JP5774382B2 - Resin composition and molded body - Google Patents

Description

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

  Polyacetal resin is excellent in the balance of physical properties such as mechanical strength, chemical resistance and slidability, and has good workability. It is widely used mainly for mechanical parts including precision parts such as mechanical parts, automobile parts, gears and cams.

  On the other hand, mechanical parts related to paper feeding functions such as office multifunctional copiers and home-use multifunction copiers, and mechanical parts installed near electronic circuits require electrical conductivity. It has been broken.

  By the way, in recent years, from the trend of weight reduction and noise reduction, attempts have been made to convert these metal mechanical parts and other materials into resins, and the resin composition having both conductivity and slidability has been made. Proposals have been made (see, for example, Patent Document 1).

In addition, depending on the part, in order to avoid the charged electric charge being gradually slowed with sparks, the material is not a material having an excessively high conductivity, but a material having an appropriate conductivity, that is, a charge is gently diffused. There is a growing demand for materials.
In order to meet such demands, a conductive filler with different percolation (a phenomenon in which conductivity is rapidly improved) is used, and the conductivity is controlled by the filling amount of the conductive filler. The proposal of the technique which obtains a composition is made | formed (for example, refer patent document 2).

JP 2010-285539 A JP 2008-239947 A

In order to have the above-described performance of being difficult to be charged and slowly diffusing charges, it is necessary to control the volume resistivity so as to have appropriate conductivity.
However, the above-mentioned materials using a combination of conductive materials having different percolation thresholds are easier to control the conductivity due to composition fluctuations compared to the case where a conductive material is used alone. The problem is that the conductivity varies greatly depending on the shape of the part.

  In view of the above-described problems of the prior art, the present invention provides a resin composition and a molded body in which the electrical properties are not affected by molding conditions while maintaining the mechanical properties such as rigidity and toughness of the polyacetal resin. With the goal.

As a result of intensive studies to solve the above-described problems of the prior art, the present inventor has found that a resin composition containing an impact modifier and at least two kinds of conductivity-imparting materials with respect to the polyacetal resin is a problem of the prior art. Has been found to solve the problem, and the present invention has been completed.
That is, the present invention is as follows.

[1]
Containing a polyacetal resin, an impact modifier, and at least two types of conductivity imparting materials,
The conductivity imparting material includes at least one carbon-based conductive material and at least one metal oxide having a number average particle diameter of 1 μm or less and a volume resistivity of 10 ³ to 10 ⁹ Ω · cm. Resin composition.
[2]
The resin composition according to [1], wherein the carbon-based conductive material is at least one selected from the group consisting of carbon black, carbon fiber, carbon nanotube, and graphite.
[3]
The resin composition according to [1] or [2], wherein the metal oxide is an oxide of at least one metal selected from the group consisting of zinc, tin, iron, and titanium.
[4]
The impact modifier is at least one selected from the group consisting of polybutadiene, a copolymer of an aromatic vinyl compound and a conjugated diene compound, a hydrogenated copolymer of an aromatic vinyl compound and a conjugated diene compound, and a polyolefin. The resin composition according to any one of [1] to [3] .
[5]
The polyolefin is polyethylene, polypropylene, ethylene / α-olefin copolymer, ethylene / propylene / α-olefin copolymer, ethylene / acrylic acid copolymer, ethylene / alkyl acrylate copolymer, ethylene The resin composition according to [4] , which is at least one selected from the group consisting of a copolymer of methacrylic acid and a copolymer of ethylene and alkyl methacrylate.
[6]
The resin composition according to any one of [1] to [5] , wherein the impact modifier is contained in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of the polyacetal resin.
[7]
The resin composition according to any one of [1] to [6] , wherein the conductivity imparting material is contained in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the polyacetal resin.
[8]
The resin composition according to any one of [1] to [7] , wherein the conductivity imparting material contains 50% by mass or more of the metal oxide.
[9]
1 wherein the metal oxide is selected from the group consisting of tin dioxide, ferric tetroxide, and titanium dioxide.
The resin composition according to any one of [1] to [8] , which is a seed or more.
[10]
The resin composition according to any one of [1] to [9] , further including a surfactant.
[11]
The molded object obtained by shape | molding the resin composition as described in any one of said [1] thru | or [10] .

  The resin composition of the present invention can maintain a stable preferable volume resistance value and maintain electrostatic diffusibility even when the molding conditions and the shape of the molded body are changed.

Hereinafter, a mode for carrying out the present invention (hereinafter referred to as “the present embodiment”) will be described.
In addition, this invention is not limited to the following description, It can implement by changing variously within the range of the summary.

(Resin composition)
The resin composition of the present embodiment contains a polyacetal resin, an impact modifier, and at least two conductivity imparting materials, and the conductivity imparting material includes at least one carbon-based conductive material and at least one type. A resin composition having a volume resistivity of 10 ³ to 10 ⁹ Ω · cm.

(Polyacetal resin)
As polyacetal resin, formaldehyde monomer or polyacetal homopolymer consisting essentially of oxymethylene units obtained by homopolymerizing formaldehyde cyclic oligomers such as trimer (trioxane) and tetramer (tetraoxane), Formaldehyde monomers or cyclic oligomers of formaldehyde such as trimers (trioxane) and tetramers (tetraoxane), ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, 1,4-butanediol formal, etc. Examples include cyclic ethers such as cyclic formals of glycol and diglycol, and polyacetal copolymers obtained by copolymerization with cyclic formal.
Moreover, the polyacetal copolymer which has a branch obtained by copolymerizing monofunctional glycidyl ether, the polyacetal copolymer which has a crosslinked structure obtained by copolymerizing polyfunctional glycidyl ether, etc. can be used.

  Furthermore, a polyacetal homopolymer having a functional group such as a hydroxyl group at both ends or one end, for example, a polyacetal homopolymer having a block component obtained by polymerizing a formaldehyde monomer or a cyclic oligomer of formaldehyde in the presence of polyalkylene glycol. Polymer or polyacetal copolymer having a functional group such as a hydroxyl group at both ends or one end, for example, formaldehyde monomer or its trimer (trioxane) or tetramer (tetraoxane) in the presence of hydrogenated polybutadiene glycol A polyacetal copolymer having a block component obtained by copolymerizing a cyclic oligomer of formaldehyde and the like with a cyclic ether or cyclic formal can also be used.

As described above, as the polyacetal resin, any of a polyacetal homopolymer and a copolymer can be used, and a polyacetal copolymer is preferable.
Hereinafter, the polyacetal copolymer will be described in detail.
In the polyacetal copolymer, the content of the comonomer such as 1,3-dioxolane is generally 0.1 to 60 mol%, preferably 0.1 to 20 mol%, based on 1 mol of the trioxane, and more Preferably it is 0.13-10 mol%.
Moreover, as a polyacetal resin which comprises the resin composition of this embodiment, a melting point is a polyacetal copolymer with 164 to 173 degreeC, More preferably, it is 164 to 171 degreeC.
The melting point of the polyacetal resin is a differential scanning calorimeter (DSC-2C, manufactured by Perkin Elmer Co., Ltd.). The sample once heated to 200 ° C. and melted is cooled to 100 ° C., and again 2.5 ° C. The temperature of the peak of the exothermic spectrum generated in the process of raising the temperature at a rate of / min.

