JP2017197636A - Polyacetal resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal resin composition, wherein, even when adopting a molding method in which a resin composition is exposed to high temperature for a long time, the pyrolysis of polyacetal resin is suppressed, and the amount of formaldehyde released from an obtained molding and die contamination are also suppressed.SOLUTION: A polyacetal resin composition contains (A) polyacetal resin 100 pts.mass, (B) hindered phenolic compound containing nitrogen of 0.001-0.2 pts.mass, (C) hindered phenolic compound containing no nitrogen of 0.001-0.3 pts.mass, and (D) talc 0.0001-0.1 pts.mass.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polyacetal resin composition. In particular, the present invention relates to a polyacetal resin composition suitable for a molding method in which a resin composition such as continuous molding using a hot runner mold is exposed to a high temperature for a long time.

Polyacetal resin is a crystalline resin, and since it is a resin material with excellent rigidity, strength, toughness, slidability, and creep, it has been used for mechanical parts such as automobile parts, electrical / electronic parts, and industrial parts. Widely used as a material.
In recent years, polyacetal resins have been increasingly demanded for low VOC mainly in the automobile field, and there is an increasing demand for polyacetal resins with a small amount of formaldehyde emission from the parts as resins used for automobile interior parts.

By the way, generally the cold runner metal mold | die is used for shaping | molding of polyacetal resin. However, when molding using a cold runner mold, unnecessary runner parts are also molded together with the target molded product, so the runner parts are discarded or crushed with a pulverizer etc. There is no choice but to rework molding by mixing a small amount with the raw material polyacetal resin pellets.
However, when the runner part is rework-molded, the runner is subjected to a thermal history, which may affect the resin fluidity in the molding machine cylinder, causing molding defects such as burrs and warpage, and stable productivity. May be difficult. Therefore, in recent years, from the viewpoint of stable productivity and production cost, there is an increasing tendency to select a hot runner mold for molding automobile interior parts and the like.
When continuous molding is performed using a hot runner mold, the manifold temperature in the hot runner mold (part where the molten resin stays: hot runner part) is generally set to a temperature equal to or higher than the molding machine cylinder temperature. Therefore, higher thermal stability is required for the polyacetal resin than in the case of continuous molding using a cold runner mold.

  Conventionally, various techniques have been proposed to solve the above-described requirements. For example, a method of adding calcium hydroxystearate and a metal deactivator to a polyacetal resin (for example, see Patent Document 1 below), a method of adding a hydrazide compound to a polyacetal resin (for example, see Patent Document 2 below), a polyacetal resin. A method of adding a polyvalent carboxylic acid hydrazide containing an aryl group to a polymer (for example, see Patent Document 3 below), a method of adding a hindered amine light stabilizer, an ultraviolet absorber, and a stabilizer having formaldehyde-reactive nitrogen to a polyacetal resin (See, for example, Patent Document 4 below), a method of adding an acid anhydride, a carboxylic acid metal salt, and a metal deactivator to a polyacetal resin (see, for example, Patent Document 5 below), and a small amount of talc in a polyacetal resin. A method of adding (for example, see Patent Document 6 below) has been proposed. .

Japanese Patent No. 312799 International Publication No. 2005/040275 Pamphlet (2005) Japanese Patent No. 4568018 JP 2012-92185 A JP 2013-23506 A Japanese Patent No. 4799534

However, the polyacetal resin composition obtained by various conventionally proposed methods has an improvement effect on moldability in a short time continuous molding using a cold runner mold. However, when continuously molded using a hot runner mold, the resin composition will stay in the hot runner manifold at a high temperature for a long time. It is difficult to reduce formaldehyde emission. Moreover, since it is continuous molding, there is a problem that the inside of the mold is easily contaminated with mold deposits.
Therefore, the present invention provides less thermal decomposition of the polyacetal resin when applying a molding method in which a resin composition such as continuous molding using a hot runner mold is exposed to a high temperature for a long time. It is an object of the present invention to provide a polyacetal resin composition with less formaldehyde emission and mold contamination.

  As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have found that a polyacetal resin composition containing a nitrogen-containing hindered phenol compound and talc in a specific ratio with respect to the polyacetal resin. In addition to this, it has been found that the use of a nitrogen-free hindered phenol compound in combination with the product can significantly improve the thermal stability and solve the above-mentioned problems. It came to complete.

That is, the present invention is as follows.
[1]
(A) 100 parts by mass of a polyacetal resin, (B) 0.001 to 0.2 parts by mass of a nitrogen-containing hindered phenol compound, and (C) 0.001 to 0.3 parts by mass of a nitrogen-free hindered phenol compound. (D) Polyacetal resin composition containing 0.0001-0.1 mass part of talc.
[2]
(B) Polyacetal resin composition as described in said [1] whose content of a nitrogen-containing hindered phenol compound is 0.001-0.15 mass part with respect to 100 mass parts of (A) polyacetal resin.
[3]
(B) The polyacetal resin composition according to [1] or [2], wherein the nitrogen-containing hindered phenol compound includes a hydrazine structure.
[4]
Furthermore, (E) as the other stabilizer, containing at least one selected from the group consisting of amino-substituted triazine compounds, urea derivatives, hydrazide derivatives, amide compounds, polyamides, and acrylamide copolymers, [1] to [ 3] The polyacetal resin composition according to any one of the above.

  According to the present invention, even when the polyacetal resin composition is molded under severe molding conditions in which the resin composition is exposed to a high temperature for a long time, such as continuous molding using a hot runner mold. In addition, it is possible to produce a molded product that suppresses thermal decomposition of the polyacetal resin, reduces mold contamination, and emits less formaldehyde.

The schematic of the molding machine used when evaluating a hot runner metal mold mold deposit property in an Example is shown.

Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail.
In addition, this invention is not limited to the following embodiment, It can implement by changing variously within the range of the summary.

<Polyacetal resin composition>
The polyacetal resin composition of the present embodiment includes (A) 100 parts by mass of a polyacetal resin, (B) 0.001 to 0.2 parts by mass of a nitrogen-containing hindered phenol compound, and (C) a nitrogen-free hindered phenol compound. 0.001-0.3 mass part and (D) talc 0.0001-0.1 mass part are contained.

