Polyacetal resin composition

Abstract

The present invention provides a polyacetal resin composition that is to be used by being kneaded with a metal powder, said polyacetal resin composition including 100 parts by weight of a polyacetal resin (A), 0.2-10.0 parts by weight of a fatty acid metal salt (B), and 0.2-10.0 parts by weight of a fatty acid ester compound (C), wherein the fatty acid metal salt (B) is a fatty acid zinc salt, a fatty acid magnesium salt, or a combination thereof, and the fatty acid ester compound (C) is a compound in which there are three or more ester bonds per molecule.

Description

Polyacetal resin composition

[0001] The present invention relates to a polyacetal resin composition to be kneaded with a metal powder for use. The present invention also relates to a method for producing the polyacetal resin composition, a metal resin composition containing the polyacetal resin composition and a metal powder, and a method for producing a powder injection molded product using the polyacetal resin composition as a binder resin composition.

[0002] In recent years, powder injection molding has become popular, in which a metal molded product is manufactured by injection molding a kneaded mixture obtained by kneading a binder resin composition with a metal powder. Powder injection molding is advantageous in terms of the degree of freedom in the shape and material of the molded product, and dimensional accuracy.

[0003] Polyacetal resins are widely used as engineering plastics due to their mechanical properties, friction and wear properties, chemical resistance, heat resistance, and electrical properties. Polyacetal resins can be easily removed by combustion, and the amount of residual ash can be reduced, making them suitable as binder resin compositions for metal powders in powder injection molding.

[0004] Patent Document 1 discloses an invention providing a polyacetal resin composition that is excellent in extrudability, thermal stability, and foreign matter suppression, as well as excellent dispersibility with metal powder, and a metal resin composition that is excellent in extrudability and thermal stability, contains little foreign matter, and has effectively dispersed metal powder, and is made of a metal powder and a polyacetal resin composition. This polyacetal resin composition contains 100 parts by mass of (A) a polyacetal resin, 0.005 to 0.2 parts by mass of (B) a nitrogen-containing compound, and 0.01 to 0.8 parts by mass of (C) a fatty acid metal salt, and has a melt flow index measured under conditions of 190°C and 2.16 kg of 60 g / 10 min or more and less than 200 g / 10 min, and a ratio of the content of the (C) fatty acid metal salt to the content of the (B) nitrogen-containing compound ((C) / (B)) of 1 to 15.

[0005] Japanese Patent Application Laid-Open No. 2020-041133

[0006] When the polyacetal resin composition is kneaded with a metal powder and used (i.e., when used as a binder for the metal powder), the kneaded product (metal-resin composition) is required to have both excellent bending strain and fluidity properties.

[0007] In view of the above circumstances, an object of the present invention is to provide a polyacetal resin composition to be kneaded with a metal powder for use. The present invention also provides a method for producing the polyacetal resin composition, a metal resin composition containing the polyacetal resin composition and a metal powder, and a method for producing a powder injection molded product using the polyacetal resin composition as a binder resin composition.

[0008] The present invention includes the following aspects [1] to [9]. [1] A polyacetal resin composition to be used by kneading with a metal powder, comprising: 100 parts by weight of a polyacetal resin (A); 0.2 to 10.0 parts by weight of a fatty acid metal salt (B); and 0.2 to 10.0 parts by weight of a fatty acid ester compound (C), wherein the fatty acid metal salt (B) is a zinc fatty acid, a magnesium fatty acid, or a combination thereof, and the fatty acid ester compound (C) is a compound having three or more ester bonds in the same molecule. [2] The polyacetal resin composition according to [1], wherein the fatty acid of the fatty acid metal salt (B) is a fatty acid having 12 to 28 carbon atoms. [3] The polyacetal resin composition according to [1] or [2], wherein the fatty acid metal salt (B) is at least one selected from the group consisting of magnesium laurate, zinc laurate, magnesium stearate, zinc stearate, magnesium behenate, zinc behenate, magnesium montanate, and zinc montanate. [4] The polyacetal resin composition according to any one of [1] to [3], wherein the fatty acid of the fatty acid ester compound (C) is a fatty acid having 12 to 28 carbon atoms. [5] The polyacetal resin composition according to any one of [1] to [4], wherein the fatty acid ester compound (C) is pentaerythritol tetrastearate, sorbitan tristearate, sorbitan tribehenate, or a combination thereof. [6] The polyacetal resin composition according to any one of [1] to [5], wherein the polyacetal resin (A) has a melt index of 40 to 100 g / 10 min (2.16 kg, 190°C). [7] A metal resin composition comprising the polyacetal resin composition according to any one of [1] to [6] and a metal powder (D).[8] A method for producing a polyacetal resin composition to be kneaded with metal powder, comprising the step of melt-kneading 100 parts by weight of a polyacetal resin (A), 0.2 to 10.0 parts by weight of a fatty acid metal salt (B), and 0.2 to 10.0 parts by weight of a fatty acid ester compound (C), wherein the fatty acid metal salt (B) is a zinc fatty acid, a magnesium fatty acid, or a combination thereof, and the fatty acid ester compound (C) is a compound having three or more ester bonds in the same molecule. [9] A method for producing a powder injection molded product, comprising the step of melt-kneading a metal powder and a binder resin composition and injecting the resulting kneaded product into a mold, wherein the binder resin composition is the polyacetal resin composition according to any one of [1] to [6].

