Liquid for object forming and method for manufacturing object

Abstract

Provided are an object-forming liquid and an object-making method. The object-forming liquid contains a resin and an organic solvent and is substantially free of water, the resin containing at least one structural unit selected from a structural unit represented by a predetermined structural formula (1) and a structural unit represented by a predetermined structural formula (2). The object-forming liquid is applied to a layer of a powder containing metal particles.

Description

Technical Field

[0001] The present disclosure relates to an object forming liquid and an object manufacturing method. Background Art

[0002] In recent years, the demand for manufacturing complex micro-objects formed of, for example, metal has been increasing. As a technology that meets these demands particularly in terms of high productivity, there is a method of forming a sintering precursor by a binder spraying method and sintering and densifying the sintering precursor by a powder metallurgy method.

[0003] For example, a method disclosed as an example of a method for manufacturing an object such as a precursor for sintering by a binder jetting method applies a liquid containing a resin acting as a binder to particles, the particles comprising a sinterable core and a resin coating layer that covers at least a portion of the core and can be removed by decomposition such as heating (see the Japanese translation of PCT International Application Publication No. JP-T-2020-511593). Summary of the invention

[0004] According to one aspect of the present disclosure, the object-forming liquid comprises a resin and an organic solvent, and is substantially free of water, the resin comprising at least one structural unit selected from the group consisting of a structural unit represented by the following structural formula (1) and a structural unit represented by the following structural formula (2). The object-forming liquid is applied to a layer of a powder containing metal particles.

[0005]

[0006] BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1A A schematic diagram for explaining an example of the operation of a three-dimensional object manufacturing apparatus;

[0008] Figure 1B A schematic diagram for explaining another example of the operation of a three-dimensional object manufacturing apparatus;

[0009] Figure 1C A schematic diagram for explaining another example of the operation of a three-dimensional object manufacturing apparatus;

[0010] Figure 1D A schematic diagram for explaining another example of the operation of a three-dimensional object manufacturing apparatus; and

[0011] Figure 1E A schematic diagram illustrating another example of the operation of a three-dimensional object manufacturing apparatus. DETAILED DESCRIPTION

[0012] According to the prior art, when an object is manufactured by applying an object forming liquid containing a resin to a layer of a powder containing metal particles, there are problems that the viscosity of the object forming liquid is high, the bending strength of the green body is insufficient, and the sintered density of the sintered body is insufficient.

[0013] The present disclosure can provide an object-forming liquid having low viscosity, improving the bending strength of a green body, and improving the sintering density of a sintered body.

[0014] Embodiments of the present disclosure will be described below.

[0015] <<Liquid for forming objects>>

[0016] The "object-forming liquid" of the present disclosure is a liquid composition used for manufacturing an object and a layer applied to a powder containing metal particles.

[0017] The manufacture of the object is implemented by a manufacturing method including a layer-by-layer step, wherein the layer-by-layer step includes a powder layer forming step of forming a layer of powder containing metal particles and an object forming liquid applying step of applying an object forming liquid to the layer of powder, and includes sequentially repeating the powder layer forming step and the object forming liquid applying step to form a laminated body.

[0018] The manufacture of the object is preferably carried out by the following manufacturing method: the manufacturing method includes, in addition to the above-mentioned layer stacking step, for example, a heating step of heating the stacked body to form a solidified product, a step of removing excess powder (which is powder adhering to the solidified product) to obtain a green body, a drying step of drying the green body to remove liquid components remaining in the green body, a degreasing step of heating the green body to remove resin such as resin derived from the applied object forming liquid to obtain a degreasing body, a sintering step of heating the degreasing body to obtain a sintered body, and a post-treatment step of applying post-treatment to the sintered body.

[0019] In the present disclosure, "object" is a general term for a three-dimensional object maintained in a fixed three-dimensional shape, and means a solidified product or a structure derived from a solidified product. Specifically, "object" is a concept representing, for example, a solidified product, a green body, a degreased body, and a sintered body.

[0020] In the present disclosure, the object forming part that has undergone the heating step may be referred to as a "green body (unsintered body"), the object forming part that has undergone the degreasing step may be referred to as a "degreasing body", and the object forming part that has undergone the sintering step may be referred to as a "sintered body".

[0021] The object-forming liquid contains a resin, an organic solvent, and additives such as a surfactant. The various components contained in the object-forming liquid will be described in detail below.

[0022] <Resin>

[0023] The object-forming liquid contains a resin containing at least one structural unit selected from the structural unit represented by the following structural formula (1) and the structural unit represented by the following structural formula (2). In the present disclosure, a "structural unit" means a partial structure derived from one or more polymerizable compounds in a resin.

[0024]

[0025] - A resin comprising a structural unit represented by the structural formula (1) -

[0026] The resin containing the structural unit represented by the structural formula (1) spreads in the powder layer when the object-forming liquid is applied to the layer of the powder containing metal particles, and acts as a binder for bonding the metal particles to each other in the region to which the object-forming liquid is applied by a suitable heating step in accordance with the softening point of the resin to form a pre-sintered object such as a cured product or a green body derived from the cured product. These pre-sintered objects have improved bending strength because they are formed of a resin containing the structural unit represented by the structural formula (1) and having flexibility (flexibility) imparting properties.

[0027] The resin containing the structural unit represented by the structural formula (1) can be suitably removed in the degreasing step due to its excellent thermal decomposition property, and the sintered body produced by the subsequent sintering step has improved density.

[0028] Therefore, when metal particles (which are materials that are presumably sintered or preferably sintered) are used as a material for forming an object as in the present disclosure, the effect obtained is remarkable.

[0029] Specifically, it is preferred that the resin containing the structural unit represented by the structural formula (1) thermally decomposes by 95% by mass or more, more preferably 97% by mass or more, when subjected to a temperature increase from 30 degrees Celsius to 550 degrees Celsius.

[0030] In the present disclosure, when "resin thermal decomposition", for example, the resin main chain randomly degrades or the molecular chain end of the resin depolymerizes, so the resin is removed by, for example, evaporation, oxidative decomposition or combustion. Thermal decomposition is measured with a thermogravimetric analysis-differential thermal analysis system (TG-DTA). Specifically, the weight reduction rate between before and after the temperature increase is obtained when the resin is subjected to a temperature increase of 10 degrees Celsius / minute from 30 degrees Celsius to 550 degrees Celsius in an atmosphere or a nitrogen atmosphere, and then subjected to a 2-hour temperature maintenance after the temperature reaches 550 degrees Celsius.

[0031] The resin containing the structural unit represented by the structural formula (1) has improved solubility in an organic solvent because the structural unit represented by the structural formula (1) has hydrophobicity. Therefore, when the object-forming liquid contains an organic solvent, the resin containing the structural unit represented by the structural formula (1) has improved solubility and can suppress the viscosity of the object-forming liquid. This makes it possible to suitably discharge the object-forming liquid by, for example, an inkjet method.

[0032] It is preferred that the resin containing the structural unit represented by the structural formula (1) is soluble in the organic solvent of the object-forming liquid and insoluble in water.

[0033] The Tg of the resin containing the structural unit represented by the structural formula (1) is preferably 0 degrees Celsius or higher, more preferably 10 degrees Celsius or higher, and still more preferably 20 degrees Celsius or higher. The Tg of the resin containing the structural unit represented by the structural formula (1) is preferably 100 degrees Celsius or lower, more preferably 90 degrees Celsius or lower, and still more preferably 80 degrees Celsius or lower.

[0034] The softening point of the resin containing the structural unit represented by the structural formula (1) is preferably 70 degrees Celsius or higher, more preferably 80 degrees Celsius or higher, and still more preferably 90 degrees Celsius or higher. The softening point of the resin containing the structural unit represented by the structural formula (1) is preferably 150 degrees Celsius or lower, more preferably 140 degrees Celsius or lower, and still more preferably 30 degrees Celsius or lower.

[0035] The number average molecular weight (Mn) of the resin containing the structural unit represented by the structural formula (1) is preferably 5,000 or more but 50,000 or less, and more preferably 10,000 or more but 30,000 or less. When the number average molecular weight (Mn) of the resin containing the structural unit represented by the structural formula (1) is in the above range, both improvement in strength and object manufacturing accuracy and suppression of increase in viscosity of the object molding liquid and resin concentration in the object molding liquid can be satisfied.

[0036] The resin containing the structural unit represented by the structural formula (1) may be any one selected from the group consisting of a resin containing a structural unit represented by an arbitrary formula different from the structural formula (1) and a resin not containing a structural unit represented by an arbitrary formula different from the structural formula (1). As the structural unit represented by an arbitrary formula different from the structural formula (1), for example, a structural unit represented by the following structural formula (3) and a structural unit represented by the following structural formula (4) are preferred.

[0037]

[0038] The resin containing the structural unit represented by the structural formula (3) in addition to the structural unit represented by the structural formula (1) improves the bending strength of a pre-sintered object such as a cured product and a green body derived from the cured product.

[0039] Like the structural unit represented by the structural formula (1), the structural unit represented by the structural formula (3) also has hydrophobicity and improves the solubility of the resin in an organic solvent.

[0040] From these viewpoints, the total amount of the structural unit represented by the structural formula (1) and the structural unit represented by the structural formula (3) is preferably 60 mol% or more, more preferably 65 mol% or more, still more preferably 70 mol% or more, even more preferably 75 mol% or more, and particularly preferably 80 mol% or more, relative to the total amount of the structural unit represented by the structural formula (1), the structural unit represented by the structural formula (3) and the structural unit represented by the structural formula (4).

