Materials for 3D modeling, molded articles, and methods for manufacturing the same.

Abstract

The present invention provides a 3D printing material containing a resin composition that utilizes existing resin powders, maintains safety during powder manufacturing, and exhibits excellent moldability in 3D printing and impact resistance of the resulting molded product. [Solution] A material for three-dimensional molding comprising resin powder (A) and resin powder (B) having a different resin composition from resin powder (A), wherein the average particle size (D50) of resin powder (A) is 30 μm or more and 250 μm or less as measured by laser diffraction, and the average particle size (D50) of resin powder (B) is 1 μm or more and less than 30 μm as measured by laser diffraction. A method for manufacturing a molded body, comprising the step of molding a molded body in three dimensions by powder bed fusion using this three-dimensional molding material.

Description

Technical Field

[0001] The present invention relates to a material for three-dimensional shaping, and more particularly to a material for three-dimensional shaping containing two kinds of resin powders having different resin compositions and particle sizes. The present invention also relates to a molded body using this material for three-dimensional shaping and a method for manufacturing the same.

Background Art

[0002] Today, three-dimensional printers (hereinafter sometimes referred to as "3D printers") using various additive manufacturing methods (such as binder jetting, material extrusion, vat photopolymerization, etc.) are being sold. Among these, a 3D printer system using the powder bed fusion method, for example, a system manufactured by 3D Systems in the United States, heats and melts a thin layer (powder bed) of a powder material such as resin to a temperature near the melting point of the resin powder using a heating means such as a high-power CO2 laser, and is used to construct a three-dimensional object in layers based on a computer-aided design (CAD) model. Here, the laser used as the heating means scans the cross-section in the X-Y direction on the surface of the powder bed formed based on the 3D CAD data to selectively melt the powder material. In this way, a three-dimensional molded body can be obtained by repeating the formation of the powder bed and melting by the laser to form a laminate. This system does not require the use of a mold, can use various resin powders as raw materials as long as they have a certain degree of heat resistance, and the reliability of the obtained molded body is also high, so it is a technology that has attracted attention in recent years.

[0003] As the material type of the resin powder used in 3D printers, crystalline thermoplastic resins are used due to their shaping principle. In particular, polyamide-based resins such as nylon 12 and nylon 11 are widely used. In recent years, in addition to polyamide-based resins, polyester-based resins such as polybutylene terephthalate, polyolefin-based resins such as polypropylene, and elastomer-based resins such as thermoplastic polyurethane are also used.

[0004] Traditionally, 3D printers have been widely used for product prototyping, but in recent years, their application to functional parts used in actual applications has also been considered. When considering actual applications, such as for components in home appliances, building materials, aircraft, and automobiles, it is desirable that molded parts produced using 3D printing materials possess high mechanical properties. However, due to the molding principle, molded products produced by powder bed fusion tend to have voids within the molded body, resulting in inferior mechanical properties. In particular, it is difficult to impart the high impact resistance of materials currently used in automotive components and other applications.

[0005] As an investigation into improving the mechanical properties of molded articles produced by powder bed fusion, for example, Patent Document 1 discloses a method for obtaining powder with excellent tensile elongation at break by specifying the ethylene content molar ratio and melt flow rate of the polypropylene resin within a specific range. Furthermore, Patent Document 2 discloses a method for obtaining a powder with excellent strength in the lamination direction of a molded body by melt-kneading talc as a filler into a polypropylene resin and specifying the mass ratio of silicon dioxide to the total mass of the resulting resin powder within a specific range. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] International Publication No. 2020 / 213586 [Patent Document 2] Japanese Patent Publication No. 2020-93515 [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] For 3D printers to be widely applied to functional parts used in real-world applications, it is desirable that existing resin powders be used to improve the formability of 3D printing and the impact resistance of the resulting molded parts, and that safety during material manufacturing be ensured.

[0008] However, Patent Document 1 requires polymerization of an ethylene-propylene copolymer of a specific composition, which is undesirable from the viewpoint of raw material production and procurement. Patent Document 2 contains talc that falls under the GHS classification, raising concerns about safety during grinding. Furthermore, in none of the examples was an improvement in the impact resistance of the resulting molded body observed.

[0009] The present invention aims to solve the above problems by providing a 3D printing material containing a resin composition that uses existing resin powders, maintains safety during powder manufacturing, and exhibits excellent moldability in 3D printing and impact resistance of the resulting molded articles. [Means for solving the problem]

[0010] The inventors of this invention conducted extensive research to solve the above problems and discovered that these problems can be solved by using a 3D molding material containing two types of resin powders with different resin compositions and particle sizes, leading to the development of this invention.

[0011] In other words, the gist of this invention is as follows:

[0012] [1] A material for three-dimensional molding comprising a resin powder (A) and a resin powder (B) having a different resin composition from the resin powder (A), wherein the average particle size (D50) of the resin powder (A) is 30 μm or more and 250 μm or less as measured by laser diffraction, and the average particle size (D50) of the resin powder (B) is 1 μm or more and less than 30 μm as measured by laser diffraction.

[0013] [2] The average particle diameter (D50) of the resin powder (B) is 3% or more and 30% or less of the average particle diameter (D50) of the resin powder (A), and the three-dimensional shaping material according to [1].

[0014] [3] The resin powder (B) is a powder of polyethylene and / or a thermosetting elastomer, and the three-dimensional shaping material according to [1] or [2].

[0015] [4] The viscosity average molecular weight (Mv) of the polyethylene is 500,000 or more and 10,000,000 or less, and the three-dimensional shaping material according to [3].

