JP7368946B2 - Polyacetal resin compositions and molded products - Google Patents

Description

The present invention relates to a polyacetal resin composition and a molded article. In particular, it relates to polyacetal resin compositions and molded articles that have a metallic feel.

Polyacetal resin has high mechanical strength and rigidity, excellent oil resistance and organic solvent resistance, is well-balanced over a wide temperature range, and is easily processable. Therefore, polyacetal resin is widely used as a typical engineering plastic in OA equipment, digital home appliances, automobile parts, and other industrial parts.

For example, Patent Document 1 describes 100 parts by mass of a polyacetal resin with a melt flow rate of 1.0 to 5.0 g/10 minutes, 0.01 to 5 parts by mass of a hydrazide compound, and a number average molecular weight of 5,000 to 25,000. The following polyacetal resin composition containing 0.01 to 1 part by weight of polyethylene glycol and 0.01 to 5 parts by weight of a colored pigment is disclosed.
Furthermore, Patent Document 2 states that (A) 100 parts by mass of polyacetal, (B) 0.1 to 10 parts by mass of flat aluminum particles having an average particle size of 3 to 200 μm and an average thickness of 0.1 to 40 μm; , (C) 0.01 to 5 parts by weight of a hindered amine light stabilizer, (D) 0.1 to 5 parts by weight of an ultraviolet absorber, and (E) 0.01 to 5 parts by weight of a stabilizer having formaldehyde-reactive nitrogen. Disclosed is a polyacetal resin composition characterized by containing:

Japanese Patent Application Publication No. 2015-074724 JP2012-092185A

However, polyacetal resin has a problem in that a slight thermal decomposition reaction occurs due to the thermal history during its production, processing and molding, and formaldehyde is generated, albeit in an extremely small amount. In particular, when polyacetal resin is used in a closed space such as an interior part of an automobile, the generation of formaldehyde can be a serious problem.
Furthermore, molded articles formed from polyacetal resin may be required to have a metallic tone depending on the purpose. In order to impart a metallic tone, it is conceivable to add a metallic pigment, for example, as described in Patent Document 2. However, in the aluminum-based design pigment, which is a metallic pigment described in Patent Document 2, rust may occur due to oxidation in the air. Therefore, depending on the application, polyacetal resin compositions exhibiting other metallic tones are required. Additionally, when pigments are generally added, formaldehyde tends to be generated more easily.
The present invention aims to solve such problems, and provides a polyacetal resin composition that suppresses the generation of formaldehyde and has a metallic tone, and a molded article formed from the resin composition. With the goal.

Based on the above problem, the present inventor conducted studies and found that the above problem can be solved by using a non-metallic design pigment as a pigment that imparts a metallic tone.
Specifically, the above problem was solved by the following means.
<1> Contains 0.3 to 1.5 parts by mass of a non-metallic design pigment and a formaldehyde scavenger per 100 parts by mass of the polyacetal resin, and the formaldehyde scavenger reacts with formaldehyde per 1 g of the polyacetal resin. A polyacetal resin composition containing possible reactive groups in a proportion of 3.0 μmol or more.
<2> The polyacetal resin further contains at least one of 0.1 to 0.7 parts by mass of an ultraviolet absorber and 0.05 to 0.5 parts by mass of a hindered amine light stabilizer, based on 100 parts by mass of the polyacetal resin. The resin composition according to item 1>.
<3> The resin composition according to <1> or <2>, wherein the formaldehyde scavenger contains at least one selected from the group consisting of a hydrazide compound, a hydrazone compound of a hydrazine compound, a guanamine compound, and a urea compound. thing.
<4> Furthermore, 0.01 to 3 parts by mass of a polyamide resin is contained based on 100 parts by mass of the polyacetal resin, and the polyamide resin satisfies the following (A) or (B), <1> to <3>. The resin composition according to any one of the above;
(A) The melting point and/or softening point of the polyamide resin is 180°C or lower. (B) The amine value of the polyamide resin is 2 mgKOH/g or higher.
<5> The resin composition according to any one of <1> to <4>, which contains the formaldehyde scavenger in an amount of 0.05 to 0.5 parts by mass based on 100 parts by mass of the polyacetal resin.
<6> The nonmetallic design pigment according to any one of <1> to <5>, wherein the nonmetallic design pigment contains at least one of a mica-based design pigment, a borosilicate glass-based design pigment, and a silica flake-based design pigment. Resin composition.
<7> The resin composition according to any one of <1> to <6>, wherein the nonmetallic design pigment includes a mica design pigment.
<8> The resin composition according to any one of <1> to <7>, wherein the nonmetallic design pigment includes a borosilicate glass design pigment.
<9> A molded article formed from the resin composition according to any one of <1> to <8>.
<10> A metallic molded article formed from the resin composition according to any one of <1> to <9>.

EFFECT OF THE INVENTION According to the present invention, it has become possible to provide a metallic polyacetal resin composition in which formaldehyde generation is suppressed and a molded article formed from the resin composition.

The content of the present invention will be explained in detail below. In addition, in this specification, "~" is used to include the numerical values described before and after it as a lower limit value and an upper limit value.

The polyacetal resin composition of the present invention (hereinafter sometimes referred to as "the composition of the present invention") contains 0.3 to 1.5 parts by mass of a non-metallic design pigment and a formaldehyde scavenger to 100 parts by mass of the polyacetal resin. The formaldehyde scavenger is characterized in that the formaldehyde scavenger contains 3.0 μmol or more of reactive groups capable of reacting with formaldehyde per gram of the polyacetal resin.
By using a non-metallic design pigment and blending a formaldehyde scavenger in a ratio such that the number of reactive groups capable of reacting with formaldehyde is 3.0 μmol or more per gram of polyacetal resin, the generation of formaldehyde is suppressed, and We have succeeded in providing a metallic-like polyacetal resin composition. Although the reason for this is not clear, it is presumed that when a non-metallic design pigment is used, aldehyde is relatively less likely to be generated in the polyacetal resin.
Furthermore, they succeeded in increasing light resistance.

