JP7217385B2 - Polyacetal resin composition and fuel contactor - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyacetal resin composition and a fuel contact body formed by molding it.

Polyacetal resins (hereinafter also referred to as "POM resins") are excellent in chemical resistance, so molded articles made from POM resins are widely used as automobile parts. For example, it is used as a large-sized part such as a fuel transfer unit represented by a fuel pump module that directly contacts fuel oil.

In recent years, in order to comply with environmental regulations in various countries, efforts are being made to reduce the sulfur content of fuels. However, high sulfur fuel is still in circulation in some countries due to the high cost of desulfurization equipment. These high sulfur fuels tend to degrade the POM resin more easily than low sulfur fuels.

By the way, an injection molded product manufactured from POM resin has residual stress inside the molded product due to cooling during injection molding. If this injection molded product comes into contact with high-sulfur fuel or the like, cracks may occur at locations where residual stress is large, which may cause troubles such as fuel leakage. Therefore, for countries where high-sulfur fuel is distributed, it is necessary to use a resin material having high resistance to high-sulfur fuel as a raw material.

The present applicant has reported that these problems can be greatly improved by adding alkaline earth metal oxides, polyalkylene glycol, and specific esters to the polyacetal resin (see Patent Document 1). . Significant improvements were seen, especially for parts such as fuel transfer units that come into contact with high sulfur fuel.

On the other hand, the molded article used around the fuel pump as described above is required to have electrical conductivity and be free from static electricity in order to prevent ignition of the fuel due to static electricity. As one measure for imparting conductivity to POM resin, it is known to add a conductive filler such as carbon black or carbon fiber (see Patent Documents 2 and 3).

Japanese Patent No. 5814419 Japanese Patent Publication No. 07-002891 Japanese Patent Publication No. 2004-526596

However, in the POM resin composition, when an alkaline earth metal oxide is added to impart durability to fuel, and a conductive filler such as carbon black is added to develop an antistatic effect, the toughness is greatly improved. is a problem. That is, in the POM resin composition, if an attempt is made to achieve both antistatic effect and resistance to acid components at the same time, the toughness is significantly lowered.

The present invention has been made in view of the above-mentioned conventional problems, and its object is to provide a POM resin composition and a fuel contact resin composition which are endowed with durability against high-sulfur fuel and antistatic effect without a large decrease in toughness. It is to provide the body.

One aspect of the present invention for solving the above problems is as follows.
(1) (A) 100 parts by mass of polyacetal 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 polyalkylene glycol,
(E) 0.01 to 1.0 parts by mass of a polyhydric alcohol fatty acid ester having an esterification rate of 80% or more;
(F) 0.3 to 2.5 parts by mass of a carbon-based conductive additive,
The (F) carbon-based conductive additive is one selected from (F1) carbon nanostructures only, and (F1) carbon nanostructures and (F2) a combination of carbon black having a BET specific surface area of 300 m ² /g or more. A polyacetal resin composition.

(2) The polyacetal resin is a copolymer having a cyclic oligomer of formaldehyde as a main monomer and a compound selected from cyclic ethers and/or cyclic formals having at least one carbon-carbon bond as a comonomer, the above ( 1) The polyacetal resin composition as described in 1).

(3) The polyacetal resin composition according to (1) or (2) above, wherein the magnesium oxide (C) has a BET specific surface area of 100 m ² /g or more.

(4) The mass ratio ((F2)/(F1)) between the (F1) carbon nanostructure and the (F2) carbon black is 10 or less, according to any one of (1) to (3). Polyacetal resin composition.

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

(6) A fuel contactor comprising a molded article of the polyacetal resin composition according to any one of (1) to (5).

According to the present invention, it is possible to provide a POM resin composition and a fuel contactor which are endowed with durability against high-sulfur fuel and an antistatic effect without a large decrease in toughness.

FIG. 2 is a diagram schematically showing the state of carbon nanostructures (A) before melt-kneading, (B) immediately after the start of melt-kneading, and (C) after melt-kneading. FIG. 2A is a top view and (B) a back view of a test piece used for measuring surface resistivity and volume resistivity in Examples.