[0016] [5] The resin powder (A) is a powder of a polyolefin resin, and the three-dimensional shaping material according to any one of [1] to [4].

[0017] [6] The polyolefin resin is a propylene-based polymer, and the three-dimensional shaping material according to [5].

[0018] [7] It is in powder form, and the three-dimensional shaping material according to any one of [1] to [6].

[0019] [8] It is a three-dimensional shaping material by the powder bed fusion method, and the three-dimensional shaping material according to any one of [1] to [7].

[0020] [9] A molded body obtained by using the three-dimensional shaping material according to any one of [1] to [8].

[0021]

[10] A method for manufacturing a molded body, including a step of three-dimensionally shaping a molded body by the powder bed fusion method using the three-dimensional shaping material according to any one of [1] to [8].

Advantages of the Invention

[0022] According to the present invention, it is possible to provide a three-dimensional shaping material that uses existing resin powder and, while maintaining the safety during powder production, is excellent in shaping properties in a 3D printer and the impact resistance of the resulting shaped body. Further, according to the present invention, there are provided a shaped body by powder bed fusion and a method for producing the same using this three-dimensional shaping material.

Mode for Carrying Out the Invention

[0023] Hereinafter, a mode for carrying out the present invention (hereinafter referred to as "the present embodiment") will be described in detail. The following present embodiment is an exemplification for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be variously modified and implemented within the scope of its gist.

[0024] 〔Three-dimensional shaping material〕 The three-dimensional shaping material of the present invention includes a resin powder (A) (hereinafter sometimes referred to as "the resin powder (A) of the present invention") and a resin powder (B) having a resin composition different from the resin powder (A) (hereinafter sometimes referred to as "the resin powder (B) of the present invention"), wherein the average particle diameter (D50) of the resin powder (A) is 30 μm or more and 250 μm or less as measured by the laser diffraction method, and the average particle diameter (D50) of the resin powder (B) is 1 μm or more and less than 30 μm as measured by the laser diffraction method. Hereinafter, the resin that is the material of the resin powder (A) may be referred to as "resin (a)", and the resin that is the material of the resin powder (B) may be referred to as "resin (b)".

[0025] The three-dimensional shaping material of the present invention is used in the powder bed fusion method and contains at least the resin powder (A) and the resin powder (B) of the present invention.

[0026] The three-dimensional shaping material of the present invention is preferably a material used for shaping a three-dimensional shaped object (resin shaped body) by a 3D printer, particularly by the powder bed fusion method.

[0027] The shape of the 3D printing material can be any shape that is applicable to various types of 3D printers, such as powder bed fusion and multi-jet fusion. The 3D printing material of the present invention is preferably used in powder bed fusion.

[0028] [mechanism] Although the details of the mechanism by which the present invention achieves the aforementioned effects are not clear, it can be inferred as follows. In other words, in the 3D modeling material of the present invention, the resin composition of resin powder (A) and resin powder (B) are different, and the particle sizes of resin powder (A) and resin powder (B) are within a predetermined range, with the particle size of resin powder (B) being smaller than the particle size of resin powder (A). As a result, resin powder (B) is present between the particles of resin powder (A), and is more easily incorporated into the layer of the modeled object produced by the melting and flowing of resin powder (A). Therefore, it is presumed that this will reduce the likelihood of cracks and defects occurring in the molded body, improve the mechanical strength of the three-dimensional object, and enable the manufacture of impact-resistant molded bodies with excellent formability.

[0029] [Definition of physical properties] The various physical properties in this invention are measured as follows:

[0030] <Viscosity average molecular weight (Mv)> The viscosity-average molecular weight (Mv) of resin powder (A) and resin powder (B) is calculated using the specific viscosity ηsp (dl / g) of a 0.05% decalin solution at 135°C instead of the intrinsic viscosity [η] (dl / g), in accordance with the method specified in JIS K-7367, or ASTM D4020 for ultra-high molecular weight polyethylene.

[0031] <Average particle size (D50)> The average particle size (D50) of resin powder (A), resin powder (B), and 3D modeling material powder is determined by measuring the particle size distribution of the powder on a volume basis using a particle size distribution analyzer that employs laser diffraction, and then determining the particle size that falls within the 50% frequency distribution of the powder within the detected particle size distribution.

[0032] <Melting point (Tm) · Glass transition temperature (Tg)> The melting points (Tm) of resin powder (A) and resin powder (B) are determined from the thermogram obtained using a differential scanning calorimeter in accordance with JIS K7121. The temperature was raised from room temperature to 200°C at a heating rate of 10°C / min, held at that temperature for 1 minute, then cooled to 50°C at a cooling rate of 10°C / min, and then raised again to 200°C at a heating rate of 10°C / min. The glass transition temperature (Tg) is determined from the thermogram obtained using a differential scanning calorimeter in accordance with JIS K7121. The temperature was raised from room temperature to 200°C at a heating rate of 10°C / min, held at that temperature for 1 minute, then cooled to 50°C at a cooling rate of 10°C / min, and then raised again to 200°C at a heating rate of 10°C / min.

[0033] <Resin composition> In this invention, "different resin compositions" means that the constituent units (monomer species of the resin raw material) that make up the resin are different, specifically the constituent units that constitute the main component (constituent units that make up 50% by mass or more of the resin). Therefore, for example, propylene copolymers that differ in constituent units other than propylene units are considered to have the same resin composition.