<Polyacetal resin>
The resin composition of the present invention contains a polyacetal resin.
The polyacetal resin is not particularly limited, and even if it is a homopolymer containing only divalent oxymethylene groups as a constituent unit, it may contain a divalent oxymethylene group and a divalent oxyalkylene having 2 to 6 carbon atoms. It may also be a copolymer containing the group as a constituent unit.

Examples of the oxyalkylene group having 2 to 6 carbon atoms include oxyethylene group, oxypropylene group, and oxybutylene group.

In the polyacetal resin, the proportion of the oxyalkylene group having 2 to 6 carbon atoms in the total number of moles of the oxymethylene group and the oxyalkylene group having 2 to 6 carbon atoms is not particularly limited, and is 0.5 to 10 mol. % is sufficient.

In order to manufacture the above polyacetal resin, trioxane is usually used as the main raw material. Further, in order to introduce an oxyalkylene group having 2 to 6 carbon atoms into the polyacetal resin, a cyclic formal or a cyclic ether can be used. Specific examples of cyclic formals include 1,3-dioxolane, 1,3-dioxane, 1,3-dioxepane, 1,3-dioxocane, 1,3,5-trioxepane, 1,3,6-trioxocane, etc. Specific examples of the cyclic ether include ethylene oxide, propylene oxide, and butylene oxide. To introduce oxyethylene groups into polyacetal resin, 1,3-dioxolane may be used as the main raw material, and to introduce oxypropylene groups, 1,3-dioxane may be used as the main raw material. In order to introduce an oxybutylene group, 1,3-dioxepane may be used as the main raw material. In addition, in the polyacetal resin, the amount of hemiformal terminal groups, the amount of formyl terminal groups, and the amount of terminal groups unstable to heat, acids, and bases is preferably small. Here, the hemiformal terminal group is represented by --OCH ₂ OH, and the formyl terminal group is represented by --CHO.

The melt index (ASTM-D1238 standard: 190° C., 2.16 kg) of the polyacetal resin is preferably 1.0 g/10 minutes to 100 g/10 minutes.

As the polyacetal resin, in addition to the above, polyacetal resins described in paragraphs 0018 to 0043 of JP 2015-074724A can be used, the contents of which are incorporated herein.

The resin composition of the present invention preferably contains polyacetal resin in an amount of 70% by mass or more, more preferably 75% by mass or more, and even more preferably 78% by mass or more. The upper limit is preferably 99.8% by mass or less. By setting it as such a range, the effect of this invention tends to be exhibited more effectively.
The resin composition of the present invention may contain only one type of polyacetal resin, or may contain two or more types of polyacetal resin. When two or more types are included, it is preferable that the total amount falls within the above range.

<Non-metallic design pigments>
The resin composition of the present invention contains a non-metallic design pigment.
Non-metallic design pigments refer to design pigments whose base material is composed of something other than an elemental metal or a metal alloy. When it is composed only of a base material, it refers to a design pigment in which the base material itself is composed of something other than an elemental metal or a metal alloy.
Examples of the nonmetallic design pigment include mica-based design pigments, borosilicate glass-based design pigments, and silica flake-based design pigments, and preferably include mica-based design pigments and/or borosilicate glass-based design pigments.
By using non-metallic design pigments, it is possible to obtain an excellent metallic appearance and to trap formaldehyde more effectively.

The mica-based design pigment refers to a material in which the surface of mica is coated with a metal oxide and/or a metalloid oxide. The refractive index is adjusted depending on the type and degree of coating of the metal oxide and/or metalloid oxide that coats the surface, and a desired metallic tone is achieved. Examples of semimetals include B, Si, Ge, As, Sb, Te, and Po. The metals or semimetals constituting the metal oxide or semimetal oxide include Li, Be, B, Na, Mg, Al, Si, K, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, Ge, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, In, Sn, Sb, Cs, Ba, Hf, Ta, W, Examples include Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi and Po, Be, B, Na, Mg, Al, Si, K, Ca, Ti, V, Cr, Mn, Fe, Rb , Cs, and Ba, and preferably Ti, Fe, Zr, Ir, Nb, Ta, Zn, Ab, Sn, and Bi.

The density of the nonmetallic design pigment is preferably 3.0 to 4.0 g/cm ³ , more preferably 3.2 to 3.4 g/cm ³ . The number average particle diameter of the nonmetallic design pigment is preferably 1 to 1000 μm, more preferably 1 to 500 μm, and even more preferably 10 to 200 μm. The number average particle size is determined according to ISO 13320-1 (laser diffraction method).

The resin composition of the present invention contains 0.3 to 1.5 parts by mass of a nonmetallic design pigment based on 100 parts by mass of polyacetal resin. When the amount is 0.3 parts by mass or more, a metallic tone can be effectively exhibited, and when the amount is 1.5 parts by mass or less, generation of formaldehyde can be effectively suppressed. The content of the nonmetallic design pigment may be 0.3 parts by mass or more, 0.5 parts by mass or more, 0.8 parts by mass or more, or 1.2 parts by mass or less.
The resin composition of the present invention may contain only one type of nonmetallic design pigment, or may contain two or more types of nonmetallic design pigments. When two or more types are included, it is preferable that the total amount falls within the above range.
The resin composition of the present invention can also be configured to be substantially free of metallic design pigments. "Substantially free" means that the content of the metallic design pigment in the resin composition of the present invention is 10% by mass or less of the content of the nonmetallic design pigment, and is 5% by mass or less. The content is preferably 1% by mass or less, and more preferably 1% by mass or less.
On the other hand, in the resin composition of the present invention, it is also preferable to use a nonmetallic design pigment and a metallic design pigment (for example, an aluminum design pigment) in combination. With such a configuration, it is possible to obtain a resin composition that has both the useful properties of a nonmetallic design pigment and a nonmetallic design pigment.

