JP7123531B2 - Polyoxymethylene resin composition - Google Patents

Description

The present invention relates to polyoxymethylene resin compositions.

Polyoxymethylene resins have an excellent balance of mechanical strength, chemical resistance, slidability and wear resistance, and can be easily processed. Therefore, polyoxymethylene resins are widely used as one of representative engineering plastics for mechanical parts of electrical equipment, automobile parts and other parts.

There is also a market demand for improved impact strength for polyoxymethylene resins in many potential applications. Various techniques for improving the impact strength by blending a specific component in a resin such as polyoxymethylene resin have been disclosed.

As a technique for improving such impact strength, Patent Document 1 discloses a resin-made hollow molded product obtained by blending a core-shell polymer and/or a thermoplastic polyurethane resin 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 comprising a polyoxymethylene resin, a rubber-elastic graft polymer based on poly(meth)acrylic acid ester or silicone rubber, and a polymer. Further, Patent Document 4 discloses a composition containing a polyoxymethylene resin and a thermoplastic polyurethane resin and/or a core-shell polymer impact modifier.

JP-A-7-195496 Japanese Patent No. 3929896 JP-A-6-57097 JP-A-7-126483

However, the technology described in Patent Literature 1 focuses on blow molding. In addition, Patent Document 1 discloses an example of a composition using a thermoplastic polyurethane resin and a core-shell polymer in combination. had room for
In addition, Patent Document 2 does not disclose a polyoxymethylene resin composition, and the composition described in Patent Document 2 is at least in terms of the color tone of a molded product of the polyoxymethylene resin composition. There was room for improvement.
In addition, the composition described in Patent Document 3 has room for improvement in terms of compatibility between impact resistance and rigidity, sliding properties, and the like.
The technique described in Patent Document 4 also has room for improvement in terms of slidability and material rigidity.

As described above, in the above-described conventional techniques, there is room for improvement in impact resistance, rigidity, slidability, and color tone of molded articles regarding polyoxymethylene resins, and further improvement is desired.

Therefore, an object of the present invention is to provide a polyoxymethylene resin composition which is excellent in impact resistance, rigidity, and slidability, and also excellent in color tone of molded articles. Another object of the present invention is to provide a molded article which is excellent in impact resistance, rigidity and slidability, and which is excellent in color tone.

As a result of intensive studies to solve the above problems, the present inventors found that the above problems can be solved by including a modifier consisting of multiple components in a specific ratio in polyoxymethylene resin, and completed the present invention. came to.

That is, the present invention is as follows.
[1]
(A) 100 parts by mass of a polyoxymethylene resin and (B) 0.5 to 50 parts by mass of a modifier,
The (B) modifier comprises (b-1) a thermoplastic polyurethane and (b-2) a graft rubber copolymer,
The (b-2) graft rubber copolymer has a structure of two or more layers,
The ratio of the (b-1) thermoplastic polyurethane to the total of the (b-1) thermoplastic polyurethane and the (b-2) graft rubber copolymer is 1 to 16% by mass.
A polyoxymethylene resin composition characterized by:
[2]
The polyoxymethylene resin composition according to item [1], wherein the (b-1) thermoplastic polyurethane is an ester polyurethane.
[3]
Item [2], wherein the ester-based polyurethane has an ester component ratio (molar ratio) of 4 to 5 and a polyol component ratio (molar ratio) of 5 to 6, when the isocyanate component is 1. The polyoxymethylene resin composition described.
[4]
The polyoxymethylene resin composition according to item [2] or [3], wherein the ester-based polyurethane contains two types of polyol components.
[5]
The polyoxymethylene according to any one of items [1] to [4], wherein the (b-2) graft rubber copolymer has a Si element content of 1 to 25% by mass in ICP-MS analysis. Resin composition.
[6]
Items [1] to [5], wherein the (b-2) graft rubber copolymer contains a silicone/acrylic polymer, and the amount of Si element in ICP-MS analysis is 2 to 10% by mass. Polyoxymethylene resin composition according to any one of.
[7]
The polyoxymethylene resin composition according to any one of items [1] to [6], which has a sulfate ion concentration of 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 article comprising the polyoxymethylene resin composition according to any one of items [1] to [9].

ADVANTAGE OF THE INVENTION According to this invention, the polyoxymethylene resin composition which is excellent in impact resistance, rigidity, and slidability, and is also excellent in the color tone of a molded article can be provided. Moreover, according to the present invention, it is possible to provide a molded article having excellent impact resistance, rigidity and slidability, and excellent color tone.

Hereinafter, the mode for carrying out the present invention (hereinafter referred to as "this embodiment") will be described in detail, but the present invention is not limited to the following description, and within the scope of the gist Various modifications can be made.

(Polyoxymethylene resin composition)
The polyoxymethylene resin composition of the present embodiment contains (A) 100 parts by mass of a polyoxymethylene resin and (B) 0.5 to 50 parts by mass of a modifier, and the (B) modifier is , (b-1) a thermoplastic polyurethane and (b-2) a graft rubber copolymer, wherein the (b-2) graft rubber copolymer has a structure of two or more layers. . In addition, the polyoxymethylene resin composition of the present embodiment may contain (C) a colorant and other additives as optional components.

Furthermore, in the polyoxymethylene resin composition of the present embodiment, the ratio of (b-1) thermoplastic polyurethane to the total of (b-1) thermoplastic polyurethane and (b-2) graft rubber copolymer is 1 to 16. One feature is that it is % by mass. When the above ratio is 1% by mass or more, the stability during heat retention in a molding machine can be improved, and when it is 16% by mass or less, the color tone of the molded product can be improved. can. From the same viewpoint, the ratio is preferably 2% by mass or more, more preferably 4% by mass or more, further preferably 6% by mass or more, and 14% by mass or less. is preferred, 12% by mass or less is more preferred, and 10% by mass or less is even more preferred.
Each component constituting the polyoxymethylene resin composition of the present embodiment will be described in detail below.

