WO2022201669A1

WO2022201669A1 - Polyacetal resin composition, and sulfur-containing fuel contact body including molded article of said polyacetal resin composition

Info

Publication number: WO2022201669A1
Application number: PCT/JP2021/046191
Authority: WO
Inventors: 悠平細井; 章宏玉岡; 智宏門間
Original assignee: ポリプラスチックス株式会社
Priority date: 2021-03-26
Filing date: 2021-12-15
Publication date: 2022-09-29
Also published as: JP2022150444A; CN117083344A

Abstract

The purpose of the present invention is to provide a polyacetal resin composition that, when made into a molded article, makes it possible to inhibit deterioration due to exposure to sunlight at a portion that contacts a high sulfur fuel.　This purpose of the present invention is achieved by a polyacetal resin composition comprising, at least: (A) 100 parts by mass of a polyacetal polymer; (B) 0.1-1.0 parts by mass of a hindered-phenol-based antioxidant; (C) 0.3-2.0 parts by mass of at least one substance selected from oxides of zinc and magnesium; (D) 0.5-3.0 parts by mass of polyalkylene glycol; (E) 0.1-1.5 parts by mass of a hindered amine compound; (F) 0.2-1.5 parts by mass of an ultraviolet absorbing agent; and (G) 0.01-1.0 mass of a fatty acid ester of a polyalcohol in which the esterification rate is not less than 80%.

Description

Polyacetal resin composition and sulfur fuel contactor comprising molded article of polyacetal resin composition

The present invention relates to a polyacetal resin composition and a sulfur fuel contactor comprising a molded article of this polyacetal resin composition.

Due to the excellent chemical resistance of polyacetal resin, molded products made from polyacetal resin are widely used as automotive 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, efforts have been made to reduce the sulfur content of fuel in order to comply with the environmental regulations of each country. 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 polyacetal resins more easily than low sulfur fuels.

By the way, an injection-molded product manufactured from polyacetal 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 fuels are distributed, it is necessary to use resin materials having high resistance to high-sulfur fuels (hereinafter abbreviated as fuel resistance) as raw materials.

The applicant of the present application reports that this problem can be greatly improved by adding a hindered phenolic antioxidant, an alkaline earth metal oxide, a polyalkylene glycol and a polyvalent fatty acid ester to the polyacetal resin. (Patent Document 1).

JP 2015-209474 A

On the other hand, automobile parts such as fuel transfer units that come into contact with high-sulfur fuel are often covered with a housing such as a bonnet, but when in use, there is contact with high-sulfur fuel from the inside and sunlight from the outside. It may hit. In addition, depending on the type of vehicle, there are some vehicles in which the fuel tank is not covered with a housing and the fuel transfer unit is used in a state where it is exposed to sunlight. A major problem is that the occurrence of cracks in automobile parts made of polyacetal resin, which has undergone photodegradation due to sunlight, is accelerated.

An object of the present invention is to provide a polyacetal resin composition that, when formed into a molded product, can suppress deterioration of parts that come into contact with high-sulfur fuel when exposed to sunlight.

As a result of extensive research to solve the above problems, the present inventors found that the above problems can be solved by making the composition of the polyacetal resin composition a specific composition.

