Modeling fluid, modeling kit, and method for manufacturing modeled objects

Abstract

To provide molding liquids, etc. that enable molded objects with excellent dimensional accuracy to be obtained.SOLUTION: A molding liquid to be applied to a layer of powder containing inorganic particles has a powder contact angle θ with the metal particles of 50° or more and satisfy the following formula: y cos θ / η≤1.5(m / s). In the formula, θ represents the powder contact angle (°) of the molding liquid with inorganic particles, γ represents the surface tension of the molding liquid at 23°C (mN / m), and η represents the viscosity of the molding liquid at 25°C (mPa-s).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a molding fluid, a molding kit, and a method for manufacturing molded objects. [Background technology]

[0002] Recently, there has been a growing need to produce complex and intricate molded objects made of metals and other materials. To meet this need, particularly from the perspective of high productivity, there is a method of densifying a sintered precursor fabricated using the binder jetting method (hereinafter sometimes referred to as the "BJ method") by sintering it using powder metallurgy.

[0003] In the BJ (Ballpoint Jack) method, water-based molding fluids are generally used, making it difficult to apply powders containing metal particles that do not like contact with water, such as aluminum or magnesium. For this reason, organic solvent-based molding fluids are being investigated as a molding fluid for metal particles that do not like contact with water. However, organic solvent-based molding fluids generally have higher wettability to the surface of metal particles compared to water-based molding fluids, which presents a problem in obtaining molded objects with the desired dimensional accuracy. To solve this problem, methods have been proposed to control the wettability of organic solvent-based molding fluids to the surface of metal particles, such as coating the metal particles with resin (see, for example, Patent Document 1) or adding organic particles to the molding fluid (see, for example, Patent Document 2). [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention aims to provide a molding fluid that can produce molded objects with excellent dimensional accuracy. [Means for solving the problem]

[0005] The molding liquid of the present invention, as a means to solve the above problem, is a molding liquid applied to a powder layer containing inorganic particles, wherein the powder contact angle θ with the inorganic particles is 50° or more, and satisfies the following equation, γcosθ / η≦1.5(m / s). However, in the formula, θ represents the powder contact angle (°) between the modeling liquid and inorganic particles, γ represents the surface tension (mN / m) of the modeling liquid at 23°C, and η represents the viscosity (mPa·s) of the modeling liquid at 25°C.

Effects of the Invention

[0006] According to the present invention, a modeling liquid capable of obtaining a molded article excellent in dimensional accuracy can be provided.

Brief Description of Drawings

[0007] [Figure 1A] FIG. 1A is a schematic diagram showing an example of a state molded to a target dimension. [Figure 1B] FIG. 1B is a schematic diagram showing an example of a state where the modeling liquid oozes out from the target dimension to a non-modeling region. [Figure 1C] FIG. 1C is a schematic diagram showing an example of a state where local oozing occurs from the target dimension. [Figure 2] FIG. 2 is a graph showing the relationship between the amount of applied modeling liquid and the bending strength of the molded article. [Figure 3A] FIG. 3A is a schematic diagram showing an example of the operation of an apparatus for manufacturing a three-dimensional molded article. [Figure 3B] FIG. 3B is a schematic diagram showing another example of the operation of an apparatus for manufacturing a three-dimensional molded article. [Figure 3C] FIG. 3C is a schematic diagram showing another example of the operation of an apparatus for manufacturing a three-dimensional molded article. [Figure 3D] FIG. 3D is a schematic diagram showing another example of the operation of an apparatus for manufacturing a three-dimensional molded article. [Figure 3E] FIG. 3E is a schematic diagram showing another example of the operation of an apparatus for manufacturing a three-dimensional molded article. [Figure 4] FIG. 4 is a front view (view seen from the side) of an apparatus showing the overall configuration of an apparatus for manufacturing a three-dimensional molded article. [Figure 5] FIG. 5 is a diagram for explaining conditions under which a discharged medium may adhere to a nozzle surface due to droplet discharge. [Figure 6]FIG. 6 is a diagram illustrating an example of an embodiment in which the nozzle surface is dipped in a cleaning liquid. [Figure 7] FIG. 7 is a diagram illustrating an example of an embodiment in which the nozzle surface is cleaned by a cleaning liquid ejection mechanism. [Figure 8A] FIG. 8A is a diagram showing a pattern state with no blurring of ejection lines (non-color-mixed state: ◯). [Figure 8B] FIG. 8B is a diagram showing a pattern state with blurring of ejection lines (color-mixed state: △). [Figure 8C] FIG. 8C is a diagram showing a pattern state with considerable blurring of ejection lines (color-mixed state: ×). [Figure 9] FIG. 9 is a schematic diagram showing an example of the nozzle surface cleaning liquid ejection mechanism used in the example. [Figure 10A] FIG. 10A is a photograph showing the state of a cleaned nozzle surface. [Figure 10B] FIG. 10B is a photograph showing a state where powder adheres to the nozzle surface. [Figure 10C] FIG. 10C is a photograph showing the state of the nozzle surface after cleaning maintenance at a moving speed of 10 mm / s. [Figure 10D] FIG. 10D is a photograph showing the state of the nozzle surface after cleaning maintenance at a moving speed of 30 mm / s. [Figure 10E] FIG. 10E is a photograph showing the state of the nozzle surface after cleaning maintenance at a moving speed of 50 mm / s. MODE FOR CARRYING OUT THE INVENTION

[0008] (Modeling liquid) The modeling liquid of the present invention is a modeling liquid applied to a powder layer containing inorganic particles, wherein a powder contact angle θ thereof with respect to the inorganic particles is 50° or more, and the liquid satisfies the following formula: γcosθ / η≦1.5 (m / s). In the formula, θ represents the powder contact angle (°) of the modeling liquid with respect to the inorganic particles, γ represents the surface tension (mN / m) of the modeling liquid at 23°C, and η represents the viscosity (mPa·s) of the modeling liquid at 25°C.

[0009] Here, when measuring the powder contact angle θ between the molding fluid and the inorganic particles, the inorganic particles used for molding are those known to be used when the type of inorganic particles used for molding is known. On the other hand, when the type of inorganic particles used for molding is unknown, aluminum particles are used. This allows us to determine the "powder contact angle θ" and "γcosθ / η≦1.5" even when the type of inorganic particles used for molding is unknown (when the inorganic particles cannot be identified), as long as the molding fluid can be identified, by using aluminum particles as the inorganic particles. For example, ALSI3-30B manufactured by Toyo Aluminum Co., Ltd. can be used as the aluminum particles.

[0010] Conventional methods of coating metal particles with resin and adding organic particles to the molding fluid have a problem in that when an organic solvent-based molding fluid is used, the vapor of the organic solvent generated during the drying process of the molding fluid dissolves the coating resin and organic particles on the metal particles in the non-molded areas where the molding fluid was not applied, causing the non-molded areas to solidify as well, resulting in a deterioration of dimensional accuracy.

[0011] The molding fluid of the present invention is an organic solvent-based molding fluid used in the BJ method. By controlling the "powder contact angle θ between the molding fluid and inorganic particles," the "viscosity γ of the molding fluid at 25°C," the "surface tension η of the molding fluid at 23°C," and "γcosθ / η" to be within an appropriate range, the fluid exhibits good discharge properties, suppresses leakage of the molding fluid into non-molded areas, and enables the production of molded objects with high bending strength and the desired dimensional accuracy.

[0012] <Viscosity η of the molding fluid> The viscosity η of the molding fluid at 25°C is preferably 6 mPa·s or higher, more preferably 12 mPa·s or higher, and even more preferably 15 mPa·s or higher. Furthermore, it is preferably 50 mPa·s or lower, more preferably 30 mPa·s or lower, even more preferably 25 mPa·s or lower, even more preferably 21 mPa·s or lower, particularly preferably 19 mPa·s or lower, and most particularly preferably 18.5 mPa·s or lower. When the viscosity η 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 the accurate ejection of the molding fluid further 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 improves the dimensional accuracy of the molded product. The viscosity η of the molding fluid at 25°C can be measured at 25°C using, for example, a cone-plate type viscometer VISCOMETER TV-25 manufactured by Toki Sangyo Co., Ltd.

[0013] <Surface tension γ of the molding fluid> The surface tension γ of the molding fluid at 23°C is preferably 20 mN / m or more, more preferably 22 mN / m or more, even more preferably 25 mN / m or more, and particularly preferably 27 mN / m or more. Furthermore, it is preferably 40 mN / m or less, more preferably 35 mN / m or less, even more preferably 31 mN / m or less, and particularly preferably 30 mN / m or less. When the surface tension γ is within the above range, the ejection from the molding fluid application means such as the inkjet head is stabilized, and accurate ejection of the molding fluid improves the bending strength of the molded object before sintering, such as the solidified material and the green body derived from the solidified material, thereby improving the dimensional accuracy of the molded object. The surface tension γ of the molding fluid at 23°C can be measured at 23°C using the Wilhelmy method (suspension plate method) with an automatic surface tension meter DY-300 manufactured by Kyowa Interface Science Co., Ltd.

[0014] <Contact angle θn of the molding fluid (plate method)> Generally, organic solvent-based 3D printing fluids have higher wettability to inorganic particle surfaces compared to water-based 3D printing fluids, and the contact angle θn (plate method) of the 3D printing fluid is effectively 15° or less. The contact angle θn between the molding fluid and the metal plate can be measured at 25°C using the droplet method with a contact angle meter DMs-301 manufactured by Kyowa Interface Science Co., Ltd. As the metal plate, we used the aluminum free plate A 6061 LNQ-25-10-5 manufactured by Misumi Corporation. The molding fluid was filled into a syringe, and approximately 2.0 microliters of the fluid was dropped onto the metal plate using the automatic droplet formation function. The contact angle θn (plate method) was defined as the value obtained from the droplet shape after 20 seconds using the θ / 2 method.

[0015] <Contact angle θ between the molding fluid and inorganic particles> The powder contact angle θ between the molding fluid and the inorganic particles is 50° or more, preferably 52° or more, more preferably 55° or more, even more preferably 60° or more, and particularly preferably 65° or more. Furthermore, it is preferably 80° or less, more preferably 76° or less, even more preferably 75° or less, even more preferably 70° or less, particularly preferably 69° or less, and most particularly preferably 68° or less. When the powder contact angle θ is 50° or more, the seepage of the molding fluid into the non-molded areas can be suppressed, and molded objects with the desired dimensional accuracy can be stably obtained.

[0016] The powder contact angle θ between the molding fluid and inorganic particles is a value calculated from the penetration rate when the molding fluid is permeated into a column packed with powder containing inorganic particles. For example, it can be measured using an automatic surface tension meter DY-500 manufactured by Kyowa Interface Science Co., Ltd. as follows. When the type of inorganic particle to be used for molding is known, that inorganic particle is used. On the other hand, when the type of inorganic particle to be used for molding is unknown, aluminum powder (ALSI3-30B, manufactured by Toyo Aluminum Co., Ltd.) is used. 5g of powder containing inorganic particles was packed into a column, and the porosity was adjusted to 35.6% to 35.8% using a powder compressor. Acetone is used as a liquid with sufficient wettability to powders containing inorganic particles, and the capillary radius is determined assuming that the contact angle θ between acetone and the powder is 0 degrees. "Capillary radius" refers to the radius of the gap between inorganic particles when metal particles are packed into a column, and can be measured with an automatic surface tension meter DY-500 manufactured by Kyowa Interface Science Co., Ltd. Next, using an automatic surface tension meter DY-500 manufactured by Kyowa Interface Science Co., Ltd., the penetration rate of the molding fluid into the powder containing inorganic particles is measured in the range of 150 to 180 seconds from the start of measurement. The penetration rate of the molding fluid into the powder containing inorganic particles is expressed by the Lucas-Washburn equation in formula (1) below.