[(A) polyacetal resin]
The polyacetal resin (A) contained in the polyacetal resin composition of the present embodiment refers to a polymer having an oxymethylene group in the main chain. For example, a formaldehyde monomer, or a trimer (trioxane) or a tetramer ( Polyacetal homopolymers consisting essentially of oxymethylene units obtained by homopolymerizing cyclic oligomers of formaldehyde such as tetraoxane); formaldehyde monomers or formaldehyde such as trimers (trioxane) and tetramers (tetraoxane) Obtained by copolymerizing a cyclic oligomer such as ethylene oxide, propylene oxide, epichlorohydrin, glycol such as 1,3-dioxolane, 1,4-butanediol formal, cyclic ether such as cyclic formal of diglycol, or cyclic formal. The polyacetal copolymer; polyacetal copolymer having a branched obtained by copolymerizing a monofunctional glycidyl ether; polyacetal copolymer or the like having a multifunctional glycidyl ether is copolymerized to obtain crosslinked structure.
Furthermore, (A) as a polyacetal resin, a block component obtained by polymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, polyalkylene glycol A polyacetal homopolymer having a functional group such as a hydroxyl group at both ends or one end, for example, a formaldehyde monomer or its trimer (trioxane) or tetramer (tetraoxane) in the presence of hydrogenated polybutadiene glycol A polyacetal copolymer having a block component obtained by copolymerizing a cyclic oligomer of formaldehyde and the like with a cyclic ether or cyclic formal can also be used.

<Polyacetal homopolymer>
The polyacetal homopolymer is produced, for example, by feeding formaldehyde as a monomer, a chain transfer agent (molecular weight regulator) and a polymerization catalyst to a polymerization reactor into which a hydrocarbon polymerization solvent is introduced and polymerizing by a slurry polymerization method. can do.
At this time, since the raw material monomer, the chain transfer agent, and the polymerization catalyst contain components capable of chain transfer (components that generate unstable terminal groups) such as water, methanol, and formic acid, these can be chain transferred first. It is preferable to adjust the content of these components.
The content of the component capable of chain transfer at this time is preferably in the range of 1 to 1000 ppm, more preferably 1 to 500 ppm, and still more preferably 1 to 300 ppm with respect to formaldehyde as the monomer.
By adjusting the amount of the component capable of chain transfer to the above range, a polyacetal resin homopolymer excellent in thermal stability can be obtained.

The molecular weight of the polyacetal homopolymer can be adjusted by chain transfer using a molecular weight regulator such as carboxylic anhydride or carboxylic acid.
As the molecular weight regulator, propionic anhydride and acetic anhydride are particularly preferable, and acetic anhydride is more preferable.
The amount of the molecular weight regulator introduced is determined by adjusting according to the characteristics (particularly the melt flow rate) of the target polyacetal homopolymer. For example, the polyacetal homopolymer preferably has a melt flow rate (MFR value (according to ISO 1133)) in the range of 0.1 to 100 g / 10 min, more preferably 1.0 g / 10 min to The range is 70 g / 10 min.
By setting the MFR value of the polyacetal homopolymer within the above range, a polyacetal homopolymer excellent in mechanical strength can be obtained.

As the polymerization catalyst, an anionic polymerization catalyst is preferable, and an onium salt-based polymerization catalyst represented by the following general formula (I) is more preferable.
[R ₁ R ₂ R ₃ R ₄ M] ⁺ X ⁻ (I)
(In formula (I), R ₁ , R ₂ , R ₃ and R ₄ each independently represents an alkyl group, M represents an element having a lone electron pair, and X represents a nucleophilic group.)
Examples of other polymerization catalysts include onium salt polymerization catalysts. Among the onium salt polymerization catalysts, quaternary phosphonium salt compounds such as tetraethylphosphonium iodide and tributylethylphosphonium iodide, tetramethyl Quaternary ammonium salt compounds such as ammonium bromide and dimethyl distearyl ammonium acetate are preferred.
The addition amount of these quaternary phosphonium salt compounds and quaternary ammonium salt compounds is preferably 0.0003 to 0.01 mol, more preferably 0.0008 to 0.005 mol, relative to 1 mol of formaldehyde. And more preferably 0.001 to 0.003 mol.

The hydrocarbon polymerization solvent is not particularly limited as long as it does not react with formaldehyde, and examples thereof include solvents such as pentane, isopentane, hexane, cyclohexane, heptane, octane, nonane, decane, and benzene. Is mentioned.
These hydrocarbon solvents may be used alone or in combination of two or more, but hexane is particularly preferred.

In the polymerization step of the polyacetal homopolymer, first, a crude polyacetal homopolymer is obtained, and then, as described later, it is preferable to subject the unstable terminal group to a stabilization treatment.
The polymerization apparatus for producing the crude polyacetal homopolymer is not particularly limited as long as it is an apparatus that can simultaneously supply formaldehyde as a monomer, a chain transfer agent (molecular weight regulator), a polymerization catalyst and a hydrocarbon polymerization solvent, A continuous polymerization apparatus is preferable from the viewpoint of productivity.
In the crude polyacetal homopolymer obtained by the polymerization process, the end group of the polymer is thermally unstable. Therefore, the unstable end group is blocked with an esterifying agent or an etherifying agent to stabilize the polymer end group. It is preferable to perform the treatment.
The terminal stabilization of the crude polyacetal homopolymer by esterification is performed by, for example, adding the crude polyacetal homopolymer, the esterifying agent and the esterification catalyst to the terminal stabilization reactor introduced with a hydrocarbon solvent, respectively. Can be done.
Although there is no limitation about the reaction temperature and reaction time at this time, for example, the reaction temperature is 130 to 155 ° C, the reaction time is preferably 1 to 100 minutes, the reaction temperature is 135 to 155 ° C, The reaction time is more preferably 5 to 100 minutes, the reaction temperature is 140 to 155 ° C., and the reaction time is further preferably 10 to 100 minutes.

As the esterifying agent that blocks and stabilizes the terminal group of the crude polyacetal homopolymer, an acid anhydride represented by the following general formula (II) can be used.
R ₅ COOCOR ₆ (II)
(In formula (II), R ₅ and R ₆ each independently represent an alkyl group. R ₅ and R ₆ may be the same or different.)
Examples of the esterifying agent include, but are not limited to, for example, benzoic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, propionic anhydride, and acetic anhydride. Is acetic anhydride.
These esterifying agents may be used alone or in combination of two or more.

The esterification catalyst is preferably an alkali metal salt of a carboxylic acid having 1 to 18 carbon atoms, and the amount added can be appropriately selected within the range of 1 to 1000 ppm relative to the polyacetal homopolymer.
Examples of the alkali metal salt of a carboxylic acid having 1 to 18 carbon atoms include, but are not limited to, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caprylic acid, enanthic acid, caprylic acid. And alkali metal salts of pelargonic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, and stearic acid. Examples of the alkali metal include lithium, sodium, potassium, rubidium, and cesium.
Among these metal carboxylates, alkali metal salts of lithium acetate, sodium acetate, and potassium acetate are preferable.

