JP2016094577A - Polyacetal resin composition and molded body thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal resin composition excellent in conductivity, toughness and dimensional accuracy and capable of maintaining excellent toughness for a long time.SOLUTION: There is provided the polyacetal resin composition which contains at least a polyacetal resin (A), carbon black (B), an olefin resin (C) and an ester compound (D) and in which the carbon black (B) is contained in an amount of 5 pts.mass to 30 pts.mass based on 100 pts.mass of the polyacetal resin (A), a dibutyl phthalate oil absorption amount of the carbon black (B) is 100 mL/100 g to 300 mL/100 g, a BET specific surface area of the carbon black (B)by iodine adsorption method is 20 m/g to 100 m/g, volume resistivity measured according to JIS K7194 is 10Ωcm to 10Ωcm and nominal tensile stress at break measured according to ISO527-1 is 15% or more.SELECTED DRAWING: None

Description

  The present invention relates to a polyacetal resin composition and a molded body thereof.

  Polyacetal resin has a good balance of mechanical strength, chemical resistance and slidability, and is easy to process. Therefore, as a typical engineering plastic, mechanical parts including electrical equipment, automobile parts and other precision machines can be used. Widely used in the center. However, since the polyacetal resin itself is an electrical insulator, it is inferior in the performance of removing static electricity generated during sliding and the conductivity, and is difficult to be used especially for applications that require high conductivity.

  For example, a proposal has been made on a polyacetal resin composition in which conductivity is imparted to a polyacetal resin, which is an electrical insulator, by carbon black or other conductive filler (see, for example, Patent Document 1). Further, as a technique for obtaining a conductive polyacetal resin with improved conductivity and toughness, for example, a technique in which a conductive carbon black and a polyurethane elastomer are combined with a polyacetal resin has been proposed (see, for example, Patent Documents 1 and 2). .

Japanese Patent Publication No. 06-51822 Special table 2001-503559 gazette

  However, the polyacetal resin composition imparted with conductivity by carbon black or other conductive fillers has a problem that the toughness inherent to the polyacetal resin is significantly reduced and the application range is limited. In addition, the technology combining conductive carbon black and polyurethane elastomer with polyacetal resin has problems with deterioration over time and dimensional stability.

  Furthermore, in recent years, for the purpose of weight reduction and cost reduction, resin conversion of metal parts is rapidly progressing in various fields such as automobiles and electric and electronic devices. These resin parts are required to have conductivity equivalent to that of metal, toughness that does not break even when deformed, long-term maintenance of the toughness, and high dimensional accuracy.

  Then, an object of this invention is to provide the polyacetal resin composition which is excellent in electroconductivity, toughness, and dimensional accuracy, and can hold | maintain the outstanding toughness for a long period of time.

  As a result of intensive studies to solve the above-described problems of the prior art, the present inventors have found that a resin composition containing at least a polyacetal resin, a specific range of specific carbon black, a polyolefin resin, and an ester compound. And found that a polyacetal resin composition in which values of volume resistivity and tensile fracture nominal strain measured by a specific method are within a specific range can solve the above-mentioned problems of the prior art, and has led to the completion of the present invention. .

That is, this embodiment is as follows.
[1] At least a polyacetal resin (A), carbon black (B), an olefin resin (C), and an ester compound (D),
Carbon black (B) 5 mass part or more and 30 mass parts or less are included with respect to 100 mass parts of polyacetal resin (A),
Carbon black (B) has a dibutyl phthalate oil absorption of 100 mL / 100 g or more and 300 mL / 100 g or less,
The BET specific surface area by the iodine adsorption method of carbon black (B) is 20 m ² / g or more and 100 m ² / g or less,
The volume resistivity measured according to JIS K7194 is 10 ⁰ Ωcm or more and 10 ² Ωcm or less,
The polyacetal resin composition whose tensile fracture nominal strain measured based on ISO527-1 is 15% or more.
[2] The polyacetal resin composition according to [1], wherein a tensile fracture nominal strain measured according to ISO 527-1 is 20% or more.
[3] The polyacetal resin composition according to [1] or [2], wherein the polyacetal resin (A) has a number average molecular weight of 50,000 to 150,000.
[4] The polyacetal resin composition according to any one of [1] to [3], wherein the ester compound (D) is an aliphatic diester and / or an aliphatic triester.
[5] The polyacetal resin according to any one of [1] to [4], further including 0.1 to 5 parts by mass of the epoxy compound (E) with respect to 100 parts by mass of the polyacetal resin (A). Composition.
[6] A molded article comprising the polyacetal resin composition according to any one of [1] to [5].

  According to the resin composition of this invention, it is excellent in electroconductivity, toughness, and dimensional accuracy, and can hold | maintain the outstanding toughness for a long period of time.

It is a block diagram which shows a twin-screw extruder typically.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. The following embodiment is an example for explaining the present invention, and the present invention is not limited to the following contents. The present invention can be implemented with various changes within the scope of the gist.

[Polyacetal resin composition]
The polyacetal resin composition of the present embodiment includes at least a polyacetal resin (A), carbon black (B), a polyolefin compound (C), and an ester compound (D), and carbon is contained in 100 parts by mass of the polyacetal resin (A). BET containing 5 parts by mass or more and 30 parts by mass or less of black (B), wherein carbon black (B) has a dibutyl phthalate oil absorption of 100 mL / 100 g or more and 300 mL / 100 g or less, and BET by an iodine adsorption method of carbon black (B) The specific surface area is 20 m ² / g or more and 100 m ² / g or less, the volume resistivity measured according to JIS K7194 is 10 ⁰ Ωcm or more and 10 ² Ωcm or less, and the tensile measured according to ISO527-1. The nominal fracture strain is 15% or more.

<Polyacetal resin (A)>
In the present embodiment, examples of the polyacetal resin (A) include polyacetal homopolymers and polyacetal copolymers. Specific examples of polyacetal homopolymers include polymers obtained by homopolymerizing formaldehyde monomers or cyclic oligomers of formaldehyde such as trimers (trioxane) or tetramers (tetraoxane). Thus, the polyacetal homopolymer consists essentially of oxymethylene units.

  Specific examples of polyacetal copolymers are those obtained by copolymerizing formaldehyde monomers or cyclic oligomers of formaldehyde such as trimers (trioxane) or tetramers (tetraoxane) with cyclic ethers, etc. Is mentioned. Specific examples of cyclic ethers include 1,3-dioxolane and 1,4-butanediol formal, which are cyclic formals such as ethylene oxide, propylene oxide, epichlorohydrin, and glycol; cyclic ethers that are cyclic formals of diglycol, and the like; Other examples include cyclic formal. Each of the cyclic oligomer and the cyclic ether may be used alone or in combination of two or more.

  As polyacetal copolymers, branched polyacetal copolymers obtained by copolymerizing formaldehyde monomers and / or cyclic oligomers of formaldehyde with monofunctional glycidyl ethers, and polyfunctional glycidyl ethers are copolymerized. Also included are polyacetal copolymers having a cross-linked structure obtained by the treatment.

  The polyacetal resin (A) is a compound having a functional group such as a hydroxyl group at both ends or one end, in the presence of polyalkylene glycol, a monomer of formaldehyde, a trimer (trioxane) or a tetramer (tetraoxane). Examples thereof include polyacetal homopolymers or polyacetal copolymers having a block component obtained by copolymerizing a cyclic oligomer of formaldehyde and a cyclic ether.

