Polyacetal resin composition and fuel contact

Abstract

A polyacetal resin composition containing (A) a polyacetal resin 100 parts by mass, (B) an antioxidant 0.1 to 1.0 parts by mass, (C) at least one of magnesium oxide and zinc oxide 0.3 to 2.0 parts by mass, (D) a polyalkylene glycol 0.5 to 3.0 parts by mass, (E) a fatty acid ester of a polyol having an esterification rate of 80% or more 0.01 to 1.0 parts by mass, and (F) a carbon-based conductive additive 0.3 to 2.5 parts by mass, the (F) carbon-based conductive additive being selected from one of a combination of only (F1) a carbon nanostructure, and (F1) a carbon nanostructure and (F2) a carbon black having a BET specific surface area of 300 m 2 / g or more.

Description

Technical Field

[0001] This invention relates to a polyacetal resin composition and a fuel contact body formed therefrom. Background Technology

[0002] Due to the excellent chemical resistance of polyacetal resin (hereinafter also known as "POM resin"), molded products made from POM resin are widely used as automotive parts. For example, they are used in large components such as fuel delivery units, which come into direct contact with fuel oil, such as fuel pump modules.

[0003] In recent years, efforts have been made to reduce the sulfur content of fuels in order to comply with environmental regulations in various countries. However, due to the high cost of desulfurization equipment, high-sulfur fuels are still circulating in some countries. These high-sulfur fuels tend to degrade POM resin more easily compared to low-sulfur fuels.

[0004] Furthermore, injection-molded parts made from POM resin retain residual stress due to cooling during the injection molding process. When these injection-molded parts come into contact with high-sulfur fuels, cracks can form in areas with high residual stress, potentially causing fuel leaks. Therefore, countries that distribute high-sulfur fuels require resin materials with high resistance to such fuels as raw materials.

[0005] In response to these challenges, the applicant reports that by incorporating alkaline earth metal oxides, polyalkylene glycols, and specific esters into polyacetal resins, significant improvements can be achieved (see Patent Document 1). Particularly, substantial improvements have been found for components such as fuel delivery units that come into contact with high-sulfur fuels.

[0006] On the other hand, for molded articles used around the aforementioned fuel pump, in order to prevent the fuel from igniting due to static electricity, it is sought to impart conductivity to the molded article so that it is not charged. As a countermeasure to impart conductivity to POM resin, it is known to add conductive fillers such as carbon black and carbon fiber (see Patent Documents 2 and 3).

[0007] Existing technical documents

[0008] Patent documents

[0009] Patent Document 1: Japanese Patent No. 5814419

[0010] Patent Document 2: Japanese Patent Publication No. 07-002891

[0011] Patent Document 3: Japanese Patent Publication No. 2004-526596 Summary of the Invention

[0012] The problem that the invention aims to solve

[0013] However, when alkaline earth metal oxides are added to POM resin compositions to impart fuel durability and conductive fillers such as carbon black are added to provide antistatic effects, a significant decrease in toughness occurs. In other words, in POM resin compositions, simultaneously achieving both antistatic properties and acid resistance results in a substantial reduction in toughness.

[0014] The present invention was made in view of the above-mentioned problems, and its objective is to provide a POM resin composition and a fuel contact that do not significantly reduce toughness and impart durability and antistatic effect to high-sulfur fuels.

[0015] Solution for solving the problem

[0016] One aspect of the present invention that solves the aforementioned problems is as follows.

[0017] (1) A polyacetal resin composition comprising:

[0018] (A) 100 parts by weight of polyacetal resin;

[0019] (B) Antioxidant 0.1–1.0 parts by weight;

[0020] (C) 0.3 to 2.0 parts by weight of at least one of magnesium oxide and zinc oxide;

[0021] (D) Polyalkylene glycol 0.5–3.0 parts by weight;

[0022] (E) 0.01 to 1.0 parts by weight of fatty acid esters of polyols with an esterification rate of 80% or higher; and

[0023] (F) 0.3–2.5 parts by weight of carbon-based conductive additives.

[0024] The (F) carbon-based conductive additive is selected from (F1) carbon nanostructures only, and (F1) carbon nanostructures with a BET specific surface area of ​​300m². 2 One of the combinations of carbon black with a density of / g or more.

[0025] (2) The polyacetal resin composition according to (1) above, wherein the polyacetal resin is a copolymer of a cyclic oligomer of formaldehyde as the main monomer and a compound selected from cyclic ethers and / or cyclic methyl acetals having at least one carbon-carbon bond as the comonomer.

[0026] (3) In the polyacetal resin composition according to (1) or (2) above, the BET specific surface area of ​​the (C) magnesium oxide is 100 m². 2 / g or more.

