Slurry for three-dimensional shaping and method for manufacturing three-dimensional shaped object

Abstract

To reduce change in viscosity of a slurry for three-dimensional molding over time.SOLUTION: A slurry for three-dimensional molding includes inorganic particles, an association in which a part of amino groups included in polyalkyleneimine is associated with a carboxy group of aliphatic acid, an acrylate monomer polymerizable by light, a photoinitiator, and a non-aqueous solvent. A ratio of mol number of aliphatic acid to a mol number of the amino group included in the polyalkyleneimine is 10-20%. The acrylate monomer is a monomer having three or four acryloyl groups in a molecule, and a ratio thereof to the inorganic particles is 7.5-20 mass%.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a slurry for three-dimensional shaping and a method for manufacturing a three-dimensional shaped object.

Background Art

[0002] Conventionally, as a method for manufacturing a three-dimensional shaped object using photopolymerization with a slurry for three-dimensional shaping, the following method is known. That is, after forming an uncured layer using a slurry for three-dimensional shaping, a series of operations of irradiating the uncured layer with light to form a processed layer in which the portions not irradiated with light are not cured and the portions irradiated with light are cured is repeated until a predetermined number of processed layers are laminated. Thereafter, a three-dimensional shaped object composed of the cured portions among the predetermined number of laminated processed layers is taken out. As such a slurry for three-dimensional shaping, a slurry in which inorganic particles are dispersed in a liquid UV-curable resin is known. However, in this slurry, since the shrinkage during curing of the liquid UV-curable resin by UV irradiation is large, high dimensional accuracy could not be achieved. Further, when taking out the three-dimensional shaped object, it is necessary to remove the uncured liquid UV-curable resin remaining inside, but since its fluidity is low, it could not be easily removed. The photocurable slurry described in Patent Document 1 was developed in consideration of such problems. This photocurable slurry contains inorganic particles, an aggregate of a polyalkyleneimine and a fatty acid, a polyfunctional acrylate, a photopolymerization initiator, and a non-aqueous solvent. The aggregate of a polyalkyleneimine and a fatty acid adsorbs on the surface of the inorganic particles. The polyfunctional acrylate polymerizes by a photopolymerization reaction. The reactive amino group contained in the aggregate binds to the acryloyl group remaining in the polymer by Michael addition. Thereby, the inorganic particles having the aggregate adsorbed on the surface are crosslinked via the polymer and cured. The obtained three-dimensional shaped object has high dimensional accuracy because the curing shrinkage is small. Further, since the uncured slurry has a relatively low viscosity, it can be relatively easily removed from the inside of the three-dimensional shaped object.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the viscosity of the photocurable slurry of Patent Document 1 may vary significantly between immediately after preparing the slurry and after several hours have passed. Since manufacturing a three-dimensional shaped object requires a long time, if the viscosity of the slurry changes significantly over time during manufacturing, lamination defects are likely to occur.

[0005] The present invention has been made to solve such problems, and the main object is to suppress the change in the viscosity of the slurry for three-dimensional shaping over time.

Means for Solving the Problems

[0006] The slurry for three-dimensional shaping of the present invention is inorganic particles, an aggregate in which a part of the amino groups contained in the polyalkyleneimine is associated with the carboxy group of the fatty acid, an acrylate monomer polymerizable by light, a photoinitiator, a non-aqueous solvent, and is a slurry for three-dimensional shaping containing the ratio of the number of moles of the fatty acid to the number of moles of the amino groups contained in the polyalkyleneimine is 10 to 20% for the aggregate, the acrylate monomer is a monomer having 3 or 4 acryloyl groups in one molecule, and the ratio to the inorganic particles is 7.5 to 20% by mass, the inorganic particles are at least one of inorganic oxide particles, inorganic nitride particles, and inorganic carbide particles, and the inorganic oxide particles are at least one of alumina, zirconia, and yttria, is such.

