Manufacturing method for molded objects

Abstract

To provide a sinter inhibition liquid capable of sufficiently reducing relative sinter density in a sinter inhibition region, when a sinter inhibition region is formed by imparting a sinter inhibition liquid to a layer of powder containing sinterable particles, and having high storage stability.SOLUTION: A manufacturing method of a molding comprising: a powder layer forming step of forming a powder layer 101 containing sinterable particles; a molding liquid application step of applying a molding liquid to the powder layer to form a molding region 104; a sintering inhibiting liquid application step of applying a sintering inhibiting liquid to the layer of powder to form a sintering inhibiting region 103 where sintering of the particles is inhibited; and a lamination step for forming a laminate by repeating these steps sequentially, the molding region and the sinter inhibition region are adjacent, the sinter inhibition liquid contains a first resin, the sinter inhibition region contains a first resin or a second resin derived from the first resin, an estimated residue amount calculated by a predetermined method is 800 ppm or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

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

[0003] However, deformation such as warping or distortion may occur in the sintered body obtained through the sintering process. As a method to suppress this deformation, a method using a support material that has a shape along the sintering precursor and supports the sintering precursor has been considered. However, if the sintering precursor is sintered while in contact with the support material, the sintered body and the support material may bond together, making it difficult to remove the support material.

[0004] Patent Document 1 discloses a technique for improving the peelability between a sintered body and a support material by forming an interface containing powder of a material that inhibits sintering, such as ceramics, between a sintering precursor and a support material, and then sintering the resulting material. [Overview of the project] [Problems that the invention aims to solve]

[0005] However, when a sintering inhibition region is formed by applying a sintering inhibition liquid to a powder layer containing sinterable particles, there is a challenge in providing a method for manufacturing a molded object using a sintering inhibition liquid that can sufficiently reduce the relative sintering density in the sintered product of the sintering inhibition region and also has high storage stability. [Means for solving the problem]

[0006] The present invention provides a method for manufacturing a molded object, comprising: a powder layer formation step of forming a layer of powder containing sinterable particles; a molding fluid application step of applying a molding fluid to the powder layer to form a molded region; and a sintering inhibitor application step of applying a sintering inhibitor to the powder layer to form a sintering inhibitor region in which the sintering of the particles is inhibited, wherein the method for manufacturing a molded object includes a lamination step of sequentially repeating the powder layer formation step, the molding fluid application step, and the sintering inhibitor application step to form a laminate, wherein the molded region and the sintering inhibitor region are adjacent, the sintering inhibitor contains a first resin, the sintering inhibitor region contains the first resin or a second resin derived from the first resin, and the predicted amount of residue calculated by multiplying the mass ratio of the first resin or the second resin to the powder in the sintering inhibitor region formed by laminating the sintering inhibitor regions by the thermal decomposition residue rate of the first resin or the second resin at 550°C is 1000 ppm or more. 1604ppm or less This invention relates to a method for manufacturing a molded object characterized by the following: [Effects of the Invention]

[0007] According to the present invention, it is possible to provide a method for manufacturing a molded object using a sintering inhibitor that can sufficiently reduce the relative sintering density in the sintered material in the sintering inhibition region and has high storage stability. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic diagram showing an example of a powder layer having a build region, a sintering inhibition region, and a support region. [Figure 2] Figure 2 is a schematic diagram showing an example of a structure having a molding section, a sintering inhibition section, and a support section. [Figure 3] Figure 3 is a schematic diagram showing an example of a powder layer having a build region and a sintering inhibition region surrounding the build region. [Figure 4] Figure 4 is a schematic diagram showing an example of a single integrated object in which multiple molded parts and multiple connecting parts are integrated. [Figure 5]Figure 5 is a schematic diagram showing an example of a laminate having a molded area and a sintering inhibiting area that covers the entire circumference of the molded area. [Figure 6A] Figure 6A is a schematic diagram showing an example of the operation of a three-dimensional object manufacturing apparatus. [Figure 6B] Figure 6B is a schematic diagram showing another example of the operation of a three-dimensional object manufacturing apparatus. [Figure 6C] Figure 6C is a schematic diagram showing another example of the operation of a three-dimensional object manufacturing apparatus. [Figure 6D] Figure 6D is a schematic diagram showing another example of the operation of a three-dimensional object manufacturing apparatus. [Figure 6E] Figure 6E is a schematic diagram showing another example of the operation of a three-dimensional object manufacturing apparatus. [Figure 7] Figure 7 shows a microscope image of the sintered material in the fabrication section. [Figure 8] Figure 8 shows a microscope image of the sintered material in the sintering inhibition area. [Modes for carrying out the invention]

[0009] The following describes one embodiment of the present invention.

[0010] <<Manufacturing Method for Molded Objects>> A method for manufacturing a molded object includes a powder layer formation step of forming a layer of powder containing sinterable particles, a molding fluid application step of applying a molding fluid to the powder layer to form a molding region, and a sintering inhibitor application step of applying a sintering inhibitor to the powder layer to form a sintering inhibitor region in which the sintering of particles is inhibited, and includes a lamination step of forming a laminate by sequentially repeating the powder layer formation step, the molding fluid application step and the sintering inhibitor application step. In this case, the molding region and the sintering inhibition region are adjacent to each other. Furthermore, the laminate has a molded portion formed by stacking molded regions and a sintering inhibiting portion formed by stacking sintering inhibiting regions. In this disclosure, “molding fluid” is a liquid composition that is applied to a layer of powder containing sinterable particles to form a molding region. Further, the "sintering inhibitor liquid" is a liquid composition that is applied to a layer of powder containing sinterable particles and forms a sintering inhibition region where the sintering of the particles is inhibited. In the present disclosure, the "shaping part" is a precursor structure of the shaped object. The "sintering inhibition part" means a structure that is formed in advance between the shaping part (sintering precursor) and the support material for supporting the sintering precursor during sintering so that they can be easily separated after sintering. The sintering inhibition part means that sintering does not progress by the sintering process, or the relative sintering density is sufficiently lower compared to the sintering precursor or the support material. Note that the "sintering inhibition part" is not a precursor structure of the shaped object, but a structure that detaches from the shaped object after sintering, and has the characteristic that the relative sintering density of the sintered product formed by sintering the sintering inhibition part is lower than the relative sintering density of the sintered product formed by sintering the shaped object.

[0011] Further, the above shaping liquid application step may be a step of applying a shaping liquid to a layer of powder to form a shaping region and a support region. At this time, the shaping region and the sintering inhibition region are adjacent, and the shaping region and the support region are adjacent via the sintering inhibition region. Also, in this case, the laminate has a shaping part formed by laminating the shaping regions, a sintering inhibition part formed by laminating the sintering inhibition regions, and a support part formed by laminating the support regions. In the present disclosure, the "support part" is not a precursor structure of the shaped object, but a structure that supports the shaping part via the sintering inhibition part and detaches from the shaped object after sintering. Also, when the shaping liquid application step is a step of forming a shaping region and a support region as described above, the shaping liquid is a liquid composition that is applied to a layer of powder containing sinterable particles and forms the shaping region and the support region.

[0012] Furthermore, the manufacturing method of the molded object preferably includes, in addition to the above-mentioned lamination step, a heating step of heating the lamination at a temperature corresponding to the softening point of the resin contained in the lamination, an excess powder removal step of removing excess powder which is powder to which liquid such as molding fluid or sintering inhibitor has not been applied, a drying step of removing liquid components remaining in the molded part and sintering inhibitor part, a degreasing step of obtaining a degreased material by heating the molded part and sintering inhibitor part to remove at least a portion of the resin contained in each part, a sintering step of obtaining a sintered material by heating the degreased material such as the molded part and sintering inhibitor part, and a post-processing step of performing post-processing on the sintered material such as the molded part and sintering inhibitor part (for example, a process of separating sintered material such as the sintering inhibitor part from the sintered material of the molded part). In this disclosure, the molded part after the heating step may be called a "green body (unsintered body)", the molded part after the degreasing step may be called a "degreased body", and the molded part after the sintering step may be called a "sintered body". In this disclosure, "formed object" refers to a general term for three-dimensional objects that maintain a certain three-dimensional shape, such as a green body or a structure derived from a green body, and specifically, it is a concept that represents green bodies, degreased bodies, and sintered bodies. The following provides a detailed explanation of each step.

[0013] <Powder layer formation process> The manufacturing method for the molded object includes a powder layer formation step in which a layer of powder containing sinterable particles is formed. The powder layer is formed on a support (on the molding stage). There are no particular limitations on the method for forming a thin layer of powder by arranging powder on a support, and can be appropriately selected depending on the purpose. Examples include a method using a known counter rotation mechanism (counter roller) used in the selective laser sintering method described in Japanese Patent Publication No. 3607300, a method of spreading the powder using a brush, roller, blade, or other component, a method of spreading the powder by pressing the surface with a pressing component, and a method using a known additive manufacturing apparatus.

[0014] 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 way. 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.

[0015] 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. When the average thickness is 30 μm or more, the strength of the green body 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, when the average thickness is 500 μm or less, the dimensional accuracy of the molded object derived from the green body 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.

[0016] 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.

[0017] -Sinterable particles- The "sinterable particles" (which may also be referred to as "particles" in the following description) in this disclosure are particles used in the manufacture of molded objects and contain a sinterable material such as metal as a constituent material. The constituent material of the particles is not particularly limited as long as it contains a sinterable material, and may contain materials other than sinterable materials, but it is preferable that the main material is a sinterable material. The main material being a sinterable material means that the mass of the sinterable material contained in the particles is 50.0% by mass or more of the mass of the particles, preferably 60.0% by mass or more, more preferably 70.0% by mass or more, even more preferably 80.0% by mass or more, and particularly preferably 90.0% by mass or more.

[0018] The sinterable material that constitutes the particles is preferably a metal, such as magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), lead (Pd), silver (Ag), indium (In), tin (Sn), tantalum (Ta), tungsten (W), neodymium (Nd), and alloys of these metals. Among these, stainless steel (SUS), iron (Fe), copper (Cu), silver (Ag), titanium (Ti), aluminum (Al), and alloys of these metals are preferably used. An example of an aluminum alloy is AlSi 10 Mg, AlSi 12 AlSi7Mg 0.6 , AlSi3Mg, AlSi9Cu3, Scalmalloy, ADC 12 These are some examples. These can be used individually or in combination of two or more.

[0019] The particles can be manufactured using conventionally known methods. Methods for producing particles include, for example, pulverization methods that subdivide a solid by applying compression, impact, friction, etc.; atomization methods that obtain rapidly cooled powder by spraying molten metal; precipitation methods that precipitate components dissolved in a liquid; and gas-phase reaction methods that vaporize and crystallize. Among these, atomization is preferred because it yields a spherical shape and has little variation in particle size. Examples of atomization methods include water atomization, gas atomization, centrifugal atomization, and plasma atomization, all of which can be suitably used.

[0020] Commercially available particles may be used. Examples of commercially available particles whose constituent material is metal 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), and ZrO2 (manufactured by Tosoh Corporation, product name: TZ-B53).