[0027] (4) In the polyacetal resin composition according to any one of (1) to (3) above, the mass ratio of the (F1) carbon nanostructure to the (F2) carbon black ((F2) / (F1)) is 10 or less.

[0028] (5) The polyacetal resin composition according to any one of (1) to (4) above, wherein the fatty acid ester of the (E) polyol is an ester compound of a polyol and a fatty acid having 3 or more carbon atoms.

[0029] (6) A fuel contact body having a molded article comprising the polyacetal resin composition described in any one of (1) to (5) above.

[0030] Invention Effects

[0031] According to the present invention, a POM resin composition and a fuel contact can be provided that do not significantly reduce toughness and provide durability and antistatic effects for high-sulfur fuels. Attached Figure Description

[0032] Figure 1 This is a schematic diagram showing the state of carbon nanostructures at (A) before melt mixing, (B) at the beginning of melt mixing, and (C) after melt mixing.

[0033] Figure 2 The figures are (A) top view and (B) rear view of the test piece used to measure surface resistivity and volume resistivity in the embodiments. Detailed Implementation

[0034] <Polyacetal Resin Composition>

[0035] The POM resin composition of this embodiment contains: (A) 100 parts by weight of polyacetal resin, (B) 0.1 to 1.0 parts by weight of antioxidant, (C) 0.3 to 2.0 parts by weight of at least one of magnesium oxide and zinc oxide, (D) 0.5 to 3.0 parts by weight of polyalkylene glycol, (E) 0.01 to 1.0 parts by weight of a fatty acid ester of a polyol with an esterification rate of 80% or more, and (F) 0.3 to 2.5 parts by weight of a carbon-based conductive additive. Furthermore, the carbon-based conductive additive is characterized by being selected from (F1) carbon nanostructures only, and (F1) carbon nanostructures having a BET specific surface area of ​​300 m². 2 One of the combinations of (F2) carbon black of / g or more.

[0036] In the POM resin composition of this embodiment, durability against high-sulfur fuels can be imparted by mixing at least one of (C) magnesium oxide and zinc oxide with the POM resin. Furthermore, conductivity can be imparted by mixing in (F) carbon-based conductive additives, thereby exhibiting an antistatic effect. Conventionally, when carbon black or the like is added to exhibit an antistatic effect, its combination with magnesium oxide or the like results in a significant decrease in toughness. However, in this embodiment, since conductivity is imparted by (F) carbon-based conductive additives, the significant decrease in toughness can be suppressed. The mechanism will be described later. Furthermore, "high-sulfur fuel" refers to fuel with a sulfur content of 0.1% by mass or more.

[0037] The components of the POM resin composition of this embodiment will be described below.

[0038] [(A) Polyacetal resin (POM resin)]

[0039] The (A)POM resin used in this embodiment refers to a polymer compound whose main structural unit is oxymethylene (-CH2O-). Examples include polyoxymethylene polymers that are essentially composed only of repeating oxymethylene units, and polyacetal copolymers that contain a small amount of other structural units besides oxymethylene. Although all of these can be used, from the viewpoint of fuel resistance, it is preferable to use a polyacetal copolymer as the matrix resin.

[0040] (A) In the case of a polyacetal copolymer, the polyacetal copolymer is preferably a polyacetal copolymer copolymer formed by copolymerizing 0.5 to 30% by mass of the comonomer component, and particularly preferably a polyacetal copolymer copolymer formed by copolymerizing 0.5 to 10% by mass of the comonomer component. Polyacetal copolymers formed by copolymerizing the comonomer component exhibit excellent acid resistance and maintain excellent thermal stability and mechanical strength. Furthermore, polyacetal copolymers are not only substances with a linear molecular structure, but also substances with a branched structure and a cross-linked structure.

[0041] In manufacturing such polyacetal copolymers, cyclic oligomers of formaldehyde, represented by trioxymethylene, can be used as the main monomer. Furthermore, compounds selected from cyclic ethers and / or cyclic methyl acetals having at least one carbon-carbon bond can be used as comonomer components. Examples of such comonomers include ethylene oxide, 1,3-dioxolane, diethylene glycol methyl acetal, 1,4-butanediol methyl acetal, 1,3-dioxane, and propylene oxide.

[0042] In the aforementioned (A)POM resin, especially polyacetal copolymers, there are no particular limitations on the degree of polymerization, etc., which can be adjusted according to the intended use and molding method. However, from the viewpoint of combining acid resistance and moldability, the melt flow rate (MFR) measured according to ISO 1133 at a test temperature of 190°C and a load of 2.16 kg is preferably 1 to 100 g / 10 min, and particularly preferably 5 to 30 g / 10 min.

