Powder composition, method for manufacturing three-dimensional object using powder bed fusion method with powder composition, and three-dimensional object

Abstract

To provide a powder composition that effectively absorbs laser light with a beam wavelength of 400 nm to 2000 nm.SOLUTION: A powder composition consisting of (A) thermoplastic resin powder with a D50 particle size of 1 μm to 100 μm and a sphericity of 80 or higher, and (B) a heat-absorbing material of 0.02 wt.% to 2 wt.%, is used in a powder bed fusion method using laser light with a beam wavelength of 400 nm to 2000 nm.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a powder composition for use in powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm, a method for manufacturing a three-dimensional object using the powder composition, and a three-dimensional object. [Background technology]

[0002] Powder bed fusion is known as one of the manufacturing methods for obtaining three-dimensional objects. Metal powder or thermoplastic resin powder is generally used as the raw material for manufacturing using powder bed fusion. In particular, three-dimensional objects can be obtained by selective laser sintering, which melts the raw material by selectively irradiating a laser beam onto a layer of raw material powder. The features of powder bed fusion include the ability to selectively irradiate laser beam, which allows for strong mechanical strength, and the fact that no support members are required makes it suitable for precision manufacturing. As a result, it is increasingly being used in industrial applications such as aircraft, railways, and automobiles, as well as precision machinery and medical equipment.

[0003] In the selective laser sintering method, a carbon dioxide laser with a wavelength of approximately 10,000 nm is used because it can effectively melt thermoplastic resin powder. Meanwhile, in recent years, vigorous research has been conducted into ways to improve the manufacturing speed, and one example of this is the use of a fiber laser that uses near-infrared light, which is expected to increase speed because its wavelength range is approximately 1 / 10 that of conventional lasers, the laser itself is high-powered, and no complex device structure is required to transmit the laser light (Patent Document 1). However, because thermoplastic resin powders generally have low absorption of fiber lasers, Patent Document 2 discloses a manufacturing method in which carbon black is mixed into thermoplastic resin powder to improve fiber laser absorption. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] CN-A-106626379 [Patent Document 2] US-A-20210403714 [Patent Document 3] International Publication No. 2016 / 104140 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention aims to obtain a powder composition that effectively absorbs laser light with a beam wavelength of 400 nm to 2000 nm for use in powder bed fusion manufacturing using a fiber laser as the laser light. Patent Document 2 describes a technique for dispersing carbon black more uniformly than thermoplastic resin powder, but the amorphous nature of thermoplastic resin powder limits the dispersibility of the carbon black and also complicates the manufacturing process. Patent Document 3 describes a powder for three-dimensional modeling in which carbon black is encapsulated in spherical polyamide microparticles, and is characterized by the fact that the encapsulation prevents the carbon black from agglomerating or separating, but does not describe the type of laser light preferred or the absorption of near-infrared light.

[0006] Therefore, the present invention aims to provide a powder composition that contains highly spherical polyamide microparticles and a heat absorbing material, thereby allowing the heat absorbing material to be uniformly dispersed in the polyamide microparticles, and that can effectively absorb laser light when the powder composition is applied to a powder bed fusion method that uses a fiber laser as the laser light. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following configuration. <1> A powder composition comprising (A) a thermoplastic resin powder having a D50 particle size of 1 μm to 100 μm and a sphericity of 80 or more, and (B) a heat absorbing material at 0.02 wt % to 2 wt %, said powder composition being used for powder bed fusion manufacturing using a laser beam with a beam wavelength of 400 nm to 2000 nm. <2> The powder composition is obtained by powder mixing of a heat absorbing material and a thermoplastic resin powder. <1> The powder composition according to claim 1. <3> 9500cm -1 The transmittance of near-infrared light is 40% or less. <1> or <2> The powder composition according to claim 1. <4> The angle of repose is 40 degrees or less <1> ~ <3> 1. The powder composition according to any one of the preceding claims. <5> The thermoplastic resin constituting the thermoplastic resin powder is polyamide. <1> ~ <4> 1. The powder composition according to any one of the preceding claims. <6> The heat absorbing material is carbon black. <1> ~ <5> 1. The powder composition according to any one of the preceding claims. <7> The D50 particle size of the heat absorbing material is 100 nm to 1000 nm. <1> ~ <6> 1. The powder composition according to any one of the preceding claims. <8> Laser light with a beam wavelength of 400nm to 2000nm is laser light produced by a fiber laser. <1> ~ <7> 1. The powder composition according to any one of the preceding claims. <9> The powder composition contains 5% by weight or more and 60% by weight or less of a reinforcing filler. <1> ~ <8> 1. The powder composition according to any one of the preceding claims. <10> <1> ~ <9> 1. A method for producing a three-dimensional object by powder bed fusion bonding using the powder composition according to any one of the above items 1 to 4, and irradiating it with laser light having a beam wavelength of 400 nm to 2000 nm. <11> A three-dimensional object obtained by powder bed fusion, which irradiates laser light with a beam wavelength of 400 nm to 2000 nm, containing at least (A) a thermoplastic resin and (B) 0.02% by weight to 2% by weight of a heat absorbing material, and having a surface roughness of 20 μm or less. <12> Used in automotive, aerospace or robot parts <11> The three-dimensional object according to claim 1. [Effects of the Invention]

[0008] According to the present invention, a powder composition containing polyamide microparticles with high sphericity and a heat absorbing material can be obtained by a simple method, in which the heat absorbing material is uniformly dispersed in the polyamide microparticles, and a powder composition that can effectively absorb near-infrared light even with the addition of a small amount of heat absorbing material can be obtained. [Brief explanation of the drawings]

[0009] [Figure 1] 1 is a schematic diagram illustrating an example of a manufacturing apparatus for a three-dimensional object according to the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0010] The thermoplastic resin in the present invention is a thermoplastic resin suitable for producing three-dimensional objects by powder bed fusion, and examples thereof include polyamide, polyphenylene sulfide, polyethylene, polypropylene, polyester, polyether ether ketone, polyetherimide, polyamideimide, polyethersulfone, polytetrafluoroethylene, and mixtures thereof. Polyester, polyamide, and polyphenylene sulfide are preferred in that the resulting three-dimensional objects have excellent heat resistance and a clear difference between their melting points and crystallization temperatures, resulting in excellent formability and reproducibility. Polyamide is more preferred in that it has an optimal forming temperature range for powder bed fusion.