<Polyacetal resin composition>
The POM resin composition of the present embodiment comprises (A) 100 parts by mass of a polyacetal resin, (B) 0.1 to 1.0 parts by mass of an antioxidant, and (C) magnesium oxide and zinc oxide. At least one of 0.3 to 2.0 parts by mass, (D) 0.5 to 3.0 parts by mass of polyalkylene glycol, and (E) an esterification rate of 80% or more, of polyhydric alcohol 0.01 to 1.0 parts by mass of fatty acid ester and (F) 0.3 to 2.5 parts by mass of carbon-based conductive additive. and (F) the carbon-based conductive additive is one selected from (F1) carbon nanostructures only, and (F1) carbon nanostructures and (F2) a combination of carbon black having a BET specific surface area of 300 m ² /g or more. It is characterized by being one.

In the POM resin composition of the present embodiment, by adding (C) at least one of magnesium oxide and zinc oxide to the POM resin, durability against high-sulfur fuel can be imparted. Further, by blending (F) a carbon-based conductive additive, conductivity can be imparted, and an antistatic effect can be exhibited. Here, conventionally, if carbon black or the like is added to develop an antistatic effect, the addition of carbon black or the like causes a significant decrease in toughness in combination with magnesium oxide or the like. However, in the present embodiment, the conductivity is imparted by (F) the carbon-based conductive additive, so a significant decrease in toughness can be suppressed. The mechanism will be described later. The term "high sulfur fuel" refers to fuel having a sulfur component concentration of 0.1% by mass or more.
Each component of the POM resin composition of the present embodiment will be described below.

[(A) polyacetal resin (POM resin)]
The (A) POM resin used in the present embodiment refers to a polymer compound having an oxymethylene group ₍ --CH.sub.2O--) as a main structural unit, and is a polyacetal polymer consisting essentially of repeating units of oxymethylene groups. , polyacetal copolymers containing a small amount of structural units other than oxymethylene groups, and the like. Any of these can be used, but from the viewpoint of fuel resistance, it is preferable to use a polyacetal copolymer as the base resin.

When the component (A) is a polyacetal copolymer, the polyacetal copolymer is preferably a polyacetal copolymer obtained by copolymerizing 0.5 to 30% by mass of a comonomer component, particularly preferably 0.5 to 10% by mass of a comonomer component. It is made by polymerizing. Polyacetal copolymers obtained by copolymerizing comonomer components are excellent in acid resistance and can retain excellent thermal stability, mechanical strength, and the like. Moreover, the polyacetal copolymer may have a branched structure or a crosslinked structure as well as a linear molecular structure.

In producing such a polyacetal copolymer, a cyclic oligomer of formaldehyde represented by trioxane is used as the main monomer. Also, as a comonomer component, a compound selected from cyclic ethers and/or cyclic formals having at least one carbon-carbon bond is used. Examples of such comonomers include ethylene oxide, 1,3-dioxolane, diethylene glycol formal, 1,4-butanediol formal, 1,3-dioxane, propylene oxide and the like.

The degree of polymerization of the (A) POM resin, particularly the polyacetal copolymer, is not particularly limited, and can be adjusted according to the purpose of use and molding means. However, from the viewpoint of compatibility between acid resistance and moldability, the melt mass flow rate (MFR) measured at a measurement temperature of 190 ° C. and a load of 2.16 kg according to ISO 1133 is preferably 1 to 100 g / 10 minutes. Particularly preferably, it is 5 to 30 g/10 minutes.

[(B) Antioxidant]
The (B) antioxidant used in the present embodiment includes aromatic amine-based antioxidants, hindered phenol-based antioxidants, and the like. Aromatic amine antioxidants include N-phenyl-1-naphthylamine, bis(4-octylphenyl)amine, 4,4′-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonyl) amido)diphenylamine, N,N'-di-2-naphthyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, N-phenyl-N'-(1,3-dimethylbutyl)- p-phenylenediamine, N-phenyl-N'-(3-methacryloyloxy-2-hydroxypropyl)-p-phenylenediamine and the like. Among them, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine is preferred.