[0021] There are no particular restrictions on the volume-average particle size of the particles, and they can be appropriately selected according to 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 particles is 2 μm or more, particle aggregation is suppressed, which can prevent a decrease in the manufacturing efficiency of the molded product and a decrease in the handling of the particles. Furthermore, when the average particle diameter of the particles is 100 μm or less, a decrease in the contact points between 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, and it can be appropriately selected according to the purpose, but a sharper particle size distribution is preferable. The volume-average particle size and particle size distribution of particles can be measured using known particle size measuring devices, such as the Microtrac MT3000II series particle size distribution analyzer (manufactured by Microtrac Bell).

[0022] -Powder containing sinterable particles- The above-mentioned particles are used as a powder, which is an aggregate containing multiple particles, and a sintering inhibitor and a molding fluid are applied to the layer of this powder. The powder may contain, as optional, other components in addition to sinterable particles. Examples of other components include fillers, leveling agents, sintering aids, and polymer resin particles. Fillers are effective materials for adhering to the surface of particles or filling voids between particles. By using fillers, for example, the fluidity of powders can be improved, and the contact points between particles can be increased, reducing voids and thereby improving the strength and dimensional accuracy of the fabricated object. Leveling agents are effective materials for controlling the wettability of a powder layer's surface. By using leveling agents, for example, the penetration of the molding fluid into the powder layer can be increased, thereby improving the strength of the molded object. Sintering aids are effective materials for increasing sintering efficiency when sintering molded objects. By using sintering aids, for example, the strength of the molded object can be improved, the sintering temperature can be lowered, and the sintering time can be shortened. Polymer resin particles are effective materials for adhering to the surface of particles and are also called organic additives. The average particle size of polymer resin particles is not particularly limited, but is preferably 0.1 μm or more and 10 μm or less, and more preferably 0.1 μm or more and 1 μm or less.

[0023] The angle of repose of the powder is preferably 60° or less, more preferably 50° or less, and even more preferably 40° or less. An angle of repose of 60° or less allows the powder to be efficiently and stably placed at the desired location on the support. The angle of repose can be measured using, for example, a powder property measuring device (Powder Tester PT-N type, manufactured by Hosokawa Micron Corporation).

[0024] <Forming fluid application process> The method for manufacturing a molded object includes a step of applying a molding liquid to a powder layer to form a molding region. Furthermore, the molding fluid application step is preferably a step in which molding fluid is applied to the powder layer to form the molding region and support region. Furthermore, when forming support regions in the molding fluid application process, the molding fluid that forms the support regions is applied so that the support regions 102 formed in the powder layer 101 are adjacent to the molding region 104 via the sintering inhibition region 103, as shown in Figure 1. As a result, during the degreasing and sintering processes, as shown in Figure 2, the support portion 201 formed by stacking the support regions is positioned to support the molding region 203 via the sintering inhibition region 202 (in other words, the support portion 201 is provided along the undulations of the molding region 203 via the sintering inhibition region 202), thereby suppressing damage or deformation of the molding region. In particular, in molding regions with a shape that includes a protruding portion at the top, such as an overhang, and without a structure to support the protruding portion below it, damage or deformation due to its own weight is likely to occur during the degreasing or sintering processes. Therefore, providing a support portion below the overhang can suppress damage or deformation. Note that when forming support regions in the molding fluid application process, the timing of the formation of the molding region and the support regions does not have to be consecutive. For example, the formation of a sintering inhibition region may occur after the formation of the fabrication region but before the formation of the support region.

[0025] 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 accurately and efficiently form complex molding areas.

[0026] 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. As the inkjet head, an inkjet head from a known inkjet printer can be suitably used. 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 manufactured by Ricoh Co., Ltd.

[0027] Furthermore, the molding fluid application step may include not only the step of applying the molding fluid to the powder layer to form a molding region, but also the step of subsequently applying the molding fluid to the sintering-inhibiting region formed by the sintering-inhibiting fluid application step described later. This improves the strength of the sintering-inhibiting region before the degreasing step and improves the handling of the green body (unsintered body). In addition, since two types of resin (the second resin and molding resin described later) are contained in the sintering-inhibiting region, the degreasing of the resin in the degreasing step becomes a two-stage process, which suppresses excessive cracking of the sintering-inhibiting region during the degreasing step.

[0028] 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.

[0029] -Modeling liquid- The molding fluid contains resin, organic solvents, and additives such as surfactants. The various components contained in the molding fluid are described in detail below. Furthermore, in order to distinguish between the resin contained in the molding fluid, the resin contained in the sintering inhibitor (first resin) described later, the resin derived from the resin contained in the sintering inhibitor (second resin), and the resin produced by the contact between resin generating liquid X and resin generating liquid Y (third resin), the resin contained in the molding fluid may be referred to as the "molding resin."

[0030] --Resin (modeling resin)-- The resin contained in the molding fluid is placed within the powder layer when the molding fluid is applied to a layer of powder containing sinterable particles. Through an appropriate heating process corresponding to the resin's softening point, it functions as a binder that binds the sinterable particles together in the molding area.

[0031] The resin used in the molding fluid is not particularly limited, but examples include resins having a structural unit represented by the following structural formula (1). In this disclosure, "structural unit" refers to a substructure in the resin derived from one or more polymerizable compounds. [ka]

[0032] Resins having structural units represented by structural formula (1) exhibit excellent thermal decomposition properties, allowing them to be properly removed in the degreasing process, which in turn improves the relative sintering density of the sintered body produced through the subsequent sintering process. Specifically, the resin having the structural unit represented by structural formula (1) is preferably thermally decomposed by 95% by mass or more when the temperature is raised from 30°C to 550°C, and more preferably by 97% by mass or more. Furthermore, the thermal decomposition rate is measured using TG-DTA (Differential Thermal Analysis and Thermogravimetric Analysis System). Specifically, the weight loss rate before and after heating is determined when the temperature is increased from 30°C to 550°C at a rate of 10°C / min in an atmospheric or nitrogen atmosphere, and then the temperature is maintained for 2 hours after reaching 550°C.

[0033] 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. These resins may be used individually or in combination of two or more. Both commercially available and synthetic products can be used. Partially saponified polyvinyl acetate resin is a resin obtained by partially saponifying polyvinyl acetate resin. Furthermore, the partially saponified polyvinyl acetate resin in this disclosure has a degree of saponification of 40 or less, preferably 35 or less, more preferably 30 or less, even more preferably 25 or less, and even more preferably 20 or less.

[0034] The content of the resin having the structural unit represented by structural formula (1) is preferably 5.0% by mass or more, more preferably 7.0% by mass or more, even more preferably 10.0% by mass or more, and particularly preferably 11.0% by mass or more, relative to the mass of the molding liquid. Furthermore, the content of the resin having the structural unit represented by structural formula (1) is preferably 30.0% by mass or less, more preferably 25.0% by mass or less, and even more preferably 20.0% by mass or less.

[0035] --Organic Solvents-- The molding fluid contains an organic solvent. The organic solvent is a liquid component used to keep the molding fluid in a liquid state at room temperature. Furthermore, it is preferable that the molding fluid is a non-aqueous type of molding fluid, as it contains an organic solvent. In this disclosure, "non-aqueous molding fluid" means a molding fluid that contains an organic solvent as a liquid component, and in which the component having the largest mass is the organic solvent. Furthermore, it is preferable that the content of the organic solvent relative to the content of the liquid component in the molding fluid is 90.0% by mass or more, and more preferably 95.0% by mass or more. This is because, with 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 3D printing fluids can sometimes be described as 3D printing fluids that are substantially water-free. This allows the 3D printing fluid to be applied even when the materials constituting the sinterable particles are highly reactive metals, or in other words, water-reactive materials (e.g., aluminum, zinc, and magnesium). For example, aluminum is difficult to handle because it generates hydrogen when it comes into contact with water, but this problem can be mitigated by using a 3D printing fluid that does not contain water.

[0036] 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, and triacetin. 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.

[0037] The content of the organic solvent is preferably 60.0% by mass or more and 95.0% by mass or less, and more preferably 70.0% by mass or more and 95.0% by mass or less, relative to the mass of the molding liquid.

[0038] --Additives-- The molding fluid may contain surfactants, drying inhibitors, viscosity modifiers, penetrating agents, defoaming agents, pH adjusters, preservatives, fungicides, colorants, preservatives, stabilizers, etc., as appropriate, depending on the purpose. Conventionally known materials can be used for these.

[0039] --Other ingredients-- In the molding fluid, water is substantially absent. In this disclosure, "substantially absent" means that the water content is 10.0% by mass or less relative to the mass of the molding fluid, preferably 5.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably the molding fluid contains no water at all. Furthermore, in this disclosure, "the molding fluid contains no 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 material constituting the particles is a highly reactive metal, in other words, a water-reactive material (for example, aluminum, zinc, and magnesium). For example, aluminum is difficult to handle because it generates hydrogen when it comes into contact with water, but this problem is mitigated because the molding fluid does not contain water.

[0040] --Manufacturing method-- There are no particular restrictions on the method for manufacturing the molding fluid, and it can be appropriately selected depending on the purpose. For example, one method is to mix and stir the above-mentioned materials.

[0041] --Physical Properties-- As described above, the viscosity of the molding fluid is preferably low. Specifically, at 25°C, it is preferably 5 mPa·s to 50 mPa·s, more preferably 5 mPa·s to 40 mPa·s, and even more preferably 5 mPa·s to 30 mPa·s. When the viscosity of the molding fluid is within the above range, the ejection from the molding fluid application means, such as an inkjet head, becomes stable, and dimensional accuracy improves. Viscosity can be measured, for example, in accordance with JIS K7117.

[0042] The surface tension of the molding fluid is preferably 40 mN / m or less at 25°C, and more preferably 10 mN / m to 30 mN / m. When the surface tension is 40 mN / m or less, the ejection from the molding fluid application means, such as an inkjet head, is stabilized, and dimensional accuracy is improved. Surface tension can be measured, for example, using the DY-300 manufactured by Kyowa Interface Science Co., Ltd.

[0043] <Sintering inhibitor application process> The method for manufacturing a molded object includes a step of applying a sintering inhibitor to a powder layer to form a sintering inhibitory region where the sintering of particles is inhibited. Furthermore, in the sintering inhibitor application step, the sintering inhibitor is applied so that the formed sintering inhibitory region is adjacent to the fabrication region.

[0044] As a method for applying a sintering inhibitor to a powder layer, a method of dispensing the sintering inhibitor is preferred. There are no particular restrictions on the method of dispensing the sintering inhibitor, 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 large coating area and excellent coating performance, but droplet quantity is poor and scattering of the sintering inhibitor occurs 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 larger coating area compared to the dispenser method, and is preferred because it can accurately and efficiently form complex sintering inhibition regions.

[0045] When using the inkjet method, the means for applying the sintering inhibitor by ejecting the sintering inhibitor is an inkjet head having a nozzle for ejecting the sintering inhibitor. As the inkjet head, an inkjet head from a known inkjet printer can be suitably used. 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 manufactured by Ricoh Co., Ltd.

[0046] In the sintering inhibitor application step, it is preferable that the amount of sintering inhibitor applied per unit area to form a sintering inhibitory region is greater than the amount of molding fluid applied per unit area to form a molding region in the molding fluid application step. This is because the strength of the sintering inhibitory region before the degreasing step is improved, thereby improving handling, and the relative sintering density in the sintering inhibitory region after the sintering step is further reduced, making it easier to separate the sintered material of the sintering inhibitory region from the sintered material of the molding region.

