Sulfur fuel contact body comprising a polyacetal resin composition and a molded article of this polyacetal resin composition

Abstract

To provide a polyacetal resin composition which can minimize deterioration upon contact with a sulfur fuel when formed into a molded article and is excellent in conductivity.SOLUTION: The purpose of the present invention is achieved by the polyacetal resin composition obtained by blending (A) 100 pts.mass of a polyacetal resin, (B) 0.1-1.5 pts.mass of an antioxidant, (C) 0.3-2.0 pts.mass of an oxide of magnesium or zinc, (D) 0.5-3.0 pts.mass of a polyalkylene glycol, (E) 0.01-1.0 pt.mass of a fatty acid ester of a polyhydric alcohol having an esterification rate of 80% or more, and (F) 3.0-15 pts.mass of carbon black.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a polyacetal resin composition and a sulfur fuel contact member including a molded article of the polyacetal resin composition.

Background Art

[0002] Since polyacetal resins are excellent in chemical resistance, molded articles made of polyacetal resins are widely used as automotive parts. For example, they are used as large parts such as fuel transfer units typified by fuel pump modules that come into direct contact with fuel oil.

[0003] In recent years, in order to comply with environmental regulations in various countries, the sulfur content of fuels has been reduced. However, since desulfurization equipment is very expensive, high-sulfur fuels are still circulated in some countries. These high-sulfur fuels tend to deteriorate polyacetal resins more easily than low-sulfur fuels.

[0004] By the way, injection molded articles such as fuel transfer units made of polyacetal resins are easily charged because they are resins, and there is a risk of fuel ignition due to sparks derived from static electricity. Therefore, it is necessary to suppress static electricity by imparting conductivity to the resin material.

[0005] As a polyacetal resin composition having high acid resistance, a polyacetal resin composition is proposed in which 100 parts by mass of (A) polyacetal resin, 0.1 to 1.0 parts by mass of (B) hindered phenol-based antioxidant, 0.1 to 2.0 parts by mass of (C) alkaline earth metal oxide, 0.5 to 3.0 parts by mass of (D) polyalkylene glycol, and 0.01 to 1.0 parts by mass of (E) polyvalent fatty acid ester having an esterification rate of 80% or more are blended (see Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0007] However, although the resin composition is a polyacetal resin composition having high acid resistance, it is not sufficient in terms of conductive properties.

[0008] An object of the present invention is to provide a polyacetal resin composition that can minimize deterioration when in contact with sulfur fuel when formed into a molded article and further has excellent conductive properties.

MEANS FOR SOLVING THE PROBLEMS

[0009] The object of the present invention has been achieved as follows.

[0010] 1. A polyacetal resin composition comprising: (A) 100 parts by mass of a polyacetal resin, (B) 0.1 to 1.5 parts by mass of an antioxidant, (C) 0.3 to 2.0 parts by mass of an oxide of magnesium or zinc, (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 polyhydric alcohol having an esterification rate of 80% or more, (F) 3.0 to 15 parts by mass of carbon black. 2. The polyacetal resin composition according to 1 above, wherein the (A) polyacetal resin is a copolymer having 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 polyacetal resin composition according to 1 or 2 above, wherein the oxide of (C) magnesium or zinc is magnesium oxide having a BET specific surface area of 100 m2 / g or more. 4. The polyacetal resin composition according to any one of 1 to 3 above, wherein the BET specific surface area of the (F) carbon black is 350 m2 / g or more. 5. The polyacetal resin composition according to any one of 1 to 4 above, wherein the fatty acid ester of the (E) polyhydric alcohol is an ester compound of a polyhydric alcohol having 3 or more carbon atoms and a fatty acid. 6. A fuel contact member comprising a molded article of the polyacetal resin composition according to any one of 1 to 5 above.

Advantages of the Invention

[0011] According to the present invention, it is possible to provide a polyacetal resin composition that can minimize deterioration when in contact with sulfur fuel when formed into a molded article and that has excellent electrical conductivity characteristics.

Brief Description of the Drawings

[0012]

Figure 1

Modes for Carrying Out the Invention

[0013] Hereinafter, specific embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments, and can be implemented with appropriate modifications within the scope of the object of the present invention.

