JP6814548B2 - Polyacetal resin composition - Google Patents

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 is a resin material with excellent rigidity, strength, toughness, slidability, and creepability. Therefore, it has been conventionally used for mechanical parts such as automobile parts, electrical / electronic parts, and industrial parts. It is widely used as a material.
In recent years, there has been an increasing demand for low VOC in polyacetal resins mainly in the field of automobiles, and there is an increasing demand for polyacetal resins having a small amount of formaldehyde emission from parts as resins used for automobile interior parts.

By the way, a cold runner mold is generally used for molding a polyacetal resin. However, when molding is performed using a cold runner mold, unnecessary runner parts are also molded together with the target molded product, so the runner part is discarded or after crushing with a crusher or the like. There is no choice but to mix a small amount with the raw material polyacetal resin pellets and rework.
However, when the runner portion is rework-molded, since the runner receives a heat history, it 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 (the part where the molten resin stays: the hot runner part) in the hot runner mold is generally set to a temperature equal to or higher than the molding machine cylinder temperature. Therefore, the polyacetal resin is required to have higher thermal stability than the case of continuous molding using a cold runner mold.

Various techniques have been conventionally proposed in order to solve the above-mentioned requirements. For example, a method of adding calcium hydroxystearate and a metal deactivator to a polyacetal resin (see, for example, Patent Document 1 below), a method of adding a hydrazide compound to a polyacetal resin (see, for example, Patent Document 2 below), and a polyacetal resin. A method of adding a polyvalent carboxylic acid hydrazide containing an aryl group or the like (see, for example, 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. (For example, see 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 adding a small amount of talc to a polyacetal resin. A method of addition (see, for example, Patent Document 6 below) has been proposed.

Japanese Patent No. 3129799 International Publication No. 2005/040275 Pamphlet (2005) Japanese Patent No. 4568018 Japanese Unexamined Patent Publication No. 2012-921185 Japanese Unexamined Patent Publication No. 2013-23506 Japanese Patent No. 4799534

However, the polyacetal resin compositions obtained by various conventionally proposed methods have an effect of improving the moldability in continuous molding in a short time using a cold runner mold. However, in the case of continuous molding using a hot runner mold, the resin composition stays in the hot runner manifold portion for a long time at a high temperature, so that the polyacetal resin is thermally decomposed and the obtained molded product is obtained. It is difficult to reduce the amount of formaldehyde emission. Further, since the molding is continuous, there is a problem that the inside of the mold is easily contaminated with the mold deposit.
Therefore, according to the present invention, when a molding method such as continuous molding using a hot runner mold is applied in which the resin composition is exposed to a high temperature for a long time, the polyacetal resin is less thermally decomposed, and the obtained molded product is used. An object of the present invention is to provide a polyacetal resin composition with a small amount of formaldehyde emission and mold contamination.

As a result of diligent research to solve the above-mentioned problems of the prior art, the present inventors have a polyacetal resin composition containing a nitrogen-containing hindered phenol compound and talc in a specific ratio with respect to the polyacetal resin. We have found that the product has good thermal stability, and in addition to this, when a nitrogen-free hindered phenol compound is used in combination, the thermal stability is remarkably improved and the above-mentioned problems can be solved. It came to be completed.

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

According to the present invention, even when the polyacetal resin composition is molded under severe molding conditions such as continuous molding using a hot runner mold, in which the resin composition is exposed to a high temperature for a long time. , It is possible to suppress thermal decomposition of polyacetal resin, reduce mold contamination, and manufacture a molded product with a small amount of formaldehyde emission.

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

Hereinafter, embodiments for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail.
The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

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

[(A) Polyacetal resin]
The (A) polyacetal resin 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 tetramer thereof (trioxane) or a tetramer (trioxane). Polyacetal homopolymer consisting substantially only of oximethylene units obtained by homopolymerizing a cyclic oligomer of formaldehyde such as tetraoxane); formaldehyde monomer or formaldehyde such as a trimeric (trioxane) or tetramer (tetraoxane) thereof. Is obtained by copolymerizing the cyclic oligomer of the above with a glycol such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, and 1,4-butanediol formal, a cyclic ether such as cyclic formal of diglycol, or cyclic formal. Examples of the polyacetal copolymer obtained; a polyacetal copolymer having a branch obtained by copolymerizing a monofunctional glycidyl ether; a polyacetal copolymer having a crosslinked structure obtained by copolymerizing a polyfunctional glycidyl ether, and the like.
Further, as the (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. Polyacetal homopolymer having a formaldehyde monomer or its trimeric (trioxane) or tetramer (tetraoxane) in the presence of a compound having a functional group such as a hydroxyl group at both ends or one end, for example, hydrogenated polybutadiene glycol. A polyacetal copolymer having a blocking component obtained by copolymerizing a cyclic oligomer of formaldehyde such as the above with a cyclic ether or a cyclic formal can also be used.

