Three dimensional shaped article manufacturing method using resin granular material, three dimensional shaped article, and resin granular material

Abstract

To provide a resin granule for producing a shaped article having a small surface roughness in three dimensional shaping, a method for producing a three dimensional shaped article using the same, and a three dimensional shaped article.SOLUTION: A method for producing a three dimensional shaped article by a powder bed fusion method, wherein the sphericity of the polymer powder (A) is 80 or more and 100 or less, the D80 particle size of the polymer powder (A) is 60 μm or less, the D20 particle size is 1 μm or more, and the amount of the fluidizing aid (B) is more than 0.01 parts by mass and less than 5 parts by mass relative to 100 parts by mass of the polymer powder (A).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for producing a three-dimensional object using resin granules, a three-dimensional object obtained thereby, and resin granules. [Background technology]

[0002] Powder bed fusion (PFB) is a well-known technology for producing three-dimensional (3D) objects (hereinafter sometimes referred to as "models"). Models produced using PFB are produced by sequentially repeating a thin-layer formation process, in which powder is spread into thin layers, and a cross-sectional shape formation process, in which the formed thin layers are selectively melted into a shape corresponding to the cross-sectional shape of the object to be modeled, thereby bonding together resin powder particles. Methods for selectively melting powder include selective laser sintering (using a laser), selective absorption sintering (using a melting aid), and selective suppression sintering (masking areas that should not be melted). Compared to other modeling methods, this method can produce models with smooth surfaces. It also has advantages, such as the elimination of support members. Furthermore, due to the increasing demand for models with complex shapes and contours that could not be achieved using conventional processing methods, it is important to obtain models with smooth surfaces without irregularities.

[0003] To address these issues, Patent Document 1 discloses a method for producing a shaped object with a smooth surface by using a polyamide powder with a D50 particle size of 98 μm and containing a large amount of irregular particles as a resin powder and hydrophobic silicic acid as a flow aid. Patent Document 2 also discloses a method for producing a shaped object with a smooth surface by using a polyamide powder with a D50 particle size of 40 to 70 μm. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 4878102 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-109492 Summary of the Invention [Problem to be solved by the invention]

[0005] However, while Patent Document 1 uses a resin powder with excellent fluidity to produce a molded product with reduced surface defects, the shape of the polyamide powder is irregular, which is not sufficient to produce a molded product with low surface roughness. Patent Document 2 uses a polyamide powder with excellent sinterability, but contains coarse powder, and the height (stacking height) of the resin powder particles during 3D printing is high at 0.15 mm. This results in increased surface roughness in the height direction (hereinafter, referring to the X and Y directions in the plane direction in which the resin powder particles are stacked, and may be referred to as the X direction and Y direction) and in the height direction (hereinafter, sometimes referred to as the Z direction) of the resin powder particles during 3D printing, resulting in a problem of poor surface smoothness (quality).

[0006] Therefore, the present invention aims to provide a resin powder for producing a molded object in three-dimensional modeling that has small surface roughness in the X and Y directions, which are the plane directions in which the resin powder is stacked, and in the Z direction, which is the height direction in which the resin powder is stacked, a method for producing a three-dimensional molded object using the same, and a three-dimensional molded object. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following configuration. (1) A resin powder for producing a three-dimensional object by powder bed fusion, the resin powder comprising a resin powder (A) and a flow aid (B), wherein the resin powder (A) has a sphericity of 80 or more and 100 or less, the resin powder (A) has a D80 particle size of 60 μm or less and a D20 particle size of 1 μm or more, and the resin powder (A) contains more than 0.01 parts by mass and less than 5 parts by mass of the flow aid (B) per 100 parts by mass of the resin powder (A). (2) The resin powder granules according to (1), wherein the D50 particle size of the resin powder (A) is 1 μm or more and 50 μm or less. (3) The resin powder according to (1) or (2), wherein the flow aid (B) has a D50 particle size of 20 nm or more and 1 μm or less. (4) The resin powder granule according to any one of (1) to (3), wherein D50(A) is the D50 particle diameter of the resin powder (A), D50(B) is the D50 particle diameter of the flow aid (B), and X parts by mass of the flow aid (B) is contained per 100 parts by mass of the resin powder (A), D50(A) × X / D50(B) is greater than 30 and less than 300. (5) The resin powder granule according to any one of (1) to (4), which contains 10 parts by mass or more and 200 parts by mass or less of an inorganic reinforcing material (C) per 100 parts by mass of the resin powder (A). (6) A method for producing a three-dimensional object by powder bed fusion using the resin powder or granules according to any one of (1) to (5). (7) A three-dimensional object manufactured by powder bed fusion bonding using resin powder granules, characterized in that the surface roughness of the object in the plane direction in which the resin powder granules are stacked is 20 μm or less, and the surface roughness of the object in the height direction in which the resin powder granules are stacked is 20 μm or less. (8) The three-dimensionally shaped object according to (7), wherein the average equivalent sphere diameter of the pores in the three-dimensionally shaped object as observed by X-ray CT measurement is 1 μm or more and 100 μm or less. [Effects of the Invention]

[0008] According to the present invention, in three-dimensional modeling, it is possible to obtain a molded object having small surface roughness in the X and Y directions, which are the plane directions in which the resin powder particles are stacked, and in the Z direction, which is the height direction in which the resin powder particles are stacked. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an example of a three-dimensional object manufacturing apparatus according to the present invention. [Figure 2] FIG. 1 is a schematic diagram illustrating an example of a three-dimensional object according to the present invention. [Figure 3] 1 is a scanning electron microscope photograph of the resin powder (polyamide powder) obtained in Production Example 1 and used in Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below with reference to embodiments. When manufacturing 3D objects, the stack height of the resin powder particles was previously set to be too low, which slowed down the modeling speed, so the tank stage was set to be lowered to 0.10 mm or more, making it impossible to create objects with a surface roughness of 20 μm or less in the Z direction.

[0011] Unless the stacking height during 3D printing is set to a value exceeding the maximum particle size contained in the resin powder, the resulting object will have poor surface roughness in the X and Y directions. Furthermore, resin powders with small particle sizes lack fluidity due to the high contact resistance between the resin powder particles, making them unsuitable for 3D printing. However, even with small particle sizes, if certain conditions are met, surprisingly, it has been found that a fluidity suitable for 3D printing can be ensured, and objects can be produced with low surface roughness in the X and Y directions along the surface of the resin powder stack, as well as in the Z direction, which is the height direction of the resin powder stack.

[0012] That is, the method for producing a three-dimensional object of the present invention is, for example, a method for producing a three-dimensional object by powder bed fusion using resin oil powder particles, The resin granules contain a resin powder (A) and a flow aid (B), the resin powder (A) has a sphericity of 80 or more and 100 or less, a D80 particle size of 60 μm or less, and a D20 particle size of 1 μm or more; The flow aid (B) is contained in an amount of more than 0.01 parts by mass and less than 5 parts by mass per 100 parts by mass of the resin powder (A), A method for manufacturing a three-dimensional object, characterized by repeating the following steps (a) to (c) in this order: (a) The stage of the tank for forming the three-dimensional object is lowered by 0.01 mm or more and less than 0.10 mm. (b) Resin powder is fed into a tank that forms a three-dimensional object, and the resin powder is layered. (c) Thermal energy is applied to the resin powder particles to selectively melt and sinter them.

[0013] Each step of the method for manufacturing a three-dimensional object will be described below with reference to FIG. In step (a), the stage 2 of the tank 1 in which the shaped object is formed is lowered within a range of 0.01 mm or more and less than 0.10 mm. By lowering the stage 2 within this range, a space into which the resin powder P can be filled is formed.

[0014] In step (b), the stage 4 of the tank 3 (hereinafter sometimes referred to as the supply tank), which has been pre-filled with resin powder P to be supplied to the tank 1 where the molded object is formed, is raised to a height that allows for the supply of a sufficient amount of resin powder P to fill the tank 1 with the specified stack height. Then, the recoater 5 is moved from the left end of the supply tank 3 to the right end of the tank 1, stacking the resin powder P in the tank 1. The direction parallel to the movement of the recoater 5 is the X direction, and the direction perpendicular to the direction of movement of the recoater 5 on the powder surface of the resin powder P is the Y direction. Reference numeral 7 denotes a coordinate system representing the X, Y, and Z directions. Reference numeral 8 denotes the surface direction in which the resin powder is stacked, and reference numeral 9 denotes the height direction in which the resin powder is stacked.

