Powder composition, method for producing three dimensional shaped article by powder bed fusion method using powder composition, and three dimensional shaped article

Abstract

To provide a powder composition for obtaining a three dimensional shaped article free from color unevenness and spots and exhibiting a uniform hue.SOLUTION: (A) a thermoplastic-resin powder having a D50 particle size of 1 μm to 100 μm and (B) 0.02% by weight or more and 5% by weight or less of a colorant having a D50 particle size of 10nm to 1000nm, wherein aggregates having a particle size of 150 μm or more are 0.1% by weight or less.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a powder composition containing a colorant, a method for producing the powder composition, a method for producing a three-dimensional object by powder bed fusion using the powder composition, and the three-dimensional object. [Background technology]

[0002] Powder bed fusion is known as one of the manufacturing methods for obtaining three-dimensional objects. Powder bed fusion generally uses metal powder or thermoplastic resin powder as raw materials. This method involves repeating the process of selectively irradiating the powder surface of a building tank containing the raw material powder with laser light to melt the raw material, and then sweeping the raw material powder from the supply tank into the building tank to laminate it into thin layers. The three-dimensional object is obtained by allowing it to cool after molding. Features of powder bed fusion include the ability to selectively irradiate the laser light and the lack of support members, making it suitable for precision molding. It is expected to be used for precision machinery, medical devices, and other materials that require dimensional accuracy.

[0003] Furthermore, in powder bed fusion, it is possible to optionally add colorants to improve the appearance of three-dimensional objects, protect the contents, improve light resistance, and improve thermal properties. Patent Document 1 discloses a method for producing a powder composition in which raw materials containing polyamide 6 and carbon black are mixed in an extruder and then precipitated in a caprolactam solution. Patent Document 2 discloses a production method in which carbon black is mixed with thermoplastic resin powder to improve fiber laser absorption. Patent Document 3 discloses that powder mixing of a highly spherical thermoplastic resin powder with a colorant minimizes color change even when subjected to thermal history and maintains high fluidity suitable for powder bed fusion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2020-506991 [Patent Document 2] U.S. Patent Application Publication No. 2021 / 0403714 [Patent Document 3] Japanese Patent Application Laid-Open No. 2024-35214 Summary of the Invention [Problem to be solved by the invention]

[0005] In the past, when a powder composition was prepared by powder mixing a colorant that tends to agglomerate, and a three-dimensional object was manufactured using the powder composition by powder bed fusion, there was a problem that the agglomerated colorant caused color unevenness or spots on the three-dimensional object. Furthermore, since the agglomerated colorant is irregularly present on the three-dimensional object, there is a possibility that the characteristics of the three-dimensional object may become inhomogeneous. However, while Patent Document 3 mentions that the color of the powder composition is uniform, it does not mention whether or not agglomerates originating from the colorant are present.

[0006] Therefore, an object of the present invention is to provide a powder composition containing a colorant for obtaining a three-dimensionally shaped object that exhibits a uniform color without color unevenness or spots. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention has the following configuration. <1> A powder composition for use in powder bed fusion manufacturing, in which (A) thermoplastic resin powder having a D50 particle size of 1 μm to 100 μm and (B) colorant having a D50 particle size of 10 nm to 1000 nm are powder-mixed at 0.02 wt % to 5 wt % with the thermoplastic resin powder being 100 wt % (however, if a reinforcing filler is included, the total of the thermoplastic resin powder and the reinforcing filler is taken as 100 wt %), and in which agglomerates with particle sizes of 150 μm or more account for 0.1 wt % or less. <2> The D50 particle size of the powder composition is 1 μm to 100 μm. <1> The powder composition according to claim 1. <3> The D50 particle size of the colorant (B) is 100 nm to 1000 nm. <1> or <2> The powder composition according to claim 1. <4> The colorant (B) is carbon black. <1> ~ <3> 1. The powder composition according to any one of the preceding claims. <5> The amount of aggregates with particle diameters of 150 μm or more is 0.05% by weight or less <1> ~ <4> 1. The powder composition according to any one of the preceding claims. <6> The powder composition further contains a reinforcing filler, and the reinforcing filler is contained in an amount of 5% by weight to 60% by weight relative to 100% by weight of the powder composition, where the total of the thermoplastic resin powder and the reinforcing filler is 100% by weight. <1> ~ <5> 1. The powder composition according to any one of the preceding claims. <7> The sphericity of the thermoplastic resin powder (A) is 80 or more. <1> ~ <6> 1. The powder composition according to any one of the preceding claims. <8> The thermoplastic resin constituting the thermoplastic resin powder (A) is a polyamide. <1> ~ <7> 1. The powder composition according to any one of the preceding claims. <9> The method includes a step of powder-mixing (A) a thermoplastic resin powder having a D50 particle size of 1 μm to 100 μm and (B) a colorant having a D50 particle size of 10 nm to 1000 nm in an amount of 0.02 wt % to 5 wt % based on 100 wt % of the thermoplastic resin powder (however, if a reinforcing filler is included, the total of the thermoplastic resin powder and the reinforcing filler is taken as 100 wt %), and a step of removing any aggregates. <1> ~ <8> 10. A method for producing the powder composition according to any one of the preceding claims. <10> The step of removing agglomerates from the powder composition includes a step of passing the powder composition through a sieve with an opening of 150 μm or less. <9> A method for producing the powder composition described in claim 1. <11> The powder mixing is carried out at a temperature that is 20°C or more lower than the melting point of the thermoplastic resin that constitutes the thermoplastic resin powder (A). <9> or <10> A method for producing the powder composition described in claim 1. <12> The powder mixing is performed by hand, by a rotating container mixer, or by a fixed container mixer. <9> ~ <11> 10. A method for producing the powder composition according to any one of the preceding claims. <13> <1> ~ <8> 1. A method for producing a three-dimensional object by powder bed fusion using the powder composition according to any one of claims 1 to 9. <14> <1> ~ <8> A three-dimensional object obtained by powder bed fusion using the powder composition according to any one of the preceding items, wherein 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 powder bed fusion, 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 of recoater movement 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), and the number of spots with a diameter of 150 μm or more observed on the 10 mm x 80 mm front plane is 2 or less per 12 test pieces. <15> Used for automotive parts, aerospace parts, or robot parts <14> The three-dimensional object according to claim 1. [Effects of the Invention]

[0008] According to the present invention, a powder composition containing a thermoplastic resin powder and a colorant is obtained, and the thermoplastic resin powder and the colorant are uniformly mixed, with almost no agglomerates containing the colorant with particle diameters of 150 μm or more. A three-dimensional object manufactured using this powder composition by powder bed fusion bonding has no color unevenness or spots and exhibits a uniform color. [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 constituting the thermoplastic resin powder in the present invention is a thermoplastic resin suitable for producing three-dimensional objects by powder bed fusion, and examples thereof include polyethylene, polypropylene, polyester, polyamide, polyphenylene sulfide, 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. 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) and polyhexamethylene adipamide (polyamide 66) being most preferred.

