Polyacetal resin composition for three-dimensional molding, filament for three-dimensional molding, three-dimensional molded article and method for manufacturing the same, and three-dimensional sintered article and method for manufacturing the same

Abstract

To provide a polyacetal resin composition for three-dimensional molding which enables three-dimensional molding by a hot-melt lamination method, and prevents generation of a residue and residual coal after a three-dimensional molded article has been sintered, and a filament for three-dimensional molding containing the same.SOLUTION: A polyacetal resin composition for three-dimensional molding contains a polyacetal resin having a difference (Tm2-Tc) between a melting point Tm2 and a crystallization temperature Tc measured by a differential scanning calorimeter of 22 to 40°C, and a melt flow rate measured at a temperature of 190°C and a load of 2.16 kg of 0.8 to 50 g / 10 min, and at least one inorganic powder selected from metal powder, metal alloy powder, and ceramic precursor powder, in which a ratio of the inorganic powder with respect to 100 pts. mass of the total amount of the polyacetal resin and the inorganic powder in the polyacetal resin composition is 70 to 95 pts. mass.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present disclosure relates to a polyacetal resin composition for three-dimensional modeling, a filament for three-dimensional modeling, a three-dimensional modeled object and a method for producing the same, and a three-dimensional sintered object and a method for producing the same. [Background technology]

[0002] 3D printers have become increasingly popular in recent years because they can create three-dimensional objects without using molds or large-scale melting equipment. Known methods of modeling using 3D printers include the Fused Filament Fabrication (FFF) method, the Stereolithography (STL) method, and the Selective Laser Sintering (SLS) method. The Fused Deposition Modeling method is a method of forming three-dimensional objects by heating and melting thermoplastic resin and layering it, and because the equipment is low-cost, it is becoming widely used not only for industrial purposes but also for personal use.

[0003] Meanwhile, the development of a molding method that uses the principle of fused deposition modeling to obtain three-dimensional sintered objects made of inorganic materials (hereinafter simply referred to as "three-dimensional sintered objects") is also underway. Specifically, inorganic powder is mixed with thermoplastic resin as a binder material, and formed into filaments or pellets, which are then used to obtain three-dimensional objects using the principle of fused deposition modeling. After that, the binder is removed in a degreasing process, and the sintering process promotes the bonding between inorganic particles to obtain three-dimensional sintered objects. Compared to the powder sintering method, which directly creates three-dimensional objects from inorganic powder, the use of the principle of fused deposition modeling makes it possible to achieve precise molding, and also significantly reduces the cost of the equipment.

[0004] As a method for obtaining a three-dimensional sintered product, for example, Patent Document 1 describes a method in which a three-dimensional modeling composition containing a sinterable inorganic powder, an organic binder such as a polyolefin polymer modified polyacetal as an organic binder, and an organic compound is used, and the resulting composition is layered using a 3D printer and then sintered to obtain a three-dimensional sintered product. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-015848 A Summary of the Invention [Problem to be solved by the invention]

[0006] When using injection molding or fused deposition modeling to produce a three-dimensional sintered product from a three-dimensional model, it is necessary to remove the binder made of thermoplastic resin by degreasing or burning after the formation of the three-dimensional model. However, the degreasing process uses liquids such as organic solvents that are the source of industrial wastewater, which not only places a heavy burden on the environment but also increases the process cost. In addition, when olefin resins such as polyethylene resins and polypropylene resins or resins containing aromatic rings are used as binders, residues and charcoal are generated during the combustion and sintering process, and these residues may affect the appearance and physical properties of the three-dimensional sintered product.

[0007] On the other hand, polyacetal resin is highly combustible and leaves almost no risk of carbon residue, so it is expected to be used as a binder in the above-mentioned fused deposition modeling method for three-dimensional sintered objects. However, polyacetal resin has a large shrinkage rate when the temperature drops, so warping may occur during modeling using the fused deposition modeling method. In particular, if the dimensions of the object to be modeled are large, warping may occur on the surface that comes into contact with the modeling stage during the modeling process, causing the object to peel off from the modeling stage. In such cases, three-dimensional modeling using the fused deposition modeling method becomes difficult.

[0008] A first object of the present disclosure is to provide a polyacetal resin composition for three-dimensional modeling, which enables three-dimensional modeling by fused deposition modeling and is less likely to leave residue or carbon residue after sintering the three-dimensional model, and a filament for three-dimensional modeling containing the same. A second object of the present disclosure is to provide a three-dimensional object and a manufacturing method thereof using a novel polyacetal resin composition for three-dimensional modeling, the three-dimensional object being capable of being manufactured by fused deposition modeling. A third object of the present disclosure is to provide a three-dimensional sintered product and a method for producing the same, which are obtained from a three-dimensional object formed using a novel polyacetal resin composition for three-dimensional modeling, and which are less likely to leave residues or carbon residue after sintering the three-dimensional object, and a method for producing the same. [Means for solving the problem]

[0009] As a result of intensive research, the present inventors have found that all of the above-mentioned first to third problems can be solved by a polyacetal resin composition for three-dimensional printing, the polyacetal resin composition comprising a polyacetal resin having a difference (Tm2-Tc) between the melting point Tm2 and the crystallization temperature Tc measured by a differential scanning calorimeter of 22°C or more and 40°C or less, and a melt flow rate measured at a temperature of 190°C and a load of 2.16 kg of 0.8 g / 10 min or more and 50.0 g / 10 min or less, and at least one inorganic powder selected from a metal powder, a metal alloy powder, and a ceramic precursor powder, wherein the proportion of the inorganic powder in the polyacetal resin composition is 70 to 95 parts by mass relative to 100 parts by mass of the total amount of the polyacetal resin and the inorganic powder in the polyacetal resin composition. Effect of the Invention

[0010] According to the present disclosure, it is possible to provide a polyacetal resin composition for three-dimensional modeling, which enables three-dimensional modeling by fused deposition modeling and is less likely to leave residue or carbon residue after sintering the three-dimensional model, and a filament for three-dimensional modeling containing the same. The present disclosure also provides a three-dimensional object using a novel polyacetal resin composition for three-dimensional modeling and a method for producing the same, the three-dimensional object being capable of being produced by fused deposition modeling, and a method for producing the same. Furthermore, according to the present disclosure, it is possible to provide a three-dimensional sintered product and a method for producing the same obtained from a three-dimensional object using a novel polyacetal resin composition for three-dimensional modeling, which is less likely to produce residue or carbon residue after sintering the three-dimensional object, and a method for producing the same. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a conceptual diagram showing a flow of a method for manufacturing a three-dimensional object by a fused deposition modeling method. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present disclosure will be described in detail, but the scope of the present disclosure is not limited to the embodiment described here, and various modifications can be made within the scope of the present disclosure. Each aspect disclosed in this specification can be combined with any other feature disclosed in this specification. In addition, when multiple upper and lower limit values ​​are described for a specific parameter, any upper and lower limit values ​​among these upper and lower limit values ​​can be combined to form a suitable numerical range. In addition, the lower and / or upper limit values ​​of the numerical range described in this disclosure are numerical values ​​within the numerical range and may be replaced with numerical values ​​shown in the examples. The expression "X to Y" indicating a numerical range means "X or more and Y or less". When a specific description described for one embodiment is also applicable to other embodiments, the description may be omitted in other embodiments. The configurations and combinations thereof in each embodiment are merely examples, and addition, omission, substitution, and other modifications of the configurations are possible as appropriate without departing from the spirit of the present disclosure. The present disclosure is not limited to the embodiments. Each feature disclosed herein may be combined with any other feature disclosed herein.