<Polyacetal homopolymer>
The polyacetal homopolymer is produced, for example, by feeding a monomer such as formaldehyde, a chain transfer agent (molecular weight modifier) and a polymerization catalyst into a polymerization reactor into which a hydrocarbon-based 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 chain transferable components (components that generate unstable terminal groups) such as water, methanol, and formic acid, these chain transferable components are possible first. It is preferable to adjust the content of various components.
The content of the chain transferable component at this time is preferably in the range of 1 to 1000 ppm, more preferably 1 to 500 ppm, and further preferably 1 to 300 ppm with respect to formaldehyde as a monomer.
By adjusting the amount of chain-transferable components within the above range, a polyacetal resin homopolymer having excellent thermal stability can be obtained.

The molecular weight of the polyacetal homopolymer can be adjusted by chain transfer using a molecular weight modifier such as carboxylic acid anhydride or carboxylic acid.
As the molecular weight modifier, propionic anhydride and acetic anhydride are particularly preferable, and acetic anhydride is more preferable.
The amount of the molecular weight modifier introduced is adjusted and determined according to the characteristics (particularly melt flow rate) of the target polyacetal homopolymer. For example, the polyacetal homopolymer preferably has a melt flow rate (MFR value (based on ISO1133)) in the range of 0.1 to 100 g / 10 minutes, more preferably 1.0 g / 10 minutes to. The range should be 70 g / 10 minutes.
By setting the MFR value of the polyacetal homopolymer in the above range, a polyacetal homopolymer having excellent 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 represent 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-based polymerization catalysts, and among the onium salt-based polymerization catalysts, quaternary phosphonium salt-based compounds such as tetraethylphosphonium iodide and tributylethylphosphonium iodide, and tetramethyl Quaternary ammonium salt compounds such as ammonium bromide and dimethyl distearyl ammonium acetate are preferred.
The amount of the quaternary phosphonium salt compound or the quaternary ammonium salt compound added is preferably 0.0003 to 0.01 mol, more preferably 0.0008 to 0.005 mol, based on 1 mol of formaldehyde. It is more preferably 0.001 to 0.003 mol.

The hydrocarbon-based polymerization solvent may be any solvent that does not react with formaldehyde, and is not particularly limited. For example, a solvent such as pentane, isopentane, hexane, cyclohexane, heptane, octane, nonane, decane, and benzene. Can be mentioned.
Only one of these hydrocarbon solvents may be used alone, or two or more of them may be mixed and used, but hexane is particularly preferable.

In the polymerization step of the polyacetal homopolymer, it is preferable to first obtain a crude polyacetal homopolymer, and then to perform a stabilization treatment on the unstable terminal group as described later.
The polymerization apparatus for producing the crude polyacetal homopolymer is not particularly limited as long as it can simultaneously supply the monomer formaldehyde, the chain transfer agent (molecular weight modifier), the polymerization catalyst and the hydrocarbon-based polymerization solvent. From the viewpoint of productivity, a continuous polymerization apparatus is preferable.
Since the terminal groups of the polymer of the crude polyacetal homopolymer obtained by the polymerization step are thermally unstable, the unstable terminal groups are stabilized by blocking the polymer terminal groups with an esterifying agent or an etherifying agent. It is preferable to carry out a polymerization treatment.
In the terminal stabilization of the crude polyacetal homopolymer by esterification, for example, the crude polyacetal homopolymer and the esterifying agent and the esterification catalyst are put into a terminal stabilizing reactor into which a hydrocarbon solvent is introduced, and the reaction is carried out. It can be done by letting it.
The reaction temperature and reaction time at this time are not limited, but for example, the reaction temperature is preferably 130 to 155 ° C, the reaction time is preferably 1 to 100 minutes, and 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 even more preferably 10 to 100 minutes.

As the esterifying agent that seals 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, benzoic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, propionic anhydride, and acetic anhydride, which are preferable. Is acetic anhydride.
Only one of these esterifying agents may be used alone, or two or more thereof may be mixed and used.

As the esterification catalyst, an alkali metal salt of a carboxylic acid having 1 to 18 carbon atoms is preferable, and the addition amount thereof can be appropriately selected in the range of 1 to 1000 ppm with respect to the polyacetal homopolymer.
The alkali metal salt of the carboxylic acid having 1 to 18 carbon atoms is not limited to the following, but for example, the carboxylic acid is formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caprylic acid, enanthic acid, caprylic acid. , Pelargonic acid, caprylic acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid alkali metal salts, and examples of the alkali metals include lithium, sodium, potassium, rubidium, and cesium.
Among these metal carboxylic acid salts, alkali metal salts of lithium acetate, sodium acetate, and potassium acetate are preferable.