It is also possible to stabilize the end groups of the above-mentioned crude polyacetal homopolymer by etherification.
As etherifying agents in this case, orthoesters of aliphatic or aromatic acids with aliphatic, alicyclic or aromatic alcohols such as methyl or ethyl orthoformate, methyl or ethyl orthoacetate and methyl or Selected from ethyl orthobenzoate and ortho carbonate, specifically ethyl ortho carbonate, medium strength organic acids such as p-toluenesulfonic acid, acetic acid and odorous acid, medium strength mineral acids such as dimethyl and diethyl sulfate, etc. It can be obtained using a Lewis acid type catalyst.
The solvent used for the etherification reaction when the end group of the crude polyacetal homopolymer is blocked and stabilized by etherification is not limited to the following, but examples include pentane, hexane, cyclohexane and benzene. Low-boiling aliphatic organic solvents such as alicyclic and aromatic hydrocarbon-based organic solvents; organic solvents such as halogenated lower aliphatics such as methylene chloride, chloroform and carbon tetrachloride.

  The polyacetal homopolymer whose end group is stabilized by the above method is sealed with nitrogen gas adjusted to 100 to 150 ° C. using a dryer such as a hot air drier or a vacuum drier to remove moisture. By drying, the desired polyacetal homopolymer is obtained.

<Polyacetal copolymer>
The polyacetal copolymer is not limited to the following, but, for example, 1,3-dioxolane, glycol such as 1,4-butanediol formal, cyclic ether such as cyclic formal of diglycol, or cyclic formal is used as a comonomer. These can be produced by copolymerizing these and monomers such as trioxane.
The proportion of the comonomer to be copolymerized is preferably 0.03 to 20 mol%, more preferably 0.03 to 7 mol%, still more preferably 0.04 to 3 mol% with respect to 1 mol of formaldehyde. .
If the ratio of a comonomer is the said range, the polyacetal resin pellet which was excellent in mechanical strength will be obtained.

In addition, the polymerization catalyst in the polymerization of the polyacetal copolymer is not limited to the following, and examples thereof include cationically active catalysts such as Lewis acid, protonic acid and ester or anhydride thereof.
Examples of Lewis acids include, but are not limited to, boric acid, tin, titanium, phosphorus, arsenic, and antimony halides. Specifically, boron trifluoride, tin tetrachloride, tetra Examples thereof include titanium chloride, phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof.
In addition, the protonic acid and its ester or anhydride are not limited to the following, but examples include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate, trimethyloxonium hexa A fluorophosphate etc. are mentioned.
Among these, boron trifluoride; boron trifluoride hydrate; and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable. For example, boron trifluoride diethyl ether, Preferred is boron trifluoride di-n-butyl ether.
The amount of boron trifluoride added is preferably 0.10 × 10 ⁻⁴ mol or less, more preferably 0.07 × 10 ⁻⁴ mol or less, with respect to 1 mol of formaldehyde, Preference is given to 0.03 to 0.05 × 10 ⁻⁴ mol.
When the amount of boron trifluoride added is in the above range, a polyacetal resin composition having excellent thermal stability can be provided.

The polymerization method of the polyacetal copolymer exemplified above is not particularly limited, but in addition to the slurry polymerization method, for example, it may be carried out by a bulk polymerization method, and both batch type and continuous type are applicable. It is.
Although it does not specifically limit as a superposition | polymerization apparatus, For example, self-cleaning type extrusion kneaders, such as a kneader, a twin screw type continuous extrusion kneader, and a biaxial paddle type continuous mixer, are mentioned.
Molten monomer is supplied to the polymerization machine, and solid agglomerated polyacetal copolymer is obtained as the polymerization proceeds.

In the polyacetal copolymer obtained by the above polymerization, there may be a thermally unstable terminal portion [-(OCH ₂ ) _n —OH group]. It is preferable to implement. As a method for decomposing and removing the unstable terminal portion, a known method can be used.
As described above, in the present embodiment, (A) the polyacetal resin is not limited, and both a polyacetal homopolymer and a polyacetal copolymer can be used.
Among these, polyacetal comopolymer is preferable.

[(B) Nitrogen-containing hindered phenol compound]
In the present embodiment, the nitrogen-containing hindered phenol compound is a hindered phenol compound containing at least one nitrogen atom in its structural formula (a phenol compound having a tertiary alkyl group in at least one ortho position of the hydroxyl group). I mean.
(B) The nitrogen-containing hindered phenol compound is not limited to the following. For example, 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) propionyl] Hydrazine, N, N′-hexamethylenebis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) propanamide], 1,3,5-tris [[3,5-bis (1, 1-dimethylethyl) -4-hydroxyphenyl] methyl] -1,3,5-triazine-2,4,6 (1H, 3H, 5H) -trione, 4-[[4,6-bis (octylthio)- 1,3,5-triazin-2-yl] amino] -2,6-di-t-butylphenol.
Among these nitrogen-containing hindered phenol compounds, 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) propionyl] hydrazine, N, N′-hexamethylenebis [3- ( 3,5-di-t-butyl-4-hydroxyphenyl) propanamide], more preferably 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) Propionyl] hydrazine.

(B) As for melting | fusing point of a nitrogen-containing hindered phenol compound, 50-300 degreeC is preferable, More preferably, it is the range of 100-300 degreeC, More preferably, it is the range of 150-250 degreeC.
(B) If the melting point of the nitrogen-containing hindered phenol compound is within the above range, a polyacetal resin composition having more excellent thermal stability can be provided.

In the polyacetal resin composition of the present embodiment, (B) the nitrogen-containing hindered phenol compound is contained in an amount of 0.001 to 0.2 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin described above. From the viewpoint of the effect of improving the thermal stability, it has been found by the present inventors that the content of (B) the nitrogen-containing hindered phenol compound has an appropriate range. (B) The nitrogen-containing hindered phenol compound is preferably contained in an amount of 0.005 to 0.2 parts by mass, and 0.005 to 0.15 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. More preferably.
(B) If content of a nitrogen-containing hindered phenol compound is the said range, the polyacetal resin composition excellent in thermal stability can be provided.
As a method for quantifying the (B) nitrogen-containing hindered phenol compound in the polyacetal resin composition of the present embodiment, for example, polyacetal resin pellets are freeze-pulverized, subjected to Soxhlet extraction with a solvent such as chloroform, GCMS, or ¹ H -The method of quantifying by NMR is mentioned.