[0007] According to this slurry for three-dimensional shaping, it is possible to suppress the change in viscosity over time. The reason for obtaining such an effect is considered as follows. Since the ratio of the number of moles of fatty acid to the number of moles of amino groups contained in polyalkyleneimine is 10 to 20%, the reactive amino groups contained in polyalkyleneimine are appropriately capped by the fatty acid, and the number of reaction initiation points (the number of reactive amino groups not capped) is adjusted to an appropriate number. Therefore, the reaction in which amino groups in the aggregate naturally add to acryloyl groups of acrylate monomer (or its polymer) can be suppressed, and thus the change in slurry viscosity over time can be suppressed. Further, the acrylate monomer has 3 or 4 acryloyl groups in one molecule, and since the ratio to inorganic particles is 7.5 to 20% by mass, compared with the case where there are 5 or more acryloyl groups or the ratio to inorganic particles exceeds 20% by mass, it is considered that the photopolymerization reaction hardly proceeds naturally, and the change in slurry viscosity over time can be suppressed.

[0008] The method for manufacturing a three-dimensional shaped object of the present invention is a series of operations in which an uncured layer is formed on a stage using the above-described slurry for three-dimensional shaping, and then the portion not irradiated with light is not cured and the portion irradiated with light is cured to form a processed layer by irradiating the uncured layer with light, and then the stage is lowered, which is repeated until a predetermined number of the processed layers are laminated, and then the three-dimensional shaped object is taken out by washing and removing the uncured portion among the processed layers laminated in the predetermined number.

[0009] According to this method for manufacturing a three-dimensional shaped object, a three-dimensional shaped object with few lamination defects can be manufactured with high dimensional accuracy. The amount of lowering of the stage may be, for example, one layer of the processed layer.

Brief Description of the Drawings

[0010]

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Mode for Carrying Out the Invention

[0011] Preferred embodiments of the present invention will be described below.

[0012] The slurry for 3D shaping in the present embodiment contains inorganic particles, an aggregate, an acrylate monomer, a photopolymerization initiator, and a non-aqueous solvent.

[0013] The inorganic particles are preferably at least one of inorganic oxide particles, inorganic nitride particles, and inorganic carbide particles. Examples of the inorganic oxide particles include alumina particles, zirconia particles, and yttria particles. Examples of the inorganic nitride particles include silicon nitride and boron nitride. Examples of the inorganic carbide particles include silicon carbide. The specific surface area diameter of the inorganic particles is preferably from 10 nm to 10 μm, more preferably from 30 nm to 5 μm. If the specific surface area diameter of the inorganic particles is 10 nm or more, it becomes easier to perform surface modification with the aggregates. On the other hand, if the specific surface area diameter of the inorganic particles is 10 μm or less, it is possible to mold a complex-shaped member without the shape collapsing. The "specific surface area diameter" can be obtained by geometrically calculating the diameter when the shape of the inorganic particles is regarded as spherical from the specific surface area of the inorganic particles determined by the gas adsorption method.

[0014] In the slurry for three-dimensional shaping of the present embodiment, the content of the inorganic particles is preferably from 20% by volume to 60% by volume, more preferably from 30% by volume to 40% by volume. If the content of the inorganic particles is 20% by volume or more, it becomes easier to maintain the mechanical strength of the inorganic molded body provided with a complex shape. On the other hand, if the content of the inorganic particles is 40% by volume or less, the inorganic particles modified with the aggregate of polyalkyleneimine and fatty acid are likely to be uniformly and stably dispersed in the non-aqueous solvent.

[0015] The aggregate is one in which a part of the amino groups contained in the polyalkyleneimine is associated with the carboxy group of the fatty acid.

[0016] Examples of the polyalkyleneimine include polyethyleneimine, polypropyleneimine, polybutadieneimine, etc. Among these, polyethyleneimine is preferred from the viewpoint of the dispersion stability of the inorganic particles in a slurry containing a high concentration of the inorganic particles. The weight average molecular weight (Mw) of the polyalkyleneimine is preferably from 300 to 30,000, more preferably from 600 to 10,000. If the weight average molecular weight (Mw) of the polyalkyleneimine is 300 or more, the polyalkyleneimine and the fatty acid are likely to associate to form an aggregate. On the other hand, if the weight average molecular weight (Mw) of the polyalkyleneimine is 30,000 or less, in the slurry for three-dimensional shaping, the inorganic particles modified with the aggregate of the polyalkyleneimine and the fatty acid are likely to be uniformly and stably dispersed in the non-aqueous solvent.