[0034] [Resin powder] The resin powder used in the 3D modeling material of the present invention, namely resin powder (A) and resin powder (B), and especially resin powder (A), is preferably obtained using a thermoplastic resin. The resin powder may contain other resins, additives, reinforcing materials, etc., other than thermoplastic resins, to the extent that it does not impair the effects of the present invention. Alternatively, commercially available 3D modeling materials made of thermoplastic resin may be used as the resin powder.

[0035] <Method for producing resin powder> The pulverization methods for producing the resin powder according to the present invention include melt granulation, in which a resin or resin composition (hereinafter sometimes referred to as "resin material") melted near its melting point is formed into fibers and then cut, and pulverization, in which the resin material is cut or destroyed by applying impact or shear. In order to improve the applicability of the powder in powder bed fusion molding, it is preferable that the powder does not contain fine powder of about 10 μm and has a certain particle size and particle size distribution. Therefore, it is preferable to select a suitable pulverization method so that such a suitable powder shape can be obtained.

[0036] As for grinding methods, for example, stamp mills, ring mills, stone mills, mortars, roller mills, jet mills, high-speed rotary mills, hammer mills, pin mills, container-driven mills, disc mills, and media-stirring mills can be employed.

[0037] Furthermore, to prevent the stretching of the resin material due to shear heat generation during pulverization, there is a method of lowering the resin temperature during pulverization by cooling the powder system with liquid nitrogen or the like, thereby producing powder through brittle fracture rather than ductile fracture. This is called low-temperature pulverization or freeze pulverization. In particular, for grinding, it is preferable to use a high-speed rotary mill capable of obtaining powder with a particle size distribution and shape suitable for powder bed fusion molding, as this improves fluidity and powder application during molding. In addition, it is preferable to produce powder by brittle fracture of the resin material using liquid nitrogen, as this suppresses changes in the physical properties and color of the resin material due to grinding.

[0038] Furthermore, it is preferable to perform a classification process after grinding, from the viewpoint of increasing the circularity by removing stretched powder from the ground powder and from the viewpoint of removing fine powder and preventing the powder from flying up during handling. In this case, classification methods include wind classification and sieving classification. In addition, inorganic particles and reinforcing materials described later may be added and mixed to the obtained powder as needed.

[0039] [Resin powder (A)] The resin powder (A) of the present invention may be used alone, or two or more types with different resin compositions and different physical properties may be mixed and used.

[0040] <Resin composition of resin powder (A)> The resin (a) constituting the resin powder (A) used in the present invention is preferably a thermoplastic resin. The thermoplastic resin can be any material that exhibits thermoplasticity due to the heat or light of the 3D printer, and can be appropriately selected depending on the function to be imparted to the molded body.

[0041] As the thermoplastic resin of the resin powder (A), commercially available thermoplastic resin 3D printing materials may be used. Furthermore, when using 3D printing materials for powder bed fusion, the remaining 3D printing material after creating an object using powder bed fusion may be reused. In the three-dimensional molding material of the present invention, by using a combination of resin powder (A) and resin powder (B) described later, it is possible to fabricate a molded body with excellent impact resistance under excellent moldability by using an existing resin powder for powder bed fusion as resin powder (A). However, the resin powder (A) used in the present invention is not limited in any way to an existing resin powder for powder bed fusion.

[0042] Examples of resin (a) in resin powder (A) include polyacetal, polyacrylate, polyacrylic acid, polyamide, polyamide-imide, polyacid anhydride, polyarylate, polyarylene ether, polyarylene sulfide, polybenzoxazole, polyester, polyetherether ketone, polyetherimide, polyetherketone ketone, polyetherketone, polyethersulfone, polyimide, polymethacrylate, polyolefin, polyphthalide, polysilazane, polysiloxane, polystyrene, polysulfide, polysulfonamide, polysulfonate, polythioester, polytriazine, polyurea, polyurethane, polyvinyl alcohol, polyvinyl ester, polyvinyl ether, polyvinyl halide, polyvinyl ketone, polyvinylidene fluoride, polyvinyl aromatic, polysulfone, polyarylene sulfone, polyaryl Examples include ether ketones, polylactic acid, polyglycolic acid, poly-3-hydroxybutyrate, polyhydroxyalkanoate, starch, cellulose esters, poly(phenylene ether), poly(methyl methacrylate), styrene-acrylonitrile copolymer resin, poly(ethylene oxide), epichlorohydrin polymer, polycarbonate homopolymer, polycarbonate copolymer, poly(ester carbonate), poly(ester-siloxane carbonate), poly(carbonate-siloxane), vinyl polymers, acrylonitrile-butadiene-styrene copolymer resin (ABS resin), methyl methacrylate-butadiene-styrene copolymer resin (MBS resin), polyvinyl chloride, olefin-based thermoplastic elastomers, styrene-based thermoplastic elastomers, polyurethane-based thermoplastic elastomers, and polyester-based thermoplastic elastomers.

[0043] These resins may be used in mixtures of two or more types, as appropriate. Furthermore, resin (a) can be appropriately mixed with fillers such as carbon black, carbon fiber, glass fiber, talc, mica, nanoclay, and magnesium, as well as additives such as antioxidants, lubricants, and colorants.

[0044] Among the thermoplastic resins mentioned above, polyolefin resins are preferred as resin (a). Polyolefin resins are particularly useful for a wide range of articles, have good processability, and are recyclable.

[0045] <Polyolefin resins> The polyolefin resin used in this invention is a polymer obtained by polymerization of monomers having a polyolefin backbone. Polyolefins are hydrocarbon resins having carbon double bonds.

