Molded body, method for manufacturing molded body, and method for manufacturing sintered body

Abstract

This invention provides a molded body capable of suppressing plastic deformation during transport. The molded body of this invention comprises a sinterable inorganic powder and an organic binder, characterized in that the flexural modulus (MPa) of the molded body at a strain of 0.05% to 0.1% is 4000 to 15000, and the flexural yield strength (MPa) of the molded body is 10 or more.

Description

Technical Field

[0001] This invention relates to a molded body, a method for manufacturing a molded body, and a method for manufacturing a sintered body. Background Technology

[0002] Sintered bodies, especially those with precision and complex shapes, are manufactured using sinterable powders such as metals, ceramics, and cermets. First, a composition for sintering bodies containing sinterable powders and a binder is prepared. Next, the prepared composition for sintering bodies is heated and mixed to produce a raw material for sintering bodies, which is then injection molded to form a green body. Next, the green body undergoes a debinding process, removing the binder from the green body through heat treatment or solvent treatment. Finally, the green body with the binder removed is sintered at a specified temperature. A sintered body is obtained in this manner.

[0003] In the manufacturing process of the sintered body described above, the green body obtained by injection molding the sintered body with the composition sometimes undergoes plastic deformation such as strain and breakage when it is transported to the degreasing process. Regarding such plastic deformation of the green body, the bending strength (green strength) of the green body has been used as an indicator to evaluate the plastic deformability of the green body (for example, see Patent Documents 1 to 3).

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Publication No. 2009-542880

[0007] Patent Document 2: Japanese Patent Application Publication No. 2001-106581

[0008] Patent Document 3: Japanese Patent Application Publication No. 2005-205805 Summary of the Invention

[0009] The problem that the invention aims to solve

[0010] However, in evaluations using flexural strength as an indicator, as described in Patent Documents 1-3, green bodies that exhibit a yield point outside the elastic region are evaluated as acceptable products without defects. As a result, when an external force near the maximum flexural strength is applied during the transport of the green body, plastic deformation sometimes occurs.

[0011] The present invention was made in view of the above-mentioned problems, and its object is to provide a molded body capable of suppressing plastic deformation during transport.

[0012] means for solving problems

[0013] In order to solve the above problems, the inventors conducted in-depth research and found that by having a green molded body that not only has a specified flexural yield strength but also a specified flexural modulus, the above problems can be solved, thus completing the present invention.

[0014] That is, the present invention is as follows.

[0015] [1] A molded body comprising a sinterable inorganic powder and an organic binder, wherein, The flexural modulus (MPa) of the molded body at a strain of 0.05% to 0.1% is 4000 to 15000. The flexural yield strength (MPa) of the molded body is 10 or higher.

[0016] [2] According to the molded body described in [1], the product of the flexural modulus (MPa) and the flexural yield strength (MPa) is 50,000 or more.

[0017] [3] According to the molded body described in [1] or [2], wherein, when observing the cross-section of the molded body using a microscope, every 1 mm 2 The number of voids larger than 30μm is less than 10.

[0018] [4] The molded body according to any one of [1] to [3], wherein the maximum particle size of the sinterable inorganic powder is less than 30 μm.

[0019] [5] The molded body according to any one of [1] to [4], wherein the molded body comprises polyacetal resin as the organic binder.

[0020] [6] According to the molded body of [5], wherein the melt flow rate of the polyacetal resin is 70 g / 10 min to 200 g / 10 min.

[0021] [7] A molded body according to any one of [1] to [6], wherein, relative to 100% by mass of the molded body, the molded body comprises 75% by mass and 95% by mass of the sinterable inorganic powder.

[0022] [8] The molded body according to any one of [1] to [7], wherein the sinterable inorganic powder is a metal powder.

[0023] [9] A molded body according to any one of [1] to [8], wherein a 100 mm diameter is present in the molded body. 2 The above refers to parts with a thickness of less than 1mm.

[0024]

[10] A method for manufacturing a molded body, comprising a sinterable inorganic powder and an organic binder, characterized in that the method for manufacturing the molded body includes the following steps: A mixing process in which sinterable inorganic powders and organic binders are mixed to obtain a compound; and The molding process of shaping the compound to obtain a molded body. The flexural modulus (MPa) of the molded body at a strain of 0.05% to 0.1% is 4000 to 15000. The flexural yield strength (MPa) of the molded body is 10 or higher.

[0025]

[11] According to the method for manufacturing the molded body described in

[10] , the mixing temperature in the mixing process is 160°C to 200°C.

[0026]

[12] In the manufacturing method of the molded body according to

[10] or

[11] above, the temperature of the barrel in the molding process is 150°C to 190°C.

[0027]

[13] The method for manufacturing a molded body according to any one of

[10] to

[12] above, wherein the injection pressure in the molding process is 50 MPa or more.

[0028]

[14] The method for manufacturing a molded body according to any one of

[10] to

[13] above, wherein, relative to 100% by mass of the molded body, the molded body contains 75% by mass and 95% by mass of the sinterable inorganic powder.

[0029]

[15] A method for manufacturing a sintered body, wherein the method for manufacturing the sintered body comprises the following steps: A degreasing process for obtaining a sintering precursor by removing the organic binder from a molded body according to any one of [1] to [9] or a molded body manufactured by any one of

[10] to

[14] through heating or chemical treatment; and A sintering process for sintering the sintering precursor to obtain a sintered body.

[0030] Invention Effects

[0031] According to the present invention, it is possible to provide a molded article capable of suppressing plastic deformation during transport. Detailed Implementation

[0032] The following describes in detail the methods for implementing the present invention. It should be noted that the present invention is not limited to the following description and can be implemented in various ways within its scope.

[0033] [Molded body]

[0034] The molded body of this embodiment comprises sinterable inorganic powder and organic binder. The molded body of this embodiment is a pre-molded body (green body) obtained by injection molding a sintered body comprising the above-mentioned inorganic powder and organic binder using a composition before degreasing and sintering. In this specification, "molded body" refers to a "green body," clearly distinguished from a "sintered body" obtained by degreasing and sintering a green body.

[0035] In this embodiment, it is important that the flexural modulus (MPa) of the molded body at a strain of 0.05% to 0.1% is 4000 to 15000. Furthermore, it is important that the flexural yield strength (MPa) of the molded body in this embodiment is 10 or higher. If the flexural modulus (MPa) of the molded body at a strain of 0.05% to 0.1% is 4000 to 15000 and the flexural yield strength (MPa) is 10 or higher, then plastic deformation such as strain and breakage of the molded body during transport can be suppressed. The flexural modulus and flexural yield strength can be measured using the methods described in the embodiments described later.

[0036] From the viewpoint of the strength of the molded body, the flexural modulus (MPa) of the molded body at a strain of 0.05% to 0.1% is preferably 5000 or more, more preferably 6000 or more, and even more preferably 7000 or more. Furthermore, from the viewpoint of thin-film formability, the upper limit is preferably 14500 or less, more preferably 14000 or less, and even more preferably 13000 or less.

[0037] From the viewpoint of the strength of the molded article, the flexural yield strength is preferably greater than 10 MPa, more preferably 15 MPa or more. From the viewpoint of the molded article not easily breaking upon drop, the upper limit is preferably 40 MPa or less, more preferably 35 MPa or less.

[0038] The product of the flexural modulus of elasticity (MPa) and the flexural yield strength (MPa) is preferably 50,000 or more, and more preferably 100,000 or more. If the product of the flexural modulus of elasticity and the flexural yield strength is 50,000 or more, it is possible to further suppress plastic deformation such as strain and breakage of the molded body during conveying.

