JP2019065221A - Polyacetal resin composition and molded body thereof - Google Patents

Abstract

To provide a polyacetal resin composition excellent in heat stability, less in elution of a component of a resin composition in the case in contact with a fuel, good in releasability from a mold during molding, having suppressed generation of silver streaks in a molded article even when a resin is molten and kept by a molding machine, and excellent in heat stability, fuel oiliness resistance, mold releasability and appearance.SOLUTION: There is provided a polyacetal resin composition containing a polyacetal resin (A), a mold release agent (B) and a specific layered double hydroxide (C), in which the mold release agent (B) is a polyolefin-based wax, and content of the mold release agent (B) in the polyacetal resin composition is 0.01 pts.mass to 1.0 pts.mass based on 100 pts.mass of the polyacetal resin (A).SELECTED DRAWING: None

Description

  The present invention relates to a polyacetal resin composition and a molded article thereof.

  The polyacetal resin composition has a good balance of mechanical properties, thermal properties, electrical properties, slidability, moldability, etc., and is widely used as structural materials, mechanical parts, etc. in electric devices, automobile parts, precision machine parts, etc. It is done. For example, as automobile parts, large parts such as a fuel transfer unit represented by a fuel pump module or the like in direct contact with fuel (fuel oil) are used. In the polyacetal resin composition used for parts in direct contact with fuel, if the elution of the components of the resin composition upon contact with fuel is large, it causes a decrease in mechanical strength of the parts.

  From such a point of view, several polyacetal resin compositions used for automotive application related parts in contact with fuel are disclosed. For example, Patent Document 1 shows that a molded product of a polyacetal resin composition containing a specific hindered phenol-based antioxidant and a fatty acid calcium salt in specific amounts, respectively, hardly deteriorates even when immersed in high-temperature fuel for a long time It is disclosed.

  Moreover, the polyacetal resin composition and molded object which each contain specific amount of a specific hindered phenolic antioxidant and fatty acid calcium salt have patent document 2 very excellent heat resistance, solvent resistance, and acid resistance. It is disclosed that it can be applied to parts in contact with automotive fuels, particularly diesel fuel.

  Further, in Patent Document 3, even if a molded article of a polyacetal resin composition containing an antioxidant, a fatty acid metal salt, a nitrogen-containing compound, a nucleating agent and polyethylene glycol or polypropylene glycol in specific amounts, respectively comes in direct contact with automobile fuel It is disclosed to have excellent durability.

JP, 2013-112728, A JP 2011-32379 A JP, 2009-132768, A

In polyacetal resin compositions used for parts in direct contact with fuel, if the components of the dissolved resin composition are deposited on the surface of the parts, it causes defective appearance of the parts and malfunction of the device using the parts. Become. In addition, the releasability from the mold when molded into a part in direct contact with fuel is also regarded as important. That is, as a polyacetal resin composition used for parts in direct contact with fuel, not only the thermal stability but also the elution of the components of the resin composition at the time of contact with fuel is small, and from the mold at the time of molding There is a demand from the market for polyacetal resin compositions which have good releasability, and which are excellent in heat stability, fuel oil resistance and releasability.
From such a point of view, calcium stearate which is a fatty acid calcium salt disclosed in Patent Documents 1 to 3 mentioned above by the present inventors, and pentaerythritol tetrastearate which is a fatty acid ester generally used as a releasing agent. As a result of examining fuel oil resistance and releasability using a polyacetal resin, polyacetal resin compositions using these compounds have poor thermal stability, and there is a lot of elution of components when in contact with fuel, and direct contact with fuel As a polyacetal resin composition used for parts to contact, it was not satisfactory.

  The present inventors have found a polyacetal resin composition in which a specific amount of a polyolefin-based wax or the like is blended as a release agent as a method for solving the above-mentioned problems. However, when the polyacetal resin composition is melted and retained by a molding machine and then molded, depending on the retention and molding conditions, silver streaks may be significantly generated.

  That is, the subject of the present invention is excellent in thermal stability, less elution of components of the resin composition when in contact with fuel, and good releasability from the mold at the time of molding, and the resin is melted by a molding machine It is an object of the present invention to provide a polyacetal resin composition and a molded article thereof excellent in thermal stability, fuel oil resistance, releasability and appearance in which generation of silver streaks in molded articles is suppressed even when retained. .

  As a result of intensive studies to solve the above problems, the present inventors have found that the polyacetal resin contains a polyacetal resin, a polyolefin wax as a mold release agent, and a specific layered double hydroxide. The polyacetal resin composition using a specific amount of mold release agent is excellent in thermal stability, less elution of resin composition components when in contact with fuel, good releasability from the mold at the time of molding, molding It was found that the generation of silver streaks in molded articles was suppressed even when the resin was melted and retained by a machine, and that the resin was excellent in terms of heat stability, fuel oil resistance, releasability and appearance, and the present invention was completed.

That is, the present invention is as follows.
<1>
A polyacetal resin composition comprising a polyacetal resin (A), a releasing agent (B) and a layered double hydroxide (C) represented by the following general formula (1), wherein the releasing agent (B) is A polyolefin-based wax, wherein the content of the release agent (B) in the polyacetal resin composition is 0.01 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A) , Polyacetal resin composition.
[(M 2 ⁺ ) _x (M ^{3 +} ) _y (OH) _{2 (x + y)} ] (A ^{n −} ) _{x / n} · z (H ₂ O) (1)
(In the formula (1), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-represents an n-valent anion, may include a plurality of anions. Further, x is in the range of 0 <x ≦ 6.0, n is an integer of 1 to 3, and y and z are numbers of 0 or more.)
<2>
The polyacetal resin composition as described in <1> whose said mold release agent (B) is a polyethylene-type wax.
<3>
The polyacetal resin composition as described in <2> whose viscosity average molecular weights of the said polyethylene-type wax are 500 or more and 15000 or less.
<4>
Content of the said mold release agent (B) in the said polyacetal resin composition is 0.04 mass part or more and 0.15 mass part or less with respect to 100 mass parts of said polyacetal resin (A), <1> The polyacetal resin composition as described in any one of <3>.
<5>
The content of the layered double hydroxide (C) in the polyacetal resin composition is 0.01 parts by mass or more and 0.07 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A), <1 The polyacetal resin composition as described in any one of>-<4>.
<6>
The polyacetal resin composition as described in any one of <1>-<5> whose said layered double hydroxide (C) is a hydrotalcite.
<7>
The hydrotalcite is described in <6>, wherein M ²⁺ in the general formula (1) is Mg ²⁺ , M ³⁺ is Al ³⁺ , and A ^{n −} is CO ₃ ²⁻ and / or OH ^−. Polyacetal resin composition.
<8>
Furthermore, as described in any one of <1> to <7>, the antioxidant (D) is contained in an amount of 0.01 to 3.0 parts by mass with respect to 100 parts by mass of the polyacetal resin (A). Polyacetal resin composition.
<9>
The antioxidant (D) is pentaerythritol-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-tris. (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, and 3,3 ′, 3 ′ ′, 5,5 ′, 5 ′ ′-hexa-tert-butyl-α, α ′, α ′ ′- The polyacetal resin composition as described in <8> which is one or more types chosen from the group which consists of a mesitylene 2,4,6- triyl) tri-p-cresol.
<10>
Content of the said antioxidant (D) in the said polyacetal resin composition is 0.03 mass part or more and 0.20 mass parts or less with respect to 100 mass parts of said polyacetal resin (A), <8> Or the polyacetal resin composition as described in <9>.
<11>
The molded object which has a polyacetal resin composition as described in any one of <1>-<10>.
<12>
The polyacetal resin composition as described in <1>-<10> used for the components which contact a fuel.
<13>
The molded object as described in <11> which is a component which contacts a fuel.
<14>
The molded object as described in <13> whose said fuel is 1 type, or 2 or more types chosen from the group which consists of gasoline fuel, gasohol fuel, diesel fuel, and a biofuel.