  As described above, as the polyacetal resin (A) contained in the polyacetal resin composition of the present embodiment, the polyacetal homopolymer and the polyacetal copolymer may be used singly or in combination of two or more. Good.

  The number average molecular weight of the polyacetal resin (A) used in the present embodiment is preferably 50,000 or more and 150,000 or less, more preferably 55,000 or more and 120,000 or less, from the viewpoint of keeping high tensile fracture nominal strain. The number average molecular weight of the polyacetal resin (A) is determined by gel permeation chromatography (GPC).

  As a method for obtaining the polyacetal resin (A) having a number average molecular weight within the above range, specifically, in the production of the polyacetal resin (A), the addition amount of a chain transfer agent represented by methylal or the like is adjusted. Etc.

  When the polyacetal copolymer of the present embodiment is obtained using a trimer of formaldehyde (trioxane), the cyclic ether is preferably 0.1 mol% or more and 60 mol% or less with respect to 100 mol% of trioxane. Preferably they are 0.1 mol% or more and 20 mol% or less, More preferably, they are 0.13 mol% or more and 10 mol% or less. Further, when the polyacetal copolymer is obtained using a tetramer of formaldehyde (tetraoxane), the amount of the cyclic ether added is preferably 0.13 mol% or more and 90 mol% or less with respect to 100 mol% of tetraoxane. More preferably, it is 0.13 mol% or more and 30 mol% or less, and further preferably 0.16 mol% or more and 13 mol% or less.

  In the present embodiment, the melting point of the polyacetal copolymer is preferably 162 ° C. or higher and 173 ° C. or lower, more preferably 162 ° C. or higher and 167 ° C. or lower, from the viewpoint of thermal stability or the like. For example, a polyacetal copolymer having a melting point of 162 ° C. or more and 167 ° C. or less is obtained by using the above cyclic ether of 3.0 mol or more and 6.0 mol% or less with respect to 100 mol% of formaldehyde trimer (trioxane). Can do. In the present embodiment, the melting point of the polyacetal resin (A) is measured by a differential scanning calorimeter (DSC).

  The polyacetal copolymer is a copolymer of formaldehyde monomer or a cyclic oligomer of formaldehyde such as trimer (trioxane) or tetramer (tetraoxane) and the above cyclic ether, using a predetermined polymerization catalyst. Can be manufactured.

  As the polymerization catalyst used for the polymerization of the polyacetal copolymer, cationically active catalysts such as Lewis acids, proton acids and esters or anhydrides thereof are preferable.

  Specific examples of Lewis acids include boric acid, tin, titanium, phosphorus, arsenic, and antimony halides. More specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, and pentafluoride. Examples thereof include phosphorus, phosphorus pentachloride, antimony pentafluoride, and complex compounds or salts thereof.

  Specific examples of the protonic acid and its ester or anhydride include perchloric acid, trifluoromethanesulfonic acid, perchloric acid tertiary butyl ester, acetyl perchlorate, trimethyloxonium hexafluorophosphate, and the like.

  Among the polymerization catalysts described above, from the viewpoint of polymerization reaction control, 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 included. Preferable examples include boron trifluoride diethyl ether and boron trifluoride di-n-butyl ether.

  Polyacetal copolymers can be obtained by known methods, for example, U.S. Pat. Nos. 3,027,352, 3,803,094, German Patent Nos. 1,161,421, 1,495,228, and 1,720,358. No. 3018898, JP-A-58-98322, and JP-A-7-70267.

As described above, formaldehyde monomer or a cyclic oligomer of formaldehyde such as trimer (trioxane) or tetramer (tetraoxane) and the cyclic ether are copolymerized using the polymerization catalyst. The polyacetal copolymer thus obtained has a thermally unstable terminal portion (for example, [— (OCH ₂ ) _n —OH group]). In view of this, it is preferable to disassemble and remove unstable terminal portions, and to disassemble and remove specific unstable terminal portions described below.

As a specific method for decomposing the unstable terminal portion, specifically, a temperature of not less than the melting point of the polyacetal copolymer and not more than 260 ° C. in the presence of at least one quaternary ammonium compound represented by the following general formula (1): And a method of subjecting the polyacetal copolymer to a molten state and heat treatment.
[R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ⁻ _n (1)
Here, in formula (1), R ¹ , R ² , R ³ and R ⁴ 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 in an aryl group having 6 to 20 carbon atoms An alkylaryl group in which the hydrogen atom is substituted with a substituted or unsubstituted alkyl group having 1 to 30 carbon atoms. The substituted or unsubstituted alkyl group is linear, branched or cyclic. The substituent in the substituted alkyl group is a halogen atom, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, or an amide group. In the unsubstituted alkyl group, aryl group, aralkyl group, and alkylaryl group, a hydrogen atom may be substituted with a halogen atom. n shows the 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 a hydrogen halide, an oxo acid, 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 a compound represented by the above general formula (1), but R in the general formula (1) is used from the viewpoint of more effectively and surely achieving the above effect according to the present embodiment. ¹ , R ² , R ³ , and R ⁴ are each independently preferably an alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 4 carbon atoms, and R ¹ , R ² , R ³ More preferably, at least one of R ⁴ and R ⁴ is a hydroxyethyl group.

  Specific examples of the quaternary ammonium compound represented by the general formula (1) 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, triethylbenzylammoni , Tripropylbenzylammonium, tri-n-butylbenzylammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, okdadecyltri (2- Hydroxyethyl) ammonium, tetrakis (hydroxyethyl) ammonium, etc .; hydroxides thereof; hydrogenates such as hydrochloric acid, odorous acid, hydrofluoric acid; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodine Oxic acid salts such as acid, silicic acid, perchloric acid, chlorous acid, hypochlorous acid, chlorosulfuric acid, amidosulfuric acid, disulfuric acid and tripolyphosphoric acid; thioic acid salts such as sulfuric acid; these formic acid, acetic acid and propion Acid, butanoic acid, isobutyric acid, pentane , Caproic acid, caprylic acid, capric acid, benzoic acid, carboxylic acid salts such as oxalic acid.

Among these, hydroxide (OH ⁻ ), sulfuric acid (HSO ₄ ⁻ , SO ₄ ²⁻ ), carbonic acid (HCO ₃ ⁻ , CO ₃ ²⁻ ), Boric acid (B (OH) ₄ ⁻ ) and carboxylic acid salts are preferred. Of the carboxylic acids, formic acid, acetic acid, and propionic acid are more preferable.

  A quaternary ammonium compound may be used individually by 1 type, and may be used in combination of 2 or more type. Further, in addition to the quaternary ammonium compound, amines such as ammonia and triethylamine which are known decomposition accelerators for unstable terminals may be used in combination.

The suitable usage-amount of a quaternary ammonium compound is calculated | required by converting into the nitrogen amount derived from the quaternary ammonium compound represented by following formula (2) with respect to the total mass of a polyacetal copolymer and a quaternary ammonium compound. The amount of the quaternary ammonium compound used is preferably 0.05 mass ppm or more and 50 mass ppm or less, more preferably 1 mass ppm or more and 30 mass ppm or less.
P × 14 / Q (2)
Here, in Formula (2), P shows the density | concentration (mass ppm) with respect to the polyacetal copolymer of a quaternary ammonium compound, 14 is the atomic weight of nitrogen, Q shows the molecular weight of a quaternary ammonium compound.

  When the amount of the quaternary ammonium compound used is within the above range, the rate of decomposition and removal of the unstable end portion is improved, and the color tone of the polyacetal copolymer after the decomposition and removal of the unstable end portion tends to be good. .

