JP6938266B2 - Polyoxymethylene resin composition and molded article - Google Patents

Description

The present invention relates to a polyoxymethylene resin composition and a molded product.

The polyoxymethylene resin has an excellent balance of mechanical strength, chemical resistance, slidability, and abrasion resistance, and can be easily processed. Therefore, polyoxymethylene resin is widely used as one of typical engineering plastics in mechanical parts, automobile parts, and other parts of electrical equipment.

In addition, there is a market demand for polyoxymethylene resins to improve impact strength in many potential applications. Then, various techniques for improving the impact strength by blending a specific component with a resin such as a polyoxymethylene resin have been published.

As a technique for improving such impact strength, Patent Document 1 discloses a hollow molded product made of a resin in which a core-shell polymer and / or a thermoplastic polyurethane resin is blended with a polyoxymethylene resin. Further, Patent Document 2 discloses a composition containing a brittle plastic such as polystyrene and a rubber mixture. Further, Patent Document 3 discloses a composition containing a polyoxymethylene resin, a rubber elastic graft polymer based on poly (meth) acrylic acid ester or silicone rubber, and the polymer. Further, Patent Document 4 discloses a composition containing a polyoxymethylene resin and a thermoplastic polyurethane resin and / or a core-shell polymer-based impact resistance improving agent.

Japanese Unexamined Patent Publication No. 7-195496 Japanese Patent No. 3929896 Japanese Unexamined Patent Publication No. 6-57097 Japanese Unexamined Patent Publication No. 7-126483

However, the technique described in Patent Document 1 focuses on blow molding. Further, Patent Document 1 discloses an example of a composition in which a thermoplastic polyurethane resin and a core-shell polymer are used in combination, but such a composition is described in terms of the rigidity of the material and when heat is retained in a molding machine or the like. There was room for improvement in terms of stability.
Further, Patent Document 2 does not disclose the polyoxymethylene resin composition, and the composition described in Patent Document 2 has stability during heat retention, which is a problem peculiar to the polyoxymethylene resin composition. In that respect, there was room for improvement.
Further, the composition described in Patent Document 3 has room for improvement in terms of both impact resistance and rigidity, stability during heat retention in a molding machine, and sliding characteristics. rice field.
Further, the technique described in Patent Document 4 also has room for improvement in terms of slidability and stability during heat retention in a molding machine or the like.

As described above, in the above-mentioned conventional technique, there is room for improvement in impact resistance, rigidity, slidability, and stability during heat retention of the polyoxymethylene resin, and further improvement is desired.

Therefore, an object of the present invention is to provide a polyoxymethylene resin composition having excellent impact resistance, rigidity, slidability, and stability during heat retention. Another object of the present invention is to provide a molded product having excellent impact resistance, rigidity and slidability, as well as excellent stability during heat retention.

As a result of diligent studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned problems can be solved by incorporating a specific modifier in a predetermined ratio in a polyoxymethylene resin, and complete the present invention. I came to do it.

That is, the present invention is as follows.
[1]
It contains 100 parts by mass of (A) polyoxymethylene resin and 0.5 to 50 parts by mass of (B) modifier.
The (B) modifier contains (b-1) thermoplastic polyurethane and (b-2) graft rubber copolymer.
The (b-2) graft rubber copolymer has a structure of two or more layers.
A polyoxymethylene resin composition.
[2]
The polyoxymethylene resin composition according to item [1], wherein the graft rubber copolymer (b-2) has an amount of Si element of 1 to 25% by mass in ICP-MS analysis.
[3]
The polyoxymethylene resin composition according to item [1] or [2], wherein the thermoplastic polyurethane (b-1) is an ester polyurethane.
[4]
In the item [3], the ester-based polyurethane has an ester component ratio (mol ratio) of 4 to 5 and a polyol component ratio (mol ratio) of 5 to 6 when the isocyanate component is 1. The polyoxymethylene resin composition according to the above.
[5]
The polyoxymethylene resin composition according to item [3] or [4], wherein the ester-based polyurethane contains two types of polyol components.
[6]
Items [1] to [5], wherein the graft rubber copolymer (b-2) contains a silicone / acrylic polymer and the amount of Si element in ICP-MS analysis is 2 to 10% by mass. The polyoxymethylene resin composition according to any one of the above.
[7]
The polyoxymethylene resin composition according to any one of items [1] to [6], wherein the concentration of sulfate ions is 0.01 to 0.2 ppm.
[8]
The polyoxymethylene resin composition according to any one of items [1] to [7], wherein the polyoxymethylene resin (A) has a melt flow rate of 0.1 to 60 g / 10 minutes.
[9]
The polyoxymethylene resin composition according to any one of items [1] to [8], which is in the form of pellets.
[10]
A molded product comprising the polyoxymethylene resin composition according to any one of items [1] to [9].

According to the present invention, it is possible to provide a polyoxymethylene resin composition having excellent impact resistance, rigidity and slidability, and also having excellent stability during heat retention. Further, according to the present invention, it is possible to provide a molded product having excellent impact resistance, rigidity and slidability, and also having excellent stability during heat retention.

Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail, but the present invention is not limited to the following description and is within the scope of the gist thereof. It can be modified in various ways.

(Polyoxymethylene resin composition)
The polyoxymethylene resin composition of the present embodiment contains (A) 100 parts by mass of the polyoxymethylene resin and (B) 0.5 to 50 parts by mass of the modifier. , (B-1) thermoplastic polyurethane and (b-2) graft rubber copolymer, and the above (b-2) graft rubber copolymer has a structure of two or more layers. Further, the polyoxymethylene resin composition of the present embodiment may contain (C) a colorant and other additives as optional components.
Hereinafter, each component constituting the polyoxymethylene resin composition of the present embodiment will be described in detail.

<(A) Polyoxymethylene resin>
(A) Polyoxymethylene resin contained in the polyoxymethylene resin composition of the present embodiment (in this specification, it may be referred to as component (A) or component (A). Hereinafter, component (B), etc. The same applies to the component (b-1), the component (b-2), and the component (C))) will be described in detail.

Examples of the (A) polyoxymethylene resin that can be used in the present embodiment include polyoxymethylene homopolymers and polyoxymethylene copolymers.

Specifically, the polyoxymethylene homopolymer is substantially obtained by homopolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) or a tetramer (tetraoxane) of formaldehyde. Examples include polyoxymethylene homopolymers consisting only of oximethylene units.
Specifically, the polyoxymethylene copolymer includes a formaldehyde monomer, a cyclic oligomer of formaldehyde such as a trimer (trioxane) or a tetramer (tetraoxane) of formaldehyde, and a cyclic ether or a cyclic as a comonomer. Examples thereof include a polyoxymethylene copolymer obtained by copolymerizing with formaldehyde. Here, examples of the cyclic ether or cyclic formal include ethylene oxide; propylene oxide; epichlorohydrin; 1,3-dioxolane; glycol such as 1,4-butanediol formal, or cyclic formal of diglycol.

When a polyoxymethylene copolymer is obtained using trioxane, the amount of comonomer such as 1,3-dioxolane used is generally preferably 0.1 to 60 mol with respect to 100 mol of trioxane, preferably 0.1 to 20 mol. More preferably, 0.13 to 10 mol is further preferable. Further, in the present embodiment, the melting point of the polyoxymethylene copolymer is preferably 162 ° C to 173 ° C, more preferably 167 ° C to 173 ° C, still more preferably 167 ° C to 171 ° C. A polyoxymethylene copolymer having a melting point of 162 ° C. to 173 ° C. can be obtained by using a comonomer of about 1.3 to 3.5 mol with respect to 100 mol of trioxane. The melting point can be measured by DSC.

The polyoxymethylene copolymer includes a branched polyoxymethylene copolymer obtained by copolymerizing a formaldehyde monomer and / or a cyclic oligomer of formaldehyde with a monofunctional glycidyl ether, and a single amount of formaldehyde. Examples thereof include a polyoxymethylene copolymer having a crosslinked structure obtained by copolymerizing a cyclic oligomer of body and / or formaldehyde with a polyfunctional glycidyl ether.

Further, the (A) polyoxymethylene resin may contain a block copolymer having a different block portion different from the repeating structural unit of polyoxymethylene.

When the (A) polyoxymethylene resin contains a block copolymer, the (B) modifier containing the polyoxymethylene resin composition of the present embodiment is selectively and stably present in the dissimilar block portion thereof. Can be made to. This makes it possible to develop even more stable wear resistance.

The block copolymer referred to here is a polyoxymethylene homopolymer having at least one of the block portions represented by any of the following general formulas (1) to (4), or a polyoxymethylene copolymer (both of which are collectively described below). Also referred to as "block copolymer") is preferred.

In the above general formulas (1), (2) and (3), R ₁ and R ₂ are independently selected from the group consisting of a hydrogen atom, an alkyl group, a substituted alkyl group, an aryl group and a substituted aryl group, respectively. When one chemical species is indicated and R ₁ and R ₂ are plural, they may be the same or different from each other.

In the above general formulas (1), (2), and (4), R ₃ , R 5, R _6, is one kind of chemistry selected from the group consisting of an alkyl group, a substituted alkyl group, an aryl group and a substituted aryl group. Indicates the species.