[0046] The polyolefin resin is not particularly limited, and homopolymers, block copolymers, and random copolymers of olefins can be suitably used. Examples include polypropylene; propylene copolymers obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, and 4-methyl-1-pentene; polyethylene such as low-density polyethylene, linear low-density polyethylene, medium-density polyethylene, and high-density polyethylene; ethylene copolymers obtained by copolymerizing ethylene with α-olefins such as 1-butene, 1-hexene, and 4-methyl-1-pentene; and poly(1-butene) and poly(4-methyl-1-pentene). These may be used individually or mixed together in groups of two or more with different copolymer component compositions and physical properties.

[0047] In particular, from the viewpoint of obtaining molded articles with excellent heat resistance, propylene polymers are preferred as polyolefin resins. Furthermore, from the viewpoint of moldability, propylene copolymers obtained by copolymerizing propylene with α-olefins such as ethylene, 1-butene, 1-hexene, and 4-methyl-1-pentene are even more preferred, as they can suppress deformation such as crystallization shrinkage during cooling and warping of the molded article during molding. Here, a propylene copolymer is a polypropylene resin containing 50% by mass or more of propylene units in the total monomer units.

[0048] Examples of the propylene copolymers mentioned above include "Novatec® PP," "Wintec®," "Newcon®," and "Wellnex®" manufactured by Nippon Polypropylene Co., Ltd., "Vistamax®" manufactured by ExxonMobil Corporation, and "Versify®" manufactured by Dow Chemical Corporation. These products can be appropriately selected and used individually or in combination of two or more.

[0049] Furthermore, as mentioned above, commercially available polypropylene resin 3D printing materials may be used as the propylene copolymer. When using 3D printing materials for powder bed fusion, the 3D printing material remaining after producing a molded body by powder bed fusion may be reused.

[0050] <Melting point and glass transition temperature of resin powder (A)> The resin powder (A) of the present invention preferably has a melting point or glass transition temperature of 50°C or higher, and more preferably 100°C or higher. Furthermore, from the viewpoint of moldability for obtaining a molded body with excellent impact resistance using resin powder (B), which will be described later, if resin powder (B) is a thermoplastic resin, it can be selected according to the thermal properties such as the melting point and crystallization temperature of resin powder (B). However, it is preferable that the melting points (Tm) measured by differential scanning calorimetry (DSC) are similar for resin powder (A) and resin powder (B). Specifically, the melting point (Tm) of resin powder (A) is preferably 70°C or less, more preferably 40°C or less, and even more preferably 20°C or less than the melting point (Tm) of resin powder (B). This similarity between the melting points (Tm) of resin powder (A) and resin powder (B) is preferable because, during powder bed fusion molding, both resins melt, allowing for sufficient adhesion between them and resulting in high interlayer adhesion in the molded object.

[0051] <Average particle size (D50) of resin powder (A)> The average particle size (D50) of the resin powder (A) of the present invention depends, for example, on the specifications of the system used to fabricate resin molded articles by the powder bed fusion method to which the three-dimensional molding material of the present invention is applied. However, from the viewpoint of applying the powder to a predetermined thickness during fabrication, it is usually 30 μm or more, preferably 35 μm or more, more preferably 40 μm or more, even more preferably 45 μm or more, particularly preferably 50 μm or more, and usually 250 μm or less, preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 120 μm or less.

[0052] <Viscosity-average molecular weight (Mv) of resin powder (A)> The viscosity-average molecular weight (Mv) of the resin powder (A) of the present invention is the viscosity-average molecular weight (Mv) of the resin (a), and is preferably less than 500,000. If the viscosity-average molecular weight (Mv) of the resin powder (A) is 500,000 or higher, the melt viscosity of the resin powder (A) will be high, which may impair the dispersibility and moldability of the molding material during powder bed fusion molding, and is therefore undesirable. There is no particular lower limit to the viscosity-average molecular weight (Mv) of the resin powder (A), but it is preferably 10,000 or higher. If the viscosity-average molecular weight of the resin powder (A) is less than 10,000, the mechanical strength of the molded article obtained by the powder bed fusion method may be insufficient, and it may not be possible to obtain an article with sufficient mechanical strength. From these viewpoints, the viscosity-average molecular weight (Mv) of the resin powder (A), i.e., resin (a), is preferably 500,000 or less, and more preferably 450,000 or less. On the other hand, it is more preferably 50,000 or more, and even more preferably 100,000 or more.

[0053] [Resin powder (B)] The resin powder (B) of the present invention is obtained using a thermoplastic resin or a thermosetting resin. The resin powder (B) may contain other resins, additives, reinforcing materials, etc., other than thermoplastic resins or thermosetting resins, to the extent that they do not impair the effects of the present invention. Alternatively, commercially available thermoplastic resin 3D printing materials may be used as the resin powder (B). When using 3D printing materials for powder bed fusion (PBL) 3D printing, the 3D printing material remaining after producing a molded body by PBL may be reused.

[0054] The resin powder (B) may be of one type only, or it may be a mixture of two or more types with different physical properties such as resin composition, viscosity-average molecular weight (Mv), and average particle size (D50).

[0055] <Resin composition of resin powder (B)> The resin (b) constituting the resin powder (B) of the present invention can be appropriately selected according to the function to be imparted to the molded article. Furthermore, in order to improve the impact resistance of the resulting molded article, it is an essential component that the resin powder (B) of the present invention has a different resin composition from the resin powder (A) of the present invention, and it is particularly preferable to use a resin with different thermal properties and mechanical properties.