  The unstable terminal portion of the polyacetal copolymer is decomposed and removed when it is heat-treated at a temperature not lower than the melting point of the polyacetal copolymer and not higher than 260 ° C. while the polyacetal copolymer is melted. Specifically, an extruder, a kneader, etc. are suitable as an apparatus used for this decomposition and removal treatment. Formaldehyde generated by decomposition is removed under reduced pressure.

  When the unstable terminal portion of the polyacetal copolymer is decomposed and removed, a method of adding a quaternary ammonium compound in the polyacetal copolymer, specifically, a method of adding an aqueous solution in the step of deactivating the polymerization catalyst, polymerization And a method of spraying on the polyacetal copolymer powder produced by the above. Whichever method is used, the quaternary ammonium compound may be present in the polyacetal copolymer in the step of heat-treating the polyacetal copolymer. More specifically, a method of injecting a quaternary ammonium compound into an extruder in which the polyacetal copolymer is melt-kneaded and extruded, and when the filler or pigment is blended with the polyacetal copolymer using the extruder or the like, the polyacetal copolymer First, a quaternary ammonium compound is first attached to the resin pellet, and then the unstable terminal portion is decomposed and removed at the time of blending the filler or pigment.

  Further, the decomposition and removal treatment of the unstable terminal portion of the polyacetal copolymer may be performed after the polymerization catalyst coexisting with the polyacetal copolymer obtained by polymerization is deactivated or may be performed without deactivating the polymerization catalyst. Is possible. Specific examples of the deactivation treatment of the polymerization catalyst include a method of neutralizing and deactivating the polymerization catalyst in a basic aqueous solution such as amines. When the polymerization catalyst is not deactivated, the polyacetal copolymer is heated in an inert gas atmosphere at a temperature below the melting point of the polyacetal copolymer, and the polymerization catalyst is reduced by volatilization, and then the unstable end portion is decomposed and removed. Performing operations is also an effective method.

  By the decomposition and removal treatment of the unstable terminal portion as described above, a polyacetal copolymer excellent in thermal stability having almost no unstable terminal portion can be obtained.

  The melt flow rate (hereinafter also referred to as “MFR”) of the polyacetal resin (A) is preferably from 0.1 g / 10 min to 100 g / 10 min, and preferably from 1 g / 10 min to 50 g / 10 min. Is more preferably 3 g / 10 min or more and 30 g / 10 min or less. As a method for obtaining the polyacetal resin (A) having an MFR within the above range, specifically, in the production of the polyacetal resin (A), the addition amount of a chain transfer agent such as methylal is adjusted. Is mentioned. In the present embodiment, MFR is a value measured under conditions of 190 ° C. and 2.16 kg according to JIS K7210 A method.

<Carbon black (B)>
The polyacetal resin composition of this embodiment contains carbon black (B). Moreover, 5 mass parts or more and 30 mass parts or less of carbon black (B) are included with respect to 100 mass parts of polyacetal resin (A). Further, the carbon black (B) has a dibutyl phthalate oil absorption of 100 mL / 100 g or more and 300 mL / 100 g or less, and a BET specific surface area of 20 m ² / g or more and 100 m ² / g or less by the iodine adsorption method of the carbon black (B). It is.

  Carbon black (B) in this embodiment contains 5 mass parts or more and 30 mass parts or less with respect to 100 mass parts of polyacetal resin (A), Preferably it is 8 mass parts or more and 30 mass parts or less, More preferably, it is 10 parts. It is not less than 25 parts by mass. If it is 5 mass parts or more, high electroconductivity will be acquired, and if it is 30 mass parts or less, the crack of a molded object will be suppressed.

The carbon black (B) in this embodiment is not a superconductive carbon black, but has a low dibutyl phthalate (DBP) oil absorption and a low BET specific surface area by the iodine adsorption method. Specifically, the dibutyl phthalate oil absorption is 100 mL / 100 g or more and 300 mL / 100 g or less, and the BET specific surface area by the iodine adsorption method is 20 m ² / g or more and 100 m ² / g or less. If it exists in this range, the crack of a molded object can be suppressed and the polyacetal resin composition excellent in the dimensional accuracy can be obtained.

  A preferable range of the DBP oil absorption is 120 mL / 100 g or more and 250 mL / 100 g or less, and a more preferable range is 150 mL / 100 g or more and 200 mL / 100 g or less.

A preferable range of the BET specific surface area by the iodine adsorption method is 30 m ² / g or more and 90 m ² / g or less, and a more preferable range is 40 m ² / g or more and 80 m ² / g or less.

  The BET specific surface area by the iodine adsorption method is a value measured based on ISO1304, and the dibutyl phthalate oil absorption is a value measured based on ISO4656. Also, the production method of carbon black (B) is not particularly limited, and any of oil furnace method, lamp black method, channel method, gas furnace method, acetylene decomposition method, thermal method and the like may be used.

<Olefin resin (C)>
The polyacetal resin composition of this embodiment contains an olefin resin (C). The olefin resin (C) in this embodiment is a homopolymer of an olefin compound represented by the following general formula (3), and 60 mol% of the olefin compound represented by the following general formula (3) with respect to the total monomer units. It is at least one olefin resin selected from the group consisting of copolymers contained in the above range and modified products thereof.
In the formula (3), R ₁ represents a hydrogen atom or a methyl group, R ₂ represents a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, a carboxyl group, alkylated carboxy group containing 2-5 carbon atoms, An acyloxy group having 2 to 5 carbon atoms or a vinyl group is represented.

  As the olefin resin (C), specifically, polyethylene (high density polyethylene, medium density polyethylene, high pressure method low density polyethylene, linear low density polyethylene, ultra low density polyethylene), polypropylene, ethylene-propylene copolymer, Ethylene-butene copolymer, polypropylene-butene copolymer, polybutene, hydrogenated polybutadiene, ethylene-acrylic acid ester copolymer, ethylene-methacrylic acid ester copolymer, ethylene-acrylic acid copolymer, ethylene -Vinyl acetate copolymer etc. are mentioned.

  As the olefin resin (C), a modified one (modified product) can also be applied. Specifically, as a modified body, a graft copolymer obtained by grafting one or more of other vinyl compounds different from the polymer forming the olefin resin; α, β-unsaturated carboxylic acid (acrylic acid, methacrylic acid) Acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid, etc.) or modified with acid anhydride (with peroxide if necessary); copolymerized olefin compound and acid anhydride Etc.

  The olefin resin (C) is preferably 5 parts by mass or more and 25 parts by mass with respect to 100 parts by mass of the polyacetal resin (A) from the viewpoint of obtaining a polyacetal resin composition in which sufficient conductivity and toughness are imparted to the composition. Or less, more preferably 5 parts by mass or more and 20 parts by mass or less, and further preferably 7 parts by mass or more and 15 parts by mass or less.

  In the present embodiment, the olefin resin (C) is preferably an olefin resin that has not been acid-modified from the viewpoint of the thermal stability and high conductivity of the polyacetal resin. Here, “unmodified with acid” means that the olefin resin is α, β-unsaturated carboxylic acid (acrylic acid, methacrylic acid, maleic acid, fumaric acid, itaconic acid, citraconic acid, nadic acid) and / or its It means that it is not modified with an acid anhydride or the like (with a peroxide if necessary) and is not a copolymer of various olefins and acid anhydrides.