[0041] The same applies when the resin does not contain the structural unit represented by the structural formula (3) or the structural formula (4). The above ratio can be calculated while regarding the amount of the structural unit not contained in the resin as zero.

[0042] The resin containing the structural unit represented by the structural formula (4) in addition to the structural unit represented by the structural formula (1) has improved affinity with metal particles contained in the powder layer to which the object-forming liquid is applied by virtue of the hydroxyl group of the structural unit represented by the structural formula (4). This better improves the bending strength of pre-sintered objects such as cured products and green bodies derived from the cured products and better improves the density of pre-sintered objects and the density of post-sintered objects.

[0043] From these viewpoints, the amount of the structural unit represented by structural formula (4) in the resin is preferably 5 mol% or more, more preferably 15 mol% or more, and still more preferably 25 mol% or more, relative to the total amount of the structural unit represented by structural formula (1), the structural unit represented by structural formula (3) and the structural unit represented by structural formula (4).

[0044] However, the structural unit represented by the structural formula (4) has hydrophilicity. Therefore, when the ratio of the structural unit represented by the structural formula (4) becomes higher, the resin containing the structural unit represented by the structural formula (1) cannot have improved solubility when the object-forming liquid contains an organic solvent, and cannot better suppress the viscosity of the object-forming liquid.

[0045] From this viewpoint, the amount of the structural unit represented by the structural formula (4) in the resin is preferably 40 mol% or less, more preferably 35 mol% or less, still more preferably 30 mol% or less, even more preferably 25 mol% or less, and particularly preferably 20 mol% or less, relative to the total amount of the structural unit represented by the structural formula (1), the structural unit represented by the structural formula (3) and the structural unit represented by the structural formula (4).

[0046] This also applies when the resin does not contain the structural unit represented by the structural formula (3). The above ratio can be calculated while regarding the amount of the structural unit not contained in the resin as zero.

[0047] Specific examples of the resin containing the structural unit represented by the structural formula (1) include polyvinyl acetate resins, partially saponified polyvinyl acetate resins and polyvinyl butyral resins. Among these resins, polyvinyl acetate resins and predetermined partially saponified polyvinyl acetate resins are preferred because these resins can suppress the viscosity of the liquid for object molding.

[0048] Here, it is preferred that the predetermined partially saponified polyvinyl acetate resin represents a partially saponified polyvinyl acetate resin in which the amount of the structural unit represented by the structural formula (1) is 75 mol% or more, preferably 80 mol% or more, relative to the total amount of the structural unit represented by the structural formula (1) and the structural unit represented by the structural formula (4).

[0049] These resins may be used alone or two or more of these resins may be used in combination. Both commercially available products and synthesized products may be used.

[0050] In the present disclosure, a polyvinyl acetate resin is a resin comprising a structural unit represented by the structural formula (1) but substantially free of a structural unit represented by the structural formula (3) and a structural unit represented by the structural formula (4). A partially saponified polyvinyl acetate resin is a resin comprising a structural unit represented by the structural formula (1) and a structural unit represented by the structural formula (4) but substantially free of a structural unit represented by the structural formula (3). A polyvinyl butyral resin is a resin comprising a structural unit represented by the structural formula (1) and a structural unit represented by the structural formula (3), or a resin comprising a structural unit represented by the structural formula (1), a structural unit represented by the structural formula (3), and a structural unit represented by the structural formula (4).

[0051] The partially saponified polyvinyl acetate resin is a resin obtained by partially saponifying a polyvinyl acetate resin. In the partially saponified polyvinyl acetate resin of the present disclosure, the amount of the structural unit represented by the structural formula (4) is 40 mol% or less, preferably 35 mol% or less, more preferably 30 mol% or less, still more preferably 25 mol% or less and even more preferably 20 mol% or less, relative to the total amount of the structural unit represented by the structural formula (1) and the structural unit represented by the structural formula (4). In other words, the partially saponified polyvinyl acetate resin of the present disclosure has a saponification degree of 40 or less, preferably 35 or less, more preferably 30 or less, still more preferably 25 or less and even more preferably 20 or less.

[0052] The content of the resin containing the structural unit represented by the structural formula (1) is preferably 5.0% by mass or more, more preferably 7.0% by mass or more, still more preferably 10.0% by mass or more, and particularly preferably 11.0% by mass or more, and is preferably 30.0% by mass or less, more preferably 25.0% by mass or less, and still more preferably 20.0% by mass or less, relative to the mass of the object-forming liquid. When the content of the resin containing the structural unit represented by the structural formula (1) is 5.0% by mass or more, the bending strength of the pre-sintered object such as the cured product and the green body derived from the cured product is better improved. When the content of the resin containing the structural unit represented by the structural formula (1) is 30.0% by mass or less, the viscosity of the object-forming liquid is better suppressed and the object-forming liquid can be suitably discharged by the inkjet method.

[0053] The following resin has improved solubility in organic solvents and suppresses the viscosity of the object-forming liquid: the total amount of the structural unit represented by the structural formula (1) and the structural unit represented by the structural formula (3) is 95 mol% or more relative to the total amount of the structural unit represented by the structural formula (1), the structural unit represented by the structural formula (3) and the structural unit represented by the structural formula (4). Therefore, the resin can be added in a large amount (for example, 15.0 mass% or more or 20.0 mass% or more relative to the mass of the object-forming liquid) to the object-forming liquid. This better improves the bending strength of the pre-sintered object such as the cured product and the green body derived from the cured product.

[0054] The amount (mol %) of the structural unit represented by each structural formula in the resin can be obtained by, for example, the polyvinyl alcohol testing method described in JIS-K6276-1994.

[0055] - A resin comprising a structural unit represented by the structural formula (2) -

[0056] The resin containing the structural unit represented by the structural formula (2) is spread in the powder layer when the object-forming liquid is applied to the layer of the powder containing metal particles, and acts as a binder for bonding the metal particles to each other in the area to which the object-forming liquid is applied by a suitable heating step in accordance with the softening point of the resin to form a pre-sintered object such as a cured product or a green body derived from the cured product. The pre-sintered object is formed by the resin containing the structural unit represented by the structural formula (2), which has a five-membered ring lactam structure having a high affinity for metal. Therefore, the metal particles are strongly bonded to each other and the bending strength of the object is improved.

[0057] The resin containing the structural unit represented by the structural formula (2) achieves excellent thermal decomposition when the temperature rise profile is appropriately controlled. Therefore, the resin containing the structural unit represented by the structural formula (2) is appropriately removed in the degreasing step, and the sintered body produced by the subsequent sintering step has an improved density. Therefore, when metal particles (which are materials presumed to be sintered or preferably sintered) are used as materials for forming objects as in the present disclosure, the obtained effect is significant. Specifically, it is preferred that the resin containing the structural unit represented by the structural formula (2) thermally decomposes 95% by mass or more, more preferably 97% by mass or more, when subjected to a temperature rise from 30 degrees Celsius to 550 degrees Celsius.

[0058] However, depending on the temperature conditions (e.g., heating conditions of 160 degrees Celsius or higher), the resin containing the structural unit represented by the structural formula (2) forms a cross-linked structure that can suppress the effect of high thermal decomposition. Therefore, when metal particles (which are materials that are presumed to be sintered or preferably sintered) are used as a material for forming an object as in the present disclosure, the use of a resin containing the structural unit represented by the structural formula (1) can be preferred to the use of a resin containing the structural unit represented by the structural formula (2) in terms of simple handleability.

[0059] Due to the five-membered ring lactam structure, the resin containing the structural unit represented by the structural formula (2) has improved solubility in specific organic solvents (mainly polar solvents) and can suppress the viscosity of the object forming liquid. This makes it possible to suitably discharge the object forming liquid by, for example, an inkjet method. Moreover, the resin containing the structural unit represented by the structural formula (2) can better suppress the viscosity of the object forming liquid when used in combination with, for example, the component 1 (e.g., cyclic ester (lactone)) and component 2 (e.g., glycol diether) described below that act as an organic solvent. The resin containing the structural unit represented by the structural formula (2) can be added to the object forming liquid in a high mass (e.g., 15.0 mass % or more, relative to the mass of the object forming liquid) because the viscosity of the object forming liquid can be suppressed, as described above. This better improves the bending strength of pre-sintered objects such as cured products and green bodies derived from the cured products.

[0060] The softening point of the resin containing the structural unit represented by structural formula (2) is preferably 70 degrees Celsius or higher, more preferably 80 degrees Celsius or higher, and even more preferably 90 degrees Celsius or higher and is preferably 180 degrees Celsius or lower, more preferably 170 degrees Celsius or lower, and even more preferably 160 degrees Celsius or lower.

[0061] The number average molecular weight (Mn) of the resin containing the structural unit represented by the structural formula (2) is preferably 3,000 or more but 50,000 or less, and more preferably 5,000 or more but 40,000 or less. When the number average molecular weight (Mn) of the resin containing the structural unit represented by the structural formula (2) is in the above range, both improvement in strength and object manufacturing accuracy and suppression of increase in viscosity of the object molding liquid and resin concentration in the object molding liquid can be satisfied.

[0062] Specific examples of the resin containing the structural unit represented by the structural formula (2) include polyvinyl pyrrolidone resins. Both commercially available products and synthesized products can be used.