<Formaldehyde scavenger>
The resin composition of the present invention contains a formaldehyde scavenger.
The formaldehyde scavenger preferably contains at least one selected from the group consisting of a hydrazide compound, a hydrazone compound of a hydrazine compound, a guanamine compound, and a urea compound.
The resin composition of the present invention preferably contains at least one of a hydrazide compound and a hydrazone compound of a hydrazine compound, and more preferably contains both a hydrazide compound and a hydrazone compound of a hydrazine compound.
The mass ratio of the hydrazide compound to the hydrazone form of the hydrazine compound is preferably 0.1 to 1:1, more preferably 0.1 to 0.5:1. By blending in such a ratio, the effects of the present invention can be more effectively exhibited.

<<Hydrazide compound>>
As the hydrazide compound, a hydrazide compound having two or more hydrazide groups is preferable.
Examples of the dihydrazide compound include aliphatic dihydrazide compounds and aromatic dihydrazide compounds.

Examples of aliphatic dihydrazide compounds include carbodihydrazide, oxalic acid dihydrazide, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, azelaic acid dihydrazide, sebacic acid dihydrazide, dodecanedioic acid dihydrazide (1,12-dodecane dihydrazide), hydrazide), 1,18-octadecane dicarbohydrazide, stearic acid dihydrazide, maleic acid dihydrazide, fumaric acid dihydrazide, 7,11-octadecadiene-1,18-dicarbohydrazide, and the like.

Aromatic dihydrazide compounds include isophthalic acid dihydrazide, terephthalic acid dihydrazide, 1,5-naphthalene dicarbohydrazide, 1,8-naphthalene dicarbohydrazide, 2,6-naphthalene dicarbohydrazide, 4,4'-oxybisbenzene Examples include sulfonyl hydrazide and 1,5-diphenylcarbonohydrazide.

上記式中、Ｒ¹¹は、炭素数２～１８の脂肪族炭化水素基、炭素数６～１０の脂環式炭化水素基または炭素数６～１０の芳香族炭化水素基を表す；Ｒ¹²～Ｒ¹⁵は、それぞれ独立に、水素原子、または、炭素数１～６のアルキル基を表す；Ｒ¹²とＲ¹³、および、Ｒ¹⁴とＲ¹⁵は互いに結合して環を形成していてもよい。 The hydrazide compound used in the present invention is preferably represented by the following formula (1).
Formula (1)

In the above formula, R ¹¹ represents an aliphatic hydrocarbon group having 2 to 18 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms; R ¹² - R ¹⁵ each independently represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms; R ¹² and R ¹³ and R ¹⁴ and R ¹⁵ may be bonded to each other to form a ring. .

In formula (1), R ¹¹ represents an aliphatic hydrocarbon group having 2 to 18 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms; 2 to 18 aliphatic hydrocarbon groups are preferred. The number of carbon atoms in the aliphatic hydrocarbon group having 2 to 18 carbon atoms is preferably 4 or more, preferably 6 or more, and more preferably 8 or more. Further, the number of carbon atoms in the aliphatic hydrocarbon group having 2 to 18 carbon atoms is preferably 16 or less, more preferably 14 or less, and even more preferably 12 or less.
The aliphatic hydrocarbon group may be saturated or unsaturated, and may be linear or branched. Specific examples of aliphatic hydrocarbon groups include butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group. , alkylene groups such as heptadecylene group, octadecylene group, and nonadecylene group.

The alicyclic hydrocarbon group may be saturated or unsaturated.
Examples of the alicyclic hydrocarbon group include a cycloalkylene group having 6 to 10 carbon atoms. Examples of the cycloalkylene group include a cyclohexylene group.

Examples of the aromatic hydrocarbon group include arylene groups such as a phenylene group and a naphthylene group.
A substituent may be bonded to at least some of the carbon atoms of the aromatic hydrocarbon group. Examples of this substituent include a halogen group, a nitro group, and an alkyl group having 1 to 20 carbon atoms.

In formula (1), R ¹² to R ¹⁵ are each independently preferably a hydrogen atom, a methyl group, or an ethyl group, and more preferably a hydrogen atom.

（式（２）中、Ｒ¹は炭素数４～２０の脂肪族炭化水素基、炭素数６～１０の脂環式炭化水素基または炭素数６～１０の芳香族炭化水素基を表す。Ｒ²～Ｒ⁵はそれぞれ独立に、水素原子、または炭素数１もしくは２のアルキル基を表し、Ｒ²およびＲ³のうち少なくとも一方は炭素数１または２のアルキル基を表し、Ｒ⁴およびＲ⁵のうち少なくとも一方は炭素数１または２のアルキル基を表す。） <<Hydrazone compound of hydrazine compound>>
As the hydrazone compound of the hydrazine compound, a hydrazone compound of at least one hydrazine compound selected from the group selected from the compound represented by the following formula (2) and the compound represented by the following formula (3) is preferable.
Formula (2)

(In formula (2), R ¹ represents an aliphatic hydrocarbon group having 4 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms. ² to R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 or 2 carbon atoms, at least one of R ² and R ³ represents an alkyl group having 1 or 2 carbon atoms, and R ⁴ and R ⁵ At least one of them represents an alkyl group having 1 or 2 carbon atoms.)