The polyacetal copolymer can be produced by a conventionally known polymerization method, and a polymerization catalyst is preferably used in the polymerization step.
As the polymerization catalyst, cationically active catalysts such as Lewis acids, proton acids and esters or anhydrides thereof are 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, pentachloride. Examples thereof include phosphorus, antimony pentafluoride, and complex compounds or salts thereof.
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.
In particular, 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 Boron trifluoride di-n-butyl ether can be mentioned as a suitable example.

  A conventionally known method can be applied as a polymerization method of the polyacetal copolymer. For example, the methods described in US30273352A, US3803094A, DE11614121C, DE1495228C, DE172080C, DE3018898C, and JP-A-58-98322 and JP-A-7-70267 can be applied.

The polyacetal copolymer obtained by the polymerization method has a thermally unstable terminal portion [— (OCH ₂ ) _n —OH group], so that it is difficult to put it to practical use as it is. Therefore, it is necessary to carry out the decomposition and removal processing of the unstable terminal portion, and it is preferable to perform the decomposition and removal processing of the following specific unstable terminal portion.

The decomposing / removing treatment of the specific unstable terminal is a polyacetal in the presence of at least one quaternary ammonium compound represented by the following general formula (1) at a temperature not lower than the melting point of the polyacetal copolymer and not higher than 260 ° C. The copolymer is heat-treated in a molten state.
[S ¹ S ² S ³ S ⁴ N ⁺ ] _n X ⁻ _n (1)

In the general formula (1), S ¹ , S ² , S ³ and S 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 the unsubstituted alkyl group having 1 to 30 carbon atoms or the substituted alkyl group is substituted with at least one aryl group having 6 to 20 carbon atoms; or the aryl group having 6 to 20 carbon atoms has at least one carbon number It represents an alkylaryl group substituted with 1 to 30 unsubstituted alkyl groups or substituted alkyl groups, and the unsubstituted alkyl group or substituted alkyl group is linear, branched, or cyclic.
The substituent of the substituted alkyl group is a halogen, a hydroxyl group, an aldehyde group, a carboxyl group, an amino group, or an amide group.
In the aryl group, aralkyl group, and alkylaryl group, a hydrogen atom may be substituted with a halogen.
n represents an integer of 1 to 3.
X represents a hydroxyl group or an acid residue of a carboxylic acid having 1 to 20 carbon atoms, a hydrogen acid other than hydrogen halide, an oxo acid, an inorganic thioacid, or an organic thioacid having 1 to 20 carbon atoms.

The quaternary ammonium compound used for the decomposition removal treatment of the specific unstable terminal portion is not particularly limited as long as it is represented by the general formula (1), but S ¹ and S ² in the general formula (1) are not limited. , S ³ and S 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 in particular, S ¹ , S ² , S ³ and S ^4. More preferably, at least one is a hydroxyethyl group.
Specifically, tetramethylammonium, tetoethylammonium, tetrapropylammonium, tetra-n-butylammonium, cetyltrimethylammonium, tetradecyltrimethylammonium, 1,6-hexamethylenebis (trimethylammonium), decamethylene-bis- ( Trimethylammonium), trimethyl-3-chloro-2-hydroxypropylammonium, trimethyl (2-hydroxyethyl) ammonium, triethyl (2-hydroxyethyl) ammonium, tripropyl (2-hydroxyethyl) ammonium, tri-n-butyl ( 2-hydroxyethyl) ammonium, trimethylbenzylammonium, triethylbenzylammonium, tripropylbenzylammonium, tri-n-butylbenzene Zirammonium, trimethylphenylammonium, triethylphenylammonium, trimethyl-2-oxyethylammonium, monomethyltrihydroxyethylammonium, monoethyltrihydroxyethylammonium, okdadecyltri (2-hydroxyethyl) ammonium, tetrakis (hydroxyethyl) ammonium, etc. Hydroxides of hydrochloric acid, odorous acid, hydrofluoric acid, etc .; sulfuric acid, nitric acid, phosphoric acid, carbonic acid, boric acid, chloric acid, iodic acid, silicic acid, perchloric acid, chlorous acid, hypochlorous acid Oxoacid salts such as chlorosulfuric acid, amidosulfuric acid, disulfuric acid, tripolyphosphoric acid; thioacid salts such as thiosulfuric acid; formic acid, acetic acid, propionic acid, butanoic acid, isobutyric acid, pentanoic acid, caproic acid, caprylic acid, capric acid Carboxylic acid salts such as benzoic acid and 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.

The quaternary ammonium compound used for the decomposition removal treatment of the specific unstable terminal portion may be used alone or in combination of two or more.
Further, in addition to the quaternary ammonium compound, there may be used any known amines such as ammonia and triethylamine, which are known decomposition accelerators for unstable terminals.

The amount of the quaternary ammonium compound used for the decomposition removal treatment of the specific unstable terminal portion is 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. In terms of the amount of nitrogen, it is preferably 0.05 to 50 ppm by mass, more preferably 1 to 30 ppm by mass.
P × 14 / Q (2)
(In the formula (2), P represents the concentration (mass ppm) of the quaternary ammonium compound relative to the polyacetal copolymer, 14 represents the atomic weight of nitrogen, and Q represents the molecular weight of the quaternary ammonium compound.)

  If the addition amount of the quaternary ammonium compound is less than 0.05 mass ppm, the decomposition and removal rate of the unstable terminal portion decreases, and if it exceeds 50 mass ppm, the color tone of the polyacetal copolymer after the decomposition and removal of the unstable terminal portion is reduced. Getting worse.

The decomposition and removal treatment of the unstable end portion of the polyacetal copolymer is preferably performed at a temperature not lower than the melting point and not higher than 260 ° C. while the polyacetal copolymer is melted.
Although there is no restriction | limiting in particular in the apparatus to be used, It is suitable to heat-process using an extruder, a kneader, etc.
Moreover, it is preferable that the formaldehyde generated in the decomposition removal treatment of the unstable terminal portion is removed under reduced pressure.

Although the addition method of the quaternary ammonium compound mentioned above includes a method of adding it as an aqueous solution in the step of deactivating the polymerization catalyst, a method of spraying on the polyacetal copolymer powder generated by the polymerization, etc., it is not limited thereto.
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, A quaternary ammonium 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 portion can be decomposed and removed 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 heat the polymerization catalyst under an inert gas atmosphere at a temperature below the melting point without deactivating the polymerization catalyst, and to volatilize and reduce the polymerization catalyst, and then perform the decomposition and removal treatment of the unstable end portion. It is.
By the above-described decomposition and removal treatment of the specific unstable terminal portion, it is possible to obtain a polyacetal copolymer with very few unstable terminal portions and excellent in thermal stability.

  Further, the melt flow rate (MFR, JIS-K7210 compliant 190 ° C., 2.16 kg load) of the polyacetal resin constituting the resin composition of the present embodiment is preferably 0.5 to 100 g / 10 minutes, more preferably 1 0.0 to 80 g / 10 min.

(Impact modifier)
Next, the impact improving material constituting the resin composition of the present embodiment will be described in detail.
Examples of the impact modifier include at least one selected from polybutadiene, a copolymer of an aromatic vinyl compound and a conjugated diene compound, a hydrogenated product of a copolymer of an aromatic vinyl compound and a conjugated diene compound, and a polyolefin. It is done.

