Polyacetal resin composition

Abstract

To provide a polyacetal resin composition in which an amount of formaldehyde emissions and mold deposits are sufficiently reduced.SOLUTION: A polyacetal resin composition comprises 100 pts.mass of a polyacetal resin (A), and 0.05-5 pts.mass of a fatty acid monohydrazide (B), where the fatty acid monohydrazide (B) comprises at least one kind of C18-42 fatty acid monohydrazide (B1) represented by a general formula (1), and one kind of C3-17 fatty acid monohydrazide (B2) represented by the general formula (1), where n is an integer from 16 to 40 in the case of the component (B1) and an integer from 1 to 15 in the case of the component (B2).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a polyacetal resin composition. [Background technology]

[0002] Polyacetal resin is a material with excellent rigidity, strength, toughness, sliding properties and creep resistance. It is used in a wide range of applications as a resin material for various mechanical parts such as automobile parts, electrical and electronic parts and industrial parts.

[0003] Polyacetal resin generates formaldehyde when decomposed by the action of heat, light, oxygen, acid, base, etc. In particular, there are concerns that formaldehyde gas generated by thermal decomposition during manufacturing and molding processing will worsen the working environment, and that formaldehyde gas generated from resin products will worsen the indoor environment.

[0004] As a method for suppressing the generation of formaldehyde from polyacetal resin, a method of adding a hydrazide compound is known (Patent Document 1).

[0005] However, polyacetal resin compositions containing hydrazide compounds tend to cause mold deposits, which reduce work efficiency and deteriorate the surface condition of molded products.

[0006] As methods for using a hydrazide compound to reduce mold deposits while suppressing the amount of formaldehyde generated, there have been disclosed a method using a long-chain aliphatic hydrazide compound or an alicyclic hydrazide compound (Patent Document 2), a method using a monohydrazide compound and a dihydrazide compound in combination (Patent Documents 3 and 4), and a method using two different dihydrazide compounds in combination (Patent Document 5). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 4-345648 [Patent Document 2] International Publication No. 2005 / 033200 [Patent Document 3] JP 2012-233129 A [Patent Document 4] JP 2014-9309 A [Patent Document 5] JP 2010-155972 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, the methods described in the above Patent Documents 1 to 5 may not be sufficient in suppressing the amount of formaldehyde generated, and may also result in mold deposits.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a polyacetal resin composition in which the amount of formaldehyde generated and mold deposits are sufficiently suppressed. [Means for solving the problem]

[0010] The present inventors have discovered that by mixing fatty acid monohydrazide compounds having different chain lengths in a specific ratio and incorporating the mixture in a polyacetal resin, both the amount of formaldehyde generated and mold deposits can be reduced, and have completed the present invention.

[0011] That is, the present invention is as follows. [1] (A) 100 parts by mass of polyacetal resin, (B) 0.05 to 5 parts by mass of a fatty acid monohydrazide, The (B) fatty acid monohydrazide is at least (B1) one fatty acid monohydrazide having 18 to 42 carbon atoms represented by the following general formula (1), (B2) One fatty acid monohydrazide having 3 to 17 carbon atoms and represented by the following general formula (1): A polyacetal resin composition comprising: [ka] (In the formula, in the case of component (B1), n ​​is an integer of 16 to 40, and in the case of component (B2), n is an integer of 1 to 15.) [2] The polyacetal resin composition according to [1], wherein a mass ratio of the component (B1) to the component (B2), (B1):(B2), is 99.99:0.01 to 65:35. [3] The polyacetal resin composition according to [1] or [2], further comprising (C) 0.01 to 5 parts by mass of a fatty acid dihydrazide represented by the following general formula (2): [ka] (In the formula, n is an integer of 1 to 40.) [4] The polyacetal resin composition according to [3], wherein a mass ratio (B):(C) of the component (B) to the component (C) is 99:1 to 51:49. [5] The polyacetal resin composition according to any one of [1] to [4], wherein the component (B1) is stearic acid hydrazide. [6] The polyacetal resin composition according to any one of [1] to [5], wherein the component (B2) is palmitic acid hydrazide. [7] The polyacetal resin composition according to any one of [3] to [6], wherein the component (C) is at least one member selected from the group consisting of adipic acid dihydrazide, sebacic acid dihydrazide, and dodecanedioic acid dihydrazide. [8] The polyacetal resin composition according to [7], wherein the component (C) is sebacic acid dihydrazide and / or dodecanedioic acid dihydrazide. [9] The polyacetal resin composition according to [8], wherein the component (C) is sebacic acid dihydrazide. Effect of the Invention

[0012] According to the present invention, it is possible to provide a polyacetal resin composition which generates less formaldehyde and less mold deposits. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, an embodiment of the present invention (hereinafter, simply referred to as "the present embodiment") will be described in detail. Note that the present invention is not limited to the following description, and can be practiced in various modifications within the scope of the gist of the present invention.