[0011] 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 (poly 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), polycaproamide / polylauroamide copolymer (6 / 12), etc. 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. Among these, in terms of the heat resistance of the molded object, polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), polyhexamethylene sebacamide (polyamide 610), polyhexamethylene dodecamide (polyamide 612), polycaproamide / polyhexamethylene adipamide copolymer (polyamide 6 / 66), and polycaproamide / polylauroamide copolymer (6 / 12) are particularly preferred, with polycaproamide (polyamide 6) being the most preferred.

[0012] The D50 particle size of the thermoplastic resin powder in the present invention is in the range of 1 to 100 μm. If the D50 particle size exceeds 100 μm, the dispersibility of the heat absorbing material will be poor, making it difficult to improve the near-infrared light absorption and the surface of the resulting shaped product will be rough. If the D50 particle size is less than 1 μm, the flowability will be reduced and fusion of the powder will occur after shaping. The upper limit of the D50 particle size of the thermoplastic resin powder is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. The lower limit is preferably 5 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more.

[0013] The D50 particle size of the thermoplastic resin powder is the particle size (D50 particle size) at which the cumulative frequency from the small particle size side of the particle size distribution measured with a laser diffraction particle size distribution analyzer is 50%.

[0014] The particle size distribution of the thermoplastic resin powder is expressed as D90 / D10, which is the ratio of D90 to D10 of the particle size distribution, and is preferably less than 5.0. A narrow particle size distribution is preferable because it suppresses deterioration of the absorbency of the heat absorption material and fusion of the powder after molding. Therefore, D90 / D10 is more preferably less than 4.0, even more preferably less than 3.0, and particularly preferably less than 2.0. Theoretically, the lower limit is 1.0.

[0015] D90 / D10, which indicates the particle size distribution of the thermoplastic resin powder in the present invention, is a value obtained by dividing the particle size (D90) at which the cumulative frequency from the small particle size side of the particle size distribution measured by the above-mentioned laser diffraction particle size distribution analyzer is 90% by the particle size (D10) at which the cumulative frequency from the small particle size side is 10%.

[0016] The sphericity, which indicates the sphericity of the thermoplastic resin powder in the present invention, is preferably 80 to 100. If the sphericity is less than 80, the dispersibility of the heat absorbing material will be poor, the near-infrared light absorption will not be improved, and excess heat absorbing material will cause the powder to fuse together after shaping, resulting in a deterioration in the properties of the shaped product. The sphericity is preferably 85 to 100, more preferably 90 to 100, even more preferably 93 to 100, particularly preferably 95 to 100, and extremely preferably 97 to 100.

[0017] The sphericity of the thermoplastic resin powder of the present invention is determined by observing 30 particles randomly selected from a scanning electron microscope photograph and averaging the value of minor axis / major axis×100 for each particle.

[0018] The main purpose of adding a heat absorbing material in the present invention is to obtain a powder composition that easily absorbs near-infrared light by uniformly dispersing the heat absorbing material in a thermoplastic resin powder that does not easily absorb near-infrared light.

[0019] The absorber is a substance that absorbs near-infrared light. Examples of such substances include carbon black, graphite, graphene, activated carbon, carbon nanotubes, hollow carbon spheres, fullerene, anthracite powder, carbon fiber, copper hydroxyphosphate, metal nanoparticles, silicon, iron oxide, dye molecules such as aniline black, perylene black, nigrosine, porphyrin, chlorophyll, and carotenoid, 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 may be used alone or in combination.

[0020] As the heat absorbing material to be used, carbon black, graphite, graphene, activated carbon, anthracite powder, iron oxide, etc. are preferred because they do not impair the properties of the powder composition and are effective even in small amounts. Among these, carbon black is more preferred from the viewpoint of dispersibility with the thermoplastic resin powder. Examples of such carbon black include furnace black, acetylene black, thermal black, channel black, etc., and furnace black and acetylene black are particularly preferred from the viewpoint of carbon black's high specific surface area and the ability to exert an effect in smaller amounts, and furnace black is most preferred from the viewpoint of less impairing the properties of the powder composition.

[0021] One index used to characterize the properties of heat-absorbing materials such as carbon black is DBP (dibutyl phthalate) absorption. DBP (dibutyl phthalate) absorption is the amount of DBP absorbed on the surface of heat-absorbing material particles such as carbon black and in the voids formed by agglomerated particles, i.e., an index for evaluating oil absorption. It can be measured according to JIS K6217-4:2008. A preferred DBP absorption is 10 ml / 100 mg or more and 500 ml / 100 mg or less. DBP absorption below 10 ml / 100 mg results in uneven coverage of the heat-absorbing material on the thermoplastic resin powder surface, preventing the laser energy from being distributed throughout the entire surface and resulting in inconsistent sintering of the thermoplastic resin powder. Furthermore, DBP absorption above 500 ml / 100 mg can lead to aggregation of the heat-absorbing material, potentially resulting in surface inconsistencies when three-dimensionally modeling a product from the powder composition.