In formula (2), R ¹ represents an aliphatic hydrocarbon group having 4 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms.
The aliphatic hydrocarbon group may be saturated or unsaturated, and may be linear or branched.
Specific examples of aliphatic hydrocarbon groups include butylene group, pentylene group, hexylene group, heptylene group, octylene group, nonylene group, decylene group, undecylene group, dodecylene group, tridecylene group, tetradecylene group, pentadecylene group, hexadecylene group. , heptadecylene group, octadecylene group, nonadecylene group, and alkylene group such as icosylene group.
The aliphatic hydrocarbon group is preferably an aliphatic hydrocarbon group having 6 to 12 carbon atoms. In this case, the reactivity between the hydrazone compound of the hydrazine compound and formaldehyde becomes higher, and the generation of formaldehyde is more effectively suppressed. Furthermore, contamination of the mold during molding can be more fully suppressed.
The alicyclic hydrocarbon group may be saturated or unsaturated.
Examples of the alicyclic hydrocarbon group include a cycloalkylene group having 6 to 10 carbon atoms. Examples of the cycloalkylene group include a cyclohexylene group.
Examples of the aromatic hydrocarbon group include arylene groups such as a phenylene group and a naphthylene group.
A substituent may be bonded to at least some of the carbon atoms of the aromatic hydrocarbon group. Examples of this substituent include a halogen group, a nitro group, and an alkyl group having 1 to 20 carbon atoms.
In formula (2), R ² to R ⁵ each independently represent a hydrogen atom or an alkyl group having 1 or 2 carbon atoms, and at least one of R ² and R ³ represents an alkyl group having 1 or 2 carbon atoms. and at least one of R ⁴ and R ⁵ represents an alkyl group having 1 or 2 carbon atoms.
Here, in formula (2), when R ² and R ⁴ are ethyl groups, R ³ and R ⁵ are hydrogen atoms, and when R ² and R ⁴ are methyl groups, R ³ and R ⁵ is preferably a hydrogen atom or a methyl group.
In this case, the reactivity between the hydrazone form of the hydrazine compound and formaldehyde becomes higher, and the generation of formaldehyde is more effectively suppressed.

Specific examples of the compound represented by the above formula (2) include 1,12-bis[2-(1-methylethylidene)hydrazino]]-1,12-dodecanedione, 1,12-bis(2-ethylidene) hydrazino)-1,12-dodecanedione, 1,12-bis(2-propylidenehydrazino)-1,12-dodecanedione, 1,12-bis[2-(1-methylpropylidene)hydrazino]- 1,12-dodecanedione, 1,12-bis[2-(1-ethylpropylidene)hydrazino]-1,12-dodecanedione, 1,10-bis[2-(1-methylethylidene)hydrazino]]- 1,10-Decanedione, 1,10-bis(2-propylidenehydrazino)-1,10-decanedione, 1,10-bis(2-propylidenehydrazino)-1,10-decanedione, 1,10- Bis[2-(1-methylpropylidene)hydrazino]-1,10-decanedione, 1,10-bis[2-(1-ethylpropylidene)hydrazino]-1,10-decanedione, 1,6-bis[ 2-(1-methylethylidene)hydrazino]-1,6-hexanedione, 1,6-bis(2-ethylidenehydrazino)-1,6-hexanedione, 1,6-bis(2-propylidenehydrazino) )-1,6-hexanedione, 1,6-bis[2-(1-methylpropylidene)hydrazino]-1,6-hexanedione, 1,6-bis[2-(1-ethylpropylidene)hydrazino ]-1,6-hexanedione and the like.

（式（３）中、Ｒ⁸は炭素数４～２０の脂肪族炭化水素基、炭素数６～１０の脂環式炭化水素基または炭素数６～１０の芳香族炭化水素基を表す。Ｒ⁶およびＲ⁷はそれぞれ独立に、炭素数３～１２の脂環式炭化水素基を表す。） Formula (3)

(In formula (3), R ⁸ represents an aliphatic hydrocarbon group having 4 to 20 carbon atoms, an alicyclic hydrocarbon group having 6 to 10 carbon atoms, or an aromatic hydrocarbon group having 6 to 10 carbon atoms. ⁶ and R ⁷ each independently represent an alicyclic hydrocarbon group having 3 to 12 carbon atoms.)

In formula (3), R ⁸ is the same as R ¹ and its preferred range is also the same.
R ⁶ and R ⁷ each independently represent an alicyclic hydrocarbon group having 3 to 12 carbon atoms.
Examples of the alicyclic hydrocarbon group having 3 to 12 carbon atoms include a cyclohexylene group.
Specific examples of the compound represented by the above formula (3) include 1,12-bis(2-cyclohexylidenehydrazino)-1,12-dodecanedione, 1,10-bis(2-cyclohexylidenehydrazino) dino)-1,10-decanedione, 1,6-bis(2-cyclohexylidenehydrazino)-1,6-hexanedione, and the like.

<<Guanamine compound>>
Examples of the guanamine compound include benzoguanamine and N-methylolated benzoguanamine.

<<Urea compound>>
Examples of urea compounds include ethylene urea, dimethyl ethylene urea, propylene urea, and tetrabutyl urea.