[0009] By kneading the polyacetal resin composition of the present invention with a metal powder, the resulting kneaded body (metal-resin composition) has excellent bending strain and flowability. In particular, the metal-resin composition is suitable as a raw material for producing small and / or complex products by powder injection molding.

[0010] [Polyacetal Resin Composition] The polyacetal resin composition of the present invention contains 100 parts by weight of a polyacetal resin (A), 0.2 to 10.0 parts by weight of a fatty acid metal salt (B), and 0.2 to 10.0 parts by weight of a fatty acid ester compound (C). The fatty acid metal salt (B) is a zinc fatty acid, a magnesium fatty acid, or a combination thereof, and the fatty acid ester compound (C) is a compound having three or more ester bonds in the same molecule.

[0011] The polyacetal resin composition of the present invention is used by kneading with a metal powder (D) and is a binder resin composition for the metal powder (D). The polyacetal resin composition may be in the form of a solid, powder, strand, pellet, or a combination thereof. The polyacetal resin composition of the present invention is used by kneading with the metal powder (D), and the kneaded product (metal-resin composition) has both excellent bending strain and flowability.

[0012] The fatty acid metal salt (B) in the polyacetal resin composition of the present invention is believed to primarily improve the stability and therefore adhesion of the interface between the polyacetal resin (A) and the metal powder (D), suppress interfacial peeling due to external stresses such as tension and bending, and thereby improve the bending strain of the metal resin composition. Fatty acid ester compounds (C) having three or more ester bonds in the same molecule generally have a three-dimensional molecular shape and therefore have a larger molecular volume than fatty acid ester compounds having two or fewer ester bonds in the same molecule. Therefore, the fatty acid ester compound (C) is primarily located between the metal powders (D) in the metal resin composition, thereby suppressing collisions and friction between the metal powders and ultimately improving the flowability of the metal resin composition. Therefore, in a polyacetal resin composition that provides a metal resin composition with excellent bending strain and flowability properties, the fatty acid metal salt (B) and the fatty acid ester compound (C) having three or more ester bonds in the same molecule are each blended in an amount of 0.2 to 10.0 parts by weight per 100 parts by weight of the polyacetal resin (A).

[0013] The method for producing a polyacetal resin composition of the present invention includes a step of melt-kneading 100 parts by weight of a polyacetal resin (A), 0.2 to 10.0 parts by weight of a fatty acid metal salt (B), and 0.2 to 10.0 parts by weight of a fatty acid ester compound (C). The fatty acid metal salt (B) is a zinc fatty acid, a magnesium fatty acid, or a combination thereof, and the fatty acid ester compound (C) is a compound having three or more ester bonds in the same molecule. The melt-kneading step is carried out at a temperature equal to or higher than the melting point of the polyacetal resin composition (generally 180°C or higher) (under atmospheric pressure).