[0017]

number

[0018] <γcosθ / η> The molding fluid of the present invention satisfies the following equation, γcosθ / η≦1.5(m / s), preferably satisfies the following equation, γcosθ / η≦1(m / s), and more preferably satisfies the following equation, γcosθ / η≦0.8(m / s). Furthermore, γcosθ / η is preferably 0.1(m / s) or higher, more preferably 0.3(m / s) or higher, even more preferably 0.4(m / s) or higher, even more preferably 0.5(m / s) or higher, and particularly preferably 0.6(m / s) or higher. By ensuring that the molding fluid satisfies the following equation, γcosθ / η≦1.5(m / s), the leakage of the molding fluid into non-molded areas can be suppressed, and the desired dimensional accuracy can be stably obtained. The value "γcosθ / η" is calculated as an indicator representing the penetration rate of the molding fluid into inorganic particles. However, in the formula, θ represents the powder contact angle (°) between the molding fluid and inorganic particles, γ represents the surface tension (mN / m) of the molding fluid at 23°C, and η represents the viscosity (mPa·s) of the molding fluid at 25°C.

[0019] In one aspect of the present invention, the amount of modeling liquid to be applied is 0.033 μl / mm 3 or more and 0.33 μl / mm 3 or less is preferable, and 0.148 μl / mm 3 or more and 0.33 μl / mm 3 or less is more preferable. When the amount of modeling liquid to be applied is 0.033 μl / mm 3 or more and 0.33 μl / mm 3 or less, local bleeding of the modeling liquid can be prevented. Further, when the amount of modeling liquid to be applied is 0.148 μl / mm 3 or more and 0.33 μl / mm 3 or less, the bending strength of the modeled article can be increased. When the amount of modeling liquid to be applied is less than 0.033 μl / mm 3 , the modeled article may collapse. When the amount of modeling liquid to be applied exceeds 0.33 μl / mm 3 , the modeling liquid may locally bleed out.

[0020] The amount of modeling liquid to be applied can be determined, for example, by the following procedure. A desired number of droplets are dropped from an inkjet head onto a weighed OHP sheet, and the total weight of the dropped modeling liquid is obtained from the difference from the weight before dropping. Thereafter, the volume of the modeling liquid per one droplet from one nozzle is calculated by dividing the total weight of the modeling liquid by the number of nozzles used for dropping, the number of droplets, and the specific gravity of the modeling liquid. After multiplying the volume of the modeling liquid per one droplet from one nozzle by the number of droplets discharged into one voxel to obtain the volume of the modeling liquid dropped into one voxel, the amount of modeling liquid to be applied can be obtained by converting it to the volume of modeling liquid per 1 mm 3 . The size of one voxel can be calculated from the resolution in the main scanning direction and the sub scanning direction and the lamination thickness.

[0021] In the present invention, by controlling the following to be within an appropriate range in the molding fluid: "the powder contact angle θ between the molding fluid and metal particles", "the viscosity γ of the molding fluid at 25°C", "the surface tension η of the molding fluid at 23°C", and "γcosθ / η", as shown in Figures 1A and 1B, the leakage of the molding fluid 2 from the target dimension 1 to the non-molded area can be suppressed, and a molded object with the target dimensional accuracy can be obtained. On the other hand, the amount of molding fluid to be applied is 0.033 μl / mm². 3 More than 0.33μl / mm 3 By doing the following, the molding fluid is less likely to overflow, and localized seepage 3, where the molding fluid seeps out locally from the target dimension 1, can be prevented, as shown in Figure 1C.

[0022] In one embodiment of the present invention, the resolution is preferably 600 dpi or higher, and preferably 600 dpi or higher and 1200 dpi or lower. Even with the same volume of material, increasing the resolution brings adjacent droplets closer together, making them easier to merge. The stronger bonding between droplets increases the bending strength of the printed object. Resolution can be adjusted, for example, by controlling the ejection frequency and the head's scanning speed in the primary scanning direction. In addition, the resolution in the secondary scanning direction can be adjusted by moving the head a desired distance perpendicular to the primary scanning direction with each scan.

[0023] In one embodiment of the present invention, when applying a cleaning solution to the nozzle surface on which a nozzle for discharging molding fluid is provided, the pressure applied to the nozzle is controlled to be 0 mmAq or higher. By controlling the pressure applied to the nozzle to be 0 mmAq or higher during cleaning maintenance, it is possible to prevent the cleaning solution from entering the nozzle, thereby preventing the molding fluid inside the nozzle from mixing with the cleaning solution, which could impair the properties of the molding fluid or cause unstable discharging of the molding fluid. When applying a cleaning solution to the nozzle surface, which is equipped with a nozzle for discharging molding fluid, the pressure applied to the nozzle is preferably 0 mmAq or more and 25 mmAq or less. One way to control the pressure applied to the nozzle so that it is between 0 mmAq and 25 mmAq is, for example, to control the pressure in the tank to which the molding fluid is supplied using a pump or the like. There are no particular restrictions on the cleaning solution; it can be selected appropriately depending on the purpose. For example, water-based or organic solvent-based cleaning solutions can be used. In particular, using an organic solvent similar to the one used in the molding fluid as the cleaning solution can reduce the risk of the physical properties of the molding fluid changing due to color mixing.

[0024] In one embodiment of the present invention, it is preferable that the time for applying the cleaning solution to the nozzle surface is 1 second or more and 2 seconds or less. This embodiment has the advantage that powder adhering to the nozzle surface can be removed and no color mixing occurs.

[0025] The molding fluid of the present invention is a liquid composition used in the manufacture of molded objects and applied to a layer of powder containing inorganic particles. The manufacturing of the molded object is carried out by a method for manufacturing molded objects that includes a powder layer formation step of forming a layer of powder containing inorganic particles, a molding liquid application step of applying molding liquid to the powder layer, and a lamination step of forming a laminate by sequentially repeating the powder layer formation step and the molding liquid application step. Furthermore, it is preferable that the manufacturing of the molded object is carried out by a method for manufacturing molded objects 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, which is 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 liquid; 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.

[0026] In this invention, "formed object" refers to a general term for three-dimensional objects that maintain a certain three-dimensional shape, and for example, a solidified object or a structure derived from a solidified object, and specifically, a concept that represents solidified objects, green bodies, degreased bodies, and sintered bodies. Furthermore, in this invention, "powder" may also be referred to as "powder" or "powder material." "Shaping liquid" may also be referred to as "curing liquid" or "reaction liquid." Also, "solidified material" may also be referred to as "cured material." Furthermore, a three-dimensional object formed by stacking solidified materials may also be referred to as a "green body," "sintered body," "molded body," or "shaped object." A "green body" that has been heat-treated and degreased may also be referred to as a "degreased body." The "green body" and the "degreased body" together may also be referred to as a "sintering precursor."

[0027] The molding fluid of the present invention contains a resin, an organic solvent, and a surfactant, and further contains other components as needed.

[0028] <Resin> The molding fluid contains a resin having a structural unit represented by the following structural formula (1).

[0029] [ka]

[0030] -A resin having structural units represented by structural formula (1)- The resin having the structural unit represented by structural formula (1) is arranged within the powder layer when the molding liquid is applied to the powder layer containing inorganic particles. Through an appropriate heating process corresponding to the resin's softening point, it functions as a binder that binds the inorganic particles together in the area where the molding liquid is applied, forming pre-sintered molded objects such as solidified material and green bodies derived from the solidified material. These pre-sintered molded objects are formed from a resin having the structural unit represented by structural formula (1) which imparts flexibility, thus improving their bending strength. Note that "structural unit" refers to a substructure in the resin derived from one or more polymerizable compounds.

[0031] Furthermore, resins having structural units represented by structural formula (1) exhibit excellent thermal decomposition properties, allowing them to be appropriately removed in the degreasing process, resulting in improved density in the sintered body produced through the subsequent sintering process. Therefore, the effects become more pronounced when metal particles, which are materials intended for or preferably sintered, are used as the material for forming molded objects. Specifically, resins having structural units represented by structural formula (1) are preferably thermally decomposed by 95% or more by mass when heated to 30°C to 550°C, and more preferably by 97% or more by mass. Note that "thermal decomposition of the resin" refers to random decomposition of the main chain or depolymerization at the molecular chain ends, resulting in the removal of the resin by vaporization, oxidative decomposition, combustion, etc. Thermal decomposition properties can be measured using TG-DTA (Differential Thermal Analysis-Thermogravimetric Analysis). Specifically, the weight loss rate before and after heating is determined when the temperature is raised from 30°C to 550°C at a rate of 10°C / min in an air or nitrogen atmosphere, and the temperature is maintained for 2 hours after reaching 550°C.

[0032] Furthermore, resins having structural units represented by structural formula (1) exhibit improved solubility in organic solvents due to the hydrophobicity of these structural units. Therefore, when the molding fluid contains an organic solvent, the solubility of the resin having structural units represented by structural formula (1) improves. This allows for a reduction in the viscosity of the molding fluid, enabling, for example, proper ejection of the molding fluid using an inkjet method. It is preferable that the resin having structural units represented by structural formula (1) is soluble in the organic solvent of the molding fluid and insoluble in water.

[0033] The glass transition temperature (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.

[0034] 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.

[0035] 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 improved resin content in the molding fluid.

[0036] A resin having a structural unit represented by structural formula (1) may be either a resin having a structural unit other than that represented by structural formula (1) or a resin not having a structural unit other than that represented by structural formula (1). Examples of structural units other than that represented by structural formula (1) include, for example, the structural unit represented by the following structural formula (3) and / or the structural unit represented by the following structural formula (4).

[0037] [ka]

[0038] [ka]

[0039] A resin having structural units represented by structural formula (3) 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 (3) is hydrophobic, just like the structural unit represented by structural formula (1), which improves the solubility of the resin in organic solvents. From these perspectives, in a resin, the total amount of structural units represented by structural formula (1) and structural units represented by structural formula (3) is preferably 60 mol% or more, more preferably 65 mol% or more, even more preferably 70 mol% or more, particularly preferably 75 mol% or more, and most preferably 80 mol% or more, relative to the total amount of structural units represented by structural formula (1), structural formula (3), and structural formula (4). The same applies when the resin does not contain structural units represented by structural formula (3) and / or structural formula (4); the above percentages can be calculated by setting the amount of the missing structural units to 0.

[0040] A resin having structural units represented by structural formula (4) in addition to structural units represented by structural formula (1) improves the affinity with inorganic particles in the powder layer to which the molding liquid is applied, due to the hydroxyl groups in the structural units represented by structural formula (4). 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, and the density of the molded product before sintering and the density of the molded product after sintering are also further improved. From these viewpoints, in the resin, the amount of structural units represented by structural formula (4) 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 (3), and structural units represented by structural formula (4). However, since the structural unit represented by structural formula (4) is hydrophilic, an increase in the proportion of structural units represented by structural formula (4) 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 viewpoint, in the resin, the amount of structural units represented by structural formula (4) is preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 30 mol% or less, particularly preferably 25 mol% or less, and most preferably 20 mol% or less, relative to the total amount of structural units represented by structural formula (1), structural units represented by structural formula (3), and structural units represented by structural formula (4). The same applies when the resin does not have structural units represented by structural formula (3), in which case the above proportions can be calculated by setting the amount of the absent structural units to 0.