[(C) Nitrogen-free hindered phenol compound]
In the present embodiment, the nitrogen-free hindered phenol compound refers to a hindered phenol compound that does not contain a nitrogen atom in its structural formula. Although hindered phenol compounds are generally known as antioxidants, in the present embodiment, both those containing nitrogen and those not containing nitrogen are used in combination, thereby realizing very good thermal stability.
(C) The nitrogen-free hindered phenol compound is not limited to the following, but, for example, n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) -Propionate, n-octadecyl-3- (3'-methyl-5'-t-butyl-4'-hydroxyphenyl) -propionate, n-tetradecyl-3- (3 ', 5
'-Di-t-butyl-4'-hydroxyphenyl) -propionate, 1,6-hexanediol-bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate], 1 , 4-Butanediol-bis- [3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate], triethylene glycol-bis- [3- (3-tert-butyl-5-methyl) -4-hydroxyphenyl) -propionate], pentaerythritol tetrakis [methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate] methane, and the like.
Preferably, triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] and pentaerythritol tetrakis [methylene-3- (3 ′, 5′-di-t -Butyl-4'-hydroxyphenyl) propionate] methane, more preferably triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate].

(C) As for melting | fusing point of a nitrogen-free hindered phenol compound, 30-120 degreeC is preferable, More preferably, it is 50-120 degreeC, More preferably, it is the range of 50-100 degreeC.
(C) If the melting point of the nitrogen-free hindered phenol compound is within the above range, a polyacetal resin composition having more excellent thermal stability can be provided.

In the polyacetal resin composition of the present embodiment, (C) the nitrogen-free hindered phenol compound is contained in an amount of 0.001 to 0.3 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin described above. (C) The nitrogen-free hindered phenol compound is preferably contained in an amount of 0.005 to 0.3 parts by mass, and 0.005 to 0.27 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. More preferably.
(C) If content of a nitrogen-free hindered phenol compound is the said range, the polyacetal resin composition excellent in thermal stability can be provided.
As a method for quantifying (C) the nitrogen-free hindered phenol compound in the polyacetal resin composition of the present embodiment, for example, polyacetal resin pellets are freeze-pulverized and subjected to Soxhlet extraction with a solvent such as chloroform, GCMS, or ¹ The method of quantifying by H-NMR is mentioned.

[(D) Talc]
(D) Talc is a particle made of hydrous magnesium silicate, and its composition is generally represented by [Mg ₃ Si ₄ O ₁₀ (OH) ₂ ], and SiO _{2 is} about 60% by mass, MgO is about 30% by mass. The main component is 4.8% by mass of crystal water. The true specific gravity is generally 2.7 to 2.8, the whiteness is 93% or more measured according to JIS K-8123, and the PH is measured 9.0 to 10 according to JIS K-5101. It is preferable that it is the range of these. The 45 μm sieve residue is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, more preferably 0.08% by mass or less, as measured according to JIS K-5101. is there. (D) The average particle diameter of talc is preferably 1 to 30 μm, more preferably 2 to 25 μm, and still more preferably 2 to 20 μm. (D) When the average particle diameter of talc is in the above range, a polyacetal resin composition having more excellent thermal stability can be provided.
In this embodiment, (D) talc may be surface-treated using a known surface treating agent in order to improve the affinity with (A) polyacetal resin.
Examples of surface treatment agents include silane coupling agents such as amino silane and epoxy silane, titanate coupling agents, fatty acids (saturated fatty acids and unsaturated fatty acids), alicyclic carboxylic acids, resin acids and metal soaps. Can do. The addition amount of the surface treatment agent is preferably 3% by mass or less, more preferably 2% by mass or less, and most preferably, it is not substantially added.

In the polyacetal resin composition of the present embodiment, the content of (D) talc is 0.0001 to 0.1 parts by mass with respect to 100 parts by mass of (A) polyacetal resin. (D) If the content of talc is small, sufficient thermal stability improvement effect cannot be obtained. On the other hand, even if it is too much, the thermal stability is affected by the basicity of talc itself or impurities contained It has been found by the present inventors' study that the decrease is caused. For these reasons, it is preferable that (D) talc is contained in an amount of 0.0005 to 0.1 parts by mass, and 0.0005 to 0.05 parts by mass with respect to 100 parts by mass of (A) polyacetal resin. More preferably.
(D) If content of talc is the said range, the polyacetal resin composition excellent in thermal stability can be provided.

  In order to quantify the (D) talc content in the polyacetal resin composition of the present embodiment, for example, a method of hydrolyzing polyacetal resin pellets with hydrochloric acid and the like to quantify talc, or high frequency inductively coupled plasma (ICP) emission A method of quantifying metallic components (Si, Mg) that are caused by talc by analysis

[(E) Stabilizer]
In the polyacetal resin composition of the present embodiment, good thermal stability is achieved by the combined addition of the above-mentioned (B) to (D). In order to improve thermal stability and other physical properties, (E) various stabilizers may be further included.
Examples of (E) stabilizer include amino-substituted triazine compounds, urea derivatives, hydrazide derivatives, amide compounds, polyamides, and acrylamide polymers.

  Examples of the amino-substituted triazine compound include, but are not limited to, 2,4-diamino-sym-triazine, 2,4,6-triamino-sym-triazine, N-butylmelamine, and N-phenyl. Melamine, N, N-diphenylmelamine, N, N-diallylmelamine, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine), acetoguanamine (2,4-diamino-6-methyl-sym-triazine) 2,4-diamino-6-butyl-sym-triazine and the like.

Examples of the urea derivative include, but are not limited to, N-substituted urea, urea condensate, ethylene urea, hydantoin compound, ureido compound, and the like.
Examples of the N-substituted urea include, but are not limited to, methylurea having a substituent such as an alkyl group, alkylenebisurea, and aryl-substituted urea. Examples of the urea condensate include, but are not limited to, urea and formaldehyde condensates. Examples of the hydantoin compound include, but are not limited to, hydantoin, 5,5-dimethylhydantoin, and 5,5-diphenylhydantoin. Examples of the ureido compound include, but are not limited to, allantoin.