[0043] (B) Antioxidants

[0044] Examples of antioxidants used in this embodiment (B) include aromatic amine antioxidants and hindered phenolic antioxidants. Examples of aromatic amine antioxidants include N-phenyl-1-naphthylamine, bis(4-octylphenyl)amine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonamide)diphenylamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)-p-phenylenediamine, and N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine. Among these, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine is preferred.

[0045] Examples of hindered phenolic antioxidants include 2,2'-methylenebis(4-methyl-6-tert-butylphenol), hexamethylene-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], tetra[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, triethylene glycol-bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], 1,3,5-trimethyl-2,4,6-tris(3',5'-di-tert-butyl-4-hydroxybenzyl)benzene, n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenyl)propionate, 4,4'-methylenebis(2,6-di-tert-butylphenol), and 4,4'-butylenebis(6-tert-butyl- 3-Methylphenol), distearate (3,5-di-tert-butyl-4-hydroxybenzyl)phosphonate, 2-tert-butyl-6-(3-tert-butyl-5-methyl-2-hydroxybenzyl)-4-methylphenyl acrylate, 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxospiro[5,5]undecane, etc., preferably triethylene glycol-bis[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionate], tetra[methylene-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane, hexamethylene-bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate].

[0046] In this embodiment, at least one or more of these antioxidants may be used.

[0047] In this embodiment, the amount of antioxidant (B) mixed with 100 parts by weight of (A) POM resin is 0.1 to 1.0 parts by weight, more preferably 0.2 to 0.8 parts by weight.

[0048] [(C) Magnesium oxide, zinc oxide]

[0049] The POM resin composition of this embodiment contains at least one of magnesium oxide and zinc oxide (hereinafter also referred to as "component (C)"). Component (C) used in this embodiment is preferred because it offers an excellent balance between improved resistance to high-sulfur fuels (durability relative to high-sulfur fuels (hereinafter also referred to as "fuel resistance")) and mechanical and physical properties, moldability, and other properties.

[0050] Regarding magnesium oxide, preferably, its BET specific surface area is 100 m². 2 The particle size is above 1.5 μm / g and the average particle size is below 1.5 μm. By meeting these conditions, the reduction in toughness is suppressed and fuel resistance is obtained. The BET specific surface area of ​​magnesium oxide is preferably 100–500 m² / g. 2 / g, more preferably 120-300m 2 / g. Furthermore, the average particle size of magnesium oxide is preferably 0.2–1.3 μm, more preferably 0.3–1.0 μm. The average particle size is determined by the particle size representing 50% of the cumulative value of the particle size distribution (volume basis) measured by laser diffraction / scattering.

[0051] In this embodiment, the mixing amount of component (C) is 0.3 to 2.0 parts by weight, preferably 1.0 to 1.8 parts by weight, relative to 100 parts by weight of (A) POM resin. A mixing amount of component (C) of 0.3 parts by weight or more results in particularly excellent fuel resistance, stable production can be achieved at 2.0 parts by weight or less, and a particularly excellent balance of mechanical properties is achieved at 1.8 parts by weight or less. While increasing the amount of component (C) may sometimes promote the decomposition of unstable ends in the POM resin, the (A) POM resin of this embodiment suppresses this decomposition, thus exhibiting the improved fuel resistance resulting from the increased amount of component (C).

[0052] [(D) Polyalkylene glycol]

[0053] The type of (D) polyalkylene glycol used in this embodiment is not particularly limited. From the viewpoint of affinity with POM resin, it is preferable to contain polyethylene glycol and / or polypropylene glycol, and more preferably polyethylene glycol.

[0054] The number-average molecular weight (Mn) of the polyalkylene glycol is not particularly limited, but from the viewpoint of dispersibility in POM resin, it is preferably 1,000 to 50,000, more preferably 5,000 to 30,000. Furthermore, in this specification, the number-average molecular weight is the molecular weight converted from polystyrene obtained by size exclusion chromatography (SEC) using tetrahydrofuran (THF) as a solvent.

[0055] In this embodiment, the content of (D) polyalkylene glycol is 0.5 to 3.0 parts by weight, more preferably 1.0 to 2.0 parts by weight, relative to 100 parts by weight of (A) POM resin. When the amount of (D) polyalkylene glycol is low, sufficient stress relief may not be achieved. When the amount of (D) polyalkylene glycol is excessive, the mechanical and physical properties of the molded article may decrease.