[0015] In step (c), the resin powder P filled in the tank 1 to a predetermined stack height in step (b) is given thermal energy 6 capable of melting, and is selectively melted and sintered in accordance with the modeling data.

[0016] By repeating the above steps (a) to (c), a three-dimensional object 10 (also shown in Figure 2) is obtained. In Figure 2, reference numeral 11 denotes the surface of the object in the planar direction in which the resin powder particles are layered, and reference numeral 12 denotes the surface of the object in the height direction in which the resin powder particles are layered.

[0017] The stacking height in the present invention is 0.01 mm or more and less than 0.10 mm. If it is less than 0.01 mm, unevenness will occur on the stacking surface, resulting in a molded product with high surface roughness in the X and Y directions. If it is 0.10 mm or more, layer-like steps will occur in the stacking height direction of the resin powder particles, resulting in a molded product with high surface roughness in the Z direction. In terms of widening the allowable range of the maximum particle size contained in the resin powder, a stacking height of 0.02 mm or more is preferred, more preferably 0.03 mm or more, and even more preferably 0.04 mm or more. In terms of reducing the surface roughness in the Z direction ...6 mm or less is preferred, more preferably 0.06 mm or more.

[0018] The height by which stage 4 of the supply tank is raised in step (b) is preferably 0.03 mm or more, more preferably 0.04 mm or more, even more preferably 0.05 mm or more, and particularly preferably 0.06 mm or more, from the viewpoint of a height that allows a sufficient amount of resin powder to be supplied to fill the space formed in tank 1 in step (a).Furthermore, since supplying an excess of resin powder will result in excessive consumption of the resin powder prepared in tank 3, the height is preferably 0.15 mm or less, more preferably 0.13 mm or less, even more preferably 0.11 mm or less, and particularly preferably 0.10 mm or less.

[0019] Furthermore, the speed at which the recoater 5 is moved in step (b) is preferably a speed at which a uniform powder surface of resin powder particles can be formed in the tank 1. The upper limit of this speed is preferably 1.00 m / s or less, more preferably 0.70 m / s or less, even more preferably 0.50 m / s or less, and particularly preferably 0.30 m / s or less. A slow recoater movement speed reduces the modeling speed, which affects the production efficiency of three-dimensional models, so the lower limit is preferably 0.01 m / s or more, more preferably 0.02 m / s or more, even more preferably 0.03 m / s or more, and particularly preferably 0.05 m / s or more.

[0020] Examples of the selective melt-sintering method in step (c) include selective laser sintering, in which a laser is irradiated onto a shape corresponding to the cross-sectional shape of the object to bond resin powder particles, etc. Other examples include a printing step in which an energy absorption promoter or an energy absorption inhibitor is printed onto a shape corresponding to the cross-sectional shape of the object to be shaped, and selective absorption (or suppression) sintering, in which electromagnetic radiation is used to bond resin powder.

[0021] The laser light used in the selective laser sintering method is not particularly limited as long as it does not impair the quality of the resin powder or granules or the molded object. Examples include carbon dioxide lasers, YAG lasers, excimer lasers, He-Cd lasers, and semiconductor-pumped solid-state lasers. Among these, carbon dioxide lasers are preferred because they are easy to operate and control.

[0022] In the present invention, in step (c), thermal energy sufficient to melt the resin powder and granules filled in tank 1 to a predetermined stack height in step (b) is applied. In the present invention, for example, the energy applied to the resin powder and granules by a laser can be evaluated in terms of laser energy per unit area, Ea. Ea is calculated from the laser output, laser scanning speed, and laser scanning interval using the following formula: Ea=Q / (vw) In the formula, Q is the laser output, v is the laser scanning speed, w is the laser scanning interval, and Ea is the laser energy per unit area.

[0023] If the Ea value is small, the resin powder tends not to be sintered sufficiently, which may result in a decrease in the strength of the molded object. 2 More than 0.3J / cm is preferable. 2 More preferably, 0.4 J / cm or more 2 More preferably, 0.5 J / cm or more 2 On the other hand, if the value of Ea is too large, the laser energy applied may exceed the stack height, causing the molded object to bulge downward. 2 Less than 1.8 J / cm is preferable.2 Less than 1.6 J / cm is more preferable. 2 Less than 1.5 J / cm is more preferable. 2 Less than 1000 is particularly preferred.

[0024] The electromagnetic radiation used in selective absorption (suppression) sintering may be any radiation that does not impair the quality of the resin powder or granules or the molded object, but infrared radiation is preferred because it is relatively inexpensive and provides energy suitable for molding. The electromagnetic radiation may or may not be coherent.

[0025] The energy absorption enhancer is a substance that absorbs electromagnetic radiation. Examples of such substances include carbon black, carbon fiber, copper hydroxyphosphate, near-infrared absorbing dyes, near-infrared absorbing pigments, metal nanoparticles, polythiophene, poly(p-phenylene sulfide), polyaniline, poly(pyrrole), polyacetylene, poly(p-phenylene vinylene), polyparaphenylene, poly(styrene sulfonate), poly(3,4-ethylenedioxythiophene)-poly(styrene phosphonate) p-diethylaminobenzaldehyde diphenylhydrazone, and conjugated polymers formed from combinations thereof. These substances may be used alone or in combination.

[0026] The energy absorption inhibitor is a substance that does not easily absorb electromagnetic radiation. Examples of such substances include substances that reflect electromagnetic radiation, such as titanium, heat-insulating powders, such as mica powder and ceramic powder, and water. These substances may be used alone or in combination.

[0027] These selective absorbers or selective inhibitors may be used alone or in combination.

[0028] In the step of printing the selective absorbent or selective inhibitor in a shape corresponding to the cross-sectional shape of the object to be shaped, a known method such as inkjet printing can be used. In this case, the selective absorbent or selective inhibitor may be used as is, or may be dispersed or dissolved in a solvent.

[0029] Next, the resin powder and resin granules used in the present invention will be described in detail. The D50 particle size of the resin powder (A) in the present invention is preferably in the range of 1 μm to 50 μm. If the D50 particle size exceeds 50 μm, the largest particle size in the resin powder will be equal to or greater than the stacking height, making it impossible to reduce the stacking height during molding, and it will be impossible to obtain a molded product with low surface roughness in the Z direction, which is undesirable. If the D50 particle size is less than 1 μm, the resin powder (A) will be too fine and will easily adhere to a recoater or the like during molding, making it impossible to raise the molding chamber temperature to the required level, which is undesirable. The upper limit of the D50 particle size of the resin powder is more preferably 45 μm or less, even more preferably 40 μm or less, and particularly preferably 35 μm or less. The lower limit is more preferably 3 μm or more, even more preferably 5 μm or more, and particularly preferably 10 μm or more.

[0030] The D50 particle size of the resin powder (A) can be measured using a laser diffraction particle size distribution analyzer. The D50 particle size refers to the particle size at which the cumulative frequency from the small particle size side of the particle size distribution obtained by such measurement is 50%.

[0031] In the present invention, the D80 particle size of the resin powder (A) is 60 μm or less. When the D80 particle size is 60 μm or less, the number of particles with a particle size equal to or greater than the stack height is reduced, and the irregularities in the X and Y directions of the molded object are reduced, resulting in a molded object with low surface roughness. The D80 particle size is preferably 55 μm or less, more preferably 50 μm or less, even more preferably 48 μm or less, particularly preferably 46 μm or less, and most preferably 45 μm or less. Theoretically, the lower limit is equal to or greater than the D50 particle size.

[0032] The D80 particle size of the resin powder (A) in the present invention can be measured by the laser diffraction particle size distribution analyzer described above. The D80 particle size refers to the particle size at which the cumulative frequency from the small particle size side of the particle size distribution obtained by such measurement is 80%.