[0022] The heat absorbing material may be contained inside or outside the thermoplastic resin powder. When the heat absorbing material is contained inside, it can be obtained by adding the heat absorbing material during polymerization of the thermoplastic resin powder. When the heat absorbing material is added externally, it can be obtained by powder mixing the thermoplastic resin powder and the heat absorbing material. When the heat absorbing material is contained inside, by using a thermoplastic resin powder with high sphericity, the heat absorbing material can be uniformly dispersed and the near-infrared light can be absorbed more effectively. When the heat absorbing material is contained outside, by using a thermoplastic resin powder with high sphericity, the heat absorbing material can be uniformly coated on the surface of the thermoplastic resin powder, and the near-infrared light can be absorbed more effectively, which is preferable.

[0023] From the viewpoint of producing a powder composition by a simpler method, it is preferable to obtain the powder composition by powder mixing the thermoplastic resin powder and the heat absorbing material. Powder mixing can be performed by hand, or a rotating container mixer such as a W-type mixer, a V-type mixer, or a drum-type mixer, or a fixed container mixer such as a ribbon mixer, but the powder mixing method is not particularly limited as long as the materials constituting the powder composition are mixed uniformly.

[0024] Since powder mixing is performed on the premise that the thermoplastic resin powder and heat absorbing material that constitute the powder composition are mixed in powder form, it is preferable to perform the powder mixing at a temperature that is at least 20°C lower than the melting point of the thermoplastic resin. If the powder mixing is performed at a temperature other than this, the thermoplastic resin powder may melt during powder mixing, resulting in a decrease in the sphericity of the thermoplastic resin powder. Although the lower limit of the powder mixing temperature is not particularly specified, it is preferable to perform the powder mixing at a temperature above room temperature.

[0025] The heat absorbing material in the present invention may be in the form of particles or fibers, but in terms of dispersibility of the heat absorbing material in the thermoplastic resin powder, particles are preferred. When the ratio of the average major axis diameter to the average minor axis diameter, that is, the average major axis diameter / average minor axis diameter, of the heat absorbing material is less than 2, it is defined as being in the form of particles, and when it is 2 or more, it is defined as being in the form of fibers.

[0026] When the heat absorbing material is particulate, the D50 particle size is preferably in the range of 10 to 1000 nm. If the D50 particle size exceeds 1000 nm, dispersibility in the thermoplastic resin powder deteriorates, making it difficult to improve near-infrared light absorption. The upper limit of the D50 particle size of the heat absorbing material is more preferably 500 nm or less, even more preferably 300 nm or less, and particularly preferably 200 nm or less. From the viewpoint of ease of handling of the heat absorbing material, the lower limit is more preferably 15 nm or more, even more preferably 20 nm or more, particularly preferably 30 nm or more, and most preferably 100 nm or more.

[0027] The smaller the D50 particle size of the particulate heat absorbing material, the lower the L value of the powder composition with a smaller amount of addition. -1 However, the D50 particle size of the heat absorption material in the present invention is most preferably about 100 nm because the heat absorption material is likely to aggregate and cause sintering defects, and the powder composition is likely to accumulate heat during shaping and fuse after shaping.

[0028] The ease of fusion of a powder composition can be confirmed by applying a thermal history under certain conditions. For example, a test method in which the powder composition is immersed in an oil bath set to a predetermined temperature, or a test method in which the powder composition is placed in a vial and left to stand in a thermal oven set to a specified temperature, is preferred. When a thermal history is applied to a powder composition at a temperature lower than but close to the melting point of the thermoplastic resin powder that constitutes the powder composition, a powder composition with high heat storage properties is more likely to fuse. If the powder composition does not fuse even after the thermal history, this suggests that the powder composition will not easily fuse to a three-dimensionally molded object when used in a three-dimensionally molded object.

[0029] The D50 particle size of the particulate heat absorption material can be measured by dynamic light scattering. The particle size at which the cumulative frequency from the small particle size side of the particle size distribution reaches 50% was defined as the D50 particle size.

[0030] When the heat absorbing material is fibrous, the average major axis diameter is preferably 10 nm to 300 μm. If the average major axis diameter exceeds 300 μm, dispersibility in the thermoplastic resin powder deteriorates, making it difficult to improve the near-infrared light absorption. The upper limit of the average major axis diameter of the heat absorbing material is more preferably 200 μm or less, even more preferably 150 μm or less, and particularly preferably 100 μm or less. From the viewpoint of ease of handling of the heat absorbing material, the lower limit is more preferably 15 nm or more, even more preferably 20 nm or more, and particularly preferably 30 nm or more.

[0031] The average major axis diameter / average minor axis diameter of the fibrous heat absorption material is preferably 2 or more and 15 or less. From the viewpoint of improving the dispersibility of the heat absorption material in the thermoplastic resin powder, the average major axis diameter / average minor axis diameter is more preferably 3 or more and 13 or less, further preferably 4 or more and 12 or less, and particularly preferably 5 or more and 10 or less.

[0032] The average major axis diameter and average minor axis diameter of the heat absorbing material are the number average values obtained by observing the major axis diameter and minor axis diameter of 100 heat absorbing materials randomly selected from a photograph obtained by capturing an image of the heat absorbing material with a scanning electron microscope. The major axis diameter is the diameter at which the distance between the parallel lines is greatest when the image of the heat absorbing material is sandwiched between two parallel lines, and the minor axis diameter is the diameter at which the distance between the parallel lines is smallest when the image of the heat absorbing material is sandwiched between two parallel lines in a direction perpendicular to the major axis diameter.