[0063] The content of the resin containing the structural unit represented by the structural formula (2) is preferably 7.0% by mass or more, more preferably 10.0% by mass or more, still more preferably 11.0% by mass or more, and particularly preferably 13.0% by mass or more and preferably 25.0% by mass or less, more preferably 20.0% by mass or less, and still more preferably 15.0% by mass or less, relative to the mass of the object-forming liquid. When the content of the resin containing the structural unit represented by the structural formula (2) is 7.0% by mass or more, the bending strength of the pre-sintered object such as the cured product and the green body derived from the cured product is better improved. When the content of the resin containing the structural unit represented by the structural formula (2) is 25.0% by mass or less, the viscosity of the object-forming liquid is better suppressed and the object-forming liquid can be suitably discharged by, for example, an inkjet method.

[0064] <Organic Solvents>

[0065] The object-forming liquid contains an organic solvent. The organic solvent is a liquid component for keeping the object-forming liquid in a liquid state at normal temperature.

[0066] Furthermore, it is preferred that the object-forming liquid is a nonaqueous object-forming liquid by containing an organic solvent.

[0067] In the present disclosure, "non-aqueous object-forming liquid" means an object-forming liquid containing an organic solvent as a liquid component of the object-forming liquid and the component having the largest mass among the liquid components is the organic solvent. The content of the organic solvent is preferably 90.0% by mass or more and more preferably 95.0% by mass or more relative to the content of the liquid component of the object-forming liquid. This is because when the object-forming liquid is non-aqueous, the resin containing the structural unit represented by the structural formula (1) particularly has improved solubility and suppresses the viscosity of the object-forming liquid.

[0068] The non-aqueous object-forming liquid can be rephrased as an object-forming liquid that is substantially free of water. Therefore, even when the material constituting the metal particles is a highly active metal, i.e., a material reactive with water (e.g., aluminum, zinc, and magnesium), the object-forming liquid can be applied to the material. As an example, when the water content in the object-forming liquid is high, when aluminum contacts water, the aluminum forms a coating film formed of aluminum hydroxide, resulting in the following problem: the sintering density of the sintered body is low. This problem can be avoided when a non-aqueous object-forming liquid is used. As another example, when aluminum contacts water, there is the following problem: the manipulation of aluminum is difficult because aluminum releases hydrogen. This problem can also be avoided when a non-aqueous object-forming liquid is used.

[0069] Examples of the organic solvent 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 n-octanoate, ethyl octanoate, ethyl acetoacetate, ethyl 3-ethoxypropionate, diethyl oxalate, diethyl malonate, diethyl succinate, diethyl adipate, bis-2-ethylhexyl maleate, triacetin, tributylin, 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. One of these organic solvents may be used alone or two or more of these organic solvents may be used in combination.

[0070] When a resin containing a structural unit represented by the structural formula (1) is used, the organic solvent used in combination is not particularly limited. It is preferred to use an organic solvent containing at least one structure selected from an alkoxy group, an ether bond and an ester bond. It is more preferred to use an organic solvent containing an ether bond. Alkylene glycol dialkyl ether is particularly preferred. When such an organic solvent as described above is used, the resin containing a structural unit represented by the structural formula (1) has a more improved solubility and can better suppress the viscosity of the object forming liquid. This makes it possible to suitably discharge the object forming liquid by, for example, an inkjet method.

[0071] In the present disclosure, "alkylene glycol dialkyl ether" is represented by R1-(O-R2) m -OR3 represents, wherein R1 and R3 are each independently an alkyl group containing 1 or more but 5 or less carbon atoms and may be linear or branched, wherein the number of carbon atoms is preferably 1 or 2, and R2 is an alkylene group containing 2 or more but 5 or less carbon atoms and may be linear or branched, wherein the number of carbon atoms is more preferably 2 or 3, and m represents an integer of 1 or more but 5 or less and is more preferably 2 or 3.

[0072] Specific examples of the alkylene glycol dialkyl ethers include diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether and diethylene glycol butyl methyl ether. Among these alkylene glycol dialkyl ethers, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether are preferred, and triethylene glycol dimethyl ether is more preferred.

[0073] When a resin containing a structural unit represented by structural formula (2) is used, a polar solvent is preferably used as the organic solvent used in combination. Specifically, it is preferred to use at least one selected from component 1, which is a group consisting of cyclic esters (lactones), cyclic ketones and alkylene glycol monoalkyl ethers. More preferably, in addition to at least one selected from component 1, at least one selected from component 2 is further used, which is a group consisting of alkylene glycol dialkyl ethers. The resin containing the structural unit represented by structural formula (2) has improved solubility in these types of organic solvents and can better suppress the viscosity of the liquid for object forming. This makes it possible to discharge the liquid for object forming appropriately by, for example, an inkjet method. In terms of improving the solubility of the resin containing the structural unit represented by structural formula (2), component 1 is preferably a group consisting of cyclic esters (lactones) and cyclic ketones.

[0074] When a resin containing a structural unit represented by the structural formula (2) is used, and at least one selected from component 1 and at least one selected from component 2 are both used as the organic solvent, the mass ratio of the total amount of component 1 to the total amount of component 2 (component 1 / component 2) is preferably 60 / 40 to 100 / 0. When the mass ratio of the total amount of component 1 to the total amount of component 2 is 60 / 40 to 100 / 0, the resin containing a structural unit represented by the structural formula (2) has improved solubility and can better suppress the viscosity of the object-forming liquid.

[0075] Specific examples of component 1, which is the group consisting of cyclic esters (lactones), cyclic ketones and alkylene glycol monoalkyl ethers, include γ-butyrolactone, propylene carbonate and cyclohexanone.

[0076] Specific examples of component 2, which is a group consisting of alkylene glycol dialkyl ethers, include diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, diethylene glycol ethyl methyl ether, and diethylene glycol butyl methyl ether. Of these components 2, diethylene glycol dimethyl ether and triethylene glycol dimethyl ether are preferred.

[0077] In the present disclosure, "alkylene glycol monoalkyl ether" is represented by R4-(O-R5) n -OH represents, wherein R4 represents an alkyl group containing 1 or more but 5 or less carbon atoms and may be linear or branched, R5 represents an alkylene group containing 2 or more but 5 or less carbon atoms and may be linear or branched, and n represents an integer of 1 or more but 5 or less.

[0078] When it is desired to further suppress the viscosity of the object-forming liquid, the type of the organic solvent used in combination with the resin has a greater influence on the use of the resin containing the structural unit represented by the structural formula (2) than on the use of the resin containing the structural unit represented by the structural formula (1), and it is necessary to selectively use the above-mentioned organic solvents (component 1 and component 2). Therefore, from the viewpoint that the material for producing the object-forming liquid can be selected from a wide range, the use of the resin containing the structural unit represented by the structural formula (1) is preferred to the use of the resin containing the structural unit represented by the structural formula (2).

[0079] The content of the organic solvent is preferably 60.0% by mass or more but 95.0% by mass or less and more preferably 70.0% by mass or more but 95.0% by mass or less relative to the mass of the object forming liquid. When the content of the organic solvent is 60.0% by mass or more but 95.0% by mass or less, the resin has improved solubility and the viscosity of the object forming liquid can be better suppressed. This makes it possible to suitably discharge the object forming liquid by, for example, an inkjet method. Moreover, the drying of the object forming liquid in the object forming liquid application unit is suppressed, and excellent discharge stability is achieved.

[0080] The mass ratio of the amount of organic solvent to the amount of resin (organic solvent / resin) is preferably 75 / 25 or more but 95 / 5 or less. When the mass ratio of the amount of organic solvent to the amount of resin is 75 / 25 or more, the resin has improved solubility and the viscosity of the object forming liquid can be better suppressed. This makes it possible to discharge the object forming liquid appropriately by, for example, an inkjet method. When the mass ratio of the amount of organic solvent to the amount of resin is 95 / 5 or less, the bending strength of the pre-sintered object such as a cured product and a green body derived from the cured product is better improved.

[0081] The sum of the amount of the organic solvent and the amount of the resin is preferably 90.0% by mass or more, more preferably 95.0% by mass or more, still more preferably 99.0% by mass or more, and even more preferably 99.5% by mass or more, relative to the mass of the object-forming liquid. The object-forming liquid may be substantially free of any other components except the organic solvent and the resin. The object-forming liquid substantially free of any other components except the organic solvent and the resin means an object-forming liquid produced without actively using any other components except the organic solvent and the resin as a material, or an object-forming liquid in which the content of any other components except the organic solvent and the resin is less than or equal to the detection limit when measured by a known method in ordinary public technical knowledge.

[0082] When the sum of the amount of the organic solvent and the amount of the resin relative to the mass of the object-forming liquid is 90.0% by mass or more, the object-forming liquid has a high resin content and better improves the bending strength of the pre-sintered object such as the cured product and the green body derived from the cured product. The object-forming liquid having a low content or substantially free of any other components other than the organic solvent and the resin (any other component is, for example, a material insoluble in the object-forming liquid such as metal particles) has suppressed viscosity and improved discharge stability, and also has improved storage stability.

[0083] It is preferred that the viscosity of the organic solvent is low. Specifically, the viscosity of the organic solvent at 25 degrees Celsius is preferably 5.0 mPa·s or higher but 50.0 mPa·s or lower, and more preferably 8.0 mPa·s or higher but 30.0 mPa·s or lower. When the viscosity of the organic solvent is in the above range, the viscosity of the object-forming liquid containing the organic solvent also tends to be low. This stabilizes the discharge of the object-forming liquid from the object-forming liquid applying unit such as an inkjet head, and the accurate discharge of the object-forming liquid better improves the bending strength and also the three-dimensional accuracy of the pre-sintered object such as the solidified product and the green body derived from the solidified product.

[0084] The viscosity can be measured according to, for example, JIS K7117.

