Patent Description:
A three-dimensional (3D) printer is a technology for calculating the shapes of thin cross-sections from three-dimensional data input by a CAD or the like and depositing layer upon layer of a material based on the calculation results to shape a 3D object and is also referred to as additive manufacturing technology. The three-dimensional printer requires no mold assembly that should be used in injection molding, enables the shaping of complicated 3D structures that could not be molded by injection molding, and has therefore received attention as a high-mix low-volume manufacturing technology.

As materials for the three-dimensional printer (also referred to as additive manufacturing materials), various materials have been developed according to the process or usage of the three-dimensional printer. The major materials used include light curable resins, thermoplastic resins, metals, ceramics, and wax.

The three-dimensional printer technology is classified, based on how to three-dimensionally shape an object from a material, into (<NUM>) binder jetting process, (<NUM>) directed energy deposition process, (<NUM>) material extrusion process, (<NUM>) material jetting process, (<NUM>) powder bed fusion process, (<NUM>) sheet lamination process, (<NUM>) vat photopolymerization process, and others. Three-dimensional printers adopting, among the above processes, the material extrusion process (also referred to as the fused deposition modeling process) are decreasing in price and therefore increasing in demand as those for home use and office use. Furthermore, in relation to three-dimensional printers adopting the powder bed fusion process, the development of a system achieving improvements in recyclability of powder materials has advanced. Therefore, the powder bed fusion process is a process attracting much attention.

The fused deposition modeling process is a process for shaping an object by fluidizing a thermoplastic resin having the shape of a thread called a filament or other shapes with a heating device inside an extrusion head, then discharging the fluid resin through a nozzle onto a platform, and cooling the resin into a solid state while gradually depositing layer upon layer of it according to the cross-sectional shapes of a desired object to be shaped. However, if the shaping is made using a thermoplastic resin not blended with any additive (so-called neat resin), there arise problems including delamination of a shaped object and warpage of the shaped object. Furthermore, if a thermoplastic resin blended with a fibrous filler, such as glass fibers or carbon fibers, is used, there arises a problem of difficulty of shaping due to clogging of the extrusion head, wear of the extrusion head, and so on.

Meanwhile, Patent Literature <NUM> discloses that with the use of a thermoplastic resin blended with a nanofiller, such as carbon nanotubes, for a fused deposition modeling-based three-dimensional printer, a shaped object can be obtained which has a desired function that could not be achieved by a thermoplastic resin only.

The powder bed fusion process is a process for shaping an object by forming a thin layer of resin powder, melting it with an energy source, such as laser or electronic beam, according to the cross-sectional shape of a desired object to be shaped, solidifying it, depositing a new thin layer of resin powder on top of the solid, likewise melting it with the energy source, such as laser or electronic beam, according to the cross-sectional shape of the desired object to be shaped, solidifying it, and repeating these steps.

However, it is known that uniform dispersion of a nanofiller in a thermoplastic resin as in Patent Literature <NUM> is not easy and that the melting viscosity of an obtained thermoplastic resin composition increases. Furthermore, Patent Literature <NUM> discloses no specific method for improving the resistance to delamination of a shaped object and the resistance to warpage and shrinkage of the shaped object. Also in the powder bed fusion process, since resin is deposited layer by layer, there arise problems of, like the fused deposition modeling process, delamination of a shaped object and warpage and shrinkage of the shaped object.

An object of the present invention is to provide a filament for a three-dimensional printer, a shaped object, and a production method for the shaped object, all of which make it easy to produce a shaped object and can improve, in shaping using a three-dimensional printer, the resistance to delamination of the shaped object and the resistance to warpage and shrinkage of the shaped object.

The present invention provides a a filament for a three-dimensional printer, a shaped object, and a method for producing the shaped object which are described below.

More specifically, the objects of the present invention are solved by the features of the independent claims. Further advantageous embodiments are defined in the dependent claims.

The present invention makes it easy to produce a shaped object and can improve, in shaping using a three-dimensional printer, the resistance to delamination of the shaped object and the resistance to warpage and shrinkage of the shaped object.

Hereinafter, a description will be given of an example of a preferred embodiment for working of the present invention. However, the following embodiment is simply illustrative. The present invention is not at all limited by the following embodiment.