[0014] [Polyacetal Resin (A)] Polyacetal resin (A) is a polymer having an acetal bond: —O—CRH— (where R represents a hydrogen atom or an organic group) in a repeating unit, and is usually an oxymethylene group (—OCH ２-) as the main structural unit. The polyacetal resin (A) may be a copolymer (block copolymer) or a terpolymer containing one or more repeating structural units other than the oxymethylene group. The polyacetal resin (A) may have not only a linear structure but also a branched or crosslinked structure formed by using a glycidyl ether compound, an epoxy compound, an allyl ether compound, or the like as a comonomer and / or termonomer. Examples of structural units other than the oxymethylene group include an oxyethylene group (-OCH ２ CH ２ -or-OCH(CH ３ )-), oxypropylene group (—OCH ２ CH ２ CH ２ -, -OCH(CH ３ ) CH ２ -or-OCH ２ CH (CH ３ )-), oxybutylene group (—OCH ２ CH ２ CH ２ CH ２ -, -OCH(CH ３） CH ２ CH ２ -, -OCH ２ CH (CH ３ ) CH ２ -, -OCH ２ CH ２ CH (CH ３ ) -, -OCH(C ２ H ５ ) CH ２ -or-OCH ２ CH(C ２ H ５ )-) and the like, which may be branched and have 2 to 10 carbon atoms, and among these, an oxyalkylene group having 2 to 4 carbon atoms, which may be branched, or an oxyethylene group (—OCH ２ CH ２The content of the comonomer (structural unit other than an oxymethylene group) in the polyacetal resin (A) is 0.1 to 20 mass%, 0.5 to 20 mass%, 1.0 to 20 mass%, 2.0 to 20 mass%, 4.0 to 20 mass%, 1.0 to 15 mass%, 1.0 to 10 mass%, 1.0 to 15 mass%, 1.0 to 10 mass%, 1.0 to 10 mass%, 2.0 to 15 mass%, 2.0 to 10 mass%, 2.0 to 8.0 mass%, 4.0 to 10 mass%, or 4.0 to 8.0 mass%, based on the weight of the polyacetal resin (A).

[0015] The polyacetal resin (A) may be either terminal-stabilized or unterminal-stabilized. That is, the polyacetal resin composition may be prepared by melt-kneading the terminal-stabilized polyacetal resin (A), the fatty acid metal salt (B), and the fatty acid ester compound (C), or the polyacetal resin composition may be prepared by melt-kneading the terminal-stabilized polyacetal resin (A), the fatty acid metal salt (B), and the fatty acid ester compound (C).

[0016] Preferably, the polyacetal resin (A) is a copolymer of a cyclic acetal such as trioxane or tetraoxane with ethylene oxide or 1,3-dioxolane, for example, an acetal copolymer using 1,3-dioxolane as a comonomer.

[0017] The polyacetal resin (A) has a melt flow rate, measured in accordance with ASTM-D1238 (conditions: 190°C, load: 2.16 kg), of 1 to 100 g / 10 min, 10 to 100 g / 10 min, 15 to 100 g / 10 min, 20 to 100 g / 10 min, 25 to 100 g / 10 min, 30 to 100 g / 10 min, 35 to 100 g / 10 min, 40 to 100 g / 10 min, 45 to 100 g / 10 min, or 45 to 95 g / 10 min. Preferably, the polyacetal resin (A) has a melt flow rate of 30 to 100 g / 10 min, 40 to 100 g / 10 min, or 45 to 95 g / 10 min.

[0018] The method for producing the polyacetal resin (A) is not particularly limited, and the polyacetal resin (A) can be produced by a known method. For example, the polyacetal resin (A) having an oxymethylene group and an oxyalkylene group having 2 to 4 carbon atoms as constituent units can be produced by copolymerizing a cyclic acetal of an oxymethylene group, such as a trimer (trioxane) or tetramer (tetraoxane) of formaldehyde, with a cyclic acetal containing an oxyalkylene group having 2 to 5 carbon atoms, such as ethylene oxide, 1,3-dioxolane, 1,3,6-trioxocane, or 1,3-dioxepane.

[0019] For example, polyacetal resin (A) can be obtained by bulk polymerization of a cyclic acetal containing an oxymethylene group and a comonomer cyclic acetal containing an oxyalkylene group having 2 to 5 carbon atoms using a polymerization catalyst. A reaction terminator may be used as needed to deactivate the polymerization catalyst and the growing polymer terminals. Furthermore, a molecular weight regulator may be used as needed to adjust the molecular weight of polyacetal resin (A).

[0020] The types and amounts of the polymerization catalyst, reaction terminator, and molecular weight modifier are not limited as long as they do not impair the effects of the present invention, and known polymerization catalysts, reaction terminators, and molecular weight modifiers may be used as appropriate.

