Resin composition, shaft body and electrophotographic image forming apparatus

Abstract

To provide a resin composition exhibiting a high elastic modulus even in an initial period in which stress starts to act.SOLUTION: A resin composition contains a crystalline thermoplastic resin (A), a carbon fiber (B) and talc (C), wherein an average length of the carbon fiber in the resin composition is 250-800 μm, an amount of the carbon fiber contained in the resin composition is 10 mass% or more and 50 mass% or less, the resin composition has a flexural elastic modulus at the time of 0.1 mm pushing of a molding with a length of 80.0 mm, a width of 10.0 mm and a thickness of 4.0 mm of 10 GPa or more, and when a calculated density determined from the product of densities and blending ratio of the components of the molding is represented by X, and an actual density of the molding is represented by Y, the resin composition gives a molding in which (Y / X)×100[%] is 90% or more.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a resin composition, a resin shaft member (hereinafter also referred to as a shaft body) made of the resin composition, and further to an electrophotographic image forming apparatus using the shaft body. [Background technology]

[0002] Iron has traditionally been used for the shaft of a rotating body, such as the drive roller 21 in an electrophotographic image forming apparatus as shown in FIG. 1. This is because an iron shaft is less likely to deform even when a load is applied. However, high precision is required for the shaft of a rotating body used in an electrophotographic image forming apparatus, and iron shafts with high precision are expensive to manufacture. In addition, iron shafts are heavy.

[0003] For this reason, studies have been conducted to replace the shaft material with resin. To increase the strength of a resin shaft, studies have been conducted to mix a fibrous filler, particularly carbon fiber, into the resin material (Patent Document 1). Studies have also been conducted to improve the modulus of elasticity by mixing a crystal nucleating agent into glass fiber and a crystalline resin to increase the degree of crystallinity (Patent Document 2). The present inventors incorporated a rotating body equipped with a shaft made of a resin composition with an increased modulus of elasticity using the techniques described in Patent Documents 1 and 2 into an electrophotographic image forming apparatus, and found that the shaft sometimes deformed when a load was first applied to the shaft. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 7-292224 [Patent Document 2] Japanese Patent Application Publication No. 61-66745 Summary of the Invention [Problem to be solved by the invention]

[0005] One aspect of the present disclosure is to provide a resin composition that gives a molded article that exhibits a high elastic modulus even in the early stages when stress begins to act. Another aspect of the present disclosure is to provide a resin molded article that exhibits a high elastic modulus even in the early stage when stress begins to act. Still another aspect of the present disclosure is to provide an electrophotographic image forming apparatus that can provide high-quality electrophotographic images. [Means for solving the problem]

[0006] According to one embodiment of the present disclosure, there is provided a resin composition containing a crystalline thermoplastic resin (A), carbon fibers (B), and talc (C), the average length of the carbon fibers in the resin composition is 250 to 800 μm, the amount of the carbon fiber contained in the resin composition is 10% by mass or more and 50% by mass or less, The resin composition provides a molded article having a length of 80.0 mm, a width of 10.0 mm, and a thickness of 4.0 mm, which has a flexural modulus of 10 GPa or more when pressed down by 0.1 mm, and which satisfies (Y / X) × 100 [%] of 90% or more, where X is the calculated density calculated from the product of the density of each of the constituent materials of the molded article and their blending ratio, and Y is the actual density of the molded article. According to another aspect of the present disclosure, there is provided a resin molded article made from the resin composition. According to another aspect of the present disclosure, there is provided an electrophotographic image forming apparatus including a roller having a shaft body, the shaft body being a molded article made of the resin composition. [Effects of the Invention]

[0007] According to one aspect of the present disclosure, a resin composition can be provided that has high initial rigidity when stress begins to act and has an elastic modulus close to that of metal. Also, according to another aspect of the present disclosure, a resin molded product and an electrophotographic image forming apparatus using the resin composition can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram of an example of an electrophotographic image forming apparatus according to the present disclosure. [Figure 2] This is the elongation-stress curve of a general metal and a carbon fiber reinforced resin. [Figure 3] FIG. 1 is a schematic diagram of a mixture of resin and carbon fiber in an amorphous state. [Figure 4] 1 is a schematic diagram of a mixture of resin and carbon fiber in a crystalline state. [Figure 5] FIG. 1 is a schematic diagram of a mixture of crystalline resin, talc, and carbon fiber according to the present disclosure. [Figure 6] 1 is an elongation-stress curve of a resin composition according to the present disclosure. [Figure 7] FIG. 7 is an enlarged view of the region of the elongation-stress curve shown in FIG. 6 where the elongation is up to 0.1 mm. [Figure 8] 1 is a schematic diagram of a production apparatus for a resin composition according to the present disclosure. [Figure 9] FIG. 9 is a schematic view of a die used in the manufacturing apparatus shown in FIG. [Figure 10] FIG. 10 is a schematic diagram of a strand discharged from the die shown in FIG. 9. [Figure 11] FIG. 2 is a schematic diagram for explaining the shape of a shaft body. [Figure 12] FIG. 12 is a schematic view showing an injection molding device used to manufacture the shaft shown in FIG. [Figure 13] 1 is an electron microscope photograph showing a state in which the adhesion between the resin and the carbon fiber is insufficient. [Figure 14] 1 is an electron microscope photograph showing sufficient adhesion between resin and carbon fiber. DETAILED DESCRIPTION OF THE INVENTION