[0041] Specific examples of resins having the 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 partially saponified polyvinyl acetate resin are preferred because they can reduce the viscosity of the molding fluid. Here, "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 (4), and preferably refers to 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. Furthermore, both commercially available products and synthetic products may be used.

[0042] Polyvinyl acetate resin is a resin that has structural units represented by structural formula (1) and substantially does not have structural units represented by structural formula (3) and structural formula (4). Partially saponified polyvinyl acetate resin is a resin that has structural units represented by structural formula (1) and structural units represented by structural formula (4), but substantially does not have structural units represented by structural formula (3). Polyvinyl butyral resin is a resin having structural units represented by structural formula (1) and structural units represented by structural formula (3), or a resin having structural units represented by structural formula (1), structural units represented by structural formula (3), and structural units represented by structural formula (4).

[0043] Partially saponified polyvinyl acetate resin is a resin obtained by partially saponifying polyvinyl acetate resin. Furthermore, the amount of structural units represented by structural formula (4) in the partially saponified polyvinyl acetate resin is preferably 40 mol% or less, more preferably 35 mol% or less, even more preferably 30 mol% or less, particularly preferably 25 mol% or less, and most preferably 20 mol% or less, relative to the total amount of structural units represented by structural formula (1) and structural formula (4). In other words, the degree of saponification of the partially saponified polyvinyl acetate resin is preferably 40 or less, more preferably 35 or less, even more preferably 30 or less, particularly preferably 25 or less, and most preferably 20 or less.

[0044] The resin content having the structural unit represented by structural formula (1) is preferably 5% by mass or more, more preferably 7% by mass or more, even more preferably 10% by mass or more, and particularly preferably 11% by mass or more, relative to the total amount of the molding fluid. Furthermore, it is preferably 30% by mass or less, more preferably 25% by mass or less, and even more preferably 20% by mass or less. A resin content of 5% by mass or more 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. In addition, a resin content of 30% by mass or less further reduces the viscosity of the molding fluid, 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 units represented by structural formula (3) is 95 mol% or more of the total amount of structural units represented by structural formula (1), structural units represented by structural formula (3), and structural units represented by structural formula (4) 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% or more by mass or 20% or more by mass relative to the total amount of 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] In addition to the resin having the structural unit represented by structural formula (1), the molding liquid of the present invention may also contain, as necessary, a resin having the structural unit represented by the following structural formula (2) and a polyvinyl alcohol resin.

[0047] -A resin having structural units represented by structural formula (2)- [ka]

[0048] The resin having the structural unit represented by structural formula (2) 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 (2), which has a five-membered ring lactam structure with high affinity for metal, the metal particles are strongly bound together, improving flexural strength.

[0049] Furthermore, resins having structural units represented by structural formula (2) exhibit excellent thermal decomposition properties if the heating profile is appropriately controlled, allowing them to be properly removed in the degreasing process, thereby improving the density of the sintered body produced through the subsequent sintering process. Therefore, the effects become particularly pronounced when metal particles, which are materials intended for or preferably sintered, are used as the material for forming the molded object. Specifically, resins having structural units represented by structural formula (2) are preferably thermally decomposed by 95% by mass or more when heated from 30°C to 550°C, and more preferably by 97% by mass or more. However, resins having structural units represented by structural formula (2) may form crosslinked structures under certain temperature conditions (e.g., heating conditions of 160°C or higher), which can suppress the effect of high thermal decomposition. Therefore, when using metal particles as a material for forming molded objects, which are materials intended for or preferably sintered, it may be preferable to use a resin having structural units represented by structural formula (1) rather than a resin having structural units represented by structural formula (2), based on the viewpoint of ease of handling.

[0050] Furthermore, the resin having the structural unit represented by structural formula (2) has a five-membered ring lactam structure, which improves its solubility in certain organic solvents (mainly polar solvents), thereby reducing the viscosity of the molding fluid. For example, this allows for the proper ejection of the molding fluid using an inkjet method. In addition, when the resin having the structural unit represented by structural formula (2) is used in combination with organic solvents such as component 1 (cyclic esters (lactones), etc.) and component 2 (glycol diethers, etc.), the viscosity of the molding fluid can be further reduced. Because the viscosity of the molding fluid can be reduced in this way, the resin having the structural unit represented by structural formula (2) can be included in the molding fluid in high mass (for example, 15% by mass or more of the total volume of the molding fluid). This further improves the flexural strength of the molded product before sintering, such as the solidified product and the green body derived from the solidified product.

[0051] The softening point of the resin having the structural unit represented by structural formula (2) is preferably 70°C or higher, more preferably 80°C or higher, and even more preferably 90°C or higher. Furthermore, it is preferably 180°C or lower, more preferably 170°C or lower, and even more preferably 160°C or lower.

[0052] The number-average molecular weight (Mn) of the resin having the structural unit represented by structural formula (2) is preferably 3,000 to 50,000, and more preferably 5,000 to 40,000. 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.

[0053] Specific examples of resins having the structural unit represented by structural formula (2) include, for example, polyvinylpyrrolidone resin. Both commercially available and synthetic products can be used.

[0054] -Polyvinyl alcohol resin- Polyvinyl alcohol resin is placed within a layer of powder containing inorganic particles when the molding liquid is applied to it. Through an appropriate heating process corresponding to the resin's softening point, it functions as a binder, binding the inorganic particles together in the area where the molding liquid is applied, and forming a pre-sintered molded object such as a solidified product and a green body derived from the solidified product. Polyvinyl alcohol resin includes not only polyvinyl alcohol resin, but also polymers containing vinyl alcohol as a constituent unit, or saponified products thereof. The average degree of polymerization and saponification of polyvinyl alcohol can be appropriately adjusted by appropriately adjusting the vinyl acetate used as a raw material. The average degree of polymerization of the polyvinyl alcohol resin (measured in accordance with JIS K6726) is preferably between 100 and 2,000, and more preferably between 100 and 1,000. If the average degree of polymerization is too high, the melt viscosity increases, and the moldability or formability tends to decrease. On the other hand, if the average degree of polymerization is too low, the mechanical strength of the molded or shaped product tends to be insufficient. The degree of saponification of polyvinyl alcohol resin (measured in accordance with JIS K 6726) is not particularly limited and can be appropriately selected depending on the intended use, solubility, moisture resistance, etc., but it is preferably between 0 mol% and 100 mol%, and a partially saponified type of 80 mol% or less is more preferable than a fully saponified type.

[0055] <Organic solvents> Organic solvents are liquid components used to keep the molding fluid in a liquid state at room temperature. Furthermore, the molding fluid is preferably a non-aqueous molding fluid that contains an organic solvent. A "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. Moreover, the content of the organic solvent relative to the liquid component content in the molding fluid is preferably 90% by mass or more, and more preferably 95% by mass or more. This is because, in the case of non-aqueous molding fluids, solubility is improved, particularly in resins having structural units represented by structural formula (1), and the viscosity of the molding fluid decreases. Furthermore, non-aqueous molding fluids can sometimes be described as molding fluids that are substantially water-free. This makes it possible to apply the molding fluid even when the material constituting the metal particles as inorganic particles is a highly reactive metal, in other words, a water-reactive material (e.g., aluminum, zinc, magnesium, or alloys thereof). For example, aluminum forms an aluminum hydroxide film when it comes into contact with water, so a high water content in the molding fluid leads to a decrease in the sintering density of the sintered body, but this problem is suppressed by using a molding fluid that does not contain water. As another example, aluminum generates hydrogen when it comes into contact with water, making it difficult to handle, but this problem is also suppressed by using a molding fluid that does not contain water.

[0056] 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, triacetate Examples include tributyline, 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, 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.

[0057] 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 depending on the purpose. However, it is preferable to use an organic solvent having at least one structure selected from the group consisting of alkoxy groups, ether bonds, and ester bonds, more preferably an organic solvent having an ether bond, and even more preferably an alkylene glycol dialkyl ether compound. 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.

[0058] "Alkylene glycol dialkyl ether compounds" refers to R1-(O-R2) mRepresented 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. Specific examples of alkylene glycol dialkyl ether compounds include, for example, 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.

[0059] When using a resin having a structural unit represented by structural formula (2), it is preferable that the organic solvent used in combination be a polar solvent. Specifically, it is preferable to use at least one selected from the group consisting of cyclic esters (lactones), cyclic ketones, and alkylene glycol monoalkyl ethers as component 1, and it is even more preferable to use at least one selected from the group consisting of alkylene glycol dialkyl ethers in addition to at least one selected from component 1 as component 1. When these organic solvents are used, the solubility of the resin having a structural unit represented by structural formula (2) is further improved, and the viscosity of the molding liquid can be further reduced, allowing the molding liquid to be appropriately ejected, for example, in an inkjet method. From the viewpoint of further improving the solubility of the resin having a structural unit represented by structural formula (2), it is preferable that component 1 is from the group consisting of cyclic esters (lactones) and cyclic ketones.

[0060] When using a resin having structural units represented by structural formula (2), and using both at least one selected from component 1 and at least one selected from component 2 as the organic solvent, the mass ratio (component 1 / component 2) of the total amount of component 1 to the total amount of component 2 is preferably 60 / 40 to 100 / 0. By having a mass ratio (component 1 / component 2) of 60 / 40 to 100 / 0, the solubility of the resin having structural units represented by structural formula (2) is further improved, and consequently, the viscosity of the molding fluid can be further reduced.

[0061] Specific examples of component 1, which is a group consisting of cyclic esters (lactones), cyclic ketones, and alkylene glycol monoalkyl ethers, include, for example, γ-butyrolactone, propylene carbonate, and cyclohexanone. Specific examples of component 2, which is comprised of alkylene glycol dialkyl ethers, include, for example, 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. "Alkylene glycol monoalkyl ethers" refers to R4-(O-R5) n Represented as -OH, R4 is an alkyl group having 1 to 5 carbon atoms, which may be linear or branched. R5 is an alkylene group having 2 to 5 carbon atoms, which may be linear or branched. n is an integer between 1 and 5.

[0062] Furthermore, if you want to further reduce the viscosity of the molding fluid, using a resin with structural units represented by structural formula (2) is more affected by the type of organic solvent used than using a resin with structural units represented by structural formula (1). Therefore, it is necessary to selectively use the organic solvents (component 1 and component 2) as described above. For this reason, from the viewpoint of broadening the range of material selection when preparing the molding fluid, it is preferable to use a resin with structural units represented by structural formula (1) rather than a resin with structural units represented by structural formula (2).

[0063] The viscosity of the organic solvent is preferably low, specifically, at 25°C, it is preferably 5 mPa·s to 50 mPa·s, and more preferably 8 mPa·s to 30 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 inkjet heads, 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.

[0064] The boiling point of the organic solvent is preferably high, more preferably 150°C or higher, and even 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. There are no particular restrictions on high-boiling-point organic solvents, and they can be appropriately selected depending on the purpose. Examples include the above-mentioned 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), and triethylene glycol dimethyl ether (boiling point: 216°C).

[0065] The content of the organic solvent is preferably 60% to 95% by mass, and more preferably 70% to 95% by mass, relative to the total amount of the molding fluid. When the organic solvent content is 60% to 95% by mass, the solubility of the resin is further improved, and consequently 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.

