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

Technical Field

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

Background Art

[0002] In recent years, a powder injection molding method for producing a metal molded article has been carried out by injection molding a kneaded product obtained by kneading a binder resin composition and metal powder. The powder injection molding method is excellent in terms of the freedom of shape and material of the molded article and dimensional accuracy.

[0003] Polyacetal resin is widely used as an engineering plastic by utilizing its mechanical properties, friction and wear characteristics, chemical resistance, heat resistance, or electrical properties. Polyacetal resin is easily removable by combustion and the remaining amount of ash can also be reduced, so it is also preferable as a binder resin composition for metal powder in the powder injection molding method.

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

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-041133 [Overview of the project] [Problems that the invention aims to solve]

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

[0007] In view of these circumstances, the present invention aims to provide a polyacetal resin composition for use in combination with metal powder. The present invention also provides a method for producing a polyacetal resin composition, a metal resin composition containing a polyacetal resin composition and metal powder, and a method for producing a powder injection molded article using the polyacetal resin composition as a binder resin composition. [Means for solving the problem]

[0008] The present invention includes the following embodiments [1] to [9]. [1] A polyacetal resin composition for use by kneading with metal powder, 100 parts by weight of polyacetal resin (A), Fatty acid metal salt (B) 0.2 to 10.0 parts by weight, Fatty acid ester compound (C) 0.2 to 10.0 parts by weight and Includes, The fatty acid metal salt (B) is zinc fatty acid, magnesium fatty acid, or a combination thereof. The polyacetal resin composition wherein the fatty acid ester compound (C) is a compound having three or more ester bonds within 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 montanoate, and zinc montanoate. [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 claims [1] to [4], wherein the fatty acid ester compound (C) is pentaerythritol tetrastearate, sorbitan tristearate, sorbitan tribehenate, or a combination thereof. [6] A polyacetal resin composition according to any one of items [1] to [5], wherein the melt index of the polyacetal resin (A) is 40 to 100 g / 10 min (2.16 kg, 190°C). [7] A polyacetal resin composition according to any one of items [1] to [6], Metal powder (D) and A metal resin composition containing the following: [8] A method for producing a polyacetal resin composition for use by kneading with metal powder, The process includes a step of melting and kneading 100 parts by weight of polyacetal resin (A), 0.2 to 10.0 parts by weight of fatty acid metal salt (B), and 0.2 to 10.0 parts by weight of fatty acid ester compound (C), The fatty acid metal salt (B) is zinc fatty acid, magnesium fatty acid, or a combination thereof. The manufacturing method wherein the fatty acid ester compound (C) is a compound having three or more ester bonds within the same molecule. [9] A method for manufacturing a powder injection molded article, comprising the step of melting and kneading a metal powder and a binder resin composition to obtain a kneaded body, and injecting it into a mold, The manufacturing method wherein the binder resin composition is the polyacetal resin composition described in any one of items [1] to [6]. [Effects of the Invention]

[0009] By using the polyacetal resin composition of the present invention in combination with metal powder, the resulting mixture (metal-resin composition) possesses excellent bending strain and fluidity properties. In particular, the metal-resin composition is suitable as a raw material for manufacturing small and / or complex products by powder injection molding. [Modes for carrying out the invention]

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

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

[0012] In the polyacetal resin composition of the present invention, the fatty acid metal salt (B) mainly improves the stability and thus the adhesiveness of the interface between the polyacetal resin (A) and the metal powder (D), and suppresses the peeling of the interface due to external stresses such as tension and bending, thereby improving the bending strain of the metal resin composition. Since the fatty acid ester compound (C) having three or more ester bonds in the same molecule generally has a three-dimensional molecular shape, its molecular volume is larger than that of a fatty acid ester compound having two or fewer ester bonds in the same molecule. Therefore, the fatty acid ester compound (C) is considered to mainly improve the fluidity of the metal resin composition by suppressing the collision and friction between the metal powders by being located between the metal powders (D) in the metal resin composition. Therefore, in the polyacetal resin composition that provides a metal resin composition having excellent characteristics of both bending strain and fluidity, 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 based on 100 parts by weight of the polyacetal resin (A).

