阅读说明：本技术 聚缩醛树脂组合物 (Polyacetal resin composition ) 是由 尾坂美树 都筑隼一 鹿野泰和 于 2020-02-07 设计创作，主要内容包括：本发明的目的在于提供一种机械强度、注射成型时的热稳定性和抗菌性优异的聚缩醛树脂组合物。本发明的聚缩醛树脂组合物的特征在于,其含有100质量份的(A)聚缩醛树脂、0.01质量份～5质量份的(B)含有选自由银、铜和锌构成的组中的至少一种元素和/或该元素的离子的无机抗菌剂、和0.01质量份～5质量份的(C)聚酯树脂。优选在将相对于100质量份的(A)聚缩醛树脂的(B)无机抗菌剂的质量比例设为X质量份、并将相对于100质量份的(A)聚缩醛树脂的(C)聚酯树脂的质量比例设为Y质量份时满足Y≥-2X+0.35。(The purpose of the present invention is to provide a polyacetal resin composition having excellent mechanical strength, thermal stability during injection molding, and antibacterial properties. The polyacetal resin composition of the present invention is characterized by comprising 100 parts by mass of (A) a polyacetal resin, (B) 0.01 to 5 parts by mass of an inorganic antibacterial agent containing at least one element selected from the group consisting of silver, copper and zinc and/or an ion of the element, and (C) 0.01 to 5 parts by mass of a polyester resin. Preferably, Y.gtoreq.2X +0.35 is satisfied where X parts by mass of the inorganic antibacterial agent (B) is 100 parts by mass of the polyacetal resin (A) and Y parts by mass of the polyester resin (C) is 100 parts by mass of the polyacetal resin (A).)

1. A polyacetal resin composition, comprising:

100 parts by mass of (A) a polyacetal resin,

0.01 to 5 parts by mass of (B) an inorganic antibacterial agent containing at least one element selected from the group consisting of silver, copper and zinc and/or an ion of the element, and

0.01 to 5 parts by mass of (C) a polyester resin.

2. The polyacetal resin composition according to claim 1, wherein,

when the mass ratio of the inorganic antibacterial agent (B) to 100 parts by mass of the polyacetal resin (A) is X parts by mass and the mass ratio of the polyester resin (C) to 100 parts by mass of the polyacetal resin (A) is Y parts by mass, the relationship of Y.gtoreq.2X +0.35 is satisfied.

3. The polyacetal resin composition according to claim 1 or 2, wherein,

when the mass ratio of the inorganic antibacterial agent (B) to 100 parts by mass of the polyacetal resin (A) is X parts by mass and the mass ratio of the polyester resin (C) to 100 parts by mass of the polyacetal resin (A) is Y parts by mass, the relationship of Y.gtoreq.0.5X-0.1 is satisfied.

4. The polyacetal resin composition according to claim 1 to 3, wherein,

(C) the polyester resin is an unsaturated polyester resin.

5. The polyacetal resin composition according to claim 1 to 4, wherein,

(B) the inorganic antibacterial agent is an antibacterial agent in which at least one element selected from the group consisting of silver, copper and zinc and/or an ion of the element is supported on glass or zeolite.

6. The polyacetal resin composition according to claim 1 to 4, wherein,

(B) the inorganic antimicrobial agent contains silver and/or silver ions.

7. The polyacetal resin composition according to claim 1 to 6, wherein,

(B) the inorganic antibacterial agent is an antibacterial agent in which silver and/or silver ions are supported on glass or zeolite.

8. A molded article comprising the polyacetal resin composition according to any one of claims 1 to 7.

Technical Field

The present invention relates to a polyacetal resin composition and a molded article comprising the polyacetal resin composition.

Background

Polyacetal resins are excellent in mechanical strength, chemical resistance, slidability, and the like, and therefore are widely used as typical engineering plastics, mainly for molded articles such as electric and electronic parts, automobile parts, industrial parts, and other mechanical parts of precision equipment. However, special properties are often required in addition to the above general physical properties. Examples thereof include antibacterial properties against various bacteria and molds.

Generally, in order to impart antimicrobial properties to a resin, a method of adding an organic antimicrobial agent or an inorganic antimicrobial agent is employed. There is disclosed a technique of adding an inorganic antibacterial agent to a polyacetal resin in order to impart antibacterial properties to the polyacetal resin (for example, patent documents 1 to 4).

Further, there is disclosed a technique of adding a polyester resin to a polyacetal resin in order to improve the thermal stability of the polyacetal resin composition (for example, patent documents 5 to 8).

Disclosure of Invention

Problems to be solved by the invention

However, when the inorganic antibacterial agent is added to the polyacetal resin for use, the antibacterial agent accelerates the decomposition of the polyacetal resin, and the thermal stability of the resin composition is greatly lowered. In particular, in the case of injection molding, there is a concern about the generation of defective products and deterioration of working environment due to the generation of crazing caused by decomposition gas of the resin. Therefore, a polyacetal resin composition having both antibacterial properties and heat resistance is desired.

However, the polyacetal resin compositions disclosed in patent documents 1 to 8 cannot achieve both antibacterial properties and thermal stability at a high level, and further improvement is desired.

The present invention has been made in view of the above problems, and an object thereof is to provide a polyacetal resin composition having excellent mechanical strength, thermal stability at the time of injection molding, and antibacterial properties.

Means for solving the problems

Thus, the present inventors found that: by blending the specific inorganic antibacterial agent and the polyester resin at a specific ratio in the polyacetal resin, the polyacetal resin exhibits higher antibacterial properties than the polyacetal resin blended with only the inorganic antibacterial agent, and the above-mentioned problems can be solved. Namely, the present invention is as follows.

[1]

A polyacetal resin composition, comprising:

100 parts by mass of (A) a polyacetal resin,

0.01 to 5 parts by mass of (B) an inorganic antibacterial agent containing at least one element selected from the group consisting of silver, copper and zinc and/or an ion of the element, and

0.01 to 5 parts by mass of (C) a polyester resin.

[2]

The polyacetal resin composition according to [1], wherein Y.gtoreq.2X +0.35 is satisfied where X parts by mass of the inorganic antibacterial agent (B) is 100 parts by mass of the polyacetal resin (A) and Y parts by mass is the polyester resin (C) is 100 parts by mass of the polyacetal resin (A).

[3]

The polyacetal resin composition according to [1] or [2], wherein Y.gtoreq.0.5X-0.1 is satisfied, assuming that the mass ratio of the inorganic antibacterial agent (B) to 100 parts by mass of the polyacetal resin (A) is X parts by mass and the mass ratio of the polyester resin (C) to 100 parts by mass of the polyacetal resin (A) is Y parts by mass.

[4]

The polyacetal resin composition according to any one of [1] to [3], wherein the polyester resin (C) is an unsaturated polyester resin.