<Ester compound (D)>
The polyacetal resin composition in this embodiment contains an ester compound (D). By including the ester compound (D), the dispersibility of the carbon black (B) in the polyacetal resin (A) is improved during the extrusion process, and foreign matter generated when the strand is pushed out from the extruder (eyes) Can be kept to a small amount. Thereby, the fall of the electroconductivity by mixing of an eye spear can be suppressed. In addition to this, even when molding a polyacetal resin composition, an ester compound (D) is interposed between a mold and a substance causing mold contamination, so that the mold contamination during continuous molding is low. Contaminants can be easily removed even if they are contaminated. Moreover, long-term toughness retention performance can also be obtained by including an ester compound (D) in a polyacetal resin composition.

  The ester compound (D) in the present embodiment is an ester composed of a fatty acid having 4 to 30 carbon atoms and an aliphatic alcohol having 2 to 30 carbon atoms. The component of these ester compounds (D) may be used individually by 1 type, and may be used in combination of 2 or more type. Further, the ester compound (D) is preferably a liquid during the molding process.

  Specific examples of fatty acids include butyric acid, valeric acid, caproic acid, enane and acid, caprylic acid, capric acid, undecylic acid, lauric acid, tridecylic acid, myristic acid, pentadecylic acid, palmitic acid, pentadecylic acid, stearic acid , Nanodecanoic acid, arachidic acid, behenic acid, lignoceric acid, serotic acid, heptaconic acid, montanic acid, melissic acid, laccelic acid, undecylenic acid, oleic acid, elaidic acid, celetic acid, erucic acid, brassic acid, linoleic acid, linolenic acid And monovalent fatty acids such as acid, arachidonic acid and stearic acid; divalent fatty acids such as succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid and sebacic acid. Of these, divalent fatty acids are preferred.

  Specific examples of the aliphatic alcohol include lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, oleyl alcohol, nonadecyl alcohol, eicosyl alcohol, ceryl alcohol, behenyl alcohol, Saturated or unsaturated alcohols such as melyl alcohol, hexyl decyl alcohol, octyl dodecyl alcohol, decyl myristyl alcohol, decyl stearyl alcohol, uniline alcohol; polyols such as ethylene glycol, glycerin, trimethylol propane, pentaerythritol, dipentaerythritol, etc. Is mentioned. Among these, trivalent or higher polyols are preferable.

  The ester compound (D) used in the present embodiment is preferably one or two selected from the group consisting of aliphatic diesters and aliphatic triesters from the viewpoint of maintaining toughness.

  The substance used as the ester compound (D) of the present embodiment may be a single component or a mixture of two or more substances.

  Further, the ester compound (D) is preferably 0.05% by mass or more and 5.0% by mass or less, more preferably 0.1% by mass or more and 3% by mass or less, with respect to the whole polyacetal resin composition. It is. By setting it as such a range, it exists in the tendency which can suppress the mold contamination at the time of continuous shaping | molding, and can remove a contaminant easily even if it is contaminated. Moreover, it exists in the tendency which can maintain high electroconductivity, can provide high toughness and long-term toughness, and can suppress the crack of a molded article.

  As a blending method of the ester compound (D), a master batch of the polyacetal resin containing at least a part of the polyacetal resin (A) and the ester compound (D) is prepared in advance, and the master batch is used to perform the process of the present embodiment. When the composition is kneaded with a twin-screw extruder or the like, the dispersibility is further improved, and the effect obtained by blending the ester compound (D) is further improved, and particularly, the tensile fracture nominal strain tends to be further improved.

<Epoxy compound (E)>
It is preferable that the polyacetal resin composition of this embodiment further contains an epoxy compound (E). In addition to the epoxy compound (E), it is more preferable to further include an epoxy compound curable additive. The epoxy compound (E) and the epoxy compound curable additive are polyacetals from the viewpoint of obtaining a polyacetal resin composition with less mold contamination during long-term continuous molding and from the viewpoint of high toughness and long-term toughness retention. It is more preferably 0.1 to 10 parts by mass, and still more preferably 0.5 to 5 parts by mass with respect to 100 parts by mass of the resin (A).

  Specific examples of the epoxy compound (E) include mono- or polyfunctional glycidyl derivatives, or compounds obtained by oxidizing a compound having an unsaturated bond to generate an epoxy group. Specific examples of the epoxy curable additive include a basic nitrogen compound, a basic phosphorus compound, and other compounds having an epoxy curing action (including an effect promoting action).

  Specific examples of mono- or polyfunctional glycidyl derivatives include 2-ethylhexyl glycidyl ether, 2-methyloctyl glycidyl ether, lauryl glycidyl ether, stearyl glycidyl ether, behenyl glycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether ( Units of ethylene oxide; 2 to 30), propylene glycol diglycidyl ether, (units of propylene oxide; 2 to 30), neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, glycerin tri Glycidyl ether, trimethylolpropane diglycidyl ether, trimethylolpropane triglycidyl ether Bisphenol A diglycidyl ether, and the like.

  Other mono- or polyfunctional glycidyl derivatives include hydrogenated bisphenol A diglycidyl ether, sorbitan monoester diglycidyl ether, sorbitan monoester triglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetraglycidyl ether, diglycerin tris. Glycidyl ether, diglycerin tetraglycidyl ether, condensate of cresol novolac and epichlorohydrin (epoxy equivalent: 100-400, softening point: 20-150 ° C.), glycidyl methacrylate, palm fatty acid glycidyl ester, soybean fatty acid glycidyl ester, etc. It is done.

  Specific examples of compounds obtained by oxidizing a compound having an unsaturated bond to generate an epoxy group include 3 ′, 4′-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 1,2-epoxy-4. -Vinylcyclohexane, 1,2-epoxy-4- (2-methyloxiranyl) -1-methylcyclohexane, limonene oxide and the like.

  Specific examples of epoxy curable additives include imidazole; substituted imidazoles such as 1-hydroxyethyl-2-methylimidazole, 1-cyanoethyl-2-heptadecylimidazole, and 1-vinyl-2-phenylimidazole; octylmethylamine Aliphatic secondary amines such as laurylmethylamine; aromatic secondary amines such as diphenylamine and ditolylamine; aliphatic tertiary amines such as trilaurylamine, dimethyloctylamine, dimethylstearylamine, and tristearylamine; Aromatic tertiary amines such as amines; Morpholine compounds such as cetylmorpholine, octylmorpholine, P-methylbenzylmorpholine; Alkylene oxide adducts to dicyandiamide, melamine, urea, etc. 0 mol), triphenyl phosphine, methyl diphenyl phosphine, phosphorus compounds such as tri-tolyl phosphine.

  These epoxy compounds and epoxy compound curable additives may be used alone or in combination of two or more.

<Stabilizer>
The polyacetal resin composition of this embodiment can contain various stabilizers that have been used in conventional polyacetal resin compositions as long as the object of the present invention is not impaired. Specific examples of the stabilizer include the following antioxidants, formaldehyde or formic acid scavengers, and the like. These may be used alone or in combination of two or more.

  As the antioxidant, a hindered phenol-based antioxidant is preferable from the viewpoint of improving the thermal stability of the polyacetal resin composition. Specific examples of hindered phenol antioxidants include n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) -propionate, n-octadecyl-3- (3 '-Methyl-5'-t-butyl-4'-hydroxyphenyl) -propionate, n-tetradecyl-3- (3', 5'-di-t-butyl-4'-hydroxyphenyl) -propionate, 1, 6-hexanediol-bis- (3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate), 1,4-butanediol-bis- (3- (3,5-di-t -Butyl-4-hydroxyphenyl) -propionate), triethylene glycol-bis- (3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate) And the like.