The formaldehyde scavenger is contained in the resin composition of the present invention in such a proportion that the number of reactive groups capable of reacting with formaldehyde is 3.0 μmol or more per gram of polyacetal resin. The content is preferably 4.0 μmol or more, more preferably 5.0 μmol or more, even more preferably 8.0 μmol or more, even more preferably 10.0 μmol or more, even more preferably 12.0 μmol or more, and even more preferably 15 μmol or more. preferable. Further, the upper limit of the content is preferably 100 μmol or less, more preferably 70 μmol or less, even more preferably 50 μmol or less, even more preferably 40 μmol or less, even more preferably 30 μmol or less, and even more preferably 25 μmol or less. By setting it to the above-mentioned lower limit or more, formaldehyde generation can be effectively suppressed, and by setting it to the above-mentioned upper limit or less, mold staining can be effectively suppressed.
The resin composition of the present invention preferably contains 0.05 parts by mass or more, more preferably 0.15 parts by mass, of a formaldehyde scavenger based on 100 parts by mass of the polyacetal resin. Further, the formaldehyde scavenger is preferably contained in an amount of 0.5 parts by mass or less, more preferably 0.3 parts by mass or less, based on 100 parts by mass of the polyacetal resin.
The resin composition of the present invention may contain only one type of formaldehyde scavenger, or may contain two or more types of formaldehyde scavengers. When two or more types are included, the total amount falls within the above range.

<Ultraviolet absorber>
It is preferable that the resin composition of the present invention contains an ultraviolet absorber. By including an ultraviolet absorber, weather resistance can be improved.
The ultraviolet absorber is preferably selected from benzotriazole compounds, benzophenone compounds, aromatic benzoate compounds, cyanoacrylate compounds, and oxalic acid anilide ultraviolet absorbers.

Specific examples of ultraviolet absorbers include 2-(2'-hydroxy-5'-methyl-phenyl)benzotriazole, 2,2'-methylenebis[6-(2H-benzotriazol-2-yl)-4-( 1,1,3,3-tetramethylbutyl)phenol], 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2-(2'-Hydroxy-3',5'-di-isoamyl-phenyl)benzotriazole,2-[2'-hydroxy-3',5'-bis-(α,α-dimethylbenzyl)phenyl]benzotriazole, 2-( 2'-Hydroxy-4'-octoxyphenyl)benzotriazole, 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4-dodecyloxybenzophenone , 2,2'-dihydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4,4'-dimethoxybenzophenone, 2-hydroxy-4-oxybenzylbenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone , pt-butylphenyl salicylate, p-octylphenyl salicylate, 2-ethylhexyl-2-cyano-3,3'-diphenylacrylate, ethyl-2-cyano-3,3'-diphenylacrylate, N-(2- Examples include ethoxy-5-t-butylphenyl)oxalic acid diamide, N-(2-ethylphenyl)-N'-(2-ethoxyphenyl)oxalic acid diamide, and the like.
In addition to the above, the ultraviolet absorbers described in paragraphs 0116 to 0117 of International Publication No. 2017/018210 can be referred to, the contents of which are incorporated herein.

A preferred ultraviolet absorber is a benzotriazole compound, particularly preferably a benzotriazole ultraviolet absorber having a vapor pressure of 1×10 ⁻⁸ Pa or less at 20° C. Specifically, 2-(2H-benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol, 2,2'-methylenebis[6-(2H-benzotriazole- 2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol].

The resin composition of the present invention preferably contains 0.1 part by mass or more of an ultraviolet absorber, more preferably 0.2 part by mass or more, based on 100 parts by mass of the polyacetal resin. Further, the resin composition of the present invention preferably contains 0.7 parts by mass or less, and more preferably 0.5 parts by mass or less of an ultraviolet absorber, based on 100 parts by mass of the polyacetal resin.
The resin composition of the present invention may contain only one type of ultraviolet absorber, or may contain two or more types of ultraviolet absorbers. When two or more types are included, it is preferable that the total amount falls within the above range.

<Stabilizer>
The resin composition of the present invention may contain a stabilizer. Stabilizers include hindered amine light stabilizers and certain polyamide resins.

（式（４）中、Ｒは窒素原子との結合部が炭素原子である有機基を表し、Ｘは、酸素原子もしくは窒素原子を介してピペリジル基の４位と結合する有機基、または水素原子を表す。） <<Hindered amine light stabilizer>>
The resin composition of the present invention preferably contains a hindered amine light stabilizer. By including a hindered amine light stabilizer, weather resistance can be improved.
As the hindered amine light stabilizer, one represented by formula (4) is preferably used.
Formula (4)

(In formula (4), R represents an organic group in which the bond to the nitrogen atom is a carbon atom, and X is an organic group bonded to the 4-position of the piperidyl group via an oxygen atom or a nitrogen atom, or a hydrogen atom. )

Examples of R include a linear or branched alkyl group having 1 to 10 carbon atoms. Examples of such alkyl groups include methyl, ethyl, propyl, t-butyl, hexyl, octyl, and decyl, with methyl being preferred.

Specific examples of preferred hindered amine light stabilizers include bis(1,2,2,6,6-pentamethyl-4-piperidinyl) sebacate, 1-[2-{3-(3,5-di-t-butyl) -4-hydroxyphenyl)propionyloxy}ethyl]-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine, tetrakis (1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, 1,2,2,6,6-pentamethyl-4-piperidyl and tridecyl-1 , 2,3,4 butane tetracarboxylate (a mixture of compounds in which some of the four ester moieties of butane tetracarboxylate are 1,2,2,6,6-pentamethyl-4-piperidyl groups and others are tridecyl groups) ), 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, Condensate of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, 1, 2,2,6,6-pentamethyl-4-piperidyl methacrylate, N,N',N'',N'''-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2, 6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine, bis(1,2,2,6,6-pentamethyl-4- piperidyl)[[3,5-bis(1,1 dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate.
In addition to the above, the hindered amine light stabilizer described in paragraph 0113 of International Publication No. 2017/018210 can be referred to, and the contents thereof are incorporated herein.