[0014] <Polyacetal resin composition> The polyacetal resin composition of the present embodiment contains (A) a polyacetal resin and (B) a fatty acid monohydrazide. Each component constituting the polyacetal resin composition of the present embodiment will be described in detail below.

[0015] <(A) Polyacetal resin> The polyacetal resin (A) contained in the polyacetal resin composition of this embodiment (hereinafter, sometimes simply referred to as "component (A)") has repeating oxymethylene units (acetal structure) represented by (-CHO-) as its main structural unit, and any known polyacetal resin may be used. The polyacetal resin (A) used in this embodiment may be a homopolymer consisting of only these oxymethylene units, or may be a copolymer (including block copolymer) or terpolymer containing structural units other than the oxymethylene units. Furthermore, it may have not only a linear structure but also a branched or crosslinked structure. The (A) polyacetal resin may be used alone or in combination of two or more kinds. The polyacetal resin (A) preferably contains 30 to 100 mass %, more preferably 50 to 100 mass %, and further preferably 70 to 100 mass % of the polyacetal copolymer, with the total amount of the polyacetal resin (A) being 100 mass %.

[0016] The polyacetal resin (A) of this embodiment may be produced by a known method. For example, a polyacetal homopolymer can be obtained by homopolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde such as its trimer (trioxane) and tetramer (tetraoxane). Furthermore, the obtained polyacetal homopolymer can be stabilized by a known method (for example, a method of reacting the polymerization terminal with an ether group or an ester group). The main chain of the polyacetal homopolymer is composed substantially only of oxymethylene units, that is, it preferably contains 99% by mass or more of oxymethylene units.

[0017] In the polyacetal copolymer, the constituent unit (copolymer unit) other than the oxymethylene unit is preferably an oxyethylene unit (-CH2CH2O-). Such polyacetal copolymers can be obtained by copolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde such as its trimer (trioxane) and tetramer (tetraoxane) with a cyclic ether such as ethylene oxide or 1,3-dioxolane. When obtaining a polyacetal copolymer from trioxane and 1,3-dioxolane, it is preferable to use 0.1 to 60 mol% of 1,3-dioxolane, more preferably 0.1 to 20 mol%, and even more preferably 0.13 to 10 mol%, based on 100 mol% of trioxane. Furthermore, the obtained polyacetal copolymer can be stabilized by a known method (for example, a method of melting it together with a quaternary ammonium compound to decompose the unstable terminal portion). The polyacetal copolymer preferably contains oxyethylene units in an amount of 1 to 10% by mass, more preferably 1 to 5% by mass, and further preferably 1 to 3% by mass, of the entire main chain of the polymer.

[0018] The polyacetal resin (A) of this embodiment preferably has a melt flow rate (MFR) of 2 to 50 g / 10 min, more preferably 2 to 30 g / 10 min, and even more preferably 5 to 15 g / 10 min, from the viewpoint of achieving both fluidity and strength. The MFR can be measured in accordance with ISO 1133-1 at 190°C and a load of 2.16 kg.

[0019] In this embodiment, the content of the (A) polyacetal resin in 100% by mass of the polyacetal resin composition is preferably 80% by mass or more, more preferably 90% by mass or more, and even more preferably 95% by mass or more.

[0020] <(B) Fatty acid monohydrazide> The (B) fatty acid monohydrazide contained in the polyacetal resin composition of this embodiment includes at least one fatty acid monohydrazide (B1) having 18 to 42 carbon atoms and represented by the following general formula (1), and one fatty acid monohydrazide (B2) having 3 to 17 carbon atoms and represented by the following general formula (1). (Hereinafter, the (B) fatty acid monohydrazide, (B1) the fatty acid monohydrazide having 18 to 42 carbon atoms and represented by the following general formula (1), and (B2) the fatty acid monohydrazide having 3 to 17 carbon atoms and represented by the following general formula (1) may be simply referred to as the "(B) component," the "(B1) component," and the "(B2) component," respectively.)