[0033] The blending amount of the heat absorbing material is 0.02 wt% to 2 wt% based on 100 wt% of the thermoplastic resin. If the blending amount exceeds 2 wt%, it becomes difficult to incorporate the heat absorbing material into the thermoplastic resin powder. Even when the heat absorbing material is added externally, the heat absorbing material may excessively coat the surface of the thermoplastic resin powder, hindering sintering during three-dimensional modeling or causing fusion of the powder composition. If the blending amount is less than 0.02 wt%, the powder composition's near-infrared light absorption effect is reduced, making it unsuitable for powder bed fusion bonding using a fiber laser as the laser light. The upper limit of the blending amount is preferably 2 wt% or less, more preferably 1.0 wt% or less, and even more preferably 0.5 wt% or less. The lower limit is preferably 0.05 wt% or more, more preferably 0.1 wt% or more, and even more preferably 0.2 wt% or more. The heat absorbing material is not limited to a single type; multiple heat absorbing materials may be added as long as the total weight is between 0.02 wt% and 2 wt%.

[0034] The powder composition of the present invention refers to a mixture of the thermoplastic resin powder and the heat absorbing material described above. As will be described later, a reinforcing filler or the like may also be blended.

[0035] In the present invention, the L value can be used as an index for confirming that the thermoplastic resin powder and the heat absorbing material are uniformly dispersed. When a heat absorbing material having a smaller L value than the thermoplastic resin powder is used, it is found that the L value of the powder composition can be reduced by using a thermoplastic resin powder with high sphericity, and the heat absorbing material is uniformly dispersed without agglomeration.

[0036] The L value of a powder composition can be measured using a spectrophotometer. The L value is measured by filling a special quartz dish with the heat absorbing material in powder form.

[0037] In the present invention, the powder composition used in powder bed fusion manufacturing using a laser beam with a beam wavelength of 400 nm to 2000 nm is a powder composition having a wavelength of 9500 cm using a diffuse reflectance method. -1The moldability can be evaluated by the transmittance of near-infrared light at 9500 cm using the diffuse reflectance method. In the diffuse reflectance method, a transmission spectrum is obtained from the specular reflected light reflected from the surface of the powder composition and the diffuse reflected light transmitted through the inside of the powder composition, and therefore, the absorbency can be evaluated by comparing the transmittance of a specific wavelength. The powder composition of the present invention was measured using the diffuse reflectance method at 9500 cm using the specular reflected light. -1 The transmittance of near-infrared light is preferably 40% or less. By having a transmittance of 40% or less, it is possible to improve the formability with a laser beam having a beam wavelength of 400 nm to 2000 nm. It is more preferably 35% or less, even more preferably 30% or less, and particularly preferably 25% or less.

[0038] In the present invention, by using a thermoplastic resin powder with high sphericity, the 9500 cm -1 Therefore, the transmittance of near-infrared light can be further reduced.

[0039] In addition, the powder composition was measured at 9500 cm using a diffuse reflectance method. -1 The near-infrared light transmittance can be evaluated, for example, by installing a diffuse reflectance measuring device (DRS-8000) on a Fourier transform infrared spectrophotometer (IRPrestige-21) manufactured by Shimadzu Corporation, using a tungsten lamp as the light source, calcium fluoride as the beam splitter, and InGaAs (indium gallium arsenide) as the detector, filling a cell with potassium bromide to perform a near-infrared light blank measurement, and then filling the cell with a powder composition sample to perform near-infrared measurement.

[0040] Additives may be added as long as they do not impair the properties of the powder composition of the present invention. Examples of additives include heat stabilizers, antioxidants, flame retardants, light stabilizers, plasticizers, etc., and they may be present either inside or outside the thermoplastic resin powder. In addition, the amount of such additives can be measured by a diffuse reflectance method at 9500 cm -1 If the transmittance of near-infrared light is 40% or less, it is defined as a heat absorbing material.

[0041] From the viewpoint of moldability, it is preferable that the powder composition exhibits high fluidity. Furthermore, it is particularly preferable that the fluidity is high after being subjected to a thermal history of the same degree as the molding temperature. Any known measurement method can be used as an index of this. A specific example is the angle of repose. It is preferable that this angle is 60 degrees or less, more preferably 50 degrees or less, even more preferably 40 degrees or less, and particularly preferably 35 degrees or less. The lower limit is usually 20 degrees or more.

[0042] Furthermore, a reinforcing filler may be added as long as it does not impair the properties of the powder composition of the present invention. Examples of such reinforcing fillers 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, pumice powder, pumice balls, and the like. Examples of the filler include crushed natural minerals such as slate powder and mica powder, barium sulfate, lithopone, calcium sulfate, molybdenum disulfide, 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 fiber, 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 preferred because they are hard and can contribute to improving mechanical properties.

[0043] In addition, the reinforcing filler was measured using a diffuse reflection method at 9500 cm -1 If the transmittance of near-infrared light is 40% or less, it is defined as a heat absorbing material.

[0044] The amount of the reinforcing filler is 5% by weight or more and 60% by weight or less, based on the total weight of the powder composition. The upper limit of the amount is preferably 55% by weight or less, more preferably 50% by weight or less. The lower limit of the amount is preferably 10% by weight or more, more preferably 15% by weight or more, and even more preferably 20% by weight or more. When the amount of the reinforcing filler is 5% by weight or more, the elastic modulus and strength of the object obtained by three-dimensionally molding the powder composition can be improved. When the amount of the reinforcing filler is 60% by weight or less, the near-infrared light absorbency and fluidity of the powder composition are not impaired, and an object with excellent surface smoothness tends to be obtained.

[0045] A flow aid may be used as long as it does not impair the properties of the powder composition of the present invention. A flow aid is a substance that improves fluidity.

[0046] Examples of 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; titanium oxide, magnesium oxide, basic magnesium carbonate, potassium titanate fiber, boron fiber, and silicon carbide fiber. Silica, alumina, calcium carbonate powder, and titanium oxide are more preferred. Silica is particularly preferred because of its hardness and its ability to contribute to improved strength and flowability. Commercially available silica products include the "AEROSIL" (registered trademark) series of fumed silica manufactured by Nippon Aerosil Co., Ltd., the "Reolosil" (registered trademark) series of dry silica manufactured by Tokuyama Corporation, and the X-24 series of sol-gel silica powder manufactured by Shin-Etsu Chemical Co., Ltd.

