Conductive resin composition, resin molding, electric contact member, photoreceptor drum fringe, bearing member, copier body, and mechanism component of toner cartridge

Abstract

To provide a conductive POM resin composition containing a conductive filler which is less in thermal decomposition of a POM resin, is low in water absorption percentage, and has no practical problem as injection molding applications.SOLUTION: A conductive resin composition contains polyacetal as a main component, carbon black and graphite, and is obtained by adding an oxazoline group-containing compound and its reaction product thereto.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a conductive resin composition containing polyacetal as a main component, and a molded body made of the conductive resin composition.

Background Art

[0002] Polyacetal (POM resin) is a resin having well-balanced mechanical properties and excellent slidability. Particularly, due to its excellent slidability, it is widely used in various precision mechanical components such as gears and OA equipment. In recent years, in particular, member integration has been required in various applications. As a characteristic other than slidability, a conductive filler is added to impart conductivity, and it is applied to a member having a function of removing static electricity generated during sliding and a function as a conductive wiring. In the POM resin composition added with this conductive filler, since the melt viscosity increases due to the addition of the filler, heat generation easily occurs in the plasticization process. Further, if there are active hydrogens that promote the decomposition reaction of the POM resin, particularly organic functional groups having acidic protons, on the surface of the filler or the like, formaldehyde, which is a thermal decomposition product, is likely to be generated. Patent Document 1 discloses a POM resin composition having heat stability and high conductivity by adding conductive carbon black or graphite and then blending an olefin resin, an ester composed of a fatty acid and an aliphatic alcohol, and an epoxy compound. In such a POM resin composition, an ester composed of a fatty acid and an aliphatic alcohol acts as a lubricant to suppress heat generation in processes such as kneading and plastic molding, and the epoxy compound reacts with an organic functional group having active hydrogen to suppress the decomposition reaction.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When an epoxy compound reacts with a functional group having active hydrogen, the epoxy group undergoes ring opening to give a condensate having a hydrophilic hydroxy group at the carbon atom adjacent to the condensed functional group. Therefore, depending on the structure of the epoxy compound, the equivalent of the epoxy functional group, and the structure of the condensate partner, the water absorption rate of the reaction product generally tends to be as high as around 2%. Therefore, in the POM resin composition disclosed in Patent Document 1, generally, when an epoxy compound is added to a POM resin having a water absorption rate of 0.2% to 0.3% and extrusion kneading with the accompanying reaction is performed, an increase in the water absorption rate is expected as compared with the POM resin alone. Since the reversible phenomenon of drying and water absorption affects the dimensional stability of the resin molded body when the humidity environment changes, an increase in the water absorption rate of the POM resin composition is not preferable. An object of the present invention is to provide a conductive POM resin composition and a molded body in a POM resin composition containing a conductive filler, in which thermal decomposition of the POM resin is less and the water absorption rate is low.

Means for Solving the Problems

[0005] The first aspect of the present invention is a conductive resin composition containing polyacetal as a main component, carbon black, and graphite, characterized by containing an oxazoline group-containing compound and a reaction product thereof. The second aspect of the present invention is a resin molded body characterized by comprising the conductive resin composition of the present invention. The third aspect of the present invention is an electrical contact member, a photoreceptor drum fringe, a bearing member, a copying machine body, and a mechanism part of a toner cartridge, characterized by comprising the resin molded body of the present invention.

Effects of the Invention

[0006] According to the present invention, a conductive POM resin composition having high conductivity and low water absorption rate, and a molded body can be obtained.

Modes for Carrying Out the Invention

[0007] Hereinafter, embodiments for carrying out the present invention will be described in detail.

[0008] <Constitution of the conductive resin composition> The conductive resin composition of the present invention is a resin composition containing polyacetal (POM resin) as a main component, carbon black and graphite as conductive fillers, and characterized by containing an oxazoline group-containing compound and its reaction product. By combining carbon black and graphite in this constitution, high conductivity and slidability can be obtained.

[0009] Oxazoline is a 5-membered heterocyclic compound having the chemical formula C3H5NO. It is known that an oxazoline group-containing compound having an oxazoline group in its molecular structure reacts with an organic functional group such as a carboxylic acid or a phenol to give a condensation compound of an N-acyl ethanolamine in which the oxazoline group is ring-opened and the organic functional group. As an example, the reaction of an oxazoline compound having an aromatic ring and phenols is shown below.