[0011] 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 particle size will be equal to or greater than the stacking 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. In addition, the thermoplastic resin powder itself will easily aggregate, preventing the effects of the present invention from being achieved. The upper limit of the D50 particle size of the polyamide 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.

[0012] 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%.

[0013] The particle size distribution of the thermoplastic resin powder is expressed as the ratio of D90 to D10 of the particle size distribution, D90 / D10, and is preferably less than 5.0. A narrow particle size distribution is preferable because it eliminates differences in melting properties during molding due to differences in particle size and also makes it easier to uniformly disperse inorganic reinforcing materials, resulting in a homogeneous molded product. 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.

[0014] 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%.

[0015] In the present invention, the sphericity, which indicates the sphericity of the thermoplastic resin powder, is not particularly specified, but from the viewpoints of good moldability using the powder bed fusion method and excellent surface smoothness of the resulting three-dimensional molded object, the sphericity is preferably 80 to 100. If the sphericity is less than 80, the flowability will deteriorate and the surface of the molded object will become rough. The sphericity is preferably 85 to 100, more preferably 90 to 100, even more preferably 93 to 100, particularly preferably 95 to 100, and extremely preferably 97 to 100.

[0016] The sphericity of the thermoplastic resin powder in the present invention is determined by observing 30 particles randomly selected from a scanning electron microscope photograph and determining the minor and major diameters of the particles according to the following formula.

[0017]

number

[0018] In the above formula, S is sphericity, a is major axis, b is minor axis, and n is the number of measurements (30).

[0019] In the present invention, the main purpose of adding a colorant to the powder composition is to impart a uniform color to a three-dimensional object obtained by three-dimensional modeling using the powder composition.

[0020] The colorant may be any of inorganic pigments, organic pigments, and organic dyes. Examples of inorganic pigments include red clay, cadmium red, red lead, red iron oxide (iron oxide red), vermilion (mercury sulfide red), yellow ochre, yellow lead (lead chromium yellow), cadmium yellow, green clay, emerald green (copper arsenate), viridian (chromium oxide green), chromium oxide green, Prussian blue (ultramarine blue), cobalt blue, manganese violet, carbon black, graphite, iron oxides (red, yellow, black), ultramarine blue, titanium oxide (titanium white), lapis lazuli, cinnabar (mercury sulfide), pearl pigments, Prussian blue (iron blue), lithopone, barium yellow, cobalt violet, cobalt green, white lead, yellow titanium oxide, cyan blue, and lead tin yellow.

[0021] Examples of organic pigments include azo-based, phthalocyanine-based, threne-based, quinacridone-based, dioxazine-based, isoindoline-based, naphthol-based, indigoide-based, and anthraquinone-based pigments.

[0022] Examples of organic dyes include azoic dyes, disperse dyes, acid dyes, basic dyes, catalytic dyes, vat dyes, solvent dyes, direct dyes, and sulfur dyes.

[0023] Among these, carbon black is preferred from the viewpoints of improving the fluidity of the powder composition when mixed with the thermoplastic resin powder, improving the mechanical properties of the three-dimensionally shaped object, and providing a coloring effect even with a small amount of addition. Examples of such carbon black include furnace black, acetylene black, thermal black, and channel black.

[0024] The melting point of the colorant is preferably higher than that of the thermoplastic resin to be mixed into the powder. By using a colorant having a melting point higher than that of the thermoplastic resin, melting of the colorant can be prevented when mixed into the powder, and the shape and fluidity of the powder composition can be maintained.

[0025] The D50 particle size of the colorant in the present invention is in the range of 10 to 1,000 nm. A range of 100 to 1,000 nm is particularly preferred. If the particle size of the colorant is too small, it is prone to aggregation, and even in the method for producing the powder composition of the present invention, it may be difficult to remove colorant-derived aggregates. When the particle size is 100 nm or more, the carbon black can be uniformly dispersed as primary particles in the powder composition, is less likely to aggregate during recycling molding, and a three-dimensionally shaped object can be stably obtained. If the particle size exceeds 1,000 nm, the coloring effect on the powder composition is reduced. The upper limit of the particle size of the colorant is preferably 500 nm or less, more preferably 300 nm or less, and even more preferably 200 nm or less.

[0026] The blending amount of such colorant is 0.02 wt% or more and 5 wt% or less, when the total weight of the thermoplastic resin powder or the thermoplastic resin powder and reinforcing filler is 100 wt%. If the blending amount exceeds 5 wt%, the colorant coats the surface of the thermoplastic resin powder, inhibiting sintering during three-dimensional modeling and potentially resulting in defects in the three-dimensional model. If the blending amount is less than 0.02 wt%, the colorant's effect on the thermoplastic resin powder is reduced. The upper limit of the blending amount is preferably 3 wt% or less, more preferably 2 wt% or less, and even more preferably 1 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. Furthermore, the colorant is not limited to one type, and multiple colorants may be added as long as the total weight is in the range of 0.02 wt% to 5 wt%.

[0027] The D50 particle size of such a colorant can be measured by dynamic light scattering, and the particle size at which the cumulative frequency from the small particle size side of the particle size distribution becomes 50% was defined as the D50 particle size.

[0028] The powder composition in the present invention refers to a mixture of the thermoplastic resin powder and colorant described above, but may also contain additives, reinforcing fillers, flow aids, etc., which will be described later.