[0056] [(E) fatty acid esters of polyols]

[0057] The fatty acid ester of the (E) polyol used in this embodiment has an esterification rate of 80% or higher. When the esterification rate is lower than 80%, the fuel resistance is poor. The esterification rate of the fatty acid ester of the (E) polyol is preferably 85% or higher.

[0058] The polyol can be aliphatic or aromatic, but aliphatic is preferred in terms of affinity with (A)POM resin.

[0059] The valence of the polyol is not particularly limited, but it is preferably 3 or more and 4 or less. In addition, the number of carbon atoms in the polyol is not particularly limited, but in terms of affinity with (A)POM resin, it is preferably 3 or more and 10 or less, and more preferably 3 or more and 5 or less.

[0060] Preferred polyols for forming the (E) component include, for example, glycerol, trimethylolpropane, pentaerythritol, erythritol, pentitol, hexanol, sorbitol, etc. However, pentaerythritol is preferred as it helps to control the mass reduction of the POM resin composition after impregnation with sulfur fuel to a low level.

[0061] The type of fatty acid is not particularly limited, but in terms of affinity with (A)POM resin, fatty acids with 10 to 30 carbon atoms are preferred, and aliphatic carboxylic acids with 10 to 20 carbon atoms are more preferred.

[0062] Preferred fatty acids for forming the ester (E) component include, for example, stearic acid, palmitic acid, lauric acid, etc., with stearic acid being the most preferred.

[0063] As component (E), an ester compound of a polyol and a fatty acid having three or more carbon atoms is preferred. Specifically, glyceryl tristearate and pentaerythritol tetrastearate are preferred, and pentaerythritol tetrastearate is more preferred. Furthermore, component (E) may use two or more of the following: the polyol constituting it, esters of different fatty acids, and esters with different esterification rates.

[0064] In this embodiment, the content of fatty acid esters in the (E) polyol is 0.01 to 1.0 parts by weight relative to 100 parts by weight of the (A) POM resin, more preferably 0.05 to 1.0 parts by weight. When the amount of total fatty acid esters in the (E) polyol is less than 0.01 parts by weight, the moldability of the molded article may deteriorate. When the amount of fatty acid esters in the (E) polyol exceeds 1.0 parts by weight, the processability of the molded article may decrease.

[0065] [(F) Carbon-based conductive additives]

[0066] The POM resin composition of this embodiment contains a specified amount of (F) carbon-based conductive additive relative to (A) POM resin. The (F) carbon-based conductive additive is selected from (F1) carbon nanostructures only (hereinafter also referred to as "CNS"), and the (F1) carbon nanostructures have a BET specific surface area of ​​300 m². 2 One of the combinations of (F2) carbon black at a rate of / g or more. Furthermore, by adding (F) carbon-based conductive additives to the POM resin composition to impart conductivity, an antistatic effect can be achieved. In addition, when carbon black is added alone, the toughness of the resulting molded article decreases, but the addition of (F) carbon-based conductive additives can suppress this decrease in toughness.

[0067] The following sections discuss (F1) carbon nanostructures and BET specific surface areas of 300 m². 2 The description is based on carbon black (F2) of 1 g or more.

[0068] ((F1) Carbon Nanostructures (CNS))

[0069] The CNS used in this embodiment is a structure comprising multiple carbon nanotubes bonded together, with the carbon nanotubes linked to other carbon nanotubes via branched bonds or cross-linking structures. Detailed descriptions of such CNSs are described in U.S. Patent Application Publication No. 2013-0071565, U.S. Patent Nos. 9,113,031, 9,447,259, and 9,111,658.

[0070] The morphology of CNS is explained with reference to the attached diagram. Figure 1The CNS used in this embodiment is illustrated schematically. (A) represents the state before melt mixing with POM resin, (B) represents the state immediately after melt mixing, and (C) represents the state after melt mixing. Figure 1 As shown in (A), CNS10 before melt mixing forms a structure of multiple entangled branched carbon nanotubes 12. Then, when CNS10 is added to POM resin 20 for melt mixing, as... Figure 1 As shown in (B), CNS10 is divided into multiple portions. As the melt mixing process progresses, CNS10 is further divided, as... Figure 1 As shown in (C), each carbon nanotube 12 is connected one by one via junction 14. Figure 1 The (C) state of carbon nanotubes 12 in POM resin forms conductive pathways through multiple interconnected states over a large area, thus exhibiting conductivity. Furthermore, it can be considered that the carbon nanotubes 12 form a three-dimensional network structure by being randomly entangled together, thereby suppressing the reduction of toughness.