Hindered phenol antioxidants include 2,2′-methylenebis(4-methyl-6-t-butylphenol), hexamethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl ) propionate], tetrakis [methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane, triethylene glycol-bis[3-(3-t-butyl-4-hydroxy-5 -methylphenyl)propionate], 1,3,5-trimethyl-2,4,6-tris(3′,5′-di-t-butyl-4-hydroxy-benzyl)benzene, n-octadecyl-3-( 4'-hydroxy-3',5'-di-t-butylphenyl)propionate, 4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-butylidenebis(6-t-butyl -3-methyl-phenol), distearyl (3,5-di-t-butyl-4-hydroxybenzyl)phosphonate, 2-t-butyl-6-(3-t-butyl-5-methyl-2-hydroxy benzyl)-4-methylphenyl acrylate, 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2, Examples include 4,8,10-tetraoxaspiro[5,5]undecane, among which triethylene glycol-bis[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionate], tetrakis [methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane, hexamethylene-bis[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate] is preferred.

In this embodiment, at least one or two or more selected from these antioxidants can be used.

The amount of the (B) antioxidant in the present embodiment is 0.1 to 1.0 parts by mass and 0.2 to 0.8 parts by mass with respect to 100 parts by mass of the (A) POM resin. is more preferred.

[(C) magnesium oxide, zinc oxide]
The POM resin composition of the present embodiment contains at least one of magnesium oxide and zinc oxide (hereinafter also referred to as "component (C)"). The (C) component used in the present embodiment is a balance between improvement in high sulfur fuel resistance (durability against high sulfur fuel (hereinafter also referred to as “fuel resistance”)) and performance such as mechanical properties and moldability. is excellent and preferable.

Magnesium oxide preferably has a BET specific surface area of 100 m ² /g or more and an average particle size of 1.5 μm or less. By satisfying these conditions, fuel resistance can be obtained while suppressing a decrease in toughness. The BET specific surface area of magnesium oxide is preferably 100-500 m ² /g, more preferably 120-300 m ² /g. Also, the average particle size of magnesium oxide is preferably 0.2 to 1.3 μm, more preferably 0.3 to 1.0 μm. The average particle size is determined by the particle size at 50% of the integrated value in the particle size distribution (volume basis) measured by a laser diffraction/scattering method.

The blending amount of component (C) in the present embodiment is 0.3 to 2.0 parts by mass and preferably 1.0 to 1.8 parts by mass with respect to 100 parts by mass of (A) POM resin. preferable. When the amount of component (C) is 0.3 parts by mass or more, the fuel resistance is particularly excellent. Excellent balance of properties. In the past, when the amount of component (C) increased, the decomposition of unstable terminals in the POM resin was sometimes promoted. , and (C) were found to improve fuel resistance.

[(D) polyalkylene glycol]
The type of (D) polyalkylene glycol used in the present embodiment is not particularly limited, but from the viewpoint of affinity with the POM resin, those containing polyethylene glycol and/or polypropylene glycol are preferable, and those containing polyethylene glycol are preferred. is more preferred.

The number average molecular weight (Mn) of the polyalkylene glycol is not particularly limited, but from the viewpoint of dispersibility in the POM resin, it is preferably 1,000 or more and 50,000 or less, and 5,000 or more and 30,000 or less. It is more preferable to have In addition, in this specification, the number average molecular weight shall be the molecular weight of polystyrene conversion calculated|required by the size exclusion chromatography (SEC) which uses tetrahydrofuran (THF) as a solvent.

The content of (D) polyalkylene glycol in the present embodiment is 0.5 to 3.0 parts by mass and 1.0 to 2.0 parts by mass with respect to 100 parts by mass of (A) POM resin. is more preferred. If the blending amount of (D) polyalkylene glycol is small, sufficient stress relaxation may not be achieved. If the amount of (D) polyalkylene glycol to be blended is excessive, the mechanical properties of the molded article may deteriorate.

[(E) Fatty acid ester of polyhydric alcohol]
The (E) polyhydric alcohol fatty acid ester used in the present embodiment has an esterification rate of 80% or more. If the esterification rate is less than 80%, the fuel resistance is poor. (E) The esterification rate of the fatty acid ester of polyhydric alcohol is preferably 85% or more.