A filament for a fused deposition modeling-based three-dimensional printer according to the present invention is made of a resin composition. The resin composition contains: inorganic fibers (A) having an average fiber length of <NUM> to <NUM> and an average aspect ratio of <NUM> to <NUM>; and a thermoplastic resin (B) and may further contain other additives (C) as necessary.

The inorganic fibers for use in the present invention are powder formed of fibrous particles and have an average fiber length of <NUM> to <NUM> and an average aspect ratio of <NUM> to <NUM>. The average fiber length is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and still more preferably <NUM> to <NUM>. The average aspect ratio is preferably <NUM> to <NUM>, more preferably <NUM> to <NUM>, and still more preferably <NUM> to <NUM>. The use of the inorganic fibers having the above average fiber length and average aspect ratio makes it easy to produce a shaped object and can improve, in shaping using a three-dimensional printer, the resistance to delamination of the shaped object and the resistance to warpage and shrinkage of the shaped object.

The type of the inorganic fibers is potassium titanate.

Heretofore known potassium titanates can be widely used and examples include potassium tetratitanate, potassium hexatitanate, and potassium octatitanate. There is no particular limitation as to the dimensions of potassium titanate so long as they are within the above-described dimensions of the inorganic fibers. However, normally, its average fiber diameter is <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>, its average fiber length is <NUM> to <NUM>, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>, and its average aspect ratio is <NUM> or more, preferably <NUM> to <NUM>, and more preferably <NUM> to <NUM>. In the present invention, even marketed products can be used and examples that can be used include "TISMO D" (average fiber length: <NUM>, average fiber diameter: <NUM>) and "TISMO N" (average fiber length: <NUM>, average fiber diameter: <NUM>) both manufactured by Otsuka Chemical Co.

The above average fiber length and average fiber diameter is measured by observation with a scanning electron microscope, and the average aspect ratio (average fiber length/average fiber diameter) can be calculated from the average fiber length and the average fiber diameter. For example, a plurality of inorganic fibers are shot with a scanning electron microscope, images of <NUM> inorganic fibers are arbitrarily selected from the observed images, and their fiber lengths and fiber diameters are measured. The average fiber length is determined by adding all the fiber diameters and dividing the sum by the number of fibers, while the average fiber diameter can be determined by adding all the fiber diameters and dividing the sum by the number of fibers.

Fibrous particles as used in the present invention means particles having an L/B of <NUM> or more and an L/T of <NUM> or more where a length L represents the dimension of the longest side of, among cuboids (circumscribing cuboids) circumscribing the particle, a cuboid having the minimum volume, a breadth B represents the dimension of the second longest side of the cuboid, and a thickness T represents the dimension of the shortest side of the cuboid. The length L and the breadth B correspond to the fiber length and the fiber diameter, respectively. Platy particles herein refer to particles having an L/B of below <NUM> and an L/T of <NUM> or more.

Regarding the inorganic fibers, in order to increase the wettability with the thermoplastic resin and further improve physical properties, such as mechanical strength, of the obtained resin composition, treated layers made of a surface treatment agent may be formed on the surfaces of inorganic fibers for use in the present invention. Examples of the surface treatment agent include silane coupling agents and titanium coupling agents. Preferred among them are silane coupling agents and more preferred are aminosilane coupling agents, epoxysilane coupling agents, vinylsilane coupling agents, and alkylsilane coupling agents. These agents may be used alone or as a mixture of two or more.

Examples of the aminosilane coupling agents include N-<NUM>-(aminoethyl)-<NUM>-aminopropylmethyldimethoxysilane, N-<NUM>-(aminoethyl)-<NUM>-aminopropyltrimethoxysilane, <NUM>-aminopropyltrimethoxysilane, <NUM>-aminopropyltriethoxysilane, <NUM>-ethoxysilyl-N-(<NUM>,<NUM>-dimethylbutylidene)propylamine, N-phenyl-<NUM>-aminopropyltrimethoxysilane, and N-(vinylbenzyl)-<NUM>-aminoethyl-<NUM>-aminopropyltrimethoxysilane.