[5]

The polyacetal resin composition according to any one of [1] to [4], wherein the inorganic antibacterial agent (B) is an antibacterial agent in which at least one element selected from the group consisting of silver, copper and zinc and/or an ion of the element is supported on glass or zeolite.

[6]

The polyacetal resin composition according to any one of [1] to [4], wherein the inorganic antibacterial agent (B) contains silver and/or silver ions.

[7]

The polyacetal resin composition according to any one of [1] to [6], wherein the inorganic antibacterial agent (B) is an antibacterial agent in which silver and/or silver ions are supported on glass or zeolite.

[8]

A molded article comprising the polyacetal resin composition according to any one of [1] to [7 ].

Effects of the invention

According to the present invention, a polyacetal resin composition having excellent mechanical strength, thermal stability during injection molding, and antibacterial properties can be provided.

Detailed Description

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

[ polyacetal resin composition ]

The polyacetal resin composition of the present embodiment includes: 100 parts by mass of (A) a polyacetal resin, (B) 0.01 to 5 parts by mass of an inorganic antibacterial agent containing at least one element selected from the group consisting of silver, copper and zinc and/or an ion of the element, and (C) 0.01 to 5 parts by mass of a polyester resin. The polyacetal resin composition of the present embodiment may further contain additives other than the above-mentioned inorganic antibacterial agent, organic antibacterial agent, other components described later, and the like.

In the present specification, the "polyacetal resin composition" may be simply referred to as "resin composition".

((A) polyacetal resin)

The polyacetal resin (A) includes: as the polyacetal homopolymer and the polyacetal copolymer, known polyacetal resins can be used.

Examples of the polyacetal homopolymer include: polyacetal homopolymers obtained by homopolymerizing formaldehyde monomers or cyclic oligomers of formaldehyde such as a trimer (trioxane) and a tetramer (tetraoxymethylene). Therefore, the polyacetal homopolymer is substantially composed of oxymethylene units.

The polyacetal homopolymer may be a polyacetal homopolymer having a block component obtained by polymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde in the presence of a compound having a functional group such as a hydroxyl group at both ends or at one end, for example, a polyalkylene glycol.

As the polyacetal copolymer, there may be mentioned: a polyacetal copolymer obtained by copolymerizing a cyclic oligomer of formaldehyde such as a formaldehyde monomer or a trimer thereof (trioxymethylene) or a tetramer thereof (tetrapolyoxymethylene) with a cyclic ether or a cyclic formal such as a diol such as ethylene oxide, propylene oxide, epichlorohydrin, 1, 3-dioxolane, 1, 4-butanediol formal or a cyclic formal such as a cyclic formal of dimer diol; polyacetal copolymers obtained by copolymerizing a plurality of formaldehyde monomers or cyclic oligomers of formaldehyde such as a trimer (trioxymethylene) and a tetramer (tetraoxymethylene). Accordingly, the polyacetal copolymer may be a polymer substantially composed of an oxymethylene unit and an oxyethylene unit.

As the polyacetal copolymer, a polyacetal copolymer having a branch chain obtained by copolymerizing a formaldehyde monomer and/or a cyclic oligomer of formaldehyde with a monofunctional glycidyl ether; or a polyacetal copolymer having a crosslinked structure obtained by copolymerizing a formaldehyde monomer and/or a cyclic oligomer of formaldehyde with a polyfunctional glycidyl ether.

The polyacetal copolymer may be a polyacetal copolymer having a block component obtained by copolymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxymethylene) and a tetramer (tetraoxymethylene) thereof with a cyclic ether or a cyclic formal in the presence of a compound having a functional group such as a hydroxyl group at both ends or at one end, for example, a polyalkylene glycol.

As described above, as the polyacetal resin (a), any of a polyacetal homopolymer and a polyacetal copolymer can be used. These polyacetal resins (A) may be used singly or in combination of two or more. In this case, the polyacetal resin (a) preferably contains the polyacetal copolymer in an amount of 50% by mass or more, more preferably contains the polyacetal copolymer in an amount of 80% by mass or more, and most preferably substantially all (95% by mass or more) of the polyacetal copolymer. The percentage is based on 100% by mass of the total amount of the polyacetal resin (A).

Examples of the method for obtaining the polyacetal homopolymer include a method comprising the following steps: a formaldehyde monomer or a trimer thereof (trioxane) or a tetramer thereof (tetrapolyoxymethylene), a chain transfer agent (molecular weight regulator) and a polymerization catalyst as monomers are fed into a polymerization reactor filled with a hydrocarbon solvent, and a crude polyacetal homopolymer is obtained by a slurry polymerization method. The crude polyacetal homopolymer obtained is preferably stabilized by terminating the polymer terminal group with an esterifying agent, an etherifying agent or the like, because the terminal group of the polymer is thermally unstable. Thus, a polyacetal homopolymer was obtained. The above-mentioned crude polyacetal homopolymer may be used as the polyacetal homopolymer.

Since the oxymethylene monomer or its trimer (trioxymethylene) or tetramer (tetraoxymethylene) as a raw material monomer, the chain transfer agent, and the hydrocarbon polymerization solvent contain a component capable of causing chain transfer (a component which generates an unstable terminal group), for example, water, methanol, and formic acid, it is preferable that the content of these components capable of causing chain transfer is first adjusted, and then the polymerization is carried out to obtain a crude polyacetal homopolymer. The content of the component capable of causing chain transfer in this case is preferably in the range of 1 to 1000 mass ppm, more preferably 1 to 500 mass ppm, and still more preferably 1 to 300 mass ppm, relative to the total mass of the oxymethylene monomer as a monomer, or its trimer (trioxymethylene) or tetramer (tetraoxymethylene).

The molecular weight of the polyacetal homopolymer can be adjusted by chain transfer using a molecular weight modifier such as carboxylic anhydride or carboxylic acid. The molecular weight modifier is preferably propionic anhydride or acetic anhydride, and more preferably acetic anhydride.

These molecular weight regulators may be used alone or in combination of two or more.

The polymerization catalyst in the polymerization of the polyacetal homopolymer is not limited to, for example, an anionic polymerization catalyst is preferable, and an anionic polymerization catalyst is more preferableA salt-type polymerization catalyst. In the aboveAmong the salt type polymerization catalysts, tetraethyl iodide is preferableTributylethyl iodideWaiting seasonA salt compound; quaternary ammonium compounds such as tetramethylammonium bromide and dimethyldistearylammonium acetate.

These polymerization catalysts may be used alone or in combination of two or more.

The hydrocarbon polymerization solvent is not particularly limited as long as it is a solvent that does not react with the raw material monomer, and examples thereof include: pentane, isopentane, hexane, cyclohexane, heptane, octane, nonane, decane, benzene, and the like.

These hydrocarbon solvents may be used alone or in combination of two or more. Hexane is particularly preferred as the hydrocarbon polymerization solvent.