[0047] In the sintering inhibition region formed by the sintering inhibition liquid application step, it is preferable that the sintering inhibition region 302 is arranged in the powder layer 301 so as shown in Figure 3, surrounding the molding region 303. This suppresses the collapse of the sintering inhibition portion during the sintering process, improving the dimensional accuracy of the molded object.

[0048] At the boundary between the molding region and the sintering inhibition region, it is preferable that the sintering inhibitor is applied by the sintering inhibitor application process within 100 msec after the molding fluid is applied by the molding fluid application process. Specifically, for example, if the molding fluid and sintering inhibitor are applied to the powder layer in the form of droplets, at the boundary between the molding region and the sintering inhibition region, the locations where the molding fluid droplets are applied and the locations where the sintering inhibitor droplets are applied will be adjacent on the powder layer. Regarding the timing of the application of droplets to these locations, it is preferable that the sintering inhibitor droplets be applied within 100 msec after the molding fluid droplets are applied. This suppresses the seepage of the molding fluid applied to the powder into the sintering inhibition region, thereby improving the dimensional accuracy of the molded object.

[0049] The sintering inhibitory liquid supplied to the sintering inhibitory liquid supply means may be contained in a sintering inhibitory liquid containment section. The sintering inhibitory liquid containment section is a container or other component that contains the sintering inhibitory liquid, and examples include a storage tank, bag, cartridge, or tank.

[0050] -Sintering inhibitor- The sintering inhibitor contains a first resin, an organic solvent, and additives such as surfactants. The properties of the sintering inhibitor and the various components contained therein will be described in detail below. Furthermore, as described above, the sintering inhibitory liquid contains the first resin, and therefore, the sintering inhibitory region formed when the sintering inhibitory liquid is applied to a layer of powder containing sinterable particles contains the first resin or a second resin derived from the first resin. The second resin is not limited as long as it is derived from the first resin, and may be a resin that is chemically identical to the first resin, or a resin that is chemically different from the first resin. Cases in which the second resin becomes a resin that is chemically different from the first resin include, for example, when the first resin undergoes a chemical change due to a heating process performed after a sintering inhibitor is applied to the powder layer (for example, when a crosslinking reaction proceeds in the first resin to produce the second resin). A sintering inhibition region formed by applying a sintering inhibitor to a powder layer containing sinterable particles may contain a first resin. For example, this may occur when the first resin does not undergo chemical changes during a heating process performed after the sintering inhibitor is applied to the powder layer.

[0051] --Predicted Residue Amount-- The sintering inhibitor has predetermined properties relating to the first resin or the second resin. Specifically, the sintering inhibitor has the characteristic that the predicted residue amount, calculated by multiplying the mass ratio of the first resin or the second resin to the powder in the sintering inhibition region by the thermal decomposition residue rate of the first resin or the second resin at 550°C, is 800 ppm or more, preferably 1000 ppm or more, and more preferably 1200 ppm or more. A predicted residue amount of 800 ppm or more allows for a sufficient reduction in the relative sintering density in the sintered product of the sintering inhibition region (similarly, the relative sintering density in the "sintering inhibition section" formed by stacking sintering inhibition regions can also be sufficiently reduced), improving the peelability when separating the sintered product of the sintering inhibition section from the sintered product of the molded part. Next, the method for calculating the predicted residue amount will be described in detail.

[0052] First, in this disclosure, the "mass ratio of the first resin or the second resin to the powder in the sintering inhibiting portion formed by stacking sintering inhibiting regions" is expressed by the following formula: "mass of the first resin or the second resin in the sintering inhibiting portion / mass of the powder in the sintering inhibiting portion". The calculations based on this formula are performed using a sintering inhibitor formed according to the manufacturing method of the molded object (for example, including information on the use of the sintering inhibitor, such as the type of sinterable particles to which the sintering inhibitor is applied, the amount of sintering inhibitor applied, and the processing method after the sintering inhibitor is applied). Methods for using sintering inhibitors include, for example, if there is a specific device that uses the sintering inhibitor, the usage procedure for the sintering inhibitor stored in that specific device. A specific procedure for using a sintering inhibitor is, for example, with an aluminum alloy (material: AlSi 10 One procedure involves forming a powder layer (average thickness: 84 μm) consisting of Mg particles (volume average particle size: 35 μm), applying 45 pL of sintering inhibitory solution per 300 dpi × 300 dpi area to the powder layer, and then leaving it in an environment of 200°C for 4 hours. Calculations based on the above formula are then performed on the sintering inhibitory section produced by this procedure. The "mass of the first or second resin in the sintering inhibiting portion" mentioned above can be calculated, for example, by multiplying the proportion (w / v%) of the first resin contained in the sintering inhibiting liquid, the volume of sintering inhibiting liquid applied to the sintering inhibiting portion per layer, and the number of layers. The "mass of powder in the sintering inhibiting portion" mentioned above can be calculated, for example, by multiplying the volume of powder in the sintering inhibiting portion per layer, the density of the powder, and the number of layers.

[0053] The "mass ratio of the first or second resin to the powder in the sintering inhibiting portion" is preferably 3000 ppm or more, more preferably 4000 ppm or more, and even more preferably 5000 ppm or more. A mass ratio of 3000 ppm or more makes it easy to achieve a predicted residue amount of 800 ppm or more. Furthermore, the "mass ratio of the first or second resin to the powder in the sintering inhibitory section" is preferably 60,000 ppm or less, and more preferably 16,000 ppm or less. A mass ratio of 60,000 ppm or less prevents excessive application of the sintering inhibitory solution, thereby improving productivity.

[0054] Next, in this disclosure, "thermal decomposition residue rate of the first or second resin at 550°C" is expressed by the following formula: "mass of residue when the first or second resin is thermally decomposed at 550°C / mass of the first or second resin before thermal decomposition". The calculations based on this formula are performed using the sintering inhibitor formed according to the manufacturing method of the molded object, similar to the calculations in the "mass ratio of the first or second resin to the powder in the sintering inhibitor" described above. In other words, the second resin in this formula is the resin derived from the first resin in the sintering inhibition portion formed according to the manufacturing method of the molded object. The "residual mass when the first or second resin is thermally decomposed at 550°C" mentioned above is measured, for example, using a TG-DTA (Differential Thermal Analysis-Thermogravimetric Analysis System). Specifically, the sintering inhibition area formed according to the manufacturing method of the molded object is heated from 30°C to 550°C at a rate of 10°C / min in an air or nitrogen atmosphere, and then the temperature is maintained for 2 hours after reaching 550°C. The weight after heating (residual mass) is then determined.

[0055] The above-mentioned "thermal decomposition residue rate of the first or second resin at 550°C" is preferably 0.100 or higher, more preferably 0.130 or higher, even more preferably 0.150 or higher, and particularly preferably 0.200 or higher. A thermal decomposition residue rate of 0.100 or higher makes it easy to predict the amount of residue to be 800 ppm or higher.

[0056] --Relative sintering density-- As described above, the sintering inhibited portion formed by stacking sintering inhibited regions formed using a sintering inhibiting liquid has the characteristic of having a low relative sintering density in the sintered product formed by sintering the sintering inhibited portion. Specifically, a low relative sintering density is preferably 85% or less, more preferably 80% or less, even more preferably 75% or less, even more preferably 70% or less, even more preferably 65% ​​or less, even more preferably 60% or less, and particularly preferably 55% or less. This provides the effect of improving the peelability when separating the sintered product of the sintering inhibited portion from the sintered product of the molded portion. Relative sintering density refers to the ratio of the density of the sintered body to the true density of the materials constituting the sintered body. Furthermore, each density can be measured by known methods.

[0057] --First resin-- The sintering inhibitor contains a first resin as a material that reduces the relative sintering density of the sintered product formed by sintering the sintering inhibitory portion. Conventionally, ceramics have been used as the material that reduces the relative sintering density as described above, but such conventional materials are inferior in terms of dispersibility in the sintering inhibitor, making it difficult to eject the sintering inhibitor using, for example, an inkjet ejection method. Furthermore, such conventional materials are inferior in terms of sedimentation or redispersibility in the sintering inhibitor, making it difficult to provide a sintering inhibitor with high storage stability. On the other hand, in this disclosure, by adopting a resin instead of ceramics as the material that reduces the relative sintering density as described above, the dispersibility and storage stability of the sintering inhibitor are improved.

[0058] The first resin is preferably a resin that can increase the thermal decomposition residue rate at 550°C of the second resin, which is derived from the first resin. Specific examples of the first resin include, for example, polyvinyl chloride, polyvinylidene chloride, cellulose acetate, polyacronitrile, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, vinyl chloride-vinyl acetate copolymer, polyethylene terephthalate, phenolic resin, melamine resin, urea resin, unsaturated polyester, epoxy resin, silicone resin, polyvinylpolypyrrolidone, benzoguanamine resin, and the like. These may be used individually or in combination of two or more types.

[0059] Furthermore, when using a material in which the first resin undergoes a chemical change due to a heating process performed after the application of a sintering inhibitor to the powder layer, resulting in the first and second resins being chemically different, it is preferable to use a material in which the thermal decomposition residue rate of the second resin at 550°C is higher than that of the first resin at 550°C. Polyvinylpyrrolidone can be used as such a first resin. This is because polyvinylpyrrolidone undergoes a crosslinking reaction when heated to 170°C or higher, producing the second resin, polyvinylpolypyrrolidone. Furthermore, if the sintering inhibiting region contains the second resin, the thermal decomposition residue rate of the first resin at 550°C is measured using the first resin alone as follows. <Method for measuring the thermal decomposition residue rate of the first resin component> Using a TG-DTA (Differential Thermal and Thermogravimetric Analysis Device), the weight (residual mass) after heating is determined when the temperature is increased from 30°C to 550°C at a rate of 10°C / min in an air or nitrogen atmosphere, and then the temperature is maintained for 2 hours after reaching 550°C.

[0060] From the viewpoint of improving the dispersibility and storage stability of the sintering inhibitor, the first resin is more preferably dissolved in the sintering inhibitor, but may also be dispersed. When the first resin is dispersed in the sintering inhibitor, from the viewpoint of improving the dispersibility and storage stability of the sintering inhibitor, the volume average particle size of the first resin is preferably 1 μm or less, more preferably 500 nm or less, and even more preferably 300 nm or less.

[0061] The content of the first resin is preferably 5.0% by mass or more and 25.0% by mass or less relative to the mass of the sintering inhibitory liquid, and more preferably 10.0% by mass or more and 20.0% by mass or less. By having a content of 5.0% by mass or more and 25.0% by mass or less, it is possible to achieve both a reduction in the relative sintering density of the sintered product formed by sintering the sintering inhibitory portion, and an improvement in the dispersibility and storage stability of the sintering inhibitory liquid.