Examples of the epoxysilane coupling agents include <NUM>-glycidyloxypropyl(dimethoxy)methylsilane, <NUM>-glycidyloxypropyltrimethoxysilane, diethoxy(<NUM>-glycidyloxypropyl)methylsilane, triethoxy(<NUM>-glycidyloxypropyl)silane, and <NUM>-(<NUM>,<NUM>-epoxycyclohexyl)ethyltrimethoxysilane.

Examples of the vinylsilane coupling agents include vinyltrimethoxysilane, <NUM>-methacryloxypropylmethyldimethoxysilane, <NUM>-methacryloxypropyltrimethoxysilane, <NUM>-methacryloxypropylmethyldiethoxysilane, and <NUM>-methacryloxypropyltriethoxysilane.

Examples of the alkylsilane coupling agents include methyltrimethoxysilane, dimethyldimethoxysilane, trimethylmethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, n-propyltrimethoxysilane, isobutyltrimethoxysilane, isobutyltriethoxysilane, n-hexyltrimethoxysilane, n-hexyltriethoxysilane, cyclohexylmethyldimethoxysilane, n-octyltriethoxysilane, and n-decyltrimethoxysilane.

Known surface treatment methods can be used as the method for forming treated layers made of a surface treatment agent on the surfaces of the inorganic fibers and examples include: a wet method of dissolving the surface treatment agent in a solvent promoting hydrolysis (for example, water, an alcohol or a mixed solvent of them) to prepare a solution and spraying the solution on the inorganic fibers; and an integral blend method of blending the inorganic fibers and the surface treatment agent with the resin composition.

No particular limitation is placed on the amount of surface treatment agent in treating the surfaces of the inorganic fibers with the surface treatment agent, but, in the case of the wet method, the solution of the surface treatment agent may be sprayed so that the amount of surface treatment agent reaches <NUM> parts by mass to <NUM> parts by mass and preferably <NUM> parts by mass to <NUM> parts by mass relative to <NUM> parts by mass of inorganic fibers. On the other hand, in the case of the integral blend method, the surface treatment agent may be blended with the resin composition so that the amount of surface treatment agent reaches <NUM> parts by mass to <NUM> parts by mass relative to <NUM> parts by mass of inorganic fibers. If the amount of surface treatment agent is within the above ranges, the adhesion of the inorganic fibers to the thermoplastic resin can increase to improve the dispersibility of the inorganic fibers.

According to the present invention, the thermoplastic resin is at least one selected from the group consisting of polyacetal (POM) resin; aliphatic polyamide (PA) resins, such as polyamide <NUM> resin, polyamide <NUM> resin, polyamide <NUM> resin, polyamide <NUM> resin, polyamide <NUM> resin, polyamide <NUM> resin-polyamide <NUM> resin copolymer (polyamide <NUM>/<NUM> resin), and polyamide <NUM> resin-polyamide <NUM> resin copolymer (polyamide <NUM>/<NUM> resin); semi-aromatic polyamide (PA) resins composed of a structural unit with an aromatic ring and a structural unit free from aromatic ring, such as polyamide MXD6 resin, polyamide 6T resin, polyamide 9T resin, and polyamide 10T resin; polyphenylene sulfide (PPS) resin; polyether sulfone (PES) resin; liquid crystal polyester (LCP) resin; aromatic polyether ketone resins, such as polyether ketone (PEK) resin, polyether ether ketone (PEEK) resin, polyether ketone ketone (PEKK) resin, and polyether ether ketone ketone (PEEKK) resin; polyamide-imide (PAI) resin; and thermoplastic polyimide (TPI) resin.

Preferred in the fused deposition modeling-based three-dimensional printer is at least one selected from the group consisting of polyacetal (POM) resin, aliphatic polyamide (PA) resin, semi-aromatic polyamide (PA) resin, polyphenylene sulfide (PPS) resin, and polyether ether ketone (PEEK) resin.

Mixtures of at least two compatible thermoplastic resins selected from among the above thermoplastic resins, i.e., polymer alloys can also be used.