[0085] Preferably, the boiling point of the organic solvent is high. Specifically, the boiling point of the organic solvent is preferably 150 degrees Celsius or higher and more preferably 180 degrees Celsius or higher. When the boiling point of the organic solvent is high, when the object forming liquid is discharged by, for example, an inkjet method, the object forming liquid can be suppressed from drying in the nozzle or near the nozzle, and the resin precipitation and clogging of the nozzle can be suppressed. There is no particular restriction on the organic solvent with a high boiling point. Examples of organic solvents with a high boiling point include the above-mentioned γ-butyrolactone (boiling point of 204 degrees Celsius), propylene carbonate (boiling point of 242 degrees Celsius), cyclohexanone (boiling point of 155.6 degrees Celsius), glycol dimethyl ether (boiling point of 162 degrees Celsius) and triethylene glycol dimethyl ether (boiling point of 216 degrees Celsius).

[0086] <Additives>

[0087] The object-forming liquid may suitably contain, for example, surfactants, anti-drying agents, viscosity regulators, penetrants, defoamers, pH adjusters, antibacterial agents, fungicides, colorants, preservatives and stabilizers, depending on the intended purpose. As these additives, hitherto known materials can be used.

[0088] <Other components>

[0089] -water-

[0090] The object forming liquid is substantially free of water. In the present disclosure, the object forming liquid "substantially free of water" means an object forming liquid having a water content of 10.0 mass % or less relative to the mass of the object forming liquid. The water content in the object forming liquid is preferably 5.0 mass % or less, more preferably 3.0 mass % or less, and still more preferably 1.0 mass % or less, and it is particularly preferred that the object forming liquid is free of water. The resin has improved solubility in the object forming liquid that is substantially free of water and the viscosity of the object forming liquid can be better suppressed. Moreover, the formation of a hydrogel containing a large amount of water around the resin and the accompanying increase in the viscosity of the object forming liquid are suppressed. This makes it possible to suitably discharge the object forming liquid by, for example, an inkjet method. In the present disclosure, "a water-free object forming liquid" means an object forming liquid produced without actively using water as a material, or an object forming liquid in which the water content is less than or equal to the detection limit when measured by a known method in ordinary known technical knowledge.

[0091] Moreover, even when the material constituting the metal particles is a highly active metal, i.e., a material reactive with water (e.g., aluminum, zinc, and magnesium), an object-forming liquid that does not substantially contain water may be applied to the material. As an example, when the water content in the object-forming liquid is high, when aluminum contacts water, the aluminum forms a coating film formed of aluminum hydroxide, resulting in a problem that the sintered density of the sintered body is low. This problem can be avoided when the object-forming liquid does not contain water. As another example, there is a problem that the handling of aluminum is difficult because aluminum releases hydrogen when it contacts water. This problem can also be avoided when the object-forming liquid does not contain water.

[0092] <Method for producing liquid for object forming>

[0093] The method for producing the object-forming liquid is not particularly limited and may be appropriately selected depending on the intended purpose. Examples of the method include a method of mixing and stirring the above-mentioned materials.

[0094] <Properties of Liquids for Forming Objects>

[0095] It is preferred that the viscosity of the object-forming liquid is low, as described above. Specifically, the viscosity of the object-forming liquid at 25 degrees Celsius is preferably 5 mPa·s or more but 50 mPa·s or less, more preferably 5 mPa·s or more but 40 mPa·s or less, and still more preferably 5 mPa·s or more but 30 mPa·s or less. When the viscosity of the object-forming liquid is in the above range, the discharge of the object-forming liquid from the object-forming liquid applying unit such as an inkjet head is stabilized and the accurate discharge of the object-forming liquid is better improved, and the bending strength and also the three-dimensional accuracy of the pre-sintered object such as a solidified product and a green body derived from the solidified product are improved.

[0096] The viscosity can be measured according to, for example, JIS K7117.

[0097] The surface tension of the object-forming liquid at 25 degrees Celsius is preferably 40 mN / m or less and more preferably 10 mN / m or more but 30 mN / m or less. When the surface tension of the object-forming liquid is 40 mN / m or less, the discharge of the object-forming liquid from the object-forming liquid applying unit such as an inkjet head is stabilized, and the accurate discharge of the object-forming liquid better improves the bending strength and also the three-dimensional accuracy of the pre-sintered object such as the solidified product and the green body derived from the solidified product.

[0098] Surface tension can be measured using, for example, DY-300 available from Kyowa Interface Science Co., Ltd.

[0099] <<Metal Particles>>

[0100] In the present disclosure, "metal particles" refer to particles used for manufacturing an object and containing metal as a constituent material. The constituent material of the metal particles is not particularly limited as long as metal is included in the constituent material. The metal particles may contain any other material besides the metal, but it is preferred that the main material of the metal particles is a metal. When the main material of the metal particles is a metal, the mass of the metal contained in the metal particles is 50.0 mass % or more, preferably 60.0 mass % or more, more preferably 70.0 mass % or more, still more preferably 80.0 mass % or more, and particularly preferably 90.0 mass % or more, relative to the mass of the metal particles.

[0101] Examples of metals serving as constituent materials of the metal particles include magnesium (Mg), aluminum (Al), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), yttrium (Y), zirconium (Zr), niobium (Nb), molybdenum (Mo), lead (Pd), silver (Ag), indium (In), tin (Sn), tantalum (Ta), tungsten (W), neodymium (Nd), and alloys of these metals. Among these metals, stainless (SUS) steel, iron (Fe), copper (Cu), silver (Ag), titanium (Ti), aluminum (Al), and alloys of these metals are suitably used. Examples of aluminum alloys include AlSi 10 Mg、AlSi 12 、AlSi7Mg 0.6 , AlSi3Mg, AlSi9Cu3, SCALMALLOY, ADC 12 And AlSi 3. One of these metals may be used alone or two or more of these metals may be used in combination.

[0102] Metal particles can be manufactured by known methods. Examples of methods for manufacturing metal particles include a grinding method in which a solid is subjected to compression, impact or friction to break the solid into pieces, an atomization method in which a molten metal is sprayed and the resultant is rapidly cooled to obtain a powder, a precipitation method in which a component dissolved in a liquid is precipitated, and a gas phase reaction method in which a material is evaporated and crystallized. Among these methods, an atomization method in which a spherical shape can be obtained with a small particle size difference is preferred. Examples of atomization methods include water atomization methods, gas atomization methods, centrifugal atomization methods, and plasma atomization methods. Any of these atomization methods can be suitably used.

[0103] Commercially available products can be used as metal particles. Examples of commercially available products include pure Al (available from Toyo Aluminium K.K., A1070-30BB), pure Ti (available from Osaka Titanium Technologies Co., Ltd.), SUS316L (available from Sanyo Special Steel Co., Ltd., product name: PSS316L), AlSi 10 Mg (available from ToyoAluminium KK, Si 10 MgBB), SiO2 (available from Tokuyama Corporation, product name: EXCELLICASE-15K), AlO2 (available from Taimei Chemicals Co., Ltd., product name: TAIMICRON TM-5D), and ZrO2 (available from Tosoh Corporation, product name: TZ-B53).

[0104] The volume average particle size of the metal particles is not particularly limited, can be appropriately selected depending on the intended purpose, and is preferably 2 micrometers or more but 100 micrometers or less and more preferably 8 micrometers or more but 50 micrometers or less. When the volume average particle size of the metal particles is 2 micrometers or more, the aggregation of the metal particles is suppressed, so that the deterioration of the object manufacturing efficiency and the deterioration of the handleability of the metal particles can be suppressed. When the average particle size of the metal particles is 100 micrometers or less, the reduction of the contact points between the metal particles and the increase of the voids can be suppressed and the deterioration of the strength of the object can be suppressed.

[0105] The particle size distribution of the metal particles is not particularly limited and may be appropriately selected depending on the intended purpose. A sharper particle size distribution is more preferred.

[0106] The volume average particle size and particle size distribution of the metal particles can be measured using a known particle size measuring instrument. Examples of known particle size measuring instruments include a particle size distribution measuring instrument MICROTRAC MT3000II SERIES (available from Microtrac Bel Corporation).

[0107] The method for manufacturing an object known so far uses metal particles of a coated resin containing a metal base material and a coated base material, and applies a liquid to the metal particles so that the coated resin functions as an adhesive to manufacture the object. In the present disclosure, the object forming liquid contains a resin having an adhesive function. Therefore, the surface of the metal particles of the present disclosure does not need to be coated with a resin. The use of metal particles whose surfaces are not coated with resin makes it possible to suppress the formation of undesirable solidified products due to the bonding of any metal particles to each other by the coated resin through a heating step even in the powder area (i.e., non-object forming area) to which the liquid is not applied. Here, the metal particles whose surfaces are not coated with resin refer to metal particles in which the ratio of the surface area of ​​the resin to the surface area of ​​the metal particles (surface coverage) is less than 15%. The surface coverage may be 0%. The surface coverage is measured by, for example, acquiring an image of the metal particles and measuring the ratio (%) of the area of ​​the portion coated with the resin relative to the total area of ​​the surface of the metal particles within the range acquired in the two-dimensional image. For the determination of the portion coated with the resin, such a method as element mapping by energy dispersive X-ray spectroscopy such as SEM-EDS can be used.

[0108] <Powder containing metal particles>

[0109] The above-mentioned metal particles are used as powder, which is an aggregate including a plurality of metal particles. When an object-forming liquid is applied to the powder layer, an object is produced.

