JP2006058538A - Manufacturing method of conductive rubber roller, conductive rubber roller and transfer roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a conductive rubber roller constituted of a tube of a rubber composition which has uniform cell distribution in a peripheral direction, has no unevenness of hardness and resistance and especially consists of a single layer and to provide the conductive rubber roller obtained by the manufacturing method and a transfer roller using the same. <P>SOLUTION: In the manufacturing method of the conductive rubber roller which is constituted by molding a rubber layer on a conductive core material, the rubber layer comprises acrylonitrile rubber and epichlorohydrin rubber and is subjected to vulcanization foaming by a process in which temperature of the rubber layer becomes 200 to 250°C when the rubber layer is irradiated with a microwave in a microwave vulcanization furnace having heating air atmosphere of temperature lower than vulcanization foaming temperature of rubber materials of the rubber layer. The conductive rubber roller and the transfer roller can be obtained by this manufacturing method. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a conductive rubber roller used in an image forming apparatus such as an electrophotographic copying apparatus, a printer, and an electrostatic recording apparatus, and a method for manufacturing the conductive rubber roller. The present invention relates to a transfer roller of a transfer device that transfers a transfer image formed by a toner image formed and supported by an image forming unit such as an electric recording process onto a recording medium such as paper or a transfer material.

  In many electrophotographic image forming apparatuses such as copying machines and printers, conductive rubber rollers such as a charging roller, a transfer roller and a developing roller are used. In order to impart conductivity to these rubber rollers, a method of adding a conductive filler such as carbon black, or a method of blending an ion conductive rubber material such as acrylonitrile butadiene rubber or epichlorohydrin rubber can be mentioned. Each of these rollers is in contact with the drum in a state where a load is applied, and these rubber rollers are energized for a long period of time depending on the application. Therefore, a rubber material having a small resistance variation is desirable, and rubber materials such as acrylonitrile butadiene rubber and epichlorohydrin rubber are widely used in transfer rollers and charging rollers due to problems in the manufacturing method and the like (Patent Document 1 and Patent Document 1). 2).

  The rubber material used for these rollers is a raw material composition obtained by kneading a vulcanizing agent, a foaming agent, a filler, etc., and this uncured cylindrical rubber molded body is formed with a mold, an extruder, etc. A vulcanized molded body is vulcanized and foamed by heating to prepare a cylindrical foam. Thereafter, a method is used in which a core metal is press-fitted into a cylindrical foam and the outer diameter is cylindrically polished to form a roller shape.

  As a method for producing the cylindrical foam, for example, vulcanization can vulcanization using high-pressure steam, mold vulcanization using a cylindrical mold, or UHF vulcanization using microwave irradiation is known (for example, Patent Documents 3 to 6). ). However, in the vulcanization can vulcanization, the foam cells are uneven and a large amount of polishing must be performed to bring the desired cells to the surface. Since it is necessary to perform mold cleaning, it was unsuitable for making large quantities. On the other hand, in UHF vulcanization, the setup is good and the cells can be uniform. However, when the rubber tube is softened in the furnace, the contact surface with the conveyor and the roller increases, and the cell foaming unevenness may increase. Further, when the temperature of the UHF furnace is high, the rubber is further softened, the inner diameter of the tube cannot be maintained, and it may be difficult to manufacture the tube. Furthermore, due to the non-uniformity of the tube, it has caused circumferential hardness and uneven resistance (Patent Document 5). It has been reported that the inner diameter of the tube is maintained by selectively vulcanizing the rubber composition of the inner layer using a tube having a multilayer structure against the non-uniformity of the inner and outer diameters (Patent Document 6).

However, the method for producing a tube of a rubber composition comprising a single layer has not been improved yet.
JP-A-10-171210 JP 2002-70835 A JP 11-114978 A JP-A-11-201140 Japanese Patent Laid-Open No. 2002-221859 JP 2003-246485 A

  An object of the present invention is to solve the above-mentioned problem, and in regard to a method for producing a conductive rubber roller used in an image forming apparatus, the circumferential cell distribution is uniform, and hardness and resistance are not uneven. It is providing the manufacturing method of the conductive rubber roller of the tube of the rubber composition which consists of a single layer.

  Another object of the present invention is to provide a conductive rubber roller as a result of the above-described method for producing a conductive rubber roller, and a transfer roller as its application form.