[0013] [Polyacetal resin composition for three-dimensional modeling] A first embodiment of the present disclosure relates to a polyacetal resin composition for three-dimensional modeling. The polyacetal resin composition for three-dimensional modeling according to the first embodiment (hereinafter, sometimes simply referred to as "resin composition") includes a polyacetal resin having a difference (Tm2-Tc) between the melting point Tm2 and the crystallization temperature Tc measured by a differential scanning calorimeter of 22°C or more and 40°C or less, and a melt flow rate measured at a temperature of 190°C and a load of 2.16 kg of 0.8g / 10min or more and 50.0g / 10min or less, and at least one inorganic powder selected from metal powder, metal alloy powder, and ceramic precursor powder, and the ratio of the inorganic powder to the total amount of the polyacetal resin and the inorganic powder in the polyacetal resin composition is 70 to 95 parts by mass. According to the resin composition according to the first embodiment, three-dimensional modeling by fused deposition modeling is possible, and residues and carbon residues are unlikely to be generated after sintering the three-dimensional model.

[0014] <Polyacetal resin> The resin composition according to the first embodiment includes a polyacetal resin, which has a difference (Tm2-Tc) between a melting point Tm2 and a crystallization temperature Tc measured by a differential scanning calorimeter of 22°C or more and 40°C or less, and a melt flow rate measured at a temperature of 190°C and a load of 2.16 kg of 0.8g / 10min or more and 50.0g / 10min or less.

[0015] (Melting point Tm2 and crystallization temperature Tc of polyacetal resin) In the polyacetal resin according to the first embodiment, the difference (Tm2-Tc) between the melting point Tm2 and the crystallization temperature Tc measured by a differential scanning calorimeter is 22°C or more and 40°C or less. When the (Tm2-Tc) of the polyacetal resin is 22°C or more and 40°C or less, three-dimensional modeling by the fused deposition modeling method is possible. In addition, a large-sized model can be stably modeled. Furthermore, after sintering the three-dimensional model, residues and carbon residues are unlikely to be generated. The (Tm2-Tc) of the polyacetal resin is more preferably 22°C or more and 35°C or less, and further preferably 22°C or more and 30°C or less. In one embodiment, the (Tm2-Tc) of the polyacetal resin may be 22°C or more and 25°C or less.

[0016] The melting point Tm2 refers to the peak top temperature of the endothermic peak observed in the 2nd RUN when a polyacetal resin is heated from 40°C to 200°C at a heating rate of 10°C / min (1st RUN), held at 200°C for 5 minutes, cooled to 40°C at a heating rate of 10°C / min, held at 40°C for 5 minutes, and then heated again from 40°C to 200°C at a heating rate of 10°C / min (2nd RUN) according to a method based on JIS K-7121 (2012).

[0017] The crystallization temperature Tc is the peak top temperature of the exothermic peak observed when a polyacetal resin is heated from 40°C to 200°C at a heating rate of 10°C / min (1st RUN), held at 200°C for 5 minutes, and then cooled to 40°C at a cooling rate of 10°C / min, according to a method based on JIS K-7121 (2012).

[0018] In one embodiment, the melting point Tm2 of the polyacetal resin may be 160° C. or more and less than 170° C., or 162° C. or more and 167° C. or less. In one embodiment, the crystallization temperature Tc of the polyacetal resin may be 135° C. or more and 150° C. or less, or 137° C. or more and 147° C. or less.

[0019] In order to achieve the above-mentioned (Tm2-Tc), for example, when the polyacetal resin is a copolymer described later, the value of the melting point Tm2 can be controlled by adjusting the proportion of the comonomer unit in the polyacetal resin. For example, the melting point Tm2 tends to be lower as the proportion of the comonomer unit increases. The crystallization temperature Tc can also be adjusted by adjusting the proportion of the comonomer unit. For example, the crystallization temperature Tc tends to be lower as the proportion of the comonomer unit increases.

[0020] (Melt flow rate (MFR) of polyacetal resin) The polyacetal resin has an MFR of 0.8 g / 10 min or more and 50.0 g / 10 min or less, preferably 0.8 g / 10 min or more and 30.0 g / 10 min or less, more preferably 0.8 g / 10 min or more and 10.0 g / 10 min or less, and particularly preferably 0.8 g / 10 min or more and 5.0 g / 10 min or less, when the (Tm2-Tc) of the polyacetal resin is within the above-mentioned predetermined range, the MFR of 0.8 g / 10 min or more and 50.0 g / 10 min or less makes it easy to perform three-dimensional modeling by the fused deposition modeling method even when a large-sized object is produced. In addition, after sintering the three-dimensional object, residues and carbon residues are unlikely to be generated. The MFR of the polyacetal resin is measured based on ISO 1133-1:2011 (condition D) at a temperature of 190 °C and a load of 2.16 kg.

[0021] The MFR is adjusted mainly by the weight average molecular weight (Mw) of the polyacetal resin. For example, the larger the weight average molecular weight (Mw) of the polyacetal resin, the lower the MFR tends to be.

[0022] (Resin Composition) The polyacetal resin according to the first embodiment is not particularly limited as long as it can achieve the above-mentioned (Tm-Tc) and MFR. The polyacetal resin capable of achieving such properties may be a polyacetal homopolymer or a polyacetal copolymer. In one embodiment, from the viewpoint of the balance between mechanical properties and thermal properties, the polyacetal resin preferably contains a polyacetal copolymer. The polyacetal resin may contain only linear molecular chains, or may have a branched chain or a crosslinked structure. It may also be a modified polyoxymethylene containing other organic groups.

[0023] Polyacetal homopolymer is a polymer that has only oxymethylene units (-CH2O-) in its main chain. A polyacetal copolymer is a copolymer resin containing an oxymethylene unit (-CHO-) as a main constituent unit and further containing a comonomer unit other than the oxymethylene unit. The "main constituent unit" means a monomer unit that accounts for more than 50% by mass, preferably 70% by mass or more, of all the constituent units (100% by mass) that constitute the polyacetal copolymer.

[0024] The comonomer unit contained in the polyacetal copolymer may be one type or two or more types. In one embodiment, the comonomer unit is preferably an oxyalkylene unit having 2 or more carbon atoms, preferably 2 to 6 carbon atoms. When the comonomer unit is an oxyalkylene unit having 2 or more carbon atoms, the thermal stability tends to be good. The comonomer unit is more preferably at least one oxyalkylene unit selected from an oxyethylene group, an oxypropylene group, and an oxytetramethylene group, and particularly preferably contains an oxyethylene group.

