Method for producing powder composition, powder composition, method for producing three-dimensional shaped object, and three-dimensional shaped object

Abstract

Provided is a method for producing a powder composition to be used in a powder additive manufacturing system, the method having: (a) a step for blending 100 parts by weight of thermoplastic resin particles with 0.2-50 parts by weight of carbon black having a DBP (dibutyl phthalate) absorption amount of 10-500 ml / 100 g, and mixing to obtain a premix powder (P1); and (b) a step for obtaining a mixed powder (P2) by additionally blending thermoplastic resin particles with the premix powder (P1) so that the amount of carbon black is 0.02-5 parts by weight relative to 100 parts by weight of the thermoplastic resin particles. The present invention is capable of providing: a powder composition which can yield a three-dimensional shaped object at high speed and with high precision; and a method for producing a powder composition.

Description

Method for producing powder composition, powder composition, method for producing three-dimensional shaped object, and three-dimensional shaped object

[0001] The present invention relates to a method for rapidly and accurately producing three-dimensional objects suitable for a wide range of applications, such as automotive, aerospace, industrial, and medical applications, as well as a powder composition suitable for use as a material for such objects and a method for producing such objects.

[0002] Three-dimensional (3D) printing allows for a high degree of freedom in designing shapes, and is therefore widely used in applications such as automotive, aerospace, industrial, and medical applications. Powder additive manufacturing (PAM) is a suitable method for this type of printing, as it can achieve good mechanical strength and does not require support members. In recent years, application development has progressed, and it is being considered for functional prototyping to verify the performance of designed shapes, as well as for end-product applications that actually use 3D printed objects. This has led to a growing demand for faster manufacturing processes and higher precision for the resulting 3D printed objects.

[0003] Among powder additive manufacturing methods, the powder bed fusion method is a manufacturing method that involves sequentially repeating a thin layer formation process in which resin particles are spread into a thin layer, and a cross-sectional shape formation process in which laser light is irradiated onto the formed thin layer in a shape that corresponds to the cross-sectional shape of the object to be manufactured, thereby bonding the powder, and this method has excellent manufacturing accuracy.

[0004] Among these, the use of a thermoplastic resin powder composition containing carbon black in the production of three-dimensional objects by powder bed fusion is known. For example, Patent Document 1 discloses a method of improving the molding accuracy by adding carbon black to thermoplastic resin particles in order to reduce the electromagnetic reflectance of a three-dimensional object to 10% or less. Patent Document 2 also discloses a polyarylene ketone powder to which carbon black has been added as a flame retardant and laser absorber. Furthermore, a technology is known for speeding up the manufacturing process in powder bed fusion using resin particles by using a laser with a beam wavelength of 400 to 2000 nm, such as a fiber laser.

[0005] JP 2019-162846 A JP 2007-39631 A

[0006] An object of the present invention is to provide a powder composition and a method for producing the same that can rapidly and accurately produce a three-dimensional object. In particular, an object of the present invention is to provide a method for producing a highly accurate three-dimensional object without color unevenness or spots, using a powder bed fusion method that uses a laser with a beam wavelength of 400 to 2000 nm, such as a fiber laser, which can speed up the production process, and to provide a three-dimensional object produced using the method.

[0007] As a result of extensive research aimed at solving these problems, the present inventors have arrived at the following invention. Specifically, the present invention is as follows: <1> A method for producing a powder composition for use in a powder additive manufacturing system, comprising the following steps (a) and (b): (a) blending 0.2 to 50 parts by weight of carbon black having a DBP (dibutyl phthalate) absorption of 10 ml / 100 g or more and 500 ml / 100 g or less with respect to 100 parts by weight of thermoplastic resin particles, and mixing them to obtain a premixed powder (P1); (b) blending additional thermoplastic resin particles with the premixed powder (P1) so that the amount of carbon black is 0.02 to 5 parts by weight with respect to 100 parts by weight of the thermoplastic resin particles, to obtain a mixed powder (P2). <2> A method for producing the powder composition according to <1>, further comprising the step (c). <3> A method for producing a powder composition according to <1> or <2>, wherein the steps (a) and / or (b) are mixing steps that involve shear force using a stirring blade. <4> A powder composition comprising 0.02 to 5 parts by weight of carbon black with a DBP absorption of 10 ml / 100 g or more and 500 ml / 100 g or less per 100 parts by weight of thermoplastic resin particles, the carbon black having an average particle diameter of 1 μm or more and 100 μm or less, and a DBP absorption of 9500 cm －１A powder composition for use in powder additive manufacturing, having a near-infrared light transmittance of 75% or less. <5> The powder composition according to <4>, wherein the content of coarse particles having a particle diameter of 250 μm or more is 0.1% by weight or less. <6> The powder composition according to <4> or <5>, wherein the thermoplastic resin constituting the thermoplastic resin particles is at least one selected from polyarylene sulfide, polyamide, polybutylene terephthalate, and polyether ether ketone. <7> The powder composition according to any one of <4> to <6>, wherein the average particle size of the carbon black is 100 nm to 1,000 nm. <8> The powder composition according to any one of <4> to <7>, wherein an inorganic reinforcing material is contained in an amount of 1 to 100 parts by weight per 100 parts by weight of the thermoplastic resin particles. <9> The powder composition according to <8>, wherein the inorganic reinforcing material is at least one selected from glass fiber, glass beads, and carbon fiber. <10> The powder composition according to any one of <4> to <9>, wherein the powder additive manufacturing method is a powder bed fusion method using a laser beam having a beam wavelength of 400 nm to 2000 nm. <11> The powder composition according to <10>, wherein the laser beam having a beam wavelength of 400 nm to 2000 nm is laser beam from a fiber laser. <12> A method for producing a powder composition by the method according to any one of <1> to <3>, and then producing a three-dimensional object by a powder additive manufacturing method. <13> A method for producing a three-dimensional object by powder bed fusion, comprising irradiating the powder composition according to any one of <4> to <11> with laser beam having a beam wavelength of 400 nm to 2000 nm. <14> A three-dimensional object obtained by a powder additive manufacturing method, wherein spots having a size of 150 μm or more in diameter observed on the surface of the three-dimensional object are formed on a surface of 100 cm2 of the three-dimensional object. ２<15> A three-dimensionally shaped object having two or less spots with a diameter of 150 μm or more per 12 test pieces. <15> A three-dimensionally shaped object obtained by powder additive manufacturing using the powder composition according to any one of <4> to <11>, wherein when 12 test pieces each having a width of 10 mm, a length of 80 mm, and a thickness of 4.0 mm are produced by a powder additive manufacturing method, with the 80 mm length direction being the direction of movement of a recoater (X direction), the 10 mm width direction being the direction on the plane along which the recoater moves that is perpendicular to the direction of movement of the recoater (Y direction), and the 4.0 mm thickness direction being the direction perpendicular to the direction of movement of the recoater (Z direction), the number of spots with a diameter of 150 μm or more observed on the front surface of 10 mm x 80 mm is two or less per 12 test pieces. <16> The three-dimensionally shaped object according to <15>, which is used for an automotive part, an aerospace part, or a robot part.

[0008] The present invention provides a powder composition and a method for producing the same that can rapidly and accurately produce three-dimensional objects. In particular, powder bed fusion using a laser with a beam wavelength of 400 to 2000 nm, such as a fiber laser, can be used to speed up the production process, resulting in highly accurate objects without uneven color or spots.