[0009] A shaft made using the resin composition described in Patent Document 2 was incorporated into an electrophotographic image forming apparatus, and the bending of the shaft upon application of a load was observed in detail. Specifically, as shown in Figure 2, when the flexural modulus was measured, the resin shaft (B) deformed more than 30 times more than the iron shaft (A) at the very beginning of load application, for example, up to a load of 2 N in Figure 2. As the load continued to increase, the increase in elongation relative to the load decreased from an elongation of 1.0 mm or more in Figure 2. In other words, the modulus of elasticity increased. However, even if the shaft had a high modulus of elasticity in the already deformed, bent state, it was difficult to use it for parts requiring high precision, such as shafts for electrophotographic image forming apparatuses. Thus, although carbon fiber-containing resin compositions with a high modulus of elasticity exist, there was still room for improvement before they could be used as materials for shafts of rollers used in electrophotographic image forming apparatuses. Here, the reason why a molded body (resin molded body) made of a resin composition reinforced with carbon fiber deforms in the early stages of application of the above-mentioned stress was considered as follows.

[0010] First, when the binder resin containing carbon fiber is an amorphous resin, the presence of an uncrystallized portion (amorphous resin 202) means that even if the carbon fiber 201 is hard, the resin 202 is soft and lacks rigidity, as shown in Figure 3. For this reason, when a shaft made of such a resin composition is pressed 0.1 mm, if a load is applied to the resin portion indicated by arrow 205 in the direction indicated by arrow 205, it cannot support the load and is prone to deformation.

[0011] On the other hand, when the binder resin containing carbon fiber is a crystalline thermoplastic resin, the presence of rigid crystalline resin 203, as shown in Figure 4, suggests that deformation is less likely than when the binder resin is an amorphous resin. However, when a shaft made of a carbon fiber-containing resin composition in which the binder resin is a crystalline thermoplastic resin is pressed 0.1 mm, the deformation amount is only slightly smaller than that of the shaft made of the resin composition in which the binder resin is an amorphous resin. This is because, even with a crystalline resin, the crystallinity cannot be 100% and amorphous portions 202 are always present. As described above, the amorphous portions 202 are prone to deformation under load. For this reason, even when the binder resin is a crystalline thermoplastic resin, deformation is thought to occur at the initial stage of stress application. Based on these considerations and further investigations, the present inventors have discovered a resin composition capable of forming a shaft with a bending deformation rate of 10 GPa or more when pressed 0.1 mm.

[0012] That is, a resin composition according to one embodiment of the present disclosure contains a crystalline thermoplastic resin, carbon fiber, and talc. The average length of the carbon fiber in the resin composition is 250 to 800 μm, and the amount of the carbon fiber contained in the resin composition is 10% by mass or more and 50% by mass or less. Furthermore, (Y / X)×100[%] calculated from the following X and the following Y is 90% or more. X: the calculated density of the resin composition obtained by multiplying the density of each of the crystalline thermoplastic resin (A), the carbon fiber (B), and the surface-treated talc (C) by the blending ratio. Y: Actual density of the resin composition The resin composition gives a molded article having a Charpy shape (length 80.0 mm, width 10.0 mm, thickness 4.0 mm) with a flexural modulus of 10 GPa when pressed down 0.1 mm.

[0013] The reason why the bending modulus of the molded article of the resin composition according to the present disclosure is 10 GPa or more when indented 0.1 mm is presumed to be as follows. In a molded article (resin molded article) of the resin composition according to the present disclosure, crystalline resin 203 is generated around talc 204. In other words, the talc supports crystalline resin around itself. The talc supporting the crystalline resin then clings to the carbon fiber monofilaments. This configuration is believed to reduce the impact of easily deformable amorphous portions 202 in the binder resin on the physical properties of the molded article. As a result, it is believed that deformation when an extremely small stress of 0.1 mm is applied can be effectively suppressed.

[0014] In FIG. 6, A shows the elongation-stress curve of a test piece made of iron. B shows the elongation-stress curve of a molded article made of a carbon fiber reinforced resin composition according to Patent Document 2. C shows the elongation-stress curve of a resin composition containing a crystal nucleating agent other than talc. D shows the elongation-stress curve of a molded article made of a resin composition according to the present disclosure. The elongation-stress curve shown in FIG. 7 is an enlarged version of the elongation-stress curve shown in FIG. 6, covering the elongation range from 0.0 mm to 0.1 mm. As shown in FIG. 7, the elongation-stress curve D of the molded article made of a resin composition according to the present disclosure is close to the curve A of iron. Note that the shape of the elongation-stress curve C of the molded article made of a resin composition containing a crystal nucleating agent other than talc indicates that a molded article made by simply crystallizing a crystalline resin does not develop stress when indented 0.1 mm, and does not exhibit the same properties as a molded article made of a resin composition according to the present disclosure.