The polymerization apparatus for producing the crude polyacetal homopolymer is not particularly limited as long as it can simultaneously supply the raw material monomer, the chain transfer agent (molecular weight regulator), the polymerization catalyst and the hydrocarbon polymerization solvent, and a continuous polymerization apparatus is preferred from the viewpoint of productivity.

As described above, the polyacetal homopolymer is preferably stabilized by terminating the terminal groups of the polymer with an esterifying agent, because the terminal groups of the polymer are not thermally stable.

The esterification agent may be an acid anhydride, and examples of the acid anhydride include: benzoic anhydride, succinic anhydride, maleic anhydride, glutaric anhydride, phthalic anhydride, propionic anhydride, acetic anhydride, preferably acetic anhydride. These esterification agents may be used alone or in combination of two or more.

The method for obtaining the polyacetal copolymer will be described below, and the polymerization method of the polyacetal copolymer is not limited to the following method, and examples thereof include a bulk polymerization method. The polymerization method may be either a batch method or a continuous method.

The polymerization apparatus is not limited to the following apparatuses, and examples thereof include: self-cleaning extrusion mixers such as co-kneaders, twin screw continuous extrusion mixers, and twin screw paddle continuous mixers. Specific polymerization methods include the following methods: the molten monomer, the chain transfer agent and the polymerization catalyst are fed to the above-mentioned polymerization apparatus, and the polymerization proceeds while the solid block-like polyacetal copolymer is obtained. There may be a case where a thermally unstable terminal part [ - (OCH) exists in the polyacetal copolymer obtained after the polymerization step₂)_n-OH group]Therefore, it is preferable to perform decomposition and removal treatment of the unstable terminal portion.

When the polyacetal copolymer is obtained using trioxymethylene, the comonomer such as 1, 3-dioxolane is usually used in an amount of 0.1 to 60 mol%, preferably 0.1 to 20 mol%, and more preferably 0.13 to 10 mol%, based on 100 mol% of trioxymethylene.

The melting point of the polyacetal copolymer is preferably 160 to 173 ℃, more preferably 160 to 170 ℃, and still more preferably 163 to 167 ℃. The polyacetal copolymer having a melting point of 163 to 167 ℃ can be obtained by using about 3.0 to about 6.0 mol% of a comonomer with respect to 100 mol% of trioxane.

As the polymerization catalyst used for the polymerization of the polyacetal copolymer, a cationic active catalyst such as Lewis acid, protonic acid, and ester or anhydride thereof is preferable. Examples of lewis acids include: halides of boron, tin, titanium, phosphorus, arsenic and antimony, more specifically, there may be mentioned: boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, phosphorus pentachloride, antimony pentafluoride and complexes or salts thereof. Further, as specific examples of the protonic acid, ester thereof or acid anhydride thereof, there can be mentioned: perchloric acid, trifluoromethanesulfonic acid, tert-butyl perchlorate, acetyl perchlorate and trimethyloxyA hexafluorophosphate salt. Among them, boron trifluoride hydrate, and a coordination complex of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable, and specifically, boron trifluoride diethyl ether and boron trifluoride di-n-butyl ether are preferable examples.

In addition, when the polyacetal copolymer is obtained, a polymerization chain agent (chain transfer agent) such as methylal may be suitably used in addition to the polymerization catalyst. When methylal is further used, methylal having a water content of 100 mass ppm or less and a methanol content of 1 mass% or less is preferable, and methylal having a water content of 50 mass ppm or less and a methanol content of 0.7 mass% or less is more preferable.

The polyacetal copolymer can be polymerized by a conventionally known method, for example, U.S. Pat. No. 3027352The methods described in the specification, U.S. Pat. No. 3803094, German patent invention No. 1161421, German patent invention No. 1495228, German patent invention No. 1720358, German patent invention No. 3018898, Japanese patent application laid-open No. Sho 58-98322, and Japanese patent application laid-open No. Hei 7-70267. The polyacetal copolymer obtained by the above polymerization has a thermally unstable terminal part (- (OCH)₂)_n-OH groups; hereinafter referred to as "unstable terminal part"), and thus it is difficult to supply it as it is for practical use. Therefore, it is preferable to perform the decomposition and removal treatment of the unstable terminal portion, specifically, the decomposition and removal treatment of a specific unstable terminal portion as described below. That is, in the treatment for removing the specific unstable terminal part from the polyacetal, the polyacetal copolymer is subjected to a heating treatment in a molten state in the presence of at least one quaternary ammonium compound represented by the following general formula (1) at a temperature of not lower than the melting point of the polyacetal copolymer but not higher than 260 ℃.

[R¹R²R³R⁴N⁺]_nX^n－(1)

In the formula (1), R is¹、R²、R³And R⁴Each independently represents 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 an alkylaryl group in which at least one hydrogen atom in an aryl group having 6 to 20 carbon atoms is substituted with a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms, wherein the substituted or unsubstituted alkyl group is a straight chain, branched chain or cyclic group. The substituent in the substituted alkyl group is preferably a halogen atom, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group or an amide group. In addition, in the above unsubstituted alkyl, aryl, aralkyl and alkylaryl groups, a hydrogen atom may be substituted with a halogen atom.

n represents an integer of 1 to 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 a hydrogen halide, an oxo acid, an inorganic thio acid or an organic thio acid having 1 to 20 carbon atoms.

The quaternary ammonium compound is not particularly limited as long as it is represented by the above general formula (1), and from the viewpoint of more effectively and reliably exhibiting the above effects, R in the general formula (1) is preferable¹、R²、R³And R⁴Each independently is an alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 4 carbon atoms. Specifically, there may be mentioned: hydroxides such as tetramethylammonium, tetraethylammonium, tetrapropylammonium, tetra-n-butylammonium, hexadecyltrimethylammonium, and tetradecyltrimethylammonium; hydrochlorides such as hydrochloride, hydrobromide and hydrofluoride of ammonium; oxygen-containing acid salts such as sulfates, nitrates, phosphates, carbonates, borates, chlorates, iodates, silicates, perchlorates, chlorites, hypochlorites, chlorosulfonates, aminosulfates, pyrosulfates, and tripolyphosphates of ammonium; thiosulfate salts such as thiosulfate salts of ammonium; and carboxylates such as formate, acetate, propionate, butyrate, isobutyrate, valerate, hexanoate, octanoate, decanoate, benzoate and oxalate of these ammonium salts. Among them, ammonium hydroxide (OH) is preferred^-) And Sulfate (HSO)₄ ^-、SO₄ ^2-) Carbonate (HCO)₃ ^-、CO₃ ^2-) Borate (B (OH)₄ ^-) And a carboxylate. Among the carboxylic acids, formic acid, acetic acid and propionic acid are particularly preferable. The quaternary ammonium compounds may be used singly or in combination of two or more. In addition to the quaternary ammonium compounds, amines such as ammonia and triethylamine, which are known as a decomposition accelerator for unstable terminal portions, may be used in combination.

