Powder composition and production method for three-dimensional fabricated article

Abstract

A powder composition from which a molded body having high thermal conductivity can be obtained, the powder composition containing an aluminum nitride powder and a polyamide powder, wherein the aluminum nitride powder content is 70-95 mass%.

Description

Powder composition and method for producing three-dimensional object

[0001] The present invention relates to a powder composition and a method for producing a three-dimensional object.

[0002] Additive manufacturing is a technology used in three-dimensional modeling methods, such as 3D printers, to create three-dimensional shapes by attaching modeling materials, and has been rapidly gaining popularity in recent years.

[0003] Additive manufacturing techniques can be classified into several methods based on the type of material and modeling method (e.g., ISO 17296-2:2015). One of these methods is powder bed fusion (PBF). In PBF, a three-dimensional object is obtained by layering and melting powder materials. The properties of the three-dimensional object obtained in PBF depend on the powder material.

[0004] For example, Patent Document 1 discloses a molding powder used in powder additive manufacturing, which is made of a powder containing a ceramic and a binder. Patent Document 2 discloses a molding material used in powder additive manufacturing, which is made of an inorganic material and at least partly contains a resin material.

[0005] Japanese Patent Publication No. 2017-127997 Japanese Patent Publication No. 2018-172739

[0006] Additive manufacturing technology is expected to be applied in a variety of fields because it can easily produce three-dimensional objects. Conventionally, composite compositions of resin and aluminum nitride, which has high thermal conductivity, have been used for heat dissipation materials. However, if additive manufacturing technology can be used to easily produce objects, it is expected that it will be used in a variety of situations where high thermal conductivity is required.

[0007] However, Patent Documents 1 and 2 do not describe or suggest how to obtain a molded body with high thermal conductivity. Furthermore, when a molded body is obtained using a powder composition containing aluminum nitride powder and a resin as a material, it is unclear what physical properties, including thermal conductivity, the molded body will have depending on the type of resin.

[0008] An object of one aspect of the present invention is to provide a powder composition or the like that can give a molded product with high thermal conductivity.

[0009] In order to solve the above-mentioned problems, a powder composition according to one aspect of the present invention contains aluminum nitride powder and polyamide powder, and the content of the aluminum nitride powder is 70 mass % or more and 95 mass % or less.

[0010] According to one aspect of the present invention, a powder composition or the like that can give a molded product with high thermal conductivity can be realized.

[0011] Hereinafter, one embodiment of the present invention will be described in detail.

[0012] [Powder composition] A powder composition according to one embodiment of the present invention contains aluminum nitride powder and polyamide powder, and the content of the aluminum nitride powder is 70% by mass or more and 95% by mass or less. Hereinafter, in this specification, the term "powder composition" refers to the powder composition according to one embodiment of the present invention, unless otherwise specified.

[0013] The use of the powder composition is not particularly limited, but it is preferably used as a material for molding a compact, and more preferably used as a material for forming a three-dimensional object by an additive manufacturing method.

[0014] (Aluminum Nitride Powder) The aluminum nitride powder is composed of a plurality of aluminum nitride particles formed from aluminum nitride.

[0015] The content of aluminum nitride powder in the powder composition is 70% by mass or more and 95% by mass or less, with the entire powder composition being 100% by mass. This configuration effectively improves the thermal conductivity of a molded body formed using the powder composition. From the viewpoint of obtaining excellent thermal conductivity in the molded body, the content of aluminum nitride powder may be 80% by mass or more, or may be 90% by mass or more.

[0016] The aluminum nitride powder preferably has an average particle size of 20 μm or more and 60 μm or less. A powder composition containing aluminum nitride powder having such an average particle size tends to have good flowability.

[0017] For example, when a powder composition is layered by an additive manufacturing method to form a structure, the powder composition is spread in a layer of uniform thickness over the entire surface of the forming region of each layer. In this case, the better the fluidity of the powder composition, the easier it is to layer the powder composition to a uniform thickness. If the average particle size of the aluminum nitride powder is within the above-mentioned range, the fluidity of the powder composition is improved, and the powder composition can be easily layered to a uniform thickness.