[0066] The mass ratio (organic solvent / resin) of the organic solvent content to the resin content is preferably 75 / 25 or more and 95 / 5 or less. When the mass ratio (organic solvent / resin) is 75 / 25 or more, the solubility of the resin is further improved, and consequently the viscosity of the molding fluid can be further reduced, allowing for proper ejection of the molding fluid, for example, using an inkjet method. Furthermore, when the mass ratio (organic solvent / resin) is 95 / 5 or less, 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.

[0067] The total content of organic solvents and resins is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 99.5% by mass or more, based on the total amount of the molding fluid. Furthermore, it is not necessary for the molding fluid to substantially contain components other than organic solvents and resins. The statement that the molding fluid substantially contains no components other than organic solvents and resins means that no components other than organic solvents and resins are actively used as materials during the manufacture of the molding fluid, or that the content of components other than organic solvents and resins in the molding fluid is below the detection limit when using known and commonly used methods. When the combined content of organic solvents and resins is 90% by mass or more of the total volume of the molding fluid, the resin content in the molding fluid increases, and the flexural strength of the molded product before sintering, such as solidified material and green body derived from the solidified material, is further improved. In addition, when the content of components other than organic solvents and resins (for example, materials that are insoluble in the molding fluid, such as metal particles) 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.

[0068] <Surfactants> Surfactants are added to increase the powder contact angle θ between the inorganic particles of the molding fluid and the surfactant, thereby improving the dimensional accuracy of the resulting molded object. As the surfactant, at least one of a fluorine surfactant and a silicone surfactant is preferred. By using such a fluorine surfactant and a silicone surfactant in the molding fluid, the leakage of the molding fluid into the non-molded areas can be suppressed, and molded objects with the desired dimensional accuracy can be stably obtained. Commercially available fluorinated surfactants can be used, and examples of such commercial products include Surflon S-693 (manufactured by AGC Seikamika Co., Ltd.) and KF-353 (manufactured by Shin-Etsu Chemical Co., Ltd.). Such silicone surfactants can be commercially available products, such as Silface SAG020 (manufactured by Nisshin Chemical Industry Co., Ltd.).

[0069] The surfactant content is preferably 0.001% by mass or more, more preferably 0.01% by mass or more, even more preferably 0.05% by mass or more, particularly preferably 0.1% by mass or more, and most preferably 0.3% by mass or more, relative to the total amount of the molding liquid. Furthermore, it is preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably 0.5% by mass or less. When the surfactant content is within the above range, the powder contact angle θ between the molding fluid and the inorganic particles can be increased, resulting in good dimensional accuracy of the molded object.

[0070] <Other ingredients> Other ingredients are not particularly limited and can be selected as appropriate depending on the purpose. Examples include water, drying agents, viscosity modifiers, penetrating agents, defoaming agents, pH adjusters, preservatives, fungicides, colorants, preservatives, and stabilizers.

[0071] -water- In the molding fluid, water is substantially absent. In this invention, "substantially absent water" means that the water content is 10% by mass or less of the total volume of the molding fluid, preferably 5% by mass or less, more preferably 3% by mass or less, even more preferably 1% by mass or less, and particularly preferably the molding fluid contains no water at all. By substantially absent 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. Note that "substantially absent water" 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 known and commonly used methods. Furthermore, because the molding fluid contains virtually no water, it can be applied even if the materials constituting the inorganic particles are highly reactive metals, in other words, water-reactive materials (e.g., aluminum, zinc, magnesium, or alloys thereof). 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.

[0072] <Method for manufacturing molding fluid> There are no particular restrictions on the method of manufacturing the molding fluid, and it can be appropriately selected according to the purpose. For example, a method of mixing and stirring the above-mentioned materials can be used.

[0073] <Inorganic particles> Inorganic particles are not particularly limited as long as they are in the form of powder or particles, and can be appropriately selected depending on the purpose. Examples include metals, ceramics, carbon, sand, and magnetic materials. However, from the viewpoint of obtaining extremely high-strength three-dimensional structures, metals and ceramics that can ultimately undergo sintering (process) are preferred. Examples of ceramics include oxides, carbides, nitrides, and hydroxides. Examples of oxides include metal oxides. Examples of metal oxides include silica (SiO2), alumina (Al2O3), zirconia (ZrO2), and titania (TiO2). These may be used individually or in combination of two or more.

[0074] Metal particles are particles that 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 mass of metal contained in the metal particles is 50% by mass or more of the total mass of the metal particles, preferably 60% by mass or more, more preferably 70% by mass or more, even more preferably 80% by mass or more, and particularly preferably 90% by mass or more.

[0075] 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), or alloys of these metals. These may be used individually or in combination of two or more. Among these, stainless steel (SUS), iron (Fe), copper (Cu), silver (Ag), titanium (Ti), magnesium (Mg), zinc (Zn), aluminum (Al), or alloys of these metals are preferred, aluminum, zinc, magnesium, or alloys of these metals are more preferred, and aluminum alloys are particularly preferred. Examples of aluminum alloys include AlSi 10 Mg, AlSi 12 AlSi7Mg 0.6 , AlSi3Mg, AlSi9Cu3, Scalmalloy, ADC 12 Examples include AlSi3.

[0076] Metal particles are not particularly limited and 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 produce crystallized particles. Among these, atomization is preferred because it yields a spherical shape and has little variation in particle size. There are no particular limitations on atomization methods, and they can be appropriately selected depending on the purpose. Examples include water atomization, gas atomization, centrifugal atomization, and plasma atomization.

[0077] Commercially available metal particles may be used. Examples of commercially available products include 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), and AlSi 10 Mg (manufactured by Toyo Aluminum Co., Ltd., Si 10 Examples include MgBB, SiO2 (manufactured by Tokuyama Corporation, product name: Excelica SE-15K), AlO2 (manufactured by Daimyo Chemical Industry Co., Ltd., product name: Tymicron TM-5D), ZrO2 (manufactured by Tosoh Corporation, product name: TZ-B53), and aluminum powder (manufactured by Toyo Aluminum Co., Ltd., ALSI3-30B).

[0078] 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 particle size distribution analyzers (Microtrac MT3000II series, manufactured by Microtrac Bell Co., Ltd.).

[0079] 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 the binder function of the coating resin, the present invention contains a resin having a binder function in the molding liquid. Therefore, the metal particles do not need to be coated on the surface with resin. By using metal particles whose surfaces are not coated with resin, it is possible to suppress the formation of unintended solidified objects, for example, in areas of powder where the molding liquid has not been applied (in other words, non-molded areas), by preventing the coating resin from binding the metal particles together during the heating process. Here, "not coated with resin" means, for example, that the ratio of the resin surface area to the surface area of ​​the metal particles (surface coverage rate) is less than 15%, and the surface coverage rate may be 0%. The surface coverage rate can be 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. In determining the resin-coated portion, for example, elemental mapping techniques using energy-dispersive X-ray spectroscopy such as SEM-EDS can be used.

[0080] <Powder containing inorganic particles> The inorganic particles described above are used as a powder, which is an aggregate containing multiple inorganic particles. A molded object is manufactured by applying a molding liquid to a layer of this powder. The powder may contain inorganic particles as well as other components as needed.

[0081] Other components include, for example, fillers, leveling agents, sintering aids, and polymer resin particles. Fillers are effective materials for adhering to the surface of inorganic particles or filling the voids between them. By using fillers, for example, the fluidity of powders can be improved, and the contact points between inorganic particles can be increased, reducing voids and thereby improving the strength and dimensional accuracy of the fabricated object.

[0082] 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.

[0083] 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.

[0084] Polymer resin particles are effective materials for adhering to the surface of inorganic particles and are also called organic additives. The average particle size of polymer resin particles is not particularly limited and can be appropriately selected depending on the purpose, but it is preferably 0.1 μm to 10 μm, and more preferably 0.1 μm to 1 μm.

[0085] (Modeling kit) The molding kit of the present invention comprises the molding fluid of the present invention and inorganic particles, and may optionally include other components such as a powder removal liquid. Furthermore, the molding kit only needs to consist of the inorganic particles and the molding fluid in separate states, and is not limited to cases where the molding fluid container and the inorganic particle container are integrated. For example, even if the molding fluid and inorganic particles are contained in separate containers, the kit is included if it is assumed that the inorganic particles and the molding fluid will be used together, or if the kit substantially induces the use of the inorganic particles and the molding fluid together.

[0086] The inorganic particles used in the molding kit are the same as those used in the molding fluid. The inorganic particles are preferably metal particles, and preferably contain at least one selected from aluminum, zinc, magnesium, and their alloys. It is preferable that the inorganic particles are not coated on the surface with resin.

[0087] (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 inorganic particles; a molding liquid application step of applying a molding liquid to the powder layer; and a lamination step of forming a laminate by sequentially repeating the powder layer formation step and the molding liquid application step. Furthermore, 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 solidified object to obtain a green object, a drying step of drying the green object to remove any remaining liquid components in the green object, a degreasing step of heating the green object to remove resin and other substances derived from the applied molding fluid to obtain a degreased object, a sintering step of heating the degreased object to obtain a sintered object, and a post-processing step of performing post-processing on the sintered object.

[0088] <Powder layer formation process> The powder layer formation process is a process of forming a layer of powder containing inorganic particles, and is carried out by a powder layer formation means. The powder layer is formed on the support (on the building stage). There are no particular limitations on the method of forming a thin layer of powder by placing the powder on the support, and a suitable method can be selected depending on the purpose. Examples include using a known counter rotation mechanism (counter roller) used in the selective laser sintering method described in Japanese Patent Publication No. 3607300, spreading the powder using components such as brushes, rollers, and blades, spreading the powder by pressing the surface of the powder with a pressing member, and using a known additive manufacturing apparatus.

[0089] 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.

[0090] 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. Furthermore, there are no particular restrictions on the average thickness, and it can be measured according to known methods.

[0091] 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.

[0092] <Forming fluid application process> The molding fluid application step is a step in which molding fluid is applied to the powder layer formed in the powder layer formation step, and is carried out by a molding fluid application means. 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.

[0093] 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.

[0094] 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.

[0095] <Lamination process> The lamination process is a process of forming a laminate by sequentially repeating the powder layer formation process and the molding fluid application process, and is carried out by a lamination means. 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.

[0096] The lamination process includes 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). This forms a region of the powder layer to which molding fluid has been applied. Furthermore, the lamination process includes a step of placing powder on a thin layer (lamination) that is a layer of powder having a region to which molding fluid has been applied, 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). This forms a region to which molding fluid has been applied in the newly laminated powder layer. At this time, the region to which molding fluid has been applied in the uppermost laminated powder thin layer is continuous with the region to which molding fluid has been applied in the powder thin layer below it. As a result, a region to which molding fluid has been applied with a thickness equivalent to two layers of powder is obtained.

[0097] <Heating process> The heating process involves heating the laminate formed in the lamination process to create a solidified material, and is carried out by a heating means. "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.

[0098] The heating temperature in the heating process is preferably higher than the softening point of the resin. This allows the resin to function as a binder that binds inorganic particles together in the area where the molding liquid is applied, enabling the formation of pre-sintered molded objects such as solidified material and green material derived from the solidified material. There are no particular restrictions on the heating method, and it can be appropriately selected depending on the purpose. Examples include dryers and constant temperature and humidity chambers.