The copolymer of an aromatic vinyl compound and a conjugated diene compound comprises a polymer block mainly composed of at least one aromatic vinyl compound and a polymer block mainly composed of at least one conjugated diene compound. It is a copolymer including a block copolymer.
“Mainly” in a polymer block mainly composed of an aromatic vinyl compound refers to a block in which at least 50% by mass or more of the block is an aromatic vinyl compound. More preferably, it is 70 mass% or more, More preferably, it is 80 mass% or more, More preferably, it is 90 mass% or more.
The same applies to “mainly” in a polymer block mainly composed of a conjugated diene compound, and refers to a block in which at least 50% by mass or more is a conjugated diene compound. More preferably, it is 70 mass% or more, More preferably, it is 80 mass% or more, More preferably, it is 90 mass% or more.
In this case, for example, even in the case of a block in which a small amount of a conjugated diene compound or other compound is randomly bonded in the aromatic vinyl compound block, 50% by mass of the block is formed from the aromatic vinyl compound. If it is, it is regarded as a block copolymer mainly composed of an aromatic vinyl compound. The same applies to the case of a conjugated diene compound.

Specific examples of the aromatic vinyl compound include styrene, α-methylstyrene, vinyltoluene, and the like. One or more compounds selected from these are used, and styrene is particularly preferable.
Specific examples of the conjugated diene compound include butadiene, isoprene, piperylene, 1,3-pentadiene and the like. One or more compounds selected from these are used, but butadiene, isoprene and combinations thereof are particularly preferable.

  The microstructure of the block part of the conjugated diene compound in the block copolymer contained in the copolymer of the aromatic vinyl compound and the conjugated diene compound is 1,2-vinyl content, or 1,2-vinyl content, and 3,4- The total amount with the vinyl content is preferably 5 to 80%, more preferably 10 to 50%, and still more preferably 15 to 40%.

The block copolymer contained in the copolymer of the aromatic vinyl compound and the conjugated diene compound includes a polymer block [A] mainly composed of the aromatic vinyl compound and a polymer block [B] mainly composed of the conjugated diene compound. Is preferably a block copolymer having a bond type selected from the A-B type, A-B-A type, or A-B-A-B type, and may be a mixture thereof.
Among these, the ABA type, the ABAB type, or a mixture thereof is more preferable, and the ABA type is more preferable.

The hydrogenated product of the copolymer of the aromatic vinyl compound and the conjugated diene compound is mainly composed of the conjugated diene compound by hydrogenating the block copolymer of the aromatic vinyl compound and the conjugated diene compound. The amount of the aliphatic double bond in the polymer block is controlled in the range of more than 0 to 100%.
A preferable hydrogenation rate of the hydrogenated block copolymer is 80% or more, and more preferably 98% or more.
These block copolymers can be used without any problem as a mixture of a non-hydrogenated block copolymer and a hydrogenated block copolymer.

  In addition, the block copolymers of the aromatic vinyl compound and the conjugated diene compound are different in bonding type, different in aromatic vinyl compound type, and different in conjugated diene compound type unless contrary to the spirit of the present invention. , 1,2-bonded vinyl content and 3,4-bonded vinyl content different from each other, aromatic vinyl compound component content different, etc. may be used as a mixture.

The block copolymer used as the impact modifier and the hydrogenated product thereof may be a mixture of a low molecular weight block copolymer and a high molecular weight block copolymer.
Examples thereof include a mixture of a low molecular weight block copolymer having a number average molecular weight of less than 120,000 and a high molecular weight block copolymer having a number average molecular weight of 120,000 or more.
The number average molecular weight of a block copolymer here refers to the number average molecular weight measured with an ultraviolet spectroscopic detector using a gel permeation chromatography measuring device (GPC) and converted to standard polystyrene. At this time, a low molecular weight component due to catalyst deactivation during polymerization may be detected. In this case, the low molecular weight component is not included in the molecular weight calculation.

Further, the block copolymer used as an impact modifier and its hydrogenated product may be a completely modified block copolymer or its hydrogenated product, even if it is an unmodified block copolymer and its hydrogenated product. And a modified block copolymer and a hydrogenated product thereof.
The modified block copolymer and the hydrogenated product as used herein include at least one carbon-carbon double bond or triple bond in the molecular structure, and at least one carboxylic acid group, acid anhydride group, A block copolymer modified with at least one modified compound having an amino group, a hydroxyl group, or a glycidyl group.

  The polyolefin that can be used as the impact modifier is not particularly limited. For example, polyethylene, polypropylene, a copolymer of ethylene and α-olefin, a copolymer of ethylene, propylene, and α-olefin, and ethylene and acrylic acid. Examples thereof include one or more selected from a copolymer, a copolymer of ethylene and alkyl acrylate, a copolymer of ethylene and methacrylic acid, and a copolymer of ethylene and alkyl methacrylate.

  Since the polyethylene and polypropylene do not deteriorate the toughness of the resin composition of the present embodiment, polyethylene and polypropylene having a weight average molecular weight of 1,000 or more can be preferably used. More preferably, the weight average molecular weight is 2,000 or more, and still more preferably the weight average molecular weight is 10,000 or more. The upper limit weight average molecular weight is not particularly limited, but polyethylene and polypropylene of 500,000 or less are preferable because the fluidity of the resin composition is not extremely lowered.

The α-olefin constituting the copolymer of ethylene and α-olefin and the copolymer of ethylene, propylene and α-olefin is preferably an α-olefin having 3 to 20 carbon atoms, more preferably 3 carbon atoms. Is an α-olefin having 16 to 16 carbon atoms, and more preferably an α-olefin having 3 to 12 carbon atoms.
Specifically, butene-1, pentene-1, 4-methylpentene-1, hexene-1, heptene-1, octene-1, nonene-1, decene-1, undecene-1, dodecene-1, tridecene- 1, tetradecene-1, pentadecene-1, hexadecene-1, heptadecene-1, octadecene-1, nonadecene-1, or eicosene-1.
These may be used alone or in combination of two or more.

  The molecular weight of the ethylene-α-olefin copolymer, the copolymer of ethylene, propylene, and α-olefin is a 150c-GPC apparatus manufactured by Waters, using 1,2,4-trichlorobenzene as a solvent, 140 ° C., It is preferable that the number average molecular weight (Mn) measured by the polystyrene standard is 10,000 or more, more preferably 10,000 to 100,000, and further preferably 20,000 to 60,000.

  In addition, the molecular weight distribution (weight average molecular weight / number average molecular weight: Mw / Mn) of the ethylene-α-olefin copolymer determined by measurement with the GPC apparatus is preferably 3 or less, and more preferably 1.8 to 2.7 is more preferable.

  Moreover, the preferable content rate of the ethylene unit of the said ethylene-alpha-olefin copolymer and the copolymer of ethylene, a propylene, and an alpha olefin is 30-95 mass% with respect to these copolymers whole quantity.

The ethylene-α-olefin copolymer and the ethylene-propylene-α-olefin copolymer are one or more selected from α, β-unsaturated dicarboxylic acid and derivatives thereof. It may be an ethylene-α-olefin copolymer modified with, and a copolymer of ethylene, propylene and α-olefin.
Specific examples of the α, β-unsaturated dicarboxylic acid and derivatives thereof mentioned here include maleic acid, fumaric acid, maleic anhydride, and fumaric anhydride. Among these, maleic anhydride is preferable.

