JP2016084388A - Polyacetal resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal resin composition excellent in heat stability, flowability (low melt viscosity) and mechanical physical property.SOLUTION: There is provided a polyacetal resin composition containing 100 pts.mass of (A) a polyacetal resin, 0.01 to 10 pts.mass of (B) at least one kind of siloxane-based compound represented by the formula (I). (I), where Ris each independently a C1 to 11 alkyl group, Ris each independently a C12 to 36 alkyl group, n, m and p are 0 to 58, m or p are not 0 at same time and N represented by n+m+p+2 is 15 to 75.SELECTED DRAWING: None

Description

  The present invention relates to a polyacetal resin composition having excellent thermal stability, fluidity (low melt viscosity), and mechanical properties.

  Polyacetal resin has excellent properties in mechanical properties, thermal properties, electrical properties, slidability, moldability, etc., mainly as electrical materials, automotive parts, precision machine parts as structural materials and mechanical parts. Widely used in etc.

  With the expansion of the field in which polyacetal resins are used, the required characteristics tend to become more sophisticated, complex and specialized. Among them, a polyacetal resin composition excellent in fluidity and thermal stability has been studied.

  For example, Patent Document 1 proposes a polyacetal resin composition having oxymethylene (polyacetal) as a main constituent unit, 2-10 mol% comonomer units, a polyacetal oligomer content of 50-5000 ppm, and a fluorine content of 3-13 ppm. Has been. Patent Document 2 proposes a thermoplastic molding material containing polyoxymethylene (polyacetal) containing branched polycarbonate or branched polyester.

International Publication No. 96/13548 Special table 2008-517114 gazette

  However, the polyacetal resin composition described in Patent Document 1 has room for further improvement in terms of fluidity and thermal stability, and the degree of mechanical properties is unknown. Further, the thermoplastic molding material described in Patent Document 2 has room for further improvement in terms of fluidity, and the degree of thermal stability and mechanical properties is unknown. As described above, it is difficult to obtain a resin composition having all of thermal stability, fluidity (low melt viscosity), and mechanical properties by a conventionally known technique.

  An object of the present invention is to solve these problems and to provide a polyacetal resin composition excellent in thermal stability, fluidity (low melt viscosity), and mechanical properties.

  As a result of intensive studies to solve the above problems, the present inventors have solved the above problems and achieved the object by combining (A) a polyacetal resin and a specific (B) siloxane compound. The inventors have found that a polyacetal resin composition can be obtained, and have completed the present invention. More specifically, the present invention provides the following.

［式（Ｉ）中、
Ｒ^１は、互いに無関係に、１以上１１以下の炭素原子を有するアルキル基であり、
Ｒ^２は、互いに無関係に、１２以上３６以下の炭素原子を有するアルキル基であり、
ｎ、ｍ、ｐは、０以上５８以下であり、
ｍ又はｐは、同時に０ではなく、
ｎ＋ｍ＋ｐ＋２で表されるＮは、１５以上７５以下である。］ (1) The present invention contains (A) 100 parts by mass of a polyacetal resin, and (B) 0.01 parts by mass or more and 10 parts by mass or less of at least one siloxane compound represented by the following formula (I). It is a polyacetal resin composition.

[In the formula (I),
R ¹ is an alkyl group having 1 to 11 carbon atoms independently of each other;
R ² is an alkyl group having 12 or more and 36 or less carbon atoms regardless of each other;
n, m, and p are 0 or more and 58 or less,
m or p are not simultaneously 0,
N represented by n + m + p + 2 is 15 or more and 75 or less. ]

(2) In the present invention, in Formula (I), R ¹ is an alkyl group having 1 to 4 carbon atoms independently of each other, and R ² is 20 or more independently of each other. An alkyl group having 30 or less carbon atoms, the n is 0 or more and 30 or less, the m is 10 or more and 58 or less, the p is 0 or more and 10 or less, and the N is 30 or more and 60 or less. The polyacetal resin composition according to (1).