[0033] In the present invention, the D20 particle size of the resin powder (A) is 1 μm or more. If the D20 particle size is less than 1 μm, the powder is likely to be caught in the recoater during lamination, and mottled patterns may occur due to the powder falling from the recoater, which is undesirable. The D20 particle size is preferably 2 μm or more, more preferably 3 μm or more, even more preferably 5 μm or more, particularly preferably 7 μm or more, and most preferably 10 μm or more. Theoretically, the upper limit is equal to or less than the D50 particle size.

[0034] The D20 particle size of the resin powder (A) in the present invention can be measured by the laser diffraction particle size distribution analyzer described above. The D20 particle size refers to the particle size at which the cumulative frequency from the small particle size side of the particle size distribution obtained by such measurement is 20%.

[0035] The sphericity in the present invention indicates the sphericity of the resin powder (A) and is 80 to 100. If the sphericity is less than 80, the flowability deteriorates and the surface of the shaped product becomes rough. The sphericity is preferably 85 to 100, more preferably 90 to 100, even more preferably 93 to 100, particularly preferably 95 to 100, and most preferably 97 to 100.

[0036] The sphericity in the present invention is the average value of the ratio of the minor axis to the major axis when 30 particles are randomly selected and observed from a photograph taken with a scanning electron microscope.

[0037] The surface smoothness and internal solidity of the resin powder (A) of the present invention can be expressed by the BET specific surface area determined by gas adsorption. If the surface of the resin powder is smooth and the internal solidity is high, the surface area is small, which improves the flowability and makes the surface of the molded product smoother, which is preferable. Here, the smoother the surface, the smaller the BET specific surface area. Specifically, the BET specific surface area is determined by the gas adsorption of 10 m2 / g or less, and more preferably 5m 2 / g or less, and more preferably 3m 2 / g or less, and particularly preferably 1m 2 / g or less, and most preferably 0.5m 2 The lower limit is theoretically 0.05 m / g when the particle diameter is 100 μm. 2 / g.

[0038] The BET specific surface area can be measured in accordance with the Japanese Industrial Standards (JIS) JIS R 1626 (1996) "Method for measuring specific surface area by gas adsorption BET method."

[0039] In the present invention, the theoretical specific surface area of ​​a resin powder in the case of a perfectly spherical particle can be expressed as the ratio of the surface area of ​​a single sphere calculated from the D50 particle diameter of the resin powder to the weight of the single sphere, which is the product of the volume and density of the single sphere calculated from the D50 particle diameter of the resin powder. The solidity of the resin powder (A) can also be evaluated by the ratio of the theoretical specific surface area calculated from the BET specific surface area and the D50 particle diameter. The closer this ratio is to 1, the more adsorption occurs only on the outermost surface of the particle, indicating a smoother and more solid particle. The ratio is preferably 5 or less, more preferably 4 or less, even more preferably 3 or less, and most preferably 2 or less. The lower limit is theoretically 1.

[0040] The resin powder of the present invention exhibits high fluidity. Any known measurement method can be used as an index of fluidity. A specific example is the angle of repose, which is preferably 40 degrees or less, more preferably 37 degrees or less, even more preferably 35 degrees or less, and particularly preferably 33 degrees or less. The lower limit is 20 degrees or more.

[0041] The polymer constituting the resin powder in the present invention is a polymer suitable for producing three-dimensional objects by powder bed fusion, and preferably includes polyethylene, polypropylene, polyester, polyamide, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyamideimide, polyethersulfone, polytetrafluoroethylene, or a mixture thereof. Polyester, polyamide, polyphenylene sulfide, polyether ether ketone, polyetherimide, polyamideimide, polyethersulfone, and polytetrafluoroethylene are more preferred in that the resulting three-dimensional objects have excellent heat resistance. Polyester, polyamide, polyphenylene sulfide, polyether ether ketone, and polytetrafluoroethylene are even more preferred in that they have a clear difference between their melting point and crystallization temperature, resulting in excellent formability and reproducibility. Of these, polyester and polyamide are particularly preferred in that they offer excellent formability using general-purpose molding machines, and polyamide is particularly preferred in that the resulting molded objects have excellent mechanical properties such as toughness and strength.

[0042] The polyamide in the present invention is obtained by polycondensation of a lactam having three or more ring members, a polymerizable aminocarboxylic acid, a dibasic acid and a diamine or a salt thereof, or a mixture thereof. Specific examples of such polyamides include polycaproamide (polyamide 6), polyundecaamide (polyamide 11), polylauroamide (polyamide 12), polyhexamethylene adipamide (polyamide 66), polydecamethylene sebacamide (polyamide 1010), polydodecamethylene sebacamide (polyamide 1012), polydodecamethylene dodecamide (polyamide 1212), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide ( Examples include polyamide 612), polydecamethylene adipamide (polyamide 106), polydodecamethylene adipamide (polyamide 126), polyhexamethylene terephthalamide (polyamide 6T), polydecamethylene terephthalamide (polyamide 10T), polydodecamethylene terephthalamide (polyamide 12T), polycaproamide / polyhexamethylene adipamide copolymer (polyamide 6 / 66), and polycaproamide / polylauroamide copolymer (6 / 12). Among these, polycaproamide (polyamide 6), polyundecaamide (polyamide 11), polylauroamide (polyamide 12), polyhexamethylene adipamide (polyamide 66), polydecamethylene sebacamide (polyamide 1010), polydodecamethylene sebacamide (polyamide 1012), polydodecamethylene dodecamide (polyamide 1212), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), and the like are preferred because they can be easily controlled to have a spherical shape. Furthermore, in terms of thermal properties suitable for molding, polycaproamide (polyamide 6), polyundecaamide (polyamide 11), polylauroamide (polyamide 12), polyhexamethylene adipamide (polyamide 66), polydecamethylene sebacamide (polyamide 1010), and polydodecamethylene sebacamide (polyamide 1012) are particularly preferred. Among these, polycaproamide (polyamide 6) and polyhexamethylene adipamide (polyamide 66) are particularly preferred in terms of heat resistance during molding.

[0043] The polyester in the present invention is obtained by polycondensation of a lactone or lactide having a three- or higher ring member, a polymerizable hydroxycarboxylic acid, a dibasic acid and a polyhydric alcohol or a salt thereof, or a mixture thereof. Specific examples of such polyesters include polycaprolactone, polylactic acid, polyglycolic acid, polyethylene terephthalate, polypropylene terephthalate, polybutylene terephthalate, polycyclohexanedimethylene terephthalate, polyhexylene terephthalate, polyethylene naphthalate, polypropylene naphthalate, polybutylene naphthalate, polyethylene succinate, polypropylene succinate, polybutylene succinate, polyethylene adipate, polypropylene adipate, polybutylene adipate, and copolymers thereof. Among these, polylactic acid, polyglycolic acid, polybutylene terephthalate, polybutylene succinate, polybutylene adipate, and copolymers thereof are preferred due to their thermal properties suitable for molding. Furthermore, polylactic acid and polybutylene succinate are particularly preferred because of their excellent biodegradability.

[0044] The polyamides and polyesters may be copolymerized to the extent that the effects of the present invention are not impaired. Examples of copolymerizable components include elastomer components such as polyolefins and polyalkylene glycols that impart flexibility, and rigid aromatic components that improve heat resistance and strength. Furthermore, as will be described later, copolymerizable components that modify the end groups may be used to reuse resin powder in powder bed fusion bonding. Examples of such copolymerizable components include monocarboxylic acids such as acetic acid, hexanoic acid, lauric acid, and benzoic acid, and monoamines such as hexylamine, octylamine, and aniline.