  According to the present invention, the thermal stability is excellent, the elution of the components of the resin composition when contacting the fuel is small, and the releasability from the mold during molding is good, and the resin is melted and retained by the molding machine Even in this case, generation of silver streaks in molded articles can be suppressed, and a polyacetal resin composition excellent in thermal stability, fuel oil resistance, releasability and appearance can be provided and a molded article thereof.

It is the schematic of the apparatus used for fuel-proof oil evaluation in an Example and a comparative example.

  Hereinafter, the present invention will be described in detail. The polyacetal resin composition of the present invention comprises a polyacetal resin (A), a releasing agent (B) and a layered double hydroxide (C) represented by the above general formula (1), and the releasing agent (B) Is a polyolefin wax, and the content of the releasing agent (B) in the polyacetal resin composition is 0.01 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A) is there. Such a polyacetal resin composition is excellent in thermal stability, less elution of components of the resin composition when in contact with fuel, and good releasability from the mold at the time of molding, and the resin Even when molten and retained, generation of silver streaks in molded articles can be suppressed, and it is characterized in that it is excellent in heat stability, fuel oil resistance, releasability, and appearance. The reason is not particularly limited, but when the polyacetal resin composition contains a specific amount of a polyolefin-based wax and a layered double hydroxide represented by the general formula (1), the polyolefin-based wax can be used as a fuel described later. In addition to being considered to have low solubility and low reactivity with fuel, the combined use of the layered double hydroxide (C) represented by the general formula (1) in addition to fuel oil resistance and releasability It is considered that the generation of silver streaks in molded articles can be further suppressed. Silver streaks (hereinafter also referred to as silver) are streaky appearance defects on the surface of a molded article generated due to air in the molding material, volatile gas, decomposition gas derived from the molding material, and the like.

  The polyacetal resin composition of the present invention can be suitably used for parts in contact with fuel. Here, the fuel is not particularly limited, but, for example, gasoline fuel, gasohol fuel, diesel fuel, biofuel, solid fuel such as wax, solid, liquid, gas (vapor) state, hetero It refers to an aliphatic and / or aromatic hydrocarbon compound which may have an atom.

Hereinafter, the component which comprises the polyacetal resin composition of this invention is demonstrated.
<Polyacetal resin (A)>
The polyacetal resin composition of the present invention contains a polyacetal resin (A). The polyacetal resin (A) is a polymer having an acetal bond: -O-CRH- (wherein R represents a hydrogen atom or an organic group) as a repeating unit, and usually an oxymethylene in which R is a hydrogen atom The group (-OCH _2- ) is the main constituent unit. The polyacetal resin used in the present invention contains a copolymer (block copolymer) containing at least one repeating structural unit other than the above-mentioned oxymethylene group, a terpolymer, etc., and further has not only a linear structure but also glycidyl ether compounds, epoxy compounds, It may have a branched or crosslinked structure formed by using an allyl ether compound or the like as a comonomer and / or termonomer. As the structural unit other than the oxymethylene group, for example, oxyethylene group (-OCH ₂ CH ₂ - or -OCH _(CH 3) -), oxypropylene group _{(-OCH 2 CH 2 CH 2 -} , - OCH (CH ₃₎ CH ₂ - or _{-OCH 2 CH (CH 3) -} ), oxybutylene group _{(-OCH 2 CH 2 CH 2 CH} 2 -, - OCH (CH 3) CH 2 CH 2 -, - OCH 2 CH (CH _{And 3} ) CH _2- , -OCH ₂ CH ₂ CH (CH ₃ )-, -OCH (C ₂ H ₅ ) CH ₂ -or -OCH ₂ CH (C ₂ H ₅ )-), etc. And an oxyalkylene group which may be branched is mentioned, and among them, an oxyalkylene group which has 2 or more and 4 or less carbon atoms and which may be branched is preferable, and an oxyethylene group (-OCH ₂ CH _{2 is} particularly preferable. -) Is preferred. Further, the content of the constituent unit (oxyalkylene group) other than the oxymethylene group in the polyacetal resin (A) is preferably 0.1% by mass or more and 20% by mass or less, and more preferably 0.5% by mass or more It is more preferable that it is mass% or less, and it is further more preferable that it is 0.5 mass% or more and 6.0 mass% or less.

  The method for producing the polyacetal resin (A) is not particularly limited, and it may be produced by any conventionally known method. For example, as a method for producing a polyacetal resin (A) having an oxymethylene group and an oxyalkylene group having 2 or more and 4 or less carbon atoms as structural units, a trimer (trioxane) or tetramer (tetraoxane) of formaldehyde Copolymerization of a cyclic acetal of an oxymethylene group and a cyclic acetal containing an oxyalkylene group having 2 to 5 carbon atoms such as ethylene oxide, 1,3-dioxolane, 1,3,6-trioxocan, and 1,3-dioxepane It can be manufactured by Among them, as the polyacetal resin (A) which can be used in the present invention, a copolymer of a cyclic acetal such as trioxane or tetraoxane and ethylene oxide or 1,3-dioxolane is preferable, and trioxane and 1, 1 are preferable. Particularly preferred is a copolymer with 3-dioxolane.