The polyhydric alcohol may be aliphatic or aromatic, but is preferably aliphatic in terms of affinity with (A) the POM resin.

Although the valence of the polyhydric alcohol is not particularly limited, it is preferably 3 or more and 4 or less. The number of carbon atoms in the polyhydric alcohol is not particularly limited, but is preferably 3 or more and 10 or less, more preferably 3 or more and 5 or less in terms of affinity with (A) the POM resin. more preferred.

Preferred polyhydric alcohols for forming the ester of component (E) include, for example, glycerin, trimethylolpropane, pentaerythritol, mesoerythritol, pentitose, hexitol, and sorbitol. The polyhydric alcohol is preferably pentaerythritol in that the weight loss of the resin composition can be kept low.

Although the type of fatty acid is not particularly limited, (A) fatty acids having 10 to 30 carbon atoms are preferable from the viewpoint of affinity with the POM resin, and aliphatic acids having 10 to 20 carbon atoms Carboxylic acid is more preferred.

Preferable fatty acids for forming the component (E) ester include, for example, stearic acid, palmitic acid and lauric acid, preferably stearic acid.

Component (E) is preferably an ester compound of a polyhydric alcohol having 3 or more carbon atoms and a fatty acid. Specifically, glycerin tristearate and pentaerythritol tetrastearate are preferably used, and pentaerythritol tetrastearate is more preferably used. The component (E) may be used in combination of two or more esterified products with different polyhydric alcohols or fatty acids, or esterified products with different esterification ratios.

The content of (E) fatty acid ester of polyhydric alcohol in the present embodiment is 0.01 to 1.0 parts by mass, and 0.05 to 1.0 parts by mass, with respect to 100 parts by mass of (A) POM resin. is more preferable. (E) If the blending amount of the fatty acid full ester of polyhydric alcohol is less than 0.01 parts by mass, the releasability of the molded product may deteriorate. (E) If the blending amount of the polyhydric alcohol fatty acid ester is more than 1.0 parts by mass, the processability of the molded product may deteriorate.

[(F) Carbon-based conductive additive]
In the POM resin composition of the present embodiment, a predetermined amount of (F) a carbon-based conductive additive is blended with (A) the POM resin. (F) Carbon-based conductive additives include (F1) carbon nanostructures (hereinafter also referred to as “CNS”) only, and (F1) carbon nanostructures and (F2) carbon having a BET specific surface area of 300 m ² /g or more It is one selected from the combination with black. By adding (F) a carbon-based conductive additive to the POM resin composition, conductivity is imparted and an antistatic effect is exhibited. In addition, when carbon black is added alone, the toughness of the obtained molded product is lowered, but the addition of (F) the carbon-based conductive additive can suppress the decrease in toughness.
(F1) carbon nanostructure and (F2) carbon black having a BET specific surface area of 300 m ² /g or more will be described below.

((F1) carbon nanostructure (CNS))
The CNS used in this embodiment is a structure containing a plurality of carbon nanotubes bonded together, and the carbon nanotubes are bonded to other carbon nanotubes in a branched bond or crosslinked structure. Details of such CNS can be found in US Patent Application Publication No. 2013-0071565, US Patent Nos. 9,113,031, 9,447,259, 9,111,658. described in the specification.

The configuration of the CNS will be described with reference to the drawings. FIG. 1 schematically shows the CNS used in this embodiment, (A) is the state before melt-kneading with the POM resin, (B) is the state immediately after the start of melt-kneading, and (C) is after melt-kneading. indicates the state of As shown in FIG. 1A, the CNS 10 before melt-kneading has a structure in which a large number of branched carbon nanotubes 12 are entangled and bonded. When the CNS 10 is put into the POM resin 20 and melt-kneaded, the CNS 10 is divided into a large number as shown in FIG. 1(B). As the melt-kneading progresses, the CNS 10 is further divided, and each carbon nanotube 12 is brought into contact with each other through the contact 14 as shown in FIG. 1(C). That is, in the state of FIG. 1(C), a large number of carbon nanotubes 12 are in contact with each other over a wide area in the POM resin to form a conductive path, thereby exhibiting conductivity. In addition, since the carbon nanotubes 12 are randomly entangled to form a three-dimensional network structure, it is thought that a decrease in toughness can be suppressed.