Examples of the hydrazide derivative include, but are not limited to, hydrazide compounds.
Examples of the hydrazide compound include a carboxylic acid mono / or dihydrazide compound and an alkyl group-substituted mono / or dihydrazide compound synthesized by a reaction of a carboxylic acid (containing aromatic or alicyclic ring) with hydrazine. Examples of the carboxylic acid constituting the carboxylic acid mono / or dihydrazide compound include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, lauric acid, myristic acid, Palmitic acid, margaric acid, stearic acid, behenic acid. Dicarboxylic acids are oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, naphthalic acid, salicylic acid, gallic acid Mellitic acid, cinnamic acid, pyruvic acid, lactic acid, malic acid, citric acid, fumaric acid, maleic acid, aconitic acid, amino acid, nitrocarboxylic acid. Examples of unsaturated carboxylic acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, and eicosapentaenoic acid. Carboxylic acid mono (di) hydrazide compounds synthesized using these carboxylic acids include, for example, carbodihydrazine, oxalic acid mono (di) hydrazide, malonic acid mono (di) hydrazide, succinic acid mono (di) hydrazide, glutar Acid mono (di) hydrazide, adipic acid mono (di) hydrazide, sebacic acid mono (di) hydrazide, lauric acid mono (di) hydrazide, malic acid dihydrazide, tartaric acid dihydrazide, propionic acid monohydrazide, lauric acid monohydrazide, stearic acid Monohydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2,6-naphthalic acid dihydrazide, p-hydroxybenzoic hydrazine, p-hydroxybenzoic hydrazine, 1,4-cyclohexanedicarboxylic acid dihydride Rajin, acetohydrazide, acryloxypropyl hydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, benzohydrazide, nicotinonitrile hydrazide, isonicotinohydrazide, isobutyl hydrazine, and hydrazide oleate. Among these carboxylic acids, dicarboxylic acids such as adipic acid, sebacic acid, and lauric acid are preferable, and adipic acid mono (di) hydrazide, sebacic acid mono (di) hydrazide, and lauric acid mono (di) hydrazide are the most preferable carboxylic acids. It is a hydrazide compound.

  Examples of the amide compound include, but are not limited to, polyvalent carboxylic acid amides such as isophthalic acid diamide and anthranilamides.

  Examples of the polyamide include polyamide resins such as nylon (registered trademark) 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 12, and polymers thereof such as nylon. 6 / 6-6 / 6-10, nylon 6 / 6-12 and the like.

Although the acrylamide polymer is not limited to the following, for example, using an alkali earth metal alcoholate as a catalyst, polymerization of acrylamide, or polymerization of acrylamide and a monomer having a vinyl group other than acrylamide is performed. Can be manufactured.
Examples of the monomer having a vinyl group other than acrylamide constituting the acrylamide polymer include monomers having one or two vinyl groups.
Examples of the monomer having one vinyl group include, but are not limited to, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, Examples include cecil methacrylate, pentadecyl methacrylate, stearyl methacrylate, behenyl methacrylate, hydroxypropyl methacrylate, polypropylene glycol methacrylate, and polyethylene glycol methacrylate.
Examples of the monomer having two vinyl groups include, but are not limited to, divinylbenzene, ethylene bisacrylamide, N, N′-methylene bisacrylamide, and the like.
Among these monomers having a vinyl group, N, N′-methylenebisacrylamide is preferable.
The amount of the vinyl group-containing monomer introduced into the acrylamide polymer is preferably 0.05 to 20% by mass with respect to the total amount of the acrylamide component and the vinyl group-containing monomer.
By copolymerizing with the above-mentioned monomer having a vinyl group (providing a crosslinked structure), the extrusion productivity of polyacetal resin pellets can be improved.
The average particle diameter of the acrylamide polymer is preferably from 0.1 to 20 μm, more preferably from 0.1 to 15 μm, still more preferably from 0.1 to 10 μm.
When the average particle diameter of the acrylamide polymer is within the above range, a polyacetal resin composition having excellent extrusion productivity can be obtained.

  Among the above (E) stabilizers, polyamide and acrylamide polymers are particularly preferable.

(E) As addition amount of a stabilizer, 0.001-5 mass parts is preferable with respect to 100 mass parts of polyacetal resin, More preferably, it is 0.001-3 mass parts, More preferably, 0.01- 1 part by mass.
The polyacetal resin composition which is more excellent in heat stability can be obtained by making the addition amount of the heat stabilizer with respect to polyacetal resin into the said range.

[Other additives]
In addition to the above-described polyacetal resin composition of the present embodiment, known additives such as formic acid scavengers, weathering stabilizers, release agents, lubricants, conductive agents, thermoplastic resins, thermoplastic elastomers, Dyeing pigments, pigments, inorganic fillers or organic fillers may be added.
These additives may be used alone or in combination of two or more.

Examples of formic acid scavengers include, but are not limited to, for example, (E) amino-substituted triazine compounds and condensates of amino-substituted triazine compounds and formaldehyde listed as specific examples of stabilizers, such as melamine / formaldehyde A condensate etc. can be mentioned.
Examples of other formic acid scavengers include, but are not limited to, alkali metal or alkaline earth metal hydroxides, inorganic acid salts, carboxylate salts, or alkoxides. Examples thereof include hydroxides such as sodium, potassium, magnesium, calcium, and barium; carbonates, phosphates, silicates, borates, carboxylates, and layered double hydroxides of the above metals.
The carboxylic acid of the carboxylate is preferably a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms, and these carboxylic acids may be substituted with a hydroxyl group. Examples of the saturated or unsaturated aliphatic carboxylate include, but are not limited to, for example, calcium dimyristic acid, calcium dipalmitate, calcium distearate, (myristic acid-palmitic acid) calcium, (myristic acid) -Stearic acid) calcium, (palmitic acid-stearic acid) calcium, and 12 hydroxy calcium stearate are preferable. Among them, calcium dipalmitate, calcium distearate, and calcium 12-hydroxy distearate are preferable.
Only one type of formic acid scavenger may be used alone, or two or more types may be used in combination.