The amount of the quaternary ammonium compound used is preferably 0.05 to 50 mass ppm, more preferably 1 to 30 mass ppm, in terms of the amount of nitrogen derived from the quaternary ammonium compound represented by the following formula (2), relative to the total mass of the polyacetal copolymer and the quaternary ammonium compound.

P×14/Q(2)

In the formula (2), P represents the concentration (mass ppm) of the quaternary ammonium compound relative to the polyacetal copolymer, 14 represents the atomic weight of nitrogen, and Q represents 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 lowering of the decomposition removal rate of the unstable terminal portion is easily suppressed, and when the amount of the quaternary ammonium compound used is 50 mass ppm or less, the deterioration of the color tone of the polyacetal copolymer after the decomposition removal of the unstable terminal portion is easily suppressed.

It is preferable that the unstable terminal part of the polyacetal resin (A) is decomposed and removed when the polyacetal copolymer is heat-treated in a molten state at a temperature of not less than the melting point and not more than 260 ℃. The apparatus used for the decomposition and removal treatment is not particularly limited, and an extruder, a kneader, or the like is preferable. The formaldehyde generated by the decomposition is usually removed under reduced pressure. The method for allowing the quaternary ammonium compound to exist in the polyacetal copolymer is not particularly limited, and examples thereof include: a method of adding the polyacetal copolymer as an aqueous solution in the step of deactivating the polymerization catalyst, and a method of blowing the polyacetal copolymer powder produced by the polymerization. In any of the methods, the quaternary ammonium compound may be present in the polyacetal copolymer in the step of heating the copolymer. For example, the quaternary ammonium compound may be injected into an extruder that melt-kneads and extrudes the polyacetal copolymer. Alternatively, when the polyacetal copolymer is blended with the filler or the pigment using the extruder or the like, the quaternary ammonium compound may be added to the resin particles containing the polyacetal copolymer first, and then the decomposition and removal treatment of the unstable terminal portion may be performed when the filler or the pigment is blended.

The decomposition removal treatment of the unstable terminal portion may be performed after the deactivation of the polymerization catalyst coexisting with the polyacetal copolymer obtained by polymerization, or may be performed without the deactivation of the polymerization catalyst. Examples of the deactivation treatment of the polymerization catalyst include: a method of neutralizing and deactivating a polymerization catalyst in an aqueous alkaline solution such as an amine (e.g., triethylamine). In the case where the deactivation of the polymerization catalyst is not performed, it is also an effective method to heat the polyacetal copolymer at a temperature not higher than the melting point thereof in an inert gas atmosphere to volatilize the copolymer and thereby reduce the polymerization catalyst, and then to perform the decomposition removal operation of the unstable terminal portion.

By the above-mentioned decomposition and removal treatment of the unstable terminal portion, a polyacetal copolymer having very excellent thermal stability substantially free of the unstable terminal portion can be obtained.

(A) The melt flow rate (hereinafter also referred to as "MFR") of the polyacetal resin is preferably 0.1g/10 min to 100g/10 min, more preferably 1g/10 min to 80g/10 min, still more preferably 5g/10 min to 80g/10 min, and still more preferably 15g/10 min to 80g/10 min.

The melt flow rate is a value measured at 190 ℃ in accordance with ISO 1131-1:2011(JIS K7210-1:2014) using a load of 2.16 kg.

(B) an inorganic antibacterial agent containing at least one element selected from the group consisting of silver, copper and zinc and/or an ion of the element)

As the inorganic antibacterial agent (B) containing at least one element selected from the group consisting of silver, copper and zinc and/or an ion of the element, known antibacterial agents can be used without limitation, and examples thereof include: particles of the above metal, inorganic salts, oxides, inorganic compounds supporting the above metal, and the like. Among them, from the viewpoint of more excellent antibacterial properties, it is preferable to use an inorganic compound carrying the metal. As the inorganic compound supporting the metal, there can be used: glass such as zeolite, phosphate glass, and silicate glass, talc, silica gel, silicate, phosphate, zirconium phosphate, titanium oxide, diatomaceous earth, and alumina. Two or more metals may be supported on one inorganic compound, like zeolite supporting silver and copper and aluminosilicate supporting silver and zinc. From the viewpoint of more excellent antibacterial properties and persistence thereof, the inorganic compound supporting the metal is preferably glass, zeolite, or zirconium phosphate, more preferably glass or zeolite, and even more preferably phosphate glass. In addition, from the viewpoint of more excellent thermal stability and antibacterial property, silver and zinc are preferable, and silver is more preferable as the element and/or the ion of the element contained. The content of the metal in the inorganic compound as the inorganic antibacterial agent is preferably 0.01 to 20 mass%, more preferably 0.1 to 10 mass%, and still more preferably 0.5 to 5 mass% in terms of atom, relative to 100 mass% of the inorganic compound.

The average particle diameter of the inorganic compound as the inorganic antibacterial agent (B) is preferably 1 to 10 μm, more preferably 1 to 5 μm, and still more preferably 2 to 4 μm.

The inorganic antibacterial agent (B) may be an inorganic compound having a specific composition, or two or more inorganic compounds may be used in combination.

The content of the inorganic antibacterial agent (B) is 0.01 to 5 parts by mass with respect to 100 parts by mass of the polyacetal resin (a), and the lower limit is preferably 0.03 part by mass, more preferably 0.05 part by mass, and particularly preferably 0.07 part by mass. The upper limit is preferably 3 parts by mass, more preferably 1.1 parts by mass, still more preferably 1 part by mass, yet more preferably 0.6 parts by mass, and particularly preferably 0.5 parts by mass. (B) When the content of the inorganic antibacterial agent is less than 0.01 part by mass, the antibacterial performance is insufficient, and when the content of the inorganic antibacterial agent is more than 5 parts by mass, the thermal stability of the resin composition is lowered.

((C) polyester resin)

(C) The polyester resin is a polymer obtained by bonding one or more monomers through an ester group. As the (C) polyester resin, a polyester obtained by subjecting a monomer having a carboxylic acid group and a monomer having an alcohol group to dehydration condensation (polycondensation) or a polyester obtained by subjecting a monomer having a carboxylic acid group and a monomer having an epoxy group to ring-opening polymerization can be used. Examples of the combination of monomers include: a combination of polycondensing a dicarboxylic acid (polycarboxylic acid) and a diol (polyol), a combination of polycondensing a hydroxycarboxylic acid having a carboxyl group and an alcohol group, and the like. In addition, there can be enumerated: a combination of ring-opening polymerization of a dicarboxylic acid (polycarboxylic acid) and a diepoxy compound (polyepoxy compound), and a combination of ring-opening polymerization of a monomer having a carboxyl group and an epoxy group. Typical monomer compositions are described below.

