JP2013241505A - Polyacetal resin composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyacetal resin composition having excellent electroconductivity, and causing extremely little staining of a mold when carrying out continuous molding.SOLUTION: There is provided a polyacetal resin composition containing a polyacetal resin (A), carbon black (B), graphite (C) and a substance (D) liquid at 23°C, wherein the content of the carbon black (B) is >5 mass% and ≤15 mass%, and the content of the substance (D) liquid at 23°C is ≥0.05 mass% and ≤0.5 mass%.

Description

  The present invention relates to a polyacetal resin composition.

  Polyacetal resin is an engineering resin with well-balanced mechanical properties and excellent slidability. Especially, since it has excellent slidability, it is suitable for various precision mechanism parts such as gears and OA equipment. Widely used. However, since polyacetal resin is an electrical insulator like other resins, it is inferior in the performance of removing static electricity or electrical conductivity generated during sliding, and for applications that require high conductivity as well as sliding properties. Is usually not used. In recent years, polyacetal resins to which conductive fillers typified by carbon black have been added have begun to be used for the above applications, but the surface of such a molded product is inferior in smoothness, and is inherently a sliding property of polyacetal resins. However, there is a problem that the contact property cannot be exhibited, the contact electric resistance is large, and the conductivity is not sufficiently exhibited. In addition, such a conductive polyacetal resin composition is often used in parts that are used while sliding with other materials, and can maintain stable conductivity over a long period of time under such conditions. Desired.

  In response to such a request, for example, in Patent Document 1, a polyacetal resin composition excellent in wear resistance and conductivity when sliding against a metal is blended with conductive carbon black, graphite, and fatty acid ester in a polyacetal resin. Things are disclosed. Patent Document 2 describes a molded article formed by melt-molding a composition containing a thermoplastic resin and a conductive agent and blending a substance that changes from solid to liquid or gas between 25 ° C. and 250 ° C. In addition, there is a disclosure of a technique in which the dependence of electrical conductivity on molding conditions is small and the variation in physical properties is small. Further, Patent Document 3 discloses that the inside of a copying machine that exhibits excellent slidability even in an environment where toner is present by adding 3 parts by mass or more of carbon black, graphite, or lubricating oil that is liquid at room temperature to polyacetal resin. A composition suitable for various bearing parts is disclosed.

  On the other hand, in response to the recent trend toward resin-related parts for automobiles and electrical and electronic equipment, more and more complicated conductive resin parts are required. Thermal stability that does not occur and performance that does not contaminate the mold due to decomposition products from the composition have been demanded.

JP 2009-269996 A Japanese Patent No. 4110832 Japanese Patent No. 3965251

  However, within the range of the above prior art, a conductive polyacetal resin composition excellent in slidability and conductive stability can be obtained, but the problem of mold contamination during continuous molding has not been solved, and the actual market Currently, there are not a few complaints regarding mold contamination.

  The present invention has been made in view of the above-mentioned problems of the prior art, and an object of the present invention is to provide a polyacetal resin composition having excellent conductivity and extremely low mold contamination during continuous molding.

As a result of intensive studies to achieve the above-mentioned problems, the inventors of the present invention are compositions comprising a polyacetal resin, carbon black, graphite, and a substance that is liquid at 23 ° C. Thus, a polyacetal resin composition in which the carbon black exceeds 5% by mass and is 15% by mass or less and the substance that is liquid at 23 ° C. is 0.05% by mass or more and 0.5% by mass or less solves the above-described problem. As a result, the present invention has been completed.
That is, the present invention is as follows.

[1]
Polyacetal resin (A);
Carbon black (B),
Graphite (C);
A substance (D) which is liquid at 23 ° C.,
The carbon black (B) content is more than 5% by mass and 15% by mass or less,
The polyacetal resin composition wherein the content of the substance (D) that is liquid at 23 ° C. is 0.05% by mass or more and 0.5% by mass or less.
[2]
The polyacetal resin composition according to [1], wherein the substance (D) that is liquid at 23 ° C has a kinematic viscosity at 23 ° C of 200 cSt or less.
[3]
In [1] or [2], the substance (D) that is liquid at 23 ° C. is one or more selected from the group consisting of liquid paraffin, aliphatic diester, and aliphatic triester. The polyacetal resin composition as described.
[4]
In any one of [1] to [3], the substance (D) that is liquid at 23 ° C. is one or two selected from the group consisting of aliphatic diesters and aliphatic triesters. The polyacetal resin composition as described.
[5]
The polyacetal resin composition according to any one of [1] to [4], wherein the carbon black (B) has a dibutyl phthalate oil absorption of 350 mL / 100 g or more.
[6]
The polyacetal resin composition according to any one of [1] to [5], wherein the graphite (C) is natural graphite.
[7]
Furthermore, the polyacetal resin composition as described in any one of [1] to [6] above, which contains an aliphatic ester (E) that is solid at 23 ° C.
[8]
[7] The mass ratio (E) / (D) of the fatty acid ester (E) that is solid at 23 ° C. to the substance (D) that is liquid at 23 ° C. is more than 10 and 20 or less. The polyacetal resin composition as described.

  According to the present invention, it is possible to obtain a polyacetal resin composition which is excellent in conductivity and has very little mold contamination during continuous molding.

It is the schematic of the twin-screw extruder used in the Example of this invention.

  Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described in detail.

[Polyacetal resin composition]
The polyacetal resin composition of the present embodiment includes a polyacetal resin (A),
Carbon black (B),
Graphite (C);
A substance (D) which is liquid at 23 ° C.,
The carbon black (B) content is more than 5% by mass and 15% by mass or less,
The content of the substance (D) that is liquid at 23 ° C. is 0.05% by mass or more and 0.5% by mass or less.

