the resin in the resulting green body even when using a molding liquid containing a binder resin that has excellent extrusion properties and a low glass transition temperature in a binder jetting method. [Prior art documents] [Patent Documents]

[0131] [Patent Document 1] Japanese Patent Publication No. 2020-015848

Claims

1. A molding fluid applied to a layer of powder containing metal particles, It contains an oligomer having a ring structure with a number average molecular weight of 3,000 or less, and an organic solvent. The oligomer having the ring structure is selected from copolymers having aromatic rings, copolymers having hydrogenated aromatic rings, polyterpene resins, hydrogenated terpene resins, aromatically modified terpene resins, terpene phenol resins, rosin-modified phenol resins, rosin ester resins, and alkylphenol resins. A molding liquid characterized in that the water content is 5.0% by mass or less relative to the mass of the molding liquid.

2. A molding fluid applied to a layer of powder containing metal particles, It contains an oligomer having a ring structure with a number average molecular weight of 3,000 or less, and an organic solvent. The oligomer having the aforementioned ring structure includes a thermoplastic oligomer having an unsaturated bond in the ring structure, A molding liquid characterized in that the water content is 5.0% by mass or less relative to the mass of the molding liquid.

3. A molding fluid applied to a layer of powder containing metal particles, It contains an oligomer having a ring structure with a number average molecular weight of 3,000 or less, an organic solvent, and a resin having a structural unit represented by the following structural formula (1). A molding liquid characterized in that the water content is 5.0% by mass or less relative to the mass of the molding liquid. 【Chemistry 1】

4. The molding liquid according to any one of claims 1 to 3, wherein the metal particles contain at least one selected from the group consisting of aluminum, zinc, and magnesium.

5. The molding liquid according to any one of claims 1 to 3, wherein the metal particles are not coated on the surface with resin.

6. The molding liquid according to any one of claims 1 to 3, wherein the viscosity at 25°C is 5 mPa·s or more and 50 mPa·s or less.

7. A powder layer formation process that forms a layer of powder containing metal particles, A molding liquid application step in which molding liquid is applied to the powder layer, The process includes a lamination step of forming a laminate by sequentially repeating the powder layer formation step and the molding liquid application step, A method for producing a molded object, characterized in that the molding liquid contains an oligomer having a ring structure with a number average molecular weight of 3,000 or less, an organic solvent, and a resin having a structural unit represented by the following structural formula (1), and the water content is 5.0% by mass or less relative to the mass of the molding liquid. 【Chemistry 2】

8. The method for manufacturing a molded object according to claim 7, wherein the molding liquid application step is a step of ejecting the molding liquid onto the powder layer using an inkjet method.

9. A heating step in which the laminate is heated to form a solidified material, A method for manufacturing a molded object according to claim 7, further comprising a step of removing excess powder, which is the powder adhering to the solidified material, to obtain a green object.

10. A degreasing step in which the green body is heated to form a degreased body from which the oligomer having the ring structure is removed, The method for manufacturing a molded object according to claim 9, further comprising a sintering step of heating the degreased body to form a sintered body.

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