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

(A) polyoxymethylene resins 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. Polyoxymethylene homopolymers consisting only of oxymethylene units are mentioned.
Further, specifically, the polyoxymethylene copolymer includes a formaldehyde monomer or a formaldehyde cyclic oligomer such as a trimer (trioxane) or a tetramer (tetraoxane) of formaldehyde, and a cyclic ether or cyclic polymer as a comonomer. A polyoxymethylene copolymer obtained by copolymerizing formal is mentioned. Here, the cyclic ether or cyclic formal includes ethylene oxide; propylene oxide; epichlorohydrin; 1,3-dioxolane; cyclic formal of glycol or diglycol such as 1,4-butanediol formal;

When obtaining a polyoxymethylene copolymer using trioxane, the amount of the comonomer such as 1,3-dioxolane used is generally preferably 0.1 to 60 mol, more preferably 0.1 to 20 mol, per 100 mol of trioxane. More preferably 0.13 to 10 mol. 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, even 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 about 1.3 to 3.5 mol of comonomer per 100 mol of trioxane. The melting point can be measured by DSC.

Further, the polyoxymethylene copolymer includes a branched polyoxymethylene copolymer obtained by copolymerizing a formaldehyde monomer and/or a formaldehyde cyclic oligomer with a monofunctional glycidyl ether, and a formaldehyde monomer. Also included are polyoxymethylene copolymers having a crosslinked structure obtained by copolymerizing a cyclic oligomer of formaldehyde and/or formaldehyde with a polyfunctional glycidyl ether.

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

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

The block copolymer referred to herein is a polyoxymethylene homopolymer or polyoxymethylene copolymer having at least one block moiety represented by any one of the following general formulas (1) to (4) (both collectively hereinafter referred to as " Also referred to as "block copolymer".) is preferred.

In general formulas (1), (2) and (3) above, R ₁ and R ₂ are each 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. When one chemical species is shown and there are a plurality of R ₁ and R ₂ , they may be the same or different.

In general formulas (1), (2), and (4) above, R ₃ , R 5 , and R ₆ are one chemical group selected from the group consisting of alkyl groups, substituted alkyl groups, aryl groups, and substituted aryl groups. indicate species.

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

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

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

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

In the above general formula (4), q and r each represent a positive number, q is 2 to 100 mol%, r is 0 to 98 mol% with respect to the total 100 mol% of q and r, and - The (CH(CH ₂ CH ₃ )CH ₂ )- units and --(CH ₂ CH ₂ CH ₂ CH ₂ )- units are each present randomly or in blocks.

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

Block copolymers having the block portion are, for example, JP-A-57-31918, JP-A-60-170652, JP-A-2002-3696, JP-A-2002-234922, 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 obtained by adding a compound constituting a block having a functional group such as a hydroxyl group at both ends or one end to the terminal portion in the polymerization process of the polyoxymethylene resin. obtained by reacting with

The amount of the block moieties represented by the formulas (1) to (4) inserted in the block copolymer is not particularly limited, but the ratio of the block moieties to 100% by mass of the block copolymer is 0.001. % by mass to 30% by mass. When the above ratio is 0.001% by mass or more, the slidability can be stably maintained, and when it is 30% by mass or less, the polyoxymethylene resin composition of the present embodiment It is possible to suppress a decrease in rigidity of a molded body made of. From the same point of view, the above ratio is more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, and even more preferably 1% by mass or more. % by mass or less is more preferable, and 8% by mass or less is even more preferable.

In addition, the molecular weight of the block portion in the block copolymer is preferably 10000 or less, more preferably 8000 or less, from the viewpoint of not reducing the rigidity of the molded article containing the polyoxymethylene resin composition of the present embodiment. , 5000 or less. On the other hand, although the lower limit of the molecular weight of the block portion in the block copolymer is not particularly limited, it 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, but _{examples include C18H37O ( CH2CH2O} ) _{40C18H37 and C11H23CO2 ( CH2CH2O} ) _. ) 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 having hydroxyl groups at both ends, and hydroxyl groups at both ends Polypropylene glycol, hydrogenated polybutadiene with hydroxyl groups at both ends, hydroxyalkylated polyethylene glycol at both ends, polypropylene glycol with hydroxyalkylated at both ends, hydroxyalkylated hydrogenated polybutadiene at both ends, glycidyl compound (monofunctional, polyfunctional) etc.

Although the polymerization catalyst used for polymerization of the polyoxymethylene copolymer is not particularly limited, cationic active catalysts such as Lewis acids, protonic acids and their esters or anhydrides are preferred. Examples of Lewis acids include, but are not limited to, boric acid, tin, titanium, phosphorus, arsenic and antimony halides, more specifically boron trifluoride, tin tetrachloride, titanium tetrachloride, Phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof. Moreover, the protonic acid and its ester or anhydride are not particularly limited, but examples thereof include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate, and trimethyloxonium hexafluorophosphate. . Among these, as the polymerization catalyst, boron trifluoride, boron trifluoride hydrate, and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable, and more specific. Preferable 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. , JP-A-1495228, JP-A-1720358, JP-A-3018898, JP-A-58-98322 and JP-A-7-70267. In addition, since the polyoxymethylene copolymer obtained by the above method has thermally unstable terminal portions [--(OCH ₂ ) _n -OH group], the unstable terminal portions are decomposed and removed. is preferred.

Specifically, in the decomposing and removing treatment of the unstable terminal, in the presence of at least one quaternary ammonium compound represented by the following formula (5), a temperature above the melting point of the polyoxymethylene copolymer and below 260 ° C. , the polyoxymethylene copolymer is heat-treated in a molten state.

Here, in formula (5), R ^a , R ^b , R ^c and R ^d are each independently a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms; an aryl group 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 hydrogen atom in an aryl group having 6 to 20 carbon atoms represents an alkylaryl group in which a hydrogen atom of 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 substituted alkyl group is a halogen atom, hydroxyl group, aldehyde group, carboxyl group, amino group, or amide group. Further, in the unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group, hydrogen atoms may be substituted with halogen atoms. n' represents an integer of 1-3. X represents a hydroxyl group or an acid residue of a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than hydrogen halide, an oxoacid, an inorganic thioacid or an organic thioacid 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). ^b , R ^c and R ^d are each independently preferably an alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 4 carbon atoms, and further R ^a , R ^b , R ^c and R It is particularly preferred that at least one of ^d is a hydroxyethyl group. Such quaternary ammonium compounds are not particularly limited, but specific examples include tetramethylammonium, tetoethylammonium, 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 hydroxides such as ammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, octadecyltri(2-hydroxyethyl)ammonium, tetrakis(hydroxyethyl)ammonium; Hydrates of ammonium compounds such as hydrochloric acid, hydrobromic acid and hydrofluoric acid; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, nitrous oxoacid salts such as chloric acid, hypochlorous acid, chlorosulfuric acid, amidosulfuric acid, disulfuric acid, tripolyphosphoric acid; thioacid salts such as thiosulfuric acid of the above quaternary ammonium compounds; formic acid of the above quaternary ammonium compounds , acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, caproic acid, caprylic acid, capric acid, benzoic acid, oxalic acid and the like. Among these, hydroxide (OH ⁻ ), sulfuric acid (HSO ⁴⁻ , SO ₄ ²⁻ ), carbonic acid (HCO ³⁻ , CO ³²⁻ ) and boric acid (B(OH)) of the quaternary ammonium compounds ^4- ), and salts of carboxylic acids are preferred. Among carboxylic acids, formic acid, acetic acid and propionic acid are particularly preferred. A quaternary ammonium compound may be used individually by 1 type, and may be used in combination of 2 or more type. In addition to the quaternary ammonium compound, a known accelerator for decomposing unstable terminals such as ammonia or amines such as triethylamine may be used in combination.