[0021] Examples of the polymerization catalyst include Lewis acids such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride, arsenic pentafluoride, and antimony pentafluoride, or complex compounds or salt compounds of these Lewis acids; protonic acids such as trifluoromethanesulfonic acid or perchloric acid; esters of protonic acids such as esters of perchloric acid and lower aliphatic alcohols; anhydrides of protonic acids such as mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids; or triethyloxonium hexafluorophosphate, triphenylmethylhexafluoroarsenate, acetylhexafluoroborate, heteropolyacids or acid salts thereof, isopolyacids or acid salts thereof, and perfluoroalkylsulfonic acids or acid salts thereof.

[0022] The reaction terminator is, for example, a trivalent organic phosphorus compound, an amine compound, a hydroxide of an alkali metal or an alkaline earth metal, or a combination thereof. The molecular weight regulator is, for example, methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, or oxymethylene di-n-butyl ether.

[0023] Furthermore, if necessary, the polyacetal resin (A) may contain known additives such as antioxidants, heat stabilizers, colorants, nucleating agents, plasticizers, fluorescent brighteners, sliding agents, antistatic agents, ultraviolet absorbers, or light stabilizers.

[0024] [Fatty Acid Metal Salt (B)] The fatty acid metal salt (B) is a zinc fatty acid, a magnesium fatty acid, or a combination thereof. The fatty acid metal salt (B) is a salt of a fatty acid having 12 to 28 carbon atoms with zinc or magnesium. Examples of fatty acids having 12 to 28 carbon atoms include lauric acid, palmitic acid, stearic acid, behenic acid, montanic acid, 12-hydroxystearic acid, oleic acid, and erucic acid. Preferably, the zinc fatty acid is zinc stearate, zinc laurate, zinc behenate, or zinc montanate, and the magnesium fatty acid is magnesium laurate, magnesium stearate, magnesium behenate, or magnesium montanate.

[0025] The content of the fatty acid metal salt (B) in the polyacetal resin composition is 0.2 to 10.0 parts by weight based on 100 parts by weight of the polyacetal resin (A). The content of the fatty acid metal salt (B) in the polyacetal resin composition may be 0.3 to 10.0 parts by weight, 0.5 to 10.0 parts by weight, 1.0 to 10.0 parts by weight, 3.0 to 10.0 parts by weight, 5.0 to 10.0 parts by weight, 8.0 to 10.0 parts by weight, 0.2 to 8.0 parts by weight, 0.3 to 8.0 parts by weight, 0.5 to 8.0 parts by weight, 1.0 to 8.0 parts by weight, 3.0 to 8.0 parts by weight, 5.0 to 8.0 parts by weight, 6.0 to 8.0 parts by weight, 0.2 to 6.0 parts by weight, 0.3 to 6.0 parts by weight, 0.5 to 6.0 parts by weight, 1.0 to 6.0 parts by weight, 3.0 to 6.0 parts by weight, or 5.0 to 6.0 parts by weight.

[0026] [Fatty Acid Ester Compound (C)] The fatty acid ester compound (C) is a compound having three or more ester bonds in the same molecule. The fatty acid ester compound (C) is an ester compound of a fatty acid having 12 to 28 carbon atoms and a polyhydric alcohol having three or more hydroxyl groups in one molecule. The fatty acid having 12 to 28 carbon atoms is preferably lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, montanic acid, oleic acid, linoleic acid, linolenic acid, ricinoleic acid, or 12-hydroxystearic acid. The polyhydric alcohol having three or more hydroxyl groups in one molecule is preferably erythritol, pentaerythritol, sorbitan, glycerin, diglycerin, triglycerin, sorbitol, arabitol, ribitol, xylitol, sorbitol, or mannitol.

[0027] More preferably, the fatty acid ester compound (C) is glycerin tripalmitate, glycerin tristearate, glycerin tribehenate, glycerin trimontanate, pentaerythritol tripalmitate, pentaerythritol tetrapalmitate, pentaerythritol tristearate, pentaerythritol tetrastearate, pentaerythritol tribehenate, pentaerythritol tetrabehenate, pentaerythritol trimontanate, pentaerythritol tetramontanate, or sorbitan tripalmitate. sorbitan tristearate, sorbitan tribehenate, sorbitan trimontanate, sorbitol tripalmitate, sorbitol tristearate, sorbitol tribehenate, sorbitol trimontanate, sorbitan trioleate, triacylglycerol, dipentaerythritol hexalaurate, dipentaerythritol hexamyristate, dipentaerythritol hexapalmitate, dipentaerythritol hexastearate, dipentaerythritol hexabehenate, or combinations thereof.