The filament according to the present invention may contain other additives without any loss of its preferred physical properties. Examples of the other additives include inorganic fillers other than the above-mentioned inorganic fibers, a stabilizer, a nucleating agent, an antistat, an antioxidant, a weatherproofer, a metal deactivator, a ultraviolet ray absorber, a germ- and mildew-proofing agent, a deodorant, a conductive additive, a dispersant, a softener (plasticizer), a colorant, a flame retardant, a sound deadener, a neutralizer, an antiblocking agent, a flow modifier, a mold release agent, a lubricant, and an impact resistance improver. The resin composition may contain at least one of these additives.

The resin composition, of which the filament according to the present invention is made, can be produced by mixing and heating (particularly, melt kneading) the above components, i.e., the inorganic fibers (A), the thermoplastic resin (B), and, as necessary, the other additives (C).

For melt kneading, any known melt kneader, for example, a biaxial extruder, can be used. Specifically, the resin composition can be produced by: (<NUM>) a method of preliminarily mixing the components with a mixer (a tumbler, a Henschel mixer or the like), melt kneading the mixture with a melt kneader, and then pelletizing it with a pelletization device (such as a pelletizer); (<NUM>) a method of adjusting a master batch of desired components, mixing it with other components as necessary, and melt kneading the mixture into pellets with a melt kneader; (<NUM>) a method of feeding the components into a melt kneader to form pellets; or other methods.

No particular limitation is placed on the processing temperature during melt kneading so long as it is within a temperature range in which the thermoplastic resin (B) can melt. Normally, the cylinder temperature of a melt kneader for use in the melt kneading is controlled within this range.

The content of the inorganic fibers (A) in the resin composition is, in a total amount of <NUM>% by mass of the resin composition, preferably <NUM>% by mass to <NUM>% by mass, more preferably <NUM>% by mass to <NUM>% by mass, and still more preferably <NUM>% by mass to <NUM>% by mass.

The content of the thermoplastic resin (B) in the resin composition is, in a total amount of <NUM>% by mass of the resin composition, preferably <NUM>% by mass to <NUM>% by mass, more preferably <NUM>% by mass to <NUM>% by mass, and still more preferably <NUM>% by mass to <NUM>% by mass.

No particular limitation is placed on the content of other additives (C) which are additives except for the above-described essential components and allowed to be used in the present invention, without any loss of the preferred physical properties of the resin composition. The content of the other additives is normally <NUM>% by mass or less and preferably <NUM>% by mass or less in a total amount of <NUM>% by mass of the resin composition.

By controlling the components of the resin composition within the above ranges, the resistance to delamination of a shaped object and the resistance to warpage and shrinkage of the shaped object in shaping using a three-dimensional printer can be improved.

In this manner, a resin composition exerting desired effects is produced.

The filament according to the present invention is a shaping material for a three-dimensional printer. The shaping material for a three-dimensional printer in the present invention refers to a material for use in applying it to a three-dimensional printer (also referred to as an additive manufacturing apparatus) to obtain a three-dimensional shaped object and is composed of the resin composition.

The shaping material for a three-dimensional printer can be used in any method so long as the method is to shape an object by melting the shaping material by heat based on a design on a computer. For example, the shaping material can be suitably used in the fused deposition modeling process.

The fused deposition modeling process is a process for shaping a desired shaped object by fluidizing a thermoplastic resin having the shape of pellets, the shape of a thread called a filament or other shapes with a heating device inside an extrusion head, then discharging the fluid resin through a nozzle onto a platform, and cooling the resin into a solid state while gradually depositing layer upon layer of it. The use of the filament according to the present invention as a shaping material enables shaping using a fused deposition modeling-based three-dimensional printer without clogging of the extrusion head or wear of the extrusion head that might occur with the use of a resin composition blended with a fibrous filler, such as glass fibers or carbon fibers. For example, even through a thin nozzle having a head diameter of <NUM> or less, shaping can be achieved without the occurrence of clogging of the extrusion head or wear of the extrusion head. In addition, it can be assumed that, although the reason is not clear, the inorganic fibers (A) can not only improve the resistance to warpage and shrinkage of the shaped object but also increase the interfacial strength between the layered resin portions, thus preventing delamination of the shaped object.