[0029] In the present invention, the term "aggregate" refers to an aggregate of two or more primary particles contained in a powder composition at room temperature (approximately 20 to 25°C), atmospheric pressure, and standard relative humidity (approximately 40 to 60%). The agglomerates of the present invention include agglomerates composed of a single component, such as a thermoplastic resin powder or a colorant, as well as agglomerates composed of a thermoplastic resin powder and a colorant, and agglomerates composed of multiple components including additives, reinforcing fillers, and flow aids contained in the powder composition.

[0030] In the powder composition of the present invention, the weight of agglomerates containing a colorant and having a particle size of 150 μm or more is 0.1 wt % or less. If the weight exceeds 0.1 wt %, a three-dimensional object produced using the powder composition by powder bed fusion will suffer from color unevenness and spots due to the agglomerates. In order to suppress color unevenness and spots on the three-dimensional object, the weight of the agglomerates 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.

[0031] In the case of an aggregate containing a colorant, the colorant in the aggregate can be determined by a scanning electron microscope photograph or energy dispersive X-ray analysis.

[0032] The term "agglomerates containing a colorant and having a particle size of 150 μm or more" refers to agglomerates that are captured by a sieve when the powder composition is passed through the 150 μm sieve specified in JIS Z8801-1 (2006). The agglomerates may be composed only of a colorant, or may be composed of a colorant and other components contained in the powder composition, or may contain agglomerates composed only of components other than the colorant.

[0033] The weight of agglomerates containing a colorant and having a particle size of 150 μm or more can be determined by passing the powder composition through a 150 μm sieve and measuring the difference in weight between before and after sieving. Specifically, 2 kg of the powder composition is placed through a 150 μm sieve 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 between before and after sieving is defined as the agglomerates having a particle size of 150 μm or more. To prevent variations in weight due to differences in the sieving method, it is preferable to pass the agglomerates through the sieve at room temperature (approximately 20-25°C), atmospheric pressure, and standard relative humidity (approximately 40-60%), with the sieve left stationary or with only slight vibration. Therefore, agglomerates must not be weighed using any method that intentionally breaks up the agglomerates, such as physical treatment such as crushing, rubbing, or loosening 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.

[0034] Additives may be added to the powder composition of the present invention as long as they do not impair its properties. Examples of additives include heat stabilizers, antioxidants, flame retardants, light stabilizers, and plasticizers. These additives may be present either inside or outside the thermoplastic resin powder. However, when such additives are present outside the thermoplastic resin powder, have a D50 particle size of 10 nm to 1000 nm, and are contained in the inorganic pigments, organic pigments, and organic dyes listed as examples of colorants, they are defined as colorants.

[0035] In the present invention, the color difference ΔE between the powder composition and the aggregates contained in the powder composition with particle diameters of 150 μm or more is preferably 10 or less. A color difference ΔE of more than 10 indicates that the color of the powder composition and the aggregates differs, suggesting that the colorant in the powder composition is likely to selectively aggregate. Furthermore, a three-dimensional object manufactured using the powder composition by powder bed fusion bonding will have more noticeable color unevenness and spots due to the aggregates. The color difference ΔE is more preferably 8 or less, even more preferably 5 or less, and particularly preferably 3 or less. The lower limit of the color difference ΔE is 0.

[0036] In the present invention, the color difference ΔE between the powder composition and the colorant is preferably 10 or more. By using a colorant with a large color difference ΔE between the powder composition and the colorant, a significant coloring effect is achieved. The color difference ΔE is more preferably 15 or more, even more preferably 20 or more, and particularly preferably 25 or more.

[0037] In the present invention, the color difference ΔE between the colorant and the aggregates having a particle size of 150 μm or more contained in the powder composition is preferably 10 or more. A color difference ΔE of less than 10 indicates that the colorant and the aggregates are similar in color, suggesting that the colorant in the powder composition is likely to be selectively aggregated. The color difference ΔE is more preferably 15 or more, even more preferably 20 or more, and particularly preferably 25 or more.

[0038] The color difference ΔE is calculated according to the following formula in accordance with the Japanese Industrial Standards (JIS) (JIS Z 8781-4 (2013)).

[0039]

number

[0040] In the above formula, ΔE represents color difference, L represents lightness, a* represents redness, and b* represents yellowness. In the present invention, L P , a P *, b P * indicates powder composition, L C , a C *, b C * indicates colorant, L A , a A *, b A * indicates the color difference, brightness, redness, and yellowness of aggregates with particle diameters of 150 μm or more contained in the powder composition. Also, ΔE P-A is the color difference between the powder composition and the aggregates with particle diameters of 150 μm or more contained in the powder composition, ΔE P-C is the color difference between the powder composition and the colorant, ΔE C-A represents the color difference between the colorant and the aggregates with particle sizes of 150 μm or more contained in the powder composition.

[0041] The D50 particle size of the powder composition containing a thermoplastic resin powder, a colorant, and, if necessary, additives such as a reinforcing filler and a flow aid, as described below, 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 difficult 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.

[0042] 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%.

[0043] 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.

[0044] Furthermore, when powders are mixed, 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-based fillers, nepheline syenite fine powder, calcined clay such as montmorillonite and bentonite, clay (aluminum silicate powder) such as silane-modified clay, silicic acid-containing compounds such as talc, diatomaceous earth, and silica sand, and crushed natural minerals such as pumice powder, pumice balloon, slate powder, and mica powder. Examples of the filler include minerals such as barium sulfate, lithopone, calcium sulfate, molybdenum disulfide, and graphite, glass fillers such as glass fibers, glass beads, glass flakes, and foamed glass beads, fly ash spheres, volcanic glass hollow bodies, synthetic inorganic hollow bodies, single-crystal potassium titanate, carbon fibers, carbon nanotubes, carbon hollow spheres, fullerenes, anthracite powder, artificial cryolite, titanium oxide, magnesium oxide, basic magnesium carbonate, dolomite, potassium titanate, calcium sulfite, mica, asbestos, calcium silicate, molybdenum sulfide, boron fiber, and silicon carbide fiber. Preferred examples include silica, alumina, calcium carbonate powder, glass fillers, and titanium oxide, which are hard and can contribute to improving mechanical properties.

