JP7216496B2 - Polyoxymethylene resin composition and molded article - Google Patents

Description

TECHNICAL FIELD The present invention relates to a polyoxymethylene resin composition and a molded article.

Polyoxymethylene resin is a crystalline resin, and is a resin material excellent in rigidity, strength, toughness, slidability, and creep resistance.
Polyoxymethylene resins are widely used as resin materials for various mechanical parts such as automobile parts, electric/electronic parts and industrial parts.

However, polyoxymethylene resin is very weak against light energy such as sunlight and heat energy, and when exposed to the atmosphere for a long time, cracks occur on the surface of the molded product, causing a decrease in strength. ing. Therefore, when used in an environment exposed to sunlight or the like, it is common to add a weather resistance stabilizer such as a hindered amine compound.

By the way, in recent years, there have been increasing demands for smaller, thinner, and more precise molded products of polyoxymethylene resin. tends to take place.
Examples of such molding methods include molding with a pin gate mold and high cycle molding. In these molding methods, screw rotation and molding are used to increase the shear rate and shorten the plasticization time. Since the temperature is raised, the polyoxymethylene resin is subjected to a higher heat history than the conventional normal molding method.

Also, in other general molding methods, when molding defects such as flow marks, weld lines, jetting, etc. occur, it is often dealt with by raising the resin temperature. This is the reason why the oxymethylene resin is subjected to a high heat history.
Furthermore, when a hot runner is used in the mold in the molding process, the resin may be partially retained, causing the resin temperature to rise further, which may cause the resin to decompose.

When polyoxymethylene resin is molded by setting molding methods and molding conditions that are subject to various heat histories as described above, a weather stabilizer is added to the polyoxymethylene resin to improve its weather resistance stability. When added, there is a problem that it becomes difficult to achieve a good balance of properties in relation to thermal stability. That is, if a large amount of weather stabilizer is blended with emphasis on weather resistance stability, the thermal stability deteriorates, and there is a problem that volatile organic compounds (VOC) including formaldehyde are likely to be released from the resin.
In particular, in the field of automobile interior parts, the demand for reducing the amount of volatile organic compounds emitted has increased, and resin compositions with an excellent balance between weather resistance and thermal stability are in demand. is the current situation.

By the way, various techniques have conventionally been proposed in order to improve the weather resistance stability of polyoxymethylene resins.
For example, a technique of using a hindered amine light stabilizer and an oxalic acid anilide ultraviolet absorber together (see Patent Document 1 below), a technique of using a hindered amine light stabilizer and a benzophenone ultraviolet absorber together (see Patent Document 2 below), benzo Technology using a combination of a triazole UV absorber and a hindered amine light stabilizer (see Patent Document 3 below), a technology using various UV absorbers, fatty acid esters and a hindered amine light stabilizer in combination (see Patent Document 4 below), and benzo Techniques using a combination of a triazole-based ultraviolet absorber, a hindered amine-based light stabilizer, and an antioxidant (see Patent Document 5 below) and the like can be mentioned.

Techniques for reducing the amount of formaldehyde released from polyoxymethylene resin molded articles include, for example, a technique of adding a polyamide and a hydrazine derivative (see Patent Document 6 below) and a technique of adding a hydrazide compound (see Patent Document 7 below). ), a technique of adding a nitrogen compound selected from melamine, melamine derivatives and dicarboxylic acid hydrazides (see Patent Document 8 below), a technique of adding benzoguanamine (see Patent Document 9 below), a fatty acid of a polyhydric alcohol compound on the pellet surface A method of attaching a partial ester (see Patent Document 10 below), a technique of adding mono N-substituted urea (see Patent Document 11 below), a technique of adding a carboxyl group-containing compound having an acid dissociation index of 3.6 or more (see Patent Document 11 below). Patent Document 12), a technique of adding a condensate of a phenol, a basic nitrogen-containing compound and an aldehyde (see Patent Document 13 below), a technique of adding hydantoin or imidazole (see Patent Document 14 below), and a base A technique of adding a low-molecular-weight amino compound having a dissociation index of 2 to 8 (see Patent Document 15 below) has been proposed.

In addition, as a technique for reducing formaldehyde released from weather resistance stability and molded articles, a technique of adding a hindered amine light stabilizer with a specific structure, an ultraviolet absorber, and a hydrazide compound such as an aromatic hydrazide compound (Patent Document 16 below) ), and a technique of adding a weathering agent (a hindered amine light stabilizer and an ultraviolet absorber) and a hydrazide compound to a polyoxymethylene resin that suppresses the amount of formaldehyde generated (see Patent Document 17 below).

JP-A-57-98545 JP-A-59-133245 JP-A-60-195155 JP-A-61-47744 JP-A-6-157871 JP-A-51-111857 JP-A-4-345648 Japanese Patent No. 3024802 JP-A-62-190248 JP-A-6-107900 JP-A-11-335519 JP-A-2000-239484 Japanese Unexamined Patent Application Publication No. 2002-212384 Japanese Patent No. 3310467 Japanese Patent Publication No. 2002-541288 JP-A-2006-232937 JP 2006-306944 A

Here, in each application of the molded article using the polyoxymethylene resin composition, the resin composition can contain a pigment to improve the appearance and visibility of the molded article. As described above, polyoxymethylene resin compositions are required to have an excellent balance between weather resistance and heat stability. It was found that the creep property (stiffness) in Thus, the inventors have found that polyoxymethylene resin compositions require an excellent balance of weathering stability, thermal stability, and creep properties.
However, the techniques disclosed in Patent Documents 2 to 17 also describe the addition of pigments, but all of them have the problem of poor pigment dispersibility, pigment aggregation, and deterioration of creep characteristics. there is
In addition, the techniques disclosed in Patent Documents 1 to 5 all improve the weather resistance stability, but have the problem that the amount of formaldehyde released from the polyoxymethylene resin molded article is not sufficiently reduced. there is
Furthermore, the techniques disclosed in Patent Documents 6 to 15 have the problem of insufficient weather resistance stability.
In addition, the techniques disclosed in Patent Documents 16 and 17 are found to have an improvement effect in terms of weather resistance stability and reduction of formaldehyde emission, but the polyoxymethylene resin composition was retained in the molding machine cylinder during molding processing. There is room for improvement in terms of reducing the amount of formaldehyde emitted from the molded product during molding and creep characteristics, and in particular, reducing formaldehyde emissions from the molded product when the polyoxymethylene resin homopolymer composition is retained in the molding machine cylinder. It has a problem that the reduction of the amount emitted is not sufficient.

Therefore, in the present invention, there is provided a polyoxymethylene resin composition which is excellent in weather resistance stability and creep properties and in which the amount of formaldehyde emitted is reduced, and which also reduces the amount of formaldehyde emitted during retention during molding. An object is to provide a composition and a molded article.