[0010] [Chemical formula] In the above formula, R represents hydrogen or an oxazoline group, X represents a single bond or a hydrocarbon chain having 5 or less carbon atoms, and the end thereof may be copolymerized with other copolymer components. Further, X represents a non-bonding electron pair (without an element or a functional group), or an oxygen atom or a hydroxyl group.

[0011] Organic functional groups such as carboxylic acids and phenols derived from the manufacturing process remain on the surface of carbon black. Since these organic functional groups have acidic active hydrogens (protons), they promote the decomposition reaction of POM resin and tend to generate formaldehyde, which is a thermal decomposition product. An oxazoline group-containing compound reacts with this proton-bearing organic functional group to form a condensation compound. Therefore, by including an oxazoline group-containing compound in the resin composition, the organic functional groups on the surface of carbon black are consumed. As a result, the decomposition reaction of POM resin promoted by the organic functional groups can be suppressed. Also, unlike the product obtained by the reaction of an organic functional group and an epoxy compound, the condensation compound, which is the reaction product of an oxazoline group-containing compound and an organic functional group, does not have a hydroxy group, so the water absorption rate can be lowered.

[0012] The structure of the oxazoline group-containing compound used in the present invention is not particularly limited, but it preferably has an aromatic ring in its molecular structure. When the oxazoline group-containing compound has an aromatic ring, it is expected that the oxazoline group-containing compound will be adsorbed on the carbon black having sp 2 hybridized orbital conductive carbon atoms or graphite due to the electronic interaction. As a result, the proton-bearing organic functional group and the oxazoline group on the surface of the carbon black react preferentially, and the decomposition reaction of POM resin can be suppressed more effectively.

[0013] Examples of the oxazoline group-containing compound having an aromatic ring include oxazoline derivatives represented by the following formula (1).

[0014]

Chemical formula

[0015] As the above oxazoline derivative, it is also possible to use commercially available oxazoline compounds. For example, "CP Resin A 1,3-BPO (product name)" manufactured by Sankyo Pharmaceutical Co., Ltd. represented by the following formula (2) can be mentioned. Also, "Epocros (registered trademark) RPS-1005S (model number)" manufactured by Nippon Shokubai Co., Ltd., which is an oxazoline-modified polystyrene having the structure represented by the following formula (3) as the main component, can also be mentioned. These may be used in combination of multiple types. Further, other compounds that react with active hydrogen, specifically, isocyanates that are raw materials for urethanes, and nitrogen-containing compounds such as urea and urea resins may be used in combination.

[0016] [Chemical formula] In the above formula (3), m and n each represent an integer.

[0017] Further, in the conductive resin composition of the present invention, it is preferable to add an aromatic phosphorus compound in order to promote the reaction between the oxazoline group and the organic functional group. Examples of the aromatic phosphorus compound include triphenylphosphine, triphenylphosphite, triphenylphosphate, and those in which hydrogen on the aromatic ring of these compounds is substituted with an organic functional group. In particular, triphenylphosphine can be preferably used. Also, these compounds may be added alone or in combination of multiple ones. Usually, in the reaction between the oxazoline group and the organic functional group, the amount of the aromatic phosphorus compound used is typically a catalytic amount (about 1% by mass) with respect to the oxazoline group-containing compound. However, when the reaction is carried out not in a solution system but in a highly viscous fluid such as a molten resin, especially when the reaction is carried out by passing through a continuous reactor such as a kneading extruder, it is desirable to use an excessive amount because the reaction rate and time are limited. Specifically, from the viewpoint of completing the reaction, a range of 1% by mass or more and 200% by mass or less with respect to the oxazoline group-containing compound is preferable. A range of 10% by mass or more and 100% by mass or less is more preferable in order not to impair the physical properties of the composition.