In the above general formula (4), R ₄ represents one chemical species selected from the group consisting of hydrogen atom, alkyl group, substituted alkyl group, aryl group and substituted aryl group, and when R ₄ is plural, it represents one kind. They may be the same or different.

In the general formulas (1), (2), and (3), m represents an integer of 2 to 6, and an integer of 2 to 4 is preferable.

In the general formulas (1), (2), and (3), n represents an integer of 1 to 1000, and an integer of 10 to 250 is preferable.

In the above general formula (4), p represents an integer of 2 to 6, and the two ps may be the same or different.

In the above general formula (4), q and r represent positive numbers, respectively, and q is 2 to 100 mol% and r is 0 to 98 mol% with respect to a total of 100 mol% of q and r. (CH (CH ₂ CH ₃ ) CH ₂ ) -Units and- _{(CH 2 CH 2} CH ₂ CH ₂ ) -Units exist at random or in blocks, respectively.

The group represented by the general formula (1) is a residue obtained by desorbing a hydrogen atom from the (poly) alkylene oxide adduct of alcohol, and the group represented by the general formula (2) is a carboxylic acid. It is a residue obtained by desorbing a hydrogen atom from the (poly) alkylene oxide adduct, and the group represented by the above general formula (3) is a residue obtained by desorbing a hydrogen atom from the (poly) alkylene oxide.

Block copolymers having the above block portions include, for example, JP-A-57-31918, JP-A-60-170652, JP-A-2002-3696, JP-A-2002-234922, and JP-A-2002-3694. It can be prepared by referring to the method described in the publication.

The block portion of the block copolymer represented by these formulas (1) to (4) is a compound constituting a block having a functional group such as a hydroxyl group at both ends or one end, and the terminal portion in the polymerization process of the polyoxymethylene resin. It is obtained by reacting with.

The amount of the block portions represented by the above formulas (1) to (4) in the block copolymer is not particularly limited, but the ratio of the block portions when the block copolymer is 100% by mass is 0.001. It is preferably mass% to 30% by mass. When the above ratio is 0.001% by mass or more, stable slidability can be maintained, and when it is 30% by mass or less, the polyoxymethylene resin composition of the present embodiment can be maintained. It is possible to suppress a decrease in the rigidity of the molded product made of the above. From the same viewpoint, the above ratio is more preferably 0.01% by mass or more, further preferably 0.1% by mass or more, further preferably 1% by mass or more, and 15 It is more preferably mass% or less, and further preferably 8 mass% or less.

Further, the molecular weight of the block portion in the block copolymer is preferably 10,000 or less, more preferably 8,000 or less, from the viewpoint of not reducing the rigidity of the molded product containing the polyoxymethylene resin composition of the present embodiment. It is more preferably 5000 or less. On the other hand, the lower limit of the molecular weight of the block portion in the block copolymer is not particularly limited, but is preferably 100 or more from the viewpoint of maintaining stable slidability.

The compound forming the block portion in the block copolymer is not particularly limited, and is, for example, C ₁₈ H ₃₇ O (CH ₂ CH ₂ O) ₄₀ C ₁₈ H ₃₇ , C ₁₁ H ₂₃ CO ₂ (CH ₂ CH ₂ O). ) ₃₀ H, C ₁₈ H ₃₇ O (CH ₂ CH ₂ O) ₇₀ H, C ₁₈ H ₃₇ O (CH ₂ CH ₂ O) ₄₀ H, polyethylene glycol with hydroxyl groups at both ends, hydroxyl groups at both ends Polypropylene glycol, hydrogenated polybutadiene with hydroxyl groups at both ends, hydroxyalkylated polyethylene glycol at both ends, hydroxyalkylated polypropylene glycol at both ends, polybutadiene with hydroxyalkylated hydrogen at both ends, glycidyl compound (monofunctional, polyfunctional) And so on.

The polymerization catalyst used for the polymerization of the polyoxymethylene copolymer is not particularly limited, but for example, a cationically active catalyst such as Lewis acid, protonic acid and an ester or anhydride thereof is preferable. Lewis acid is not particularly limited, and examples thereof include halides of boric acid, tin, titanium, phosphorus, arsenic, and antimony, and more specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, and the like. Phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof can be mentioned. The protonic acid and its ester or anhydride are not particularly limited, and examples thereof include perchloric acid, trifluoromethanesulfonic acid, percarolic acid-quaternary butyl ester, acetylparklorate, and trimethyloxonium hexafluorophosphate. .. Among these, as the polymerization catalyst, boron trifluoride, boron trifluoride hydrate, and a coordination compound compound of boron trifluoride and an organic compound containing an oxygen atom or a sulfur atom are preferable, and more specific. Examples of suitable examples include boron trifluoride diethyl ether and boron trifluoride di-n-butyl ether.

The method for producing the polyoxymethylene copolymer is not particularly limited, and conventionally known methods can be used. For example, US Pat. No. 3,027,352, No. 3803094, and German Patent Invention No. 1161421 can be used. , No. 1495228, No. 1720358, No. 3018898, JP-A-58-98322, and JP-A-7-70267. Further, since the polyoxymethylene copolymer obtained by the above method has a thermally unstable terminal portion [-(OCH ₂ ) _n- OH group], the unstable terminal portion is decomposed and removed. Is preferable.

Specifically, in the decomposition removal treatment of the unstable end portion, the temperature of the polyoxymethylene copolymer or more and 260 ° C. or less is present in the presence of at least one quaternary ammonium compound represented by the following formula (5). Then, the polyoxymethylene copolymer is heat-treated in a molten state.

Here, in the formula (5), R ^a , R ^b , R ^c and R ^d are independently substituted or unsubstituted alkyl groups having 1 to 30 carbon atoms; and aryl groups having 6 to 20 carbon atoms; An aralkyl group in which at least one hydrogen atom in a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms is substituted with an aryl group having 6 to 20 carbon atoms; or at least one in an aryl group having 6 to 20 carbon atoms. Indicates an alkylaryl group in which the hydrogen atom of 1 to 30 is substituted with a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, and the substituted or unsubstituted alkyl group is linear, branched, or cyclic. The substituent in the above-mentioned substituted alkyl group is a halogen atom, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, or an amide group. Further, in the above-mentioned unsubstituted alkyl group, aryl group, aralkyl group and alkylaryl group, the hydrogen atom may be substituted with a halogen atom. n'indicates an integer of 1 to 3. X represents a hydroxyl group, a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than hydrogen halide, an oxo acid, an inorganic thioic acid, or an acid residue of an organic thioic acid having 1 to 20 carbon atoms.

The quaternary ammonium compound is not particularly limited as long as it is represented by the above formula (5), but from the viewpoint of more effectively and surely exerting the above effect according to the present embodiment, ^Ra , R in the above formula (5). ^{It is preferable that b} , R ^c and R ^d are independently alkyl groups having 1 to 5 carbon atoms or hydroxyalkyl groups having 2 to 4 carbon atoms, and further, R ^a , R ^b , R ^c and R. It is particularly preferable that at least one of ^{d is a hydroxyethyl group.} Such a quaternary ammonium compound is not particularly limited, but specifically, tetramethylammonium, tetethylammonium, tetrapropylammonium, tetra-n-butylammonium, cetyltrimethylammonium, tetradecyltrimethylammonium, 1 , 6-Hexamethylenebis (trimethylammonium), Decamethylene-bis- (trimethylammonium), trimethyl-3-chloro-2-hydroxypropylammonium, trimethyl (2-hydroxyethyl) ammonium, triethyl (2-hydroxyethyl) ammonium, Tripropyl (2-hydroxyethyl) ammonium, tri-n-butyl (2-hydroxyethyl) ammonium, trimethylbenzylammonium, triethylbenzylammonium, tripropylbenzylammonium, tri-n-butylbenzylammonium, trimethylphenylammonium, triethylphenyl Hydroxide such as ammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, octadesyltri (2-hydroxyethyl) ammonium, tetrakis (hydroxyethyl) ammonium; Hydrochlorides of ammonium compounds such as hydrochloric acid, odorous acid and hydrofluoric acid; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodine acid, silicic acid, perchloric acid, subchlorite of the above quaternary ammonium compounds. Oxoates such as chloric acid, hypochlorous acid, chlorosulfate, amidosulfate, disulfate, and tripolyphosphoric acid; thioate salts such as thiosulfate of the above quaternary ammonium compound; and formic acid of the above quaternary ammonium compound. , Acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, caproic acid, capric acid, capric acid, benzoic acid, carboxylic acid salts such as ammonium acid; Among these, the quaternary ammonium compound, a hydroxide (OH ^-), sulfate _{^{(HSO 4-, SO 4 2-)}} , carbonate (HCO ^3-, CO ^32-), boric acid (B (OH) ^4- ), and salts of carboxylic acids are preferred. Of the carboxylic acids, formic acid, acetic acid and propionic acid are particularly preferred. As the quaternary ammonium compound, one type may be used alone, or two or more types may be used in combination. Further, amines such as ammonia and triethylamine, which are known decomposition accelerators at unstable ends, may be used in combination with the quaternary ammonium compound.