[0013] The method for producing the polyacetal resin composition of the present invention includes a step of melt-kneading 100 parts by weight of the polyacetal resin (A), 0.2 to 10.0 parts by weight of the fatty acid metal salt (B), and 0.2 to 10.0 parts by weight of the fatty acid ester compound (C). The fatty acid metal salt (B) is zinc fatty acid, 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 performed at a temperature not lower than the melting temperature of the polyacetal resin composition (generally 180°C or higher) (under atmospheric pressure).

[0014] [Polyacetal resin (A)] The polyacetal resin (A) is a polymer having an acetal bond: -O-CRH- (where R represents a hydrogen atom or an organic group) as a repeating unit, and usually has an oxymethylene group (-OCH2-) in which R is a hydrogen atom as a main constituent unit. The polyacetal resin (A) may be a copolymer (block copolymer) or a terpolymer containing one or more repeating constituent units other than the oxymethylene group. Further, 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, etc. as a comonomer and / or a termonomer. Examples of the constituent unit other than the oxymethylene group include, for example, an oxyethylene group (-OCH2CH2- or -OCH(CH3)-), an oxypropylene group (-OCH2CH2CH2-, -OCH(CH3)CH2- or -OCH2CH(CH3)-), an oxybutylene group (-OCH2CH2CH2CH2-, -OCH(CH 3) CH2CH2-, -OCH2CH(CH3)CH2-, -OCH2CH2CH(CH3)-, -OCH(C2H5)CH2- or -OCH2CH(C2H5)-), etc., and among them, an oxyalkylene group having 2 to 4 carbon atoms which may be branched, or an oxyethylene group (-OCH2CH2-) is preferable. Further, the content of the comonomer (constituent unit other than the oxymethylene group) in the polyacetal resin (A) is 0.1% by weight to 20% by mass, 0.5 to 20% by weight, 1.0 to 20% by weight, 2.0 to 20% by weight, 4.0 to 20% by weight, 1.0 to 15% by weight, 1.0 to 10% by weight, 1.0 to 15% by weight, 1.0 to 10% by weight, 2.0 to 15% by weight, 2.0 to 10% by weight, 2.0 to 8.0% by weight, 4.0 to 10% by weight, or 4.0 to 8.0% by weight based on the weight of the polyacetal resin (A).

[0015] The polyacetal resin (A) may be end-stabilized or unend-stabilized. That is, the polyacetal resin composition may be prepared by melt-kneading the end-stabilized polyacetal resin (A), the fatty acid metal salt (B), and the fatty acid ester compound (C), or by melt-kneading the unend-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, the polyacetal resin (A) is an acetal copolymer using 1,3-dioxolane as the comonomer.

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

[0018] The method for producing polyacetal resin (A) is not particularly limited and can be produced by known methods. For example, polyacetal resin (A), which has 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-trioxocan, or 1,3-dioxepane.

[0019] For example, polyacetal resin (A) can be obtained by bulk polymerization of a cyclic acetal with an oxymethylene group and a cyclic acetal containing a C2-C5 oxyalkylene group, which is a comonomer, using a polymerization catalyst. A reaction termination agent may be used as needed to deactivate the polymerization catalyst and the polymerization growth ends. A molecular weight modifier may also be used as needed to adjust the molecular weight of polyacetal resin (A).

[0020] The type and amount of polymerization catalyst, reaction stopper, and molecular weight modifier are not limited as long as they do not hinder the effects of the present invention, and known polymerization catalysts, reaction stoppers, and molecular weight modifiers may be used as appropriate.

[0021] Polymerization catalysts include, for example, 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, triphenylmethylhexafluoroalzenate, acetylhexafluoroborate, heteropoly acids or their acidic salts, isopoly acids or their acidic salts, perfluoroalkyl sulfonic acids or their acidic salts.

[0022] Reaction stoppers include, for example, trivalent organophosphorus compounds, amine compounds, alkali metals, alkaline earth metal hydroxides, or combinations thereof. Molecular weight modifiers include, for example, methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, or oxymethylenedi-n-butyl ether.

