JP7829675B2 - Method for manufacturing a three-dimensional object, a three-dimensional object, a material powder for three-dimensional printing, and a device for printing three-dimensional objects. - Google Patents

Description

The present invention relates to a method for manufacturing a three-dimensional object, a three-dimensional object obtained thereby, a material powder for three-dimensional molding suitably used to obtain the same, and a three-dimensional object molding apparatus used therefor.

Known technologies for manufacturing three-dimensional objects (hereinafter sometimes referred to as "objects") include material extrusion, powder bed fusion, liquid bath photopolymerization, and sheet lamination. Among these, the powder bed fusion method forms a three-dimensional object by creating layers of powder, then selectively melting the areas corresponding to the cross-section of the object, and bonding and laminating these layers together. Methods for selectively melting the powder include selective laser sintering using a laser, selective absorption sintering using a melting aid, and selective suppression sintering that masks areas that should not be melted. Compared to other manufacturing methods, the powder bed fusion method has the advantages of being suitable for precision manufacturing and not requiring support members during manufacturing.

The three-dimensional objects produced by the aforementioned method, leveraging their excellent mechanical properties and dimensional accuracy, are being explored for use in a wide range of fields, such as mobility applications in automobiles, aerospace, and other similar industries; medical applications such as prosthetics, orthotics, hearing aids, and catheters; sports applications; and electrical/electronic materials. In these applications, it is crucial that the three-dimensional objects possess a certain level of performance, that is, stable quality and reliability.

On the other hand, in powder bed fusion fusion, the majority of the powder used does not become part of the fabricated object and is recovered as residual powder. While it is preferable to reuse the residual powder in the fabrication process to reduce waste (hereinafter sometimes simply referred to as "recycled fabrication"), the residual powder is exposed to temperatures slightly below its melting point for extended periods during fabrication. Therefore, it undergoes degradation compared to unused, new powder, resulting in a problem where the quality stability and reliability of the resulting three-dimensional objects are reduced.

To address these challenges, Patent Document 1 discloses a technique for preventing a defect phenomenon (known as orange skin) where the surface of a molded object becomes rough during recycled molding, using polyamide 12 powder containing an antioxidant. Patent Document 2 discloses a technique for suppressing the increase in viscosity of polyamide during recycled molding by using branched polyamide powder.

Japanese Patent Publication No. 2010-189610 Special table 2011-514420 publication

This invention newly reveals that in powder bed fusion bonding, a portion of the residual powder, particularly powder that has undergone thermal history, forms fused aggregates of a specific size. These aggregates probabilistically mix into the fabricated object during recycled fabrication, affecting the quality stability of the fabricated object during recycled fabrication. While the technologies described in Patent Documents 1 and 2 can suppress the modification of material powder during three-dimensional fabrication and reduce the quality difference between fabricated objects made with new powder and recycled powder, it has been found that there are challenges regarding quality stability between recycled fabricated objects.

Therefore, the present invention aims to provide a three-dimensional molding technology that exhibits excellent quality stability and reliability of molded objects, as well as good mechanical properties without variation, even during recycled molding, by subjecting a powder composition having a specific particle size to a thermal history equivalent to three-dimensional molding, and then removing fused aggregates.

To solve the above problems, the following configuration is provided.
<1> A material powder (C) for three-dimensional molding, comprising a powder composition (A1) in which a powder composition having a D50 particle size of 1 μm or more and 100 μm or less, containing thermoplastic resin particles and reinforcing filler, is subjected to a thermal load at a temperature above the crystallization temperature or below the melting point of the thermoplastic resin, wherein the amount of fused aggregates is 1.0% by mass or less based on the material powder (C).
<2> The material powder for three-dimensional molding according to <1>, wherein the material powder (C) contains a powder composition (B) that has not been subjected to a thermal load in a ratio of 0 parts by mass to 200 parts by mass per 100 parts by mass of powder composition (A1).
<3> The material powder for three-dimensional molding according to <2>, wherein the ratio (MwA)/(MwB) of the weight-average molecular weight of the thermoplastic resin constituting the powder composition (A1) to the weight-average molecular weight of the powder composition (B) is 1.0 or more and 2.0 or less.
<4> A material powder for three-dimensional molding according to any one of <1> to <3>, wherein the sphericity of the thermoplastic resin particles is 80 or more and 100 or less.
<5> A method for manufacturing a three-dimensional object, comprising supplying a material powder (C) for three-dimensional molding to a three-dimensional molding apparatus, the material powder (C) comprising a powder composition (A1) having a D50 particle size of 1 μm or more and 100 μm or less, which contains thermoplastic resin particles and reinforcing fillers, to a three-dimensional molding apparatus, wherein the material powder (C) has a fusion aggregate content of 1.0% by mass or less based on the material powder (C).
<6> A method for producing a three-dimensional molded object according to <5>, comprising the step of removing fused aggregates from a powder composition (A1) to which a thermal load has been applied at a temperature above the crystallization temperature and below the melting point of the thermoplastic resin.
<7> The method for manufacturing a three-dimensional object according to <6>, wherein the step of removing fused aggregates from the powder composition (A1) is to pass the powder composition through a filter having an opening of 2 to 6 times the D50 particle size of the powder composition.
<8> A method for manufacturing a three-dimensional object according to any one of <5> to <7>, wherein the thermal load in the powder composition (A1) is due to three-dimensional molding.
<9> A method for manufacturing a three-dimensional object according to any one of <6> to <8>, wherein a material powder (C) is supplied to a three-dimensional molding apparatus in a proportion of 0 to 200 parts by mass of a powder composition (B) which contains the particles of the thermoplastic resin and a reinforcing filler, has a D50 particle diameter of 1 μm or more and 100 μm or less, and has not been subjected to a heat load, with respect to 100 parts by mass of a powder composition (A2) obtained by performing a step of removing fused aggregates from the powder composition (A1).
<10> A method for manufacturing a three-dimensional object according to any one of <5> to <9>, wherein the brightness of the powder composition (A1) is 20 or more and 95 or less.
<11> A method for manufacturing a three-dimensional object according to any one of <5> to <10>, wherein the powder composition (A1) contains 5% by mass or more and 60% by mass or less of a reinforcing filler based on the powder composition (A1).
<12> A three-dimensional object formed using a material powder that contains at least a portion of a powder composition to which a thermal load has been applied at a temperature above the crystallization temperature or below the melting point of a thermoplastic resin constituting the powder composition, characterized in that the content of aggregates observed by X-ray CT observation of the object is 0.1 volume% or less.
<13> The three-dimensional object described in <12>, wherein the load deflection temperature at 0.45 MPa is 150°C or higher.
<14> A three-dimensional object as described in <12> or <13>, wherein the bending modulus of elasticity is 3000 MPa or more.
<15> A three-dimensional molding apparatus having the following means (a) to (c).
(a) A means for filling a layer to form a molded object with material powder and selectively melting and sintering the powder composition by applying thermal energy to melt the powder composition while applying a thermal load at a temperature above the crystallization temperature or below the melting point of the thermoplastic resin constituting the powder composition of the material powder; (b) A means for recovering the powder composition that remains in the layer to form the molded object without melting and sintering; (c) A means for removing fused aggregates from the recovered powder composition <16> The three-dimensional molded object molding apparatus according to <15>, further comprising the means of (d) below.
(d) A means for mixing a reused powder composition that has passed through the means for removing the fused aggregates in (c) with an unused powder composition. <17> The means for removing the fused aggregates in (c) is a means for passing the recovered powder composition through a filter having an opening of 2 to 6 times the D50 particle size of the powder composition, as described in <15> or <16>, a three-dimensional molding apparatus.