The resin composition of the present invention preferably contains 0.05 parts by mass or more, and more preferably 0.1 parts by mass or more, of a hindered amine light stabilizer based on 100 parts by mass of the polyacetal resin. Further, the resin composition of the present invention preferably contains 0.5 parts by mass or less, and more preferably 0.3 parts by mass or less, of a hindered amine light stabilizer based on 100 parts by mass of the polyacetal resin. By setting it above the above lower limit, weather resistance tends to be further improved. Further, by setting the amount to be equal to or less than the above upper limit, mold staining can be effectively suppressed.
The resin composition of the present invention may contain only one kind of hindered amine light stabilizer, or may contain two or more kinds of hindered amine light stabilizers. When two or more types are included, it is preferable that the total amount falls within the above range.

<<Polyamide resin (stabilizer)>>
The resin composition of the present invention preferably contains a polyamide resin as a stabilizer. The polyamide resin as a stabilizer used in the present invention is preferably a polyamide resin that satisfies the following (A) or (B).
(A) The melting point and/or softening point of the polyamide resin is 180°C or lower. (B) The amine value of the polyamide resin is 2 mgKOH/g or higher.

It is preferable that the polyamide resin has a melting point and/or softening point of 180° C. or lower. By lowering the melting point and/or softening point, it can be brought into a molten state at the temperature at which it is kneaded with the polyacetal resin, and the dispersibility of the polyamide resin is further improved. As such polyamide resin, any of aliphatic polyamide resin, alicyclic polyamide resin, and aromatic polyamide resin can be used.

The polyamide resin may be composed of one type of structural unit or may be composed of two or more types of structural units. Raw materials for the polyamide resin include ω-amino acids, preferably linear ω-amino acids having 6 to 12 carbon atoms, and lactams thereof; adipic acid, sebacic acid, dodecanedicarboxylic acid, heptadecanedicarboxylic acid, isophthalic acid, terephthalic acid, etc. Examples include dicarboxylic acids and dimethyl esters thereof; diamines such as hexamethylene diamine. In the case of a copolyamide comprising a plurality of types of structural units, the copolymerization ratio, copolymerization form (random copolymer, block copolymer, crosslinked polymer), etc. can be arbitrarily selected. The polyamide resin is preferably polyamide 12, polyamide 6/12 copolymer, polyamide 6/66/610 copolymer, polyamide 6/66/610/12 copolymer, or a mixture of two or more thereof. In this case, the generation of formaldehyde can be suppressed more effectively.

The melting point and/or softening point of the polyamide resin is preferably 175°C or lower, more preferably 170°C or lower. The lower limit is, for example, 100°C or higher.

In the present invention, polyamide resins having an amine value of 2 mgKOH/g or more are also preferred. Such a polyamide resin having many amino groups at its terminals can neutralize the acidity caused by formic acid generated by oxidation of formaldehyde, and can effectively suppress the decomposition of the polyacetal resin. The amine value is preferably 2.5 mgKOH/g or more. The amine value is usually 100 mgKOH/g or less, preferably 80 mgKOH/g or less, more preferably 60 mgKOH/g or less, still more preferably 40 mgKOH/g or less, even more preferably 20 mgKOH/g or less, and more More preferably it is 10 mgKOH/g or less, even more preferably 5 mgKOH/g or less. When a coloring agent is blended with polyacetal resin, the polyacetal resin becomes more easily decomposed and formaldehyde is more likely to be generated. When this formaldehyde is oxidized, it becomes formic acid, and the acidity caused by this formic acid further accelerates the decomposition of the polyacetal resin. In the present invention, by blending a polyamide resin with many amino groups at the terminals, it is possible to neutralize the acidity caused by formic acid generated by oxidation of formaldehyde and suppress the decomposition of the polyacetal resin.

The amine value of the polyamide resin can be adjusted by adjusting the charging ratio of dicarboxylic acid and diamine and polymerizing it, or by heating and reacting the polyamide resin obtained by polymerization with a terminal regulator such as an amine. Can be done. The amine used as the terminal regulator preferably has 6 to 22 carbon atoms, and examples include aliphatic amines such as hexylamine, octylamine, decylamine, laurylamine, myristylamine, palmitylamine, stearylamine, and behenylamine. Examples include primary amines.

Moreover, it is also preferable to use dimer acid as the dicarboxylic acid in the polyamide resin. That is, as the polyamide resin, a dimer acid polyamide resin obtained by reacting a dimer acid with a diamine is also preferable. In this case, the generation of formaldehyde can be suppressed more effectively. Dimer acid is a dimerization of unsaturated fatty acids such as oleic acid, linoleic acid, and erucic acid, and one of its representative acids is mainly composed of dibasic acids with 36 carbon atoms and/or hydrogenated substances. It also contains a small amount of a monobasic acid (monomer) having 18 carbon atoms and a tribasic acid (trimer) having 54 carbon atoms. A dimer acid polyamide resin obtained by reacting a dimer acid with a diamine has a softening point of 180° C. or lower and can be suitably used.

The weight average molecular weight of the polyamide resin is arbitrary, but is, for example, 500 to 100,000, preferably 1,000 to 50,000. Note that the weight average molecular weight refers to a value measured by gel permeation chromatography (GPC) in terms of polystyrene.

The polyamide resin in the present invention is preferably a dimer acid polyamide resin having a melting point and/or softening point of 180°C or lower and an amine value of 2 mgKOH/g or higher. In this case, the generation of formaldehyde can be suppressed more effectively.