The amount of the quaternary ammonium compound used is 0 in terms of the amount of nitrogen derived from the quaternary ammonium compound represented by the following formula (6) with respect to the total mass of the polyoxymethylene copolymer and the quaternary ammonium compound. .05 to 50 mass ppm is preferable, and 1 to 30 mass ppm is more preferable.
Amount of quaternary ammonium compound used = P × 14 / Q ・ ・ ・ (6)

Here, in the formula (6), P indicates the concentration (mass ppm) of the quaternary ammonium compound with respect to the polyoxymethylene copolymer, 14 is the atomic weight of nitrogen, and Q indicates the molecular weight of the quaternary ammonium compound.

When the amount of the quaternary ammonium compound used is 0.05 mass ppm or more, the decomposition / removal rate of the unstable end portion tends to be further improved. Further, when the content is 50 mass ppm or less, the color tone of the polyoxymethylene copolymer after decomposition and removal of the unstable terminal portion tends to be more excellent.

The unstable end portion of the polyoxymethylene resin in the present embodiment can be decomposed and removed by heat treatment in a state where the polyoxymethylene copolymer is melted at a temperature of melting point or higher and 260 ° C. or lower. The apparatus used for this decomposition / removal treatment is not particularly limited, but an extruder, a kneader, or the like is suitable. Formaldehyde generated by decomposition is usually removed under reduced pressure. The method of mixing the quaternary ammonium compound and the polyoxymethylene copolymer is not particularly limited, but for example, a method of adding the quaternary ammonium compound as an aqueous solution in the step of inactivating the polymerization catalyst, or a poly produced by polymerization. A method of spraying a quaternary ammonium compound on the oxymethylene copolymer powder can be mentioned. Regardless of which method is used, it is sufficient that the quaternary ammonium compound is present in the copolymer in the step of heat-treating the polyoxymethylene copolymer. For example, the quaternary ammonium compound may be injected into an extruder in which the polyoxymethylene copolymer is melt-kneaded and extruded. Alternatively, when a filler or pigment is blended into the polyoxymethylene copolymer using the extruder or the like, the quaternary ammonium compound is first adhered to the resin pellet of the polyoxymethylene copolymer, and then the filler or pigment is not blended. Decomposition and removal treatment of the stable end portion may be performed.

The decomposition and removal treatment of the unstable end portion can be performed after deactivating the polymerization catalyst coexisting with the polyoxymethylene copolymer obtained by polymerization, or can be performed without deactivating the polymerization catalyst. It is possible. Examples of the deactivation treatment of the polymerization catalyst include a method of neutralizing and deactivating the polymerization catalyst in a basic aqueous solution such as amines. When the polymerization catalyst is not deactivated, the polyoxymethylene copolymer is heated at a temperature below the melting point of the polyoxymethylene copolymer in an inert gas atmosphere to reduce the polymerization catalyst by volatilization, and then the unstable terminal is formed. It is also effective to perform the disassembly and removal operation of the part.

By the decomposition and removal treatment of the unstable end portion as described above, a polyoxymethylene copolymer having excellent thermal stability can be obtained.

The polyoxymethylene resin (A) constituting the polyoxymethylene resin composition preferably has an OH group amount at the terminal portion of 5 to 95% with respect to the total number of terminals of the molecule. When the amount of OH groups at the terminal portion is 95% or less, it is preferable because microvoids can be intentionally formed during the production of the resin composition, and when the amount of OH groups at the terminal portion is 5% or more. , (B) The adhesion of the modifier can be improved. From the same viewpoint, the amount of OH groups at the terminal portion is more preferably 90% or less, further preferably 85% or less, further preferably 80% or less, and 6% or more. More preferably, it is more preferably 7% or more, and even more preferably 10% or more.

The polyoxymethylene resin (A) constituting the polyoxymethylene resin composition preferably has an OH group amount at the terminal portion of 10 to 200 mmol / kg. When the amount of OH groups at the end is 200 mmol / kg or less, the thermal stability of the polyoxymethylene resin composition can be made very excellent at the time of production, and when it is 10 mmol / kg or more, poly The crystallinity of the oxymethylene resin tends to increase, which is preferable. From the same viewpoint, the amount of OH groups at the terminal portion is more preferably 150 mmol / kg or less, further preferably 100 mmol / kg or less, further preferably 90 mmol / kg or less, and 15 mmol / kg. It is more preferably kg or more, further preferably 20 mmol / kg or more, and even more preferably 40 mmol / kg or more.

The amount of OH groups at the end ^{can be measured directly and indirectly by 1} H-NMR, ¹³ C-NMR, or the like.
The direct measurement is not limited to the following methods, ^{but can be directly observed by two-dimensional NMR such as 1} H-NMR and ¹³ C-NMR, presaturation method, WET method and the like.
In the indirect measurement, the method is not limited to the following, but (A) the polyoxymethylene resin is dissolved in the NMR measurement solvent, and then derivatized with a silylating agent or the like capable of reacting with the OH group at the terminal portion. After that, it can be measured.

The silylating agent is not limited to the following, but is not limited to hexamethyldisilazane, dimethyldichlorosilane, trimethylchlorosilane, trimethylchlorosilane, N, O-bis (trimethylsilyl) acetamido, N-methyl-N-trimethylsilylacetamide, N-Methyl-N-trimethylsilyltrifluoroacetamide, N-trimethylsilyldimethylamine, N-trimethylsilyldiethylamine, N, O-bis (trimethylsilyl) trifluoroacetamide, N-trimethylsilylimidazole, tert-butyldimethylchlorosilane, N-methyl-N -Tert-Butyldimethylsilyltrifluoroacetamide and the like can be used.

The (A) polyoxymethylene resin constituting the polyoxymethylene resin composition of the present embodiment includes a polyoxymethylene homopolymer, a polyoxymethylene copolymer, a branched polyoxymethylene copolymer, and a polyoxymethylene copolymer having a crosslinked structure. , A homopolymer-based block copolymer having a block moiety, and a copolymer-based block copolymer having a block moiety can be used, and these can be used in combination.

Further, as the (A) polyoxymethylene resin, for example, a combination having a different molecular weight, a combination of polyoxymethylene copolymers having a different amount of comonomer, and the like can be appropriately used.

The ratio of the copolymer and the block copolymer in the molded product made of the polyoxymethylene resin composition of the present embodiment ^{can be measured by 1} H-NMR, ¹³ C-NMR or the like.

Further, the structure of the block portion is obtained by dissolving a polyoxymethylene resin composition containing a block copolymer or a molded product made of the same, performing operations such as reprecipitation and filtration to isolate the block copolymer, and then decomposing the block copolymer with hydrochloric acid. As a result, the block portion can be isolated and purified, and the block portion can be ^{determined by performing various measurements such as 1} H-NMR, ¹³ C-NMR, and two-dimensional NMR.

The melt flow rate of the polyoxymethylene resin (A) is not particularly limited, but the melt flow rate measured according to ISO-1133 Condition D is preferably 0.1 to 60 g / 10 minutes. When the melt flow rate is 0.1 g / 10 minutes or more, it is preferable in terms of molding fluidity, and when it is 60 g / 10 minutes or less, the impact strength can be further improved. In addition, if the melt flow rate is within the above range, the modifier (B) can be uniformly dispersed in the polyoxymethylene resin composition of the present embodiment. From the same viewpoint, the melt flow rate of the (A) polyoxymethylene resin is more preferably 50 g / 10 minutes or less, further preferably 20 g / 10 minutes or less, and 10 g / 10 minutes or less. Is more preferable, and 5 g / 10 minutes or less is particularly preferable. On the other hand, from the same viewpoint, the melt flow rate of the (A) polyoxymethylene resin is more preferably 0.2 g / 10 minutes or more, further preferably 0.5 g / 10 minutes or more, and 1 g / 10 minutes or more. It is more preferably 10 minutes or more, and particularly preferably 2 g / 10 or more.

The melt viscosity of the polyoxymethylene resin (A) is not particularly limited. For example, the polyoxymethylene resin (A) preferably has a viscosity of 100 to 4000 Pa · s at a ^{share rate of 100 sec -1 at 190 ° C.} When the viscosity is within the above range, the modifier (B) can be uniformly dispersed in the polyoxymethylene resin composition of the present embodiment. Further, the viscosity of the polyoxymethylene resin (A) at a share rate of 100 sec ^-1 at 190 ° C. is more preferably 3000 Pa · s or less, further preferably 2000 Pa · s or less, and 1500 Pa · s. It is more preferably 1000 Pa · s or less, and particularly preferably 1000 Pa · s or less. On the other hand, the viscosity of the polyoxymethylene resin (A) at a share rate of 100 sec ^-1 at 190 ° C. is more preferably 150 Pa · s or more, further preferably 200 Pa · s or more, and 300 Pa · s. The above is more preferable, and 400 Pa · s or more is particularly preferable.

Further, for example, the polyoxymethylene resin (A) preferably has a viscosity of 50 to 2000 Pa · s at a ^{share rate of 1000 sec -1 at 190 ° C.} When the viscosity is within the above range, the modifier (B) can be uniformly dispersed in the polyoxymethylene resin composition of the present embodiment. Further, the viscosity of the polyoxymethylene resin (A) at a share rate of 1000 sec ^-1 at 190 ° C. is more preferably 1500 Pa · s or less, further preferably 1000 Pa · s or less, and 500 Pa · s. It is more preferably 400 Pa · s or less, and particularly preferably 400 Pa · s or less. On the other hand, the viscosity of the polyoxymethylene resin (A) at a share rate of 1000 sec ^-1 at 190 ° C. is more preferably 60 Pa · s or more, further preferably 75 Pa · s or more, and 90 Pa · s. The above is more preferable, and 150 Pa · s or more is particularly preferable.
The viscosity can be measured by a twin capillary rheometer (Malvern, Rosand, RH10) or the like, and can be appropriately measured at a predetermined temperature and share rate.