In order to obtain the CNS having the form shown in FIG. 1(C), it is preferable that the CNS shown in FIG. 1(A) have a predetermined flake shape. The flake-like CNS shown in FIG. 1(A) comprises a plurality of carbon nanotubes that are branched, cross-linked, and share common walls with one another. In this case, the plurality of carbon nanotubes do not all have structural features such as branching, cross-linking, and sharing a common wall, and the plurality of carbon nanotubes as a whole exhibit at least one of these structural features. should have Then, by using the flake-shaped CNS as described above, the shape shown in FIG. 1(C) is obtained by melt-kneading.

The flake-like CNS as described above can be obtained by growing the grown CNS on a growth substrate such as a fibrous material and removing the grown CNS from the growth substrate. CNS growth processes can use growth substrates such as fibers, tows, threads, fabrics, nonwovens, sheets, tapes, belts, and the like. That is, the growth substrate can be a fibrous material with dimensions that permit spooling, and the formation of the CNS can be carried out continuously while the growth substrate is transported.
More specifically, a catalyst can be applied to the growth substrate and CNS growth can be achieved by a pore CVD process. The growth substrate with the CNS formed can then be stored and then rolled up to retrieve the CNS.

In growing CNS on a growth substrate, it is preferred to use a catalyst comprising a plurality of transition metal nanoparticles. Catalyst coating on the growth substrate may be carried out, for example, via particle adsorption, such as direct catalyst coating using vapor deposition with liquid or colloidal precursors. Transition metal nanoparticle catalysts include d-block transition metals or d-block transition metal salts. The transition metal salt may be applied to the growth substrate without heat treatment, or the transition metal salt may be converted to a zero-valent transition metal on the growth substrate by heat treatment.

CNSs contain carbon nanotubes in networks with complex structural morphologies, which grow on growth substrates under carbon nanotube growth conditions that produce rapid growth rates on the order of several microns per second. It is thought that this originates from the formation of

Various techniques for forming carbon nanotubes can be employed in synthesizing carbon nanotubes on fibrous materials, including those disclosed in US Patent Application Publication No. 2004/0245088. CNS grown on fibers can be formed by techniques such as microcavity, thermal and plasma enhanced CVD techniques, laser ablation, arc discharge, and high pressure carbon monoxide (HiPCO). Acetylene gas can also be ionized to produce a low temperature carbon plasma for carbon nanotube synthesis. The plasma is then directed at the fibrous material with the catalyst. Thus, synthesizing CNS on a fibrous material involves two conditions: (a) forming a carbon plasma; and (b) directing the carbon plasma to a catalyst disposed on the fibrous material. is preferred. The diameter of the growing carbon nanotubes is defined by the size of the carbon nanotube forming catalyst. Also, by heating the sized fiber material to about 550 to 800° C., CNS synthesis can be facilitated. To initiate carbon nanotube growth, two gases are flowed into the reactor. process gases such as argon, helium, or nitrogen, and carbon-containing gases such as acetylene, ethylene, ethanol, or methane. Carbon nanotubes then grow at the location of the carbon nanotube formation catalyst.

The CNS used in this embodiment may be a commercial product. For example, CABOT ATHLOS 200, ATHLOS 100, etc. can be used.

((F2) Carbon black having a BET specific surface area of 300 m ² /g or more)
In this embodiment, among carbon blacks, carbon black having a BET specific surface area of 300 m ² /g or more is used. However, the carbon black is not used alone, but used in combination with CNS. Since the POM resin composition containing the carbon black has high electrical conductivity, the electrical conductivity can be maintained even when used in combination with CNS. Conversely, a POM resin composition containing carbon black having a BET specific surface area of less than 300 m ² /g has low electrical conductivity, and it is necessary to increase the blending amount in order to ensure sufficient electrical conductivity. cannot stop the decline. The BET specific surface area is preferably 310 m ² /g or more, more preferably 350 m ² /g or more, and although the upper limit is not particularly limited, it is about 2000 m ² /g.
The BET specific surface area can be measured according to ASTM D4820.