No particular limitation is placed on the method for obtaining the filament according to the present invention and an example is a method including: an extrusion step of extruding a resin composition as a molten strand through a die hole in a molder and guiding the molten strand into a cooling water bath to obtain a strand; a stretching step of hot stretching the strand to obtain a filament; and the step of rolling up the filament.

No particular limitation is placed on the shape of the filament. Examples that can be cited as the cross-sectional shape thereof include circular, rectangular, flattened, ellipsoidal, cocoon-like, trefoil, and like non-circular shapes. Circular is preferred from the viewpoint of ease of handling. No limitation is placed on the length of the filament and it can be set at any value according to industrial production conditions or without interfering with the use for a fused deposition modeling-based three-dimensional printer. No particular limitation is also placed on the diameter of the filament and, for example, it is <NUM> to <NUM> and particularly <NUM> to <NUM>. Note that the diameter of the filament refers to the maximum of diameters measured on cross-sections of the filament perpendicular to the direction of length of the filament.

In contrast to the fused deposition modeling process, a powder bed fusion process is a process for shaping an object by depositing resin powder layer by layer, melting each layer into a particular cross-sectional shape with an energy source, such as laser or electronic beam, and solidifying it.

A shaped object according to the present invention is an object shaped from the filament according to the present invention with a three-dimensional printer. In using the resin composition in the form of a filament, a shaped object can be produced, for example, by performing shaping by feeding the filament into a fused deposition modeling-based three-dimensional printer.

In a method for producing a shaped object according to the present invention, a shaped object is produced by a three-dimensional printer using the filament according to the present invention.

In using the filament according to the present invention, a shaped object can be produced, for example, by feeding the filament into a fused deposition modeling-based three-dimensional printer. Specifically, a shaped object can be produced by feeding the filament into a fused deposition modeling-based three-dimensional printer, fluidizing the filament with a heating device inside an extrusion head, then discharging the fluid through a nozzle onto a platform, and cooling it into a solid state while gradually depositing layer upon layer of it according to the cross-sectional shape of a desired object to be shaped.

Hereinafter, a specific description will be given of the present invention with reference to Examples and Comparative Examples, but the present invention is not limited to these examples. Details of raw materials used in Examples and Comparative Examples are as described below. The average fiber diameter and the average aspect ratio were measured using a field-emission scanning electron microscope (SEM, S-<NUM> manufactured by Hitachi High-Technologies Corporation), the shapes of particles were confirmed by the SEM, the average particle diameter was measured using, with the exception of carbon black, a laser diffraction particle size distribution measurement device (SALD-<NUM> manufactured by Shimadzu Corporation), and the average particle diameter of carbon black was measured using the.

Materials were melt-kneaded in each composition ratio shown in Tables <NUM> and <NUM> using a biaxial extruder to produce pellets. The cylinder temperature of the biaxial extruder was <NUM> to <NUM> in Examples <NUM> to <NUM> and Reference Example <NUM> and Comparative Examples <NUM> to <NUM>, <NUM> to <NUM> in Examples <NUM> and <NUM> and Comparative Example <NUM>, <NUM> to <NUM> in Reference Examples <NUM> and <NUM> and Comparative Example <NUM>, <NUM> to <NUM> in Reference Example <NUM> and Comparative Example <NUM>, and <NUM> to <NUM> in Reference Examples <NUM> and <NUM> and Comparative Example <NUM>.

The obtained pellets were loaded into a filament extruder, thus obtaining a filament with a filament diameter of <NUM>.

The filament obtained in each of Examples <NUM> to <NUM>, <NUM> and <NUM>, Comparative Examples <NUM> to <NUM>, and Reference Examples <NUM> and <NUM> to <NUM> was deposited into layers in a thickness direction by a fused deposition modeling-based three-dimensional printer (manufactured by MUTOH INDUSTRIES, LTD. , trade name: MF1100) under the associated printing conditions shown in Tables <NUM> and <NUM>, thus producing a flat-plate shaped object <NUM> long, <NUM> wide, and <NUM> thick.

<FIG> shows a photograph of a shaped object (Comparative Test Example <NUM>) produced using the resin composition according to Comparative Example <NUM>, and <FIG> shows a photograph of a shaped object (Test Example <NUM>) produced using the resin composition according to Example <NUM>.