(Polyacetal resin (A))
The polyacetal resin (A) used in the present embodiment is not particularly limited, but specifically, a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) or a tetramer (tetraoxane) alone is used. A polyacetal homopolymer consisting essentially of oxymethylene units obtained by polymerization, a cyclic oligomer of formaldehyde such as formaldehyde monomer or trimer (trioxane) or tetramer (tetraoxane), ethylene oxide, propylene oxide , Epichlorohydrin, 1,3-dioxolane, 1,4-butanediol formal, and the like, and cyclic ethers of diglycol, such as cyclic formal, and / or polyformal copolymers obtained by copolymerization with cyclic formal It can be cited as a typical example. Moreover, the polyacetal copolymer which has a branch obtained by copolymerizing monofunctional glycidyl ether, and the polyacetal copolymer which has a crosslinked structure obtained by copolymerizing polyfunctional glycidyl ether can also be used. Furthermore, 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 one end, for example, polyalkylene glycol, A compound having a functional group such as a hydroxyl group at both ends or one end, for example, a formaldehyde monomer or a cyclic oligomer of formaldehyde such as a trimer (trioxane) or tetramer (tetraoxane) in the presence of hydrogenated polybutadiene glycol; , A cyclic ether, and / or a polyacetal copolymer having a block component obtained by copolymerization with cyclic formal can also be used. As described above, in the present embodiment, either a polyacetal homopolymer or a polyacetal copolymer can be used, but a polyacetal copolymer is preferable.

  A comonomer such as 1,3-dioxolane is generally used in an amount of 0.1 to 60 mol%, preferably 0.1 to 20 mol%, more preferably 0.13 to 10 mol%, relative to 1 mol of trioxane. The melting point of the polyacetal resin (A) used in the present embodiment is preferably 162 ° C to 173 ° C, more preferably 167 ° C to 173 ° C, and further preferably 167 ° C to 171 ° C. A polyacetal copolymer having a melting point of 167 ° C. to 171 ° C. can be obtained by using a comonomer of about 1.3 to 3.5 mol% with respect to trioxane.

  The polymerization catalyst in the polymerization of the polyacetal copolymer is not particularly limited. Specifically, a cationically active catalyst such as a Lewis acid, a protonic acid, an ester thereof, or an anhydride thereof is preferable. Examples of the Lewis acid include boric acid, tin, titanium, phosphorus, arsenic, and antimony halides. Specifically, boron trifluoride, tin tetrachloride, titanium tetrachloride, phosphorus pentafluoride, pentafluoride, and the like. Examples thereof include phosphorus chloride, antimony pentafluoride, complex compounds thereof, and salts. Specific examples of the protonic acid, its ester, or its anhydride include perchloric acid, trifluoromethanesulfonic acid, perchloric acid-tertiary butyl ester, acetyl perchlorate, trimethyloxonium hexafluorophosphate, and the like. Among these, boron trifluoride; boron trifluoride hydrate; and a coordination complex compound of an organic compound containing an oxygen atom or a sulfur atom and boron trifluoride are preferable. Specifically, boron trifluoride diethyl ether is used. Boron trifluoride di-n-butyl ether can be mentioned as a preferred example.

Examples of the polymerization method of the polyacetal copolymer include conventionally known methods such as US-A-3027352, US-A-383094, DE-C-11161421, DE-C-1495228, DE-C-1720358, DE-C-3018898, Polymerization can be carried out by the methods described in JP-A-58-98322 and JP-A-7-70267. Since the polyacetal copolymer obtained by the above polymerization has a thermally unstable terminal [-(OCH ₂ ) _n —OH group], the unstable terminal is decomposed and removed. As the decomposing / removing process, for example, it is preferable to perform the following decomposing / removing process for a specific unstable terminal portion. The specific unstable terminal decomposition and removal treatment is a treatment of the polyacetal copolymer at a temperature not lower than the melting point of the polyacetal copolymer and not higher than 260 ° C. in the presence of at least one quaternary ammonium compound represented by the following formula (1). Is heat-treated in a melted state.
[R ¹ R ² R ³ R ⁴ N ⁺ ] _n X ^-n Formula (1)
(Wherein R ¹ , R ² , R ³ , and R ⁴ are each independently an unsubstituted alkyl group or substituted alkyl group having 1 to 30 carbon atoms; an aryl group having 6 to 20 carbon atoms; An aralkyl group in which a hydrogen atom of -30 unsubstituted alkyl group or substituted alkyl group is substituted with at least one aryl group having 6 to 20 carbon atoms; or at least one hydrogen atom in an aryl group having 6 to 20 carbon atoms Represents an unsubstituted alkyl group having 1 to 30 carbon atoms or an alkylaryl group substituted with a substituted alkyl group, and the unsubstituted alkyl group or substituted alkyl group is linear, branched, or cyclic. The substituent is a halogen, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, or an amide group, and the above-mentioned unsubstituted alkyl group, aryl group, aralkyl group, alkylaryl. May be substituted with a halogen atom, n represents an integer of 1 to 3. X is a hydroxyl group, a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than hydrogen halide, an oxo acid, an inorganic Represents an acid residue of a thioacid or an organic thioacid having 1 to 20 carbon atoms.)

The quaternary ammonium compound used in the present embodiment is not particularly limited as long as it is represented by the above formula (1), but R ¹ , R ² , R ³ , and R ⁴ in the formula (1) are each Independently, an alkyl group having 1 to 5 carbon atoms or a hydroxyalkyl group having 2 to 4 carbon atoms is preferable, and among these, at least one of R ¹ , R ² , R ³ , and R ⁴ is hydroxyethyl. What is a group is more preferable. Specifically, such quaternary ammonium compounds 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-hydroxy) Ethyl) ammonium, tri-n-butyl (2-hydroxyethyl) ammonium, trimethylbenzylammonium, triethylbenzylammonium, tripropylethyl Zirammonium, tri-n-butylbenzylammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, okdadecyltri (2-hydroxyethyl) ammonium , Hydroxides such as tetrakis (hydroxyethyl) ammonium; hydrogenates such as hydrochloric acid, odorous acid, hydrofluoric acid; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, Oxo acid salts such as chlorous acid, hypochlorous acid, chlorosulfuric acid, amidosulfuric acid, disulfuric acid, tripolyphosphoric acid; thioic acid salts such as thiosulfuric acid; formic acid, acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, Caproic acid, caprylic acid, capric acid, benzo Acid, and carboxylic acid salts such as oxalic acid. Among them, 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 included. preferable. Of the carboxylic acids, formic acid, acetic acid, and propionic acid are more preferable. These quaternary ammonium compounds may be used alone or in combination of two or more. Moreover, in addition to the quaternary ammonium compound, amines such as ammonia and triethylamine which are known decomposition accelerators for unstable terminals can be used in combination.