[0025] The ratio of the comonomer unit in the polyacetal copolymer is preferably 1.0% by mass or more and 6.0% by mass or less with respect to the total structural units (100% by mass) of the polyacetal resin. In one embodiment, the ratio of the comonomer unit is preferably 3.0% by mass or more and 6.0% by mass or less, more preferably 3.0% by mass or more and 5.5% by mass or less, even more preferably 3.0% by mass or more and 5.0% by mass or less, and particularly preferably 3.0% by mass or more and 4.0% by mass or less. By having the ratio of the comonomer unit be 1.0 to 6.0% by mass, more preferably 3.0 to 6.0% by mass, with respect to the total structural units (100% by mass) of the polyacetal copolymer, warping and voids can be further reduced, and three-dimensional modeling by the fused deposition modeling method becomes easier. In addition, a three-dimensional model with better appearance can be produced. When oxyethylene units are contained as comonomer units, the proportion of the oxyethylene units in all comonomer units (100% by mass) is preferably from 90% to 100% by mass, more preferably from 95% to 100% by mass. The ratio of the comonomer units in the polyacetal copolymer is as follows: 1 For example, the resin composition is dissolved in deuterated hexafluoroisopropanol to a concentration of 5% by mass to prepare a sample. 1 It can be calculated by a method of analyzing by H-NMR to determine the ratio of the integral fraction of the peak of a comonomer unit (for example, an oxyalkylene unit having 2 or more carbon atoms, described later) to the integral fraction of the peak of all monomers in the polyacetal copolymer.

[0026] The polyacetal copolymer may be any of a random copolymer, a block copolymer, and a graft copolymer. From the viewpoint of thermal stability, a random copolymer is preferred.

[0027] The degree of polymerization, branching and crosslinking of the polyacetal resin can be appropriately adjusted within the range of an MFR of 0.8 to 50.0 g / 10 min.

[0028] The weight average molecular weight (Mw) of the polyacetal resin is not particularly limited as long as the effects of the present disclosure are achieved, and can be appropriately adjusted within a range in which the MFR is 0.8 to 50.0 g / 10 min. In one embodiment, the Mw of the polyacetal resin may be 10,000 or more and 400,000 or less, in that the strength of the resulting shaped object is likely to be good. The weight average molecular weight (Mw) is a value measured (in terms of polystyrene) by size exclusion chromatography (SEC).

[0029] The resin composition according to the first embodiment may contain only one type of polyacetal resin, or may contain a combination of two or more types selected from polyacetal homopolymers and polyacetal copolymers. When the resin composition contains a polyacetal copolymer, the resin composition may contain two or more types of polyacetal copolymers that differ in the type and / or content of comonomers, and / or form (random copolymer, block copolymer, graft copolymer, etc.). When the resin composition contains two or more types of polyacetal resins, the blending ratio is adjusted so as to satisfy the difference (Tm2-Tc) between the melting point Tm2 and the crystallization temperature Tc of the filament, and the MFR value.

[0030] (Manufacturing method of polyacetal resin) The polyacetal resin can be produced by a method such as bulk polymerization of a monomer (or a monomer mixture) containing a cyclic trimer or tetramer of formaldehyde (preferably trioxane, which is a cyclic trimer of formaldehyde) and, if necessary, a comonomer, with the addition of an appropriate amount of a molecular weight regulator, using a cationic polymerization catalyst. Trioxane is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acid catalyst, and is used after being purified by a method such as distillation. It is preferable that the trioxane used in the polymerization contains as little impurities as possible, such as water, methanol, and formic acid.

[0031] The polymerization apparatus is not particularly limited, and a known apparatus can be used. In addition, any method such as a batch type or a continuous type can be adopted. The polymerization temperature is preferably kept at 65 to 135°C. The polymerization catalyst after polymerization can be deactivated by adding a basic compound or an aqueous solution thereof to the reaction product recovered from the polymerization apparatus or the reaction product in the polymerization apparatus.

[0032] Examples of the cationic polymerization catalyst include lead tetrachloride, tin tetrachloride, titanium tetrachloride, aluminum trichloride, zinc chloride, vanadium trichloride, antimony trichloride, phosphorus pentafluoride, antimony pentafluoride, boron trifluoride, boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride dioxanate, boron trifluoride acetic anhydrate, boron trifluoride triethylamine complex and other boron trifluoride coordination compounds, perchloric acid, acetyl perchlorate, t-butyl Examples of the catalyst include inorganic and organic acids such as perchlorate, hydroxyacetic acid, trichloroacetic acid, trifluoroacetic acid, and p-toluenesulfonic acid; complex salt compounds such as triethyloxonium tetrafluoroborate, triphenylmethylhexafluoroantimonate, allyldiazonium hexafluorophosphate, and allyldiazonium tetrafluoroborate; alkyl metal salts such as diethylzinc, triethylaluminum, and diethylaluminum chloride; heteropolyacids; and isopolyacids. Among these, boron trifluoride coordination compounds such as boron trifluoride, boron trifluoride diethyl etherate, boron trifluoride dibutyl etherate, boron trifluoride dioxanate, boron trifluoride acetic anhydrate, and boron trifluoride triethylamine complex compounds are particularly preferred. These catalysts can also be used by diluting them in advance with an organic solvent or the like.

[0033] The molecular weight regulator may be a linear formal compound. Examples of the linear formal compound include methylal, ethylal, dibutoxymethane, bis(methoxymethyl)ether, bis(ethoxymethyl)ether, bis(butoxymethyl)ether, etc. Among them, it is preferable to use at least one selected from the group consisting of methylal, ethylal, and dibutoxymethane.

[0034] Examples of basic compounds for neutralizing and deactivating the polymerization catalyst include ammonia, amines such as triethylamine, tributylamine, triethanolamine, and tributanolamine, hydroxide salts of alkali metals and alkaline earth metals, and other known catalyst deactivators. After the polymerization reaction is completed, it is preferable to quickly add an aqueous solution of these to the reaction product to deactivate it. After the polymerization and deactivation methods, washing, separation and recovery of unreacted monomers, drying, and the like are further carried out by conventionally known methods as necessary to obtain a polyacetal resin.

[0035] If necessary, various stabilizers can be added to perform stabilization treatment such as decomposition and removal or blocking of unstable terminals of the polyacetal resin. As the stabilizer, conventionally known antioxidants, heat stabilizers, etc. can be used. For example, hindered phenol compounds, nitrogen-containing compounds, hydroxides, inorganic salts, carboxylates, etc. of alkali or alkaline earth metals can be used alone or in combination of two or more.

[0036] Furthermore, as necessary, one or more types of general additives for polyacetal resins, such as colorants such as dyes and pigments, lubricants, crystal nucleating agents, release agents, antistatic agents, surfactants, or organic polymer materials, may be added to the extent that the effects of the present disclosure are not impaired.

[0037] <Inorganic powder> The resin composition according to the first embodiment includes at least one inorganic powder selected from metal powder, metal alloy powder, and ceramic precursor powder. The resin composition according to the first embodiment is a resin composition that can be used for three-dimensional molding by fused deposition modeling and is less likely to leave residue or carbon residue after sintering the three-dimensionally molded object by combining the aforementioned polyacetal resin and the inorganic powder and setting the ratio of the inorganic powder to 70 to 95 parts by mass relative to 100 parts by mass of the total amount of the polyacetal resin and the inorganic powder.

[0038] In this disclosure, the term "metal powder" refers to a powder of a pure metal consisting of a single metal element. The metal powder may be composed of a powder of one kind of pure metal, or may be a mixed powder containing powders of two or more kinds of pure metals. Examples of the metal powder include at least one metal powder selected from the group consisting of pure iron, aluminum, yttrium, titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, carbonyl iron powder (CIP), cobalt, nickel, copper, silver, zinc, and cadmium. Among these, at least one metal powder selected from the group consisting of titanium, niobium, chromium, molybdenum, tungsten, manganese, iron, carbonyl iron powder (CIP), nickel, and copper is more preferable, and at least one metal powder selected from the group consisting of titanium, iron, and carbonyl iron powder (CIP) is even more preferable.