It is also possible to seal and stabilize the terminal groups of the crude polyacetal homopolymer described above by etherification.
Examples of the etherifying agent in this case include orthoesters of aliphatic or aromatic acids and aliphatic, alicyclic or aromatic alcohols, such as methyl or ethyl orthoformates, methyl or ethyl orthoacetate and methyl or methyl. Select from ethyl orthobenzoate and orthocarbonate, specifically ethyl orthocarbonate, medium-strength organic acids such as p-toluenesulfonic acid, acetic acid and odoric acid, medium-strength mineral acids such as dimethyl and diethylsulfate, etc. It can be obtained by using the Lewis acid type catalyst of.
The solvent used for the etherification reaction when the terminal group of the crude polyacetal homopolymer is sealed and stabilized by etherification is not limited to the following, but is, for example, pentane, hexane, cyclohexane and benzene. Low-boiling aliphatic organic solvents such as; alicyclic group and aromatic hydrocarbon-based organic solvents; organic solvents such as halogenated lower aliphatic solvents such as methylene chloride, chloroform and carbon tetrachloride can be mentioned.

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

<Polyacetal copolymer>
The polyacetal copolymer uses, but is not limited to, a glycol such as 1,3-dioxolane or 1,4-butanediolformal as a comonomer, a cyclic ether such as cyclic formal of diglycol, or a cyclic formal. , These can be produced by copolymerizing with a monomer 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%, and further preferably 0.04 to 3 mol% with respect to 1 mol of formaldehyde. ..
When the proportion of comonomer is in the above range, polyacetal resin pellets having more excellent mechanical strength can be obtained.

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 its ester or anhydride.
Lewis acids include, but are not limited to, halides of boric acid, tin, titanium, phosphorus, arsenic and antimony, specifically boron trifluoride, tin tetrachloride, tetrafluoride. Examples thereof include titanium chloride, phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride and complex compounds or salts thereof.
The protonic acid and its ester or anhydride are not limited to the following, and include, for example, percrolic acid, trifluoromethanesulfonic acid, perchloric acid-quaternary butyl ester, acetylparklorate, and trimethyloxonium hexa. Fluorophosphate and the like can be mentioned.
Among these, boron trifluoride; boron trifluoride hydrate; and a coordination compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable, and for example, boron trifluoride diethyl ether, Boron trifluoride di-n-butyl ether is preferred.
The amount of boron trifluoride added is preferably 0.10 × 10 ^-4 mol or less, more preferably 0.07 × 10 ^-4 mol or less, and further preferably 0.07 × 10 ^-4 mol or less, based on 1 mol of formaldehyde. Preferred is 0.03 to 0.05 × 10 ^-4 mol.
When the amount of boron trifluoride added is within 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, a massive polymerization method may be used, and either a batch method or a continuous method can be applied. Is.
The polymerization apparatus is not particularly limited, and examples thereof include self-cleaning extrusion kneaders such as a conider, a twin-screw type continuous extrusion kneader, and a twin-screw paddle type continuous mixer.
The melted monomer is supplied to the polymerization machine, and as the polymerization progresses, a solid mass polyacetal copolymer is obtained.

Since the polyacetal copolymer obtained by the above polymerization may have a thermally unstable terminal portion [-(OCH ₂ ) _n- OH group], the decomposition and removal treatment of this unstable terminal portion may be performed. It is preferable to carry out. As a method for decomposing and removing the unstable end portion, a known method can be used.
As described above, in the present embodiment, the (A) polyacetal resin is not limited, and both the polyacetal homopolymer and the polyacetal copolymer can be used.
Of 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 at at least one ortho position of a hydroxyl group). It means that.
(B) The nitrogen-containing hindered phenol compound is not limited to the following, but is, for example, 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], 1,3,5-tris [[3,5-bis (1,5-bis) 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 can be mentioned.
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)]. Propionil] Hydradin.

The melting point of the nitrogen-containing hindered phenol compound (B) is preferably in the range of 50 to 300 ° C, more preferably 100 ° C to 300 ° C, and even more preferably 150 to 250 ° C.
When the melting point of the nitrogen-containing hindered phenol compound (B) is in the above range, a polyacetal resin composition having more excellent thermal stability can be provided.

In the polyacetal resin composition of the present embodiment, the (B) 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 above-mentioned (A) polyacetal resin. From the viewpoint of the effect of improving thermal stability, it was found by the studies of the present inventors that the content of the nitrogen-containing hindered phenol compound (B) has an appropriate range. The nitrogen-containing hindered phenol compound is preferably contained in an amount of 0.005 to 0.2 parts by mass, preferably 0.005 to 0.15 parts by mass, based on 100 parts by mass of the (A) polyacetal resin. Is more preferable.
When the content of the nitrogen-containing hindered phenol compound (B) is within the above range, a polyacetal resin composition having excellent thermal stability can be provided.
Polyacetal resin composition of the present embodiment the (B) nitrogen-containing hindered phenolic compounds as a method of quantifying, for example, a polyacetal resin pellets were frozen ground and Soxhlet extraction with a solvent such as chloroform, GCMS, or ¹ H, -A method of quantifying by NMR can be mentioned.