The present invention is as follows.
1. at least,
(A) for 100 parts by mass of polyacetal polymer,
(B) 0.1 to 1.0 parts by mass of a hindered phenol antioxidant;
(C) 0.3 parts by mass to 2.0 parts by mass of at least one selected from oxides of magnesium and zinc;
(D) 0.5 to 3.0 parts by mass of polyalkylene glycol,
(E) 0.1 to 1.5 parts by mass of a hindered amine compound,
(F) 0.2 to 1.5 parts by mass of an ultraviolet absorber,
(G) 0.01 to 1.0 mass of a fatty acid ester of a polyhydric alcohol having an esterification rate of 80% or more;
A polyacetal resin composition containing
2. 2. The polyacetal resin composition according to 1 above, wherein (A) is a polyacetal copolymer obtained by copolymerizing a cyclic oligomer of formaldehyde with a cyclic ether or a cyclic formal.
3. 3. The polyacetal resin composition according to 1 or 2 above, wherein (C) is magnesium oxide having a BET specific surface area of 100 cm ² /g or more.
4. 4. The polyacetal resin composition according to any one of 1 to 3 above, wherein the (G) 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.
5. 5. The polyacetal resin composition according to any one of 1 to 4 above, wherein (F) the ultraviolet absorber is at least one selected from benzotriazole compounds and oxalic acid diamide compounds.
6. (F) the UV absorber is 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol and N-(2-ethylphenyl)-N' 6. The polyacetal resin composition according to any one of 1 to 5 above, which is at least one selected from -(2-ethoxyphenyl)oxalic acid diamide.
7. A fuel contactor comprising a molded article of the polyacetal resin composition according to any one of 1 to 6 above.

According to the present invention, it is possible to provide a polyacetal resin composition that, when formed into a molded product, can suppress deterioration of parts that come into contact with high-sulfur fuel when exposed to sunlight.

Hereinafter, specific embodiments of the present invention will be described in detail, but the present invention is not limited to the following embodiments at all, and can be implemented with appropriate modifications within the scope of the purpose of the present invention. can do.

<Polyacetal resin composition>
The polyacetal resin composition of the present invention is
(A) per 100 parts by mass of the polyacetal polymer, (B) 0.1 to 1.0 parts by mass of a hindered phenolic antioxidant,
(C) 0.3 parts by mass to 2.0 parts by mass of at least one selected from oxides of magnesium or zinc;
(D) 0.5 to 3.0 parts by mass of polyalkylene glycol,
(E) 0.1 to 1.5 parts by mass of a hindered amine compound,
(F) 0.2 to 1.5 parts by mass of an ultraviolet absorber,
(G) 0.01 to 1.0 mass of a fatty acid ester of a polyhydric alcohol having an esterification rate of 80% or more;
It is characterized by containing and.

<(A) Polyacetal polymer>
The (A) polyacetal polymer used in the present invention may be a homopolymer having an oxymethylene group (—OCH ₂ —) as a constituent unit, or may be a copolymer having other comonomer units in addition to the oxymethylene unit. , is preferably a copolymer.

In general, it is produced by copolymerizing formaldehyde or a cyclic compound of formaldehyde as a main monomer and a compound selected from cyclic ethers and cyclic formals as a comonomer. It is stabilized by removing unstable parts.

In particular, it is common to use trioxane, which is a cyclic trimer of formaldehyde, as the main monomer. Trioxane is generally obtained by reacting an aqueous formaldehyde solution in the presence of an acidic catalyst, and is used after being purified by a method such as distillation. The trioxane used for polymerization preferably contains as little impurities as possible such as water, methanol and formic acid.

As comonomers, general cyclic ethers and cyclic formals, as well as glycidyl ether compounds capable of forming branched or crosslinked structures can be used alone or in combination of two or more.

The above polyacetal polymer can generally be obtained by adding an appropriate amount of molecular weight modifier and cationic polymerization using a cationic polymerization catalyst. Molecular weight modifiers to be used, cationic polymerization catalysts, polymerization methods, polymerization equipment, catalyst deactivation treatment after polymerization, terminal stabilization treatment methods for crude polyacetal polymers obtained by polymerization, etc. are known from many documents. Yes, you can basically use any of them.

As a polymerization apparatus, a reaction tank with a stirrer that is generally used in a batch system can be used, and as a continuous system, a co-kneader, a twin-screw continuous extrusion mixer, a twin-screw paddle type continuous mixer, etc. A continuous polymerization apparatus such as trioxane that has been proposed so far can be used, and a combination of two or more types of polymerization apparatuses can also be used.