[0039] In this disclosure, the term "metal alloy" refers to a material that contains multiple metal elements, or metal elements and nonmetal elements, and exhibits metallic properties. The metal alloy powder may be composed of a powder of one metal alloy, or may be a mixed powder containing powders of two or more metal alloys. Examples of the metal alloy powder include powders of iron-based alloys such as iron-nickel, iron-cobalt, iron-silicon, and stainless steel, tungsten carbide (WC), cemented carbide (WC-Co alloys, etc.), aluminum alloys, and copper alloys. These may be used alone or in combination of two or more.

[0040] In this disclosure, the term "ceramic precursor powder" refers to any inorganic powder that can form a ceramic after being molded and sintered. Examples of such ceramic precursor powders include TCP (tricalcium phosphate), MCP (monocalcium phosphate), DCP (dicalcium phosphate), tetracalcium phosphate, hydroxyapatite, α-TCP, β-TCP, titanium oxide (titania), aluminum oxide (alumina), zirconium oxide (zirconia), yttrium oxide (yttria), yttria-stabilized zirconia, indium oxide, indium tin oxide, beryllium oxide, boron nitride, silicon carbide, boron carbide, tungsten carbide, titanium carbide, zirconium carbide, beryllium oxide, zeolite, cerium oxide (ceria), tungsten disilicide, sodium silicate, platinum silicate, titanium nitride, chromium nitride, zirconium nitride, tungsten nitride, vanadium nitride, tantalum nitride, niobium nitride, carbon nitride, silicon boride, clay, earth, soil, cement, Portland cement, silica, barium titanate, lead zirconate titanate, lead zirconate Examples of the ceramic precursor powder include titanium, zinc oxide, potassium niobate, lithium niobate, sodium tungstate, glass, geopolymer, sodium chloride, sodium nitrate, potassium nitrate, potassium chloride, magnesium chloride, calcium chloride, calcium nitrate, magnesium nitrate, strontium oxide, strontium phosphate, calcium sulfate, barium sulfate, calcium carbonate, sodium carbonate, and sodium fluoride. The ceramic precursor powder may be used alone or in combination of two or more of these.

[0041] In the three-dimensional sintered product obtained by using the resin composition according to the first embodiment, at least one inorganic powder selected from a metal powder, a metal alloy powder, and a ceramic precursor powder contained in the ternary sintered product may have a changed composition. As described below, the three-dimensional sintered product is obtained by further sintering a ternary shaped product, so that the inorganic powder may be oxidized or decomposed. For example, when the resin composition contains pure iron as an inorganic powder, the inorganic powder contained in the three-dimensional sintered product may contain iron oxide.

[0042] In one embodiment, the inorganic powder may be a cermet powder. The cermet powder is a composite material powder obtained by sintering a ceramic precursor powder with a metal powder and / or a metal alloy powder. Examples of the cermet powder include Al2O3-Fe-based, TiC-Ni-based, TiC-Co-based, and B4C-Fe-based cermet powders. These may be used alone or in combination of two or more.

[0043] In one embodiment, the inorganic powder preferably comprises a ceramic precursor powder, more preferably at least one ceramic precursor powder selected from alumina and zirconia, which may be yttria partially stabilized zirconia. In one embodiment, the average particle size (D50) of the inorganic powder is preferably 0.1 to 200 μm, more preferably 1 to 100 μm. If the average particle size (D50) of the inorganic powder is within the above range, the flowability is likely to be good. The inorganic powder may be granulated to about 0.1 to 100 μm using a binder such as an acrylic resin or a urethane resin from a powder of about 0.001 to 1 μm. The average particle size (D50) of the inorganic powder means the particle size D50 at which the cumulative frequency is 50% in the arithmetic average particle size on a volume basis measured by a laser diffraction / scattering particle size distribution measurement method. The average particle size can be measured using a laser diffraction / scattering particle size distribution measurement device (for example, product name: LA-960, manufactured by Horiba, Ltd.).

[0044] In the resin composition according to the first embodiment, the ratio of the inorganic powder to the total amount of 100 parts by mass of the polyacetal resin and the inorganic powder is 70 to 95 parts by mass. If the ratio of the inorganic powder is 95 parts by mass or less, the fluidity of the resin composition itself is not reduced, and lamination by the fused deposition modeling method is possible. If the ratio of the inorganic powder is 70 parts by mass or more, the shape of the obtained three-dimensional object can be maintained when sintered. In one embodiment, the ratio of the inorganic powder to the total amount of 100 parts by mass of the polyacetal resin and the inorganic powder is preferably 75 to 90 parts by mass, more preferably 80 to 85 parts by mass.

[0045] <Other ingredients> The resin composition according to the first embodiment may contain other components other than the polyacetal resin and the inorganic powder. The other components include thermoplastic resins other than the polyacetal resin; various additives such as weather (light) stabilizers, colorants such as dyes and pigments, lubricants, nucleating agents, release agents, antistatic agents, and surfactants; fibrous and / or plate-like inorganic fillers other than the inorganic powder; and organic fillers. These may be used alone or in combination of two or more. In addition, from the viewpoint of obtaining a three-dimensional sintered product with less residue and carbon residue when sintering a three-dimensional molded product, it is preferable to contain only the polyacetal resin as the thermoplastic resin.

[0046] <Method for producing polyacetal resin composition for three-dimensional modeling> The method for producing the resin composition according to the first embodiment is not particularly limited. For example, the above-mentioned polyacetal resin, inorganic powder, and other components as necessary may be melt-mixed, and then molded into pellets to obtain the resin composition according to the first embodiment.

[0047] [Filament for 3D modeling] A second embodiment of the present disclosure is a filament for three-dimensional modeling (hereinafter, may be simply referred to as "filament") containing the resin composition according to the first embodiment. The filament according to the second embodiment may contain a solid material used for three-dimensional modeling, which is a continuous fibrous solid material having a substantially circular cross section. Since the filament according to the second embodiment contains the resin composition according to the first embodiment, it is possible to perform three-dimensional modeling by the fused deposition modeling method, and residues and charcoal are unlikely to be generated after sintering the three-dimensional model. In addition, the filament according to the second embodiment can also be used to model a three-dimensional model with a large size. Here, examples of "a three-dimensional model with a large size" include a model with a size of 10 cm or more x 10 cm or more when the surface in contact with the modeling stage is rectangular, a model with a diameter of 10 cm or more when the surface in contact with the modeling stage is approximately circular, and a model with a height of 10 cm or more from the modeling stage. Usually, when a large-sized model is produced, the surface area of ​​the modeling stage is large, so that the temperature within the modeling stage surface may vary. In addition, a longer modeling time is required than when a small-sized model is produced. In the conventional method, when using a resin mainly composed of polyacetal resin, if there is a temperature variation in the modeling stage surface or if a certain modeling time is required, the base layer of the model (the layer in contact with the modeling stage) may peel off from the modeling stage during the modeling process, making it difficult to continue modeling in such cases. Therefore, in the past, the dimensions of three-dimensional models produced by fused deposition modeling using a resin mainly composed of polyacetal resin were limited to about several centimeters. According to the filament of the second embodiment, even if there is a temperature variation in the stage surface during modeling or the modeling time is long, peeling of the base layer from the stage during the modeling process is easily suppressed, and a three-dimensional model can be more stably produced.