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 preferred, and 1 to 30 mass ppm is more preferred.
Amount of quaternary ammonium compound used=P×14/Q (6)

Here, in formula (6), P indicates the concentration (mass ppm) of the quaternary ammonium compound relative 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 ppm by mass or more, the rate of decomposition and removal of the unstable terminal portion tends to be further improved. Further, when the concentration is 50 ppm by mass or less, the color tone of the polyoxymethylene copolymer after decomposing and removing the unstable terminal portion tends to be more excellent.

The unstable terminal portion of the polyoxymethylene resin in the present embodiment can be decomposed and removed by heat-treating the polyoxymethylene copolymer in a melted state at a temperature above the melting point and below 260°C. 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. A method of spraying the oxymethylene copolymer powder with a quaternary ammonium compound can be used. Whichever 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 where the polyoxymethylene copolymer is melt compounded and extruded. Alternatively, when blending a filler or pigment with a polyoxymethylene copolymer using such an extruder, the resin pellets of the polyoxymethylene copolymer are first impregnated with a quaternary ammonium compound, and then the filler or pigment is blended. A treatment to decompose and remove the stable terminal portion may be performed.

The treatment for decomposing and removing the unstable terminal 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. The deactivation treatment of the polymerization catalyst includes a method of neutralizing and deactivating the polymerization catalyst in a basic aqueous solution of amines or the like. If the polymerization catalyst is not deactivated, the polyoxymethylene copolymer is heated under an inert gas atmosphere at a temperature below the melting point of the polyoxymethylene copolymer, the polymerization catalyst is reduced by volatilization, and then the unstable terminal is It is also effective to disassemble and remove the part.

A polyoxymethylene copolymer having extremely excellent thermal stability can be obtained by the decomposition removal treatment of the unstable terminal portion as described above.

The (A) polyoxymethylene resin constituting the polyoxymethylene resin composition preferably has a terminal OH group content of 5 to 95% with respect to the total number of molecular terminals. If the amount of OH groups at the terminal is 95% or less, it is preferable because it is possible to intentionally form microvoids during the production of the resin composition, and if the amount of OH groups at the terminal is 5% or more, and (B) the adhesion of the modifier can be improved. From the same point of view, the amount of OH groups at the end is more preferably 90% or less, more preferably 85% or less, still more preferably 80% or less, and 6% or more. is more preferably 7% or more, and even more preferably 10% or more.

The (A) polyoxymethylene resin constituting the polyoxymethylene resin composition preferably has a terminal OH group content of 10 to 200 mmol/kg. If the amount of OH groups at the terminal portion is 200 mmol/kg or less, the thermal stability of the polyoxymethylene resin composition can be made very excellent during production. It is preferable because the crystallinity of the oxymethylene resin tends to increase. From the same point of view, the amount of OH groups at the end is more preferably 150 mmol/kg or less, still more preferably 100 mmol/kg or less, even more preferably 90 mmol/kg or less, and 15 mmol/kg or less. It is more preferably 20 mmol/kg or more, even more preferably 40 mmol/kg or more.

The terminal OH group content can be measured directly and indirectly by ¹ H-NMR, ¹³ C-NMR and the like.
Direct measurement can be performed by two-dimensional NMR such as ¹ H-NMR and ¹³ C-NMR, presaturation method, WET method, etc., although the method is not limited to the following.
In indirect measurement, the method is not limited to the following, but (A) polyoxymethylene resin is dissolved in an NMR measurement solvent, and then derivatized using a silylating agent or the like that can react with the terminal OH group. After that, it can be measured.

Silylating agents include, but are not limited to, hexamethyldisilazane, dimethyldichlorosilane, trimethylchlorosilane, trimethylchlorosilane, N,O-bis(trimethylsilyl)acetamide, 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 portion, and a copolymer-based block copolymer having a block portion can be used, and these can also be used in combination.

As the (A) polyoxymethylene resin, for example, a combination of different molecular weights, a combination of polyoxymethylene copolymers with different comonomer amounts, and the like can be used as appropriate.

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

In addition, the structure of the block portion is obtained by dissolving the polyoxymethylene resin composition containing the block copolymer or a molded article made of the same, isolating the block copolymer by performing operations such as reprecipitation and filtering, and then decomposing the block copolymer with hydrochloric acid. Thus, 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.

(A) The melt flow rate of the polyoxymethylene resin 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. A melt flow rate of 0.1 g/10 minutes or more is preferable in terms of molding fluidity, and a melt flow rate of 60 g/10 minutes or less can further improve impact strength. 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 point of view, the melt flow rate of (A) the 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 point of view, the melt flow rate of (A) the polyoxymethylene resin is more preferably 0.2 g/10 minutes or more, more 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.

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

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

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

The polyoxymethylene resin composition of the present embodiment contains 0.5 to 50 parts by mass of the (B) modifier with respect to 100 parts by mass of the (A) polyoxymethylene resin. When the content of component (B) is 0.5 parts by mass or more per 100 parts by mass of component (A), impact resistance tends to be improved, and the content is 50 parts by mass or less. This tends to improve impact resistance while maintaining rigidity.
From the same point of view, the content of component (B) with respect to 100 parts by mass of component (A) in the polyoxymethylene resin composition of the present embodiment is preferably 1 part by mass or more, and is 3 parts by mass or more. more preferably 5 parts by mass or more, preferably 45 parts by mass or less, more preferably 40 parts by mass or less, and even more preferably 35 parts by mass or less.