(3) Further, the present invention is the above formula (I), wherein R ¹ is a methyl group, and R ² is an alkyl group having 24 to 30 carbon atoms regardless of each other, and the n Is a polyacetal resin composition according to (2), in which m is from 30 to 48, m is from 30 to 48, p is 0, and N is from 40 to 50.

  (4) Moreover, this invention is a polyacetal resin composition of any one of (1) to (3) whose content of the said (B) component is 0.1 mass part or more and 4 mass parts or less. It is.

  (5) In the present invention, the (A) polyacetal resin comprises: (a1) / (a2): (a1) trioxane and (a2) one or more compounds selected from cyclic ether and cyclic formal The polyacetal according to any one of (1) to (4), comprising a polyacetal copolymer obtained by copolymerization at a ratio (mass ratio) of 99.5 / 0.5 to 90.0 / 10.0 It is a resin composition.

  (6) Further, the present invention provides (1) to (5), wherein the amount of unstable terminal groups of the (A) polyacetal resin is 0.5 parts by mass or less with respect to the mass of the (A) polyacetal resin. It is the polyacetal resin composition of any one.

(7) Further, in the present invention, the melt viscosity (measured with a capillary rheometer at 200 ° C., 1216 s ⁻¹ ) of the polyacetal resin (A) is from 50 MPa to 700 MPa in (1) to (6) It is the polyacetal resin composition of any one.

(8) Moreover, this invention is a polyacetal resin composition of any one of Claim 1 to 7 whose thermal stability index | alpha (alpha) shown by following formula (II) is 0.03 or less.
α = log (MI ₃₀ ) −log (MI ₇ ) (II)
[In the formula (II),
MI ₇ is a melt index value obtained by measuring a residence time in a cylinder at 200 ° C. and a load of 2.16 kg in 7 minutes,
MI ₃₀ is a melt index value obtained by measuring the residence time in a cylinder at 200 ° C. and a load of 2.16 kg in 30 minutes. ]

  The polyacetal resin composition of the present invention is excellent in thermal stability, fluidity (low melt viscosity), and mechanical properties, and is particularly suitable as a raw material for injection molded parts.

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

<Polyacetal resin composition>
The polyacetal resin composition according to the present invention contains (A) 100 parts by mass of a polyacetal resin and (B) 0.01 parts by mass or more and 10 parts by mass or less of a specific siloxane compound. Hereinafter, (A) polyacetal resin is also referred to as “component (A)”, and (B) a specific siloxane compound is also referred to as “component (B)”.

[(A) polyacetal resin]
The polyacetal resin of component (A) is a polymer compound having an oxymethylene group (—OCH ₂ —) as a main constituent unit, and includes a polyacetal homopolymer consisting essentially of repeating oxymethylene units, in addition to oxymethylene units. Polyacetal copolymers containing other comonomer units are representative resins. Furthermore, polyacetal resins include copolymers in which a branched structure or a crosslinked structure has been introduced by copolymerizing a branch-forming component or a crosslinking-forming component, polymer units composed of repeating oxymethylene groups, and other polymer units. Also included are block copolymers, graft copolymers and the like. These polyacetal resins can be used alone or in combination of two or more.

  In general, a polyacetal homopolymer is produced by polymerization of anhydrous formaldehyde or trioxane (a cyclic trimer of formaldehyde), and is usually stabilized against thermal decomposition by esterifying its terminal.

On the other hand, polyacetal copolymer is generally formaldehyde or a cyclic oligomer of formaldehyde (for example, trioxane) represented by general formula (CH ₂ O) _n [wherein n represents an integer of 3 or more] It is produced by copolymerization with a comonomer such as cyclic ether or cyclic formal, and is usually stabilized against thermal decomposition by removing terminal unstable parts by hydrolysis.

  Examples of the main raw material of the polyacetal copolymer include trioxane and tetraoxane, and (a1) trioxane is usually used.