The copolymer of ethylene and acrylic acid, the copolymer of ethylene and alkyl acrylate, the copolymer of ethylene and methacrylic acid, and the copolymer of ethylene and alkyl methacrylate are described in detail.
As said alkyl acrylates and alkyl methacrylates, the alkyl acrylate and alkyl methacrylate which have a C1-C15 alkyl group can be used.
The fluidity of the copolymer of ethylene and acrylic acid, the copolymer of ethylene and alkyl acrylate, the copolymer of ethylene and methacrylic acid, and the copolymer of ethylene and alkyl methacrylate is the resin composition of this embodiment. It affects the fluidity of things. The preferred MFR of these copolymers (JIS K7210 compliant 190 ° C., 2.16 kg load) is 0.5 to 200 g / 10 min. More preferably, it is 1.0 g / 10 minutes.
A more preferred upper limit is 150 g / 10 minutes, a still more preferred upper limit is 100 g / 10 minutes, and a still more preferred upper limit is 80 g / 10 minutes.

The preferable content of the impact modifier in the resin composition of the present embodiment is 1 to 20 parts by mass with respect to 100 parts by mass of the polyacetal resin.
A more preferred lower limit is 2 parts by mass, and a more preferred lower limit is 5 parts by mass. A more preferred upper limit is 18 parts by mass, a still more preferred upper limit is 15 parts by mass, and a still more preferred upper limit is 12 parts by mass.
In order to keep the impact strength of the resin composition of this embodiment high, the lower limit amount is preferably 1 part by mass or more, and in order not to lower the heat resistance, it is preferably 20 parts by mass or less.

  A copolymer of ethylene and acrylic acid, a copolymer of ethylene and alkyl acrylate, a copolymer of ethylene and methacrylic acid, and a copolymer of ethylene and alkyl methacrylate that can be used as the impact modifier are a part thereof. Alternatively, all may be a copolymer modified with one or more selected from α, β-unsaturated dicarboxylic acids and derivatives thereof. Specific examples of the α, β-unsaturated dicarboxylic acid and derivatives thereof mentioned here include maleic acid, fumaric acid, maleic anhydride, and fumaric anhydride. Among these, maleic anhydride is particularly preferable.

(Conductivity imparting material)
Next, the conductivity imparting material constituting the resin composition of the present embodiment will be described.
The conductivity imparting material includes at least one carbon-based conductive material and at least one metal oxide.
<Carbon-based conductive material>
The carbon-based conductive material is not particularly limited as long as it is a conductive material mainly composed of carbon. “Consisting mainly of carbon” means that 80% by mass or more of the carbon-based conductive material is carbon, and any material having conductivity can be used without any problem.
For example, 1 or more types chosen from carbon black, carbon fiber, a carbon nanotube, and a graphite are mentioned.
Examples of the carbon black include various types such as acetylene black, channel black, and thermal black, and any of them can be used. Among the features that can be particularly preferably used, those having a small particle size or a large surface area and having a chain structure developed are preferred, and those having a particle size of 0.05 μm or less are preferred. The dibutyl phthalate oil absorption (ASTM D2415 or less, DBP oil absorption) is preferably 200 mL / 100 g or more, more preferably 300 mL / 100 g or more and 500 mL / 100 g or less. By using the DBP oil absorption amount of 200 mL / 100 g or more, good conductivity can be obtained with a small addition amount, and by using 500 mL / 100 g or less, good mechanical properties can be obtained.
Examples of commercially available carbon black that can be suitably used include Ketjen Black EC [DBP oil absorption: 350 mL / 100 g, manufactured by Lion Corporation], EC-600JD [DBP oil absorption: 495 mL / 100 g, Lion ( Co., Ltd.], Printex XE2 [DBP oil absorption: 420 mL / 100 g] (Evonik Degussa Japan Co., Ltd.).
Carbon black may be used alone or in combination of two or more.

The carbon fiber includes all fibers obtained by firing and carbonizing a polyacrylonitrile (PAN) or a fiber made from pitch or the like between 1000 ° C. and 3500 ° C. in an inert atmosphere.
The carbon fiber has a fiber diameter of preferably 3 to 30 μm, more preferably 5 to 20 μm.
Examples of carbon nanotubes include fine carbon-based fibers described in International Publication No. 94/023433. Among these, carbon nanotubes having an average fiber diameter of 75 nm or less and L / D5 or more are preferable. Examples of commercially available carbon nanotubes include BN fibrils available from Hyperion Catalysis International.

Examples of the graphite include those obtained by heating anthracite, pitch and the like in an arc furnace at a high temperature, and naturally produced graphite.
The weight average particle diameter of graphite is preferably 0.1 to 100 μm, more preferably 10 to 80 μm.
In order to maintain the appearance of the resin composition of the present embodiment and suppress a decrease in impact strength, the weight average particle diameter is preferably 100 μm or less. It is preferable to be 1 μm or more.

  The carbon-based conductive material, which is the above-described conductivity imparting material, may improve adhesion and handleability with a resin by using various known coupling agents and / or sizing agents.

<Metal oxide>
The metal oxide refers to an oxide of a transition metal or a typical metal, and preferably has conductivity alone.
The preferred metal species is at least one selected from zinc, tin, iron, and titanium, and oxides of these metals can be suitably used.
Among these, tin oxide, tin dioxide, triiron tetroxide, and titanium dioxide are preferable, and tin dioxide and triiron tetroxide are more preferable.

The upper limit of the preferable number average particle diameter of these metal oxides is 1 μm or less. More preferably, it is 500 nm. Even more preferably, it is 300 nm. There is no particular lower limit, but it is preferably 50 nm.
In order to suppress changes due to the conductive molding conditions of the resin composition of the present embodiment, the number average particle diameter is preferably 1 μm or less. From the viewpoint of handleability, the lower limit is preferably 50 nm.
The particle diameter of the metal oxide can be measured by using water or alcohol as a dispersion medium with a laser particle size measuring device. Depending on the type of metal oxide, a dispersion aid such as sodium hexametaphosphate may be used.

  In the resin composition of the present embodiment, the preferable amount of the above-described conductivity imparting material is in the range of 1 to 50 parts by mass with respect to 100 parts by mass of the polyacetal resin. A more preferred lower limit is 3 parts by mass, and a more preferred lower limit is 5 parts by mass. A more preferred upper limit is 45 parts by mass, a still more preferred upper limit is 40 parts by mass, and a still more preferred upper limit is 30 parts by mass.

Moreover, in the resin composition of this embodiment, when all the electroconductivity imparting materials are 100 mass%, it is preferable that the mass ratio of a metal oxide is 50 mass% or more. More preferably, it is 60 mass% or more, More preferably, it is 70 mass% or more, More preferably, it is 75 mass% or more. The upper limit mass ratio of the preferred metal oxide is 95% by mass.
In order to suppress variation in conductivity due to the molding conditions and the shape of the molded piece of the resin composition of the present embodiment, the mass ratio of the metal oxide is preferably 50% by mass or more.