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

[0024] [Fatty acid metal salt (B)] The fatty acid metal salt (B) is zinc fatty acid, 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 are lauric acid, palmitic acid, stearic acid, behenic acid, montanic acid, 12-hydroxystearic acid, oleic acid, or 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 amount of fatty acid metal salt (B) contained in the polyacetal resin composition is 0.2 to 10.0 parts by weight per 100 parts by weight of polyacetal resin (A). The content of 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 compounds (C)] Fatty acid ester compounds (C) are compounds that have three or more ester bonds within the same molecule. Fatty acid ester compounds (C) are ester compounds of a fatty acid having 12 to 28 carbon atoms and a polyhydric alcohol having three or more hydroxyl groups in one molecule. Fatty acids having 12 to 28 carbon atoms are 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. Polyhydric alcohols having three or more hydroxyl groups in one molecule are 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 tripehenate, glycerin trimontanate, pentaerythritol tripalmitate, pentaerythritol tetrapalmitate, pentaerythritol tristearate, pentaerythritol tetrastearate, pentaerythritol tripehenate, pentaerythritol tetrabehenate, pentaerythritol trimontanate, pentaerythritol tetramontanate, sorbitan tripalmitate These include sorbitan tristearate, sorbitan tribehenate, sorbitan trimontanate, sorbitol tripalmitate, sorbitol tristearate, sorbitol tribehenate, sorbitol trimontanate, sorbitan triolate, triacylglycerol, dipentaerythritol hexalourate, dipentaerythritol hexamiristate, dipentaerythritol hexapalmitate, dipentaerythritol hexastearate, dipentaerythritol hexabéhenate, or combinations thereof.

[0028] The amount of fatty acid ester compound (C) contained in the polyacetal resin composition is 0.2 to 10.0 parts by weight per 100 parts by weight of polyacetal resin (A). The content of fatty acid ester compound (C) 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 present invention relates to a method for producing a polyacetal resin composition, comprising a step of melt-kneading a polyacetal resin (A), a fatty acid metal salt (B), and a fatty acid ester compound (C) (a melt-kneading step). The melt-kneading can be carried out using, for example, a Banbury mixer, rolls, plasticizer, single-screw extruder or twin-screw extruder or kneader.

[0030] The temperature, pressure, and other conditions of the melt-kneading process can be appropriately selected in view of conventionally known methods for producing polyacetal resin compositions. For example, the melt-kneading process can be carried out at or above the melting temperature of the polyacetal resin, but it is usually preferable to carry it out at 180-240°C, and more preferably at 200-220°C.

[0031] A polyacetal resin composition may be prepared by melting and kneading polyacetal resin (A), fatty acid metal salt (B), and fatty acid ester compound (C) all at once so that the final amounts of fatty acid metal salt (B) and fatty acid ester compound (C) are as described above, or the fatty acid metal salt (B) and fatty acid ester compound (C) may be added separately to the polyacetal resin (A) in the same process. Alternatively, a polyacetal resin composition containing high concentrations of fatty acid metal salt (B) and fatty acid ester compound (C) may be prepared first, and then further diluted by kneading with another polyacetal resin (A) to prepare a polyacetal resin composition.

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

[0033] The metal-resin composition exhibits excellent fluidity of 20 g / 10 min or more, as measured according to ASTM-D1238 at a temperature of 190°C and a load of 10 kg. Furthermore, the metal-resin composition was measured according to ASTM-D1238 at a temperature of 190°C and a load of 10 kg, with values ​​of 20-10000 g / 10 min, 20-9000 g / 10 min, 20-8000 g / 10 min, 20-7000 g / 10 min, 20-6000 g / 10 min, 20-5000 g / 10 min, 20-4000 g / 10 min, 20-3000 g / 10 min, 20-2800 g / 10 min, 20-2600 g / 10 min, 150-10000 g / 10 min, 150-9000 g / 10 min, 150-8000 g / 10 min, 150-7000 g / 10 min, and 15 It has a fluidity of 0-6000g / 10 min, 150-5000g / 10 min, 150-4000g / 10 min, 150-3000g / 10 min, 150-2800g / 10 min, 150-2600g / 10 min, 300-10000g / 10 min, 300-9000g / 10 min, 300-8000g / 10 min, 300-7000g / 10 min, 300-6000g / 10 min, 300-5000g / 10 min, 300-4000g / 10 min, 300-3000g / 10 min, 300-2800g / 10 min, or 300-2600g / 10 min.