[0009] The present invention will be described in detail below with reference to the embodiments. In order to obtain a three-dimensional object at high speed and with high precision, it is important that the powder additive manufacturing method has excellent energy absorption and processability. The present invention relates to a powder composition containing 0.02 to 5 parts by weight of carbon black having a DBP absorption of 10 ml / 100 g or more and 500 ml / 100 g or less per 100 parts by weight of thermoplastic resin particles, which can be used to produce a 3D object with a 9500 cm －１ Based on the property that the material has excellent near-infrared light absorption (low transmittance), it has been found that the material is suitable for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm.

[0010] Furthermore, the present invention relates to a method for producing a powder composition for use in a powder additive manufacturing system, characterized by comprising the steps of: blending 0.2 to 50 parts by weight of carbon black having a DBP absorption of 10 ml / 100 g or more and 500 ml / 100 g or less with 100 parts by weight of thermoplastic resin particles, and mixing them to obtain a premixed powder (P1); and further blending thermoplastic resin particles with the premixed powder (P1) so that the carbon black is 0.02 to 5 parts by weight with respect to 100 parts by weight of thermoplastic resin particles, to obtain a mixed powder (P2). The present invention was based on the discovery that by comprising the steps (a) and (b), three-dimensionally molded objects obtained by three-dimensionally molding using the obtained powder composition were free of color unevenness or spots and were highly accurate molded objects.

[0011] The type of carbon black used in the present invention is not particularly limited as long as it does not impair the properties of the powder composition, but carbon black that is particularly excellent in absorbency of lasers with beam wavelengths of 400 to 2000 nm is preferred. Specific examples include furnace black, channel black, acetylene black, thermal black, and ketjen black. Furnace black and acetylene black are more preferred because they have a high specific surface area and can be effective with a smaller amount, and furnace black is most preferred because it is less likely to impair the properties of the powder composition.

[0012] In the present invention, neutral carbon black is preferably used because it can reduce the amount of gas generated during laser irradiation. In addition, acidic carbon black can be used after preheating and drying to reduce the amount of gas generated.

[0013] DBP (dibutyl phthalate) absorption is the amount of DBP absorbed on the surface of carbon black particles and in the voids formed by agglomerated particles, i.e., an index for evaluating oil absorption, and can be measured in accordance with JIS K6217-4:2008. In the present invention, the DBP absorption is 10 ml / 100 g or more and 500 ml / 100 g or less. If the DBP absorption is 10 ml / 100 g or less, the carbon black will not cover the thermoplastic resin particle surfaces uniformly, the laser energy will not be distributed throughout, and uniform sintering of the thermoplastic resin particles will not occur. 15 ml / 100 g or more is more preferable, 20 ml / 100 g or more is even more preferable, and 25 ml / 100 g or more is particularly preferable. Furthermore, if the DBP absorption is 500 ml / 100 g or more, the specific surface area of ​​the carbon black will increase, making it prone to agglomeration and preventing the production of uniform three-dimensional objects. More preferably, it is 400 ml / 100 g or less, even more preferably, 300 ml / 100 g or less, and particularly preferably, 200 ml / 100 g or less.

[0014] The average particle size of the carbon black of the present invention is preferably 10 to 1,000 nm, and particularly preferably 100 to 1,000 nm. Having an average particle size of 100 nm or more allows the carbon black to be uniformly dispersed as primary particles in the powder composition, making it less likely to aggregate during recycling molding, and enabling stable production of three-dimensionally shaped objects. Furthermore, having an average particle size of 1,000 nm or less allows sufficient energy absorption to be achieved with a small amount added.

[0015] Carbon black that has been crushed in advance can also be used. Known methods for crushing carbon black can be used, including mechanical crushing using a high-speed mixer or ball mill, airflow pulverization using a jet mill, electrostatic treatment, and electromagnetic field treatment. Coarse particles and aggregates of carbon black can be removed by passing the carbon black through an appropriate double-sided sieve. Mechanical crushing using a high-speed mixer is particularly preferred. Mechanical crushing using a high-speed mixer provides excellent uniformity in the powder composition and dispersion stability during recycling molding. This allows the carbon black to be suitably used in three-dimensional molding using a laser with a beam wavelength of 400 to 2000 nm, resulting in three-dimensional objects with excellent quality and mechanical properties.

[0016] The amount of carbon black in the present invention is 0.02 to 5 parts by weight per 100 parts by weight of resin particles. If it is less than 0.02 parts by weight, energy absorption is insufficient and the resin is not sintered sufficiently. 0.03 parts by weight or more is preferred, 0.05 parts by weight or more is more preferred, 0.08 parts by weight or more is even more preferred, and 0.1 parts by weight or more is particularly preferred. If it exceeds 5 parts by weight, the adhesion between the resin particles weakens and the strength of the three-dimensionally shaped object decreases. 3 parts by weight or less is preferred, 2 parts by weight or less is more preferred, 1 part by weight or less is even more preferred, and 0.5 parts by weight or less is particularly preferred.

[0017] The thermoplastic resin in the present invention is preferably a thermoplastic resin because it has excellent fluidity when melted. Examples of such thermoplastic resins include polyarylene sulfide resins, particularly polyphenylene sulfide resins (PPS), polyamide resins, particularly various nylons, such as nylon 6, nylon 66, nylon 610, nylon 612, nylon 11, nylon 12, and nylon 46; polyesters, such as polybutylene terephthalate resins (PBT), polycarbonate resins (PC), polyimide resins, polyetherimide resins, polyether ketone ketone resins, polyether ether ketone resins, polymethyl methacrylate, polytetrafluoroethylene resins, polyvinylidene fluoride resins, polyvinyl acetate, polyacetal, polysulfone resins, polystyrene resins, polylactic acid, polycaprolactone, methyl acrylate-methyl methacrylate copolymers, acrylonitrile-styrene copolymers, ethylene-vinyl acetate copolymers (EVA), ethylene resin-acrylic acid copolymers, ethylene-propylene copolymers, and ABS (acrylonitrile-butadiene-styrene copolymers). The thermoplastic resin in the present invention may be any of a random copolymer, a block copolymer, and a composition thereof. Among them, from the viewpoints of mechanical strength, heat resistance, etc., it is preferably at least one of polyarylene sulfide resin, polyamide resin, polybutylene terephthalate resin, polypropylene resin, and polyether ketone ketone resin, and polyarylene sulfide resin is particularly preferred from the viewpoints of low water absorption and excellent dielectric properties.

[0018] The melt viscosity of the thermoplastic resin used in the present invention is preferably 150 Pa s or more and 500 Pa s or less. If the melt viscosity is less than 150 Pa s, the strength of the produced three-dimensional object will be low, while if the melt viscosity is higher than 500 Pa s, when the resin is melted by irradiating it with laser light, the molten resin will not penetrate into the lower layer, resulting in weak adhesion between the layers and the risk of a significant decrease in the strength of the object in the height direction.

[0019] Here, the melt viscosity was measured using a Capillograph 1C manufactured by Toyo Seiki Seisakusho Co., Ltd., with a die having a hole length of 10.00 mm and a hole diameter of 0.50 mm. The melt viscosity was measured by placing approximately 20 g of a sample into a cylinder set at a temperature 20°C higher than the melting point of the thermoplastic resin, holding it for 5 minutes, and then measuring the melt viscosity at a shear rate of 1216 sec. －１ The melt viscosity is a measured value. The lower limit of the melt viscosity is preferably 150 Pa s, more preferably 160 Pa s, even more preferably 170 Pa s, and particularly preferably 180 Pa s. The upper limit of the melt viscosity is preferably 500 Pa s, more preferably 450 Pa s, even more preferably 400 Pa s, and particularly preferably 350 Pa s.