The amount of the quaternary ammonium compound used is 0.05 to 50 mass in terms of the amount of nitrogen derived from the quaternary ammonium compound represented by the following formula (2) with respect to the total mass of the polyacetal copolymer and the quaternary ammonium compound. ppm is preferable, and more preferably 1 to 30 ppm by mass.
P × 14 / Q Formula (2)
(In the formula, 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.)

  If the content of the quaternary ammonium compound is 0.05 mass ppm or more, the rate of decomposition and removal of the unstable end portion is improved, and if it is 50 mass ppm or less, the color tone of the polyacetal copolymer after the decomposition and removal of the unstable end portion is achieved. Is good.

  The decomposition and removal treatment of the unstable end portion of the polyacetal resin used in the present embodiment is achieved by heat treatment in a state where the polyacetal copolymer is melted at a temperature of the melting point or higher and 260 ° C. or lower. Although it does not specifically limit to the apparatus to be used, It is suitable to heat-process using an extruder, a kneader, etc. In addition, formaldehyde generated by decomposition is removed under reduced pressure. Although there are no particular limitations on the method of adding the quaternary ammonium compound, there are a method of adding it as an aqueous solution in the step of deactivating the polymerization catalyst, a method of spraying the polyacetal copolymer powder produced by polymerization, and the like. Any addition method may be used as long as it is added in the step of heat-treating the polyacetal copolymer, and if it is a variety that is injected into an extruder or blends fillers and pigments using an extruder or the like, The compound may be attached to the resin pellet, and the unstable terminal removal operation may be performed in the subsequent blending step.

  The unstable terminal removal operation can be performed after the polymerization catalyst in the polyacetal copolymer obtained by polymerization is deactivated, or can be performed without deactivating the polymerization catalyst. A typical example of the deactivation operation of the polymerization catalyst is a method of neutralizing and deactivating the polymerization catalyst in a basic aqueous solution such as amines. It is also effective to perform this unstable terminal removal operation after heating in an inert gas atmosphere at a temperature below the melting point without deactivating the polymerization catalyst to reduce the volatilization of the polymerization catalyst. .

  By the above-mentioned specific unstable terminal decomposition and removal treatment, it is possible to obtain a polyacetal copolymer with very few unstable terminals and excellent in thermal stability.

(Carbon black (B))
The carbon black (B) used in the present embodiment is not particularly limited. Specifically, it is preferable that the carbon black (B) has a small particle diameter or a large surface area and has a chain structure developed. Specifically, those having a particle size of 0.05 μm or less are preferred, those having a particle size of 0.03 μm or less are more preferred, and those having a particle size of 0.01 μm or less are more preferred. The particle diameter can be measured, for example, by observing carbon black with a transmission electron microscope and directly measuring the particle diameter in the obtained image.

  The carbon black (B) dibutyl phthalate (DBP) oil absorption (ASTM D2415-65T) is preferably 350 mL / 100 g or more, more preferably 400 mL / 100 g or more, and 420 mL / 100 g or more. More preferably it is. When the dibutyl phthalate oil absorption is 350 mL / 100 g or more, good conductivity can be imparted with a small content of carbon black (B).

  The carbon black (B) is not particularly limited, and specifically, Ketjen Black EC-300J [dibutyl phthalate: 365 mL / 100 g], Ketjen Black EC-600JD [dibutyl phthalate: 480 mL] / 100 g] (Ketjen Black International Co., Ltd.), Printex XE2-B [Dibutyl phthalate: 420 mL / 100 g] (Orion Engineered Carbons Co., Ltd.), and the like. Two or more carbon blacks may be used in combination.

  The content of carbon black (B) is more than 5% by mass and not more than 15% by mass with respect to the entire polyacetal resin composition, and is preferably 6% by mass, more preferably 7% by mass with respect to the lower limit of the content. The upper limit of the content is preferably 12% by mass, and more preferably 10% by mass. When the content is more than 5% by mass, sufficient conductivity can be obtained, and when it is 15% by mass or less, it is possible to obtain a polyacetal resin composition in which various properties are balanced.

(Graphite (C))
The graphite used for the component (C) of the present embodiment is not particularly limited, but specifically, it can be appropriately selected from artificial graphite and natural graphite according to the purpose. When the graphite (C) used in the present embodiment is a powder, the shape of the graphite powder may be any of a scale shape, a block shape, a spherical shape, and the like. As the component (C), natural graphite is preferable and scale-like natural graphite is more preferable from the viewpoint of better electrical conductivity.

  When the graphite (C) used in the present embodiment is a powder, the average particle size is preferably in the range of 0.5 to 100 μm, more preferably 1 to 80 μm, and further preferably 5 to 50 μm. 0.5 μm or more is preferable from the viewpoint of sufficient conductivity, and 100 μm or less is preferable from the viewpoint of handling and maintaining the appearance of the molded product surface. The average particle size can be determined, for example, by observing graphite with a transmission electron microscope and directly measuring the particle size in the obtained image.

  Moreover, it is preferable that content of graphite (C) is 0.1-10 mass% with respect to the whole polyacetal resin composition, More preferably, it is 1-5 mass%, More preferably, it is 2-5 mass %. When the graphite content is 0.1% by mass or more, the conductivity can be stabilized, and when it is 10% by mass or less, the thermal stability of the composition can be maintained.

  The graphite (C) as described above is not particularly limited. Specifically, F # 3 [average particle size 60 μm], CPB [average particle size 19 μm], J-CPB [average particle size 5 μm] (Japan) Graphite Co., Ltd.), CNP15 [average particle size 15 μm], Z-5F [average particle size 5 μm] (manufactured by Ito Graphite Industries Co., Ltd.), and the like. Two or more types of graphite may be used in combination.

  The mass ratio (C) / (B) of graphite (C) to carbon black (B) is preferably in the range of 1/99 to 50/50, more preferably 5/95 to 40/60, and further Preferably it is 10 / 90-35 / 65. When the mass ratio is 1/99 or more, more stable conductivity can be obtained, and when the mass ratio is 50/50 or less, the composition molded piece has higher conductivity without adding a large amount of conductive filler. Can be given.