The inventors of the present invention have made intensive studies to solve the above problems, and found that a resin composition containing a polyoxymethylene resin homopolymer, a lubricant, a polyolefin resin, and a pigment contains a lubricant and a polyolefin resin. The inventors have found that the above-described conventional problems can be solved by blending a specific amount of the lubricant and the polyolefin resin in a specific ratio, and have completed the present invention.
That is, the present invention is as follows.

[1]
100 parts by mass of polyoxymethylene resin homopolymer (A),
Lubricant (B) 0.01 to 0.1 parts by mass,
0.1 to 1.0 parts by mass of a polyolefin resin (C),
containing a pigment (D),
A polyoxymethylene resin, characterized in that the mass ratio of the (B) lubricant and the (C) polyolefin resin is 5/95 to 30/70, that is, (B) lubricant/(C) polyolefin resin. Composition.
[2]
0.01 to 0.4 parts by mass of a nitrogen-containing compound (E) having formaldehyde-scavenging ability;
0.1 to 0.5 parts by mass of an ultraviolet absorber (F),
0.1 to 0.5 parts by mass of a hindered amine light stabilizer (G);
The polyoxymethylene resin composition according to [1] above, further containing 0.01 to 0.05 parts by mass of an antioxidant (H).
[3]
The nitrogen-containing compound (E) is at least one selected from the group consisting of amino-substituted triazine compounds, urea derivatives, amide compounds, polyamides, acrylamide copolymers, and hydrazide compounds, the poly according to [2] above. Oxymethylene resin composition.
[4]
A molded article comprising the polyoxymethylene resin composition according to any one of [1] to [3].

According to the present invention, there is provided a polyoxymethylene resin composition which is excellent in weather resistance stability and creep properties and in which the amount of formaldehyde emitted is reduced, and in which the amount of formaldehyde emitted during retention during molding processing is also reduced. Compositions and molded bodies can be provided.

EMBODIMENT OF THE INVENTION Hereinafter, the form (henceforth "this embodiment") for implementing this invention is demonstrated in detail.
It should be noted that the present embodiment below is an example for explaining the present invention, and is not intended to limit the present invention to the following contents. The present invention can be carried out with various modifications within the scope of its gist.

[Polyoxymethylene resin composition]
The polyoxymethylene resin composition of the present embodiment is
100 parts by mass of polyoxymethylene resin homopolymer (A),
Lubricant (B) 0.01 to 0.1 parts by mass,
0.1 to 1.0 parts by mass of a polyolefin resin (C),
containing a pigment (D),
The mass ratio of the (B) lubricant to the (C) polyolefin resin, that is, (B) lubricant/(C) polyolefin resin is 5/95 to 30/70.
Furthermore, 0.01 to 0.4 parts by mass of a nitrogen-containing compound (E) having formaldehyde scavenging ability,
0.1 to 0.5 parts by mass of an ultraviolet absorber (F),
0.1 to 0.5 parts by mass of a hindered amine light stabilizer (G);
0.01 to 0.05 parts by mass of an antioxidant (H) may also be contained.

Here, the melt flow rate (according to ISO 1133 D) of the polyoxymethylene resin composition of the present embodiment is preferably 0.5 g/10 min or more from the viewpoint of moldability, and from the viewpoint of durability. Therefore, it is preferably 10 g/10 minutes or less, more preferably 1.0 g/10 minutes to 7 g/10 minutes, still more preferably 1.5 g/10 minutes to 4 g/10 minutes.
Each component that can be contained in the polyoxymethylene resin composition of the present embodiment will be described below.

(Polyoxymethylene resin homopolymer (A))
The polyoxymethylene resin composition of this embodiment contains a polyoxymethylene resin homopolymer (A).
Polyoxymethylene resin homopolymer (A) refers to a polyoxymethylene polymer in which 99.8 mol% or more of the main chain excluding both ends is composed of oxymethylene groups, and 99.8 mol% of the main chain excluding both ends The above is preferably composed of polyoxymethylene groups, and more preferably a polyoxymethylene homopolymer composed of only polyoxymethylene groups in the main chain excluding both ends. In particular, it is preferably a polyoxymethylene homopolymer in which both ends of the polymer chain are blocked with ester groups.
The polyoxymethylene resin homopolymer (A) may contain 5 parts by weight, preferably 3 parts by weight, more preferably 1 part by weight of polyoxymethylene copolymer per 100 parts by weight.
The amount of formaldehyde generated from the polyoxymethylene resin homopolymer (A) at 230° C. under a nitrogen atmosphere is preferably 2.0% by mass or less. More preferably, the amount of formaldehyde generated is 1.0% by mass or less, and even more preferably 0.8% by mass or less. Also, the amount of formaldehyde generated can be 0.001% by mass or more, and more preferably 0.1% by mass.
When the amount of formaldehyde generated from the polyoxymethylene resin homopolymer (A) is 2.0% by mass or less, the polyoxymethylene resin composition has improved thermal stability and a reduced amount of formaldehyde released, It is possible to provide a polyoxymethylene resin composition in which the amount of formaldehyde released during retention during molding is also reduced. If the amount of formaldehyde generated is about 0.1% by mass, the influence of formaldehyde emission can be sufficiently suppressed, so the preferable lower limit of the amount of formaldehyde generated is 0.001% by mass, and further 0.1% by mass. can do.

The amount of formaldehyde generated from the polyoxymethylene resin homopolymer (A) at 230° C. under a nitrogen atmosphere is the amount of formaldehyde released mainly from hydroxyl groups (—OH), which are unstable terminal groups. It can be quantified by the method shown below.
The polyoxymethylene resin homopolymer (A) in a SUS container is placed in an oil bath having a SUS pipe at 230° C. and heated for 90 minutes. Thereafter, nitrogen gas is flowed through the pipe, and formaldehyde gas generated by thermal decomposition of the polyoxymethylene resin homopolymer (A) is extracted outside and absorbed in an aqueous sodium sulfite solution. The sodium sulfite aqueous solution that has absorbed the formaldehyde is titrated with sulfuric acid to determine the amount of formaldehyde generated.

((Production of polyoxymethylene resin homopolymer (A)))
The polyoxymethylene resin homopolymer (A) is not particularly limited, but can be produced, for example, by carrying out a polymerization step and a terminal stabilization step, which will be described later.

<(1) Polymerization step>
In the polymerization step, a known slurry polymerization method (e.g., the method described in Japanese Patent Publication No. 47-6420 and Japanese Patent Publication No. 47-10059) is used in a reactor to obtain a monomer using a chain transfer agent or a polymerization catalyst. to obtain a crude polyoxymethyl weathering-stable ren resin homopolymer that is not end-stabilized.
As a material for the polyoxymethylene resin composition of the present embodiment, the crude polyoxymethylene resin homopolymer itself can be used. It is preferable to use the stabilized one.