Specific carbon blacks such as those described above include Ketjenblack EC300J (BET specific surface area: 800 m ² /g), Ketjenblack EC600JD (BET specific surface area: 1270 m ² /g), and Lionite EC200L manufactured by Lion Corporation. (BET specific surface area: 377 m ² /g).

In the POM resin composition of this embodiment, 0.3 to 2.5 parts by mass of the (F) carbon-based conductive additive is blended with 100 parts by mass of the POM resin. If the amount of the carbon-based conductive additive (F) is less than 0.3 parts by mass, the conductivity is poor, and if it exceeds 2.5 parts by mass, the toughness is lowered. The content of the CNS is preferably 0.5 to 2.0 parts by mass, more preferably 0.6 to 1.8 parts by mass, even more preferably 0.8 to 1.5 parts by mass.

When (F1) CNS and (F2) carbon black are used in combination, the mass ratio ((F2)/(F1)) between (F1) CNS and (F2) carbon black is preferably 10 or less. , more preferably greater than 0 and 5 or less. When the mass ratio is 10 or less, a balance between conductivity and toughness can be ensured. Also, as the value of F2/F1 approaches 0, it means that the CNS is blended in an excessive amount, and the CNS may be blended in such an excessive amount. However, considering that CNS is expensive, the lower limit of the value of F2/F1 is preferably 0.1 from the viewpoint of cost-effectiveness.

[Other ingredients]
The POM resin composition of this embodiment may contain other components as necessary. One or two or more known stabilizers for the POM resin composition may be added as long as the objects and effects of the POM resin composition of the present embodiment are not impaired.

A method for producing a molded product using the POM resin composition of the present embodiment is not particularly limited, and known methods can be employed. For example, the POM resin composition of the present embodiment can be put into an extruder, melted and kneaded to form pellets, put the pellets into an injection molding machine equipped with a predetermined mold, and be injection molded. can.

The POM resin composition of the present embodiment described above can be used as an automobile part described later, or can be used as a molded product having an antistatic function and resistance to fuel.

<Fuel contactor>
The fuel contactor of this embodiment includes a molded article of the POM resin composition. The molded article is obtained by molding the POM resin composition by a conventional molding method such as injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, and rotational molding. be able to.

The fuel contact body of the present embodiment is not limited to high-sulfur fuel, and may be in contact with low-sulfur fuel.

EXAMPLES The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to the following examples.

[Examples 1 to 20, Comparative Examples 1 to 14]
In each example and comparative example, after dry-blending each raw material component shown in Tables 1 to 4, the mixture was put into a twin-screw extruder with a cylinder temperature of 200° C., melt-kneaded, and pelletized. In Tables 1 to 4, the numerical value of each component indicates parts by mass.
Further, the details of each raw material component used are shown below.
(A) Polyacetal resin (POM resin)
A-1: A polyacetal copolymer obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane. MFR (according to ISO1133, measured at 190°C and a load of 2160g): 9g/10min)

(B) Antioxidant B-1: Tetrakis [methylene-3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate] methane (manufactured by BASF, Irganox1010)
B-2: 4,4′-bis(α,α-dimethylbenzyl)diphenylamine (manufactured by Ouchi Shinko Chemical Industry Co., Ltd., Nocrac CD)

(C) Magnesium oxide, etc. C-1: Magnesium oxide, BET specific surface area 135 m ² /g, average particle size 0.9 μm (manufactured by Kyowa Chemical Industry Co., Ltd., Kyowamag MF150)
C-2: Magnesium oxide, BET specific surface area 30 m ² /g, average particle size 0.6 μm (manufactured by Kyowa Chemical Industry Co., Ltd., Kyowamag MF30)
C-3: Magnesium oxide, BET specific surface area 155 m ² /g, average particle size 7 μm (manufactured by Kyowa Chemical Industry Co., Ltd., Kyowamag 150)
C-4: Zinc oxide (BET specific surface area 60 to 90 m ² /g) (manufactured by Seido Chemical Industry Co., Ltd., active zinc oxide AZO)