  In addition, hindered phenol antioxidants other than the above include tetrakis- (methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate methane, 3,9- Bis (2- (3- (3-t-butyl-4-hydroxy-5-methylphenyl) propionyloxy) -1,1-dimethylethyl) -2,4,8,10-tetraoxaspiro (5,5 ) Undecane, N, N′-bis-3- (3 ′, 5′-di-t-butyl-4-hydroxyphenol) prepionylhexamethylenediamine, N, N′-tetramethylenebis-3- (3 '-Methyl-5'-t-butyl-4-hydroxyphenol) propionyldiamine, N, N'-bis- (3- (3,5-di-t-butyl-4-hydroxyphenol) propionyl) Razine, N-salicyloyl-N′-salicylidenehydrazine, 3- (N-salicyloyl) amino-1,2,4-triazole, N, N′-bis (2- (3- (3,5-di- Also included are butyl-4-hydroxyphenyl) propionyloxy) ethyl) oxyamide and the like.

  Among the hindered phenol-based antioxidants described above, from the viewpoint of improving the thermal stability of the polyacetal resin composition, triethylene glycol-bis- (3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -Propionate), tetrakis- (methylene-3- (3 ', 5'-di-tert-butyl-4'-hydroxyphenyl) propionate) methane.

  Specific examples of formaldehyde or formic acid scavengers include compounds containing formaldehyde-reactive nitrogen and polymers thereof, alkali metal or alkaline earth metal hydroxides, inorganic acid salts, and carboxylate salts.

  Specific examples of compounds containing formaldehyde-reactive nitrogen and polymers thereof include dicyandiamide, melamine, co-condensates of melamine and formaldehyde, nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon Polyamide resins such as 6-12, nylon 12, nylon 6 / 6-6, nylon 6 / 6-6 / 6-10, nylon 6 / 6-12, poly-β-alanine, polyacrylamide and the like. Among these, a co-condensate of melamine and formaldehyde, a polyamide resin, poly-β-alanine and polyacrylamide are preferable. From the viewpoint of improving the thermal stability of the polyacetal resin composition, the polyamide resin and poly-β-alanine are preferred. More preferred.

  As alkali metal or alkaline earth metal hydroxides, inorganic acid salts, and carboxylate salts, specifically, hydroxides such as sodium, potassium, magnesium, calcium or barium, carbonates of the above metals, phosphoric acid Examples thereof include salts, silicates, borates, and carboxylates. From the viewpoint of improving the thermal stability of the polyacetal resin composition, a calcium salt is preferred. Specific examples of calcium salts include calcium hydroxide, calcium carbonate, calcium phosphate, calcium silicate, calcium borate, and fatty acid calcium salts (calcium stearate, calcium myristate, etc.), and these fatty acids are substituted with hydroxyl groups. May be. Among these, fatty acid calcium salts (calcium stearate, calcium myristate, etc.) are more preferable from the viewpoint of improving the thermal stability of the polyacetal resin composition.

  A preferred combination of the various stabilizers described above is triethylene glycol-bis- (3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate from the viewpoint of improving the thermal stability of the polyacetal resin composition. ) Or tetrakis- (methylene-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) propionate) methane, a hindered phenolic antioxidant, polyamide resin and poly-β -A combination of a polymer containing formaldehyde-reactive nitrogen represented by alanine and an alkaline earth metal fatty acid salt represented by a fatty acid calcium salt.

  The content of each stabilizer mentioned above is 0.1 mass part or more and 2 mass parts or less of hindered phenolic antioxidant as an antioxidant with respect to 100 mass parts of polyacetal resin (A). As the formic acid scavenger, for example, the polymer containing formaldehyde-reactive nitrogen is in the range of 0.1 to 3 parts by mass, and the alkaline earth metal fatty acid salt is in the range of 0.1 to 1 part by mass. And preferred.

<Additives>
The polyacetal resin composition of the present embodiment can contain various additives conventionally used in polyacetal resin compositions within a range that does not impair the object of the present invention and according to desired properties. Specific examples of the additive include the following inorganic filler, crystal nucleating agent, conductive agent, thermoplastic resin, thermoplastic elastomer, and pigment. These may be used alone or in combination of two or more.

  Specifically, fillers such as fibrous, powder particle, plate, and hollow shapes are used as the inorganic filler.

  Specific examples of the fibrous filler include glass fiber, carbon fiber, silicone fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber; stainless steel, aluminum, titanium, Examples thereof include inorganic fibers such as metal fibers such as copper and brass. In addition, whiskers such as potassium titanate whisker and zinc oxide whisker having a short fiber length; high melting point organic fibrous materials such as aromatic polyamide resin, fluororesin, and acrylic resin are also included.

  Specific examples of powder particulate fillers include silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, silicates such as wollastonite, iron oxide, titanium oxide, Examples thereof include metal oxides such as alumina, metal sulfates such as calcium sulfate and barium sulfate, carbonates such as magnesium carbonate and dolomite, silicon carbide, silicon nitride, boron nitride, and various metal powders.

  Specific examples of the plate filler include mica, flaky glass, various metal foils, and the like.

  Specific examples of the hollow filler include glass balloons, silica balloons, shirasu balloons, and metal balloons.

  These inorganic fillers may be used alone or in combination of two or more.

  These inorganic fillers can be used either surface-treated or unsurface-treated, but from the viewpoint of surface smoothness and mechanical properties of the molded article containing the polyacetal resin composition, What has been applied may be preferred.

  As the surface treatment agent, conventionally known ones can be used, and specific examples include various silane-based, titanate-based, aluminum-based and zirconium-based coupling treatment agents. As the coupling treatment agent, specifically, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyltristearoyl titanate, diisopropoxyammonium ethyl acetate, Examples thereof include n-butyl zirconate.

  The inorganic filler is preferably 0.1 parts by mass or more and 200 parts by mass or less, more preferably 0.5 parts by mass or more and 100 parts by mass or less, with respect to 100 parts by mass of the polyacetal resin (A). More preferably, it is at least 50 parts by mass.

  Specific examples of the crystal nucleating agent include boron nitride. The crystal nucleating agent is preferably 0.001 to 10 parts by mass, more preferably 0.003 to 7 parts by mass, based on 100 parts by mass of the polyacetal resin (A). More preferably, it is 0.005 parts by mass or more and 5 parts by mass or less.

  Specific examples of the conductive agent include carbon black, acetylene black, graphite, carbon fiber, carbon nanotube, metal powder, or metal fiber other than those listed as the component (B). The conductive agent is preferably from 0.1 parts by weight to 100 parts by weight, more preferably from 0.3 parts by weight to 70 parts by weight, based on 100 parts by weight of the polyacetal resin (A). More preferably, they are 5 to 50 mass parts.

  Specific examples of the thermoplastic resin include olefin resins other than those listed as the component (C), and more specifically, the olefin compound represented by the general formula (3) is used as a whole monomer. Examples thereof include a copolymer, a styrene resin, and a polycarbonate resin that are contained in a range of less than 40 mol% with respect to the unit. These modified products are also included. The thermoplastic resin is preferably from 0.1 parts by weight to 200 parts by weight, more preferably from 0.3 parts by weight to 150 parts by weight, based on 100 parts by weight of the polyacetal resin (A). More preferably, it is 5 parts by mass or more and 100 parts by mass or less.