(Substance (D) which is liquid at 23 ° C.)
The substance used for the component (D) of the present embodiment is not particularly limited as long as it is a liquid substance at 23 ° C., and may be a single component or a mixture of two or more substances. . By adding a liquid substance at 23 ° C., the dispersibility of the carbon black (B) and the graphite (C) in the polyacetal resin (A) is improved during extrusion, and the strand is extruded from the extruder. The amount of generated spear can be kept to a very small amount. Thereby, the fall of the electroconductivity by mixing of an eye spear (foreign substance) can be suppressed. In addition to this, even during molding, a liquid substance is interposed at 23 ° C. between the mold and the substance that causes mold contamination, so that mold contamination during continuous molding is kept to a very low level. Can do.

  Among the substances (D) that are liquid at 23 ° C. as described above, those that do not undergo a phase change between 23 ° C. and 240 ° C. under normal pressure are preferably used. Specifically, mineral oils such as liquid paraffin, baby oil, ceresin, mineral wax, petroleum wax, silicone oil, cocoon oil, oil shale, creosote oil, bitumen; synthetic oil, castor oil, paulownia oil, oilseed oil, mortar Oil, flaxseed oil, shortening, salad oil, white squeezed oil, corn oil, soybean oil, sesame oil, rapeseed oil, safflower oil, sunflower oil, rice bran oil, coconut oil, coconut oil, palm oil, palm kernel oil, coconut oil, cottonseed oil, hemp seed Oil, grape oil, poppy oil, crow oil, wheat germ oil, evening primrose oil, perilla oil, camellia oil, apricot oil, akebi oil, wild tea flower oil, tea oil, walnut oil, birch oil, dairy oil, coconut oil, olive Oil, peanut oil, almond oil, hazelnut oil, avocado oil, grape seed oil, macadamia nut oil, argan oil, -Rel oil, pumpkin seed oil, pecan nut oil, pistachio oil, jojoba oil, cacao butter, babas oil, cacao butter, borage oil, shea butter, baobab oil, melon seed oil, mango butter, salva butter, crumb butter, kokum butter, meadow foam oil, coffee bean oil , Marula nut oil, broccoli seed oil, peach kernel oil, cherry kernel oil, cranberry seed oil, pomegranate seed oil, kukui nut oil, neem oil, kiwi fruit seed oil, rosehip oil, seabaxon, mongoigo oil, chink oil, Vegetable oil such as beeswax oil, wood wax, candelilla wax, carnauba wax, essential oil; beef tallow, bone oil, fish oil, chicken oil, duck oil, coconut oil, horse oil, lanolin, schmalz, ba -Emul oil, Su oil, Gee, Whale oil, Dolphin oil, Mink oil, Squalane, Egg yolk oil, Liver oil, Cocktail oil, Beef leg oil, Beeswax and other animal oils; Synthetic oils such as ester oil and olefin oil .

  Among these, from the viewpoint of improving the smoothness of the surface of the molded piece and reducing mold contamination during continuous molding, the kinematic viscosity at 23 ° C. is preferably 200 cSt or less, more preferably 150 cSt or less. More preferably 100 cSt or less. The kinematic viscosity can be measured by a generally used viscometer.

  The component (D) is preferably one or more selected from the group consisting of ester oils such as liquid paraffin, aliphatic diesters and aliphatic triesters. It is more preferable that it is 1 type or 2 types selected from the group which consists of ester.

  In addition, the content of the component (D) is 0.05% by mass or more and 0.5% by mass or less, preferably 0.1% by mass or more and 0.3% by mass or less, more preferably based on the whole polyacetal composition. Is 0.1 mass% or more and 0.2 mass% or less. By setting it as such a range, the mold contamination at the time of continuous molding can be suppressed, and high electroconductivity can be obtained.

(Fatty ester (E) which is solid at 23 ° C.)
The polyacetal resin composition of the present embodiment further contains an aliphatic ester (E) that is solid at 23 ° C. from the viewpoint of improving the smoothness of the surface of the molded piece and reducing mold contamination during continuous molding. Is preferred. Specific examples of the aliphatic ester (E) that is solid at 23 ° C. are not particularly limited, and specifically, from a monovalent fatty acid having 12 to 30 carbon atoms and a monovalent aliphatic alcohol having 10 to 30 carbon atoms. The ester which becomes is mentioned. These (E) components which work as a slidability improver may be used alone or in combination of two or more.

  Although it does not specifically limit as (E) component, Specifically, it is ester of the monohydric fatty acid and monohydric aliphatic alcohol shown below. Although it does not specifically limit as monovalent fatty acid, Specifically, undecyl acid, lauric acid, tridecyl acid, myristic acid, pentadecylic acid, palmitic acid, pentadecylic acid, stearic acid, nanodecanoic acid, arachidic acid, behenic acid, lignoserine Examples include acids, serotic acid, heptaconic acid, montanic acid, melissic acid, lacteric acid, undecylenic acid, oleic acid, elaidic acid, cetreic acid, erucic acid, brassic acid, linoleic acid, linolenic acid, arachidonic acid, stearic acid . Although it does not specifically limit as monohydric aliphatic alcohol, Specifically, lauryl alcohol, tridecyl alcohol, myristyl alcohol, pentadecyl alcohol, cetyl alcohol, heptadecyl alcohol, stearyl alcohol, oleyl alcohol, nonadecyl alcohol, Eico Examples thereof include saturated / unsaturated alcohols such as sil alcohol, ceryl alcohol, behenyl alcohol, melyl alcohol, hexyl decyl alcohol, octyl dodecyl alcohol, decyl myristyl alcohol, decyl stearyl alcohol, and unilin alcohol. Further, it may be a naturally occurring fatty acid containing these components or a mixture thereof. These fatty acids may be substituted with a hydroxy group. Moreover, the synthetic fatty acid which carried out carboxyl modification | denaturation of the terminal of unilin alcohol which is a synthetic aliphatic alcohol may be sufficient. Of the monovalent fatty acids and monovalent fatty alcohols described above, cetyl myristate, which is an ester of myristic acid and cetyl alcohol, is particularly preferred.

  Further, from the viewpoint of improving the smoothness of the surface of the molded piece and reducing the mold contamination during continuous molding, the mass ratio of the aliphatic ester (E) that is solid at 23 ° C. and the substance (D) that is liquid at 23 ° C. (E) / (D) is preferably more than 10 and 20 or less, more preferably 12 or more and 18 or less, and still more preferably 13 or more and 17 or less.