[0062] --Organic Solvents-- Organic solvents are liquid components used to keep the sintering inhibitor liquid in a liquid state at room temperature. When dissolving the first resin in the sintering inhibitor liquid, an organic solvent that dissolves the first resin is selected. When dispersing the first resin in the sintering inhibitor liquid, an organic solvent that does not dissolve the first resin is selected. Furthermore, the sintering inhibitor is preferably a non-aqueous sintering inhibitor that contains an organic solvent. In this disclosure, "non-aqueous sintering inhibitor" refers to a sintering inhibitor that contains an organic solvent as a liquid component, and in which the component with the largest mass is the organic solvent. Furthermore, the content of the organic solvent relative to the content of the liquid component in the sintering inhibitor is preferably 90.0% by mass or more, and more preferably 95.0% by mass or more. In addition, a non-aqueous sintering inhibitor can sometimes be rephrased as a sintering inhibitor that is substantially free of water. This allows the sintering inhibitor to be applied even if the material constituting the sinterable particles is a highly active metal, in other words, a water-reactive material (e.g., aluminum, zinc, and magnesium). For example, aluminum is difficult to handle because it generates hydrogen when it comes into contact with water, but this problem can be suppressed by using a sintering inhibitor that does not contain water.

[0063] The organic solvent is not particularly limited and can be appropriately selected depending on the type of first resin used in combination, but examples 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, and maleic acid. Examples include bis-2-ethylhexyl, triacetin, 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.

[0064] The content of the organic solvent is preferably 50.0% by mass or more and 95.0% by mass or less relative to the mass of the sintering inhibitor, and more preferably 70.0% by mass or more and 90.0% by mass or less. A content of 50.0% by mass or more and 95.0% by mass or less improves the dispersibility and storage stability of the sintering inhibitor.

[0065] --Additives-- The sintering inhibitor may contain, depending on the purpose, surfactants, drying inhibitors, viscosity modifiers, penetrating agents, defoaming agents, pH adjusters, preservatives, fungicides, colorants, preservatives, stabilizers, etc. These can be conventionally known materials.

[0066] --Other ingredients-- In the sintering inhibitor, water is substantially free. In this disclosure, "substantially free of water" means that the water content is 10.0% by mass or less relative to the mass of the sintering inhibitor, preferably 5.0% by mass or less, more preferably 3.0% by mass or less, even more preferably 1.0% by mass or less, and particularly preferably the sintering inhibitor does not contain water. Furthermore, in this disclosure, "the sintering inhibitor does not contain water" means that water is not actively used as a material during the manufacture of the sintering inhibitor, or that the water content in the sintering inhibitor is below the detection limit when using known and commonly used methods. Because the sintering inhibitor is substantially water-free, it can be applied even if the material constituting the sinterable particles is a highly reactive metal, in other words, a water-reactive material (e.g., aluminum, zinc, and magnesium). For example, aluminum is difficult to handle because it generates hydrogen when it comes into contact with water, but this problem is mitigated because the sintering inhibitor does not contain water.

[0067] Ceramics are not contained in the sintering inhibitor. In this disclosure, "ceramics-free" means that ceramics are not actively used as materials during the manufacture of the sintering inhibitor, or that the ceramics content in the sintering inhibitor is below the detection limit when using known and commonly used methods. By not containing ceramics in the sintering inhibitor, the dispersibility and storage stability of the sintering inhibitor can be improved.

[0068] --Manufacturing method-- There are no particular limitations on the method for producing the sintering inhibitor, and it can be appropriately selected depending on the purpose. For example, a method of mixing and stirring the above materials can be used.

[0069] --Physical Properties-- The viscosity of the sintering inhibitor is preferably low, as described above. Specifically, at 25°C, it is preferably 5 mPa·s to 50 mPa·s, more preferably 5 mPa·s to 40 mPa·s, and even more preferably 5 mPa·s to 30 mPa·s. When the viscosity of the sintering inhibitor is within the above range, ejection from a sintering inhibitor application means such as an inkjet head is stabilized. Viscosity can be measured, for example, in accordance with JIS K7117.

[0070] The surface tension of the sintering inhibitor is preferably 40 mN / m or less at 25°C, and more preferably 10 mN / m to 30 mN / m. When the surface tension is 40 mN / m or less, ejection from a sintering inhibitor application means such as an inkjet head is stabilized. Surface tension can be measured, for example, using the DY-300 manufactured by Kyowa Interface Science Co., Ltd.

[0071] --Applications-- As described above, when the sintering inhibitor is applied to a layer of powder, it forms a sintering inhibitory region. When these sintering inhibitory regions are stacked, they form a sintering inhibitory section. The relative sintering density of the sintered material formed by sintering the sintering inhibitory section is lower than the relative sintering density of the sintered material formed by sintering the molded object. This improves the release properties when separating the sintered material of the sintering inhibitory section from the sintered material of the molded object. The applications of the sintering inhibitor based on this effect are not particularly limited, but include, for example, improving the release properties of support sections from the molded object, using it as a connecting section to connect multiple molded objects, and eliminating the need for the excess powder removal process.

[0072] This section describes the use of a sintering inhibitor to improve the release properties of the support portion from the molded portion. Specifically, for example, when a support portion is provided to support the molded portion via a sintering inhibitor, an interface consisting of a sintering inhibitor with a low relative sintering density is formed between the sintered material (sintered body) of the molded portion and the sintered material of the support portion. This suppresses adhesion between the sintered material of the molded portion and the sintered material of the support portion, thereby improving the release properties when separating the sintered material of the support portion from the sintered material of the molded portion.

[0073] This section describes the use of a sintering inhibitor as a connecting part for linking multiple molded parts. A connecting part is a component used to form a single integrated object by connecting multiple molded parts. For example, it could be a rod-shaped component whose end is connected to a molded part. By forming multiple molded parts into the above-mentioned integrated object, the number of steps required to rearrange the multiple molded parts and place them in a sintering furnace during the sintering process can be reduced, improving work efficiency during the manufacturing of the molded object. Furthermore, by forming the connecting part so that at least the area in contact with the molded part acts as a sintering inhibitor, the peelability when separating the sintered material of the connecting part from the sintered material of the molded part can be improved. Figure 4 is a schematic diagram showing an example of an integrated product in which multiple molded parts and multiple connecting parts are integrated. The integrated product shown in Figure 4 has a molded part 401 and a connecting part 402, and the connecting part 402 is formed by a sintering inhibiting part.

[0074] This section describes the use of a sintering inhibitor to omit the excess powder removal process. Normally, in the manufacturing of molded objects, an excess powder removal process is performed to remove excess powder, which is powder that was not treated with a molding fluid or sintering inhibitor. However, if the entire circumference of the molded area is covered with a sintering inhibitor, the excess powder cannot adhere to the molded area, and therefore the excess powder removal process can be omitted. However, omitting the excess powder removal process means that the use of excess powder removal means such as an air-blowing device or removal fluid can be omitted, and removal to the extent of manually brushing off excess powder is not included in the omission. Furthermore, if the sintering inhibitor covering the entire circumference of the molded area is continuous to the outer surface of the laminate, and the outer surface of the laminate is divided into two or more regions with the exposed sintering inhibitor as the boundary, it is preferable because it becomes easier to detach the sintering inhibitor and the sintered excess powder from the sintered material of the molded area after the sintering process. Figure 5 is a schematic diagram showing an example of a laminate having a molded section and a sintering inhibitor section covering the entire circumference of the molded section. The laminate shown in Figure 5 has a molded section 501, a sintering inhibitor section 502A that has the molded section 501 inside and covers the entire circumference of the molded section, a plate-shaped sintering inhibitor section 502B that is continuous with the sintering inhibitor section 502A and the outer surface of the laminate, and excess powder 503. The outer surface of the laminate is divided into two regions 504 and 505 with the sintering inhibitor section 502B as the boundary.

[0075] <Process of applying sintering inhibitor set> The method for manufacturing a molded object may include a "sintering inhibitor set application step" instead of the "sintering inhibitor application step" described above. The sintering inhibitor set application step is a step in which resin generating liquid X and resin generating liquid Y are independently applied to a powder layer, and a sintering inhibition region is formed in the powder layer after application where the resin generating liquid X and resin generating liquid Y come into contact, thereby inhibiting the sintering of particles. In other words, the sintering inhibitor set application step includes a resin generating liquid X application step in which resin generating liquid X is applied to the powder layer, a resin generating liquid Y application step in which resin generating liquid Y is applied to the powder layer, and a contact step in which a sintering inhibition region is formed in the powder layer where the applied resin generating liquid X and resin generating liquid Y come into contact, thereby inhibiting the sintering of particles. That is, a sintering inhibitor set containing resin generating liquid X and resin generating liquid Y can be used in place of the above-mentioned sintering inhibitor liquid and have the same function as the sintering inhibitor liquid, and can be used for the same purposes.

[0076] As a method for applying resin-generating liquid X and resin-generating liquid Y to the powder layer, the same method as described in the "sintering inhibitor application step" above can be used. The resin-generating solution X application step is suitably carried out by a resin-generating solution X application means. The resin-generating solution Y application step is suitably carried out by a resin-generating solution Y application means. The resin-generating liquid X application means and the resin-generating liquid Y application means can be the same as the sintering-inhibiting liquid application means described above.

[0077] The resin-generating liquid X supplied to the resin-generating liquid X supply means may be contained in a resin-generating liquid X containment section. The resin-generating liquid X containment section is a container or other component that contains the resin-generating liquid X, and examples include storage tanks, bags, cartridges, and tanks. Furthermore, the resin-generating liquid Y supplied to the resin-generating liquid Y supply means may be contained in a resin-generating liquid Y containment section. The resin-generating liquid Y containment section is a container or other component that contains the resin-generating liquid Y, and examples include storage tanks, bags, cartridges, and tanks.

[0078] -Sintering Inhibitor Set- Resin-generating solution X contains resin precursor X, an organic solvent, and additives such as surfactants. Resin-generating solution Y contains resin precursor Y, an organic solvent, and additives such as surfactants. The characteristics of the sintering inhibitory solution set and the various components contained in resin-generating solution X and resin-generating solution Y will be described in detail below. However, the organic solvent and additives such as surfactants contained in resin-generating solution X and resin-generating solution Y can be the same as those contained in the sintering inhibitory solution, so their description will be omitted. Furthermore, the sintering inhibition region contains a third resin that is produced when resin generating solution X and resin generating solution Y come into contact. More specifically, the third resin is produced when resin generating solution X and resin generating solution Y come into contact, causing a reaction between resin precursor X contained in resin generating solution X and resin precursor Y contained in resin generating solution Y.

[0079] --Predicted Residue Amount-- The sintering inhibitor set has predetermined properties related to the third resin. Specifically, the sintering inhibitory liquid set has the characteristic that the predicted residue amount, calculated by multiplying the mass ratio of the third resin to the powder in the sintering inhibitory region by the thermal decomposition residue rate of the third resin at 550°C, is 800 ppm or more, preferably 1000 ppm or more, and more preferably 1200 ppm or more. By having a predicted residue amount of 800 ppm or more, the relative sintering density in the sintered product of the sintering inhibitory region can be sufficiently reduced (similarly, the relative sintering density in the "sintering inhibitory part" formed by stacking the sintering inhibitory regions can also be sufficiently reduced), and the peelability when separating the sintered product of the sintering inhibitory part from the sintered product of the molded part is improved. Next, the method for calculating the predicted residue amount will be explained in detail.