[0015] As described above, in the molded article according to the present disclosure, the adhesion between the carbon fiber and the crystalline resin supported on the talc is high. In the present disclosure, the ratio of Y to X is introduced as a parameter representing the adhesion. X: Calculated density of a Charpy molded article of the resin composition, calculated from the product of the density and the blending ratio of each of the crystalline thermoplastic resin (A), the carbon fiber (B), and the talc (C). Y: Actual density of the molded product Specifically, (Y / X) x 100 [%] is defined as 90% or more. In other words, if the actual density of the molded article is close to the theoretical density, it means that the resin is more closely adhered to the carbon fibers in the molded article. In the present disclosure, the value of (Y / X) x 100 is preferably 92% or more, and more preferably 93% or more.

[0016] A suitable method for producing a resin composition according to the present disclosure includes the steps of: first, forming crystals of a thermoplastic resin around talc; and wrapping the talc carrying a crystalline resin around carbon fibers. Specifically, an example of a method for forming crystals of a thermoplastic resin around talc is a method using a masterbatch in which a small amount of a thermoplastic resin and talc are mixed in advance.

[0017] The following method can be mentioned as an example of a method for wrapping talc carrying thermoplastic resin crystals around carbon fibers. The masterbatch is thoroughly mixed with a large amount of a thermoplastic resin using a twin-screw mixer. A method (roving method) in which long carbon fibers are added from a carbon fiber bobbin to a molten mixture in which the masterbatch and a large amount of thermoplastic resin are thoroughly mixed, and the molten mixture containing the carbon fibers is further mixed using a reverse feed single notched screw (BMS). During the process of further kneading a molten mixture containing long carbon fibers with a BMS, the carbon fibers are cut and broken into single fibers (defibrillation), and talc carrying thermoplastic resin crystals penetrates between the carbon fiber single fibers. As a result, the carbon fiber single fibers are coated with talc carrying thermoplastic resin crystals. Here, when carbon fibers that have been cut short in advance (chopped fibers) are used as the carbon fibers instead of long carbon fibers, the carbon fibers are not sufficiently broken into single fibers (defibrillation), and it is not possible to sufficiently wrap the talc carrying thermoplastic resin crystals around the carbon fibers. Even when short-cut carbon fibers are kneaded with a BMS together with the molten mixture, it is thought that defibrillation of the carbon fibers does not proceed because sufficient shear is not applied to the carbon fibers.

[0018] Fig. 14 is a photograph taken with an electron microscope showing a carbon fiber single filament 201 that is surrounded by talc carrying thermoplastic resin crystals 206. The presence of talc could not be confirmed in the electron microscope photograph shown in Fig. 14. This is presumably because the talc is surrounded by resin crystals.

[0019] Hereinafter, each element constituting the resin composition according to the present disclosure will be described. However, the scope of the present invention is not limited to the following embodiment. In this disclosure, the resin composition also includes so-called resin molded products, such as resins molded using a mold or the like from a resin composition, and sheet-like or flat-plate-like resins obtained by extrusion molding, injection molding, or the like.

[0020] <Crystalline thermoplastic resin (A)> The crystalline thermoplastic resin contained in the resin composition of the present disclosure is not particularly limited, and examples thereof include polyester resins such as polyethylene terephthalate (PET) and polybutylene terephthalate (PBT). PET is preferred for achieving a high elastic modulus, but PBT is preferred for achieving excellent shape stability, so a mixture of the two is more preferred.

[0021] <Carbon fiber (B)> The type of carbon fiber is not particularly limited, and examples include PAN-based carbon fibers made from polyacrylonitrile and pitch-based carbon fibers made from coal tar pitch or petroleum pitch. Furthermore, either female phase pitch or isotropic pitch, which differ in the crystalline state of the pitch used for spinning, may be used. From the perspective of enhancing wettability with resin, it is preferable for the carbon fiber to be surface-treated with an epoxy-based resin. Here, surface treatment also includes bundling with a binder. Furthermore, the diameter of the carbon fiber is preferably 5 μm or more and 10 μm or less.

[0022] <Carbon fiber length> The carbon fibers have an average length of 250 μm to 800 μm. Carbon fibers with such an average length can more reliably reinforce the resin composition. In particular, entanglement of carbon fibers, which tends to occur when the carbon fibers are too long, can be suppressed. If the carbon fibers are entangled, the adhesion between the carbon fibers and the crystalline thermoplastic resin (A) serving as the binder resin may decrease, and the effect of improving the elastic modulus of a molded product of the resin composition may be impaired.