[0014] <Polyacetal Resin Composition> The polyacetal resin composition of the present invention is characterized by being formulated with 100 parts by mass of (A) polyacetal resin, 0.1 to 1.5 parts by mass of (B) antioxidant, 0.3 to 2.0 parts by mass of an oxide of (C) magnesium or zinc, 0.5 to 3.0 parts by mass of (D) polyalkylene glycol, 0.01 to 1.0 parts by mass of a fatty acid ester of (E) polyhydric alcohol having an esterification rate of 80% or more, and 3.0 to 15 parts by mass of (F) carbon black.

[0015] Hereinafter, the (A) polyacetal resin is also referred to as the (A) component, the (B) antioxidant is also referred to as the (B) component, the oxide of (C) magnesium or zinc is also referred to as the (C) component, the (D) polyalkylene glycol is also referred to as the (D) component, the (E) fatty acid ester is also referred to as the (E) component, and the (F) carbon black is also referred to as the (F) component.

[0016] ≪(A) Polyacetal Resin≫ The (A) polyacetal resin used in the present invention refers to a polymer compound having an oxymethylene group (-CH2O-) as a main structural unit, and examples thereof include a polyacetal polymer substantially composed only of repeating units of an oxymethylene group, and a polyacetal copolymer containing a small amount of other structural units in addition to the oxymethylene group. Any of these can be used, but from the viewpoint of acid resistance which is an object of the present invention, it is preferable to use a polyacetal copolymer as the base resin.

[0017] When the (A) component 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, and particularly preferably a polyacetal copolymer obtained by copolymerizing 0.5 to 10% by mass of a comonomer component. The polyacetal copolymer obtained by copolymerizing a comonomer component is excellent in acid resistance and can maintain excellent thermal stability, mechanical strength, etc. Further, the polyacetal copolymer may have not only a linear structure but also a branched structure or a crosslinked structure.

[0018] In producing such a polyacetal copolymer, a cyclic oligomer of formaldehyde represented by trioxane is used as the main monomer. Further, as the comonomer component, a compound selected from cyclic ethers and / or cyclic formals having at least one carbon-carbon bond is used.

[0019] 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.

[0020] In the above (A) polyacetal resin, particularly the polyacetal copolymer, there are no particular restrictions on the degree of polymerization and the like, and it is possible to adjust the degree of polymerization and the like according to the purpose of use and molding means. However, from the viewpoint of achieving both acid resistance and moldability, the melt flow rate (MFR) measured at 190 °C and a load of 2160 g in accordance with ISO 1133 is preferably 1 to 100 g / 10 min, and particularly preferably 5 to 30 g / 10 min.

[0021] ≪(B) Antioxidant≫ Examples of the antioxidant (B) used in the present invention 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-hydroxybenzyl)-4-methylphenyl acrylate, 3,9-bis{2-[3-(3-t-butyl-4-hydroxy-5-methylphenyl)propionyloxy]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane and other hindered phenol antioxidants, N-phenyl-1-naphthylamine, bis(4-octylphenyl)amine, 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, p-(p-toluenesulfonylamide)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 other aromatic amine antioxidants. In the present invention, it is preferably a hindered phenol antioxidant or an aromatic amine antioxidant.

[0022] At least one or two or more selected from these antioxidants can be used.

[0023] In the present invention, the compounding amount of the antioxidant (B) is 0.1 to 1.5 parts by mass, more preferably 0.2 to 1.0 parts by mass, based on 100 parts by mass of the polyacetal resin (A). When the compounding amount of the antioxidant (B) is small, not only the antioxidant properties, which are the original purpose, become insufficient, but also the fuel resistance, which is the purpose of the present invention, deteriorates. When the compounding amount of the antioxidant (B) is excessive, unfavorable effects on the mechanical properties, moldability, etc. of the resin composition occur.

[0024] ≪(C) Oxide of magnesium or zinc≫ Examples of the oxide of magnesium or zinc (C) used in the present invention include magnesium oxide and zinc oxide. Among these, magnesium oxide is most preferable because it has an excellent balance between improvement of fuel resistance and performance such as mechanical properties and moldability.