[0080] First, in this disclosure, "the mass ratio of the third resin to the powder in the sintering inhibiting portion formed by stacking the sintering inhibiting regions" is expressed by the following formula: "mass of the third resin in the sintering inhibiting portion / mass of the powder in the sintering inhibiting region". The calculations based on this formula are performed using a sintering inhibitor formed according to the manufacturing method of the molded object (for example, including information on the use of the sintering inhibitor set, such as the type of sinterable particles to which resin generating liquid X and resin generating liquid Y are applied, the amount of resin generating liquid X and resin generating liquid Y applied, and the processing method after the application of resin generating liquid X and resin generating liquid Y). Methods for using the sintering inhibitor set include, for example, if there is a specific device that uses the sintering inhibitor set, the usage procedure for the sintering inhibitor set stored in that specific device. A specific procedure for using the sintering inhibitor set is, for example, for aluminum alloy (material: AlSi 10 One procedure involves forming a powder layer (average thickness: 84 μm) consisting of Mg particles (volume average particle size: 35 μm), applying 22.5 pL of resin generating liquid X and 22.5 pL of resin generating liquid Y per 300 dpi × 300 dpi area to the powder layer, and then leaving it in an environment of 200°C for 4 hours. Calculations based on the above formula are performed in the sintering inhibition region created by this procedure.

[0081] Next, in this disclosure, the "percentage of thermal decomposition residue of the third resin at 550°C" is expressed by the following formula: "mass of residue when the third resin is thermally decomposed at 550°C / mass of the third resin before thermal decomposition". The calculations based on this formula are performed using the sintering inhibitor formed according to the manufacturing method of the molded object, similar to the calculations in the "mass ratio of the third resin to the powder in the sintering inhibitor" described above. That is, the resins derived from resin precursors X and Y contained in the sintering inhibitor formed according to the manufacturing method of the molded object are considered the third resin in this formula.

[0082] --Relative sintering density-- As described above, the sintering inhibited portion formed by stacking sintering inhibited regions formed using a sintering inhibiting liquid set has the characteristic of having a low relative sintering density in the sintered product formed by sintering the sintering inhibited portion. Specifically, a low relative sintering density is preferably 85% or less, more preferably 80% or less, even more preferably 75% or less, even more preferably 70% or less, even more preferably 65% ​​or less, even more preferably 60% or less, and particularly preferably 55% or less. This provides the effect of improving the peelability when separating the sintered product of the sintering inhibited portion from the sintered product of the molded portion.

[0083] --Resin precursor X and resin precursor Y-- Since resin precursor X and resin precursor Y are components that do not easily settle in resin generating solution X and resin generating solution Y, respectively, the dispersibility and storage stability of resin generating solution X and resin generating solution Y are excellent. Furthermore, the usable resin precursors X and Y are not limited as long as they can react to produce a third resin. Also, the reaction between resin precursors X and Y is not limited to a reaction that proceeds simply by contact between resin generating solution X and resin generating solution Y, but may also proceed by contact between resin generating solution X and resin generating solution Y and accompanied by a predetermined treatment (such as heating). Specifically, one of the resin precursor X and resin precursor Y can be selected from diglycidyl ether and polyisocyanate, and the other can be selected from diamine, etc. Examples of the third resin produced from such resin precursors X and Y include epoxy resin and urea resin.

[0084] The content of resin precursor X is preferably 20.0% by mass or more relative to the mass of resin generating solution X. Furthermore, the content of resin precursor Y is preferably 20.0% by mass or more relative to the mass of resin generating solution Y. By having a content of 20.0% by mass or more for both resin precursor X and resin precursor Y, the relative sintering density of the sintered product formed by sintering the sintering inhibiting portion can be further reduced.

[0085] <Lamination process> The method for manufacturing a molded object includes a lamination process that forms a laminate by sequentially repeating a powder layer formation process, a molding fluid application process, and a sintering inhibitor application process. The molding fluid application process and the sintering inhibitor application process are performed after the powder layer formation process, but the order of the molding fluid application process and the sintering inhibitor application process is not particularly limited. A "laminated object" is a structure in which multiple layers of powder having a molding region and a sintering inhibitor region are stacked, and may also be a structure in which multiple layers of powder having a molding region, a sintering inhibitor region, and a support region are stacked.

[0086] <Heating process> The manufacturing method for the molded object preferably includes a heating step in which the laminate is heated to a temperature corresponding to the softening point of the resin contained in the laminate. The softened resin causes sinterable particles to bond together, creating a molded part (green body, unsintered body) that maintains a certain three-dimensional shape. Furthermore, if the first resin contained in the sintering inhibitor changes into a chemically different second resin due to heating performed after the sintering inhibitor is applied to the powder layer, the heating step may be at a temperature that promotes this change. The heating method is not particularly limited, but for example, a dryer or a constant temperature and humidity chamber can be used.

[0087] <Excess powder removal process> The method for manufacturing a shaped object preferably includes a surplus powder removing step of removing surplus powder which is powder not applied with a shaping liquid, a sintering inhibiting liquid, or the like. The surplus powder removing step preferably includes at least one step selected from a step of removing surplus powder by air blow and a step of removing surplus powder by immersing in a removing liquid, and more preferably includes both steps.

[0088] When removing surplus powder by air blow, the shaping part or the like preferably has a strength capable of withstanding the pressure of the air blow. For example, the three-point bending stress is preferably 3 MPa or more, and more preferably 5 MPa or more.

[0089] When removing surplus powder by immersing in a removing liquid, the used removing liquid contains an organic solvent or the like and may contain other components as required.

[0090] Examples of the organic solvent include ketones, halogens, alcohols, esters, ethers, hydrocarbons, glycols, glycol ethers, glycol esters, pyrrolidones, amides, amines, and carbonates.

[0091] <Drying step> The method for manufacturing a shaped object preferably includes a drying step of removing liquid components remaining in the shaping part, the sintering inhibiting part, or the like. As drying means, for example, a known dryer, a thermostatic and humidistatic chamber, or the like can be used.

[0092] <Debinding step> The method for manufacturing a shaped object preferably includes a debinding step of obtaining a debound object by heating the shaping part, the sintering inhibiting part, or the like to remove at least a part of a resin or the like contained in each part. The debinding step uses debinding means and is performed at a temperature not lower than the thermal decomposition temperature of an organic component such as a resin and not higher than the melting point or solidus temperature of a material constituting sinterable particles (for example, AlSi 10If Mg particles are used, the organic components are decomposed and removed by heating at a temperature lower than approximately 570°C for a certain period of time (for example, 1 to 10 hours). Examples of degreasing methods include known sintering furnaces and electric furnaces.

[0093] <Sintering process> The manufacturing method for the molded object preferably includes a sintering step in which degreased material such as the molding section and the sintering inhibiting section is heated to obtain a sintered product. The sintering process involves using a sintering means to heat the degreased material for a certain period of time (e.g., 1 to 10 hours) at a heating temperature above the solidus temperature and below the liquidus temperature of the material constituting the sinterable particles, thereby integrating the material constituting the sinterable particles. As for the heating temperature, for example, if aluminum-containing particles are used as the sinterable particles, a temperature of 550°C to 600°C is preferred. More specifically, if AlSi is used as the sinterable particle... 10 If Mg particles are used, a temperature of 570°C to 600°C is preferred. Examples of sintering methods include known sintering furnaces, but the same method as the degreasing method described above may also be used. Furthermore, the degreasing and sintering processes may be performed consecutively.

[0094] <Post-processing steps> The manufacturing method for a molded object preferably includes a post-processing step that performs post-treatment on the molded part and the sintering-inhibiting part of the sintered material. There are no particular limitations on the post-processing step, and it can be appropriately selected depending on the purpose. Examples include a step of separating the sintering-inhibiting part and other sintered material from the sintered material of the molded part, a step of performing surface protection treatment, and a step of painting.

[0095] <The process of creating the sculpture> The molding process in the manufacturing method of the molded object described herein will be explained with reference to Figures 6A to 6E. Figures 6A to 6E are schematic diagrams showing an example of the operation of the molded object manufacturing apparatus.

[0096] First, we will explain the state in which the first layer of powder 30 has been formed on the molding stage of the molding tank. When forming the next layer of powder on top of the first layer of powder 30, as shown in Figure 6A, the supply stage 23 of the supply tank is raised and the molding stage 24 of the molding tank is lowered. At this time, the lowering distance of the molding stage 24 is set so that the distance (layer pitch) between the upper surface of the powder layer in the molding tank 22 and the lower part (lower tangential part) of the flattening roller 12 is Δt1. The distance Δt1 is not particularly limited, but it is preferably about several tens to 100 μm.

[0097] In this disclosure, the flattening roller 12 is positioned such that a gap is created between it and the upper surfaces of the supply tank 21 and the molding tank 22. Therefore, when the powder 20 is transferred and supplied to the molding tank 22 for flattening, the upper surface of the powder layer is higher than the upper surfaces of the supply tank 21 and the molding tank 22. This reliably prevents the flattening roller 12 from 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 are likely to appear on the surface of the powder layer 31 (see Figure 6D) supplied to the molding tank 22, reducing its flatness.

[0098] Next, as shown in Figure 6B, the powder 20, which is positioned higher than the upper end surface of the supply tank 21, is transferred and supplied to the build tank 22 by moving the flattening roller 12 toward the build tank 22 while rotating it in the direction of the arrow (powder supply). Furthermore, as shown in Figure 6C, the flattening roller 12 is moved parallel to the stage surface of the build stage 24 of the build tank 22 to form a powder layer 31 of a predetermined thickness Δt1 on the build tank 22 of the build stage 24 (flattening). At this time, any excess powder 20 that was not used to form the powder layer 31 falls into the excess powder receiving tank 29. After the powder layer 31 is formed, the flattening roller 12 is moved toward the supply tank 21 and returned to its initial position (origin position) as shown in Figure 6D (return).

[0099] 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 region and sintering inhibition region 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.

[0100] Subsequently, as shown in Figure 6E, droplets 10 of the molding fluid and sintering inhibitory fluid are discharged from the head 52 of the liquid discharge unit, respectively, to laminate and form a molding region and a sintering inhibitory fluid 30 of the desired shape on the next powder layer 31. Next, the powder layer formation step, molding fluid application step, and sintering inhibitory fluid application step described above are repeated to form and laminate new molding regions and sintering inhibitory fluid 30. At this time, the new molding regions and sintering inhibitory fluid 30 and the molding regions and sintering inhibitory fluid 30 of the layer below them become one. Thereafter, the powder layer formation step, molding fluid application step, and sintering inhibitory fluid application step are repeated to complete the laminate. [Examples]

[0101] The following describes embodiments of the present invention, but the present invention is not limited in any way to these embodiments.

[0102] <Preparation of sintering inhibitor solution and sintering inhibitor solution set> (Adjustment Example 1) Polyvinylpyrrolidone (product name: PVP-K15, weight-average molecular weight (Mw): 10,000, manufactured by Tokyo Chemical Industry Co., Ltd.) and γ-butyrolactone were mixed and dissolved by stirring with a magnetic stirrer for 6 hours. After stirring, the solution was passed through a 1 μm filter to obtain the sintering inhibitor solution of Preparation Example 1. The content of polyvinylpyrrolidone, the first resin, in the sintering inhibitor solution of Preparation Example 1 was 20.0% (w / v).