[0023] <Method for measuring the average length of carbon fibers> To measure the average length of carbon fibers, resin pellets containing carbon fibers are dissolved in a solvent and evenly dispersed on filter paper. If the fiber length is less than 1 mm, a measuring microscope (e.g., Nikon's "MM-40" (trade name)) is used to capture five images with a 5x objective lens, and length and number data are obtained using an image analyzer (trade name: Luzex, Nireco). If the fiber length is 1 mm or greater, a digital single-lens reflex camera (trade name: EOS70D, Canon) equipped with a macrophoto lens (trade name: MP-E65mm F2.8 1-5x, Canon) is used to capture five images at a 4x magnification (effective magnification: 6.4x). The length and number data are then obtained using the image analyzer. The fiber length is the arithmetic mean length calculated from this measurement data.

[0024] <Carbon fiber content> The carbon fiber content in the resin composition according to one embodiment of the present disclosure is 10% by mass or more and 50% by mass or less. By setting the carbon fiber content within this range, the amount of deformation in the initial stage when stress begins to act on a molded article of the resin composition according to the present disclosure can be reduced. If the content is less than 10% by mass, the rigidity of the resin composition itself is insufficient. On the other hand, if the content exceeds 50% by mass, the amount of carbon fiber in the resin composition becomes too large, which may cause the molded article to become brittle.

[0025] <Talc> Talc functions as a crystallization promoter for the crystalline thermoplastic resin (A). Talc (Mg3(SiO10 Simply blending talc (a mineral mainly composed of hydroxymethylcellulose (OH)2) and carbon fiber makes it difficult to improve the elastic modulus of a molded product in the early stages of stress application. It is important to integrate talc and binder resin crystals in the resin composition. To achieve this, it is effective to use the so-called masterbatch method, in which talc is mixed in advance with a small amount of binder resin to prepare a talc masterbatch in which the surface of the talc is coated with the binder resin, and the masterbatch is then mixed with the binder resin and carbon fiber.

[0026] The talc contained in the resin composition of the present disclosure preferably has a number-average particle size of 1 μm or more and 5 μm or less. This is because a number-average particle size of 5 μm or less allows efficient crystallization of the resin without the need for a large amount of filler. On the other hand, if the number-average particle size is less than 1 μm, the size of the talc is too small, making it difficult to produce a rigid talc and crystal composition.

[0027] The number-average particle diameter can be measured, for example, by the following method. First, the filler is observed using a scanning electron microscope (SEM). The SEM measurement magnification is changed depending on the particle size being measured, as shown in Table 1. From the obtained two-dimensional image, 100 particles that do not overlap are randomly selected. The unidirectional tangential diameter (Feret diameter) is measured from the distance between two parallel lines in a certain direction that sandwich the particle in the obtained two-dimensional image, and this is used as the particle diameter of each particle. The arithmetic mean value of the particle diameters of the 100 particles obtained in this way can be used as the number-average particle diameter.

[0028] [Table 1]

[0029] When a crystalline polyester is used as the binder resin, it is preferable to use talc that has been surface-treated to prevent the polyester resin from being decomposed, since the moisture contained in the talc can decompose the resin. An example of a masterbatch in which such surface-treated talc is blended at a high concentration with a crystalline polyester resin is "Hicon Talc Master" (trade name, manufactured by Matsumura Sangyo Co., Ltd.). When a crystalline polyester is used as the binder resin, it is preferable to further use a thermoplastic resin containing a bisphenol A structure and an epoxy group in the molecule to further improve the adhesion between the crystalline polyester and the carbon fiber. As the thermoplastic resin containing an epoxy group and a bisphenol A structure in the molecule, a phenoxy resin having a structure represented by the following formula (1) is preferred.

[0030] [ka] In formula (1), n ​​represents an integer of 1 or more.

[0031] The epoxy groups of such phenoxy resin react with the binder applied to the carbon fiber surface, and the bisphenol A structure is compatible with PET because its SP value is similar. Therefore, the presence of phenoxy resin can further improve the adhesion between PET and carbon fiber. Specifically, (Y / X) can be increased to 98%, for example. As a result, deformation when stress is applied to a molded article made from the resin composition according to the present disclosure can be more reliably suppressed.

[0032] <Additives> In addition to the materials described above, various additives may be added to the resin composition of the present disclosure, such as fillers, dispersants, antioxidants, weathering agents, and anti-decomposition agents. There are no particular limitations on the type of filler to be added. For example, inorganic fillers include mica, glass spheres, cryolite, zinc oxide, titanium oxide, calcium carbonate, clays, silica, wollastonite, zeolite, diatomaceous earth, silica sand, pumice powder, slate powder, alumina, alumina white, aluminum sulfate, barium sulfate, fly ash, calcium sulfate, and molybdenum disulfide. The amount of filler added is set to an amount that does not hinder the maintenance of the talc crystal structure.

[0033] The organic filler may be, for example, one or more of the following: tetrafluoroethylene resin particles, trifluorochloroethylene resin particles, tetrafluoroethylene hexafluoropropylene resin particles, vinyl fluoride resin particles, vinylidene fluoride resin particles, difluorodichloroethylene resin particles and copolymers thereof, fluorocarbon, silicone resin particles, silicone rubber particles and other silicone compound rubber powders, ebonite powder, ceramic, wood flour, coconut shell powder, cork powder, cellulose powder, wood pulp, etc.