[0099] <Excess powder removal process> The excess powder removal process is a process of removing excess powder, which is powder adhering to the solidified material, to obtain a green material, and is carried out by an excess powder removal means. "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 a solidified material, and preferably refers to a three-dimensional object that is substantially free of excess powder. Furthermore, the excess powder removal process preferably includes at least one step selected from a step of removing excess powder from the solidified material by air blowing and a step of removing excess powder from the solidified material by immersion in a removal liquid, and more preferably includes both steps.

[0100] 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, the solidified product formed using the molding liquid of the present invention is formed from the above-mentioned resin, and therefore has improved flexural strength and strength to withstand the pressure of an air blow. In this case, the flexural strength of the solidified product is preferably 3 MPa or more, and more preferably 5 MPa or more, based on a three-point bending stress.

[0101] -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.

[0102] Examples of organic solvents include ketones, halogens, alcohols, esters, ethers, hydrocarbons, glycols, glycol ethers, glycol esters, pyrrolidones, amides, amines, and carbonate esters.

[0103] 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.

[0104] Examples of halogens include methylene chloride, trichloroethylene, perchloroethylene, HCFC141-b, HCFC-225, 1-bromopropane, chloroform, and orthodichlorobenzene.

[0105] 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.

[0106] 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).

[0107] 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.

[0108] 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.

[0109] Examples of glycols include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and dimethoxytetraethylene glycol.

[0110] Examples of glycol esters include ethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate.

[0111] Examples of glycol ethers include methyl carbitol, ethyl carbitol, butyl carbitol, and methyl triglycol.

[0112] Examples of pyrrolidones include 2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0113] Examples of amides include dimethylformamide, dimethylacetamide, and formamide.

[0114] 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.

[0115] Examples of carbonate esters include diethyl carbonate, dimethyl carbonate, propylene carbonate, and ethylmethyl carbonate.

[0116] Other components in the removal solution include, for example, surfactants, defoamers, preservatives and fungicides, pH adjusters, chelating agents, and rust inhibitors.

[0117] <Drying process> The drying process involves drying the green material to remove any remaining liquid components, such as removal solutions, and is carried out using a drying method. The drying process may remove not only liquid components such as removal solutions contained in the green material, but also organic matter. There are no particular restrictions on the drying method, and it can be appropriately selected depending on the purpose. Examples include well-known dryers and constant temperature and humidity chambers.

[0118] <Degreasing process> The degreasing process involves heating the green material to remove the resin, thereby forming a degreased material, and is carried out using a degreasing method. A "degreased body" is a three-dimensional object obtained by degreasing the above-mentioned resin and other organic components from the green body. The degreasing process uses a degreasing means to ensure that the temperature is above the thermal decomposition temperature of the organic components such as the resin, and is also above the melting point or solidus temperature of the material (metal) constituting the metal particles (for example, AlSi 10 If using Mg particles, 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 (for example, 1 to 10 hours). There are no particular restrictions on the degreasing method, and it can be appropriately selected depending on the purpose. Examples include known sintering furnaces and electric furnaces.

[0119] <Sintering process> The sintering process is a process in which a sintered body is formed by heating the degreased body formed in the degreasing process, and is carried out by a sintering means. A "sintered body" is a three-dimensional object formed by the integration of metal materials that constitute metal particles as inorganic particles, and is formed by sintering a degreased body. The sintering process uses sintering means to raise the solidus temperature of the metal material constituting the metal particles as inorganic particles (for example, AlSi 10 If Mg particles are used, the temperature must be above approximately 570°C and above the liquidus temperature (for example, AlSi 10 If using Mg particles, the degreased body is heated at a temperature of approximately 600°C or lower for a certain period of time (for example, 1 to 10 hours) to integrate the metal material that makes up the metal particles. There are no particular restrictions on the sintering means, and they can be appropriately selected depending on the purpose. For example, known sintering furnaces can be used. The sintering means may be the same as the degreasing means described above. Furthermore, the degreasing step and the sintering step may be performed consecutively.

[0120] <Post-processing steps> The manufacturing method for the molded object preferably includes a post-processing step for the sintered body. There are no particular limitations on the post-processing step, and it can be appropriately selected depending on the purpose. Examples include a surface protection treatment step and a painting step.

[0121] The surface protection treatment process involves forming a protective layer on the three-dimensional molded object (green body) formed by stacking solidified materials in the solidified material formation process. This surface protection treatment process provides the surface of the solidified material with durability, allowing it to be used as is, for example. Specific examples of protective layers include water-resistant layers, weather-resistant layers, light-resistant layers, heat-insulating layers, and glossy layers. Examples of surface protection treatment methods include known surface protection treatment devices, such as spray devices and coating devices.

[0122] The painting process involves applying paint to the three-dimensional molded object (green body) formed by the layering of solidified material created in the solidification process. By performing the painting process, the green body can be colored to the desired color. Painting methods include known painting devices such as sprayers, rollers, brushes, and the like.

[0123] <The process of creating the sculpture> Here, the molding process in the manufacturing method of the present invention will be explained with reference to Figures 3A to 3E. Figures 3A to 3E are schematic diagrams showing an example of the operation of the manufacturing apparatus for molded objects.

[0124] The manufacturing apparatus for molded objects includes a supply tank 21, a molding tank 22, and an excess powder receiving tank 29. The supply tank 21 and the molding tank 22 each have a supply stage 23 and a molding stage 24 that can move up and down. Powder 20 for three-dimensional molding is placed on the molding stage 24 provided in the molding tank 22 to form a powder layer 31 consisting of the powder 20.

[0125] First, we will explain the state in which the first layer of the molding fluid-applied layer 30 is formed on the molding stage 24 of the molding tank 22. When forming the next layer of powder containing inorganic particles on the first layer of the molding fluid-applied layer 30, the supply stage 23 of the supply tank 21 is raised and the molding stage 24 of the molding tank 22 is lowered, as shown in Figure 3A. 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 of μm to 100 μm.

[0126] The flattening roller 12 is positioned so as to create a gap between it and the upper surfaces of the supply tank 21 and the molding tank 22. Therefore, when powder 20 containing inorganic particles is transferred and supplied to the molding tank 22 for flattening, the upper surface of the powder layer containing inorganic particles is higher than the upper surfaces of the supply tank 21 and the molding tank 22. This reliably prevents the flattening roller 12 from contacting 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 will easily form on the surface of the powder layer 31 (see Figure 3D) supplied to the molding tank 22, reducing its flatness. The flattening roller 12 is equipped with a powder removal plate 13, which is a powder removal member that contacts the circumferential surface of the flattening roller 12 to remove powder 20 adhering to the flattening roller 12.

[0127] Next, as shown in Figure 3B, the powder 20 containing inorganic particles, 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 3C, 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 containing inorganic particles 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 3D (return).

[0128] 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.

[0129] Subsequently, as shown in Figure 3E, 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.

[0130] Here, Figure 4 is a front view (side view) of the apparatus showing the overall configuration of the apparatus for manufacturing three-dimensional objects. In the configuration of Figure 4, the nozzle surface state detection means 107 is an optical camera with a light source 108 and is positioned outside the molding tank 101. One of the purposes of this nozzle surface state detection means 107 is to detect liquid or extruded medium 102 that is blocking the nozzle. When using an optical camera, it is necessary to observe it with a certain degree of magnification, which narrows the field of view and makes it impossible to capture the entire extrusion head 110 (all nozzles) at once. Therefore, the entire nozzle is observed in multiple images by having the extrusion head 110 scan over the optical camera. However, it is also possible to capture images with multiple optical cameras without scanning the extrusion head 110. In addition, nozzle surface observation may be performed using means that capture the shape three-dimensionally, such as a laser displacement meter, instead of an optical camera. Furthermore, the light source associated with the optical camera can be a light source with a wavelength that can distinguish between the nozzle surface and the extruded medium, or it can be positioned at an angle. Furthermore, in order to capture the ejected medium adhering to the nozzle surface in three dimensions using an optical camera, methods such as shining light in striped patterns of multiple widths can also be employed.

[0131] Figure 5 illustrates the conditions under which the extrusion medium 102 can adhere to the nozzle surface 116 due to the discharge of droplets 111 of the molding fluid. Using Figure 5, the conditions under which the extruded medium 102 can adhere to the nozzle surface 116 due to the discharge of liquid droplets 111 of the printing medium will be explained. Unlike Figure 4, Figure 5 shows the state in which the discharge head 110 is discharging liquid into the extruded medium 102 in the printing tank. Furthermore, in order to explain the conditions under which the extruded medium 102 can adhere to the nozzle surface 116 due to the discharge of liquid droplets 111 of the printing medium, the discharge head 110 discharging the liquid droplets 111 is shown in an enlarged view.

[0132] To accurately land the print fluid droplets 111 on the extruded medium 102, the extrusion speed of the print fluid droplets should be above a certain speed. This is because the actual velocity vector of the print fluid droplet 111 is determined by the extrusion speed (Vj) plus the carriage movement speed (Vc), causing the droplet 111 to fly diagonally. Therefore, errors in the landing location of the print fluid droplet 111 occur due to fluctuations in the carriage speed 109 and deviations in the extrusion gap (Dt) between the nozzle surface 116 and the extruded medium. The influence of this deviation (error) between Vc and Dt on the landing position decreases as Vj is faster (larger). Also, the larger Vj, the shorter the time until landing, and the less influence the airflow (generated by carriage movement, etc.) has on the landing position. For the same reason, the extrusion gap (Dt) should also be kept below a certain level. Furthermore, in order to improve the productivity (speed) of layering three-dimensional objects, we want to increase the size (Mj) of the liquid modeling fluid droplets 111 above a certain level. Also, the larger the Mj, the less influence the airflow (airflow generated by carriage movement, etc.) has on the impact point. In addition, in order to improve the resolution (surface quality and precision) of the printed object, we want to reduce the size (particle size) of the powder above a certain level.

[0133] Under these conditions, powder tends to adhere to the nozzle surface 116, which can lead to poor extrusion of the molding fluid and a decrease in reliability. At this time, cleaning the nozzle surface 116 is necessary, but if the nozzle surface 116 with powder attached is wiped with a wiper blade or the like, the powder will enter the nozzle and clog it. In contrast, by performing cleaning maintenance by washing the nozzle surface 116 with a cleaning solution to wash away the attached powder, the nozzle surface 116 can be cleaned without the powder entering the nozzle.

[0134] Examples of cleaning and maintenance are shown in Figures 6 and 7. Figure 6 illustrates an embodiment in which the nozzle surface is immersed in a cleaning solution. Figure 6 shows an example of cleaning the nozzle surface 116, where dirt is removed by immersing the nozzle surface 116 in a cleaning tank 113 filled with cleaning solution 112. In Figure 6, the cleaning tank 113, filled with cleaning solution, rises toward the nozzle surface 116, thereby immersing the nozzle surface 116 in the cleaning solution 112. This embodiment is just one example, and the nozzle surface 116 may be lowered into the washing tank 113. By storing the cleaning solution 112 in the cleaning tank 113, a large amount of cleaning solution is used, and the cleaning solution needs to be replaced periodically. The cleaning tank 113 may also be equipped with a device that applies external force, such as ultrasound, to enhance the cleaning effect. After cleaning, wiper cleaning may be performed to create a meniscus for the 3D printing fluid.