[0103] (Adjustment Example 2) Polyvinylpyrrolidone (product name: PVP K-25, weight-average molecular weight (Mw): 25,000, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and γ-butyrolactone were mixed and dissolved by stirring with a magnetic stirrer for 6 hours. After stirring, the solution was passed through a 1 μm filter to obtain the sintering inhibitor solution of Preparation Example 2. The content of polyvinylpyrrolidone, the first resin, in the sintering inhibitor solution of Preparation Example 2 was 16.7% (w / v).

[0104] (Adjustment Example 3) A vinyl chloride-vinyl acetate copolymer (product name: Solvine TAO, weight-average molecular weight (Mw): 26,000, manufactured by Nisshin Chemical Co., Ltd.) was mixed with octyl acetate and dissolved by stirring with a magnetic stirrer for 6 hours. After stirring, the solution was passed through a 1 μm filter to obtain the sintering inhibitor solution of Preparation Example 3. The content of the first resin, the vinyl chloride-vinyl acetate copolymer, in the sintering inhibitor solution of Preparation Example 3 was 9.0% (w / v).

[0105] (Adjustment Example 4) Cellulose acetate (manufactured by Daicel Corporation) and triethyl phosphate were mixed and dissolved by stirring with a magnetic stirrer for 6 hours. After stirring, the mixture was passed through a 1 μm filter to obtain the sintering inhibitor solution of Preparation Example 4. The content of cellulose acetate, the first resin, in the sintering inhibitor solution of Preparation Example 4 was 6.0% (w / v).

[0106] (Adjustment example 5) Melamine microparticles (product name: Epostor SS, volume-average particle size: 100 nm, manufactured by Nippon Shokubai Co., Ltd.) were mixed with triethylene glycol dimethyl ether and dispersed using a homogenizer to obtain the sintering inhibitor solution of Preparation Example 5. The content of melamine microparticles, which are the first resin, in the sintering inhibitor solution of Preparation Example 5 was 8.0% (w / v).

[0107] (Adjustment example 6) Benzoguanamine microparticles (product name: Epostor MS, volume-average particle size: 2 μm, manufactured by Nippon Shokubai Co., Ltd.) and triethylene glycol dimethyl ether were mixed and dispersed using a homogenizer to obtain the sintering inhibitor solution of Preparation Example 6. The content of benzoguanamine microparticles, which are the first resin, in the sintering inhibitor solution of Preparation Example 6 was 8.0% (w / v).

[0108] (Adjustment Example 7) By combining the following resin-generating solutions X and Y, the sintering inhibitory solution set of adjustment example 7 was obtained.

[0109] -Preparation of resin-forming solution X- Bisphenol A-diglycidyl ether and neopentyl glycol diglycidyl ether were mixed and stirred for 6 hours using a magnetic stirrer. After stirring, the mixture was passed through a 1 μm filter to obtain resin-producing solution X. The content of bisphenol A-diglycidyl ether and neopentyl glycol diglycidyl ether, which are resin precursors X, in resin-producing solution X was 100.0% (w / v).

[0110] -Preparation of resin-forming solution Y- Polyamine (product name: Fujicure FXH-8095, manufactured by T&K TOKA) and 1,3-bisaminomethylcyclohexane were mixed and stirred for 6 hours using a magnetic stirrer. After stirring, the mixture was passed through a 1 μm filter to obtain resin-producing solution Y. The content of polyamine and 1,3-bisaminomethylcyclohexane, which are the resin precursors Y, in resin-producing solution Y was 100.0% (w / v).

[0111] (Adjustment example 8) By combining the following resin-generating solutions X and Y, the sintering inhibitory solution set of adjustment example 8 was obtained.

[0112] -Preparation of resin-forming solution X- Cyanatomethylcyclohexane-trimethylolpropane adduct (trade name: Takenate D120N, manufactured by Mitsui Chemicals, Inc.) and propylene glycol monomethyl ether acetate were mixed and stirred for 6 hours using a magnetic stirrer. After stirring, the mixture was passed through a 1 μm filter to obtain resin-producing solution X. The content of the resin precursor X, cyanatomethylcyclohexane-trimethylolpropane adduct, in resin-producing solution X was 30.0% (w / v).

[0113] -Preparation of resin-forming solution Y- 1,3-bisaminomethylcyclohexane was passed through a 1 μm filter to obtain resin-producing solution Y. The content of 1,3-bisaminomethylcyclohexane, the resin precursor Y, in resin-producing solution Y was 100.0% (w / v).

[0114] (Comparison and adjustment example 1) Ceramic microparticles (zirconia powder, trade name: TZ-3Y-E, manufactured by Tosoh Corporation) and triethylene glycol dimethyl ether were mixed and dispersed using a homogenizer to obtain the sintering inhibitory solution of Comparative Adjustment Example 1. The content of ceramic microparticles in the sintering inhibitory solution of Comparative Adjustment Example 1 was 8.0% (w / v). For convenience in the table 1, ceramic microparticles are listed under the "First Resin" column, and their content is listed under the "Content of First Resin [%(w / v)]" column.

[0115] (Comparison and adjustment example 2) Polyvinylpyrrolidone (product name: PVP-K15, weight-average molecular weight (Mw): 10,000, manufactured by Tokyo Chemical Industry Co., Ltd.) and γ-butyrolactone were mixed and dissolved by stirring with a magnetic stirrer for 6 hours. After stirring, the solution was passed through a 1 μm filter to obtain the sintering inhibitor solution for comparative adjustment example 2. The polyvinylpyrrolidone content in the sintering inhibitor solution for comparative adjustment example 2 was 9.0% (w / v).

[0116] (Comparison and adjustment example 3) By combining the following resin-generating solutions X and Y, the sintering inhibitory solution set of comparative adjustment example 3 was obtained.

[0117] -Preparation of resin-forming solution X- Cyanatomethylcyclohexane-trimethylolpropane adduct (trade name: Takenate D120N, manufactured by Mitsui Chemicals, Inc.) and propylene glycol monomethyl ether acetate were mixed and stirred for 6 hours using a magnetic stirrer. After stirring, the mixture was passed through a 1 μm filter to obtain resin-producing solution X. The content of cyanatomethylcyclohexane-trimethylolpropane adduct in resin-producing solution X was 30.0% (w / v).

[0118] -Preparation of resin-forming solution Y- 1,3-propanediol and propylene glycol monomethyl ether acetate were mixed and stirred using a magnetic stirrer for 6 hours. After stirring, the mixture was passed through a 1 μm filter to obtain resin-forming solution Y. The 1,3-propanediol content in resin-forming solution Y was 30.0% (w / v).

[0119] The compositions of the sintering inhibitors mentioned above are shown in Table 1 below, and the compositions of the sintering inhibitor sets are shown in Table 2 below.

[0120] [Table 1]

[0121] [Table 2]

[0122] [Dispersibility (discharge stability)] The prepared sintering inhibitor and each resin-generating liquid constituting the sintering inhibitor set were each filled into an inkjet head GH5420 (manufactured by Ricoh Co., Ltd.) and allowed to stand for a certain period of time. Afterward, the stability of the ejection state was observed using a strobe camera. An expanded coating device EV2500 (manufactured by Ricoh Co., Ltd.) was used for ejection. The observation results were evaluated based on the following evaluation criteria, and the evaluation results are shown in Tables 3 and 4 below. (Evaluation Criteria) A: When the standing time is set to 10 minutes, the discharge can be made without bending or nozzle slippage. B: When the standing time is 3 minutes, the discharge can be performed without any misalignment or nozzle detachment. When the standing time is 10 minutes, misalignment or nozzle detachment occurs, but the discharge can be restored to a normal state by maintenance operations such as pressurized discharge. C: When the standing time is set to 3 minutes, discharge bends or nozzle detachment occurs, and the normal discharge state cannot be restored even by maintenance operations such as pressurized discharge.

[0123] [Storage stability] The prepared sintering inhibitor and each resin-generating solution constituting the sintering inhibitor set were sealed and stored in 100 mL vials. After standing for a certain period of time, the state of each liquid was evaluated based on the evaluation criteria below. The evaluation results are shown in Tables 3 and 4 below. (Evaluation Criteria) A: No precipitate forms after standing for a day, and there is no concentration unevenness between the upper and lower parts of the liquid. B: When left standing for a day, uneven concentration will occur between the upper and lower parts of the liquid, but it will return to a uniform state after shaking 2-3 times. C: When left standing for a day, a precipitate forms and does not return to a uniform state unless shaken thoroughly. Even with shaking, uneven concentration occurs between the upper and lower parts of the liquid.

[0124] [viscosity] The viscosity of the prepared sintering inhibitor and each resin-forming liquid constituting the sintering inhibitor set was measured at 25°C, and all were found to be 30 mPa·s or less.

[0125] <Preparation of sample> (Examples 1-8, Comparative Examples 1-3) Prepared sintering inhibitor or sintering inhibitor set, and powder (AlSi 10 Using Mg powder (manufactured by Toyo Aluminum Co., Ltd., Si10Mg-30BB, volume-average particle size: 35 μm), a sample body that can be considered a sintering inhibition region was prepared as follows.

[0126] 1) First, using a known manufacturing apparatus for molded objects as shown in Figures 6A to 6E, powder was transferred from the supply-side powder storage tank to the molding-side powder storage tank, and a thin layer (1 layer) of powder with an average thickness of 84 μm was formed on the support.

[0127] 2) Next, a sintering inhibitor or each resin-generating liquid constituting the sintering inhibitor set was dispensed onto the surface of the thin layer formed by the powder from the nozzle of a known inkjet ejection head. When applying the sintering inhibitor, it was dispensed at a rate of 45 pL per 300 dpi × 300 dpi area. When applying each resin-generating liquid constituting the sintering inhibitor set, resin-generating liquid X was dispensed at a rate of 22.5 pL per 300 dpi × 300 dpi area, and then resin-generating liquid Y was dispensed at a rate of 22.5 pL per 300 dpi area.

[0128] 3) Next, sample bodies containing "the first resin or the second resin" or "the third resin" were prepared by placing them in a vacuum environment at 200°C for 4 hours using a vacuum dryer.

[0129] 4) Next, the sample was degreased by heating to obtain a degreased product. Furthermore, the degreased product was sintered by heating to produce a sintered product.

[0130] Next, the thermal decomposition residue rate at 550°C for the "first resin or second resin" or "third resin" contained in the sample body prepared in step 3) above was calculated, and the evaluation results are shown in Tables 3-4 below. The pyrolysis residue rate was calculated based on the following formula: "Mass of residue when the first or second resin is pyrolyzed at 550°C / Mass of the first or second resin before pyrolysis". The mass of residue when the first or second resin is pyrolyzed at 550°C was measured using a TG-DTA (Differential Thermal Analysis and Thermogravimetric Analysis System). Specifically, the temperature was raised from 30°C to 550°C at a rate of 10°C / min in an air or nitrogen atmosphere, and then the temperature was maintained for 2 hours after reaching 550°C. The weight after the temperature increase (residue mass) was then determined. Furthermore, the polyvinylpyrrolidones used as the first resin in the sintering inhibitors of Examples 1 and 2 and Comparative Example 2 underwent a crosslinking reaction during the heating step described in 3) above, producing polyvinylpolypyrrolidone as the second resin.