In the present invention, in preparing a polyacetal copolymer by polymerizing the above main monomer and comonomer, chain transfer agents known as molecular weight modifiers for controlling the degree of polymerization, such as low molecular weight linear acetals such as methylal, etc. can also be added.

In addition, the polymerization reaction is desirably carried out in a state in which impurities having active hydrogen, such as water, methanol, formic acid, etc., are substantially absent, for example, in a state in which each of these is 10 ppm or less. It is desirable to use trioxane, cyclic ethers and/or cyclic formals prepared to contain as little as possible as main monomers and comonomers.

The molecular weight of the (A) polyacetal polymer used in the present invention is not particularly limited, but the weight average molecular weight corresponding to PMMA (polymethyl methacrylate) determined by size exclusion chromatography is 10,000 to 400,000. A degree is preferable. Further, the melt index (measured at 190° C. and a load of 2.16 kg according to ASTM-D1238), which is an index of resin fluidity, is preferably 0.1 to 100 g/10 minutes, more preferably 0.5 to 100 g/10 minutes. 80 g/10 minutes.

The (A) polyacetal polymer used in the present invention particularly preferably has specific terminal properties. Specifically, the amount of hemiformal terminal groups is 1.0 mmol/kg or less, the amount of formyl terminal groups is 0.5 mmol/kg or less, and the amount of unstable terminals is 0.5% by mass or less.

Here, the hemiformal terminal group is represented by —OCH ₂ OH, and is also called a hydroxymethoxy group or a hemiacetal terminal group. A formyl end group is also indicated by -OCHO. The amounts of such hemiformal terminal groups and formyl terminal groups can be determined by ¹ H-NMR measurement, and the specific measuring method can be referred to the method described in JP-A-2001-11143.

In addition, the amount of unstable terminal indicates the amount of the portion existing at the terminal portion of the polyacetal polymer, unstable to heat and base, and easily decomposed. Such an unstable terminal amount was obtained by placing 1 g of polyacetal polymer together with 100 ml of a 50% (% by volume) methanol aqueous solution containing 0.5% (% by volume) of ammonium hydroxide in a sealed pressure-resistant vessel and heat-treating at 180° C. for 45 minutes. After cooling, the amount of formaldehyde decomposed and eluted in the solution obtained by opening the package was quantified and expressed in mass % with respect to the polyacetal polymer.

The (A) polyacetal polymer used in the present invention preferably has a hemiformal terminal group content of 1.0 mmol/kg or less, more preferably 0.6 mmol/kg or less. The amount of formyl terminal groups is preferably 0.5 mmol/kg or less, more preferably 0.1 mmol/kg or less. The amount of unstable ends is preferably 0.5% by mass or less, more preferably 0.3% by mass or less. The lower limits of the amount of hemi-formal terminal groups, the amount of formyl terminal groups, and the amount of unstable terminals are not particularly limited.

The (A) polyacetal polymer having specific terminal properties as described above can be produced by reducing impurities contained in the main monomer and comonomer, selecting the production process and optimizing the production conditions.

As for the method for producing the (A) polyacetal polymer having specific terminal properties that satisfy the requirements of the present invention, for example, the method described in JP-A-2009-286874 can be used. However, it is not limited to this method.

In the present invention, a polyacetal polymer having a branched or crosslinked structure may be added to the polyacetal polymer (A), and in that case, the blending amount is 0.01 per 100 parts by mass of the polyacetal polymer (A). 20 parts by mass, particularly preferably 0.03 to 5 parts by mass.

<(B) Hindered Phenolic Antioxidant>
The (B) hindered phenol antioxidant used in the present invention includes 2,2′-methylenebis(4-methyl-6-t-butylphenol), 1,6-hexanediolbis[3-(3,5 -di-t-butyl-4-hydroxyphenyl)propionate], pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate], bis[3-t-butyl-4- Hydroxy-5-methylbenzenepropionic acid]ethylenebis(oxyethylene), 1,3,5-trimethyl-2,4,6-tris(3′,5′-di-t-butyl-4′-hydroxybenzyl) Benzene, n-octadecyl-3-(3,5-di-t-butyl-4-hydroxyphenyl)propionate, 4,4'-methylenebis(2,6-di-t-butylphenol), 4,4'-butylidene -bis(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 the like are exemplified.