The filament obtained in each of Examples <NUM> to <NUM>, <NUM> and <NUM>, Comparative Examples <NUM> to <NUM>, and Reference Examples <NUM> and <NUM> to <NUM> was produced into a dumbbell tensile specimen having a shape shown in <FIG> by a fused deposition modeling-based three-dimensional printer (manufactured by MUTOH INDUSTRIES, LTD. , trade name: MF1100) under the associated printing conditions shown in Tables <NUM> and <NUM>.

The filament obtained in each of Examples <NUM> to <NUM>, <NUM> and <NUM>, Comparative Example <NUM>, Comparative Examples <NUM> to <NUM>, and Reference Examples <NUM> and <NUM>-<NUM> was produced into a bending specimen having a shape shown in <FIG> by a fused deposition modeling-based three-dimensional printer (manufactured by MUTOH INDUSTRIES, LTD. , trade name: MF1100) under the associated printing conditions shown in Tables <NUM> and <NUM>.

The flat-plate shaped objects produced under the conditions in Tables <NUM> and <NUM> were measured in terms of amount of warpage with a caliper. The amount of warpage W is, as shown in <FIG>, a difference in height along a build-up direction during shaping between the middle and ends of the shaped object in a traveling direction during shaping. The results are shown in Tables <NUM> and <NUM>.

The flat-plate shaped objects produced under the conditions in Tables <NUM> and <NUM> were measured in terms of shrinkage. The shrinkage was measured in the build-up direction and the traveling direction. The shrinkage in the build-up direction is a shrinkage in the thickness b along the build-up direction during shaping shown in <FIG>. The shrinkage in the traveling direction is a shrinkage in the length a along the traveling direction during shaping shown in <FIG>. The results are shown in Tables <NUM> and <NUM>.

The flat-plate shaped objects produced under the conditions in Tables <NUM> and <NUM> were cut along the build-up direction into <NUM>-wide strips, the obtained strips were measured in terms of bending stress by a <NUM>-span three-point bending test with a tester Autograph AG-<NUM> (manufactured by Shimadzu Corporation), and the measured values were assumed as interface adhesions. The results are shown in Tables <NUM> and <NUM>.

Dumbbell tensile specimens produced under the conditions in Tables <NUM> and <NUM> were measured in terms of tensile strength with a tester Autograph AG-<NUM> (manufactured by Shimadzu Corporation). The results are shown in Tables <NUM> and <NUM>.

Bending specimens produced under the conditions in Tables <NUM> and <NUM> were measured in terms of flexural strength and flexural modulus by a <NUM>-span three-point bending test with a tester Autograph AG-<NUM> (manufactured by Shimadzu Corporation). The test results are shown in Tables <NUM> and <NUM>.

Tables <NUM> and <NUM> show that Test Examples <NUM> to <NUM>, <NUM> and <NUM> as well as Reference Example <NUM> and <NUM> to <NUM>, in which inorganic fibers were blended with PA12 resin, PAMXD6 resin, ABS resin, COC resin or PBT resin exhibited significantly low amounts of warpage and significantly low shrinkages both in the build-up direction and traveling direction as compared to Comparative Test Examples <NUM> to <NUM> in which no inorganic fibers were blended with PA12 resin, PAMXD6 resin, ABS resin, COC resin or PBT resin. Furthermore, it is shown that their interface adhesions were significantly improved.

As is obvious from comparison of Comparative Test Example <NUM> with Comparative Test Examples <NUM> to <NUM>, the addition of an inorganic additive, such as carbon black or talc, into a thermoplastic resin generally decreases the interface adhesion. However, for example, comparison of Test Examples <NUM> to <NUM>, and Reference Example <NUM> with Comparative Test Example <NUM> shows that the addition of the inorganic fibers into a thermoplastic resin offered an unforeseen effect of increased interface adhesion.

Tables <NUM> and <NUM> show that Test Examples <NUM> to <NUM>, <NUM> and <NUM>, and Reference Examples <NUM> and <NUM> to <NUM> in which inorganic fibers were blended with the resin also exhibited high tensile strengths as compared to Comparative Test Examples <NUM> to <NUM> in which no inorganic fibers were blended with the resin.