[0045] However, if such a reinforcing filler exists outside the thermoplastic resin powder, has a D50 particle diameter of 10 nm to 1000 nm, and is contained in an inorganic pigment, organic pigment, or organic dye listed as an example of a colorant, it is defined as a colorant.

[0046] 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, where the sum of the thermoplastic resin powder and the reinforcing filler is 100% by weight. 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 flowability of the powder composition is not impaired, and an object with excellent surface smoothness tends to be obtained.

[0047] 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.

[0048] 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.

[0049] 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.

[0050] 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 light from a laser using dynamic light scattering is set to 100% to calculate the cumulative curve.

[0051] The amount of such flow aid is preferably 0% by weight, but preferably 2.0% by weight or less, based on 100% by weight of the thermoplastic resin powder or the sum of the thermoplastic resin powder and the reinforcing filler. The upper limit of the amount is more preferably 1.0% by weight or less, even more preferably 0.5% by weight or less, particularly preferably 0.1% by weight or less, and significantly preferably 0.05% by weight or less, while the lower limit is preferably 0.01% by weight or more, and preferably 0.02% by weight or more. The incorporation 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. However, if such a flow aid is present outside the thermoplastic resin powder, has a D50 particle size of 10 nm to 1000 nm, and is contained in an inorganic pigment, organic pigment, or organic dye, as listed as an example of a colorant, it is defined as a colorant.

[0052] 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.

[0053] 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.

[0054] The powder composition of the present invention can be prepared by powder mixing a thermoplastic resin powder having a D50 particle size of 1 μm to 100 μm and 0.02 wt % to 5 wt % of a colorant having a D50 particle size of 10 nm to 1000 nm. The powder composition may be prepared by any method as long as the amount of colorant-containing agglomerates with a particle size of 150 μm or more is 0.1 wt % or less. However, powder compositions prepared solely by powder mixing of a thermoplastic resin powder and a colorant typically result in a uniform dispersion of the colorant, but because the colorant is fine and prone to agglomeration, some of the colorant aggregates aggregate together. Such colorant aggregates, or aggregates formed by the interaction of colorant aggregates with the thermoplastic resin powder, may have particle sizes of 150 μm or more and may be present in a powder composition at a concentration of more than 0.1 wt %. The composition of the present invention can be obtained by removing the agglomerates from a composition containing a thermoplastic resin powder and a colorant.

[0055] Therefore, the powder composition of the present invention is preferably prepared by step (1) of powder-mixing a thermoplastic resin powder having a D50 particle size of 1 μm to 100 μm with 0.02% by weight to 5% by weight of a colorant having a D50 particle size of 10 nm to 1000 nm, and step (2) of removing aggregates. The order of steps (1) and (2) does not matter, and each may be performed multiple times, or they may be performed alternately.

[0056] Examples of suitable methods for step (1) include manual mixing, rotating container mixers such as W-type mixers, V-type mixers, and drum-type mixers, and fixed container mixers such as ribbon mixers. However, the powder mixing method is not particularly limited as long as the materials constituting the powder composition are mixed uniformly.

[0057] Since powder mixing is performed on the premise that the thermoplastic resin powder and colorant constituting the powder composition are mixed in powder form, it is preferable to perform the powder mixing at a temperature at least 20°C lower than the melting point of the thermoplastic resin. If the powder mixing is performed at a temperature other than the melting point, the thermoplastic resin powder may melt during powder mixing, and the colorant may become encapsulated in 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.

[0058] When a reinforcing filler, a flow aid, or other additives are added, they may be powder-mixed together with the thermoplastic resin powder and the colorant, or may be powder-mixed separately.

[0059] Examples of step (2) include a method of capturing the aggregates with a removable double-sided sieve, ultrasonic treatment, mechanical disintegration using a high-speed mixer or ball mill, dispersion in a solution, fluidized bed treatment, airflow pulverization, electrostatic treatment, electromagnetic field treatment, centrifugation, high-pressure homogenizer, salting out, etc. The method of capturing the aggregates with a removable double-sided sieve is preferred as a simple method that does not use any raw materials other than those constituting the powder composition and does not impair the appearance or physical properties of the powder composition.

[0060] When a method of capturing agglomerates with a double-spread sieve capable of removing agglomerates to remove agglomerates with a particle size of 150 μm or more, including colorants, from a powder composition, the preferred sieve spread size varies depending on the order of steps (1) and (2). When step (1) is performed first, agglomerates composed of a single component, such as thermoplastic resin powder or colorant, as well as agglomerates composed of thermoplastic resin powder and colorant, and agglomerates composed of multiple components, including additives, reinforcing fillers, and flow aids, contained in the powder composition, can be removed in step (2). The upper limit of the spread of the sieve used in step (2) is preferably 150 μm, more preferably 140 μm or less, and even more preferably 130 μm or less. If the spread is too small, the thermoplastic resin powder and reinforcing filler will be captured by the sieve; therefore, the lower limit is preferably 100 μm or more, more preferably 110 μm or more, and even more preferably 120 μm or more. When step (2) is performed first, agglomerates composed of colorants only can be removed. The upper limit of the sieve opening size used to remove aggregates contained in the colorant is preferably 150 μm, more preferably 125 μm or less, and even more preferably 100 μm or less. If the opening size is too small, it takes a long time for the colorant to pass through the sieve, so the lower limit is preferably 30 μm, more preferably 40 μm or more, and even more preferably 50 μm or more.

[0061] Note that, by performing a step of removing the agglomerates after performing step (1), the composition of the powder composition may change before and after the removal of the agglomerates. Since the amount of agglomerates removed in the agglomerate removal step is very small, the composition ratio of the powder composition after the removal of the agglomerates is the composition ratio at the time of blending the thermoplastic resin powder, colorant, other additives, etc. when preparing the powder composition.

[0062] 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.

[0063] Each step of the method for manufacturing a three-dimensional object will be described below with reference to FIG.

[0064] In step (a), the stage 2 of the tank 1 in which the object is formed is lowered.