[0071] In order to obtain Figure 1 The CNS in the form shown in (C) Figure 1 The CNS shown in (A) is preferably in the form of a specified sheet. Figure 1 The sheet-like CNS shown in (A) comprises multiple carbon nanotubes that are branched, cross-linked, and share common walls. In this case, not all the multiple carbon nanotubes possess the structural features of being branched, cross-linked, and sharing common walls; rather, the multiple carbon nanotubes as a whole only need to possess at least one of these structural features. Furthermore, by using the sheet-like CNS described above, it can be melt-blended to form… Figure 1 The shape shown in (C).

[0072] The aforementioned sheet-like CNS is obtained by growing it on a growth substrate such as a fiber material and then removing the grown CNS from the growth substrate. In the CNS growth process, growth substrates such as fibers, rattan, silk, fabrics, non-woven fabrics, sheets, tapes, and belts can be used. That is, the growth substrate can be a fibrous material of roll size, allowing for continuous CNS formation while the growth substrate is being transported.

[0073] More specifically, a catalyst can be coated onto a growth substrate, and CNS can be grown using a fine-pore CVD process. The growth substrate with the CNS formed is then preserved, and subsequently, the CNS can be wound up to be removed.

[0074] When growing CNS on a growth substrate, a catalyst containing multiple transition metal nanoparticles is preferably used. To coat the catalyst onto the growth substrate, particle adsorption can be performed, for example, by direct catalyst coating using vapor deposition from a liquid or colloidal precursor. The transition metal nanoparticle catalyst comprises d-block transition metals or d-block transition metal salts. The transition metal salt can be coated onto the growth substrate without heat treatment, or heat treatment can be used to convert the transition metal salt onto the growth substrate to a zero-valent transition metal.

[0075] Although CNS contains carbon nanotubes in a network with a complex structure, this complex structure is believed to originate from the growth conditions under which carbon nanotubes are generated at a rapid growth rate of a few micrometers per second, forming CNS on the growth substrate.

[0076] When synthesizing carbon nanotubes on fibrous materials, various techniques for forming carbon nanotubes can be employed, including those disclosed in U.S. Patent Application Publication No. 2004 / 0245088. CNS grown on fibers can be formed, for example, through microcavity, thermal and plasma-enhanced CVD, laser ablation, arc discharge, and high-pressure carbon monoxide (HiPCO) techniques. Low-temperature carbon plasma for carbon nanotube synthesis can also be generated by ionizing acetylene gas. In this case, the plasma is directed towards the fibrous material containing the catalyst. Therefore, for the synthesis of CNS on fibrous materials, it is preferable to include two conditions: (a) forming a carbon plasma and (b) the carbon plasma being directed towards the catalyst disposed on the fibrous material. The diameter of the grown carbon nanotubes can be determined by the size of the carbon nanotube-forming catalyst. Furthermore, CNS synthesis can be easily carried out by heating the sizing fibrous material to a temperature of 550–800°C. Two gases are introduced into the reactor to initiate carbon nanotube growth: process gases such as argon, helium, or nitrogen, and carbon-containing gases such as acetylene, ethylene, ethanol, or methane. Moreover, carbon nanotubes grow at the sites where they form catalysts.

[0077] The CNS used in this embodiment can be a commercially available product. For example, CABOT's ATHLOS 200, ATHLOS 100, etc., can be used.

[0078] (BET specific surface area is 300m²) 2 / g or more of (F2) carbon black

[0079] In this embodiment, carbon black with a BET specific surface area of ​​300 m² can also be used. 2Carbon black of / g or higher. However, this carbon black is not used alone, but in combination with CNS. POM resin compositions mixed with this carbon black maintain conductivity even when used in combination with CNS due to its high conductivity. Conversely, those mixed with BET have a specific surface area of ​​less than 300m². 2 The POM resin composition containing / g of carbon black has low conductivity, requiring an increased mixing amount to ensure sufficient conductivity, which fails to suppress the decrease in toughness. The preferred BET specific surface area is 310m². 2 / g or more, preferably 350m 2 Above / g, as an upper limit, there is no specific limitation, but above 2000m 2 / g degree.

[0080] In addition, the BET specific surface area can be determined according to ASTM D4820.

[0081] As specific examples of carbon black mentioned above, one can list KETJEN BLACK EC300J (BET specific surface area: 800m²) manufactured by Lion Corporation. 2 / g), KETJEN BLACK EC600JD (BET specific surface area: 1270m²) 2 / g), Lionite EC200L (BET specific surface area: 377m²) 2 / g), etc.