[0047] The D50 particle size of such a flow aid is preferably 20 nm or more and 3000 nm or less. The upper limit of the D50 particle size of the flow aid is more preferably 2000 nm, even more preferably 1000 nm, particularly preferably 500 nm, extremely preferably 300 nm, and most preferably 200 nm. The lower limit is more preferably 30 nm, even more preferably 50 nm, particularly preferably 100 nm, extremely preferably 120 nm, and most preferably 140 nm. If the D50 particle size of the flow aid is within the above range, the fluidity of the powder composition is improved and the flow aid tends to be uniformly dispersed in the powder composition.

[0048] The D50 particle size of a flow aid is the particle size (D50) at which the cumulative curve from the small particle side reaches 50% when the total volume of the microparticles obtained by analyzing scattered laser light using dynamic light scattering is set to 100% to calculate the cumulative curve.

[0049] In addition, the flow aid was measured at 9500 cm using the diffuse reflectance method. -1 If the transmittance of near-infrared light is 40% or less, it is defined as a heat absorbing material.

[0050] The amount of such a flow aid is preferably 0 wt % based on the total weight of the powder composition, but is preferably 2.0 wt % or less. The upper limit of the amount is more preferably 1.0 wt % or less, even more preferably 0.5 wt % or less, particularly preferably 0.1 wt % or less, and most preferably 0.05 wt % or less. The addition of a flow aid is undesirable because it can inhibit sintering, resulting in a deterioration in the appearance of the molded product and a decrease in mechanical strength.

[0051] The D50 particle size of the powder composition containing these additives is in the range of 1 to 100 μm. If the D50 particle size exceeds 100 μm, the particle size will be equal to or greater than the stack height, resulting in a rough surface. If the D50 particle size is less than 1 μm, the particles will be too fine and will easily adhere to the recoater during molding, making it impossible to raise the molding chamber temperature to the required level. The upper limit of the D50 particle size of the powder composition is preferably 90 μm or less, more preferably 80 μm or less, and even more preferably 70 μm or less. The lower limit is preferably 5 μm or more, more preferably 20 μm or more, and even more preferably 30 μm or more.

[0052] The D50 particle size of the powder composition is the particle size (D50 particle size) at which the cumulative frequency from the small particle size side of the particle size distribution measured with a laser diffraction particle size distribution analyzer is 50%.

[0053] Furthermore, the difference between the crystallization temperature and the melting point of the powder composition is preferably 20°C or more. If the difference between the crystallization temperature and the melting point is small, the temperature conditions for producing a three-dimensional object become strict, which is undesirable as it makes the object more susceptible to warping. The difference between the crystallization temperature and the melting point of the powder composition is more preferably 25°C or more, even more preferably 30°C or more, particularly preferably 35°C or more, and most preferably 40°C or more.

[0054] In the present invention, the melting point and crystallization temperature of the powder composition refer to the peaks of the endothermic peak associated with melting and the exothermic peak associated with crystallization, measured using a differential scanning calorimeter (DSC, for example, DSCQ20 manufactured by TA Instruments) in a nitrogen atmosphere, by raising the temperature once at a rate of 20°C / min through a temperature range from 30°C to a temperature 30°C higher than the melting point of the polymer, holding the temperature for 1 minute, and then lowering the temperature to 30°C at a rate of 20°C / min and holding the temperature for 1 minute.

[0055] The powder composition of the present invention is a material useful for producing a three-dimensional object by powder bed fusion. The method for producing a three-dimensional object will be described below with reference to FIG.

[0056] 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 object is formed is lowered.

[0057] In step (b), the stage 4 of the tank 3 (hereinafter sometimes referred to as the supply tank), which has been pre-filled with the powder composition P to be supplied to the tank 1 where the molded object will be formed, is raised to a height that allows for the supply of a sufficient amount of powder composition P to fill the tank 1 with the desired layer height. Then, the recoater 5 is moved from the left end of the supply tank 3 to the right end of the tank 1, layering the powder composition P into 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 powder composition P is the Y direction. Reference numeral 7 denotes a coordinate system representing the X, Y, and Z directions. Reference numeral 8 denotes the plane direction in which the powder composition is layered, and reference numeral 9 denotes the height direction in which the powder composition is layered.

[0058] In step (c), the powder composition 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.

[0059] In the powder bed fusion method, the three-dimensional structure 10 is obtained by repeating the above steps (a) to (c).

[0060] The selective melt-sintering method in step (c) may be, for example, selective laser sintering, in which a laser is irradiated onto a shape corresponding to the cross-sectional shape of the shaped object to bond the powder composition.

[0061] When the powder composition of the present invention is applied to selective laser sintering, a laser beam having a beam wavelength of 400 nm to 2000 nm is used. The type of laser beam is not particularly limited as long as it does not impair the quality of the powder composition or the shaped object. Examples include fiber lasers, Nd:YAG lasers, semiconductor pumped solid-state lasers, semiconductor lasers, He-Cd lasers, He-Ne lasers, argon ion lasers, and titanium sapphire lasers. Among these, fiber lasers, Nd:YAG lasers, and semiconductor lasers, which are near-infrared lasers with wavelengths of around 1000 nm, are preferred. Fiber lasers are particularly preferred from the viewpoints of ease of operation and control, and the ability to produce more dense shaped objects due to their high laser irradiation speed and narrow laser diameter.

