Semiconductive polyamide-based resin composition, semiconductive belt using the same, image forming apparatus, and method for manufacturing conductive belt

Abstract

To provide a semi-conductive resin composition for obtaining a semi-conductive belt in which a polyamide-based resin composition exhibits semi-conductivity, uniformity of volume resistivity is good (small in-plane variation), variation in the volume resistivity is small even when a high voltage is continuously applied, and surface glossiness is high.SOLUTION: A semi-conductive polyamide-based resin composition contains a polyamide-based resin and a conductive agent, wherein the conductive agent contains both a fine carbon fiber and carbon black, and 0.3-2.5 pts.wt. of the fine carbon fiber and 7-25 pts.wt. of the carbon black are blended with respect to 100 pts.wt. of the polyamide-based resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a semiconductive polyamide resin composition, a semiconductive belt using the same, an image-forming apparatus, and a method for producing the semiconductive belt. [Background technology]

[0002] Conventionally, electrophotographic printers, copiers, facsimiles, and other image forming devices use materials with a volume resistivity of 10 6 ~10 12 Seamless semiconductive belts with a semiconductivity of Ω·cm are currently in use. However, molded articles obtained from semiconductive resin compositions in which an electronically conductive material (e.g., carbon black) is blended with a thermoplastic resin have problems such as large variations in electrical resistance due to slight changes in the concentration of carbon black or the state of dispersion of the carbon black, and changes in conductivity over time, making it difficult to consistently achieve electrical resistance in the semiconductive range.

[0003] To address this issue, Patent Document 1 describes a method for producing a seamless belt for electrophotography made of semiconductive polyamide resin, which has uniform electrical resistance and little change in electrical resistance when electricity is continuously passed through it, by melt-extruding a semiconductive polyamide resin composition containing a polyamide resin and fine carbon fibers through a die, and then cooling and solidifying the extruded material by a cooling means.

[0004] On the other hand, electrophotographic seamless belts are required to have a high surface glossiness in order to detect toner with a density sensor, and Patent Document 2 discloses an intermediate transfer member having a surface glossiness of 40 or more, which is made of a polyvinylidene fluoride resin blended with an additive containing a polyalkylene oxide structure having a number average molecular weight of 1000 or more and a conductive agent.

[0005] Further, Patent Document 3 discloses that a polyimide tubular material containing 0.1 to 40 parts by weight of carbon nanotubes with respect to 100 parts by weight of a polyimide resin has little variation in resistance value due to between samples, changes in addition amount, voltage changes, and environmental changes. Example 3 discloses a polyimide tubular material obtained by blending carbon nanotubes and carbon black into a DMF solution in which 100 parts by weight of polyamic acid is dissolved and casting the mixture onto a cylindrical SUS. (10 parts by weight of carbon nanotubes and 4 parts by weight of carbon black with respect to 100 parts by weight of polyimide solid content), but there is no description regarding glossiness.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0007] The inventors of the present invention focused on the surface glossiness of a semiconductive belt in which a conductive agent is blended with a polyamide-based resin. An object of the present invention is to provide a semiconductive resin composition for obtaining a semiconductive belt that exhibits semiconductivity, has good uniformity in volume resistivity (small in-plane variation), has high surface glossiness, and has little change in volume resistivity even when continuously printed.

Means for Solving the Problems

[0008] According to the present invention, (1) A semiconductive polyamide resin composition containing a polyamide resin and a conductive agent, wherein the conductive agent contains both fine carbon fibers and carbon black, and 0.3 to 2.5 parts by weight of the fine carbon fibers and 7 to 25 parts by weight of the carbon black are blended based on 100 parts by weight of the polyamide resin; (2) The semiconductive polyamide resin composition according to (1), wherein the polyamide resin is one or more selected from nylon 6, nylon 12, and nylon 6,12; (3) The semiconductive polyamide resin composition according to (1) or (2), wherein the fine carbon fibers contain at least one selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, and aggregates of bell-shaped structural units; (4) A semiconductive belt formed from the semiconductive polyamide resin composition according to any one of (1) to (3); (5) An image forming apparatus having the semiconductive belt according to (4); (6) A method for manufacturing a semiconductive belt, comprising supplying a semiconductive polyamide resin composition prepared by blending 100 parts by weight of a polyamide resin, 0.3 to 2.5 parts by weight of fine carbon fibers, and 7 to 25 parts by weight of carbon black to an extruder, extruding the semiconductive polyamide resin composition from an annular die, and cooling and solidifying it; (7) The method for manufacturing a semiconductive belt according to claim 6, wherein the surface glossiness at an incident angle of 60° is 50 or more; is provided.