(Other ingredients)
If necessary, the polyacetal resin composition of the present embodiment may further contain a formaldehyde-reactive nitrogen-containing compound, an antioxidant, a formic acid scavenger, a weathering (light) stabilizer, and a release agent. Although it does not specifically limit as these content, Preferably, it can add in 0.01-1 mass part with respect to 100 mass parts of polyacetal resin (A), respectively.

  The formaldehyde-reactive nitrogen-containing compound is not particularly limited, and specifically, polyamide resins such as nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 12, and the like, and Examples of these polymers include nylon 6 / 6-6 / 6-10 and nylon 6 / 6-12. Other examples include acrylamide and its derivatives, and copolymers of acrylamide and its derivatives and other vinyl monomers, such as those obtained by polymerizing acrylamide and its derivatives and other vinyl monomers in the presence of a metal alcoholate. And poly-β-alanine copolymer. Other examples include amide compounds, amino-substituted triazine compounds, adducts of amino-substituted triazine compounds and formaldehyde, condensates of amino-substituted triazine compounds and formaldehyde, urea, urea derivatives, hydrazine derivatives, imidazole compounds, and imide compounds.

  Specific examples of the amide compound include, but are not limited to, polycarboxylic acid amides such as isophthalic acid diamide and anthranilamides. Specific examples of the amino-substituted triazine compound include, but are not limited to, 2,4-diamino-sym-triazine, 2,4,6-triamino-sym-triazine (melamine), N-butylmelamine, N-phenylmelamine, N, N-diphenylmelamine, N, N-diallylmelamine, benzoguanamine (2,4-diamino-6-phenyl-sym-triazine), acetoguanamine (2,4-diamino-6-methyl-sym-triazine), 2 , 4-diamino-6-butyl-sym-triazine and the like. Specific examples of the adduct of an amino-substituted triazine compound and formaldehyde include, but are not limited to, N-methylol melamine, N, N′-dimethylol melamine, N, N ′, N ″ -trimethylol melamine. Specific examples of condensates of amino-substituted triazine compounds and formaldehyde are not particularly limited, and examples thereof include melamine-formaldehyde condensates, and examples of urea derivatives include, but are not limited to, N-substituted ureas. , Urea condensates, ethylene urea, hydantoin compounds, and ureido compounds Specific examples of N-substituted urea include, but are not limited to, methylurea substituted with a substituent such as an alkyl group, alkylenebisurea, Examples of urea-condensates are aryl-substituted ureas. Is not particularly limited, and examples thereof include urea and formaldehyde condensates, etc. Specific examples of the hydantoin compound include, but are not particularly limited to, hydantoin, 5,5-dimethylhydantoin, 5,5-diphenylhydantoin, and the like. Specific examples of the ureido compound include, but are not limited to, allantoin, etc. The hydrazine derivative is not particularly limited, and may be a hydrazide compound, although specific examples of the hydrazide compound are not particularly limited. Dicarboxylic acid dihydrazide, and more specifically, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, speric acid dihydrazide, azelaic acid dihydrazide, Specific examples of imidazole compounds include, but are not limited to, imidazole dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, phthalic acid dihydrazide, 2,6-naphthalenedicarbodihydrazide, and the like. Specific examples of imide compounds include, but are not limited to, succinimide, glutarimide, and phthalimide, and formaldehyde-reactive nitrogen. The polymer or compound containing an atom may be used alone or in combination of two or more, and melamine is particularly preferred among these formaldehyde-reactive nitrogen-containing compounds or polymers.

  Although it does not specifically limit as antioxidant, Specifically, hindered phenolic antioxidant is preferable. Specific examples of the hindered phenol antioxidant are not particularly limited, but n-octadecyl-3- (3 ′, 5′-di-t-butyl-4′-hydroxyphenyl) -propionate, n-octadecyl- 3- (3'-Methyl-5'-t-butyl-4'-hydroxyphenyl) -propionate, n-tetradecyl-3- (3 ', 5'-di-t-butyl-4'-hydroxyphenyl)- Propionate, 1,6-hexanediol-bis- [3- (3,5-di-t-butyl-4-hydroxyphenyl) -propionate], 1,4-butanediol-bis- [3- (3,5 -Di-t-butyl-4-hydroxyphenyl) -propionate], triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) Propionate], pentaerythritol tetrakis [methylene-3- (3 ', 5'-di -t- butyl-4'-hydroxyphenyl) propionate], and methane. Of these, triethylene glycol-bis- [3- (3-tert-butyl-5-methyl-4-hydroxyphenyl) -propionate] and pentaerythritol tetrakis [methylene-3- (3 ′, 5 '-Di-t-butyl-4'-hydroxyphenyl) propionate] methane. These antioxidants are used alone or in combination of two or more.

  The formic acid scavenger is not particularly limited, and examples thereof include the above-mentioned amino-substituted triazine compounds and condensates of amino-substituted triazine compounds with formaldehyde, such as melamine / formaldehyde condensates. Examples of other formic acid scavengers include alkali metal or alkaline earth metal hydroxides, inorganic acid salts, and alkoxides. More specifically, for example, hydroxides of sodium, potassium, magnesium, calcium or barium, carbonates, phosphates, silicates and borates of the above metals can be mentioned. These formic acid scavengers are used singly or in combination of two or more.

  The weather resistance (light) stabilizer is not particularly limited, but specifically, it is preferably at least one selected from benzotriazole-based and oxalic acid anilide-based UV absorbers and hindered amine-based light stabilizers.

  Although it does not specifically limit as a specific example of a benzotriazole type ultraviolet absorber, 2- (2'-hydroxy-5'-methyl-phenyl) benzotriazole, 2- (2'-hydroxy-3 ', 5'-di). -T-butyl-phenyl) benzotriazole, 2- [2'-hydroxy-3 ', 5'-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- [2'-hydroxy-3 Examples include ', 5'-bis- (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole and 2- (2′-hydroxy-4′-octoxyphenyl) benzotriazole. The benzotriazole-based ultraviolet absorber is preferably 2- [2′-hydroxy-3 ′, 5′-bis- (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (2′-hydroxy- 3 ', 5'-di-tert-butyl-phenyl) benzotriazole. These benzotriazole-based ultraviolet absorbers are used alone or in combination of two or more.

  Specific examples of the oxalic acid alinide ultraviolet absorber are not particularly limited, but 2-ethoxy-2′-ethyloxalic bisanilide, 2-ethoxy-5-t-butyl-2′-ethyloxalic acid Bisanilide and 2-ethoxy-3′-dodecyloxalic acid bisanilide are mentioned.