<(B) Modified material>
The polyoxymethylene resin composition of the present embodiment contains (B) a modifier. Further, the modifier (B) contains (b-1) thermoplastic polyurethane and (b-2) graft rubber copolymer, and (b-2) graft rubber copolymer has a structure of two or more layers. Have.

The polyoxymethylene resin composition of the present embodiment contains (B) a modifier in an amount of 0.5 to 50 parts by mass with respect to 100 parts by mass of the (A) polyoxymethylene resin. By setting the content of the component (B) to 0.5 parts by mass or more with respect to 100 parts by mass of the component (A), the impact resistance tends to be improved, and the content is set to 50 parts by mass or less. As a result, the impact resistance tends to be improved while maintaining the rigidity.
From the same viewpoint, the content of the component (B) with respect to 100 parts by mass of the component (A) in the polyoxymethylene resin composition of the present embodiment is preferably 1 part by mass or more, and is preferably 3 parts by mass or more. More preferably, it is more preferably 5 parts by mass or more, further preferably 45 parts by mass or less, further preferably 40 parts by mass or less, and further preferably 35 parts by mass or less.

In the polyoxymethylene resin composition of the present embodiment, the (A) polyoxymethylene resin and the (B) modifier can form a sea-island structure. This structure can be observed with an instrument such as an electron microscope (transmission electron microscope (TEM), scanning electron microscope (SEM)) or an optical microscope. These devices are common, and examples thereof include a transmission electron microscope H-7650 manufactured by Hitachi, Ltd.

Further, those skilled in the art can easily determine the distinction between the (A) polyoxymethylene resin and the (B) modifier. Specifically, in the case of a transmission electron microscope, the difference in screen color due to the difference in electron beam permeability due to the molecular structure, the difference due to dyeing agents such as osmic acid and ruthenium tetroxide, and the crystalline polymer. It can be judged by the difference in lamella structure caused by.

In the present embodiment, the modifier (B) can be isolated and purified from the polyoxymethylene resin composition by a separation operation such as reprecipitation or dissolution, and the composition ratio, structure, molecular weight, etc. are calculated. It is possible. Further, for example, ^{by performing various measurements such as 1} H-NMR, ¹³ C-NMR, two-dimensional NMR, MALDI-TOF MS, and GPC, molecular structures such as repeating structure and branched structure, and position information of various functional groups can be obtained. Etc. can be decided.

-(B-1) Thermoplastic polyurethane-
The thermoplastic polyurethane is a polymer compound having a urethane bond in the main chain and is an elastomer that can be treated thermoplasticly. Examples of the structure of the polymer include a multi-block copolymer composed of a rigid urethane segment (hard segment) and a flexible diol segment (soft segment).

Rigid urethane segments are obtained, for example, by reacting polyfunctional isocyanates with what is known as a chain extender. As the polyfunctional isocyanates, aromatic diisocyanates, alicyclic diisocyanates, aliphatic diisocyanates and the like can be used.

Examples of the aromatic diisocyanate include 4,4'-diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI) (for example, isomers 2,4-toluene diisocyanate and 2,6-toluene diisocyanate and mixtures thereof). , M-xylylene diisocyanate, p-xylylene diisocyanate, 1,5-naphthylene diisocyanate (NDI), 3,3'-dimethyl-4,4'-diphenylene diisocyanate (TODI), 2,2-diphenylpropane- Examples thereof include 4,4''-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate and the like.

Examples of the alicyclic diisocyanate include 4,4'-dicyclohexylmethane diisocyanate (H ₁₂ MDI), isophorone diisocyanate (IPDI), cyclopentylene-1,3-diisocyanate and the like.

Examples of the aliphatic diisocyanate include 1,6-hexamethylene diisocyanate (HMDI) and 1,4-butylenediocyanate.

Examples of the chain extender (sometimes referred to as a cross-linking agent) include short-chain aliphatic, alicyclic or aromatic diols having a molecular weight (molar mass) of less than 500 g / mol, preferably less than 300 g / mol. , Diamines, and triols.

Examples of diols include ethylene glycol, propylene 1,3-glycol, propylene 1,2-glycol, 1,4-butanediol, 1,3-butanediol, 1,5-pentanediol, and 1,6-hexane. Glycol, 1,4-cyclohexanediol 2,2-dimethyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2butyl-1,3-propanediol, 2- Methyl-2,4-pentanediol, 2,2,4-trimethyl-1,3-pentanediol, dihydroxy-cyclopentane, 1,4-cyclohexanedimethylol, thiodiglycol, diethylene glycol, dipropylene glycol, 2-methyl Examples thereof include -1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, hydroquinone dihydroxyethyl ether, and hydride bisphenol A. Examples of diamines include ethylenediamine, hexamethylenediamine, xylylenediamine, 4,4'-diaminodiphenylmethane and the like. Examples of triols include trimethylolpropane and glycerin.

Examples of the flexible diol segment include polyether diols, polyester diols, polyether ester diols, and polycarbonate diols having a number average molar mass of 500 to 5000 g / mol, preferably 1000 to 3000 g / mol. Be done.

Examples of the polyether diols include poly (tetramethylene ether) glycol (PTMEG), poly (propylene oxide) glycol, polybutadiene diol and copolymers thereof (for example, copolymers of propylene oxide and ethylene oxide, tetrahydrofuran and ethylene oxide). Copolymer) and the like. Further, these can be obtained by, for example, ring-opening polymerization of ethylene oxide, propylene oxide or tetrahydrofuran.

The polyester diols include the above-mentioned polyether diols or dialcohols (for example, ethylene glycol, propylene 1,3-glycol, propylene 1,2-glycol, 1,4-butane diol, 1,3-butane diol, 2). -Methylpropanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, nonanediol, 1,10-decanediol, etc.) Obtained by esterification reaction with dicarboxylic acids (eg, glutaric acid, adipic acid, pimeric acid, suberic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, etc.) or by the corresponding ester exchange reaction. be able to. Further, these polyester diols can also be obtained by ring-opening polymerization of lactones (for example, caprolactone, propiolactone, valerolactone and the like).

Polycarbonate diols include the above-mentioned polyether diols or dialcohols (for example, ethylene glycol, propylene 1,3-glycol, propylene 1,2-glycol, 1,4-butanediol, 1,3-butanediol, 2). -Methylpropanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, neopentyl glycol, nonanediol, 1,10-decanediol, etc.) It can be obtained by reacting with diphenyl carbonates or phosgens.

(B-1) Examples of the thermoplastic polyurethane include ester-based polyurethane (sometimes referred to as "polyurethane-based polyurethane"), ether-based polyurethane (sometimes referred to as "polyether-based polyurethane"), and the like. Examples include ether ester polyurethane (sometimes referred to as "polyether ester polyurethane") and caprolactone polyurethane (sometimes referred to as "polycaprolactone polyurethane"). Further, the (b-1) thermoplastic polyurethane is preferably an ester-based polyurethane or an ether ester-based polyurethane, and more preferably an ester-based polyurethane, from the viewpoint of more sufficiently exhibiting impact resistance. Further, the ester-based polyurethane preferably contains two types of polyol components (also referred to as "polyol units") from the viewpoint of more sufficiently exhibiting impact resistance.

(B-1) The hardness of the thermoplastic polyurethane falls within the range of about Shore A65 to about Shore D75. This hardness is determined by the ratio of rigid urethane segments to flexible diol segments.

(B-1) The melt index of the thermoplastic polyurethane is measured at various temperatures and depends on the melting behavior of the rigid urethane segment. This is also a measurement of the degree of addition (molar mass of the entire chain).

Further, by setting the component ratio range as follows, the thermoplastic polyurethane (b-1) has an appropriate melt viscosity during processing of the composition, and improvement in impact resistance can be expected.

The ether-based polyurethane has a ratio (mol ratio) of an ether diol component (also referred to as an "ether diol unit") when the isocyanate component (also referred to as an "isocyanate unit") is 1. , 100 or less, more preferably 50 or less, further preferably 20 or less, preferably 8 or more, more preferably 10 or more, and 13 or more. Is even more preferable.

On the other hand, the ester-based polyurethane, the ether ester-based polyurethane, and the carbonate-based polyurethane have an ester component (also referred to as an "ester unit") when the isocyanate component is 1 (also referred to as a carbonate component (also referred to as a "carbonate unit"). The ratio (mol ratio) of)) is preferably 10 or less, more preferably 8 or less, further preferably 5 or less, and preferably 1 or more. It is more preferably 2 or more, further preferably 3 or more, and even more preferably 4 or more. When the ratio of the ester component is not more than the above upper limit, good shock absorption tends to be exhibited, and when it is not more than the above lower limit, better fluidity can be ensured.
The above ester component refers to a component produced by the reaction of the carboxylic acid component and the isocyanate component.