[(C) Nitrogen-free hindered phenolic compound]
In the present embodiment, the nitrogen-free hindered phenol compound refers to a hindered phenol compound whose structural formula does not contain a nitrogen atom. Hindered phenol compounds are generally known as antioxidants, but in the present embodiment, both nitrogen-containing and nitrogen-free compounds are used in combination, thereby achieving very good thermal stability.
The nitrogen-free hindered phenol compound (C) is not limited to the following, but is, 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-Butandiol-bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate], triethylene glycol-bis- [3- (3-t-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-t-butyl-5-methyl-4-hydroxyphenyl) -propionate].

The melting point of the nitrogen-free hindered phenol compound (C) is preferably in the range of 30 to 120 ° C, more preferably 50 ° C to 120 ° C, and even more preferably 50 to 100 ° C.
When the melting point of the nitrogen-free hindered phenol compound (C) is in the above range, a polyacetal resin composition having more excellent thermal stability can be provided.

In the polyacetal resin composition of the present embodiment, the (C) 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 above-mentioned (A) polyacetal resin. The nitrogen-free hindered phenol compound is preferably contained in an amount of 0.005 to 0.3 parts by mass, preferably 0.005 to 0.27 parts by mass, based on 100 parts by mass of the (A) polyacetal resin. It is more preferable that it is.
When the content of the nitrogen-free hindered phenol compound (C) is in the above range, a polyacetal resin composition having excellent thermal stability can be provided.
As a method for quantifying the (C) nitrogen-free hindered phenol compound in the polyacetal resin composition of the present embodiment, for example, polyacetal resin pellets are freeze-ground, soxhlet extracted with a solvent such as chloroform, GCMS, or ¹ A method of quantifying by H-NMR can be mentioned.

[(D) Talc]
(D) Talc is a particle composed of hydrous magnesium silicate, and its composition is generally shown by [Mg ₃ Si ₄ O ₁₀ (OH) ₂ ], and SiO _{2 is} about 60% by mass and MgO is about 30% by mass. The main component is 4.8% by mass of water of crystallization. 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 9.0 to 10 measured according to JIS K-5101. It is preferably in the range of. The 45 μm sieve residue is preferably 0.2% by mass or less, more preferably 0.1% by mass or less, and more preferably 0.08% by mass or less, as measured according to JIS K-5101. is there. The average particle size of (D) talc is preferably 1 to 30 μm, more preferably 2 to 25 μm, and even more preferably 2 to 20 μm. When the average particle size of (D) talc is in the above range, a polyacetal resin composition having more excellent thermal stability can be provided.
In the present embodiment, (D) talc may be surface-treated with a known surface treatment agent in order to improve the affinity with (A) polyacetal resin.
Examples of the surface treatment agent include silane coupling agents such as aminosilane and epoxysilane, titanate-based coupling agents, fatty acids (saturated fatty acids and unsaturated fatty acids), alicyclic carboxylic acids, resin acids and metal soaps. Can be done. The amount of the surface treatment agent added is preferably 3% by mass or less, more preferably 2% by mass or less, and most preferably substantially not 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 the (A) polyacetal resin. (D) If the content of talc is low, a sufficient effect of improving thermal stability cannot be obtained, but if it is too high, the thermal stability is affected by the basicity of talc itself or the impurities contained in it. Has been found to decrease by the studies of the present inventors. For this reason, (D) talc is preferably contained in an amount of 0.0005 to 0.1 parts by mass, preferably 0.0005 to 0.05 parts by mass, based on 100 parts by mass of the (A) polyacetal resin. Is more preferable.
When the content of (D) talc is within the above range, a polyacetal resin composition having excellent thermal stability can be provided.

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 or the like to quantify talc, or high frequency inductively coupled plasma (ICP) emission. A method of quantifying metallic components (Si, Mg) caused by talc by analysis can be mentioned.

[(E) Stabilizer]
In the polyacetal resin composition of the present embodiment, good thermal stability is achieved by the combination addition of (B) to (D) described above, so that no other stabilizer may be added, but further In order to improve the thermal stability and the stability of other physical properties, (E) various stabilizers may be further contained.
Examples of the stabilizer (E) include amino-substituted triazine compounds, urea derivatives, hydrazide derivatives, amide compounds, polyamides, and acrylamide polymers.

The amino-substituted triazine compound is not limited to the following, and is, for example, 2,4-diamino-sim-triazine, 2,4,6-triamino-sim-triazine, N-butylmelamine, N-phenyl. Melamine, N, N-diphenylmelamine, N, N-diallylmelamine, benzoguanamine (2,4-diamino-6-phenyl-sim-triazine), acetoganamin (2,4-diamino-6-methyl-sim-triazine) , 2,4-Diamino-6-butyl-sim-triazine and the like.