[(1) Monomer]
Monomers used for the production of polyoxymethylene resin homopolymers include, for example, formaldehyde monomers and cyclic oligomers of formaldehyde such as trimers (trioxane) and tetramers (tetraoxane) thereof.

In order to continuously obtain a polyoxymethylene resin homopolymer having a stable molecular weight in the polymerization process, it is preferable to use a purified, stable formaldehyde gas with a low impurity concentration.
As a method for purifying formaldehyde, a known method (for example, the method described in JP-B-5-32374 and JP-A-2001-521916) can be applied.

When formaldehyde gas is used as a monomer in the polymerization step, it is preferable to use one containing as little impurities as possible, such as water, methanol, and formic acid, which have a polymerization terminating action and a chain transfer action during the polymerization reaction.
By using a formaldehyde gas containing less of these impurities, an unexpected chain transfer reaction can be avoided and a polyoxymethylene resin homopolymer having a desired molecular weight can be obtained. In particular, the content of impurities that induce hydroxyl groups to polymer terminal groups is preferably 100 ppm by mass or less, more preferably 50 ppm by mass or less, relative to the total amount of monomers.

[(2) Chain transfer agent]
Chain transfer agents used in the production of polyoxymethylene resin homopolymers are not particularly limited, but include, for example, alcohols and acid anhydrides.
As the chain transfer agent, it is preferable to use one containing as little impurities as possible, such as water, methanol, formic acid, and acetic acid, which have a polymerization terminating action and a chain transfer action during the polymerization reaction. As a method for obtaining a chain transfer agent with few impurities, for example, dry nitrogen is bubbled through a generally available chain transfer agent having a moisture content exceeding a specified amount, and impurities are removed with an adsorbent such as activated carbon or zeolite. , purification methods, and the like.
A chain transfer agent may be used individually by 1 type, and may use 2 or more types together.

[(3) Polymerization catalyst]
Although the polymerization catalyst used for producing the polyoxymethylene resin homopolymer is not particularly limited, examples thereof include onium salt-based polymerization catalysts.
Examples of the onium salt-based polymerization catalyst include compounds represented by the following general formula (1).
[R ₁ R ₂ R ₃ R ₄ M] ⁺ X ^- (1)
(In general formula (1), R ₁ , R ₂ , R ₃ and R ₄ each independently represent an alkyl group, M represents an element having a lone pair of electrons, and X represents a nucleophilic group. R ₁ , R ₂ , R ₃ and R ₄ may be the same or different.)

The onium salt-based polymerization catalyst is not limited to the following, but includes, for example, quaternary ammonium salt-based compounds and quaternary phosphonium salt-based compounds, particularly tetramethylammonium bromide and dimethyl distearyl. Ammonium acetate, tetraethylphosphonium iodide, tributylethylphosphonium iodide are preferred.

[(4) Reactor]
The reactor used for the production of the polyoxymethylene resin homopolymer is not particularly limited. A mixer etc. are mentioned.
The reactor preferably has a structure, such as a jacket, which can heat or cool the reaction mixture on the outer circumference of the barrel.

<(2) terminal stabilization step>
In the terminal stabilization step, the terminal of the crude polyoxymethylene resin homopolymer obtained in the polymerization step is converted to an ether group by an etherification agent by a known method (for example, the method described in JP-B-63-452). and/or with an ester group by an esterifying agent to stabilize.

The etherifying agent for blocking with an ether group is not particularly limited, but examples thereof include orthoesters.

Examples of orthoesters include, but are not limited to, orthoesters of aliphatic acids or aromatic acids with aliphatic alcohols, alicyclic alcohols or aromatic alcohols. include orthocarbonates such as methyl or ethyl orthoformate, methyl or ethyl orthoacetate and methyl or ethyl orthobenzoate, and ethyl orthocarbonate, and the like.
The etherifying agent may be used alone or in combination of two or more.

The reaction that is blocked by an etherifying agent, ie, the etherification reaction, is performed using Lewis acids such as medium strength organic acids such as p-toluenesulfonic acid, acetic acid and hydrobromic acid, and medium strength mineral acids such as dimethyl and diethyl sulfate. 0.001 to 0.02 parts by mass of the acid type catalyst may be introduced with respect to 1 part by mass of the etherifying agent.
Etherification reactions include, but are not limited to, low boiling aliphatics such as pentane, hexane, cyclohexane and benzene; cycloaliphatic and aromatic hydrocarbons; halogenation such as methylene chloride, chloroform and carbon tetrachloride; Organic solvents such as lower aliphatic compounds can be used.

As a method for terminal stabilization by blocking the ends of a crude polyoxymethylene resin homopolymer with an ester group, for example, a large amount of acid anhydride described in US Pat. and a gas phase method using an acid anhydride gas described in US Pat. No. 3,172,736.

The esterifying agent for blocking with an ester group is not particularly limited, but examples thereof include organic acid anhydrides.

Examples of organic acid anhydrides include organic acid anhydrides represented by the following general formula (2).
R ₅ COOCOR ₆ (2)
(In general formula (2), R ₅ and R ₆ each independently represent an alkyl group or a phenyl group. R ₅ and R ₆ may be the same or different.)

Examples of organic acid anhydrides include, but are not limited to, propionic anhydride, benzoic anhydride, acetic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, and phthalic anhydride. Acetic anhydride is preferred.
Esterifying agents may be used alone or in combination of two or more.

As a method for terminal blocking with an ester group in the gas phase, it is preferable to block the terminal after removing the onium salt-based polymerization catalyst by, for example, the method described in JP-A-11-92542. By removing the onium salt-based polymerization catalyst in the polyoxymethylene, it is possible to avoid the decomposition reaction of the polyoxymethylene resin homopolymer derived from the onium salt-based polymerization catalyst when performing terminal blocking, and stabilize the terminal. It is possible to improve the polymer yield in the polymerization step and suppress the coloring of the polyoxymethylene resin homopolymer.

The end of the polyoxymethylene resin homopolymer is preferably blocked with an ether group and/or an ester group to reduce the concentration of terminal hydroxyl groups to 5×10 ⁻⁷ mol/g or less. A concentration of terminal hydroxyl groups of 5×10 ⁻⁷ mol/g or less is preferable because the thermal stability is excellent and the quality of the original polyoxymethylene resin homopolymer can be maintained. From the same point of view, the concentration of terminal hydroxyl groups is more preferably 0.5×10 ⁻⁷ mol/g or less, further preferably 0.3×10 ⁻⁷ mol/g or less.