[0018] Further, it is preferable that the stoichiometric amount (converted to oxazoline group units) of the sum of the oxazoline group-containing compound and its reaction product in the resin composition is 0.02 mmol or more and 2 mmol or less with respect to 1 g of carbon black in the conductive resin composition of the present invention. More preferably, this stoichiometric amount is 0.02 mmol or more and 0.2 mmol or less. If this amount is less than 0.02 mmol, the amount of oxazoline groups is not sufficient for the organic functional groups present on the carbon black surface, and the organic functional groups remain, so that the inhibitory effect on the decomposition reaction of the POM resin becomes weak. On the other hand, if the stoichiometric amount exceeds 2 mmol, unreacted oxazoline groups tend to remain in the resin composition, and the long-term stability of the conductive resin composition and its molded article is likely to be impaired.

[0019] Next, the constituent components of the conductive resin composition of the present invention will be described.

[0020] <POM resin> The conductive resin composition of the present invention is a resin composition mainly composed of a POM resin. Here, the main component means that the proportion of the POM resin in the conductive resin composition is 50% by mass or more. From the viewpoint of ensuring the original slidability and strength of polyacetal, the proportion of the POM resin is more preferably 70% by mass or more.

[0021] Examples of the POM resin that can be used in the present invention include polyacetal homopolymers substantially composed only of oxymethylene units obtained by homopolymerizing formaldehyde monomers or their multimers (such as trioxane), and formaldehyde monomers or their multimers (such as trioxane) and glycols such as ethylene oxide, propylene oxide, epichlorohydrin, 1,3-dioxolane, and cyclic ethers and cyclic formals. Representative examples include polyacetal copolymers obtained by copolymerizing them.

[0022] Preferably, a polyacetal copolymer can be used due to its chemical stability. Also, depending on the type of copolymer, it is possible to use a polyacetal copolymer having a crosslinked structure or a block structure, and there are no particular restrictions on the structural characteristics of the polyacetal copolymer.

[0023] Although there are no particular restrictions on the terminal structure of the polymer, when a hydroxyl group or an aldehyde of an oxymethylene unit is present at the terminal, this terminal becomes the starting point of thermal decomposition and it is difficult to use it as it is in practice. It is preferable to perform a chemical sealing treatment on the terminal of the oxymethylene unit, or to perform a decomposition treatment on the unstable terminal with amines, ammonium compounds, etc., and use a POM resin having a copolymer component other than the oxymethylene unit at the terminal.

[0024] The POM resin that can be used in the present invention may be a commercially available POM resin added with various additives according to the application. For example, "Duracon (registered trademark)" series manufactured by Polyplastics Co., Ltd., "Tenac (trademark)" series, "Tenac (registered trademark)-C" series manufactured by Asahi Kasei Corporation, "Hifax (registered trademark)" series manufactured by Mitsubishi Engineering-Plastics Corporation. Also, these POM resins may be mixed and used.

[0025] The melt flow rate (MFR, measured under JIS-K7210 conditions) of the POM resin that can be used in the present invention is 0.5 g / 10 min to 100 g / 10 min at 190°C, preferably 1 g / 10 min to 50 g / 10 min.

[0026] <Carbon black> The carbon black that can be used in the present invention is conductive and has a developed chain structure. Preferably, those having an average primary particle diameter (aggregate diameter) as an aggregate in the range of 0.05 μm or more and 1 μm or less are used. Further, the addition amount of the carbon black is preferably 5% by mass or more and 25% by mass or less in the conductive resin composition. When the addition amount of the carbon black is 5% by mass or more, good conductivity can be obtained, and when it is 25% by mass or less, the heat generation during molding processing is small, and the thermal decomposition of the POM resin hardly occurs, which is preferable. Further, 15% by mass or less, which provides good fluidity during the molding process of the resin composition, is more preferable. In order to balance both the thermal decomposition and conductivity of the POM resin, it is particularly preferably 7% by mass or more and 13% by mass or less.

[0027] In addition, in order to obtain a resin composition having sufficient conductivity within the above addition amount range, the carbon black preferably has a dibutyl phthalate oil absorption amount (DBP oil absorption amount, ASTM D2415-65T) of 250 ml / 100 g or more.