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

Further, identification of (A) polyoxymethylene resin and (B) modifier can be easily determined by those skilled in the art. Specifically, in the case of a transmission electron microscope, there are differences in screen color due to differences in electron beam transparency due to molecular structures, differences due to staining agents such as osmic acid and ruthenium tetroxide, and crystalline polymers. It can be determined by the difference in lamellar 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, dissolution, etc., and the composition ratio, structure, molecular weight, etc. are calculated. It is possible. In addition, for example, by performing various measurements such as ¹ H-NMR, ¹³ C-NMR, two-dimensional NMR, MALDI-TOF MS, GPC, molecular structures such as repeating structures and branched structures, and positional information of various functional groups etc. can be determined.

-(b-1) thermoplastic polyurethane-
A thermoplastic polyurethane is a polymer compound having urethane bonds in its main chain and an elastomer that can be thermoplastically processed. Examples of polymer structures include multi-block copolymers composed of rigid urethane segments (hard segments) and flexible diol segments (soft segments).

Rigid urethane segments are obtained, for example, by reaction of polyfunctional isocyanates with what are known as chain extenders. As polyfunctional isocyanates, aromatic diisocyanates, alicyclic diisocyanates, aliphatic diisocyanates, or the like can be used.

Aromatic diisocyanates include, for example, 4,4'-diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI) (including 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- 4,4''-diisocyanate, p-phenylene diisocyanate, m-phenylene diisocyanate and the like.

Alicyclic diisocyanates include, for example, 4,4′-dicyclohexylmethane diisocyanate (H ₁₂ MDI), isophorone diisocyanate (IPDI), cyclopentylene-1,3-diisocyanate and the like.

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

As chain extenders (sometimes referred to as crosslinkers), for example, short-chain aliphatic, cycloaliphatic or aromatic diols with 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. diol, 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 -1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, dihydroxyethyl ether of hydroquinone, hydrogenated bisphenol A and the like. Examples of diamines include ethylenediamine, hexamethylenediamine, xylylenediamine, 4,4'-diaminodiphenylmethane and the like. Examples of triols include trimethylolpropane and glycerin.

Flexible diol segments include, for example, polyether diols, polyester diols, polyether ester diols, polycarbonate diols, etc., having a number average molar mass of 500 to 5000 g/mol, preferably 1000 to 3000 g/mol. be done.

Examples of polyether diols include poly(tetramethylene ether) glycol (PTMEG), poly(propylene oxide) glycol, polybutadiene diol, and copolymers thereof (e.g., copolymers of propylene oxide and ethylene oxide, tetrahydrofuran and ethylene oxide). copolymer). They can also be obtained, for example, by ring-opening polymerization of ethylene oxide, propylene oxide or tetrahydrofuran.

Polyester diols are the polyether diols or dialcohols described above (e.g., 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.); Obtained by an esterification reaction with dicarboxylic acids (e.g., glutaric acid, adipic acid, pimelic acid, suberic acid, sebacic acid, dodecanedioic acid, terephthalic acid, isophthalic acid, etc.) or by corresponding transesterification reaction be able to. These polyester diols can also be obtained by ring-opening polymerization of lactones (eg, caprolactone, propiolactone, valerolactone, etc.).

Polycarbonate diols are polyether diols or dialcohols described above (e.g., 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 phosgenes.

(b-1) Thermoplastic polyurethanes include, for example, ester-based polyurethanes (sometimes referred to as "polyether-based polyurethanes"), ether-based polyurethanes (sometimes referred to as "polyether-based polyurethanes"), Ether ester-based polyurethanes (sometimes referred to as "polyether ester-based polyurethanes") and caprolactone-based polyurethanes (sometimes referred to as "polycaprolactone-based polyurethanes") can be mentioned. The (b-1) thermoplastic polyurethane is preferably an ester-based polyurethane or an ether-ester-based polyurethane, more preferably an ester-based polyurethane, from the viewpoint of 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 sufficiently exhibiting impact resistance.

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

(b-1) The melt index of thermoplastic polyurethanes is measured at various temperatures and depends on the melting behavior of rigid urethane segments. It is also a measure of the degree of addition (molar mass of the entire chain).

In addition, by setting the component proportions within the following range, the thermoplastic polyurethane (b-1) has an appropriate melt viscosity during processing of the composition, and an improvement in impact resistance can be expected.

The ether-based polyurethane has a ratio (molar ratio) of an ether diol component (also referred to as an "ether diol unit") to an isocyanate component (also referred to as an "isocyanate unit") of 1. , preferably 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 more preferred.

On the other hand, ester-based polyurethanes, ether-ester-based polyurethanes, and carbonate-based polyurethanes are ester components (also referred to as "ester units") when the isocyanate component is 1 (carbonate component (also referred to as "carbonate units"). )) is preferably 10 or less, more preferably 8 or less, even more preferably 5 or less, and preferably 1 or more, It is more preferably 2 or more, still more preferably 3 or more, and still more preferably 4 or more. When the ratio of the ester component is equal to or less than the above upper limit, good impact absorption tends to be exhibited, and by making it equal to or more than the above lower limit, better fluidity can be ensured.
In addition, said ester component points out the component produced|generated by reacting a carboxylic acid component and a polyol component.

Further, in ester-based polyurethanes, ether-ester-based polyurethanes, and carbonate-based polyurethanes, the ratio (molar ratio) of the polyol component to the isocyanate component is preferably 10 or less, more preferably 8 or less. , more preferably 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. By setting the ratio of the polyol component to the above upper limit or less, a favorable sea-island structure tends to be exhibited, and by setting the ratio to the above lower limit or more, a more favorable viscosity can be secured.

The dispersed particle size of the (b-1) thermoplastic polyurethane in the polyoxymethylene resin composition and the molded article made of the resin composition is preferably 10 to 2000 nm in terms of circle equivalent diameter. (b-1) If the thermoplastic polyurethane has a dispersed particle size of 10 nm or more, it has good dispersibility and can effectively exhibit impact resistance. Further, when the (b-1) thermoplastic polyurethane has dispersed particle diameters of 2000 nm or less, more sufficient impact resistance can be exhibited. From the same point of view, the dispersion particle size of (b-1) thermoplastic polyurethane in the polyoxymethylene resin composition and the molded article made of the resin composition is more preferably 1500 nm or less in terms of equivalent circle diameter. It is more preferably 1000 nm or less, even more preferably 800 nm or less, more preferably 30 nm or more, still more preferably 40 nm or more, and even more preferably 50 nm or more.