[0110] In addition to the metal particles, the powder may contain any other components used as required. Examples of other components include fillers, leveling agents, sintering aids, and polymer resin particles.

[0111] Fillers are materials that effectively adhere to the surface of metal particles or fill in the gaps between metal particles. For example, when fillers are used, the powder has improved flowability and can include more contact points and fewer gaps between metal particles. As a result, the strength and three-dimensional accuracy of the object can be improved.

[0112] The leveling agent is a material that effectively controls wettability on the surface of the powder layer. When the leveling agent is used, the object-forming liquid has improved permeability in the powder layer and the strength of the object can be improved.

[0113] The sintering aid is a material that effectively improves the sintering efficiency during the sintering of an object. For example, when the sintering aid is used, the strength of the object can be improved, the sintering temperature can be reduced, and the sintering time can be shortened.

[0114] The polymer resin particles are materials that effectively adhere to the surfaces of the metal particles and are also referred to as organic external additives. The average particle size of the polymer resin particles is not particularly limited, and is preferably 0.1 micrometers or more but 10 micrometers or less and more preferably 0.1 micrometers or more but 1 micrometer or less.

[0115] The angle of repose of the powder is preferably 60 degrees or less, more preferably 50 degrees or less and still more preferably 40 degrees or less. When the angle of repose of the powder is 60 degrees or less, the powder can be efficiently and stably placed on a desired support position. The angle of repose can be measured, for example, with a powder property measuring instrument (POWDER TESTER PT-N TYPE, available from Hosokawa Micron Corporation).

[0116] <<Object Manufacturing Kit>>

[0117] The object manufacturing kit disclosed in the present invention includes object forming liquid and the above-mentioned powder, and may further include other components as needed, such as the removal liquid described below. In the object manufacturing kit, at least the powder and the object forming liquid are required to exist independently of each other. This is not limited to the following situation: an object forming liquid storage device that stores the object forming liquid and a powder storage device that stores the powder are integrated with each other. For example, even if the object forming liquid and the powder are stored in separate storage devices, respectively, the situation in which the powder and the object forming liquid are used in combination and the situation in which the user is essentially guided to use the powder and the object forming liquid in combination are also covered in the object manufacturing kit.

[0118] <<Object Manufacturing Method>>

[0119] The object manufacturing method disclosed in the present invention includes a powder layer forming step of forming a layer of powder containing metal particles, an object forming liquid applying step of applying object forming liquid to the powder layer, and a layer stacking step of sequentially repeating the powder layer forming step and the object forming liquid applying step to form a stacked body.

[0120] The object manufacturing method may further include a heating step of heating the laminated body to form a solidified product, a step of removing excess powder (which is powder adhering to the solidified product) to obtain a green body, a drying step of drying the green body to remove liquid components remaining in the green body, a degreasing step of heating the green body to remove resin such as resin derived from the applied object forming liquid to obtain a degreasing body, a sintering step of heating the degreasing body to obtain a sintered body, and a post-treatment step of applying post-treatment to the sintered body.

[0121] Each step will be described in detail below.

[0122] <Powder layer forming step>

[0123] The object manufacturing method includes a powder layer forming step of forming a layer of powder containing metal particles. The layer of powder is formed on a support (object forming platform (stage)). The method for placing the powder on the support and forming a thin layer of powder is not particularly limited and can be appropriately selected depending on the intended purpose. Examples of the method include a method using a known reverse rotating mechanism (reverse roller) used in a selective laser sintering method such as described in Japanese Patent No. 3607300, a method of spreading the powder using such components as a brush, a roller and a scraper, a method of squeezing the powder surface with an extrusion component to spread the powder, and a method using a known additive manufacturing device.

[0124] The formation of the powder layer using the powder layer forming unit such as a reverse rotation mechanism (reverse roller), a brush, a scraper, and a pressing member can be performed in the following manner.

[0125] That is, the reverse rotating mechanism (reverse roller), brush, roller or scraper or pressing member places the powder on a support body arranged in an outer frame (which may also be referred to as, for example, a "mold", "hollow cylinder" or "tubular structure") in such a manner that the support body can move upward and downward while sliding relative to the inner wall of the outer frame. When a support body that can move upward and downward in the outer frame is used as a support body, the powder is placed on the support body, which is arranged at a position slightly lower than the upper end opening of the outer frame, that is, at a position lower by an amount equivalent to the thickness of one powder layer. In the above manner, a thin layer of powder can be placed on the support body.

[0126] The powder layer thickness is not particularly limited and may be appropriately selected depending on the intended purpose.The average thickness of each layer is preferably 30 micrometers or more but 500 micrometers or less and more preferably 60 micrometers or more but 300 micrometers or less.

[0127] When the average thickness of the powder layer is 30 micrometers or more, the solidified product formed by applying the object-forming liquid to the powder has improved strength and can suppress shape collapse that may occur in a subsequent step such as a sintering step. When the average thickness of the powder layer is 500 micrometers or less, an object derived from the solidified product formed by applying the object-forming liquid to the powder has improved three-dimensional accuracy.

[0128] The average thickness can be measured by a known method without particular limitation.

[0129] The powder supplied by the powder layer forming unit may be stored in a powder storage device. The powder storage device is a component such as a container that stores powder. Examples of the powder storage device include a storage tank, a bag, a cassette, and a tank.

[0130] <Object Forming Liquid Application Step>

[0131] The object manufacturing method includes an object forming liquid application step of applying an object forming liquid to a layer of powder. As a method for applying an object forming liquid to a layer of powder, a method of discharging an object forming liquid is preferred. The method of discharging an object forming liquid is not particularly limited and can be appropriately selected depending on the intended intention. Examples of the method include a dispenser method, a spray method, and an inkjet method. Among these methods, the dispenser method has excellent droplet quantification but has a small coating area coverage. The spray method can easily form a tiny material jet and has a wide coating area coverage and excellent coating, but has insufficient droplet quantification and has the scattering of the object forming liquid caused by the spray flow. Therefore, the inkjet method is preferred. The inkjet method is preferred because the inkjet method has a droplet quantification that is superior to the droplet quantification of the spray method, a coating area coverage that is greater than the coating area coverage of the dispenser method, and can efficiently form complex objects with good accuracy.

[0132] When the inkjet method is used, the object forming liquid applying unit configured to apply the object forming liquid by discharging the object forming liquid is an inkjet head including a nozzle through which the object forming liquid is discharged. As the inkjet head, an inkjet head of a known inkjet printer can be suitably used. Examples of inkjet heads of inkjet printers include industrial grade inkjet RICOH MH / GH SERIES available from Ricoh Company, Ltd. Examples of inkjet printers include SG7100 available from Ricoh Company, Ltd.

[0133] The object forming liquid supplied to the object forming liquid applying unit may be stored in an object forming liquid storage device. The object forming liquid storage device is a component such as a container that stores the object forming liquid. Examples of the object forming liquid storage device include a storage tank, a bag, a cartridge, and a tank.

[0134] <Layer stacking step>

[0135] The object manufacturing method includes a step of sequentially repeating a powder layer forming step and an object forming liquid applying step to form a laminated body. A "laminated body" is a structure in which a plurality of powder layers each including an area to which an object forming liquid is applied are laminated. Here, the structure does not need to include a three-dimensional object held in a specific three-dimensional shape inside, or may include a three-dimensional object held in a specific three-dimensional shape inside.

[0136] The layer stacking step includes a step of placing the powder in the form of a thin layer (powder layer forming step) and a step of applying an object-forming liquid to the thin layer (object-forming liquid applying step), and a region to which the object-forming liquid is applied is formed in the layer of the powder by these steps. The layer stacking step further includes a step of placing (stacking) the powder in the form of a thin layer (powder layer forming step) and a step of applying an object-forming liquid to the thin layer (object-forming liquid applying step) on the thin layer (which is a layer of powder including a region to which the object-forming liquid is applied) by the same manner as described above, and a region to which the object-forming liquid is applied is formed in the newly stacked powder layer by these steps. The region to which the object-forming liquid is applied in the topmost stacked powder layer is continuous from the region to which the object-forming liquid is applied in the lower powder layer. Therefore, a region to which the object-forming liquid is applied having a thickness of two powder layers is obtained.

[0137] <Heating Step>

[0138] Preferably, the object manufacturing method includes a heating step of heating the laminate to form a cured product. An object that has been "cured" means an object that has been retained in a specific shape. A "cured product" is a structure including a three-dimensional object retained in a specific three-dimensional shape. A cured product means a product that has not yet undergone an excess powder removal step to remove excess powder (powder that does not constitute a three-dimensional object).

[0139] The heating temperature in the heating step is preferably higher than the softening point of the resin. At such a heating temperature, the resin can act as a binder that binds the metal particles to each other in the region to which the object forming liquid is applied, and form a pre-sintered object such as a solidified product and a green body derived from the solidified product.

[0140] The heating unit is not particularly limited. Examples of the heating unit include a drying device and a constant temperature and humidity device.

[0141] <Excess powder removal step>

[0142] Preferably, the object manufacturing method includes an excess powder removal step of removing excess powder (which is powder adhering to the solidified product) to obtain a green body. A "green body" is a three-dimensional object that is maintained in a specific three-dimensional shape and has undergone an excess powder removal step of removing excess powder (which is powder that does not constitute a solidified product). A "green body" preferably means a three-dimensional object to which substantially no excess powder adheres. In the present disclosure, the object forming portion that has undergone a heating step may be referred to as a "green body (unsintered body)", the object forming portion that has undergone a degreasing step may be referred to as a "degreasing body", and the object forming portion that has undergone a sintering step may be referred to as a "sintered body".