[0025] As for magnesium oxide, the BET specific surface area is 20 to 200 m 2 / g, and preferably 100 m 2 / g or more. Here, the BET specific surface area is determined by the nitrogen gas adsorption method (JIS Z 8830:2013). Magnesium oxide may be surface-treated.

[0026] In the present invention, the compounding amount of the oxide of magnesium or zinc (C) is 0.3 to 2.0 parts by mass, more preferably 1.0 to 2.0 parts by mass, based on 100 parts by mass of the polyacetal resin (A). When the compounding amount of the oxide of magnesium or zinc (C) is small, the fuel resistance, which is the purpose of the present invention, deteriorates. When the compounding amount of the oxide of magnesium or zinc (C) is excessive, the decomposition of unstable ends in the polyacetal resin is promoted, and unfavorable effects on mechanical properties, moldability, etc. occur.

[0027] ≪(D) Polyalkylene glycol≫ The type of (D) polyalkylene glycol used in the present invention is not particularly limited, but from the viewpoint of affinity with the polyacetal resin, those containing polyethylene glycol and / or polypropylene glycol are preferred, and those containing polyethylene glycol are more preferred.

[0028] The number average molecular weight (Mn) of the polyalkylene glycol is not particularly limited, but from the viewpoint of dispersibility in the polyacetal resin, it is preferably 1,000 or more and 50,000 or less, and more preferably 5,000 or more and 30,000 or less. In this specification, the number average molecular weight is the molecular weight in terms of polystyrene determined by gel permeation chromatography (GPC) using tetrahydrofuran (THF) as a solvent.

[0029] The blending amount of (D) polyalkylene glycol in the present invention is 0.5 to 3.0 parts by mass, more preferably 1.0 to 2.0 parts by mass, based on 100 parts by mass of the (A) polyacetal resin. If the blending amount of (D) polyalkylene glycol is small, sufficient stress relaxation may not be achieved. If the blending amount of (D) polyalkylene glycol is excessive, the mechanical properties of the molded product may deteriorate.

[0030] ≪(E) Fatty acid ester of polyhydric alcohol with an esterification rate of 80% or more≫ The fatty acid ester of polyhydric alcohol with an esterification rate of 80% or more used in the present invention is preferably a polyvalent fatty acid ester which is an ester compound of a polyhydric alcohol having 3 or more carbon atoms and a fatty acid. In this specification, the esterification rate does not necessarily have to be 100%, and 80% or more is sufficient, preferably 85% or more, and more preferably 90% or more.

[0031] The polyhydric alcohol may be aliphatic or aromatic, but is preferably aliphatic in terms of affinity with the polyacetal resin.

[0032] The valence of the polyhydric alcohol is not particularly limited, but is preferably 3 or more and 4 or less. Also, the number of carbon atoms of the polyhydric alcohol is not particularly limited, but in terms of affinity with the polyacetal resin, it is preferably 3 or more and 10 or less, and more preferably 3 or more and 5 or less.

[0033] Preferred polyhydric alcohols for forming the ester of component (E) include, for example, glycerin, trimethylolpropane, pentaerythritol, mesoerythritol, pentose, hexitol, sorbitol, etc. However, in terms of keeping the weight loss of the polyacetal resin composition low after immersion in sulfur fuel, the polyhydric alcohol is preferably pentaerythritol.

[0034] The type of fatty acid is not particularly limited, but in terms of affinity with the polyacetal resin, it is preferably a fatty acid having 10 to 30 carbon atoms, and more preferably an aliphatic carboxylic acid having 10 to 20 carbon atoms.

[0035] Preferred fatty acids for forming the ester of component (E) include, for example, stearic acid, palmitic acid, lauric acid, etc., and preferably stearic acid.

[0036] As the ester of component (E), glycerin tristearate and pentaerythritol tetrastearate are preferably used, and pentaerythritol tetrastearate is more preferably used. Note that component (E) may be a combination of two or more esterified products having different polyhydric alcohols and fatty acids constituting it, or esterified products having different esterification rates.