Tables <NUM> and <NUM> show that Test Examples <NUM> to <NUM>, <NUM> and <NUM> and Reference Examples <NUM> and <NUM> to <NUM> in which inorganic fibers were blended with the resin also exhibited high flexural strengths and flexural moduli as compared to Comparative Test Examples <NUM> and <NUM> to <NUM> in which no inorganic fibers were blended with the resin. Comparative Test Example <NUM> in which platy particles were blended with the resin exhibited high flexural strength and flexural modulus, but was shown from Tables <NUM> and <NUM> not to have increased the shrinkages, interface adhesion, and tensile strength.

Materials were melt-kneaded in each composition ratio shown in Table <NUM> using a biaxial extruder to produce pellets. The cylinder temperature of the biaxial extruder was <NUM> to <NUM>. The obtained pellets and polyethylene oxide were melt-mixed at <NUM> to <NUM> and the resultant mixture was immersed in water to dissolve polyethylene oxide in water, thus obtaining spherical resin powder. The average particle diameter of the spherical resin powder was measured with a laser diffraction particle size distribution measurement device (SALD-<NUM> manufactured by Shimadzu Corporation). The average particle diameters of Example <NUM>, Comparative Example <NUM>, and Comparative Example <NUM> were <NUM>, <NUM>, and <NUM>, respectively.

The spherical resin powder obtained in each of Example <NUM> and Comparative Examples <NUM> to <NUM> was produced into a bending specimen having a shape shown in <FIG> by a powder bed fusion-based three-dimensional printer (manufactured by ASPECT Inc. , trade name: RaFaEl II <NUM>-HT) under the associated printing conditions shown in Table <NUM>.

The shaped objects of bending specimens produced under the conditions in Table <NUM> were measured in terms of amount of warpage with a non-contact roughness and shape measurement device (a one-shot 3D shape measuring microscope VR-<NUM> manufactured by Keyence Corporation). The amount of warpage W is, as shown in <FIG>, a difference in height along a build-up direction during shaping between the middle and ends of the bending specimen. The results are shown in Table <NUM>.

The shaped objects of bending specimens produced under the conditions in Table <NUM> were measured in terms of shrinkage. The shrinkage was measured in the build-up direction. The shrinkage in the build-up direction is a shrinkage in the thickness of the bending specimen along the build-up direction during shaping.

Respective flexural strengths of the shaped objects of bending specimens produced under the conditions in Table <NUM> were divided by their respective packing densities and the obtained values were assumed as interface adhesions. The packing density is a value obtained by dividing the specific gravity of the shaped object of each bending specimen by the density of an injection-molded piece (a piece of the same shape injection-molded using pellets having the same composition). The flexural strength of the shaped object of each bending specimen obtained by the powder bed fusion process is the sum of interface strengths between powder particles. As the packing density decreases, the interface area correspondingly decreases and the flexural strength also correspondingly decreases.

The flexural strength was obtained by measuring each bending specimen produced under the conditions in Table <NUM> in terms of bending stress by a <NUM>-span three-point bending test with a tester Autograph AG-<NUM> (manufactured by Shimadzu Corporation). The specific gravity of each shaped object was measured in conformity to JIS Z8807.

The shaped objects of the bending specimens produced under the conditions in Table <NUM> were measured in terms of flexural strength by a <NUM>-span three-point bending test with a tester Autograph AG-<NUM> (manufactured by Shimadzu Corporation).

Claim 1:
A filament for a fused deposition modeling-based three-dimensional printer, the filament being made of a resin composition containing: inorganic fibers having an average fiber length of <NUM> to <NUM> and an average aspect ratio of <NUM> to <NUM>; and a thermoplastic resin,
wherein the thermoplastic resin is at least one selected from the group consisting of polyacetal resin, aliphatic polyamide resins, semi-aromatic polyamide resins, polyphenylene sulfide resin, polyether sulfone resin, liquid crystal polyester resin, aromatic polyether ketone resins, polyamide-imide resin, and thermoplastic polyimide resin and
wherein the type of the inorganic fibers is potassium titanate, and wherein the average fiber length and the average aspect ratio are determined according to the description.