[0039] Furthermore, when observing the cross-section of the molded body of this embodiment using a microscope, it is preferable to measure every 1 mm. 2 The number of voids larger than 30 μm is less than 10. This further suppresses plastic deformation such as strain and breakage during the transport of the molded body. The microscopic observation of the cross-section described above can be performed using the method described in the embodiments below.

[0040] The molded body of this embodiment preferably has at least a portion with a thickness of 1 mm or less. Furthermore, it is preferable to have a portion with a thickness of 1 mm or less. 2 The above refers to portions with a thickness of 1 mm or less, and more preferably portions with a thickness of 100 mm. 2 The above refers to portions with a thickness of 1 mm or less. Generally, the more widely a molded body has thin portions with a thickness of 1 mm or less, the more prone it is to plastic deformation during transport. However, the molded body of this embodiment can effectively suppress plastic deformation during transport even when it has thin portions with a thickness of 1 mm or less.

[0041] The molded body of this embodiment is obtained by manufacturing a sinterable body composition comprising a sinterable inorganic powder constituting the molded body and an organic binder, and then injection molding the manufactured sinterable body composition using a heated screw-type and piston-type injection molding machine.

[0042] In addition to inorganic powder and organic binder, the above-mentioned sintered body composition and molded body may also contain other additives.

[0043] Sinterable Inorganic Powders

[0044] In this embodiment, the "sinterable inorganic powder" (hereinafter, sometimes simply referred to as "inorganic powder") can be selected from all known suitable sinterable inorganic powders. Preferably, it is selected from metal powders, alloy powders, carbonyl metal powders, and mixtures of these powders. Among these, metal powders and ceramic powders are more preferred for imparting functionality, and metal powders are particularly preferred.

[0045] The above-mentioned sinterable inorganic powders can be used alone or in combination.

[0046] Specific examples of the aforementioned metal powders include: aluminum, magnesium, barium, calcium, cobalt, zinc, copper, nickel, iron, silicon, titanium, tungsten, and powders of metal compounds and alloys based on these metals. Here, not only pre-made alloys can be used, but mixtures of the various alloy components can also be used.

[0047] Examples of ceramic powders include: oxides such as zinc oxide, aluminum oxide, and zirconium oxide; hydroxides such as hydroxyapatite; carbides such as silicon carbide; nitrides such as silicon nitride and boron nitride; halides such as fluorite; silicates such as block talc; titanates such as barium titanate and lead zirconate titanate; carbonates; phosphates; ferrites; and high-temperature superconducting materials.

[0048] The aforementioned inorganic powders can be used alone or in combination with various inorganic substances such as metals, metal alloys, or ceramics. Particularly preferred metals and alloys include titanium alloys and stainless steel such as SUS316L; for ceramics, examples include Al2O3 and ZrO2.

[0049] The average particle size of the inorganic powder is preferably 30 μm or less, more preferably 20 μm or less. Furthermore, the maximum particle size of the inorganic powder is preferably 30 μm or less, more preferably 20 μm or less. If the maximum particle size of the inorganic powder is 30 μm or less, the metal powder dispersion results in injection-molded articles with higher strength. The aforementioned average particle size and maximum particle size can be measured, for example, using a particle size distribution measuring device employing laser diffraction.

[0050] The mass ratio of the sinterable inorganic powder to 100% of the molded body is preferably 70% to 95% by mass, more preferably 75% to 95% by mass, and particularly preferably 80% to 95% by mass. With the sinterable inorganic powder within the above range, a composition for sintered bodies having a melt viscosity suitable for injection molding can be obtained, and a molded body with high strength can also be obtained.

[0051] <Organic adhesives>

[0052] There are no particular limitations on the organic binder, but polyacetal resin is preferred. By using polyacetal resin, which is a depolymerizing polymer, as the organic binder, and taking advantage of the rigidity of polyacetal resin, molded articles with excellent shape retention can be obtained. The molded articles also exhibit excellent shape retention after a heat degreasing process, and no residue remains after heat degreasing. Furthermore, the heat degreasing process can be performed quickly, thus improving production efficiency.

[0053] (Polyacetal resin)

[0054] Examples of the aforementioned polyacetal resins include: polyacetal homopolymers, polyacetal copolymers, or mixtures thereof. From the viewpoint of thermal stability, polyacetal copolymers are preferred.

[0055] The aforementioned polyacetal resins can be used alone or in combination.

[0056] Examples of the aforementioned polyacetal homopolymers include polymers containing oxymethylene units in the main chain, and the ends of the polymer can be closed using ester or ether groups. Polyacetal homopolymers can be obtained using formaldehyde and a known molecular weight regulator as raw materials, and can utilize known... Salt polymerization catalysts are obtained from these raw materials by a known slurry method using hydrocarbons or the like as solvents, such as those described in Japanese Patent Publication No. 47-6420 or Japanese Patent Publication No. 47-10059.

[0057] It should be noted that the polyacetal homopolymer preferably has more than 99.8 mol% of the main chain, excluding the two ends, composed of oxymethylene units, and more preferably is a polyacetal homopolymer whose main chain, excluding the two ends, is composed only of oxymethylene units.

[0058] Examples of polyacetal copolymers include polymers having oxymethylene and oxyethylidene units in the main chain, such as those obtained by copolymerizing trioxymethylene with cyclic ethers and / or cyclic formaldehyde in the presence of a polymerization catalyst. Trioxymethylene is a cyclic trimer of formaldehyde, generally obtained by reacting an aqueous solution of formaldehyde in the presence of an acidic catalyst.

[0059] The aforementioned trioxymethylene sometimes contains impurities such as water, methanol, formic acid, and methyl formate, which can cause chain transfer. Therefore, it is preferable to purify it by removing these impurities, for example, through distillation. In this case, relative to 1 mole of trioxymethylene, it is preferable to adjust the total amount of impurities that cause chain transfer to 1 × 10⁻⁶. -3 Below 10 moles, a more preferable setting is 0.5 × 10⁻⁶. -3 Below the molar level. By reducing the amount of impurities to values ​​as described above, the polymerization rate can be significantly increased in practical applications, and the resulting polymer exhibits excellent thermal stability.

[0060] Cyclic ethers and / or cyclic formaldehydes are components capable of copolymerizing with the aforementioned trioxymethylene, and examples include: ethylene oxide, propylene oxide, epibutylene oxide, epichlorohydrin, epibromopropane, styrene oxide, oxetane, 1,3-dioxacyclopentane, ethylene glycol formaldehyde, propylene glycol formaldehyde, diethylene glycol formaldehyde, triethylene glycol formaldehyde, 1,4-butanediol formaldehyde, 1,5-pentanediol formaldehyde, 1,6-hexanediol formaldehyde, etc. Ethylene oxide and 1,3-dioxacyclopentane are particularly preferred. These substances can be used alone or in combination of two or more.

[0061] Relative to 1 mole of the above-mentioned trioxymethylene, the amount of cyclic ether and cyclic formaldehyde added is preferably 1.0 mol% or more, more preferably 3.0 mol% or more, and even more preferably 3.5 mol% or more. Furthermore, relative to 1 mole of the above-mentioned trioxymethylene, the amount of cyclic ether and cyclic formaldehyde added is preferably 8.0 mol% or less, more preferably 7.0 mol% or less, and even more preferably 5.0 mol% or less.

[0062] Examples of polymerization catalysts include compounds of boron, tin, titanium, phosphorus, arsenic, and antimony, represented by Lewis acids. Boron trifluoride, boron trifluoride hydrates, and coordination complexes of boron trifluoride with organic compounds containing oxygen or sulfur atoms are particularly preferred. Preferred examples include boron trifluoride, boron trifluoride diethyl ether complexes, and boron trifluoride di-n-butyl ether complexes. These substances can be used individually or in combination of two or more.