[0021] [ka] (In the formula, in the case of component (B1), n ​​is an integer of 16 to 40, and in the case of component (B2), n is an integer of 1 to 15.)

[0022] In this embodiment, the mass ratio (B1):(B2) of the (B1) component to the (B2) component is preferably 99.99:0.01 to 65:35. When the mass ratio (B1):(B2) is within this range, the generation of formaldehyde and mold deposits from a molded article obtained by molding the polyacetal resin composition of this embodiment can be suppressed. The mass ratio (B1):(B2) is more preferably 99.99:0.01 to 90:10, and further preferably 99.99:0.01 to 99:1. When the mass ratio (B1):(B2) is within the above range, the amount of formaldehyde generated from a molded article obtained by molding the polyacetal resin composition of the present embodiment can be suppressed, particularly in a humid atmosphere.

[0023] In the polyacetal resin composition of the present embodiment, the content of (B) fatty acid monohydrazide is 0.05 to 5 parts by mass relative to 100 parts by mass of (A) polyacetal resin. If the content of (B) fatty acid monohydrazide is less than 0.05 parts by mass, the suppression of formaldehyde generation tends to be insufficient, whereas if it exceeds 5 parts by mass, the fatty acid monohydrazide cannot be sufficiently kneaded during extrusion, and tends to flow out into the strand cooling water. The content of (B) fatty acid monohydrazide is preferably from 0.05 to 1 part by mass, and more preferably from 0.05 to 0.7 parts by mass, relative to 100 parts by mass of (A) polyacetal resin.

[0024] The component (B1) in this embodiment is represented by the above general formula (1), where n is an integer of 16 to 40, preferably 16 to 20, and more preferably 16. Specific examples of the component (B1) include stearic acid hydrazide, arachidic acid hydrazide, behenic acid hydrazide, lignoceric acid hydrazide, cerotic acid hydrazide, montanic acid hydrazide, melissic acid hydrazide, etc. Among these, stearic acid hydrazide, arachidic acid hydrazide, and behenic acid hydrazide are preferred, and stearic acid hydrazide is more preferred. The component (B1) may be used alone or in combination of two or more different types.

[0025] The component (B2) in this embodiment is represented by the above general formula (1), where n is an integer of 1 to 15, preferably 1 or an integer of 10 to 15, and more preferably 14. Specific examples of the (B2) component include propionic acid hydrazide, butyric acid hydrazide, valeric acid hydrazide, caproic acid hydrazide, heptyl acid hydrazide, caprylic acid hydrazide, pelargonic acid hydrazide, capric acid hydrazide, lauric acid hydrazide, myristic acid hydrazide, palmitic acid hydrazide, margaric acid hydrazide, etc. Among these, propionic acid hydrazide, lauric acid hydrazide, myristic acid hydrazide, palmitic acid hydrazide, and margaric acid hydrazide are preferred, and palmitic acid hydrazide is more preferred. The component (B2) may be used alone or in combination of two or more types.

[0026] <(C) Fatty acid dihydrazide> The polyacetal resin composition of the present embodiment may further contain (C) a fatty acid dihydrazide represented by the following general formula (2) (hereinafter sometimes simply referred to as "component (C)"). [ka] (In the formula, n is an integer of 1 to 40.)

[0027] The fatty acid dihydrazide (C) in this embodiment is represented by the above general formula (2), where n is an integer of 1 to 40, preferably an integer of 1 to 20, more preferably 1 to 15, and even more preferably 4 to 10. Specific examples of the (C) fatty acid dihydrazide include adipic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide, etc. Among these, sebacic acid dihydrazide and dodecanedioic acid dihydrazide are preferred, and sebacic acid dihydrazide is more preferred. The (C) fatty acid dihydrazides may be used alone or in combination of two or more.

[0028] In the polyacetal resin composition of the present embodiment, the content of the fatty acid dihydrazide (C) is preferably 0.01 to 5 parts by mass, more preferably 0.01 to 0.5 parts by mass, and even more preferably 0.01 to 0.15 parts by mass, relative to 100 parts by mass of the polyacetal resin (A). When the content of the fatty acid dihydrazide (C) is within the above range, the amount of formaldehyde generated in a dry atmosphere can be further suppressed.

[0029] In this embodiment, the mass ratio (B):(C) of the (B) fatty acid monohydrazide to the (C) fatty acid dihydrazide is preferably 99:1 to 51:49. When the (C) fatty acid dihydrazide is contained in the above range of mass ratio (B):(C), mold deposits can be further suppressed. The mass ratio (B):(C) is more preferably from 95:5 to 51:49, and more preferably from 90:10 to 51:49. When the mass ratio (B):(C) is within the above range, the amount of formaldehyde generated in a dry atmosphere can be particularly reduced.