[0028] The content of the fatty acid ester compound (C) contained in the polyacetal resin composition is 0.2 to 10.0 parts by weight based on 100 parts by weight of the polyacetal resin (A). The content of the fatty acid ester compound (C) contained in the polyacetal resin composition may be 0.3 to 10.0 parts by weight, 0.5 to 10.0 parts by weight, 1.0 to 10.0 parts by weight, 3.0 to 10.0 parts by weight, 5.0 to 10.0 parts by weight, 8.0 to 10.0 parts by weight, 0.2 to 8.0 parts by weight, 0.3 to 8.0 parts by weight, 0.5 to 8.0 parts by weight, 1.0 to 8.0 parts by weight, 3.0 to 8.0 parts by weight, 5.0 to 8.0 parts by weight, 6.0 to 8.0 parts by weight, 0.2 to 6.0 parts by weight, 0.3 to 6.0 parts by weight, 0.5 to 6.0 parts by weight, 1.0 to 6.0 parts by weight, 3.0 to 6.0 parts by weight, or 5.0 to 6.0 parts by weight.

[0029] [Method for Producing Polyacetal Resin Composition] The method for producing the polyacetal resin composition of the present invention includes a step of melt-kneading the polyacetal resin (A), the fatty acid metal salt (B), and the fatty acid ester compound (C) (melt-kneading step). The melt-kneading can be carried out using, for example, a Banbury mixer, a roll, a plasticizer, a single-screw extruder, a twin-screw extruder, or a kneader.

[0030] The conditions of the melt-kneading step, such as temperature and pressure, may be appropriately selected in consideration of conventionally known methods for producing polyacetal resin compositions. For example, the melt-kneading step may be carried out at a temperature equal to or higher than the melting temperature of the polyacetal resin, and is usually preferably carried out at 180 to 240°C, more preferably 200 to 220°C.

[0031] The polyacetal resin composition may be prepared by melt-kneading the polyacetal resin (A), the fatty acid metal salt (B), and the fatty acid ester compound (C) all at once so that the fatty acid metal salt (B) and the fatty acid ester compound (C) ultimately have the above-mentioned contents, or the fatty acid metal salt (B) and the fatty acid ester compound (C) may be added separately to the polyacetal resin (A) in the same process. Alternatively, the polyacetal resin composition may be prepared by first preparing a polyacetal resin composition containing high concentrations of the fatty acid metal salt (B) and the fatty acid ester compound (C), and then diluting the resulting composition by kneading it with another polyacetal resin (A).

[0032] [Metal Resin Composition] The metal resin composition of the present invention contains the polyacetal resin composition and metal powder (D). The metal resin composition is produced by melt-kneading the polyacetal resin composition and metal powder (D). The melt-kneading step is carried out at a temperature equal to or higher than the melting point of the polyacetal resin composition (generally 180°C or higher). The metal resin composition (kneaded body) may be in the form of a solid, powder, strand, or pellet.

[0033] The metal-resin composition has excellent fluidity of 20 g / 10 min or more when measured at a temperature of 190° C. and a load of 10 kg in accordance with ASTM-D1238. Furthermore, the metal-resin composition has a compressibility of 20 to 10,000 g / 10 min, 20 to 9,000 g / 10 min, 20 to 8,000 g / 10 min, 20 to 7,000 g / 10 min, 20 to 6,000 g / 10 min, 20 to 5,000 g / 10 min, 20 to 4,000 g / 10 min, 20 to 3,000 g / 10 min, 20 to 2,800 g / 10 min, 20 to 2,600 g / 10 min, 150 to 10,000 g / 10 min, 150 to 9,000 g / 10 min, 150 to 8,000 g / 10 min, 150 to 7,000 g / 10 min, 15 The fluidity is 0 to 6000 g / 10 min, 150 to 5000 g / 10 min, 150 to 4000 g / 10 min, 150 to 3000 g / 10 min, 150 to 2800 g / 10 min, 150 to 2600 g / 10 min, 300 to 10000 g / 10 min, 300 to 9000 g / 10 min, 300 to 8000 g / 10 min, 300 to 7000 g / 10 min, 300 to 6000 g / 10 min, 300 to 5000 g / 10 min, 300 to 4000 g / 10 min, 300 to 3000 g / 10 min, 300 to 2800 g / 10 min, or 300 to 2600 g / 10 min.