[0020] Furthermore, the difference between the melting point and recrystallization temperature of the thermoplastic resin used in the present invention is preferably 30°C or more. If the difference between the melting point and recrystallization temperature of the thermoplastic resin is less than 30°C, the molten resin may crystallize upon laser light irradiation, causing shrinkage and warping. In powder bed fusion bonding, if warping occurs in the molten resin, the warped molten resin may be dragged when a powder layer is layered on top of the molten resin, making it impossible to obtain a three-dimensional object of the desired shape.

[0021] Here, the recrystallization temperature refers to the apex temperature of the exothermic peak during crystallization when a thermoplastic resin is heated in a nitrogen atmosphere using a differential scanning calorimeter from 50° C. to a temperature 40° C. higher than the melting point at a rate of 20° C. / min, held for 5 minutes, and then cooled at a rate of 20° C. / min to 50° C. When there are multiple peaks, the apex of the highest peak is taken as the melting point and crystallization temperature.

[0022] The average particle size of the thermoplastic resin particles of the present invention is preferably greater than 1 μm and less than 100 μm. A more preferred lower limit of the average particle size is 3 μm, even more preferably 5 μm, particularly preferably 8 μm, significantly more preferably 10 μm, and most preferably 15 μm. A more preferred upper limit of the average particle size is 90 μm, even more preferably 85 μm, particularly preferably 80 μm, significantly more preferably 75 μm, and most preferably 70 μm. If the average particle size exceeds 100 μm, uniformity is lost during powder layering in a powder bed fusion 3D printer, resulting in a decrease in the strength of the three-dimensionally molded object. On the other hand, if the average particle size is less than 1 μm, static electricity causes aggregation of the resin particles, which similarly impairs uniformity during powder layering and reduces the strength of the three-dimensionally molded object.

[0023] In the present invention, the sphericity, which indicates the sphericity of the thermoplastic resin particles, is not particularly specified, but from the viewpoint of good moldability by powder additive manufacturing and excellent surface smoothness of the resulting three-dimensionally molded object, the sphericity is preferably 0.8 to 1. The sphericity is more preferably 0.85 to 1, and even more preferably 0.9 to 1.

[0024] The sphericity of the thermoplastic resin particles in the present invention is determined by observing 30 particles randomly selected from a scanning electron microscope photograph and determining the ratio of their minor axis to their major axis.

[0025] The production of thermoplastic resin particles in the present invention is not particularly limited, and can be performed using particles obtained by polymerization. Alternatively, particles can be obtained from resins molded into pellets, fibers, or films. Furthermore, a pulverization process, as described below, can be performed depending on the form of the resin particles used. Other methods include spray drying, in which raw materials are dissolved in a solvent and then an emulsion is formed in the solvent and then the resulting mixture is brought into contact with a poor solvent; submerged drying, in which an emulsion is formed in the solvent and then the organic solvent is removed by drying; and forced melt kneading, in which a resin component to be granulated and another resin component are mechanically kneaded to form a sea-island structure, and then the sea component is removed with a solvent. Among these, pulverization is preferred from an economical standpoint. The pulverization method is not particularly limited, and examples include a disk mill, a jet mill, a bead mill, a hammer mill, a ball mill, a sand mill, a turbo mill, and freeze pulverization. Dry pulverization, such as a turbo mill, a jet mill, or freeze pulverization, is preferred, with freeze pulverization being even more preferred.

[0026] In the present invention, the powder composition may be a powder mixture of thermoplastic resin particles and carbon black, or carbon black may be encapsulated within the thermoplastic resin particles. However, a powder mixture is preferred because it is more likely to absorb energy and is advantageous for melt sintering between the thermoplastic resin particles.

[0027] Particles containing carbon black can be obtained by a number of methods: a poor solvent precipitation method in which a mixture of thermoplastic resin and carbon black is dissolved in advance, an emulsion is formed in a solvent, and the resulting mixture is then brought into contact with a poor solvent; a submerged drying method in which an emulsion is formed in a solvent, and the organic solvent is then dried and removed; a forced melt kneading method in which a resin component to be turned into particles is mechanically kneaded with a different resin component to form a sea-island structure, and then the sea component is removed with a solvent; or a method in which carbon black is melt-kneaded into a polymer and then pulverized.

[0028] In the case of a powder mixture, the thermoplastic resin particles and carbon black are preferably mixed by rotating a rotary blade attached to a container rotary mixer, since this allows for uniform mixing while breaking down carbon black agglomerates. Other methods that can be used include a mixing method involving pulverization using a ball mill or coffee mill, a mixing method using stirring blades such as a Nauta mixer or a Henschel mixer, a mixing method involving rotating the entire container such as a V-type mixer, a method involving liquid-phase mixing in a solvent followed by drying, a mixing method using an airflow using a flash blender or the like to stir the mixture, and a mixing method involving spraying the powder and / or slurry using an atomizer or the like.

[0029] The method for producing a powder composition of the present invention is characterized by comprising the steps of: (a) blending 0.2 to 50 parts by weight of carbon black with 100 parts by weight of thermoplastic resin particles and mixing them to obtain a premixed powder (P1); and (b) blending additional thermoplastic resin particles with the premixed powder (P1) so that the carbon black is 0.02 to 5 parts by weight with respect to 100 parts by weight of thermoplastic resin particles to obtain a mixed powder (P2). It has been found that by producing the premixed powder (P1) in advance as a master batch, aggregation of the carbon black can be suppressed, and by obtaining a mixed powder (P2) using the premixed powder (P1) as a raw material, a powder composition in which the carbon black is uniformly dispersed and suitable for use in three-dimensional modeling can be obtained.

[0030] In the method for producing a powder composition of the present invention, the amount of carbon black blended per 100 parts by weight of thermoplastic resin particles in step (a) of obtaining the premixed powder (P1) is 0.2 to 50 parts by weight. If it is less than 0.2 parts by weight, the amount of thermoplastic resin particles relative to the carbon black in the masterbatch production is too high, resulting in localized uneven distribution of the carbon black and making it difficult to disperse. An amount of 0.3 parts by weight or more is preferred, more preferably 0.5 parts by weight or more, even more preferably 1 part by weight or more, and particularly preferably 3 parts by weight or more. Furthermore, if it exceeds 50 parts by weight, the carbon black concentration becomes high, which may result in secondary aggregation of the carbon black. An amount of 40 parts by weight or less is preferred, more preferably 30 parts by weight or less, even more preferably 25 parts by weight or less, and particularly preferably 20 parts by weight or less.

[0031] In the step (a) of obtaining the premixed powder (P1), it is preferable to mix the powders until there is no visible color unevenness or variation. By obtaining the premixed powder (P1) as homogeneous as possible, it becomes possible to obtain a homogeneous mixed powder (P2) in the step (b).

[0032] The method for producing a powder composition of the present invention preferably further includes step (c) of passing the premixed powder (P1) or the mixed powder (P2) through a filter with a mesh size of 100 μm or more and 500 μm or less. Filtering the premixed powder (P1) also has the effect of dissolving the carbon black, allowing for a more homogeneous masterbatch to be obtained. Filtering the mixed powder (P2) also allows for filtering all of the thermoplastic resin particles, physically removing coarse particles and thereby suppressing the generation of coarse black powder coated with carbon black. Therefore, it is more preferable to pass both the premixed powder (P1) and the mixed powder (P2) through a filter.

[0033] The lower limit of the filter opening size preferably used in step (c) of the powder composition manufacturing method of the present invention is 100 μm or more, so that thermoplastic resin particles with particle sizes suitable for three-dimensional modeling are not removed, and only coarse particles can be selectively removed. Therefore, 115 μm or more is more preferable, 130 μm or more is even more preferable, and 145 μm or more is particularly preferable. If the upper limit is 500 μm or less, it is possible to remove coarse particles that cause defects in three-dimensional models. 400 μm or less is more preferable, 350 μm or less is even more preferable, and 300 μm or less is particularly preferable.