(Surfactant)
A surfactant may be added to the resin composition of the present embodiment.
As the surfactant, any of an anionic surfactant, a cationic surfactant, a nonionic surfactant, and an amphoteric surfactant can be applied.
Examples of the anionic surfactant include sodium octoate, sodium decanoate, sodium laurate, sodium myristate, sodium palmitate, sodium stearate, perfluorononanoic acid, sodium N-lauroyl sarcosine, sodium cocoyl glutamate, alpha Sulfo fatty acid methyl ester salt, sodium 1-hexanesulfonate, sodium 1-octanesulfonate, sodium 1-decanesulfonate, sodium 1-dodecanesulfonate, perfluorobutanesulfonic acid, sodium linear alkylbenzene sulfonate, sodium toluenesulfonate , Sodium cumene sulfonate, sodium octylbenzene sulfonate, sodium dodecylbenzene sulfonate, naphthalene sulfonic acid Thorium, disodium naphthalene disulfonate, trisodium naphthalene trisulfonate, sodium butyl naphthalene sulfonate, sodium lauryl sulfonate, sodium myristyl sulfonate, sodium laureth sulfonate, sodium polyoxyethylene alkylphenol sulfonate, ammonium lauryl sulfonate, lauryl Examples thereof include phosphoric acid, sodium lauryl phosphate, and potassium lauryl phosphate.
Examples of the cationic surfactant include tetramethylammonium chloride, tetramethylammonium hydroxide, tetrabutylammonium chloride, dodecyldimethylbenzylammonium chloride, alkyltrimethylammonium chloride, octyltrimethylammonium chloride, decyltrimethylammonium chloride, dodecyltrimethylammonium chloride. , Tetradecyltrimethylammonium chloride, cetyltrimethylammonium chloride, stearyltrimethylammonium chloride, alkyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, benzyltrimethylammonium chloride, benzyltriethylammonium chloride, benzalkonium chloride, benzalkonium bromide , Benzethonium chloride, dialkyldimethylammonium chloride , Didecyldimethylammonium chloride, and the like distearyl dimethyl ammonium chloride and the like.
Examples of the nonionic surfactant include glyceryl laurate, glyceryl monostearate, sorbitan fatty acid ester, sucrose fatty acid ester, polyoxyethylene alkyl ether, pentaethylene glycol monododecyl ether, octaethylene glycol monododecyl ether, and polyoxyethylene. Alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene hexitan fatty acid ester, sorbitan fatty acid ester polyethylene glycol, lauric acid diethanolamide, oleic acid diethanolamide, stearic acid diethanolamide, octylglucoside , Decyl glucoside, lauryl glucoside, cetanol, stearyl al Examples include coal and oleyl alcohol.
Examples of the amphoteric surfactant include lauryldimethylaminoacetic acid betaine, stearyldimethylaminoacetic acid betaine, dodecylaminomethyldimethylsulfopropylbetaine, octadecylaminomethyldimethylsulfopropylbetaine, cocamidopropyl betaine, cocamidopropylhydroxysultain, 2- Examples include alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine, sodium lauroyl glutamate, potassium lauroyl glutamate, lauroylmethyl-β-alanine, lauryldimethylamine-N-oxide, oleyldimethylamine-N-oxide, and the like. .

  Among these, particularly excellent surfactants are nonionic surfactants and cationic surfactants. In particular, neutral surfactants having a pH of 6 to 8 when dissolved in water are more preferred.

Although there is no restriction | limiting in particular in the quantity of these surfactant, A preferable upper limit is 10 mass parts or less with respect to 100 mass parts of polyacetals. More preferably, it is 8 mass parts or less, More preferably, it is 5 mass parts or less, More preferably, it is 3 mass parts or less.
Since the surfactant is an additional component, the lower limit amount is zero, but the preferable lower limit amount when added is 0.01 parts by mass with respect to 100 parts by mass of the polyacetal. More preferably, it is 0.1 mass part, More preferably, it is 0.5 mass part.
In order to suppress bleed-out to the molded body made of the resin composition, the amount of the surfactant is preferably 10 parts by mass or less with respect to 100 parts by mass of the polyacetal.
Moreover, in order to suppress the fluctuation | variation by the molding conditions of the volume resistivity of a molded object, it is more preferable to mix | blend 0.01 mass part or more.

(Additive)
In the resin composition of the present embodiment, an appropriate additive can be blended depending on the application.
<Hindered amine light stabilizer>
The resin composition of this embodiment may contain a hindered amine light stabilizer as an additional component.
Examples of the hindered amine light stabilizer include 1,2,2,6,6-pentamethyl-4-piperidyl methacrylate, 1,2,2,6,6-pentamethyl-4-piperidyl acrylate, Bis (1,2,2,6,6-pentamethyl-4-piperidyl) -malonate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -sebacate, bis (1,2,2, 6,6-pentamethyl-4-piperidyl) -adipate, bis (1,2,2,6,6-pentamethyl-4-piperidyl) -terephthalate, bis (2,2,6,6-tetramethyl-4-piperidyl) ) -Malonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate, bis (2,2,6,6-tetramethyl-4-piperidyl) -adipate, bis (2,2, , 6-Tetramethyl-4-piperidyl) -terephthalate, 1,2-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -ethane, α, α′-bis (2,2,6 , 6-tetramethyl-4-piperidyloxy) -p-xylene, bis (2,2,6,6-tetramethyl-4-piperidyl) tolylene-2,4-dicarbamate, bis (2,2,6, 6-tetramethyl-4-piperidyl) -hexamethylene-1,6-dicarbamate.
Among these, bis (2,2,6,6-tetramethyl-4-piperidyl) -malonate, bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate, bis (2,2, 6,6-tetramethyl-4-piperidyl) -adipate, bis (2,2,6,6-tetramethyl-4-piperidyl) -terephthalate, 1,2-bis (2,2,6,6-tetramethyl) -4-piperidyloxy) -ethane, α, α'-bis (2,2,6,6-tetramethyl-4-piperidyloxy) -p-xylene, bis (2,2,6,6-tetramethyl- 4-piperidyl) tolylene-2,4-dicarbamate and bis (2,2,6,6-tetramethyl-4-piperidyl) -hexamethylene-1,6-dicarbamate are preferred, and bis (2,2 2, 6, 6 Tetramethyl-4-piperidyl) - sebacate.

  The preferable addition amount of a hindered amine light stabilizer is 0.1-3 mass parts with respect to 100 mass parts of polyacetals, and a more preferable lower limit amount is 0.5 mass. A more preferred upper limit is 2 parts by mass, and a more preferred upper limit is 1.5 parts by mass. In order to impart good resistance to deterioration oils and fats, the addition amount is preferably in the range of 0.1 to 3 parts by mass.

<Epoxy compound>
An epoxy compound may be added to the resin composition of this embodiment.
Preferable epoxy compounds include mono- or polyfunctional glycidyl derivatives, or compounds obtained by oxidizing a compound having an unsaturated bond to generate an epoxy group.
For example, 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 (ethylene oxide units; 2 to 30), propylene glycol Diglycidyl ether, (unit of propylene oxide; 2-30), neopentyl glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, glycerin diglycidyl ether, glycerin triglycidyl ether, trimethylolpropane diglycidyl ether, tri Methylolpropane triglycidyl ether, bisphenol A diglycidyl ether, water Addition bisphenol A diglycidyl ether, sorbitan monoester diglycidyl ether, sorbitan monoester triglycidyl ether, pentaerythritol triglycidyl ether, pentaerythritol tetraglycidyl ether, diglycerin triglycidyl ether, diglycerin tetraglycidyl ether, cresol novolak and epichlorohydrin Condensates (epoxy equivalents: 100 to 400, softening point: 20 to 150 ° C.), glycidyl methacrylate, coconut fatty acid glycidyl ester, soybean fatty acid glycidyl ester, and the like, but are limited to these. Absent.
Among these, a condensate of cresol novolak and epichlorohydrin is preferably used from the viewpoint of improving the thermal stability of the composition.