  The comonomer includes a cyclic ether, a glycidyl ether compound, a cyclic formal, a cyclic ester (eg, β-propiolactone), a vinyl compound (eg, styrene, vinyl ether, etc.), and the like.

  Examples of the cyclic ether include ethylene oxide, propylene oxide, butylene oxide, cyclohexene oxide, epichlorohydrin, epibromohydrin, styrene oxide, oxetane, 3,3-bis (chloromethyl) oxetane, tetrahydrofuran and the like.

  Examples of the glycidyl ether compound include alkyl or aryl glycidyl ether (for example, methyl glycidyl ether, ethyl glycidyl ether, phenyl glycidyl ether, naphthyl glycidyl ether, etc.), alkylene or polyalkylene glycol diglycidyl ether (for example, ethylene glycol diglycidyl ether). , Triethylene glycol diglycidyl ether, butanediol diglycidyl ether, etc.), alkyl or aryl glycidyl alcohol, and the like.

  Examples of the cyclic formal include 1,3-dioxolane, propylene glycol formal, diethylene glycol formal, triethylene glycol formal, 1,4-butanediol formal, 1,5-pentanediol formal, 1,6-hexanediol formal, and trioxepane. Etc.

  These comonomers can be used alone or in combination of two or more. Of these comonomers, (a2) cyclic ethers and / or cyclic formals are usually used, and in particular, cyclic ethers such as ethylene oxide, and cyclics such as 1,3-dioxolane, 1,4-butanediol formal, and diethylene glycol formal. Formal is preferred.

  The ratio of these comonomer (for example, cyclic ether and / or cyclic formal) units is not particularly limited, but is generally 0.1 parts by mass or more and 20 parts by mass or less, preferably 0 with respect to the entire polyacetal resin. 5 parts by mass or more and 10 parts by mass or less, more preferably 1 part by mass or more and 5 parts by mass or less. When the ratio of the comonomer unit is not in the range of 0.1 parts by mass or more and 20 parts by mass or less, the thermal stability and mechanical properties of the polyacetal resin may be lowered.

  The type of the polyacetal resin as the component (A) is not particularly limited, but among them, the component (A) is composed of (a1) trioxane and (a2) cyclic ether in that it is more excellent in thermal stability and molding processability. And one or more compounds selected from cyclic formal are copolymerized at a ratio (mass ratio) of (a1) / (a2) = 99.5 / 0.5 to 90.0 / 10.0. It is preferable that it contains a polyacetal copolymer.

  The polyacetal resin (A) component preferably has an amount of unstable terminal groups of 0.5 parts by mass or less based on the mass of the (A) polyacetal resin. In this specification, the “unstable end group amount” refers to the amount of a portion present in the end portion of the polyacetal copolymer that is unstable to heat and base and easily decomposes. The amount of such unstable end groups is as follows: 1 g of polyacetal copolymer is placed in a pressure-resistant airtight container with 100 ml of 50% (volume%) aqueous methanol solution containing 0.5% (volume%) ammonium hydroxide, and at 180 ° C. for 45 minutes. The amount of formaldehyde decomposed and dissolved in the solution obtained by cooling and opening after heat treatment was quantified, and expressed in mass% with respect to the polyacetal copolymer.

  When the polyacetal resin of the component (A) does not have the above terminal properties and exceeds the upper limit value, it becomes difficult to obtain a polyacetal resin composition having excellent thermal stability. From such a viewpoint, the polyacetal resin of component (A) preferably has an unstable terminal group amount of 0.5 parts by mass or less, particularly 0.4 parts by mass or less, based on the mass of (A) polyacetal resin. Those are preferred. In addition, the minimum of the amount of unstable terminal groups is not specifically limited.