[0034] In the method for producing a powder composition of the present invention, steps (a) and / or (b) preferably involve mixing using a stirring blade that involves shear force. Carbon black tends to agglomerate due to friction or static electricity during mixing, which can result in problems with uniform mixing with the thermoplastic resin particles. To solve this problem, mixing using a stirring blade that involves shear force during mixing allows the carbon black to be mixed while breaking down agglomerates, resulting in more uniform mixing. Preferably, one or more stirring blades are installed per container. When mixing the thermoplastic resin particles and carbon black, the rotation speed of the container of the container rotary mixer is preferably 3.5 rpm to 35 rpm, more preferably 15 rpm to 30 rpm. The rotation speed of the stirring blade is preferably 100 rpm to 1,000 rpm, more preferably 400 rpm to 700 rpm.

[0035] When an inorganic reinforcing material is included, it is preferable to perform mixing in two separate steps, mixing carbon black with thermoplastic resin particles in the first mixing step, and then mixing the first mixture with the inorganic reinforcing material in the second mixing step. If the inorganic reinforcing material and carbon black are mixed simultaneously, the surface of the inorganic reinforcing material will also be coated with carbon black, and the surface of the resin particles will not be sufficiently coated. By mixing the carbon black with the thermoplastic particles first, the particle surfaces can be coated with carbon black, and the resin particles can sufficiently absorb the energy of the irradiated laser.

[0036] The average particle size of the powder composition of the present invention is 1 μm or more and 100 μm or less. The preferred lower limit of the average particle size is 3 μm, more preferably 5 μm, even more preferably 8 μm, particularly preferably 10 μm, and most preferably 15 μm. The preferred upper limit of the average particle size is 90 μm, more preferably 85 μm, even more preferably 80 μm, particularly preferably 75 μm, and most preferably 70 μm. If the average particle size of the powder composition exceeds 100 μm, uniformity is lost during powder layering in powder additive manufacturing, resulting in a decrease in the strength of the three-dimensionally molded object. On the other hand, if the average particle size is less than 1 μm, static electricity causes aggregation of the powder composition, which similarly reduces uniformity during powder layering and decreases the strength of the three-dimensionally molded object.

[0037] In the powder composition of the present invention, the weight of coarse particles having a particle diameter of 250 μm or more is preferably 0.1 wt% or less. If the weight exceeds 0.1 wt%, a three-dimensional object manufactured using the powder composition by powder additive manufacturing will suffer from color unevenness and spots due to the coarse particles. In order to suppress color unevenness and spots on the three-dimensional object, the weight of the coarse particles is preferably 0.05 wt% or less, more preferably 0.03 wt% or less, even more preferably 0.02 wt% or less, and particularly preferably 0.01 wt% or less.

[0038] Coarse particles having a particle diameter of 250 μm or more refer to coarse particles that are captured by a sieve having a mesh size of 250 μm as defined in JIS Z8801-1 (2006) when the powder composition is passed through the sieve. The coarse particles may be composed only of carbon black, or may be composed of carbon black and other components contained in the powder composition, or may contain coarse particles composed only of components other than carbon black.

[0039] The weight of coarse particles with a particle size of 250 μm or more can be determined by passing the powder composition through a sieve with a mesh size of 250 μm and measuring the difference in weight of the sieve before and after passing through the sieve. Specifically, 2 kg of the powder composition is added to a sieve with a mesh size of 250 μm as defined in Japanese Industrial Standards (JIS) Z8801-1 (2006), and the sieve is vibrated until no powder composition passes through the sieve. The difference in weight of the sieve before and after passing through the sieve is defined as the coarse particles with a particle size of 250 μm or more. To prevent changes in the weighing value due to differences in the sieve passing method, it is preferable to pass the coarse particles through the sieve at room temperature (about 20 to 25°C), atmospheric pressure, and standard relative humidity (about 40 to 60%) while leaving the sieve stationary or applying only slight vibration. Therefore, coarse particles should not be weighed by any method that intentionally disintegrates the coarse particles, such as physical treatment such as crushing, rubbing, or disintegrating the powder composition through a sieve, treatment with heating or cooling, treatment in a solvent, ultrasonic treatment, addition of a surfactant, pH adjustment, electrophoresis, electroosmosis, or magnetic treatment.

[0040] In the present invention, it is preferable for the powder bed fusion method using laser light that the carbon black be uniformly dispersed in the powder composition. The deviation in the L value can be used as an index to evaluate the uniform dispersion. The deviation in the L value is preferably 0.018 or less, more preferably 0.015 or less. If the deviation in the L value exceeds 0.018, the carbon black will be unevenly distributed on the resin surface, preventing the laser energy from reaching all of the resin particles, resulting in reduced accuracy in three-dimensional modeling. The closer the L value deviation is to 0, the more uniformly the carbon black in the powder composition is dispersed and the more uniform it is. The deviation in the L value can be determined by randomly collecting three samples from the powder composition, measuring the L values, and dividing the standard deviation of the L values ​​by the average of the three L values. The L value can be measured using a spectrophotometer.

[0041] After mixing the thermoplastic resin particles and carbon black using the above method, the inorganic reinforcing material can be mixed into the resulting mixture. Mixing can be performed using a mixing method using a stirring blade, such as a Nauta mixer or Henschel mixer, or a mixing method that rotates the entire container, such as a V-type mixer or cross rotary mixer. However, a container-rotating mixer is preferred to prevent breakage of the inorganic reinforcing material. The preferred container rotation speed is 3.5 rpm to 35 rpm.

[0042] In the present invention, the L value of the powder composition is preferably 80 or less. A low L value of the powder composition enhances the effect of suppressing discoloration when the powder composition is subjected to thermal history. Furthermore, a low L value facilitates absorption of laser light during shaping by powder bed fusion, enabling the powder composition to be effectively laser sintered. The lower limit of the L value of the powder composition is theoretically 0, and the L value of the powder composition of the present invention usually exhibits a value of 10 or more.

[0043] 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. －１ The 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 specular reflected light reflected from the surface of the powder composition and 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 diffuse reflectance method. －１ The transmittance of near-infrared light is 75% or less. By being 75% 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 preferably 70% or less, more preferably 65% ​​or less, and even more preferably 60% or less.

[0044] The powder composition was measured at 9500 cm using a diffuse reflectance method. －１The near-infrared transmittance can be evaluated, for example, by installing a diffuse reflectance measurement device (DRS-8000) on a Fourier transform infrared spectrophotometer (IRPrestige-21) manufactured by Shimadzu Corporation, using a tungsten lamp as a light source, calcium fluoride as a beam splitter, and InGaAs (indium gallium arsenide) as a detector, filling a cell with potassium bromide to perform a near-infrared blank measurement, and then filling the cell with a powder composition sample to perform near-infrared measurement.

[0045] Additives may be added to the powder composition of the present invention as long as they do not impair the properties of the composition. Examples of additives include heat stabilizers, antioxidants, flame retardants, plasticizers, and flow aids, and the additives may be present either inside or outside the thermoplastic resin particles.

[0046] The shape of the inorganic reinforcing material in the present invention is preferably spherical, needle-like, plate-like, fibrous, or the like, in order to improve the mechanical properties of the three-dimensionally shaped product.