(Lubricant (B))
The polyoxymethylene resin composition of this embodiment contains a lubricant (B). By containing the lubricant (B) in the polyoxymethylene resin composition, the dispersibility of the pigment in the polyoxymethylene resin composition is improved, and poor pigment dispersion, which may be the starting point of destruction, can be alleviated. Therefore, weather resistance stability and creep properties can be improved.
Examples of lubricants (B) include, but are not limited to, polyalkylene glycols and aliphatic compounds having amide groups.
These may be used individually by 1 type, and may use 2 or more types together.
Examples of polyalkylene glycol include, but are not limited to, polyethylene glycol, polypropylene glycol, and the like. The molecular weight of polyalkylene glycol can be selected depending on the purpose, and polyalkylene glycol having a molecular weight of 500 to 20,000 can generally be used. More preferably, the polyalkylene glycol having a molecular weight of 4,000 to 20,000 can be used. In addition, the molecular weight said here means a number average molecular weight.
Examples of aliphatic compounds having an amide group include, but are not limited to, ethylenebispalmitamide, ethylenebisstearicamide , ethylenebislauricamide, ethylenebisoleicamide, and ethylene biserucamide and the like.
In the present embodiment, as the lubricant (B), from the viewpoint of improving thermal stability and reducing the amount of formaldehyde released, it is preferable to use an aliphatic compound having an amide group, polyethylene glycol, more preferably ethylene bis. It is a stearic acid amide.

The content of the lubricant (B) is in the range of 0.01 to 0.1 parts by mass, preferably 0.015 to 0.07 parts by mass, based on 100 parts by mass of the polyoxymethylene resin homopolymer (A). and more preferably 0.02 to 0.06 parts by mass.
When the content of the lubricant (B) is within the above range, the polyoxymethylene resin composition has weather resistance stability and a reduced amount of formaldehyde emitted, and the amount of formaldehyde emitted during retention during molding is also reduced. A reduced polyoxymethylene resin composition can be provided, and a molded article having excellent weather resistance stability and creep properties can be provided. Specifically, the content of the lubricant (B) is 0.01 parts by mass or more with respect to 100 parts by mass of the polyoxymethylene resin homopolymer (A), so that the pigment in the polyoxymethylene resin composition Dispersibility is improved, and poor pigment dispersion that can be the starting point of destruction can be alleviated. By doing the following, thermal stability can be improved and the amount of formaldehyde released can be reduced.

(Polyolefin resin (C))
The polyoxymethylene resin composition of this embodiment contains a polyolefin resin (C). When the polyoxymethylene resin composition contains the polyolefin resin (C), the dispersibility of the pigment in the polyoxymethylene resin composition is improved, and poor pigment dispersion, which may be the starting point of destruction, can be alleviated. , and therefore weathering stability and creep properties can be improved.
Polyolefin resin (C) is not limited to the following, but for example, polyethylene (high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene), polypropylene, ethylene - propylene copolymers, ethylene-butene copolymers, ethylene-octene copolymers, polypropylene-butene copolymers, polybutene, hydrogenated polybutadiene, ethylene-acrylic acid ester copolymers, ethylene-methacrylic acid esters A copolymer and an ethylene-acrylic acid copolymer can be mentioned.
Examples of the copolymer include, but are not limited to, graft copolymers grafted with one or more other vinyl compounds, more specifically polyethylene-g-polystyrene, ethylene Glycidyl methacrylate copolymer-g-polystyrene, low density polyethylene-g-acrylonitrile styrene copolymer, polypropylene-g-acrylonitrile strain copolymer, ethylene glycidyl methacrylate copolymer-g-acrylonitrile styrene copolymer, ethylene Ethyl acrylate copolymer-g-acrylonitrile styrene copolymer can be mentioned.

Among these, polyethylene (high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, ultra low density polyethylene) is preferred.
These polyolefin resins are not particularly limited, but preferably have a melt flow rate (according to JIS K7210-4) of 0.01 g/10 min to 150 g/10 min, more preferably 0.1 g/10 min to 120 g. /10 minutes, more preferably 0.5 g/10 minutes to 100 g/10 minutes.
When the melt flow rate is 0.01 g/10 min or more, the dispersibility of the polyolefin resin (C) in the molded article of the polyoxymethylene resin composition is good, and when it is 150 g/10 min or less, , the molded article is less likely to peel off during molding.

The content of the polyolefin resin (C) is in the range of 0.1 to 1.0 parts by mass, preferably 0.1 to 0.6 parts by mass, based on 100 parts by mass of the polyoxymethylene resin homopolymer (A). It is in the range of parts by mass, more preferably in the range of 0.13 to 0.4 parts by mass.
When the content of the polyolefin-based resin (C) is within the above range, the polyoxymethylene resin composition has a reduced amount of formaldehyde released, and the polyoxymethylene also has a reduced amount of formaldehyde released during retention in the molding process. A resin composition can be provided, and a molded article having excellent weather resistance stability and creep properties can be provided. Specifically, by setting the content of the polyolefin resin (C) to 0.1 parts by mass or more with respect to 100 parts by mass of the polyoxymethylene resin homopolymer (A), The dispersibility of the pigment is improved, and the poor dispersion of the pigment, which can be the starting point of destruction, can be alleviated. , 1.0 parts by mass or less, the thermal stability is improved and the amount of formaldehyde released can be reduced.

(Mass ratio of ((B) lubricant/(C) polyolefin resin))
In the polyoxymethylene resin composition of the present embodiment, the mass ratio of the lubricant (B) to the polyolefin resin (C), that is, the mass ratio of the lubricant (B)/olefin resin (C) is 5/ 95 to 30/70. Further, it is preferably 7/93 to 30/70, more preferably 10/90 to 30/70.
A polyoxymethylene resin composition in which the amount of formaldehyde emitted is reduced by setting the mass ratio to the range described above, and in which the amount of formaldehyde emitted during retention in the molding process is also reduced. It is possible to provide a molded article having excellent weather resistance stability and creep properties. Specifically, by setting the mass ratio of the lubricant (B)/olefin resin (C) to 5/95 or more, weather resistance stability and croup characteristics can be imparted, and the mass ratio is set to 30/70 or less. By doing so, the thermal stability is improved and the amount of formaldehyde released can be reduced.