[0135] Figure 7 illustrates an embodiment in which the nozzle surface is cleaned by a cleaning fluid ejection mechanism. Figure 7 shows an example of cleaning the head surface 116, where cleaning solution 112 is sprayed towards the nozzle surface 116 to remove dirt. In Figure 7, the nozzle surface 116 is cleaned by spraying cleaning fluid 112 using the cleaning fluid ejection mechanism 114 mounted on the stage 115. The stage 115 moves to apply the cleaning solution 112 to the entire surface of the nozzle 116. This embodiment is just one example, and may also be a cleaning fluid ejection mechanism that covers the entire nozzle surface. The cleaning fluid ejection mechanism 114 may be based on a hydrostatic head difference, or a pump may be used. After cleaning, wiper cleaning may be performed to create a meniscus for the 3D printing fluid. Because the nozzle surface 116 is treated with a water-repellent coating, the cleaning solution 112 easily forms droplets. [Examples]

[0136] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments.

[0137] (Examples 1-19 and Comparative Examples 1-6) <Preparation of molding fluid> The materials shown in Tables 1 to 5 were mixed, and the mixture was stirred with a magnetic stirrer for 2 hours while heating at 80°C. After 2 hours of stirring, the heating was stopped and stirring continued until the mixture reached room temperature (25°C) to prepare the molding solutions for Examples 1 to 19 and Comparative Examples 1 to 6. Note that the units of the numerical values ​​indicating the content of each material in Tables 1 to 5 are in mass percent. Also, each content represents the total amount, not the solid content.

[0138] Next, the physical properties of each resulting molding fluid were measured as follows. The results are shown in Tables 1 to 5.

[0139] <Viscosity η of the molding fluid> The viscosity η of each molding fluid at 25°C was measured at 25°C using a cone-plate viscometer VISCOMETER TV-25 manufactured by Toki Sangyo Co., Ltd.

[0140] <Surface tension γ of the molding fluid> The surface tension γ of each molding medium at 23°C was measured at 23°C using the Wilhelmy method (suspension plate method) with an automatic surface tension meter DY-300 manufactured by Kyowa Interface Science Co., Ltd.

[0141] <Contact angle θn (plate method)> The contact angle θn between each molding fluid and the metal plate was measured at 25°C using the droplet method with a contact angle meter DMs-301 manufactured by Kyowa Interface Science Co., Ltd. For the metal plate, we used the aluminum free plate A 6061 LNQ-25-10-5 manufactured by Misumi Corporation. The molding fluid was filled into a syringe, and approximately 2.0 microliters of the fluid was dropped onto the metal plate using the automatic droplet formation function. The contact angle θn (plate method) was defined as the value obtained from the droplet shape after 20 seconds using the θ / 2 method.

[0142] <Powder contact angle θ> The powder contact angle θ between the molding fluid and inorganic particles was measured using an automatic surface tension meter DY-500 manufactured by Kyowa Interface Science Co., Ltd. As the powder containing inorganic particles, aluminum powder (ALSI3-30B, manufactured by Toyo Aluminum Co., Ltd.) was used. 5g of powder containing inorganic particles was packed into a column, and the porosity was adjusted to 35.6% to 35.8% using a powder compressor. Acetone was used as a liquid with sufficient wettability for powders containing inorganic particles, and the capillary radius was determined assuming a powder contact angle θ of acetone to 0 degrees. "Capillary radius" refers to the radius of the gap between inorganic particles when metal particles are packed into a column, and was measured using an automatic surface tension meter DY-500 manufactured by Kyowa Interface Science Co., Ltd. Next, using an automatic surface tension meter DY-500 manufactured by Kyowa Interface Science Co., Ltd., the penetration rate of the molding fluid into the powder containing inorganic particles was measured in the range of 150 to 180 seconds from the start of measurement. The penetration rate of the molding fluid into the powder containing inorganic particles is expressed by the Lucas-Washburn equation in formula (1) below.

[0143]

number

[0144] <γcosθ / η> The penetration rate was calculated as γcosθ / η (m / s). θ represents the powder contact angle (°) between the molding fluid and inorganic particles, γ represents the surface tension (mN / m) of the molding fluid at 23°C, and η represents the viscosity (mPa·s) of the molding fluid at 25°C.

[0145] <Method of manufacturing molded objects> Each molding fluid and aluminum powder (ALSI3-30B, manufactured by Toyo Aluminum Co., Ltd.) were used as inorganic particles, and additive manufacturing was performed as follows to obtain each molded object. (1) First, using the manufacturing apparatus for molded objects shown in Figures 3A to 3E, aluminum powder was transferred from the supply tank 21 to the molding tank 22, and a thin layer of aluminum powder with an average thickness of 84 μm was formed on the molding stage 24. (2) Next, each type of printing fluid was applied to the surface of the thin layer of aluminum powder formed from the nozzle of an inkjet ejection head (RICOH MH5421 industrial inkjet manufactured by Ricoh Co., Ltd.) in the manufacturing apparatus for the printed object. The amount of printing fluid was 140 picoliters per layer, calculated at a resolution of 300 dpi. The printing fluid ejection areas were a rectangle of 54 mm × 10 mm and a rectangle of 28 mm × 10 mm. (3) Next, the operations described in (1) and (2) above were repeated until the 54mm x 10mm rectangle had a total average thickness of 2mm and the 28mm x 10mm rectangle had a total average thickness of 3mm, thereby sequentially laminating thin layers of aluminum powder to form a laminate (lamination process). (4) Next, the laminate was heated and dried under vacuum to obtain a solidified product (heating step). (5) Next, excess powder was removed from the solidified material by air blowing (excess powder removal process). Based on the above, the 54mm x 10mm rectangular object was used to evaluate dimensional accuracy, and the 28mm x 10mm rectangular object was used to evaluate bending strength.

[0146] <Evaluation of dimensional accuracy> The dimensions of each 54mm x 10mm rectangular object were measured with calipers, and the dimensional accuracy was evaluated based on the following evaluation criteria. [Evaluation Criteria] ◎: The error between the dimensions of the modeling data and the actual dimensions is 0.5 mm or less, and the outline is clearly defined. ○: The error in dimensions from the modeling data is 0.5 mm or less, but the outline is slightly blurred, or there are areas of seepage that can be easily removed during the excess powder removal process (it is marked with ○ here because it can be removed). ×: Errors from the 3D printing data dimensions are greater than 0.5 mm, or seepage occurs that cannot be easily removed during the excess powder removal process.

[0147] <Evaluation of bending strength> The bending strength of each 28mm x 10mm rectangular object was measured using a Shimadzu Autograph AG-I universal testing machine. Specifically, using a 1kN load cell and a three-point bending jig, the stress was plotted against the strain when each object was displaced at a load point speed of 1mm / min with a support distance of 24mm. The stress at the fracture point was defined as the bending strength (MPa), and it was evaluated based on the following evaluation criteria. [Evaluation Criteria] ◎: Bending strength of 5 MPa or more ○: Bending strength of 3 MPa or more and less than 5 MPa ×: Bending strength less than 3 MPa

[0148] <Evaluation of discharge capacity> The number of nozzles that failed per 100 nozzles was counted when the nozzles of the inkjet ejection head (RICOH MH5421 industrial inkjet manufactured by Ricoh Co., Ltd.) in the manufacturing equipment for the molded objects using each molding fluid were subjected to 100 repetitions of 3 seconds of ejection followed by a 10-second pause under ejection conditions of 2kHz and 24kHz, and the ejection performance was evaluated based on the following evaluation criteria. [Evaluation Criteria] ◎: Discharge at 2kHz and 24kHz with 2 or fewer nozzles. ○: At 2kHz discharge, the number of detachable nozzles is 2 or less, but at 24kHz discharge, the number of detachable nozzles is greater than 2. ×: At 2kHz and 24kHz discharge, the number of nozzles is greater than 2.

[0149] [Table 1]

[0150] [Table 2]

[0151] [Table 3]

[0152] [Table 4]

[0153] [Table 5]

[0154] Tables 1 to 5 detail the various materials as follows: -resin- • Resin A: JMR-10LL, manufactured by Nippon Vivaceum Co., Ltd., partially saponified polyvinyl acetate resin • Resin B: S-Rec BL-10, manufactured by Sekisui Chemical Co., Ltd., polyvinyl butyral resin

[0155] -Organic Solvents- • triglyme: manufactured by Sankyo Chemical Co., Ltd., triethylene glycol dimethyl ether • DESU: Diethyl succinate, manufactured by Tokyo Chemical Industry Co., Ltd. • TG / Tac: A mixture of triglime manufactured by Sankyo Chemical Co., Ltd. and triacetin manufactured by Tokyo Chemical Industry Co., Ltd. in a mass ratio of 60:40.

[0156] - Surfactants - • S-693, manufactured by AGC Seika Chemical Co., Ltd., Surflon S-693, fluorine surfactant • BYK333, manufactured by Big Chemie Japan Co., Ltd., BYK-333, silicone surfactant • BYK378, manufactured by Big Chemie Japan Co., Ltd., BYK-378, silicone surfactant • S-611, manufactured by AGC Seika Chemical Co., Ltd., Surflon S-611, fluorine surfactant • S-647, manufactured by AGC Seika Chemical Co., Ltd., Surflon S-647, fluorine surfactant SAG020, manufactured by Nisshin Chemical Industry Co., Ltd., Silface SAG020, silicone surfactant • KF353, manufactured by Shin-Etsu Chemical Co., Ltd., fluorine surfactant

[0157] Table 1 shows that in Examples 1-5 and Comparative Example 1, the molding solution was prepared by varying the resin content. It was found that when the resin content decreases, the viscosity of the molding fluid at 25°C decreases, the penetration rate increases ("γcosθ / η" becomes larger), and the bending strength of the molded object decreases. Furthermore, it was found that dimensional accuracy is good when "γcosθ / η" is 1.5 or less, and even better when "γcosθ / η" is 1 or less. Furthermore, it was found that when the viscosity of the printing fluid at 25 is 6 mPa·s or higher, the bending strength of the printed object is good, and when the viscosity of the printing fluid at 25 is 12 mPa·s or higher, the bending strength of the printed object is even better.

[0158] Table 2 shows that in Comparative Example 2 and Examples 6-11, the molding solution was prepared by varying the surfactant content. It was found that when the molding fluid does not contain a surfactant, the powder contact angle θ becomes small, resulting in poor dimensional accuracy of the molded object. When the molding fluid contains a surfactant, the powder contact angle θ increases. A higher surfactant content tends to result in a larger powder contact angle θ, and it was found that a powder contact angle θ of 50° or more indicates good dimensional accuracy of the molded object. It was also found that dimensional accuracy is even better when "γcosθ / η" is 1.0 or less. Furthermore, it was found that when the surface tension of the printing medium at 23°C is 22 mN / m or higher, the extrusion performance of the printing medium is excellent.

[0159] Tables 3 and 5 show that in Comparative Examples 3-6 and Examples 15-19, the molding solution was prepared by changing the type of surfactant. The surfactants in Comparative Examples 3-6 ("BYK333", "BYK378", "S-611", and "S-647") all had a powder contact angle θ of less than 50°, indicating poor dimensional accuracy. The surfactants used in Examples 15-19 ("SAG020" and "KF353") were found to exhibit good dimensional accuracy, flexural strength, and discharge properties.

[0160] Table 4 shows that in Examples 12-13, the molding fluid was prepared by changing the type of organic solvent. In all of Examples 12-13, the organic solvents ("DESU" and "TG / TAc") yielded good results in terms of dimensional accuracy, bending strength, and extrusion performance. Furthermore, in Example 14 of Table 4, the molding fluid was prepared by changing the type of resin. The resin used in Example 14 (Resin B) was found to have good dimensional accuracy, bending strength, and extrusion properties.