The weather stabilizer is not limited to the following, but for example, at least one selected from the group consisting of benzotriazole compounds, oxalic acid anilide compounds, and hindered amine light stabilizers is preferred. It is done.
Examples of the benzotriazole-based compound include, but are not limited to, 2- (2′-hydroxy-5′-methyl-phenyl) benzotriazole, 2- (2′-hydroxy-3,5- Di-t-butyl-phenyl) benzotriazole, 2- [2′-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] benzotriazole, 2- (2′-hydroxy-3,5-di) -T-amylphenyl] benzotriazole, 2- (2'-hydroxy-3,5-di-isoamyl-phenyl) benzotriazole, 2- [2'-hydroxy-3,5-bis- (α, α-dimethyl) Benzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole, and the like.
These compounds may be used alone or in combination of two or more.
Examples of the oxalic acid alinide compound include, but are not limited to, 2-ethoxy-2′-ethyloxalic bisanilide, 2-ethoxy-5-tert-butyl-2′-ethyloxy, for example. Examples include zalic acid bisanilide, 2-ethoxy-3′-dodecyl oxalic acid bisanilide, and the like.
These compounds may be used alone or in combination of two or more.
Examples of the hindered amine light stabilizer include, but are not limited to, 4-acetoxy-2,2,6,6-tetramethylpiperidine, 4-stearoyloxy-2,2,6,6- Tetramethylpiperidine, 4-acryloyloxy-2,2,6,6-tetramethylpiperidine, 4- (phenylatoxy) -2,2,6,6-tetramethylpiperidine, 4-benzoyloxy-2,2, 6,6-tetramethylpiperidine, 4-methoxy-2,2,6,6-tetramethylpiperidine, 4-stearyloxy-2,2,6,6-tetramethylpiperidine, 4-cyclohexyloxy-2,2, 6,6-tetramethylpiperidine, 4-benzyloxy-2,2,6,6-tetramethylpiperidine, 4-phenoxy-2,2,6,6- Tramethylpiperidine, 4- (ethylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (cyclohexylcarbamoyloxy) -2,2,6,6-tetramethylpiperidine, 4- (phenylcarbamoyloxy) ) -2,2,6,6-tetramethylpiperidine, bis (2,2,6,6-tetramethyl-4-piperidyl) -carbonate, bis (2,2,6,6-tetramethyl-4-piperidyl) ) -Oxalate, bis (2,2,6,6-tetramethyl-4-piperidyl) -malonate, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis- (N-methyl) -2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) -seba Bis (2,2,6,6-tetramethyl-4-piperidyl) -adipate, bis (2,2,6,6-tetramethyl-4-piperidyl) -terephthalate, 1,2-bis (2 , 2,6,6-tetramethyl-4-piperidyloxy) -ethane, α, α′-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -p-xylene, bis (2, 2,6,6-tetramethyl-4-piperidyltolylene-2,4-dicarbamate, bis (2,2,6,6-tetramethyl-4-piperidyl) -hexamethylene-1,6-dicarbamate, Tris (2,2,6,6-tetramethyl-4-piperidyl) -benzene-1,3,5-tricarboxylate, tris (2,2,6,6-tetramethyl-4-piperidyl) -benzene- 1,3,4-tricarbo Sylate, 1- [2- {3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy} butyl] -4- [3- (3,5-di-t-butyl-4- Hydroxyphenyl) propionyloxy] 2,2,6,6-tetramethylpiperidine, 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, and the like.
Each of the hindered amine light stabilizers may be used alone or in combination of two or more.

Among them, preferred weathering stabilizers are 2- [2′-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] benzotriazole, 2- (2′-hydroxy-3,5-di-t-butyl). Phenyl) benzotriazole, 2- (2′-hydroxy-3,5-di-t-amylphenyl] benzotriazole, bis (1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, bis- ( N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, bis (2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 1,2,3,4-butanetetra Carboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β ′, β ′,-tetramethyl-3,9- [2,4,8,10-tetraoxaspiro ( 5 5) it is a condensation product of undecane] diethanol.

Examples of the release agent and lubricant are not limited to the following, but preferable examples include alcohols, fatty acids and fatty acid esters thereof, olefin compounds having an average polymerization degree of 10 to 500, and silicone. .
Only one type of release agent and lubricant may be used alone, or two or more types may be used in combination.

Examples of the conductive agent include, but are not limited to, conductive carbon black, metal powder, or fiber.
Only one type of conductive agent may be used alone, or two or more types may be used in combination.

Examples of the thermoplastic resin include, but are not limited to, polyolefin resins, acrylic resins, styrene resins, polycarbonate resins, and uncured epoxy resins.
Only one type of thermoplastic resin may be used alone, or two or more types may be used in combination.
Further, the thermoplastic resin includes a modified product of the above-described resin.

Examples of the thermoplastic elastomer include, but are not limited to, polyurethane elastomers, polyester elastomers, polystyrene elastomers, and polyamide elastomers.
Only one type of thermoplastic elastomer may be used alone, or two or more types may be used in combination.

Examples of the dye / pigment include, but are not limited to, inorganic pigments, organic pigments, metallic pigments, and fluorescent pigments.
Inorganic pigments are those commonly used for coloring resins and are not limited to the following, but include, for example, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, Examples thereof include pigments, carbonates, phosphates, acetates, carbon black, acetylene black, and lamp black.
Examples of organic pigments include, but are not limited to, for example, condensed zozo, inone, furothocyanin, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennon, quinacridone And pigments such as thioindico, berylene, dioxazine, and phthalocyanine pigments.
Only one type of dyeing pigment may be used alone, or two or more types may be used in combination.
Since the addition ratio of the pigment varies greatly depending on the color tone, it is difficult to clarify, but generally it is used in the range of 0.05 to 5 parts by mass with respect to 100 parts by mass of the polyacetal resin.

The resin other than the thermoplastic resin is not particularly limited, and examples thereof include polyolefin resin, acrylic resin, styrene resin, polycarbonate resin, and uncured epoxy resin.
Other resins may be used alone or in combination of two or more.

The inorganic filler is not limited to the following, but for example, fibrous, powder particle, plate and hollow fillers are used.
Examples of the fibrous filler include, but are not limited to, glass fiber, carbon fiber, silicone fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, and potassium titanate. Examples thereof include inorganic fibers such as fibers and metal fibers such as stainless steel, aluminum, titanium, copper, and brass. In addition, whiskers such as potassium titanate whisker and zinc oxide whisker having a short fiber length are included.
Examples of powder particulate fillers include, but are not limited to, carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, magnesium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, wort Silicates such as rustonite; metal oxides such as iron oxide, titanium oxide and alumina; metal sulfates such as calcium sulfate and barium sulfate; carbonates such as magnesium carbonate and dolomite; other silicon carbide, silicon nitride, boron nitride, Various metal powders etc. are mentioned.
Examples of the plate filler include, but are not limited to, mica, glass flakes, and various metal foils.
Examples of the hollow filler include, but are not limited to, glass balloons, silica balloons, shirasu balloons, and metal balloons.
Examples of the organic filler include, but are not limited to, high melting point organic fibrous fillers such as aromatic polyamide resin, fluorine resin, and acrylic resin.
These fillers may be used alone or in combination of two or more.

These fillers can be either surface-treated or non-surface-treated, but the use of surface-treated fillers in terms of the smoothness of the molding surface and mechanical properties. May be preferred.
It does not specifically limit as a surface treating agent, A conventionally well-known surface treating agent can be used.
Examples of the surface treatment agent include, but are not limited to, various coupling treatment agents such as silane, titanate, aluminum, and zirconium, resin acids, organic carboxylic acids, salts of organic carboxylic acids, and the like. A surfactant can be used.
Specifically, although not limited to the following, for example, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltrisstearoyl titanate, di- Examples thereof include isopropoxyammonium ethyl acetate and n-butyl zirconate.