[0034] Furthermore, the metal-resin composition possesses excellent fluidity properties as well as excellent bending strain properties. 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 equipment such as Shimadzu Corporation's "Autograph® AGS-X," and determining the point where 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. In addition, the metal-resin composition has bending strain properties of 1.0-10%, 1.0-9.5%, 1.0-9.0%, 1.0-8.5%, 1.0-8.0%, or 1.1-7.9%.

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

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

[0037] [Method for manufacturing powder injection molded products] The present invention relates to a method for manufacturing a powder injection molded article, which includes the step of injecting a mixture obtained by melt-kneading a metal powder (D) and a binder resin composition into a mold, wherein the binder resin composition is the polyacetal resin composition described above. The manufacturing method may also include the steps of removing the binder resin composition from the molded mixture by heating or using a gaseous acid in a degreasing furnace, and sintering the molded mixture in a sintering furnace to form a powder injection molded article.

[0038] [Optional ingredients] The polyacetal resin composition may optionally contain other additives such as stabilizers, nucleating agents, mold release agents, fillers, pigments, lubricants, plasticizers, ultraviolet absorbers, flame retardants, or flame retardant enhancers, as long as they do not impair the objectives of the present invention. Examples of optional additives include glass fibers, glass flakes, glass beads, wolastonite, mica, talc, boron nitride, calcium carbonate, kaolin, silicon dioxide, clay, asbestos, silica, diatomaceous earth, graphite, molybdenum disulfide, glass fibers, middle fibers, potassium titanate fibers, poron fibers, carbon fibers, aramid fibers, potassium titanate whiskers, carbon black, or pigments. [Examples]

[0039] An embodiment of the present invention is described below. The materials used in the example and comparative example are shown below.

[0040] [Polyacetal resin (A)] As the polyacetal resin (A-1), we used "Yupital® F40-05" polyacetal resin manufactured by Mitsubishi Engineering Plastics Corporation. The melt flow rate of the polyacetal resin (A-1) was 47 g / 10 min (measured according to ASTM-D1238, with a load of 2.16 kg and at 190°C). As the polyacetal resin (A-2), we used "Yupital® F50-05" polyacetal resin manufactured by Mitsubishi Engineering Plastics Corporation. The melt flow rate of the polyacetal resin (A-2) was 90 g / 10 min (measured according to ASTM-D1238, with a load of 2.16 kg and at 190°C).

[0041] [Fatty acid metal salt (B)] The fatty acid metal salt (B-1) is magnesium stearate, manufactured by NOF Corporation. The fatty acid metal salt (B-2) is zinc stearate, manufactured by NOF Corporation. The fatty acid metal salt (B-3) is zinc laurate "ZS-3" manufactured by Nitto Chemical Industries, Ltd. The fatty acid metal salt (B-4) is zinc behenate "ZS-7" manufactured by Nitto Chemical Industries, Ltd. The fatty acid metal salt (B-5) is zinc montanate "ZS-8" manufactured by Nitto Chemical Industries, Ltd. The fatty acid metal salt (B-6) is calcium stearate, manufactured by NOF Corporation.

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

[0043] [Metal powder (D)] The metal powder (D) is SUS630 powder (average particle size approximately 10 μm) manufactured by Epson Atomics 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 it in a Toyo Seiki Mfg. Co., Ltd. kneading machine "Laboplastmill® 4C150" at a set temperature of 220°C and a rotation speed of 30 rpm for 20 minutes under a nitrogen atmosphere. 20 g of this polyacetal resin composition (10% by weight based on the weight of the kneaded body) and 180 g of metal powder (D) (90% by weight based on the same) were kneaded in a Toyo Seiki Mfg. Co., Ltd. kneading machine "Laboplastmill® 4C150" at a set temperature of 180°C and a rotation speed of 60 rpm for 40 minutes under a nitrogen atmosphere, and then cooled and solidified to prepare a kneaded body (metal resin composition). This kneaded material was crushed using the "Grand Cutter (registered trademark) SPC-400" granulator manufactured by Harmo Co., Ltd.

[0045] [Examples 2-42] Similar to Example 1, polyacetal resin compositions of Examples 2 to 42 were prepared by melt-kneading polyacetal resin (A), fatty acid metal salt (B), and fatty acid ester compound (C) 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 Tables 1 to 3.