  According to the present invention, there is provided a method for producing a conductive rubber roller in which a rubber layer is molded on a conductive core material, the rubber layer comprising acrylonitrile rubber and epichlorohydrin rubber, and a rubber material for the rubber layer Vulcanizing and foaming by a step in which the temperature of the rubber layer becomes 200 ° C. to 250 ° C. when irradiated with microwaves in a microwave vulcanizing furnace having a heated air atmosphere lower than the vulcanization foaming temperature of A method of manufacturing a conductive rubber roller is provided.

  According to the present invention, a conductive rubber roller in which a rubber layer is formed on a conductive core material used in an image forming apparatus is manufactured by the method for manufacturing a conductive rubber roller. A conductive rubber roller is provided.

  Furthermore, according to the present invention, there is provided a transfer roller, wherein the transfer roller mounted on the transfer device of the image forming apparatus is the conductive rubber roller.

  By the above manufacturing method, it is possible to provide a conductive rubber roller having no cell unevenness in the circumferential direction and having no hardness and resistance unevenness, particularly in a tube of a rubber composition comprising a single layer.

  Therefore, the conductive rubber roller produced by the above production method can be suitably used as a roller for an image forming apparatus, particularly as a transfer roller.

  The present invention relates to a method for producing a conductive rubber roller in which a rubber layer is formed on a conductive core material, wherein the rubber layer contains acrylonitrile rubber and epichlorohydrin rubber, and the rubber material of the rubber layer is added. The rubber layer is vulcanized and foamed by a process in which the temperature of the rubber layer becomes 200 ° C. to 250 ° C. when irradiated with microwaves in a microwave vulcanizing furnace having a heated air atmosphere lower than the vulcanized foaming temperature. It is preferable that the rubber layer contains a thiuram accelerator and a thiazole accelerator, and the molecular weight of the thiuram accelerator is 200 or more and 650 or less. Moreover, it is the electroconductive rubber roller manufactured as mentioned above, and is a transfer roller as a use.

  The best mode for carrying out the present invention in more detail will be described below.

(Image forming device)
FIG. 2 shows an example in which the conductive rubber roller according to the present invention is used in an image forming apparatus. The image forming apparatus shown in the figure is a laser printer using an electrophotographic process cartridge, and the figure is a longitudinal sectional view showing a schematic configuration thereof. Further, the image forming apparatus shown in the figure is equipped with a transfer device having a transfer roller.

  The image forming apparatus shown in FIG. 1 includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 1 as an image carrier. In the photosensitive drum 1, a photosensitive layer made of an organic photoconductor (OPC) is provided on the outer peripheral surface of a grounded cylindrical aluminum substrate. The photosensitive drum 1 is driven to rotate at a predetermined process speed (circumferential speed), for example, 50 mm / sec, in the direction of arrow R1 by a driving means (not shown).

  The surface of the photosensitive drum 1 is uniformly charged by a charging roller 2 as a contact charging member. The charging roller 2 is disposed in contact with the surface of the photosensitive drum 1 and is driven to rotate in the direction of arrow R2 as the photosensitive drum 1 rotates in the direction of arrow R1. An oscillating voltage (AC voltage VAC + DC voltage VDC) is applied to the charging roller 2 by a charging bias application power source (high voltage power source), whereby the surface of the photosensitive drum 1 is uniformly charged to −600 V (dark portion potential Vd). Is done. The surface of the photosensitive drum 1 after charging is subjected to scanning exposure by laser light 3 output from a laser scanner and reflected by a mirror, that is, laser light modulated in accordance with a time-series electric digital image signal of target image information. receive. As a result, an electrostatic latent image corresponding to the target image information (bright part Vl = −150 V) is formed on the surface of the photosensitive drum 1.

  The electrostatic latent image is reversely developed as a toner image with negatively charged toner attached thereto by a developing bias applied to the developing sleeve of the developing device 4.

  On the other hand, a transfer material 7 such as paper fed from a paper feeding unit is guided by a transfer guide and is transferred to a transfer unit (transfer nip unit) T between the photosensitive drum 1 and the transfer roller 6 on the photosensitive drum 1. The toner image is supplied so as to match the timing of the toner image. The toner image on the photosensitive drum 1 is transferred to the surface of the transfer material 7 supplied to the transfer portion T by a transfer bias applied to the transfer roller 6 by a transfer bias application power source. At this time, the toner (residual toner) that is not transferred to the transfer material 7 and remains on the surface of the photosensitive drum 1 is removed by the cleaning device 9.

  The transfer material 7 that has passed through the transfer portion T is separated from the photosensitive drum 1 and introduced into the fixing device 10, where the toner image is subjected to fixing processing, and is discharged out of the image forming apparatus main body as an image formed product (print). The

(Conductive rubber roller)
The manufacturing method of the conductive rubber roller concerning this invention is demonstrated below.