Advantages of the Invention

[0009] The semiconductive polyamide-based resin composition of the present invention contains a polyamide-based resin and a conductive agent. The conductive agent contains both fine carbon fibers (hereinafter sometimes abbreviated as CNT) and carbon black, and with respect to 100 parts by weight of the polyamide-based resin, 0.3 to 2.5 parts by weight of the fine carbon fibers and 7 to 25 parts by weight of the carbon black are blended. The semiconductive belt formed from the semiconductive polyamide-based resin composition exhibits semiconductivity, has good uniformity of volume resistivity (small in-plane variation), has a small change in volume resistivity even when printed continuously, and further, a semiconductive belt with a high surface gloss can be obtained.

Brief Description of the Drawings

[0010]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0011] Hereinafter, the present invention will be described in detail. The term "semiconductive" as used herein means that the volume resistivity is in the range of 1×10 6 ~1×10 12 Ω·cm at a temperature of 23°C, a relative humidity of 50%RH, and an applied voltage of 250V.

[0012] [Polyamide-based Resin] Polyamide resins are thermoplastic resins obtained by polycondensation of diamines and dicarboxylic acids, polycondensation of α,ω-aminocarboxylic acids, ring-opening polymerization of lactams, etc., and have a sufficient molecular weight. Examples of polyamide resins include nylon 6, nylon 4, nylon 6,6, nylon 11, nylon 12, nylon 6,10, nylon 6,12, nylon 6 / 6,6, nylon 6 / 6,6 / 12, nylon 6,MXD (MXD represents an m-xylylenediamine component), nylon 6,6T (T represents a terephthalic acid component), nylon 6,6I (I represents an isophthalic acid component), and the like. Among these, polyamide resins with low water absorption are preferred. Polyamide resins with low water absorption are excellent in the dispersibility of carbon black and the stability of electrical resistance in a high-humidity environment. The water absorption of the polyamide resin is preferably 1.5% or less, and more preferably 1.0% or less. Examples of polyamide resins with a water absorption of 1.5% or less include nylon 11, nylon 12, nylon 6,10, nylon 6,12, etc., and examples of polyamide resins with a water absorption of 1.0% or less include nylon 11 and nylon 12. These polyamide resins may be used alone or in combination of two or more.

[0013] [Conductive agent] The conductive agent of the present invention is characterized by using both fine carbon fibers and carbon black in combination. As a result of various studies to develop a semiconductive belt with high surface glossiness, the inventors found that a semiconductive belt formed from a semiconductive polyamide resin composition containing only fine carbon fibers as a conductive agent had a large surface roughness and a small surface glossiness. This phenomenon was presumably due to the fact that although the average fiber diameter of the fine carbon fibers is small, the average fiber length is long, which increased the surface roughness and decreased the surface glossiness of the semiconductive belt. On the other hand, since the primary particle diameter of carbon black is small, it is considered that its influence on the surface roughness is small. It was also clarified that a semiconductive belt formed from a semiconductive polyamide resin composition containing only carbon black as a conductive agent requires a large amount of carbon black to be blended, and when a voltage is continuously applied, the increase in volume resistivity is large.

[0014] The fine carbon fiber used in the present invention has a hollow space in the core part of the fiber, and is preferably a fibrous material with a small fiber diameter and a large aspect ratio, and also includes those commonly referred to as carbon nanotubes. Specifically, it is preferably within the range of an average fiber diameter of 1 nm to 200 nm, an average fiber length of 0.1 μm to 100 μm, and an aspect ratio of 10 to 10,000.