[0048] In one embodiment, the average diameter of the filament is preferably 1 to 3 mm, more preferably 1 to 2.5 mm, and further preferably 1.5 to 2 mm. By setting the average diameter of the filament to 1 to 3 mm, it can be used as a modeling material in a commercially available three-dimensional modeling device. The average diameter of the filament is determined by taking a 5 m sample, randomly selecting 20 points, measuring the diameters (or the longest linear distance in the cross section) of the samples to three decimal places using a micrometer, and rounding off the arithmetic mean value to two decimal places.

[0049] In one embodiment, the filament can be wound into a spool around a core, which makes it easier to attach to a 3D printer and to model using the 3D printer.

[0050] In a preferred embodiment, the filament is composed only of the resin composition according to the first embodiment. The filament according to the second embodiment uses a polyacetal resin in which the difference between the melting point Tm2 and the crystallization temperature Tc (Tm2-Tc) is 22°C or more and 40°C or less, so that the solidification speed during modeling can be prevented from becoming too fast due to the high mixing ratio of inorganic powder. Therefore, despite the high ratio of inorganic powder, three-dimensional modeling by the fused deposition modeling method is possible.

[0051] [Three-dimensional objects and their manufacturing methods] A third embodiment of the present disclosure is a three-dimensional object including the resin composition according to the first embodiment, and a method for producing the same.

[0052] <Three-dimensional object> The three-dimensional object according to the third embodiment includes the resin composition according to the first embodiment. The three-dimensional object may be formed by injection molding, but is preferably formed by a manufacturing method described below, i.e., fused deposition modeling. Whether the three-dimensional object according to the third embodiment is formed by fused deposition modeling can be determined by observing the surface of the three-dimensional object with the naked eye or a stereomicroscope to see whether there are modeling lines (drawing lines) and lamination marks. The thickness of the modeling lines (drawing lines) is not limited, and may be, for example, 100 to 1000 μm.

[0053] In one embodiment, the three-dimensional object may have one or more faces having two points on an outer edge, the linear distance between the two points being 10 cm or more. In one embodiment, the three-dimensional object may have a height from one face of 10 cm or more.

[0054] In another embodiment, the three-dimensional object may have one or more polygonal faces, and one or more sides of the polygonal shape may have a length of 10 cm or more. In another embodiment, the three-dimensional object may have one or more circular faces, and the diameter of the circular shape may be 10 cm or more.

[0055] <Method of manufacturing 3D objects> The method for producing a three-dimensional object according to the third embodiment includes forming a three-dimensional object by fused deposition modeling using the polyacetal resin composition for three-dimensional modeling according to the first embodiment. The resin composition according to the first embodiment includes 70 to 95 parts by mass of inorganic powder with respect to 100 parts by mass of the total amount of polyacetal resin and inorganic powder. As a method for obtaining a three-dimensional object, particularly a large three-dimensional object exceeding 20 cm, using such a resin composition, it is preferable to adopt the fused deposition modeling method, which is easy to ensure good fluidity. The production method according to the third embodiment may be a method including forming a three-dimensional object by fused deposition modeling using the filament according to the second embodiment. In one embodiment, forming the three-dimensional object includes discharging a melt of the resin composition (or filament) onto a modeling stage. In one embodiment, the modeling stage may be provided in a 3D printer.

[0056] In one embodiment, the step of forming a three-dimensional structure (hereinafter also referred to as the "first step") is preferably carried out by reacting a compound represented by the following formula 1: Tm2>Ts≧Tc, and Tc>Ta>Tc-100 (Equation 1) [In formula 1, Ts is the temperature of the modeling stage (°C), Tc is the crystallization temperature of the polyacetal resin (°C), Tm2 is the melting point of the polyacetal resin (°C), and Ta is the ambient temperature of the modeling area (°C)] forming a three-dimensional object on a modeling stage under a temperature condition satisfying After forming the three-dimensional object on the modeling stage, the three-dimensional object is subjected to a process represented by the following formula 2: Tc>Ts (Formula 2) [In formula 2, Ts and Tc are the same as those in formula 1] and peeling the three-dimensional object from the surface of the modeling stage under temperature conditions that satisfy the above condition (hereinafter, also referred to as the "second step").

[0057] The "modeling area" refers to a space on the modeling stage where a three-dimensional object can be formed. In one embodiment, the modeling area is preferably a chamber that forms an enclosed space in order to facilitate temperature control.

[0058] The ambient temperature (Ta) of the build area and the build stage temperature (Ts) can be adjusted by raising or lowering the settings on the fused deposition model 3D printer. However, both the ambient temperature (Ta) of the build area and the build stage temperature (Ts) do not refer to the temperature as a set value for the operation of the 3D printer, but rather to the actual measured values ​​of the build stage temperature and the ambient temperature of the build area for certain set conditions.

[0059] In the first step, by making the temperature of the modeling stage and the ambient temperature during lamination of the resin composition (or filament) satisfy the ranges defined by formula 1, it is possible to further suppress the occurrence of warping of the laminate due to a temperature drop during lamination. In addition, the laminate can be firmly fixed onto the modeling stage. As a result, it becomes easier to manufacture a three-dimensional object with large dimensions. In the second step, when the temperature of the modeling stage after modeling satisfies the range defined by the formula 2, the formed three-dimensional object can be easily peeled off from the modeling stage.

[0060] Fig. 1 conceptually shows the flow of a method for manufacturing a three-dimensional object by fused deposition modeling. Fig. 1(A) to (C) show the first step, and Fig. 1(D) shows the second step. Below, the flow of the manufacturing method according to the second embodiment will be described in detail with reference to Fig. 1 (the filament according to the second embodiment is used as the raw material). First, the temperature Ts of the modeling stage 1 and the atmospheric temperature Ta of the modeling area in the fused deposition modeling 3D printer are set to predetermined temperatures (for example, temperatures that satisfy the above formula 1) as necessary (FIG. 1(A)). In one embodiment, for example, when the melting point Tm2 of polyacetal resin is 163.9°C and the crystallization temperature Tc is 140.5°C, the temperature of the modeling stage 1 is preferably set to 141°C or higher and lower than 163.9°C, and the atmospheric temperature of the modeling area is preferably set to more than 40°C and lower than 140°C.