[0037] In the present invention, the blending amount of the fatty acid ester of the polyhydric alcohol having an esterification rate of 80% or more of component (E) is 0.01 to 1.0 parts by mass, and more preferably 0.05 to 1.0 parts by mass with respect to 100 parts by mass of component (A) polyacetal resin.

[0038] ≪(F) Carbon black≫ The (F) carbon black of the present invention is not particularly limited as long as it is generally available for resin coloring, but the BET specific surface area is preferably 100 to 1500 m 2 / g, and more preferably 150 to 1300 m 2 / g. Here, the BET specific surface area is determined by the nitrogen gas adsorption method (JIS K6217-2:2017).

[0039] Examples of commercially available products include the Ketjenblack series manufactured by Lion Corporation, Denka Black by Denka Co., Ltd., and the like. Examples of the Ketjenblack series include Ketjenblack EC600JD, Ketjenblack EC300J, Carbon ECP, and Carbon ECP600JD. Particularly preferred is Ketjenblack produced by the gasification method.

[0040] The DBP oil absorption amount is preferably 50 to 550 cm 3 / 100 g, and more preferably 100 to 500 cm 3 / 100 g. The DBP oil absorption amount is measured according to JIS K6221. The surface of the carbon black may be chemically treated.

[0041] The blending amount of the (F) carbon black in the present invention is 3.0 to 15 parts by mass, and more preferably 5.0 to 13 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. Since insufficient conductivity results from too little carbon black and a decrease in tensile elongation results from too much, this range is preferred.

[0042] <Fuel contact body> The fuel contact body of the present invention includes a molded article of the above polyacetal resin composition. This molded article can be obtained by molding the above polyacetal resin composition using a conventional molding method, for example, injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, or the like.

[0043] ≪Conductivity≫ The volume resistivity of the polyacetal resin composition of the present invention is 1×10 10 Ω·cm or less, preferably less than 1×10 4 Ω·cm. Therefore, the resistance resistivity of the fuel contact body is also low and it has good electrical conductivity characteristics.

[0044] The fuel contact body of the present invention may be in contact with not only low-sulfur fuel but also high-sulfur fuel. Even when in contact with high-sulfur fuel, the occurrence of cracks can be suppressed and a good molded product surface appearance can be maintained, so that fuel leakage can be suppressed.

[0045] In this specification, "low-sulfur fuel" refers to fuel with a sulfur concentration of 50 ppm or less, and examples include JIS No. 2 light oil in Japan, EN590 light oil in Europe, etc. On the other hand, "high-sulfur fuel" refers to fuel with a sulfur concentration exceeding 50 ppm, and examples include high-sulfur diesel fuel distributed in China, India, etc.

Examples

[0046] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited thereto. It is not.

[0047] The various components in Tables 1 and 2 below, which are the present examples, are as follows. (A) Polyacetal resin A polyacetal copolymer obtained by copolymerizing 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane. MFR (measured at 190 °C and a load of 2160 g in accordance with ISO1133): 9 g / 10 min) (B) Antioxidant (B1) Tetrakis[methylene 3(3,5-di-t-butyl-4-hydroxyphenyl)propionate]methane (product name: Irganox1010, manufactured by BASF) (B2) 4,4'-Bis(α,α-dimethylbenzyl)diphenylamine (product name: No Crack CD, manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.)

[0048] (C) Magnesium or zinc oxides (C1) Magnesium oxide (BET specific surface area 30 m2 / g) (Product name: MF-30, manufactured by Kyowa Mag Co., Ltd.) (C2) Magnesium oxide (BET specific surface area 135 m2 / g) (Product name: MF-150, manufactured by Kyowa Mag Co., Ltd.) (C3) Zinc oxide (BET specific surface area 60 - 90 m2 / g) (Product name: Activated zinc white AZO, manufactured by Shodo Chemical Industry Co., Ltd.) (D) Polyalkylene glycol Product name: PEG6000S (manufactured by Sanyo Chemical Industries, Ltd.)