The urea derivative is not limited to the following, and examples thereof include N-substituted urea, a urea condensate, ethylene urea, a hydantoin compound, and a ureido compound.
The N-substituted urea is not limited to the following, and examples thereof include methyl urea having a substituent such as an alkyl group, alkylene bisurea, and aryl substituted urea. The urea condensate is not limited to the following, and examples thereof include a condensate of urea and formaldehyde. Examples of the hydantoin compound include, but are not limited to, hydantoin, 5,5-dimethylhydantoin, 5,5-diphenylhydantoin and the like. The ureido compound is not limited to the following, and examples thereof include allantoin and the like.

The hydrazide derivative is not limited to the following, and examples thereof include 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 the reaction of a carboxylic acid (aromatic, alicyclic) with hydrazine. Carboxylic Acids Examples of carboxylic acids that make up mono / or dihydrazide compounds include formic acid, acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, lauric acid, and myristic acid. Palmitic acid, margaric acid, stearic acid, behenic acid. Dicarboxylic acids include 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, and gallic acid. , Melitoic acid, silicic acid, pyruvate, lactic acid, malic acid, citric acid, fumaric acid, maleic acid, aconitic acid, amino acids, nitrocarboxylic acid. Examples of unsaturated carboxylic acids include oleic acid, linoleic acid, linolenic acid, arachidonic acid, docosahexaenoic acid, and eicosapentaenoic acid. The carboxylic acid mono (di) hydrazide compounds synthesized using these carboxylic acids include, for example, carbodihydrazine, mono (di) hydrazide oxalate, mono (di) hydrazide malonic acid, mono (di) hydrazide succinate, and glutal. Acid mono (di) hydrazide, adipate mono (di) hydrazide, sebacic acid mono (di) hydrazide, laurate mono (di) hydrazide, malic acid dihydrazide, tartrate dihydrazide, propionate monohydrazide, laurate 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-cyclohexandicarboxylic acid dihydrazine, aceto Examples thereof include hydrazide, acrylohydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, benzohydrazide, nicotine hydrazide, isonicotinohydrazide, isobutyl hydrazine and oleate hydrazide. Among these carboxylic acids, dicarboxylic acids such as adipic acid, sebacic acid and lauric acid are preferable, and mono (di) hydrazide of adipic acid, mono (di) hydrazide of sebacic acid and mono (di) hydrazide of laurate 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 anthranilamide.

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, and nylon 12, and polymers thereof, for example, nylon. Examples thereof include 6 / 6-6 / 6-10 and nylon 6 / 6-12.

The acrylamide polymer is not limited to the following, but for example, acrylamide is polymerized or a monomer having a vinyl group other than acrylamide is polymerized using an alkylate earth metal alcoholate as a catalyst. Can be manufactured by.
Examples of the monomer having a vinyl group other than acrylamide constituting the acrylamide polymer include a monomer having one or two vinyl groups.
The monomer having one vinyl group is not limited to the following, but for example, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, ethyl methacrylate, cyclohexyl methacrylate, 2-ethylhexyl methacrylate, and the like. Examples thereof include cecil methacrylate, pentadecyl methacrylate, stearyl methacrylate, behenyl methacrylate, hydroxypropyl methacrylate, polypropylene glycol methacrylate, polyethylene glycol methacrylate and the like.
The monomer having two vinyl groups is not limited to the following, and examples thereof include divinylbenzene, ethylene bisacrylamide, and N, N'-methylene bisacrylamide.
Among these vinyl-containing monomers, N, N'-methylenebisacrylamide is preferable.
The amount of the monomer having a vinyl group 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 monomer having a vinyl group.
By copolymerizing with the above-mentioned monomer having a vinyl group (having a crosslinked structure), the extrusion productivity of the polyacetal resin pellets can be improved.
The average particle size of the acrylamide polymer is preferably 0.1 to 20 μm, more preferably 0.1 to 15 μm, and even more preferably 0.1 to 10 μm.
When the average particle size of the acrylamide polymer is in 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.

The amount of the stabilizer (E) added is preferably 0.001 to 5 parts by mass, more preferably 0.001 to 3 parts by mass, and further preferably 0.01 to 0.01 parts by mass with respect to 100 parts by mass of the polyacetal resin. It is 1 part by mass.
By setting the amount of the heat stabilizer added to the polyacetal resin within the above range, a polyacetal resin composition having more excellent thermal stability can be obtained.

[Other additives]
In addition to those described above, the polyacetal resin composition of the present embodiment includes known additives such as formic acid trapping agent, weather stabilizer, mold release agent, lubricant, conductive agent, thermoplastic resin, and thermoplastic elastomer. Dyeing pigments, pigments, inorganic fillers, organic fillers and the like may be added.
Only one type of these additives may be used alone, or two or more types may be used in combination.