[0061] Next, the filament for three-dimensional modeling described above is melted and discharged from the discharge nozzle 2 onto the modeling stage 1. The base layer 4 can be formed by discharging the molten filament from the discharge nozzle 2 while scanning the discharge nozzle 2 above the modeling stage 1 (FIG. 1(B)). Furthermore, the molten filament is discharged from the discharge nozzle 2 while scanning the discharge nozzle 2 above the base layer 4 to form the structure 5 on the base layer 4 (FIG. 1(C)). More specifically, based on the three-dimensional data of the structure 5 to be formed, the shape corresponding to the cross section of the structure 5 is sequentially laminated to form the structure 5. In the process of forming the structure 5, air may be sprayed from the air duct 3 located near the discharge nozzle 2 to cool and solidify the modeling material after lamination. After completing the formation of the structure 5, if necessary, the temperature of the modeling stage 1 can be lowered to lower the temperature of the base layer below the crystallization temperature of the filament. As a result, crystallization progresses in the base layer 4, the adhesive strength of the base layer 4 to the modeling stage 1 decreases, and the three-dimensional object 6 consisting of the base layer 4 and the structure 5 can be easily peeled off from the modeling stage 1 (FIG. 1(D)). In one embodiment, the temperature of the modeling stage 1 after the formation of the structure 5 can be set to a temperature that satisfies the above formula 2. In one embodiment, for example, when the crystallization temperature Tc of polyacetal resin is 140.5°C, it is preferable to lower the temperature of the modeling stage 1 to less than 140°C after the formation of the structure 5. The peeled structure 5 (or the base layer 4 and the structure 5) can be obtained as the three-dimensional object 6. Thereafter, the base layer 4 may be removed by cutting, polishing, or the like, as necessary.

[0062] The base layer 4 is a base formed under the structure 5, and may be formed to have an area larger than the structure 5 and / or to prevent voids or gaps. By forming the base layer 4, it is possible to better prevent the structure 5 from peeling off from the modeling stage when the modeling time is extended. In one embodiment, forming the three-dimensional object may include forming a base layer on the modeling stage, and then forming the three-dimensional object on the base layer.

[0063] In the above-described method for manufacturing a three-dimensional object, even when the modeling time is long, peeling of the base layer from the stage during the modeling process is suppressed, so that it is not necessarily required to form the base layer 4. When the base layer 4 is not formed, the structure 5 may be formed directly on the modeling stage 1.

[0064] In one embodiment, the size of the modeling stage may be such that the length (or diameter) of one side is 10 cm or more, may be 15 to 100 cm, or may be 20 to 90 cm, so that a large-sized three-dimensional object can be formed.

[0065] In one embodiment, the three-dimensional object obtained by forming the three-dimensional object can have two points on the outer edge of the surface in contact with the modeling stage or the surface in contact with a base layer provided on the modeling stage, the two points being 10 cm or more apart in a straight line. The manufacturing method according to the third embodiment makes it possible to perform three-dimensional modeling by the fused deposition modeling method even for such three-dimensional objects that are larger in size than conventional ones.

[0066] In another embodiment, the three-dimensional object obtained by forming the three-dimensional object may have a polygonal surface in contact with the modeling stage or a surface in contact with a base layer provided on the modeling stage, and one or more sides of the polygonal surface may have a length of 10 cm or more. In another embodiment, the three-dimensional object obtained by forming the three-dimensional object may have a circular surface in contact with the modeling stage or a surface in contact with a base layer provided on the modeling stage, and the diameter of the circular surface may be 10 cm or more.

[0067] In one embodiment, the three-dimensional object obtained by forming the three-dimensional object may have a height of 10 cm or more from the modeling stage. Even if the three-dimensional object has a size larger than conventional three-dimensional objects, such as a height of 10 cm or more from the modeling stage, it is possible to perform three-dimensional modeling by the fused deposition modeling method.

[0068] [Three-dimensional sintered product and its manufacturing method] A fourth embodiment of the present disclosure is a three-dimensional sintered product and a method for producing the same. The three-dimensional sintered product according to the fourth embodiment is a sintered product of the three-dimensionally shaped product according to the third embodiment. That is, the three-dimensional sintered product can be manufactured by a method including sintering the three-dimensionally shaped product. Note that, as the three-dimensionally shaped product, the three-dimensionally shaped product obtained by the manufacturing method according to the third embodiment described above can be preferably used.

[0069] Examples of sintering a three-dimensional sintered product include a method of sintering the three-dimensional shaped product in a sintering furnace, a baking furnace, laser sintering, etc. The sintering temperature is preferably lower than the melting temperature of the inorganic powder. By sintering at such a temperature, adjacent atoms constituting the inorganic powder are bonded to obtain a sintered product.

[0070] In one embodiment, when the three-dimensional object is formed from a resin composition containing a ceramic precursor powder (preferably an alumina powder) as an inorganic powder, the three-dimensional object is heated and held at a temperature in the range of 350 to 500° C. to remove the polyacetal resin from the three-dimensional object. Thereafter, the three-dimensional sintered object is obtained by heating the object to 590 to 655° C. in an inert gas atmosphere and sintering the object.

[0071] In one embodiment, when the three-dimensional object is formed from a resin composition containing zirconia as an inorganic powder, the three-dimensional object is heated and held at about 450 to 550° C. to remove the polyacetal resin in the three-dimensional object. The three-dimensional object is then heated to 1300 to 1600° C. for sintering to obtain a three-dimensional sintered object. When a three-dimensional object made of a resin composition containing a metal powder and / or a metal alloy powder as an inorganic powder is sintered, it is preferable to sinter the object under an inert gas atmosphere such as argon or nitrogen in order to prevent oxidation of the metal powder and / or the metal alloy powder. EXAMPLES

[0072] The present disclosure will be described in more detail below by showing examples, but interpretation of the present disclosure is not limited to these examples.

[0073] [Production Example 1] (Production of Polyacetal Resin I) Polymerization was carried out using a continuous mixer reactor having a paddle-equipped rotating shaft with a cross section of two overlapping circles, which was equipped with a jacket for passing a heat transfer medium (or a coolant) on the outside. Specifically, trioxane and a comonomer (1,3-dioxolane) were added to the reactor in the ratio shown in Table 1 while rotating the two rotating shafts with paddles at 150 rpm. Furthermore, methylal was added as a molecular weight modifier in the ratio shown in Table 1. Next, a catalyst mixture (catalyst concentration: 0.005% by mass of boron trifluoride relative to trioxane) in which boron trifluoride gas was mixed as a catalyst was continuously added and supplied to the reactor to carry out bulk polymerization. After the polymerization was completed, the reaction product discharged from the reactor was quickly passed through a crusher and introduced into an aqueous solution containing 0.1% by mass of triethylamine at 80°C to deactivate the catalyst. Furthermore, after separation, washing, and drying, a crude polyacetal resin was obtained. Next, 4 parts by mass of a 5% by mass aqueous solution of triethylamine and 0.03 parts by mass of pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] (antioxidant) were added to 100 parts by mass of this crude polyacetal resin, and the mixture was melt-kneaded at 210°C in a twin-screw extruder to remove unstable parts of the crude polyacetal resin. 0.3 parts by mass of pentaerythrityl-tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate] and 0.15 parts by mass of melamine were further added as stabilizers to 100 parts by mass of the polyacetal resin obtained by the above method, and the mixture was melt-kneaded at 210°C in a twin-screw extruder to obtain a pellet-shaped polyacetal resin I. The melting point Tm2, ​​crystallization temperature Tc, MFR and proportion of comonomer units of the obtained polyacetal resin I were measured by the methods described below. The results are shown in Table 1.

[0074] [Production Example 2] (Production of Polyacetal Resin II) A pellet-shaped polyacetal resin II was obtained in the same manner as in Production Example 1, except that the amounts of trioxane, comonomer (1,3-dioxolane), and methylal were changed to the amounts shown in Table 1. The melting point Tm2, ​​crystallization temperature Tc, MFR, and comonomer unit ratio of the obtained polyacetal resin II were measured by the methods described below. The results are shown in Table 1.