(Pigment (D))
The polyoxymethylene resin composition of this embodiment contains a pigment (D). By containing the pigment (D) in the polyoxymethylene resin composition, it is possible to improve the appearance and visibility of the molded article using the resin composition.
Specific examples of the pigment (D) include, but are not limited to, inorganic pigments, organic pigments, metallic pigments, and fluorescent pigments.
Examples of inorganic pigments include those commonly used for coloring resins. Examples of inorganic pigments include, but are not limited to, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, combustion pigments, carbonates, phosphates, acetates, carbon black, acetylene black, and lamp black. etc.
Examples of organic pigments include, but are not limited to, condensed ouzo-based, inone-based, phlotacyanine-based, monoazo-based, diazo-based, polyazo-based, anthraquinone-based, heterocyclic, pennone-based, quinacridone-based, thioindico-based, berylene pigments. and dioxazine-based and phthalocyanine-based pigments.
These may be used individually by 1 type, and may use 2 or more types together.
In the present embodiment, as the pigment (D), it is preferable to use an inorganic pigment or an organic pigment from the viewpoint of reducing the amount of formaldehyde emitted.

The content of the pigment (D) is preferably in the range of 0.05 to 3.0 parts by mass, more preferably 0.1 to 2 parts by mass, based on 100 parts by mass of the polyoxymethylene resin homopolymer (A). 0 parts by mass, more preferably 0.15 to 1.0 parts by mass.
When the content of the pigment (D) is within the above range, the polyoxymethylene resin composition has a reduced amount of formaldehyde emitted, and a reduced amount of formaldehyde emitted during retention during molding. can provide things. Specifically, by setting the content of the pigment (D) to 0.05 parts by mass or more with respect to 100 parts by mass of the polyoxymethylene resin homopolymer (A), the visibility can be improved. By setting the content of (D) to 3.0 parts by mass or less with respect to 100 parts by mass of the polyoxymethylene resin homopolymer (A), the amount of formaldehyde released can be reduced.

(Nitrogen-containing compound (E) having formaldehyde scavenging ability)
The polyoxymethylene resin composition of the present embodiment preferably contains a nitrogen-containing compound (E) (hereinafter also referred to as "nitrogen-containing compound (E)") having formaldehyde scavenging ability. By containing the nitrogen-containing compound (E) in the polyoxymethylene resin composition, the amount of formaldehyde released from the resin composition can be reduced.
Nitrogen-containing compounds (E) having formaldehyde scavenging ability include, but are not limited to, amino-substituted triazine compounds, urea derivatives, amide compounds, polyamides, acrylamide copolymers, and hydrazide compounds. be done.
These may be used individually by 1 type, and may use 2 or more types together.
In the present embodiment, the nitrogen-containing compound (E) is preferably an acrylamide copolymer or a hydrazide compound from the viewpoint of reducing the amount of formaldehyde released.

The content of the nitrogen-containing compound (E) having formaldehyde scavenging ability is preferably in the range of 0.01 to 0.4 parts by mass with respect to 100 parts by mass of the polyoxymethylene resin homopolymer (A), and more It is preferably in the range of 0.05 to 0.35 parts by mass, more preferably in the range of 0.1 to 0.3 parts by mass.
When the content of the nitrogen-containing compound (E) having formaldehyde scavenging ability is within the above range, the polyoxymethylene resin composition has a reduced amount of formaldehyde released, and the amount of formaldehyde released during retention in the molding process is also reduced. It is possible to provide a polyoxymethylene resin composition having a high temperature resistance and to provide a molded article having excellent weather resistance stability and creep properties.

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

Examples of the urea derivative include, but are not limited to, N-substituted urea, urea condensates, ethylene urea, hydantoin compounds, and ureido compounds.
Examples of the N-substituted urea include, but are not limited to, methyl urea, alkylenebis urea, and aryl-substituted urea having a substituent such as an alkyl group.
Examples of the urea condensate include, but are not limited to, 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.
Examples of the ureido compound include, but are not limited to, allantoin.

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

Examples of the polyamide include, but are not limited to, polyamide 4/6, polyamide 6, polyamide 66, polyamide 11, polyamide 12, polyamide 6/10, polyamide 6/11, polyamide 6/12, polyamide A 6/66/610 terpolymer and the like are included.

The acrylamide copolymer is preferably in the form of particles having a primary amide group content of 30 to 70 mol % and an average particle diameter of 0.1 to 10 μm.
A particularly preferred acrylamide copolymer is a crosslinked polyacrylamide having an average particle size of 10 μm or less. More preferably, it is a polyacrylamide having an average particle size of 5 μm or less, and even more preferably a crosslinked polyacrylamide having an average particle size of 3 μm or less.

The hydrazide compound is synthesized by reacting a carboxylic acid (aromatic or alicyclic) with hydrazine. Carboxylic acid mono(di)hydrazide compounds synthesized using carboxylic acid include, for example, carbodihydrazine, oxalic acid mono(di)hydrazide, malonic acid mono(di)hydrazide, succinic acid mono(di)hydrazide, glutaric acid mono(di)hydrazide, adipic acid mono(di)hydrazide, sebacic acid mono(di)hydrazide, lauric acid mono(di)hydrazide, malic acid dihydrazide, tartaric acid dihydrazide, propionic acid monohydrazide, lauric acid monohydrazide, mono stearic acid hydrazide, dihydrazide phthalate, dihydrazide isophthalate, dihydrazide terephthalate, 2,6-naphthalate dihydrazide, p-hydroxybenzoic hydrazine, p-hydroxybenzoic hydrazine, dihydrazine 1,4-cyclohexanedicarboxylate, acetohydrazide , acrylohydrazide, maleic dihydrazide, fumaric dihydrazide, benzohydrazide, nicotinohydrazide, isonicotinohydrazide, isobutylhydrazine, oleic hydrazide and the like. Among these carboxylic acids, dicarboxylic acids such as adipic acid and sebacic acid are preferred, and adipic acid mono(di)hydrazide and sebacic acid mono(di)hydrazide are the most preferred carboxylic acid hydrazide compounds.

(Ultraviolet absorber (F))
The polyoxymethylene resin composition of the present embodiment preferably contains an ultraviolet absorber (F).
Examples of the ultraviolet absorber (F) include, but are not limited to, benzotriazole-based ultraviolet absorbers and oxalic acid anilide-based ultraviolet absorbers.
These may be used individually by 1 type, and may use 2 or more types together.

The content of the ultraviolet absorber (F) is in the range of 0.1 to 0.5 parts by mass, preferably 0.15 to 0.4 parts by mass, with respect to 100 parts by mass of the polyoxymethylene resin homopolymer (A). It is in the range of parts by mass, more preferably in the range of 0.2 to 0.35 parts by mass.
When the content of the ultraviolet absorber (F) is within the above range, it is possible to provide a polyoxymethylene resin composition in which the amount of formaldehyde released during retention during molding is reduced.