According to the present invention, by removing fused aggregates of a specific size from a powder composition subjected to a thermal history equivalent to three-dimensional molding, it is possible to obtain a three-dimensional molded object that exhibits excellent quality stability and reliability, as well as good mechanical properties without variation, even during recycled molding.

This is a schematic diagram showing an example of a manufacturing apparatus for three-dimensional objects according to the present invention. This is an X-ray CT image of the three-dimensional object obtained in Example 1. The images show (A) an X-ray CT scan of the three-dimensional object obtained in Comparative Example 1, and (B) a magnified view of a portion of it.

The present invention will be described in detail below, along with its embodiments.
Previously, quality assurance of three-dimensional printed objects has been a problem when applying them to industrial applications. In the manufacturing of three-dimensional printed objects, even when using material powders considered to be equivalent and producing objects with the same printing data, unexpected variations in quality could occur. In this invention, it has been newly revealed that in the residual powder of the powder bed fusion bonding method, a portion of the powder, especially those that have undergone thermal history, forms fused aggregates of a specific size, which are probabilistically mixed into the printed object during recycled printing, affecting the quality stability of the printed object during recycled printing.

In other words, the present invention provides a material powder (C) for three-dimensional molding, which includes a powder composition (A1) having a D50 particle diameter of 1 μm or more and 100 μm or less, containing thermoplastic resin particles and reinforcing fillers, and subjected to a thermal load at a temperature above the crystallization temperature or below the melting point of the thermoplastic resin, wherein the material powder (C) has a fusion aggregate content of 1.0% by mass or less based on the material powder (C), and is supplied to a three-dimensional molding apparatus.

The three-dimensional fabrication process using the powder bed fusion method of the present invention will be explained below with reference to Figure 1.

In the first step, the stage 2 of the tank 1, which forms the molded object, is lowered.

In the second step, the stage 4 of the tank 3 (hereinafter sometimes referred to as the supply tank), which is pre-filled with material powder P to be supplied to the tank 1 for forming the molded object, is raised to a height sufficient to supply enough material powder P to fill the tank 1 to a predetermined stacking height. Then, the recoater 5 is moved from the left end of the supply tank 3 to the right end of the tank 1, and the material powder P is stacked in the tank 1. The direction parallel to the movement of the recoater 5 is the X direction, and the direction perpendicular to the direction of movement of the recoater 5 on the surface of the material powder P is the Y direction. Reference numeral 7 indicates a coordinate system representing the X, Y, and Z directions. Reference numeral 8 indicates the surface direction in which the material powder is stacked, and reference numeral 9 indicates the height direction in which the material powder is stacked.

In the third step, the material powder P, which was filled into the tank 1 to a predetermined stacking height in the second step, is given meltable thermal energy 6 to selectively melt and sinter according to the molding data. Examples of methods for selective melt and sinter include a selective laser sintering method in which a laser is irradiated in a shape corresponding to the cross-sectional shape of the molded object to bond the powder composition. Other methods include a printing step in which an energy absorption accelerator or energy absorption inhibitor is printed in a shape corresponding to the cross-sectional shape of the object to be molded, and a selective absorption (or suppression) sintering method in which electromagnetic radiation is used to bond the resin powder.

In the powder bed fusion method, a three-dimensional object 10 is obtained by repeatedly performing the first to third steps described above, and material powder that has been subjected to a heat load at a temperature above the crystallization temperature of the thermoplastic resin but below its melting point remains in the tank 1.

The powder composition (A1) in the present invention is subjected to the thermal load described above. The method of applying the thermal load is not particularly limited as long as it is a known method, and may be related to the three-dimensional molding process or a treatment performed in advance in another process. However, by using it in three-dimensional molding, a thermal load is applied to the thermoplastic resin constituting the powder that is above the crystallization temperature and below the melting point, so the recycled powder composition used in three-dimensional molding can be a thermally loaded powder composition.

The temperature of the heat load applied to the powder composition (A1) in the present invention is above the crystallization temperature of the thermoplastic resin constituting the powder and below its melting point. Preferably, since the heat load is related to the three-dimensional molding process, below the crystallization temperature, the portion corresponding to the selectively melted molded object will crystallize, causing warping. Therefore, the lower limit of the heat load temperature is preferably above the crystallization temperature + 5°C, more preferably above the crystallization temperature + 10°C, even more preferably above the crystallization temperature + 15°C, and particularly preferably above the crystallization temperature + 20°C. The upper limit of the heat load temperature is preferably below the melting point - 5°C, more preferably below the melting point - 10°C, even more preferably below the melting point - 15°C, and particularly preferably below the melting point - 20°C, because above the melting point, material powder other than the portion corresponding to the selectively melted molded object will also melt.

The present invention relates to a method for manufacturing a three-dimensional molded object, characterized in that the material powder (C) for three-dimensional molding contains the heat-loaded powder composition, and the amount of fused aggregates is 1.0% by mass or less based on the material powder (C). In the present invention, in order to exhibit excellent quality stability and reliability of the molded object even during recycled molding, and to show good mechanical properties without variation, the amount of fused aggregates is preferably 0.1% by mass or less, more preferably 0.05% by mass or less, even more preferably 0.03% by mass or less, and particularly preferably 0.01% by mass or less.

In the present invention, methods for reducing the amount of fused aggregates to 1.0% by mass or less based on the material powder (C) include a method of performing a step to remove fused aggregates, a method of performing three-dimensional molding at a sufficiently low part bed temperature for thermoplastic resins, and a method of using a material powder with a sufficiently small amount of fine thermoplastic resin particles and low molecular weight thermoplastic resin particles that cause fusion. However, the method of performing a step to remove fused aggregates is preferred because it allows for the physical removal of the fused aggregates.

In the method for manufacturing a three-dimensional object of the present invention, it is preferable to perform a step to remove fused aggregates from a heat-loaded powder composition (A1) before performing a three-dimensional molding step. The method for removing fused aggregates from the material powder is not particularly limited as long as it is a known method, and methods such as physically removing them using a filter with a specified mesh size, an airflow classification method separating them while applying compressed air in the gas phase, and a method separating them in the liquid phase by the difference in buoyancy can be used. However, in terms of the accuracy of the separation size, the method of passing through a filter with a specified mesh size is more preferable.