The melt viscosity of the polyacetal resin (A) is preferably in the range of 50 MPa to 700 MPa, particularly preferably in the range of 100 MPa to 500 MPa. In this specification, melt viscosity shall mean the value in 200 degreeC and 1216s < ^-1 > measured with the capillary-type rheometer. If the melt viscosity is too low or too high, the effects of the present invention may not be sufficiently obtained, and the molding processability and mechanical properties may be lowered.

[(B) Specific siloxane compound]
The polyacetal resin composition according to the present invention contains (B) a specific siloxane compound, specifically, a siloxane compound represented by the following formula (I). (B) When the structure of a specific siloxane compound is different from that of the compound of formula (I), improving the thermal stability, mechanical properties and melt viscosity of the polyacetal resin composition, as will be described later in the examples, Difficult and the improvement effect is insufficient.

In the formula (I), R ¹ is an alkyl group having 1 to 11 and preferably 1 to 4 carbon atoms independently of each other, and particularly preferably a methyl group. R ² is an alkyl group having 12 to 36 carbon atoms, independently of each other, preferably an alkyl group having 20 to 30 carbon atoms, and particularly preferably 24 to 30 carbon atoms. It is an alkyl group. n, m, and p are 0 or more and 58 or less, and m or p are not 0 at the same time. n is preferably 0 or more and 30 or less, and particularly preferably 0 or more and 18 or less. m is preferably 10 or more and 58 or less, and particularly preferably 30 or more and 48 or less. p is preferably 0 or more and 10 or less, particularly preferably 0. Further, N represented by n + m + p + 2 is 15 or more and 75 or less, preferably 30 or more and 60 or less, and particularly preferably 40 or more and 50 or less.

Examples of compounds satisfying formula (I)
A siloxane having a methyl group as R ¹ and an alkyl group having 24 to 28 carbon atoms as R ² , n is 0, m is 38, p is 0, and N is 40 Compounds,
A siloxane having a methyl group as R ¹ and an alkyl group having from 24 to 28 carbon atoms as R ² , n is 0, m is 48, p is 0, and N is 50 Compounds,
A siloxane compound having a methyl group as R ¹ and an alkyl group having 30 carbon atoms as R ² , n is 18, m is 30, p is 0 and N is 50;
Etc.

  Moreover, as an example of the commercial item which satisfies Formula (I), TEGOPREN 6846 etc. obtained from Evonik Goldschmidt GmbH is mentioned.

  The compounds of formula (I) can be obtained by reaction of the corresponding hydrogen siloxanes with unsaturated hydrocarbons or by direct reaction of unsaturated polyesters with hydrogen siloxanes. The reaction can be carried out by hydrosilylation or by dehydrogenative hydrosilylation as described in EP 1640418.

  (B) Content of component is 0.01 mass part or more and 10 mass parts or less with respect to 100 mass parts of polyacetal resin of (A) component, and 0.1 mass by the point from which a higher mechanical physical property is obtained. It is preferable that they are 4 parts by mass or more. When the content of the component (B) is less than 0.01 parts by mass, the improvement of the melt viscosity of the polyacetal resin composition is insufficient, and when it exceeds 10 parts by mass, it is difficult to uniformly mix both components.

[Other ingredients]
In addition to (A) polyacetal resin and (B) specific siloxane compound, various known stabilizers can be further blended in the polyacetal resin composition of the present invention. Examples of stabilizers include one or more of hindered phenol compounds, nitrogen-containing compounds, alkali or alkaline earth metal hydroxides, inorganic salts, carboxylates, and the like. . Moreover, in order to improve the physical properties according to the intended use, various known additives can be further blended. Examples of additives include various colorants, lubricants, nucleating agents, surfactants, heterogeneous polymers, organic polymer modifiers, and inorganic, organic, metal, etc. fibrous, granular, and plate-like fillers. 1 type or 2 types or more can be mixed and used.