[0028] The carbon black that can be used in the present invention is, for example, "Denka Black (registered trademark)" manufactured by Denki Kagaku Kogyo Co., Ltd. (DBP oil absorption amount of granular product: 160 ml / 100 g), "Seast (product name)" series manufactured by Tokai Carbon Co., Ltd. (DBP oil absorption amount: 40 ml / 100 g to 160 ml / 100 g), "Torcablack (product name)" series (DBP oil absorption amount: 50 ml / 100 g to 170 ml / 100 g), "Mitsubishi Carbon Black (product name)" series manufactured by Mitsubishi Chemical Corporation (DBP oil absorption amount: 40 ml / 100 g to 180 ml / 100 g). Also, as those having a DBP oil absorption amount exceeding 250 ml / 100 g, "Ketjenblack (product name)" series of Lion Specialty Chemicals Co., Ltd. (DBP oil absorption amount: 350 ml / 100 g to 500 ml / 100 g), "Lionite (product name)" series (DBP oil absorption amount: 250 ml / 100 g to 400 ml / 100 g), There is a series of "PRINTEX (product name)" manufactured by Orion Engineered Carbons Co., Ltd. (50 ml / 100 g to 420 ml / 100 g). The above carbon black may be used in combination of two or more kinds.

[0029] <Graphite> The graphite that can be used in the present invention can be appropriately selected from artificial or natural products according to the purpose. The shape of the graphite is not particularly limited, and it may be, for example, flaky, massive, spherical, earthy, etc. However, from the viewpoint of better manifestation of conductivity, flaky graphite is preferred.

[0030] The average particle size of the graphite powder that can be used in the present invention is preferably in the range of 0.5 μm to 100 μm, more preferably in the range of 20 μm to 80 μm. From the viewpoints of high conductivity and dimensional stability during temperature change, 20 μm or more is preferred, and from the viewpoints of handleability and surface property of the molded body, 100 μm or less is preferred.

[0031] Examples of flaky graphite include the "CP (product name)" series, "F♯ (product name)" series manufactured by Nippon Graphite Co., Ltd., the "CNP (product name)" series, "Z (product name)" series manufactured by Ito Graphite Industry Co., Ltd., etc. Also, two or more kinds of graphite may be used in combination. Further, the addition amount of graphite is preferably in the range of 2% by mass to 8% by mass in the conductive resin composition.

[0032] <Other additives> In the conductive resin composition of the present invention, various other additives may be blended as necessary. As various additives for improving functionality, there are flame retardants, waxes, various fatty acids, fatty acid amides, fatty acid esters, lubricants and mold release agents such as metal salts of fatty acids, various antistatic agents, fatty acid esters, sliding property improvers such as polyolefins, olefin copolymer elastomers, and polysiloxanes, polymers of polyamide resins and acrylamide, amide compounds, amino-substituted triazine compounds and their derivatives, urea and its derivatives, hydrazine derivatives, imidazole compounds, imide compounds, epoxy compounds, etc., which are decomposition inhibitors of POM resins, formic acid scavengers such as melamine, hydroxides and carbonates of alkali metals, impact resistance improvers such as polyurethane elastomers, polyester elastomers, and polystyrene elastomers, and flame retardants such as organophosphorus compounds. Further, as various additives for improving long-term stability, there are also ultraviolet absorbers such as benzotriazole compounds, benzophenone compounds, phenyl salicylate compounds, hindered amine light stabilizers, and hindered phenol antioxidants, etc.

[0033] Among them, polyolefins, olefin copolymer elastomers, and fatty acid esters are preferably used. As the polyolefin, polyethylene, particularly low-density polyethylene, is preferably used, and as the olefin copolymer elastomer, a styrene / butadiene block copolymer is preferably used. It is more preferable that their tensile yield stress is 10 MPa or more. By using these additives, improvement in wear resistance can be expected. The addition amount of these additives is preferably 10% by mass or less in the resin composition.

[0034] Fatty acid esters are effective in improving slidability and reducing kneading torque during the production of resin compositions, and can be preferably used. For example, esters of monovalent fatty acids and monovalent aliphatic alcohols are preferred. Examples of monovalent fatty acids that are naturally derived and easily available include myristic acid, stearic acid, montanic acid, oleic acid, linoleic acid, linolenic acid, etc., and esters obtained from these and aliphatic alcohols can be preferably used. In particular, cetyl myristate and stearyl stearate are more preferable in terms of the balance of properties such as slidability, heat distortion temperature, and reduction in kneading torque when used as additives. The addition amount of fatty acid esters is preferably 10% by mass or less in the resin composition for the purpose of ensuring the balance of these properties.