[0143] Preferably, the excess powder removing step includes either or both of a step of removing the excess powder from the cured product by blowing air and a step of removing the excess powder from the cured product by immersing the cured product in a removal liquid. More preferably, the excess powder removing step includes both of the steps.

[0144] The solidified product obtained by the heating step is in a state of being embedded in excess powder (which is powder to which the object forming liquid is not applied). When the solidified product is taken out from the embedded state, the excess powder adheres to the surface or the inside of the solidified product. It is difficult to remove the excess powder adhering to these parts. When the surface shape of the solidified product is complicated or the internal structure of the solidified product is like a flow path, it is even more difficult to remove the excess powder. Because the pre-sintered object made by the typical binder jetting method does not have high strength, there is a risk that the object may collapse when the blowing pressure caused by the air supply unit is high.

[0145] On the other hand, the cured product formed using the object forming liquid of the present disclosure and formed from the above-mentioned resin has improved bending strength and strength, whereby the cured product can withstand the blowing pressure. Here, the strength of the cured product expressed as three-point bending stress is preferably 3MPa or higher and more preferably 5MPa or higher.

[0146] -Removal liquid-

[0147] The removing liquid contains, for example, an organic solvent, and further contains other components as required. In order to distinguish between the organic solvent contained in the object-forming liquid and the organic solvent contained in the removing liquid, the organic solvent contained in the object-forming liquid may be referred to as a first organic solvent and the organic solvent contained in the removing liquid may be referred to as a second organic solvent.

[0148] Examples of the organic solvent include ketones, halogens, alcohols, esters, ethers, hydrocarbons, glycols, glycol ethers, glycol esters, pyrrolidones, amides, amines, and carbonates.

[0149] Examples of the ketone include acetone, methyl ethyl ketone, diethyl ketone, methyl propyl ketone, methyl isobutyl ketone, methyl amyl ketone, cyclohexanone, isophorone, acetophenone, and diacetone alcohol.

[0150] Examples of the halogens include dichloromethane, trichloroethylene, perchloroethylene, HCFC141-b, HCFC-225, 1-bromopropane, chloroform, and o-dichlorobenzene.

[0151] Examples of the alcohol include methanol, ethanol, butanol, isobutanol, isopropanol, n-propanol, tert-butanol, sec-butanol, 1,3-butanediol, 1,4-butanediol, 2-ethylhexanol, and benzyl alcohol.

[0152] Examples of esters include methyl acetate, ethyl acetate, butyl acetate, isobutyl acetate, sec-butyl acetate, methoxybutyl acetate, 3-methoxybutyl acetate, 3-methoxy-3-methylbutyl acetate, ethyl-3-ethoxy propionate, amyl acetate, n-propyl acetate, isopropyl acetate, methyl lactate, ethyl lactate, butyl lactate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether propionate, ethyl 3-ethoxypropionate, and dibasic acid esters (DBE).

[0153] Examples of the ether include dimethyl ether, ethyl methyl ether, diethyl ether, ethylene oxide, tetrahydrofuran, furan, benzofuran, diisopropyl ether, methyl cellosolve, ethyl cellosolve, butyl cellosolve, 1,4-dioxane, methyl tert-butyl ether (MTBE), ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, diethylene glycol dibutyl ether, dipropylene glycol dimethyl ether, and dipropylene glycol monomethyl ether.

[0154] Examples of hydrocarbons include benzene, toluene, xylene, solvent naphtha, n-hexane, isohexane, cyclohexane, ethylcyclohexane, methylcyclohexane, cyclohexene, cycloheptane, cyclopentane, heptane, pentamethylbenzene, pentane, methylcyclopentane, n-heptane, isooctane, n-decane, n-pentane, isopentane, mineral spirits, dimethyl sulfoxide, and linear alkylbenzenes.

[0155] Examples of the diol include ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and dimethoxytetraethylene glycol.

[0156] Examples of the glycol esters include ethylene glycol monoethyl ether acetate and diethylene glycol monobutyl ether acetate.

[0157] Examples of glycol ethers include methyl carbitol, ethyl carbitol, butyl carbitol, and methyl triglycol.

[0158] Examples of pyrrolidone include 2-pyrrolidone, N-ethyl-2-pyrrolidone, and N-methyl-2-pyrrolidone.

[0159] Examples of amides include dimethylformamide, dimethylacetamide and formamide.

[0160] Examples of the amine include tetramethylethylenediamine, N,N-diisopropylethylamine, ethylenediamine, triethylamine, diethylamine, aniline, pyrrolidine, piperidine, morpholine, pyrrole, pyridine, pyridazine, oxazole, thiazole, and 1,3-dimethyl-2-imidazolidinone.

[0161] Examples of the carbonate ester include diethyl carbonate, dimethyl carbonate, propylene carbonate, and ethyl methyl carbonate.

[0162] As other components, additives such as surfactants, defoamers, antibacterial / fungicides, pH adjusters, chelating agents, and anticorrosives may be added.

[0163] <Drying Step>

[0164] Preferably, the object manufacturing method includes a drying step of drying the green body to remove a liquid component, such as a removing liquid, remaining in the green body.

[0165] In the drying step, not only liquid components such as the removal liquid but also organic substances contained in the green body can be removed. As the drying unit, for example, a known drying device and a known constant temperature and humidity device can be used.

[0166] <Degreasing step>

[0167] Preferably, the object manufacturing method includes a degreasing step of heating the green body to remove resin such as from the applied object forming liquid to obtain a degreased body. A "degreased body" is a three-dimensional object obtained by degreasing an organic substance such as resin from a green body.

[0168] In the debinding step, the green body is degreased using a debinding unit at a temperature higher than or equal to the thermal decomposition temperature of an organic substance such as a resin and lower than the melting point or solidus temperature of the material (metal) constituting the metal particles (e.g., about 570 degrees Celsius, when using AlSi 10 The degreasing unit is heated at a temperature of 100°C for a predetermined time (for example, one to ten hours) to decompose and remove organic matter. Examples of the degreasing unit include a known sintering furnace and a known electric furnace.

[0169] <Sintering step>

[0170] Preferably, the object manufacturing method includes a sintering step of heating the degreased body to obtain a sintered body. The "sintered body" is a three-dimensional object formed by integrating metal materials constituting metal particles and produced by sintering the degreased body.

[0171] In the sintering step, the degreased body is sintered using a sintering unit at a temperature higher than or equal to the solidus temperature of the metal material constituting the metal particles (e.g., about 570 degrees Celsius when AlSi is used). 10 Mg particles) and below or equal to the liquidus temperature (e.g., about 600 degrees Celsius, when using AlSi 10 The sintering unit is heated at a temperature of 100°C for a predetermined time (e.g., one to ten hours) to integrate the metal materials constituting the metal particles. Examples of the sintering unit include known sintering furnaces. The sintering unit may be the same unit as the degreasing unit described above. The degreasing step and the sintering step may be performed continuously.

[0172] <Post-processing steps>

[0173] It is preferred that the object manufacturing method includes a post-treatment step of applying a post-treatment to the sintered body. The post-treatment step is not particularly limited and may be appropriately selected depending on the intended purpose. Examples of the post-treatment step include a surface protection treatment step and a painting step.

[0174] <Object Manufacturing Process>

[0175] Reference Figures 1A to 1E The object manufacturing process of the object manufacturing method of the present disclosure is described. Figures 1A to 1E A schematic diagram for explaining an example of operation of an object manufacturing apparatus.

[0176] First, the description will start from a state in which the first powder layer 30 has been formed on the object forming platform of the object forming trough. When the next powder layer is formed on the first powder layer 30, the supply platform 23 of the supply trough is moved upward, and the object forming platform 24 of the object forming trough is moved downward, as shown in FIG. Figure 1A Here, the distance by which the object forming platform 24 is moved downward is set in such a manner that the interval (stacked layer spacing) between the upper surface of the powder layer in the object forming groove 22 and the lower part (the lower tangent part) of the leveling roller 12 is Δt1. The interval Δt1 is not particularly limited, and is preferably about several tens of micrometers to 100 micrometers.

[0177] In the present disclosure, the leveling roller 12 is arranged in such a manner that there is a gap from the upper end surfaces of the supply trough 21 and the object forming trough 22. Therefore, when the leveling roller 12 conveys and supplies the powder 20 into the object forming trough 22 and level the powder, the upper surface of the powder layer is at a position higher than the upper end surfaces of the supply trough 21 and the object forming trough 22. This makes it possible to safely prevent the leveling roller 12 from contacting the upper end surfaces of the supply trough 21 and the object forming trough 22 and reduce damage to the leveling roller 12. When the surface of the leveling roller 12 is damaged, the leveling roller 12 tends to be on the powder layer 31 (see FIG. 1 ) supplied to the object forming trough 22. Figure 1D ) and reduce the flatness of the layer.

[0178] Then, if Figure 1B As described in FIG. 1 , the leveling roller 12 rotates in the arrow direction and moves the powder 20 placed at a position higher than the upper end surface of the supply trough 21 to the object forming trough 22 side to convey and supply the powder 20 to the object forming trough 22 (powder supply). Then, as Figure 1CAs described in the figure, the leveling roller 12 moves parallel to the table surface of the object forming platform 24 of the object forming tank 22, and forms a powder layer 31 having a predetermined thickness Δt1 on the object forming platform 24 of the object forming tank 22 (leveling). Here, any excess powder 20 remaining that is not used to form the powder layer 31 falls into the excess powder receiving tank 29. After the powder layer 31 is formed, the leveling roller 12 is moved to the side of the supply tank 21 and returned to the initial position (home position), as shown in FIG. Figure 1D In the description.