(Rubber material)
The raw rubber used for the conductive rubber roller according to the present invention contains acrylonitrile butadiene rubber, epichlorohydrin rubber, or a mixture thereof as a main rubber component, and a predetermined amount thereof is mixed. In addition, polystyrene polymer materials, polyolefin polymer materials, polyester polymer materials, polyurethane polymer materials, thermoplastic elastomers such as RVC, acrylic resins, styrene vinyl acetate copolymers, butadiene-acrylonitrile copolymers Or a mixture of these rubbers, elastomers, and resins.

(Conductive material / filler)
In addition, a known material can be used as a conductive material such as carbon black, a filler such as calcium carbonate, and a conductive material added to impart conductivity to the rubber. For example, as conductive particles, conductive carbon black, TiO ₂ , SnO ₂ , ZnO, a metal oxide such as a solid solution of SnO ₂ and SbO ₃ , metal powder such as Cu, Ag, etc., and as an ionic conductive agent, LiClO ₄ , NaSCN, etc. are mentioned, It is possible to obtain a desired electrical resistance by adding or dispersing a single or a plurality of the rubbers. It can also be made conductive by introducing molecules having polarity in the rubber main chain or in the side chain.

(Foaming agent)
Examples of the foaming agent include organic foaming agents such as A.I. D. C. A (azodicarbonamide) system, D.I. P. T (dinitrosopentamethylenetetraamine) type, T.I. S. H (P. toluenesulfonyl hydrazide) system, O.D. B. S. H (oxybisbenzenesulfenyl hydrazide) and the like can be used alone or in combination. The decomposition temperature of the foaming agent can be lowered by adding a foaming aid such as urea resin or zinc oxide.

(Foaming aid)
Examples of the foaming aid include urea compounds, metal oxides such as zinc oxide and lead oxide, compounds mainly composed of salicylic acid, stearic acid, and the like, and can be added corresponding to the foaming agent.

(Vulcanizing agent / Vulcanization accelerator)
Examples of the vulcanizing agent used in the present invention include sulfur and metal oxides. Various vulcanization accelerators are known, but thiazole accelerators and thiuram accelerators are used. It is generally known that the combined use of a thiazole accelerator and a thiuram accelerator is effective for C-set properties. Specific examples of thiazole accelerators include 2-mercaptobenzothiazole and dibenzothiazyl disulfide. In the present invention, scorch is low, and dibenzothiazyl disulfide used in combination with a thiuram accelerator is preferable. . As thiuram accelerators, tetramethylthiuram monosulfide, tetraethylthiuram disulfide, tetrakis (2-ethylhexyl) thiuram disulfide, dipentamethylenethiuram tetrasulfide and the like are known. Tetrakis (2-ethylhexyl) thiuram disulfide having excellent scorch properties is applied. In addition, other thiazole accelerators and thiuram accelerators can be applied to the present invention by adjusting the use conditions.

  The molecular weight of the thiuram accelerator (A) in the present invention is preferably 200 or more and 650 or less. If the molecular weight is less than 200, the vulcanization speed is increased and it is difficult to obtain sufficient foaming in UHF vulcanization. On the other hand, if it exceeds 650, the crosslink density becomes low, which causes a problem that white streaks due to the roller C set are generated on the image.

  Next, a conductive rubber roller (FIG. 1) demonstrating the present invention was produced as follows.

(Production method)
FIG. 3 shows a production apparatus by continuous vulcanization using a microwave of a conductive rubber roller. The extrusion vulcanization apparatus used in this experiment has a total length of 13 m, 11 is an extruder, and 12 is a microwave vulcanization apparatus ( (Hereinafter referred to as UHF), 13 is a hot air vulcanizer (hereinafter referred to as HAV), 14 is a take-up machine, and 15 is a regular cutting machine.

  The rubber material is kneaded using a closed kneader such as a Banbury mixer or a kneader, then formed into a ribbon shape using an open roll and a ribbon forming / dispensing machine, and charged into the extruder 11. The UHF 12 conveys a rubber belt extruded from the extruder 11 with a mesh belt coated with PTFE (polytetrafluoroethylene) resin or a roller coated with PTFE resin, and the HAV 13 is a roller coated with PTFE resin. Is being transported. The UHF 12 and the HAV 13 are connected by a roller coated with PTFE resin.

  The lengths of the devices 12, 13, and 14 are as shown in the figure, and in this embodiment, the lengths are 4m, 6m, and 1m, respectively. The distance between the UHF 12 and the HAV 13 and the distance between the HAV 13 and the take-up machine 14 are set to be 0.1 to 1.0 m.