In this invention, fused aggregates refer to secondary aggregates formed when two or more primary particles fuse together when a heat load is applied to a powder composition. Fused aggregates contain thermoplastic resin particles and may also contain reinforcing fillers and flow aids, which are preferably used in this invention. Furthermore, in this invention, fusion includes both a state in which multiple primary particles melt and bond together, and a state in which particles are surface-bonded to each other.

In the step of removing fused aggregates according to the present invention, it is preferable to remove the fused aggregates to a content of 1.0% by mass or less based on the powder composition. A lower amount of fused aggregates in the material powder used for three-dimensional molding reduces the probability of aggregate formation in the molded object. Therefore, a fused aggregate content of 0.5% by mass or less in the powder composition is more preferable, 0.2% by mass or less is even more preferable, 0.1% by mass or less is particularly preferable, and 0.05% by mass or less is significantly preferable.

In this invention, the content of fused aggregates is determined by capturing the fused aggregates generated when the material powder is subjected to heat load using a filter with a mesh size that can remove them, and weighing the difference in weight of the filter before and after passing the material through the filter. In this invention, the mesh size of the filter used to determine the content of fused aggregates is set to a nominal mesh size of 4.6 to 5.4 times the D50 particle size of the powder composition, as defined in the Japanese Industrial Standard (JIS) JIS Z8801-1 (2006). For example, if the D50 particle size is 22 μm, a filter with a mesh size of 106 μm is used; if the D50 particle size is 45 μm, a filter with a mesh size of 212 μm is used; if the D50 particle size is 51 μm, a filter with a mesh size of 250 μm is used; and if the D50 particle size is 60 μm, a filter with a mesh size of 300 μm is used.

In the step of removing fused aggregates according to the present invention, the mesh size of the filter preferably used is 2 to 6 times the D50 particle size of the powder composition. The lower limit of the filter mesh size is more preferably 2.5 times or more, even more preferably 3 times or more, and particularly preferably 3.5 times or more, in order to reduce the loss of material powder that can be molded normally. The upper limit of the filter mesh size is more preferably 5.5 times or less, even more preferably 5 times or less, and particularly preferably 4.5 times or less, in order to improve the performance of removing fused aggregates. A specific preferred size for the filter mesh size is 50 μm to 300 μm. Note that in the present invention, the mesh size of the filter used to determine the content of fused aggregates and the mesh size of the filter preferably used in the step of removing fused aggregates are different.

In the method for manufacturing a three-dimensional molded object of the present invention, it is preferable to carry out the three-dimensional molding process using a material powder (C) which contains, in a proportion of 0 to 200 parts by mass, a powder composition (B) that has a D50 particle diameter of 1 μm or more and 100 μm or less, and has not been subjected to heat load, with respect to 100 parts by mass of a powder composition (A2) obtained by performing a step of removing fused aggregates from a powder composition (A1). It is more preferable that the powder composition (B) is the same as the powder composition (A1) before heat load is applied.

The upper limit of the proportion of powder composition (B) per 100 parts by mass of the above powder composition (A2) is more preferably 150 parts by mass or less, even more preferably 100 parts by mass or less, particularly preferably 70 parts by mass or less, and significantly preferably 50 parts by mass or less, in terms of higher recyclability and reduced amount of discarded powder. The lower limit is 0 parts by mass, which does not contain powder composition (B).

As for the method of mixing powder composition (A2) and powder composition (B), known methods can be used. For example, a method of mixing by putting the powder in a mortar and stirring it with a pestle, a method of mixing by putting the powder in a container equipped with stirring blades and using stirring power, and a method of mixing by putting the powder in a container that can rotate and revolve and using oscillating power. Mixing by oscillating power is preferred because it is possible to mix the powder compositions uniformly without altering them and is excellent in terms of productivity.

The three-dimensional object fabrication apparatus of the present invention has the following means (a) to (c).
(a) A means of filling a layer into which a molded object is to be formed with material powder, and selectively melting and sintering the powder composition by applying thermal energy to melt the powder composition while applying a thermal load at a temperature above the crystallization temperature or below the melting point of the thermoplastic resin constituting the powder composition of the material powder; (b) A means of recovering the powder composition that remains in the layer into which the molded object is to be formed without melting and sintering; (c) A means of removing fused aggregates from the recovered powder composition (for example, a means of passing the recovered powder composition through a filter having an opening of 2 to 6 times the D50 particle size of the powder composition).

Each of the means (a) to (c) may be a separate set of devices, or two or three may be integrated into a single device. However, from the viewpoint of improving work efficiency and saving space, an integrated device is preferable. For example, a device in which means (a) for molding is attached to a line for means (b) for recovering the powder composition, and means (c) (for example, a filter as described above) is attached to the recovery line.

The three-dimensional object fabrication apparatus of the present invention preferably further has the following means (d).
(d) A means for mixing a reused powder composition that has passed through the means for removing the fused aggregates described in (c) above with an unused powder composition.

The means in (d) may be a set of devices separate from the means in (a) to (c) above, or it may be an integrated device, but an integrated device is preferable from the viewpoint of improving work efficiency and saving space. For example, an example is a device that includes means for introducing the reused powder composition that has passed through means in (c) (e.g., a filter) in the recovery line in (b) into a tank that supplies material powder, and mixing it with the unused powder composition by shaking or stirring power.

The material powder used in the method for manufacturing three-dimensional molded objects of the present invention is a powder composition having a D50 particle diameter of 1 μm to 100 μm, containing thermoplastic resin particles with a sphericity of 80 to 100, and includes a powder composition (A1) that has been subjected to a thermal load at a temperature above the crystallization temperature and below the melting point of the thermoplastic resin. The powder composition of the present invention will be described below.

The thermoplastic resin particles contained in the powder composition of the present invention are particles composed of a thermoplastic resin. The thermoplastic resin used in the present invention is a thermoplastic resin suitable for manufacturing three-dimensional molded objects by powder bed fusion bonding, and preferably contains polyethylene, polypropylene, polyester, polyamide, polyphenylene sulfide, polyetheretherketone, polyetherimide, polyamideimide, polyethersulfone, polytetrafluoroethylene, or mixtures thereof. Polyester, polyamide, polyphenylene sulfide, polyetheretherketone, polyetherimide, polyamideimide, polyethersulfone, and polytetrafluoroethylene are more preferred in that the resulting three-dimensional molded object has excellent heat resistance, polyester, polyamide, and polyphenylene sulfide are even more preferred in that the difference between the melting point and crystallization temperature is clear and the moldability and reproducibility are excellent, and polyamide is particularly preferred in that the resulting molded object has excellent mechanical properties such as toughness and strength.