In the present invention, at least one or two or more selected from these antioxidants can be used.

The content of (B) the hindered phenolic antioxidant in the present invention is 0.1 to 1.0 parts by mass, and 0.2 to 0.5 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. is more preferable.

<(C) At least one selected from oxides of magnesium or zinc>
Examples of (C) at least one selected from oxides of magnesium and zinc (hereinafter abbreviated as (C) compound) used in the present invention include magnesium oxide and zinc oxide. Among these compounds, magnesium oxide is most preferable because it has the best balance between improvement in fuel properties and performance such as mechanical properties and moldability. Regarding magnesium oxide, magnesium oxide having a BET specific surface area of 100 m ² /g or more is more preferable.

The content of the (C) compound in the present invention is 0.3 to 2.0 parts by mass, more preferably 0.5 to 2.0 parts by mass, relative to 100 parts by mass of the (A) polyacetal resin. .

When the amount exceeds 0.3 parts by mass, the fuel resistance is particularly excellent. When the amount is within 2.0 parts by mass, stable production is possible, and when the amount is within 2.0 parts by mass, the balance of mechanical properties is particularly excellent.

In the past, when the amount of the compound (C) increased, the decomposition of the unstable terminal in the polyacetal resin was sometimes promoted. , and (C) were found to improve fuel resistance and weather resistance by adjusting the amount of compound (C) to a predetermined amount. In addition, the (C) compound and the (E) and (F) compounds do not negatively interfere with each other, and have a synergistic effect in suppressing deterioration when sunlight is irradiated to the part in contact with the high sulfur fuel. showed that.

<(D) Polyalkylene glycol>
It is also preferable to contain the (D) polyalkylene glycol used in the present invention. These types are not particularly limited, but from the viewpoint of affinity with the polyacetal resin, those containing polyethylene glycol or polypropylene glycol are preferred, and those containing polyethylene glycol are more preferred.

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 5,000 or more and 30,000 or less. It is more preferable to have In this specification, the number-average molecular weight is the polystyrene-equivalent molecular weight obtained by size exclusion chromatography using tetrahydrofuran (THF) as a solvent.

The content of (D) polyalkylene glycol in the present invention is 0.5 to 3.0 parts by mass, preferably 1.0 to 2.0 parts by mass, with respect to 100 parts by mass of (A) polyacetal resin. more preferred. The upper limit of the amount to be added is selected in balance with the mechanical properties of the molded article. These may be used in combination of two or more.

<(E) Hindered Amine Compound>
The hindered amine compound (hereinafter also referred to as HALS) used in the present invention is not particularly limited, and a hindered amine compound in which the nitrogen of a piperidine derivative having a sterically hindering group such as a methyl group on the adjacent carbon is secondary or tertiary is preferably used. be done.

Hindered amine stabilizers in which the nitrogen of the piperidine derivative having a sterically hindered group is secondary for use in the present invention include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, 1,2,3 ,4-butanetetracarboxylic acid, 2,2,6,6-tetramethyl-4-piperidinol and β,β,β',β'-tetramethyl-3,9-(2,4,8,10-tetra oxaspiro[5.5]undecane)-diethanol condensate, tetrakis(2,2,6,6-tetramethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate, 1,2, A condensate of 3,4-butanetetracarboxylic acid, 2,2,6,6-tetramethyl-4-piperidinol and tridecyl alcohol is included.