Examples of the benzotriazole-based ultraviolet absorber include, but are not limited to, 2-(2'-hydroxy-5'-methyl-phenyl)benzotriazole, 2-(2'-hydroxy-3',5'- di-t-butyl-phenyl)benzotriazole, 2-[2′-hydroxy-3′,5′-bis(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-[2′-hydroxy- 3′,5′-bis-(α,α-dimethylbenzyl)phenyl]-2H-benzotriazole, 2-(2′-hydroxy-4′-octoxyphenyl)benzotriazole and the like.
Examples of the oxalic acid alinide-based ultraviolet absorber include, but are not limited to, 2-ethoxy-2'-ethyloxalic acid bisanilide, 2-ethoxy-5-t-butyl-2'-ethyloxalic acid bisanilide, 2-ethoxy-3'-dodecyloxalic acid bisanilide and the like.
In the present embodiment, the ultraviolet absorber (F) is 2-[2′-hydroxy-3′,5′-bis(α,α-dimethylbenzyl)phenyl] from the viewpoint of reducing the amount of formaldehyde emitted. Preference is given to using benzotriazole, 2-(2'-hydroxy-3',5'-di-t-butyl-phenyl)benzotriazole.

(Hindered amine light stabilizer (G))
The polyoxymethylene resin composition of the present embodiment preferably contains a hindered amine light stabilizer (G).
Examples of the hindered amine light stabilizer (G) include, but are not limited to, 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, dibutylamine 1,3,5-triazine N , N′-Bis(2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine Condensate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl- 4-piperidyl)imino}hexamethylene {(2,2,6,6-tetramethyl-4-piperidyl)imino}], dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1- Condensate of piperidine ethanol, reaction product of decanedioic acid bis[2,2,6,6-tetramethyl-1(octyloxy)-4-piperidinyl] ester with 1,1-dimethylethyl hydroperoxide and octane, bis (1,2,2,6,6-pentamethyl-4-piperidyl)[{3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl}methyl]butylmalonate, methyl 1,2,2 ,6,6-pentamethyl-4-piperidyl sebacate, bis(2,2,6,6-tetramethyl-4-piperidyl)-sebacate, 1,2,3,4-butanetetracarboxylic acid and 1,2, 2,6,6-pentamethyl-4-piperidinol and β,β,β',β'-tetramethyl-3,9-[2,4,8,10-tetraoxaspiro(5,5)undecane]diethanol and and condensates of.
In the present embodiment, the hindered amine light stabilizer (G) includes 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6 from the viewpoint of reducing the amount of formaldehyde released. -condensation of pentamethyl-4-piperidinol with β,β,β',β'-tetramethyl-3,9-(2,4,8,10-tetraoxaspiro[5,5]undecane)-diethanol It is preferred to use objects.
These may be used individually by 1 type, and may use 2 or more types together.

The content of the hindered amine light stabilizer (G) is in the range of 0.1 to 0.5 parts by mass, preferably 0.15 to 0, per 100 parts by mass of the polyoxymethylene resin homopolymer (A). 0.4 parts by mass, more preferably 0.2 to 0.3 parts by mass.
When the content of the hindered amine light stabilizer (G) is within the above range, it is possible to provide a polyoxymethylene resin composition in which the amount of formaldehyde released during retention during molding is reduced.

(Antioxidant (H))
The polyoxymethylene resin composition of the present embodiment preferably contains an antioxidant (H). By containing the antioxidant (H) in the polyoxymethylene resin composition, the creep property can be further improved.
Antioxidants (H) include, but are not limited to, n-octadecyl-3-(3′,5′-di-t-butyl-4′-hydroxyphenyl)-propionate, n-octadecyl-3 -(3'-methyl-5-t-butyl-4'-hydroxyphenyl)-propionate, n-tetradecyl-3-(3',5'-di-t-butyl-4'-hydroxyphenyl)-propionate, 1,6-hexanediol-bis-[3-(3,5-di-t-butyl-4-hydroxyphenyl)-propionate], 1,4-butanediol-bis-[3-(3,5-di -t-butyl-4-hydroxyphenyl)-propionate], triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate], tetrakis-[methylene-3- (3′,5′-di-t-butyl-4′-hydroxyphenyl)propionate]methane, 3,9-bis[2-{3-(3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy}-1,1-dimethylethyl]2,4,8,10-tetraoxaspiro(5,5)undecane, N,N'-bis-3-(3',5'-di-t-butyl -4-hydroxyphenol)pripionylhexamethylenediamine, N,N'-tetramethylenebis-3-(3'-methyl-5'-t-butyl-4-hydroxyphenol)propionyldiamine, N,N'- bis-[3-(3,5-di-t-butyl-4-hydroxyphenol)propionyl]hydrazine, N-salicyloyl-N'-salicylidenehydrazine, 3-(N-salicyloyl)amino-1,2, 4-triazole, N,N'-bis[2-{3-(3,5-di-butyl-4-hydroxyphenyl)propionyloxy}ethyl]oxyamide and the like.
Among said antioxidants, triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate] and tetrakis-[methylene-3-(3′,5 '-Di-t-butyl-4'-hydroxyphenyl)propionate]methane is preferred.
These may be used individually by 1 type, and may use 2 or more types together.

The content of the antioxidant (H) is in the range of 0.01 to 0.05 parts by mass, preferably 0.015 to 0.045, with respect to 100 parts by mass of the polyoxymethylene resin homopolymer (A). It is in the range of parts by mass, more preferably in the range of 0.02 to 0.04 parts by mass.
When the content of the antioxidant (E) is within the above range, it is possible to provide a polyoxymethylene resin homopolymer composition with excellent weather resistance stability.

(other ingredients)
In the polyoxymethylene resin composition of the present embodiment, within a range that does not impair the properties of the polyoxymethylene resin homopolymer (A), for example, preferably 2% by mass or less with respect to 100% by mass of the polyoxymethylene resin composition Furthermore, various additives such as dyes and various reinforcing materials can be added.

(Method for producing polyoxymethylene resin composition)
The polyoxymethylene resin composition of the present embodiment contains the above-described components (A) to (D), optional components (E) to (H) and other additive components, for example, a Henschel mixer, a tumbler, a V After mixing with a letter-shaped blender, etc., it can be produced by melt-kneading using a kneader such as a single-screw extruder, a twin-screw extruder, a heating roll, a kneader, or a Banbury mixer. It can be obtained as a product in various forms such as a shape.
Alternatively, each component can be continuously fed to an extruder singly or in batches of several types by a quantitative feeder or the like without being mixed in advance. Alternatively, a high-concentration masterbatch consisting of each component may be prepared in advance and diluted with a polyoxymethylene resin homopolymer during extrusion melt-kneading.
The kneading temperature may follow the preferred processing temperature of the polyoxymethylene resin homopolymer (A) used, and is generally in the range of 180°C or higher and 240°C or lower, preferably in the range of 190°C or higher and 220°C or lower. .
The pellets and the like of the polyoxymethylene resin composition obtained as described above may be dried in advance and then used for the production of molded articles. The drying method is not particularly limited, but for example, a drying method using a box-type dryer (atmospheric pressure, vacuum), a rotary and ventilation rotary dryer, a groove-type stirring dryer, a fluid bed dryer, etc. is mentioned.
As for the drying temperature, the temperature of the heat medium is preferably 80° C. or higher, more preferably 100° C. or higher. The drying time is preferably 0 to 10 hours, more preferably 0 to 6 hours, more preferably 1 to 10 hours, when the temperature of the polyoxymethylene resin composition pellets reaches 100 ° C. or higher as the starting time. 6 hours is more preferred.