[0015] Examples of the fine carbon fiber include single-walled carbon nanotubes, multi-walled carbon nanotubes (Japanese Patent Laid-Open Nos. 1-270543, 3-64606, 3-77288, 2004-299986), cup-stacked carbon nanotubes (Japanese Patent Laid-Open Nos. 2003-73928, 2004-360099), platelet-type carbon nanofibers (Japanese Patent Laid-Open No. 2004-300631), bell-shaped structure unit aggregates (Japanese Patent Laid-Open Nos. 2012-46864, 2011-47081, 2011-46852), etc. Among these, single-walled carbon nanotubes, multi-walled carbon nanotubes, and bell-shaped structure unit aggregates are preferred. In particular, the bell-shaped structure unit aggregate is preferred because the connecting part of the aggregate of bell-shaped structure units connected by a weak van der Waals force is easily cut by the shearing force caused by kneading or extrusion, and it is difficult to form an aggregate in which the fine carbon fibers are entangled with each other, and it has excellent dispersibility.

[0016] Examples of the carbon black used in the present invention include conductive carbon blacks such as furnace black, channel black, ketjen black, and acetylene black. In particular, carbon black with an average particle diameter of 50 nm or less is preferred because it can reduce the electrical resistance with a small amount of blending. Also, from the viewpoint of developing the structure of the carbon black and forming a conductive path, the DBP (Dibutyl phthalate) oil absorption amount of 100 to 500 ml / 100 g is preferred, 100 to 300 ml / 100 g is preferred, and 150 to 250 ml / 100 g is more preferred. Also, from the viewpoint of conductivity, 30 to 1500 m 2Carbon black having a BET specific surface area in the range of / g is preferred. In the present invention, grafted carbon black obtained by grafting a polymer having one or more functional groups selected from a carboxyl group, a hydroxyl group, an epoxy group, an amino group, and an oxazoline group, or carbon black surface-treated with a low molecular weight compound can also be used.

[0017] Next, regarding the composition ratio of the semiconductive polyamide resin composition of the present invention, it is necessary to blend 0.3 to 2.5 parts by weight of fine carbon fiber and 7 to 25 parts by weight of carbon black with respect to 100 parts by weight of the polyamide resin. It is more preferable to blend 0.4 to 2.0 parts by weight of fine carbon fiber, and even more preferably 0.4 to 1.5 parts by weight, with respect to 100 parts by weight of the polyamide resin. By setting the fine carbon fiber within the above range, the value of the surface roughness when molded into a semiconductive belt can be reduced, and as a result, the surface glossiness can be increased. Further, it is preferable that the polyamide resin composition contains carbon black in a proportion of 7 to 25 parts by weight, more preferably 8 to 23 parts by weight, and even more preferably 10 to 20 parts by weight, with respect to 100 parts by weight of the polyamide resin composition. By setting the carbon black within the above range, it becomes possible to adjust to a desired semiconductive region. If the blending amount of carbon black is less than 7 parts by weight, a composition showing a predetermined semiconductivity may not be obtained even in combination with the blending amount of the fine carbon fiber. If it exceeds 25 parts by weight, the melt viscosity becomes high and melt extrusion becomes difficult. As described above, the blending amount of the fine carbon fiber is reduced so as to obtain a predetermined surface glossiness. However, if the blending amount of the fine carbon fiber is decreased, the electrical resistance increases. Therefore, the blending amount of carbon black can be appropriately determined so as to show a predetermined semiconductive electrical resistance.

[0018] Additives may be blended in the polyamide resin composition of the present invention as long as the properties thereof are not impaired as necessary. Examples of the additives include antioxidants, heat stabilizers, organic fillers and inorganic fillers, antiblocking agents, plasticizers, lubricants, and processing aids. These resins and additives can be used in appropriate amounts according to the purpose.

[0019] [Method for Producing Polyamide-Based Resin Composition] The method for producing the polyamide-based resin composition of the present invention is not particularly limited. For example, a method of dry blending by mixing a polyamide-based resin, a conductive agent, and additives used as necessary, and then melt-kneading; a method of previously melt-kneading a conductive agent into a polyamide-based resin to prepare a masterbatch, and then melt-kneading by blending a polyamide-based resin and additives as necessary can be mentioned.

[0020] Examples of the apparatus for melt-kneading include various known kneaders such as batch kneaders, kneaders, conical kneaders, Banbury mixers, roll mills, single-screw or twin-screw extruders, etc. Among these, single-screw extruders and twin-screw extruders are preferably used because of their excellent kneading ability and productivity.