  For example, polyacetal resin (A) can be obtained by bulk polymerization of a cyclic acetal of an oxymethylene group and a cyclic acetal containing 2 to 5 carbon atoms as a comonomer using a polymerization catalyst. it can. If necessary, a reaction terminator may be used to deactivate the polymerization catalyst and the polymerization growth terminal. Moreover, you may use a molecular weight modifier as needed for molecular weight control of polyacetal resin (A). The type and amount of the polymerization catalyst, reaction terminator and molecular weight modifier that can be used for producing the polyacetal resin (A) of the present invention are not particularly limited as long as the effects of the present invention are not impaired. Any known polymerization catalyst, reaction terminator, molecular weight modifier can be used as appropriate.

  The polymerization catalyst is not particularly limited, and, for example, Lewis tris such as boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentachloride, phosphorus pentafluoride, arsenic pentafluoride, and antimony pentafluoride And acids, as well as complexes or salts of these Lewis acids. Also, protic acids such as trifluoromethanesulfonic acid and perchloric acid; esters of protic acids such as esters of perchloric acid and lower aliphatic alcohols; protonic acids such as mixed anhydrides of perchloric acid and lower aliphatic carboxylic acids And the anhydrides of In addition, triethyl oxonium hexafluorophosphate, triphenylmethyl hexafluoro arsenate, acetyl hexafluoroborate, heteropoly acid or its acid salt, isopoly acid or its acid salt, perfluoroalkyl sulfonic acid or its acid salt, etc. Can be mentioned. Among them, compounds containing boron trifluoride are preferable, and boron trifluoride diethyl etherate and boron trifluoride dibutyl etherate which are coordination complexes with ethers are particularly preferable.

The use amount of the polymerization catalyst is not particularly limited, but when boron trifluoride is used, it is usually 1.0 × 10 ^{-8 to} 2.0 × 10 with respect to 1 mol of all monomers in total of trioxane and the comonomer. ^{It is in the range of -3} mol, preferably 5.0 × 10 ^{-8 to} 8.0 × 10 ^-4 mol, particularly preferably 5.0 × 10 ^{-8 to} 1.0 × 10 ^-4 mol.

  The reaction terminator is not particularly limited, and examples thereof include trivalent organic phosphorus compounds, amine compounds, and hydroxides of alkali metals or alkaline earth metals. These reaction terminators can be used alone or in combination of two or more. Among them, trivalent organophosphorus compounds, tertiary amines and hindered amines are preferred.

The amount of reaction terminator used is not particularly limited as long as it is an amount sufficient to deactivate the polymerization catalyst, but the molar ratio to the polymerization catalyst is usually 1.0 × 10 ^{−1 to} 1.0 × 10 ¹ Range.

  The molecular weight modifier is not particularly limited, and examples thereof include methylal, methoxymethylal, dimethoxymethylal, trimethoxymethylal, oxymethylene di-n-butyl ether and the like. Among them, preferred is methylal. The amount of the molecular weight modifier to be used can be appropriately determined depending on the target molecular weight. Usually, the addition amount is adjusted in the range of 0 to 0.1% by mass with respect to all the monomers.

<Release agent (B)>
The polyacetal resin composition of the present invention contains a release agent (B), and it is essential to use a polyolefin wax as the release agent (B). This is because the polyacetal resin composition contains a polyolefin-based wax as a mold release agent (B), so that the elution of the components of the resin composition when contacting the fuel is small, and the release from the mold at the time of molding This is because the moldability is good and the balance between fuel oil resistance and releasability is excellent. In addition, polyacetal resin compositions to which a polyolefin wax is added are generally obtained from resin compositions to which a fatty acid calcium salt (for example, calcium stearate) or a fatty acid ester (for example, pentaerythritol tetrastearate) which is generally used as a mold release agent is added. It is also characterized by excellent heat stability. The polyolefin waxes may be used alone or in combination of two or more. Among them, as the releasing agent (B), polyethylene-based wax described later is preferable.

  The polyolefin wax is not particularly limited as long as it is a chemically synthesized low molecular weight polymer (synthetic wax) having a skeleton derived from an olefin, and, for example, polyethylene wax, polypropylene wax, ethylene-acrylic acid copolymer Wax, ethylene-vinyl acetate copolymer wax and the like can be mentioned. In addition, these waxes may be oxidatively modified or acid modified to introduce polar groups. The polyolefin-based wax may be used alone or in combination of two or more with different types and viscosities.

  The molecular weight of the polyolefin wax is not particularly limited, but is preferably 500 to 30,000, more preferably 500 to 15,000, still more preferably 1,000 to 10,000, and particularly preferably 2,000 to 8,000 in terms of viscosity average molecular weight. If the viscosity average molecular weight of the polyolefin wax is 500 or more, it tends to be possible to suppress the elution of the release agent when in contact with the fuel. On the other hand, if the viscosity average molecular weight is 30,000 or less, the releasability at the time of molding tends to be improved by the addition of a small amount of a release agent.

  Among the above-described polyolefin waxes, the release agent (B) is preferably a polyethylene wax and / or a polypropylene wax, particularly preferably a polyethylene wax.

  The polyethylene-based wax is not particularly limited as long as it is a low molecular weight polymer having a skeleton derived from ethylene, and, for example, a low molecular weight polyethylene polymer (hereinafter, also simply referred to as low molecular weight polyethylene) or a low molecular weight polyethylene copolymer And oxidized modified polyethylene wax or acid modified polyethylene wax in which polar groups are introduced by oxidatively modifying or acid modifying them. These low molecular weight polyethylene, low molecular weight polyethylene copolymer, oxidized modified polyethylene wax, and acid modified polyethylene wax may be used alone or in combination of two or more.

  The low molecular weight polyethylene is a low molecular weight polymer obtained by polymerizing ethylene, and the structure may be linear (high density polyethylene) or branched (low density polyethylene).

  The low molecular weight polyethylene copolymer is a low molecular weight copolymer obtained by polymerizing ethylene and an α-olefin, and the structure thereof is branched (low density) even if it is linear (high density polyethylene). Density polyethylene). The low molecular weight polyethylene copolymer is preferably a low molecular weight polyethylene copolymer in which the α-olefin is propylene.

  Although the composition ratio of ethylene and α-olefin in the low molecular weight polyethylene copolymer is not particularly limited, the amount of ethylene relative to the total molar amount of ethylene and α-olefin in the low molecular weight polyethylene copolymer is It is preferable that it is 50 mol% or more and less than 100 mol%, and the amount of α-olefin is more than 0 mol% and 50 mol% or less. When the α-olefin is propylene, the amount of ethylene is 50% by mole or more and less than 100% by mole, and the amount of propylene is more than 0% by mole based on the total molar amount of ethylene and propylene in the low molecular weight polyethylene copolymer. It is preferable that it is 50 mol% or less.