[0082] In the POM resin composition of this embodiment, the carbon-based conductive additive (F) is mixed in at 0.3 to 2.5 parts by weight relative to 100 parts by weight of POM resin. When the amount of the carbon-based conductive additive (F) is less than 0.3 parts by weight, the conductivity is poor; when it exceeds 2.5 parts by weight, the toughness decreases. The mixing amount of this CNS is preferably 0.5 to 2.0 parts by weight, more preferably 0.6 to 1.8 parts by weight, and even more preferably 0.8 to 1.5 parts by weight.

[0083] Furthermore, when (F1)CNS and (F2) carbon black are used in combination, the mass ratio of (F1)CNS to (F2) carbon black ((F2) / (F1)) is preferably 10 or less, more preferably greater than 0 and less than 5. When this mass ratio is 10 or less, a balance between conductivity and toughness can be ensured. Although a value closer to 0 for F2 / F1 indicates an over-mixing of CNS, it is permissible to mix too much CNS. However, considering the high price of CNS, and taking into account cost-effectiveness, a lower limit for the value of F2 / F1 is preferably 0.1.

[0084] [Other ingredients]

[0085] The POM resin composition of this embodiment may also contain other components as needed. One or more known stabilizers may be added to the POM resin composition, provided it does not impair the purpose / effect of the POM resin composition of this embodiment.

[0086] There are no particular limitations on the method for producing molded articles using the POM resin composition of this embodiment, and known methods can be used. For example, it can be produced by feeding the POM resin composition of this embodiment into an extruder for melt mixing and granulation, and then feeding the granules into an injection molding machine equipped with a predetermined mold for injection molding.

[0087] The POM resin composition of this embodiment described above can be used as an automotive part as described later, or as a molded article with antistatic properties and fuel resistance.

[0088] <Fuel Contactor>

[0089] The fuel contact body of this embodiment comprises a molded article of the above-described POM resin composition. This molded article can be obtained by using the above-described POM resin composition and molding it using conventional molding methods, such as injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, etc.

[0090] The fuel contactor in this embodiment is not limited to high-sulfur fuels, but can also be a fuel contactor that contacts low-sulfur fuels.

[0091] Example

[0092] The following examples will provide a more detailed description of this implementation method, but this implementation method is not limited to the following examples.

[0093] [Examples 1-20, Comparative Examples 1-14]

[0094] In each embodiment / comparative example, the raw material components shown in Tables 1-4 were dry-mixed, then fed into a twin-screw extruder at a cylinder temperature of 200°C for melt mixing and granulation. Furthermore, in Tables 1-4, the values ​​for each component represent parts by mass.

[0095] In addition, the following details the ingredients used.

[0096] (A) Polyacetal resin (POM resin)

[0097] A-1: A polyacetal copolymer synthesized by copolymerizing 96.7% by mass of trioxymethylene with 3.3% by mass of 1,3-dioxolane. MFR (based on ISO 1133, determined at 190°C and 2160 g load): 9 g / 10 min.

[0098] (B) Antioxidants

[0099] B-1: Tetramethyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate]methane (BASF, Irganox 1010)

[0100] B-2: 4,4'-Bis(α,α-dimethylbenzyl)diphenylamine (manufactured by Ouchi Shinsei Chemical Industry Co., Ltd., crack-free CD)

[0101] (C) Magnesium oxide, etc.

[0102] C-1: Magnesium oxide, BET specific surface area 135m² 2 / g, average particle size 0.9μm (manufactured by Kyowa Chemical Industry Co., Ltd., KYOWAMAG MF150)

[0103] C-2: Magnesium oxide, BET specific surface area 30m² 2 / g, average particle size 0.6μm (manufactured by Kyowa Chemical Industry Co., Ltd., KYOWAMAG MF30)

[0104] C-3: Magnesium oxide, BET specific surface area 155m² 2 / g, average particle size 7μm (manufactured by Kyowa Chemical Industry Co., Ltd., KYOWAMAG 150)

[0105] C-4: Zinc oxide (BET specific surface area 60-90m²) 2 / g)(Made by Zhengtong Chemical Industry Co., Ltd., Active Zinc Hua AZO)

[0106] (Determination of average particle size)

[0107] Using the LA-920 laser diffraction / scattering particle size distribution measuring device manufactured by Horiba Manufacturing Co., Ltd., the particle size distribution was measured by laser diffraction / scattering under the following measurement conditions, and the average particle size (50% d) of the cumulative value was determined.