[0062] In addition, lasers with beam wavelengths other than 400 nm to 2000 nm may be used in combination, as long as the quality of the powder composition and the shaped object is not impaired. Examples of lasers with beam wavelengths of less than 400 nm include UV lasers, excimer lasers, and nitrogen lasers, and examples of lasers with beam wavelengths greater than 2000 nm include carbon dioxide lasers, Er:YAG lasers, and Ho:YAG lasers.

[0063] The three-dimensional structure of the present invention can be obtained by shaping the powder composition of the present invention by powder bed fusion. The three-dimensional structure of the present invention will be described below.

[0064] The surface roughness of the three-dimensionally shaped object of the present invention 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 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. There is no particular lower limit, and a smaller value is preferable, but the lower limit is usually about 1 μm.

[0065] The surface roughness of the object was determined by observing the surface of the object with an optical microscope, creating a three-dimensional 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 by arithmetic averaging.

[0066] Even if the heat absorbing material in the powder composition of the present invention is present on the outer surface of the thermoplastic resin powder, the thermoplastic resin powder melts when irradiated with a laser during modeling, and the heat absorbing material is contained within the thermoplastic resin powder or on the inner surface thereof in a powder state, or in a molten state, thereby maintaining the heat absorbing material in the modeled object, and preventing discoloration of the modeled object.

[0067] Furthermore, since the heat absorbing material is uniformly present on the surface or inside the thermoplastic resin powder in the powder composition of the present invention, the powder composition is uniformly melted when irradiated with a laser, thereby enabling the production of a three-dimensional object with almost no color unevenness.

[0068] The three-dimensionally shaped product of the present invention can be applied to automobile parts, aerospace parts, robot parts, medical equipment parts, secondary material parts, construction parts, electrical and electronic equipment parts, etc. In particular, the powder bed fusion method allows for the production of dense three-dimensionally shaped products with high mechanical properties and high heat resistance, making it preferable to apply the product to automobile parts, aerospace parts, and robot parts. [Example]

[0069] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0070] (1) Particle shape of thermoplastic resin powder The sphericity of the thermoplastic resin powder was calculated by observing 30 randomly selected particles in a photograph taken with a scanning electron microscope (JEOL Ltd., Scanning Electron Microscope JSM-6301NF) and calculating the average value of the minor axis / major axis x 100 for each particle.

[0071] (2) D50 particle size of thermoplastic resin powder and powder composition A dispersion of approximately 100 mg of thermoplastic resin powder or powder composition dispersed in approximately 5 mL of deionized water was added to a laser diffraction particle size distribution analyzer (Microtrac MT3300EXII) manufactured by Nikkiso Co., Ltd. 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 reached 50% was taken as the D50 particle size. The refractive index used during measurement was 1.52, and the refractive index of the medium (deionized water) was 1.333.

[0072] (3) Color tone measurement The L values of the thermoplastic resin powder, heat absorbing material, and powder composition were measured using a spectrophotometer (SE2000) manufactured by Nippon Denshoku Industries Co., Ltd. The samples were placed in a special colorless and transparent quartz dish, densely packed while being vibrated, and then measured.

[0073] (4) D50 particle size of heat absorption material Samples prepared by dispersing the flow aid in deionized water or ethanol at a concentration of 0.1% by weight were measured using the dynamic light scattering method with a zeta potential / particle size analyzer (ELSZ-2) manufactured by Otsuka Electronics Co., Ltd., and the particle size at which the cumulative frequency from the small particle size side of the particle size distribution reaches 50% was defined as the D50 particle size.

[0074] (5) Amount of heat absorbing material added The amount of heat absorbing material added relative to 100% by weight of the thermoplastic resin powder is expressed as % by weight.

[0075] (6) Method for preparing powder composition A powder composition was prepared by powder mixing thermoplastic resin powder and heat absorbing material using a pulverizer (Wonder Crusher WC-3) manufactured by Osaka Chemical Industry Co., Ltd. The specified amounts of thermoplastic resin powder and heat absorbing material were added and mixed at 10,000 rpm for 90 seconds. When the prepared powder composition was observed with a scanning electron microscope (JSM-IT700HR) manufactured by JEOL Ltd., it was confirmed that the heat absorbing material was adhered to the surface of the thermoplastic resin powder.

[0076] (7) Additives For additives other than the heat absorbing material, the type and the amount added relative to 100% by weight of the thermoplastic resin powder are shown.

[0077] (8)Angle of repose Measurements were made using a powder property measuring instrument (Tap Denser KYT-5000) manufactured by Seishin Enterprise Co., Ltd. The powder composition was passed through a 300 μm sieve and deposited on a stage. The stage was rotated 120 degrees and 240 degrees, and the angle of repose was measured visually, and the average value of three measurements was calculated.

[0078] (9) Diffuse Reflectance Measurement of Powder Composition at 9500cm -1 Near-infrared light transmittance A diffuse reflectance measurement device (DRS-8000) was installed on a Shimadzu Corporation Fourier transform infrared spectrophotometer (IRPrestige-21), with a tungsten lamp as the light source, calcium fluoride as the beam splitter, and InGaAs (indium gallium arsenide) as the detector. Potassium bromide was filled into the cell to perform a near-infrared blank measurement, and then the powder composition sample was filled into the cell and near-infrared measurement was performed. -1 The transmittance of near-infrared light was calculated.

[0079] (10) Fusion properties of powder composition The fusibility of the powder composition was examined by adding 50 g of the powder composition to a separable flask, immersing it in an oil bath set at a temperature 10°C lower than the melting point of the thermoplastic resin, and leaving it to stand for 6 hours under a nitrogen flow to apply heat history. A case in which the powder composition remained smooth after the heat history was defined as "A," a case in which some of the powder composition was stuck together was defined as "B," and a case in which the entire powder composition was stuck together was defined as "C."