[0045] Known methods can be used to produce the resin powder of the present invention, including a submerged drying method in which a polymer is dissolved in an organic solvent and added to water to form an O / W emulsion, and then the organic solvent is dried and removed under reduced pressure to produce fine particles; a method of producing fine particles by dissolving a polymer and polyvinyl alcohol in an organic solvent to form an emulsion, and then contacting water, which is a poor solvent for the polymer, as described in International Publication WO2012 / 043509; or a method of producing fine particles by polymerizing a polyamide monomer in the presence of a polymer incompatible with the polyamide at a temperature higher than the crystallization temperature of the polyamide, and then washing and drying the resin powder, as previously disclosed by the present inventors, as described in International Publication WO2018 / 207728. Among these, the method described in International Publication WO2018 / 207728 is preferred because washing the resin powder reduces the content of minor components used in the resin powder production process, etc., and produces a resin powder with excellent shapeability.

[0046] In the production of the resin powder of the present invention, the purification step for isolating the resin powder preferably includes a step of removing coarse particles and fine particles so that the D80 particle size is 60 μm or less and the D20 particle size is 1 μm or more. Either wet classification or dry classification can be used to remove the coarse particles and fine particles, but wet classification is preferred because it allows the particles to be monodispersed and classified with high precision.

[0047] In the present invention, the wet classification method preferably used for removing coarse particles can be a known method, such as a wet sieving method using a sieve, a liquid cyclone method utilizing a difference in sedimentation velocity, or a decantation method. However, the wet sieving method is preferred in that it can efficiently remove coarse particles.

[0048] As the wet classification method preferably used for removing fine particles in the present invention, known methods can be used, such as wet sieving, a liquid cyclone method utilizing a difference in sedimentation velocity, and a decantation method. The liquid cyclone method and decantation method are preferred in that they can selectively remove only fine particles.

[0049] The resin powder preferably used in the present invention has a content of minor components used in the resin powder production process, etc., of less than 0.1% by mass. Because such minor components can reduce the fluidity and recyclability of the powder composition, the content is preferably less than 0.05% by mass, even more preferably less than 0.01% by mass, particularly preferably less than 0.007% by mass, significantly more preferably less than 0.004% by mass, and most preferably less than 0.001% by mass. The content of such minor components can be analyzed by known methods. For example, the content can be quantified by gel permeation chromatography using water as the solvent after extraction from the resin powder with water or an organic solvent, followed by removal of the solvent.

[0050] The obtained resin powder may be subjected to additional heat treatment as long as the effects of the present invention are not impaired. Known heat treatment methods can be used, including atmospheric heat treatment using an oven or the like, reduced-pressure heat treatment using a vacuum dryer or the like, and pressurized heat treatment in which the resin powder is heated together with water in a pressure vessel such as an autoclave. Heat treatment can control the molecular weight, crystallinity, and melting point of the resin powder within desired ranges.

[0051] Other compounds may be added to the resin powder of the present invention as long as they do not impair the effects of the present invention. Examples of such compounds include antioxidants and heat stabilizers to suppress thermal degradation caused by heating during shaping in powder bed fusion. Examples of antioxidants and heat stabilizers include hindered phenols, hydroquinone, phosphites and their substituted derivatives, phosphites, and hypophosphites. Other compounds include pigments and dyes for coloring, plasticizers for viscosity adjustment, flow aids for improving flowability, antistatic agents for functionalization, flame retardants, and fillers such as carbon black, silica, titanium dioxide, glass fiber, glass beads, and carbon fiber. These compounds may be known and may be present either inside or outside the resin powder.

[0052] The resin powder granules of the present invention are characterized by containing a flow aid (B). In the present invention, the flow aid (B) refers to a substance that suppresses aggregation of the resin powder due to the adhesive force between resin particles. By containing the flow aid (B), the fluidity of the resin powder granules can be improved, and the packing ability of the resin powder when formed into a molded object increases. As a result, defects that cause poor mechanical properties tend to be reduced, and the strength of the resulting molded object can be further improved.

[0053] Examples of such flow aids include silica (silicon dioxide) such as fused silica, crystalline silica, and amorphous silica; alumina (aluminum oxide), alumina colloid (alumina sol), and alumina white; calcium carbonate such as light calcium carbonate, heavy calcium carbonate, finely powdered calcium carbonate, and special calcium carbonate fillers; nepheline syenite fine powder, calcined clay such as montmorillonite and bentonite; clay (aluminum silicate powder) such as silane-modified clay; silicic acid-containing compounds such as talc, diatomaceous earth, and silica sand; and crushed natural minerals such as pumice powder, pumice balloons, slate powder, and mica powder. Examples of suitable fillers include minerals such as barium sulfate, lithopone, calcium sulfate, molybdenum disulfide, and graphite; glass fillers such as glass fibers, glass beads, glass flakes, and foamed glass beads; fly ash spheres, hollow volcanic glass, synthetic inorganic hollow bodies, single-crystal potassium titanate, carbon fibers, carbon nanotubes, hollow carbon spheres, fullerenes, anthracite powder, artificial cryolite, titanium oxide, magnesium oxide, basic magnesium carbonate, dolomite, potassium titanate, calcium sulfite, mica, asbestos, calcium silicate, molybdenum sulfide, boron fiber, and silicon carbide fiber. Silica, alumina, calcium carbonate powder, glass fillers, and titanium oxide are particularly preferred. Silica is particularly preferred because of its hardness and ability to contribute to improving strength and flowability.

[0054] Commercially available examples of such silica include the fumed silica "AEROSIL" (registered trademark) series manufactured by Nippon Aerosil Co., Ltd., the dry silica "Reolosil" (registered trademark) series manufactured by Tokuyama Corporation, and the sol-gel silica powder X-24 series manufactured by Shin-Etsu Chemical Co., Ltd.

[0055] The D50 particle size of such flow aid (B) is preferably 20 nm or more and 1 μm or less. The upper limit of the D50 particle size of the flow aid (B) is preferably 1 μm or less, since the smaller the particle size and the larger the surface area, the more easily the resin powder can be prevented from agglomerating. It is more preferably 500 nm or less, even more preferably 400 nm or less, particularly preferably 300 nm or less, and extremely preferably 250 nm or less. The lower limit is preferably 20 nm or more, since an excessively large surface area inhibits packing and reduces the density of the molded product. It is more preferably 30 nm or more, even more preferably 50 nm or more, and particularly preferably 100 nm or more. When the average particle size of the flow aid (B) is within the above range, the fluidity of the resin powder granules is improved and the flow aid (B) tends to be uniformly dispersed in the resin powder.

[0056] The D50 particle size of the flow aid (B) in the present invention is the value at which the cumulative curve from the small particle side becomes 50% when the total volume of the microparticles obtained by analyzing scattered light from a laser by dynamic light scattering is set to 100% to calculate the cumulative curve.

[0057] The blending amount of the flow aid (B) is more than 0.01 parts by mass and less than 5 parts by mass per 100 parts by mass of the resin powder (A). The upper limit of the blending amount is preferably less than 4 parts by mass, more preferably less than 3 parts by mass, even more preferably less than 2 parts by mass, and particularly preferably less than 1 part by mass. The lower limit of the blending amount is preferably more than 0.02 parts by mass, more preferably more than 0.03 parts by mass, even more preferably more than 0.05 parts by mass, and particularly preferably more than 0.1 parts by mass. If the blending amount of the flow aid (B) is 0.01 parts by mass or less, the flowability is insufficient, which can lead to deterioration in the surface roughness of the resulting molded object, chipping of the edges of the molded object, and the occurrence of voids. Furthermore, the filling ability during molding is reduced, which can easily cause voids that result in mechanical defects, resulting in reduced strength of the resulting molded object. If the blending amount of the flow aid is 5 parts by mass or more, the surface of the resin powder is coated with the flow aid, inhibiting sintering and reducing the strength of the molded object.

[0058] In the present invention, the blending amount of the flow aid (B) relative to the resin powder (A) can be selected from a preferred range depending on the particle size of the resin powder and the particle size of the flow aid. When the D50 particle diameter of the resin powder (A) is D50(A), the D50 particle diameter of the flow aid (B) is D50(B), and the content of the flow aid (B) per 100 parts by mass of the resin powder (A) is X parts by mass, D50(A) × X / D50(B) is preferably greater than 30 and less than 300. When D50(A) × X / D50(B) is 30 or less, the flow aid cannot sufficiently suppress aggregation of the resin powder particles, resulting in reduced fluidity, which is undesirable. The lower limit is more preferably greater than 35, even more preferably greater than 40, and particularly preferably greater than 50. When D50(A) × X / D50(B) is 300 or more, the flow aid completely coats the resin powder, inhibiting sintering, which is undesirable. The upper limit is more preferably less than 250, even more preferably less than 200, particularly preferably less than 150, and most preferably less than 100.