[0063] The preferred amount of polymerization catalyst added relative to 1 mole of the above-mentioned trioxymethylene is 0.1 × 10⁻⁶. -5 moles ~ 0.1 × 10 -3 Within the range of moles, more preferably within 0.3 × 10⁻⁶. -5 moles ~ 0.5 × 10 -4 Within the range of moles, a further preferred value is 0.5 × 10⁻⁶. -5 moles ~ 0.4 × 10 -4 Within the above range of molar amounts, a stable and long-term polymerization reaction can be carried out when the amount of polymerization catalyst added is within the above range.

[0064] In the manufacture of polyacetal copolymers, the deactivation of the polymerization catalyst is carried out as follows: The polyacetal resin obtained by the polymerization reaction is added to an aqueous solution or organic solvent containing at least one of the following catalyst neutralizing and deactivating agents: amines such as ammonia, triethylamine, and tri-n-butylamine, or hydroxides of alkali metals or alkaline earth metals, inorganic acid salts, or organic acid salts. The mixture is stirred in a slurry state for several minutes to several hours. After catalyst neutralization and deactivation, the slurry is filtered and washed to remove unreacted monomers, catalyst neutralizing and deactivating agents, and catalyst neutralizing salts, and then dried.

[0065] In addition, the following methods can be used to deactivate the polymerization catalyst: deactivating the polymerization catalyst by contacting the vapor of ammonia, triethylamine, etc. with the polyacetal copolymer; and deactivating the catalyst by contacting at least one of hindered amines, triphenylphosphine, and calcium hydroxide with the polyacetal resin using a mixer.

[0066] Alternatively, instead of deactivating the polymerization catalyst, the end-stabilization treatment described later can be performed on the polyacetal copolymer after reducing the volatilization of the polymerization catalyst by heating it at a temperature below the melting point of the polyacetal copolymer under an inactive gas atmosphere. The above-described deactivation and volatilization reduction operations of the polymerization catalyst can also be performed, if necessary, after pulverizing the polyacetal resin obtained through the polymerization reaction.

[0067] The obtained polyacetal resin is subjected to end-stabilization treatment by decomposing and removing unstable end portions using the following method. For example, a single-screw extruder or a twin-screw extruder with a vent can be used to melt the polyacetal resin and decompose and remove the unstable end portions in the presence of a known alkaline substance capable of decomposing unstable end portions, such as ammonia or aliphatic amines like triethylamine or tributylamine, hydroxides of alkali metals or alkaline earth metals represented by calcium hydroxide, inorganic weak acid salts, or organic weak acid salts.

[0068] The mass ratio of the polyacetal resin in the organic binder to 100% by mass is preferably 5% to 95% by mass, more preferably 5% to 70% by mass, and particularly preferably 5% to 60% by mass.

[0069] When the organic binder is removed from the molded body by heating, the mass ratio of polyacetal resin to 100% by mass of organic binder is preferably 5% to 50% by mass, more preferably 5% to 45% by mass, and particularly preferably 10% to 40% by mass.

[0070] By setting the ratio of polyacetal resin in the organic binder within the above range, there is a tendency to maintain the shape of the green molded body well.

[0071] The melt flow rate of the aforementioned polyacetal resin was determined according to ASTM-D-1238-57T at 190°C and 2.16 kg, preferably 70 g / 10 min or more and 200 g / 10 min or less, more preferably 90 g / 10 min or more and less than 200 g / 10 min, and even more preferably 90 g / 10 min or more and less than 140 g / 10 min. By adjusting the melt flow rate to 70 g / 10 min or more, the fluidity of the composition for sintering is improved, and by adjusting the melt flow rate to 200 g / 10 min or less, the strength of the molded body can be improved.

[0072] It should be noted that the melt flow rate of polyacetal resin can be increased by increasing the amount of molecular weight regulators (e.g., methyl acetal, methanol, formic acid, methyl formate, etc.) added during polymerization.

[0073] The preferred melting point of the aforementioned polyacetal resin is 100°C to 200°C, more preferably 140°C to 180°C. This melting point is the melting peak temperature determined by JIS K7121, and is the melting point on the high-temperature side when multiple melting temperatures exist.

[0074] In addition, the organic binder preferably includes a polyolefin resin, and more preferably includes a polyacetal resin and a polyolefin resin.

[0075] Polyacetal resin and polyolefin resin each have different thermal decomposition onset temperatures, thus allowing the organic binder to be gradually removed from the molded body during the heating and degreasing process. Furthermore, in acid degreasing, the polyacetal resin is decomposed by acids such as nitric acid and removed from the molded body; however, by incorporating a polyolefin resin that is not decomposed by acids, the shape of the molded body after the removal of the polyacetal resin can be maintained.

[0076] (Polyolefin resin)

[0077] The aforementioned polyolefin resin is a homopolymer or copolymer having structural units derived from olefins having 2 to 8 carbon atoms, preferably 2 to 4 carbon atoms.

[0078] From the viewpoint of the compatibility of the composition for sintering with sinterable inorganic powders during preparation and the injection molding properties when using the composition for sintering to manufacture molded articles, the melt flow rate of the above-mentioned polyolefin resin, measured at 190°C and 2.16 kg, is preferably 40 g / 10 min or more.

[0079] Examples of the aforementioned polyolefin resins include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyisoprene, and polybutadiene. Polyethylene, polypropylene, and mixtures thereof are preferred. From the viewpoint of maintaining the shape of the molded article when it is transported to the degreasing process and suppressing cracking and bulging during the degreasing process, polyethylene or polypropylene is more preferred. Among commercially available polyethylene products, suitable examples include: SUNTEC HD series (manufactured by Asahi Kasei Corporation), SUNTEC LD series (manufactured by Asahi Kasei Corporation), SUNTEC EVA series (manufactured by Asahi Kasei Corporation), NEO-ZEX, ULTZEX, and Evolue (all manufactured by Prime Polymer Co., Ltd.). For polypropylene, examples include: Sumitomo NOBLEN (manufactured by Sumitomo Chemical Co., Ltd.), NOVATEC PP (manufactured by Nippon Polypropylene Co., Ltd.), SunAllomer PM series (manufactured by SunAllomer Co., Ltd.), and Prime Polypro (manufactured by Prime Polymer Co., Ltd.).

[0080] From the viewpoint of maintaining the shape of the molded article after acid degreasing, the aforementioned polyolefin resin is preferably not easily decomposed by acid. From the viewpoint of maintaining the shape of the molded article after acid degreasing, the weight of the aforementioned polyolefin resin after immersion in a 30% nitric acid aqueous solution at 23°C (room temperature) and 70°C for 24 hours according to the method described in JIS K 7114 is preferably less than 10% of the weight before immersion, more preferably less than 5% of the weight before immersion, and particularly preferably less than 1% of the weight before immersion.

[0081] From the viewpoint of maintaining the shape of the molded body and being able to maintain the shape of the molded body after acid degreasing well, the mass ratio of the polyolefin resin in the organic binder to 100% by mass is preferably 5% to 95% by mass, more preferably 5% to 70% by mass, and particularly preferably 5% to 60% by mass.

[0082] When the organic binder comprises polyacetal resin and polyolefin resin, the mass ratio of the polyolefin resin to 100 parts by mass of the polyacetal resin is preferably 1 to 200 parts by mass, more preferably 5 to 150 parts by mass, and even more preferably 10 to 120 parts by mass.

[0083] Furthermore, the ratio of the total mass of the polyacetal resin and the polyolefin resin in the 100% by mass of the aforementioned organic binder is preferably 45% by mass or more. Additionally, the ratio of the total mass of the polyacetal resin, the polyolefin resin, and the flowability imparting agent (described later) in the 100% by mass of the aforementioned organic binder is preferably 90% by mass or more, more preferably 95% by mass or more, and even more preferably 98% by mass or more.