(1) Polycarboxylic acid: dicarboxylic acids and anhydrides such as phthalic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, sebacic acid, azelaic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, endomethylenetetrahydrophthalic anhydride, chlorendic acid, tetrabromophthalic anhydride, maleic acid, maleic anhydride, fumaric acid, citraconic acid, mesaconic acid, itaconic acid, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride, and glutaric acid.

(2) A dihydric alcohol: glycols such as ethylene glycol, 1, 3-propanediol, 1, 4-butanediol, 1, 5-pentanediol, 1, 6-hexanediol, 1, 2-propanediol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol, 1, 3-butanediol, hydrogenated bisphenol a, bisphenol a propylene oxide adduct, cyclohexanedimethanol, dibromoneopentyl glycol, and the like.

(3) Hydroxycarboxylic acid: lactic acid, tartaric acid, malic acid, and the like have a carboxyl group and a hydroxyl group in one molecule.

(4) Epoxy compound (c): epoxy compounds synthesized from bisphenol a and epichlorohydrin, epoxy compounds synthesized from ethylene glycol and epichlorohydrin, and epoxy compounds such as 3 ', 4 ' -epoxy-6 ' -methylcyclohexanecarboxylic acid 3, 4-epoxy-6-methylcyclohexylmethyl ester.

(C) The polyester resin is preferably a polyester resin obtained by polycondensation of one or two or more of the above (1) polycarboxylic acids and one or two or more of the above (2) diols as acid components. More preferably a polyester resin obtained by polycondensation of maleic acid or fumaric acid with a bisphenol A propylene oxide adduct. Further preferred is a polyester resin obtained by polycondensation of fumaric acid with a bisphenol a propylene oxide adduct.

(C) The polyester resin may contain a vinyl monomer (styrene, methacrylic acid, methyl methacrylate, acrylamide, acrylic acid, divinylbenzene, etc.) as a crosslinking agent contained in a general unsaturated polyester, and an accelerator for accelerating crosslinking (for example, a vanadium metal salt, a manganese-based accelerator, a tertiary amine-based accelerator, a cobalt-based accelerator).

In order to facilitate the treatment of the (C) polyester resin, an aromatic solvent such as benzene, toluene, xylene, or alkylbenzene, a ketone solvent such as acetone or methyl ethyl ketone, or an ester compound such as butyl benzyl phthalate or dibutyl phthalate may be used as the solvent used together with the (C) polyester resin.

The (C) polyester resin is preferably an unsaturated polyester, from the viewpoint of further excellent thermal stability and antibacterial property. The unsaturated polyester includes, for example, an unsaturated polybasic acid such as maleic acid, maleic anhydride, fumaric acid, itaconic anhydride, mesaconic acid, citraconic acid, or citraconic anhydride as one component, and is obtained by esterification with a polyhydric alcohol such as ethylene glycol and its polymer, propylene glycol and its polymer, diethylene glycol, dipropylene glycol, or bisphenol.

(C) The weight average molecular weight of the polyester resin is preferably 10000 to 100000, and more preferably 10000 to 50000. The softening point is preferably 80 ℃ or higher, more preferably 90 ℃ or higher.

The weight average molecular weight is a value measured by Gel Permeation Chromatography (GPC).

The content of the polyester resin (C) is 0.01 to 5 parts by mass with respect to 100 parts by mass of the polyacetal resin (a), and the lower limit is preferably 0.03 part by mass, more preferably 0.05 part by mass, still more preferably 0.10 part by mass, and particularly preferably 0.15 part by mass. The upper limit is preferably 3 parts by mass, more preferably 1 part by mass, still more preferably 0.5 part by mass, yet more preferably 0.41 part by mass, and particularly preferably 0.25 part by mass. (C) When the content of the polyester resin is less than 0.01 part by mass, thermal stability cannot be obtained, and when the content of the polyester resin is more than 5 parts by mass, mechanical properties are deteriorated.

In the polyacetal resin composition of the present embodiment, the content (mass ratio) of the polyester resin (C) is preferably such that Y.gtoreq.2X +0.35 is satisfied, more preferably Y.gtoreq.2X +0.4, when the mass ratio of the inorganic antibacterial agent (B) to the polyacetal resin (A) is X parts by mass and the mass ratio of the polyester resin (C) to the polyacetal resin (A) is Y parts by mass, based on 100 parts by mass of the polyacetal resin (A). (C) When the content of the polyester resin satisfies the above range, (C) the polyester resin contributes to the action of (B) the inorganic antibacterial agent, and the antibacterial property of the composition is improved.

In the polyacetal resin composition of the present embodiment, the content (mass ratio) of the (C) polyester resin preferably satisfies Y.gtoreq.0.5X-0.1, more preferably satisfies Y.gtoreq.0.5X-0.05. (C) When the content of the polyester resin satisfies the above range, thermal stability during injection molding is improved, and the amount of gas generated due to decomposition of the resin can be suppressed.

(other Components)

The resin composition of the present embodiment may contain, as components other than the polyacetal resin (a), the polyacetal resin (B), the inorganic antibacterial agent (C), and the polyester resin (C), various resins and additives which may be conventionally added to polyacetal resin compositions. Specifically, for example, there may be mentioned: heat stabilizers, antioxidants, weather (light) -resistant stabilizers, mold release agents, colorants (including color concentrates) such as pigments and dyes, lubricants, fluorescent bleaches, plasticizers, antistatic agents, flow improvers, inorganic fillers, reinforcing agents, extenders, rubbers, reinforcing agents, and other polymers, and these components may be added within a range not impairing the object of the present invention.

Examples of the heat stabilizer include nitrogen compounds. Examples thereof include a polymer reactive nitrogen compound and a non-polymer reactive nitrogen compound. Examples of the polymer reactive nitrogen compound include polyamide resins having an amide bond in the molecular structure. Specific examples thereof include: polyamide 4,6, polyamide 6,10, polyamide 6,12, polyamide 12, and copolymers of monomer components constituting them. Examples of the non-polymer reactive nitrogen compound include: guanamine compounds, melamine, hydrazide compounds, reaction products thereof with formaldehyde, and the like.

Examples of the guanamine compound include: aliphatic guanamine compounds, alicyclic guanamine compounds, aromatic guanamine compounds and guanamine compounds containing hetero atoms.

Examples of the aliphatic guanamine compounds include: monoguanamines such as butylguanamine, pentylguanamine, hexylguanamine, heptylguanamine, and heptadecyguanamine; alkylene biguanides such as ethylene biguanide, propylene biguanide, butylene biguanide, pentylene biguanide, hexylene biguanide, heptylene biguanide and octylene biguanide; and the like.

Examples of the alicyclic guanamine compounds include: monoguanamines such as cyclohexylguanamine, norbornenylguanamine, cyclohexenylguanamine and norbornanylguanamine; and derivatives in which the cycloalkyl residue is substituted with 1 to 3 functional groups selected from the group consisting of alkyl, hydroxyl, amino, acetylamino, nitrile, carboxyl, alkoxycarbonyl, carbamoyl, alkoxy, phenyl, cumyl and hydroxyphenyl groups.