Further, in the ester-based polyurethane, the ether ester-based polyurethane, and the carbonate-based polyurethane, the ratio (mol ratio) of the polyol component when the isocyanate component is 1 is preferably 10 or less, and more preferably 8 or less. , 6 or less, more preferably 1 or more, more preferably 2 or more, still more preferably 3 or more, and even more preferably 5 or more. When the ratio of the polyol component is not more than the above upper limit, a good sea-island structure tends to be exhibited, and when it is not more than the above lower limit, a better viscosity can be secured.

The dispersed particle size of the (b-1) thermoplastic polyurethane in the polyoxymethylene resin composition and the molded product composed of the resin composition is preferably 10 to 2000 nm in terms of the equivalent circle diameter. (B-1) When the dispersed particle size of the thermoplastic polyurethane is 10 nm or more, good dispersibility can be obtained and impact resistance can be effectively exhibited. Further, when the dispersed particle size of the (b-1) thermoplastic polyurethane is 2000 nm or less, the impact resistance can be more sufficiently exhibited. From the same viewpoint, the dispersed particle size of the (b-1) thermoplastic polyurethane in the polyoxymethylene resin composition and the molded product composed of the resin composition is more preferably 1500 nm or less in terms of the equivalent circle diameter. It is more preferably 1000 nm or less, further preferably 800 nm or less, further preferably 30 nm or more, further preferably 40 nm or more, still more preferably 50 nm or more.

In the present specification, the equivalent circle diameter refers to the diameter of a circle having the same area as the value of the product of the minor axis and the diameter of the projected target substance. Further, the dispersed particle size of the target substance ((b-1) thermoplastic polyurethane, (b-2) graft rubber copolymer, etc.) in the molded product can be determined as follows. That is, the plane perpendicular to the resin flow direction of the molded body is observed with a transmission electron microscope or the like, and the minor axis and the diameter of what is recognized as the dispersion domain of the target substance are measured. Next, the value of the product of the minor axis and the diameter is calculated, and the diameter of a circle having the same area as the value is obtained. Then, the diameters of the circles can be obtained for any 10 or more target substances, and the averaged diameter can be used as the dispersed particle size.

-(B-2) Graft rubber copolymer-
The graft rubber copolymer is a core-shell rubber, and is a polymer composed of a core layer and one or more shell layers covering the core layer. Here, the number of layers of the shell layer is not particularly limited, and may be two or more layers.

(B-2) The component constituting the core layer of the graft rubber copolymer is preferably one having rubber elasticity in order to improve impact resistance. For example, an acrylic polymer, a silicone polymer, or a silicone / acrylic polymer. Examples thereof include polymers, styrene-based polymers, nitrile-based polymers, conjugated diene-based polymers, urethane-based polymers, and olefin-based polymers. The components constituting the core layer of the (b-2) graft rubber copolymer are an acrylic polymer, a silicone polymer, a silicone / acrylic polymer, a conjugated diene polymer, and a urethane polymer. Is preferable. Among them, the components constituting the core layer of the (b-2) graft rubber copolymer are preferably a silicone-based polymer, an acrylic-based polymer, or a silicone / acrylic-based polymer from the viewpoint of impact resistance and heat-resistant aging property. ..

Further, as a component constituting the core layer, a rubber component obtained by polymerizing a siloxane compound such as dimethylsiloxane and phenylmethylsiloxane; an acrylic compound such as ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate; or a rubber component thereof. A copolymerization component of the above components is preferably used.

(B-2) The components constituting the outermost shell layer of the graft rubber copolymer include unsaturated carboxylic acid ester-based units, glycidyl group-containing vinyl-based units, aliphatic vinyl-based units, and aromatic vinyl-based units. Examples thereof include polymers containing vinyl cyanide-based units, maleimide-based units, unsaturated dicarboxylic acid anhydride-based units, and other vinyl-based units. Among them, a polymer containing a (meth) acrylic acid ester-based unit is preferable from the viewpoint of impact resistance and heat aging resistance.

(B-2) From the viewpoint of thermal stability and rigidity during aging, the graft rubber copolymer preferably has an amount of Si element of 1 to 25% by mass in ICP-MS analysis. The amount of the Si element is not particularly limited, but is more preferably 20% by mass or less, further preferably 15% by mass or less, and further preferably 10% by mass or less. , 1.5% by mass or more, more preferably 2% by mass or more, and even more preferably 2.5% by mass or more.

(B-2) The method for producing the graft rubber copolymer is not particularly limited, and a known polymerization method, for example, a mixture containing a monomer and a polyfunctional vinyl monomer in a specific ratio is subjected to suspension polymerization. It can be obtained by a method of polymerizing by emulsion polymerization or the like.

The particle size of the (b-2) graft rubber copolymer is preferably 20 to 2000 nm. (B-2) If the particle size of the graft rubber copolymer is 20 nm or more, the dispersibility during melt-kneading can be improved, and if it is 2000 nm or less, the resin composition can be handled during production. It can be easier. From the same viewpoint, the particle size of the (b-2) graft rubber copolymer is more preferably 30 nm or more, further preferably 40 nm or more, further preferably 50 nm or more, and 1500 nm. It is more preferably less than or equal to, more preferably 1000 nm or less, and even more preferably 800 nm or less.

The dispersed particle size of the (b-2) graft rubber copolymer in the molded product is preferably 20 to 2000 nm in terms of equivalent circle diameter. (B-2) When the dispersed particle size of the graft rubber copolymer is 20 nm or more, good dispersibility can be obtained and impact resistance can be effectively exhibited. Further, when the dispersed particle size of the (b-2) graft rubber copolymer is 2000 nm or less, the impact resistance can be more sufficiently exhibited. From the same viewpoint, the dispersed particle size of the (b-2) graft rubber copolymer in the molded product is more preferably 1500 nm or less, further preferably 1000 nm or less, and 800 nm or less in terms of equivalent circle diameter. It is more preferably 30 nm or more, further preferably 40 nm or more, and even more preferably 50 nm or more.

The mass ratio of the core layer and the shell layer of the graft rubber copolymer (b-2) is not particularly limited.
(B-2) The mass ratio of the core layer when the entire graft rubber copolymer is 100 parts by mass is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and 30 parts by mass. The above is more preferable. By setting the mass ratio of the core layer to the above lower limit or more, the entanglement of the chains between the (b-2) graft rubber copolymers is reduced, and the dispersibility can be further improved.

Further, the mass ratio of the core layer when the entire graft rubber copolymer (b-2) is 100 parts by mass is preferably 95 parts by mass or less, more preferably 90 parts by weight or less, and 85 parts by mass. It is more preferably parts by mass or less. By setting the mass ratio of the core layer to the above upper limit or less, the impact resistance can be further improved.

(B-2) The graft rubber copolymer preferably has a sulfate ion concentration of 0.1 to 5 ppm. (B-2) When the concentration of sulfate ion in the graft rubber copolymer is 0.1 ppm or more, it is preferable because microvoids can be intentionally formed during melt-kneading, and when it is 5 ppm or less, it is preferable. The thermal stability can be further improved. From the same viewpoint, the concentration of sulfate ion in the (b-2) graft rubber copolymer is more preferably 4 ppm or less, further preferably 3 ppm or less, and further preferably 2.5 ppm or less. .. Further, the concentration of sulfate ion in the (b-2) graft rubber copolymer is more preferably 0.2 ppm or more, further preferably 0.3 ppm or more, and further preferably 0.4 ppm or more. preferable.

(B-2) The graft rubber copolymer preferably has a calcium ion concentration of 10 to 500 ppm. (B-2) When the concentration of calcium ions in the graft rubber copolymer is 10 ppm or more, it is preferable because microvoids can be intentionally formed during melt-kneading, and when it is 500 ppm or less, it is thermally stable. The sex can be further improved. From the same viewpoint, the concentration of calcium ions in the (b-2) graft rubber copolymer is more preferably 400 ppm or less, further preferably 350 ppm or less, further preferably 300 ppm or less, and further. , 15 ppm or more, more preferably 20 ppm or more, and even more preferably 30 ppm or more.

(B-2) Commercially available graft rubber copolymers include, for example, "Metabrene (registered trademark)" (manufactured by Mitsubishi Rayon), "Kaneace (registered trademark)" (manufactured by Kaneka), and "Staffyloid (registered)". "Trademark" (manufactured by Aika Kogyo Co., Ltd.), or "Parapet (registered trademark) SA" (manufactured by Kuraray), "PARALOID (registered trademark)" (manufactured by DOWN), "Clearstrength (registered trademark)" (manufactured by ARKEMA) , "Durastrength (registered trademark)" (manufactured by ARKEMA), etc., and these may be used alone or in combination of two or more.

Among these, as a commercially available product of the (b-2) graft rubber copolymer, Metabrene, more specifically, S2001, S2006, S2030, S2100, S2200, S2501, SX-006, SRK-200, SX- 005 and MR-01 can be used more preferably.

<(C) Colorant>
The polyoxymethylene resin composition of the present embodiment may contain (C) a colorant as an additional component (optional component). Here, the (C) colorant refers to a substance that changes its appearance by the action of absorption, scattering, reflection, etc. of visible light.

The (C) colorant that can be present in the molded product of the polyoxymethylene resin composition in the present embodiment is important to further improve the wear resistance by combining with the component (B) in addition to the original purpose of coloring. Can have a role. Then, from the viewpoint of obtaining excellent wear resistance, the colorant (C) can be contained in the polyoxymethylene resin composition of the present embodiment in an amount within the range described later.