[0084] From the viewpoint of further reducing cracking and blistering during the degreasing process, the difference between the thermal decomposition initiation temperature (°C) of the aforementioned polyacetal resin and the thermal decomposition initiation temperature (°C) of the aforementioned polyolefin resin is preferably 30°C or more, and more preferably 30°C to 100°C. The aforementioned thermal decomposition initiation temperature is a temperature measured using a thermogravimetric differential calorimeter.

[0085] (Liquidity enhancer)

[0086] The composition for obtaining the sintered body preferably further comprises a flowability improver. By including the flowability improver, the flowability of the composition for the sintered body is further improved.

[0087] The aforementioned flowability imparting agent is a compound other than the polyacetal resin and polyolefin resin mentioned above, such as waxes. Examples of waxes include: paraffin wax, polyethylene wax, polypropylene wax, carnauba wax, polyethylene glycol, polytetramethylene glycol, polytetraethylene glycol, polyisobutylene, microcrystalline wax, lignite wax, beeswax, wood wax, synthetic wax, poly-1,3-dioxacyclopentane, poly-1,3-dioxacycloheptane, etc. From the viewpoint of superior flowability of the composition for sintered bodies in injection molding, paraffin wax, polyethylene glycol, and polytetramethylene glycol are preferred.

[0088] From the viewpoint of having better flowability of the composition for sintered bodies in injection molding, the mass ratio of the flowability imparting agent to 100% by mass of the above-mentioned organic binder is preferably 5% to 60% by mass, more preferably 5% to 50% by mass, and particularly preferably 10% to 50% by mass.

[0089] (Nitrogen-containing compounds, fatty acid metal salts)

[0090] The aforementioned polyacetal resin preferably further comprises nitrogen-containing compounds and / or fatty acid metal salts, and more preferably further comprises nitrogen-containing compounds and fatty acid metal salts.

[0091] By including the aforementioned nitrogen-containing compound and the aforementioned fatty acid metal salt, the extrudability, thermal stability, and foreign matter suppression of the composition during the manufacture of polyacetal resin are excellent. Furthermore, it tends to simultaneously improve the flowability and strength of the sintered body composition obtained by compounding with metal powder. The thermal stability of the sintered body composition is improved by including the aforementioned nitrogen-containing compound and the aforementioned fatty acid metal salt.

[0092] There are no particular limitations on the nitrogen-containing compounds mentioned above, and examples include polyamide resins, amide compounds, urea derivatives, triazine derivatives, etc. Among them, polyamide resins are preferred from the viewpoint that the composition for sintering has better thermal stability and the strength of the molded body is also better. These nitrogen-containing compounds can be used alone or in combination of two or more.

[0093] There are no particular limitations on the polyamide resins mentioned above. Examples include nylon 6, nylon 11, nylon 12, nylon 66, and nylon 6 obtained through the condensation of diamines and dicarboxylic acids, the condensation of amino acids, and the ring-opening polymerization of lactams. 10. Nylon 6 / 6 10. Nylon 6 / 6 6. Nylon 6 6 / 6 10. Nylon 6 / 6 6 / 6 10. Poly-β-alanine, etc.

[0094] There are no particular limitations on the aforementioned amide compounds. Examples include stearoylstearamine, oleoylstearamine, mustardoylstearamine, distearyl ethylenediamine, dibenzyl ethylenediamine, distearyl hexamethylenediamine, dimusyl ethylenediamine, dimusyl ethylenediamine, dimusyl phenyldiamine, distearyl phenyldiamine, sebacamide, etc., which are formed by aliphatic monocarboxylic acids, aliphatic dicarboxylic acids, aromatic monocarboxylic acids, or aromatic dicarboxylic acids with aliphatic monoamines, aliphatic diamines, aromatic monoamines, or aromatic diamines.

[0095] There are no particular limitations on the aforementioned urea derivatives, and examples include N-phenylurea, N,N'-diphenylurea, N-phenylthiourea, and N,N'-diphenylthiourea.

[0096] There are no particular limitations on the above-mentioned triazine derivatives, and examples include: melamine, phenylguanidine, N-phenylmelamine, melamine, N,N'-diphenylmelamine, N-hydroxymethylmelamine, N,N',N”-trihydroxymethylmelamine, 2,4-diamino-6-cyclohexyltriazine, melamine, etc.

[0097] The mass ratio of the nitrogen-containing compound relative to 100 parts by mass of polyacetal resin is preferably 0.005 parts by mass to 0.2 parts by mass, and particularly preferably 0.005 parts by mass to 0.1 parts by mass. When the mass ratio of the nitrogen-containing compound is within the above range, it is preferable from the viewpoint of improving the thermal stability of the polyacetal resin when the sinterable inorganic powder and the organic binder are mixed.

[0098] There are no particular limitations on the aforementioned fatty acid metal salts. Examples include fatty acid metal salts obtained by reacting saturated or unsaturated fatty acids or hydroxyl-substituted fatty acids with alkali metal or alkaline earth metal hydroxides, oxides or chlorides, having 10 to 35 carbon atoms.

[0099] Examples of fatty acids that are metal salts of the aforementioned fatty acids include: decanoic acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, pentadecanoic acid, palmitic acid, heptadecanoic acid, stearic acid, nonadecanoic acid, arachidic acid, behenic acid, ceramide, ceramide, heptadecanoic acid, linoleic acid, undecanoic acid, oleic acid, transoleic acid, cetearic acid, erucic acid, brassinolic acid, sorbic acid, linoleic acid, linolenic acid, arachidonic acid, propargyl acid, stearylene acid, 12-hydroxy-dodecanoic acid, 3-hydroxy-decanoic acid, 16-hydroxy-hexadecanoic acid, 10-hydroxy-hexadecanoic acid, 12-hydroxy-octadecanoic acid, 10-hydroxy-8-octadecanoic acid, etc. Additionally, the metal compounds include alkali metals such as lithium, sodium, and potassium; alkaline earth metals such as magnesium, calcium, strontium, and barium; and hydroxides or chlorides of zinc or aluminum. The preferred fatty acids are myristic acid, palmitic acid, and stearic acid, and the metal compounds are calcium hydroxide, oxide, and chloride, with calcium myristicate, calcium palmitate, and calcium stearate being more preferred.

[0100] When the above-mentioned nitrogen-containing compound and the above-mentioned fatty acid metal salt are added to the composition for sintered bodies, the ratio of the mass of the fatty acid metal salt to the mass of the nitrogen-containing compound (mass of fatty acid metal salt / mass of nitrogen-containing compound) is preferably within a specific range, specifically, 1 to 15, preferably 1 to 10. Setting this ratio to 1 to 15 is preferred in terms of improving the thermal stability of the polyacetal resin in the organic binder.

[0101] From the viewpoint of maintaining good formability during injection molding and further suppressing cracking and bulging during the degreasing process, the mass ratio of the organic binder in the above-mentioned sintered body composition is preferably 5 to 30 parts by mass, more preferably 5 to 20 parts by mass, and even more preferably 5 to 15 parts by mass relative to 100 parts by mass of the sintered body composition.

[0102] The resin components contained in the organic binder are preferably only the above-mentioned polyacetal resin, the above-mentioned polyolefin resin, the above-mentioned flowability imparting agent, and the above-mentioned nitrogen-containing compound (e.g., polyamide resin), but may also contain other additives.

[0103] (Other additives)

[0104] There are no limitations on other additives that can be added to the above-mentioned sintered body composition besides the above-mentioned components, as long as they do not impair the effect of the present invention. Antioxidants are a preferred additive.