[0018] Specifically, in additive manufacturing, the thickness of each layer formed from the powder composition is generally about 100 μm. The average particle size of the aluminum nitride powder is preferably smaller than the thickness of each layer, and is preferably 60 μm or less. However, if the average particle size is too small, the flowability of the powder composition will deteriorate, so the average particle size of the aluminum nitride powder is preferably 20 μm or more.

[0019] The average particle size of the aluminum nitride powder is the particle size (median diameter) at which the cumulative 50% value is reached on a volume basis in the particle size distribution measured by a laser diffraction scattering method.

[0020] The aluminum nitride powder preferably has an average circularity of 0.8 or more, more preferably 0.9 or more. Generally, the closer the circularity of a particle is to 1.0, the closer the particle is to a perfect sphere. Aluminum nitride powder with an average circularity of 0.8 or more can be said to be composed of approximately spherical aluminum nitride particles.

[0021] The powder composition contains 70 mass% or more of aluminum nitride powder. As such, it is preferable that the aluminum nitride powder, which accounts for a large portion of the powder composition, has an average circularity of 0.8 or more. Spherical powder with a high average circularity exhibits good fluidity, and can therefore improve the fluidity of the powder composition.

[0022] The circularity of a particle contained in an aluminum nitride powder can be calculated by the following formula (1), where S is the projected area of ​​the imaged particle and L is the perimeter.

[0023] Circularity = 4πS / L ２ (1) The average circularity of the aluminum nitride powder may be the number average value of the circularity of a plurality of particles contained in the aluminum nitride powder.

[0024] (Polyamide Powder) The polyamide powder is composed of a plurality of polyamide particles formed from polyamide.

[0025] The polyamide used as the raw material for the polyamide powder may be an aliphatic polyamide such as nylon, or an aromatic polyamide such as aramid. Examples of polyamides include nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 612, nylon 6T, nylon 6I, nylon 9T, and nylon M5T. Of these, nylon 6, nylon 11, or nylon 12 is preferred, and nylon 12 is more preferred. The polyamide may be any one of these, or may contain two or more of them.

[0026] As described above, aluminum nitride powder is effective in improving the thermal conductivity of compacts molded from a powder composition containing aluminum nitride powder. Generally, the surface of aluminum nitride powder is oxidized, resulting in the presence of hydroxyl groups. The polyamide that constitutes the polyamide powder has amide groups that have a high affinity for the hydroxyl groups present on the surface of the aluminum nitride powder. When such a powder composition is molded using additive manufacturing methods or the like, the high affinity between the resin and the aluminum nitride powder allows the aluminum nitride powder to disperse appropriately, facilitating the formation of thermal conduction paths between the aluminum nitride powder particles in the molded body. The formation of these thermal conduction paths is believed to result in excellent thermal conductivity in the molded body.

[0027] In the manufacturing method of resin-containing molded bodies by melt-kneading, it was possible to disperse aluminum nitride powder appropriately in the resin due to the load during melt-kneading, and form thermal conduction paths between the aluminum nitride powder particles. However, unlike melt-kneading, additive manufacturing requires a high affinity between the resin and aluminum nitride powder to achieve high thermal conductivity.

[0028] The polyamide powder preferably has an average particle size of 20 μm or more and 60 μm or less. A powder composition containing a polyamide powder having such an average particle size tends to have good flowability. The reason for this is as explained above regarding the average particle size of the aluminum nitride powder.

[0029] The average particle size of the polyamide powder is the particle size (median diameter) at which the cumulative 50% value is reached on a volume basis in the particle size distribution measured by the laser diffraction scattering method, as in the case of the aluminum nitride powder.

[0030] In the powder composition, it is preferable that the aluminum nitride powder has an average particle size of 20 μm or more and 60 μm or less, and the polyamide powder has an average particle size of 20 μm or more and 60 μm or less. In this configuration, the average particle sizes of the aluminum nitride powder and the polyamide powder are not significantly different from each other, and therefore, the powder composition has good flowability.