  Specific examples of the thermoplastic elastomer include styrene-based elastomer, polybutadiene, polyisoprene, ethylene-propylene rubber, acrylic rubber, chlorinated polyethylene, and the like. The thermoplastic elastomer is preferably from 0.1 parts by weight to 200 parts by weight, more preferably from 0.3 parts by weight to 150 parts by weight, based on 100 parts by weight of the polyacetal resin (A). More preferably, it is 5 parts by mass or more and 100 parts by mass or less.

  Specific examples of the pigment include inorganic pigments, organic pigments, metallic pigments, and fluorescent pigments. Inorganic pigments are those commonly used for resin coloring. Specifically, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, combustion pigments, carbonates, phosphorus Acid salts, acetate salts; carbon black, acetylene black, lamp black and the like. Specific examples of organic pigments include condensed azo, inone, furotacyanine, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennon, quinacridone, thioindico, berylene, dioxazine. And phthalocyanine pigments. The amount of the pigment can be selected according to the desired color tone, but it is preferably in the range of 0.05 to 5 parts by mass with respect to 100 parts by mass of the polyacetal resin (A).

[Volume resistivity]
The polyacetal resin composition of the present embodiment has a volume resistivity measured in accordance with JIS K7194 using a multipurpose test piece molded in conformity with ISO294-1, and is 10 ⁰ Ωcm or more and 10 ² Ωcm or less. Yes, it is preferably 10 ⁰ Ωcm or more and 7 × 10 ¹ Ωcm or less, more preferably 10 ⁰ Ωcm or more and 5 × 10 ¹ Ωcm or less. When the volume resistivity is 10 ⁰ Ωcm or more and 10 ² Ωcm or less, a polyacetal resin composition applicable to a wider range of uses can be obtained.

  Specific examples of a method for obtaining a polyacetal resin composition having a volume resistivity within the above range include a method of adjusting the amount of carbon black (B) added.

[Tensile fracture nominal strain]
The polyacetal resin composition of this embodiment has a tensile fracture nominal strain measured in accordance with ISO 527-1 of 15% or more, preferably 20% or more. A polyacetal resin composition having a tensile fracture nominal strain of 15% or more is excellent in mechanical properties and the molded body is less likely to crack. The upper limit value of the tensile fracture nominal strain is not particularly limited, but is, for example, 200%.

  As a method for obtaining a polyacetal resin composition having a tensile strain at nominal strain in the above range, specifically, a method for adjusting the molecular weight of the polyacetal resin (A), a method for adjusting the addition amount of carbon black (B), and an olefin resin Examples thereof include a method of adjusting the amount of addition of (C) and / or ester compound (D).

[Production Method of Polyacetal Resin Composition]
The polyacetal resin composition of the present embodiment includes 100 parts by mass of the above-described polyacetal resin (A), 5 to 30 parts by mass of the specific carbon black (B), an olefin resin (C), and an ester compound (D ) And, if necessary, other components can be produced by melt-kneading.

  As a device for producing the polyacetal resin composition of the present embodiment, a kneader that is generally used can be applied. Specific examples of the kneader include a uniaxial or multi-axial kneading extruder, a roll, and a Banbury mixer. Among these, a twin-screw extruder equipped with a decompression device and side feeder equipment is preferable.

  As a method of melt kneading, specifically, a method in which a blend of all components is continuously fed from an extruder top feeder (hereinafter referred to as a top feeder) and melt kneaded, other than the carbon black (B) component After continuously feeding a blend of these components from an extruder top feeder and melt-kneading them, a carbon black (B) component is continuously fed from a feeder (hereinafter referred to as a side feeder) provided on the side of the extruder. And then melt-kneading the ester compound (D) and at least a part of the polyacetal resin (A) into a master batch, and using the master batch, the rest is melt-kneaded as described above. Examples include a method using the method. Among these, from the viewpoint of stable performance expression, the ester compound (D) and at least a part of the polyacetal resin (A) are melt-kneaded in advance to form a master batch, and the carbon black (B) is obtained using the master batch. A method is preferred in which a blend other than the components is supplied from an extruder top feeder and melt-kneaded, and then the carbon black (B) component is added from the side feeder and further melt-kneaded.

  The decompression degree of the extruder is preferably 0 MPa or more and 0.07 MPa or less.

  The set temperature of the extruder during melt-kneading is higher in the range of 1 ° C. or higher and 100 ° C. or lower than the melting point determined by the differential scanning calorimeter (DSC) measurement according to JIS K7121 of the polyacetal resin (A) to be used. Is preferred. More preferably, it is 160 ° C. or higher and 240 ° C. or lower, but from the viewpoint of more effectively expressing the effects of the present invention, the dibutyl phthalate oil absorption (hereinafter referred to as “DBP oil absorption” of carbon black (B) used in the polyacetal resin composition. In the case where the amount is 100 mL / 100 g or more, it is preferable that the region adjacent to the extruder die and having a length of at least 1/10 of the total screw length is set to 160 ° C. or more and 180 ° C. or less. preferable.

[Molded body]
The molded product of the present embodiment includes the above-described polyacetal resin composition. For that purpose, the molded article of the present embodiment can be obtained by molding the above-mentioned polyacetal resin composition. The method for molding the polyacetal resin composition is not particularly limited, and a known molding method can be applied. Specifically, extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, other material molding, gas assist injection molding, foam injection molding, low pressure molding, ultra-thin injection molding (ultra-high-speed injection) And molding methods such as molding) and in-mold composite molding (insert molding, outsert molding).

[Use of molded body]
As the application of the molded body of the present embodiment, an application requiring toughness and high conductivity is suitable. Specifically, the molded body of the present embodiment is suitably used for conductive gears, conductive flanges, conductive drum gears, conductive bearing applications, and the like.

  In addition, cams, sliders, levers, arms, clutches, felt clutches, idler gears, pulleys, rollers, rollers, key stems, key tops, shutters, reels, shafts, joints, shafts, bearings, which are common polyacetal resin applications Mechanical parts typified by guides, etc .; resin parts for outsert molding, resin parts for insert molding, chassis, trays, side plates, printers, parts for office automation equipment typified by copiers; VTR (Video Tape Recorder), Video movie, digital video camera, camera, camera or digital device parts represented by digital camera; cassette player, DAT, LD (Laser Disk), MD (Mini Disk), CD (Compact Disk) [CD -ROM (including Read Only Memory), CD-R (Recordable), CD-RW (Rewriteable)], DVD (Digital Video Disk) [DVD-ROM, DVD-R, DVD + R, DVD-RW, DVD + RW, DVD- RDL, DVD + RDL, DVD-RAM (including Random Access Memory), DVD-Audio), Blu-ray (registered trademark) Disc, HD-DVD, and other optical disk drives; MFD, MO, navigation system, mobile personal Examples include music, video or information equipment typified by computers, parts for communication equipment typified by mobile phones and facsimiles; parts for electrical equipment; parts for electronic equipment. Further, the molded body of the present embodiment is a fuel-related part typified by a gasoline tank, a fuel pump module, valves, a gasoline tank flange, etc. as an automobile part; a door lock, a door handle, a window regulator, a speaker grill, etc. Parts around the door represented by: Seat belt peripheral parts represented by seat belt slip rings, press buttons, etc .; parts such as combination switch parts, switches, clips, etc .; mechanical pencil pen tip, mechanical pencil core Mechanical parts to be taken in and out; wash basin, drain port, drain valve opening and closing mechanism parts; vending machine opening and closing part locking mechanism, product discharge mechanism parts; clothing cord stopper, adjuster, button; sprinkling nozzle, sprinkling hose connection joint ; Stair railing, building supplies that support floor materials; Discarded camera, toys, fasteners, chains, conveyors, buckle, sports equipment, vending machines, furniture, musical instruments, industrial parts typified by housing equipment is also suitably used.