[0161] <Amount of molding fluid to be applied> In Example 2, the amount of printing fluid applied was varied by adjusting the volume of printing fluid per drop per nozzle, the resolution, or the number of drops per voxel, and rectangular parallelepiped objects No. 1 to 14, measuring 30 mm × 10 mm × 3 mm, were fabricated in the same manner as in Examples 1 to 19 and Comparative Examples 1 to 6, as shown in Table 6 below. Next, for the obtained molded objects No. 1 to 14, the presence or absence of localized seepage was evaluated, the bending strength was measured, and an overall evaluation was performed as follows. The results are shown in Table 6 and Figure 2.

[0162] <Evaluation of localized seepage> Each 30mm x 10mm x 3mm rectangular object was visually inspected for the presence or absence of what is referred to as localized seepage, and evaluated according to the following criteria. Characteristics of localized seepage include being larger than the intended dimensions and occurring on the sides. This characteristic is caused by the build fluid coating being pushed when the powder is transported to the top of the build tank by the flattening roller, causing the build fluid to spread across the powder surface. Localized seepage can be easily removed by the impact when removing the surrounding powder from the object, and therefore does not pose a problem for the final product. [Evaluation Criteria] ○: No localized bleeding. ×: Localized bleeding present

[0163] <Bending strength> The bending strength of each rectangular parallelepiped object measuring 30mm x 10mm x 3mm was measured using a Shimadzu Corporation Autograph AG-I universal testing machine. Specifically, using a 1kN load cell and a three-point bending jig, the stress was plotted against the strain when each object was displaced at a load point speed of 1mm / min with a support distance of 24mm. The stress at the fracture point was defined as the bending strength (MPa), and it was evaluated based on the following evaluation criteria. [Evaluation Criteria] ○: Bending strength of 3 MPa or more △: Bending strength between 0.5 MPa and less than 3 MPa ×: Bending strength is less than 0.5 MPa

[0164] <Overall Rating> Based on the evaluation results of localized seepage and bending strength, an overall evaluation was conducted according to the following criteria. [Evaluation Criteria] ○: When both localized seepage and bending strength are evaluated as ○. △: When either the evaluation of localized seepage or bending strength is △. ×: When either the evaluation of localized seepage or flexural strength is ×, or both are ×.

[0165] [Table 6]

[0166] From the results in Table 6 and Figure 2, the amount of molding fluid to be applied is 0.033 μl / mm². 3 More than 0.33μl / mm 3 In the area shown in Figure 2A below, it was found that even when the build fluid-coated layer is pressed when the powder is transported to the top of the build tank by the flattening roller, there is enough space on both sides of each droplet for wetting to spread, and localized seepage of the build fluid does not occur. Furthermore, the amount of build fluid applied is 0.033 μl / mm². 3 It was found that the structure would collapse under the following conditions. Furthermore, the amount of molding fluid to be applied is 0.148 μl / mm². 3 More than 0.33μl / mm 3In the range B shown in Figure 2, it was found that increasing the amount of resin supporting the molded object resulted in a bending strength of 3 MPa or more. A bending strength of 3 MPa or more means that a rectangular prism of 30 mm × 10 mm × 3 mm will not break even if dropped from a height of 100 mm.

[0167] <Evaluation of cleaning and maintenance> Regarding cleaning maintenance, the nozzle may suck in the cleaning solution while it is being applied to the nozzle surface, causing the printing fluid inside the nozzle to mix with the cleaning solution. Here, we will refer to this mixing of the printing fluid and the cleaning solution as color mixing. For cleaning maintenance, we used the nozzle surface cleaning solution ejection mechanism shown in Figure 9, and triethylene glycol dimethyl ether was used as the cleaning solution. After extruding the molding fluid from Example 2 onto a transparent sheet (OHP sheet VF-1420N, manufactured by Kokuyo Co., Ltd.), aluminum powder (ALSI3-30B, manufactured by Toyo Aluminum Co., Ltd.) was sprinkled on it to make the extruded areas visible, forming patterns as shown in Figures 8A to 8C. In this way, the aluminum powder adheres to the areas where the molding fluid landed, forming a pattern. As shown in Figure 8A, the ejected line is clearly visible under normal conditions, whereas as shown in Figures 8B and 8C, the ejected line is blurred after cleaning and maintenance. This indicates that the 3D printing fluid landed at a position different from the target, or that it landed as multiple droplets rather than a single droplet. This is thought to be because the cleaning and maintenance caused the 3D printing fluid inside the nozzle to mix with the cleaning solution, altering the properties of the 3D printing fluid and making the ejection unstable. Such alterations in 3D printing fluid properties or unstable ejection negatively affect the quality of the printed object, including its strength and dimensional accuracy. Therefore, the objective is to prevent the molding fluid inside the nozzle from mixing with the cleaning fluid by controlling the pressure applied to the nozzle during cleaning maintenance (which we will refer to here as "control pressure"). Normally, in order to eject the molten material from the extrusion head, it is necessary to apply and maintain an appropriate negative pressure to the molten material inside the head. Typically, the applied negative pressure is around -25 mmAq to -10 mmAq. In this invention, the pressure (control pressure) applied to the molten material inside the extrusion head is controlled.

[0168] Next, using a cleaning solution (triethylene glycol dimethyl ether) and the nozzle surface cleaning solution ejection mechanism shown in Figure 9, cleaning maintenance was performed at a moving stage speed of 10 mm / s while varying the control pressure as shown in Table 7. After that, the molding fluid from Example 2 was dispensed onto a transparent sheet (OHP sheet VF-1420N, manufactured by Kokuyo Co., Ltd.), and aluminum powder (Toyo Aluminum Co., Ltd., ALSI3-30B) was sprinkled on it. Patterns were printed as shown in Figures 8A to 8C, and the degree of blurring (color mixing) of the ejected lines was determined according to the following criteria. The results are shown in Table 7. [Evaluation Criteria] As shown in Figure 8B, if the discharge lines are blurred (color mixing state: △), as shown in Figure 8C, if the discharge lines are quite blurred (color mixing state: ×), and as shown in Figure 8A, if there is no blurring of the discharge lines (no color mixing state: ○), it was considered as such.

[0169] [Table 7] The results in Table 7 show that while cleaning maintenance performed under normal control pressure levels of -25 mmAq to -10 mmAq resulted in color mixing, color mixing did not occur when the control pressure was set to 0 mmAq or higher. In other words, by creating a positive pressure on the printing fluid inside the head during cleaning maintenance, the cleaning fluid is not drawn into the nozzle, thus preventing color mixing. Furthermore, it was found that color mixing did not occur even when no droplets of printing fluid came out of the nozzle at control pressure levels of 0 mmAq to 25 mmAq. When the control pressure exceeds 25 mmAq, droplets of the printing fluid are released from the nozzle (purging state), so droplets of the printing fluid remain on the nozzle surface after cleaning and maintenance is complete. Therefore, it is necessary to remove the remaining droplets of printing fluid by wiping or other maintenance. If the printing fluid is prone to hardening, wiping may leave some of the printing fluid on the nozzle surface, potentially causing it to harden. On the other hand, when the control pressure is set to 0 mmAq to 25 mmAq, the printing fluid is not purged, so only the cleaning fluid remains on the nozzle surface after cleaning maintenance is complete. Therefore, the possibility of printing fluid adhering to the nozzle surface is lower than when the control pressure is set to more than 25 mmAq. Alternatively, as will be described later, depending on the cleaning maintenance conditions, it is possible to prevent any cleaning fluid from remaining on the nozzle surface, in which case wiping maintenance is unnecessary, and deterioration of the water-repellent film on the nozzle surface due to wiping maintenance can be prevented.

[0170] <Evaluation of powder removal performance, residual cleaning solution, and color mixing> The nozzle surface, which had powder attached, was cleaned and maintained. The condition of the nozzle surface before and after cleaning and maintenance was photographed with a camera, and the powder removal efficiency, residual cleaning solution, and color mixing were evaluated by comparing the images. For cleaning and maintenance, the nozzle surface cleaning solution ejection mechanism shown in Figure 9 was used, and the movement speed of the cleaning solution ejection mechanism was changed as shown in Table 8, and the control pressure was changed to -25 mmaq and +25 mmaq for evaluation. For cleaning and maintenance, cleaning solution (triethylene glycol dimethyl ether), the molding solution from Example 2, and aluminum powder (Toyo Aluminum Co., Ltd., ALSI3-30B) were used. To evaluate the color mixing state, after cleaning and maintenance, the molding solution from Example 2 was ejected onto a transparent sheet (OHP sheet VF-1420N, Kokuyo Co., Ltd.), and then aluminum powder (Toyo Aluminum Co., Ltd., ALSI3-30B) was sprinkled on it. Patterns were printed as shown in Figures 8A to 8C, and the degree of blurring of the ejection lines (color mixing) was determined according to the following criteria.

[0171] The results are shown in Table 8. Figure 10A is a photograph showing the condition of the cleaned nozzle surface. Figure 10B is a photograph showing the condition of the nozzle surface with powder adhering to it. Figure 10C is a photograph showing the condition of the nozzle surface after cleaning and maintenance at a travel speed of 10 mm / s. Figure 10D is a photograph showing the condition of the nozzle surface after cleaning and maintenance at a travel speed of 30 mm / s. Figure 10E is a photograph showing the condition of the nozzle surface after cleaning and maintenance at a travel speed of 50 mm / s.

[0172] [Evaluation Criteria] (i) For powder removal performance, a score of ○ was given if 90% or more of the powder adhering to the nozzle surface was removed, and a score of × was given if less than 90% of the powder was removed. (ii) Regarding the remaining cleaning solution, a ○ was given if no cleaning solution remained on the nozzle surface after cleaning maintenance, a △ was given if a small amount of cleaning solution remained, and a × was given if a considerable amount of cleaning solution remained. (iii) When performing cleaning maintenance, the control pressure was kept at the same level as normal (-25 mmAq), and the results of the color mixing judgment are shown in Figures 8A to 8C. If color mixing occurred as in Figure 8B, it was evaluated as △; if color mixing occurred as in Figure 8C, it was evaluated as ×; and if no color mixing occurred as in Figure 8A, it was evaluated as ○. (iv) When performing cleaning maintenance, the control pressure was controlled to +25 mmAq, and color mixing was determined in the same manner as in (iii).

[0173] [Table 8] The results in Table 8 show that a travel speed of 20 mm / s or less is necessary to remove powder adhering to the nozzle surface. Regarding color mixing, the slower the travel speed, the longer the cleaning solution is in contact with the nozzle surface, thus increasing the risk of color mixing. In fact, when cleaning maintenance was performed at a control pressure of -25 mmAq, the degree of color mixing tended to worsen as the travel speed decreased. Conversely, it was confirmed that color mixing was suppressed when cleaning maintenance was performed at a control pressure of +25 mmAq. However, at a travel speed of 5 mm / s, some color mixing remained even with a control pressure of +25 mmAq. Therefore, in order to remove powder adhering to the nozzle surface and prevent color mixing during cleaning maintenance, it is desirable that the movement speed of the cleaning liquid ejection mechanism be 10 mm / s to 20 mm / s. In this experiment, the cleaning liquid ejection mechanism was found to have a contact distance of 20 mm between the cleaning liquid and the nozzle surface (see Figure 9), meaning that it was sufficient for the cleaning liquid to be applied to a single point on the nozzle surface for 1 to 2 seconds. Furthermore, an evaluation of whether droplets of the molding fluid or cleaning fluid remained on the nozzle surface after cleaning maintenance revealed that no droplets remained at a travel speed of 10 mm / s or less. If droplets remain on the nozzle surface, they need to be removed by wiping maintenance, but this becomes unnecessary at a travel speed of 10 mm / s. Eliminating the need for wiping maintenance reduces the time required for wiping maintenance and prevents deterioration of the water-repellent film caused by wiping maintenance. Furthermore, it was found that even if some color mixing remains, as in the case of a travel speed of 5 mm / s, the color mixing can be eliminated (the blurring of the extrusion line disappears) by draining the printing fluid from the nozzle with an empty extrusion after cleaning and maintenance.