[0031] It is generally known that the more uniform the particle size of the powder contained in a powder composition, the better the fluidity. This is thought to be because when powders with large particle sizes and powders with small particle sizes are mixed, the powders with small particle sizes get into the gaps between the powders with large particle sizes and inhibit the flow of the powders with large particle sizes, thereby reducing the fluidity of the powder as a whole. If the average particle size of the aluminum nitride powder and the average particle size of the polyamide powder are close to each other, the powder composition will have good fluidity.

[0032] The ratio of the average particle size of the polyamide powder to the average particle size of the aluminum nitride powder (average particle size of the polyamide powder / average particle size of the aluminum nitride powder) is preferably in the range of 0.5 or more and 2.0 or less, and more preferably in the range of 0.7 or more and 1.4 or less.

[0033] The content of polyamide powder in the powder composition according to one embodiment of the present invention is not particularly limited, but from the viewpoint of ease of molding in an additive manufacturing method, it is preferably 3% by mass or more, and more preferably 5% by mass or more.

[0034] (Other Powders) The powder composition may contain other powders in addition to aluminum nitride powder and polyamide powder. The other powders may be, for example, inorganic or organic powders. The inorganic powders may be, for example, powders of glass beads, glass fibers, carbon fibers, or alumina. The organic powders may be powders of resins other than polyamides or cellulose fibers, etc. The resins other than polyamides are not particularly limited, but are preferably polar resins such as polyurethane and polyether ether ketone, or may be non-polar resins such as polyolefins.

[0035] The content of the other powder in the powder composition may be, for example, 25% by mass or less, 10% by mass or less, or 1% by mass or less. The average particle size of the other powder is not particularly limited, but is preferably close to the average particle size of the aluminum nitride powder or polyamide powder from the viewpoint of flowability of the powder composition.

[0036] The average particle size of the other powders may be measured in the same manner as the average particle size of the aluminum nitride powder and the polyamide powder.

[0037] [Method for manufacturing a three-dimensionally shaped object] A method for manufacturing a three-dimensionally shaped object according to one embodiment of the present invention is a method for manufacturing a three-dimensionally shaped object by an additive manufacturing method using the powder composition described above. Hereinafter, in this specification, the term "method for manufacturing a three-dimensionally shaped object" refers to the method for manufacturing a three-dimensionally shaped object according to one embodiment of the present invention, unless otherwise specified.

[0038] Additive manufacturing is a technology for creating three-dimensional shapes by depositing a material for creation. A method for creating a three-dimensional object using additive manufacturing can be implemented, for example, using a 3D printer.

[0039] Additive manufacturing can be classified into several types based on the type of material and fabrication method (e.g., ISO 17296-2:2015). Examples of such additive manufacturing methods include powder bed fusion (PBF), liquid-phase photopolymerization, binder jetting, material jetting, material extrusion, directed energy deposition, and sheet lamination. Additionally, additive manufacturing methods not classified by ISO 17296-2:2015 are also known.

[0040] The method for manufacturing a three-dimensional object is preferably a powder additive manufacturing method. The powder additive manufacturing method is a method for forming a desired shape by repeatedly laying raw material powder for forming in layers and irradiating the portion to be formed with a laser to melt and solidify or sinter the raw material powder. Examples of the powder additive manufacturing method include the SLS method (Selective Laser Sintering), which is a type of powder bed fusion method classified in ISO 17296-2:2015.

[0041] The powder composition according to one embodiment of the present invention contains polyamide powder, which is a thermoplastic resin. Therefore, it is possible to mold the polyamide resin by melting and solidifying it with a laser, for example, and it is also possible to mold the powder composition by partially melting and solidifying the surface of the powder composition.