The reason why the wear resistance is improved by the presence of the (C) colorant is not clear, but it is considered that the (C) colorant improves the surface hardness of the molded product.

Examples of the (C) colorant include, but are not limited to, inorganic pigments and organic dyes.

Examples of the inorganic pigment include inorganic pigments generally used for coloring resins, for example, oxides of at least one metal selected from the group consisting of iron, zinc and titanium, iron and zinc. Carbonate of at least one metal selected from the group consisting of and titanium, zinc sulfide, titanium oxide, zinc oxide, iron oxide, barium sulfate, titanium dioxide, barium sulfate, chromium hydroxide-containing, chromium oxide, cobalt aluminate, barite Powder, 1 type of zinc yellow, 2 types of zinc yellow, ferrocyanide potassium iron, kaolin, titanium yellow, cobalt blue, ultramarine blue, cadmium, nickel titanium, lithopon, strontium, amber, shenna, azurite, malakite, azuromalakite, Opiment, Realger, Tatsusago, Turkish Stone, Ryomanganese, Yellow Oxide, Tailbelt, Rosenna, Low Amber, Cassel Earth, Cretaceous, Gypsum, Burnt Senna, Burnt Amber, Lapis Lazuri, Azrite, Malakite, Coral Powder, White Mica, Cobalt Blue, Cerulean Blue, Cobalt Violet, Cobalt Green, Zinc White, Titanium White, Light Red, Chrome Oxide Green, Mars Black, Villijan, Yellow Oaker, Alumina White, Cadmium Yellow, Cadmium Red, Vermilion, Tarku, White Carbon, Clay , Mineral Violet, Rose Cobalt Violet, Silver White, Gold Powder, Bronze Powder, Aluminum Powder, Prussian Blue, Aureolin, Tarku, Wallastnite, Mica Titanium, Carbon Black, Acetylene Black, Lamp Black, Furnas Black, Vegetable Black, Examples include bone charcoal, calcium carbonate, and dark blue.
The above-mentioned "metal oxide" also includes a "composite metal oxide" composed of two or more kinds of metals selected from iron, zinc or titanium.

In particular, as the (C) colorant, an oxide of at least one metal selected from the group consisting of iron, zinc and titanium, and a carbonate of at least one metal selected from the group consisting of iron, zinc and titanium. Zinc sulfide, zinc oxide, iron oxide, zinc yellow 1 type, zinc yellow 2 types, zinc white, titanium white, alumina white, talc, white carbon, silver white, carbon black, acetylene black, lamp black, funus black, calcium carbonate However, it is mentioned as preferable.

Among these, as the colorant (C), a colorant having a Mohs hardness of 8 or less is preferable from the viewpoint of abrasion resistance of the polyoxymethylene resin composition of the present embodiment. Further, the colorant (C) preferably has a Mohs hardness of 7 or less, and more preferably 6 or less.
The Mohs hardness of the colorant (C) can be measured with a Mohs hardness meter.

Organic dyes are not limited to the following, but are not limited to, for example, condensed azo, quinone, phthalocyanine, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennon, and quinacridone. Examples thereof include organic dyes such as thioindic, berylene, dioxazine, and phthalocyanine.

In particular, the organic dyes include condensed azo, quinone, phthalocyanine, anthraquinone, heterocyclic, pennon, and quinacridone from the viewpoint of thermal stability of the polyoxymethylene resin composition of the present embodiment. , Thioindico-based, berylene-based, dioxazine-based, or phthalocyanine-based organic dyes and pigments are preferable. More preferably, it is a condensed azo-based, quinone-based, phthalocyanine-based, anthracinone-based, heterocyclic, pennon-based, quinacridone-based, verylene-based, or phthalocyanine-based organic dyeing pigment. More preferably, it is a quinone-based, phthalocyanine-based, anthraquinone-based, heterocyclic, quinacridone-based, verylene-based, or phthalocyanine-based organic dyeing pigment.

The polyoxymethylene resin composition of the present embodiment preferably contains (C) a colorant in an amount of 0.01 to 3 parts by mass with respect to 100 parts by mass of the (A) polyoxymethylene resin. By setting the content of the component (C) to 0.01 parts by mass or more with respect to 100 parts by mass of the component (A), sufficient coloring property can be provided to the polyoxymethylene resin composition, and 3 parts by mass. By setting the content to less than or equal to the mass, the effect of improving the wear characteristics of the polyoxymethylene resin composition when sliding under a small load can be sufficiently obtained.
From the same viewpoint, the content of the (C) colorant with respect to 100 parts by mass of the (A) polyoxymethylene resin in the polyoxymethylene resin composition of the present embodiment is more preferably 2.5 parts by mass or less. It is more preferably 2.0 parts by mass or less, further preferably 1.5 parts by mass or less, particularly preferably 1.0 part by mass or less, and most preferably 0.8 parts by mass or less. It is preferable, more preferably 0.05 part by mass or more, and further preferably 0.1 part by mass or more.

<Other additives>
The polyoxymethylene resin composition of the present embodiment has various stabilizers used in the polyoxymethylene resin composition, which are conventionally known as additional components (optional components), as long as the object of the present invention is not impaired. Additives can be contained.

Stabilizers include, but are not limited to, antioxidants, scavengers such as formaldehyde and formic acid, and the like.
These may be used individually by 1 type, and may be used in combination of 2 or more type.

As the antioxidant, a hindered phenolic antioxidant is preferable from the viewpoint of improving the thermal stability of the polyoxymethylene resin composition of the present embodiment. The hindered phenolic antioxidant is not particularly limited, and known ones can be appropriately used.
The trapping agent for formaldehyde, formic acid and the like is not limited to the following, and for example, compounds containing formaldehyde-reactive nitrogen such as melamine and polyamide resins and their polymers, alkali metals or alkali earth metal hydroxides. , Inorganic acid salts, and carboxylates. Specific examples include calcium hydroxide, calcium carbonate, calcium phosphate, calcium silicate, calcium borate, and calcium fatty acid salts (calcium stearate, calcium myristate, etc.). The fatty acid in the above fatty acid calcium salt may be substituted with a hydroxyl group.

The content of the antioxidant, for example, a hindered phenolic antioxidant with respect to 100 parts by mass of the polyoxymethylene resin (A) is preferably 0.1 to 2 parts by mass.
Further, the content of the scavenger, for example, the polymer containing formaldehyde-reactive nitrogen with respect to 100 parts by mass of the polyoxymethylene resin (A) is preferably 0.1 to 3 parts by mass.
The content of the supplement, for example, the fatty acid salt of an alkaline earth metal with respect to 100 parts by mass of the (A) polyoxymethylene resin is preferably 0.1 to 1 part by mass.

(Various properties of polyoxymethylene resin composition)
The polyoxymethylene resin composition of the present embodiment preferably has a sulfate ion concentration of 0.01 to 2.0 ppm. When the concentration of sulfate ion in the polyoxymethylene resin composition is 0.01 ppm or more, it is preferable because microvoids can be intentionally formed during melt-kneading, and when it is 2.0 ppm or less, it is thermally stable. The sex can be further improved. From the same viewpoint, the concentration of sulfate ion in the polyoxymethylene resin composition is more preferably 1.0 ppm or less, further preferably 0.8 ppm or less, and further preferably 0.7 ppm or less. , 0.6 ppm or less, more preferably 0.02 ppm or more, further preferably 0.03 ppm or more, and even more preferably 0.04 ppm or more.

The polyoxymethylene resin composition of the present embodiment preferably has a calcium ion concentration of 2 to 100 ppm. When the concentration of calcium ions in the polyoxymethylene resin composition is 2 ppm or more, it is preferable because microvoids can be intentionally formed during melt-kneading, and when it is 100 ppm or less, the thermal stability is further improved. Can be made to. From a similar point of view. The concentration of calcium ions in the polyoxymethylene resin composition is more preferably 90 ppm or less, further preferably 80 ppm or less, further preferably 70 ppm or less, and even more preferably 3 ppm or more. It is more preferably 4 ppm or more, and even more preferably 5 ppm or more.

(Manufacturing method of polyoxymethylene resin composition)
In the polyoxymethylene resin composition of the present embodiment, for example, a predetermined amount of (A) polyoxymethylene resin and (B) modifier, and if necessary, (C) colorant and other additives are melted. It can be obtained by kneading.

Examples of the device for obtaining the composition of the polyoxymethylene resin molded product of the present embodiment include known devices such as a uniaxial or multiaxial extruder, a roll, and a Banbury mixer, among which a decompression device and a side feeder are used. A twin-screw extruder equipped with equipment or the like is particularly preferable.

The method of mixing and melt-kneading the raw material components is not particularly limited, and a method well known to those skilled in the art can be used. For example, a method in which the components (A) and (B) are all mixed in advance with a super mixer, tumbler, V-shaped blender, etc. and collectively melt-kneaded with a twin-screw extruder, and the component (A) is mixed with a twin-screw extruder. A method in which the component (B) is added from the middle of the device while being melt-kneaded, and a part of the component (A) is supplied to a device such as a twin-screw extruder, and the device is melt-kneaded. A method of adding the remaining part of the component (A) and the component (B) from the middle of the above, and the like can be mentioned.