[Evaluation of thermal stability]
The present invention provides a resin composition having excellent thermal stability, fluidity (low melt viscosity), and mechanical properties by combining (A) a polyacetal resin and a specific (B) siloxane compound. Is to get. Here, the thermal stability can be determined by a thermal stability index α represented by the following formula (II).
α = log (MI ₃₀ ) −log (MI ₇ ) (II)

In formula (II),
MI ₇ is a melt index value obtained by measuring a residence time in a cylinder at 200 ° C. and a load of 2.16 kg in 7 minutes,
MI ₃₀ is a melt index value obtained by measuring the residence time in a cylinder at 200 ° C. and a load of 2.16 kg in 30 minutes.

  When the thermal stability index α of the polyacetal resin composition is equal to the value of the (A) polyacetal resin, it indicates that the thermal stability is not deteriorated due to the blending of the thermal stability of the (B) siloxane compound. ing. Further, when the thermal stability index α of the polyacetal resin composition is lower than the value of the (A) polyacetal resin, the thermal stability is improved by blending the thermal stability of the (B) siloxane compound. It is shown that. On the other hand, when the thermal stability index α of the polyacetal resin composition is higher than that of the (A) polyacetal resin, the thermal stability deteriorates due to the blending of the thermal stability of the (B) siloxane compound. It shows that you are doing.

  If a preferable value of the thermal stability index α of the polyacetal resin composition is defined, it is 0.03 or less, while the lower limit of the thermal stability index α is not particularly limited.

[Method for preparing polyacetal resin composition]
In this invention, the specific aspect of the preparation method of the said polyacetal resin composition is not specifically limited, Generally, it can prepare with a well-known equipment and method as a preparation method of a synthetic resin composition or its molded article. That is, necessary components can be mixed and kneaded using an extruder or other melt kneader to prepare pellets for molding. A plurality of extruders or other melt kneaders may be used. In particular, as an extruder used for the preparation of the resin composition of the present invention, a twin-screw extruder is used from the viewpoint of improving mechanical properties and (B) compatibility of specific siloxane compounds. preferable.

  The composition of the components constituting the polyacetal resin composition may be added to any stage, for example, once added to the polyacetal resin of component (A), or may be added at the time of adjusting the resin composition, and the final molded product may be added. It is also possible to add and mix immediately before obtaining.

[Molding method and use of polyacetal resin composition]
Conventionally known molding methods (for example, injection molding, extrusion molding, compression molding, blow molding, vacuum molding, foam molding, rotational molding, gas injection molding, etc.) are employed using the polyacetal resin composition of the present invention as a raw material. Thus, various molded products can be molded. In particular, it is suitable for injection molding. The molded product formed by molding the resin composition of the present invention can be used for various applications such as automobile parts, electrical / electronic parts, machine parts, building materials, life-related parts, makeup-related parts, and medical-related parts.

  Hereinafter, the present invention will be described more specifically based on examples, but the present invention is not limited to these examples.

<Examples and Comparative Examples>
[Preparation of polyacetal resin composition]

The raw materials in Table 1 and Table 2 are as follows.
(A) Polyacetal resin (A1) (a1) A polyacetal resin obtained by copolymerizing 96.3% by mass of trioxane and 3.7% by mass of (a2) 1,3-dioxolane. It is 0.4 mass% with respect to polyacetal resin, and the melt viscosity in 200 degreeC and 1216s < ^-1 > is 292.9 Mpa.
(A2) A polyacetal resin obtained by copolymerizing 96.3% by weight of (a1) trioxane and 3.7% by weight of (a2) 1,3-dioxolane, wherein the amount of unstable terminal groups is relative to that of the polyacetal resin. 0.4% by mass, and the melt viscosity at 200 ° C. and 1216 s ⁻¹ is 425.4 MPa.
(B) Specific siloxane-based compound (B1) TEGOPREN 6846 (Evonik Goldschmidt GmbH)
(B) Siloxane-based compound different from component (B) (b2) TEGOMER HSi6440P (Evonik Goldschmidt GmbH)
(B3) TEGOMER FR100 (Evonik Goldschmidt GmbH)
(B4) TEGOMER PP-Si401 (Evonik Goldschmidt GmbH)
(B5) TEGOMER ANTISCRATCH 200 (Evonik Goldschmidt GmbH)