Examples of the aromatic guanamine compound include: phenyl guanamine, derivatives of phenyl guanamine in which a phenyl residue of phenyl guanamine is substituted with 1 to 5 functional groups, for example, one or more functional groups selected from the group consisting of alkyl groups, hydroxyl groups, amino groups, acetylamino groups, nitrile groups, carboxyl groups, alkoxycarbonyl groups, carbamoyl groups, alkoxy groups, phenyl groups, cumyl groups, and hydroxyphenyl groups (for example, tolylguanamine, ditolyl guanamine, phenyl guanamine, hydroxyphenyl guanamine, 4- (4' -hydroxyphenyl) phenyl guanamine, cyanophenyl guanamine, 3, 5-dimethyl-4-hydroxyphenyl guanamine, and 3, 5-di-t-butyl-4-hydroxyphenyl guanamine), naphthyl guanamine, and monoguanamines in which a naphthyl residue of naphthyl guanamine is substituted with 1 to 7 functional groups, for example, derivatives of the functional groups; polyguanamines such as o-phenylendiguanamine, m-phenylendiguanamine, p-phenylendiguanamine, naphthalene biguanamine, and biphenyl biguanamine; aralkyl or aralkylene guanamines such as benzyl guanamine, β -phenethylguanamine and xylylene biguanideamine; and the like.

Examples of the guanamine compound containing a hetero atom include: guanamines containing an acetal group such as 2, 4-diamino-6- (3, 3-dimethoxypropyl) s-triazine; guanamines having a dioxane ring such as [2- (4 ', 6' -diamino-s-triazin-2 '-yl) ethyl ] -1, 3-dioxane and [2- (4', 6 '-diamino-s-triazin-2' -yl) ethyl ] -4-ethyl-4-hydroxymethyl-1, 3-dioxane; guanamines containing tetraoxaspiro such as CTU-guanamine and CMTU-guanamine; and isocyanuric ring-containing guanidines such as 1,3, 5-tris [2- (4 ', 6' -diaminos-triazin-2 '-yl) ethyl ] isocyanurate and 1,3, 5-tris [3- (4', 6 '-diaminos-triazin-2' -yl) propyl ] isocyanurate.

Examples of the hydrazide compound include: aliphatic or alicyclic carboxylic acid hydrazides and aromatic carboxylic acid hydrazides.

Examples of the aliphatic carboxylic acid hydrazide or the alicyclic carboxylic acid hydrazide include: saturated or unsaturated fatty acid hydrazides such as lauric acid hydrazide, palmitic acid hydrazide, stearic acid hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecane diacid dihydrazide, eicosane diacid dihydrazide and sorbic acid hydrazide; hydroxy fatty acid hydrazides such as α -hydroxybutyric acid hydrazide and glyceric acid hydrazide; 7, 11-octadecadien-1, 18-diformylhydrazine, 1, 3-bis (hydrazinocarbonylethyl) -5-isopropylhydantoin) and tris (hydrazinocarbonylethyl) isocyanurate; and the like.

Examples of the aromatic carboxylic acid hydrazide include: 1-naphthoic acid hydrazide, 2-naphthoic acid hydrazide, phthalic acid dihydrazide, isophthalic acid dihydrazide, terephthalic acid dihydrazide, 2, 6-naphthoic acid dihydrazide, and the like.

Among these non-polymer reactive nitrogen compounds, one or more selected from the group consisting of melamine, benzoguanamine, stearic acid hydrazide, adipic acid dihydrazide, sebacic acid dihydrazide, dodecane diacid dihydrazide, and reaction products thereof with formaldehyde are preferable, and melamine and reaction products of melamine and formaldehyde are more preferable.

Examples of the heat stabilizer include fatty acid metal salt compounds.

The fatty acid in the fatty acid metal salt compound has a structure in which a carboxyl group is bonded to a hydrocarbon group. Examples thereof include: saturated fatty acids containing only carbon-carbon single bonds (carbon-carbon saturated bonds), unsaturated fatty acids having carbon-carbon double or triple bonds (carbon-carbon unsaturated bonds). Among them, saturated fatty acids having high heat aging resistance are preferable. Specific examples of saturated fatty acids include: dodecanoic acid (lauric acid), tridecanoic acid, tetradecanoic acid (myristic acid), pentadecanoic acid, hexadecanoic acid (palmitic acid), heptadecanoic acid (pearlitic acid), octadecanoic acid (stearic acid), nonadecanoic acid (tuberculostearic acid), eicosanoic acid (arachidic acid), docosanoic acid (behenic acid), tetracosanoic acid (lignoic acid), hexacosanoic acid (cerotic acid), octacosanoic acid (montanic acid), and melissic acid. Among them, fatty acids having 14 to 22 carbon atoms are preferable. Specifically, there may be mentioned: myristic acid (myristic acid), pentadecanoic acid, palmitic acid (palmitic acid), margaric acid (pearlescent acid), stearic acid (stearic acid), nonadecanoic acid (tuberculostearic acid), arachidic acid (arachidic acid), and behenic acid (behenic acid). Further, among them, myristic acid (myristic acid), stearic acid (stearic acid), and behenic acid (behenic acid) are more preferable. As more preferred fatty acids, there may be mentioned: palmitic acid, stearic acid and behenic acid.

In addition, as the metal element forming the salt of the fatty acid metal salt compound, an alkali metal element or an element of the second group of the periodic table is preferable, among which sodium, potassium, magnesium and calcium are more preferable, and calcium is particularly preferable.

Specific examples of the fatty acid metal salt compound include: calcium palmitate, calcium stearate and calcium behenate. These may be used singly or in combination of two or more.

As a preferable antioxidant in the present embodiment, a hindered phenol-based antioxidant can be mentioned. Specific examples of the hindered phenol-based antioxidant include: octadecyl 3- (3 ', 5' -di-tert-butyl-4 '-hydroxyphenyl) propionate, n-octadecyl 3- (3' -methyl-5 '-tert-butyl-4' -hydroxyphenyl) propionate, n-tetradecyl 3- (3 ', 5' -di-tert-butyl-4 '-hydroxyphenyl) propionate, 1, 6-hexanediol bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], 1, 4-butanediol bis [3- (3, 5-di-tert-butyl-4-hydroxyphenyl) propionate ], triethylene glycol bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate ], and pentaerythritol tetrakis [3- (3', 5 '-di-tert-butyl-4' -hydroxyphenyl) propionate ]. Among them, triethylene glycol bis [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) propionate ] and pentaerythritol tetrakis [3- (3 ', 5 ' -di-tert-butyl-4 ' -hydroxyphenyl) propionate ] are more preferable. These antioxidants may be used singly or in combination of two or more.