  The method for producing the low molecular weight polyethylene and the low molecular weight polyethylene copolymer is not particularly limited. For example, a method of directly polymerizing ethylene or ethylene and an α-olefin with a Ziegler catalyst or the like, high molecular weight polyethylene or copolymer It can be produced by a method of obtaining it as a by-product during production, a method of thermally decomposing high molecular weight polyethylene or a copolymer, or the like.

  The oxidation-modified polyethylene wax is particularly limited as long as it is obtained by treating the above-described low molecular weight polyethylene polymer or low molecular weight polyethylene copolymer with a peroxide or oxygen to introduce a polar group such as a carboxyl group or a hydroxyl group. I will not.

  The acid-modified polyethylene wax may be treated with an inorganic acid, an organic acid, an unsaturated carboxylic acid or the like, if necessary, in the presence of a peroxide or oxygen, in the presence of a low molecular weight polyethylene polymer or a low molecular weight polyethylene copolymer. If it introduce | transduces polar groups, such as a carboxyl group and a sulfonic acid group, by this, it will not specifically limit.

  The viscosity average molecular weight of the polyethylene wax is not particularly limited, but is preferably 500 to 15,000, more preferably 1,000 to 10,000, and particularly preferably 2,000 to 8,000. If the viscosity average molecular weight of the polyethylene-based wax is 500 or more, it tends to be possible to suppress the elution of the release agent when in contact with the fuel. On the other hand, when the viscosity average molecular weight is 15000 or less, the releasability at the time of molding tends to be improved by the addition of a small amount of a release agent.

  The polyethylene-based waxes described above may be used alone or in combination of two or more with different types and viscosities.

  The polyethylene type wax mentioned above may use a commercial item, for example, general polymerization type high density type polyethylene wax, general polymerization type low density type polyethylene wax, oxidation type polyethylene wax (low acid number), oxidation type polyethylene wax (high It is possible to use those commercially available under the names of acid value), acid-modified polyethylene wax, special monomer-modified polyethylene wax, and low density polyethylene, general-type polyethylene wax. For example, Hi Wax 220MP manufactured by Mitsui Chemicals, Inc. can be used as the polyethylene wax of the oxidation type. Further, as the high density type polyethylene wax, Hi Wax 800P manufactured by Mitsui Chemicals, Inc. can be used.

  Content of the mold release agent (B) in the polyacetal resin composition of this invention is 0.01 mass part or more and 1.0 mass part or less with respect to 100 mass parts of polyacetal resin (A). When the content of the release agent (B) in the polyacetal resin composition is 0.01 parts by mass or more, the releasability of the molded article from the mold tends to be good. On the other hand, if the content is 1.0 parts by mass or less, the thermal stability and the fuel oil resistance tend to be excellent.

  0.02 mass part or more and 0.7 mass part or less are preferable with respect to 100 mass parts of polyacetal resin (A), as for content of the mold release agent (B) in a polyacetal resin composition, 0.03 mass part or more 0.2 parts by mass or less is more preferable, 0.04 parts by mass or more and 0.15 parts by mass or less are more preferable, and 0.08 parts by mass or more and 0.12 parts by mass or less are particularly preferable. When the content of the release agent (B) is 0.03 parts by mass or more and 0.2 parts by mass or less, the resin compositions and molded articles are excellent in thermal stability, fuel oil resistance, and releasability, and 0. It is more excellent in thermal stability, fuel oil resistance, and releasability as it is 04 parts by mass or more and 0.15 parts by mass or less, and heat stability and resistance when it is 0.08 parts by mass or more and 0.12 parts by mass or less It is particularly excellent in fuel oiliness and releasability.

<Layered double hydroxide (C)>
The layered double hydroxide (C) in the present invention is a compound having a metal hydroxide layer having an anion exchange ability, and specifically, a compound represented by the following general formula (1).
[(M 2 ⁺ ) _x (M ^{3 +} ) _y (OH) _{2 (x + y)} ] (A ^{n −} ) _{x / n} · z (H ₂ O) (1)
(In the formula (1), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-represents an n-valent anion, may include a plurality of anions. Further, x is in the range of 0 <x ≦ 6.0, n is an integer of 1 to 3, and y and z are numbers of 0 or more.)

Although it does not specifically limit as a bivalent metal ion (M ^<2+> ), Alkaline earth metal ion (Mg ^<2+> etc.), Mn ^<2+> , Fe ^<2+> , Co ^<2+> , Ni ^<2+> , Cu ^<2+> , Zn ^<2+> is mentioned. Moreover, it does not specifically limit as trivalent metal ion (M ^<3+> ), However, Al ^<3+> , Fe ^<3+> , Cr ^<3+> , Co ^<3+> , In ^<3+> is mentioned. Furthermore, the n-valent anion (A ^{n −} ) is not particularly limited, but OH ⁻ , F ⁻ , Cl ⁻ , Br ⁻ , NO ₃ ⁻ , CO ₃ ²⁻ , SO ₄ ²⁻ , Fe (CN) ₆ ^{3 -,} _CH 3 COO ^-, oxalic acid ion, salicylic acid ion.

Among them, in the layered double hydroxide (C) in the present invention, the divalent metal ion (M 2 ⁺ ) in the above general formula (1) is an alkaline earth metal ion, and the trivalent metal ion (M ^{3 +} ) It is preferable that it is hydrotalcite which is Al ³⁺ and whose n-valent anion (A ⁿ⁻ ) is CO ₃ ²⁻ and / or OH ⁻ . Furthermore, among the hydrotalcites, the divalent metal ion (M 2 ⁺ ) in the above-mentioned general formula (1) is Mg 2 ⁺ , and the trivalent metal ion (M ^{3 +} ) is Al ^{3 +} , an n-valent anion ^{(A n-)} is _CO ^{3 2-} and / or OH ^- compounds represented by is particularly preferred.

Examples of the above-mentioned hydrotalcite include natural hydrotalcite represented by Mg _1.5 Al _0.5 (OH) ₄ (CO ₃ ) _0.75 · 1.0 H ₂ O, Mg _4.5 Al ₂ ( Mention may be made of synthetic hydrotalcites represented by OH) ₁₃ CO ₃ .1.5 H ₂ O. Hydrotalcite, it can be a commercially available product, for example, CLARIANT Co., can be used _{Hycite713 (Mg 4 Al 2 (OH} ) 12 CO 3 · 1.5H 2 O).