[0056] For example, resin (b) can be any resin that can be used as an impact modifier for resins in general, such as polyethylene, polypropylene, polyolefin copolymer, acrylate copolymer, acrylic acid copolymer, vinyl acetate copolymer, styrene copolymer, styrene block copolymer, ionic ethylene copolymer in which some of the acid groups are neutralized with metal ions, core-shell impact modifiers, and mixtures thereof. Among these, it is preferable to use ultra-high molecular weight polyethylene, which has excellent impact resistance. Furthermore, as resin (b), not only thermoplastic resins as described above but also thermosetting resin powders may be used. Examples of thermosetting resins (b) include thermosetting elastomers, such as silicone rubber, fluororubber, acrylic rubber, urethane rubber, polyamide rubber, polysulfide rubber, and natural rubber.

[0057] These resins may be used in mixtures of two or more types as appropriate. Furthermore, resin (b) may be appropriately mixed with fillers such as carbon black, carbon fiber, glass fiber, talc, mica, nanoclay, and magnesium, as well as additives such as antioxidants, lubricants, and colorants.

[0058] <Ultra-high molecular weight polyethylene> The ultra-high molecular weight polyethylene preferably used as the resin (b) in the resin powder (B) of the present invention is an ultra-high molecular weight polyethylene having a viscosity-average molecular weight (Mv) of 500,000 to 10,000,000. Ultra-high molecular weight polyethylene with a viscosity-average molecular weight (Mv) of 500,000 or more is a polyethylene resin with an extremely large molecular weight and a linear molecular structure with almost no branched chains, and is known to have excellent impact resistance-imparting effects.

[0059] If the viscosity-average molecular weight (Mv) of the ultra-high molecular weight polyethylene is less than 500,000, the effect of the present invention, namely the effect of imparting impact resistance to molded articles obtained by 3D printing, may not be achieved. From the viewpoint of imparting impact resistance, the viscosity-average molecular weight (Mv) of the ultra-high molecular weight polyethylene used in the present invention is preferably 1 million or more, and more preferably 2 million or more. On the other hand, if the viscosity-average molecular weight (Mv) of the ultra-high molecular weight polyethylene is excessively large, the fluidity of the ultra-high molecular weight polyethylene will be poor, which may impair the dispersibility and moldability of the molding material during powder bed fusion molding. Therefore, the viscosity-average molecular weight (Mv) of the ultra-high molecular weight polyethylene is preferably 10 million or less, preferably 6 million or less, and more preferably 3 million or less.

[0060] Examples of commercially available ultra-high molecular weight polyethylene include the product names "Hyzex Million (registered trademark)" and "Mipelon (registered trademark)" manufactured by Mitsui Chemicals, and the product name "GUR (registered trademark)" manufactured by Celanese.

[0061] <Average particle size of resin powder (B) (D50)> When used as a material for powder bed fusion, the average particle size (D50) of the resin powder (B) of the present invention is smaller than 30 μm, from the viewpoint of being present between the resin powder (A) particles and being easily incorporated into the layer of the molded object produced by the melting and flowing of the resin powder (A). That is, the average particle size (D50) of the resin powder (B) is smaller than that of the resin powder (A), which has an average particle size (D50) of 30 μm or more and 250 μm.

[0062] If the average particle size (D50) of the resin powder (B) is less than 30 μm, it is preferable because it is smaller than the average particle size (D50) of the molding material for the powder bed fusion method, which is usually between 30 μm and 250 μm. In this case, these molding materials can be suitably used as the resin powder (A), and the uneven distribution of coarse particles tends to be reduced, resulting in better dispersion in the 3D molding material of the present invention. This is preferable because the moldability is maintained when molding a molded body by the powder bed fusion method.

[0063] If the average particle size (D50) of resin powder (B) is 30 μm or larger, resin powder (B) will not adhere to the surface of resin powder (A) but will exist between resin powder (A). In this case, during the molding process of the molded body by the powder bed fusion method, the resin powder (B) present between resin powder (A) inhibits the melting of resin powder (A), making the molded body more prone to cracks and defects, which is undesirable. From this perspective, it is preferable that the average particle size (D50) of the resin powder (B) is 30 μm or less, and particularly 20 μm or less.

[0064] On the other hand, if the average particle size (D50) of the resin powder (B) is 1 μm or larger, scattering and aggregation tend to be less likely to occur when handling or during molding as a material for 3D modeling, which is preferable. From this viewpoint, the average particle size (D50) of the resin powder (B) is preferably 5 μm or larger, and more preferably 10 μm or larger.

[0065] In particular, when using ultra-high molecular weight polyethylene as the resin powder (B), if the average particle size (D50) of the resin powder (B) is smaller than 10 μm, it will adhere to the surface of the resin powder (A), inhibiting the melting of the resin powder (A), and making it easier for cracks and defects to occur in the three-dimensional molded object. Therefore, it is preferable that the average particle size (D50) of the ultra-high molecular weight polyethylene be 10 μm or larger.

[0066] In this invention, the average particle size (D50) of the resin powder (B) may be the particles before they are made into a 3D modeling material, or it may be the average particle size of the particles dispersed in the 3D modeling material by melt mixing or the like. As mentioned above, the average particle size of the particles before they are used as the material for 3D printing is the particle size (D50) located at 50% of the powder frequency distribution in the particle size distribution detected by laser diffraction. Alternatively, the average particle size may be measured by electrical resistance. If dispersed in the material for 3D printing, the average particle size may be obtained from 50 representative particles of the resin powder (B) magnified with an optical microscope or the like. It has been confirmed that nearly equivalent values ​​can be obtained regardless of the average particle size.