  Specific examples of the hindered amine light stabilizer are not particularly limited, but N, N ′, N ″, N ′ ″-tetrakis- (4,6-bis (butyl- (N-methyl-2,2, 6,6-tetramethylpiperidin-4-yl) amino) -triazin-2-yl) -4,7-diazadecane-1,10-diamine, dibutylamine, 1,3,5-triazine, N, N′- A polycondensate of bis (2,2,6,6-tetramethyl-4-piperidyl-1,6-hexamethylenediamine and N- (2,2,6,6-tetramethyl-4-piperidyl) butylamine; 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, -Tetramethyl-4-piperidyl) imino}], a condensate of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, bis (2,2,6) decanoate , 6-Tetramethyl-1 (octyloxy) -4-piperidinyl) ester, 1,1-dimethylethyl hydroperoxide and octane, bis (1,2,2,6,6-pentamethyl-4- Piperidyl) [[3,5-bis (1,1-dimethylethyl) -4-hydroxyphenyl] methyl] butyl malonate, methyl-1,2,2,6,6-pentamethyl-4-piperidyl sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis (N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate 1,2,3,4-butanetetracarboxylic acid, 1,2,2,6,6-pentamethyl-4-piperidinol and β, β, β ′, β′-tetramethyl-3,9- [2,4 , 8,10-tetraoxaspiro (5,5) undecane] diethanol, and the hindered amine light stabilizer is preferably bis (2,2,6,6-tetramethyl-4-piperidyl). Sebacate, bis (N-methyl-2,2,6,6-tetramethyl-4-piperidinyl) sebacate, 1,2,3,4-butanetetracarboxylic acid and 1,2,2,6,6-pentamethyl- It is a condensate of 4-piperidinol and β, β, β ′, β′-tetramethyl-3,9- [2,4,8,10-tetraoxaspiro (5,5) undecane] diethanol. Light stability It is used alone or in combination of two or more kinds.

  Although it does not specifically limit as a mold release agent, Specifically, alcohol, polyoxyalkylene glycol, and the olefin compound whose average degree of polymerization is 10-500 are used preferably.

(Additive)
The polyacetal resin composition of the present embodiment may further contain a known additive as necessary. Specific examples of such additives include crystal nucleating agents, conductive materials, thermoplastic resins, thermoplastic elastomers, and pigments.

  Although it does not specifically limit as a crystal nucleating agent, For example, boron nitride etc. are mentioned.

  The conductive agent is not particularly limited, and examples thereof include carbon fiber, artificial or natural graphite, single-walled or multi-walled carbon nanotube, metal powder, and metal fiber.

  Although it does not specifically limit as a thermoplastic resin, For example, polyolefin resin, an acrylic resin, a styrene resin, a polycarbonate resin, and an uncured epoxy resin (A resin hardening accelerator may be included as needed). It is done. Moreover, you may use the modified material of these resin as a thermoplastic resin.

  Although it does not specifically limit as a thermoplastic elastomer, For example, a polyurethane-type elastomer, a polyester-type elastomer, a polystyrene-type elastomer, and a polyamide-type elastomer are mentioned.

  Although it does not specifically limit as a pigment, Specifically, an inorganic pigment, an organic pigment, a metallic pigment, and a fluorescent pigment are mentioned. Here, the inorganic pigment is not particularly limited, and specific examples thereof include those generally used for coloring resins, such as zinc sulfide, titanium oxide, barium sulfate, titanium yellow, and cobalt blue. Examples thereof include combustion pigments, carbonates, phosphates, acetates, carbon black, acetylene black, and lamp black. Further, the organic pigment is not particularly limited. For example, condensed azo, inone, furothocyanin, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennon, quinacridone, thioindico , Berylene-based, dioxazine-based, and phthalocyanine-based pigments. The addition ratio of the pigment to the polyacetal resin composition of the present embodiment is difficult to define clearly because it varies greatly depending on the required color tone, but in general, it is 100 parts by mass of the polyacetal resin (A). On the other hand, it can be used in the range of 0.05 to 5 parts by mass.

[Method for producing polyacetal resin composition]
Next, the suitable manufacturing method of the polyacetal resin composition of this embodiment is demonstrated. The manufacturing method of the polyacetal resin composition of this embodiment can use the melt kneader generally used. Examples of the melt kneader include a kneader, a roll mill, a single screw extruder, a twin screw extruder, and a multi screw extruder. The processing temperature at this time is preferably 180 to 240 ° C., and in order to maintain the quality and the working environment, it is preferable to perform deaeration by substitution with an inert gas or single-stage and multistage vents.

  Among these, a twin screw extruder equipped with a decompression device and a side feeder is preferable, and a twin screw extruder equipped with a plurality of side feeders is more preferable. The polyacetal resin composition of the present embodiment can be obtained by melting and kneading the above components using such an apparatus. Melt-kneading methods include a method of melt-kneading all components simultaneously, a method of melt-kneading a premixed mixture, and successively supplying each component from the side feeder in the middle of the barrel of the extruder and melt-kneading. A method is mentioned.

  Among these, a blend obtained by mixing substances other than carbon black (B) in a solid state is supplied from the upstream side of the twin-screw extruder, and carbon black (B) is supplied from a side feeder provided downstream thereof. A melt kneading method is preferred. Thereby, carbon black (B) will be mix | blended with polyacetal resin (A) in presence of the substance (D) which is liquid at 23 degreeC, and carbon black (B) in polyacetal resin (A) will be mix | blended. Dispersibility can be further improved.

  Although the pressure reduction degree of an extruder is not specifically limited, 0-0.07 Mpa is preferable. The melt kneading temperature is preferably 1 to 100 ° C. higher than the melting point obtained by differential scanning calorimetry (DSC) measurement according to JIS K7121 of the polyacetal resin (A) to be used. More specifically, the melt kneading temperature is preferably 160 ° C to 240 ° C. The shear rate in the kneader is preferably 100 rpm or more, and the average residence time during kneading is preferably 30 seconds to 1 minute.