[0021] The temperature during melt-kneading can be appropriately selected according to the type of polyamide-based resin used, the melt viscosity, etc. Usually, it is in the range of 150 to 300 °C, and preferably 170 to 280 °C from the viewpoint of preventing resin deterioration.

[0022] [Semiconductive Belt] The semiconductive belt of the present invention is a seamless belt having at least one layer made of a semiconductive polyamide-based resin composition. In the case of multiple layers, an elastic layer or a surface coat layer may be provided on the base material layer made of the semiconductive polyamide-based resin composition of the present invention according to the purpose.

[0023] The semiconductive belt of the present invention can be manufactured by an extrusion molding method, a centrifugal molding method, a dipping method, or the like. The extrusion molding method, particularly the extrusion molding method using an annular die, is preferable because a seamless belt can be obtained. As the extrusion molding method using an annular die, for example, an extruder, an annular die is disposed below the extruder in communication with the extruder, and below the annular die, a mandrel for supporting the molten resin extruded downward from the annular die on its outer periphery and cooling and solidifying it is provided. An extrusion molding apparatus can be used. A semiconductive resin composition is supplied to the extruder, co-extruded in a tube shape from the annular die, and cooled and solidified along the outer periphery of the mandrel to obtain a tube-shaped molded body, and the belt can be obtained by cutting the tube-shaped molded body to a desired width. Further, the obtained belt can be inserted into a mold and annealed in an oven set at a temperature below the melting point of the polyamide-based resin to obtain a semiconductive belt with further improved circumferential accuracy. Note that these explanations are for the single-layer case, but in the case of multiple layers, an extruder and a die corresponding to the number of layers may be prepared. Also, as another example of the extrusion molding method using an annular die, an extruder, an annular die is disposed above the extruder in communication with the extruder, and above the annular die, a mandrel for supporting the molten resin extruded upward from the annular die on its outer periphery and cooling and solidifying it is provided. An extrusion molding apparatus can be used.

[0024] The semiconductive polyamide-based resin composition of the present invention can be suitably used as semiconductive belts such as an intermediate transfer belt, a transfer conveyance belt, a paper conveyance belt, and automotive-related parts, electronic and electrical parts, mechanical parts, semiconductor packaging films, and the like.

[0025] The surface glossiness of the semiconductive belt of the present invention at an incident angle of 60° is preferably 50 or more, more preferably 60 or more, and even more preferably 70 or more. By blending 2.5 parts by weight or less of fine carbon fibers with respect to 100 parts by weight of the polyamide-based resin, the above performance can be achieved. Further, the surface roughness Rz of the conductive belt of the present invention is preferably 1.00 μm or less, more preferably 0.80 μm or less, and even more preferably 0.60 μm or less. By blending 2.5 parts by weight or less of fine carbon fiber with respect to 100 parts by weight of the polyamide resin, the performance of the surface roughness Rz described above can be satisfied. Furthermore, the variation digit of the volume resistivity in the continuous energization test described later of the conductive belt of the present invention is preferably less than 1.00 digit, more preferably less than 0.50 digit, and most preferably less than 0.35 digit. By blending 0.3 parts by weight or more of fine carbon fiber with respect to 100 parts by weight of the polyamide resin, the variation digit of the volume resistivity in the continuous energization test described later can be satisfied.

Examples

[0026] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. The measurement methods of physical properties in the examples are as follows. (1) Melt viscosity The melt viscosity was measured using a Koka type flow tester manufactured by Shimadzu Corporation equipped with a die having a hole with a length of 10 mm and a diameter of 1 mm. (2) Surface resistivity and volume resistivity The surface resistivity and volume resistivity were measured at random 10 points at an applied voltage of 250 V for a sample cut out to 460 mm × 400 mm using a high resistance meter UX (MCP-HT800, manufactured by Diain Instruments Co., Ltd.) equipped with a URS probe (load 2 kg). Also, the uniformity (variation) of the volume resistivity was determined by the following formula. Uniformity [digit] of volume resistivity = log10 (maximum value of volume resistivity / minimum value of volume resistivity) (3) Surface roughness Using Surfcom 580A (manufactured by Tokyo Seimitsu Co., Ltd.), in accordance with JIS B0601-1982, the surface roughness Rz was measured at a stylus tip radius of 2 μm, a cut-off value of 0.8 mm, a measurement length of 2.5 mm, and a speed of 0.3 mm / sec. (4) Surface glossiness The surface glossiness was measured at an incident angle of 60° using a handy gloss meter Gross Checker IG-320 (manufactured by Horiba, Ltd.). (5) Continuous power-on test Using the voltage application device shown in Fig. 3, a semiconductive belt (2) was attached with an adhesive tape onto a sample roll (3) with a copper plate attached to its surface. The variation digit number of the volume resistivity of the semiconductive belt was determined by removing the semiconductive belt after rotating the sample roll 4,000 times at 5 revolutions per minute while applying a voltage of 1,000 V between the conductive rubber roll (1) and the sample roll, measuring the volume resistivity after leaving it in 23°C for 24 hours, and using the following formula to calculate the variation digit number of the volume resistivity. Variation digit number of volume resistivity [digit] = log10 (volume resistivity after continuous power-on test / volume resistivity before continuous power-on test)