  The content of the layered double hydroxide (C) in the polyacetal resin composition of the present invention is 0.001 to 0.5 parts by mass with respect to 100 parts by mass of the polyacetal resin (A), and preferably 0. The content is preferably from 0.55 to 0.1 parts by mass, more preferably from 0.01 to 0.07 parts by mass, still more preferably from 0.01 to 0.05 parts by mass, particularly preferably from 0.02 to 0.04 It is a mass part. When the content of the layered double hydroxide (C) is 0.001 parts by mass or more, the generation of silver after the melt retention of the polyacetal resin composition is suppressed, and when it is 5.0 parts by mass or less, from the resin composition Component elution can be further suppressed.

<Antioxidant (D)>
The polyacetal resin composition of the present invention preferably further comprises an antioxidant (D). Since the heat resistance of the resin composition is improved by the polyacetal resin composition containing the antioxidant (D), the heat stability tends to be excellent during molding, and as a result, the mechanical strength and the fuel oil resistance are improved. There is a tendency to obtain a good molded product.

  The type of the antioxidant (D) is not particularly limited. For example, ethylenebis (oxyethylene) bis [3- (5-tert-butyl-4-hydroxy-m-tolyl) propionate] (eg, BASF, IRGANOX) (Registered trademark) 245), N, N′-hexane-1,6-diylbis [3- (3,5-di-tert-butyl-4-hydroxyphenylpropionamide)] (eg, BASF, IRGANOX®) 1098), pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (eg, BASF, IRGANOX® 1010), 1,3,5-trimethyl-2, 4,6-Tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene For example, Rianlon, THANOX® 330), 3,3 ′, 3 ′ ′, 5,5 ′, 5 ′ ′-hexa-tert-butyl-α, α ′, α ′ ′-(mesitylene-2,4,6 -Triyl) tri-p-cresol (e.g. BASF, IRGANOX (R) 1330), 1,3,5-tris (3,5-di-tert-butyl-4-hydroxybenzyl) -1,3,5 -Triazine-2, 4, 6 (1 H, 3 H, 5 H) -trione (e.g. BASF, IRGANOX (R) 3114).

  Among them, the antioxidant (D) is pentaerythritol-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (for example, BASF, IRGANOX (registered trademark) 1010), 1 , 3,5-trimethyl-2,4,6-tris (3,5-di-tert-butyl-4-hydroxybenzyl) benzene (e.g., Rianlon, THANOX (R) 330), and 3,3 ', and 3,3', 3 ′ ′, 5,5 ′, 5 ′ ′-hexa-tert-butyl-α, α ′, α ′ ′-(mesitylene-2,4,6-triyl) tri-p-cresol (eg, BASF, IRGANOX® 1) at least one selected from the group consisting of 1330), while maintaining the thermal stability of the resin composition and the molded article by the antioxidant (D) More preferable because elution of antioxidant from the resin composition and molded article (D) is excellent hardly undergoes fuel oil.

  Although content of antioxidant (D) in a polyacetal resin composition is not specifically limited, 0.01 mass part or more and 3.0 mass parts or less are 100 mass parts of polyacetal resin (A), preferable. If the content of the antioxidant (D) in the resin composition is 0.01 parts by mass or more, the heat resistance of the resin composition and the molded article tends to be improved. On the other hand, when the content is 3.0 parts by mass or less, elution of the antioxidant (D) from the resin composition and the molded article is difficult to occur, the fuel oil resistance is excellent, and the releasability tends to be excellent. The content of the antioxidant (D) is more preferably 0.01 parts by mass or more and 0.5 parts by mass or less, further preferably 0.02 parts by mass or more and 0.25 parts by mass or less, and 0.03 parts by mass. The content is particularly preferably 0.2 parts by mass or less. When the content of the antioxidant (D) is 0.02 parts by mass or more and 0.25 parts by mass or less, the resin composition and the molded article are excellent in thermal stability, fuel resistance, and releasability, and 0. When the content is 03 parts by mass or more and 0.2 parts by mass or less, the heat stability, fuel oil resistance, and releasability are particularly excellent.

  In a preferred embodiment of the present invention, an antioxidant (D) is used in combination in addition to the polyolefin wax as the release agent (B) and the layered double hydroxide (C) represented by the above general formula (1). As a result, the fuel oil resistance is excellent, generation of silver streaks in molded articles can be suppressed, and releasability and thermal stability can be further improved.

<Other optional components to be added>
Moreover, when implementing this invention, in the range which does not impair the objective of the present invention, nitrogen-containing compounds other than the said antioxidant (D), alkali metals or alkaline earths other than the said layered double hydroxide (C) Metal-containing compounds represented by the group consisting of metalloid hydroxides, carbonates, inorganic acid salts, and alkoxides can be further added.

  The nitrogen-containing compound is not particularly limited, and examples thereof include amino-substituted triazine compounds, polyamide resins, and hindered amine compounds.

  The addition amount of the nitrogen-containing compound is not particularly limited, but is preferably 0.01 to 5.0 parts by mass, more preferably 0.01 to 5.0 parts by mass with respect to 100 parts by mass of the polyacetal resin (A). It is 3.0 parts by mass, particularly preferably 0.02 to 2.0 parts by mass. When the addition amount of the nitrogen-containing compound is 0.01 parts by mass or more, the thermal stability of the polyacetal resin composition is improved, and when the addition amount is 5.0 parts by mass or less, the tensile elongation and the impact resistance are remarkable. The thermal stability of the polyacetal resin composition can be improved without degradation.

  The amino-substituted triazine compound is not particularly limited. For example, guanamine, melamine, N-butylmelamine, N-phenylmelamine, N, N-diphenylmelamine, N, N-diallylmelamine, N, N ′, N ′ ′-tri Methylolmelamines such as phenylmelamine, N, N ', N "-trimethylolmelamine, alkylated melamines such as hexamethoxymethylmelamine, benzoguanamine, 2,4-diamino-6-methyl-sym-triazine, 2,4- Diamino-6-butyl-sym-triazine, 2,4-diamino-6-benzyloxy-sym-triazine, 2,4-diamino-6-butoxy-sym-triazine, 2,4-diamino-6-cyclohexyl-sym -Triazine, 2,4-diamino-6-chloro-sym-triazine , 2,4-diamino-6-mercapto--sym- triazine, ammeline (N, N, N ', N'- tetra-cyanoethyl benzoguanamine), water-soluble melamine - formaldehyde resins. Among them, melamine, methylolmelamine, alkylated melamine, benzoguanamine, and water-soluble melamine-formaldehyde resin are preferable. The above-mentioned amino-substituted triazine compounds may be used alone or in combination of two or more. These amino substituted triazine compounds are used as heat stabilizers.