Preferred weather (light) -resistant stabilizers in the present embodiment include: at least one selected from the group consisting of benzotriazole and oxalic anilide ultraviolet absorbers, and hindered amine light stabilizers.

Specific examples of the benzotriazole-based ultraviolet absorber include: 2- (2 '-hydroxy-5' -methylphenyl) benzotriazole, 2- (2 '-hydroxy-3', 5 '-di-tert-butylphenyl) benzotriazole, 2- [ 2' -hydroxy-3 ', 5' -bis (. alpha.,. alpha. -dimethylbenzyl) phenyl ] -2H-benzotriazole and 2- (2 '-hydroxy-4' -octyloxyphenyl) benzotriazole. These benzotriazole-based ultraviolet absorbers may be used singly or in combination of two or more.

Specific examples of the oxanilide-based ultraviolet absorber include: 2-ethoxy-2 ' -ethyloxanilide, 2-ethoxy-5-tert-butyl-2 ' -ethyloxanilide and 2-ethoxy-3 ' -dodecyloxanilide. These oxalanilide-based ultraviolet absorbers may be used singly or in combination of two or more.

Specific examples of the hindered amine-based light stabilizer include: n, N '-tetrakis {4, 6-bis [ butyl- (N-methyl-2, 2,6, 6-tetramethylpiperidin-4-yl) amino ] -triazin-2-yl } -4, 7-diazepane-1, 10-diamine, dibutylamine-1, 3, 5-triazine-N, N' -bis (2,2,6, 6-tetramethyl-4-piperidinyl-1, 6-hexamethylenediamine and N- (2,2,6, 6-tetramethyl-4-piperidinyl) butylamine, polycondensates of poly [ {6- (1,1,3, 3-tetramethylbutyl) amino-1, 3, 5-triazine-2, 4-diyl } { (2,2,6, 6-tetramethyl-4-piperidyl) imino } hexamethylene { (2,2,6, 6-tetramethyl-4-piperidyl) imino } ], a condensate of dimethyl succinate and 4-hydroxy-2, 2,6, 6-tetramethyl-1-piperidylethanol, a reaction product of bis [2,2,6, 6-tetramethyl-1-octyloxy-4-piperidyl ] sebacate and 1, 1-dimethylethyl hydroperoxide with octane, [ {3, 5-bis (1, 1-dimethylethyl) -4-hydroxyphenyl } methyl ] butylmalonic acid bis (1,2,2,6, 6-pentamethyl-4-piperidyl) ester, sebacic acid methyl ester 1,2,2,6, 6-pentamethyl-4-piperidyl ester, bis (2,2,6, 6-tetramethyl-4-piperidyl) sebacate, bis (N-methyl-2, 2,6, 6-tetramethyl-4-piperidyl) sebacate, and a condensate of 1,2,3, 4-butanetetracarboxylic acid with 1,2,2,6, 6-pentamethyl-4-piperidinol and β, β, β ', β' -tetramethyl-3, 9- [2,4,8, 10-tetraoxaspiro [5.5] undecane ] diethanol, and the like. The hindered amine-based light stabilizer is preferably bis (2,2,6, 6-tetramethyl-4-piperidyl) sebacate, bis (N-methyl-2, 2,6, 6-tetramethyl-4-piperidyl) sebacate, a condensate of 1,2,3, 4-butanetetracarboxylic acid with 1,2,2,6, 6-pentamethyl-4-piperidinol and β, β, β ', β' -tetramethyl-3, 9- [2,4,8, 10-tetraoxaspiro [5.5] undecane ] diethanol. These hindered amine-based light stabilizers may be used singly or in combination of two or more.

Examples of the release agent that can be used in the present embodiment include: alcohols, fatty acids and their fatty acid esters, polyoxyalkylene glycols, and olefin compounds having an average degree of polymerization of 10 to 500. Among them, polyoxyalkylene glycol is preferable.

As the pigment, there can be mentioned: inorganic and organic pigments, metallic pigments and fluorescent pigments. Here, the inorganic pigment is an inorganic pigment for coloring which is generally used as a resin, and examples thereof include: titanium oxide, barium sulfate, titanium yellow, cobalt blue, firing pigments, carbonates, phosphates, acetates, carbon black, acetylene black and lamp black. Examples of the organic pigment include: condensed azo compounds, quinones, phthalocyanines, monoazos, bisazos, polyazos, anthraquinones, heterocycles, violanthrones, quinacridones, thioindigoids, perylenes, and diarylsOxazine and phthalocyanine pigments. In the polyacetal resin composition of the present embodiment, the content of the pigment greatly varies depending on the color tone required, and therefore, it is difficult to clearly define the content, but generally, the content of the pigment is in the range of about 0.005 parts by mass to about 5 parts by mass with respect to 100 parts by mass of the polyacetal resin (a).

Examples of the inorganic filler include fibrous, powdery, plate-like and hollow fillers. Examples of the fibrous filler include: glass fibers, carbon fibers, silicon fibers, silica-alumina fibers, zirconia fibers, boron nitride fibers, silicon nitride fibers, boron fibers, potassium titanate fibers, and inorganic fibers typified by metal fibers such as stainless steel, aluminum, titanium, and brass. Examples of the particulate filler include: silicates such as carbon black, silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, and wollastonite; metal oxides such as iron oxide, titanium oxide, and aluminum oxide; metal sulfates such as calcium sulfate and barium sulfate; carbonates such as magnesium carbonate and dolomite; and silicon carbide, silicon nitride, boron nitride, and various metal powders. Examples of the plate-like filler include: mica, glass flakes and various metal foils. Examples of the hollow filler include: hollow glass microspheres, hollow silica microspheres, hollow pozzolan microspheres, and hollow metal microspheres. Further, as the inorganic filler, whiskers such as potassium titanate whiskers having a short fiber length may be used. The polyacetal resin composition of the present embodiment may contain a high-melting organic fibrous substance such as an aromatic polyamide resin, a fluorine-containing resin, or an acrylic resin.

These fillers may be used singly or in combination of two or more. Any of the surface-treated fillers and non-surface-treated fillers can be used as the filler, and a surface-treated filler is sometimes preferable from the viewpoint of surface smoothness and mechanical properties of the molded article. As the surface treatment agent, conventionally known surface treatment agents can be used. As the surface treatment agent, for example, there can be used: various coupling agents such as silanes, titanates, aluminum, and zirconium. Specifically, there may be mentioned: n- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyl tristearyl titanate, ethyl acetoacetate diisopropoxyaluminum and N-butyl zirconate.

The antibacterial activity of the polyacetal resin composition of the present embodiment measured according to JIS Z2801 is preferably 0.5 or more, more preferably 1.4 or more, even more preferably 2.0 or more, and particularly preferably 2.7 or more, from the viewpoint of further excellent antibacterial properties.