The resin composition of the present invention preferably contains 0.01 parts by mass or more of polyamide resin, more preferably 0.05 parts by mass or more, and 0.1 parts by mass or more of polyamide resin based on 100 parts by mass of polyacetal resin. is even more preferable. Further, it is preferable that the polyamide resin is contained in 3 parts by mass or less, more preferably 2.0 parts by mass or less, and even more preferably 1.0 parts by mass or less. By setting it to the above lower limit or more, generation of formaldehyde can be effectively suppressed. Furthermore, by setting the amount to be less than or equal to the above upper limit, the mechanical strength of the molded product can be increased.
The resin composition of the present invention may contain only one type of polyamide resin, or may contain two or more types of polyamide resin. When two or more types are included, it is preferable that the total amount falls within the above range.

<Other ingredients>
The resin composition of the present invention may contain any conventionally known additives and fillers within a range that does not impair the purpose of the present invention. Examples of additives and fillers used in the present invention include thermoplastic resins other than polyacetal resins, antistatic agents, carbon fibers, glass fibers, glass flakes, potassium titanate whiskers, and general pigments. For these details, the descriptions in paragraphs 0113 to 0124 of JP 2017-025257 A can be referred to, and the contents thereof are incorporated herein.

<<General pigments>>
As the general pigment, for example, general inorganic pigments and organic pigments listed in the "Pigment Handbook (edited by the Japan Pigment Technology Association)" can be used (excluding those that fall under design pigments).
Examples of inorganic pigments include (composite) metal oxides containing titanium such as titanium white and titanium yellow, zinc oxide, iron oxide, carbon black, ultramarine blue, zinc sulfide, and antimony trioxide. Examples of organic pigments include phthalocyanine-based, anthraquinone-based, quinacridone-based, azo-based, isoindolinone-based, quinophthalone-based, perinone-based, and perylene-based pigments.
In the present invention, inorganic pigments are preferred, and carbon black is more preferred.
In addition to the above-mentioned general pigments, colored pigments described in paragraph 0051 of JP-A-2015-074724 can be used, the contents of which are incorporated herein.
The resin composition of the present invention preferably contains 0.01 to 5 parts by mass of a general pigment based on 100 parts by mass of polyacetal resin.
The resin composition of the present invention may contain only one type of general pigment, or may contain two or more types of general pigment. When two or more types are included, it is preferable that the total amount falls within the above range.

<Method for producing polyacetal resin composition>
The polyacetal resin composition of the present invention contains the above-mentioned essential components and, if necessary, the above-mentioned arbitrary components. The manufacturing method is arbitrary, and any conventionally known manufacturing method for resin compositions may be used to mix and knead these raw materials.

Examples of the kneading machine include a kneader, a Banbury mixer, and an extruder. The various conditions and equipment for mixing and kneading are also not particularly limited, and may be determined by appropriately selecting from any conventionally known conditions. The kneading is preferably carried out at a temperature higher than the melting temperature of the polyacetal resin, specifically at a temperature higher than the melting temperature of the polyacetal resin (generally 180° C. or higher).

<Molded product>
The molded article of the present invention is formed from the polyacetal resin composition of the present invention. The molded article of the present invention preferably has a metallic finish.
Furthermore, pellets obtained by pelletizing the polyacetal resin composition of the present invention can be molded into molded products using various molding methods. Alternatively, the resin composition melt-kneaded in an extruder can be directly molded into a molded product without going through pellets.
The shape of the molded product is not particularly limited and can be appropriately selected depending on the use and purpose of the molded product, such as plate, plate, rod, sheet, film, cylindrical, annular, etc. Examples include circular shapes, elliptical shapes, gear shapes, polygonal shapes, irregularly shaped products, hollow products, frame shapes, box shapes, panel shapes, cap shapes, and the like. The molded product of the present invention may be a finished product, a component, or a welded product.

The method for molding the molded product is not particularly limited, and conventionally known molding methods can be employed, such as injection molding, injection compression molding, extrusion molding, profile extrusion, transfer molding, blow molding, Gas-assisted blow molding, blow molding, extrusion blow molding, IMC (in-mold coating molding), rotational molding, multilayer molding, two-color molding, insert molding, sandwich molding, foam molding, processing Examples include pressure molding method.

<Application>
The polyacetal resin composition of the present invention and molded articles formed from the polyacetal resin composition are preferably used in applications requiring resistance to liquids containing fluorine ions.
Specifically, as described above, it is particularly suitable for vehicle-related parts, particularly automotive interior parts such as seat belt guides, and automotive parts such as switches, shift lever-related parts, and gear change hooks.

The present invention will be explained in more detail with reference to Examples below. The materials, usage amounts, ratios, processing details, processing procedures, etc. shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention is not limited to the specific examples shown below.

Raw material (P) polyacetal resin (POM)
An acetal copolymer obtained by copolymerizing trioxane and 1,3-dioxolane such that the content of 1,3-dioxolane in POM is 3.8% by mass (4.6% by mole), , an acetal copolymer with a melt index (ASTM-D1238 standard: 190°C, 2.16 kg) of 10.5 g/10 minutes.

(A) Formaldehyde scavenger additive A-1: 1,12-bis[2-(1-methylethylidene)hydrazino]]-1,12-dodecanedione, manufactured by Nippon Finechem Additive A-2: Adipic acid dihydrazide , Nippon Finechem Co., Ltd. Additive A-3: Dodecanedioic acid dihydrazide, Nippon Finechem Co., Ltd. Additive A-4: Benzoguanamine, Nippon Kagaku Co., Ltd. Additive A-5: Ethylene urea, Kanto Kagaku Co., Ltd.