A preferable upper limit of the epoxy compound is 10 parts by mass with respect to 100 parts by mass of the polyacetal. A more preferred upper limit is 7 parts by mass, a more preferred upper limit is 5 parts by mass, and a still more preferred upper limit is 3 parts by mass.
Since the epoxy compound is an additional component, the lower limit is zero, but the preferred lower limit when adding is 0.1 parts by mass, the more preferred lower limit is 0.5 parts by mass, and the even more preferred lower limit is 1 part by mass.
In order to further improve the thermal stability during processing of the resin composition, the amount of these epoxy compounds is preferably 0.1 parts by mass or more and 10 parts by mass or less.

<Epoxy resin curable additive>
Furthermore, when adding an epoxy compound to the resin composition of the present embodiment, an epoxy resin curable additive may be added in addition to the epoxy compound.
As the epoxy curable additive, a basic nitrogen compound and a basic phosphorus compound can be used, but all other compounds having an epoxy curing action (including a curing accelerating action) can also be used.
The upper limit of the addition amount of the epoxy curable additive is 100 parts by mass with respect to 100 parts by mass of the epoxy compound. A more preferred upper limit is 80 parts by mass. Although there is no lower limit in particular, Preferably it is 1 mass part, and a more preferable lower limit is 30 mass parts.

Specific examples of the epoxy resin curable additive include imidazole; substituted imidazoles such as 1-hydroxyethyl-2-methylimidazole, 1-cyanoethyl-2-heptadecylimidazole, and 1-vinyl-2-phenylimidazole; Aliphatic secondary amines such as octylmethylamine and laurylmethylamine; aromatic secondary amines such as diphenylamine and ditolylamine; aliphatic tertiary amines such as trilaurylamine, dimethyloctylamine, dimethylstearylamine and tristearylamine; Aromatic tertiary amines such as triphenylamine; morpholine compounds such as cetylmorpholine, octylmorpholine and p-methylbenzylmorpholine; alkylene oxide adducts (addition compounds) to dicyandiamide, melamine, urea, etc. 1-20 mol); triphenylphosphine, methyl diphenyl phosphine, there are phosphorus compounds such as tri-tolylphosphine, but is not limited thereto.
Among these, dicyandiamide and triphenylphosphine are preferably used from the viewpoint of improving the thermal stability of the resin composition of the present embodiment.
These epoxy compounds and epoxy resin curable additives may be used alone or in combination of two or more.

  Further, the mass ratio [E / A: addition amount of epoxy compound / addition amount of hindered amine light stabilizer] of the epoxy compound and the hindered amine light stabilizer described above is the resin composition of the present embodiment and the molded product thereof. In order to obtain a balanced mechanical property, it is preferably 60/40 to 85/15, more preferably 65/35 to 80/20.

(Other additives)
In the resin composition of the present embodiment, a known additive for polyacetal such as an antioxidant, a polymer or compound containing formaldehyde-reactive nitrogen, a formic acid scavenger, a release agent, a lubricant, and a pigment, and 100 parts by mass of polyacetal On the other hand, it can contain 0.01-3 mass parts, respectively.

<Antioxidant>
Examples of the antioxidant include hindered phenol antioxidants.
For example, 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] methane and the like.
Preferably, triethylene glycol-bis- [3- (3-t-butyl-5-methyl-4-hydroxyphenyl) -propionate], pentaerythritol tetrakis [methylene-3- (3 ′, 5′-di-t -Butyl-4'-hydroxyphenyl) propionate] methane and mixtures thereof.
These may be used alone or in combination of two or more.

<Polymer or compound containing formaldehyde-reactive nitrogen>
Examples of polymers or compounds containing formaldehyde-reactive nitrogen include polyamide resins such as nylon 4-6, nylon 6, nylon 6-6, nylon 6-10, nylon 6-12, nylon 12, and polymers thereof. Examples thereof 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. For example, it is obtained by polymerizing acrylamide and its derivatives and other vinyl monomers in the presence of a metal alcoholate. Examples thereof include poly-β-alanine copolymers obtained.
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.
Examples of the amide compound include polycarboxylic acid amides such as isophthalic acid diamide and anthranilamides.
Examples of the amino-substituted triazine compound include 2,4-diamino-sym-triazine, 2,4,6-triamino-sym-triazine, 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 etc. are mentioned.
Examples of the adduct of the amino-substituted triazine compound and formaldehyde include N-methylol melamine, N, N′-dimethylol melamine, and N, N ′, N ″ -trimethylol melamine.
Examples of the condensate of the amino-substituted triazine compound and formaldehyde include melamine / formaldehyde condensate.
Examples of the urea derivative include N-substituted urea, urea condensate, ethylene urea, hydantoin compound, and ureido compound. Specific examples of the N-substituted urea include methylurea, alkylenebisurea, and aryl-substituted urea substituted with a substituent such as an alkyl group.
Examples of urea condensates include urea and formaldehyde condensates.
Specific examples of the hydantoin compound include hydantoin, 5,5-dimethylhydantoin, 5,5-diphenylhydantoin and the like.
Examples of the ureido compound include allantoin.
Examples of the hydrazine derivative include hydrazide compounds. Specific examples of the hydrazide compound include dicarboxylic acid dihydrazide, and more specifically, malonic acid dihydrazide, succinic acid dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, pimelic acid dihydrazide, superic acid dihydrazide, azelaic acid dihydrazide, sebatin Examples thereof include acid dihydrazide, dodecanedioic acid dihydrazide, isophthalic acid dihydrazide, phthalic acid dihydrazide, and 2,6-naphthalenedicarbodihydrazide.
Examples of the imidazole compound include 2-formylimidazole, 4-formylimidazole, 2-cyanoimidazole, 4-cyanoimidazole, imidazole-4-dithiocarboxylic acid, 2-methylimidazole-4-dithiocarboxylic acid, and imidazole-4. -Carboxylic acid monohydrate, 2-hydroxymethylimidazole hydrochloride, 2-mercaptoimidazole.
Examples of the imide compound include succinimide, glutarimide, and phthalimide.
The above-mentioned polymers or compounds containing formaldehyde-reactive nitrogen atoms may be used alone or in combination of two or more.

<Formic acid supplement>
Examples of the formic acid scavenger include amino-substituted triazine compounds or condensates of amino-substituted triazine compounds and formaldehyde described in the above <Polymer or compound containing formaldehyde-reactive nitrogen>, such as melamine / formaldehyde condensate Can be mentioned.
Other formic acid scavengers include alkali metal or alkaline earth metal hydroxides, inorganic acid salts, carboxylate salts or alkoxides. Examples thereof include hydroxides such as sodium, potassium, magnesium, calcium, and barium, and carbonates, phosphates, silicates, borates, and carboxylates of the above alkali metals or alkaline earth metals.
The carboxylic acid of the carboxylate is preferably a saturated or unsaturated aliphatic carboxylic acid having 10 to 36 carbon atoms, and these carboxylic acids may be substituted with a hydroxyl group. Examples of the saturated or unsaturated aliphatic carboxylate include calcium dimyristic acid, calcium dipalmitate, calcium distearate, (myristic acid-palmitic acid) calcium, (myristic acid-stearic acid) calcium, and palmitic acid. -Calcium stearate) is mentioned, and calcium dipalmitate and calcium distearate are particularly preferable.
These formic acid scavengers may be used alone or in combination of two or more.