[0105] Examples of antioxidants mentioned above include: octadecyl 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, octadecyl 3-(3'-methyl-5'-tert-butyl-4'-hydroxyphenyl)propionate, tetradecyl 3-(3',5'-di-tert-butyl-4'-hydroxyphenyl)propionate, 1,6-hexanediol-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), 1,4-butanediol-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate), octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, triethylene glycol-bis(3-(3-tert-butyl-5-methyl-4-hydroxyphenyl)propionate), tetradecyl (...) Methyl 3-(3'-tert-butyl-4'-hydroxyphenyl)propionate methane, N,N'-bis(3-(3,5-di-tert-butyl-4-hydroxyphenol)propionyl)hydrazine, N,N'-bis-(3-(3'-methyl-5'-tert-butyl-4-hydroxyphenol)propionyl)tetramethylenediamine, N,N'-bis-(3-(3',5'-di-tert-butyl-4-hydroxyphenol)propionyl)hexamethylenediamine, 3-(N-salicylicoyl)amino-1,2,4-triazole, N,N'-bis(2-(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionyloxy)ethyl)oxalamide, N,N'-hexamethylene-bis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionamide), etc. These antioxidants can be used individually or in combination of two or more.

[0106] The antioxidant content is 0.01 to 1.0 parts by weight, preferably 0.05 to 0.5 parts by weight, relative to 100 parts by weight of polyacetal resin. By keeping the antioxidant content within the above range, thermal stability is improved.

[0107] The melt flow rate of the composition for sintering is determined according to ASTM-D-1238-57T at 190°C and 2.16 kg, preferably greater than or equal to 80 g / 10 min and less than 200 g / 10 min, more preferably greater than or equal to 90 g / 10 min and less than 180 g / 10 min, and even more preferably greater than or equal to 90 g / 10 min and less than 140 g / 10 min. By adjusting the melt flow rate to 80 g / 10 min or more, the fluidity of the composition for sintering is improved, and by adjusting the melt flow rate to less than 200 g / 10 min, the strength of the green body can be improved.

[0108] It should be noted that the melt flow rate of the sintered body composition can be controlled within the above range, for example, by the type or mass ratio of the polyacetal resin used. The greater the melt flow rate of the polyacetal resin, the greater the melt flow rate of the sintered body composition tends to be.

[0109] (Method for manufacturing composition for sintered body)

[0110] The composition for the sintered body described above is not particularly limited and can be manufactured by known methods. Specifically, it can be manufactured by mixing the above-mentioned sinterable inorganic powder and organic binder, for example using a Henschel mixer, roller, V-type blender, etc., and then performing melt mixing in a semi-molten state using a single-screw extruder or twin-screw extruder, heated roller, kneader, Banbury mixer, etc., and can obtain products in various forms such as filaments and granules.

[0111] [Manufacturing method of molded body]

[0112] The method for manufacturing the molded body of the present invention is a method for manufacturing a molded body comprising sinterable inorganic powder and an organic binder, comprising the following steps: a mixing step of mixing the sinterable inorganic powder and the organic binder to obtain a mixture; and a molding step of molding the mixture to obtain the molded body. The mixing step and the molding step can be performed under desired conditions.

[0113] During mixing, it is desirable to use a mixing machine such as a pressure kneader, and the mixing temperature is preferably 160°C to 200°C, more preferably 160°C to 190°C, and even more preferably 160°C to 180°C. By setting the mixing temperature to 160°C or higher, mixing is carried out near the resin's melting temperature, which improves the resin's dispersibility and increases the flexural modulus of elasticity of the green body. Furthermore, by setting the mixing temperature to 200°C or lower, resin decomposition during mixing is suppressed, which reduces the number of voids in the cross-section of the green body. Additionally, even with the same composition, setting the mixing temperature within the aforementioned preferred range can suppress the decrease in flexural modulus of elasticity and yield strength.

[0114] During injection molding, the barrel temperature is preferably set to 150°C to 190°C, more preferably 160°C to 190°C, and even more preferably 165°C to 185°C. Setting the barrel temperature to 150°C or higher improves resin flowability, thereby enhancing moldability and increasing the density and strength of the green molded body. Setting the barrel temperature to 190°C or lower suppresses resin segregation during injection molding, thereby increasing the strength of the green molded body. Furthermore, even with the same composition, setting the barrel temperature within the aforementioned preferred range can suppress the decrease in flexural modulus and yield strength.

[0115] The injection pressure during injection molding is preferably 50 MPa or higher. Increasing the injection pressure reduces the porosity of the resulting molded article, improves the adhesion between the organic binder and the metal powder, and thus increases the resin filling density, resulting in a molded article with high strength. The injection pressure is preferably 60 MPa or higher, and more preferably 70 MPa or higher. There is no particular upper limit to the injection pressure; a realistic upper limit is the injection pressure that allows the molding apparatus to operate safely. Specifically, the upper limit of the injection pressure is approximately 200 MPa.

[0116] It should be noted that while exceeding a certain injection pressure is important to improve the strength of the molded part, exceeding the necessary injection pressure is not crucial. If the strength of the resulting molded part is the same, a lower injection pressure is preferable from a safety perspective.

[0117] In this way, it is possible to manufacture molded bodies with a flexural modulus (MPa) of 4000 to 15000 and a flexural yield strength (MPa) of 10 or more at a strain of 0.05% to 0.1%.

[0118] The flexural modulus (MPa) of the above-mentioned green molded body at a strain of 0.05% to 0.1% is preferably in the range of 4000 to 15000, more preferably 4000 to 12000, and particularly preferably 7000 to 12000. With a flexural modulus within the above range, it is possible to prevent plastic deformation during transport while suppressing impact damage caused by falling objects.

[0119] Furthermore, the flexural strength (MPa) of the green molded body is preferably 10 or more, more preferably 10 to 100, and particularly preferably 10 to 40. With the flexural strength within the above range, a high-strength molded body capable of withstanding loads such as those from ejection devices can be obtained.

[0120] Furthermore, relative to 100% by mass of the molded body, it is preferable to include 75% by mass and 95% by mass of sinterable inorganic powder. If the content of sinterable inorganic powder is 75% by mass or more, separation during injection molding can be prevented, and the strength of the molded body can be improved. Additionally, if the content of sinterable inorganic powder is 95% by mass or less, brittleness of the molded body can be prevented. More preferably, it includes 90% by mass and 95% by mass of sinterable inorganic powder.

[0121] [Manufacturing method of sintered body]

[0122] The method for manufacturing the sintered body of the present invention includes the following steps: a debinding step to remove the organic binder from the molded body of the present invention or the molded body manufactured by the method of manufacturing the molded body of the present invention by heating or chemical treatment to obtain a sintering precursor; and a sintering step to sinter the sintering precursor to obtain the sintered body. The debinding step and the sintering step can be performed under desired conditions.

[0123] In the case of degreasing by heating, degreasing is carried out by raising the temperature from room temperature to 500°C to 600°C under a nitrogen atmosphere. Alternatively, the flowability enhancer can be dissolved in a solvent before heating.

[0124] Next, the temperature is raised to the sintering temperature of the sinterable inorganic powder to obtain a sintered body.

[0125] In the case of degreasing using acid, degreasing is carried out by passing nitric acid gas through a nitrogen atmosphere and raising the temperature from room temperature to 110°C to 120°C.

[0126] Next, a sintered body can be obtained by heating the material to the sintering temperature of the sinterable inorganic powder.

[0127] Example

[0128] The present invention will be described in detail below with specific embodiments and comparative examples, but the present invention is not limited to the following embodiments.

[0129] It should be noted that the methods for determining the terms and characteristics in the embodiments and comparative examples are as follows.