[0047] In the present invention, the inorganic reinforcing material added to the powder composition is not particularly limited, but one having a maximum dimension of 1 μm or more and 400 μm or less can be used. To further improve the mechanical properties of the three-dimensionally shaped object, 20 μm or more is more preferable, and 50 μm or more is even more preferable. Furthermore, since the fluidity of the powder composition deteriorates as the dimension increases, 200 μm or less is preferable, and 170 μm or less is even more preferable. Here, the maximum dimension is the average value of the values ​​measured by observing the inorganic reinforcing material using a scanning electron microscope, randomly selecting 100 inorganic reinforcing materials from an image magnified 100 times, and measuring the maximum length between two points on the outer contour of each inorganic reinforcing material.

[0048] The upper limit of the maximum dimension of the inorganic reinforcing material is preferably 400 μm, more preferably 390 μm, more preferably 380 μm, and particularly preferably 370 μm. The lower limit is preferably 1 μm, more preferably 5 μm, more preferably 10 μm, and particularly preferably 15 μm. If the maximum dimension of the inorganic reinforcing material is 400 μm or less, a uniform powder surface can be formed during powder layering in a powder bed fusion 3D printer without impairing the flowability of the powder composition. Furthermore, if the maximum dimension of the inorganic reinforcing material is 1 μm or more, the strength of a three-dimensional object produced using the powder composition can be improved.

[0049] When the inorganic reinforcing material is fibrous, the fiber length is the longest dimension, and the average value of the longest dimension is the average value of the fiber length. Furthermore, the fiber diameter is preferably 0.1 μm or more and 50 μm or less. The preferred lower limit of the fiber diameter is 0.1 μm, more preferably 0.5 μm, and particularly preferably 1 μm. The preferred upper limit of the fiber diameter is 5 μm, more preferably 40 μm, and particularly preferably 30 μm.

[0050] Examples of inorganic reinforcing materials in the present invention include talc, silicic acid-containing compounds, minerals, glass fibers, glass beads, glass flakes, foamed glass beads, single-crystal potassium titanate, carbon fibers, carbon nanotubes, anthracite powder, titanium oxide, magnesium oxide, potassium titanate, mica, asbestos, calcium sulfite, calcium silicate, molybdenum sulfide, boron fibers, and silicon carbide fibers, with glass beads, glass fibers, and carbon fibers being more preferred.

[0051] The amount of inorganic reinforcing material in the present invention is preferably 1 to 100 parts by weight, more preferably 10 to 100 parts by weight, per 100 parts by weight of thermoplastic resin particles. The greater the proportion of reinforcing material, the more improved the strength of the molded object. By setting the amount of inorganic reinforcing material to 100 parts by weight or less, it is possible to prevent a decrease in powder fluidity during three-dimensional molding, which is preferable.

[0052] The three-dimensional structure of the present invention can be obtained by molding the powder composition of the present invention using a powder additive manufacturing method. The three-dimensional structure of the present invention will be described below.

[0053] In the powder composition of the present invention, the carbon black is present on the outer surface of the thermoplastic resin powder, but because the thermoplastic resin powder is melted by laser irradiation during modeling, the carbon black is encapsulated in the thermoplastic resin powder or on the inner surface thereof in a powdered state or in a molten state. This maintains the carbon black in the three-dimensional model, preventing discoloration of the three-dimensional model.

[0054] The carbon black content of the three-dimensionally shaped product of the present invention is 0.02% by weight or more and 5% by weight or less. When the carbon black is uniformly mixed in the powder composition, the weight of the carbon black contained in the powder composition and the weight of the carbon black contained in the three-dimensionally shaped product produced by three-dimensionally shaping the powder composition are the same.

[0055] The carbon black content of a three-dimensional object can be quantified, for example, by thermogravimetric analysis (TGA). Specifically, a small piece of the three-dimensional object is placed in the sample pan of a TGA instrument as a sample, heated at a constant rate until the thermoplastic resin thermally decomposes and volatilizes. The carbon black content can be quantified based on the change in sample weight. If TGA is not feasible, high-performance liquid chromatography (HPLC) can be used. A small piece of the three-dimensional object is dissolved in an appropriate solvent to prepare a sample. An appropriate column and mobile phase are installed in an HPLC instrument, and the sample solution is injected. The carbon black separates in the column, and the peak area is measured by a detector. Furthermore, carbon black standard solutions of known concentrations are prepared, and a standard curve is created based on the peak area of ​​the standard sample. Finally, the carbon black content can be calculated by converting the sample peak area to the carbon black concentration based on the standard curve.

[0056] Furthermore, in the powder composition of the present invention, the carbon black is uniformly distributed on the surface of the thermoplastic resin powder, and there are almost no agglomerates containing carbon black with particle diameters of 250 μm or more. Therefore, the composition is uniformly melted when irradiated with a laser, and a three-dimensional object having almost no color unevenness or spots can be obtained.

[0057] The three-dimensional structure of the present invention is characterized in that the number of spots having a diameter of 150 μm or more observed on the surface of the three-dimensional structure is within a surface area of ​​100 cm2. ２ The surface area of ​​the three-dimensional object can be measured by a known method, for example, by scanning the three-dimensional object with a 3D scanner, converting it into three-dimensional CAD data, and then calculating the surface area using software. ２ If the size is less than 100cm, combine multiple three-dimensional objects to form a 100cm ２ The number of spots can be evaluated as the surface area above.

[0058] A specific method for evaluating the presence of mottles on a three-dimensional object involves preparing 12 test pieces, each 10 mm wide, 80 mm long, and 4.0 mm thick, using powder bed fusion bonding. The 80 mm length corresponds to the direction of recoater movement (X direction), the 10 mm width corresponds to the plane along which the recoater moves, perpendicular to the direction of recoater movement (Y direction), and the 4.0 mm thickness corresponds to the direction perpendicular to the plane along which the recoater moves (Z direction). The number of test pieces with mottles can be counted. Preferably, the number of mottles with a diameter of 150 μm or more observed on the 10 mm × 80 mm front surface of each of the 12 test pieces is two or less. The presence of mottles on a three-dimensional object can be visually confirmed. When the three-dimensional object is observed under an optical microscope, a mottle with a diameter of 150 μm or more is defined as a mottle, and the average of the major and minor diameters of the mottle is taken as the size diameter. It is preferred that no mottles with a diameter of 150 μm or more are observed on the three-dimensional object.

[0059] The surface area refers to the topmost plane of the 10 mm × 80 mm surface of the test piece. When a powder composition is three-dimensionally fabricated using powder bed fusion, the dimensions of the set value may differ from the dimensions of the three-dimensional object actually obtained due to crystallization shrinkage, so the surface area is evaluated using the surface area calculated from the set value.

[0060] In the present invention, a three-dimensionally shaped object having uneven color refers to a three-dimensionally shaped object having a mottled pattern or gradation as a result of being three-dimensionally shaped using a powder composition in which carbon black is not uniformly dispersed. A three-dimensionally shaped object having spots is a three-dimensionally shaped object in which the presence of scattered areas of different colors can be visually confirmed as a result of being three-dimensionally shaped using a powder composition in which coarse particles containing carbon black with a particle diameter of 250 μm or more are present.

[0061] 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.

[0062] The present invention will be explained in more detail below with reference to examples and comparative examples, but the present invention is not limited to these examples. Various measurement methods are as follows.

[0063] [Average particle size of powder composition] The average particle size of the powder composition was measured using a laser diffraction / scattering particle size distribution analyzer (MT3300EXII, manufactured by Nikkiso Co., Ltd.) and a 0.5 wt % aqueous solution of polyoxyethylene cumyl phenyl ether (trade name Nonal 912A, manufactured by Toho Chemical Industry Co., Ltd.) as a dispersion medium. Specifically, a cumulative curve was obtained by analyzing scattered laser light using the Microtrack method, with the total volume of the fine particles obtained being 100%, and the particle size (median size: d50) at the point where the cumulative curve from the small particle size side reached 50% was taken as the average particle size.