In this specification, the equivalent circle diameter refers to the diameter of a circle having the same area as the value obtained by calculating the product of the minor axis and the diameter of the object to be projected. 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 surface of the molded article perpendicular to the direction of resin flow is observed with a transmission electron microscope or the like, and the minor axis and diameter of the dispersed 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 that value is obtained. Then, the diameters of the above-mentioned circles are determined for any 10 or more target substances, and the average of these diameters can be used as the dispersed particle size.

-(b-2) Graft rubber copolymer-
A 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 preferably has rubber elasticity in order to improve impact resistance. Polymers, styrene polymers, nitrile polymers, conjugated diene polymers, urethane polymers, olefin polymers and the like. In addition, 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 preferred. Among them, the component constituting the core layer of the graft rubber copolymer (b-2) is preferably a silicone polymer, an acrylic polymer, or a silicone/acrylic polymer from the viewpoint of impact resistance and heat aging resistance. .

Further, the components constituting the core layer include siloxane compounds such as dimethylsiloxane and phenylmethylsiloxane; acrylic compounds such as ethyl acrylate, butyl acrylate and 2-ethylhexyl acrylate; A copolymer component of the component of is preferably exemplified.

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

From the viewpoint of thermal stability and rigidity during aging, the (b-2) graft rubber copolymer preferably contains 1 to 25% by mass of Si element in ICP-MS analysis. In addition, the amount of the Si element is not particularly limited, but it is more preferably 20% by mass or less, further preferably 15% by mass or less, and even more preferably 10% by mass or less. , more preferably 1.5% by mass or more, still 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. It can be obtained by a method of polymerization such as emulsion polymerization.

(b-2) The particle size of the 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. It can be made easier. From the same point of view, the particle size of the (b-2) graft rubber copolymer is more preferably 30 nm or more, still more preferably 40 nm or more, still more preferably 50 nm or more, and 1500 nm. It is more preferably 1000 nm or less, even more preferably 800 nm or less.

The dispersed particle size of the (b-2) graft rubber copolymer in the molded article is preferably 20 to 2000 nm in terms of circle equivalent diameter. (b-2) If the dispersed particle diameter of the graft rubber copolymer is 20 nm or more, it will have good dispersibility and can effectively exhibit impact resistance. Further, when the dispersed particle size of the (b-2) graft rubber copolymer is 2000 nm or less, more sufficient impact resistance can be exhibited. From the same point of view, the dispersed particle size of the (b-2) graft rubber copolymer in the molded article is more preferably 1500 nm or less, more preferably 1000 nm or less, and 800 nm or less in terms of circle equivalent diameter. is more preferably 30 nm or more, more 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 to 100 parts by mass of the entire graft rubber copolymer is preferably 10 parts by mass or more, more preferably 20 parts by mass or more, and 30 parts by mass. It is more preferable that it is above. By setting the mass ratio of the core layer to be equal to or higher than the above lower limit, the entanglement of 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 to 100 parts by mass of the whole (b-2) graft rubber copolymer is preferably 95 parts by mass or less, more preferably 90 parts by mass or less, and 85 parts by mass. It is more preferably not more than parts by mass. 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 ions in the graft rubber copolymer is 0.1 ppm or more, it is preferable because it is possible to intentionally form microvoids during melt-kneading. Thermal stability can be further improved. From the same point of view, the concentration of sulfate ions in the (b-2) graft rubber copolymer is more preferably 4 ppm or less, still more preferably 3 ppm or less, and even more preferably 2.5 ppm or less. . In addition, the concentration of sulfate ions in the (b-2) graft rubber copolymer is more preferably 0.2 ppm or more, still more preferably 0.3 ppm or more, and even more 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 it is possible to intentionally form microvoids during melt-kneading. It is possible to further improve the quality. From the same point of view, the concentration of calcium ions in the (b-2) graft rubber copolymer is more preferably 400 ppm or less, still more preferably 350 ppm or less, even more preferably 300 ppm or less, and , more preferably 15 ppm or more, more preferably 20 ppm or more, and even more preferably 30 ppm or more.

(b-2) Examples of commercially available graft rubber copolymers include "Metabrene (registered trademark)" (manufactured by Mitsubishi Rayon), "Kaneace (registered trademark)" (manufactured by Kaneka Corporation), and "Staphyloid (registered trademark)". Trademark)” (manufactured by Aica Kogyo Co., Ltd.), or “Parapet (registered trademark) SA” (manufactured by Kuraray Co., Ltd.), “PARALOID (registered trademark)” (manufactured by DOW), “Clearstrength (registered trademark)” (manufactured by ARKEMA) , “Durastrength (registered trademark)” (manufactured by ARKEMA), etc., and these may be used singly or in combination of two or more.

Among these, commercial products of (b-2) graft rubber copolymers include METABLEN, 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, (C) a coloring agent refers to a substance that changes the appearance by actions such as absorption, scattering, and reflection of visible light.

Coloring agent (C), which may be present in the molded article of the polyoxymethylene resin composition in the present embodiment, is important for further improving wear resistance by combining with component (B) in addition to the original purpose of coloring. role. From the viewpoint of obtaining excellent abrasion resistance, the polyoxymethylene resin composition of the present embodiment can contain (C) a colorant in an amount within the range described below.

Although the reason why the presence of (C) the coloring agent improves the abrasion resistance is not clear, it is thought that it is caused by the fact that the (C) coloring agent improves the surface hardness of the molded article.

(C) Colorants include, but are not limited to, inorganic pigments, organic dyes and pigments, and the like.

Examples of inorganic pigments include inorganic pigments that are commonly used for coloring resins. For example, at least one metal oxide selected from the group consisting of iron, zinc and titanium, iron, zinc and at least one metal carbonate selected from the group consisting of titanium, zinc sulfide, titanium oxide, zinc oxide, iron oxide, barium sulfate, titanium dioxide, barium sulfate, hydrous chromium oxide, chromium oxide, cobalt aluminate, barite powder, zinc yellow 1, zinc yellow 2, ferrocyanide potash, kaolin, titanium yellow, cobalt blue, ultramarine blue, cadmium, nickel titanium, lithopone, strontium, amber, sienna, azurite, malachite, azuromalachite, Orpiment, realgar, cinnabar, turquoise, rhodochrosite, yellow ocher, tailbelt, raw sienna, raw umber, cassel earth, chalk, gypsum, burnt sienna, burnt umber, lapis lazuli, azurite, malachite, coral powder, white mica, cobalt Blue, Cerulean Blue, Cobalt Violet, Cobalt Green, Zinc White, Titanium White, Light Red, Chrome Oxide Green, Mars Black, Viridian, Yellow Ochre, Alumina White, Cadmium Yellow, Cadmium Red, Vermillion, Talc, White Carbon, Clay , Mineral Violet, Rose Cobalt Violet, Silver White, Gold Powder, Bronze Powder, Aluminum Powder, Prussian Blue, Aureolin, Talc, Wollastonite, Titanium Mica, Carbon Black, Acetylene Black, Lamp Black, Furnas Black, Vegetable Black, Bone char, calcium carbonate, Prussian blue, etc., can be mentioned.
The above-mentioned "metal oxide" also includes "composite metal oxide" composed of two or more metals selected from iron, zinc and titanium.