[0130] [raw material]

[0131] (A) Polyacetal resin

[0132] (A-1)

[0133] A twin-shaft paddle-type continuous polymerization reactor (manufactured by Kurimoto Iron Works Co., Ltd., diameter 2B, L / D=14.8) with a jacket allowing the passage of a heat medium was adjusted to a temperature of 80°C. A catalyst preparation solution containing boron trifluoride-di-n-butyl ether complex diluted to 0.26% by mass using cyclohexane was continuously fed into the polymerization reactor at a rate of 69 g / h, trioxymethylene at 3500 g / h, 1,3-dioxane at 121 g / h, and methylal as a molecular weight regulator at 7.9 g / h, and polymerization was carried out.

[0134] The material discharged from the polymerization reactor is added to a 0.5% by mass triethylamine aqueous solution to deactivate the polymerization catalyst, followed by filtration, washing, and drying.

[0135] Next, the mixture was fed into a twin-screw extruder (L / D=40) with a vent set at 200°C. In the final stabilization zone, 0.8% by mass of triethylamine aqueous solution was added at a nitrogen content equivalent to 20 ppm. Stabilization was carried out simultaneously with degassing under reduced pressure at 90 kPa, and the mixture was then granulated using a granulator. Finally, it was dried at 100°C for 2 hours to obtain (A-1) polyacetal resin.

[0136] The obtained (A-1) polyacetal resin has a melting point of 164℃ and a melt flow rate of 90 g / 10 min. Details of the obtained polyacetal resin (A-1) are shown in Table 1.

[0137] [Table 1]

[0138] (A-2)

[0139] Except that the flow rate of methyl acetal, used as a molecular weight regulator, was adjusted to 9.4 g / h, polyacetal resin (A-2) was manufactured using the same method as that used for (A-1) polyacetal resin. The resulting polyacetal resin (A-2) had a melting point of 164°C and a melt flow rate of 121 g / 10 min. Details of the obtained polyacetal resin (A-2) are shown in Table 1.

[0140] (A-3)

[0141] Except that the flow rate of methyl acetal, used as a molecular weight regulator, was adjusted to 10.6 g / h, polyacetal resin (A-3) was manufactured using the same method as that used for (A-1) polyacetal resin. The resulting polyacetal resin (A-3) had a melting point of 164°C and a melt flow rate of 180 g / 10 min. Details of the obtained polyacetal resin (A-3) are shown in Table 1.

[0142] (B. Polyolefin resin)

[0143] Polypropylene (manufactured by Sumitomo Chemical Co., Ltd., Sumitomo NOBLEN UH501E1)

[0144] (C Nitrogen-containing compounds)

[0145] Nylon 66 (molecular weight 10,000)

[0146] (D fatty acid metal salt)

[0147] Calcium stearate

[0148] (E. Liquidity enhancer)

[0149] Paraffin wax (manufactured by Nippon Seiwa Co., Ltd., Paraffin wax-14)

[0150] [Preparation of Compositions for Molded Articles]

[0151] 0.05 parts by weight of (C) nylon 66 and 0.3 parts by weight of (D) calcium stearate were uniformly added and mixed into 100 parts by weight of any one of (A-1) to (A-3) polyacetal resins, and fed into a twin-screw extruder (L / D=40) with a vent set at 200°C. Granulation was achieved by degassing under reduced pressure at 90 kPa. The granules were then dried at 100°C for 2 hours to prepare the (A) polyacetal resin composition.

[0152] SUS316L, a sinterable inorganic powder, and a binder were mixed in the proportions shown in Table 2. When the binder component was set to 100% by mass, the binder was mixed in the proportions of (A) polyacetal resin 25% by mass, (B) polyolefin resin 25% by mass, and (E) flowability imparting agent 50% by mass. Thus, the compositions for manufacturing molded articles of Comparative Examples 1 to 5 and Examples 1 to 8 were prepared.

[0153] It should be noted that, except for Example 6, the maximum particle size of the SUS316L metal powder was adjusted to 30 μm using a sieve with a mesh size of 30 μm. The maximum particle size before sieving was 40 μm. Details of the composition for molding (molded body) are shown in Table 2.

[0154] [Table 2]

[0155] [evaluate]

[0156] (Mel flow rate (MI))

[0157] According to ASTM-D-1238, the MI (melt flow rate: g / 10 min) was determined using a MELT INDEXER manufactured by Toyo Seiki Co., Ltd. at 190°C and 2160 g.

[0158] (Preparation of molded test pieces)

[0159] The prepared molding composition was kneaded at 170°C for 1 hour using a pressure kneader. The kneaded mixture was then cooled and pulverized to obtain injection molding material. This material was then used in an injection molding machine (ROBOSHOT α-50iA, FANUC Corporation) at a molding temperature of 170°C and an injection pressure of 80 MPa to produce a flat plate with a length of 60 mm, a width of 60 mm, and a thickness of 1 mm or 2 mm. At this point, it was confirmed whether the composition filled the mold to the end. A 'filled to the end' condition was rated as '○', and a 'not filled to the end' condition was rated as '×'. The evaluation results are shown in Table 2. Strip-shaped molding test pieces according to JIS K 7139 were cut from the obtained flat plates.

[0160] It should be noted that for compositions rated as × in the above evaluation, in order to evaluate the flexural yield strength and flexural modulus of the molded specimens described later, molded specimens are also obtained by cutting out the flat portion filled into the mold.

[0161] In addition, the test piece can be cut not only from the flat plate, but also from any molded body.

[0162] (Flexural yield strength of the molded specimen)

[0163] The flexural yield strength of the molded specimen was evaluated using a three-point bending test. Specifically, using an Autograph (Instron, Dual column floor model 5581), with the support clamps spaced 50 mm apart, the flexural yield strength and flexural modulus were measured when the elongated molded specimen was lowered at a load sensor speed of 2 mm / min. Furthermore, the product of the measured flexural yield strength (MPa) and flexural modulus (MPa) was calculated. The measured flexural yield strength, flexural modulus, and calculated product values ​​are shown in Table 2.

[0164] (Microscopic observation)

[0165] Observe the cross-section of the strip-shaped test piece cut from the molded plate. Evaluate each 1 mm. 2 The number of voids larger than 30 μm was determined. Specifically, the entire cross-section was observed using an electron microscope (VHX-7000) manufactured by Keyence Corporation, and the diameter of each void was measured. The largest void larger than 30 μm was found to be 1 mm. 2 The number of voids in each area was measured. Test pieces with fewer than 10 voids were rated ○, and all other test pieces were rated ×. The evaluation results are shown in Table 2.

[0166] (Conveying Test 1: Push-out Test)

[0167] The composition used in the above moldability evaluation, which is filled to the end of the mold with the composition, is injection molded again under the same conditions, and it is tested whether cracking occurs due to ejection by the ejector device.

[0168] Specifically, the ejection speed of the ejector device was changed to 10 mm / s, 20 mm / s, 30 mm / s, 40 mm / s, and 50 mm / s, and the observed breakage speed of the test piece was recorded. Additionally, the test piece that did not break under the ejection speed of 50 mm / s was a very high-strength test piece and was recorded as 0. The observed breakage speeds of the test pieces are shown in Table 2.

[0169] (Conveying Test 2: Drop Test)

[0170] The composition used in the above moldability evaluation was filled to the end of the mold with the composition and then injection molded again under the same conditions, and it was tested whether deformation / cracks occurred due to dropping the resulting flat plate.

[0171] Specifically, 10 flat plates were dropped from a height of 1 meter, and the number of deformed and broken plates was counted. Deformation was evaluated as follows: when a plate was placed on a flat metal plate, any plate that was confirmed to be warped was evaluated as a deformed plate. Breakage was evaluated as follows: upon careful examination of the appearance, any plate with missing parts or cracks was evaluated as a broken plate.

[0172] The number of plates that deformed / fractured was counted and recorded. The number of plates that deformed / fractured is shown in Table 2.