(Measurement of average particle size)
Using a laser diffraction/scattering particle size distribution analyzer LA-920 manufactured by Horiba, Ltd., the particle size distribution is measured by a laser diffraction/scattering method under the following measurement conditions, and the average particle diameter with an integrated value of 50%. (50% d) was determined.
～Measurement conditions～
・Circulation speed: 5
・ Laser light source: 632.8 nm He-Ne laser 1 mW, tungsten lamp 50 W ・ Detector: Ring-shaped 75-split silicon photodiode x 1, silicon photodiode x 12
・Dispersion medium: distilled water ・Ultrasonic waves: Yes ・Transmittance: 75 to 90%
・Relative refractive index with water: 1.32
・Particle size standard: Volume

(D) polyalkylene glycol D-1: polyethylene glycol (manufactured by Sanyo Chemical Industries, Ltd., PEG6000S)

(E) Fatty acid ester of polyhydric alcohol E-1: Pentaerythritol tetrastearate (fatty acid ester of polyhydric alcohol with an esterification rate of 80% or more, manufactured by NOF Corporation, Unistar H476)
E-2: Glycerin tristearate (fatty acid ester of polyhydric alcohol with an esterification rate of 80% or more, manufactured by Riken Vitamin Co., Ltd., Poem S-95)
E-3: Glycerin monostearate (fatty acid ester of polyhydric alcohol with an esterification rate of less than 80%, manufactured by Riken Vitamin Co., Ltd., Rikemar S-100A)

(F) carbon nanostructure, carbon black F-1: carbon nanostructure (manufactured by CABOT, ATHLOS 200)
F-2: Carbon black (manufactured by Lion Corporation, Ketjenblack EC300J, BET specific surface area: 800 m ² /g)
F-3: Carbon black (Lionite EC200L, manufactured by Lion Corporation, BET specific surface area: 377 m ² /g)
F-4: Carbon black (manufactured by Denka Co., Ltd., Denka black, BET specific surface area: 65 m ² /g)

<Evaluation>
The following evaluations were performed using the POM resin compositions prepared in Examples and Comparative Examples.

(1) Evaluation of fuel resistance Using pellets of the prepared POM resin composition, an ASTM No. 4 dumbbell test piece having a thickness of 1 mm was produced by injection molding. Then, in order to evaluate the fuel resistance of the POM resin composition, the dumbbell test piece was immersed in diesel fuel (product name: CEC RF 90-A-92, manufactured by Haltermann) at 100° C. for 14 days. The mass reduction rate due to fuel immersion was calculated from the mass of the test piece, and evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 1-4.
[Evaluation criteria]
A: 20% or less B: More than 20%

Next, using the POM resin compositions prepared in Examples and Comparative Examples, multi-purpose test pieces described in ISO294-1 were molded under conditions according to ISO9988-1 and 2 using an injection molding machine (EC40, manufactured by Toshiba Machine Co., Ltd.). ) and used for the following evaluations (2) and (3).

(2) Evaluation of Nominal Tensile Fracture Strain (Toughness) Using the multi-purpose test piece, the nominal tensile strain at failure was measured according to ISO527-1 and 2, and evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 1-4.
[Evaluation criteria]
A: 10% or more B: less than 10%

(3) Conductivity The following evaluations were made using the multipurpose test piece.
(Surface resistivity/Volume resistivity)
FIG. 2 shows the appearance of the multipurpose test piece obtained as described above. FIG. 2A shows the front surface, and FIG. 2B shows the back surface. A conductive paint (Dotite D500, manufactured by Fujikura Kasei Co., Ltd.) was applied to a predetermined area (hatched area in FIG. 2) on each surface of the test piece and dried. Then, using a low resistivity measuring device (DIGITAL MULTIMETER R6450, manufactured by ADVANTEST), the resistance between AB in FIG. Also, the resistance between CD in FIG. 2 was measured and taken as the volume resistivity. Each of surface resistivity and volume resistivity was evaluated according to the following evaluation criteria. The evaluation results are shown in Tables 1-4.
[Evaluation Criteria for Surface Resistivity]
A: 1.0×10 ⁴ Ω/□ or less B: More than 1.0×10 ⁴ Ω/□ or less than 1.0×10 ⁷ Ω/□ C: More than 1.0×10 ⁷ Ω/□ [volume resistivity evaluation criteria]
A: 1.0×10 ⁴ Ω・cm or less B: More than 1.0×10 ⁴ Ω・cm and 1.0×10 ⁷ Ω・cm or less C: More than 1.0×10 ⁷ Ω・cm