[0034] The constituent ratios of the resin composition of the present disclosure can be determined by combining known separation and analysis techniques. The methods and procedures are not particularly limited, but for example, a solution obtained by extracting organic components from the resin composition can be separated into components using various chromatographic methods, and then the components can be analyzed. To extract organic components from a resin composition, the resin composition can be immersed in a solvent capable of dissolving the organic components and dissolved therein. The time required for extraction can be shortened by crushing the resin composition into small pieces or by heating and stirring the solvent in advance. The solvent to be used can be selected arbitrarily depending on the polarity of the organic components constituting the resin composition. Preferred solvents include aromatic solvents such as toluene and xylene, and solvents such as tetrahydrofuran, dioxane, methylene chloride, chloroform, and N-methylpyrrolidone. These solvents may also be mixed in any ratio.

[0035] The residue remaining after separating the organic components is dried and weighed to determine the content of inorganic components in the resin composition. Another method for determining the content of inorganic components in a resin composition is to quantify the ash content by raising the temperature above the decomposition temperature of the resin using thermogravimetric analysis (TGA) or the like. In addition, by performing X-ray fluorescence analysis (XRF) on the dried sample of the residue remaining after extracting the organic components, it is possible to determine the elements contained in the inorganic components and their composition ratios.

[0036] The solution obtained by extracting organic components from the resin composition can be separated using various chromatographic methods. Low-molecular-weight additives can be separated using gas chromatography (GC) or high-performance liquid column chromatography (HPLC), while high-molecular-weight polymers can be separated using gel permeation chromatography (GPC). When crosslinked polymers or gels with high molecular weights are present, 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 using known analytical methods such as nuclear magnetic resonance (NMR) spectroscopy, infrared absorption (IR) spectroscopy, Raman spectroscopy, mass spectroscopy, and elemental analysis.

[0037] (Method of producing resin composition) The method for producing the resin composition of the present disclosure is not particularly limited. For example, the resin composition can be produced by mixing a resin, carbon fiber, and a filler, and methods include kneading and molding using various extruders such as a twin-screw extrusion method, a single-screw extrusion method, and a wire coating method. Other methods include kneading and molding using various mixers such as a kneader or a Banbury mixer, or various roll mills such as a two-roll mill or a three-roll mill. Among these, a method for adjusting the length of carbon fibers, which is a feature of the present disclosure, will be described.

[0038] FIG. 8 is a diagram illustrating a method for producing carbon fiber-containing pellets using a roving method in which continuous carbon fibers are supplied to a twin-screw extruder. Twin-screw extruder 301 melts and kneads resin fed into hopper 302 using twin-screw 303. Carbon fiber 312 wound around bobbin 311 is fed into the melt-kneaded resin from hopper 310 provided between hopper 302 and die 304. The fed carbon fiber 312 is kneaded by the screw, impregnated with resin, and cut to shorten the fiber length. The fiber length at this time can be controlled by the shape of the screw and the screw rotation speed. For example, the fiber length can be shortened by shearing using multiple screws with a shape called kneading screws.Furthermore, the fiber length can be shortened by increasing the number of screw rotations per unit time while keeping the amount of extruded resin constant.

[0039] The kneaded carbon fiber-containing resin is extruded as string-like resin melt (hereinafter also referred to as strand) 309 from a die outlet 307 (diameter 308 is about 3 to 4 mm) of an extrusion die 304 shown in FIG. FIG. 10 is a cross-sectional view showing how the carbon fiber-containing resin is extruded as strands 309 from a die outlet 307 of an extrusion die 304 . The extruded strands 309 are cooled in a cooling device such as a water bath 305, and then formed into cylindrical pellets 320 with a length of about 2 to 6 mm and a diameter of about 2 to 3 mm by a strand cutter 306 or the like. Thus, the roving method is preferable because the length of the fibers can be freely adjusted.

[0040] <Method of manufacturing the shaft molded product> The method for producing the shaft molded product of the present disclosure is not particularly limited. For example, injection molding, extrusion molding, press molding, transfer molding, etc. can be used. Among these, injection molding is preferred because injection molding has a short molding cycle time and allows for efficient production. To adapt the resin composition to this injection molding, the resin composition is preferably in the form of pellets as described above.

[0041] <Method for manufacturing surface-treated talc> The method for producing the surface-treated talc of the present disclosure is not particularly limited, and any known method can be used, such as a masterbatch method or a method using a mixer. In the masterbatch method, a small amount of resin, a resin decomposition inhibitor, and talc are mixed in advance to produce a masterbatch in which the talc is coated with the resin and the concentration of talc is higher than the final concentration.The masterbatch has a low resin content of about 50% by mass, and the talc is coated with a resin containing a decomposition inhibitor. The masterbatch is then kneaded with an amount of resin that will result in the final talc concentration in a kneading device such as a twin-screw extruder and pelletized. When the masterbatch is mixed with an amount of resin that will result in the final talc concentration, the talc is already coated with the resin that contains the decomposition inhibitor, so decomposition of the resin coating the talc is suppressed, and further decomposition of resins other than the resin coating the talc is also suppressed. Examples of the resin decomposition inhibitor include various antioxidants such as hindered phenols, various heat stabilizers such as phosphites, etc. A plurality of these additives can also be blended in combination. The method using a mixer is mainly a treatment using a coupling agent. Treatment using a coupling agent can be either dry or wet, but the dry method is preferred because it does not require post-treatment of the liquid.