The formic acid trapping agent is not limited to the following, but is, for example, (E) an amino-substituted triazine compound or a condensate of an amino-substituted triazine compound and formaldehyde as specific examples of the stabilizer, for example, melamine / formaldehyde. Condensates and the like can be mentioned.
Other formic acid trapping agents include, but are not limited to, hydroxides, inorganic acid salts, carboxylates or alkoxides of alkali metals or alkaline earth metals. Examples include hydroxides such as sodium, potassium, magnesium, calcium or barium; carbonates, phosphates, silicates, borates, carboxylates and layered double hydroxides of the above metals.
The carboxylic acid of the carboxylic acid salt 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. Saturated or unsaturated aliphatic carboxylates include, but are not limited to, calcium dimyristate, calcium dipalmitate, calcium distearate, calcium (myristic acid-palmitate), (myristic acid). Calcium (stearic acid), calcium (palmitic acid-stearic acid), calcium 12hydroxystearate can be mentioned, and calcium dipalmitate, calcium distearate, and calcium 12-hydroxydistearate are preferable.
Only one type of formic acid trapping agent may be used alone, or two or more types may be used in combination.

The weather-resistant stabilizer is not limited to the following, and for example, at least one selected from the group consisting of benzotriazole-based compounds, oxalic acid-anilide-based compounds, and hindered amine-based light stabilizers is preferable. Be done.
The benzotriazole-based compound is not limited to the following, but is, for example, 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 can be mentioned.
Only one of these compounds may be used alone, or two or more of these compounds may be used in combination.
The oxalic acid alinide-based compound is not limited to the following, and is, for example, 2-ethoxy-2'-ethyloxalic acid bisanilide, 2-ethoxy-5-t-butyl-2'-ethyloxy. Examples thereof include oxalic acid bisanilide and 2-ethoxy-3'-dodecyl oxalic acid bisanilide.
Only one of these compounds may be used alone, or two or more of these compounds may be used in combination.
The hindered amine-based light stabilizer is not limited to the following, but is, for example, 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-tetramethylpiperidine, 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) -sevacate, 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-piperidyltrilen-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-tricarboxy Rate, tris (2,2,6,6-tetramethyl-4-piperidyl) -benzene-1,3,4-trical Boxylate, 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-tetramethylpiperidin, 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] condensate with diethanol, and the like.
As the hindered amine-based light stabilizer, only one type may be used alone, or two or more types may be used in combination.

Among them, preferred weather-resistant stabilizers are 2- [2'-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] benzotriazole and 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) sevacate, bis (2,2,6,6-tetramethyl-4-piperidinyl) sevacate, 1,2,3,4-butanetetra Carboxylic acid and 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β', β', -tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (2,4,8,10-tetraoxaspiro) 5,5) Undecane] A condensate with diethanol.

The release agent and the lubricant are not limited to the following, and examples thereof include alcohols, fatty acids and fatty acid esters thereof, olefin compounds having an average degree of polymerization of 10 to 500, and silicones. ..
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, and fibers.
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.
The thermoplastic resin also includes the above-mentioned modified resin.

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

The dyeing pigment is not limited to the following, and examples thereof include inorganic pigments, organic pigments, metallic pigments, and fluorescent pigments.
Inorganic pigments are those generally used for coloring resins, and are not limited to the following, for example, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, and fuel. Pigments, carbonates, phosphates, acetates, carbon blacks, acetylene blacks, lamp blacks and the like can be mentioned.
Organic pigments are not limited to the following, but are not limited to the following, for example, condensed uso-based, inone-based, phthalocyanine-based, monoazo-based, diazo-based, polyazo-based, anthraquinone-based, heterocyclic, pennon-based, and quinacridone-based pigments. , Thioindico-based, berylene-based, dioxazine-based, phthalocyanine-based pigments and the like.
Only one type of dyeing pigment may be used alone, or two or more types may be used in combination.
It is difficult to clarify the addition ratio of the pigment because it varies greatly depending on the color tone, but it is generally 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 a polyolefin resin, an acrylic resin, a styrene resin, a polycarbonate resin, and an uncured epoxy resin.
Only one type of other resin may be used alone, or two or more types may be used in combination.

The inorganic filler is not limited to the following, and for example, fibrous, powdery, plate-like, and hollow fillers are used.
The fibrous filler is not limited to the following, and includes, for example, glass fiber, carbon fiber, silicone fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate. Examples thereof include fibers and inorganic fibers such as metal fibers such as stainless steel, aluminum, titanium, copper and brass. In addition, whiskers such as potassium titanate whiskers and zinc oxide whiskers having short fiber lengths are also included.
The powdery filler is not limited to the following, but is not limited to, for example, carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, magnesium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, and wow. Silicates such as lastnite; 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, etc. Examples include various metal powders.
The plate-shaped filler is not limited to the following, and examples thereof include mica, glass flakes, and various metal foils.
The hollow filler is not limited to the following, and examples thereof include 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, fluororesin, and acrylic resin.
Only one kind of these fillers may be used alone, or two or more kinds thereof may be used in combination.