[0035] Also, within a range that does not impair the conductive performance of the present invention, for the purpose of improving functions such as low coefficient of thermal expansion and rigidity, inorganic components such as metal oxides, metal hydroxides, carbonates, sulfates, silicate compounds, glass-based fillers, silicate compounds, metal powders, metal fibers, carbon fibers, carbon nanotubes, etc. may be included.

[0036] Examples of the metal oxide include alumina, zinc oxide, titanium oxide, cerium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, antimony oxide, etc. Examples of the metal hydroxide include calcium hydroxide, magnesium hydroxide, aluminum hydroxide, etc. Examples of the carbonate include basic magnesium carbonate, calcium carbonate, magnesium carbonate, zinc carbonate, barium carbonate, dawsonite, hydrotalcite, etc. Examples of the sulfate include calcium sulfate, barium sulfate, magnesium sulfate, gypsum fiber, etc. Examples of the silicate compound include calcium silicate (wollastonite, zonnolite, etc.), talc, clay, mica, montmorillonite, bentonite, activated clay, sepiolite, imogolite, sericite, kaolin, vermiculite, smectite, etc. Examples of the glass-based filler include glass fiber, milled glass fiber, glass bead, glass flake, glass balloon, etc. Examples of the silicate compound include silica (such as white carbon), silica sand, etc. Examples of the main element constituting the metal powder and metal fiber include iron, aluminum, titanium, copper, etc., and those obtained by compounding these elements with other elements may also be used.

[0037] These inorganic fillers may have their surfaces treated with various surface treatment agents such as silane coupling agents, titanium coupling agents, organic fatty acids, alcohols, amines, etc., waxes, silicone resins, etc. The above additives may be used in combination of one or more kinds.

[0038] <Regarding the components> Regarding the components of the conductive resin composition of the present invention, they can be known by combining known separation techniques and analysis techniques. The method and procedure are not particularly limited, but as an example, after separating the components of the solution obtained by extracting the organic components from the conductive resin composition by various chromatographic methods, etc., component analysis can be carried out.

[0039] To extract the organic components from the conductive resin composition, the conductive resin composition may be dissolved in a soluble solvent. By previously crushing the conductive resin composition finely or heating and stirring the solvent, the time required for extraction can be shortened. The solvent to be used can be arbitrarily selected according to the properties of the organic components constituting the conductive resin composition. In the case of a resin composition containing a POM resin as in the present invention, a solvent such as hexafluoropropanol is preferably used.

[0040] Here, by drying and weighing the residue remaining after separating the organic components, the content of the inorganic components contained in the conductive resin composition can be known. As another method for knowing the content of the inorganic components in the conductive resin composition, there is also a method of quantifying the ash content by raising the temperature above the decomposition temperature of the resin by thermogravimetric analysis (TGA) or the like.

[0041] The solution obtained by extracting the organic components from the conductive resin composition can separate the components by methods such as various chromatographs. Low molecular weight additives can be separated by gas chromatography (GC), high performance liquid column chromatography (HPLC), etc., and high molecular weight polymers can be separated by gel permeation chromatography (GPC) etc. In particular, when cross-linked polymers or gels with large molecular weights are contained, or when micelles are formed in the liquid, separation by centrifugation or a semipermeable membrane can also be selected. The separated organic components can be analyzed by known analytical methods such as nuclear magnetic resonance (NMR) spectrum measurement, infrared absorption (IR) spectrum measurement, Raman spectrum measurement, mass spectrum measurement, and elemental analysis.

[0042] Regarding inorganic components, particularly carbon black, graphite, and oxazoline group-containing compounds chemically bonded to the organic functional groups on their surfaces, they can be recovered from the residue obtained after centrifugation following the dissolution and extraction of other organic components in a soluble solvent. This residue can be separated into fragments of each component through appropriate chemical treatment, such as treatment with strong acids, etc. After separating the soluble components by centrifugation, the solvent is removed after neutralization, washed, and then its structure can be confirmed by known analytical methods such as gas chromatography (GC), high-performance liquid column chromatography (HPLC), nuclear magnetic resonance (NMR) spectrum measurement, infrared absorption (IR) spectrum measurement, Raman spectrum measurement, mass spectrum measurement, and elemental analysis.