Using a twin screw extruder, the raw materials were melt-kneaded under the ratios shown in Tables 1 and 2 and the conditions shown in [Extrusion Conditions] below to prepare a pellet-like polyacetal resin composition.
[Extrusion conditions]
Extruder: TEX-30, manufactured by Nippon Steel Works, Ltd. Screw rotation speed: 150 rpm
Extrusion flow rate: 12kg / h
Barrel temperature: 160-200 ° C
Die temperature: 200 ° C

[Evaluation]
Using the obtained pellets, a predetermined test piece was molded by an injection molding machine under the conditions shown in [Molding conditions] below.
[Molding condition]
Molding machine: ROBOSHOT S2000i100B, screw diameter 28mm, manufactured by FANUC Cylinder temperature: 200 ° C
Mold temperature: 90 ° C (water temperature control)

  Subsequently, the test piece was evaluated for thermal stability, fluidity, tensile properties, bending properties, and Charpy impact strength. The results are shown in Tables 3 and 4.

(1) Thermal stability Melt index value MI ₇ (190 ° C., load 2.16 kg, residence time in cylinder 7 minutes), and melt index value MI ₃₀ (200 ° C., residence time in cylinder 30 minutes) A load of 2.16 kg and a residence time in the cylinder of 30 minutes were measured, and a thermal stability index α was calculated according to the following formula (II).
α = log (MI ₃₀ ) −log (MI ₇ ) (II)
Here, when α is high, the resin is decomposed due to an increase in the residence time in the cylinder, indicating that the thermal stability is poor. On the other hand, when α is low, the thermal stability is excellent. It shows that.

(2) Tensile properties Tensile strength (MPa) was measured in accordance with ISO527-1,2.

(3) Bending characteristics Based on ISO178, bending strength (MPa) was measured.

(4) Charpy impact strength (with notch)
Charpy impact strength (notched) (kJ / m ² ) was measured according to ISO 179 / 1eA.

(5) Fluidity (melt viscosity)
Using the pellet-like sample, the melt viscosity (Pa · s) at 200 ° C. and 1216 s ⁻¹ was measured with a capillary rheometer (Capillograph manufactured by Toyo Seiki Co., Ltd.).

表３において、「＊」は、押出成形の際、ベントに析出物が顕著に見られ、樹脂組成物を均一に混合するのが難しかったことを示す。

In Table 3, “*” indicates that precipitates were significantly observed in the vent during extrusion molding, and it was difficult to uniformly mix the resin composition.

[Comparison between Examples 1 to 3 and Comparative Examples 1 to 6]
From the comparison of the results in Table 3, it can be seen that Examples 1 to 3 of the polyacetal resin composition satisfying the requirements of the present invention have a lower thermal stability index than Comparative Example 1 and are excellent in thermal stability. Similarly, it can be seen that the melt viscosity is extremely lower than that of Comparative Example 1, and the molding processability is excellent. In addition, it can be seen that Examples 1 and 2 have good mechanical properties with little decrease in mechanical properties.

  On the other hand, in the case of Comparative Example 2 that does not satisfy the requirements of the present invention, the amount of component B1 is excessive, so that precipitates are noticeably seen in the vent during extrusion, and it can be seen that uniform mixing is difficult. Moreover, in the case of the comparative example 3, it turns out that a thermal stability index is high and it is inferior to thermal stability. In addition, in the case of Comparative Example 4, the mechanical properties (tensile strength, bending strength) are low, and it can be seen that the improvement in melt viscosity is insufficient compared to Example 2 of the same blending amount. Moreover, in the case of the comparative example 5, it turns out that a thermal stability index | exponent is high, is inferior to thermal stability, and improvement of melt viscosity is inadequate compared with Example 1 of the same compounding quantity. And in the case of the comparative example 6, it turns out that the improvement of melt viscosity is inadequate compared with Example 2 of the same compounding quantity.