[0034] The metal-resin composition also has excellent fluidity and excellent bending strain. The bending strain (%) is measured by performing a three-point bending test on a molded piece of the metal-resin composition at a bending speed of 2 mm / min using an apparatus such as the "Autograph (registered trademark) AGS-X" manufactured by Shimadzu Corporation, and determining the point at which the bending strength is maximum. The metal-resin composition has a fluidity of 20 g / 10 min or more and a bending strain of 1.0% or more. The metal-resin composition also has a bending strain of 1.0 to 10%, 1.0 to 9.5%, 1.0 to 9.0%, 1.0 to 8.5%, 1.0 to 8.0%, or 1.1 to 7.9%.

[0035] [Metal Powder (D)] The metal of the metal powder (D) is iron, aluminum, magnesium, cobalt, zinc, copper, nickel, titanium, tungsten, or a metal compound or metal alloy based on these. Preferably, the metal powder (D) is a powder of stainless steel (SUS), and the stainless steel is an austenitic stainless steel (SUS300 series), a ferritic or martensitic stainless steel (SUS400 series), or a precipitation-hardened stainless steel (SUS600 series). The particle size (average particle size) of the metal powder (D) is not particularly limited, but is 1 to 100 μm, 1 to 50 μm, 1 to 25 μm, or 1 to 10 μm, as measured by electron microscopy or laser diffraction / scattering particle size distribution measurement.

[0036] The content of the metal powder (D) in the metal-resin composition is 60 to 95 wt %, 65 to 95 wt %, 70 to 95 wt %, 80 to 95 wt %, 85 to 95 wt %, or 70 to 90 wt %, based on the weight of the metal-resin composition.

[0037] [Method for producing powder injection molded article] The method for producing a powder injection molded article of the present invention includes a step of melt-kneading a metal powder (D) and a binder resin composition, and injecting the resulting kneaded body into a mold, where the binder resin composition is the polyacetal resin composition. The method may also include a step of removing the binder resin composition from the molded kneaded body in a degreasing furnace by heating or using a gaseous acid, and a step of sintering the molded body in a sintering furnace to form the powder injection molded article.

[0038] [Optional Components] Optional additives such as other stabilizers, nucleating agents, release agents, fillers, pigments, lubricants, plasticizers, UV absorbers, flame retardants, or flame retardant aids may be added to the polyacetal resin composition as needed, within the scope of the present invention. Examples of optional additives include glass fiber, glass flakes, glass beads, wollastonite, mica, talc, boron nitride, calcium carbonate, kaolin, silicon dioxide, clay, asbestos, silica, diatomaceous earth, graphite, molybdenum disulfide, glass fiber, middle fiber, potassium titanate fiber, boron fiber, carbon fiber, aramid fiber, potassium titanate whiskers, carbon black, and pigments.

[0039] An example of the present invention will be described below. Materials used in the example and comparative examples are shown below.

[0040] [Polyacetal Resin (A)] As polyacetal resin (A-1), a polyacetal resin "Iupital (registered trademark) F40-05" manufactured by Mitsubishi Engineering Plastics Corporation was used. The melt flow rate of polyacetal resin (A-1) was 47 g / 10 min (measured in accordance with ASTM-D1238, under a load of 2.16 kg, at 190°C). As polyacetal resin (A-2), a polyacetal resin "Iupital (registered trademark) F50-05" manufactured by Mitsubishi Engineering Plastics Corporation was used. The melt flow rate of polyacetal resin (A-2) was 90 g / 10 min (measured in accordance with ASTM-D1238, under a load of 2.16 kg, at 190°C).

[0041] [Fatty Acid Metal Salts (B)] Fatty acid metal salt (B-1) is magnesium stearate "Magnesium Stearate" manufactured by NOF Corporation. Fatty acid metal salt (B-2) is zinc stearate "Zinc Stearate" manufactured by NOF Corporation. Fatty acid metal salt (B-3) is zinc laurate "ZS-3" manufactured by Nitto Kasei Kogyo Co., Ltd. Fatty acid metal salt (B-4) is zinc behenate "ZS-7" manufactured by Nitto Kasei Kogyo Co., Ltd. Fatty acid metal salt (B-5) is zinc montanate "ZS-8" manufactured by Nitto Kasei Kogyo Co., Ltd. Fatty acid metal salt (B-6) is calcium stearate "Calcium Stearate" manufactured by NOF Corporation.