In particular, as the (C) colorant, at least one metal oxide selected from the group consisting of iron, zinc and titanium, at least one metal carbonate selected from the group consisting of iron, zinc and titanium, Zinc sulfide, zinc oxide, iron oxide, zinc yellow type 1, zinc yellow type 2, zinc white, titanium white, alumina white, talc, white carbon, silver white, carbon black, acetylene black, lamp black, furnace black, calcium carbonate are preferred.

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

Examples of organic dyes and pigments include, but are not limited to, condensed azo, quinone, phthalocyanine, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennone, quinacridone and thioindico-based, berylene-based, dioxazine-based, and phthalocyanine-based organic dyes and pigments.

In particular, from the viewpoint of the thermal stability of the polyoxymethylene resin composition of the present embodiment, the organic dyes and pigments include condensed azo-based, quinone-based, phthalocyanine-based, anthraquinone-based, heterocyclic, pennone-based, and quinacridone-based dyes. , thioindico-based, berylene-based, dioxazine-based, or phthalocyanine-based organic dyes and pigments are preferred. More preferred are condensed azo, quinone, phthalocyanine, anthraquinone, heterocyclic, pennon, quinacridone, berylene, or phthalocyanine organic dyes and pigments. More preferred are quinone, phthalocyanine, anthraquinone, heterocyclic, quinacridone, berylene, or phthalocyanine organic dyes and pigments.

The polyoxymethylene resin composition of the present embodiment preferably contains 0.01 to 3 parts by mass of the (C) colorant with respect to 100 parts by mass of the (A) polyoxymethylene resin. By setting the content of component (C) to 0.01 parts by mass or more with respect to 100 parts by mass of component (A), the polyoxymethylene resin composition can be sufficiently colored, and 3 parts by mass By setting it to less than or equal to 10 parts, it is possible to sufficiently obtain the effect of improving the wear characteristics of the polyoxymethylene resin composition during sliding under a very small load.
From the same point of view, 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, still more preferably 1.5 parts by mass or less, particularly preferably 1.0 parts by mass or less, and most preferably 0.8 parts by mass or less. It is preferably 0.05 parts by mass or more, and even more preferably 0.1 parts by mass or more.

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

Examples of 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.

From the viewpoint of improving the thermal stability of the polyoxymethylene resin composition of the present embodiment, the antioxidant is preferably a hindered phenol-based antioxidant. The hindered phenol-based antioxidant is not particularly limited, and known ones can be used as appropriate.
Scavengers such as formaldehyde and formic acid are not limited to the following. For example, compounds containing formaldehyde-reactive nitrogen such as melamine and polyamide resins and their polymers, hydroxides of alkali metals or alkaline earth metals , inorganic acid salts, and carboxylic acid salts. Specific examples include calcium hydroxide, calcium carbonate, calcium phosphate, calcium silicate, calcium borate, and fatty acid calcium salts (calcium stearate, calcium myristate, etc.). The fatty acid in the fatty acid calcium salt may be substituted with a hydroxyl group.

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

(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 ions in the polyoxymethylene resin composition is 0.01 ppm or more, it is preferable because it is possible to intentionally form microvoids during melt-kneading. It is possible to further improve the performance. From the same point of view, the concentration of sulfate ions in the polyoxymethylene resin composition is more preferably 1.0 ppm or less, more preferably 0.8 ppm or less, and even more preferably 0.7 ppm or less. , is particularly preferably 0.6 ppm or less, more preferably 0.02 ppm or more, still more 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. If the concentration of calcium ions in the polyoxymethylene resin composition is 2 ppm or more, it is possible to intentionally form microvoids during melt-kneading, which is preferable, and if it is 100 ppm or less, thermal stability is further improved. can be made From a similar point of view,. The concentration of calcium ions in the polyoxymethylene resin composition is more preferably 90 ppm or less, more preferably 80 ppm or less, even more preferably 70 ppm or less, and more preferably 3 ppm or more. , more preferably 4 ppm or more, and even more preferably 5 ppm or more.

(Method for producing polyoxymethylene resin composition)
The polyoxymethylene resin composition of the present embodiment includes, for example, predetermined amounts of (A) polyoxymethylene resin and (B) modifier, and optionally (C) colorant and other additives, which are melted. It can be obtained by kneading.

Apparatuses for obtaining the composition of the polyoxymethylene resin molded article of the present embodiment include known apparatuses such as single-screw or multi-screw extruders, rolls, Banbury mixers, etc. Among them, decompression apparatuses and side feeders. A twin-screw extruder equipped with such equipment is particularly preferred.

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

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

(Use of polyoxymethylene resin composition and molded article)
The polyoxymethylene resin composition of the present embodiment and the molded article made of the polyoxymethylene resin composition can be suitably used in applications requiring impact resistance. Specifically, although 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, Mechanical parts typified by shafts, joints, shafts, bearings, and guides; outsert-molded resin parts, insert-molded resin parts, chassis, trays, side plates, printers, and office automation equipment typified by copiers Parts; parts for video equipment such as digital video cameras and digital cameras; drives for CD, DVD, Blu-ray (registered trademark) discs, and other optical discs; music, video, or information represented by navigation systems and mobile personal computers equipment, parts for communication equipment represented by mobile phones and facsimiles; parts for electric equipment; parts for electronic equipment;

In addition, the polyoxymethylene resin composition of the present embodiment and the molded article made of the resin composition can be used as automotive parts, such as gasoline tanks, fuel pump modules, valves, and fuel-related parts such as gasoline tank flanges. ; Door-related parts such as door locks, door handles, window regulators, and speaker grills; Seat belt peripheral parts such as seat belt slip rings and press buttons; Combination switch parts, switches, clips, etc. Applicable to parts.