Specific examples of polyamides preferably used in the present invention include polycaproamide (polyamide 6), polyundekaamide (polyamide 11), polylauroamide (polyamide 12), polyhexamethylene adipamide (polyamide 66), polydecamethylene sebaamide (polyamide 1010), polydodecamethylene sebaamide (polyamide 1012), polydodecamethylene dodecamide (polyamide 1212), polyhexamethylene sebaamide (polyamide 610), and polyhexamethylene dodecamide. Examples include camido (polyamide 612), polydecamethylene adipamide (polyamide 106), polydodecamethylene adipamide (polyamide 126), polyhexamethylene terephthalamide (polyamide 6T), polydecamethylene terephthalamide (polyamide 10T), polydodecamethylene terephthalamide (polyamide 12T), polycaproamide/polyhexamethylene adipamide copolymer (polyamide 6/66), and polycaproamide/polylauroamide copolymer (6/12). Among these, polycaproamide (polyamide 6), polyundekaamide (polyamide 11), polylauroamide (polyamide 12), polyhexamethylene adipamide (polyamide 66), polydecamethylene sebaamide (polyamide 1010), polydodecamethylene sebaamide (polyamide 1012), polydodecamethylene dodecamide (polyamide 1212), polyhexamethylene sebaamide (polyamide 610), and polyhexamethylene dodecamide (polyamide 612) are particularly preferred due to their ease of control to a perfect sphere shape. Furthermore, polycaproamide (polyamide 6), polyundekaamide (polyamide 11), polylauroamide (polyamide 12), polyhexamethylene adipamide (polyamide 66), polyhexamethylene sebaamide (polyamide 610), polydecamethylene sebaamide (polyamide 1010), and polydodecamethylene sebaamide (polyamide 1012) are particularly preferred due to their thermal properties suitable for molding. Among these, polycaproamide (polyamide 6), polyhexamethylene adipamide (polyamide 66), and polyhexamethylene sebaamide (polyamide 610) are significantly preferred due to their excellent heat resistance during molding and high load deflection temperature of the resulting molded object, while polycaproamide (polyamide 6) is most preferred because it has thermal properties that make it less likely for aggregates to form during molding.

The polyamide may be copolymerized to the extent that it does not impair the effects of the present invention. Suitable copolymerizable components include elastomer components such as polyolefins and polyalkylene glycols that impart flexibility, and rigid aromatic components that improve heat resistance and strength. Copolymerization components that adjust the end groups may also be used. Examples of such copolymerization components include monocarboxylic acids such as acetic acid, hexanoic acid, lauric acid, and benzoic acid, and monoamines such as hexylamine, octylamine, and aniline.

The thermoplastic resin particles contained in the powder composition of the present invention may be mixed with other ingredients as long as it does not impair the present invention. Examples of additives include antioxidants and heat stabilizers to suppress thermal degradation due to heating during molding using the powder bed fusion method. Examples of antioxidants and heat stabilizers include hindered phenols, hydroquinones, phosphites and their derivatives, as well as phosphates and hypophosphates. Other examples include pigments and dyes for coloring, plasticizers for viscosity adjustment, flow aids for fluidity modification, antistatic agents for functionalization, flame retardants, and fillers such as carbon black, silica, titanium dioxide, potassium titanate, glass fibers, glass beads, carbon fibers, and cellulose nanofibers. Known substances can be used, and they may be present either inside or outside the thermoplastic resin particles.

The sphericity of the thermoplastic resin particles contained in the powder composition of the present invention is preferably 80 or more and 100 or less. If the sphericity is less than 80, the fluidity deteriorates and the surface of the molded object becomes rough. The sphericity is more preferably 85 or more and 100 or less, even more preferably 90 or more and 100 or less, particularly preferably 93 or more and 100 or less, and significantly preferably 95 or more and 100 or less.

The sphericity of the thermoplastic resin particles of the present invention is determined by observing 30 particles randomly from scanning electron microscope images and using the following formula based on their short and long axes.

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

The D50 particle size of the powder composition of the present invention is in the range of 1 to 100 μm. If the D50 particle size exceeds 100 μm, the particle size may exceed the layer height in three-dimensional molding, resulting in a rough surface. If the D50 particle size is less than 1 μm, it is too fine and tends to adhere to the recoater during molding, preventing the molding chamber from reaching the required temperature. 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.

The D50 particle size of the powder composition is the particle size (D50 particle size) at which the cumulative frequency from the smallest particle size side of the particle size distribution, as measured by a laser diffraction particle size distribution analyzer, reaches 50%.

The weight-average molecular weight range of the thermoplastic resin particles contained in the heat-loaded powder composition (A1) of the present invention is preferably 30,000 to 1,000,000. The higher the weight-average molecular weight, the slower the crystallization rate, which suppresses warping and other issues associated with crystallization during molding. Therefore, the lower limit is more preferably 40,000 or higher, even more preferably 50,000 or higher, particularly preferably 60,000 or higher, significantly preferably 65,000 or higher, and most preferably 70,000 or higher. If the molecular weight is too high, the viscosity becomes high, which worsens the dispersibility and uniformity of the reinforcing material during molding. Therefore, the upper limit is more preferably 700,000 or lower, even more preferably 500,000 or lower, particularly preferably 300,000 or lower, significantly preferably 200,000 or lower, and most preferably 100,000 or lower.

The ratio (MwA)/(MwB) of the weight-average molecular weight of the thermoplastic resin contained in powder composition (A1) of the present invention to the weight-average molecular weight of the thermoplastic resin contained in powder composition (B) is preferably 1.0 or more and 2.0 or less. The upper limit of (MwA)/(MwB) is more preferably 1.8 or less, even more preferably 1.6 or less, and particularly preferably 1.5 or less, because a large difference in weight-average molecular weights is undesirable as it results in uneven properties such as melt viscosity in the mixed material powder. The lower limit is more preferably 1.1 or more, even more preferably 1.2 or more, and particularly preferably 1.3 or more, because higher molecular weight materials generally have better mechanical properties and can be increased in molecular weight when subjected to sufficient thermal load.

Furthermore, the weight-average molecular weight of the thermoplastic resin constituting the thermoplastic resin particles refers to the value obtained by measuring the weight-average molecular weight using gel permeation chromatography with a solvent that dissolves the thermoplastic resin, such as hexafluoroisopropanol, and then converting it to polymethyl methacrylate.

The powder composition may be pre-treated with heat, provided that the effects of the present invention are not impaired. Known heat treatment methods can be used, and appropriate selections can be made from atmospheric pressure heat treatment using an oven, reduced pressure heat treatment using a vacuum dryer, or pressurized heat treatment in a pressure vessel such as an autoclave with water. By performing heat treatment, the molecular weight, crystallinity, and melting point of the thermoplastic resin particles contained in the powder composition can be controlled to a desired range.

The powder composition of the present invention contains a reinforcing filler. Preferably, the reinforcing filler is present in an amount of 5% to 60% by weight. The upper limit of the reinforcing filler is preferably 55% or less by weight, and more preferably 50% or less by weight. The lower limit of the reinforcing filler is preferably 10% or more by weight, more preferably 15% or more by weight, and even more preferably 20% or more by weight. If the reinforcing filler content is 5% or more by weight, the elastic modulus and strength of the molded object obtained by three-dimensional molding of the powder composition can be improved. Furthermore, if the reinforcing filler content is 60% or less by weight, the fluidity of the powder composition is not deteriorated, and molded objects with excellent surface smoothness tend to be obtained.