[0059] Furthermore, in powder bed fusion (PBF) processes, a molded object is created using only a portion of the resin powder used, leaving much of the remaining powder behind. Reusing this resin powder is important from a cost perspective. To achieve this, it is important to prevent the properties of the resin powder from changing during the heating and molding process. Examples of such methods include incorporating stabilizers such as antioxidants into the particles to suppress thermal degradation and reducing the end groups of polyamides to suppress molecular weight changes during molding. Polyamide end groups are carboxyl and amino groups, and reducing amino groups is preferred due to their high reactivity during heating for molding. One method for reducing these groups is to use monofunctional capping agents, such as monocarboxylic acids (e.g., acetic acid, hexanoic acid, lauric acid, and benzoic acid) or monoamines (e.g., hexylamine, octylamine, and aniline) during polyamide polymerization. By appropriately using such adjustments, it is becoming increasingly possible to achieve both moldability and reuse.

[0060] The resin powder granules of the present invention may contain an inorganic reinforcing material (C) composed of an inorganic compound, which can improve the dimensional accuracy of the molded product. When an inorganic reinforcing material is contained, the volume change associated with melt bonding can be suppressed. The inorganic reinforcing material may be dry-blended with the resin powder (A) or may be contained within the resin powder (A). However, dry-blending is preferred in order to control the resin powder (A) to a spherical shape and improve flowability.

[0061] Examples of such inorganic reinforcing materials (C) include glass fillers such as glass fibers, glass beads, glass flakes, and foamed glass beads; nepheline syenite fine powder, calcined clays such as montmorillonite and bentonite; clays (aluminum silicate powders) such as silane-modified clay; silicic acid-containing compounds such as talc, diatomaceous earth, and silica sand; crushed natural minerals such as pumice powder, pumice balloons, slate powder, and mica powder; minerals such as barium sulfate, lithopone, calcium sulfate, molybdenum disulfide, and graphite; silica (silicon dioxide) such as fused silica, crystalline silica, and amorphous silica; alumina (aluminum oxide); and alumina colloids. Examples of suitable inorganic reinforcing materials include alumina (alumina sol), alumina white, and other aluminas; light calcium carbonate, heavy calcium carbonate, finely powdered calcium carbonate, and calcium carbonate fillers such as special calcium carbonate fillers; fly ash spheres; hollow volcanic glass; synthetic inorganic hollow bodies; single-crystal potassium titanate; potassium titanate fibers; carbon fibers; carbon nanotubes; hollow carbon spheres; fullerenes; anthracite powder; cellulose nanofibers; artificial cryolite (cryolite); titanium oxide; magnesium oxide; basic magnesium carbonate; dolomite; calcium sulfite; mica; asbestos; calcium silicate; molybdenum sulfide; boron fibers; and silicon carbide fibers. Glass-based fillers, minerals, and carbon fibers are preferred due to their hardness and significant strength-enhancing properties, with glass-based fillers being even more preferred due to their narrow particle size and fiber size distributions. These inorganic reinforcing materials can be used alone or in combination of two or more.

[0062] Examples of glass-based fillers preferably used in the present invention include glass fibers, glass beads, glass flakes, and foamed glass beads. Glass fibers and glass beads are particularly preferred because they can impart a high elastic modulus to the three-dimensionally shaped object. Among these, glass fibers are particularly preferred because they impart high strength to the shaped object. Glass fibers may have either a circular or flat cross section. Glass beads are particularly preferred because they impart small anisotropy to the strength of the shaped object.

[0063] To improve the adhesion between the inorganic reinforcing material and the resin powder, the inorganic reinforcing material may be surface-treated, as long as the effects of the present invention are not impaired. Examples of such surface treatments include silane coupling agents such as aminosilane, epoxysilane, and acrylicsilane. These surface treatment agents may be immobilized on the surface of the inorganic reinforcing material by a coupling reaction or may coat the surface of the inorganic reinforcing material. However, in terms of recycling the powder used in three-dimensional modeling, those immobilized by a coupling reaction are preferred because they are less likely to be modified by heat or the like.

[0064] The average major axis diameter of the inorganic reinforcing material of the present invention is preferably in the range of 3 to 100 μm. If the average major axis diameter exceeds 100 μm, the inorganic reinforcing material will have irregularities on the molded surface, impairing surface smoothness, which is undesirable. If the average major axis diameter is less than 3 μm, it will not contribute to improving the elastic modulus, which is undesirable. The upper limit of the average major axis diameter of the inorganic reinforcing material is preferably 80 μm or less, more preferably 70 μm or less, even more preferably 60 μm or less, and particularly preferably 50 μm or less. The lower limit is preferably 5 μm or more, more preferably 8 μm or more, and even more preferably 10 μm or more.

[0065] The shape of the inorganic reinforcing material of the present invention is expressed by the ratio of the average major axis diameter to the average minor axis diameter, i.e., the average major axis diameter / average minor axis diameter, and is 1 to 15. If the average major axis diameter / average minor axis diameter exceeds 15, the orientation in the X direction of the shaped object becomes significant, and the strength anisotropy with respect to the Z direction increases, which is undesirable. Therefore, the average major axis diameter / average minor axis diameter is preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. Theoretically, the lower limit is 1. Among these, from the viewpoint of increasing strength, a ratio of 2 to 8 is particularly preferable, and a ratio of 3 to 8 is extremely preferable. From the viewpoint of reducing anisotropy, a ratio of 1 to 5 is particularly preferable, and a ratio of 1 to 3 is extremely preferable.

[0066] In the present invention, the average major axis diameter and average minor axis diameter of an inorganic reinforcing material are the number average values ​​of the major axis diameter and minor axis diameter of 100 randomly selected fibers or particles in a photograph of the inorganic reinforcing material taken with a scanning electron microscope. The major axis diameter is the diameter at which the distance between two parallel lines is greatest when the particle image is sandwiched between two parallel lines in a direction perpendicular to the major axis diameter. When measuring the average major axis diameter and average minor axis diameter of an inorganic reinforcing material, the major axis diameter and minor axis diameter may be measured by selecting inorganic reinforcing materials from a scanning electron microscope photograph of a powder composition such as that shown in Figure 2.

[0067] The amount of such inorganic reinforcing material to be added is preferably 10 parts by mass or more and 200 parts by mass or less per 100 parts by mass of resin powder (A). The upper limit of the amount to be added is more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, and particularly preferably 75 parts by mass or less, in order to obtain a shaped product with excellent surface smoothness without impairing the flowability of the resin powder granules. The lower limit of the amount to be added is more preferably 15 parts by mass or more, even more preferably 20 parts by mass or more, and particularly preferably 25 parts by mass or more, in order to improve the elastic modulus and strength of the shaped product.

[0068] The surface roughness of the shaped object of the present invention in the X and Y directions, which are the plane directions along which the resin powder particles are layered, is 20 μm or less. The smaller the surface roughness, the better the adhesion at the joints between the shaped objects. Therefore, the surface roughness of the shaped object in the X and Y directions is preferably 18 μm or less, more preferably 15 μm or less, even more preferably 12 μm or less, and particularly preferably 10 μm or less.

[0069] The surface roughness in the Z direction, which is the height direction in which the resin powder particles of the shaped object of the present invention are stacked, refers to the surface roughness in the direction perpendicular to the X and Y directions. The surface roughness in the Z direction of the shaped object of the present invention is 20 μm or less, preferably 18 μm or less, more preferably 15 μm or less, even more preferably 12 μm or less, and particularly preferably 10 μm or less. Since the surface roughness in the Z direction depends on the stacking height during shaping, the lower limit of the surface roughness in the Z direction is preferably 1 μm or more, more preferably 3 μm or more, and even more preferably 5 μm or more.