  The method for producing a molded product by molding the polyacetal resin composition of the present embodiment is not particularly limited as long as it is the same as the method for molding a conventional polyacetal resin composition. The methods include, for example, extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, other material molding, gas assist injection molding, firing injection molding, low pressure molding, ultra-thin injection molding (ultra-thin molding) High speed injection molding) and in-mold composite molding (insert molding, outsert molding).

〔Molding〕
A molded product obtained from the polyacetal resin composition of the present embodiment by the molding method described above, for example, an injection molded product obtained by injection molding, can be used as a molded product for various applications. Examples of such molded products include gears, cams, sliders, levers, arms, clutches, felt clutches, idler gears, pulleys, rollers, rollers, key stems, key tops, shutters, reels, shafts, joints, shafts. Mechanical parts typified by bearings and guides; Outsert molded resin parts; Insert molded resin parts; Mechanical parts inside office automation equipment typified by chassis, trays, side plates, printers and copiers; VTR (Video) Tape Recorder, video movie, digital video camera, camera and parts for video equipment represented by digital camera; cassette player, DAT, LD (Laser Disk), MD (Mini Disk), CD (Compact Di) k) [including CD-ROM (Read Only Memory), CD-R (Recordable), CD-RW (Rewriteable)], DVD (Digital Video Disk) [DVD-ROM, DVD-R, DVD + R, DVD-RW, DVD + RW, DVD-R DL, DVD + R DL, DVD-RAM (including Random Access Memory), DVD-Audio, Blu-ray Disc, HD-DVD, other optical disk drives, MFD, MO, navigation system and mobile personal computer Music, video or information equipment represented by: parts for communication equipment represented by mobile phones and facsimiles; parts for electrical equipment; parts for electronic equipment.

  The molded product can also be used as parts for automobiles, for example, fuel-related parts such as gasoline tanks, fuel pump modules, valves, gasoline tank flanges, etc .; door locks, door handles , Door regulators such as window regulators and speaker grills; seat belt peripherals such as seat belt slip rings and press buttons; combination switch parts, switches and clips; and mechanical pencils Mechanical parts for putting in and out the nib and mechanical pencil core; wash basin and drain and drain valve opening / closing mechanism parts; vending machine opening / closing part locking mechanism and product discharge mechanism parts; clothing cord stopper, adjuster, and Button; nozzle for watering and watering hose connection Joints; building materials that support stair railings and floor materials; disposable cameras, toys, fasteners, chains, conveyors, buckles, sports equipment; vending machines; furniture; musical instruments; and industries represented by housing equipment It is also suitably used as a part.

  As mentioned above, although the form for implementing this invention was demonstrated, this invention is not limited to the said this embodiment. The present invention can be variously modified without departing from the gist thereof.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention more concretely, this invention is not limited at all by these.

The following were used for each component used in the examples of the present application.
[Polyacetal resin (A)]
A twin-screw self-cleaning type polymerization machine with a jacket through which a heat medium can pass (L / D = 8 (L: distance (m) from the raw material supply port to the discharge port of the polymerization reactor, D: of the polymerization reactor) The inner diameter (m), the same applies hereinafter))) to 80 ° C., 4 kg / hr of trioxane, 128.3 g / h of 1,3-dioxolane as a comonomer (3.9 mol% with respect to 1 mol of trioxane), Methylal was continuously added as a chain transfer agent so that the resulting polyacetal resin had a melt flow rate of 30 g / 10 min. Further, boron trifluoride di-n-butyl etherate was continuously added as a polymerization catalyst at 1.5 × 10 ⁻⁵ mol with respect to 1 mol of trioxane to carry out polymerization.

  The polyacetal copolymer discharged from the polymerization machine was put into a 0.1% aqueous solution of triethylamine to deactivate the polymerization catalyst. After filtering the deactivated polyacetal copolymer with a centrifuge, an aqueous solution containing choline formate (triethyl-2-hydroxyethylammonium formate) as a quaternary ammonium compound with respect to 100 parts by mass of the polyacetal copolymer. 1 part by mass was added and mixed uniformly and then dried at 120 ° C. The addition amount of the hydroxycholine formate was adjusted by adjusting the concentration of the hydroxycholine formate in the aqueous solution containing the added choline formate, and was 20 mass ppm in terms of the amount of nitrogen. The dried polyacetal copolymer is supplied to a vented twin screw extruder, and 0.5 parts by mass of water is added to 100 parts by mass of the melted polyacetal copolymer in the extruder, and the extruder set temperature is 200 ° C. The unstable terminal portion was decomposed and removed in a residence time of 7 minutes in the extruder. The polyacetal copolymer whose unstable terminal portion was decomposed was devolatilized under a condition of a vent vacuum of 20 Torr, extruded as a strand from the extruder die, and pelletized. Triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate] 0.3 as an antioxidant with respect to 100 parts by mass of the polyacetal resin thus obtained. Polyacetal resin pellets were produced by adding parts by mass and melt-kneading with a vented twin-screw extruder.

[Carbon black (B)]
(B-1) Ketjen Black EC300J (Ketjen Black International Co., Ltd., dibutyl phthalate oil absorption 360 mL / 100 g)
(B-2) Printex XE2-B (manufactured by Orion Engineered Carbons Co., Ltd., dibutyl phthalate oil absorption 420 mL / 100 g)
(B-3) Ensaco 350G (manufactured by Timical Co., Ltd., dibutyl phthalate oil absorption 320 mL / 100 g)

  In addition to the two components (A) and (B) described above, the polyacetal composition of this example contains a condensate of cresol novolak and epichlorohydrin as an epoxy resin as necessary (Asahi Kasei E-Materials Co., Ltd.). Manufactured by ECN-1299), and triphenylphosphine (made by Hokuko Chemical Co., Ltd.) and dicyandiamide (made by Nippon Carbide Industries Co., Ltd.) were used as epoxy resin curing accelerators.

[Graphite (C)]
(C-1) F # 3 [scale-like natural graphite, average particle size 19 μm] (manufactured by Nippon Graphite Co., Ltd.)
(C-2) AGB-20 [granular artificial graphite, average particle size 18 μm] (manufactured by Ito Graphite Industries Co., Ltd.)