Both of these fillers can be used as surface-treated fillers or unsurface-treated fillers, but in terms of the smoothness and mechanical properties of the molded surface, the use of surface-treated fillers is used. May be preferable.
The surface treatment agent is not particularly limited, and conventionally known surface treatment agents can be used.
The surface treatment agent is not limited to the following, but is, for example, various coupling treatment agents such as silane type, titanate type, aluminum type and zirconium type, resin acid, organic carboxylic acid, salt of organic carboxylic acid and the like. , Surfactants can be used.
Specifically, but not limited to the following, for example, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltristearoyl titanate, di Examples thereof include isopropoxyammonium ethyl acetate and n-butylzirconeate.

The method for producing the polyacetal resin composition of the present embodiment is not particularly limited.
In general, (A) a polyacetal resin, (B) a nitrogen-containing hindered phenol compound, (C) a nitrogen-free hindered phenol compound, and (D) talc are optionally provided as described above. Is obtained by mixing the components of the above with, for example, a Henschel mixer, a tumbler, a V-shaped blender, or the like, and then kneading with a kneader such as a single-screw or multi-screw extruder, a heating roll, a kneader, or a Banbury mixer. Be done. Above all, kneading with an extruder equipped with a vent decompression device is preferable from the viewpoint of productivity. Further, in order to stably produce a polyacetal resin composition in a large amount, a single-screw or twin-screw extruder is preferably used.
Further, it is also possible to continuously feed each component individually or in groups of several types to the extruder without mixing in advance with a quantitative feeder or the like.
It is also possible to prepare a high-concentration masterbatch composed of each component in advance and dilute it with a polyacetal resin at the time of extrusion melt kneading.
The kneading temperature may be in accordance with the preferable 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 assisted injection molding, and foam injection molding. , Low-pressure molding, ultra-thin wall injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, outsert molding), or any other molding method.
Among these, the injection molding method is preferable from the viewpoint of stable productivity.

[Use]
In the polyacetal resin composition of the present embodiment, even if continuous molding is performed using a hot runner mold, the polyacetal resin is less thermally decomposed, and therefore the mold is less contaminated.
Further, even if the polyacetal resin composition of the present 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 products 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, trays, 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.
Also, as parts for automobiles, fuel parts such as gasoline tanks, fuel pump modules, valves, and gasoline tank flanges; door parts; seatbelt peripheral parts; combination switch parts; switches are preferably used. To.
Further, it can be suitably used as an industrial part represented by housing equipment.

Hereinafter, the present embodiment will be described with reference to specific examples and comparative examples thereof, but the present embodiment is not limited to the following examples.
The measurement / evaluation methods applied in the examples and comparative examples are shown below.
[Measurement / evaluation method]
<Evaluation of mold deposit by hot runner mold>
Using a molding machine having the configuration shown in FIG. 1, the mold deposit property of the polyacetal resin composition was evaluated according to the following (a) molding conditions. The following (b) was used as the evaluation standard.
(A) Molding conditions-Injection molding machine: Toshiba Machine Co., Ltd. IS-100GN
(No degassing part at the end of the molten resin flow path, with weld part)
・ Cylinder set temperature: 230 ℃
・ Manifold set temperature: 240 ° C (nozzle automatic opening / closing type)
・ Mold set temperature: 80 ℃
-Molding cycle: Injection time / Cooling time = 20/20 seconds-Mold size: 70 x 60 mm x 3 mm
(B) Evaluation Criteria Based on the following evaluation criteria, the state of adhesion of mold deposits 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: Adhesions were observed in the range of 5% or more and less than 10% in the mold cavity 3: Adhesions 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% or more and less than 30% in the mold cavity.
5: Deposits were observed in the range of 30% or more in the mold cavity.

<Method of measuring the amount of formaldehyde emitted from molded products>
(1) Molding machine No retention in the cylinder Tested using an IS-100GN injection molding machine manufactured by Toshiba Corporation with a cylinder temperature of 220 ° C., 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. The piece was molded. The molded product from the start of molding to the 5th shot was discarded, and the amount of formaldehyde released from the molded product was measured for the 6th shot molded product under the conditions shown below (VDA275 method).
(2) Molding machine with retention in the cylinder Using an IS-100GN injection molding machine manufactured by Toshiba Corporation, a test was performed at a cylinder temperature of 220 ° C., 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. The piece was molded.
While molding the 5th shot (the molten resin is weighed in the molding machine cylinder and is in the cooling zone), the molding machine is stopped and the cylinder temperature is maintained at 220 ° C. in the molding machine cylinder. The molten resin was allowed to stay in the water 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 the 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 to form a test piece. Obtained. The amount of formaldehyde released from the molded product was measured under the following conditions (VDA275 method) for the molded product molded immediately after the residence.
* VDA275 method:
A test piece (length 100 mm x width 40 mm x thickness 3 mm) of a specified size of 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 a 0.4% by mass aqueous solution of acetylacetone and 5 mL of a 20% by mass aqueous solution of ammonium acetate were added to 5 mL of distilled water having absorbed formaldehyde, and the mixture was heated at 40 ° C. for 15 minutes to react formaldehyde with acetylacetone.
Further, after cooling the mixed solution to room temperature, the amount of formaldehyde in the distilled water was quantified from the absorption peak at 412 nm using a UV spectrophotometer.
The amount of formaldehyde (mg / kg) released from the molded product was calculated by the following formula.
Amount of formaldehyde released from the molded product (mg / kg)
= Amount of formaldehyde in distilled water (mg) / Mass of polyacetal resin molded product used for measurement (kg)