[0070] The surface roughness of the object was determined by observing the surface of the object with an optical microscope, creating a 3D image of the irregularities on the surface of the object using the automatic synthesis mode, obtaining a cross-sectional height profile over a length of 1 mm or more, and calculating the surface roughness Ra (arithmetic mean roughness) by arithmetic averaging.

[0071] Furthermore, in 3D modeling, a powder is filled into a molded object through melt sintering under normal pressure, which usually involves density changes due to shrinkage. Therefore, in order to obtain highly accurate dimensions of the 3D object based on the desired modeling data, it is preferable for the object to have a moderate amount of voids inside. The proportion and shape of voids present in the 3D model of the present invention can be observed using X-ray CT.

[0072] The 3D object of the present invention is imaged by X-ray CT, and the ratio of the portions observed as voids to the volume of the entire object can be expressed as the porosity. The porosity observed by X-ray CT measurement of the 3D object of the present invention is preferably 0.1 vol% or more and 5.0 vol% or less. The lower limit of the porosity is more preferably 0.2 vol% or more, even more preferably 0.3 vol% or more, and particularly preferably 0.5 vol% or more, because a too small porosity can cause the entire object to shrink relative to the shaping data. Furthermore, the upper limit is more preferably 4.0 vol% or less, even more preferably 3.0 vol% or less, and particularly preferably 2.0 vol% or less, because a large number of voids can cause a decrease in strength.

[0073] The size of each independent pore observed as a void when the three-dimensionally shaped object of the present invention is imaged by X-ray CT can be expressed as a sphere-equivalent diameter. The average sphere-equivalent diameter of the voids observed by X-ray CT measurement of the three-dimensionally shaped object of the present invention is preferably 1 μm or more and 100 μm or less. In the case of melt molding that does not involve a three-dimensional shaping process, the average sphere-equivalent diameter of the voids is typically designed to be less than 1 μm. In cases where voids are intentionally formed, such as in foam molding, the average sphere-equivalent diameter of the voids typically exceeds 100 μm. Therefore, a three-dimensionally shaped object is characterized by an average sphere-equivalent diameter of 1 μm or more and 100 μm or less. As mentioned above, a certain amount of voids are generated during three-dimensional shaping under normal pressure, and the lower limit is preferably 3 μm or more, more preferably 5 μm or more, and even more preferably 10 μm or more, because this can cause the problem of the entire shaped object shrinking. The upper limit is preferably 80 μm or less, more preferably 60 μm or less, and even more preferably 50 μm or less, since large pores become defects and cause a decrease in the strength of the molded product.

[0074] Furthermore, compared to conventional melt molding, three-dimensional objects are obtained by crystallization in a process of slowly lowering the temperature at normal pressure, and so the state of the crystals differs from that of conventional melt molding. However, it is difficult to express this as a characteristic of the object, and therefore the object is limited by the manufacturing method, namely, three-dimensional molding, preferably by powder bed fusion. It is well known that conventional melt molding can produce molded objects with smooth surfaces depending on the structure of the mold, but it has not been possible to obtain molded objects with smooth surfaces in three-dimensional molding, which is capable of molding complex shapes, and this has only been possible with the present invention.

[0075] The three-dimensional object of the present invention can be manufactured with small surface roughness in the X and Y directions, as well as in the Z direction. Furthermore, the joints between the objects have excellent adhesion, and good sliding and adhesion are achieved in male-female structures such as screws. Furthermore, the good adhesion in pipes and other structures can reduce leakage from joints. [Example]

[0076] The present invention will be described below based on examples. (1) D80 particle size, D50 particle size, and D20 particle size of resin powder A dispersion of approximately 100 mg of resin powder particles in approximately 5 mL of deionized water was added to a Nikkiso laser diffraction particle size distribution analyzer (Microtrac MT3300EXII) until a measurable concentration was reached. After ultrasonic dispersion for 60 seconds at 30 W in the analyzer, the particle size at which the cumulative frequency from the small particle size side of the particle size distribution measured over a 10-second measurement period was 80%, the D80 particle size of the resin powder was determined as the particle size at which the cumulative frequency was 50%, and the D20 particle size was determined as the particle size at which the cumulative frequency was 20%. The refractive index used during the measurement was 1.52, and the refractive index of the medium (deionized water) was 1.333.

[0077] (2) Sphericity of resin powder The sphericity of the resin powder was calculated as the average ratio of the minor axis to the major axis by observing 30 randomly selected particles in a photograph taken with a scanning electron microscope (JEOL Ltd., scanning electron microscope: JSM-6301NF).

[0078] (3) Solidity of resin powder based on the ratio of BET specific surface area to theoretical specific surface area In accordance with the Japanese Industrial Standards (JIS) JISR1626 (1996) "Method for measuring specific surface area by gas adsorption BET method," approximately 0.2 g of resin powder was placed in a glass cell using a BELSORP-max manufactured by BEL Japan Co., Ltd., and after degassing under reduced pressure at 80°C for approximately 5 hours, the krypton gas adsorption isotherm at liquid nitrogen temperature was measured and calculated using the BET method.

[0079] Furthermore, the theoretical specific surface area of ​​the resin powder was calculated from the ratio of the surface area of ​​a single sphere calculated from the D50 particle size of the resin powder to the weight of a single sphere, which is the product of the volume of a single sphere calculated from the D50 particle size of the resin powder and the density. The solidity of the resin powder was evaluated by calculating the ratio of the BET specific surface area to the theoretical specific surface area.

[0080] (4) Crystallization temperature and melting point of resin powder Using a TA Instruments differential scanning calorimeter (DSCQ20), the sample was heated in a nitrogen atmosphere from 30°C to a temperature 30°C higher than the endothermic peak indicating the resin's melting point at a rate of 20°C / min, and then held for 1 minute. The temperature was then cooled to 30°C at a rate of 20°C / min, and the peak of the exothermic peak that appeared was taken as the crystallization temperature. After cooling, the temperature was further increased at 20°C / min, and the endothermic peak was taken as the melting point. Approximately 8 mg of resin powder was required for the measurement.

[0081] (5) Content of secondary components in resin powder 400 g of water was added to 200 g of resin powder and allowed to stand at 80°C for 1 hour to extract the minor components. The weight of the extract sample was measured using gel permeation chromatography, and compared with a calibration curve prepared for the minor components. The minor component content (mass%) of the resin powder was calculated by dividing the weight of the minor components by the weight of the resin powder. Equipment: Shimadzu Corporation LC-10A series Column: TSKgel G3000PWXL manufactured by Tosoh Corporation Mobile phase: 100mmol / L sodium chloride aqueous solution Flow rate: 0.8ml / min Temperature: 40℃ Detection: Differential refractometer.

[0082] (6) Average major axis diameter and average minor axis diameter of inorganic reinforcement The inorganic reinforcing material was observed using a scanning electron microscope (JSM-6301NF) manufactured by JEOL Ltd., and the average values ​​of the major and minor axes of 100 inorganic reinforcing materials randomly selected from the photograph were taken as the average major axis diameter and average minor axis diameter.

[0083] (7) Evaluation of the fluidity of resin powder Using a Multitester MT-1 manufactured by Seishin Enterprise Co., Ltd., 100g of resin powder was dropped from a funnel onto a flat plate, and the angle of repose, the angle between the slope of the pile and the plate, was measured. If the angle of repose was 40 degrees or less, the fluidity was evaluated as "good," and if it was over 40 degrees, it was evaluated as "poor."

[0084] (8) Surface roughness of the object The surface roughness of 3D models fabricated using resin powder was measured by creating test specimens measuring 20 mm wide, 20 mm long, and 10 mm thick using a powder bed fusion 3D printer (Aspect Corporation, RaFaEl II 150C-HT powder bed fusion printer). The surfaces of the models were then observed at 200x magnification using a Keyence Corporation optical microscope (VHX-5000) with a VH-ZST (ZS-20) objective lens. Using the accompanying software (system version 1.04), 3D images of the surface irregularities were captured in the automated synthesis mode. Cross-sectional height profiles were then obtained over a length of 1 mm or more, and the surface roughness Ra (centerline average surface roughness) was calculated by arithmetic averaging. A smaller surface roughness Ra indicates better surface smoothness (quality).