[0042] The powder composition according to one embodiment of the present invention can be suitably used as a material for forming a three-dimensional object by an additive manufacturing method such as powder layer modeling. For example, a resin composition having a desired shape and high thermal conductivity can be easily produced by spreading the powder composition according to one embodiment of the present invention in layers and irradiating the portion to be formed with a laser to melt and solidify the resin. That is, by using a powder composition containing an aluminum nitride powder according to one embodiment of the present invention and a polyamide powder as a material, a three-dimensional object having excellent thermal conductivity can be easily produced.

[0043] The thermal conductivity of a three-dimensional object obtained by additive manufacturing using the powder composition is preferably 1.0 W / m K or more, and more preferably 1.3 W / m K or more. There is no particular upper limit to the thermal conductivity, and the higher the thermal conductivity, the better, but it is usually 5.0 W / m K or less. Furthermore, in the method for producing a three-dimensional object by additive manufacturing using the powder composition, the strength, density, appearance, etc. of the molded object can also be improved.

[0044] Additive manufacturing is suitable for rapid prototyping, on-demand production of jigs and tools, custom production of parts for commercial products, and small-lot production. In these applications, three-dimensional objects obtained by additive manufacturing may require high thermal conductivity. Examples of three-dimensional objects requiring high thermal conductivity include thermal sinks for drones or electric vehicles, heat exchangers and heat recovery systems for solar hot water heaters, heat sinks for light-emitting diodes (LEDs), molds for vacuum forming, and functional parts that combine thermal conductivity and electromagnetic wave shielding.

[0045] A powder composition according to one embodiment of the present invention and a method for producing a three-dimensionally shaped object using the powder composition can be suitably used for producing such three-dimensionally shaped objects that require high thermal conductivity.

[0046] [Summary] The powder composition according to aspect 1 of the present invention contains aluminum nitride powder and polyamide powder, and the content of the aluminum nitride powder is 70% by mass or more and 95% by mass or less.

[0047] In the powder composition according to Aspect 2 of the present invention, in Aspect 1, the aluminum nitride powder may have an average particle size of 20 μm or more and 60 μm or less, and the polyamide powder may have an average particle size of 20 μm or more and 60 μm or less.

[0048] A powder composition according to a third aspect of the present invention may be the powder composition according to the first or second aspect, wherein the aluminum nitride powder has an average circularity of 0.8 or more.

[0049] The powder composition according to Aspect 4 of the present invention may be used as a material for forming a three-dimensional object by an additive manufacturing method in any one of Aspects 1 to 3.

[0050] A method for manufacturing a three-dimensional structure according to a fifth aspect of the present invention is a method for manufacturing a three-dimensional structure by an additive manufacturing method using the powder composition according to any one of the first to fourth aspects.

[0051] A method for manufacturing a three-dimensional structure according to a sixth aspect of the present invention may be the method for manufacturing a three-dimensional structure according to the fifth aspect, in which the additive manufacturing method is a powder additive manufacturing method.

[0052] The use of a powder composition according to a seventh aspect of the present invention in additive manufacturing is the use of a powder composition comprising an aluminum nitride powder and a polyamide powder, wherein the content of the aluminum nitride powder is 70% by mass or more and 95% by mass or less.

[0053] An embodiment of the present invention will now be described.

[0054] A thermoplastic resin powder and aluminum nitride powder (average particle size 30 μm) were mixed and stirred for 2 hours using a roller mixer. The mixed powder was then passed through an ultrasonic sieve (mesh opening 250 μm) to obtain a powder composition according to the example or comparative example. The obtained powder composition was used to create a three-dimensional object by powder layer modeling using a 3D printer (SINTERIT LISA PRO manufactured by SINTERIT).

[0055] In Examples 1 and 2, nylon 12 (PA12, PA12 smooth manufactured by SINTERIT, average particle size 40 μm) was used as the thermoplastic resin powder. In Comparative Example 1, polypropylene (PP, Bapolene 4082NA manufactured by Bamberger Polymers, average particle size 22 μm) was used as the thermoplastic resin powder. Tokuyama aluminum nitride powder HFS-30 (average particle size 30 μm, average circularity 0.94) was used as the aluminum nitride powder. The contents of the thermoplastic resin powder and aluminum nitride powder in the powder composition are shown in Table 1 below.