  The polyamide resin is not particularly limited as long as it is a resin having two or more amide bonds in the molecule, but, for example, nylon-6, nylon-6,6, nylon-6,10, their terpolymer, polymerization Examples include fatty acid-based polyamide resins and polyamide elastomers. Among these, a polymeric fatty acid-based polyamide resin or a polyamide elastomer is particularly preferable. These polyamide resins may be used alone or in combination of two or more.

  Here, the polymeric fatty acid-based polyamide resin refers to a polyamide resin composed of a polycondensate of a polymeric fatty acid and a diamine.

  The polymerized fatty acid is a polymer of unsaturated fatty acid or one obtained by hydrogenating this polymer, and as the polymerized fatty acid, for example, having a carbon number of 10 to 24 and having a double bond or a triple bond A dimer of one or more monobasic fatty acids (dimer acid) or a hydrogenated product thereof can be mentioned. Examples of dimer acids include dimers such as oleic acid, linoleic acid and erucic acid.

  Examples of the diamine include hexamethylenediamine, heptamethylenediamine, octamethylenediamine, decamethylenediamine and metaxylylenediamine.

  The polyamide elastomer refers to a polyamide resin having a hard segment and a soft segment, wherein the hard segment is composed of polyamide and the soft segment is composed of a polymer other than polyamide. Examples of the polyamide constituting the hard segment include nylon-6, nylon-6,6, nylon-6,10, a terpolymer of these, and a polymeric fatty acid-based polyamide resin. Examples of polymers other than polyamides include aliphatic polyesters and aliphatic polyethers. Examples of aliphatic polyesters include poly (ε-caprolactone), polyethylene adipate, polybutylene adipate and polybutylene succinate. Examples of aliphatic polyethers include polyoxyalkylene glycols such as polyethylene oxide and polypropylene oxide.

  The hindered amine compound is not particularly limited, and examples thereof include N, N ′, N ′ ′, N ′ ′ ′-tetrakis- (4,6-bis- (butyl- (N-methyl-2,2,6,6-tetra) Methylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10-diamine, dibutylamine · 1,3,5-triazine · N, N′-bis (2,2 Polycondensate of 6,6,6-Tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-Tetramethyl-4-piperidyl) butylamine (BASF, Chimassorb® ) 2020 FDL), poly [{6- (1,1,3,3-tetramethylbutyl) amino-1,3,5-triazine-2,4-diyl} {(2,2,6,6-tetra) Methyl- 4-piperidyl} imino) hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl) imino}], dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1- Polycondensate of piperidine ethanol (BASF, Tinuvin® 622 SF), bis (1,2,2,6,6-pentamethyl-4-piperidyl) [[3,5-bis (1,1-dimethylethyl) ) -4-Hydroxyphenyl] methyl] butyl malonate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) ) Sebacate, and 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl] -4- [3- (3,5-di-t-butyl] Among them, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (bis (2,2,6,6-tetramethyl-4-piperidyl), among 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol (BASF, Tinuvin® 622 The above-mentioned hindered amine compounds may be used alone or in combination of two or more kinds.These hindered amine compounds are used as light stabilizers and antioxidants. Be done.

  As the inorganic acid salt in the metal-containing compound represented by the group consisting of alkali metal or alkaline earth metal hydroxides, carbonates, inorganic acid salts, and alkoxides, phosphates, silicates, borates, etc. may be mentioned. And alkoxides such as methoxide and ethoxide. Among them, preferred are alkaline earth metal hydroxides, carbonates, inorganic acid salts and alkoxides, and more preferred are calcium hydroxide, magnesium hydroxide, calcium carbonate or magnesium carbonate.

  Although the addition amount of at least one metal-containing compound represented by the group consisting of alkali metal or alkaline earth metal hydroxide, carbonate, inorganic acid salt, and alkoxide is not particularly limited, polyacetal resin ( A) Preferably it is 0.001-5.0 mass parts with respect to 100 mass parts, Especially preferably, it is 0.01-3.0 mass parts.

  In the practice of the present invention, various light stabilizers, UV absorbers, lubricants other than the above-mentioned mold release agent (B), nucleating agents, fillers, pigments, interfaces, as long as the object of the present invention is not impaired. An activator, an antistatic agent, etc. may be further added.

<Method of producing polyacetal resin composition>
In the method for producing the polyacetal resin composition of the present invention, a method in which the above-mentioned polyacetal resin (A), the polyolefin wax as a releasing agent (B) and the layered double hydroxide (C) are mixed and melt-kneaded It is not particularly limited as long as the method is used, and a conventionally known method for producing a polyacetal resin composition can be used. For example, the polyacetal resin (A) described above, the polyolefin wax, the layered double hydroxide (C), and, if necessary, the antioxidant (D) and the other optional components described above, It can manufacture by mixing and melt-kneading in arbitrary order.

  The conditions of the temperature and pressure of melt-kneading may be appropriately selected according to the conventionally known method for producing a polyacetal resin composition, and are not particularly limited. For example, the melt-kneading temperature is preferably equal to or higher than the melt temperature of the polyacetal resin (A) and 270 ° C. or lower, and particularly preferably 190 ° C. or higher and 250 ° C. or lower. The pressure at the time of melt-kneading is preferably 6.7 kPa or more and 66.7 kPa or less in absolute pressure, and particularly preferably 13.3 kPa or more and 40.0 kPa or less. The time for carrying out melt-kneading (residence time in the apparatus used for melt-kneading) is not particularly limited, and is preferably 1 to 60 minutes, particularly preferably 1 to 40 minutes.

  The apparatus used for melt-kneading is also not particularly limited, and a melt-kneading apparatus such as a single- or twin-screw extruder conventionally used for producing this type of resin composition can be used. The method of melt-kneading is also not particularly limited. For example, the polyacetal resin composition is continuously extruded using the above-mentioned single- or twin-screw extruder while degassing under the above-mentioned temperature and pressure. An object (pellet) can be obtained.

  Specifically, for example, a polyolefin-based wax and a layered double hydroxide (C) are added to the polyacetal resin (A), and if necessary, an antioxidant (D) or the other additives described above are further added. After adding a good optional ingredient etc., it mixes with a tumbler type blender etc. Then, the mixture obtained is melt-kneaded with a single-screw or twin-screw extruder, extruded into strands, and pelletized to obtain a polyacetal resin composition of a desired composition.

  As another method, polyolefin wax and the layered double hydroxide (C) are added to and mixed with the polyacetal resin (A), and then they are melt-kneaded and pelletized. If desired, an antioxidant (D) and other optional components as described above may be further added, mixed again, melt-kneaded and pelletized to obtain a polyacetal resin composition having a desired composition. You can also get things. Further, the resin composition melt-kneaded by the extruder can be directly made into an injection-molded article, a blow-molded article, or an extrusion-molded article without passing through the pellets.