Examples of the hindered amine compounds in which the nitrogen of the piperidine derivative having a sterically hindering group is tertiary and which are used in the present invention include bis(1,2,2,6,6-pentamethyl-4-piperidyl)adipate, bis(1 - Aliphatic di- or tricarboxylic acid such as octyloxy-2,2,6,6-tetramethyl-4-piperidyl sebacate - bis or trispiperidyl ester (aliphatic dicarboxylic acid having 2 to 20 carbon atoms - bispiperidyl ester, etc.) ), N,N′,N″,N′″-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino )-triazin-2-yl)-4,7-diazadecane-1,10-diamine, a polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, decane di acid bis(2,2,6,6-tetramethyl-1-(octyloxy)-4-piperidinyl) ester, bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5 -bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate, methyl-1,2,2, 6,6-pentamethyl-4-piperidyl sebacate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidinyl) 1,2,3,4-butane tetracarboxylate, 1,2,3 Condensation product of ,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and tridecyl alcohol, 1,2,3,4-butanetetracarboxylic acid and 1,2,2 ,6,6-pentamethyl-4-piperidinol and β,β,β',β'-tetramethyl-3,9-(2,4,8,10-tetraoxaspiro[5.5]undecane)-diethanol condensate of, peroxide-treated 4-butylamino-2,2,6,6-tetramethylpiperidine and 2,4,6-trichloro-1,3,5-triazine, and cyclohexane, N,N'-ethane -reaction product with 1,2-diylbis(1,3-propanediamine), 1-[2-{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy}ethyl]- 4-{3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy}-2,2,6,6-tetramethylpiperidine and the like.

Particularly preferred are bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidinyl) 1,2,3,4 -butanetetracarboxylate, 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and β,β,β',β'-tetramethyl-3, 9-(2,4,8,10-tetraoxaspiro[5.5]undecane)-diethanol condensate, dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidine A polymer of ethanol can be mentioned.

In the present invention, the addition amount of (E) the hindered amine compound is 0.1 to 1.5 parts by mass, preferably 0.2 to 0.8 parts by mass, per 100 parts by mass of the (A) polyacetal polymer. is.

If the amount of the hindered amine compound (E) is too small, a polyacetal resin composition with excellent weather resistance cannot be obtained. Problems such as defects occur.

<(F) UV absorber>
Examples of the ultraviolet absorber of the present invention include benzotriazole-based compounds and oxalic acid anilide-based compounds, and these light stabilizers can be used singly or in combination of two or more.

Benzotriazole compounds include 2-(2H-benzotriazol-2-yl)-p-cresol, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1- phenylethyl)phenol, 2-[5-chloro(2H)-benzotriazol-2-yl)-4-methyl-6-(t-butyl)phenol, 2,4-di-t-butyl-6-(5 -chlorobenzotriazol-2-yl)phenol, 2-(2H-benzotriazol-2-yl)-4,6-di-t-pentylphenol, 2-(2H-benzotriazol-2-yl)-4- (1,1,3,3-tetramethylbutyl) phenol, 2-(2'-hydroxy-3',5'-di-isoamylphenyl) hydroxy groups such as benzotriazole and alkyl (alkyl having 1 to 6 carbon atoms) ) group-substituted benzotriazoles 2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]benzotriazole and other hydroxyl group- and aralkyl (or aryl) group-substituted aryl Benzotriazoles having a group and benzotriazoles having a hydroxyl group and an alkoxy (C1-12 alkoxy) group-substituted aryl group such as 2-(2'-hydroxy-4'-octoxyphenyl)benzotriazole.

Among these benzotriazole compounds, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2H-benzotriazol-2-yl )-4,6-di-t-pentylphenol, 2-(2H-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol and the like are preferred.

Examples of oxalic acid anilide compounds include N-(2-ethylphenyl)-N'-(2-ethoxy-5-t-butylphenyl)oxalic acid diamide, N-(2-ethylphenyl)-N'-(2 -ethoxyphenyl)oxalic acid diamide, and oxalic acid diamides having an optionally substituted aryl group on the nitrogen atom.