[0179] Here, the leveling roller 12 can move while maintaining a constant distance from the upper end surface of the object forming groove 22 and the supply groove 21. Because the leveling roller 12 can move while maintaining a constant distance, the leveling roller 12 can form a powder layer 31 with a uniform thickness h (equivalent to the stacking interlayer spacing Δt1) on the object forming groove 22 or the already formed solidified layer 30 together with the powder 20 being transported to the object forming groove 22. In the following description, the thickness h of the powder layer 31 and the stacking interlayer spacing Δt1 may be described without distinction, but mean the same thickness and the same meaning unless otherwise specifically specified. The thickness h of the powder layer 31 can be obtained by actual measurement. In this case, the average value obtained from multiple positions is preferred.

[0180] Then, if Figure 1E As described in the figure, the head 52 of the liquid discharge unit discharges the droplets 10 of the object forming liquid to the laminated body and forms the object forming liquid-applied layer 30 having the desired shape in the next powder layer 31. Next, the above-mentioned powder layer forming step and the object forming liquid applying step are repeated to newly form and laminate the object forming liquid-applied area 30. Here, the new object forming liquid-applied area 30 and the following object forming liquid-applied area 30 are integrated with each other. Thereafter, the powder layer forming step and the object forming liquid applying step are further repeated to complete the laminated body.

[0181] Example

[0182] The present disclosure will be described below by way of examples. The present disclosure should not be construed as being limited to these examples.

[0183] <Preparation of liquid for object forming>

[0184] (Examples 1-9 and Comparative Examples 1-6)

[0185] The materials described in Table 1-2 were mixed and stirred for 2 hours with a magnetic stirrer while heating at 80 degrees Celsius. After the materials were stirred for 2 hours and the heating was stopped, the resultant was stirred until the temperature became room temperature to prepare object-forming liquids of Examples 1-9 and Comparative Examples 1-6. The resins used in Examples 1-9, Comparative Examples 1-3, and Comparative Examples 5 and 6 were soluble in the solvents (e.g., organic solvents) of the respective object-forming liquids. The resin used in Comparative Example 4 was insoluble in the solvent (organic solvent) of the object-forming liquid.

[0186] The unit of the values ​​indicating the material contents in Tables 1 and 2 is mass percent. The resin contents indicate the total amount rather than the solid amount.

[0187] The materials in Table 1-2 below represent the following. The "ratio of the hydrophobic part in the resin" described below represents the ratio of the total amount of the structural unit represented by the structural formula (1) and the structural unit represented by the structural formula (3) in the resin relative to the total amount of the structural unit represented by the structural formula (1), the structural unit represented by the structural formula (3) and the structural unit represented by the structural formula (4). The "ratio of the hydrophilic part in the resin" described below represents the ratio of the amount of the structural unit represented by the structural formula (4) in the resin relative to the total amount of the structural unit represented by the structural formula (1), the structural unit represented by the structural formula (3) and the structural unit represented by the structural formula (4).

[0188] -JMR-7LO (polyvinyl acetate, obtained from Japan Vam & Poval Co., Ltd.)-

[0189] -Structural formula

[0190]

[0191] -Ratio of hydrophobic part in resin: 98 mol% to 100 mol%

[0192] -Ratio of hydrophilic part in resin: 0 mol% to 2 mol% (The structural unit represented by structural formula (4) in the resin may be contained in a small amount due to expediency of production and not actively. Therefore, the resin is regarded as substantially free of the structural unit represented by structural formula (4).

[0193] -Tg: 30 degrees Celsius to 40 degrees Celsius

[0194] - Softening point: about 100 degrees Celsius

[0195] -Number average molecular weight (Mn): 20,000 or less

[0196] - Component concentration: 99 mass% or higher

[0197] -JMR-10LL (partially saponified polyvinyl acetate, obtained from Japan Vam & Poval Co., Ltd.)-

[0198] -Structural formula

[0199]

[0200] -Ratio of hydrophobic part in resin: 89 mol% to 91 mol%

[0201] -Ratio of hydrophilic part in resin: 9 mol% to 11 mol%

[0202] -Tg: 30 degrees Celsius to 40 degrees Celsius

[0203] - Softening point: about 105 degrees Celsius

[0204] -Number average molecular weight (Mn): 20,000 or less

[0205] - Component concentration: 99 mass% or higher

[0206] -JMR-10L (partially saponified polyvinyl acetate, obtained from Japan Vam & Poval Co., Ltd.)-

[0207] -Structural formula

[0208]

[0209] -Ratio of hydrophobic part in resin: 65 mol%

[0210] -Ratio of hydrophilic part in resin: 35 mol%

[0211] -Tg: 30 degrees Celsius to 40 degrees Celsius

[0212] - Softening point: about 110 degrees Celsius

[0213] -Number average molecular weight (Mn): 25,000 or less

[0214] - Component concentration: 99 mass% or higher

[0215] -ESLEC BL-10 (polyvinyl butyral, obtained from Sekisui Chemical Co., Ltd.)-

[0216] -Structural formula

[0217]

[0218] -Ratio of hydrophobic portion in resin: 72 mol% (3 mol% of the structural unit represented by the structural formula (1) and 69 mol% of the structural unit represented by the structural formula (3))

[0219] -Ratio of hydrophilic part in resin: 28 mol%

[0220] -Tg: 67 degrees Celsius

[0221] - Softening point: 100°C to 120°C

[0222] -Number average molecular weight (Mn): about 15,000

[0223] - Component concentration: 99 mass% or higher

[0224] -PVP K15 (polyvinyl pyrrolidone, obtained from FUJIFILM Wako Pure Chemical Corporation)-

[0225] -Structural formula

[0226]

[0227] -Ratio of hydrophobic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulae (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0228] -Ratio of hydrophilic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulas (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0229] - Softening point: 100°C to 130°C

[0230] -Number average molecular weight (Mn): about 10,000 or less

[0231] - Component concentration: 90 mass % or more

[0232] -PVP K25 (polyvinyl pyrrolidone, obtained from FUJIFILM Wako Pure Chemical Corporation)-

[0233] -Structural formula

[0234]

[0235] -Ratio of hydrophobic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulae (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0236] -Ratio of hydrophilic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulas (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0237] - Softening point: 120°C to 150°C

[0238] -Number average molecular weight (Mn): about 22,000 to 35,000

[0239] - Component concentration: 95 mass % or higher

[0240] -ARAKYD 7036 (polyester, available from Arakawa Chemical Industries, Ltd.)-

[0241] -Structural formula

[0242]

[0243] -Ratio of hydrophobic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulae (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0244] -Ratio of hydrophilic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulas (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0245] -Tg: 28 degrees Celsius

[0246] -Number average molecular weight (Mn): 14,000

[0247] - Component concentration: 50 mass%

[0248] -IUPIZETA FPC0330 (polycarbonate, obtained from Mitsubishi Gas Chemical Company, Inc.)-

[0249] -Structural formula

[0250]

[0251] -Ratio of hydrophobic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulae (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0252] -Ratio of hydrophilic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulas (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0253] -Tg: 126 degrees Celsius

[0254] -Z Average molecular weight (Mz): 32,000

[0255] - Component concentration: 99 mass% or higher

[0256] -IUPIZETA RX2136P (polycarbonate, available from Mitsubishi Gas Chemical Company, Inc.)-

[0257] -Structural formula

[0258]

[0259] -Ratio of hydrophobic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulae (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0260] -Ratio of hydrophilic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulas (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0261] -Tg: 123 degrees Celsius

[0262] -z Average molecular weight (Mz): 26,000

[0263] - Component concentration: 99 mass% or higher

[0264] -JC-25 (polyvinyl alcohol, obtained from Japan Vam & Poval Co., Ltd.)-

[0265] -Structural formula

[0266]

[0267] -Ratio of hydrophobic part in resin: 0 mol%

[0268] -Ratio of hydrophilic part in resin: 100 mol%

[0269] -Tg: 67 degrees Celsius

[0270] -Number average molecular weight (Mn): 25,000

[0271] - Component concentration: 99 mass% or higher

[0272] -OLICOX KC-1700P (acrylic acid, available from Kyoeisha Chemical Co., Ltd.)-

[0273] -Structural formula

[0274]

[0275] -Ratio of hydrophobic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulae (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0276] -Ratio of hydrophilic part in resin: cannot be calculated because the resin does not contain the structural units represented by the structural formulas (1), (3) and (4) (denoted as "-" in Tables 1 and 2 below)

[0277] -Number average molecular weight (Mn): 100,000

[0278] - Component concentration: 99 mass% or higher

[0279] Of the resins described above, the resins used in Examples 1 to 9 all had the property of thermally decomposing by 95% by mass or more when subjected to a temperature increase from 30 degrees Celsius to 550 degrees Celsius.

[0280] [Viscosity of liquid for object forming]

[0281] The viscosity of the object-forming liquid at 25 degrees Celsius was measured with an R-type viscometer (obtained from Toki Sangyo Co., Ltd.) and evaluated according to the following evaluation criteria. The measurement results and the evaluation results are shown in the following Tables 1 and 2. In Comparative Example 4, the measurement and evaluation of the viscosity were not performed because the resin of the object-forming liquid was not dissolved in the solvent (denoted as "-" in the following Tables 1 and 2).

[0282] (Evaluation Criteria)

[0283] A: The viscosity is 5 mPa·s or higher but 20 mPa·s or lower.