[0067] <Melting point (Tm) of resin powder (B)> Furthermore, the melting point (Tm) of the resin powder (B) such as ultra-high molecular weight polyethylene, i.e., the melting point (Tm) of the resin (b), is preferably 100 to 150°C, and more preferably 120 to 140°C, for reasons that the effects of the present invention are superior. Furthermore, as mentioned above, it is preferable that the melting point (Tm) of resin powder (B) is similar to the melting point (Tm) of resin powder (A).

[0068] <Ratio of average particle size (D50) of resin powder (B) to average particle size (D50) of resin powder (A)> The ratio of the average particle size (D50) of resin powder (B) of the present invention to the average particle size (D50) of resin powder (A) of the present invention is preferably 3% or more and 30% or less. A ratio of 3% or more is preferable because it tends to suppress the generation of voids when resin powder (B) and resin powder (A) are mixed, a ratio of 5% or more is more preferable, and a ratio of 10% or more is even more preferable. Furthermore, a ratio of 30% or less is preferable because resin powder (B) tends to disperse well among resin powder (A), and moldability is maintained when forming a molded article by powder bed fusion, a ratio of 25% or less is more preferable, and a ratio of 20% or less is even more preferable. On the other hand, if this ratio exceeds 30%, the resin powder (B) will not adhere to the surface of the resin powder (A) but will exist between the resin powders (A). In this case, during the molding process of the molded body by the powder bed fusion method, the resin powder (B) present between the resin powders (A) may inhibit the melting of the resin powders (A), potentially leading to cracks and defects in the molded body.

[0069] <Content of resin powder (B)> The amount of resin powder (B) in the 3D molding material of the present invention should be selected to satisfy the required impact resistance and moldability of the resulting molded article. Specifically, from the viewpoint of imparting impact resistance, 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the total of resin powder (A) and resin powder (B), is preferred. From the viewpoint of moldability, less than 50 parts by mass is preferred, more preferably 45 parts by mass or less, and even more preferably 40 parts by mass or less. If resin powder (B) is included in amounts of 50 parts by mass or more, many areas will occur in each layer during the 3D molding process where the molten resin does not flow, which may lead to a decrease in interlayer adhesion and result in poor moldability and inferior mechanical properties of the resulting molded article.

[0070] [Other ingredients] The three-dimensional molding material of the present invention may contain, in addition to the resin powder (A) and resin powder (B) of the present invention, commonly used additives as appropriate, within a range that does not significantly impede the effects of the present invention. Examples of such additives include inorganic particles such as silica, alumina, and kaolin, organic particles such as acrylic resin particles and melamine resin particles, pigments such as titanium dioxide and carbon black, weather-resistant stabilizers, heat-resistant stabilizers, antistatic agents, electromagnetic wave absorbers, melt viscosity modifiers, crosslinking agents, lubricants, nucleating agents, plasticizers, anti-aging agents, antioxidants, light stabilizers, ultraviolet absorbers, neutralizing agents, anti-fogging agents, anti-blocking agents, slip agents, and colorants, which are added for the purpose of improving and adjusting moldability, stability of three-dimensional molded objects, and various physical properties of three-dimensional molded objects.

[0071] While the content of these additives is not particularly specified, from the viewpoint of the stability of the resulting 3D molding material and the 3D molded product, the total amount of additives is preferably 0.01 parts by mass or more, more preferably 0.05 parts by mass or more, even more preferably 0.08 parts by mass or more, and particularly preferably 0.1 parts by mass or more, per 100 parts by mass of the total 3D molding material. Furthermore, from the viewpoint of suppressing a decrease in interlayer adhesion of the molded product, the upper limit of the total content of additives is preferably 30 parts by mass or less, more preferably 28 parts by mass or less, and even more preferably 25 parts by mass or less.

[0072] In addition to the additives mentioned above, the three-dimensional molding material of the present invention may appropriately contain reinforcing materials that are commonly used, as long as they do not significantly impair the effects of the present invention.

[0073] Specific examples of reinforcing materials include inorganic fillers and inorganic fibers. Specific examples of inorganic fillers include calcium carbonate, zinc carbonate, magnesium oxide, calcium silicate, sodium aluminate, calcium aluminosilicate, magnesium silicate, potassium titanate, glass balloons, glass flakes, glass powder, silicon carbide, silicon nitride, boron nitride, gypsum, calcined kaolin, zinc oxide, antimony trioxide, zeolite, hydrotalcite, wollastonite, silica, talc, mica, nanochlore, metal powders such as magnesium, alumina, graphite, carbon black, and carbon nanotubes. Specific examples of inorganic fibers include glass cut fibers, glass milled fibers, glass fibers, gypsum whiskers, metal fibers, metal whiskers, ceramic whiskers, carbon fibers, and cellulose nanofibers.

[0074] The amount of these reinforcing materials included in the 3D molding material of the present invention is not particularly specified, but from the viewpoint of the strength of the molded article, it is preferably 1 part by mass or more, more preferably 5 parts by mass or more, and even more preferably 10 parts by mass or more, per 100 parts by mass of the total 3D molding material. Furthermore, from the viewpoint of suppressing a decrease in interlayer adhesion of the molded article, it is preferably 50 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less.

[0075] [Method for manufacturing materials for 3D modeling] The three-dimensional molding material of the present invention can be manufactured by adding and mixing the resin powder (A) and resin powder (B) of the present invention with the above-mentioned other additives and reinforcing materials, which are added as needed, in predetermined proportions. The method for manufacturing the three-dimensional material of the present invention is not particularly limited as long as it contains each component. For example, the resin powder (A) and resin powder (B) of the present invention, along with other components such as additives and reinforcing materials as needed, can be pre-mixed using various mixers such as tumblers and Henschel mixers, and then melt-kneaded using a Banbury mixer, rolls, brabender, single-screw compounding extruder, twin-screw compounding extruder, kneader, etc. to produce the three-dimensional molding material of the present invention.