[0030] The polyacetal resin composition of the present embodiment may contain conventionally known additives as necessary, such as aging improvers such as fatty acid metal salts, sliding agents, weather resistance agents, light resistance agents, release agents, nucleating agents, colorants, organic and inorganic reinforcing agents, and various thermoplastic elastomers. The content of the additive is preferably 15% by mass or less based on 100% by mass of the polyacetal resin composition.

[0031] The polyacetal resin composition of the present embodiment can be produced by a known melt kneading method. For example, (A) polyacetal resin, (B) fatty acid monohydrazide, and (C) fatty acid dihydrazide, if necessary, may be mixed in a stirrer such as a Henschel mixer, and then fed to a single-screw or twin-screw melt kneading device (extruder) for melt kneading. Alternatively, (A) polyacetal resin may be fed from the upstream of a single-screw or twin-screw extruder to be in a molten state, and then (B) fatty acid monohydrazide and (C) fatty acid dihydrazide, if necessary, may be fed downstream to be melt kneaded.

[0032] A molded article can be obtained by molding the polyacetal resin composition of the present embodiment. The molding method of the polyacetal resin composition is not particularly limited, and examples of the molding method include known molding methods, such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, molding with other materials, gas-assisted injection molding, foam injection molding, low-pressure molding, ultra-thin-wall injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, outsert molding), and melt-blow molding. The shape of the molded article is not particularly limited, and examples thereof include injection molded articles, fibers / nonwoven fabrics, sheets / films, and irregular extrusion articles. The uses of the molded bodies are not particularly limited, and include, for example, mechanical parts such as gears, cams, sliders, levers, shafts, bearings, and guides; outsert molded resin parts; insert molded resin parts (chassis, trays, side panel parts); parts for printers or copiers; parts for digital cameras or digital video equipment; parts for music, video or information equipment; parts for communication equipment; parts for electrical equipment; and parts for electronic equipment. In addition, the material is suitably used for automobile parts, such as fuel-related parts typified by gasoline tanks, fuel pump modules, valves, and gasoline tank flanges; door-related parts; seat belt-related parts; combination switch parts; and switches. Furthermore, it can also be suitably used as an industrial part, such as a housing facility.

[0033] Although the embodiment of the present invention has been described above, the present invention is not limited to the embodiment. The present invention can be modified in various ways without departing from the gist of the present invention. EXAMPLES

[0034] The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention is not limited to these.

[0035] The raw material components used in the examples and comparative examples are as follows.

[0036] (A) Polyacetal resin (A-1) Polyacetal homopolymer obtained by polymerizing trioxane (MFR=2.8g / 10min) (A-2) Polyacetal copolymer obtained by copolymerizing trioxane and 1,3-dioxolane (4.2 mol of oxyethylene units per 100 mol of oxymethylene units) (MFR=9.0 g / 10 min) The MFR value was measured in accordance with ISO 1133-1 using a MELT INDEXER manufactured by Toyo Seiki Seisakusho Co., Ltd., at a cylinder temperature of 190° C. and a load of 2.16 kg.

[0037] (B) Fatty acid monohydrazide The following fatty acid monohydrazides were synthesized and mixed in the ratios shown in Table 1 for use. (B1) Fatty acid monohydrazides having 18 to 42 carbon atoms (B1-1) Stearic acid hydrazide (B1-2) Behenic acid hydrazide (B2) Fatty acid monohydrazides with 3 to 17 carbon atoms (B2-1) Palmitic acid hydrazide (B2-2) Myristic acid hydrazide (B2-3) Propionic acid hydrazide The synthesis method of each fatty acid monohydrazide is shown below.