[0075] (Melting point Tm2, ​​crystallization temperature Tc) The melting point Tm2 and crystallization temperature Tc of the polyacetal resins I and II were measured according to JIS K-7121 (2012) using a differential scanning calorimeter (manufactured by Parkin Elmer, product name: DSC8500). Specifically, after heating from 40°C to 200°C at a heating rate of 10°C / min (1st RUN), the temperature was held at 200°C for 5 minutes, and then cooled to 40°C at a heating rate of 10°C / min. The peak top temperature of the exothermic peak observed when the resin was cooled was measured as the crystallization temperature Tc. After that, the resin was held at 40°C for 5 minutes, and heated again from 40°C to 200°C at a heating rate of 10°C / min. The peak top temperature of the endothermic peak observed in the 2nd RUN was measured as the melting point Tm2.

[0076] (Melt Flow Rate (MFR)) The MFR of the polyacetal resins I and II was measured in accordance with ISO 1133 (condition D) at a temperature of 190° C. under a load of 2.16 kg.

[0077] (comonomer unit) The obtained pellet-shaped polyacetal resin I or II was cut into small pieces with nippers so as to be easily dissolved in a solvent, and the pieces were dissolved in deuterated hexafluoroisopropanol so that the polyacetal resin concentration was 5% by mass to prepare a sample. 1 The polyacetal resin was analyzed by H-NMR (Bruker, product name: AvanceIII 400, magnetic field strength: 400 MHz, reference material: tetramethylsilane, temperature: 27°C, number of accumulations: 128) to determine the ratio of the integral rate of the comonomer unit (oxyethylene group) to the integral rate of the peaks of all monomers in the polyacetal resin.

[0078] [Table 1]

[0079] [Production of resin composition and filament] <Example 1> The pellet-shaped polyacetal resin I obtained in Production Example 1 and inorganic powder (zirconia powder (average particle size (D50): 100 μm)) were mixed so that the ceramic precursor powder was 80 parts by mass relative to 100 parts by mass of the total amount of the polyacetal resin I and the ceramic precursor powder, to obtain a resin composition according to the first embodiment. Thereafter, the resin composition was charged into a tabletop extruder (manufactured by Apex Japan Co., Ltd., product name: AS-1) and extrusion was performed at a barrel temperature of 200° C. and a screw speed of 40 rpm. The extruded strand was cooled and solidified with water, and then wound up at a winding speed such that the diameter of the filament was 1.75 mm ± 0.1 mm with a filament winding machine (manufactured by Philabot Co., Ltd., product name: Spooler), to obtain a filament according to the second embodiment. The average diameter of the obtained filament was measured by the following method. The average particle size (D50) of the inorganic powder refers to the particle size D50 at which the cumulative frequency is 50% in the arithmetic average particle size based on volume measured by a laser diffraction / scattering particle size distribution measurement method. The average particle size was measured using a laser diffraction / scattering particle size distribution measurement device (manufactured by Horiba, Ltd., product name: LA-960).

[0080] (Measurement of the average diameter of the filaments) A 5 m sample was taken from the obtained filament, 20 points were randomly selected, and their diameters were measured to three decimal places using a micrometer (Mitutoyo Corporation, product name: ABSOLUTE). Next, the average value was rounded off to the nearest tenth to obtain the average diameter of the filament.

[0081] Next, a three-dimensional object was produced using the filament obtained in Example 1 by the following method. (1st step) The prepared filament was set in a fused deposition modeling 3D printer (manufactured by INTAMSYS, product name: FUNMAT HT Enhanced) to form a three-dimensional object of 80 mm x 10 mm x 4 mm. Specifically, a sheet-like base layer was first formed with a size that allowed a margin of 1 cm for the bottom shape of the object under the temperature conditions shown in the temperature conditions of the first step below, and then the structure was formed under the same temperature conditions. The inner diameter of the nozzle that ejects the filament in the 3D printer was 0.4 mm, the layer pitch was 0.2 mm, and the drawing speed of the structure was 30 mm / s. <Temperature conditions for the first step> Discharge nozzle temperature: 205℃ Build stage temperature (Ts): 155℃ Ambient temperature in the printing area (Ta): 94℃ <Temperature conditions for the second step> Build stage temperature (Ts): 120℃ In Example 1, with the three-dimensional object fixed on the modeling stage, the modeling material (melted filament) was layered without any problems until the end to create the three-dimensional object.

[0082] (2nd process) After the first step was completed, the temperature of the modeling stage was lowered to 120°C, and the 3D model was peeled off from the surface of the modeling stage. At this point, the entire base layer of the 3D model had turned white, and its adhesion to the surface of the modeling stage had decreased, so the 3D model peeled off naturally from the modeling stage without any special peeling procedure.

[0083] Next, the three-dimensional object obtained above was placed in a sintering furnace and heated at 500°C for 2 hours to remove the polyacetal resin. The temperature was then raised to 1400°C to obtain a three-dimensional sintered object. The sintered three-dimensional object obtained from the filament of Example 1 did not show any deformation or the like in its appearance. Furthermore, no residue or residual carbon was confirmed.

[0084] <Comparative Example 1> A resin composition was obtained in the same manner as in Example 1, except that the blending amount of the inorganic powder was as shown in Table 2. Filaments were prepared in the same manner as in Example 1 from the obtained resin composition. Next, a three-dimensional object was formed under the same temperature conditions and manufacturing method as in Example 1. In Comparative Example 1, the three-dimensional object was fixed on the modeling stage, and the modeling material (molten filament) was layered without any problems until the end to produce a three-dimensional object. This three-dimensional object was heated at 500°C for two hours to remove the polyacetal resin. The temperature was then raised to 1400°C to obtain a three-dimensional sintered object. However, the obtained three-dimensional sintered object was unable to maintain its shape and collapsed.

[0085] <Comparative Example 2> A resin composition was obtained in the same manner as in Example 1, except that the blending amount of the inorganic powder was as shown in Table 2. Filaments were prepared in the same manner as in Example 1 from the obtained resin composition. Next, we attempted to form a three-dimensional object using the same temperature conditions and manufacturing method as in Example 1, but it was not possible to extrude resin from the nozzle of the 3D printer, and it was not possible to layer the three-dimensional object.

[0086] <Comparative Example 3> A resin composition was obtained in the same manner as in Example 1, except that the type of polyacetal resin and the blending amount of inorganic powder were as shown in Table 2. Filaments were prepared in the same manner as in Example 1 from the obtained resin composition. Next, we attempted to form a three-dimensional object using the same temperature conditions and manufacturing method as in Example 1, but the laminate peeled off from the modeling stage during stacking, making it impossible to complete the first step of modeling and forming a three-dimensional object.

[0087] [Table 2]

[0088] The symbols in the evaluation results in Table 2 have the following meanings. A: Three-dimensional objects could be manufactured using fused deposition modeling. B: The filament could not be extruded from the nozzle, or the laminate peeled off from the printing stage, making it impossible to print. C: A three-dimensional sintered product was obtained. D: The three-dimensional sintered object did not maintain the shape of the three-dimensional object. In addition, since no three-dimensional shaped objects were obtained in Comparative Examples 2 and 3, the production of three-dimensional sintered objects was not evaluated.

[0089] As shown in Table 2, it was confirmed that the resin composition according to the first embodiment can form a three-dimensional object by the fused deposition modeling method. It was also confirmed that residues and charcoal are unlikely to be generated after sintering the three-dimensional object.