[0017] Examples of the fatty acid include saturated fatty acids and unsaturated fatty acids. As the saturated fatty acids and unsaturated fatty acids, those having 4 to 30 carbon atoms are preferred. Examples of the saturated fatty acid include lauric acid, myristic acid, palmitic acid, stearic acid, etc. Examples of the unsaturated fatty acid include oleic acid, linoleic acid, eleostearic acid, etc. Among these, oleic acid is more preferred from the viewpoint of the dispersion stability of the inorganic particles in a slurry containing a high concentration of the inorganic particles. Further, as the saturated fatty acids and unsaturated fatty acids, the above-mentioned ones can be used alone or in combination of two or more.

[0018] The aggregate is one in which the carboxy group of the fatty acid is bonded to a part of the reactive amino groups of the polyalkylamine and can be adsorbed on the surface of the inorganic particles. The ratio of the number of moles of the fatty acid to the number of moles of the amino groups contained in the polyalkyleneimine (hereinafter referred to as the association rate) is preferably 10 to 20%. If the association rate is 10% or more, the aggregate can moderately modify the surface of the inorganic particles. If the association rate is 20% or less, in the slurry for three-dimensional shaping, the inorganic particles modified with the aggregate are likely to be uniformly and stably dispersed in the non-aqueous solvent. The polyalkyleneimine has the chemical formula -(C m H 2m NH)n It is represented by -. As can be seen from this chemical formula, 1 mole of polyalkyleneimine contains n moles of amino groups. Therefore, if the number of moles of polyalkyleneimine is known, the number of moles of amino groups contained in the polyalkyleneimine can be determined. For example, if the polyalkyleneimine is polyethyleneimine and its weight average molecular weight is 1800, since the total atomic weight of the repeating unit C2H4NH is 43, n is 1800 / 43 (≈41.86).

[0019] In the slurry for three-dimensional modeling of the present embodiment, the content of the aggregate is 0.6 mg / m based on the surface area of the inorganic particles. 2 ~3.0 mg / m 2 It is preferably, and 0.8 mg / m 2 ~2.0 mg / m 2 is more preferably.

[0020] The acrylate monomer is a monomer that can be polymerized by light (for example, ultraviolet light). The acrylate monomer preferably has 3 or 4 acryloyl groups (CH2=CH-C(=O)-) in one molecule. When an acrylate monomer having 3 or 4 acryloyl groups in one molecule is used, the change in slurry viscosity over time and the change in rheological properties over time are reduced. Examples of such acrylate monomers include trimethylolpropane acrylate, trimethylolpropane propylene oxide-modified triacrylate, trimethylolpropane ethylene oxide-modified triacrylate, isocyanuric acid ethylene oxide-modified triacrylate, pentaerythritol tri(or tetra)acrylate, ditrimethylolpropane tetraacrylate, diglycerin ethylene oxide-modified acrylate, and the like. These acrylate monomers may be used alone or in combination of two or more.

[0021] In the slurry for three-dimensional shaping of the present embodiment, the proportion of the acrylate monomer is preferably 7.5% by mass to 20% by mass with respect to the inorganic particles. If this proportion is 7.5% by mass to 20% by mass, the change over time in the slurry viscosity and the change over time in the rheological properties can be reduced, and sufficient strength can be obtained even if the resulting three-dimensional shaped object is a thin plate (for example, about 1 mm thick).

[0022] In addition, the slurry for three-dimensional shaping of the present embodiment may contain a small amount (to the extent that it does not affect the performance of the slurry for three-dimensional shaping) of an acrylate monomer having 2 or less or 5 or more acryloyl groups in one molecule.