In the present invention, the reinforcing filler may be dry-blended with thermoplastic resin particles or contained within the thermoplastic resin particles, but dry-blending is preferable in that it controls the thermoplastic resin particles to a spherical shape and improves fluidity.

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

Examples of glass-based fillers preferably used in the present invention include glass fibers, glass beads, glass flakes, and foamed glass beads. However, glass fibers, glass beads, or mixtures thereof are more preferred because they enable the development of a high elastic modulus in three-dimensional molded objects. Among these, glass fibers, or mixtures of glass fibers and glass beads, are particularly preferred because they can suppress warping of the molded object. Furthermore, glass fibers are significantly preferred because they result in a high-strength molded object. The glass fibers may have a circular or flattened cross-section. Glass beads are also significantly preferred because they exhibit low strength anisotropy in the molded object.

The average major axis diameter of the inorganic reinforcement material of the present invention is preferably in the range of 3 to 300 μm. If the average major axis diameter exceeds 300 μm, uneven filling of the polymer powder occurs when the material is molded, causing warping of the molded object, which is undesirable. Furthermore, surprisingly, a smaller average fiber length is preferable because it can reduce the amount of fused aggregates when used in recycled molding. If the average major axis diameter is less than 3 μm, it is undesirable because it does not contribute to suppressing warping. The upper limit of the average major axis diameter of the inorganic reinforcement material is preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, particularly preferably 100 μm or less, significantly preferably 90 μm or less, and most preferably 60 μm or less. The lower limit is preferably 5 μm or more, more preferably 8 μm or more, even more preferably 10 μm or more, particularly preferably 20 μm or more, and significantly preferably 30 μm or more.

The shape characteristics of the inorganic reinforced material of the present invention are expressed by the ratio of the average major axis diameter to the average minor axis diameter, which is the average major axis diameter/average minor axis diameter, and are preferably between 1 and 15. If the average major axis diameter/average minor axis diameter exceeds 15, the orientation in the X direction of the fabricated object becomes pronounced, and the warp anisotropy with respect to the Z direction increases, which is undesirable. Therefore, the average major axis diameter/average minor axis diameter is preferably 12 or less, more preferably 10 or less, and even more preferably 8 or less. The lower limit is theoretically 1. Among these, from the viewpoint of increasing strength, it is particularly preferable that it is between 2 and 8, and significantly preferable that it is between 3 and 8. From the viewpoint of reducing anisotropy, it is particularly preferable that it is between 1 and 5, and significantly preferable that it is between 1 and 3.

In this invention, the average major axis diameter and average minor axis diameter of the inorganic reinforcing material are the average values obtained by randomly observing the major axis diameter and minor axis diameter of 100 fibers or particles from photographs obtained by imaging the inorganic reinforcing material with a scanning electron microscope. The major axis diameter is the diameter at which the distance between two parallel lines is maximized when the image of the particle is sandwiched between them, and the minor axis diameter is the diameter at which the distance between two parallel lines is minimized when the particle is sandwiched between them in a direction perpendicular to the major axis diameter.

To improve the adhesion between the reinforcing filler and thermoplastic resin particles, within the limits that do not impair the effects of the present invention, it is possible to use a reinforcing filler that has been surface-treated. Examples of such surface treatments include silane coupling agents such as aminosilane, epoxysilane, and acrylicsilane. These surface treatment agents may be immobilized on the surface of the reinforcing filler by a coupling reaction, or they may coat the surface of the reinforcing filler. However, for recycling the powder used in three-dimensional molding, it is preferable that the agent is immobilized by a coupling reaction, as it is less likely to be modified by heat or other factors.

The powder composition of the present invention preferably contains a flow aid in order to improve fluidity. A flow aid refers to a substance that suppresses the aggregation of powder due to the adhesive force between powder particles. By including such a flow aid, the fluidity of the powder composition can be improved, that is, the angle of repose, which is an indicator of fluidity described later, can be improved to a desired range, which tends to reduce defects that cause a decrease in mechanical properties and to further improve the appearance of the resulting molded object.

Examples of such fluidizing agents 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; titanium oxide; magnesium oxide; basic magnesium carbonate; potassium titanate fibers; boron fibers; and silicon carbide fibers. More preferably, silica, alumina, calcium carbonate powder, and titanium oxide are used. Particularly preferred is silica, due to its hardness and its ability to contribute to improved strength and fluidity.

Examples of commercially available silica products include the "AEROSIL" (registered trademark) series of fumed silica manufactured by Nippon Aerosil Co., Ltd., the "Rheoroseal" (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.

The amount of the fluidizing agent added is preferably 0.01% by weight or more and 2.0% by weight or less of the total weight of the powder composition. The upper limit of the amount added is more preferably 1.5% by weight or less, even more preferably 1.0% by weight or less, particularly preferably 0.8% by weight or less, and significantly preferably 0.7% by weight or less. The lower limit of the amount added is more preferably 0.02% by weight or more, even more preferably 0.03% by weight or more, and particularly preferably 0.04% by weight or more. If the amount of fluidizing agent added is 0.01% by weight or more, the fluidity of the powder composition is further improved, and the filling ability when forming the object is increased, so voids that result in defects in mechanical properties are less likely to occur, and the resulting object tends to exhibit high strength. Furthermore, if the amount of fluidizing agent added is 2.0% by weight or less, sintering is not inhibited due to the fluidizing agent coating the surface of the thermoplastic resin particles, and the resulting object tends to have high strength.

In the present invention, the brightness of the heat-loaded powder composition (A1) is not particularly limited, but it is preferably 20 to 95 in that there is no color change during recycled molding and the color tone of the molded object is stable. The lower limit of brightness is more preferably 50 or higher, even more preferably 70 or higher, and particularly preferably 80 or higher, in that it is preferable to have no color difference when the powder composition (B) is based on white. The upper limit is more preferably 92 or lower, even more preferably 90 or lower, and particularly preferably 88 or lower, in that it is undesirable if the brightness is low as it reduces light absorption, makes it difficult to store heat during molding, and makes the molded object prone to warping.

The brightness of the present invention can be measured by known methods, for example, using a spectrophotometer (SE2000) manufactured by Nippon Denshoku Industries Ltd., and is the L value measured with the powder composition filled in a petri dish.

The material powder for three-dimensional molding of the present invention comprises a powder composition (A2) in which a powder composition containing thermoplastic resin particles with a D50 particle size of 1 μm or more and 100 μm or less, and a reinforcing filler, is subjected to a thermal load at a temperature above the crystallization temperature or below the melting point of the thermoplastic resin, wherein the amount of fused aggregates is 1.0% by mass or less. In the present invention, in order to exhibit excellent quality stability and reliability of molded products even during recycled molding, and to show good mechanical properties without variation, the amount of fused aggregates is more preferably 0.1% by mass or less, even more preferably 0.05% by mass or less, particularly preferably 0.03% by mass or less, and significantly preferably 0.01% by mass or less.