When the polyoxymethylene resin composition of the present embodiment is produced by an apparatus such as the extruder, it is obtained in a pellet shape and can be used for molding or the like. That is, a molded product can be obtained from the polyoxymethylene resin composition of the present embodiment.

(Use of polyoxymethylene resin composition and molded product)
The polyoxymethylene resin composition of the present embodiment and a molded product made of the polyoxymethylene resin composition can be suitably used for applications requiring impact resistance. Specifically, but not limited to the following, for example, gears such as cams, sliders, levers, arms, clutches, felt clutches, idler gears, pulleys, rollers, rollers, key stems, key tops, shutters, reels, etc. Mechanical parts such as shafts, joints, shafts, bearings, and guides; for outsert-molded resin parts, insert-molded resin parts, chassis, trays, side plates, printers, and office automation equipment such as copiers. Parts; Parts for digital video cameras and video equipment such as digital cameras; CDs, DVDs, Blu-ray (registered trademark) Discs, and other optical disk drives; Music, video or information represented by navigation systems and mobile personal computers. Parts for communication equipment typified by devices, mobile phones and facsimiles; parts for electrical equipment; parts for electronic equipment and the like can be mentioned.

Further, the polyoxymethylene resin composition of the present embodiment and the molded body made of the resin composition are automobile parts such as fuel peripheral parts represented by a gasoline tank, a fuel pump module, valves, a gasoline tank flange and the like. Door locks, door handles, window regulators, speaker grills and other door parts; seatbelt slip rings, press buttons and other seatbelt peripheral parts; combination switch parts, switches, clips, etc. Applicable to parts.

Further, the polyoxymethylene resin composition of the present embodiment and a molded product made of the resin composition can be used as other products or parts, for example, a pen tip of a writing tool, a mechanical part for inserting and removing a core; a washbasin, a drain port, and the like. And drain plug opening / closing mechanism parts; cord stoppers, adjusters, buttons for clothing; nozzles for sprinkling, sprinkling hose connection joints; stair railings, and building supplies that support flooring materials; toys, fasteners, chains, conveyors, It can also be suitably used as a buckle, sporting goods, vending machines (opening / closing lock mechanism, product discharge mechanism parts), furniture, musical instruments, and housing equipment parts.

The polyoxymethylene resin composition of the present embodiment and a molded product made of the resin composition can be applied to various uses in which polyoxymethylene has been preferably used so far, and can be used for high industrial use. It has the potential.

Hereinafter, the present invention will be described in detail with reference to Examples, but the present invention is not limited to these Examples.

<Preparation or preparation of raw material ingredients>
The (A) polyoxymethylene resin was prepared as shown below, and the following was used as the (b-1) thermoplastic polyurethane and (b-2) graft rubber copolymer.

(1) Polyoxymethylene resin (A-1)
Biaxial self-cleaning type polymerization machine with a jacket that allows heat medium to pass through (L / D = 8 (L: distance from the raw material supply port to the discharge port of the polymerization machine (m), D: inner diameter of the polymerization machine ( m).) Was adjusted to 80 ° C., in this polymerization machine, trioxane was added to 4 kg / hour, 1,3-dioxolane as a comonomer was added to 200 g / hour, and methylal as a chain transfer agent was added to 1 mol of trioxane. .8 × 10 ^-3 mol was added continuously.

Further, boron trifluoride di-n-butyl etherate as a polymerization catalyst was ^{continuously added to the polymerization machine in an amount of 1.5 × 10 -5} mol with respect to 1 mol of trioxane to carry out the polymerization. The polyoxymethylene copolymer discharged from the polymerization machine was put into a 0.1% aqueous solution of triethylamine to deactivate the polymerization catalyst.

After filtering the inactivated polyoxymethylene copolymer with a centrifuge, 1 part by mass of an aqueous solution containing a quaternary ammonium compound was added to 100 parts by mass of the polyoxymethylene copolymer and mixed uniformly. It is supplied to a twin-screw extruder with a vent, and 0.5 parts by mass of water is added to 100 parts by mass of the molten polyoxymethylene copolymer in the extruder, and the set temperature of the extruder is 200 ° C. The unstable end portion of the polyoxymethylene copolymer was decomposed and removed with a residence time of 7 minutes. At this time, the amount of the quaternary ammonium compound added was 20 mass ppm in terms of the amount of nitrogen.

Triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant in a polyoxymethylene copolymer with an unstable end decomposed 0.3 A part by mass was added, and the mixture was extruded as a strand from the die part of the extruder while being devolatile under the condition of a vacuum degree of 20 Torr with a vented extruder to be pelletized.

The polyoxymethylene copolymer thus obtained was designated as a polyoxymethylene resin (A-1). The melt flow rate of the polyoxymethylene resin (A-1) was 9 g / 10 minutes (ISO-1133 condition D).

Also relates to the melt viscosity of the polyoxymethylene resin (A-1), the viscosity at a 190 ° C. of shear rate 100 sec ^-1, a 550 Pa · s, the viscosity at a 190 ° C. of shear rate of 1,000 sec ^-1, It was 250 Pa · s.

(2) Polyoxymethylene resin (A-2)
Biaxial self-cleaning type polymerization machine with a jacket that allows heat medium to pass through (L / D = 8 (L: distance from the raw material supply port to the discharge port of the polymerization machine (m), D: inner diameter of the polymerization machine ( m).) Was adjusted to 80 ° C., in this polymerization machine, trioxane was added to 4 kg / hour, 1,3-dioxolane as a comonomer was added to 200 g / hour, and methylal as a chain transfer agent was added to 1 mol of trioxane. . Addition was made continuously in an amount of 10 × 10 ^{-3 mol.}

Further, boron trifluoride di-n-butyl etherate as a polymerization catalyst was ^{continuously added to the polymerization machine in an amount of 1.5 × 10 -5} mol with respect to 1 mol of trioxane to carry out the polymerization. The polyoxymethylene copolymer discharged from the polymerization machine was put into a 0.1% aqueous solution of triethylamine to deactivate the polymerization catalyst.

After filtering the inactivated polyoxymethylene copolymer with a centrifuge, 1 part by mass of an aqueous solution containing a quaternary ammonium compound was added to 100 parts by mass of the polyoxymethylene copolymer and mixed uniformly. It is supplied to a twin-screw extruder with a vent, and 0.5 parts by mass of water is added to 100 parts by mass of the molten polyoxymethylene copolymer in the extruder, and the set temperature of the extruder is 200 ° C. The unstable end portion of the polyoxymethylene copolymer was decomposed and removed with a residence time of 7 minutes. At this time, the amount of the quaternary ammonium compound added was 20 mass ppm in terms of the amount of nitrogen.

Triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant in a polyoxymethylene copolymer with an unstable end decomposed 0.3 A part by mass was added, and the mixture was extruded as a strand from the die part of the extruder while being devolatile under the condition of a vacuum degree of 20 Torr with a vented extruder to be pelletized.

The polyoxymethylene copolymer thus obtained was designated as a polyoxymethylene resin (A-2). The melt flow rate of the polyoxymethylene resin (A-2) was 3 g / 10 minutes (ISO-1133 condition D).

Also relates to the melt viscosity of the polyoxymethylene resin (A-2), the viscosity at a 190 ° C. of shear rate 100 sec ^-1, a 900 Pa · s, the viscosity at a 190 ° C. of shear rate of 1,000 sec ^-1, It was 350 Pa · s.

(3) Polyoxymethylene resin (A-3)
Biaxial self-cleaning type polymerization machine with a jacket that allows heat medium to pass through (L / D = 8 (L: distance from the raw material supply port to the discharge port of the polymerization machine (m), D: inner diameter of the polymerization machine ( m).) Was adjusted to 80 ° C., in this polymerization machine, trioxane was added to 4 kg / hour, 1,3-dioxolane as a comonomer was added to 200 g / hour, and methylal as a chain transfer agent was added to 1 mol of trioxane. .0 × 10 ^-3 mol was added continuously.

Further, boron trifluoride di-n-butyl etherate as a polymerization catalyst was ^{continuously added to the polymerization machine in an amount of 1.5 × 10 -5} mol with respect to 1 mol of trioxane to carry out the polymerization. The polyoxymethylene copolymer discharged from the polymerization machine was put into a 0.1% aqueous solution of triethylamine to deactivate the polymerization catalyst.

After filtering the inactivated polyoxymethylene copolymer with a centrifuge, 1 part by mass of an aqueous solution containing a quaternary ammonium compound was added to 100 parts by mass of the polyoxymethylene copolymer and mixed uniformly. It is supplied to a twin-screw extruder with a vent, and 0.5 parts by mass of water is added to 100 parts by mass of the molten polyoxymethylene copolymer in the extruder, and the set temperature of the extruder is 200 ° C. The unstable end portion of the polyoxymethylene copolymer was decomposed and removed with a residence time of 7 minutes. At this time, the amount of the quaternary ammonium compound added was 20 mass ppm in terms of the amount of nitrogen.

Triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant in a polyoxymethylene copolymer with an unstable end decomposed 0.3 A part by mass was added, and the mixture was extruded as a strand from the die part of the extruder while being devolatile under the condition of a vacuum degree of 20 Torr in an extruder with a vent to be pelletized.