[0042] (Electrophotographic image forming apparatus) An example of an electrophotographic image forming apparatus according to the present disclosure is a color electrophotographic image forming apparatus of an intermediate transfer type shown in Fig. 1. In the case of this intermediate transfer type, the transfer of a toner image from an electrophotographic photosensitive member to a transfer material is mainly carried out by a primary transfer charging member, an intermediate transfer belt, and a secondary transfer charging member. In FIG. 1, intermediate transfer belt 20 is driven to rotate by drive roller 21. Tension roller 22 applies tension to intermediate transfer belt 20 in the direction indicated by arrow a, preventing the intermediate transfer belt from slackening or warping. The tension in the direction indicated by arrow a is approximately 100 N at the left end of the shaft of tension roller 22 and approximately 100 N at the right end, for a total of approximately 200 N. Image output speeds have increased in recent years, but as output speeds increase, belt distortion tends to occur, leading to an increase in tension. If the shaft's elasticity is low, the shaft bends under tension, making it more susceptible to distortion, which can result in poor image quality, unstable intermediate transfer belt movement, and belt damage.

[0043] The shaft made of the resin composition of the present disclosure is suitable for use in an electrophotographic image forming apparatus, and because it has a high elastic modulus when pressed down by 0.1 mm, it can be used to resinify parts that require rigidity and for which only metals were previously used. It can also be used to resinify precision parts used in small products such as cameras and watches. Furthermore, it can be used for small, precise parts used in large products such as automobiles. In particular, when PET / PBT or other thermoplastic resins are used, these thermoplastic resins have high heat resistance, so they can also be used for parts around automobile engines, which are exposed to high temperatures. [Example]

[0044] The present disclosure will be described in detail below using examples and comparative examples, but the present disclosure is not limited to these examples. In the examples and comparative examples, the following items were measured and evaluated.

[0045] <Flexural modulus> After injection molding a resin composition in the shape of cylindrical shaft 401 shown in Fig. 11, a jig for a three-point bending test, with a support stand and a central indenter having a diameter of 10 mm, was attached to an Instron tensile testing machine, and the molded product was placed on the jig, and measurements were made at a support distance of 23 cm and a speed of 2 mm / min. No preliminary force was applied when the measurement was started. The dimensions of each part of cylindrical shaft 401 will be described later. The measurement environment was a temperature of 25°C ± 3°C and a relative humidity of 55 ± 5%. The flexural modulus was calculated in accordance with Japanese Industrial Standards (JIS) K7017:1999 (ISO / FDIS14125:1997) "Fiber reinforced plastics -- Determination of flexural properties." In the above standard, the specified strain range is 0.05 to 0.25%, but in this disclosure, the specified strain range is 0.01 mm to 0.1 mm. The flexural modulus E was calculated using the stress σ1 when the strain ε1 was 0.01 mm, the stress σ2 when the strain ε2 was 0.1 mm, and the following formula. This flexural modulus E is also referred to as the "flexural modulus when indented 0.1 mm." Flexural modulus E=(σ2-σ1) / (ε2-ε1)

[0046] The samples used were formed into a Charpy shape (length 80.0 mm, width 10.0 mm, thickness 4.0 mm, notch depth 2 mm processed using a notch processing machine according to JIS K7144). A universal material testing machine (model number: 5582; manufactured by Instron) and a three-point bending jig (static test bending jig, model number: 2810; manufactured by Instron) were used for the bending test. The measurement pitch distance was 64 mm, and the indentation speed was 2 mm / min. On the other hand, as reference data, the flexural modulus of a general resin (in the region exceeding 0.1 mm) was measured using a method conforming to the tangent method of JIS (JIS K7074). The specified strain range is the length up to which the sample breaks or the length up to the measurement limit.

[0047] <Thermoplastic resin> Polybutylene terephthalate (PBT) 1: Duranex 2000 (Polyplastics Co., Ltd.) (density 1.404 g / cm 3 ) Polyethylene terephthalate (PET) 2 TRN-8550FF (manufactured by Teijin Limited) (Density 1.407 g / cm 3 )

[0048] <Carbon fiber> Carbon fiber 1 (trade name: "Pyrofil TRH50 60M RJ", 2500 m roll, filament diameter 6 μm, number of filaments 6,000, density 1.820 g / cm 3 (manufactured by Mitsubishi Chemical Corporation))​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​As shown schematically in Figure 8, a TEX44αII (L / D = 38.5, 11 blocks used) manufactured by The Japan Steel Works, Ltd. was used as the twin-screw extruder 301. Long carbon fiber 312 wound around a bobbin 311 was fed from a hopper 310 provided between a hopper 302 and a die 304 of the extruder. Note that while Figure 8 shows three screw blocks, the total number of screw blocks used in this example was 13. The detailed conditions of the twin-screw extruder are as follows:

[0052] Configuration of screw 303: From the tip to the rear end of the screw, the third block is a BMS (a reverse feed single notched screw), the fourth, seventh and eighth blocks are kneading screws, and the other blocks are full flight screws. Material input point other than carbon fiber: Hopper 302 Carbon fiber feeding location: Hopper 310, 5th block from front to rear Screw rotation speed: 90 rpm Extruder temperature: set to 300°C Die temperature: 300℃ Resin discharge amount: 25kg / h Carbon fiber bobbins: 2 pieces

[0053] The materials were mixed in the following proportions: PBT1: 35.0% by mass PET2: 15.0% by mass Carbon fiber 1: 30.0% by mass Talc masterbatch 1: 20.0% by mass When mixed at the above blending ratio and completely adhered, the density of the resin composition (calculated from the product of the density of each component material and the blending ratio) is 1.608 (g / cm 3 ) This mixed material was extruded as a strand 309, water-cooled in a cooling section 305, and cut into a diameter of 2.5 mm and a length of 3.5 mm by a strand cutter 306, to obtain a pellet-shaped resin composition 320.

[0054] <Production of shaft-shaped resin composition> The resulting pellet-shaped resin composition 320 was dried at a temperature of 120° C. for 6 hours. After drying, resin composition 320 was charged into hopper 511 of injection molding apparatus 501 shown in Figure 12, and injection molding was carried out with a set temperature of 280°C to produce stepped shaft 401 of the shape shown in Figure 11. The obtained shaft 401 had a shaft diameter 402 of 15 mm, an end diameter 403 of 6 mm, end lengths 404 and 406 of 20 mm, and a shaft length 405 of 240 mm. The temperature of the injection molding dies 502 and 504 was set to 150°C to promote crystallization. The actual density (Y) of the shaft 401 was 1.496 g / cm 3 The density when the material was 100% adhered (calculated density X obtained by multiplying the density of each component material by the blending ratio) was 1.608 (g / cm 3 The adhesion rate ((Y / X) x 100[%]) was 93%, which was a high level of adhesion.

[0055] <Evaluation results> The evaluation results of shaft 401 are shown in Table 2. That is, the flexural modulus when pressed in 0.1 mm was 15 GPa, and the flexural modulus by the tangent method was 23 GPa. Next, the surface of this shaft 401 was coated with elastomer and mounted as the drive roller 21 of the intermediate transfer belt of the electrophotographic image forming apparatus shown in FIG. 1. Using this electrophotographic image forming apparatus, a 6-point letter "E" was printed on recording paper using yellow, cyan, magenta, and black toners. If the intermediate transfer belt was driven accurately, the letter "E" formed using the toners of each color would be perfectly overlapping and would be recognized as a black letter. On the other hand, if the intermediate transfer belt was not driven accurately due to distortion of the shaft of the drive roller 21, the letter "E" formed using the toners of each color may not be perfectly overlapping and may be misaligned. Therefore, in this evaluation, the letter "E" formed using the toners of each color was observed using a magnifying glass to determine whether or not there was any misalignment, and was evaluated according to the following criteria. Ta. Rank A: The maximum deviation of the "E" character is 100 μm or less; Rank B: The maximum deviation of the "E" character is greater than 100 μm.

[0056] <Production and evaluation of resin compositions> Example 2 The compounding ratio of the resin composition according to Example 2 is shown in Table 2. A shaft was produced under the same conditions as in Example 1, except that the screw rotation speed was set to 150 rpm and the carbon fiber content was set to 50 mass %.

[0057] Example 3 The compounding ratio of the resin composition according to Example 3 is shown in Table 2. A shaft was produced under the same conditions as in Example 1, except that the number of carbon fiber bobbins was reduced to one, the screw rotation speed was set to 60 rpm, and the carbon fiber content was set to 10 mass %.

[0058] Example 4 The compounding ratio of the resin composition according to Example 4 is shown in Table 2. The shaft was manufactured under the same conditions as in Example 1. The shafts manufactured in Examples 2 to 4 were evaluated in the same manner as in Example 1.

[0059] <Evaluation results> As shown in Table 2, there was no image distortion and the image misalignment was 100 μm or less in all of Examples 2 to 4, resulting in an image evaluation of "Good." In Example 4, the elastic modulus was further improved, so the image misalignment was 50 μm or less, which was a further improvement.

[0060] (Comparative Example) Table 2 shows the blending ratios of the resin compositions according to Comparative Examples 1 to 3. In Comparative Examples 1 to 3, carbon black was mixed to promote the crystallization of the resin, and the compounding formulation was such that the crystallization rate and degree of crystallization were improved.

[0061] (Comparative Example 1) The shaft was produced under the same conditions as in Example 1, except that the screw rotation speed was 90 rpm and the carbon fiber content was 30 mass %.