[Molded body]
The molded article of the present embodiment contains the polyoxymethylene resin composition of the present embodiment described above, and the pellet-like product obtained as described above can be used to mold the desired molded article. .
The method for producing the molded article is not particularly limited, and commonly used known molding methods such as injection molding, extrusion molding, vacuum molding, blow molding, injection compression molding, decorative molding, and other material molding. , gas-assisted injection molding, foam injection molding, low-pressure molding, ultra-thin injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, outsert molding), etc. can be applied.

Hereinafter, the present embodiment will be described with specific examples and comparative examples, but the present embodiment is not limited to the examples described later.
The evaluation method will be described below.

〔Evaluation methods〕
((1) 80°C creep property)
Using an IS-100GN injection molding machine manufactured by Toshiba Corporation, cylinder temperature 200 ° C., injection pressure 55 MPa, injection time 15 seconds, cooling time 25 seconds, gold At a mold temperature of 90° C., a strip-shaped test piece with dimensions of 110 mm×6.5 mm×3 mm was molded and allowed to stand at an environmental temperature of 23±2° C. and a humidity of 50±10% for 24 hours or longer. Using a test piece after standing and a creep tester (Toyo Seiki creep tester: C200-6), a set temperature of 80 ° C. and a tensile stress of 20 MPa are applied, and the time until the test piece breaks (breaking time (hr)) was measured. Three pieces of each specimen were made and the failure times in Tables 1 and 2 represent the arithmetic mean times for n=3.
The longer the time until destruction, the better the creep property under conditions of 80°C and 20 MPa.

((2) Quantitative determination of formaldehyde generated from molded articles of polyoxymethylene resin composition (measurement of VDA275 value); before retention (average value of n = 3))
Pellets of the polyoxymethylene resin compositions of Examples and Comparative Examples were placed in an injection molding machine with a cylinder set temperature of 220°C (mold temperature: 80°C, gate size: 3*3 mm side gate) (manufactured by Toshiba Machine, IS -100 GN), three test pieces with a size of 100*40*3 mm were produced.
The molding cycle was 40 seconds/cycle in combination of injection and cooling. The obtained molded article (test piece) was left in a thermostatic chamber adjusted to an ambient temperature of 23±2° C. and a humidity of 50±10% for one day and night.
After that, according to the method (conditions) specified by the German Automobile Manufacturers Association, a VDA275 value (100 * 40 mm flat plate test piece was hung in a 1 liter container, filled with 50 ml of water, sealed, and then heat treated (at a temperature of 60 ° C. After the heat treatment, the formaldehyde gas absorbed by the water in the container was quantified by chemical analysis and the value) was measured. The measurements were carried out on three specimens and the pre-dwell VDA275 values in Tables 1 and 2 represent an arithmetic mean time of n=3.
The lower the VDA275 value before retention, the less formaldehyde is generated from the molded article of the polyoxymethylene resin composition.

((3) Quantification of formaldehyde generated from molded articles of polyoxymethylene resin composition (measurement of VDA275 value); after retention (average value of n = 3))
Pellets of the polyoxymethylene resin compositions of Examples and Comparative Examples were placed in an injection molding machine with a cylinder set temperature of 220°C (mold temperature: 80°C, gate size: 3*3 mm side gate) (manufactured by Toshiba Machine, IS -100 GN), and after staying there for 10 minutes, three test pieces with a size of 100*40*3 mm were produced.
The molding cycle was 40 seconds/cycle in combination of injection and cooling. The obtained molded article (test piece) was left in a thermostatic chamber adjusted to an ambient temperature of 23±2° C. and a humidity of 50±10% for one day and night.
After that, according to the method (conditions) specified by the German Automobile Manufacturers Association, a VDA275 value (100 * 40 mm flat plate test piece was hung in a 1 liter container, filled with 50 ml of water, sealed, and then heat treated (at a temperature of 60 ° C. After the heat treatment, the formaldehyde gas absorbed by the water in the container was quantified by chemical analysis and the value) was measured.
The measurements were carried out on 3 specimens and the VDA275 values after residence in Tables 1 and 2 represent an arithmetic mean time of n=3.
It means that the lower the VDA275 value after retention, the less formaldehyde is generated from the molded article of the polyoxymethylene resin composition.

((4) weather resistance stability)
Pellets of the polyoxymethylene resin compositions of Examples and Comparative Examples were cooled using an injection molding machine (manufactured by Toshiba Machine, IS-100GN) with a cylinder set temperature of 215°C, an injection pressure of 72 MPa, an injection time of 15 seconds, and cooling. Time: 20 seconds, mold temperature: 90° C. A test piece (dumbbell-shaped test piece having a total length of 170 mm, a thickness of 4 mm, a parallel portion width of 10 mm, a parallel portion length of 80 mm, and a grip portion width of 20 mm) was obtained. Weather resistance stability test evaluation was performed using the obtained test piece.
Using a weather resistance tester (Sunshine Weather Meter S80 manufactured by Suga Test Instruments Co., Ltd.), the weather resistance stability test was performed under the conditions of a black panel temperature of 83° C., no rain, and an exposure time of 2000 hours.
In addition, the tensile strength before and after the weathering stability test is measured according to ISO527 (tensile tester: AG-IS manufactured by Shimadzu Corporation), and the tensile strength retention rate (%) calculated by the following formula is the average of n = 3 calculated by value. Tables 1 and 2 show the obtained tensile strength retention (%).
Tensile strength retention (%) = Tensile strength after weather resistance test/Tensile strength before weather resistance test x 100
It was judged that the higher the tensile strength retention rate (%), the better in practical use.

[Components used in Examples and Comparative Examples]
((A) polyoxymethylene resin homopolymer)
A formaldehyde homopolymer whose end groups were stabilized by acetylation was used, which has an MFR value of 3 g/10 minutes and a formaldehyde generation amount of 0.6% (at 230° C. under a nitrogen ambient atmosphere).