  Hereinafter, the present embodiment will be specifically described by way of examples and comparative examples. However, the present embodiment is not limited to the examples and comparative examples described below as long as the gist of the present embodiment is not exceeded. Various measurement methods for the polyacetal resin compositions and molded bodies of Examples and Comparative Examples, and the raw material components of the polyacetal resin compositions and molded bodies used in Examples and Comparative Examples are shown below.

(1) Number average molecular weight measurement method Polymethyl methacrylate (hereinafter referred to as "Waters" which may be abbreviated as GPC) was prepared by gel permeation chromatography (hereinafter referred to as GPC) using 2 mg of polyacetal resin as a sample as a solvent. , Abbreviated as PMMA) as a standard substance, and a number average molecular weight represented by a PMMA equivalent molecular weight. At this time, at least 4 samples were used as the PMMA standard substance in the range of about 2,000 to 1,000,000 as the number average molecular weight.

(2) Volume resistivity measurement method Using an EC-75NII molding machine manufactured by Toshiba Machine Co., Ltd., the cylinder temperature was set to 205 ° C, the mold temperature was set to 90 ° C, the injection time was 35 seconds, and the cooling time was 15 seconds. By molding the polyacetal resin compositions obtained in Examples and Comparative Examples under injection conditions, ISO dumbbells (multipurpose test pieces molded according to ISO294-1) were obtained. A plate of 30 mm × 20 mm × 4 mm was cut out from this ISO dumbbell, and this plate was used as a sample for measuring volume resistivity. The following two types of measurement methods were used depending on the volume resistivity level.

In the case of a sample having a volume resistivity of less than 1.0 × 10 ⁴ Ωcm, the four-probe ASP probe (between pins 5 mm, pin tip 0.37 mm R × 4, spring pressure 210 g / piece, JIS K7194 compliant) is used. The sample was pressed against the sample (flat plate), and the volume resistivity of the sample was measured with a measuring voltage of 90 V using Loresta (registered trademark) -GP manufactured by Mitsubishi Chemical Corporation.

In the case of a sample having a volume resistivity of 1.0 × 10 ⁴ Ωcm or more, a URS type ring probe (conforming to JIS K6911) is pressed against the above-prepared sample (flat plate), and Hiresta (registered by Mitsubishi Chemical Corporation) is registered. The volume specific resistivity of the sample was measured with a measurement voltage of 1,000 V using a trademark-UP.

(3) Tensile Fracture Nominal Strain Measurement Method and Tensile Fracture Nominal Strain Measurement Method after Long-term Thermal Aging Using an EC-75NII molding machine manufactured by Toshiba Machine Co., Ltd., the cylinder temperature is set to 205 ° C and the mold temperature is set to 90 ° C. Multi-purpose molded in accordance with ISO dumbbell (ISO294-1) by molding and molding polyacetal resin compositions obtained in Examples and Comparative Examples under injection conditions of injection time of 35 seconds and cooling time of 15 seconds Test piece) was obtained. Using this ISO dumbbell, a tensile test based on ISO 527-1 was performed, and a tensile fracture nominal strain was measured. For long-term thermal aging, the ISO dumbbell was aged in an oven at 80 ° C. for one month, a tensile test based on ISO 527-1 was performed, and a tensile fracture nominal strain was measured.

(4) Measuring method of dimensional accuracy Using an injection molding machine (trade name “SH-75”) manufactured by Sumitomo Heavy Industries, Ltd., at a cylinder temperature of 200 ° C. and a mold temperature of 80 ° C., the right twist direction A helical gear having a pitch circle diameter of 80 mm, a module 1, a twist angle of 20 degrees, a tooth width of 12 mm, a web thickness of 2 mm, and several 12 ribs was manufactured. The helical gears obtained in this way were measured for tooth profile errors in four teeth at intervals of 90 degrees in accordance with JIS B 1702-1 using a gear accuracy measuring instrument manufactured by Osaka Seimitsu Co., Ltd. did. It was judged that the smaller the value of the tooth profile error, the better the accuracy of the helical gear.

(5) Measuring method of fragility of molded product Using an injection molding machine (trade name “ROBOSHOT (registered trademark) α-50iA”) manufactured by FANUC CORPORATION, a cylinder temperature of 200 ° C. and a mold temperature of 80 ° C. Under the conditions, a gear having a pitch circle diameter of 60 mm, a module 1, the number of teeth of 60, a twist angle of 0 degree, a tooth width of 5 mm, and a web thickness of 2 mm was manufactured. After this gear is left for 24 hours in an environment of 23 ° C. and 50 RH%, it is set on the driven side of a gear durability tester manufactured by Toshiba Corporation, and a gear of the same shape made of Tenac (registered trademark) C-45201 is driven on the drive side. Set. The operation was performed by setting the rotational speed on the pitch circle to 0.5 m / s and the torque to 4.5 kgf · cm, and continuously operating for 168 hours under the conditions of 23 ° C. and 50 RH%. The total weight loss (mg) of both the driven side and the driving side gear at that time was evaluated as the durability of the gear. The lower this value, the better the durability of the gear. In the test conditions described above, when gear breakage occurred before 168 hours had passed and the test could not be continued, “breakdown” was set.

  As the polyacetal resin (A), (A-i), (A-ii), (A-iii), and (A-iv) prepared as follows were used.

<Polyacetal resin (Ai)>
A biaxial self-cleaning type polymerization machine with a jacket through which a heat medium can pass (L / D = 8 (L: distance (m) from raw material supply port to discharge port of polymerization machine, D: inner diameter of polymerization machine ( m) The same applies hereinafter))) to 80 ° C. In the above polymerizer, trioxane is 4 kg / hour, 1,3-dioxolane is 128.3 g / hour as a comonomer, methylal is chain transfer agent, and the number average molecular weight of the resulting polyacetal resin is 30,000. Adjusted and added.

Further, boron trifluoride di-n-butyl etherate as a polymerization catalyst was continuously added to the polymerizer at 1.5 × 10 ⁻⁵ mol with respect to 1 mol of trioxane, and polymerization was performed. Next, the polyacetal copolymer discharged from the polymerization machine was put into a 0.1% aqueous solution of triethylamine to deactivate the polymerization catalyst.

  The polyacetal copolymer in which the polymerization catalyst was deactivated was filtered with a centrifuge. After adding 1 part by weight of an aqueous solution containing choline hydroxide formate (triethyl-2-hydroxyethylammonium formate) as a quaternary ammonium compound to 100 parts by weight of this polyacetal copolymer, and uniformly mixing, Dry at 120 ° C. Here, the addition amount of the hydroxycholine formate was 20 mass ppm in terms of the nitrogen amount. In addition, adjustment of the addition amount of the hydroxy choline formate was performed by adjusting the density | concentration of the hydroxy choline formate in the aqueous solution containing the hydroxy choline formate to add.

  The dried polyacetal copolymer was fed into a vented twin screw extruder. 0.5 parts by weight of water was added to 100 parts by weight of the melted polyacetal copolymer in the extruder, and the unstable terminal portion of the polyacetal copolymer was removed at a preset temperature of the extruder of 200 ° C. and a residence time of 7 minutes in the extruder. Decomposition and removal were performed.