[0023] The photopolymerization initiator is not particularly limited as long as it generates radicals for initiating radical polymerization of the acrylate monomer by irradiating the slurry for three-dimensional shaping with light. Examples of the photopolymerization initiator include benzyldimethyl ketal, benzophenone, methyl 2-benzoylbenzoate, 4,4'-bis(diethylamino)benzophenone, 1-hydroxy-cyclohexyl-phenyl-ketone, 2-hydroxy-2-methyl-1-phenyl-1-propanone, 2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone, 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide, bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide, and the like.

[0024] In the slurry for three-dimensional shaping of the present embodiment, the content of the photopolymerization initiator is preferably 0.5% by mass to 8.0% by mass with respect to the acrylate monomer, and more preferably 1.0% by mass to 5.0% by mass. If the content of the photopolymerization initiator is 0.5% by mass or more with respect to the acrylate monomer, the slurry for three-dimensional shaping can be solidified in a short time to form a complex shape. On the other hand, if the content of the photopolymerization initiator is 8.0% by mass or less with respect to the acrylate monomer, a decrease in the solidification rate of the slurry for three-dimensional shaping when forming a complex shape can be suppressed.

[0025] The non-aqueous solvent is not particularly limited as long as it can dissolve the aggregate of polyalkyleneimine and fatty acid. Examples of the non-aqueous solvent include α-terpineol, toluene, xylene, tetrahydrofuran, and the like.

[0026] In the slurry for three-dimensional shaping of the present embodiment, the content of the non-aqueous solvent is preferably 35% to 90% by volume, and more preferably 50% to 60% by volume. If the content of the non-aqueous solvent is 35% by volume or more, the inorganic particles can be uniformly dispersed in the slurry for three-dimensional shaping. On the other hand, if the content of the non-aqueous solvent is 90% by volume or less, a complex shape can be formed without causing the collapse of the shaped body.

[0027] The slurry for three-dimensional shaping of the present embodiment may contain a polymerization inhibitor for inhibiting the polymerization of the acrylate monomer. The polymerization inhibitor is not particularly limited, and a general radical polymerization inhibitor can be used according to the type of the acrylate monomer. In the slurry for three-dimensional shaping, the content of the polymerization inhibitor is not particularly limited and is appropriately adjusted according to the type of the acrylate monomer, the content in the slurry for three-dimensional shaping, and the like.

[0028] The slurry for three-dimensional shaping of the present embodiment preferably has a viscosity of 100 Pa·s or less at a shear rate of 1 s at room temperature. If the viscosity of the slurry is within this range, the slurry that has not cured when forming a three-dimensional shaped object using the slurry for three-dimensional shaping can be relatively easily removed from the three-dimensional shaped object. Also, with respect to the viscosity η0 at a shear rate of 1 s at room temperature immediately after preparing the slurry, at the time point 6 hours after preparing the slurry, at a shear rate of 1 s at room temperature -1 of -1 the slurry, -1The change rate η6 / η0 of the viscosity η6 is preferably from 0.9 to 1.6. By doing so, since the change over time of the slurry is small, there is no possibility that the behavior of the slurry will change significantly during the formation of a three-dimensional formed object using the slurry for three-dimensional shaping. Further, it is preferable that the behavior of the viscosity of the slurry when the shear rate is changed from low to high does not change significantly over time. For example, it is assumed that when the shear rate is changed from low to high, the behavior of the viscosity at room temperature immediately after slurry adjustment shows a tendency that the viscosity decreases as the shear rate increases. In that case, it is preferable that the behavior of the viscosity at the time point 6 hours after slurry adjustment when the shear rate is changed from low to high also shows a tendency that the viscosity decreases as the shear rate increases, and it is not preferable that the viscosity shows a tendency to increase as the shear rate increases.

[0029] Next, the reaction mechanism when the slurry for three-dimensional shaping of the present embodiment cures will be described. FIG. 1 is a schematic diagram showing a state where the slurry 10 for three-dimensional shaping cures into the inorganic molded body 12, FIG. 2 is an explanatory diagram showing an example of the aggregate 24, and FIG. 3 is an explanatory diagram showing a state where the aggregate adsorbed particles 20 are crosslinked to each other.