[0108] ~Measurement Conditions~

[0109] • Cycle speed: 5

[0110] • Laser source: 1mW 632.8nm He-Ne laser, 50W tungsten lamp • Detector: 1 x 75-segmented ring silicon photodiode, 12 x silicon photodiodes

[0111] • Dispersion medium: distilled water

[0112] • Ultrasound: Yes

[0113] • Transmittance: 75-90%

[0114] • Relative refractive index with water: 1.32

[0115] • Particle size criterion: volume

[0116] (D) Polyalkylene glycol

[0117] D-1: Polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., PEG6000S)

[0118] (E) Fatty acid esters of polyols

[0119] E-1: Pentaerythritol tetrastearate (a fatty acid ester of a polyol with an esterification rate of over 80%, manufactured by Nippon Oil Co., Ltd., Unister H476)

[0120] E-2: Glyceryl tristearate (a fatty acid ester of a polyol with an esterification rate of over 80%, manufactured by Riken Vitamin Co., Ltd., POEM S-95)

[0121] E-3: Glyceryl monostearate (a fatty acid ester of a polyol with an esterification rate of less than 80%, manufactured by Riken Vitamin Co., Ltd., RIKEMAL S-100A)

[0122] (F) Carbon nanostructures, carbon black

[0123] F-1: Carbon nanostructure (made by CABOT, ATHLOS 200)

[0124] F-2: Carbon Black (manufactured by Lion Corporation, KETJEN BLACK EC300J, BET specific surface area: 800m²) 2 / g)

[0125] F-3: Carbon Black (Lionite EC200L, manufactured by Lion Corporation, BET specific surface area: 377m²) 2 / g)

[0126] F-4: Carbon black (manufactured by Denka Corporation, DENKA BLACK, BET specific surface area: 65m³) 2 / g)

[0127] <Evaluation>

[0128] The following evaluation was conducted using the POM resin compositions prepared from the examples and comparative examples.

[0129] (1) Evaluation of fuel resistance

[0130] The prepared POM resin composition particles were used to produce 1 mm thick ASTM No. 4 dumbbell test pieces by injection molding. Furthermore, to evaluate the fuel resistance of the POM resin composition, the dumbbell test pieces were immersed in diesel fuel (product name: CEC RF) at 100°C.

[0131] (90-A-92, manufactured by Halterman) 14 days, the mass reduction rate due to fuel impregnation was calculated from the mass of the test pieces before and after, and evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 1-4.

[0132] [Evaluation Criteria]

[0133] A: Below 20%

[0134] B: More than 20%

[0135] Next, using the POM resin composition prepared by the examples and comparative examples, the multi-purpose test pieces described in ISO 294-1 were produced by injection molding using an injection molding machine (EC40, manufactured by Toshiba Machine Co., Ltd.) under conditions based on ISO 9988-1, 2, and used for the evaluation in (2) and (3) below.

[0136] (2) Evaluation of nominal strain (toughness) at tensile failure

[0137] The above-mentioned multi-purpose test specimens were used to determine the nominal tensile failure strain according to ISO 527-1, 2, and the results were evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 1 to 4.

[0138] [Evaluation Criteria]

[0139] A: More than 10%

[0140] B: Less than 10%

[0141] (3) Electrical conductivity

[0142] The following evaluation was conducted using the aforementioned multi-purpose test pieces.

[0143] (Surface resistivity / Volume resistivity)

[0144] The appearance of the multi-purpose test piece obtained in the above manner is shown in... Figure 2 . Figure 2 (A) represents the surface. Figure 2 (B) indicates the back side. The specified areas on each side of the test piece ( Figure 2The shaded areas were coated with a conductive coating (DOTITE D500, manufactured by Fujikura Chemicals Co., Ltd.) and dried. Then, a low resistivity measuring device (DIGITAL MULTIMETERR6450, manufactured by ADVANTEST) was used to measure the resistivity. Figure 2 The resistance between A and B of (A) was measured and used as the surface resistivity. Furthermore, the resistance between A and B was measured. Figure 2 The resistance between the CD surfaces was measured and used as the volume resistivity. The surface resistivity and volume resistivity were evaluated according to the following criteria. The evaluation results are shown in Tables 1-4.

[0145] [Evaluation Criteria for Surface Resistivity]

[0146] A: 1.0×10 4 Below Ω / □(Ω / sq)

[0147] B: Exceeding 1.0 × 10 4 Ω / □ and 1.0×10 7 Ω / □ and below

[0148] C: Exceeding 1.0 × 10 7 Ω / □

[0149] [Evaluation Criteria for Volume Resistivity]

[0150] A: 1.0×10 4 Below Ω·cm

[0151] B: Exceeding 1.0 × 10 4 Ω·cm and 1.0×10 7 Below Ω·cm

[0152] C: Exceeding 1.0 × 10 7 Ω·cm [Table 1]

[0153]

[0154] [Table 2]

[0155]

[0156] [Table 3]

[0157]

[0158] [Table 4]

[0159]

[0160] As shown in Tables 1-4, any evaluation in Examples 1-20 yielded good results. In contrast, in Comparative Examples 1-14, not all evaluations could simultaneously achieve good results.