[0065] 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.

[0066] 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.

[0067] In the powder bed fusion method, the three-dimensional structure 10 is obtained by repeating the above steps (a) to (c).

[0068] Examples of the selective melt-sintering method in step (c) include selective laser sintering, in which a laser is irradiated onto a shape corresponding to the cross-sectional shape of the object to be shaped, thereby bonding the powder composition. Other examples include a printing step in which an energy absorption promoter or an energy absorption inhibitor is printed onto a shape corresponding to the cross-sectional shape of the object to be shaped, and selective absorption (or suppression) sintering, in which electromagnetic radiation is used to bond resin powder.

[0069] The laser light used in the selective laser sintering method is not particularly limited as long as it does not impair the quality of the powder composition or the shaped object. Examples include carbon dioxide laser, YAG laser, excimer laser, He-Cd laser, and semiconductor-pumped solid-state laser. Among these, carbon dioxide laser is preferred because it is easy to operate and control.

[0070] The electromagnetic radiation used in selective absorption (restricted) sintering may be any radiation that does not impair the quality of the powder composition or the shaped object, but infrared radiation is preferred because it is relatively inexpensive and provides energy suitable for shaping. The electromagnetic radiation may or may not be coherent.

[0071] The energy absorption enhancer is a substance that absorbs electromagnetic radiation. Examples of such substances include carbon fiber, copper hydroxyphosphate, near-infrared absorbing dyes, near-infrared absorbing pigments, metal nanoparticles, polythiophene, poly(p-phenylene sulfide), polyaniline, poly(pyrrole), polyacetylene, poly(p-phenylene vinylene), polyparaphenylene, poly(styrene sulfonate), poly(3,4-ethylenedioxythiophene)-poly(styrene phosphonate) p-diethylaminobenzaldehyde diphenylhydrazone, and conjugated polymers formed from combinations thereof. These substances may be used alone or in combination.

[0072] The energy absorption inhibitor is a substance that does not easily absorb electromagnetic radiation. Examples of such substances include substances that reflect electromagnetic radiation, such as titanium, heat-insulating powders, such as mica powder and ceramic powder, and water. These substances may be used alone or in combination.

[0073] These selective absorbers or selective inhibitors may be used alone or in combination, provided that such selective absorbers or selective inhibitors are defined as colorants when they are present outside the thermoplastic resin powder, have a D50 particle size of 10 nm to 1000 nm, and are contained in the inorganic pigments, organic pigments, or organic dyes described as examples of colorants.

[0074] The selective absorbent or selective inhibitor can be printed in a shape corresponding to the cross-sectional shape of the object to be shaped by known methods such as inkjet printing. In this case, the selective absorbent or selective inhibitor may be used as is, or may be dispersed or dissolved in a solvent.

[0075] 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.

[0076] The surface roughness of the three-dimensionally shaped object of the present invention is preferably 20 μm or less. Since the smaller the surface roughness, the better the adhesion between the shaped objects, the surface roughness of the shaped object is more preferably 18 μm or less, even more preferably 15 μm or less, particularly preferably 12 μm or less, and most preferably 10 μm or less. There is no particular lower limit, and a smaller value is preferable, but the lower limit is usually 1 μm.

[0077] 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.

[0078] In the powder composition of the present invention, the colorant 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 colorant is encapsulated in the thermoplastic resin powder or on the inner surface thereof in a powdery state or in a molten state. This maintains the colorant in the three-dimensional model, preventing discoloration of the three-dimensional model.

[0079] The colorant content of the three-dimensionally shaped object of the present invention is 0.02% by weight or more and 5% by weight or less. When the colorant is uniformly mixed in the powder composition, the weight of the colorant contained in the powder composition and the weight of the colorant contained in the three-dimensionally shaped object produced by three-dimensionally shaping the powder composition are the same.

[0080] The colorant content of a 3D object can be quantified using, for example, thermogravimetric analysis (TGA). Specifically, a small piece of the 3D object is placed in the sample pan of a TGA instrument and heated at a constant rate until the thermoplastic resin thermally decomposes and volatilizes. The colorant 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 3D object is dissolved in an appropriate solvent to prepare a sample. The appropriate column and mobile phase are then installed in an HPLC instrument, and the sample solution is injected. The colorant separates within the column, and the peak area is measured by a detector. Furthermore, standard solutions of known concentrations of the colorant are prepared, and a standard curve is created based on the peak area of ​​the standard sample. Finally, the colorant content can be calculated by converting the sample peak area to the colorant concentration using the standard curve.

[0081] Furthermore, in the powder composition of the present invention, the colorant is uniformly distributed on the surface of the thermoplastic resin powder, and there are almost no agglomerates containing the colorant with particle diameters of 150 μm or more. Therefore, the composition is uniformly melted when irradiated with a laser, and a three-dimensional object with almost no color unevenness or spots can be obtained.

[0082] To evaluate the presence of specks in a three-dimensional object, 12 test pieces, each 10 mm wide, 80 mm long, and 4.0 mm thick, were fabricated using powder bed fusion bonding. The 80 mm length was aligned in the direction of recoater movement (X direction), the 10 mm length was aligned in the plane of recoater movement perpendicular to the direction of recoater movement (Y direction), and the 4.0 mm length was aligned in the direction perpendicular to the plane of recoater movement (Z direction). The number of specks with specks was counted. Specks with a diameter of 150 μm or more were observed on the 10 mm x 80 mm surface of each of the 12 test pieces. Specks on a three-dimensional object were visually inspected, and a speck with a diameter of 150 μm or more was defined as a speck, with the longest diameter of the speck being the size diameter. It is preferable that specks with a diameter of 150 μm or more are not observed on the three-dimensional object.

[0083] The term "front surface plane" refers to the plane of the top layer of the 10 mm x 80 mm plane of the test piece.

[0084] Furthermore, when a powder composition is three-dimensionally molded using the powder bed fusion method, the dimensions of the set value may differ from the dimensions of the three-dimensional object actually obtained due to crystallization shrinkage, so the evaluation is performed using the surface area calculated from the set value.