The polyoxymethylene copolymer thus obtained was designated as a polyoxymethylene resin (A-3). The melt flow rate of the polyoxymethylene resin (A-3) was 45 g / 10 minutes (ISO-1133 condition D).

Also relates to the melt viscosity of the polyoxymethylene resin (A-3), the viscosity at a 190 ° C. of shear rate 100 sec ^-1, a 350 Pa · s, the viscosity at a 190 ° C. of shear rate of 1,000 sec ^-1, It was 100 Pa · s.

(4) Thermoplastic polyurethane (b-1-1)
A commercially available ester-based polyurethane (ESTANE: registered trademark) composed of a repeating hard segment and a soft segment was used. The mol ratio of each composition is diphenylmethane diisocyanate (isocyanate component): adipate (ester component): tetramethylene glycol (polyol component): ethylene glycol (polyol component) = 1: 4.5: 3.3: 2.2. there were.

(5) Thermoplastic polyurethane (b-1-2)
A commercially available ether-based polyurethane (RESAMINE: registered trademark) composed of a repeating hard segment and a soft segment was used. The mol ratio of each composition was diphenylmethane diisocyanate: tetramethylene glycol = 1: 8.8.

(6) Thermoplastic polyurethane (b-1-3)
A commercially available caprolactone-based polyurethane (Milactran: registered trademark) composed of a repeating hard segment and a soft segment was used. The mol ratio of each composition was diphenylmethane diisocyanate: tetramethylene glycol: polycaprolactone polyol = 1: 1: 3.
These can be adjusted by the methods described in WO2011125540 and the like.

(7) Graft rubber copolymer (b-2-1)
A commercially available Metabrene S2100 was used. The amount of Si element in this graft rubber copolymer was 2.9% by mass.

(8) Graft rubber copolymer (b-2-2)
Commercially available Metabrene S2006 was used. The amount of Si element in this graft rubber copolymer was 3.5% by mass.

(9) Graft rubber copolymer (b-2-3)
Commercially available Metabrene S2030 was used. The amount of Si element in this graft rubber copolymer was 11.1% by mass.

(10) Graft rubber copolymer (b-2-4)
A commercially available KANE ACE MR-01 was used. The elemental amount of Si in this graft rubber copolymer was 27% by mass.

(11) Graft rubber copolymer (b-2-5)
Commercially available Metabrene C223A was used.

(12) Graft rubber copolymer (b-2-6)
A commercially available Metabrene E875A was used.

(13) Graft rubber copolymer (b-2-7)
A commercially available KANE ACE FM-53 was used.

<Preparation of polyoxymethylene resin composition and preparation of molded product>
The polyoxymethylene resin composition and the molded product were prepared according to the following procedure.

(1) Preparation of Polyoxymethylene Resin Composition Using an extruder (TEM-26SS extruder manufactured by Toshiba Machine Co., Ltd. (L / D = 48, with vent) according to the formulation shown in Tables 1 and 2. , The cylinder temperature was set to 200 ° C., and the pellets corresponding to 90 parts by mass of the component (A) and the component (b-2) were individually supplied from the metering feeder from the main throat portion of the top of the extruder. Further, the pellet corresponding to 10 parts by mass of the component (A) and the component (b-1) were individually supplied from the side portion of the extruder from the quantitative feeder. In some cases, the component (C) and other additives were supplied. Additional components such as, etc. were mixed together with pellets equivalent to 90 parts by mass of component (A) and supplied independently from the main throat part of the top of the extruder. Resin under the conditions of extrusion rate of 15 kg / hour and screw rotation speed of 150 rpm. The kneaded product was extruded into a strand shape, rapidly cooled in a strand bath, and cut with a strand cutter to obtain a pellet-shaped polyoxymethylene resin composition.

(2) Preparation of molded product From the obtained pellet-shaped polyoxymethylene resin composition, an injection molding machine (manufactured by Toshiba Machine Co., Ltd., EC-75NII) was used to set the cylinder temperature to 205 ° C and the mold temperature to 205 ° C. A multipurpose test piece (molded article) compliant with ISO294-1 was obtained by molding at 60 ° C. under injection conditions of an injection time of 35 seconds and a cooling time of 15 seconds.

<Characteristic evaluation>
Using the obtained pellet-shaped polyoxymethylene resin composition or multipurpose test piece, various properties were evaluated according to the following procedure.

(1) Charpy impact strength with notch (23 ° C)
The obtained multipurpose test piece was used for measurement in accordance with ISO179-1. The results are shown in Tables 1 and 2. It was judged that the larger the value, the better the impact resistance.

(2) Tension elastic modulus Using the obtained multipurpose test piece, measurement was carried out in accordance with ISO527. The results are shown in Tables 1 and 2. It was judged that the larger the value, the better the rigidity.

(3) Coefficient of friction Using a ball-on-disk type reciprocating friction and wear tester (AFT-15MS type, manufactured by Toyo Seimitsu Co., Ltd.), the load is 19.6 N and the linear velocity is 30 mm in an environment of 23 ° C. and 50% humidity. A sliding test was carried out on the surface of the obtained multipurpose test piece under the conditions of / sec, a reciprocating distance of 20 mm, and a reciprocating frequency of 10,000 times. As the ball material, a SUS304 ball (a ball having a diameter of 5 mm) was used. The coefficient of friction was measured when the number of round trips reached 10,000. The results are shown in Tables 1 and 2. It was judged that the smaller the value, the better the slidability.

(4) Heat retention limit time From the obtained pellet-shaped polyoxymethylene resin composition, use an injection molding machine (EC-75NII manufactured by Toshiba Machine Co., Ltd.) to set the cylinder temperature to 210 ° C and the mold temperature. A multipurpose test piece (molded article) compliant with ISO294-1 was obtained by molding under injection conditions of an injection time of 35 seconds and a cooling time of 15 seconds at 30 ° C. After 10-shot molding, with the resin plasticized in the cylinder, the molding operation was stopped while the heater heating was continued, and after stopping for a predetermined time, molding was started again, and the silver streaks to the first molded body The occurrence status was confirmed. The occurrence of silver streaks was confirmed at 10 minutes, 20 minutes, 30 minutes, 40 minutes, and 50 minutes when the molding machine was stopped. Then, the time when the silver streaks appeared on the entire surface of the molded product was defined as the heat retention limit time in the cylinder. The results are shown in Tables 1 and 2. It was evaluated that the longer the time limit, the better the stability during heat retention.

(5) Tensile strength retention rate after aging A long-term thermal stability evaluation was carried out using the obtained multipurpose test piece. Specifically, the multipurpose test piece was placed in a gear oven in a 145 ° C. environment and exposed to a high heat environment for 35 days. It was taken out after 35 days, and the tensile strength was measured 24 hours later by a method conforming to ISO527-1. The tensile strength before exposure was compared with the tensile strength after exposure, and the strength retention rate was calculated. The results are shown in Tables 1 and 2. It was judged that the closer this value was to 100, the better.

From Tables 1 and 2, it contains (A) a polyoxymethylene resin, and (B) a modifier containing (b-1) a thermoplastic polyurethane and (b-2) a graft rubber copolymer, and (B). The polyoxymethylene resin composition according to the example, wherein the content of the modifier is 0.5 to 50 parts by mass with respect to 100 parts by mass of the (A) polyoxymethylene resin, has impact resistance, rigidity, and sliding. It can be seen that both the mobility and the stability during heat retention are good.

According to the present invention, it is possible to provide a polyoxymethylene resin composition having excellent impact resistance, rigidity and slidability, and also having excellent stability during heat retention. Further, according to the present invention, it is possible to provide a molded product having excellent impact resistance, rigidity and slidability, and also having excellent stability during heat retention.

Claims (9)

It contains 100 parts by mass of (A) polyoxymethylene resin and 0.5 to 50 parts by mass of (B) modifier.
(B) the modifier is made (b-1) thermoplastic polyurethane and (b-2) graft rubber copolymer,
Wherein (b-2) graft rubber copolymer, have a 2 or more layers, the amount of Si element in the ICP-MS analysis is 1 to 25 wt%,
A polyoxymethylene resin composition. The polyoxymethylene resin composition according to claim 1, wherein the thermoplastic polyurethane (b-1) is an ester polyurethane. The ester-based polyurethane, the ratio of ester component when the one of isocyanate component (mol ratio) is 4-5, and the ratio of the polyol component (mol ratio) is 5-6, according to claim 2 Polyoxymethylene resin composition. The polyoxymethylene resin composition according to claim 2 or 3 , wherein the ester-based polyurethane contains two types of polyol components. Any of claims 1 to 4 , wherein the graft rubber copolymer (b-2) contains a silicone / acrylic polymer and the amount of Si element in ICP-MS analysis is 2 to 10% by mass. The polyoxymethylene resin composition according to item 1. The polyoxymethylene resin composition according to any one of claims 1 to 5 , wherein the concentration of sulfate ions is 0.01 to 0.2 ppm. The polyoxymethylene resin composition according to any one of claims 1 to 6 , wherein the polyoxymethylene resin (A) has a melt flow rate of 0.1 to 60 g / 10 minutes. The polyoxymethylene resin composition according to any one of claims 1 to 7 , which is in the form of pellets. A molded product comprising the polyoxymethylene resin composition according to any one of claims 1 to 8.