<Release agent, lubricant>
Examples of the releasing agent and lubricant include alcohol, fatty acid and fatty acid ester thereof, polyoxyalkylene glycol, olefin compound having an average polymerization degree of 10 to 500, and silicone.

  Furthermore, according to the purpose, the resin composition of the present embodiment includes various known additives that can be used in conventional polyacetal resins, such as inorganic fillers, crystal nucleating agents, other conductive materials, thermoplastic resins, and Thermoplastic elastomers such as polyurethane elastomers, polyester elastomers, and polyamide elastomers can be blended.

<Inorganic filler>
As the inorganic filler, fibrous, powder particle, plate and hollow fillers are used.
Examples of the fibrous filler include glass fiber, silicone fiber, silica / alumina fiber, zirconia fiber, boron nitride fiber, silicon nitride fiber, boron fiber, potassium titanate fiber, stainless steel, aluminum, titanium, copper, brass and the like. And inorganic fibers such as metal fibers.
Also included are whiskers such as potassium titanate whiskers with short fiber lengths. A high melting point organic fibrous material such as an aromatic polyamide resin, a fluororesin, or an acrylic resin can also be used.
Examples of the particulate filler include silica, quartz powder, glass beads, glass powder, calcium silicate, aluminum silicate, kaolin, clay, diatomaceous earth, silicates such as wollastonite, oxides such as alumina, sulfuric acid Examples thereof include metal sulfates such as calcium and barium sulfate, carbonates such as magnesium carbonate and dolomite, other silicon carbide, silicon nitride, boron nitride, and various metal powders.
Examples of the plate-like filler include mica, glass flakes, and various metal foils.
Examples of the hollow filler include glass balloons, silica balloons, shirasu balloons, metal balloons and the like.
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 it is preferable to use surface-treated ones in terms of smoothness of the molding surface and mechanical properties. There is.
A conventionally well-known thing can be used as a surface treating agent.
For example, various coupling treatment agents such as silane, titanate, aluminum, and zirconium can be used. Specifically, N- (2-aminoethyl) -3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, isopropyl trisstearoyl titanate, diisopropoxyammonium ethyl acetate, n-butyl zirconate, etc. Can be mentioned.

<Pigment>
Examples of the pigment include inorganic pigments, organic pigments, metallic pigments, fluorescent pigments, and the like.
As the inorganic pigment, those generally used for coloring a resin can be applied. For example, zinc sulfide, titanium oxide, barium sulfate, titanium yellow, cobalt blue, combustion pigment, carbonate, phosphate Acetate, carbon black, acetylene black, lamp black and the like.
Organic pigments include condensed azo, inone, furothocyanin, monoazo, diazo, polyazo, anthraquinone, heterocyclic, pennon, quinacridone, thioindico, berylene, dioxazine, phthalocyanine And the like.
Since the addition ratio of the pigment varies greatly depending on the color tone, it is difficult to clarify, but generally it is used in the range of 0.05 to 5 parts by mass with respect to 100 parts by mass of the polyacetal resin.

[Method for producing resin composition]
The resin composition of this embodiment can be produced by a conventionally known melt-kneading method.
A generally used kneader can be used as the melt kneading apparatus. For example, a single-screw or multi-screw kneading extruder, a roll, a Banbury mixer, etc. may be used. Among these, a twin-screw extruder equipped with a decompression device and side feeder equipment is most preferable.
The melt-kneading method is a method of melt-kneading all components simultaneously, a method of melt-kneading using a premixed blend in advance, and further supplying each component by using a side feeder sequentially from the middle of the extruder, Examples thereof include a melt kneading method.
Further, during melt kneading, it is preferable to reduce the pressure from the vent port of the extruder by a decompression device.
The degree of vacuum is preferably 0.07 MPa or less.
The melt kneading temperature is preferably 1 to 80 ° C. higher than the melting point obtained by differential scanning calorimetry (DSC) measurement according to JIS K7121 of the polyacetal resin to be used.
More specifically, the temperature is 160 ° C to 240 ° C.
The shear rate in the extruder is preferably 100 rpm or more.

[Physical properties of resin composition]
The resin composition of this embodiment is a resin composition having electrostatic diffusibility.
Here, the electrostatic diffusibility is a property that is difficult to be charged and diffuses charges gently, and has a moderate conductivity (volume resistivity) of about 10 ⁵ Ω · cm corresponding to an intermediate between conductivity and antistatic property. ).
When the charged electricity is removed, in the case of a material having high conductivity, an abrupt discharge (spark) occurs and the electric circuit or the like is destroyed. It is an electrostatic diffusive material that can eliminate static while suppressing this.
However, the intermediate conductive region has an electrical resistance value in the middle of a rapid change in conductivity called percolation, and has a property that the resistance value is easily changed under various conditions and is difficult to control.
The resin composition of this embodiment has a volume resistivity of 10 ³ to 10 ⁹ Ω · cm.
The volume resistivity needs to be 10 ³ Ω · cm or more so as not to cause a spark during use, and it needs to be 10 ⁹ Ω · cm or less in order to quickly remove charged static electricity. A more preferred lower limit is 5 × 10 ³ Ω · cm, and a still more preferred lower limit is 10 ⁴ Ω · cm. A more preferred upper limit is 5 × 10 ⁸ Ω · cm, and a more preferred upper limit is 10 ⁸ Ω · cm.
The volume resistivity can be calculated by the method described in Examples described later.
Specifically, this test was performed using a strip-shaped test piece having both ends of a 4 mm-thick ISO multi-purpose test piece cut and having a cut surface with a uniform cross-sectional area (10 × 4 mm) at both ends of 10 mm. The silver paste is applied to the cut surfaces at both ends of the piece, and after sufficiently drying, the resistance value between the both ends is measured using a tester, and can be calculated using the following equation.
Volume resistivity (Ω · cm) = resistance value (Ω) × cross-sectional area (cm ² ) ÷ length (cm)

[Molded body]
(Method for producing molded body)
The method for molding the polyacetal resin composition of the present embodiment is not particularly limited, and known molding methods such as extrusion molding, injection molding, vacuum molding, blow molding, injection compression molding, decorative molding, other materials Molding by any of molding methods such as molding, gas-assisted injection molding, foam injection molding, low pressure molding, ultra-thin injection molding (ultra-high-speed injection molding), in-mold composite molding (insert molding, outsert molding) Can do.

(Use of molded product)
The molded body of this embodiment can be used as various mechanical components.
The molded body of the present embodiment has a characteristic that there is no change in volume resistivity depending on a molding method and a part of the molded body. Examples of suitable applications include bearings and gears of devices that are susceptible to friction.

EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to the Example mentioned later.
First, the contents and evaluation methods of the components used in the examples and comparative examples, the molding method of the molded body, and the method of measuring physical properties are shown below.