[0173] <Evaluation Results of Transport Test 1>

[0174] In the ejection test, the test piece of the comparative example fractured at a relatively low ejection speed, while the test piece of the embodiment fractured at a higher ejection speed than the comparative example. In particular, no fracture occurred at an ejection speed of 50 mm / s for Examples 2, 3, 7, and 8, demonstrating high strength. This result indicates that the molded body of the present invention exhibits higher durability against breakage during transport.

[0175] <Evaluation Results of Transport Test 2>

[0176] In the drop test, most of the plates in the comparative examples, particularly those of Comparative Examples 1 and 3, deformed or cracked. In contrast, most of the plates in the embodiments, particularly those of Examples 1-5, 7, and 8, did not deform or crack. This result indicates that the molded articles of the present invention have higher durability against breakage during transport.

[0177] For the molded bodies of Examples 1-8, the organic binder, metal powder, mixing conditions, and molding conditions were appropriately balanced to achieve a flexural modulus (MPa) of 4000-15000 and a flexural yield strength (MPa) of 10 or more at a strain of 0.05%-0.1%, both of which showed excellent results in the conveying test. On the other hand, for the molded bodies of Comparative Examples 1-5, where the balance of metal powder content, mixing conditions, and molding conditions was changed, the flexural modulus and flexural yield strength decreased, and the formability of thin parts and the results of the conveying test were worse than those of the Examples.

Claims

1. A molded body comprising a sinterable inorganic powder and an organic binder, wherein, The organic binder comprises polyacetal resin and polyolefin resin. The flexural modulus of the molded body at a strain of 0.05% to 0.1% is 4000 MPa to 15000 MPa. The flexural yield strength of the molded body is above 10 MPa.

2. The molded body according to claim 1, wherein, The flexural modulus of the molded body at a strain of 0.05% to 0.1% is 5000 MPa to 14500 MPa.

3. The molded article according to claim 1 or 2, wherein, The flexural modulus of the molded body at a strain of 0.05% to 0.1% is 6000 MPa to 14000 MPa.

4. The molded article according to claim 1 or 2, wherein, The flexural modulus of the molded body at a strain of 0.05% to 0.1% is 7000 MPa to 13000 MPa.

5. The molded article according to claim 1 or 2, wherein, The flexural modulus of the molded body at a strain of 0.05% to 0.1% is 10000 MPa to 12000 MPa.

6. The molded article according to claim 1 or 2, wherein, The flexural yield strength of the molded body is above 15 MPa.

7. The molded article according to claim 1 or 2, wherein, The flexural yield strength of the molded body is above 24 MPa.

8. The molded article according to claim 1 or 2, wherein, The flexural yield strength of the molded body is below 40 MPa.

9. The molded article according to claim 1 or 2, wherein, The flexural yield strength of the molded body is below 35 MPa.

10. The molded article according to claim 1 or 2, wherein, The product of the flexural modulus and the flexural yield strength is greater than 50,000 MPa·MPa.

11. The molded article according to claim 10, wherein, The product of the flexural modulus and the flexural yield strength is greater than or equal to 100,000 MPa·MPa.

12. The molded article according to claim 10, wherein, The product of the flexural modulus and the flexural yield strength is greater than or equal to 240,000 MPa·MPa.

13. The molded article according to claim 10, wherein, The product of the flexural modulus and the flexural yield strength is less than 380,000 MPa·MPa.

14. The molded article according to claim 1 or 2, wherein, When observing the cross-section of the molded body under a microscope, every 1 mm 2 The number of voids larger than 30μm is less than 10.

15. The molded article according to claim 1 or 2, wherein, The maximum particle size of the sinterable inorganic powder is less than 30 μm.

16. The molded article according to claim 15, wherein, The maximum particle size of the sinterable inorganic powder is less than 20 μm.

17. The molded article according to claim 1 or 2, wherein, The polyacetal resin is a polyacetal homopolymer, a polyacetal copolymer, or a mixture thereof.

18. The molded article according to claim 17, wherein, The polyacetal copolymer is a polyacetal copolymer obtained by copolymerizing trioxymethylene with cyclic ethers and / or cyclic formaldehyde.

19. The molded article according to claim 18, wherein, The cyclic ether and / or cyclic formaldehyde is selected from one or more of the group consisting of ethylene oxide, propylene oxide, epichlorohydrin, epibromopropane, styrene oxide, oxetane, 1,3-dioxacyclopentane, ethylene glycol formaldehyde, propylene glycol formaldehyde, diethylene glycol formaldehyde, triethylene glycol formaldehyde, 1,4-butanediol formaldehyde, 1,5-pentanediol formaldehyde, and 1,6-hexanediol formaldehyde.

20. The molded article according to claim 1 or 2, wherein, The mass ratio of the polyacetal resin in the organic binder is 5% to 95% by mass relative to 100% by mass of the organic binder.

21. The molded article according to claim 1 or 2, wherein, The melt flow rate of the polyacetal resin is 70 g / 10 min to 200 g / 10 min.

22. The molded article according to claim 21, wherein, The melt flow rate of the polyacetal resin is greater than or equal to 90 g / 10 min and less than 200 g / 10 min.

23. The molded article according to claim 21, wherein, The melt flow rate of the polyacetal resin is greater than or equal to 90 g / 10 min and less than 140 g / 10 min.

24. The molded article according to claim 1 or 2, wherein, The polyolefin resin is a homopolymer or copolymer having structural units derived from olefins having 2 to 8 carbon atoms.

25. The molded article according to claim 1 or 2, wherein, The polyolefin resin is a homopolymer or copolymer having structural units derived from olefins having 2 to 4 carbon atoms.

26. The molded article according to claim 1 or 2, wherein, The polyolefin resin is polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, polyisoprene, or polybutadiene.

27. The molded article according to claim 1 or 2, wherein, The mass ratio of the polyolefin resin in the organic binder is 5% to 95% by mass relative to 100% by mass of the organic binder.

28. The molded article according to claim 27, wherein, The mass ratio of the polyolefin resin in the organic binder is 5% to 60% by mass relative to 100% by mass of the organic binder.

29. The molded article according to claim 1 or 2, wherein, The mass ratio of the polyolefin resin is 1 to 200 parts by mass relative to 100 parts by mass of the polyacetal resin.

30. The molded article according to claim 29, wherein, The polyolefin resin is in the range of 5 to 150 parts by mass relative to 100 parts by mass of the polyacetal resin.

31. The molded article according to claim 29, wherein, The mass ratio of the polyolefin resin is 10 to 120 parts by mass relative to 100 parts by mass of the polyacetal resin.

32. The molded article according to claim 1 or 2, wherein, The ratio of the total mass of the polyacetal resin and the polyolefin resin in 100% by mass of the organic binder is 45% by mass or more.

33. The molded article according to claim 1 or 2, wherein, The difference between the thermal decomposition initiation temperature of the polyacetal resin and the thermal decomposition initiation temperature of the polyolefin resin is more than 30°C.

34. The molded article according to claim 33, wherein, The difference between the thermal decomposition initiation temperature of the polyacetal resin and the thermal decomposition initiation temperature of the polyolefin resin is 30℃~100℃.

35. The molded article according to claim 1 or 2, wherein, The molded body also contains a flowability imparting agent.

36. The molded article according to claim 35, wherein, The flowability imparting agent is a wax.

37. The molded article according to claim 35, wherein, The flowability imparting agent is paraffin wax, polyethylene wax, polypropylene wax, carnauba wax, polyethylene glycol, polytetramethylene glycol, polytetraethylene glycol, polyisobutylene, microcrystalline wax, lignite wax, beeswax, wood wax, synthetic wax, poly-1,3-dioxacyclopentane, or poly-1,3-dioxacycloheptane.

38. The molded article according to claim 35, wherein, The flowability imparting agent is present in a mass ratio of 5% to 60% of 100% by mass relative to the organic binder.