  0.3 parts by mass of triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] as an antioxidant was added to the polyacetal copolymer with the unstable terminal portion decomposed. It was added and extruded as a strand from the die section of the extruder while being devolatilized under a condition of a vacuum of 20 Torr with an extruder equipped with a vent, and pelletized.

  Thus, polyacetal resin (Ai) was obtained. Moreover, MFR based on JISK7210 (190 degreeC, 2.16kg conditions) of polyacetal resin (Ai) was 30 g / 10min.

<Polyacetal resin (A-ii)>
In the production method of the polyacetal resin (Ai), the amount of methylal added as a chain transfer agent was changed to an amount such that the number average molecular weight of the resulting polyacetal resin was 60,000. The same operation as in i) was performed to obtain a polyacetal resin (A-ii). Moreover, MFR based on JISK7210 (190 degreeC, 2.16kg conditions) of polyacetal resin (A-ii) was 10 g / 10min.

<Polyacetal resin (A-iii)>
In the production method of the polyacetal resin (Ai), the amount of methylal added as a chain transfer agent was changed so that the number average molecular weight of the resulting polyacetal resin was 90,000. The same operation as in i) was performed to obtain a polyacetal resin (A-iii). Moreover, MFR based on JISK7210 (190 degreeC, 2.16kg conditions) of polyacetal resin (A-iii) was 3 g / 10min.

<Polyacetal resin (A-iv)>
In the production method of the polyacetal resin (Ai), the amount of methylal added as a chain transfer agent was changed to an amount such that the number average molecular weight of the obtained polyacetal resin was 160,000. The same operation as in i) was performed to obtain a polyacetal resin (A-iv). Moreover, MFR based on JISK7210 (190 degreeC, 2.16kg conditions) of a polyacetal resin (A-iv) was 2.7 g / 10min.

The following carbon black (B) was used.
(Bi) Carbon black (B-ii) DBP oil absorption amount 360 mL / 100 g, BET specific surface area 800 m ² / g carbon black (B-ii) DBP oil absorption amount 190 mL / 100 g, BET specific surface area 65 m ² / g carbon black (B-iii) DBP Carbon black (B-iv) DBP oil absorption 70 mL / 100 g with BET specific surface area 51 m ² / g, carbon black with BET specific surface area 17 m ² / g Oil absorption 180 mL / 100 g, BET specific surface area 51 m ² / g , And measured based on ISO1304 and ISO4656, respectively.

The following thing was used for the olefin resin (C).
(Ci) 1-butene content 90% by mass, ethylene content 10% by mass olefin copolymer, MFR based on JIS K7210 (190 ° C., 2.16 kg condition) is 40 g / 10 min (C-ii) A styrene-isoprene copolymer having a styrene content of 20% by mass and an isoprene content of 80% by mass, MFR based on JIS K7210 (190 ° C., 2.16 kg condition) is 5 g / 10 min.

The following were used for the ester compound (D).
(Di) DIDA (manufactured by Daihachi Chemical Industry Co., Ltd., diisodecyl adipate)
(D-ii) Unistar (registered trademark) H310R (manufactured by NOF Corporation, trimethylolpropane tridodecanoate)

  As the epoxy resin (E), a condensate of cresol novolak and epichlorohydrin (epoxy equivalent = 350, softening point = 80 ° C.) was used. Moreover, triphenylphosphine (made by Hokuko Chemical Co., Ltd.) was used as an epoxy compound curable additive.

  90 parts by mass of the polyacetal resin (A-ii) and 10 parts by mass of the ester compound (D-i) were kneaded with a biaxial kneader to obtain a master batch (Fi).

  50 parts by mass of polyacetal resin (A-ii), 30 parts by mass of olefin resin (C-i) and 20 parts by mass of ester compound (D-i) are kneaded with a twin-screw kneader to obtain a master batch (F-ii). Obtained.

[Production of polyacetal resin composition]
In this example, a polyacetal resin composition was produced by using a twin screw extruder (TEM-48SS extruder (L / D = 58, with vent) manufactured by Toshiba Machine Co., Ltd.). The schematic block diagram of is shown.

  The twin-screw extruder of FIG. 1 was provided with barrel zones 1 to 14 of independent extruders, and the end of the barrel zone was connected to the die head 15. The starting end of the barrel zone was connected to an extruder motor 16, and the raw material was set to move in the barrel zones 1 to 14 by driving the motor. The barrel zone 1 is provided with a top quantitative feeder 17, and the barrel zone 8 is provided with a side quantitative feeder 18. A degassing vent 19 is provided in the barrel zone 13. The temperature of all barrel zones was set to 200 ° C., and a blend of components other than the component (B) was supplied from the quantitative feeder 17 and the component (B) was supplied from the quantitative feeder 18, respectively. Extrusion was performed under the condition of a rotational speed of 240 rpm to obtain a polyacetal resin composition.

[Examples 1 to 24]
Each component was mix | blended in the ratio shown in Table 1 and Table 2, and it melt-kneaded with the above-mentioned manufacturing method. In Examples 23 and 24, the master batch (F-i) or (F-ii) was blended, but in the table, the ratio of the components (A) to (E) was used so that the final blend could be easily compared. Indicated. The extruded polyacetal resin composition was pelletized with a strand cutter. Using the obtained pellets, volume resistivity, tensile fracture nominal strain, tensile fracture nominal strain after thermal aging, dimensional stability, and ease of cracking of molded products were evaluated by the above-described methods. Tables 1 and 2 show the measurement and evaluation results.

[Comparative Examples 1 to 13]
Each component was mix | blended in the ratio shown in Table 3, and it melt-kneaded with the above-mentioned manufacturing method. The extruded polyacetal resin composition was pelletized with a strand cutter. Using the obtained pellets, volume resistivity, tensile fracture nominal strain, tensile fracture nominal strain after thermal aging, dimensional stability, and ease of cracking of molded products were evaluated by the above-described methods. Table 3 shows the measurement and evaluation results.

  According to the polyacetal resin composition of the present invention, the polyacetal resin composition can be used as a metal substitute for cost reduction and weight reduction in various fields in which the polyacetal resin composition has been suitably used. It has industrial applicability in the fields of parts and other industries.

Claims (6)

Including at least a polyacetal resin (A), carbon black (B), an olefin resin (C), and an ester compound (D),
Carbon black (B) 5 mass part or more and 30 mass parts or less are included with respect to 100 mass parts of polyacetal resin (A),
Carbon black (B) has a dibutyl phthalate oil absorption of 100 mL / 100 g or more and 300 mL / 100 g or less,
The BET specific surface area by the iodine adsorption method of carbon black (B) is 20 m ² / g or more and 100 m ² / g or less,
The volume resistivity measured according to JIS K7194 is 10 ⁰ Ωcm or more and 10 ² Ωcm or less,
The polyacetal resin composition whose tensile fracture nominal strain measured based on ISO527-1 is 15% or more.   The polyacetal resin composition of Claim 1 whose tensile fracture nominal strain measured based on ISO527-1 is 20% or more.   The polyacetal resin composition according to claim 1 or 2, wherein the number average molecular weight of the polyacetal resin (A) is from 50,000 to 150,000.   The polyacetal resin composition according to any one of claims 1 to 3, wherein the ester compound (D) is an aliphatic diester and / or an aliphatic triester.   The polyacetal resin composition according to any one of claims 1 to 4, further comprising 0.1 to 5 parts by mass of the epoxy compound (E) with respect to 100 parts by mass of the polyacetal resin (A).   The molded object containing the polyacetal resin composition of any one of Claims 1-5.