[0131] Next, the predicted amount of residue was calculated by multiplying the mass ratio of the first or second resin to the powder in the sintering inhibition region (sintering inhibition area) by the thermal decomposition residue rate of the first or second resin at 550°C, and the evaluation results are shown in Tables 3-4 below.

[0132] [Relative sintering density] First, the density of the sintered material prepared in step 4) above was measured. Next, the ratio of the density of the sintered material to the true density of the materials constituting the sintered material was calculated, and the calculation results are shown in Tables 3-4 below.

[0133] [Table 3]

[0134] [Table 4]

[0135] According to Examples 1 and 2, we were able to obtain a sintering inhibitor with excellent dispersibility and storage stability. Furthermore, we were able to obtain a sintering inhibitor that can provide a sintered product with a low relative sintering density. In addition, we were able to obtain a sintering inhibitor that improves the handling of the sintering inhibitory portion by having a binder function that binds particles together in the powder layer.

[0136] Examples 3-4 yielded sintering inhibitors with excellent dispersibility and storage stability. Furthermore, although slightly inferior to Examples 1-2 due to the different resin types, sintering inhibitors were obtained that provided sintered products with low relative sintering density. Additionally, although slightly inferior to Examples 1-2 due to the different resin types, sintering inhibitors were obtained that improved the handling of the sintering inhibitory portion through a binder function that binds particles together in the powder layer. However, these examples were superior to Examples 1-2 in that they did not require the chemical modification of the first resin through a heating process.

[0137] According to Example 5, although slightly inferior to Examples 1 and 2 due to the resin being in a dispersed form, a sintering inhibitor with excellent dispersibility and storage stability was obtained. Furthermore, a sintering inhibitor capable of producing sintered products with low relative sintering density was obtained. In addition, it was advantageous in that it could be used in combination with resins having binder functions, as it could exert a sintering inhibitory effect with only a small amount of addition.

[0138] According to Example 6, although slightly inferior to Examples 1-2 due to the dispersed resin, a sintering inhibitor with excellent dispersibility was obtained. Furthermore, a sintering inhibitor capable of producing a sintered product with low relative sintering density was obtained. Additionally, it was advantageous in that it could be used in combination with resins having binder properties, as it exerted a sintering inhibitory effect with only a small amount of addition. However, its dispersibility was poor due to the large volume-average particle size of the resin.

[0139] According to Comparative Example 1, while it was possible to provide a sintered product with a low relative sintering density, the high specific gravity of the ceramic fine particles resulted in poor dispersibility and storage stability.

[0140] According to Comparative Example 2, although the same materials as in Example 1 were used, it was difficult to provide a sintered product with a low relative sintering density due to the low resin content.

[0141] According to Example 7, a sintering inhibitor with excellent dispersibility and storage stability was obtained. Furthermore, although slightly inferior to Examples 1 and 2, a sintering inhibitor capable of providing a sintered product with a low relative sintering density was obtained.

[0142] According to Example 8, a sintering inhibitor with excellent dispersibility and storage stability was obtained. Furthermore, a sintering inhibitor capable of providing a sintered product with a low relative sintering density was obtained.

[0143] According to Comparative Example 3, because the material used in Example 8 was changed, it was difficult to provide a sintered product with a low relative sintering density.

[0144] <Preparation of molding fluid> Polyvinyl butyral (Seslec BL-10, manufactured by Sekisui Chemical Co., Ltd.) and triethylene glycol dimethyl ether (Triglime, manufactured by Sankyo Chemical Co., Ltd.) were mixed and dissolved by stirring for 30 minutes using a homomixer. After stirring, the mixture was passed through a 1 μm filter to obtain the 3D printing solution. The polyvinyl butyral content in the 3D printing solution was 7.0% by mass relative to the mass of the 3D printing solution.

[0145] <Creation of Sculptural Objects> (Example 9) The sintering inhibitor liquid, molding fluid, and powder (AlSi) are used in adjustment example 1. 10 Using Mg powder (manufactured by Toyo Aluminum Co., Ltd., Si10Mg-30BB, volume-average particle size: 35 μm), the molded object was manufactured as follows.

[0146] 1) First, using a known manufacturing apparatus for molded objects as shown in Figures 6A to 6E, powder was transferred from the supply-side powder storage tank to the molding-side powder storage tank, and a thin layer of powder with an average thickness of 84 μm was formed on the support.

[0147] 2) Next, a build medium was dispensed from the nozzle of a known inkjet ejection head onto the surface of the formed powder thin layer to form the build area and support area. When applying the build medium, 45 pL was dispensed per 300 dpi × 300 dpi area. Furthermore, a sintering inhibitor was dispensed from the nozzle of a known inkjet ejection head onto the surface of the formed powder thin layer to form a sintering inhibitor area. When applying the sintering inhibitor, 45 pL was dispensed per 300 dpi × 300 dpi area. The build medium and sintering inhibitor were dispensed so that the build area and support area were adjacent to each other with the sintering inhibitor area in between.

[0148] 3) Next, the operations described in 1) and 2) above were repeated until a predetermined average layer thickness (total thickness of the fabricated object, 15 mm) was reached, thereby forming a laminate having a fabricated section formed by stacking fabrication regions, a sintering inhibition section formed by stacking sintering inhibition regions, and a support section formed by stacking support regions, wherein the support section is arranged to support the fabricated section via the sintering inhibition section.

[0149] 4) Next, the samples were placed in a vacuum at 200°C for 4 hours using a vacuum dryer.

[0150] 5) Next, excess powder was removed by air blowing.

[0151] 6) Next, the structure consisting of the molding section, the sintering inhibition section, and the support section was degreased by heating to obtain a degreased material. Furthermore, the degreased material was sintered by heating to obtain a sintered material.

[0152] 7) Next, the sintered material from the sintering inhibitory part and the support part was removed to obtain the fabricated object.

[0153] In the sintered material obtained in 6) above, the relative sintering density of the molded area and the support area was 93%, indicating that sintering had progressed and the particle shape of the sinterable material had been densified in the molded area and the support area. On the other hand, the relative sintering density of the sintering inhibition area was 56%, indicating that sintering had hardly progressed, and the particle shape of the sinterable material was maintained in the sintering inhibition area. A microscope image of the sintered material in the molded area is shown in Figure 7, and a microscope image of the sintered material in the sintering inhibition area is shown in Figure 8. The microscope images were captured using a Keyence VHX-7000. Furthermore, during the degreasing and sintering processes described in 6) above, the deformation of the molded part was suppressed by the support structure, resulting in a molded object with high dimensional accuracy. Furthermore, in 7) above, since there were minute cracks in the sintered body of the sintering inhibiting part, it was easy to detach the sintered material of the sintering inhibiting part and the support part to obtain the sintered body of the molded part.

[0154] (Comparative Example 4) In Example 9, the fabricated object was prepared in the same manner as in Adjustment Example 1, except that the molding fluid was used instead of the sintering inhibitor. As a result, sintering progressed, and the particle shape of the sinterable material was densified in all parts: the molded area, the sintering inhibiting area, and the support area. Consequently, as described in 7) above, it was difficult to detach the sintered material from the sintering inhibiting area and the support area to obtain the sintered body of the molded area.

[0155] (Example 10) In Example 9, the fabricated object was manufactured in the same manner as in 2) above, except that the amount of sintering inhibitor applied was increased from 45 pL to 200 pL. As a result, the strength of the sintering inhibition area before degreasing as described in 6) above improved, leading to improved handling. Furthermore, in the sintered product obtained in 6) above, the relative sintering density of the sintering inhibition area was further reduced, making it easier to separate the sintered material of the sintering inhibition area and the support area to obtain the sintered body of the molded part as described in 7) above.

[0156] (Example 11) After completing step 2) of Example 9, the object was fabricated in the same manner as above, except that the sintering inhibition region was further treated by ejecting the molten material from the nozzle of a known inkjet ejection head. When the molten material was applied to the sintering inhibition region afterward, the amount dispensed was 45 pL per 300 dpi × 300 dpi area. As a result, the strength of the sintering-inhibiting area before degreasing as described in 6) above was improved, resulting in improved handling. In addition, by making the resin degreasing a two-stage process, excessive cracking of the sintering-inhibiting area during degreasing as described in 6) above was suppressed.

[0157] (Example 12) In Example 9, step 2) above, the molded object was produced in the same manner as shown in Figure 3, except that the molding fluid and sintering inhibitory liquid were dispensed so that the sintering inhibitory region was arranged to surround the molding region in the powder layer. As a result, the collapse of the sintering-inhibiting parts during the sintering process described in 6) above was suppressed, and the dimensional accuracy of the fabricated object was improved.

[0158] (Example 13) In Example 9, step 2) above, the fabricated object was manufactured in the same manner as described above, except that the timing of the application of droplets of the molding fluid ejected at the position forming the boundary between the fabrication area and the sintering inhibition area, and droplets of the sintering inhibition liquid ejected adjacent to them, was adjusted so that the droplets of the sintering inhibition liquid were applied within 100 msec after the droplets of the molding fluid were applied. As a result, the seepage of the molding fluid applied to the powder into areas that inhibit sintering was suppressed, improving the dimensional accuracy of the molded object.

[0159] (Example 14) In Example 9, the fabricated object was manufactured in the same manner as described in 3) above, except that a laminate was formed which included a composite material in which multiple fabricated parts and connecting parts consisting of sintering inhibiting parts connecting the fabricated parts were integrated, as shown in Figure 4. As a result, the amount of work required to rearrange multiple molded parts and place them in the sintering furnace before sintering (as described in 6) above) was reduced, improving work efficiency during the manufacturing of the molded object.

[0160] (Example 15) In Example 9, step 3) above, a laminate was formed including a molding section and a sintering inhibition section having a structure that covers the entire circumference of the molding section and a plate-like structure that is continuous with the outer surface of the laminate and divides the outer surface of the laminate into two regions, as shown in Figure 5. Furthermore, the molding was carried out in the same manner as in step 5) above, except that the step of removing excess powder by air blowing was omitted. As a result, excess powder cannot adhere to the molded part, eliminating the need for the excess powder removal process and improving productivity during the manufacturing of molded objects.