[0030] As shown in FIG. 1, the slurry 10 for three-dimensional shaping is a dispersion of aggregate adsorbed particles 20 in which aggregates 24 are adsorbed on the surface of inorganic particles 22 and acrylate monomers 30 in a non-aqueous solvent 40. The non-aqueous solvent 40 contains a photopolymerization initiator. FIG. 2 illustrates an aggregate 24 when polyethyleneimine is used as the polyalkyleneimine 24a and oleic acid is used as the fatty acid 24b. The polyalkyleneimine 24a is hydrophilic, and the fatty acid 24b is hydrophobic. As shown in FIG. 2, by capping a part of the amino groups of the polyalkyleneimine 24a with the carboxy groups of the fatty acid 24b, the balance between hydrophilicity and hydrophobicity can be adjusted, and the number of reaction starting points can be adjusted. The number of reaction starting points is the number of reactive amino groups (primary or secondary amino groups).

[0031] When light is irradiated onto the slurry 10 for three-dimensional shaping, first, a photoinitiator generates radicals. Then, the acrylate monomer 30 starts radical polymerization to produce the acrylate polymer 32. Fig. 3 exemplifies the acrylate polymer 32 when polymerized using pentaerythritol tri(or tetra)acrylate as the acrylate monomer 30. In the acrylate polymer 32, a part of the acryloyl groups contained in the monomer has polymerized, and the rest remains as it is.

[0032] Since radical polymerization is an exothermic reaction, heat is generated with the start of radical polymerization. Due to the heat (reaction heat) caused by this radical polymerization, the amino group of the polyalkyleneimine 24a contained in the aggregate 24 adsorbed on the surface of the inorganic particles 22 undergoes Michael addition to the acryloyl group contained in the acrylate polymer 32. The state at that time is shown by the dotted arrow in Fig. 3. As a result, the aggregate-adsorbed particles 20 are crosslinked and cured via the acrylate polymer 32 to become the inorganic molded body 12 (see Fig. 1).

[0033] In addition to the reaction mechanism described above, it is considered that after the amino group contained in the aggregate 24 undergoes Michael addition to a part of the acryloyl groups contained in the acrylate monomer 30, the acryloyl groups contained in the Michael adduct polymerize to form a polymer.

[0034] Next, a case of producing an inorganic molded body (3D-printed object) using the slurry for 3D printing of the present embodiment will be described. FIG. 4 is an explanatory diagram of a stereolithography apparatus (3D printing apparatus) 60. First, the slurry for 3D printing of the above-described embodiment is discharged along a predetermined direction (X direction) onto the stage 62 or the processed layer 70 using the dispenser 64. Next, the discharged liquid composition is stretched in a direction intersecting the X direction (for example, the Y direction orthogonal to the X direction) with the squeegee 66 to form an uncured layer 68. At this time, it is stretched with the squeegee 66 so that the thickness of the uncured layer 68 becomes the target thickness. Subsequently, laser light is irradiated. Then, the portion of the uncured layer 68 that has not been irradiated with the laser light is not cured and the portion that has been irradiated with the laser light is cured. The uncured layer after the laser light is irradiated in this way is referred to as the processed layer 70. Note that the wavelength, diameter, and output of the laser light may be appropriately set according to the characteristics of the slurry for 3D printing. In FIG. 4, the outermost layer among the plurality of layers on the stage 62 is the uncured layer 68 before the laser light irradiation, and the remaining layers are the processed layers 70. After forming the uncured layer 68 in this way and irradiating the uncured layer 68 with the laser light to form the processed layer 70, the operation of lowering the stage 62 by one layer of the processed layer 70 is repeatedly performed until a predetermined number of processed layers 70 are stacked. Such a 3D printing method is called a stage lowering method. Thereafter, the 3D-shaped inorganic molded body is taken out by removing the uncured portion of the processed layer 70. The removal of the uncured portion is performed, for example, by treating with an organic solvent that dissolves the uncured portion without dissolving the cured portion.