[0284] B: Viscosity higher than 20 mPa·s but 50 mPa·s or lower.

[0285] C: Viscosity higher than 50 mPa·s.

[0286] <Manufacturing of Objects (Green and Sintered)>

[0287] The object forming liquid and the powder containing metal particles (AlSi 10 Mg powder (obtained from ToyoAluminium KK, Si10Mg-30BB, volume average particle size of 35 μm, the surface of the metal particles is not coated with resin), each object (green body and sintered body) was manufactured in the following manner.

[0288] 1) First, use Figures 1A to 1EIn the known object manufacturing apparatus described in , powder is transferred from a supply-side powder storage tank to a forming-side powder storage tank to form a powder thin layer having an average thickness of 100 micrometers on a support.

[0289] 2) Next, the object-forming liquid was discharged from the nozzles of a known inkjet discharge head and applied to the surface of the formed powder thin layer. The area to which the object-forming liquid was discharged had a rectangular shape with a size of 70 mm×12 mm.

[0290] 3) Next, the above-mentioned 1) and 2) operations are repeated until the total average thickness becomes 5 mm, and the powder thin layers are sequentially stacked to form a laminated body. Subsequently, the laminated body is heated at an appropriate temperature suitable for the softening point of the resin contained in each object-forming liquid to form a cured product.

[0291] 4) Next, the solidified product was blown to remove any excess powder, and immersed in a hydrocarbon solvent serving as a removal liquid at 25 degrees Celsius for 1 hour to obtain a green body (unsintered body). Subsequently, the green body was dried by standing at 100 degrees Celsius for 2 hours in a vacuum environment.

[0292] 5) Next, the green body is degreased by heating to obtain a degreased body. The degreased body is sintered by further heating to produce a sintered body.

[0293] The green body bending strength, green body density, and sintered body density of the object obtained by the above-mentioned operations 1) to 5) were measured and evaluated in the following manner. The results are shown in Tables 1 and 2 below. In Comparative Example 4, since the resin of the object-forming liquid was insoluble in the solvent, object production was not performed and measurement and evaluation were not performed (represented as "-" in Tables 1 and 2 below).

[0294] [Green body bending strength]

[0295] The bending strength of the green body manufactured in 4) above was measured and evaluated according to the following evaluation criteria. For the measurement of bending strength, a universal tester, a 1 kN load cell and a three-point bending fixture from Shimadzu Corporation (autograph, model No. AG-I) were used. The stress when the distance between the fulcrums was set to 24 mm and the load point was displaced at a speed of 1 mm / min was plotted against the strain. The stress at the breaking point was used as the maximum stress.

[0296] (Evaluation Criteria)

[0297] A: The bending strength is 5 MPa or more.

[0298] B: The bending strength is 3 MPa or more but less than 5 MPa.

[0299] C: The bending strength is 2.7 MPa or more but less than 3 MPa.

[0300] D: Bending strength is less than 2.7 MPa.

[0301] [Green body density]

[0302] The density of the green body produced in the above 4) was measured. Next, the ratio of the density of the green body to the density of the metal material constituting the green body was calculated and evaluated according to the following evaluation criteria.

[0303] (Evaluation Criteria)

[0304] A: The ratio of the density of the green body is 55% or more.

[0305] B: The ratio of the density of the green body is 50% or more but less than 55%.

[0306] C: The ratio of the density of the green body is 47% or more but less than 50%.

[0307] D: The ratio of the density of the green body is lower than 47%.

[0308] [Sintered body density]

[0309] The density of the sintered body produced in the above 5) was measured. Next, the ratio of the density of the sintered body to the density of the metal material constituting the sintered body was calculated and evaluated according to the following evaluation criteria.

[0310] (Evaluation Criteria)

[0311] A: The ratio of the density of the sintered body is 97% or more.

[0312] B: The ratio of the density of the sintered body is 93% or more but less than 97%.

[0313] C: The density ratio of the sintered body is less than 93%.

[0314] Table 1

[0315]

[0316] Table 2

[0317]

[0318] According to Examples 1 to 5, the object-forming liquid including the resin including the structural unit represented by the structural formula (1) has a low viscosity and can improve the green body bending strength, green body density, and sintered body density.

[0319] According to Examples 1 to 5, the object forming liquid including the resin containing a small amount of the hydrophilic part can improve the green body bending strength, green body density and sintered body density. On the other hand, there is a tendency that the viscosity of the object forming liquid including the resin containing the hydrophilic part is high.

[0320] According to Example 5, the viscosity of the object-forming liquid containing the resin having a high hydrophobic portion ratio can be suppressed despite the high content of the resin in the object-forming liquid.

[0321] According to Examples 6 to 9, the object-forming liquid including the resin including the structural unit represented by the structural formula (2) has a low viscosity and can improve the green body bending strength, green body density, and sintered body density.

[0322] According to Example 9, the viscosity of the object-forming liquid containing at least one selected from Component 1 and at least one selected from Component 2 can be better suppressed.

[0323] According to Comparative Example 1, the object-forming liquid containing the polyester resin had a low viscosity, but it was impossible to improve the green body bending strength and the green body density with the object-forming liquid.

[0324] According to Comparative Examples 2 and 3, it was impossible to suppress the viscosity of the object-forming liquid containing the polycarbonate resin, and it was also impossible to improve the green body bending strength, green body density and sintered body density with these object-forming liquids.

[0325] According to Comparative Example 4, it is impossible to manufacture an object using polyvinyl alcohol which is insoluble in a solvent (organic solvent).

[0326] According to Comparative Example 5, the aqueous object-forming liquid cannot improve the green body density and the sintered body density.

[0327] According to Comparative Example 6, the object-forming liquid including the acrylic resin had a low viscosity but could not improve the bending strength of the green body.

Claims

1. A liquid for forming an object, comprising: A resin comprising at least one structural unit selected from the group consisting of a structural unit represented by the following structural formula (1) and a structural unit represented by the following structural formula (2); and Organic solvents, wherein the object-forming liquid is substantially free of water, and applying an object-forming liquid to a layer of a powder containing metal particles by an inkjet method, The surface of the metal particles does not contain a coating having a resin 2. The object forming liquid according to claim 1, wherein the resin comprises a structural unit represented by structural formula (1), and The resin containing the structural unit represented by the structural formula (1) includes at least one selected from the group consisting of a polyvinyl acetate resin and a partially saponified polyvinyl acetate resin.

3. The object forming liquid according to claim 1 or 2, wherein the resin comprises a structural unit represented by structural formula (1), and The total amount of the structural unit represented by the structural formula (1) and the structural unit represented by the following structural formula (3) in the resin is 60 mol% or more relative to the total amount of the structural unit represented by the structural formula (1), the structural unit represented by the structural formula (3) and the structural unit represented by the following structural formula (4), 4. The object forming liquid according to claim 1 or 2, wherein the resin comprises a structural unit represented by structural formula (1), and The organic solvent includes at least one structure selected from the group consisting of an alkoxy group, an ether bond, and an ester bond.

5. The object forming liquid according to claim 4, The organic solvent is an alkylene glycol dialkyl ether.

6. The object forming liquid according to claim 1, wherein the resin comprises a structural unit represented by structural formula (2), and The organic solvent comprises at least one selected from component 1, which is a group consisting of cyclic esters (lactones), cyclic ketones and alkylene glycol monoalkyl ethers.

7. The object forming liquid according to claim 6, The organic solvent further comprises at least one selected from component 2, which is a group consisting of alkylene glycol dialkyl ethers.

8. The object forming liquid according to claim 7, The mass ratio of the total amount of component 1 to the total amount of component 2 (component 1 / component 2) is 60 / 40 to 100 / 0.

9. The object forming liquid according to claim 1 or 2, wherein the mass ratio of the amount of the organic solvent to the amount of the resin (organic solvent / resin) is 75 / 25 or more but 95 / 5 or less.

10. The object forming liquid according to claim 1 or 2, wherein the resin thermally decomposes by 95% by mass or more when subjected to a temperature increase from 30 degrees Celsius to 550 degrees Celsius.

11. The object forming liquid according to claim 1 or 2, wherein the content of the resin is 5.0% by mass or more but 30.0% by mass or less relative to the mass of the object-forming liquid.

12. The object forming liquid according to claim 1 or 2, wherein the total amount of the resin and the organic solvent is 90.0% by mass or more relative to the mass of the object-forming liquid.

13. The object forming liquid according to claim 1 or 2, The metal particles include at least one selected from aluminum, zinc and magnesium.

14. The object-forming liquid according to claim 1 or 2, The viscosity of the object forming liquid at 25 degrees Celsius is 5 mPa·s or higher but 50 mPa·s or lower.

15. A method for manufacturing an object, comprising: forming a layer of a powder containing metal particles, wherein the surfaces of the metal particles do not have a coating layer having a resin; applying an object-forming liquid to the layer of the powder, wherein in the applying, the object-forming liquid is discharged to the layer of the powder by an inkjet method; and The forming and the applying are sequentially repeated to form a laminated body, wherein the object-forming liquid comprises: a resin comprising at least one structural unit selected from the group consisting of a structural unit represented by the following structural formula (1) and a structural unit represented by the following structural formula (2), and an organic solvent, and is substantially free of water, 16. The method for manufacturing an object according to claim 15, further comprising: heating the laminate to form a cured product; and Excess powder, which is powder adhering to the solidified product, is removed to obtain a green body.

17. The method for manufacturing an object according to any one of claims 15 to 16, further comprising: heating the green body to form a degreased body from which the resin is removed; and The degreased body is heated to form a sintered body.

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