[0080] (11) DBP absorption amount of heat absorption material The DBP absorption amount of the heat absorption material was measured using an absorption amount measuring device (S410E manufactured by Asahi Soken Co., Ltd.) based on JIS K6217-4:2008, and the DBP oil amount per 100 g was taken as the DBP absorption amount.

[0081] (12) Measurement of bending strength of three-dimensional objects The bending strength of the three-dimensional object was measured by preparing a bending test piece (80 mm long, 10 mm wide, 4 mm thick) conforming to JIS K7171 (2016) with the 80 mm length direction as the X-direction, and measuring the bending strength in the X-direction using an A&D Tensilon universal testing machine (TENSIRON TRG-1250). A three-point bending test was performed with a support distance of 64 mm and a test speed of 2 mm / min, and the maximum bending stress was taken as the bending strength of the three-dimensional object. The measurement temperature was room temperature (23°C), and n = 5 measurements were taken, and the average value was calculated.

[0082] (13) Measurement of tensile strength of three-dimensional objects The tensile strength of the three-dimensionally molded object was measured by preparing a tensile test piece (total length 170 mm, parallel section length 80 mm, parallel section width 10 mm, thickness 4 mm) conforming to ISO 527-1A, with the 170 mm length direction being the X direction, using an A&D Tensilon universal testing machine (TENSIRON TRG-1250). Tensile strength was measured in the X direction in accordance with JIS K7161 (2014), with a grip distance of 115 mm and a test speed of 0.5 mm / min. The measurement temperature was room temperature (23°C), and the number of measurements was n=5, with the average value calculated.

[0083] [Thermoplastic resin powder 1] <Method of manufacturing polyamide 6 with high sphericity> In a 3L autoclave equipped with a helical ribbon stirring blade, 300g of ε-caprolactam (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, after which the autoclave was sealed and purged with nitrogen. The stirring speed was then set to 40 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. 2The 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 polyamide 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, filtered, and 2000g of water was added to the filter cake, which was then washed at 80°C. The slurry was then passed through a 100µm sieve to remove any agglomerates. The isolated cake was then filtered again and dried at 80°C for 12 hours to yield 170g of polyamide 6 powder. The resulting polyamide powder had a sphericity of 92, a D50 particle size of 46µm, a D90 / D10 ratio of 2.7, a melting point of 220°C, and an angle of repose of 43°.

[0084] [Thermoplastic resin powder 2] <Polyamide 6 with low sphericity> Polyamide 6 with a sphericity of 66 and a D50 particle size of 51 μm was prepared.

[0085] [Thermoplastic resin powder 3] <Polyamide 6 with low sphericity> Polyamide 6 with a sphericity of 65 and a D50 particle size of 72 μm was prepared.

[0086] [Example 1] The thermoplastic resin powder was 100% by weight of polyamide 6 powder of thermoplastic resin powder 1, and the heat absorbing material was carbon black MA230 (manufactured by Mitsubishi Chemical Corporation, D50 particle size 30 nm, L value 9, DBP absorption 113 ml / 100 g, 9500 cm) using a diffuse reflectance method for the powder composition. -1 A powder composition was prepared by powder mixing of 0.1% by weight of a material with a near-infrared light transmittance of 4%. The angle of repose of the obtained powder composition was 27 degrees and the L value was 42. The powder composition was also analyzed by a diffuse reflectance method at 9500 cm -1 The near-infrared light transmittance of this powder was 27%, indicating that it can be used as a powder composition for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm. Furthermore, after the powder composition was subjected to a heat history at 210°C for 6 hours under a nitrogen flow, part of the powder composition was fused.

[0087] [Example 2] The heat absorbing material was carbon black Asahi #15 (manufactured by Asahi Carbon Co., Ltd., D50 particle size 122 nm, L value 15, DBP absorption amount 42 ml / 100 g, 9500 cm using the diffuse reflectance method of the powder composition). -1 A powder composition was prepared in the same manner as in Example 1, except that the transmittance of near-infrared light was changed to 4%. The angle of repose of the obtained powder composition was 37 degrees and the L value was 52. In addition, the powder composition was analyzed by a diffuse reflectance method at 9500 cm -1 The near-infrared light transmittance of this powder was 38%, indicating that it can be used as a powder composition for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm. Furthermore, after the powder composition was subjected to a heat history at 210°C for 6 hours under a nitrogen flow, no fusion of the powder composition was observed.

[0088] [Example 3] A powder composition was prepared in the same manner as in Example 2, except that the amount of heat absorbing material added was changed to 0.2% by weight. The angle of repose of the obtained powder composition was 36 degrees and the L value was 43. In addition, the powder composition was measured at 9500 cm using a diffuse reflectance method. -1 The near-infrared light transmittance of this powder was 27%, indicating that it can be used as a powder composition for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm. Furthermore, after the powder composition was subjected to a heat history at 210°C for 6 hours under a nitrogen flow, no fusion of the powder composition was observed.

[0089] [Example 4] A powder composition was prepared in the same manner as in Example 3, except that 0.2 wt% of trimethylsilylated amorphous silica X-24-9500 (manufactured by Shin-Etsu Chemical Co., Ltd., D50 particle size 170 nm) was further added as an additive. The angle of repose of the obtained powder composition was 37 degrees and the L value was 44. In addition, the powder composition was measured at 9500 cm using a diffuse reflectance method. -1The near-infrared light transmittance of this powder composition was 32%, indicating its suitability for use in powder bed fusion (PBF) manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm. Furthermore, after thermally treating the powder composition at 210°C for 6 hours under nitrogen flow, no fusion of the powder composition was observed. Using 10 kg of the powder composition before thermal treatment, a three-dimensional (3D) object was fabricated using a Farsoon powder bed fusion system (Flight ST252P). The laser conditions were a 300 W fiber laser, a temperature setting of 202°C, a build height of 0.1 mm, a laser scanning interval of 0.25 mm, a laser scanning speed of 20 m / s, and a laser power of 85 W. The resulting three-dimensional (3D) object had a good appearance, a bending strength of 112 MPa, a tensile strength of 83 MPa, and a surface roughness of 8 μm.