[0161] Examples of the present invention are as follows: <1> A powder layer formation step in which a powder layer containing sinterable particles is formed, A process of applying a molding liquid to the powder layer to form a molding region, The process includes a step of applying a sintering inhibitor to the powder layer to form a sintering inhibitory region where the sintering of the particles is inhibited, A method for manufacturing a molded object, comprising a lamination step in which the powder layer formation step, the molding liquid application step, and the sintering inhibitor application step are sequentially repeated to form a laminate, The molding region and the sintering inhibition region are adjacent to each other. The sintering inhibitory liquid contains a first resin, The sintering inhibiting region contains the first resin or a second resin derived from the first resin. The method for manufacturing a molded object is characterized in that the predicted amount of residue, calculated by multiplying the mass ratio of the first resin or the second resin to the powder in the sintering inhibiting portion formed by stacking the sintering inhibiting regions, by the thermal decomposition residue rate of the first resin or the second resin at 550°C, is 800 ppm or more. <2> The predicted residue amount is 1000 ppm or more. <1> This is a method for manufacturing the molded object described above. <3> In the sintering inhibitory liquid, the first resin is dissolved. <1> or <2> This is a method for manufacturing the molded object described above. <4> In the sintering inhibitory liquid, the first resin is dispersed <1> or <2> This is a method for manufacturing the molded object described above. <5> The volume-average particle size of the first resin is 1 μm or less. <4> This is a method for manufacturing the molded object described above. <6> The thermal decomposition residue rate of the first resin or the second resin at 550°C is 0.100 or more. <1> from <5> This is a method for manufacturing a molded object as described in any of the above. <7> The viscosity of the sintering inhibitor at 25°C is 30 mPa·s or less. <1> from <6> This is a method for manufacturing a molded object as described in any of the above. <8> The sintering inhibiting region contains the second resin, The thermal decomposition residue rate of the second resin in the sintering inhibitory portion at 550°C is higher than that of the first resin at 550°C. <1> from <7> This is a method for manufacturing a molded object as described in any of the above. <9> The sintering inhibiting region contains the second resin, The second resin of the sintering inhibitor is generated by the crosslinking reaction of the first resin. <1> from <8> This is a method for manufacturing a molded object as described in any of the above. <10> The first resin is polyvinylpyrrolidone. <1> from <9> This is a method for manufacturing a molded object as described in any of the above. <11> The first resin is at least one selected from the group consisting of polyvinyl chloride, polyvinylidene chloride, cellulose acetate, polyacronitrile, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, vinyl chloride-vinyl acetate copolymer, polyethylene terephthalate, phenol resin, melamine resin, urea resin, unsaturated polyester, epoxy resin, silicone resin, polyvinylpolypyrrolidone, and benzoguanamine resin. <1> from <7> This is a method for manufacturing a molded object as described in any of the above. <12> The particles contain aluminum. <1> from <11> This is a method for manufacturing a molded object as described in any of the above. <13> The relative sintering density of the sintered product formed by sintering the sintering inhibiting portion formed by stacking the aforementioned sintering inhibiting regions is 60% or less. <1> from <12> This is a method for manufacturing a molded object as described in any of the above. <14> The molding fluid application step is a step of applying the molding fluid to the powder layer to form the molding region and support region. The molding region and the support region are adjacent to the sintering inhibition region. <1> from <13> This is a method for manufacturing a molded object as described in any one of the items. <15> The amount of sintering inhibitor applied per unit area in the sintering inhibition region is greater than the amount of molding fluid applied per unit area in the molding region. <1> from <14> This is a method for manufacturing a molded object as described in any one of the items. <16> The post-formation step further involves applying the formwork fluid to the formed sintering inhibition region. <1> from <14> This is a method for manufacturing a molded object as described in any one of the items. <17> The molding region is surrounded by the sintering inhibition region. <1> from <14> This is a method for manufacturing a molded object as described in any one of the items. <18> At the boundary between the molding region and the sintering inhibition region, the sintering inhibition liquid is applied within 100 msec after the molding liquid is applied. <1> from <14> This is a method for manufacturing a molded object as described in any one of the items. <19> The laminate has a plurality of molded parts formed by stacking the molded areas, and connecting parts that connect the molded parts. At least the region of the connecting portion that contacts the molded portion is formed by stacking the sintering inhibiting regions. <1> from <14> This is a method for manufacturing a molded object as described in any one of the items. <20> The laminate has a molded portion formed by stacking the molded regions and a sintering inhibiting portion formed by stacking the sintering inhibiting regions. The molded part is covered all around by the sintering inhibiting part. <1> from <14> This is a method for manufacturing a molded object as described in any one of the items. <21> A powder layer formation step in which a powder layer containing sinterable particles is formed, A process of applying a molding liquid to the powder layer to form a molding region, The process includes a step of independently applying resin generating liquid X and resin generating liquid Y to the powder layer, thereby forming a sintering inhibiting liquid set application step in the powder layer after application, where the resin generating liquid X and resin generating liquid Y come into contact, thereby inhibiting the sintering of the particles. A method for manufacturing a molded object, comprising a lamination step of sequentially repeating the powder layer formation step, the molding liquid application step, and the sintering inhibitor set application step to form a laminate, The molding region and the sintering inhibition region are adjacent to each other. The sintering inhibition region contains a third resin produced by the contact between the resin generating liquid X and the resin generating liquid Y. The method for manufacturing a molded object is characterized in that the predicted amount of residue, calculated by multiplying the mass ratio of the third resin to the powder in the sintering inhibiting portion formed by stacking the sintering inhibiting regions by the thermal decomposition residue rate of the third resin at 550°C, is 800 ppm or more.

[0162] The aforementioned <1> from <21> According to the method for manufacturing molded objects described in any of the above, the conventional problems can be solved and the objectives of the present invention can be achieved. [Prior art documents] [Patent Documents]

[0163] [Patent Document 1] U.S. Public Notice 2019 / 0375014

Claims

1. A powder layer formation step in which a powder layer containing sinterable particles is formed, A process of applying a molding liquid to the powder layer to form a molding region, The process includes a step of applying a sintering inhibitor to the powder layer to form a sintering inhibitory region where the sintering of the particles is inhibited, A method for manufacturing a molded object, comprising a lamination step in which the powder layer formation step, the molding liquid application step, and the sintering inhibitor application step are sequentially repeated to form a laminate, The molding region and the sintering inhibition region are adjacent to each other. The sintering inhibitory liquid contains a first resin, The sintering inhibiting region contains the first resin or a second resin derived from the first resin. A method for manufacturing a molded object, characterized in that the predicted amount of residue calculated by multiplying the mass ratio of the first resin or the second resin to the powder in the sintering inhibiting portion formed by stacking the sintering inhibiting regions is 1000 ppm or more and 1604 ppm or less, by the thermal decomposition residue rate of the first resin or the second resin at 550°C.

2. The method for producing a molded product according to claim 1, wherein the first resin is at least one selected from the group consisting of polyvinyl chloride, polyvinylidene chloride, cellulose acetate, polyacronitrile, acrylonitrile-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, vinyl chloride-vinyl acetate copolymer, polyethylene terephthalate, phenolic resin, melamine resin, urea resin, unsaturated polyester, epoxy resin, silicone resin, polyvinylpolypyrrolidone, and benzoguanamine resin.

3. The method for manufacturing a molded object according to claim 1, wherein the first resin is polyvinylpyrrolidone.

4. A powder layer formation step in which a powder layer containing sinterable particles is formed, A process of applying a molding liquid to the powder layer to form a molding region, The process includes a step of applying a sintering inhibitor to the powder layer to form a sintering inhibitory region where the sintering of the particles is inhibited, A method for manufacturing a molded object, comprising a lamination step in which the powder layer formation step, the molding liquid application step, and the sintering inhibitor application step are sequentially repeated to form a laminate, The molding region and the sintering inhibition region are adjacent to each other. The sintering inhibitory liquid contains a first resin, The sintering inhibiting region contains the first resin or a second resin derived from the first resin. In the sintering inhibition portion formed by stacking the aforementioned sintering inhibition regions, the predicted amount of residue calculated by multiplying the mass ratio of the first resin or the second resin to the powder by the thermal decomposition residue rate of the first resin or the second resin at 550°C is 800 ppm or more and 1604 ppm or less. A method for manufacturing a molded object, characterized in that the first resin is polyvinylpyrrolidone.

5. A method for manufacturing a molded product according to any one of claims 1 to 4, wherein the first resin is dissolved in the sintering inhibitory liquid.

6. A method for manufacturing a molded product according to any one of claims 1 to 4, wherein the first resin is dispersed in the sintering inhibitory liquid.

7. The method for manufacturing a molded product according to claim 6, wherein the volume-average particle size of the first resin is 1 μm or less.

8. The method for manufacturing a molded product according to any one of claims 1 to 7, wherein the thermal decomposition residue rate of the first resin or the second resin in the sintering inhibiting portion at 550°C is 0.100 or more.

9. The method for manufacturing a molded product according to any one of claims 1 to 8, wherein the viscosity of the sintering inhibitory liquid at 25°C is 30 mPa·s or less.

10. The sintering inhibiting region contains the second resin, The method for manufacturing a molded product according to any one of claims 1 to 9, wherein the thermal decomposition residue rate of the second resin in the sintering inhibiting portion at 550°C is higher than the thermal decomposition residue rate of the first resin at 550°C.

11. The sintering inhibiting region contains the second resin, The method for manufacturing a molded product according to any one of claims 1 to 10, wherein the second resin of the sintering inhibiting portion is produced by a crosslinking reaction of the first resin.

12. The method for manufacturing a molded object according to any one of claims 1 to 11, wherein the particles contain aluminum.

13. The method for manufacturing a molded product according to any one of claims 1 to 12, wherein the relative sintering density of the sintered product formed by sintering the sintering inhibiting portion formed by stacking the sintering inhibiting regions is 60% or less.

14. The molding fluid application step is a step of applying the molding fluid to the powder layer to form the molding region and support region. A method for manufacturing a molded object according to any one of claims 1 to 13, wherein the molding region and the support region are adjacent via the sintering inhibition region.

15. A method for manufacturing a molded object according to any one of claims 1 to 14, wherein the amount of sintering inhibitor applied per unit area in the sintering inhibitory region is greater than the amount of molding liquid applied per unit area in the molding region.

16. The method for manufacturing a molded object according to any one of claims 1 to 14, wherein the molding fluid application step further involves applying the molding fluid to the formed sintering inhibiting region afterwards.

17. The method for manufacturing a molded object according to any one of claims 1 to 14, wherein the molding region is surrounded by the sintering inhibiting region.

18. A method for manufacturing a molded object according to any one of claims 1 to 14, wherein the sintering inhibitor liquid is applied at the boundary between the molding region and the sintering inhibitor region within 100 msec after the molding liquid is applied.

19. The laminate has a plurality of molded parts formed by stacking the molded areas, and connecting parts that connect the molded parts. The method for manufacturing a molded object according to any one of claims 1 to 14, wherein at least the region of the connection portion that contacts the molded portion is formed by stacking the sintering inhibiting regions.

20. The laminate has a molded portion formed by stacking the molded regions and a sintering inhibiting portion formed by stacking the sintering inhibiting regions. The method for manufacturing a molded object according to any one of claims 1 to 14, wherein the molded portion is covered all around with the sintering inhibiting portion.

21. A powder layer formation step in which a powder layer containing sinterable particles is formed, A process of applying a molding liquid to the powder layer to form a molding region, The process includes a step of independently applying resin generating liquid X and resin generating liquid Y to the powder layer, thereby forming a sintering inhibiting liquid set application step in the powder layer after application, where the resin generating liquid X and resin generating liquid Y come into contact, thereby inhibiting the sintering of the particles. A method for manufacturing a molded object, comprising a lamination step of sequentially repeating the powder layer formation step, the molding liquid application step, and the sintering inhibitor set application step to form a laminate, The molding region and the sintering inhibition region are adjacent to each other. The sintering inhibiting region contains a third resin that is produced when the resin generating liquid X and the resin generating liquid Y come into contact. A method for manufacturing a molded object, characterized in that the predicted amount of residue, calculated by multiplying the mass ratio of the third resin to the powder in the sintering inhibiting portion formed by stacking the sintering inhibiting regions by the thermal decomposition residue rate of the third resin at 550°C, is 800 ppm or more and 1604 ppm or less.

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