The three-dimensional object of the present invention can be obtained by fabricating the material powder for three-dimensional molding using a powder bed fusion method. The three-dimensional object of the present invention will be described below.

The three-dimensional molded object of the present invention is formed using a powder composition containing at least a portion of thermoplastic resin powder that has been subjected to a thermal load at a temperature above the crystallization temperature and below the melting point of the thermoplastic resin, and the aggregate content observed by X-ray CT observation of the molded object is 0.1 volume% or less. If the aggregate content observed by X-ray CT observation exceeds 0.1 volume%, stress concentrates in the aggregates, leading to a decrease in strength and a decrease in reliability such as fluid leakage when the molded object is used as a container, which is undesirable. The aggregate content is preferably 0.05 volume% or less, more preferably 0.02 volume% or less, even more preferably 0.01 volume% or less, and particularly preferably 0.005 volume% or less.

In this invention, the aggregate content was determined by imaging a disc-shaped fabricated object with a diameter of 40 mm and a thickness of 2 mm with a pixel size of 50 μm or less using X-ray CT observation. Areas with a higher electron density compared to other areas and observed as white bright spots were detected as aggregates, and the volume ratio was calculated relative to the total observed area.

The load deflection temperature of the three-dimensional molded object of the present invention at 0.45 MPa is preferably 150°C or higher. The higher the load deflection temperature, the less the molded object is likely to deform in a high-temperature environment. Therefore, the load deflection temperature of the molded object is more preferably 170°C or higher, even more preferably 185°C or higher, and particularly preferably 200°C or higher.

In this invention, the temperature of deflection under load was measured under a load of 0.45 MPa in accordance with the Japanese Industrial Standard (JIS) JIS K7191-1 (2015) "Plastics - Method for determining temperature of deflection under load" and the International Organization for Standardization (ISO) standard ISO 75-2.

The flexural modulus of the three-dimensional molded object of the present invention is preferably 3000 MPa or higher. The higher the flexural modulus, the more rigid and less deformable the molded object is. Therefore, the flexural modulus of the molded object is more preferably 3500 MPa or higher, even more preferably 4000 MPa or higher, particularly preferably 4500 MPa or higher, and significantly preferably 5000 MPa or higher. There is no particular upper limit, but generally, if the modulus becomes too high, it tends to become brittle and have low strength. Therefore, it is preferably 20000 MPa or lower, more preferably 15000 MPa or lower, even more preferably 12000 MPa or lower, and particularly preferably 10000 MPa or lower.

In this invention, the flexural modulus is the flexural modulus measured in accordance with the Japanese Industrial Standard (JIS) JIS K7171 (2016) "Plastics - Method for determining bending properties" and the International Organization for Standardization (ISO) standard ISO 178 for a bending test specimen fabricated in three dimensions with the longest side oriented in the aforementioned X direction.

The bending strength of the three-dimensional molded object of the present invention is preferably 65 MPa or higher. The higher the bending strength, the better it can withstand the force from the direction of greatest stress. Therefore, the bending strength of the molded object is more preferably 70 MPa or higher, even more preferably 80 MPa or higher, particularly preferably 90 MPa or higher, significantly preferably 100 MPa or higher, and most preferably 105 MPa or higher.

In this invention, the bending strength is the value of the maximum bending stress measured on a bending test specimen fabricated with the longest side oriented in the X direction, as described above, in accordance with the Japanese Industrial Standard (JIS) JIS K7171 (2016) "Plastics - Method for determining bending properties" and the International Organization for Standardization (ISO) standard ISO 178.

Furthermore, since three-dimensional molded objects are obtained by crystallization under atmospheric pressure and a slow cooling process, compared to conventional melt molding, the crystalline state differs from that of conventional melt molding. However, it is difficult to express this as a characteristic of the object, so the manufacturing method is limited to three-dimensional molding, preferably by powder bed fusion bonding. In conventional melt molding, it is known that highly reliable molded products can be obtained through careful consideration by those skilled in the art, according to the structure of the mold. However, in three-dimensional molding, which allows for the molding of complex shapes, it has not been possible to obtain highly reliable molded products until the present invention.

The present invention will be described below based on examples.

(1) D50 particle size of the powder composition A dispersion of approximately 100 mg of the powder composition, prepared by dispersing it 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 it reached a measurable concentration. After ultrasonic dispersion at 30 W for 60 seconds in the analyzer, the particle size at which the cumulative frequency from the smallest particle size side of the particle size distribution measured at a measurement time of 10 seconds reached 50% was defined 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.

(2) Sphericity of Thermoplastic Resin Particles The sphericity of thermoplastic resin particles was calculated by observing 30 randomly selected particles from images taken with a scanning electron microscope (JSM-6301NF) manufactured by JEOL Ltd., and using their short and long axes according to the following formula.

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

(3) Weight-average molecular weight of thermoplastic resin The weight-average molecular weight of thermoplastic resin was calculated by comparing it with a calibration curve using polymethyl methacrylate using gel permeation chromatography. A sample was prepared by dissolving approximately 3 mg of thermoplastic resin particles in approximately 3 g of hexafluoroisopropanol.
Equipment: Waters e-Alliance GPC system
Columns: HFIP-806M x 2 (manufactured by Showa Denko Corporation)
Mobile phase: 5 mmol/L sodium trifluoroacetate/hexafluoroisopropanol Flow rate: 1.0 mL/min
Temperature: 30℃
Detection: Differential refractometer.

(4) Brightness of the powder composition The L value and color difference ΔE of the powder composition were measured using a spectrophotometer (SE2000) manufactured by Nippon Denshoku Industries Ltd. The powder composition was added to a dedicated colorless, transparent quartz petri dish and measured while densely packed and vibrated.

(5) Measurement of fused aggregate content in material powder (C) The content of fused aggregates in material powder (C) was determined by passing 500 g of material powder (C) through a filter having a nominal mesh opening of 4.6 to 5.4 times the D50 particle size of powder composition (A1) as defined in JIS Z8801-1 (2006), weighing the material captured by the filter, and determining the content as a percentage of the amount of fused aggregates present in 500 g.

(6) Measurement of aggregate content in fabricated objects The aggregate content in the fabricated objects was measured using a powder bed fusion 3D printer (RaFaElII 300-HT) manufactured by Aspect Co., Ltd. A disc-shaped fabricated object sample with a diameter of 50 mm and a thickness of 2 mm was fabricated and observed in three dimensions using an X-ray CT scanner (Xradia 510 Versa) manufactured by ZEISS Corporation, with a resolution of 45 μm, a field of view of 46 mm, a voltage of 80 kV, and a power of 7 W. Areas that were observed as bright white spots with relatively high electron density in the observed image were labeled, and the volume of the area in question was divided by the total volume of the fabricated object in the observed image and multiplied by 100 to determine the aggregate content in the fabricated object.