There is no limitation in particular in the method of manufacturing the polyacetal resin composition of this embodiment.
In general, (A) a polyacetal resin, (B) a nitrogen-containing hindered phenol compound, (C) a nitrogen-free hindered phenol compound, and (D) talc, as described above, as necessary. For example, by mixing with a Henschel mixer, tumbler, V-shaped blender, etc., and then kneading using a kneader such as a single or multi-screw extruder, heating roll, kneader, Banbury mixer, etc. It is done. Among these, kneading by an extruder equipped with a vent pressure reducing device is preferable from the viewpoint of productivity. In order to stably produce a large amount of the polyacetal resin composition, a single-screw or twin-screw extruder is preferably used.
Moreover, it is also possible to continuously feed each component individually or in groups of several using a quantitative feeder or the like without mixing in advance.
Alternatively, a high-concentration master batch made of each component can be prepared in advance and diluted with a polyacetal resin during extrusion melt kneading.
The kneading temperature may be in accordance with the preferred processing temperature of the polyacetal resin to be used, and is generally in the range of 140 to 260 ° C, preferably in the range of 180 to 230 ° C.

[Molding method]
The polyacetal resin composition of the present embodiment can be molded and used as a molded product. The molding method is not particularly limited, and known molding methods such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, other material molding, gas assist injection molding, and gunshot injection molding. It can be molded by any one of molding methods such as low pressure molding, ultra thin injection molding (ultra high speed injection molding), and in-mold composite molding (insert molding, outsert molding).
Among these, the injection molding method is preferable from the viewpoint of stable productivity.

[Use]
Even if the polyacetal resin composition of this embodiment performs continuous shaping | molding using a hot runner metal mold | die, there is little thermal decomposition of a polyacetal resin, Therefore, there is also little contamination of a metal mold | die.
Moreover, even if the polyacetal resin composition of this embodiment is molded under severe molding conditions, the amount of formaldehyde released from the obtained molded product is small.
Therefore, it can be used for molded articles for various purposes.
For example, mechanical parts such as gears, cams, sliders, levers, shafts, bearings and guides, outsert molded resin parts or insert molded resin parts (chassis, tray, side plate parts), printer or copier parts Used for digital camera or digital video equipment parts, music, video or information equipment parts, communication equipment parts, electrical equipment parts, electronic equipment parts.
It is also suitable for automobile parts, such as gasoline tanks, fuel pump modules, valves, gasoline tank flanges, etc., fuel parts; door parts; seat belt peripheral parts; combination switch parts; The
Furthermore, it can be suitably used as an industrial part typified by residential equipment.

Hereinafter, although a specific Example and a comparative example with this are given and demonstrated about this embodiment, this embodiment is not limited to a following example.
The measurement / evaluation methods applied in the examples and comparative examples are shown below.
[Measurement and evaluation method]
<Evaluation of mold deposit by hot runner mold>
Using the molding machine having the configuration shown in FIG. 1, the mold deposit property of the polyacetal resin composition was evaluated according to the following molding conditions (a). The evaluation criteria used (b) below.
(A) Molding conditions ・ Injection molding machine: TOSHIBA MACHINE Co., Ltd. IS-100GN
(There is no gas vent at the end of the molten resin flow path, and there is a weld)
・ Cylinder set temperature: 230 ℃
・ Manifold set temperature: 240 ℃
・ Mold set temperature: 80 ℃
Molding cycle: injection time / cooling time = 20/20 seconds Mold size: 70 × 60 mm × 3 mm
(B) Evaluation Criteria Based on the following evaluation criteria, the state of mold deposit adhesion in the mold cavities at the 300th and 1000th shots from the start of molding was observed.
1: Deposits were observed in a range of less than 5% in the mold cavity.
2: Deposits were observed in the range of 5% or more and less than 10% in the mold cavity. 3: Deposits were observed in the range of 10% or more and less than 20% in the mold cavity.
4: Deposits were observed in the range of 20% to less than 30% in the mold cavity.
5: A deposit was observed in a range of 30% or more in the mold cavity.

<Method for measuring the amount of formaldehyde released from molded articles>
(1) No retention in molding machine Cylinder test using IS-100GN injection molding machine manufactured by Toshiba Corp. with cylinder temperature of 220 ° C, mold temperature of 80 ° C, injection pressure of 60 MPa, injection time of 30 seconds, cooling time of 15 seconds A piece was molded. The molded product from the start of molding to 5 shots was discarded, and the amount of formaldehyde released from the molded product was measured for the molded product of the 6th shot under the following conditions (VDA275 method).
(2) Retaining in cylinder of molding machine Using Toshiba Corporation IS-100GN injection molding machine, cylinder temperature 220 ° C, mold temperature 80 ° C, injection pressure 60MPa, injection time 30 seconds, cooling time 15 seconds A piece was molded.
The molding machine is stopped while the fifth shot is being molded (the molten resin is measured in the molding machine cylinder and is in the cooling zone), and the cylinder temperature is maintained at 220 ° C. The molten resin was allowed to stay for 5 minutes. After 5 minutes, the molding machine was started again, and the polyacetal resin retained in the injection molding machine was molded under conditions of a mold temperature of 80 ° C., an injection pressure of 60 MPa, an injection time of 30 seconds, and a cooling time of 15 seconds. Obtained. About the molded article shape | molded immediately after residence, the amount of formaldehyde discharge | released from a molded article was measured on condition (VDA275 method) shown below.
* VDA275 method:
A test piece (length 100 mm × width 40 mm × thickness 3 mm) defined as 50 mL of distilled water was placed in a polyethylene container, sealed, and formaldehyde was extracted into distilled water while heating at 60 ° C. for 3 hours, and then cooled to room temperature. .
After cooling, 5 mL of acetylacetone 0.4 mass% aqueous solution and 5 mL of ammonium acetate 20 mass% aqueous solution were added to 5 mL of distilled water that absorbed formaldehyde, and heated at 40 ° C. for 15 minutes to react formaldehyde with acetylacetone.
Furthermore, after cooling the said liquid mixture to room temperature, the amount of formaldehyde in distilled water was quantified from the absorption peak of 412 nm using the UV spectrophotometer.
The amount of formaldehyde released from the molded product (mg / kg) was determined by the following formula.
Formaldehyde released from the molded product (mg / kg)
= Formaldehyde amount in distilled water (mg) / mass of polyacetal resin molded product used for measurement (kg)