[0085] (9) Bending strength of the object The bending strength of 3D models fabricated using resin powder was measured using a powder bed fusion 3D printer (Aspect Inc., RaFaEl II 150C-HT powder bed fusion printer) to create test pieces measuring 10 mm wide, 80 mm long, and 4 mm thick. These test pieces were then measured using a Tensilon universal testing machine (TENSIRON TRG-1250, A&D Co., Ltd.). According to JIS K7171 (2008), a three-point bending test was performed with a support distance of 64 mm and a test speed of 2 mm / min. The measurement temperature was room temperature (23°C), and the number of measurements was 5 (n = 5), and the average value was calculated.

[0086] (10) Adhesion of joints between objects The adhesion between the 3D objects made using resin powder was evaluated by printing a pipe shape using a powder bed fusion 3D printer (Aspect Inc.'s powder bed fusion RaFaEl II 150C-HT), joining the two pipes, and running water through them to evaluate the water leakage from the joint. If there was no water leakage, the adhesion was considered good, and if there was water leakage, the adhesion was considered poor.

[0087] [Production Example 1] (Polyamide 12 powder suitable for use in the present invention) In a 3L autoclave equipped with a helical ribbon stirring blade, 300g of aminododecanoic acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polyamide monomer, 700g of polyethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., grade 1 polyethylene glycol 20,000, weight average molecular weight 18,600) as a polymer incompatible with polyamide, and 1000g of water were added to form a homogeneous solution, which was then sealed and purged with nitrogen. The stirring speed was then set to 60 rpm, and the temperature was raised to 210°C. During this time, the pressure of the system was kept at 10 kg / cm. 2 After reaching 10 kg / cm 2 After the temperature reached 210°C, the steam pressure was reduced to 0.2 kg / cm. 2 The pressure was released at a rate of 1 / min. The temperature was then maintained for 1 hour while nitrogen was flowing to complete the polymerization. The mixture of resin powder and polyethylene glycol was discharged into a 2000g water bath while the polyethylene glycol remained molten, yielding a slurry. The slurry was thoroughly homogenized by stirring, then filtered. 2000g of water was added to the filtered material, and the mixture was washed at 80°C. The washed slurry was first allowed to settle by decantation, and the supernatant was removed to remove fine particles that did not settle by gravity in the polyethylene glycol aqueous solution. 2000g of water was then added to reslurry the mixture. The slurry was then passed through a 100µm sieve to remove aggregates, and then passed through a 63µm sieve to remove coarse particles. The filtered material was again isolated and dried at 80°C for 12 hours, yielding 240g of polyamide 12 powder. To 100 parts by mass of this polyamide 12 powder, 0.3 parts by mass of trimethylsilylated amorphous silica (X-24-9500 manufactured by Shin-Etsu Chemical Co., Ltd.) with an average particle size of 170 nm was added as a flow aid. The resulting resin powder had a D80 particle size of 44 μm, a D50 particle size of 32 μm, a D20 particle size of 22 μm, a sphericity of 97, a content of minor components of 0.0005% by mass, and an angle of repose of 30 degrees. The BET specific surface area was 0.23 m 2 / g, and the ratio of the BET specific surface area to the theoretical specific surface area was 1.3.

[0088] [Production Example 2] (Polyamide 6 Powder 1 Suitable for Use in the Present Invention) Resin powder particles for 3D printing were produced in the same manner as in Production Example 1, except that the polyamide monomer was changed from aminododecanoic acid to ε-caprolactam and 0.5 parts by mass of trimethylsilylated amorphous silica was added to 100 parts by mass of the resulting polyamide 6 powder. The resulting resin powder had a D80 particle size of 29 μm, a D50 particle size of 21 μm, a D20 particle size of 17 μm, a sphericity of 96, a content of minor components of 0.0006% by mass, and an angle of repose of 31 degrees. The BET specific surface area was 0.41 m. 2 / g, and the ratio of the BET specific surface area to the theoretical specific surface area was 1.6.

[0089] [Production Example 3] (Polyamide 6 Powder 2 Suitable for Use in the Present Invention) A resin powder for 3D modeling was produced in the same manner as in Production Example 2, except that the stirring speed of the stirring blade attached to the autoclave was changed to 45 rpm and 0.1 parts by mass of trimethylsilylated amorphous silica was added to 100 parts by mass of the obtained polyamide 6 powder. The obtained resin powder had a D80 particle size of 56 μm, a D50 particle size of 43 μm, a D20 particle size of 30 μm, a sphericity of 94, a content of minor components of 0.0004% by mass, and an angle of repose of 36 degrees. The BET specific surface area was 0.19 m 2 / g, and the ratio of the BET specific surface area to the theoretical specific surface area was 1.5.

[0090] [Production Example 4] (Polybutylene terephthalate powder suitable for use in the present invention) A 1000 ml pressure-resistant glass autoclave was charged with 33.25 g of polybutylene terephthalate ("Treycon" (registered trademark) 1401X06), 299.25 g of N-methyl-2-pyrrolidone, and 17.5 g of polyvinyl alcohol (PVA-1500, manufactured by Wako Pure Chemical Industries, Ltd., weight-average molecular weight 29,000; the sodium acetate content was reduced to 0.05% by weight by washing with methanol). The mixture was then purged with nitrogen, heated to 180 °C, and stirred for 4 hours until the polymer was dissolved. Subsequently, 350 g of ion-exchanged water as a poor solvent was added dropwise via a liquid pump at a rate of 2.92 g / min. After the entire amount of water was added, the mixture was cooled with stirring, and the resulting suspension was filtered. 700 g of ion-exchanged water was added for reslurry washing. The filtered product was then vacuum-dried at 80 °C for 10 hours to obtain 28.3 g of polybutylene terephthalate powder. To 100 parts by mass of this polybutylene terephthalate powder, 0.5 parts by mass of trimethylsilylated amorphous silica with an average particle size of 170 nm was added as a flow aid. The resulting resin powder had a D80 particle size of 24 μm, a D50 particle size of 16 μm, a D20 particle size of 11 μm, a sphericity of 89, a content of minor components of 0.02% by mass, and an angle of repose of 39 degrees. The BET specific surface area was 0.78 m 2 / g, and the ratio of the BET specific surface area to the theoretical specific surface area was 2.7.

[0091] [Production Example 5] (Comparative example of polyamide 12 powder with large particle size) Resin powder for 3D modeling was produced in the same manner as in Production Example 1, except that the stirring speed of the stirring blade attached to the autoclave was changed to 25 rpm and the removal of coarse particles using a sieve with 63 μm openings was not performed. The D80 particle size of the obtained resin powder was 91 μm, the D50 particle size was 72 μm, the D20 particle size was 52 μm, the sphericity was 97, the content of minor components was 0.0004 mass%, and the angle of repose was 29 degrees. The BET specific surface area was 0.12 m 2 / g, and the ratio of the BET specific surface area to the theoretical specific surface area was 1.5.

[0092] [Production Example 6] (Comparative Polyamide 12 Powder with Small Particle Size) A resin powder for 3D printing was produced in the same manner as in Production Example 1, except that the stirring speed of the stirring blade attached to the autoclave was changed to 150 rpm, and polyamide 12 powder was produced without removing fine particles by decantation. 1.0 part by mass of trimethylsilylated amorphous silica was added to 100 parts by mass of the resulting polyamide 12 powder. The resulting resin powder had a D80 particle size of 7 μm, a D50 particle size of 4 μm, a D20 particle size of 0.8 μm, a sphericity of 96, and an angle of repose of 39 degrees. The BET specific surface area was 2.0 m 2 The ratio of the BET specific surface area to the theoretical specific surface area was 1.4 at 1000 kJ / g.

[0093] [Production Example 7] (Comparative example of resin powder containing no flow aid) Resin granules for 3D modeling were prepared in the same manner as in Production Example 1, except that trimethylsilylated amorphous silica was not added to 100 parts by mass of polyamide 12 powder. The resulting resin powder had a D80 particle size of 44 μm, a D50 particle size of 32 μm, a D20 particle size of 22 μm, a sphericity of 97, and an angle of repose of 46 degrees. The BET specific surface area was 0.23 m 2 / g, and the ratio of the BET specific surface area to the theoretical specific surface area was 1.3.