Furthermore, the polyoxymethylene resin composition of the present embodiment and a molded article made of the resin composition can be used as other articles or parts, such as the nib of a writing instrument, a mechanism part for inserting and removing a core; Cord stoppers, adjusters, buttons for clothing; Nozzles for watering, hose connection joints for watering; Stair railings, building supplies for supporting floor materials; Toys, Fasteners, Chains, Conveyors, Buckles, sporting goods, automatic vending machines (opening/closing lock mechanisms, product discharge mechanism parts), furniture, musical instruments, and housing equipment parts can also be suitably used.

Further, the polyoxymethylene resin composition of the present embodiment and the molded article made of the resin composition can be applied to various applications in which polyoxymethylene has been suitably used so far, and high industrial utilization is possible. It has potential.

EXAMPLES The present invention will be described in detail below with reference to Examples, but the present invention is not limited only to these Examples.

<Preparation or preparation of raw material components>
(A) Polyoxymethylene resin was prepared as shown below, and (b-1) thermoplastic polyurethane and (b-2) graft rubber copolymer were used as shown below.

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

Furthermore, 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 per 1 mol of trioxane to carry out polymerization. The polyoxymethylene copolymer discharged from the polymerization machine was put into a 0.1% triethylamine aqueous solution to deactivate the polymerization catalyst.

After filtering the deactivated polyoxymethylene copolymer with a centrifuge, 1 part by mass of an aqueous solution containing a quaternary ammonium compound is added to 100 parts by mass of the polyoxymethylene copolymer and mixed uniformly, Supply to a vented twin screw extruder, add 0.5 parts by mass of water to 100 parts by mass of the polyoxymethylene copolymer melted in the extruder, set the extruder temperature to 200 ° C., extruder The unstable ends of the polyoxymethylene copolymer were decomposed and removed at 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] 0.3 as antioxidant in polyoxymethylene copolymer with degraded unstable ends Parts by mass were added, and extruded as a strand from the die of the extruder while devolatilizing under the condition of a vacuum degree of 20 Torr with a vented extruder to obtain pellets.

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

Regarding the melt viscosity of the polyoxymethylene resin (A-1), the viscosity at a shear rate of 100 sec ⁻¹ at 190° C. is 550 Pa·s, and the viscosity at a shear rate of 1000 sec ⁻¹ at 190° C. is It was 250 Pa·s.

(2) Polyoxymethylene resin (A-2)
A biaxial self-cleaning type polymerization machine with a jacket through which a heat medium can pass (L/D = 8 (L: the distance from the raw material supply port to the discharge port of the polymerization machine (m), D: the inner diameter of the polymerization machine ( m).) was adjusted to 80° C. 4 kg/h of trioxane, 200 g/h of 1,3-dioxolane as a comonomer, and 1 mol of methylal as a chain transfer agent per 1 mol of trioxane were added to the polymerizer. It was added continuously in an amount of .10×10 ^-3 mol.

Furthermore, 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 per 1 mol of trioxane to carry out polymerization. The polyoxymethylene copolymer discharged from the polymerization machine was put into a 0.1% triethylamine aqueous solution to deactivate the polymerization catalyst.

After filtering the deactivated polyoxymethylene copolymer with a centrifuge, 1 part by mass of an aqueous solution containing a quaternary ammonium compound is added to 100 parts by mass of the polyoxymethylene copolymer and mixed uniformly, Supply to a vented twin screw extruder, add 0.5 parts by mass of water to 100 parts by mass of the polyoxymethylene copolymer melted in the extruder, set the extruder temperature to 200 ° C., extruder The unstable ends of the polyoxymethylene copolymer were decomposed and removed at 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] 0.3 as antioxidant in polyoxymethylene copolymer with degraded unstable ends Parts by mass were added, and extruded as a strand from the die of the extruder while devolatilizing under the condition of a vacuum degree of 20 Torr with a vented extruder to obtain pellets.

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

Regarding the melt viscosity of the polyoxymethylene resin (A-2), the viscosity at a shear rate of 100 sec ⁻¹ at 190° C. is 900 Pa·s, and the viscosity at a shear rate of 1000 sec ⁻¹ at 190° C. is It was 350 Pa·s.

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

Furthermore, 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 per 1 mol of trioxane to carry out polymerization. The polyoxymethylene copolymer discharged from the polymerization machine was put into a 0.1% triethylamine aqueous solution to deactivate the polymerization catalyst.

After filtering the deactivated polyoxymethylene copolymer with a centrifuge, 1 part by mass of an aqueous solution containing a quaternary ammonium compound is added to 100 parts by mass of the polyoxymethylene copolymer and mixed uniformly, Supply to a vented twin screw extruder, add 0.5 parts by mass of water to 100 parts by mass of the polyoxymethylene copolymer melted in the extruder, set the extruder temperature to 200 ° C., extruder The unstable ends of the polyoxymethylene copolymer were decomposed and removed at 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] 0.3 as antioxidant in polyoxymethylene copolymer with degraded unstable ends Parts by mass were added, and extruded as a strand from the die part of the extruder while devolatilizing under the condition of a vacuum degree of 20 Torr in a vented extruder to obtain pellets.

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

Regarding the melt viscosity of the polyoxymethylene resin (A-3), the viscosity at a shear rate of 100 sec ⁻¹ at 190° C. is 350 Pa·s, and the viscosity at a shear rate of 1000 sec ⁻¹ at 190° C. is It was 100 Pa·s.

(4) Thermoplastic polyurethane (b-1-1)
A commercially available ester-based polyurethane (ESTANE: registered trademark) composed of repeating hard segments and soft segments was used. The molar ratio of each composition is diphenylmethane diisocyanate (isocyanate component): adipic acid (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 repeating hard segments and soft segments was used. The molar 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), which is composed of repeating hard segments and soft segments, was used. The molar ratio of each composition was diphenylmethane diisocyanate:tetramethylene glycol:polycaprolactone polyol=1:1:3.
These can be adjusted by the method described in WO2011125540 or the like.

(7) Graft rubber copolymer (b-2-1)
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 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 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 production of molded product>
A polyoxymethylene resin composition was prepared and a molded article was produced according to the following procedures.