[0064] [Average Particle Diameter of Carbon Black] The average particle diameter of carbon black was determined by observing the thermoplastic resin particles of the powder composition at a magnification of 10,000 times using a scanning electron microscope (JSM-IT700HR) manufactured by JEOL Ltd., and calculating the arithmetic mean value of particle diameters of 100 carbon black particles randomly selected from the photograph. Energy dispersive X-ray analysis was used to determine whether the carbon black was the correct material.

[0065] [DBP Absorption Amount] The DBP absorption amount of carbon black was measured using an absorption amount measuring device (S410E manufactured by Asahi Soken Co., Ltd.) in accordance with JIS K6217-4:2008, and the DBP oil absorption amount per 100 g was taken as the DBP absorption amount.

[0066] [Powder composition measured at 9500 cm using diffuse reflectance method] －１ A diffuse reflectance measuring device (DRS-8000) was installed in a Fourier transform infrared spectrophotometer (IRPrestige-21) manufactured by Shimadzu Corporation, and a tungsten lamp was used 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 blank measurement of near-infrared light, and then a powder composition sample was filled into the cell to perform near-infrared measurement. －１ The transmittance of near-infrared light was calculated.

[0067] [Color Tone Measurement] The L value of the powder composition was measured using a spectrophotometer (SE2000) manufactured by Nippon Denshoku Industries Co., Ltd. The L value was measured by densely packing the powder composition into a dedicated colorless and transparent quartz dish while vibrating it. The deviation of the L value was calculated by randomly collecting three samples from the powder composition, measuring the L value, and dividing the standard deviation of the L value by the average of the L values ​​of the three samples.

[0068] [Amount of coarse particles having a particle diameter of 250 μm or more] 2.0 kg of the powder composition was passed through a test sieve (opening 250 μm) manufactured by Tokyo Screen Co., Ltd., as specified in Japanese Industrial Standards (JIS) Z8801-1 (2006), and the agglomerates were weighed from the difference in weight of the sieve before and after passing through the sieve, and expressed as weight % relative to 100 wt % of the powder composition. The powder composition was passed through the sieve once.

[0069] [Color Unevenness and Spots on Three-Dimensional Models] Color unevenness and spots on three-dimensional models were evaluated using a powder bed fusion 3D printer (RaFaElII 150C-HT) manufactured by Aspect Co., Ltd. Twelve test pieces, each 10 mm wide, 80 mm long, and 4.0 mm thick, were produced, with the 80 mm length being the direction in which the recoater moves (X direction), the 10 mm width being the direction perpendicular to the direction in which the recoater moves on the plane in which the recoater moves (Y direction), and the 4.0 mm thickness being the direction perpendicular to the direction in which the recoater moves (Z direction). Color unevenness on three-dimensional models was evaluated by visually inspecting the number of three-dimensional models that showed color unevenness. Regarding the spots on the three-dimensionally molded objects, an optical microscope (VHX-5000) manufactured by Keyence Corporation and an objective lens VH-ZST (ZS-20) manufactured by Keyence Corporation were used to evaluate the number of three-dimensionally molded objects on which spots with a diameter of 150 μm or more were observed on the front surface of the 10 mm × 80 mm three-dimensionally molded object.

[0070] [Measurement of tensile strength of three-dimensionally shaped object] The tensile strength of the three-dimensionally shaped object was measured by preparing a tensile test piece (total length 170 mm, parallel portion length 80 mm, parallel portion width 10 mm, thickness 4 mm) conforming to ISO527-1A so that the 170 mm length direction was the X direction, and measuring the tensile strength in the X direction using a Tensilon universal testing machine (TENSIRON TRG-1250) manufactured by A&D Co., Ltd. In accordance with JIS K7161 (2014), the tensile strength was measured under conditions of a gripping distance of 115 mm and a test speed of 0.5 mm / min. The measurement temperature was room temperature (23 ° C), the number of measurements was n = 10, and the average value was calculated.

[0071] [Method of Mixing Powder Composition] In the present invention, the powder composition was mixed by mixing resin particles and carbon black for 20 minutes using a cross rotary mixer equipped with a chopper in a container under conditions of nitrogen atmosphere, room temperature, and normal pressure. The chopper was used at a rotation speed of 600 rpm. When an inorganic reinforcing material was added, the inorganic reinforcing material was added to a mixture of resin particles and carbon black, and the mixture was mixed for 20 minutes using a cross rotary mixer under conditions of nitrogen atmosphere, room temperature, and normal pressure. The mixing was performed without using a chopper.

[0072] [Production Example 1] A 1-liter autoclave equipped with a stirrer was charged with 1.00 mol of 47 wt% sodium hydrosulfide, 1.05 mol of 46 wt% sodium hydroxide, 1.65 mol of N-methyl-2-pyrrolidone (NMP), 0.45 mol of sodium acetate, and 5.55 mol of ion-exchanged water, and the mixture was gradually heated to 225°C over about 2 hours under atmospheric pressure while passing nitrogen through it. After distilling off 11.70 mol of water and 0.02 mol of NMP, the reaction vessel was cooled to 160°C.

[0073] Next, 1.02 mol of p-dichlorobenzene (p-DCB) and 1.32 mol of NMP were added, and the reaction vessel was sealed under nitrogen gas. While stirring at 400 rpm, the temperature was raised in two stages, from 160°C to 240°C at a rate of 0.4°C / min and from 240°C to 270°C at a rate of 0.4°C / min. 10 minutes after reaching 270°C, 0.75 mol of water was injected into the system over 15 minutes. After 120 minutes at 270°C, the system was cooled to 200°C at a rate of 1.0°C / min, and then rapidly cooled to near room temperature, and the contents were removed.

[0074] The contents were taken out and diluted with 0.5 liters of NMP, and then the solvent and solid matter were separated by filtration using a sieve (80 mesh). The obtained solid matter was washed several times with 1 liter of warm water, and then washed with 800 g of calcium acetate monohydrate in an amount of 0.45% by weight based on the weight of the solid polyarylene sulfide, and further washed with 1 liter of warm water and separated by filtration to obtain a cake.

[0075] The resulting cake was dried at 120°C under a nitrogen stream to obtain a polyarylene sulfide resin. This polyarylene sulfide resin was pulverized to have an average particle size of 50 µm, an L value of 97, and a 9500 cm －１ Polyphenylene sulfide (PPS) resin particles having a near-infrared light transmittance of 100% were obtained.

[0076] [Production Example 2] 300 g of ε-caprolactam (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polyamide monomer, 700 g of polyethylene glycol (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., primary polyethylene glycol 20,000, weight average molecular weight 18,600) as a polymer incompatible with polyamide, and 1,000 g of water were added to a 3 L autoclave equipped with a helical ribbon stirring blade to form a homogeneous solution, which was then sealed and purged with nitrogen. The stirring speed was then set to 40 rpm, and the temperature was raised to 210°C. During this process, the pressure of the system reached 10 kg / cm2, and then the pressure was increased to 10 kg / cm2. ２ After the temperature reached 210°C, the steam pressure was controlled to maintain 0.2 kg / cm ２ The pressure was released at a rate of 1 / min. Thereafter, the temperature was maintained while flowing nitrogen for 1 hour to complete the polymerization, and the mixture of polyamide powder and polyethylene glycol was discharged into a 2000g water bath while the polyethylene glycol remained in a molten state to obtain a slurry. The slurry was thoroughly homogenized by stirring, and then filtered. 2000g of water was added to the filtered material, and washed at 80°C. The slurry was then passed through a 100µm sieve to remove agglomerates, and the isolated filtered material was filtered again. The filtered material was dried at 80°C for 12 hours to produce 170g of polyamide 6 powder. The resulting polyamide powder had a sphericity of 92, an average particle size of 51µm, an L value of 97, and a 9500cm2 diffuse reflectance spectrum of the powder composition. －１ Polyamide 6 (PA6) particles having a near-infrared light transmittance of 100% were obtained.