[0042] [Fatty Acid Ester Compounds (C)] Fatty acid ester compound (C-1) is pentaerythritol tetrastearate "Unistar H-476" manufactured by NOF Corporation. Fatty acid ester compound (C-2) is sorbitan tristearate "Poem S-65V" manufactured by Riken Vitamin Co., Ltd. Fatty acid ester compound (C-3) is sorbitan tribehenate "Rikemal B-150" manufactured by Riken Vitamin Co., Ltd. Fatty acid ester compound (C-4) is pentaerythritol distearate "Unistar H-476D" manufactured by NOF Corporation. Fatty acid ester compound (C-5) is sorbitan stearate "Poem S-60V" manufactured by Riken Vitamin Co., Ltd.

[0043] [Metal Powder (D)] Metal powder (D) is SUS630 powder (average particle size: approximately 10 μm) manufactured by Epson Atmix Corporation.

[0044] Example 1 As shown in Table 1, the polyacetal resin composition of Example 1 was prepared by adding 0.2 parts by weight of magnesium stearate (B-1) and 0.2 parts by weight of pentaerythritol tetrastearate (C-1) to 100 parts by weight of polyacetal resin (A-1), and melt-kneading the mixture under a nitrogen stream for 20 minutes at a set temperature of 220°C and a rotation speed of 30 rpm using a kneader "Labo Plastomill (registered trademark) 4C150" manufactured by Toyo Seiki Seisaku-sho, Ltd. 20 g of this polyacetal resin composition (10 wt % based on the weight of the kneaded mixture) and 180 g of metal powder (D) (90 wt %) were kneaded under a nitrogen stream for 40 minutes using a kneader "Labo Plastomill (registered trademark) 4C150" manufactured by Toyo Seiki Seisaku-sho, Ltd., at a set temperature of 180°C and a rotation speed of 60 rpm, followed by cooling and solidification to prepare a kneaded mixture (metal resin composition). This kneaded body was crushed using a granulator manufactured by Harmo Corporation, "Grand Cutter (registered trademark) SPC-400."

[0045] [Examples 2 to 42] Similarly to Example 1, the polyacetal resin compositions of Examples 2 to 42 were prepared by melt-kneading the polyacetal resin (A), the fatty acid metal salt (B), and the fatty acid ester compound (C) in accordance with the types and blending amounts (parts by weight) of the polyacetal resin (A), the fatty acid metal salt (B), and the fatty acid ester compound (C) shown in Tables 1 to 3.

[0046] As in Example 1, in each of Examples 2 to 36, 20 g (10 wt%) of the polyacetal resin composition and 180 g (90 wt%) of the metal powder (D) were kneaded in the above-mentioned kneader at a set temperature of 180°C and a rotation speed of 60 rpm for 40 minutes under a nitrogen stream, followed by cooling and solidification to prepare a kneaded body (metal resin composition). In addition, in each of Examples 37 to 42, 60 g (30 wt%) of the polyacetal resin composition and 140 g (70 wt%) of the metal powder (D) were kneaded in the above-mentioned kneader at a set temperature of 180°C and a rotation speed of 60 rpm for 40 minutes under a nitrogen stream, followed by cooling and solidification to prepare a kneaded body (metal resin composition). Each of the kneaded bodies in Examples 2 to 42 was crushed using the above-mentioned crusher.

[0047] Comparative Examples 1 to 19: Similarly to the Examples, polyacetal resin compositions of Comparative Examples 1 to 19 were prepared according to the types and amounts (parts by weight) of polyacetal resin (A), fatty acid metal salt (B), and fatty acid ester compound (C) shown in Table 4. As in the Examples, melt-kneading was carried out in a Toyo Seiki Seisaku-sho, Ltd. kneader "Laboplastomill (registered trademark) 4C150" at a set temperature of 220°C and a rotation speed of 30 rpm for 20 minutes under a nitrogen stream. In each of Comparative Examples 1 to 19, 20 g (10 wt %) of the polyacetal resin composition and 180 g (90 wt %) of the metal powder (D) were kneaded in the kneader at a set temperature of 180°C and a rotation speed of 60 rpm for 40 minutes under a nitrogen stream, followed by cooling and solidification to prepare a kneaded body (metal resin composition). These kneaded bodies were then crushed using the crusher.