[0085] In the present invention, a three-dimensional object having uneven color refers to a three-dimensional object having a mottled pattern or gradation as a result of three-dimensional modeling using a powder composition in which the colorant is not uniformly dispersed. A three-dimensional object having spots refers to a three-dimensional object having scattered spots of different colors as a result of three-dimensional modeling using a powder composition in which colorant-containing aggregates with particle diameters of 150 μm or more are present, and the scattered spots can be visually confirmed.

[0086] 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]

[0087] The present invention will be described below based on examples, but the present invention is not limited to these examples.

[0088] (1) 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.

[0089] (2) Particle shape of thermoplastic resin powder The sphericity of the thermoplastic resin powder was calculated from the minor and major diameters of 30 randomly selected particles observed in a photograph taken with a scanning electron microscope (JSM-IT700HR, manufactured by JEOL Ltd.) using the following formula:

[0090]

number

[0091] In the above formula, S is sphericity, a is major axis, b is minor axis, and n is the number of measurements (30).

[0092] (3) D50 particle size of colorant 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.

[0093] (4) Amount of colorant added The amount of colorant added was expressed in weight % with the thermoplastic resin powder or the total of the thermoplastic resin powder and reinforcing filler being 100 weight %.

[0094] (5) Amount of flow aid added The amount of flow aid added was expressed in weight % with the thermoplastic resin powder or the total of the thermoplastic resin powder and the reinforcing filler taken as 100 weight %.

[0095] (6) Amount of reinforcing filler added The total amount of the thermoplastic resin powder and the reinforcing filler was taken as 100% by weight, and the amount of the reinforcing filler added was expressed in % by weight.

[0096] (7) Powder mixing method Powder compositions were prepared using the following three powder mixing methods.

[0097] Method A: The colorant alone was passed through a test sieve (150 μm opening) manufactured by Tokyo Screen Co., Ltd., as specified in Japanese Industrial Standards (JIS) Z8801-1 (2006), to remove aggregates with a particle size of 150 μm or more. A specified amount of thermoplastic resin powder, the colorant that had passed through the sieve, a flow aid, and a reinforcing filler were placed in a plastic bag and mixed by hand 500 times to prepare a powder composition. The colorant was passed through the sieve only once.

[0098] Method B: A predetermined amount of thermoplastic resin powder, colorant, flow aid, and reinforcing filler was placed in a plastic bag and mixed by shaking 500 times by hand. The resulting powder composition was then passed through a test sieve (opening 150 μm) manufactured by Tokyo Screen Co., Ltd., as specified in Japanese Industrial Standards (JIS) JIS Z8801-1 (2006), to remove aggregates with a particle size of 150 μm or more, thereby producing a powder composition. Note that the powder composition was passed through the sieve only once.

[0099] Method C: A predetermined amount of thermoplastic resin powder, colorant, flow aid, and reinforcing filler was placed in a plastic bag and mixed by shaking it by hand 500 times. The resulting powder composition was then passed through a test sieve (opening 500 μm) manufactured by Tokyo Screen Co., Ltd., as specified in Japanese Industrial Standards (JIS) JIS Z8801-1 (2006), to produce a powder composition. Note that the powder composition was passed through the sieve once.

[0100] (8) Weighing of aggregates with particle diameters of 150 μm or more 2.0 kg of the powder composition obtained in (7) was passed through a test sieve (opening 150 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.

[0101] (9) Uneven color and spots on 3D objects The bending modulus and bending strength of the three-dimensional object were measured using a powder bed fusion 3D printer (RaFaElII 150C-HT) manufactured by Aspect Inc., with a width of 10 mm and a length of 8 mm. Twelve test pieces, each measuring 0 mm long and 4.0 mm thick, were fabricated, with the 80 mm length aligned in the direction of recoater movement (X direction), the 10 mm length aligned in the plane of recoater movement perpendicular to the direction of recoater movement (Y direction), and the 4.0 mm length aligned perpendicular to the direction of recoater movement (Z direction). The color unevenness of the 3D-printed objects was evaluated by visual inspection of the number of 3D-printed objects with visible color unevenness. The number of 3D-printed objects with visible spots measuring 150 μm or larger was evaluated using a Keyence Corporation optical microscope (VHX-5000) and a Keyence Corporation VH-ZST (ZS-20) objective lens. The number of 3D-printed objects with visible spots on the 10 mm x 80 mm front surface of the 3D-printed object was evaluated.

[0102] (10) Lightness L, redness a*, yellowness b*, and color difference ΔE of thermoplastic resin powder, colorant, and powder composition The L, a*, b*, and color difference ΔE of the thermoplastic resin powder, colorant, and powder composition were measured using a spectrophotometer (SE2000) manufactured by Nippon Denshoku Industries Co., Ltd. The samples were placed in a special colorless, transparent, round quartz cell with a diameter of 35 mm, and the cells were tightly packed while vibrating. The color difference ΔE was measured according to the Japanese Industrial Standards (JIS) JIS Z 8781-4 (2013) ) was calculated according to the following formula.

[0103]

number

[0104] ΔE: color difference, L: lightness, a*: redness, b*: yellowness. In the present invention, L P , a P *, b P * indicates powder composition, L C , a C *, b C * indicates colorant, L A , a A *, bA * indicates the color difference, brightness, redness, and yellowness of aggregates with particle diameters of 150 μm or more contained in the powder composition. Also, ΔE P-A is the color difference between the powder composition and the aggregates with particle diameters of 150 μm or more contained in the powder composition, ΔE P-C is the color difference between the powder composition and the colorant, ΔE C-A represents the color difference between the colorant and the aggregates with particle sizes of 150 μm or more contained in the powder composition.