[0077] Example 1: 250 g of the PPS resin particles obtained in Production Example 1 and 20 g of Asahi #15 carbon black (furnace black, DBP absorption 42 ml / 100 g, L value 15, average particle size 122 nm, manufactured by Asahi Carbon Co., Ltd.) were weighed into a 1 L plastic bag, shaken by hand to ensure uniform color, and then passed through a 300 μm mesh sieve to homogenize, yielding premixed powder (P1). 9.75 kg of PPS resin particles were blended with 270 g of this premixed powder (P1) so that the carbon black content in the powder composition was 0.20 parts by weight. The mixture was mixed for 20 minutes in a nitrogen atmosphere under room temperature and pressure conditions using a cross rotary mixer equipped with a chopper to yield mixed powder (P2). The chopper rotation speed was 600 rpm. This mixed powder (P2) was then passed through a vibrating sieve equipped with a 212 μm mesh sieve to produce a powder composition for three-dimensional modeling. In this case, the L value of this powder composition was 73, and the deviation of the L value was 0.009. －１ The transmittance of near-infrared light was 58%. The amount of coarse particles having a particle diameter of 250 μm or more was 0.01% by weight.

[0078] Using 1.5 kg of the obtained powder composition, a three-dimensional object was manufactured using a powder bed fusion device (RaFaElII 300C-HT) manufactured by Aspect Corporation. ２ A laser was used, with a temperature setting of 260°C, a layer height of 0.1 mm, a laser scanning interval of 0.1 mm, a laser scanning speed of 5 m / s, and a laser output of 18 W. The appearance of the resulting three-dimensional object was good, with no uneven color or spots. The tensile strength of the resulting three-dimensional object was 49 MPa. The resulting powder composition is suitable for powder bed fusion molding using a laser beam with a beam wavelength of 400 nm to 2000 nm.

[0079] A three-dimensional object was manufactured using 10 kg of this powder composition in a Farsoon powder bed fusion machine (Flight ST252P). The conditions were as follows: a 300 W fiber laser was used, the temperature was set to 258°C, the stacking height was 0.1 mm, the laser scanning interval was 0.25 mm, the laser scanning speed was 20 m / s, and the laser output was 180 W. The appearance of the obtained three-dimensional object was good, and there were no three-dimensional objects with uneven color or spots. The tensile strength of the obtained three-dimensional object was 54 MPa, and the CO ２ It exhibited tensile strength equal to or greater than that of three-dimensional objects created using a laser.

[0080] Example 2 A premixed powder (P1) was prepared in the same manner as in Example 1, except that the amount of carbon black per 250 g of PPS resin particles was changed to 10 g, resulting in a carbon black content of 0.13 parts by weight in the powder composition, and the carbon black was mechanically crushed in advance using a high-speed mixer. Then, a mixed powder (P2) was obtained in the same manner as in Example 1, except that 7.25 kg of PPS resin particles was blended with the premixed powder (P1). To this mixed powder (P2), 2.5 kg of glass fiber EPG70MD-01N (manufactured by Nippon Electric Glass Co., Ltd., fiber length 75 μm) was further added as an inorganic reinforcing material, and the mixture was mixed for 20 minutes using a cross rotary mixer in a nitrogen atmosphere at room temperature and pressure. Mixing was performed without using a chopper. The resulting mixed powder was passed through a vibrating sieve equipped with a 212 μm mesh sieve to prepare a powder composition for three-dimensional modeling. The L value of the resulting powder composition was 66, with an L value deviation of 0.006. In addition, the powder composition was analyzed using a diffuse reflectance method at 9500 cm －１ The transmittance of near-infrared light was 40%. The amount of coarse particles having a particle diameter of 250 μm or more was 0.02% by weight.

[0081] The obtained powder composition was used to perform three-dimensional modeling using the same method and conditions as in Example 1. The resulting three-dimensional model had a good appearance and was free of color unevenness or spots. The tensile strength of the resulting three-dimensional model was 60 MPa. The obtained powder composition is suitable for powder bed fusion modeling using a laser beam with a beam wavelength of 400 nm to 2000 nm.

[0082] Using 10 kg of this powder composition, three-dimensional modeling was carried out using a Farsoon powder bed fusion machine (Flight ST252P) under the same conditions as in Example 1. The resulting three-dimensional model had a good appearance and was free of color unevenness or spots. The tensile strength of the resulting three-dimensional model was 62 MPa, and the CO ２ It exhibited tensile strength equal to or greater than that of three-dimensional objects created using a laser.

[0083] Example 3 A powder composition for three-dimensional modeling was prepared in the same manner as in Example 1, except that MA230 (manufactured by Mitsubishi Chemical Corporation, furnace black, DBP absorption 113 ml / 100 g, L value 9, average particle size 30 nm) was used as carbon black. The L value of this powder composition was 63, and the deviation of the L value was 0.010. In addition, the powder composition was analyzed by a diffuse reflectance method at 9500 cm －１ The transmittance of near-infrared light was 49%. The amount of coarse particles having a particle diameter of 250 μm or more was 0.02% by weight.

[0084] The obtained powder composition was used to perform three-dimensional modeling using the same method and conditions as in Example 1. The resulting three-dimensional model had a good appearance and was free of color unevenness or spots. The obtained powder composition is suitable for powder bed fusion modeling using a laser beam with a beam wavelength of 400 nm to 2000 nm.

[0085] [Example 4] Polyamide 6 particles (average particle diameter 51 μm, L value of the particle composition measured by the diffuse reflectance method 97, 9500 cm) obtained by pulverizing polyamide 6 resin as thermoplastic resin particles －１ A powder mixture was prepared in the same manner as in Example 1, except that a carbon black having a near-infrared transmittance of 100% (100% near-infrared transmittance) was used, and the amount of carbon black added in step (a) of obtaining premixed powder (P1) was changed to 10 g, so that the carbon black content in the powder composition was 0.10 parts by weight. The L value of this powder composition was 62, with an L value deviation of 0.008. The transmittance of the powder composition at 9,500 cm-1 using a diffuse reflectance method was 43%. The amount of coarse particles having a particle diameter of 250 μm or more was 0.02% by weight.

[0086] Three-dimensional modeling was performed using the obtained powder composition under the same method and conditions as in Example 1, except that the laser output was changed to 10 W and the temperature setting was changed to 202°C. The obtained three-dimensional model had a good appearance, and none of the three-dimensional models had uneven color or spots. The obtained powder composition is suitable for powder bed fusion modeling, which uses a laser beam with a beam wavelength of 400 nm to 2000 nm.

[0087] Example 5 A powder mixture was prepared in the same manner as in Example 1, except that the polyamide 6 particles obtained in Production Example 2 were used as the thermoplastic resin particles, the amount of carbon black added in step (a) of preparing the premixed powder (P1) was 10 g, the carbon black content in the powder composition was 0.10 parts by weight, and the carbon black was mechanically crushed in advance using a high-speed mixer. The L value of this powder composition was 52, with an L value deviation of 0.008. Furthermore, the transmittance of the powder composition at 9500 cm-1 near-infrared light using a diffuse reflectance method was 43%. The amount of coarse particles with a particle diameter of 250 μm or more was substantially not measured (0.00 wt%).