39. The molded article according to claim 38, wherein, The flowability imparting agent is present in a mass ratio of 10% to 50% of the organic binder, relative to 100% by mass.

40. The molded article according to claim 1 or 2, wherein, The polyacetal resin also contains nitrogen-containing compounds and / or fatty acid metal salts.

41. The molded article according to claim 40, wherein, The nitrogen-containing compound is selected from one or more of the group consisting of amide compounds, urea derivatives, and triazine derivatives.

42. The molded article according to claim 40, wherein, The nitrogen-containing compound is a polyamide resin.

43. The molded article according to claim 42, wherein, The polyamide resin is nylon 6, nylon 11, nylon 12, nylon 66, nylon 610, nylon 6 / 610, nylon 6 / 66, nylon 66 / 610, nylon 6 / 66 / 610, or poly-β-alanine.

44. The molded article according to claim 40, wherein, The nitrogen-containing compound is present in a mass ratio of 0.005 to 0.2 parts by mass relative to 100 parts by mass of the polyacetal resin.

45. The molded article according to claim 44, wherein, The nitrogen-containing compound is present in a mass ratio of 0.005 to 0.1 parts by mass relative to 100 parts by mass of the polyacetal resin.

46. ​​The molded article according to claim 40, wherein, The fatty acid metal salt is a fatty acid metal salt obtained by reacting saturated or unsaturated fatty acids or hydroxyl-substituted fatty acids with alkali metal or alkaline earth metal hydroxides, oxides or chlorides, with 10 to 35 carbon atoms.

47. The molded article according to claim 46, wherein, The fatty acid metal salt is calcium myristate, calcium palmitate, or calcium stearate.

48. The molded article according to claim 40, wherein, The polyacetal resin comprises a nitrogen-containing compound and a fatty acid metal salt, and the mass ratio of the fatty acid metal salt to the mass of the nitrogen-containing compound (mass of fatty acid metal salt / mass of nitrogen-containing compound) is 1 to 15.

49. The molded article according to claim 48, wherein, The ratio of the mass of the fatty acid metal salt to the mass of the nitrogen-containing compound (mass of fatty acid metal salt / mass of nitrogen-containing compound) is 1 to 10.

50. The molded article according to claim 1 or 2, wherein, The organic binder accounts for 5 to 30 parts by mass relative to 100 parts by mass of the molded body.

51. The molded article according to claim 50, wherein, The organic binder accounts for 5 to 20 parts by mass relative to 100 parts by mass of the molded body.

52. The molded article according to claim 50, wherein, The organic binder accounts for 5 to 15 parts by mass relative to 100 parts by mass of the molded body.

53. The molded article according to claim 1 or 2, wherein, Relative to 100% by mass of the molded body, the molded body contains 70% by mass and less than 95% by mass of the sinterable inorganic powder.

54. The molded article according to claim 53, wherein, Relative to 100% by mass of the molded body, the molded body contains 75% by mass and less than 95% by mass of the sinterable inorganic powder.

55. The molded article according to claim 53, wherein, Relative to 100% by mass of the molded body, the molded body contains 80% by mass and less than 95% by mass of the sinterable inorganic powder.

56. The molded article according to claim 1 or 2, wherein, The sinterable inorganic powder is selected from metal powders, alloy powders, carbonyl metal powders, ceramic powders, and mixtures of these powders.

57. The molded article according to claim 56, wherein, The sinterable inorganic powder is a metal powder.

58. The molded article according to claim 56, wherein, The metal powder is selected from aluminum, magnesium, barium, calcium, cobalt, zinc, copper, nickel, iron, silicon, titanium, tungsten, and powders of metal compounds and metal alloys based on these metals.

59. The molded article according to claim 56, wherein, The ceramic powder is selected from zinc oxide, aluminum oxide, zirconium oxide, hydroxyapatite, silicon carbide, silicon nitride, boron nitride, fluorite, block talc, barium titanate, lead zirconate titanate, carbonates, phosphates, ferrites, and high-temperature superconducting materials.

60. The molded article according to claim 56, wherein, The sinterable inorganic powder is selected from titanium alloys, SUS316L, Al2O3, and ZrO2.

61. The molded article according to claim 1 or 2, wherein, There is a 100mm in the molded body 2 The above refers to parts with a thickness of less than 1mm.

62. A method for manufacturing a molded article, comprising the method for manufacturing the molded article according to any one of claims 1 to 61, characterized in that, The method for manufacturing the molded body includes the following steps: A mixing process in which sinterable inorganic powders and organic binders are mixed to obtain a compound; and A molding process in which the compound is shaped to obtain a molded body.

63. A method for manufacturing a molded article, comprising a method for manufacturing a molded article containing sinterable inorganic powder and an organic binder, characterized in that, The method for manufacturing the molded body includes the following steps: A mixing process in which sinterable inorganic powders and organic binders are mixed to obtain a compound; and The molding process of shaping the compound to obtain a molded body. The organic binder comprises polyacetal resin and polyolefin resin. The flexural modulus of the molded body at a strain of 0.05% to 0.1% is 4000 MPa to 15000 MPa. The flexural yield strength of the molded body is above 10 MPa.

64. The method for manufacturing a molded article according to claim 62 or 63, wherein, The mixing temperature in the mixing process is 160℃~200℃.

65. The method for manufacturing a molded article according to claim 64, wherein, The mixing temperature in the mixing process is 160℃~190℃.

66. The method for manufacturing a molded article according to claim 64, wherein, The mixing temperature in the mixing process is 160℃~180℃.

67. The method for manufacturing a molded article according to claim 62 or 63, wherein, The temperature of the barrel in the molding process is 150℃~190℃.

68. The method for manufacturing a molded article according to claim 67, wherein, The temperature of the barrel in the molding process is 160℃~190℃.

69. The method for manufacturing a molded article according to claim 67, wherein, The temperature of the barrel in the molding process is 165℃~185℃.

70. The method for manufacturing a molded article according to claim 62 or 63, wherein, The injection pressure in the molding process is above 50 MPa.

71. The method for manufacturing a molded article according to claim 70, wherein, The injection pressure in the molding process is above 60 MPa.

72. The method for manufacturing a molded article according to claim 70, wherein, The injection pressure in the molding process is above 70 MPa.

73. The method for manufacturing a molded article according to claim 63, wherein, Relative to 100% by mass of the molded body, the molded body contains 75% by mass and less than 95% by mass of the sinterable inorganic powder.

74. A method for manufacturing a sintered body, wherein, The method for manufacturing the sintered body includes the following steps: A degreasing process to obtain a sintering precursor by removing the organic binder from the molded body according to any one of claims 1 to 61 or the molded body manufactured by the manufacturing method of the molded body according to any one of claims 62 to 73 through heating or chemical treatment; and A sintering process for sintering the sintering precursor to obtain a sintered body.

75. The method for manufacturing a sintered body according to claim 74, wherein, characterized in that, The organic binder is removed by heating during the degreasing process. The mass ratio of the polyacetal resin in the organic binder is 5% to 50% by mass relative to 100% by mass of the organic binder.

76. The method for manufacturing a sintered body according to claim 75, wherein, The mass ratio of the polyacetal resin in the organic binder is 10% to 40% by mass relative to 100% by mass of the organic binder.

77. The method for manufacturing a sintered body according to claim 74, wherein, In the case of degreasing by heating, degreasing is carried out by raising the temperature from room temperature to 500℃~600℃ under a nitrogen atmosphere.

78. The method for manufacturing a sintered body according to claim 74, wherein, In the case of degreasing using acid, degreasing is carried out by passing nitric acid gas through a nitrogen atmosphere and raising the temperature from room temperature to 110℃~120℃.

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