From Tables 1 to 4, it can be seen that good results were obtained in all evaluations in Examples 1 to 20. On the other hand, in Comparative Examples 1 to 14, it was not possible to achieve good results in all evaluations at the same time.
Comparative Example 1 differs from Example 2 in that the components (C) to (F) are not blended, and is inferior in fuel resistance and electrical conductivity. Comparative Example 2 is inferior in electrical conductivity unlike Example 2 in that component (F) is not blended. Comparative Example 3 is inferior in fuel resistance unlike Example 2 in that component (C) is not blended. Comparative Example 4 is inferior in fuel resistance unlike Example 2 in that component (D) is not blended. Comparative Example 5 is inferior in fuel resistance unlike Example 2 in that the component (C) is too small. Comparative Example 6 is inferior in toughness unlike Example 2 in that the amount of component (C) is excessive and the amount of component (F) is slightly increased. Comparative Example 7 is inferior in fuel resistance unlike Example 2 in that the component (D) is too small. Comparative Example 8 is inferior in toughness unlike Example 2 in that the amount of component (D) is excessive and the amount of component (F) is slightly increased. Comparative Example 9 is inferior in fuel resistance unlike Example 2 in that component (E) is excessive. Comparative Example 10 is inferior in fuel resistance unlike Example 2 in that a component (E) having an esterification rate of less than 80% is used. Comparative Examples 11 and 12 differ from Example 2 in whether the component (F) is too little or too much, Comparative Example 11 is inferior in electrical conductivity, and Comparative Example 12 is inferior in toughness. Comparative Example 13 is different from Example 16 in that the component (F) used in the combination of the carbon nanostructure and carbon black is excessive, and is inferior in toughness. Comparative Example 14 differs from Example 18 in that carbon black having an excessively small BET specific surface area is used, and is inferior in electrical conductivity.
From the above, it can be seen that unless the components (A) to (F) are blended in the predetermined contents, good results in all of the toughness, fuel resistance, and antistatic effect cannot be obtained.

Claims (6)

(A) 100 parts by mass of polyacetal 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 polyalkylene glycol,
(E) 0.01 to 1.0 parts by mass of a polyhydric alcohol fatty acid ester having an esterification rate of 80% or more;
(F) 0.3 to 2.5 parts by mass of a carbon-based conductive additive,
The (F) carbon-based conductive additive is (F1) only a carbon nanostructure, which is a structure including a plurality of carbon nanotubes each bonded to other carbon nanotubes in a branched bond or crosslinked structure, and (F1) One selected from a combination of carbon nanostructure and (F2) carbon black having a BET specific surface area of 300 m ² /g or more,
When the (F) carbon-based conductive additive is a combination of the (F1) carbon nanostructure and (F2) carbon black having a BET specific surface area of 300 m ² /g or more, the (F1) carbon nanostructure is A polyacetal resin composition containing 0.3 parts by mass or more per 100 parts by mass of polyacetal resin. The polyacetal resin is a copolymer comprising a cyclic oligomer of formaldehyde as a main monomer and a compound selected from cyclic ethers and/or cyclic formals having at least one carbon-carbon bond as a comonomer. polyacetal resin composition. The polyacetal resin composition according to claim 1 or 2, wherein the (C) magnesium oxide has a BET specific surface area of 100 m ² /g or more. The polyacetal resin composition according to any one of claims 1 to 3, wherein the mass ratio ((F2)/(F1)) between the (F1) carbon nanostructure and the (F2) carbon black is 5 or less. . The polyacetal resin composition according to any one of claims 1 to 4, wherein the (E) fatty acid ester of a polyhydric alcohol is an ester compound of a polyhydric alcohol having 3 or more carbon atoms and a fatty acid. A fuel contact body comprising a molded article of the polyacetal resin composition according to any one of claims 1 to 5.

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