[0088] Three-dimensional modeling was performed using the obtained powder composition under the same method and conditions as in Example 1, except that the laser output was changed to 10 W and the temperature setting was changed to 202°C.The appearance of the obtained three-dimensional model was good, and none of the three-dimensional models had uneven color or spots.The tensile strength of the obtained three-dimensional model was 66 MPa.The obtained powder composition is suitable for powder bed fusion modeling using a laser beam with a beam wavelength of 400 nm to 2000 nm.

[0089] Using 10 kg of this powder composition, three-dimensional modeling was carried out using a Farsoon powder bed fusion machine (Flight ST252P) under the same conditions as in Example 1, except that the laser output was changed to 85 W and the temperature setting was changed to 202°C. The resulting three-dimensional model had a good appearance and was free of color unevenness or spots. The tensile strength of the resulting three-dimensional model was 81 MPa, and the CO ２ It exhibited tensile strength equal to or greater than that of three-dimensional objects created using a laser.

[0090] Comparative Example 1 A powder composition was prepared in the same manner as in Example 2, except that carbon black was not blended. The L value of this powder composition was 94. In addition, the L value of the powder composition measured at 9500 cm using a diffuse reflectance method was －１ The transmittance of near-infrared light was 86%. The obtained powder composition is not suitable for powder bed fusion molding using a laser beam with a beam wavelength of 400 nm to 2000 nm.

[0091] Comparative Example 2 A powder composition was prepared in the same manner as in Example 4, except that the amount of carbon black was changed to 0.1 g, so that the carbon black content in the powder composition was 0.001 parts by weight. The L value of this composition was 92, and the L value deviation was 0.009. In addition, the powder composition was measured using a diffuse reflectance method at 9500 cm －１ The transmittance of near-infrared light was 98%. The obtained powder composition is not suitable for powder bed fusion molding using a laser beam with a beam wavelength of 400 nm to 2000 nm.

[0092] [Comparative Example 3] A powder composition was prepared in the same manner as in Example 1, except that a premixed powder was not prepared, and 20 g of carbon black was directly mixed with 10 kg of PPS resin particles, so that the carbon black content in the powder composition was 0.20 parts by weight. The L value of this composition was 75, and the deviation of the L value was 0.020. In addition, the powder composition was analyzed by a diffuse reflectance method at 9500 cm －１ The transmittance of near-infrared light was 83%. The amount of coarse particles having a particle diameter of 250 μm or more was 2.20% by weight.

[0093] The obtained powder composition was used to perform three-dimensional modeling under the same method and conditions as in Example 1, and spots were observed on the obtained three-dimensional model. On the 10 mm × 80 mm front surface of the three-dimensional model, spots with a diameter of 150 μm or more were observed in 6 out of 12 pieces. ２ The number of spots per square meter was 6. The resulting powder composition is not suitable for powder bed fusion manufacturing using laser light with a beam wavelength of 400 nm to 2000 nm.

[0094] The properties of Examples 1 to 5 and Comparative Examples 1 to 3 are summarized in Table 1.

[0095]

[0096] The present invention provides a method for producing a three-dimensional object with excellent appearance when produced using a fiber laser, as well as a powder composition suitable for use as a material for such a three-dimensional object and a method for producing the same. Therefore, the present invention can be suitably used in a wide range of applications, such as automotive, aerospace, industrial, and medical applications.

Claims

1. A method for producing a powder composition for use in a powder additive manufacturing method, comprising the following steps (a) to (b): (a) A step of blending 0.2 to 50 parts by weight of carbon black having a DBP (dibutyl phthalate) absorption of 10 ml / 100 g or more and 500 ml / 100 g or less with 100 parts by weight of thermoplastic resin particles and powder-mixing the mixture to obtain a premixed powder (P1). (b) A step of additionally blending thermoplastic resin particles with the premixed powder (P1) so that the amount of carbon black is 0.02 to 5 parts by weight per 100 parts by weight of the thermoplastic resin particles, and powder-mixing the mixture to obtain a mixed powder (P2).

2. The method for producing the powder composition according to claim 1 , further comprising the step (c). (c) A step of passing the premixed powder (P1) or the mixed powder (P2) through a filter having an opening of 100 μm or more and 500 μm or less.

3. The method for producing a powder composition according to claim 1, wherein the steps (a) and / or (b) are mixing steps involving shear force using a stirring blade.

4. A powder composition comprising 0.02 to 5 parts by weight of carbon black with a DBP absorption of 10 ml / 100 g or more and 500 ml / 100 g or less per 100 parts by weight of thermoplastic resin particles, the carbon black having an average particle diameter of 1 μm or more and 100 μm or less, and a 9500 cm －１ A powder composition for use in powder additive manufacturing, having a near-infrared light transmittance of 75% or less.

5. 5. The powder composition according to claim 4, wherein the content of coarse particles having a particle size of 250 μm or more is 0.1% by weight or less.

6. 5. The powder composition according to claim 4, wherein the thermoplastic resin constituting the thermoplastic resin particles is at least one selected from the group consisting of polyarylene sulfide, polyamide, polybutylene terephthalate, and polyether ether ketone.

7. 5. The powder composition according to claim 4, wherein the carbon black has an average particle size of 100 nm to 1000 nm.

8. 5. The powder composition according to claim 4, comprising 1 to 100 parts by weight of an inorganic reinforcing material relative to 100 parts by weight of the thermoplastic resin particles.

9. 9. The powder composition according to claim 8, wherein the inorganic reinforcing material is at least one selected from the group consisting of glass fibers, glass beads, and carbon fibers.

10. The powder composition according to claim 4, wherein the powder additive manufacturing method is a powder bed fusion method using a laser beam having a beam wavelength of 400 nm to 2000 nm.

11. The powder composition according to claim 10, wherein the laser light having a beam wavelength of 400 nm to 2000 nm is laser light emitted by a fiber laser.

12. A method for producing a powder composition by the method according to any one of claims 1 to 3, and then producing a three-dimensional object by powder additive manufacturing.

13. A method for producing a three-dimensional object by powder bed fusion, comprising irradiating the powder composition according to any one of claims 4 to 11 with laser light having a beam wavelength of 400 nm to 2000 nm.

14. A three-dimensional object obtained by a powder bed fusion method using a laser beam with a beam wavelength of 400 nm to 2000 nm, wherein the number of spots with a diameter of 150 μm or more observed on the surface of the three-dimensional object is less than 100 cm of the surface area of ​​the three-dimensional object. ２ Three-dimensional objects with no more than two pieces per object.

15. A three-dimensional object obtainable by powder bed fusion bonding using a laser beam having a beam wavelength of 400 nm to 2000 nm, using the powder composition according to any one of claims 4 to 11, wherein twelve test pieces each having a width of 10 mm, a length of 80 mm, and a thickness of 4.0 mm are fabricated by powder bed fusion bonding using a laser beam having a beam wavelength of 400 nm to 2000 nm, with the 80 mm length being the direction in which a recoater moves (X direction), the 10 mm width being the direction on the plane in which the recoater moves that is perpendicular to the direction of recoater movement (Y direction), and the 4.0 mm thickness being the direction perpendicular to the direction of recoater movement (Z direction). The powder composition provides a three-dimensional object obtainable by powder bed fusion bonding using a laser beam having a beam wavelength of 400 nm to 2000 nm, wherein the number of spots having a diameter of 150 μm or more observed on the 10 mm x 80 mm front plane of the twelve test pieces is two or less.

16. The three-dimensionally shaped object according to claim 15, which is used as an automobile part, an aerospace part, or a robot part.