[0161] Comparative Example 1 differs from Example 2 in that it does not contain components (C) to (F), resulting in poor fuel resistance and electrical conductivity. Comparative Example 2 differs from Example 2 in that it does not contain component (F), resulting in poor electrical conductivity. Comparative Example 3 differs from Example 2 in that it does not contain component (C), resulting in poor fuel resistance. Comparative Example 4 differs from Example 2 in that it does not contain component (D), resulting in poor fuel resistance. Comparative Example 5 differs from Example 2 in that it contains too little component (C), resulting in poor fuel resistance. Comparative Example 6 differs from Example 2 in that it contains an excess of component (C) and a slightly increased component (F), resulting in poor toughness. Comparative Example 7 differs from Example 2 in that it contains too little component (D), resulting in poor fuel resistance. Comparative Example 8 differs from Example 2 in that it contains an excess of component (D) and a slightly increased component (F), resulting in poor toughness. Comparative Example 9 differs from Example 2 in that it contains an excess of component (E), resulting in poor fuel resistance. Comparative Example 10 differs from Example 2 in that it uses an (E) component with an esterification rate of less than 80%, resulting in poor fuel resistance. Comparative Examples 11 and 12 differ from Example 2 in that they contain either too little or too much (F) component; Comparative Example 11 exhibits poor electrical conductivity, while Comparative Example 12 exhibits poor toughness. Comparative Example 13 differs from Example 20 in that it uses an excessive amount of (F) component in the combination of carbon nanostructures and carbon black, resulting in poor toughness. Comparative Example 14 differs from Example 18 in that it uses carbon black with an excessively small BET specific surface area, resulting in poor electrical conductivity.

[0162] As can be seen from the above, when components (A) to (F) are not mixed in the prescribed amounts, it is impossible to obtain results that are good in terms of toughness, fuel resistance, and antistatic properties.

Claims

1. A polyoxymethylene resin composition, characterized by, contains: (A) 100 parts by mass of a polyoxymethylene resin; (B) 0.1 to 1.0 parts by mass of an antioxidant; (C) 0.3 to 2.0 parts by mass of at least one of magnesium oxide and zinc oxide; (D) 0.5 to 3.0 parts by mass of a polyalkylene glycol; (E) 0.01 to 1.0 parts by mass of a fatty acid ester of a polyol having an esterification rate of 80% or more; and (F) 0.3 to 2.5 parts by mass of a carbon-based conductive additive, The (F) carbon-based conductive additive is selected from one of only (F1) carbon nanostructures, and a combination of (F1) carbon nanostructures and (F2) carbon black having a BET specific surface area of 300 m 2 / g or more. In the case where the (F) carbon-based conductive additive is a combination of the (F1) carbon nanostructure and the (F2) carbon black having a BET specific surface area of 300 m2 / g or more, the content of the (F1) carbon nanostructure is 0.3 parts by mass or more. 2 In the case where the (F) carbon-based conductive additive is a combination of the (F1) carbon nanostructure and the (F2) carbon black having a BET specific surface area of 300 m2 / g or more, the content of the (F1) carbon nanostructure is 0.3 parts by mass or more. wherein the carbon nanostructure is a structure body comprising a plurality of carbon nanotubes combined in a branched chain bond or crosslinked structure, a mass ratio of the (F2) carbon black to the (F1) carbon nanostructure ((F2) / (F1)) is 10 or less.

2. The polyoxymethylene resin composition according to claim 1, wherein the polyoxymethylene resin is a copolymer using a cyclic oligomer of formaldehyde as a main monomer and a compound selected from a cyclic ether and / or a cyclic formal having at least one carbon-carbon bond as a comonomer.

3. The polyoxymethylene resin composition according to claim 1 or 2, wherein the (E) fatty acid ester of a polyol is an ester compound of a polyol having 3 or more carbon atoms and a fatty acid.

4. The polyoxymethylene resin composition according to claim 1 or 2, wherein the (E) fatty acid ester of a polyol is an ester compound of a polyol having 3 or more carbon atoms and a fatty acid. The BET specific surface area of the (C) magnesium oxide is 100 m 2 / g or more.

5. The polyoxymethylene resin composition according to claim 3, wherein the (E) fatty acid ester of a polyol is an ester compound of a polyol having 3 or more carbon atoms and a fatty acid. A molded article comprising the polyoxymethylene resin composition according to any one of claims 1 to 5. ​ ​ 6. A fuel contact body characterized by, ​

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