[0027] The following were used as raw materials. <Polyamide-based resin (A)> · Polyamide 12 (A-1) [melting point: 178°C, melt viscosity: 5,950 poise (measurement temperature 200°C, load 100 kg)] <Conductive agent (B)> · Carbon nanotube (B-1) [average diameter: 10 - 15 nm, length: 10 μm or less, specific surface area: 180 - 250 m 2 / g] · Carbon black (B-2) [DBP oil absorption: 190 ml / 100 g, BET surface area: 70 m 2 / g]

[0028] The polyamide-based resin and the conductive agent were melt-kneaded using a twin-screw kneading extruder with a screw diameter of 38 mm to obtain a compound so as to achieve the blending ratio shown in Table 1. Next, the obtained compound was supplied to a single-screw extruder equipped with an annular die (extrusion diameter: 50 mm), formed into a tube shape in a molten state, cut to a length of 350 mm, and a semiconductive belt with a circumference of 800 mm, a width of 350 mm, and a thickness of 140 μm was obtained. The evaluation results of the semiconductive belts prepared in the examples and comparative examples are shown in Table 1, Fig. 1, and Fig. 2.

[0029]

Table 1

[0030] As shown in Table 1, FIG. 1 and FIG. 2, in Examples 1 to 4 which are semiconductive belts in which 0.3 to 2.5 parts by weight of fine carbon fibers are blended with 100 parts by weight of a polyamide resin, the uniformity of the volume resistivity is excellent, the surface glossiness shows a high value of 50 or more, and further, the variation digit of the volume resistivity in the continuous energization test is 0.5 digit or less, showing excellent characteristics as a semiconductive belt.

[0031] On the other hand, Comparative Examples 1 and 2 in which the blending amount of fine carbon fibers is less than 0.3 parts by weight with respect to 100 parts by weight of the polyamide resin show good uniformity of volume resistivity and high surface glossiness, but the variation of the volume resistivity in the continuous energization test is large, and they are unsuitable as semiconductive belts. On the other hand, Comparative Examples 3 and 4 in which the blending amount of fine carbon fibers exceeds 2.5 parts by weight with respect to 100 parts by weight of the polyamide resin show good uniformity of volume resistivity and small variation of the volume resistivity in the continuous energization test, but the surface glossiness shows a low value of 50 or less.

Description of Reference Numerals

[0032] 1 Conductive rubber roll 2 Semiconductive belt 3 Roll for sample 4 Power supply

Claims

1. A semiconductive belt made of a semiconductive polyamide-based resin composition containing a polyamide-based resin and a conductive agent, wherein the conductive agent contains both fine carbon fibers and carbon black, and 0.3 to 2.5 parts by weight of the fine carbon fibers and 7 to 25 parts by weight of the carbon black are blended based on 100 parts by weight of the polyamide-based resin, the polyamide-based resin is composed of one or more selected from nylon 6, nylon 12, and nylon 6,12, and the semiconductive belt has a surface glossiness of 50 or more at an incident angle of 60°, and is a semiconductive belt for a toner detection method using a density sensor.

2. The semiconductive belt for a toner detection method using a density sensor according to claim 1, wherein the fine carbon fibers contain at least one selected from single-walled carbon nanotubes, multi-walled carbon nanotubes, and aggregates of bell-shaped structural units.

3. An image forming apparatus comprising the semiconductive belt for a toner detection method using a density sensor according to claim 1 or 2.

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