[0062] (Comparative Example 2) The screw rotation speed was set to 90 rpm, and carbon fiber 2 (chopped fiber) was used. Since chopped fiber cannot be roved, an amount of carbon fiber with a carbon fiber content of 50 mass % was added from hopper 302 of the device shown in Figure 8. Aside from these, a shaft was produced under the same conditions as in Example 1.

[0063] (Comparative Example 3) As in Comparative Example 1, carbon fiber 2 was added from hopper 302 of the device shown in Fig. 8 in an amount such that the carbon fiber content was 10 mass %. A shaft body was produced under the same conditions as in Example 1, except that the screw rotation speed was set to 60 rpm.

[0064] <Evaluation results> Table 2 shows the evaluation results. Carbon black was blended into the resin composition of Comparative Example 1 to promote crystallization and improve the modulus of elasticity. As a result, the flexural modulus measured by the tangent method was high at 21 GPa, but the flexural modulus when indented 0.1 mm was low at 1.4 GPa. The shaft body according to Comparative Example 1 was used as the drive roller 21 of the electrophotographic image forming apparatus shown in Fig. 1 and rotated to output an image. However, the shaft body was bent by the tension of the tension roller, causing wrinkles in the intermediate transfer belt during rotation, making it impossible to output an image, and the evaluation was poor.

[0065] In Comparative Examples 2 and 3, the bending modulus measured by the tangent method was sufficiently high, but the bending modulus when pressed 0.1 mm was 2 GPa or less in both cases. In Comparative Examples 2 and 3, as in Comparative Example 1, wrinkles occurred in the intermediate transfer belt during image output, making it impossible to output an image, and the evaluation was poor. Thus, even if the resin is sufficiently crystallized, it will not function as a shaft unless it contains surface-treated talc to complement the amorphous portion.

[0066] [Table 2] [Explanation of symbols]

[0067] 1 Photosensitive drum 2 Charging roller 3 Exposure light 15 Fixing unit 20 Intermediate transfer belt 21 Drive roller 22 Tension roller 62 Primary transfer roller 63 Secondary transfer roller 201 Carbon Fiber 202 Amorphous resin 203 Crystalline resin 204 Talc 206 Resin 301 Twin-screw Extruder 303 Twin Screw 304 Dice 401 shaft 402 Shaft diameter 403 Shaft end diameter 501 Injection molding machine 502 Molds 503 Molds

Claims

1. A resin composition containing a crystalline thermoplastic resin (A), carbon fibers (B), and talc (C), The crystalline thermoplastic resin (A) is a polyester resin, and the polyester resin contains a polyethylene terephthalate (PET) resin. the talc (C) is treated with a decomposition inhibitor that inhibits decomposition of the resin; the polyethylene terephthalate (PET) resin in a crystalline state is supported on the surface of the talc (C) treated with the decomposition inhibitor, the talc (C) carrying the crystalline polyethylene terephthalate (PET) resin on its surface clings to the carbon fiber (B); the average length of the carbon fibers (B) in the resin composition is 250 to 800 μm, the amount of the carbon fiber (B) contained in the resin composition is 10% by mass or more and 50% by mass or less, the amount of the talc (C) contained in the resin composition is 7.5% by mass or more and 15.0% by mass or less, The resin composition is characterized in that it gives a molded article having a length of 80.0 mm, a width of 10.0 mm, and a thickness of 4.0 mm, which has a flexural modulus of 10 GPa or more when pressed down 0.1 mm, and in which, when X is the calculated density obtained from the product of the density and the blending ratio of each of the constituent materials of the molded article, and Y is the actual density of the molded article, (Y / X) x 100 [%] is 90% or more.

2. The resin composition further contains a thermoplastic resin (D), 2. The resin composition according to claim 1, wherein the thermoplastic resin (D) is a thermoplastic resin having bisphenol A and an epoxy group.

3. 3. The resin composition according to claim 2, wherein the thermoplastic resin (D) is a phenoxy resin having a structure represented by the following formula (1): 【Chemical 1】 In formula (1), n ​​represents an integer of 1 or more.

4. A resin molded article comprising a molded article of the resin composition according to any one of claims 1 to 3.

5. 5. The resin molded article according to claim 4, wherein the resin molded article is a shaft of a roller used in an electrophotographic image forming apparatus.

6. An electrophotographic image forming apparatus comprising a roller having a shaft body, wherein the shaft body is a molded article made of the resin composition according to any one of claims 1 to 3.

7. A method for producing the resin composition according to any one of claims 1 to 3, comprising the following steps (I) to (III): Step (I) of preparing a masterbatch containing talc treated with a decomposition inhibitor and a polyethylene terephthalate (PET) resin; A step (II) of melt-kneading the masterbatch and the crystalline thermoplastic resin (A) to obtain a melt-kneaded product; and A step (III) of adding carbon fibers to the molten mixture and kneading the mixture to obtain a resin composition.

8. The method for producing a resin composition according to claim 7, wherein the carbon fibers added in the step (III) are long carbon fibers, and are kneaded using a screw having a reverse feed single-thread notched screw portion.

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