[0038] [Method for synthesizing fatty acid monohydrazides] (B1-1) Synthesis of stearic acid hydrazide 50 g of methyl stearate (manufactured by Fujifilm Wako Pure Chemical Industries) was added to a three-neck flask equipped with a reflux condenser, a thermometer, and a stirrer, and the mixture was stirred in a warm bath at 80°C until it was completely melted. 21 g (2.5 equivalents) of 60% hydrazine monohydrate (manufactured by Tokyo Chemical Industry Co., Ltd.) was added dropwise thereto, and the mixture was heated and stirred for 1 hour to obtain 47 g of stearic acid hydrazide. Synthesis of (B1-2) behenic acid hydrazide, (B2-1) palmitic acid hydrazide, (B2-2) myristic acid hydrazide, and (B2-3) propionic acid hydrazide (B1-2) Behenic acid hydrazide, (B2-1) Palmitic acid hydrazide, (B2-2) Myristic acid hydrazide, and (B2-3) Propionic acid hydrazide were obtained in the same manner as in (B1-1), except that methyl stearate was replaced with methyl behenate, methyl palmitate, methyl myristate, and methyl propionate (all manufactured by Tokyo Chemical Industry Co., Ltd.).

[0039] Each of the fatty acid monohydrazides synthesized above was dissolved in HFIP to a concentration of 5 mg / mL, and the purity was confirmed to be 99.95% or more based on the peak area ratio by GC / MS measurement. For the GC / MS measurements, an Agilent HP6890 / 5973 was used, and an Agilent DB-1 column was used.

[0040] (B') Aromatic monohydrazide (B'1) Benzohydrazide (Tokyo Chemical Industry Co., Ltd.)

[0041] The above (B) fatty acid monohydrazide and (B') aromatic monohydrazide were mixed in the ratio shown in Table 1 and used.

[0042] [Table 1]

[0043] (C) Fatty acid dihydrazide (C-1) Dodecanedioic acid dihydrazide (Tokyo Chemical Industry Co., Ltd.) (C-2) Sebacic acid dihydrazide (Tokyo Chemical Industry Co., Ltd.) (C-3) Adipic dihydrazide (Tokyo Chemical Industry Co., Ltd.) was used.

[0044] The measurement and evaluation methods used in the examples and comparative examples are as follows.

[0045] (1) Amount of formaldehyde generated in a dry atmosphere Using an injection molding machine (Toshiba Machine IS-100GN), test pieces (100 mm x 100 mm x 3 mm flat plates) were molded from the polyacetal resin compositions obtained in the Examples and Comparative Examples under the following conditions: mold temperature 80°C, cylinder temperature 220°C, injection pressure 35 MPa, injection time 15 seconds, and cooling time 20 seconds. The above test piece and 5L of nitrogen were put into a sampling bag with a two-way cock (GL Science Smart Bag PA, capacity 10L) and sealed. After heating this at 65°C for 2 hours, 4L of the gas in the sampling bag was extracted through a DNPH collection tube (GL Science InertSep mini AERO DNPH) at a rate of 400mL / min, and the formaldehyde in the gas was collected. After that, the reaction product of DNPH and formaldehyde was solvent extracted with acetonitrile from the DNPH collection tube, and its concentration was determined by a calibration curve method using a standard substance of the reaction product of DNPH and formaldehyde using HPLC, and the amount of formaldehyde generated per unit mass of the test piece (μg / g) was calculated. The smaller this value, the more suppressed the amount of formaldehyde generated, which is preferable.

[0046] (2) Amount of formaldehyde generated in a humid atmosphere Using an injection molding machine (Toshiba Machine IS-100GN), test pieces (100 mm x 40 mm x 3 mm flat plates) were molded from the polyacetal resin compositions obtained in the Examples and Comparative Examples under the following conditions: mold temperature 80°C, cylinder temperature 220°C, injection pressure 35 MPa, injection time 15 seconds, and cooling time 20 seconds. The amount of formaldehyde emitted from the test piece was measured according to the method described in the German Automotive Industry Association standard VDA275. Specifically, the test piece was hung in a 1L polyethylene bottle containing 50mL of distilled water and sealed so as not to touch the distilled water. This was heated at 60°C for 3 hours and left to stand at room temperature for 60 minutes. The formaldehyde in the distilled water was reacted with acetylacetone in the presence of ammonium ions, and the reaction product was measured with a UV spectrometer at a wavelength of 412 nm. The amount of formaldehyde generated was expressed as the amount of formaldehyde (μg / g) per 1g of polyacetal resin. The smaller this value, the more suppressed the amount of formaldehyde generated, which is preferable.