[Raw ingredient]
It shows below about the raw material component used for the Example and the comparative example.
<(A) polyacetal resin>
A jacketed biaxial paddle type continuous polymerization reactor (manufactured by Kurimoto Steel Works, diameter 2B, L / D = 14.8) was adjusted to 80 ° C., and the raw materials were used under the following polymerization conditions (feed rate). Etc. were supplied to polymerize the polyacetal copolymer.
Unstable end groups of the obtained crude polymer were removed under the following terminal stabilization conditions, and a polyacetal copolymer (polyacetal) having a content of 4 mol% of a comonomer component derived from 1,3-dioxolane and an MFR value of 9 g / 10 min was obtained. Resin (A-1)) was obtained.
The polymerization conditions (feed rate of raw materials) and terminal stabilization conditions of the polyacetal copolymer are shown below.
[Polymerization conditions]
The raw material was supplied to the reactor at the following supply rate.
Trioxane (main monomer): 3500 gr / hr
1,3-dioxolane (comonomer): 120.9 gr / hr
-Methylal (molecular weight regulator): 2.4 gr / hr
Cyclohexane (organic solvent): 6.5 g / hr
Boron trifluoride-di-n-butyl etherate (polymerization catalyst): 0.04 g / hr
(The feed rate was set so that boron trifluoride was 0.05 × 10 ⁻⁴ mol with respect to 1 mol of formaldehyde.)
Only the polymerization catalyst was fed in a separate line from the other components described above.
[Terminal stabilization conditions]
The crude polyacetal polymer discharged from the polymerization reactor was immersed in an aqueous triethylamine solution (0.5% by mass), then stirred for 1 hr at room temperature, filtered through a centrifuge, and 120 ° C. under nitrogen. X3 hr drying was performed to obtain a polyacetal copolymer (polyacetal resin (A-1)).

<(B) Nitrogen-containing hindered phenol compound>
B-1: 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) propionyl] hydrazine (Irganox MD1024)
B-2: N, N′-hexamethylenebis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propanamide] (Irganox 1098)
B-3: 1,3,5-tris [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] -1,3,5-triazine-2,4,6 (1H , 3H, 5H) -trione (Irganox 3114)

<(C) Nitrogen-free hindered phenol compound>
C-1: Triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] (Irganox 245)
C-2: 1,6-hexanediol-bis [3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propionate] (Irganox 259)

<(D) Talc>
D-1: MS talc (average particle size 16 μm) manufactured by Nippon Talc Co., Ltd. <(E) stabilizer>
E-1: polyacrylamide polymer (average particle size 5 μm)

[Example 1]
(A-1) 100 parts by mass of polyacetal resin, 0.05 part by mass of (B-1) 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) propionyl] hydrazine, (C-1) 0.1 parts by mass of triethylene glycol-bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate] and (D-1) 0.01 parts by mass of talc Were uniformly mixed using a Henschel mixer to obtain a mixture.

This mixture was fed from the top feed port of a 30 mm vented twin screw extruder set at 200 ° C. and melt kneaded and pelletized at a screw rotation speed of 80 rpm, a vent pressure reduction of −0.09 MPa, and a discharge rate of 5 kg / hr. Thereafter, the pellets were dried at a hot air temperature of 80 ° C. for 3 hours to obtain polyacetal resin pellets.
Using the obtained polyacetal resin pellets, the mold depositability by the hot runner mold and the amount of formaldehyde released from the molded product were measured and evaluated by the methods described above. The evaluation results are shown in Table 1 below.

[Examples 2 to 15]
Except that the composition was as shown in Table 1, the same operation as in Example 1 was performed to obtain polyacetal resin pellets.
Using the obtained polyacetal resin pellets, mold depositability by a hot runner mold and the amount of formaldehyde released from the molded product were evaluated and measured by the methods described above. The evaluation results are shown in Table 1 below.

[Comparative Example 1]
(A-1) 100 mass of polyacetal resin is fed from the top feed port of a 30 mm vented twin screw extruder set at 200 ° C., screw rotation speed 80 rpm, vent pressure reduction degree −0.09 MPa, discharge rate 5 kg / hr Then, the pellet was dried at a hot air temperature of 80 ° C. for 3 hours to obtain polyacetal resin pellets.
Using the obtained polyacetal resin pellets, mold depositability by a hot runner mold and the amount of formaldehyde released from the molded product were evaluated and measured by the methods described above. The evaluation results are shown in Table 1 below.

[Comparative Example 2]
(A-1) 100 mass parts of polyacetal resin and 0.01 mass part of (D-1) talc were mixed uniformly using the Henschel mixer, and the mixture was obtained.
This mixture was fed from the top feed port of a 30 mm vented twin screw extruder set at 200 ° C. and melt kneaded and pelletized at a screw rotation speed of 80 rpm, a vent pressure reduction of −0.09 MPa, and a discharge rate of 5 kg / hr. Thereafter, the pellets were dried at a hot air temperature of 80 ° C. for 3 hours to obtain polyacetal resin pellets.
Using the obtained polyacetal resin pellets, mold depositability by a hot runner mold and the amount of formaldehyde released from the molded product were evaluated and measured by the methods described above. The evaluation results are shown in Table 1 below.

[Comparative Examples 3 to 10]
Except that the composition was as shown in Table 1, the same operation as in Example 1 was performed to obtain polyacetal resin pellets.
Using the obtained polyacetal resin pellets, mold depositability by a hot runner mold and the amount of formaldehyde released from the molded product were evaluated and measured by the methods described above. The evaluation results are shown in Table 1 below.

As shown in Table 1, the polyacetal resin compositions obtained in Examples 1 to 15 are excellent in mold depositing property even when continuous molding using a hot runner mold is performed, and the obtained molding Although the product was molded under severe molding conditions, the amount of formaldehyde released was low.
On the other hand, the polyacetal resin compositions obtained in Comparative Examples 1 to 10 were inferior in mold depositing property and had a large amount of formaldehyde released from the obtained molded products.

  The polyacetal resin composition of the present invention can be used in a wide range of fields such as automobiles, electrical machinery / electronics, and other industries. In particular, since the polyacetal resin composition of the present invention has excellent thermal stability, it can be suitably used in a field where a molding method is employed in which the resin composition is exposed to a high temperature for a long time.

Claims (4)

  (A) 100 parts by mass of a polyacetal resin, (B) 0.001 to 0.2 parts by mass of a nitrogen-containing hindered phenol compound, and (C) 0.001 to 0.3 parts by mass of a nitrogen-free hindered phenol compound. (D) Polyacetal resin composition containing 0.0001-0.1 mass part of talc.   (B) Polyacetal resin composition of Claim 1 whose content of a nitrogen-containing hindered phenol compound is 0.001-0.15 mass part with respect to 100 mass parts of (A) polyacetal resin.   (B) The polyacetal resin composition according to claim 1 or 2, wherein the nitrogen-containing hindered phenol compound includes a hydrazine structure.   Furthermore, (E) Other stabilizers include at least one selected from the group consisting of amino-substituted triazine compounds, urea derivatives, hydrazide derivatives, amide compounds, polyamides, and acrylamide copolymers. The polyacetal resin composition according to any one of the above.