((B) lubricant)
<B-1>: Ethylene bis stearamide (EBS) (manufactured by NOF)
<B-2>: Polyethylene glycol (PEG) (manufactured by NOF: number average molecular weight 6,000)

((C) polyolefin resin)
<C-1>: Suntech LD L-1850A (LDPE) [Vicat softening point 87 ° C., MFR 6.7 g / 10 minutes] (manufactured by Asahi Kasei Corporation)
<C-2>: Suntech HD J-320 (HDPE) [Vicat softening point 123 ° C., MFR 12.0 g / 10 minutes] (manufactured by Asahi Kasei Corporation)

((D) pigment)
<D-1>: Mitsubishi Carbon Black #52 (manufactured by Mitsubishi Chemical)
<D-2>: Unipert White MK-2000 (manufactured by Toho Pigment Industry)
<D-3>: Paliogen Red K3911 (manufactured by BASF Japan)

((E) Nitrogen-containing compound having formaldehyde scavenging ability)
<E-1>: Polyamide 6/66/610 terpolymer <E-2>: Polyacrylamide compound
[Manufacturing method of E-2]
2400 g of acrylamide, 267 g of methylenebisacrylamide, and 0.54 g of zirconium tetraisopropoxide (1/10000 mol relative to acrylamide) as a catalyst were added to a batch-type 5 L reactor equipped with a stirrer, and the mixture was stirred in a stream of N ₂ . The reaction was carried out at 125°C for 4 hours.
After completion of the reaction, the solid was pulverized with a jet mill pulverizer and washed with acetone.
Then, it was dried at 120° C. for 20 hours under reduced pressure of −700 mmHg. The content of primary amide groups was 44.7 mol %, and the average particle size was 5.0 μm. The average particle size of the acrylamide copolymer <B-2> was measured with a laser diffraction particle size distribution analyzer.
<E-3>: Sebacic acid dihydrazide (SDH)
<E-4>: adipic acid dihydrazide (ADH)
<E-5>: melamine

((F) UV absorber)
2-[2'-hydroxy-3',5'-bis(α,α-dimethylbenzyl)phenyl]benzotriazole

((G) hindered amine light stabilizer)
1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol, and β,β,β',β'-tetramethyl-3,9-(2 ,4,8,10-tetraoxaspiro[5,5]undecane)-diethanol and

((H) antioxidant)
Triethylene glycol-bis-[3-(3-t-butyl-5-methyl-4-hydroxyphenyl)-propionate)

[Example 1]
Polyoxymethylene resin homopolymer (A) 100 parts by mass, lubricant (B-1) 0.02 parts by mass, olefin resin (C-1) 0.18 parts by mass (B-1/C-1 = 10/ 90) and 0.2 parts by mass of Pigment (D-1) were uniformly mixed using a Henschel mixer to obtain a mixture.
The mixture was melt-kneaded with a 30φ single-screw extruder, extruded into strands, cooled, and pelletized to obtain resin composition pellets composed of a polyoxymethylene resin homopolymer composition. The extrusion conditions were as follows: cylinder temperature set at 200° C., discharge rate at 5 kg/hr, screw rotation speed at 50 rpm, and vent pressure reduction degree at −720 mmHg.
The obtained resin composition pellets were dried at 80° C. for 4 hours.
Using the dried resin composition pellets, <(1) 80 ° C. creep characteristics>, <(2) quantification of formaldehyde released from the molded body; before retention>, <(3) formaldehyde released from the molded body. Quantification; after retention> and <(4) weather resistance> were evaluated by the various evaluation methods described above.
Table 1 shows the evaluation results.

[Examples 2 to 21]
The composition was changed as described in Table 1 or Table 2. Other conditions were the same as in [Example 1]. In Examples 10 to 21, components (E) to (H) were added to the Henschel mixer in the same manner as component (A) when obtaining a mixture from component (A).
Evaluation results are shown in Tables 1 and 2.

[Comparative Examples 1 to 9]
The composition was changed as described in Table 1 or Table 2. Other conditions were the same as in [Example 1]. In Comparative Example 9, components (E) to (H) were added to the Henschel mixer in the same manner as component (A) when obtaining a mixture from component (A).
Evaluation results are shown in Tables 1 and 2.

As is clear from the evaluation results in Table 1 above, in the resin composition containing the polyoxymethylene resin homopolymer (A), the lubricant (B), the polyolefin resin (C), and the pigment (D), Examples in which the content of the lubricant (B) and the polyolefin resin (C) were set to a predetermined content and the mass ratio of the lubricant (B)/olefin resin (C) was set to a predetermined range, weather resistance stability Thus, a polyoxymethylene resin composition was obtained which had excellent creep properties, a reduced amount of formaldehyde emitted, and a reduced amount of formaldehyde emitted during retention during molding.
Further, as is clear from the evaluation results in Table 2, a nitrogen-containing compound (E) having formaldehyde scavenging ability, an ultraviolet absorber (F), a hindered amine light stabilizer (G), and an antioxidant ( Also in the examples with a predetermined content of H), the polyoxymethylene resin composition was excellent in weather resistance stability and creep characteristics, reduced the amount of formaldehyde emitted, and reduced the amount of formaldehyde emitted during retention during molding. things were obtained.

INDUSTRIAL APPLICABILITY The polyoxymethylene resin composition of the present invention has industrial applicability as parts for automobiles, parts for various electric and electronic devices, and various industrial parts.

Claims (4)

100 parts by mass of polyoxymethylene resin homopolymer (A),
Lubricant (B) 0.01 to 0.07 parts by mass,
0.1 to 1.0 parts by mass of a polyolefin resin (C),
containing a pigment (D),
Lubricant (B)/ polyolefin resin (C) , which is the mass ratio of the lubricant (B) and the polyolefin resin (C), is 5/95 to 30/70,
The lubricant (B) is ethylenebisstearic acid amide,
The polyolefin resin (C) is low density polyethylene
A polyoxymethylene resin composition characterized by: 0.01 to 0.4 parts by mass of a nitrogen-containing compound (E) having formaldehyde scavenging ability, 0.1 to 0.5 parts by mass of an ultraviolet absorber (F),
0.1 to 0.5 parts by mass of a hindered amine light stabilizer (G);
The polyoxymethylene resin composition according to claim 1, further comprising 0.01 to 0.05 parts by mass of an antioxidant (H). The polyoxy according to claim 2, wherein the nitrogen-containing compound (E) is at least one selected from the group consisting of amino-substituted triazine compounds, urea derivatives, amide compounds, polyamides, acrylamide copolymers, and hydrazide compounds. A methylene resin composition. A molded article comprising the polyoxymethylene resin composition according to any one of claims 1 to 3 .