[0043] <Method for manufacturing conductive resin composition> The method for manufacturing the conductive resin composition of the present invention is not limited to a specific method, and a mixing method generally adopted for thermoplastic resins can be used. For example, it can be manufactured by mixing and kneading with a mixer such as a tumbler, V-type blender, Banbury mixer, kneading roll, kneader, single-screw extruder, multi-screw extruder with two or more shafts, etc. In particular, melt-kneading with a twin-screw extruder is excellent in productivity.

[0044] In the manufacture of the conductive resin composition, multiple components among the POM resin, carbon black, graphite, oxazoline group-containing compound, and other additives used as necessary may be pre-mixed or pre-kneaded in advance, or may be mixed or kneaded simultaneously. In particular, in the manufacture by an extruder, kneading can also be performed by providing individual feeders for each component and sequentially adding them during the extrusion process.

[0045] When pre-mixing other additives with any one or more of the POM resin, carbon black, graphite, and oxazoline group-containing compound, it may be treated by a dry method or a wet method. In the dry method, stirring is performed using a stirrer such as a Henschel mixer or a ball mill. In the wet method, the conductive resin is added to a solvent and stirred, and the solvent is dried and removed after mixing.

[0046] In the production by melt kneading, the kneading temperature, kneading time, and feeding rate can be arbitrarily set according to the type and performance of the kneading apparatus, the compounding components, and the properties of other additives used as required. Regarding the kneading temperature, it is usually 150°C to 250°C, preferably 160°C to 230°C, more preferably 170°C to 210°C. When the kneading temperature is 150°C or higher, the dispersibility becomes good, and by setting it to 250°C or lower, the generation of formaldehyde due to thermal decomposition and the deterioration of various physical properties can be suppressed.

[0047] The conductive resin composition of the present invention can be easily molded by commonly used molding methods such as extrusion molding, injection molding, and compression molding, and is also applicable to blow molding, vacuum molding, two-color molding, insert molding, etc. The resin molded body obtained by molding the conductive resin composition of the present invention is applied as parts of OA equipment and other electrical and electronic equipment, or as conductive functional parts of electrical and electronic equipment. Further, the resin molded body of the present invention is also applicable to structural members of automobiles and aircraft, building members, food containers, etc. That is, it is applicable to various manufacturing methods for manufacturing a molded body by molding a resin composition using a mold, and can be preferably used for mechanism parts of a copying machine main body and a toner cartridge container that particularly require high conductivity and slidability. Specifically, it is preferably used for electrical contact members in electrical and electronic equipment, photoreceptor drum flanges in image forming devices, parts of process cartridges, bearing members, etc.

Examples

[0048] The materials used in this example (including comparative examples) are as follows. (A) POM resin A: "Duracon (registered trademark) M270CA (product name)" manufactured by Polyplastics Co., Ltd.

[0049] (B) Conductive carbon black B-1: "Lionite EC200L (product name)" manufactured by Lion Specialty Chemicals Co., Ltd. (DBP oil absorption: 260 ml / 100 g) B-2: "Lionite CB" (product name) manufactured by Lion Specialty Chemicals Co., Ltd. (DBP oil absorption: 378 ml / 100 g) B-3: "Printex XE2-B" (product name) manufactured by Orion Engineered Carbons Co., Ltd. (DBP oil absorption: 420 ml / 100 g)

[0050] (C) Graphite C-1: "Z-25" (product name) manufactured by Ito Graphite Industry Co., Ltd. (scaly graphite, average particle size: 25 μm) C-2: "F#3" (product name) manufactured by Nippon Graphite Industry Co., Ltd. (scaly graphite, average particle size: 60 μm)

[0051] (D) Oxazoline group-containing compound D-1: "CP Resin A 1,3-BPO" (product name) manufactured by Sankyo Pharmaceutical Co., Ltd. (bifunctional oxazoline) D-2: "Epocros RPS-1005S" (product name) manufactured by Nippon Shokubai Co., Ltd. (oxazoline-modified polystyrene, oxazoline equivalent: 0.27 mmol / g)