[0048] The bending strain and flowability properties of the kneaded bodies (metal-resin compositions) of Examples 1 to 42 and Comparative Examples 1 to 19 were evaluated as follows.

[0049] [Measurement and Evaluation Methods] (1) Bending Strain A molded piece measuring 12.7 mm x 63.5 mm x 3.2 mm thick was prepared from the crushed kneaded body using a small desktop injection molding machine "HAAKE MiniJet" manufactured by Thermo Fisher Scientific Co., Ltd., at a cylinder temperature of 220°C. A three-point bending test was performed on the molded piece using an "Autograph (registered trademark) AGS-X" manufactured by Shimadzu Corporation, at a bending speed of 2 mm / min, and the point at which the bending strength was maximum was taken as the bending strain (%). In the present invention, a bending strain (%) value of 1.0 (%) or more is considered to be acceptable and is evaluated as having excellent bending strain properties.

[0050] (2) Fluidity The fluidity of the crushed kneaded body was measured at a temperature of 190°C and a load of 10 kg in accordance with ASTM-D1238 using a melt indexer "L241" manufactured by Takara Kogyo Co., Ltd. In the present invention, a fluidity (g / 10 min) value of 20 (g / 10 min) or more is considered to be acceptable, and is evaluated as having excellent fluidity.

[0051]

[0052]

[0053]

[0054]

[0055] As shown in Tables 1 to 3, the kneaded products (metal resin compositions) of the polyacetal resin composition and metal powder in Examples 1 to 42 had both a bending strain of 1.0% or more and a fluidity of 20 g / 10 min or more. On the other hand, as shown in Table 4, the kneaded products (metal resin compositions) of the polyacetal resin composition and metal powder in Comparative Examples 1 to 19 did not have a fluidity of at least 20 g / 10 min or more, and did not have both excellent bending strain and fluidity.

Claims

1. A polyacetal resin composition for use by kneading with a metal powder, comprising: 100 parts by weight of polyacetal resin (A), 0.2 to 10.0 parts by weight of a fatty acid metal salt (B); 0.2 to 10.0 parts by weight of a fatty acid ester compound (C); Including, The fatty acid metal salt (B) is a fatty acid zinc salt, a fatty acid magnesium salt, or a combination thereof; The polyacetal resin composition as described above, wherein the fatty acid ester compound (C) is a compound having three or more ester bonds in the same molecule.

2. 2. The polyacetal resin composition according to claim 1, wherein the fatty acid of the fatty acid metal salt (B) is a fatty acid having 12 to 28 carbon atoms.

3. 2. The polyacetal resin composition according to claim 1, wherein the fatty acid metal salt (B) is at least one selected from the group consisting of magnesium laurate, zinc laurate, magnesium stearate, zinc stearate, magnesium behenate, zinc behenate, magnesium montanate, and zinc montanate.

4. 2. The polyacetal resin composition according to claim 1, wherein the fatty acid of the fatty acid ester compound (C) is a fatty acid having 12 to 28 carbon atoms.

5. The polyacetal resin composition according to claim 1 , wherein the fatty acid ester compound (C) is pentaerythritol tetrastearate, sorbitan tristearate, sorbitan tribehenate, or a combination thereof.

6. The polyacetal resin composition according to claim 1, wherein the polyacetal resin (A) has a melt index of 40 to 100 g / 10 min (2.16 kg, 190° C.).

7. The polyacetal resin composition according to any one of claims 1 to 6, Metal powder (D); A metal-resin composition comprising:

8. A method for producing a polyacetal resin composition to be kneaded with a metal powder, comprising the steps of: The method includes a step of melt-kneading 100 parts by weight of a polyacetal resin (A), 0.2 to 10.0 parts by weight of a fatty acid metal salt (B), and 0.2 to 10.0 parts by weight of a fatty acid ester compound (C), The fatty acid metal salt (B) is a fatty acid zinc salt, a fatty acid magnesium salt, or a combination thereof; The above-mentioned production method, wherein the fatty acid ester compound (C) is a compound having three or more ester bonds in the same molecule.

9. A method for producing a powder injection molded product, comprising a step of melt-kneading a metal powder and a binder resin composition and injecting the resulting kneaded body into a mold, The above-mentioned production method, wherein the binder resin composition is the polyacetal resin composition according to any one of claims 1 to 6.