[0047] (3) Mold deposit properties Molded articles (arrowhead-shaped, 30 mm x 12 mm x 2 mm) were continuously molded from the pellets of the polyacetal resin compositions obtained in the Examples and Comparative Examples, and the presence or absence of mold deposits (MD) was confirmed after 100, 500, and 1000 shots. The presence or absence of mold deposits was determined by observing the fixed side of the mold from a direction perpendicular to the surface, and if no MD was observed, it was rated as "Good (O)", if even a small amount of colorless MD was observed, it was rated as "Poor (△)", and if interference colors (interference fringes) were observed (presumably MD with a thickness of about 200 nm or more), it was rated as "Poor (X)". The more moldings that were performed before mold deposits were observed, the more favorable the mold deposits were, as they were more suppressed. An injection molding machine (Toyo Seiki Ti-30G) was used for molding, with the mold temperature set at 60°C, cylinder temperature at 200°C, injection pressure at 34 MPa, injection time at 20 seconds, and cooling time at 15 seconds.

[0048] (4) Retention discoloration The pellets of the polyacetal resin composition obtained in the Examples and Comparative Examples were retained in a molten state in the cylinder of an injection molding machine (IS-100GN manufactured by Toshiba Machine Co., Ltd.) for 30 minutes, and then injection molded into a flat plate of 100 mm x 100 mm x 3 mm under the injection conditions of an injection pressure of 35 MPa, an injection time of 15 seconds, and a cooling time of 20 seconds. The cylinder temperature was set at 205°C, and the mold temperature was 90°C. The color tone of the central part of the obtained molded piece was measured using a color difference meter (CR-200 manufactured by Konica Minolta, Inc.) in the Lab color system, and the color difference ΔE from a blank (a molded piece obtained by normal molding without retention) was calculated according to the following formula. The lower the ΔE value, the more suppressed the retention discoloration is, which is preferable.

[0049]

number

[0050] [Examples 1 to 30, Comparative Examples 1 to 11] The components were mixed to the compositions shown in Tables 2 and 3, fed into a twin-screw extruder (Ikegai PCM30), melt-kneaded at a screw rotation speed of 60 rpm and a cylinder temperature setting of 200°C, and then pelletized. The resulting pellets were dried for 3 hours using a hot air dryer at a temperature of 80°C. The evaluation results are summarized in Tables 2 and 3. In Comparative Example 6, the polyacetal resin and the fatty acid monohydrazide were not sufficiently mixed, and an oil film formed on the water bath for cooling the strands, so extrusion was not possible (extrusion impossible).

[0051] [Table 2-1]

[0052] [Table 2-2]

[0053] [Table 3] [Industrial Applicability]

[0054] The polyacetal resin composition of the present invention emits little formaldehyde and generates little mold deposits, and therefore can be suitably used in fields such as electrical and electronic applications where high precision and good appearance are required, and automotive interior applications where reduced volatile organic compounds are required.

Claims

1. (A) 100 parts by mass of a polyacetal resin; (B) 0.05 to 5 parts by mass of a fatty acid monohydrazide, The fatty acid monohydrazide (B) is at least (B1) one fatty acid monohydrazide having 18 to 42 carbon atoms and represented by the following general formula (1), (B2) One fatty acid monohydrazide having 3 to 17 carbon atoms and represented by the following general formula (1): A polyacetal resin composition comprising: 【Chemistry 1】 (In the formula, in the case of component (B1), n ​​is an integer of 16 to 40, and in the case of component (B2), n is an integer of 1 to 15.)

2. 2. The polyacetal resin composition according to claim 1, wherein a mass ratio (B1):(B2) of the component (B1) to the component (B2) is 99.99:0.01 to 65:

35.

3. The polyacetal resin composition according to claim 1 or 2, further comprising (C) 0.01 to 5 parts by mass of a fatty acid dihydrazide represented by the following general formula (2): 【Chemistry 2】 (In the formula, n is an integer from 1 to 40.)

4. The polyacetal resin composition according to claim 3, wherein a mass ratio (B):(C) of the component (B) to the component (C) is 99:1 to 51:

49.

5. The polyacetal resin composition according to any one of claims 1 to 4, wherein the component (B1) is stearic acid hydrazide.

6. The polyacetal resin composition according to any one of claims 1 to 5, wherein the component (B2) is palmitic acid hydrazide.

7. The polyacetal resin composition according to any one of claims 3 to 6, wherein the component (C) is at least one member selected from the group consisting of adipic acid dihydrazide, sebacic acid dihydrazide, and dodecanedioic acid dihydrazide.

8. The polyacetal resin composition according to claim 7, wherein the component (C) is sebacic acid dihydrazide and / or dodecanedioic acid dihydrazide.

9. The polyacetal resin composition according to claim 8, wherein the component (C) is sebacic acid dihydrazide.

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