[0052] (E) Other additives E-1: "Spam Acetyl" (product name) manufactured by NOF Corporation (main component: cetyl myristate) E-2: "UBE Polyethylene L719" (product name) manufactured by Ube Maruzen Polyethylene Co., Ltd. (low-density polyethylene, tensile yield stress 13 MPa) E-3: "Suntech LD L1850A" (product name) manufactured by Asahi Kasei Corporation (low-density polyethylene, tensile yield stress 12 MPa) E-4: "Ultrex 20100J" (product name) manufactured by Prime Polymer Co., Ltd. (low-density polyethylene, tensile yield stress 9 MPa) E-5: "Modiper A1100" (product name) manufactured by NOF Corporation (compatibilizer) E-6: "TR2827" (product name) manufactured by JSR Corporation (styrene / butadiene block copolymer) E-7: Triphenylphosphine manufactured by Kishida Chemical Co., Ltd. E-8: Melamine (aldehyde-reactive compound) manufactured by Kishida Chemical Co., Ltd. E-9: 2-Imidazolidinone (aldehyde-reactive compound) manufactured by Tokyo Chemical Industry Co., Ltd. E-10: Phthalimide (aldehyde-reactive compound) manufactured by Kishida Chemical Co., Ltd. E-11: "Irgafos 1010 (product name)" manufactured by BASF Japan Ltd. (hindered phenolic antioxidant) E-12: "Irgafos 168 (product name)" manufactured by BASF Japan Ltd. (phosphorus-based processing stabilizer) E-13: "Adekastab ZS-27" manufactured by ADEKA Corporation (metal deactivator) E-14: 1,2,3-Benzotriazole (metal deactivator and aldehyde-reactive compound) manufactured by Tokyo Chemical Industry Co., Ltd. E-15: Dicyandiamide (epoxy curing agent) manufactured by Kishida Chemical Co., Ltd. E-16: "EPICLON-695 (product name)" manufactured by DIC Corporation (cresol novolak type epoxy resin) E-17: "Coronate 4362 (product name)" manufactured by Tosoh Corporation (isocyanate compound)

[0053] (Manufacture of conductive resin composition) The POM resin (A) was dried in advance at a temperature of 90°C for 3 hours. Then, carbon black (B), graphite (C), oxazoline group-containing compound (D), and other additives (E) were added so that the mass percentages of the respective components in the finally obtained conductive resin composition would be the blending amounts shown in Table 1, and a blend of raw materials was prepared. The blend was melt-kneaded under the condition of a cylinder temperature of 200°C using a twin-screw extruder "PCM30 (product name)" manufactured by Ikegai Corporation to produce strands, and the strands were cut by a pelletizer to obtain pellets of the conductive resin composition. The following evaluations were performed on the obtained pellets. The results are shown in Table 1 and Table 2.

[0054] (Volume resistivity evaluation) The conductive resin composition was taken in the state of the strand before cutting, and the diameter was measured with calipers. The resistance value was measured for a range of 5 cm in length using a "Handy Milliohm Tester SK-3800 (product name)" manufactured by Kaijo Corporation, and the volume resistivity of the conductive resin composition was calculated.

[0055] (Thermal stability evaluation) When the POM resin (A) contained in the conductive resin composition decomposes to generate formaldehyde gas, a weight loss of the conductive resin composition can be observed. Using a thermogravimetric analyzer (TGA) "Q500" manufactured by TA Instruments, it was held at 225 °C under a nitrogen stream for 2 hours, and the weight loss rate was measured.

[0056] (Saturated water absorption evaluation) The pellets of the obtained conductive resin composition were injection-molded using an injection molding machine "SE-180D (product name)" manufactured by Sumitomo Heavy Industries, Ltd. at a cylinder temperature of 200 °C and a mold temperature of 60 °C to produce strip-shaped test pieces type B1 (length 80 mm × width 10 mm × thickness 4 mm) specified in JIS K7152-1.

[0057] The above test pieces were immersed in water with reference to JIS K 7209 Method A, and the saturated water absorption was determined from the weight increase of the test pieces. In Method A, it is usually immersed in water at 23 ± 1 °C, but for the accelerated test, only the immersion temperature was changed to 40 ± 1 °C, and the evaluation was carried out under the same conditions as Method A for the rest.