[0035] Among the processed layers, the cured portion has a crosslinked structure in which the aggregate adsorbed particles are bonded via polyacrylate generated by the photopolymerization reaction of the acrylate monomer. The crosslinked structure is formed by the addition of the reactive amino group contained in the aggregate adsorbed particle to the acryloyl group that did not participate in the photopolymerization reaction among the polyacrylates.

[0036] Since the slurry for three-dimensional shaping of the present embodiment has the above-described composition, it is possible to suppress the change with time in the viscosity immediately after the preparation of the slurry. Therefore, when taking out the inorganic molded body, the uncured portion (slurry for three-dimensional shaping) can be removed relatively easily. In addition, the inorganic molded body produced using this slurry for three-dimensional shaping can have few lamination defects and high dimensional accuracy. The obtained inorganic molded body has the characteristics that the shrinkage rate is small due to crosslinking and curing, and it is difficult to warp even when the size is increased. The obtained inorganic molded body may be used as it is. Alternatively, the obtained inorganic molded body may be fired to obtain a sintered body. The shape of the inorganic molded body is generally maintained in the sintered body.

[0037] It should be noted that the present invention is not limited to the above-described embodiments at all, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

Example

[0038] Hereinafter, examples of the present invention will be described. Note that the following examples do not limit the present invention in any way.

[0039] [Example 1] To 9.01 mL of α-terpineol, 0.50 g (0.28 mmol) of polyethyleneimine (abbreviated as PEI, manufactured by Fujifilm Wako Pure Chemical Industries, weight average molecular weight (Mw) = 1800) and 0.50 g (1.8 mmol) of oleic acid were added, and these were stirred and mixed at room temperature for 24 hours to obtain an aggregate of PEI and oleic acid. In this example, the association rate of oleic acid with respect to PEI (the ratio of the number of moles of oleic acid to the number of moles of amino groups contained in the used PEI) was made 15%.

[0040] To α-terpineol containing a complex of PEI and oleic acid, alumina particles (trade name AKP-30, average particle size 0.3 μm, Sumitomo Chemical) and benzyl dimethyl ketal as a photoinitiator were dispersed to obtain a dispersion. The alumina particles were added so as to be 40% by volume based on the whole dispersion, and benzyl dimethyl ketal was added so as to be 0.2% by mass based on the whole dispersion. It was confirmed that the complex was adsorbed on the surface of the alumina particles in the dispersion (see Japanese Patent Application Laid-Open No. 2019-70064 for the confirmation method).

[0041] To the obtained dispersion, an acrylate monomer (trade name Aronix M-305 (reaction product of pentaerythritol and acrylic acid mainly composed of pentaerythritol tri / tetraacrylate), Toagosei) containing 3 or 4 acryloyl groups in one molecule was added, and planetary mixing was performed to obtain a slurry for three-dimensional shaping. The acrylate monomer was added so as to be 7.5% by mass based on the alumina particles.

[0042] [Example 2] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that the alumina particles were added so as to be 36% by volume based on the whole when preparing the dispersion, and the acrylate monomer was added so as to be 10% by mass based on the alumina particles.

[0043] [Example 3] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that the alumina particles were added so as to be 36% by volume based on the whole when preparing the dispersion, and the acrylate monomer was added so as to be 15% by mass based on the alumina particles.

[0044] [Example 4] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that the alumina particles were added so as to be 36% by volume based on the whole when preparing the dispersion, and the acrylate monomer was added so as to be 20% by mass based on the alumina particles.

[0045] [Example 5] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that ditrimethylolpropane tetraacrylate containing 4 acryloyl groups in one molecule was used as the acrylate monomer.

[0046] [Example 6] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that the association rate of oleic acid with respect to PEI was adjusted to 10%.

[0047] [Example 7] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that the association rate of oleic acid with respect to PEI was adjusted to 20%.

[0048] [Comparative Example 1] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that the acrylate monomer was added to the alumina particles at 5% by mass.

[0049] [Comparative Example 2] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that the association rate of oleic acid with respect to PEI was adjusted to 40%.