[Comparison between Examples 4 and 5 and Comparative Examples 1, 7 and 8]
From the comparison of the results in Table 4, it can be seen that Examples 4 and 5 of the polyacetal resin composition satisfying the requirements of the present invention have a lower thermal stability index than Comparative Example 7 and are excellent in thermal stability. Similarly, it can be seen that the melt viscosity is extremely lower than that of Comparative Example 7, and the molding processability is excellent. In addition, it can be seen that the mechanical properties are less deteriorated and have good mechanical properties. Furthermore, Examples 4 and 5 have higher Charpy impact strength than Comparative Example 1 whose melt viscosity is higher than these, and have an excellent balance of physical properties that achieves both high fluidity and impact resistance. Recognize.

  On the other hand, in the case of Comparative Example 8 that does not satisfy the requirements of the present invention, the thermal stability index is high, the thermal stability is inferior, and the mechanical properties (tensile strength, bending strength) are low. It can be seen that the improvement of the melt viscosity is insufficient as compared to Example 5.

Claims (8)

(A) 100 parts by mass of polyacetal resin;
(B) A polyacetal resin composition containing at least one siloxane compound represented by the following formula (I) in an amount of 0.01 to 10 parts by mass.

[In the formula (I),
R ¹ is an alkyl group having 1 to 11 carbon atoms independently of each other;
R ² is an alkyl group having 12 or more and 36 or less carbon atoms regardless of each other;
n, m, and p are 0 or more and 58 or less,
m or p are not simultaneously 0,
N represented by n + m + p + 2 is 15 or more and 75 or less. ] In the formula (I),
R ¹ is an alkyl group having 1 to 4 carbon atoms independently of each other;
R ² is an alkyl group having 20 to 30 carbon atoms regardless of each other;
N is 0 or more and 30 or less,
M is 10 or more and 58 or less,
The p is 0 or more and 10 or less,
The polyacetal resin composition according to claim 1, wherein the N is 30 or more and 60 or less. In the formula (I),
R ¹ is a methyl group,
R ² is an alkyl group having 24 or more and 30 or less carbon atoms regardless of each other;
N is 0 or more and 18 or less,
M is 30 or more and 48 or less,
The p is 0;
The polyacetal resin composition according to claim 2, wherein the N is 40 or more and 50 or less.   The polyacetal resin composition according to any one of claims 1 to 3, wherein a content of the component (B) is 0.1 parts by mass or more and 4 parts by mass or less.   The (A) polyacetal resin comprises (a1) trioxane and (a2) one or more compounds selected from cyclic ether and cyclic formal, (a1) / (a2) = 99.5 / 0.5 to The polyacetal resin composition according to any one of claims 1 to 4, comprising a polyacetal copolymer obtained by copolymerization at a ratio (mass ratio) of 90.0 / 10.0.   The polyacetal resin composition according to any one of claims 1 to 5, wherein the amount of unstable terminal groups of the (A) polyacetal resin is 0.5 parts by mass or less based on the mass of the (A) polyacetal resin. . The polyacetal resin composition according to any one of claims 1 to 6, wherein the melt viscosity (measured with a capillary rheometer at 200 ° C, 1216s ^-1 ) of the (A) polyacetal resin is 50 MPa or more and 700 MPa or less. . The polyacetal resin composition according to any one of claims 1 to 7, wherein a thermal stability index α represented by the following formula (II) is 0.03 or less.
α = log (MI ₃₀ ) −log (MI ₇ ) (II)
[In the formula (II),
MI ₇ is a melt index value obtained by measuring a residence time in a cylinder at 200 ° C. and a load of 2.16 kg in 7 minutes,
MI ₃₀ is a melt index value obtained by measuring the residence time in a cylinder at 200 ° C. and a load of 2.16 kg in 30 minutes. ]