[0105] [Production Example 1] Thermoplastic Resin Powder Production Method 1 A thermoplastic resin powder was produced using the method described in Example 1 of WO 2018 / 207728. Specifically, a 3L autoclave was charged with 360 g of ε-caprolactam (special grade reagent, manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) as a polyamide monomer, 240 g of polyethylene glycol (grade 1 polyethylene glycol 6,000, molecular weight 7,700, manufactured by Wako Pure Chemical Industries, Ltd.) as a polymer incompatible with the resulting polyamide, 2.5 g of antioxidant (BASF "IRGANOX" (registered trademark) 1098), and 50 g of deionized water. The autoclave was then sealed, and the process of pressurizing the autoclave to 1 MPa with nitrogen and releasing the pressure to 0.1 MPa was repeated three times. After replacing the inside of the container with nitrogen, the pressure was adjusted to 0.1 MPa and the container was sealed. The stirring speed was then set to 60 rpm and the temperature was raised to 230 °C. The pressure in the system was 1.4 MPa, and stirring was continued at 60 rpm for 3 hours while maintaining the pressure and temperature. Next, the pressure was released at a rate of 0.02 MPa / min to bring the internal pressure to 0 MPa. The polymerization temperature was then increased to 210°C, and nitrogen was introduced at a rate of 5 L / min for 2 hours. Finally, the mixture was poured into a 2000 g water bath to obtain a slurry. The slurry was thoroughly homogenized by stirring, filtered, and 2000 g of water was added to the residue and washed at 80°C. The slurry was then filtered again to remove coarse particles passed through a 100 μm sieve. The isolated residue was then dried at 80°C for 12 hours to produce 300 g of polyamide 6 powder. The resulting polyamide powder had a D50 particle size of 52 μm, a sphericity of 95, and a weight-average molecular weight of 54,000.

[0106] [Production Example 2] Thermoplastic Resin Powder Production Method 2 Polyamide 6 injection molding pellets (Toray Industries, Inc., polyamide "Amilan (registered trademark)" CM1007) were pulverized for 120 minutes using a jet mill (Hosokawa Micron 100AFG). The resulting polyamide powder had a D50 particle size of 41 μm, a sphericity of 70, and a weight-average molecular weight of 61,000.

[0107] [Example 1] The thermoplastic resin powder was 100% by weight of the polyamide 6 powder of Production Example 1, and the colorant was carbon black Asahi #15 (manufactured by Asahi Carbon Co., Ltd., D50 particle size 122 nm, L C :15, a C *:0, b C A powder composition was prepared by powder mixing method A using 0.2% by weight of PEG-100 (*: -0.2) and 0.1% by weight of trimethylsilylated amorphous silica X-24-9500 (manufactured by Shin-Etsu Chemical Co., Ltd., D50 particle size 170 nm) as a flow aid. The particle size of the obtained powder composition was 52 μm, L P :55, a P *:0.1, b P *: -0.1. The aggregates with particle diameters of 150 μm or more were 0.01% by weight, L A :55, a A *:0.1, b A *: 0. Using 1.5 kg of the obtained powder composition, a three-dimensional object was manufactured using a powder bed fusion device (RaFaElII 150C-HT) manufactured by Aspect Corporation. The conditions used were a 60W CO2 laser, 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 10 W. The temperature settings were as follows: the part bed temperature was -15°C below the melting point, and the supply tank temperature was -5°C below the crystallization temperature. The appearance of the obtained three-dimensional object was good, with no uneven color or spots.

[0108] [Example 2] A powder composition was prepared in the same manner as in Example 1, except that 40% by weight of glass fiber EPG40MD-01N (manufactured by Nippon Electric Glass Co., Ltd., fiber length 40 μm) was added so that the total of the thermoplastic resin powder and reinforcing filler was 100% by weight. The particle size of the obtained powder composition was 47 μm, L P :56, a P *:0.1, b P *: -3. The aggregates with particle diameters of 150 μm or more were 0.02% by weight, and L A :55, a A *:0.1, b A *: -2. The same conditions as in Example 1 were used except that the laser output was changed to 12 W. The appearance of the obtained three-dimensional object was good, and there were no three-dimensional objects with uneven color or spots.

[0109] [Example 3] A powder composition was prepared in the same manner as in Example 1, except that the powder mixing method was changed to powder mixing method B. The particle size of the obtained powder composition was 52 μm, L P :53, a P *:0.1, b P *: -0.1. The aggregates with particle diameters of 150 μm or more were 0.04% by weight, and L A :56, a A *:0.1, b A *: 0. Furthermore, the appearance of the three-dimensionally shaped objects obtained under the same conditions as in Example 1 was good, and none of the three-dimensionally shaped objects had uneven color or spots.

[0110] [Example 4] A powder composition was prepared in the same manner as in Example 3, except that 40% by weight of glass fiber EPG40MD-01N (manufactured by Nippon Electric Glass Co., Ltd., fiber length 40 μm) was added so that the total of the thermoplastic resin powder and reinforcing filler was 100% by weight. The particle size of the obtained powder composition was 47 μm, L P :54, a P *:0, b P *: -3. The aggregates with particle diameters of 150 μm or more were 0.04 wt %, L A :56, a A *:0, b A*: -4. The same conditions as in Example 2 were used except that the laser output was changed to 12 W. The appearance of the obtained three-dimensional object was good, and there were no three-dimensional objects with uneven color or spots.

[0111] [Example 5] A powder composition was prepared in the same manner as in Example 4, except that the amount of colorant added was changed to 0.3% by weight and no flow aid was added. The particle size of the obtained powder composition was 47 μm, L P :50, a P *:0.1, b P *: -6. The aggregates with particle diameters of 150 μm or more were 0.04% by weight, and L A :50, a A *:0.1, b A *: -5. Furthermore, the appearance of the three-dimensionally shaped objects obtained under the same conditions as in Example 2 was good, and there were no three-dimensionally shaped objects with uneven color or spots.

[0112] [Example 6] The polyamide 6 powder of Production Example 1 was heat-treated in air at 200°C for 6 hours in a rectangular vacuum constant temperature dryer DP43 (manufactured by Yamato Scientific Co., Ltd.) to obtain yellowed polyamide 6 powder. The thermoplastic resin powder was replaced with heat-treated polyamide 6 powder, and the colorant was titanium(IV) oxide (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd., D50 particle size 200 nm, L C :96, a C *:-2, b C *: A powder composition was prepared in the same manner as in Example 4, except that the powder composition was changed to 4). The particle size of the obtained powder composition was 48 μm, L P :71, a P *:3, b P *:17. The aggregates with particle diameters of 150 μm or more were 0.03 wt %, L A :72, a A *:3, b A *: 18. Furthermore, the appearance of the three-dimensionally shaped objects obtained under the same conditions as in Example 2 was good, and there were no three-dimensionally shaped objects with uneven color or spots.