[Substance (D) which is liquid at 23 ° C.]
(D-1) DIDA (manufactured by Daihachi Chemical Industry, diisodecyl adipate, kinematic viscosity at 23 ° C. 30 cSt)
(D-2) Unistar H310R (manufactured by NOF, trimethylolpropane tridodecanoate, kinematic viscosity at 23 ° C. 40 cSt)
(D-3) Sumoyle PS-120 (manufactured by Matsumura Oil, liquid paraffin, kinematic viscosity at 23 ° C. 110 cSt)
(D-4) Lucant HC-40 (manufactured by Mitsui Chemicals, liquid polyolefin oligomer, kinematic viscosity at 23 ° C. 1000 cSt)

[Fatty acid ester (E) which is solid at 23 ° C.]
(E-1) Cetyl myristate (made by Kitahiro Chemical)

[Evaluation method of conductivity]
Using an EC75-NII injection molding machine manufactured by Toshiba Machine Co., Ltd., the cylinder temperature is set to 205 ° C., the mold temperature is set to 90 ° C., and the evaluation ISO is used under injection conditions of an injection pressure of 70 MPa, an injection time of 35 seconds, and a cooling time of 15 seconds. I got a dumbbell. A 30 × 20 × 4 mm flat plate is cut out from this ISO dumbbell, and a four-probe ASP probe (pin spacing 5 mm, pin tip 0.37 mmR × 4, spring pressure 210 g / piece, JIS K7194 compatible) is pressed against this flat plate, Mitsubishi The volume resistivity was measured at a measurement voltage of 90 V using a chemical Loresta GP.

[Method for evaluating mold deposit resistance (MD) performance]
Using an IS-100GN injection molding machine manufactured by Toshiba Machine Co., Ltd., the cylinder temperature was set to 180 ° C., the mold temperature was set to 70 ° C., and the injection conditions were an injection pressure of 70 MPa, an injection time of 60 seconds, and a cooling time of 15 seconds. A test piece of a flat plate with a grain having a thickness of 2 mm and a width of 80 mm × 80 mm was formed from a polyacetal resin composition described later. The contamination state (mold deposit; hereinafter referred to as MD) in the mold after continuous molding under these conditions was visually observed every 50 shots, and the number of shots at which MD could be confirmed was recorded. Furthermore, in order to confirm the ease of removal of MD, the substance adhering to the mold was wiped off, and the ease of removal was judged according to the following criteria.
Evaluation 1: Can be completely removed by lightly wiping with a tissue. Evaluation 2: Can be completely removed by wiping with a tissue strongly. Evaluation 3: Can be removed immediately using a mold cleaner. Evaluation 4: Adhering to a mold. It is strong and cannot be removed immediately even if a mold cleaner is used.

[Production Method of Polyacetal Resin Composition]
(Explanation of Extruder (Fig. 1))
In this example, a resin composition was produced using a twin-screw extruder (TEM-26SS extruder (L / D = 48, with vent) manufactured by Toshiba Machine Co., Ltd.). 1 to 12: Extruder barrel zone (independently) 13: Die head, 14: Extruder motor, 15: Fixed feeder (top) (CE-W-1 manufactured by Kubota Corporation) (Kubota Corp., CE-W-0), 16: Fixed feeder (side) (Kubota Corp., CE-W-0), 17: Degassing vent

(Raw material feed method)
After components other than carbon black (B) were uniformly mixed with a blender, the uniform mixture was top-fed from the quantitative feeder 15, and carbon black (B) was side-fed from the quantitative feeder 16.

(Melt kneading)
In FIG. 1, the barrel zone 1 is cooled by cooling water, the barrel zone 2 is set to 180 ° C., the barrel zones 3 to 12 and the die head are set to 200 ° C., and the above feeding method is used. The raw materials were fed to the extruder at the rate shown in Table 1, deaerated with a vacuum pump from 17 deaeration vents, and melt-kneaded at a screw rotation speed of 150 rpm and an extrusion rate of 15 kg / hr. The extruded resin was pelletized with a strand cutter. Using this pellet, the volume resistivity was measured and the MD performance was evaluated by the method described above.

[Examples 1 to 14]
Each component was mix | blended in the ratio of the quantity shown in Table 1, the polyacetal resin composition was manufactured with the above-mentioned extrusion method, and physical property evaluation was performed.

[Comparative Examples 1-19]
Each component was mix | blended in the ratio of the quantity shown in Table 2, the polyacetal resin composition was manufactured with the above-mentioned extrusion method, and physical property evaluation was performed.

  The polyacetal resin composition of the present invention is excellent in electrical conductivity and has very little mold contamination during continuous molding. Therefore, it can be suitably used in a wide range of fields such as automobiles, precision parts of electrical and electronic equipment, and other industries. In this case, it is possible to dramatically suppress the deterioration of the yield.

  DESCRIPTION OF SYMBOLS 1-12 ... Barrel zone of an extruder, 13 ... Die head, 14 ... Extruder motor, 15 ... Metering feeder (top), 16 ... Metering feeder (side), 17 ... Deaeration vent

Claims (8)

Polyacetal resin (A);
Carbon black (B),
Graphite (C);
A substance (D) which is liquid at 23 ° C.,
The carbon black (B) content is more than 5% by mass and 15% by mass or less,
The polyacetal resin composition wherein the content of the substance (D) that is liquid at 23 ° C. is 0.05% by mass or more and 0.5% by mass or less.   The polyacetal resin composition according to claim 1, wherein the kinematic viscosity at 23 ° C. of the substance (D) that is liquid at 23 ° C. is 200 cSt or less.   The polyacetal according to claim 1, wherein the substance (D) that is liquid at 23 ° C. is one or more selected from the group consisting of liquid paraffin, aliphatic diester, and aliphatic triester. Resin composition.   The polyacetal according to any one of claims 1 to 3, wherein the substance (D) that is liquid at 23 ° C is one or two selected from the group consisting of aliphatic diesters and aliphatic triesters. Resin composition.   The polyacetal resin composition according to any one of claims 1 to 4, wherein the carbon black (B) has a dibutyl phthalate oil absorption of 350 mL / 100 g or more.   The polyacetal resin composition according to any one of claims 1 to 5, wherein the graphite (C) is natural graphite.   Furthermore, the polyacetal resin composition of any one of Claims 1-6 containing the aliphatic ester (E) which is solid at 23 degreeC.   The mass ratio (E) / (D) of the fatty acid ester (E) that is solid at 23 ° C and the substance (D) that is liquid at 23 ° C is more than 10 and 20 or less. Polyacetal resin composition.