[0050] [Comparative Example 3] In Example 1, a slurry for three-dimensional shaping was prepared in the same manner as in Example 1, except that a product containing 5 or 6 acryloyl groups in one molecule (trade name Aronix M-400, a reaction product of dipentaerythritol and acrylic acid mainly composed of dipentaerythritol penta / hexacrylate, Toagosei) was used as the acrylate monomer.

[0051] [Evaluation] For the three-dimensional shaping slurries of Examples 1 to 7 and Comparative Examples 1 to 3, the change in viscosity over time was measured. The viscosity was measured by changing the shear rate from low to high at each of immediately after slurry preparation, 3 hours after slurry preparation, and 6 hours after slurry preparation. Specifically, using a cone-plate type rheometer (MCR-302, manufactured by Anton Paar), the cone was changed from 0 [s -1 to 1000 [s -1 as needed to measure the viscosity at room temperature. The results are shown in Tables 1 and 2 and Figures 5 to 14. In Figures 5 to 14, "0 hr" indicates immediately after slurry preparation, "3 hr" indicates 3 hours after slurry preparation, and "6 hr" indicates 6 hours after slurry preparation.

[0052] In any of Examples 1 to 7 and Comparative Examples 1 to 3, the viscosity of the slurry when the shear rate was 1 s -1 was 100 Pa·s or less, which was a viscosity range in which it was easy to remove the slurry from the inorganic molded body after three-dimensional shaping. On the other hand, with respect to the viscosity η0 at a shear rate of 1 s -1 at room temperature immediately after slurry preparation, the change rate η6 / η0 of the viscosity η6 at a shear rate of 1 s -1 at room temperature 6 hours after slurry preparation was in the range of 0.9 to 1.6 and close to 1 in Examples 1 to 7, but deviated from this numerical range in Comparative Examples 1 to 3.

[0053] In Comparative Example 1, the type of acrylate monomer was appropriate, but since its blending amount was too low at 5% by mass with respect to the inorganic particles, the change rate η6 / η0 became too large at 3.1. In Comparative Example 2, the type and blending amount of the acrylate monomer were appropriate, but since the association rate between the polyalkyleneimine and the fatty acid was too high at 40%, the change rate η6 / η0 became too small at 0.49. In Comparative Example 3, the blending amount of the acrylate monomer was appropriate, but since there were 5 or 6 acryloyl groups in one molecule, the change rate η6 / η0 became too small at 0.46. In this Comparative Example 3, at 0 hr after slurry preparation, the viscosity decreased as the shear rate increased, but at 3 hr and 6 hr after slurry preparation, conversely, the viscosity increased as the shear rate increased. When the behavior reverses in this way, it is not preferable because lamination defects are likely to occur during the three-dimensional shaping process.

[0054] On the other hand, in Examples 1 to 7, the association rate between the polyalkyleneimine and the fatty acid was appropriate, and the type and blending amount of the acrylate monomer were also appropriate, so the change rate η6 / η0 fell within the range of 0.9 to 1.6. Also, the behavior of the viscosity with respect to the shear rate was almost the same at 0 to 6 hr after slurry preparation.

[0055]

Table 1

[0056]

Table 2

[0057] [Example 8] A laminate was fabricated using a three-dimensional shaping apparatus (photochemical SZ-2500C). First, the slurry of Example 3 was discharged along the X direction using a dispenser onto the stage of the three-dimensional shaping apparatus, and the discharged slurry was stretched in the Y direction with a squeegee to form an uncured layer. The uncured layer was formed to have a predetermined thickness (target value 165 μm) within a range of 150 mm square. The target value was determined in consideration of shrinkage during sintering, etc., based on the target thickness of 150 μm of the sintered layer of the finally obtained sintered body. Subsequently, the uncured layer was irradiated with laser light through a photomask (not shown). As a result, the portion of the uncured layer that was not irradiated with the laser light was not cured, and the portion irradiated with the laser light was cured. That is, the uncured layer became a processed layer. Here, the wavelength of the laser light was 355 nm, the diameter was 100 μm, the output was 400 mW, and a range of 50 mm square was cured. After forming the uncured layer in this way and irradiating the uncured layer with laser light to make it a processed layer, the operation of lowering the stage by the thickness of one layer of the processed layer was repeated until 10 layers of the processed layer were laminated. Thereafter, among the obtained laminate of the processed layers, the uncured portion was dissolved and removed with a mixed solution of tetrahydrofuran and α-terpineol at a weight ratio of 1:1, and an inorganic molded body having a thickness of 1 mm and a size of 50 mm square was obtained. The inorganic molded body had a handleable strength. Also, when the cross section of the inorganic molded body was examined by SEM, no lamination defects were confirmed.