(B) Non-metallic design pigment additive B-1: Pyrisma T50-10, manufactured by MERCK, mica coated with titanium oxide (number average particle size: 5 to 35 μm)
Additive B-2: Iriodin 111, manufactured by MERCK, mica coated with titanium oxide (number average particle size: 1 to 15 μm)
Additive B-3: Pyrisma T40-24, manufactured by MERCK, mica coated with titanium oxide (number average particle size: 5 to 35 μm)
Additive B-4: Iriodin 504, manufactured by MERCK, mica coated with iron oxide (number average particle size: 10 to 60 μm)
Additive B-5: Iriodin 153, manufactured by MERCK, mica coated with titanium oxide (number average particle size: 20 to 200 μm)
Additive B-6: Miraval 5401, manufactured by MERCK, based on borosilicate glass (number average particle size: 20 to 200 μm)

(C) Ultraviolet absorber additive C: Tinuvin234, manufactured by BASF, benzotriazole compound

(D) Hindered amine light stabilizer additive D: Tinuvin622, manufactured by BASF

(E) Polyamide resin (stabilizer)
Additive E: dimer acid polyamide resin, manufactured by T&K TOKA, Tomide TXM-272, softening point 125°C, amine value 3.0mgKOH/g
(F) General pigment additive F: Carbon black Pigment Black 7, manufactured by Evonik Degussa Japan Co., Ltd., product name: Printex

Examples 1 to 18, Comparative Examples 1 to 7
The components shown in Tables 1 to 3 were uniformly mixed in the proportions (parts by mass) shown in Tables 1 to 3 using a super mixer manufactured by Kawada Seisakusho. The obtained mixture was melt-sheared using a vented single-screw extruder with a screw diameter of 40 mm (VS-40 manufactured by Tanabe Plastics Machinery Co., Ltd.) at a cylinder temperature of 190°C, a screw rotation speed of 60 rpm, and a discharge rate of 18 kg/hour. The mixture was mixed to produce pellets of a polyacetal resin composition.
In Tables 1 to 3, the amount of formaldehyde-trapping groups refers to the amount (μmol/g) of reactive groups capable of reacting with formaldehyde per gram of polyacetal resin.

The pellets obtained above were heat-treated for 4 hours in a hot air circulation dryer at a temperature of 80°C.
Next, using an injection molding machine PS-40 manufactured by Nissei Jushi Kogyo Co., Ltd., the polyacetal resin compositions obtained in Examples 1 to 18 and Comparative Examples 1 to 7 were heated at a cylinder temperature of 215°C and a mold temperature of 80°C. The pellets were injection molded to produce flat test pieces measuring 100 mm x 40 mm x 2 mm.

<Formaldehyde generation amount>
On the day after the above flat test piece was prepared, the flat test piece was prepared according to the method described in German Automobile Industry Association standard VDA275 (Automotive interior parts - Determination of formaldehyde release amount by revised flask method). The amount of formaldehyde generated (μg/g-POM, which refers to the amount of formaldehyde generated (μg) per 1 g of polyacetal resin) was measured by the method.
(i) First, 50 mL of distilled water was placed in a polyethylene container, the lid was closed with the flat test piece suspended in the air, and the container was heated at 60° C. for 3 hours in a sealed state.
(ii) Subsequently, after being left at room temperature for 60 minutes, the flat test piece was taken out.
(iii) The amount of formaldehyde absorbed in the distilled water in the polyethylene container is measured using the acetylacetone colorimetric method using a UV spectrometer, and the amount of formaldehyde generated is calculated by dividing the amount of formaldehyde by the mass of POM in the flat test piece. And so.

<Exterior>
The flat test piece obtained above was visually confirmed and evaluated in the following three stages.
3: The color is close to metal, and the brightness is sufficient.
2: The color is close to metal, but there is no brightness.
1: No metallic feel.

As is clear from the above results, the polyacetal resin composition of the present invention suppressed the amount of formaldehyde generated and produced molded products with excellent metallic appearance (Examples 1 to 18). On the other hand, when the nonmetallic design pigment was not included, or even if it was included, the amount was small, the appearance was poor (Comparative Examples 1 and 2). Furthermore, when the amount of nonmetallic design pigment was large, the amount of formaldehyde generated increased (Comparative Examples 3 and 4). Furthermore, when the amount of formaldehyde scavenger was small or not included, the amount of formaldehyde generated increased (Comparative Examples 5 to 7).

Claims (7)

Contains 0.3 to 1.5 parts by mass of a non-metallic design pigment and a formaldehyde scavenger for 100 parts by mass of polyacetal resin,
The formaldehyde scavenger is contained in a proportion of 5.0 μmol or more of reactive groups capable of reacting with formaldehyde per 1 g of the polyacetal resin ,
The non-metallic design pigment includes a mica-based design pigment and/or a borosilicate glass-based design pigment, and has a number average particle size of 1 to 500 μm.
Polyacetal resin composition. 1. The method according to claim 1, further comprising at least one of 0.1 to 0.7 parts by mass of an ultraviolet absorber and 0.05 to 0.5 parts by mass of a hindered amine light stabilizer based on 100 parts by mass of the polyacetal resin. The resin composition described. The resin composition according to claim 1 or 2, wherein the formaldehyde scavenger contains at least one selected from the group consisting of a hydrazide compound, a hydrazone compound of a hydrazine compound, a guanamine compound, and a urea compound. Further, according to any one of claims 1 to 3, 0.01 to 3 parts by mass of a polyamide resin is contained based on 100 parts by mass of the polyacetal resin, and the polyamide resin satisfies the following (A) or (B). The resin composition described;
(A) The melting point and/or softening point of the polyamide resin is 180°C or lower. (B) The amine value of the polyamide resin is 2 mgKOH/g or higher. The resin composition according to any one of claims 1 to 4, wherein the formaldehyde scavenger is contained in an amount of 0.05 to 0.5 parts by mass based on 100 parts by mass of the polyacetal resin. A molded article formed from the resin composition according to any one of claims 1 to 5 . A metallic molded article formed from the resin composition according to any one of claims 1 to 5 .