[0056] The average particle size of the aluminum nitride powder was measured as follows. The aluminum nitride powder was dispersed in water at a concentration of 0.2% by mass, and the sample was dispersed by irradiating it with ultrasonic waves at about 200 W for 2 minutes. The volume frequency distribution of particle sizes (particle size distribution) was measured using a laser diffraction / scattering particle size distribution analyzer (MICROTRACK-MT3300EXII, manufactured by Microtrack-Bell Co., Ltd.). In the obtained particle size distribution, the volume frequency was accumulated from the smallest particle size, and the particle size (median diameter) at which the accumulated value reached 50% was defined as the average particle size.

[0057] The average particle size of the thermoplastic resin powder was measured using a laser diffraction / scattering particle size distribution analyzer (LS 13 320, manufactured by Beckman Coulter) equipped with a tornado dry powder module, in accordance with a method in accordance with ISO 13320. In the obtained particle size distribution, the volume frequency was accumulated from the smallest particle size, and the particle size (median diameter) at which the accumulated value reached 50% was defined as the average particle size.

[0058] The average circularity of the aluminum nitride powder was determined by measuring the area and perimeter of the two-dimensional projection of 20,000 particles using Morphologi G3 manufactured by Malvern Instruments, and then calculating it from the formula (1).

[0059] The thermal conductivity of the obtained three-dimensionally shaped object was measured using a thermal conductivity measuring device (TRIDENT manufactured by C-Therm Technologies) utilizing an improved unsteady plane heat source and a Pyroceram calibration standard, in accordance with a method in accordance with ASTM D7984.

[0060] The manufacturing conditions and the physical properties of the obtained three-dimensional objects are shown in Table 1 below.

[0061] In Table 1, PA12 represents polyamide 12 (nylon 12), PP represents polypropylene, and AlN represents aluminum nitride powder.

[0062]

[0063] As shown in Table 1, the three-dimensionally shaped objects according to Examples 1 and 2 had good thermal conductivity, with a thermal conductivity of 1.0 W / m·K or more. On the other hand, the three-dimensionally shaped object according to Comparative Example 1 had a thermal conductivity of less than 1.0 W / m·K, which was about half that of the three-dimensionally shaped objects according to Examples 1 and 2.

[0064] The above results demonstrate that three-dimensionally shaped objects obtained using the powder composition according to one embodiment of the present invention have excellent thermal conductivity. On the other hand, when polyamide was not used as the thermoplastic resin, problems with the thermal conductivity of the three-dimensionally shaped objects were observed, as shown in Comparative Example 1. In other words, it was demonstrated that the physical properties of the resulting three-dimensionally shaped objects vary significantly depending on the type of resin mixed with the aluminum nitride powder, and that polyamide powder is suitable for mixing with aluminum nitride powder.

[0065] [Additional Notes] The present invention is not limited to the above-described embodiments and examples, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments or examples are also included in the technical scope of the present invention. Furthermore, new technical features can be formed by combining the technical means disclosed in each embodiment.

Claims

1. A powder composition comprising aluminum nitride powder and polyamide powder, wherein the content of the aluminum nitride powder is 70% by mass or more and 95% by mass or less.

2. The powder composition according to claim 1, wherein the average particle size of the aluminum nitride powder is 20 μm or more and 60 μm or less, and the average particle size of the polyamide powder is 20 μm or more and 60 μm or less.

3. The powder composition according to claim 1, wherein the aluminum nitride powder has an average circularity of 0.8 or more.

4. The powder composition according to claim 1, which is used as a material for forming a three-dimensional object by an additive manufacturing method.

5. A method for manufacturing a three-dimensional object, comprising forming a three-dimensional object by an additive manufacturing method using the powder composition according to any one of claims 1 to 4.

6. The method for manufacturing a three-dimensional object according to claim 5, wherein the additive manufacturing method is by a powder lamination forming method.

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