[0058] The obtained inorganic molded body was degreased at 600 °C for 2 hours in an air degreasing furnace, and then fired at 1600 °C for 2 hours in an air firing furnace. As a result, each layer constituting the inorganic molded body became a sintered layer in which the organic components burned and disappeared and the alumina powder was sintered, and a three-dimensional sintered body in which such sintered layers were laminated was obtained.

[0059] [Example 9] As a fired body with a complex shape, a plate-like body having a quadrangular shape in plan view and having a flat internal space was fabricated. A CT transmission image of this fired body is shown in Fig. 15. The internal space of the fired body communicates with the outside through one through-hole, and a plurality of disc-shaped columns and columns in the shapes of the characters "Y", "N", and "U" are provided in the internal space. Such a fired body was fabricated according to Example 8. That is, an inorganic molded body having the same shape as this fired body was fabricated using a three-dimensional shaping apparatus, and the obtained inorganic molded body was fired. The uncured portion (the portion other than the disc-shaped columns and the columns in the shapes of the characters "Y", "N", and "U") in the laminate of the processed layers obtained by the three-dimensional shaping apparatus can be easily removed from the through-hole by dissolving it with a mixed solution of tetrahydrofuran and α-terpineol at a weight ratio of 1:1.

Explanation of Signs

[0060] 10 Slurry for three-dimensional shaping, 12 Inorganic molded body, 20 Aggregate-adsorbing particles, 22 Inorganic particles, 24 Aggregate, 24a Polyalkyleneimine, 24b Fatty acid, 30 Acrylate monomer, 32 Acrylate polymer, 62 Stage, 64 Dispenser, 66 Squeegee, 68 Uncured layer, 70 Processed layer.

Claims

1. Inorganic particles, An aggregate in which a part of the amino groups contained in the polyalkyleneimine is associated with the carboxy group of a fatty acid, An acrylate monomer polymerizable by light, A photoinitiator, A non-aqueous solvent, A slurry for three-dimensional shaping, comprising: In the aggregate, the ratio of the number of moles of the fatty acid to the number of moles of the amino groups contained in the polyalkyleneimine is 10 to 20%, The acrylate monomer is a monomer having 3 or 4 acryloyl groups in one molecule, and the ratio to the inorganic particles is 7.5 to 20% by mass, The inorganic particles are at least one of inorganic oxide particles, inorganic nitride particles, and inorganic carbide particles, and the inorganic oxide particles are at least one of alumina, zirconia, and yttria, A slurry for three-dimensional shaping.

2. At room temperature, when the shear rate is 1 s -1 the viscosity of the slurry is 100 Pa·s or less, At room temperature immediately after slurry preparation, the shear rate is 1 s -1 The change rate η6 / η0 of the viscosity η6 at room temperature when the shear rate is 1 s -1 after 6 hours from immediately after slurry preparation is 0.9 to 1.6, The slurry for three-dimensional shaping according to Claim 1.

3. After forming an uncured layer on a stage using the slurry for three-dimensional shaping according to Claim 1 or 2, irradiating the uncured layer with light to form a processed layer in which the portion not irradiated with light is not cured and the portion irradiated with light is cured, and then pulling down the stage. A series of operations are repeated until a predetermined number of the processed layers are stacked, and then the three-dimensional shaped object is taken out by washing and removing the uncured portion among the processed layers stacked in the predetermined number. A method for manufacturing a three-dimensional shaped object.

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