(7) Load deflection temperature of the fabricated object The load deflection temperature of the three-dimensional fabricated object was measured using a powder bed fusion 3D printer (RaFaElII 300-HT) manufactured by Aspect Co., Ltd. A test specimen with a width of 10 mm, a length of 80 mm, and a thickness of 4 mm was fabricated with the 80 mm length direction as the X direction. The temperature was measured using a heat distortion tester (No. 148) manufactured by Yasuda Seiki Seisakusho Co., Ltd. under a load of 0.45 MPa in accordance with JIS K7191-1 (2015) and ISO 75-2. The number of measurements was n=3, and the average value was calculated.

(8) Measurement of the flexural modulus and flexural strength of the fabricated object The flexural modulus and flexural strength of the three-dimensional fabricated object were measured using a powder bed fusion 3D printer (RaFaElII 300-HT) manufactured by Aspect Co., Ltd. Test specimens with a width of 10 mm, a length of 80 mm, and a thickness of 4 mm were fabricated so that the 80 mm length direction was in the X direction or the Z direction. The flexural modulus and flexural strength in the X direction and Z direction were measured using a Tensilon universal testing machine (TENSIRON TRG-1250) manufactured by A&D Co., Ltd. The flexural modulus was determined by measuring a three-point bending test under the conditions of a support distance of 64 mm and a test speed of 2 mm/min, in accordance with JIS K7171 (2016) and ISO 178. The flexural modulus was determined by measuring a three-point bending test. The flexural strength was defined as the maximum bending stress. The measurement temperature was room temperature (23°C), the number of measurements was n=10, and the average value was calculated.

(9) Evaluation of the quality stability of the molded object The quality stability of the three-dimensional molded object was considered good if the minimum value of the measurement was within 10% of the average value of the bending strength measured in (8) above for n=10, and poor if the difference exceeded 10%.

[Manufacturing Example 1]
360 g of ε-caprolactam (reagent grade, 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's "IRGANOX" (registered trademark) 1098), and 50 g of deionized water were added to a 3 L autoclave. After sealing, the autoclave was pressurized to 1 MPa with nitrogen and then released to 0.1 MPa, a process repeated three times. After purging the inside of the container with nitrogen, the pressure was adjusted to 0.1 MPa and the container was sealed. Subsequently, the stirring speed was set to 60 rpm and the temperature was raised to 230°C. At this time, the pressure inside 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 reduce the internal pressure to 0 MPa. Then, the polymerization temperature was set to 210°C and nitrogen was flowed at a rate of 5 L/min for 2 hours. Finally, the mixture was discharged into a 2000 g water bath to obtain a slurry. After thoroughly homogenizing the slurry by stirring, it was filtered, and 2000 g of water was added to the filtered product and washed at 80°C. After that, the slurry liquid, with coarse particles removed by passing it through a 100 μm filter, was filtered again to isolate the filtered product, which was dried at 80°C for 12 hours to prepare 300 g of polyamide 6 powder. The obtained polyamide powder had a D50 particle size of 52 μm, a sphericity of 95, and a weight-average molecular weight of 54,000.

14 kg of polyamide 6 powder obtained by repeating the above process was mixed with 6 kg of glass fiber EPG70M-01N (manufactured by Nippon Electric Glass Co., Ltd.) as a reinforcing filler. Furthermore, 60 g of trimethylsilylated amorphous silica X-24-9500 (manufactured by Shin-Etsu Chemical Co., Ltd., D50 particle size 170 nm) was added as a flow aid to obtain powder composition (B). Using 20 kg of this powder composition (B), a three-dimensional object was manufactured using a powder bed fusion fusion apparatus (RaFaElII 300-HT) manufactured by Aspect Co., Ltd. The setting conditions were as follows: a 60 WCO2 _laser was used, the layer height was 0.1 mm, the laser scanning interval was 0.1 mm, the laser scanning speed was 10 m/s, and the laser output was 17 W. The temperature settings were: part bed temperature 208 °C, feed tank temperature 177 °C, and the time the heat load was applied during manufacturing was 15 hours. The resulting three-dimensional object had a good appearance, with a flexural modulus of 5600 MPa and a flexural strength of 112 MPa. The powder composition (A1) that was subjected to thermal load during the molding process without forming an object was recovered. The D50 particle size of this powder composition (A1) was 51 μm, and the weight-average molecular weight (MwA) was 75,000.

[Manufacturing Example 2]
20 kg of powder composition (B) was obtained in the same manner as in Production Example 1, except that 12 kg of polyamide 6 powder and 8 kg of glass fiber EPG40M-01N (manufactured by Nippon Electric Glass Co., Ltd.) were mixed as a reinforcing filler. The three-dimensional object was manufactured in the same manner as in Production Example 1, except that the time for which a heat load was applied during manufacturing was 8 hours, and the heat-loaded powder composition (A1) was recovered. The D50 particle size of this powder composition (A1) was 48 μm, and the weight-average molecular weight (MwA) was 67,000.

[Manufacturing Example 3]
Toray Industries, Inc.'s polyamide "Amiran®" CM1007 was pulverized for 120 minutes using a jet mill (Hosokawa Micron 100AFG) to obtain pulverized polyamide 6 powder with a D50 particle size of 50 μm and a sphericity of 60. Three-dimensional fabrication was performed in the same manner as in Production Example 1, except that this pulverized polyamide 6 was used, and the heat-loaded powder composition (A1) was recovered. The D50 particle size of this powder composition (A1) was 54 μm, and the weight-average molecular weight (MwA) was 74,000.

[Manufacturing Example 4]
20 kg of powder composition (B) was obtained in the same manner as in Production Example 1, except that 14 kg of polyamide 6 powder and 6 kg of glass fiber EFH-150-01 (manufactured by Central Glass Co., Ltd.) as a reinforcing filler were mixed. The three-dimensional molded object was manufactured in the same manner as in Production Example 1, and the powder composition (A1) that had been subjected to heat load was recovered. The D50 particle size of this powder composition (A1) was 54 μm, and the weight-average molecular weight (MwA) was 75,000.

[Example 1]
The powder composition (A1) obtained in Production Example 1 was passed through a 70-mesh filter with a wire diameter of 0.15 mm and a mesh size of 212 μm to remove fused aggregates and obtain powder composition (A2). 5.0 kg of this powder composition (A2) and 5.0 kg of the powder composition (B) from Production Example 1 were placed in a cross-rotary mixer and mixed by oscillating force to obtain material powder (C). When 500 g of this material powder (C) was passed through a filter with a mesh size of 250 μm, the weight of the material captured by the filter was 0.02 g, or 0.004 mass%. Using 10 kg of this material powder (C), molding was performed under the same conditions as in Production Example 1, and the time during which a thermal load was applied during molding was 8 hours. No aggregates were observed in the obtained three-dimensional molded object by X-ray CT, with a volume of 0.000%, a flexural modulus of 5500 MPa, a flexural strength of 110 MPa, and a load deflection temperature of 217°C. Furthermore, the bending strength was 110 MPa on average for n=10 and 105 MPa at the minimum for n=10, indicating "good" quality stability. Figure 2 shows the X-ray CT images of the samples used for observing the aggregates.