In the present invention, the amount of (F) ultraviolet absorber added is 0.2 to 1.5 parts by mass with respect to 100 parts by mass of (A) polyacetal polymer. Preferably, it is 0.4 to 0.8 parts by mass. If the amount of the UV absorber (F) is too small, a polyacetal resin composition with excellent weather resistance cannot be obtained. Problems such as poor appearance due to

<(G) Fatty Acid Ester of Polyhydric Alcohol with Esterification Rate of 80% or More>
The (G) fatty acid ester of a polyhydric alcohol having an esterification rate of 80% or more used in the present invention is a polyhydric fatty acid ester of an ester compound of a polyhydric alcohol having 3 or more carbon atoms and a fatty acid. preferable.

The esterification rate of the ester compound is 80% or more, preferably 85% or more, more preferably 90% or more. Here, the esterification rate refers to the ratio of hydroxyl groups that have reacted with fatty acids to form ester bonds among the hydroxyl groups of the polyhydric alcohol that form esters.

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

Although the valence of the polyhydric alcohol is not particularly limited, it is preferably 3 or more and 4 or less. Although the number of carbon atoms in the polyhydric alcohol is not particularly limited, it is preferably 3 or more and 10 or less, more preferably 3 or more and 5 or less, from the viewpoint of affinity with the polyacetal resin.

Preferred polyhydric alcohols for forming the ester of component (G) 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.

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

Examples of preferred fatty acids for forming the ester of component (G) include stearic acid, palmitic acid, and lauric acid, with stearic acid being preferred.

As the ester of component (G), glycerin tristearate and pentaerythritol tetrastearate are preferably used, and pentaerythritol tetrastearate is more preferably used. For the component (G), two or more esterified products having different polyhydric alcohols or fatty acids, or two or more esterified products having different esterification rates may be used in combination.

The content of (G) polyvalent fatty acid full ester in the present invention 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) polyacetal resin. is more preferable.

<Other ingredients>
The polyacetal resin composition in the present invention may contain other components as necessary. One or two or more known stabilizers for the polyacetal resin composition may be added as long as the objects and effects of the present invention are not impaired.

<Fuel contactor>
A fuel contact body of the present invention includes a molded article of the polyacetal resin composition. The molded article is obtained by molding the polyacetal 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 invention is not limited to low-sulfur fuel, and may be in contact with high-sulfur fuel. Even if high-sulfur fuel is brought into contact with the molded product, the occurrence of cracks can be suppressed and a good surface appearance of the molded product can be maintained, so fuel leakage can be suppressed. In this specification, the term "low sulfur fuel" refers to a fuel with a sulfur concentration of 50 ppm or less, and includes, for example, Japanese JIS No. 2 light oil and European EN590 light oil. On the other hand, "high sulfur fuel" refers to fuel with a sulfur concentration exceeding 50 ppm, and includes high sulfur diesel fuel distributed in China, India and the like.

The present invention will be specifically described below with reference to examples, but the present invention is not limited to these.

The various components in Tables 1-3 are as follows. Units in the table are parts by mass.
(A) Polyacetal polymer (A-1) Polyacetal copolymer [hemiformal terminal group amount = 1.0 mmol/kg, melt index (measured at 190°C according to ASTM-D1238 and a load of 2.16 kg) = 9 g/10 minutes]
Polyacetal polymer A-1 was prepared as follows.

A-1: A mixture of 96.7% by mass of trioxane and 3.3% by mass of 1,3-dioxolane was continuously supplied to a twin-screw paddle type continuous polymerization machine, and 15 ppm of boron trifluoride was added as a catalyst. Polymerization was carried out. The mixture of trioxane and 1,3-dioxolane used for polymerization contained 10 ppm of water, 3.5 ppm of methanol and 5 ppm of formic acid as impurities.

An aqueous solution containing 1000 ppm of triethylamine is immediately added to the polymer discharged from the outlet of the polymerizer, and the catalyst is deactivated by pulverization and stirring, followed by centrifugation and drying to obtain a crude polyacetal copolymer. rice field.