(1) Preparation of polyoxymethylene resin composition according to the formulation shown in Tables 1 and 2, using an extruder (Toshiba Machine Co., Ltd. TEM-26SS extruder (L / D = 48, with vent) , and all cylinder temperatures were set to 200° C., and pellets corresponding to 90 parts by mass of component (A) and component (b-2) were individually supplied from the main throat portion of the extruder top from a constant feeder. In addition, pellets corresponding to 10 parts by mass of component (A) and component (b-1) were separately supplied from the side portion of the extruder from a quantitative feeder.In some cases, component (C) and other additives. and other additional components are mixed together with pellets corresponding to 90 parts by mass of component (A), and fed singly from the main throat section of the top of the extruder.The resin under the conditions of an extrusion rate of 15 kg / hour and a screw rotation speed of 150 rpm The kneaded product was extruded in a strand shape, quenched in a strand bath, and cut with a strand cutter to obtain a pellet-shaped polyoxymethylene resin composition.

(2) Production of Molded Body 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 A multi-purpose test piece (molded article) conforming to ISO294-1 was obtained by molding under the injection conditions of 35 seconds for injection time and 15 seconds for cooling time at 60°C.

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

(1) Notched Charpy impact strength (23°C)
Using the obtained multipurpose test piece, measurement was performed 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) Tensile modulus Using the obtained multi-purpose test piece, measurement was performed in accordance with ISO527. The results are shown in Tables 1 and 2. It was judged that the higher the value, the better the rigidity.

(3) Friction coefficient Using a ball-on-disk type reciprocating friction and wear tester (AFT-15MS type, manufactured by Toyo Seimitsu Co., Ltd.), under an environment of 23 ° C. and humidity of 50%, a load of 19.6 N and a linear velocity of 30 mm. /sec, a reciprocating distance of 20 mm, and a reciprocating number of 10,000 times, a sliding test was performed on the surface of the obtained multipurpose test piece. As the ball material, SUS304 balls (spheres with a diameter of 5 mm) were used. The friction coefficient was measured when the number of reciprocations 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) Thermal retention limit time 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 210 ° C. and the mold temperature to A multi-purpose test piece (molded article) conforming to ISO294-1 was obtained by molding under injection conditions of 30° C., injection time of 35 seconds, and cooling time of 15 seconds. After 10 shots were molded, the molding operation was stopped while the heater was still being heated while the resin was plasticized in the cylinder. Confirmed the situation. The confirmation of the occurrence of silver streaks was carried out when the molding machine was stopped for 10 minutes, 20 minutes, 30 minutes, 40 minutes, and 50 minutes. The time at which silver streaks appeared on the entire surface of the compact was taken as the limit time for heat retention in the cylinder. The results are shown in Tables 1 and 2. The longer the critical time, the more excellent the thermal stability was evaluated.

(5) Color tone of molded product Using an injection molding machine (manufactured by Toshiba Machine Co., Ltd., EC-75NII), the obtained pellet-shaped polyoxymethylene resin composition was molded at a cylinder temperature of 210 ° C. and a mold temperature of 30. ℃, injection time 35 seconds, cooling time 15 seconds to obtain a multi-purpose test piece (molded body) conforming to ISO294-1. After 10 shots of molding, the molding operation was stopped while the resin was plasticized in the cylinder while the heater was still being heated. Also, the difference (color difference) between the color tone after 30 minutes of stopping time and the color tone after 0 minute of stopping time was measured, and Δb was calculated. This value was evaluated according to the criteria shown below, and A and B were judged to be excellent in thermal stability. The results are shown in Tables 1 and 2.
A: Δb is 0 to 3, and no discoloration is visually observed or slight discoloration is observed.
B: Δb is 3 to 5, and discoloration is visually observed.
C: Δb is 5 or more, and discoloration is remarkable.

(6) Tensile Strength Retention After Aging Long-term thermal stability evaluation was carried out using the obtained multi-purpose test piece. Specifically, the multipurpose test piece was placed in a gear oven at 145° C. and exposed to a high heat environment for 35 days. After 35 days, it was taken out, and after 24 hours, the tensile strength was measured by a method based on ISO527-1. The strength retention rate was calculated by comparing the tensile strength before exposure and the tensile strength after exposure. 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, (A) polyoxymethylene resin, and (B) modifier containing (b-1) thermoplastic polyurethane and (b-2) graft rubber copolymer, (B ) The content of the modifier is (A) 0.5 to 50 parts by mass per 100 parts by mass of the polyoxymethylene resin, and (b-1) thermoplastic polyurethane and (b-2) graft rubber The polyoxymethylene resin compositions according to the examples, in which the proportion of (b-1) thermoplastic polyurethane in the total copolymer is 1 to 16% by mass, are excellent in impact resistance, rigidity, slidability, and color tone of molded articles. It can be seen that both are good.

ADVANTAGE OF THE INVENTION According to this invention, the polyoxymethylene resin composition which is excellent in impact resistance, rigidity, and slidability, and is also excellent in the color tone of a molded article can be provided. Moreover, according to the present invention, it is possible to provide a molded article having excellent impact resistance, rigidity and slidability, and excellent color tone.

Claims (9)

(A) 100 parts by mass of a polyoxymethylene resin and (B) 0.5 to 50 parts by mass of a modifier,
The (B) modifier consists only of (b-1) a thermoplastic polyurethane and (b-2) a graft rubber copolymer,
The (b-2) graft rubber copolymer is a core-shell rubber having a structure of two or more layers composed of a core layer and one or more shell layers covering the core layer,
The ratio of the (b-1) thermoplastic polyurethane to the total of the (b-1) thermoplastic polyurethane and the (b-2) graft rubber copolymer is 1 to 16% by mass.
A polyoxymethylene resin composition characterized by: 2. The polyoxymethylene resin composition according to claim 1, wherein the thermoplastic polyurethane (b-1) is an ester polyurethane. 3. The polyoxymethylene resin composition according to claim 2 , wherein the ester-based polyurethane contains two polyol components. The polyoxymethylene resin composition according to any one of claims 1 to 3 , wherein the graft rubber copolymer (b-2) has a Si element content of 1 to 25% by mass in ICP-MS analysis. . 5. The graft rubber copolymer (b-2) according to any one of claims 1 to 4 , wherein the graft rubber copolymer 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 sulfate ion concentration is 0.01 to 0.2 ppm. The polyoxymethylene resin composition according to any one of claims 1 to 6 , wherein the (A) polyoxymethylene resin 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 article comprising the polyoxymethylene resin composition according to any one of claims 1 to 8 .