  In the production apparatus by continuous vulcanization using the microwave, the rubber tube formed and extruded into a tube shape from the extruder 11 is conveyed into the UHF 12 immediately after being extruded from the extruder 11, and is fed to the rubber tube. By irradiating with microwaves, the temperature of the rubber tube is heated to 200 ° C. to 250 ° C. and vulcanized and foamed, and then conveyed to the HAV 13 to complete the vulcanization.

  In the UHF furnace, the setting of the heated air atmosphere in the furnace is set to be equal to or lower than the vulcanization foaming temperature of the rubber tube. By using this temperature, an increase in the contact surface with the conveyor and the conveyance roller due to the softening of the rubber tube is minimized, and cell unevenness in the circumferential direction is eliminated.

  That is, if the setting of the heated air atmosphere in the furnace is made higher than the vulcanization foaming temperature of the rubber tube at this time, vulcanization and foaming are accelerated, and it becomes difficult to control vulcanization and foaming. In particular, if the acceleration of the vulcanization rate becomes remarkable, vulcanization starts from the outside of the rubber tube, so that expansion at the time of foaming is suppressed, thereby reducing the diameter and deforming the inner diameter side. Even when the temperature is lower than the vulcanization foaming temperature, in order to manage the production conditions, a temperature condition that is not less than room temperature and less reduces the viscosity of the rubber tube is preferable in order to prevent the influence of seasonal fluctuations. In addition, in the rubber | gum compounding used for the Example of this invention, since the vulcanization foaming temperature is about 160 degreeC, the temperature of a UHF furnace is set to 60 to 100 degreeC.

  Furthermore, uniform foaming is realized by irradiating microwaves and setting the temperature of the rubber tube to 200 ° C. to 250 ° C. By setting the temperature of the rubber tube within the above range, the foaming reaction proceeds faster, the foamed cells are formed as the skeleton of the rubber tube, and the tube shape is maintained even with the softening of the rubber. When the temperature of the rubber tube is less than 200 ° C., both vulcanization and foaming are insufficient, and the conductive rubber roller provided in the present invention cannot be obtained. On the other hand, if the heating exceeds 250 ° C., overvulcanization may occur, and there is also a risk of ignition, causing problems not only in quality but also in production.

  Immediately after being discharged from the take-up machine 14 after vulcanization and foaming, it was cut into a desired size by a regular cutting machine 15 to produce a tubular conductive rubber molded product. Next, a conductive core material having a diameter of 4 to 10 mm coated with a hot melt adhesive or a vulcanized adhesive in a desired region is press-fitted into the inner diameter portion of the tube-shaped conductive rubber molding to obtain a roller-shaped molded body. It was. This molded body is set in a polishing machine (not shown) to which a grinding wheel GC80 is attached, and is polished so that the outer diameter is 17 mm at a rotation speed of 2000 RPM and a feed speed of 500 m / min. Was made.

  Next, the evaluation method of the present invention will be described.

(Measurement method of rubber temperature during microwave irradiation)
Using a fluorescence thermometer (Anritsu Keiki Co., Ltd., fluorescent optical fiber thermometer FL-2000), insert the detection unit of the fluorescence thermometer into the unvulcanized rubber tube extruded from the extruder, and put it in the UHF. It was conveyed with a vulcanized rubber tube, and the temperature at that time was measured.

(Measurement method of hardness unevenness)
Using a hardness tester (Asker C type, 4.9N load), measure any place on the tube made of a conductive rubber roller in 90 ° increments in the circumferential direction. The difference between the maximum and minimum values expressed. The hardness difference is preferably 0 or closer to 0.

(Measurement method for uneven electrical resistance of rollers)
Roller resistance was set at 48 ° C in an N / N (23 ° C / 55% RH) environment, after which a 4.9N load was applied to both sides of the shaft of the conductive rubber roller. The measurement was performed by applying a voltage of 2 kV between the shaft body and the aluminum drum in a state in which the drum was pressure-bonded and rotated. The difference between the maximum and minimum resistance values at this time is expressed in digits. The difference is preferably less than 1.2 digits.

(Confirmation method of cell diameter distribution)
The tube was cut at an arbitrary location, and the cross section was confirmed with a video microscope (Keyence Digital Microscope VH-8000), and the difference between the cell diameter on the outer diameter side and the cell diameter on the inner diameter side was confirmed. At this time, it is preferable that there is no difference between the cell diameter on the outer diameter side and the cell diameter on the inner diameter side.