Next, this crude polyacetal copolymer is supplied to a twin-screw extruder having a vent port, and melt-kneaded at a resin temperature of about 220 ° C. to decompose unstable terminal portions and remove volatiles containing decomposition products from the vent port. was devolatilized under reduced pressure. The polymer taken out from the die of the extruder was cooled and chopped to obtain pellet-like polyacetal copolymer A-1 from which unstable terminal ends were removed.

(B) Hindered phenol antioxidant (B-1) pentaerythritol tetrakis [3-(3,5-di-t-butyl-4-hydroxyphenyl) propionate] (product name: Irganox1010: manufactured by BASF)

(C) Magnesium or zinc oxide (C-1) Magnesium oxide, BET specific surface area 135 m ² /g, average particle size 0.9 μm (product name: Kyowamag MF150, manufactured by Kyowa Chemical Industry Co., Ltd.)
(C-2) Magnesium oxide, BET specific surface area 145 m ² /g, average particle size 0.6 μm (product name: Starmag PSF-150, manufactured by Kamijima Chemical Industry Co., Ltd.)
(C-3) Magnesium oxide, BET specific surface area 30 m ² /g, average particle size 0.6 μm (product name: Kyowamag MF30, manufactured by Kyowa Chemical Industry Co., Ltd.)
(C-4) Zinc oxide, BET specific surface area 60 to 90 m ² /g (product name: activated zinc oxide AZO, manufactured by Seido Chemical Industry Co., Ltd.)

(D) Polyalkylene glycol (D-1) Product name: PEG6000S (manufactured by Sanyo Chemical Industries Co., Ltd.)

(E) hindered amine compound (E-1) bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate (TINUVIN770DF: manufactured by BASF)
(E-2) 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol, and β,β,β',β'-tetramethyl-3,9 Condensate with -(2,4,8,10-tetraoxaspiro[5.5]undecane) diethanol (ADEKA STAB LA-63P: manufactured by ADEKA Co., Ltd.)
(E-3) Tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl) 1,2,3,4-butane tetracarboxylate (ADEKA STAB LA-52: manufactured by ADEKA Corporation)
(E-4) Condensation product of 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and tridecyl alcohol (ADEKA STAB LA-62: Co., Ltd.) manufactured by ADEKA)

(F) UV absorber (F-1) 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (TINUVIN234: manufactured by BASF)
(F-2) N-(2-ethylphenyl)-N'-(2-ethoxy-phenyl)oxalic acid diamide (SanduvorVSU: manufactured by Clariant Co., Ltd.)

(G) Fatty acid ester of polyhydric alcohol (G-1) Pentaerythritol stearate (Unistar H476, manufactured by NOF Corporation)
(G-2) Glycerin tristearate (Poem S-95, manufactured by Riken Vitamin)
(G-3) Glycerin monostearate (Rikemar S-100A, manufactured by Riken Vitamin Co., Ltd.)
(G-4) stearin stearate (Unistar M9676, manufactured by NOF Corporation)

<Examples and Comparative Examples>
Various components shown in Tables 1 and 2 were added and mixed in the proportions shown in Tables 1 and 2, and melt-kneaded with a twin-screw extruder to prepare a pellet-like polyacetal resin composition. Numerical values in the table are parts by mass. Measurements and evaluations were performed in an atmosphere of 23° C. and 50% RH unless otherwise specified. The results are shown in Tables 1-3.