[Example 2]
The powder composition (A1) obtained in Production Example 2 was passed through a 70-mesh filter with a wire diameter of 0.15 mm and a mesh size of 212 μm to remove fused aggregates and obtain powder composition (A2). 7.0 kg of this powder composition (A2) and 3.0 kg of the powder composition (B) from Production Example 2 were filled into a cross-rotary mixer and mixed by oscillating force to obtain material powder (C). When 500 g of this material powder (C) was passed through a filter with a mesh size of 250 μm, the weight of the material captured by the filter was 0.04 g, or 0.008 mass%. When a three-dimensional object was fabricated using this material powder (C), the aggregate content of the obtained three-dimensional object in X-ray CT was 0.000 volume%, the flexural modulus was 7200 MPa, the flexural strength was 113 MPa, and the load deflection temperature was 218°C. Furthermore, the bending strength averaged 113 MPa for n=10 and the minimum value for n=10 was 107 MPa, indicating "good" quality stability.

[Example 3]
The powder composition (A1) obtained in Production Example 3 was passed through a 50-mesh filter with a wire diameter of 0.21 mm and a mesh size of 300 μm to remove fused aggregates and obtain powder composition (A2). 5.0 kg of this powder composition (A2) and 5.0 kg of the powder composition (B) from Production Example 3 were filled into a cross-rotary mixer and mixed by oscillating force to obtain material powder (C). When 500 g of this material powder (C) was passed through a filter with a mesh size of 250 μm, the weight of the material captured by the filter was 0.3 g, or 0.06 mass%. When a three-dimensional object was fabricated using this material powder (C), the aggregate content in the X-ray CT of the obtained three-dimensional object was 0.03 volume%, the flexural modulus was 5300 MPa, the flexural strength was 111 MPa, and the load deflection temperature was 215°C. Furthermore, the flexural strength averaged 111 MPa for n=10 and the minimum value for n=10 was 102 MPa, indicating "good" quality stability.

[Comparative Example 1]
Material powder (C) was prepared in the same manner as in Example 1, except that the powder composition (A1) obtained in Production Example 1 was used without passing it through a filter. When 500 g of this material powder (C) was passed through a filter with a mesh size of 250 μm, the weight of the material captured by the filter was 5.52 g, or 1.1 mass%. When a three-dimensional object was fabricated using this material powder (C), the aggregates observed in the X-ray CT of the resulting three-dimensional object were 0.2 volume%, the flexural modulus was 5300 MPa, the flexural strength was 108 MPa, and the load deflection temperature was 217°C. Furthermore, the flexural strength was 108 MPa on average for n=10 and 94 MPa on minimum for n=10, indicating poor quality stability. X-ray CT images of the samples used to observe the aggregates are shown in Figures 3(A) and (B).

[Comparative Example 2]
The powder composition (A1) obtained in Production Example 4 was passed through a 16-mesh filter with a wire diameter of 0.59 mm and a mesh opening of 1000 μm to remove fused aggregates and obtain powder composition (A2). 5.0 kg of this powder composition (A2) and 5.0 kg of the powder composition (B) from Production Example 4 were filled into a cross-rotary mixer and mixed by oscillating force to obtain material powder (C). When 500 g of this material powder (C) was passed through a filter with a mesh opening of 250 μm, the weight of the material captured by the filter was 9.26 g, or 1.9 mass%. When a three-dimensional object was fabricated using this material powder (C), the aggregate content in the X-ray CT of the obtained three-dimensional object was 0.8 volume%, the flexural modulus was 4400 MPa, the flexural strength was 103 MPa, and the load deflection temperature was 213°C. Furthermore, the flexural strength was 103 MPa on average for n=10 and 85 MPa on minimum for n=10, indicating that the quality stability was "poor".

The three-dimensional molded objects of the present invention exhibit excellent quality stability and reliability even during recycled molding, and show good mechanical properties without variation. Three-dimensional molded objects obtained using the manufacturing method of the present invention can be effectively used in mobility applications such as automobiles, aerospace, and space, which require high reliability, as well as in medical applications such as prosthetics, orthotics, hearing aids, and catheters, and in electrical appliance applications such as home appliances and power tools. Furthermore, it is possible to obtain three-dimensional molded objects with complex shapes that have been optimally designed.

1. Tank for forming the molded object 2. Stage of the tank for forming the molded object 3. Supply tank for pre-filling the supplied powder composition 4. Stage of the tank for pre-filling the supplied powder composition 5. Recoater 6. Thermal energy 7. X, Y, Z coordinate system 8. Surface direction for layering the powder composition 9. Height direction for layering the powder composition 10. Three-dimensional molded object P. Material powder

Claims (9)

The present invention relates to a powder composition (A1) having a D50 particle size of 1 μm to 100 μm, wherein the powder composition (A1) contains 5% to 60% by mass of thermoplastic resin particles and glass fibers as reinforcing fillers based on the powder composition, and the powder composition (A1) has a D50 particle size of 1 μm to 100 μm, wherein a thermal load is applied to the powder composition (A1) at a temperature above the crystallization temperature and below the melting point of the thermoplastic resin during three-dimensional molding, and the powder composition (A1) that remains without melting and sintering in the layer forming the molded object is used to remove fused aggregates, in which two or more thermoplastic resin particles are fused together and contain reinforcing fillers, by passing them through a filter having a mesh opening of 50 μm to 300 μm to obtain a material powder (C).
A method for producing material powder for recycling and three-dimensional fabrication using selective laser sintering , wherein the amount of fused aggregates in the obtained material powder (C) is 1.0% by mass or less based on the material powder (C). The method for producing a material powder for three-dimensional molding according to claim 1, wherein the material powder (C) contains, in a ratio of 0 to 200 parts by mass of a powder composition (B) that has not been subjected to a thermal load, relative to 100 parts by mass of powder composition (A1). The method for producing a material powder for three-dimensional molding according to claim 2, wherein the ratio (MwA)/(MwB) of the weight-average molecular weight of the thermoplastic resin constituting the powder composition (A1) to the weight-average molecular weight of the thermoplastic resin constituting the powder composition (B) is 1.0 or more and 2.0 or less. The method for producing a material powder for three-dimensional molding according to claim 1, wherein the sphericity of the thermoplastic resin particles is 80 or more and 100 or less. The method for producing a material powder for three-dimensional molding according to claim 1, wherein the brightness of the powder composition (A1) is 20 or more and 95 or less. A method for manufacturing a three-dimensional object, comprising manufacturing a material powder for three-dimensional molding by the manufacturing method described in any one of claims 1 to 5 , and then supplying it to a three-dimensional molding apparatus. The method for producing a three-dimensional object according to claim 6 , wherein the aggregate content observed by X-ray CT observation of the obtained three-dimensional object is 0.1 volume% or less. A method for manufacturing a three-dimensional object according to claim 6 , wherein the load deflection temperature of the obtained three-dimensional object at 0.45 MPa is 150°C or higher. The method for manufacturing a three-dimensional object according to claim 6 , wherein the resulting three-dimensional object has a bending modulus of 3000 MPa or more.