  Hereinafter, the present invention will be described in detail with reference to examples. However, the present invention is not limited only to this transfer roller, but can be developed to a charging roller and a developing roller.

In addition, the rubber | gum compounding and mass part which were used by each Example and the comparative example are as follows. In this rubber compounding, the vulcanization foaming temperature is about 160 ° C.
・ Acrylonitrile butadiene rubber [trade name: DN401LL, manufactured by Nippon Zeon Co., Ltd.] 84 parts by mass ・ Epichlorohydrin rubber [trade name: Zeklon 3106, manufactured by Nippon Zeon Co., Ltd.] 16 parts by mass ・ Conductive carbon black [trade name: Asahi # 35 made by Asahi Carbon Co., Ltd.] 10 parts by mass, zinc oxide [trade name: Zinc Hana, 2 types, manufactured by Hakusuitec Co., Ltd.] 5 parts by mass, stearic acid [trade name: made by LUNAC S Kao Corporation] 1 part by mass / thiazole accelerator: dibenzothiazyl disulfide [trade name: Noxeller DM-P, manufactured by Ouchi Shinsei Chemical Co., Ltd.] 2 parts by mass / thiuram disulfide accelerator: tetrakis (2-ethylhexyl) thiuram disido [product Name: Noxeller TOT-N (molecular weight 633.18), Ouchi Shinsei Chemical Co., Ltd.] 2.5 parts by mass, sulfur [trade name: Sulfur SPM manufactured by Tsurumi Chemical Co., Ltd.] 2 parts by mass, azodicarbonamide [trade name: Selmark M257, manufactured by Sankyo Kasei Co., Ltd.] 4 parts by mass, urea [trade name: Selmarc M258, Sankyo Chemical Co., Ltd. Product] 2 parts by mass (Example)
A plurality of conditions were set when the temperature of the rubber layer composed of acrylonitrile rubber and epichlorohydrin rubber as the rubber material provided in the present invention was heated to 200 ° C. to 250 ° C., and this was taken as an example. The results are shown in Table 1.

  From this result, it can be seen that the cells are uniform, the hardness unevenness is small, and the resistance unevenness is 1.2 digits or less.

(Comparative example)
A plurality of cases outside the definition of the present invention were set as comparative examples. In an example where the rubber temperature did not reach the range of the present invention, vulcanization and foaming were insufficient, so that an appropriate rubber tube could not be obtained and could not be produced as a roller. Further, even when the rubber temperature is within the range of the present invention, when the temperature of the UHF furnace reaches the vulcanization foaming temperature, circumferential cell unevenness occurs, and therefore, hardness unevenness and resistance unevenness deteriorate. Further, when the rubber temperature is higher than the range of the present invention or the temperature of the UHF furnace is higher than the vulcanization foaming temperature, the vulcanization proceeds quickly and the tube inner diameter is crushed. The results are shown in Table 2.

It is whole sectional drawing of the transfer roller obtained by the manufacturing method of the conductive rubber roller which concerns on this invention. 1 is an overall cross-sectional view of an image forming apparatus including a conductive rubber roller according to the present invention. It is a whole sectional view of a vulcanization molding device used with a manufacturing method of a conductive rubber roller concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging device 3 Exposure means 4 Developing device 5 Toner 6 Transfer roller 61 Core metal 62 Elastic layer 7 Transfer material 8 Cleaning blade 9 Waste toner container 10 Fixing device 11 Extruder 12 Microwave vulcanizing device (UHF)
13 Hot air vulcanizer (HAV)
14 Picker 15 Standard cutting machine

Claims (4)

  A method for producing a conductive rubber roller in which a rubber layer is formed on a conductive core material, the rubber layer containing acrylonitrile rubber and epichlorohydrin rubber, and vulcanization foaming of the rubber material of the rubber layer Conductivity characterized in that the rubber layer is vulcanized and foamed by a process in which the temperature of the rubber layer becomes 200 ° C. to 250 ° C. when irradiated with microwaves in a microwave vulcanizing furnace having a heated air atmosphere lower than the temperature. Method for producing a conductive rubber roller.   The method for producing a conductive rubber roller according to claim 1, wherein the rubber layer contains a thiuram accelerator and a thiazole accelerator, and the molecular weight of the thiuram accelerator is 200 or more and 650 or less.   A conductive rubber roller in which a rubber layer is formed on a conductive core material used in an image forming apparatus is manufactured by the method for manufacturing a conductive rubber roller according to claim 1 or 2. Conductive rubber roller.   A transfer roller mounted on a transfer device of an image forming apparatus is the conductive rubber roller according to claim 3.

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