[Ingredients]
The raw material components used in Examples and Comparative Examples are shown below.
<(A) Polyacetal resin>
A twin-screw paddle type continuous polymerization reactor with a jacket (manufactured by Kurimoto, Ltd., diameter 2B, L / D = 14.8) was adjusted to 80 ° C., and the raw material was subjected to the polymerization conditions (supply rate) shown below. Etc. were supplied to polymerize the polyacetal copolymer.
The unstable terminal groups of the obtained crude polymer were removed under the terminal stabilization conditions shown below, and a polyacetal copolymer (polyacetal) having a comonomer component content derived from 1,3-dioxolane of 4 mol% and an MFR value of 9 g / 10 min was removed. Resin (A-1)) was obtained.
The polymerization conditions (raw material supply rate) and terminal stabilization conditions of the polyacetal copolymer are shown below.
[Polymerization conditions]
The raw materials were supplied to the reactor at the supply rates shown below.
-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 supply 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 on a separate line from the above other components.
[Terminal stabilization conditions]
The crude polyacetal child polymer discharged from the polymerization reactor is immersed in a triethylamine aqueous solution (0.5% by mass), then stirred at room temperature for 1 hr, filtered through a centrifuge, and 120 ° C. under nitrogen. The mixture was dried for × 3 hr 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] (Irganox1098)
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-t-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]
In 100 parts by mass of (A-1) polyacetal resin, 0.05 parts by mass of (B-1) 1,2-bis [3- (4-hydroxy-3,5-di-t-butylphenyl) propionyl] hydrazine. (C-1) Triethylene glycol-bis [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] 0.1 part by mass and (D-1) talc 0.01 part by mass And were uniformly mixed using a Henschel mixer to obtain a mixture.

This mixture was fed from the top feed port of a twin-screw extruder with a 30 mm vent set at 200 ° C., and melt-kneaded and pelletized at a screw rotation speed of 80 rpm, a vent pressure reduction degree of −0.09 MPa, and a discharge rate of 5 kg / hr. Then, the pellet was dried at a hot air temperature of 80 ° C. for 3 hours to obtain a polyacetal resin pellet.
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 above-mentioned method. The evaluation results are shown in Table 1 below.

[Examples 2 to 10, Reference Examples 1 to 5 ]
The same operation as in Example 1 was carried out except that the composition was as shown in Table 1, 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 evaluated and measured by the above-mentioned method. 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 twin-screw extruder with a 30 mm vent set at 200 ° C., screw rotation speed 80 rpm, vent decompression degree −0.09 MPa, discharge rate 5 kg / hr. After melt-kneading and pelletizing the pellets, 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 evaluated and measured by the above-mentioned method. The evaluation results are shown in Table 1 below.

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

[Comparative Examples 3 to 10]
The same operation as in Example 1 was carried out except that the composition was as shown in Table 1, 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 evaluated and measured by the above-mentioned method. The evaluation results are shown in Table 1 below.

As shown in Table 1, the polyacetal resin compositions obtained in Examples 1 to 10 are excellent in mold deposit property even when continuous molding is performed using a hot runner mold, and the obtained molding is performed. Although the product was molded under severe molding conditions, the amount of formaldehyde emission was also small.

The polyacetal resin composition of the present invention can be used in a wide range of fields such as automobiles, electric / 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 in which the resin composition is exposed to a high temperature for a long time is adopted.

Claims (3)

(A) 100 parts by mass of polyacetal resin, (B) 0.05 to 0.2 parts by mass of nitrogen-containing hindered phenol compound, and (C) 0.1 to 0.3 parts by mass of nitrogen-free hindered phenol compound. , (D) Containing 0.01 to 0.1 parts by mass of talc ,
The nitrogen-containing hindered phenolic compound (B) contains a hydrazine structure.
Polyacetal resin composition. The polyacetal resin composition according to claim 1, wherein the content of the nitrogen-containing hindered phenol compound is 0.05 to 0.15 parts by mass with respect to 100 parts by mass of the (A) polyacetal resin. Further, according to claim 1 or 2 , the (E) other stabilizer contains at least one selected from the group consisting of an amino-substituted triazine compound, a urea derivative, a hydrazide derivative, an amide compound, a polyamide, and an acrylamide copolymer. The polyacetal resin composition according to the above.