The antibacterial activity can be measured by the method described in the examples described later.

From the viewpoint of more excellent thermal stability, the time taken for the polyacetal resin composition of the present embodiment to stay in the barrel of the molding machine set at 208 ℃ until decomposition of the resin occurs is preferably 3 minutes or longer, more preferably 5 minutes or longer, still more preferably 15 minutes or longer, and particularly preferably 30 minutes or longer.

The residence time can be measured by the method described in the examples described below.

The tensile strength of the polyacetal resin composition of the present embodiment measured according to ISO-527-1 is preferably 55MPa or more, and more preferably 60MPa or more, from the viewpoint of further excellent mechanical strength.

The tensile strength can be measured by the method described in the examples described later.

The flexural modulus of the polyacetal resin composition of the present embodiment measured according to ISO-178 is preferably 2.0GPa or more, and more preferably 2.5GPa or more, from the viewpoint of further excellent mechanical strength.

The flexural modulus can be measured by the method described in the examples described below.

(production method)

In the production of the polyacetal resin composition of the present embodiment, the polyacetal resin and the above-mentioned components to be added may be mixed by a known melt-mixing method, and the melt-mixing method is not limited at all. The melt mixing temperature is preferably 180 to 240 ℃, and within this range, the resin can be sufficiently melted and mixed without causing decomposition of the molten resin.

As an apparatus that can be used for producing the polyacetal resin composition, for example, a commonly used kneader can be used. Examples of such a device include: single or multiple screw mixing extruders, rolls and banbury mixers. From the viewpoint of ease of processing and productivity, it is more preferable to use a single-screw kneading extruder or a multi-screw kneading extruder. Among them, a twin-screw extruder is particularly preferably used.

As the extruder, a twin-screw extruder having an L/D (screw length/screw diameter) of 40 or more and having one or more supply ports in addition to the upstream side supply port (top feed port) is more preferably used.

In addition, in view of productivity, the screw diameter of the extruder is preferably 40mm or more from the viewpoints of mass productivity and feed stability.

When an extruder having a supply port in addition to the upstream side is used, the raw materials may be separately supplied to the extruder. Examples of combinations thereof include: a method of supplying the polyacetal resin from the upstream side supply port and supplying all the remaining components (e.g., the antibacterial agent, the polyester, and the pigment) from the supply ports other than the upstream side; a method in which the polyacetal resin and a part or all of the other desired components are supplied from the upstream side supply port, and the remaining components are supplied from the supply ports other than the upstream side supply port. Of course, the method of supplying the raw material is not particularly limited as long as it is a known method.

Even when an extruder having only an upstream side supply port is used, it is preferable to prepare a mixture obtained by mixing components other than the polyacetal resin in advance and then supply the mixture to the extruder by a supply machine different from the supply machine for supplying the polyacetal resin, from the viewpoint of suppressing the composition fluctuation of the resin composition.

When the resin composition of the present embodiment is processed by an extruder or the like, it is preferable to remove unnecessary volatile components by adjusting a part of the inside of the cylinder to a reduced pressure atmosphere during processing. The degree of pressure reduction at this time is not particularly limited, but is preferably set to 0.06MPa or more.

The polyacetal resin composition of the present embodiment can be prepared as resin pellets.

The resin pellets are generally obtained by processing using the above-mentioned extruder. The shape of the pellets is not particularly limited, but when the pellets are extruded into a strand shape and then granulated, cylindrical pellets are obtained, and pellets obtained by a hot cutting method, an underwater cutting method, or the like are spherical pellets. The size of the particles is not particularly limited, and the upper limit of the particle diameter of the particles is preferably 3 mm. A preferred lower limit is 1 mm. Regarding the size of the cylindrical particles, the preferable upper limit is 3mm in diameter and 4mm in length, and the preferable lower limit is 1mm in diameter and 2mm in length. The upper limit is preferably the above size from the viewpoint of the seizure property at the time of subsequent molding, and the lower limit is preferably the above size in order to prevent clogging and the like at the time of pneumatic conveyance of the pellets.

(molded body)

The molded article of the present embodiment may contain the polyacetal resin composition, or may be formed only from the polyacetal resin composition.

The shape of the molded article of the present embodiment is not particularly limited, and may include any shape. Examples of the molded article of the present embodiment include: an article including the resin composition of the present embodiment is obtained by extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decoration molding, heterogeneous material molding, gas-assisted injection molding, foam injection molding, low-pressure molding, ultra-thin wall injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, insert-on molding), or the like.

The molded article includes, for example, a fiber, a sheet, a film, a profile extrusion, and the like, in addition to a general injection molded article. The molded article can be used as a member, and specific examples thereof include: mechanism components typified by gears (gears), cams, sliders, levers, arms, clutches, felt clutches, idlers, pulleys, rollers, drums, key levers, key tops, shutters, reels, handles, joints, shafts, bearings, guide rails, and the like; a resin part molded on the insert, a resin part molded by the insert, a chassis, a tray and a side plate; a member for office automation equipment represented by a printer and a copying machine; a component for a camera or video device represented by VTR, video camera, digital video camera, still camera, and digital still camera; the optical disk device includes a cassette player, DAT, LD, MD, CD [ including CD-ROM, CD-R, CD-RW ], DVD [ including DVD-ROM, DVD-R, DVD + R, DVD-RW, DVD + RW, DVD-R DL, DVD + R DL, DVD-RAM, DVD-Audio ], Blu-ray disk, HD-DVD, other optical disk drives, MFD, MO, navigation system, and mobile personal computer, a communication device component represented by a mobile phone and a facsimile machine, an electrical device component, and an electronic device component.

The molded article can also be used as an automobile part or the like, and examples thereof include: fuel peripheral parts represented by fuel tanks, fuel pump assemblies, valves, fuel tank flanges, and the like; door peripheral components typified by door locks, door handles, window regulators, speaker grilles, and the like; seat belt peripheral components typified by seat belt slip rings, push buttons, and the like; a combination switch component; and (4) switches. In addition, the present invention can be suitably used as clip-like members, as well as mechanical members for inserting and removing a tip of a mechanical pencil and a lead of a mechanical pencil, members for opening and closing a toilet seat and a drainage port and a drainage plug, cord fasteners for clothing, regulators and buttons, construction articles as a nozzle for sprinkling and a connection joint of a sprinkling hose, a stair handrail and a support member for flooring, disposable cameras, toys, fasteners, chains, conveyor belts, buckles, sporting goods, vending machines (for example, an opening and closing mechanism and a commodity discharging mechanism of a vending machine), furniture, musical instruments, and industrial members for machines typified by home equipment machines. In particular, the above-mentioned members are suitable for use in the medical, food or food fields or their surroundings.

The embodiments for carrying out the present invention have been described above, but the present invention is not limited to the above embodiments. The present invention can be variously modified within a range not departing from the gist thereof.