[0058] (Wear resistance evaluation) The pellets of the obtained conductive resin composition were injection-molded using an injection molding machine "SE-180D (product name)" manufactured by Sumitomo Heavy Industries, Ltd. at a cylinder temperature of 200 °C and a mold temperature of 30 °C to produce a molded body with a circular hole of φ7 mm. A stainless steel shaft of the same diameter was passed through this circular hole, and the wear amount when rotated at a rotational speed of 60 rpm for 24 hours was evaluated. Based on the wear amount of Example 1, those with the same wear amount were marked as 〇, those with a deterioration of 10% or more were marked as △, and those with a reduction of 10% or more were marked as ◎.

[0059]

Table 1

[0060]

Table 2

[0061] In Tables 1 and 2, D-1, D-2, E-16, and E-17 are additives that react with the functional groups present on the carbon surface.

[0062] From Tables 1 and 2, it was found that by adding the oxazoline group-containing compound, a resin composition and its molded article having high conductivity, less thermal decomposition, and further low water absorption rate were obtained as compared with the case where other reactive additives were added. In Comparative Example 1 where no reactive additive was added at all, the POM resin was severely decomposed during extrusion kneading, and pellet production could not be carried out.

[0063] The present invention is not limited to the embodiments and examples described above, and many modifications are possible within the technical idea of the present invention. In addition, the effects described in the embodiments and examples of the present invention are merely a list of the most preferable effects resulting from the present invention, and the effects according to the present invention are not limited to those described in the embodiments and examples.

Claims

1. A conductive resin composition containing polyacetal as a main component, carbon black, and graphite, characterized by containing an oxazoline group-containing compound and its reaction product.

2. The conductive resin composition according to claim 1, wherein the stoichiometric amount of the sum of the oxazoline group-containing compound and its reaction product is 0.02 mmol or more and 2 mmol or less with respect to 1 g of the carbon black.

3. The conductive resin composition according to claim 1 or 2, wherein the oxazoline group-containing compound has an aromatic ring in its molecular structure.

4. The conductive resin composition according to claim 3, wherein the oxazoline group-containing compound is an oxazoline derivative represented by the following formula (1). 【Chemical 1】 〔In the above formula, R represents hydrogen or an oxazoline group, X represents a single bond or a hydrocarbon chain having 5 or less carbon atoms, and the terminal thereof may be copolymerized with other copolymer components.〕

5. The conductive resin composition according to any one of claims 1 to 4, further containing an aromatic phosphorus compound.

6. The conductive resin composition according to claim 5, wherein the aromatic phosphorus compound is triphenylphosphine.

7. The conductive resin composition according to any one of claims 1 to 6, wherein the content of the carbon black is 7% by mass or more and 13% by mass or less in the resin composition.

8. The conductive resin composition according to any one of claims 1 to 7, wherein the carbon black has a dibutyl phthalate oil absorption of 250 ml / 100 g or more.

9. The conductive resin composition according to any one of claims 1 to 8, further containing a fatty acid ester.

10. The conductive resin composition according to claim 9, wherein the fatty acid ester is at least one of cetyl myristate and stearyl stearate.

11. The conductive resin composition according to claim 9 or 10, wherein the fatty acid ester is contained in the conductive resin composition in a content of 10% by mass or less.

12. The conductive resin composition according to any one of claims 1 to 11, further containing a polyolefin or an olefin copolymer elastomer.

13. The conductive resin composition according to claim 12, wherein the polyolefin is polyethylene having a tensile yield stress of 10 MPa or more.

14. The conductive resin composition according to claim 12 or 13, wherein the polyolefin is contained in the conductive resin composition in a content of 10% by mass or less.

15. A resin molded body comprising the conductive resin composition according to any one of claims 1 to 14.

16. An electrical contact member comprising the resin molded body according to claim 15.

17. A photoreceptor drum fringe comprising the resin molded body according to claim 15.

18. A bearing member comprising the resin molded body according to claim 15.

19. A copying machine main body comprising the resin molded body according to claim 15.

20. A mechanical component of a toner cartridge comprising the resin molded body according to claim 15.

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