<Mold of polyacetal resin composition and use thereof>
The polyacetal resin composition of the present invention can be molded into various forms in accordance with known polyacetal resin molding processing methods. As a molded object which consists of a polyacetal resin composition of this invention, although shapes, such as a pellet, a round bar, a thick plate, a sheet | seat, a tube, a cylindrical or square container, are mentioned, it is not limited to this.

  The polyacetal resin composition of the present invention and the molded article thereof can be used as mechanical, electric, automobile, building materials and other various parts conventionally known as applications of polyacetal resin compositions, but in particular, solid and liquid of fuel described later Are suitable for use as components such as fuel tank caps in direct contact with gases (especially steam).

  As described above, the fuel in the present invention is not particularly limited, and may be a solid, liquid or gas (vapor) state, and may be aliphatic and / or aromatic carbonized which may have a hetero atom. It is a fuel containing a hydrogen compound, and examples thereof include gasoline fuel, gasohol fuel, diesel fuel and biofuel. These fuels may be of one type or a mixture of two or more types. Gasoline fuel is not particularly limited as long as it is a petroleum product generally used as a fuel for automobiles, and does not refer to a special fuel. Gasohol fuel is not particularly limited as long as it is a mixture of gasoline and alcohols such as methanol and ethanol. The diesel fuel is not particularly limited as long as it is a petroleum product used as a fuel for a diesel engine, and examples include diesel fuel. The biofuel is not particularly limited as long as it is a fuel manufactured using renewable organic resources (biomass) of biological origin.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, and the embodiments and effects thereof, but the present invention is not limited to these examples.

The polyacetal resin compositions in Examples and Comparative Examples were prepared as follows.
<Manufacture of polyacetal resin (A)>
100 parts by mass of trioxane, 4 parts by mass of 1,3-dioxolane, and boron trifluoride diethyl etherate as a catalyst in a biaxial continuous polymerization machine having a self-cleaning type paddle having a jacket set at a temperature of 65 ° C. An amount of 0.05 mmol with respect to 1 mol of total monomers (trioxane and 1,3-dioxolane) is used as a benzene solution, and an amount of 500 mg of methylal with all monomers as a molecular weight modifier is used as a benzene solution continuously. The polymerization reaction was continuously carried out such that the raw materials and the polymerization reaction product stay in the continuous polymerization machine for 20 minutes.

  To the resulting polymerization reaction product, triphenylphosphine was added as a benzene solution in an amount of 2 mol per 1 mol of boron trifluoride diethyl etherate used. After deactivating the catalyst, it was pulverized to obtain polyacetal resin (A).

<Production of Polyacetal Resin Composition>
Polyacetal resin (A), mold release agent (B), layered double hydroxide or other metal hydroxide (C), antioxidant (D) in the compounding amount (unit: mass part) described in Table 1 Are mixed and heated at a temperature range of 210 to 230 ° C. with a twin screw extruder of 30 mm in diameter, and devolatized under a reduced pressure of 21.3 kPa to obtain the polyacetals of Examples 1 to 5 and Comparative Examples 1 to 4 Pellets of the resin composition were prepared.

The meanings of the symbols described in the examples and comparative examples of Table 1 are as follows.
<B: mold release agent>
B-1: Polyethylene wax (High Wax 220MP, manufactured by Mitsui Chemicals, Inc., molecular weight 2000)
<C: Layered Double Hydroxide or Other Metal Hydroxide>
C-1: Hydrotalcite (Hycite 713, manufactured by CLARIANT)
C-2: Magnesium hydroxide (KISUMA 5A, manufactured by Kyowa Chemical Industry Co., Ltd.)
<D: Antioxidant>
D-1: Pentaerythritol tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate] (IRGANOX® 1010, manufactured by BASF)

  Each physical property of the polyacetal resin composition in an Example and a comparative example was measured as follows. The evaluation results of the polyacetal resin compositions of Examples and Comparative Examples are described in Table 1.

<Removal evaluation>
The releasability evaluation was performed as follows. A container (box-shaped molded container) molded into a 30 mm × 50 mm × 30 mm box having a rib in the center using the polyacetal resin composition of the example and the comparative example, using an injection molding machine PS40 manufactured by Nissei Resin Industries The molding was carried out fully automatically. The pressing pressure applied to the ejector pin when the box-shaped molded container was released was measured using a pin-type pressure sensor. The average value of the pressing pressure applied to the ejector pins from the 11th shot to the 30th shot among the 30 shots continuously molded was taken as the release resistance value of each sample of the example and the comparative example.離 (excellent) when the mold release resistance value is 3.1 MPa or less, 、 (good) when it is over 3.1 MPa and 4.1 MPa or less, and × (poor) when it is over 4.1 MPa.

<Fuel oil resistance evaluation>
The fuel oil resistance evaluation was performed in the following procedure. The schematic of the apparatus used for fuel oil resistance evaluation was shown in FIG. First, 300 mL of a mixed solution of toluene / isooctane / methanol = 42.5 / 42.5 / 15.0 vol% was placed as a fuel for fuel oil resistance evaluation in a pressure tight container. About 10 g of glass wool was placed in a pressure-tight container containing the fuel, and the box-shaped molded container used for the evaluation of releasability described above was placed on the glass wool so as not to be in direct contact with the fuel. In a box-shaped molded container, 6 mL of the same fuel was put, and the lid of the pressure tight container was closed.
The pressure-tight container containing the box-shaped formed container was heated in a water bath at 60 ° C. for 300 hours to expose the box-shaped formed container to fuel vapor. After 300 hours, the box-shaped formed container was taken out from the pressure-resistant sealed container, and the fuel adhering to the box-shaped formed container was air-dried, and then the inner bottom surface of the box-shaped formed container was observed.
It evaluated by the ratio (eluting amount) which the eluted component occupies on the inner bottom face part of a box-shaped shaping | molding container, and evaluated it with the numerical value of the following 1-5 steps. 1 is best and 5 is not best.
1: No elution was observed. 0% ≦ elution amount ≦ 5%.
2: Very slight elution is observed. 5% <dissolution amount ≦ 10%.
3: Slight elution is observed. 10% <dissolution amount ≦ 25%.
4: Elution is observed. 25% <dissolution amount ≦ 50%.
5: A large amount of elution is observed. 50% <dissolution amount.