<Evaluation>
Using the polyacetal resin composition prepared as described above, an ISO type 1-A multi-purpose test specimen with a thickness of 4 mm was produced by injection molding under the following conditions, and the following evaluations were performed.
・Molding machine: EC-40 (Toshiba Machinery Co., Ltd.)
・Molding conditions: Cylinder temperature (°C) Nozzle - C1 - C2 - C3
205 215 205 185°C
Injection pressure 40 (MPa)
Injection speed 1.5 (m/min)
Mold temperature 90 (°C)

(1) Fuel resistance The above test piece is immersed in diesel fuel (product name: CEC RF 90-A-92, manufactured by Haltermann) at 100 ° C. for 14 days, and the mass change due to fuel immersion from the weight of the test piece before and after that The rate was calculated and used as an evaluation of fuel resistance. Evaluation was made according to the following standards.
Calculation method: (test piece mass before immersion - test piece mass after immersion) ÷ (test piece mass before immersion)
○: Less than 10% △: 10% or more and less than 20% ×: 20% or more

(2) Weather resistance According to SAE J2527, weather resistance was evaluated using the following equipment and conditions.
Test device: Ci4000 Xenon Weather-Ometer (manufactured by ATLAS)
Light source: xenon arc lamp
Irradiance: 0.55 W/m ² wavelength 340 nm
Black panel temperature: 70°C
Humidity: 50% RH
Filter: (inner) quartz, (outer) borosilicate “S” type

A test was conducted for 152 cycles (corresponding to an irradiation intensity of 600 kJ) with the following conditions as one cycle.
1. 2. Dark (0 J/m ² ), double-sided water jet - 60 min. Light (1320 J/m ² )-40 minutes3. 4. Light (660 J/m ² ), front water jet - 20 min. After the light (1980 J/m ² )-60 minutes treatment, the surface of the test piece was visually and microscopically observed, and classified as follows according to how cracks occurred.
◯: No abnormality in appearance.
Δ: Cracks can be confirmed by observation with a stereoscopic microscope (magnification of 50 times).
x: Cracks can be visually confirmed.

(3) Bleeding A multi-purpose test piece was stored under conditions of 60°C and 95% RH for 96 hours.
≪Evaluation method≫
The appearance of the cured specimens was visually classified into the following categories.
◯: No exudation was observed on the surface of the test piece.
Δ: Slight exudation is observed on the surface of the test piece.
x: A large amount of seepage is observed on the surface of the test piece.

(4) Nominal tensile strain at break The nominal tensile strain at break was measured in accordance with ISO 527-1 and 2, and judged from × to ◯ as follows.
×: Less than 25% △: 25% or more and less than 29% ○: 29% or more

As described above, in the present invention, it is possible to provide a polyacetal resin composition that, when formed into a molded product, is capable of suppressing deterioration when sunlight is applied to the part that comes into contact with high-sulfur fuel.

Claims

at least,
(A) for 100 parts by mass of polyacetal polymer,
(B) 0.1 to 1.0 parts by mass of a hindered phenol antioxidant;
(C) 0.3 parts by mass to 2.0 parts by mass of at least one selected from oxides of magnesium and zinc;
(D) 0.5 to 3.0 parts by mass of polyalkylene glycol,
(E) 0.1 to 1.5 parts by mass of a hindered amine compound,
(F) 0.2 to 1.5 parts by mass of an ultraviolet absorber,
(G) 0.01 to 1.0 mass of a fatty acid ester of a polyhydric alcohol having an esterification rate of 80% or more;
A polyacetal resin composition containing
The polyacetal resin composition according to claim 1, wherein (A) is a polyacetal copolymer obtained by copolymerizing a cyclic oligomer of formaldehyde and a cyclic ether or a cyclic formal.
The polyacetal resin composition according to claim 1 or 2, wherein (C) is magnesium oxide having a BET specific surface area of 100 cm 2 /g or more.
The polyacetal resin composition according to any one of claims 1 to 3, wherein the (G) 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.
The polyacetal resin composition according to any one of claims 1 to 4, wherein the (F) ultraviolet absorber is at least one selected from benzotriazole-based compounds and oxalic acid diamide-based compounds.
(F) the UV absorber is 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol and N-(2-ethylphenyl)-N' The polyacetal resin composition according to any one of claims 1 to 5, which is at least one selected from -(2-ethoxyphenyl)oxalic acid diamide.
A fuel contactor comprising a molded article of the polyacetal resin composition according to any one of claims 1 to 6.