[0094] [Production Example 8] (Comparative example of polyamide 12 powder with low sphericity) 400 g of polyamide 12 ("VESTAMID" (registered trademark) L1600) and 2.2 L of ethanol were heated to 140°C in a 3 L autoclave and dissolved. 0.2 L of ethanol was distilled from the mixture, and the mixture was cooled to 117°C. After maintaining the temperature for 9 hours, the mixture was cooled to 45°C. The resulting slurry was filtered and dried at 90°C to produce polyamide 12 powder. 0.1 parts by mass of hydrophobic silicic acid ("AEROSIL" (registered trademark) R972) was added to 100 parts by mass of the resulting polyamide 12 powder to produce a resin powder for 3D modeling. The resulting resin powder had a D80 particle size of 75 μm, a D50 particle size of 56 μm, a D20 particle size of 13 μm, a sphericity of 67, a content of minor components of 1.54% by mass, and an angle of repose of 32°. The BET specific surface area was 0.87 m 2 / g, and the ratio of the BET specific surface area to the theoretical specific surface area was 8.4.

[0095] [Production Example 9] (Resin Powder 1 Containing Inorganic Reinforcing Material Suitable for Use in the Present Invention) To 100 parts by mass of the polyamide 6 powder obtained in Production Example 2, 67 parts by mass of glass beads GB731A (manufactured by Potters Ballotini, average major axis diameter 27 μm, average minor axis diameter 26 μm) and 0.3 parts by mass of trimethylsilylated amorphous silica were added and dry-blended to produce a resin powder for 3D modeling containing inorganic reinforcing material.

[0096] [Production Example 10] (Resin Powder 2 Containing Inorganic Reinforcing Material Suitable for Use in the Present Invention) To 100 parts by mass of the polyamide 6 powder obtained in Production Example 3, 43 parts by mass of EPG70M-01N (manufactured by Nippon Electric Glass Co., Ltd., average major axis diameter 73 μm, average minor axis diameter 10 μm) and 0.3 parts by mass of trimethylsilylated amorphous silica were added and dry-blended to produce a resin powder for 3D modeling containing inorganic reinforcing material.

[0097] [Example 1] A three-dimensional object was produced using 1.5 kg of the resin powder granules obtained in Production Example 1 (a scanning electron microscope photograph is shown in Figure 3) in a powder bed fusion system (RaFaEl II 150C-HT) manufactured by Aspect Co., Ltd. The set conditions were as follows: a 60W CO2 laser was used, the layer height was 0.05 mm, the laser scanning interval was 0.1 mm, the laser scanning speed was 5.00 m / s, and the laser output was 5 W. In this case, the laser energy per unit area Ea was 1.0 J / cm. 2 The temperature settings were as follows: the part bed temperature was -15°C below the melting point, and the supply tank temperature was -5°C below the crystallization temperature. The properties of the resin powder and the resulting molded object are shown in Table 1.

[0098] [Example 2] A three-dimensional object was produced in the same manner as in Example 1, except that the setting conditions for three-dimensional modeling were changed to a layer height of 0.07 mm and a laser output of 7 W. The properties of the resin powder and the resulting model are shown in Table 1.

[0099] [Example 3] A three-dimensionally shaped object was produced in the same manner as in Example 1, except that the resin powder obtained in Production Example 2 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0100] [Example 4] A three-dimensionally shaped object was produced in the same manner as in Example 2, except that the resin powder obtained in Production Example 3 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0101] [Example 5] A three-dimensionally shaped object was produced in the same manner as in Example 1, except that the resin powder obtained in Production Example 4 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0102] [Comparative Example 1] A three-dimensional object was produced in the same manner as in Example 1, except that the setting conditions for three-dimensional modeling were changed to a layer height of 0.10 mm and a laser output of 10 W. The properties of the resin powder and the resulting model are shown in Table 1.

[0103] Comparative Example 2 A three-dimensionally shaped object was produced in the same manner as in Example 1, except that the resin powder obtained in Production Example 5 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0104] Comparative Example 3 A three-dimensional object was produced in the same manner as in Comparative Example 2, except that the setting conditions for three-dimensional modeling were changed to a layer height of 0.10 mm and a laser output of 10 W. The properties of the resin powder and the resulting model are shown in Table 1.

[0105] Comparative Example 4 A three-dimensionally shaped object was produced in the same manner as in Example 1, except that the resin powder obtained in Production Example 6 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0106] Comparative Example 5 A three-dimensionally shaped object was produced in the same manner as in Example 1, except that the resin powder obtained in Production Example 7 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0107] Comparative Example 6 A three-dimensionally shaped object was produced in the same manner as in Example 1, except that the resin powder obtained in Production Example 8 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0108] [Example 6] A three-dimensionally shaped object was produced in the same manner as in Example 1, except that the resin powder obtained in Production Example 9 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0109] [Example 7] A three-dimensionally shaped object was produced in the same manner as in Example 2, except that the resin powder obtained in Production Example 10 was used. The properties of the resin powder and the resulting shaped object are shown in Table 1.

[0110] [Table 1] [Industrial Applicability]

[0111] The present invention provides a method for manufacturing a 3D object having small surface roughness in the X and Y directions, which are the plane directions along which resin powder particles are layered, and in the Z direction, which is the height direction along which the resin powder particles are layered. Furthermore, since the object obtained by this manufacturing method has excellent adhesion at the joints between the objects, it can be suitably used for manufacturing precision parts and 3D objects where loads are applied to the joints. [Explanation of symbols]

[0112] 1. Tank for forming the object 2. The tank stage where the object is formed 3. Supply tank for pre-filling resin powder 4. Tank stage where resin powder is pre-filled 5 Recoater 6. Thermal Energy 7 X, Y, Z coordinate system 8. Plane direction for laminating resin powder particles 9 Height direction of resin powder layer 10 3D objects 11 Surface of the object in the direction of laminating the resin powder particles 12 Surface of the object in the height direction where resin powder particles are layered P resin powder

Claims

1. A resin powder granule for producing a three-dimensional object by powder bed fusion, the resin powder granule comprising a resin powder (A) and a flow aid (B), wherein the resin powder (A) has a sphericity of 80 or more and 100 or less, the resin powder (A) has a D80 particle size of 60 μm or less and a D20 particle size of 1 μm or more, and the flow aid (B) is contained in an amount of more than 0.01 parts by mass and less than 5 parts by mass per 100 parts by mass of the resin powder (A).

2. The resin powder granule according to claim 1, wherein the D50 particle size of the resin powder (A) is 1 μm or more and 50 μm or less.

3. The resin powder according to claim 1 or 2, wherein the flow aid (B) has a D50 particle size of 20 nm or more and 1 μm or less.

4. The resin powder granule according to any one of claims 1 to 3, wherein D50(A) is the D50 particle diameter of the resin powder (A), D50(B) is the D50 particle diameter of the flow aid (B), and the content of the flow aid (B) per 100 parts by mass of the resin powder (A) is X parts by mass, and D50(A) × X / D50(B) is more than 30 and less than 300.

5. The resin powder granule according to any one of claims 1 to 4, comprising 10 parts by mass or more and 200 parts by mass or less of an inorganic reinforcing material (C) per 100 parts by mass of the resin powder (A).

6. A method for producing a three-dimensional object by powder bed fusion bonding using the resin powder and granules according to any one of claims 1 to 5.

7. A three-dimensional object formed by a powder bed fusion method using resin powder granules, characterized in that the surface roughness of the object in the plane direction in which the resin powder granules are stacked is 20 μm or less, and the surface roughness of the object in the height direction in which the resin powder granules are stacked is 20 μm or less.

8. The three-dimensionally shaped object according to claim 7 , wherein the average equivalent sphere diameter of the pores in the three-dimensionally shaped object as observed by X-ray CT measurement is 1 μm or more and 100 μm or less.

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