[0076] [Average particle size (D50) of materials used for 3D printing] The three-dimensional molding material of the present invention is preferably in powder form, containing the resin powder (A) and resin powder (B) of the present invention, and other additives and reinforcing materials as needed, as a three-dimensional molding material using the powder bed fusion method. In this case, the average particle size (D50) of the 3D printing powder of the present invention is preferably larger than the average particle size (D50) of the resin powder (B). From this viewpoint, the average particle size (D50) of the 3D printing powder of the present invention is preferably 3 to 30 times, and particularly preferably 5 to 20 times, the average particle size (D50) of the resin powder (B). Specifically, the average particle size (D50) of the 3D molding powder of the present invention, when used as a material for the Powder Bed Fusion method, depends on the specifications of the system used for molding the molded body by the Powder Bed Fusion method. However, from the viewpoint of applying the powder to a predetermined thickness during molding, it is preferably 20 μm or more, more preferably 30 μm or more, even more preferably 40 μm or more, particularly preferably 50 μm or more, most preferably 55 μm or more, preferably 250 μm or less, more preferably 200 μm or less, even more preferably 150 μm or less, and particularly preferably 120 μm or less.

[0077] [Molded body] The molded article of the present invention is made of the three-dimensional molding material of the present invention described above. The preferred method for manufacturing the molded article of the present invention is molding using a three-dimensional printer. Detailed manufacturing instructions are provided below.

[0078] [Method for manufacturing molded products] In the method for manufacturing a molded body made from the 3D printing material of the present invention, the molded body is obtained by using the 3D printing material of the present invention and molding it with a 3D printer. Methods for 3D printing include powder bed fusion and multi-jet fusion. In particular, the present invention prefers to use powder bed fusion, in which the material to be molded is in powder form.

[0079] Powder bed fusion is a method in which particles of 3D modeling material are spread on a stage and irradiated with a laser or electron beam to sinter or fuse the particles, forming layers in the height direction. Then, particles of 3D modeling material are spread in contact with the previously formed layer and irradiated with a laser or electron beam to form the next layer. By sequentially stacking in this manner, a molded body of the desired shape can be obtained. [Examples]

[0080] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples unless it exceeds the essence of the invention.

[0081] [Methods for measuring and evaluating physical properties] <Average particle size (D50)> 5 g of powder material was weighed, and its particle size distribution was measured using a laser diffraction particle size analyzer (manufactured by Horiba, Ltd.) based on volume. The average particle size (D50) was determined from the particle size distribution that falls within the 50% frequency distribution of the powder. However, for some commercially available products, catalog values ​​were used. (These values ​​are considered to be equivalent to those obtained using the above measurement method.)

[0082] <Viscosity average molecular weight (Mv)> For ultra-high molecular weight polyethylene as resin powder (B), the viscosity-average molecular weight (Mv) was calculated using the following formula (I), instead of the intrinsic viscosity [η] (dl / g) by using the specific viscosity ηsp (dl / g) of a 0.05% decalin solution at 135°C. Mv = 5.37 × 10 4 ηsp 1.37…(I)

[0083] <Melting point (Tm)> The melting points (Tm) of resin powder (A) and resin powder (B) were measured using the following method. Using a differential scanning calorimeter manufactured by PerkinElmer, Ltd., product name "Pyris1 DSC," approximately 10 mg of a powder sample was heated from room temperature to 200°C at a heating rate of 10°C / min, held at this temperature for 1 minute, then cooled to 50°C at a heating rate of 10°C / min, and then heated again to 200°C at a heating rate of 10°C / min. The melting temperature (melting point: Tm) (°C) (during the reheating process) showing the maximum peak in the melting curve detected from the thermogram measured at this time was determined. The measured values ​​are shown rounded to the first decimal place.

[0084] <Dispersibility> A 0.3g sample of 3D modeling powder was placed in a recess of a table having a recess measuring 25mm x 30mm and 0.2mm in depth. After leveling the powder in the recess by rolling a roller on the table at a speed of approximately 64mm / second, the dispersibility of the powder was evaluated based on the state of the powder filled in the recess according to the following criteria. A: The powder is evenly distributed. B: The powder is not distributed uniformly, or there is aggregation of powder particles.

[0085] <Formability> Using a powder bed fusion (PBL) printer, the print bed was set to a temperature above the cooling crystallization temperature and below the melting temperature of the powder sample for 3D printing, and the feed bed was set to a temperature above the cooling crystallization temperature of the powder sample. A test specimen with a length of 80 mm, a width of 12.7 mm, a thickness of 5 mm, and a 2 mm V-cut was fabricated with the thickness direction of the specimen as the layering direction, at a layer pitch of 0.125 mm. The presence or absence of printing defects was observed visually, and the printability was evaluated according to the following criteria. A: It is possible to fabricate the material, and the mechanical properties can be evaluated using the resulting test specimen. B: It can be printed, but it is very brittle, or there are printing defects such as missing parts.