[0046] Similar to Example 1, in Examples 2 to 36, 20 g (10% by weight) of polyacetal resin composition and 180 g (90% by weight) of metal powder (D) were kneaded in the above kneader at a set temperature of 180°C and a rotation speed of 60 rpm for 40 minutes under a nitrogen stream, and then cooled and solidified to prepare a kneaded body (metal resin composition). In Examples 37 to 42, 60 g (30% by weight) of polyacetal resin composition and 140 g (70% by weight) of metal powder (D) were kneaded in the above kneader at a set temperature of 180°C and a rotation speed of 60 rpm for 40 minutes under a nitrogen stream, and then cooled and solidified to prepare a kneaded body (metal resin composition). The kneaded bodies from Examples 2 to 42 were each crushed using the above granulator.

[0047] [Comparative Examples 1-19] Similar to the examples, polyacetal resin compositions for 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. Similar to the examples, melt mixing was performed using a Toyo Seiki Mfg. Co., Ltd. kneading machine "Laboplastmill® 4C150" at a set temperature of 220°C and a rotation speed of 30 rpm for 20 minutes under a nitrogen atmosphere. In addition, for each of Comparative Examples 1 to 19, 20 g (10% by weight) of the polyacetal resin composition and 180 g (90% by weight) of metal powder (D) were kneaded in the above kneading machine at a set temperature of 180°C and a rotation speed of 60 rpm for 40 minutes under a nitrogen atmosphere, and then cooled and solidified to prepare a kneaded body (metal resin composition). These kneaded bodies were crushed using the above granulator.

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

[0049] [Measurement method and evaluation method] (1) Bending strain From the crushed kneaded material, molded pieces measuring 12.7 mm × 63.5 mm × 3.2 mm thick were produced using a Thermo Fisher Scientific K.K. desktop miniature injection molding machine "HAAKE MiniJet" at a cylinder temperature of 220°C. The molded pieces were subjected to a three-point bending test at a bending speed of 2 mm / min using Shimadzu Corporation's "Autograph® AGS-X," and the point at which the bending strength was maximum was adopted as the bending strain (%). In this invention, a bending strain (%) value of 1.0 (%) or higher is considered acceptable and is evaluated as having excellent bending strain characteristics.

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

[0051] [Table 1]

[0052] [Table 2]

[0053] [Table 3]

[0054] [Table 4]

[0055] As shown in Tables 1-3, the compound products (metal-resin compositions) of polyacetal resin compositions and metal powders from Examples 1-42 possess 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 compound products (metal-resin compositions) of polyacetal resin compositions and metal powders from Comparative Examples 1-19 do not have a fluidity of at least 20 g / 10 min or more, and do not possess both excellent bending strain and fluidity properties.

Claims

1. A polyacetal resin composition for use by kneading with metal powder, 100 parts by weight of polyacetal resin (A), 0.2 to 10.0 parts by weight of fatty acid metal salt (B), Fatty acid ester compound (C) 0.2 to 10.0 parts by weight and Includes, 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 montanoate, and zinc montanoate. The polyacetal resin composition wherein the fatty acid ester compound (C) is pentaerythritol tetrastearate, sorbitan tristearate, sorbitan tribehenate, or a combination thereof.

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

3. A polyacetal resin composition according to claim 1 or 2, Metal powder (D) and A metal resin composition containing the following:

4. A method for producing a polyacetal resin composition for use by kneading with metal powder, The process includes a step of melt-kneading 100 parts by weight of polyacetal resin (A), 0.2 to 10.0 parts by weight of fatty acid metal salt (B), and 0.2 to 10.0 parts by weight of fatty acid ester compound (C), 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 montanoate, and zinc montanoate. The method for producing the fatty acid ester compound (C) is pentaerythritol tetrastearate, sorbitan tristearate, sorbitan tribehenate, or a combination thereof.

5. A method for manufacturing a powder injection molded article, comprising the step of melting and kneading a metal powder and a binder resin composition to obtain a kneaded body, and injecting it into a mold, The manufacturing method wherein the binder resin composition is the polyacetal resin composition according to claim 1 or 2.

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