[0090] [Example 5] A powder composition was prepared in the same manner as in Example 1, except that the amount of heat absorbing material added was changed to 0.5% by weight. The angle of repose of the obtained powder composition was 33 degrees and the L value was 32. In addition, the powder composition was measured at 9500 cm using a diffuse reflectance method. -1 The near-infrared light transmittance of this powder was 15%, indicating that it can be used as a powder composition for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm. Furthermore, after the powder composition was subjected to a heat history at 210°C for 6 hours under a nitrogen flow, part of the powder composition was fused.

[0091] [Comparative Example 1] A powder composition was prepared in the same manner as in Example 2, except that 0.1 wt % of trimethylsilylated amorphous silica X-24-9500 (manufactured by Shin-Etsu Chemical Co., Ltd., D50 particle size 170 nm) was used as an additive instead of the heat absorbing material. The angle of repose of the obtained powder composition was 36 degrees and the L value was 97. In addition, the powder composition was measured at 9500 cm using a diffuse reflectance method. -1 It was found that the transmittance of this powder to near-infrared light was 100%, and it was therefore unsuitable for use as a powder composition for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm.

[0092] Comparative Example 2 A powder composition was prepared in the same manner as in Example 2, except that polyamide 6 powder (thermoplastic resin powder 2) was used as the thermoplastic resin powder. The angle of repose of the obtained powder composition was 39 degrees and the L value was 62. In addition, the powder composition was analyzed by a diffuse reflectance method at 9500 cm -1 The near-infrared light transmittance of this compound was 43%, and it was found that this compound is not suitable for use as a powder composition for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm.

[0093] Comparative Example 3 A powder composition was prepared in the same manner as in Example 3, except that polyamide 6 powder (thermoplastic resin powder 3) was used as the thermoplastic resin powder and the amount of additive added was changed to 0.3 wt%. The angle of repose of the obtained powder composition was 33 degrees and the L value was 59. The powder composition was also analyzed by a diffuse reflectance method at 9500 cm -1 The transmittance of near-infrared light is 47%, and it was found that it is not suitable for use in powder bed fusion manufacturing, which uses laser light with a beam wavelength of 400 nm to 2000 nm.

[0094] Comparative Example 4 A powder composition was prepared in the same manner as in Example 2, except that the amount of heat absorbing material added was changed to 5% by weight. The angle of repose of the obtained powder composition was 38 degrees and the L value was 20. In addition, the powder composition was measured at 9500 cm using a diffuse reflectance method. -1 The near-infrared light transmittance of this powder was 9%, indicating that it can be used as a powder composition for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm. Furthermore, after the powder composition was subjected to a heat history at 210°C for 6 hours under a nitrogen flow, the powder composition was fused overall.

[0095] The evaluation results of the powder compositions of Examples 1 to 5 and Comparative Examples 1 to 4 are summarized in Table 1.

[0096] [Table 1] [Industrial Applicability]

[0097] When the powder composition of the present invention is used in powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm, the powder composition effectively absorbs the laser light, resulting in a molded object with dense and uniform properties. [Explanation of symbols]

[0098] 1. Tank for forming the object 2. The tank stage where the object is formed 3. Supply tank pre-filled with powder composition 4. Stage of the bath pre-filled with the powder composition 5 Recoater 6. Thermal Energy 7 X, Y, Z coordinate system 8. Plane direction in which the powder composition is layered 9. Height direction of stacking powder composition 10 Three-dimensional objects P powder composition

Claims

1. A powder composition comprising (A) a thermoplastic resin powder having a D50 particle size of 1 μm to 100 μm and a sphericity of 80 or more, and (B) a heat absorbing material in an amount of 0.02% by weight or more and 2% by weight or less, the powder composition being used for powder bed fusion manufacturing using a laser beam having a beam wavelength of 400 nm to 2000 nm.

2. 2. The powder composition according to claim 1, wherein the powder composition is obtained by powder mixing of a heat absorbing material and a thermoplastic resin powder.

3. 9500 cm －１ 2. The powder composition according to claim 1, wherein the transmittance of near-infrared light is 40% or less.

4. 2. The powder composition according to claim 1, which has an angle of repose of 40 degrees or less.

5. 2. The powder composition according to claim 1, wherein the thermoplastic resin constituting the thermoplastic resin powder is a polyamide.

6. 2. The powder composition of claim 1, wherein said heat absorbing material is carbon black.

7. 2. The powder composition according to claim 1, wherein the heat absorbing material has a D50 particle size of 100 nm to 1000 nm.

8. 2. The powder composition according to claim 1, wherein the laser light having a beam wavelength of 400 nm to 2000 nm is laser light emitted by a fiber laser.

9. 2. The powder composition of claim 1, comprising from 5% to 60% by weight of a reinforcing filler, based on the powder composition.

10. A method for producing a three-dimensional object by powder bed fusion bonding using the powder composition according to any one of claims 1 to 9 and irradiating it with laser light having a beam wavelength of 400 nm to 2000 nm.

11. A three-dimensional object obtained by a powder bed fusion method in which laser light having a beam wavelength of 400 nm to 2000 nm is irradiated, the three-dimensional object containing at least (A) a thermoplastic resin and 0.02% by weight to 2% by weight of (B) a heat absorbing material, and having a surface roughness of 20 μm or less.

12. The three-dimensional structure according to claim 11, which is used as an automobile part, an aerospace part, or a robot part.

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