[0086] <Impact Resistance> For the evaluation of moldability, the Charpy impact strength of the fabricated test specimens was measured in accordance with JIS K7111-1. A Charpy impact test was performed on this specimen at a measurement temperature of 25°C, with a hammer capacity of 4J, and the striking surface facing the opposite side of the notch. The Charpy impact value was then measured. The impact resistance of each test specimen was evaluated by calculating the ratio to the Charpy impact value of Comparative Example 1, which used only propylene copolymer powder as the molding material, and then using this ratio according to the following criteria. AA: Charpy impact ratio is 120% or higher A: The ratio of the Charpy impact value is greater than 100% but less than 120%. B: Charpy impact value ratio is 100% or less

[0087] <Overall Rating> Based on the above evaluation results, the following criteria were used for evaluation. AA: All are "A" or higher, with at least one being "AA". A: Both are "A" B: One or more of the following are "B"

[0088] [Example 1] As a thermoplastic resin (A), 90 parts by mass of propylene copolymer powder (manufactured by Sinterit) (A-1) (Tm: 135℃, D50: 87μm) for LisaPro 3D printer powder materials were added to 10 parts by mass of ultra-high molecular weight polyethylene Mipelon (registered trademark) PM-200 (manufactured by Mitsui Chemicals, Inc.) (B-1) (Mv: 1.8 million, Tm: 137℃, D50: 10μm) and dry blended. To this mixed powder, 0.3 parts by mass of carbon powder (Fine Powder SGP-10, manufactured by SEC Carbon, average particle size 10μm) as an electromagnetic wave absorber was added per 100 parts by mass of ultra-high molecular weight polyethylene and mixed to obtain a powder for 3D modeling (D50: 79μm). Table 1 shows the results of the evaluation performed using the obtained 3D printing powder.

[0089] [Example 2] A powder for 3D modeling (D50: 79 μm) was obtained in the same manner as in Example 1, except that silicone powder KMP-597 (manufactured by Shin-Etsu Chemical Co., Ltd.) (B-2) (D50: 5 μm) was used instead of Mipelon (registered trademark) PM-200 (manufactured by Mitsui Chemicals, Inc.) (B-1). Table 1 shows the results of the evaluation performed using the obtained 3D printing powder.

[0090] [Comparative Example 1] Instead of using ultra-high molecular weight polyethylene, only the propylene copolymer powder (manufactured by Sinterit) (A-1) for LisaPro 3D printers was used. Since the propylene copolymer powder (manufactured by Sinterit) (A-1) for LisaPro 3D printers contains a laser absorber, the addition and mixing of carbon powder was unnecessary. Table 1 shows the results of the evaluation performed using the obtained 3D printing powder.

[0091] [Comparative Example 2] A powder for 3D modeling (D50: 81 μm) was obtained in the same manner as in Example 1, except that Mipelon® XM-220U (C-1) (Mv: 2 million, Tm: 136℃, D50: 30 μm) was used instead of Mipelon® PM-200 (manufactured by Mitsui Chemicals, Inc.) (B-1). Table 1 shows the results of the evaluation performed using the obtained 3D printing powder.

[0092] [Comparative Example 3] A powder for 3D modeling (D50: 80 μm) was produced in the same manner as in Example 1, except that a propylene copolymer powder (manufactured by Nippon Polypropylene Co., Ltd., powdered Wintec WFX4M, Tm: 127℃) (C-2) (D50: 18 μm) was used instead of Mipelon (registered trademark) PM-200 (manufactured by Mitsui Chemicals, Inc.) (B-1). Table 1 shows the results of the evaluation performed using the obtained 3D printing powder.

[0093] [Table 1]

[0094] As is clear from the above results, the 3D modeling material of the present invention, which contains two types of resin powder (A) and resin powder (B) with different resin compositions and particle sizes, wherein the average particle size (D50) of resin powder (A) is 30 μm or more and 250 μm or less, and the average particle size (D50) of resin powder (B) is 1 μm or more and less than 30 μm, exhibits excellent moldability in 3D printing and impact resistance of the resulting molded body. [Industrial applicability]

[0095] The present invention provides a 3D printing material that, even when using existing resin powders for powder bed fusion (PBL) fusion, maintains moldability and the safety of the powder material while providing excellent impact resistance for molded products manufactured by a 3D printer. Therefore, the 3D printing material of the present invention makes it possible to apply the resulting 3D printed objects not only to prototypes but also to practical applications such as components for home appliances, building materials, aircraft, and automotive materials.

Claims

1. The material comprises resin powder (A) and resin powder (B) having a different resin composition from resin powder (A). The average particle size (D50) of the resin powder (A) is measured by laser diffraction and is between 30 μm and 250 μm. A three-dimensional molding material characterized in that the average particle size (D50) of the resin powder (B) is 1 μm or more and less than 30 μm, as measured by laser diffraction.

2. The material for three-dimensional molding according to claim 1, characterized in that the average particle size (D50) of the resin powder (B) is 3% or more and 30% or less of the average particle size (D50) of the resin powder (A).

3. The material for three-dimensional molding according to claim 1, characterized in that the resin powder (B) is a powder of polyethylene and / or a thermosetting elastomer.

4. The three-dimensional molding material according to claim 3, characterized in that the viscosity-average molecular weight (Mv) of the polyethylene is 500,000 or more and 10,000,000 or less.

5. The material for three-dimensional molding according to claim 1, characterized in that the resin powder (A) is a polyolefin resin powder.

6. The material for three-dimensional molding according to claim 5, characterized in that the polyolefin resin is a propylene polymer.

7. The material for three-dimensional molding according to claim 1, characterized in that it is in powder form.

8. The three-dimensional material according to claim 1, characterized in that it is a material for three-dimensional fabrication by powder bed fusion.

9. A molded article obtained using a three-dimensional molding material according to any one of claims 1 to 8.

10. A method for manufacturing a molded article, comprising the step of forming a molded article in three dimensions by powder bed fusion using a three-dimensional molding material according to any one of claims 1 to 8.

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