<Stability thermal stability evaluation>
After the polyacetal resin compositions of Examples and Comparative Examples are melted and held in 12-minute intervals up to 72 minutes in a cylinder of Toshiba Machine Injection Molding Machine IS75E-2B heated to 240 ° C., the polyacetal resin composition is A thin plate having a thickness of 3 mm was formed using this, and the time (minute) in which silver streaks were observed on the formed thin plate (formed piece) was visually evaluated. It is practical if the time at which the silver streak is observed is 48 minutes or more, and it means that the longer the time, the better the thermal stability.

<Molded piece silver generation rate evaluation>
100 pieces of molded pieces of 150 mm in length, 13 mm in width, and 1.5 mm in thickness were molded using the polyacetal resin compositions of Examples and Comparative Examples with a Toshiba machine injection molding machine EC-100SA heated to 200 ° C. The number of silver streaks (silver) generated on the obtained molded piece was counted and evaluated by the following 1 to 5 numerical values. 1 is best and 5 is not best.
1: There is almost no silver occurrence. 0% ≦ silver occurrence rate ≦ 5%.
2: There is a slight silver occurrence. 5% <Silver generation rate ≦ 10%.
3: There is silver occurrence. 10% <silver occurrence rate ≦ 20%.
4: There is a lot of silver occurrence. 20% <Silver occurrence rate ≦ 40%.
5: Outstanding silver occurrence. 40% <Silver occurrence rate.

<Evaluation of the incidence of molded piece silver after melting and holding>
In addition to the above evaluation of the formation rate of silver generation rate, after polyacetal resin compositions of Examples and Comparative Examples are melted and held for 10 minutes in a molding machine, 20 pieces of formation 150 mm long, 13 mm wide and 1.5 mm thick are formed did. The number of silver streaks generated on the obtained molded piece was counted and evaluated by the following 1 to 5 numerical values. 1 is best and 5 is not best.
1: There is almost no silver occurrence. 0% ≦ silver occurrence rate ≦ 5%.
2: There is a slight silver occurrence. 5% <Silver generation rate ≦ 10%.
3: There is silver occurrence. 10% <silver occurrence rate ≦ 20%.
4: There is a lot of silver occurrence. 20% <Silver occurrence rate ≦ 40%.
5: Outstanding silver occurrence. 40% <Silver occurrence rate.

  According to Examples 1 to 5 and Comparative Examples 1 to 4, a polyacetal resin composition comprising a polyacetal resin (A), a polyolefin wax as a releasing agent (B) and a layered double hydroxide (C), which is a polyacetal The polyacetal resin composition in which the content of the release agent (B) in the resin composition is 0.01 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A) It is understood that the fuel oil resistance and the retention heat stability are excellent, and furthermore, the silver generation rate is low and the appearance is also good. Comparative Example 1 is an example of a polyacetal resin composition to which the layered double hydroxide (C) is not added, and Comparative Examples 2 to 4 are polyacetal resins to which magnesium hydroxide is added instead of the layered double hydroxide (C). It is an example of a composition. Although the releasability, fuel oil resistance, and retention heat stability are good, the silver generation rate was high because the layered double hydroxide (C) was not added.

  From the above, it contains polyacetal resin (A), mold release agent (B) and layered double hydroxide (C), and the mold release agent (B) is a polyolefin-based wax, and the above-mentioned polyacetal resin composition The polyacetal resin composition in which the content of the releasing agent (B) is 0.01 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A) is excellent in thermal stability and in contact with fuel There is little elution of the components of the resin composition at the time of molding, good releasability from the mold at the time of molding, and the generation of silver streaks in the molded product is suppressed even when the resin is melted and retained by the molding machine. It is understood that the heat stability, fuel oil resistance, releasability and appearance are excellent.

Claims (14)

A polyacetal resin composition comprising a polyacetal resin (A), a releasing agent (B) and a layered double hydroxide (C) represented by the following general formula (1), wherein the releasing agent (B) is A polyolefin-based wax, wherein the content of the release agent (B) in the polyacetal resin composition is 0.01 parts by mass or more and 1.0 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A) , Polyacetal resin composition.
[(M 2 ⁺ ) _x (M ^{3 +} ) _y (OH) _{2 (x + y)} ] (A ^{n −} ) _{x / n} · z (H ₂ O) (1)
(In the formula (1), M ²⁺ is a divalent metal ion, M ³⁺ is a trivalent metal ion, A ^n-represents an n-valent anion, may include a plurality of anions. Further, x is in the range of 0 <x ≦ 6.0, n is an integer of 1 to 3, and y and z are numbers of 0 or more.)   The polyacetal resin composition according to claim 1, wherein the release agent (B) is a polyethylene-based wax.   The polyacetal resin composition according to claim 2, wherein the viscosity average molecular weight of the polyethylene wax is 500 or more and 15,000 or less.   The content of the releasing agent (B) in the polyacetal resin composition is 0.04 parts by mass or more and 0.15 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A). The polyacetal resin composition as described in any one of 3.   The content of the layered double hydroxide (C) in the polyacetal resin composition is 0.01 parts by mass or more and 0.07 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A). Polyacetal resin composition as described in any one of 1-4.   The polyacetal resin composition according to any one of claims 1 to 5, wherein the layered double hydroxide (C) is a hydrotalcite. The hydrotalcite, wherein a general formula (1) ^{M 2+} in the ^{Mg 2+, M 3+} is the ^{Al 3+, A n-is} _CO ^{3 2-} and / or OH ^- is, according to claim 6 Polyacetal resin composition.   Furthermore, the polyacetal as described in any one of Claims 1-7 which contains an antioxidant (D) 0.01 mass part or more and 3.0 mass parts or less with respect to 100 mass parts of said polyacetal resin (A). Resin composition.   The antioxidant (D) is pentaerythritol-tetrakis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propionate], 1,3,5-trimethyl-2,4,6-tris. (3,5-di-tert-butyl-4-hydroxybenzyl) benzene, and 3,3 ′, 3 ′ ′, 5,5 ′, 5 ′ ′-hexa-tert-butyl-α, α ′, α ′ ′- The polyacetal resin composition according to claim 8, which is one or more selected from the group consisting of mesitylene-2,4,6-triyl) tri-p-cresol.   The content of the antioxidant (D) in the polyacetal resin composition is 0.03 parts by mass or more and 0.20 parts by mass or less with respect to 100 parts by mass of the polyacetal resin (A). Or polyacetal resin composition as described in 9.   The molded object which has a polyacetal resin composition as described in any one of Claims 1-10.   The polyacetal resin composition according to any one of claims 1 to 10, which is used for parts in contact with fuel.   The shaped body according to claim 11, which is a part in contact with fuel.   The molded article according to claim 13, wherein the fuel is one or more selected from the group consisting of gasoline fuel, gasohol fuel, diesel fuel and biofuel.