[0090] A non-limiting list of exemplary embodiments and combinations of exemplary embodiments of the present disclosure are set forth below. [1] A polyacetal resin composition for three-dimensional modeling, comprising: The polyacetal resin composition comprises A polyacetal resin having a difference (Tm2-Tc) between a melting point Tm2 and a crystallization temperature Tc measured by a differential scanning calorimeter of 22°C or more and 40°C or less, and a melt flow rate measured at a temperature of 190°C and a load of 2.16 kg of 0.8g / 10min or more and 50.0g / 10min or less, at least one inorganic powder selected from a metal powder, a metal alloy powder, and a ceramic precursor powder; A polyacetal resin composition for three-dimensional modeling, wherein a ratio of the inorganic powder in the polyacetal resin composition is 70 to 95 parts by mass per 100 parts by mass of the total amount of the polyacetal resin and the inorganic powder. [2] The polyacetal resin composition for three-dimensional modeling according to [1], wherein the polyacetal resin contains 3.0% by mass or more and 6.0% by mass or less of comonomer units in all constituent units (100% by mass). [3] The polyacetal resin contains a comonomer unit in all constitutional units (100 mass%), The polyacetal resin composition for three-dimensional modeling according to [1] or [2], wherein the comonomer unit contains an oxyalkylene unit having two or more carbon atoms. [4] The polyacetal resin contains a comonomer unit in all constitutional units (100 mass%), The polyacetal resin composition for three-dimensional modeling according to any one of [1] to [3], wherein the comonomer unit is at least one oxyalkylene unit selected from an oxyethylene group, an oxypropylene group, and an oxytetramethylene group. [5] A filament for three-dimensional printing, comprising the polyacetal resin composition for three-dimensional printing according to any one of [1] to [4]. [6] The filament for three-dimensional modeling according to [5], having an average diameter of 1 to 3 mm. [7] A three-dimensional object comprising the polyacetal resin composition for three-dimensional modeling according to any one of [1] to [4]. [8] A three-dimensional sintered product, which is a sintered product of the three-dimensionally molded product described in [7]. [9] [7] A method for producing a three-dimensional object according to the present invention, The manufacturing method includes forming a three-dimensional object by a fused deposition modeling process using the polyacetal resin composition for three-dimensional modeling.

[10] The formation of the three-dimensional object is carried out by using a method according to the following formula 1: Tm2>Ts≧Tc, and Tc>Ta>Tc-100 (Equation 1) [In formula 1, Ts is the temperature of the modeling stage (°C), Tc is the crystallization temperature of the polyacetal resin (°C), Tm2 is the melting point of the polyacetal resin (°C), and Ta is the ambient temperature of the modeling area (°C)] forming the three-dimensional object on a modeling stage under a temperature condition that satisfies the following: After the three-dimensional object is formed on the modeling stage, the three-dimensional object is subjected to a process represented by the following formula 2: Tc>Ts (Formula 2) [In formula 2, Ts and Tc are the same as those in formula 1] and peeling the three-dimensional object from the surface of the modeling stage under temperature conditions that satisfy the above condition.

[11] The manufacturing method according to [9] or

[10] , wherein forming the three-dimensional object includes forming a base layer on a modeling stage, and then forming the three-dimensional object on the base layer.

[12] A method for producing a three-dimensional sintered product according to [8], comprising the steps of: The manufacturing method is a method for manufacturing a three-dimensional sintered product, the method including sintering the three-dimensional model. [Industrial Applicability]

[0091] INDUSTRIAL APPLICABILITY The polyacetal resin composition for three-dimensional modeling according to the present disclosure is capable of three-dimensional modeling, and can be easily sintered to obtain a three-dimensional sintered product with little residue or residual carbon. [Explanation of symbols]

[0092] 1 Modeling stage 2 Discharge nozzle 3. Air Duct 4 Base layer 5 Structural part 6 Three-dimensional objects

Claims

1. A polyacetal resin composition for three-dimensional modeling, comprising: The polyacetal resin composition comprises a polyacetal resin having a difference (Tm2-Tc) between a melting point Tm2 and a crystallization temperature Tc measured by a differential scanning calorimeter of 22°C or more and 40°C or less, and a melt flow rate measured at a temperature of 190°C and a load of 2.16 kg of 0.8 g / 10 min or more and 50.0 g / 10 min or less; at least one inorganic powder selected from a metal powder, a metal alloy powder, and a ceramic precursor powder; A polyacetal resin composition for three-dimensional modeling, in which a ratio of the inorganic powder is 70 to 95 parts by mass relative to 100 parts by mass of the total amount of the polyacetal resin and the inorganic powder in the polyacetal resin composition.

2. The polyacetal resin composition for three-dimensional modeling according to claim 1 , wherein the polyacetal resin contains 3.0% by mass or more and 6.0% by mass or less of comonomer units based on all constituent units (100% by mass).

3. The polyacetal resin contains a comonomer unit in all structural units (100% by mass), The polyacetal resin composition for three-dimensional modeling according to claim 1 or 2, wherein the comonomer unit contains an oxyalkylene unit having two or more carbon atoms.

4. The polyacetal resin contains a comonomer unit in all structural units (100% by mass), The polyacetal resin composition for three-dimensional modeling according to claim 1 or 2, wherein the comonomer unit is at least one oxyalkylene unit selected from an oxyethylene group, an oxypropylene group, and an oxytetramethylene group.

5. A filament for three-dimensional modeling, comprising the polyacetal resin composition for three-dimensional modeling according to claim 1 or 2.

6. The filament for three-dimensional shaping according to claim 5, having an average diameter of 1 to 3 mm.

7. A three-dimensional object comprising the polyacetal resin composition for three-dimensional modeling according to claim 1 or 2.

8. A three-dimensional sintered product which is a sintered product of the three-dimensionally shaped product according to claim 7.

9. A method for producing the three-dimensional object according to claim 7, comprising the steps of: The manufacturing method includes forming a three-dimensional object by a fused deposition modeling process using the polyacetal resin composition for three-dimensional modeling.

10. The formation of the three-dimensional object is carried out by reacting the three-dimensional object with a compound represented by the following formula 1: Tm2>Ts≧Tc, and Tc>Ta>Tc−100 (Equation 1) [In formula 1, Ts is the temperature of the modeling stage (°C), Tc is the crystallization temperature of the polyacetal resin (°C), Tm2 is the melting point of the polyacetal resin (°C), and Ta is the atmospheric temperature of the modeling area (°C)] forming the three-dimensional object on a modeling stage under a temperature condition that satisfies the following: After the three-dimensional object is formed on the modeling stage, a reaction is carried out according to the following formula 2: Tc>Ts (Formula 2) [In formula 2, Ts and Tc are the same as those in formula 1] The manufacturing method according to claim 9 , further comprising: peeling the three-dimensional object from the surface of the modeling stage under a temperature condition that satisfies the above condition.

11. The manufacturing method according to claim 9 , wherein forming the three-dimensional object includes forming a base layer on a modeling stage, and then forming the three-dimensional object on the base layer.

12. A method for producing a three-dimensional sintered product according to claim 8, comprising the steps of: The manufacturing method is a method for manufacturing a three-dimensional sintered product, the method including sintering the three-dimensional model.

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