[0174] Examples of the present invention are as follows: <1> A molding fluid applied to a layer of powder containing inorganic particles, The molding liquid is characterized in that the powder contact angle θ with the inorganic particles is 50° or more, and the following equation, γcosθ / η ≤ 1.5 (m / s), is satisfied. Provided that in the above formula, θ represents the powder contact angle (°) of the modeling liquid with respect to inorganic particles, γ represents the surface tension of the modeling liquid at 23°C (mN / m), and η represents the viscosity of the modeling liquid at 25°C (mPa·s). <2> A modeling liquid applied to a layer of powder containing inorganic particles, wherein the powder contact angle θ with respect to aluminum particles is 50° or more, and satisfies the following formula: γcosθ / η≦1.5 (m / s), characterized in that it is a modeling liquid. Provided that in the above formula, θ represents the powder contact angle (°) of the modeling liquid with respect to aluminum particles, γ represents the surface tension of the modeling liquid at 23°C (mN / m), and η represents the viscosity of the modeling liquid at 25°C (mPa·s). <3> The modeling liquid according to any one of <1> to <2>, wherein the powder contact angle θ is 50° or more and 80° or less. <4> The modeling liquid according to any one of <1> to <3>, which satisfies the following formula: γcosθ / η≦1 (m / s). <5> The modeling liquid according to any one of <1> to <4>, wherein the viscosity η at 25°C is 6 mPa·s or more. <6> The modeling liquid according to any one of <1> to <5>, wherein the viscosity η at 25°C is 12 mPa·s or more. <7> The modeling liquid according to any one of <1> to <6>, wherein the surface tension γ at 23°C is 22 mN / m or more. <8> The amount of the modeling liquid to be applied is 0.033 μl / mm 3 or more and 0.33 μl / mm 3 or less, which is the modeling liquid according to any one of <1> to <7>. <9> The amount of the modeling liquid to be applied is 0.148 μl / mm 3 or more and 0.33 μl / mm 3 or less, which is the modeling liquid according to <8>. <10> The modeling liquid according to any one of <1> to <9>, wherein the resolution is 600 dpi or more. <11> When applying a cleaning solution to the nozzle surface on which the nozzle for discharging the molding fluid is provided, the pressure applied to the nozzle is controlled to be between 0 mmaq and 25 mmaq. <1> from <10> It is a molding fluid as described in one of the following. <12> The time for applying the cleaning solution to the nozzle surface is 1 second or more and 2 seconds or less. <11> This is the molding fluid described in [the relevant section]. <13> A molding fluid applied to a layer of powder containing inorganic particles, This molding fluid is characterized by containing a resin having a structural unit represented by the following structural formula (1), an organic solvent, and a surfactant. [ka] <14> The surfactant is at least one of a fluorine surfactant and a silicone surfactant. <13> This is the molding fluid described in [the relevant section]. <15> The content of the surfactant is 0.001% by mass or more and 1% by mass or less, <13> from <14> It is a molding fluid as described in one of the following. <16> The resin having the structural unit represented by the structural formula (1) includes at least one selected from polyvinyl acetate resin, partially saponified polyvinyl acetate resin, and polyvinyl butyral resin. <13> from <15> It is a molding fluid as described in one of the following. <17> The resin having the structural unit represented by the structural formula (1) is contained in an amount of 5% by mass or more and 20% by mass or less. <13> from <16> It is a molding fluid as described in one of the following. <18> The organic solvent has at least one structure selected from an alkoxy group, an ether bond, and an ester bond. <13> from <17> It is a molding fluid as described in one of the following. <19> The organic solvent comprises an alkylene glycol dialkyl ether compound. <18> This is the molding fluid described in [the relevant section]. <20> The above, which contains substantially no water. <13> from <19> It is a molding fluid as described in one of the following. <21> The powder contact angle θ with the inorganic particles is 50° or more, and the following equation, γcosθ / η ≤ 1.5 (m / s), is satisfied. <13> from <20> It is a molding fluid as described in one of the following. However, in the above formula, θ represents the powder contact angle (°) between the molding fluid and inorganic particles, γ represents the surface tension (mN / m) of the molding fluid at 23°C, and η represents the viscosity (mPa·s) of the molding fluid at 25°C. <22> The aforementioned <1> from <21> A molding kit characterized by comprising a molding liquid described in any of the above and inorganic particles. <23> The inorganic particles are metal particles, and the metal particles include at least one selected from aluminum, zinc, magnesium, and alloys thereof. <22> This is a modeling kit as described above. <24> The inorganic particles are not coated on the surface with resin, <20> from <21> This is a modeling kit as described in one of the following. <25> A powder layer formation step in which a layer of powder containing inorganic particles is formed, The powder layer <1> from <21> A molding fluid application step which involves applying a molding fluid as described in any of the following, A lamination process in which a laminate is formed by sequentially repeating the powder layer formation process and the molding liquid application process, This is a method for manufacturing molded objects, characterized by including [a specific element]. <26> The method for manufacturing a molded object according to claim 23, wherein the molding liquid application step involves ejecting the molding liquid onto the powder layer using an inkjet method. <27> A heating step in which the laminate is heated to form a solidified material, A step to remove excess powder, which is the powder adhering to the solidified material, in order to obtain a green material, The following further includes <25> from <26> This is a method for manufacturing a molded object as described in any of the above. <28> A degreasing step in which the resin is removed by heating the green body to form a degreased body, A sintering step in which a sintered body is formed by heating the degreased body, The following further includes <27> This is a method for manufacturing the molded object described above.

[0175] According to the modeling liquid according to any one of <1> to <21>, the modeling kit according to any one of <22> to <24>, and the method for producing a modeled article according to any one of <25> to <28>, various problems in the related art can be solved and the object of the present invention can be achieved. Description of Reference Numerals

[0176] 1 Target dimension 2 Bleeding into non-modeled area 3 Local bleeding 10 Droplet of modeling liquid 12 Flattening roller 13 Powder removing plate 20 Powder containing inorganic particles 21 Supply tank 22 Modeling tank 23 Supply stage 24 Modeling stage 29 Excess powder receiving tank 30 Modeling liquid applied layer 31 Powder layer 52 Head of liquid discharge unit Prior Art Documents Patent Documents

[0177] Patent Document 1 Japanese Unexamined Patent Application Publication No. 2016-107465 Patent Document 2 Japanese Unexamined Patent Application Publication No. 2018-154074

Claims

1. A molding fluid applied to a layer of powder containing inorganic particles, It contains organic solvents, A molding liquid characterized in that the powder contact angle θ with the aforementioned powder is 50° or more, and the following equation, γcosθ / η ≤ 1.5 (m / s), is satisfied. However, in the above formula, θ is the powder contact angle (°) of the molding liquid with the powder, calculated based on the penetration rate in the range from 150 seconds to 180 seconds after the start of penetration when the molding liquid is permeated into the column packed with the powder, γ is the surface tension (mN / m) of the molding liquid at 23°C, and η is the viscosity (mPa·s) of the molding liquid at 25°C.

2. A molding fluid applied to a layer of powder containing aluminum particles, It contains resin, organic solvent, and surfactant, A molding fluid characterized in that the powder contact angle θ with aluminum particles is 50° or more, and the following equation, γcosθ / η ≤ 1.5 (m / s), is satisfied. However, in the above formula, θ is the powder contact angle (°) between the molding liquid and the aluminum particles, calculated based on the penetration rate in the range from 150 seconds to 180 seconds after the start of penetration when the molding liquid is permeated into the column packed with the powder, γ is the surface tension (mN / m) of the molding liquid at 23°C, and η is the viscosity (mPa·s) of the molding liquid at 25°C.

3. The molding liquid according to any one of claims 1 to 2, wherein the powder contact angle θ is 50° or more and 80° or less.

4. A molding liquid according to any one of claims 1 to 3, satisfying the following equation, γcosθ / η ≤ 1 (m / s).

5. A molding liquid according to any one of claims 1 to 4, wherein the viscosity η at 25°C is 6 mPa·s or more.

6. A molding liquid according to any one of claims 1 to 5, comprising a resin having a structural unit represented by the following structural formula (1), an organic solvent, and a surfactant. 【Chemistry 1】

7. The molding liquid contains a surfactant, The molding liquid according to any one of claims 1 to 6, wherein the surfactant is at least one of a fluorine surfactant and a silicone surfactant.

8. The molding liquid according to claim 7, wherein the content of the surfactant is 0.001% by mass or more and 1% by mass or less.

9. The molding liquid according to claim 6, wherein the resin having the structural unit represented by the structural formula (1) comprises at least one selected from polyvinyl acetate resin, partially saponified polyvinyl acetate resin, and polyvinyl butyral resin.

10. The molding liquid according to claim 6, wherein the content of the resin having the structural unit represented by the structural formula (1) is 5% by mass or more and 20% by mass or less.

11. The molding liquid according to any one of claims 1 to 10, wherein the organic solvent has at least one structure selected from an alkoxy group, an ether bond, and an ester bond.

12. The molding liquid according to claim 11, wherein the organic solvent comprises an alkylene glycol dialkyl ether compound.

13. A molding liquid according to any one of claims 1 to 12, which is substantially free of water.

14. A molding kit characterized by comprising a molding liquid according to any one of claims 1 to 13 and a powder containing inorganic particles.

15. The molding kit according to claim 14, wherein the inorganic particles are metal particles, and the metal particles include at least one selected from aluminum, zinc, magnesium, and alloys thereof.

16. A powder layer formation step in which a layer of powder containing inorganic particles is formed, A molding liquid application step of applying the molding liquid according to any one of claims 1 to 13 to the powder layer, A lamination process in which a laminate is formed by sequentially repeating the powder layer formation process and the molding liquid application process, A method for manufacturing a molded object, characterized by including the following:

17. The method for manufacturing a molded object according to claim 16, wherein the molding liquid application step involves dispensing the molding liquid onto the powder layer using an inkjet method.

18. In the aforementioned molding fluid application step, the amount of molding fluid applied per volume of the molding section voxels is 0.033 μl / mm². ３ 0.33 μl / mm or more ３ The method for manufacturing a molded object according to claim 17 is as follows:

19. The molding liquid according to claim 17, wherein the resolution of the droplets of the molding liquid in the molding liquid application step is 600 dpi or higher.

20. A heating step in which the laminate is heated to form a solidified material, A step to remove excess powder, which is the powder adhering to the solidified material, in order to obtain a green material, A method for manufacturing a molded object according to any one of claims 16 to 19, further comprising:

21. The aforementioned green body contains resin, A degreasing step in which the resin is removed by heating the green body to form a degreased body, A sintering step in which a sintered body is formed by heating the degreased body, A method for manufacturing a molded object according to claim 20, further comprising:

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