[0049] (E) Fatty acid esters of polyhydric alcohols with an esterification rate of 80% or more (E1) Fatty acid ester 1 Pentaerythritol tetrastearate (Product name: Unister H476, manufactured by NOF Corporation) (E2) Fatty acid ester 2 Glycerin tristearate (Product name: Poem S-95, manufactured by Riken Vitamin Co., Ltd.) (E’) Fatty acid esters of polyhydric alcohols with an esterification rate of less than 80% (E‘3) Fatty acid ester 3 Glycerin monostearate (Product name: Rikemal S-100A, manufactured by Riken Vitamin Co., Ltd.)

[0050] (F) Carbon black (F1) Ketjen black EC300J (BET specific surface area 800 m 2 / g, DBP oil absorption 360 ml / 100 g, manufactured by Lion Corporation) (F2) Lionite EC200L (BET specific surface area 377 m 2 / g, DBP oil absorption 300 ml / 100 g, manufactured by Lion Corporation) (F3) Denka black (BET specific surface area 65 m 2 / g, manufactured by Denka Co., Ltd.)

[0051] <Evaluation> Using the above materials, the following evaluations were conducted. Unless otherwise specified, the evaluations were carried out in an atmosphere of 23°C and 50% RH.

[0052] ≪Tensile elongation≫ Various components shown in Tables 1 and 2 were added and mixed at the ratios shown in Tables 1 and 2, and melt-kneaded with a twin-screw extruder to prepare a pelletized polyacetal resin composition. Next, using this pellet, an ISO type 1-A test piece with a thickness of 4 mm was molded by injection molding, and the measurement of the tensile fracture nominal strain was carried out in accordance with ISO 527-1 and 2, and the judgment was made from × to ○ as follows. ×: Less than 5% △: 5% or more and less than 8% 〇: 8% or more

[0053] ≪Fuel resistance≫ In the same manner as above, an ASTM No. 4 dumbbell test piece with a thickness of 1 mm was prepared. To evaluate the fuel resistance of the polyacetal resin composition, the above dumbbell test piece was immersed in diesel fuel (product name: CEC RF 90-A-92, manufactured by Hartmann) at 100 °C for 14 days, and the mass change rate due to fuel immersion was calculated from the mass of the test piece before and after that, and the judgment was made from × to ○ as follows. ×: Less than 10% △: 10% or more and less than 20% 〇: 20% or more

[0054] ≪Conductivity≫ In the same manner as above, an ISO type 1-A test piece with a thickness of 4 mm was prepared, and the volume resistivity was measured according to the following procedure.

[0055] [Measurement procedure] As shown in Fig. 1, a conductive paint (Dotite D500, manufactured by Fujikura Kasei Co., Ltd.) was applied to the front and back surfaces of the gripping part on the non-gate side of the test piece and dried. Then, using a low resistivity measuring device (DIGITAL MULTIMETER R6450, manufactured by Advantest Corporation), the resistance between the front and back surfaces of the gripping part was measured to obtain the volume resistivity. The value of the volume resistivity was judged from × to ○ as follows. ×: 1 × 10 10 Ω·cm or more △: 1 × 10 4 Ω·cm or more and less than 1 × 10 10 Ω·cm 〇: 1×10 4 less than Ω·cm

[0056]

Table 1

[0057]

Table 2

[0058] From the results of Tables 1 and 2, it is clear that the polyacetal resin composition of the present invention is a polyacetal resin composition that can minimize deterioration when contacted with sulfur fuel and has excellent conductivity.

Claims

1. (A) 100 parts by mass of a polyacetal resin, (B) 0.3 to 1.5 parts by mass of an antioxidant, (C) 0.3 to 2.0 parts by mass of magnesium 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 polyhydric alcohol having an esterification rate of 80% or more, (F) 3.0 to 15 parts by mass of carbon black, being blended, wherein the magnesium oxide of (C) is magnesium oxide having a BET specific surface area of 20 to 30 m ２ / g, a polyacetal resin composition.

2. The polyacetal resin composition according to claim 1, wherein the polyacetal resin of (A) is a copolymer having 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 polyacetal resin composition according to claim 1 or 2, wherein the BET specific surface area of the carbon black of (F) is 350 m ２ / g or more.

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

5. A fuel contact member comprising a molded article of the polyacetal resin composition according to any one of claims 1 to 4.

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