[0113] [Example 7] A powder composition was prepared in the same manner as in Example 3, except that the polyamide 6 powder of Production Example 2 was used as the thermoplastic resin powder. The particle size of the obtained powder composition was 41 μm, L P :59, a P *:0.1, b P *: -0.2. The aggregates with particle diameters of 150 μm or more were 0.06% by weight, and L A :55, a A *:0.1, b A *: -0.1 Furthermore, the appearance of the three-dimensional objects obtained under the same conditions as in Example 1 was good, and none of the three-dimensional objects had uneven color or spots.

[0114] [Comparative Example 1] A powder composition was prepared in the same manner as in Example 1, except that the powder mixing method was changed to powder mixing method C. The particle size of the obtained powder composition was 52 μm, L P :71, a P *:0.1, b P *: 0.3. The aggregates with a particle size of 150 μm or more were 0.25% by weight, L A :48, a A *:0.2, b A *: -3. Furthermore, of the three-dimensional objects obtained under the same conditions as in Example 1, one out of 12 had color unevenness, and six out of 12 had spots.

[0115] Comparative Example 2 A powder composition was prepared in the same manner as in Comparative Example 1, except that 40% by weight of glass fiber EPG40MD-01N (manufactured by Nippon Electric Glass Co., Ltd., fiber length 40 μm) was added so that the total of the thermoplastic resin powder and reinforcing filler was 100% by weight. The particle size of the obtained powder composition was 52 μm, L P :73, a P *:0, b P *: 0.4. The aggregates with a particle diameter of 150 μm or more were 0.3% by weight, and L A :50, a A *:-0.3, b A *: -3. Furthermore, of the three-dimensional objects obtained under the same conditions as in Example 2, one out of 12 had color unevenness, and six out of 12 had spots.

[0116] Comparative Example 3 A powder composition was prepared in the same manner as in Example 6, except that the powder mixing method was changed to powder mixing method C. The particle size of the obtained powder composition was 47 μm, L P :72, a P *:3, b P *:19. The aggregates with particle diameters of 150 μm or more were 0.15 wt %, L A :95, a A *:-0.7, b A *: 5. Furthermore, the three-dimensional objects obtained under the same conditions as in Example 2 were free of color unevenness, but four out of the twelve three-dimensional objects obtained had spots.

[0117] [Table 1]

[0118] [Table 2] [Industrial Applicability]

[0119] The powder composition of the present invention contains almost no agglomerates of colorant-containing particles having a particle size of 150 μm or more, and therefore the three-dimensional object obtained by powder bed fusion exhibits a uniform color without unevenness or spots. [Explanation of symbols]

[0120] 1. Tank for forming the object 2 Stage 3 Supply tank 4. Feed tank stage 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 for use in powder bed fusion manufacturing, comprising (A) a thermoplastic resin powder having a D50 particle size of 1 μm to 100 μm and (B) a colorant having a D50 particle size of 10 nm to 1000 nm, powder-mixed in an amount of 0.02 wt % to 5 wt % based on 100 wt % of the thermoplastic resin powder (however, when a reinforcing filler is contained, the total of the thermoplastic resin powder and the reinforcing filler is taken as 100 wt %), wherein the powder composition contains 0.1 wt % or less of agglomerates with a particle size of 150 μm or more.

2. 2. The powder composition according to claim 1, wherein the D50 particle size of the powder composition is 1 μm to 100 μm.

3. 2. The powder composition according to claim 1, wherein the colorant (B) has a D50 particle size of 100 nm to 1000 nm.

4. 2. The powder composition according to claim 1, wherein the colorant (B) is carbon black.

5. 2. The powder composition according to claim 1, wherein the content of agglomerates having a particle size of 150 μm or more is 0.05% by weight or less.

6. 2. The powder composition according to claim 1, further comprising a reinforcing filler, the reinforcing filler being present in an amount of 5% by weight to 60% by weight, with the total of the thermoplastic resin powder and the reinforcing filler being 100% by weight.

7. 2. The powder composition according to claim 1, wherein the thermoplastic resin powder (A) has a sphericity of 80 or more.

8. 2. The powder composition according to claim 1, wherein the thermoplastic resin constituting the thermoplastic resin powder (A) is a polyamide.

9. 9. A method for producing the powder composition according to claim 1, comprising the steps of powder-mixing (A) a thermoplastic resin powder having a D50 particle size of 1 μm to 100 μm and (B) a colorant having a particle size of 10 nm to 1000 nm in an amount of 0.02 wt % to 5 wt %, based on 100 wt % of the thermoplastic resin powder (however, when a reinforcing filler is contained, the total of the thermoplastic resin powder and the reinforcing filler is taken as 100 wt %), and removing any aggregates.

10. The method for producing a powder composition according to claim 9, wherein the step of removing the agglomerates is a step of passing the powder through a sieve having an opening of 150 μm or less.

11. The method for producing a powder composition according to claim 9, wherein the powder mixing is carried out at a temperature that is at least 20°C lower than the melting point of the thermoplastic resin that constitutes the thermoplastic resin powder (A).

12. 10. The method for producing a powder composition according to claim 9, wherein the powder mixing is performed by hand, using a rotating container mixer, or using a fixed container mixer.

13. A method for producing a three-dimensional object by powder bed fusion using the powder composition according to any one of claims 1 to 8.

14. A three-dimensional object obtained by powder bed fusion using the powder composition according to any one of claims 1 to 8, wherein twelve test pieces each having a width of 10 mm, a length of 80 mm, and a thickness of 4.0 mm are produced by powder bed fusion, with the 80 mm length being the direction in which a recoater moves (X direction), the 10 mm width being the direction perpendicular to the direction of recoater movement on the plane in which the recoater moves (Y direction), and the 4.0 mm thickness being the direction perpendicular to the direction of recoater movement (Z direction), such that the number of spots with 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.

15. The three-dimensional structure according to claim 14, which is used as an automobile part, an aerospace part, or a robot part.

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