[Use ingredients]
<Polyacetal resin (hereinafter simply abbreviated as POM)>
Based on the preparation example described in JP 2010-285539 A, a melting point (differential scanning calorimeter (manufactured by Perkin Elmer, DSC-2C) was used to cool a sample once heated to 200 ° C. and melted to 100 ° C. MFR measured at a temperature of 164.5 ° C., 190 ° C. and 2.16 kg load based on JIS-K7210). Obtained a polyacetal pellet having a weight of 30 g / 10 min, and this was used as a polyacetal resin.
<Impact modifier (hereinafter simply abbreviated as TR)>
Polystyrene-polybutadiene-polystyrene triblock copolymer (Tufprene A: manufactured by Asahi Kasei Chemicals Corporation)
<Conductivity imparting material>
[Carbon-based conductive material]
Carbon Black Product Name Ketjen Black EC300J: manufactured by Lion Corporation (hereinafter simply referred to as C-1)
Carbon fiber Product name HTA-CMF-0160-OH: manufactured by Toho Tenax Co., Ltd. (hereinafter simply referred to as C-2)
Graphite particles Product name UF-G30: Showa Denko Co., Ltd. (hereinafter simply referred to as C-3)
[Metal oxide]
Tin dioxide (SnO ₂ ) Trade name CP004: manufactured by Teika Co., Ltd. (hereinafter simply referred to as M-1) Particle size: 500 nm

[Molding method]
<Molding method 1>
Using EC75NII manufactured by Toshiba Machine Co., Ltd., the cylinder temperature was set to 205 ° C., the mold temperature was set to 90 ° C., the injection speed was set to 200 mm / sec, and an ISO multipurpose test piece was molded.
The injection time at this time was 35 seconds, and the cooling time was 15 seconds.
<Molding method 2>
Using the same molding machine as the molding method 1, the mold temperature was set to 60 ° C., the injection speed was set to 50 mm / sec, and an ISO multipurpose test piece was molded.
The injection time at this time was 35 seconds, and the cooling time was 15 seconds.

[Physical properties]
(Volume resistivity-1)
Both ends of a 4 mm thick ISO multipurpose test piece were cut with a precision cut saw to obtain a rectangular parallelepiped test piece having a length of 10 mm, a width of 10 mm, and a thickness of 4 mm.
After applying a silver paste to two cut surfaces (10 × 4 mm surface) of this test piece and drying it sufficiently, the resistance value between both ends where the silver paste was applied was measured with a tester. Was calculated.
Volume resistivity (Ω · cm) = resistance value (Ω) × cross-sectional area (cm ² ) ÷ length (cm)
This volume resistivity is expressed as (volume resistivity-1), and this value is shown in Table 1 below.
In addition, this measurement was implemented with respect to each of five different test pieces (n = 5), and the volume resistance value was determined in consideration of the width of each measurement value.

(Volume resistivity-2)
Except for applying the silver paste to the two non-cut surfaces (10 × 4 mm surfaces) instead of the cut surfaces of the rectangular parallelepiped test pieces used in the measurement of the (volume resistivity-1), the above (volume resistivity− It implemented similarly to the measurement of 1) and measured the volume resistivity. The volume resistivity obtained here is expressed as (volume resistivity-2) and is shown in Table 1 below.

[Example 1, Comparative Examples 1 and 2]
The cylinder temperature of a TEM-26SS twin screw extruder (manufactured by Toshiba Machine Co., Ltd.) having one supply port on the upstream side and one supply port in the center of the extruder is set to 200 ° C., and the extrusion rate per hour is 15 kg / The POM, TR, and additive were supplied from the upstream supply port, and the conductivity-imparting material was supplied from the supply port at the center of the extruder, and extrusion was performed under the condition of a screw rotation speed of 150 rpm.
At this time, low-volatile components were degassed by a vacuum pump from a degassing vent port installed on the downstream side of the extruder.
The extruded strand composition was cut with a strand cutter to obtain pellets.
The obtained pellets were molded under the conditions of <Molding Method 1> and <Molding Method 2>, respectively, to obtain multipurpose test pieces. For these multipurpose test pieces, (volume resistivity-1) and ( Measurement of volume resistivity-2) was performed. The measurement results are shown in Table 1 below together with the composition.
In Examples and Comparative Examples, bis (2,2,6,6-tetramethyl-4-piperidyl) -sebacate (Sankyo Lifetech Co., Ltd.) is used as an additive component with respect to 100 parts by mass of polyacetal resin. Product, product name: Sanol LS770) is 0.2 parts by mass, condensate of cresol novolac and epichlorohydrin (epoxy equivalent = 350, softening point = 80 ° C.) is 1 part by mass, triphenylphosphine is 0.5 parts by mass. Part by mass, 2.5 parts by mass of behenyl alcohol and 0.5 parts by mass of sodium lauryl sulfonate are contained.
In addition, the quantity of the conductivity imparting material was adjusted so that the value of (volume resistivity-1) of the sample molded by the above-described <Molding method 1> was equal.

In Table 1, “POM” is a polyacetal resin, “TR” is an impact modifier, “C-1” is carbon black, “C-2” is carbon fiber, “C-3” is graphite particles, “M-1” "Represents a metal oxide.
In Table 1, the unit of the blending amount of materials is all “parts by mass”.
“-” Indicates that measurement has not been performed.

  Example 1 shows no variation in volume resistivity due to the molding method and the part of the molded piece, whereas Comparative Examples 1 and 2 composed only of carbon-based conductive materials differ in molding method and measurement site. It was confirmed that the volume resistivity fluctuated due to the difference.

  The polyacetal resin composition of the present invention can be suitably used as an electrostatic diffusion material, and the molded body can be used as a bearing part, gear, etc. for various mechanical parts such as copiers and other equipment that are susceptible to paper friction. Has the above applicability.

Claims (11)

Containing a polyacetal resin, an impact modifier, and at least two types of conductivity imparting materials,
The conductivity imparting material includes at least one carbon-based conductive material and at least one metal oxide having a number average particle diameter of 1 μm or less ,
A resin composition having a volume resistivity of 10 ³ to 10 ⁹ Ω · cm.   The resin composition according to claim 1, wherein the carbon-based conductive material is at least one selected from the group consisting of carbon black, carbon fiber, carbon nanotube, and graphite.   The resin composition according to claim 1 or 2, wherein the metal oxide is an oxide of at least one metal selected from the group consisting of zinc, tin, iron, and titanium. The impact modifier is at least one selected from the group consisting of polybutadiene, a copolymer of an aromatic vinyl compound and a conjugated diene compound, a hydrogenated copolymer of an aromatic vinyl compound and a conjugated diene compound, and a polyolefin. The resin composition according to any one of claims 1 to 3 . The polyolefin is polyethylene, polypropylene, ethylene / α-olefin copolymer, ethylene / propylene / α-olefin copolymer, ethylene / acrylic acid copolymer, ethylene / alkyl acrylate copolymer, ethylene The resin composition according to claim 4 , wherein the resin composition is at least one selected from the group consisting of a copolymer of ethylene and methacrylic acid, and a copolymer of ethylene and alkyl methacrylate. The resin composition according to any one of claims 1 to 5 , wherein the impact modifier is contained in an amount of 1 to 20 parts by mass with respect to 100 parts by mass of the polyacetal resin. The resin composition according to any one of claims 1 to 6 , wherein the conductivity imparting material is contained in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the polyacetal resin. The resin composition according to any one of claims 1 to 7 , wherein the conductivity-imparting material contains 50% by mass or more of the metal oxide. 1 wherein the metal oxide is selected from the group consisting of tin dioxide, ferric tetroxide, and titanium dioxide.
It is a seed | species or more, The resin composition as described in any one of Claims 1 thru | or 8 . The resin composition according to any one of claims 1 to 9 , further comprising a surfactant. The molded object obtained by shape | molding the resin composition as described in any one of Claims 1 thru | or 10 .