JPH08300507A - Manufacture of electrically conductive belt - Google Patents

Abstract

PURPOSE: To provide a method for manufacture of an electrically conductive belt wherein high strength physical properties can be obtained by making electric resistance homogeneous. CONSTITUTION: A rubber in which an electrically conductive material is mixed, is molded by extrusion to mold an unvulcanized rubber tube. Thereby the electrically conductive material is homogeneously dispersed to prevent irregularity in electric resistance, and the unvulcanized rubber tube 18 after the extrusion process is fitted to a core 28. Thereafter, an outer side surface of the rubber tube is covered by a bladder 22 to intercept its contact with the air. The rubber tube is stuck fast to the core 23 by applying high pressure to the pladder 22 to prevent occurrence bare, and the rubber tube is vulcanized by heating.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a transfer / transport belt which is a component of an electrophotographic image forming apparatus and a conductive belt which is a component of various devices.

[0002]

2. Description of the Related Art A transfer conveyor belt used in an electrophotographic image forming apparatus has a volume resistivity of about 10 ⁷ to 10 ¹² Ω · cm, and an electric charge is applied to the conveyor belt. The toner attached to the surface of the photoconductor is attached to the surface of the paper conveyed on the conveyor belt by the electric suction force, and the conveyor belt is driven to fix the paper on which the toner is adhered by the fixing device, and then the toner is ejected. There is. In view of such a function of the transfer / transport belt, the transport belt needs to be conductive, and a conductive belt has been conventionally manufactured and used as the transfer / transport belt.

Conventionally, the injection method shown in FIG. 3 and the press method shown in FIG. 4 have been generally adopted as the method of manufacturing the conductive belt. As shown in FIG. 3, the injection method is a method in which the molten rubber 3 is injected into the molding dies 1 and 2 and molded, and simultaneously heated and vulcanized. As shown in FIG. 4, the pressing method is a method in which an unvulcanized rubber plate 6 is wound around pressing dies 4 and 5, and high temperature and pressure are applied between the upper die 4 and the lower die 5.

[0004]

By the way, as the physical properties required for the transfer / conveying belt and the like, it is needless to say that the conductivity is ensured by mixing the conductive material, and the toner is uniformly applied to the paper without uneven density. It is essential that the electrical resistance of the belt surface must be uniform for the transfer. In addition, due to the maintenance, the belt must have durability enough to withstand copying of about 240,000 sheets. Further, corona discharge generated from a discharge wire or the like when a voltage is applied generates ozone, which may cause deterioration of rubber. Therefore, excellent ozone resistance is required.

However, in the above-mentioned conventional method for manufacturing a conductive belt, according to the injection method, at the time of press-fitting unvulcanized rubber, especially at the injection portion 7 or the injection end portion 8, and according to the pressing method, the upper mold is used. When the extra rubber 6a flows out of the mold at the mating surfaces of the lower mold 4 and the lower mold 5, turbulent flow is generated respectively, and the flow of the rubber becomes uneven, so that the conductive material dispersed in the rubber, for example, carbon black It will be in a non-homogeneous dispersed state and will be fixed at the end of vulcanization. As a result, the electric resistance of the surface of the belt product becomes uneven, which in turn causes a shading in the copied image.

In addition to the above, as a method for manufacturing a rubber belt, a cylindrical unvulcanized rubber tube 1 is formed by extrusion molding.
There is also a method in which 0 is manufactured, inserted into the mandrel 9 (inner diameter core metal), and then placed in a vulcanization can 11 and heated by a steam 12 to vulcanize, as shown in FIG. According to this method,
Since the unvulcanized rubber tube 10 is molded by extrusion molding, the rubber flow is constant, and electric resistance unevenness does not occur by that amount, but since steam heating is performed by the vulcanizing can 11, high temperature in the presence of oxygen is used. Will be vulcanized. As a result, the rubber easily ages, and as described above, the strength and physical properties required of the conductive belt are significantly reduced.

Further, in the manufacturing method using this vulcanizing can,
Since the contact pressure between the mandrel 9 and the rubber tube 10 is low, the presence of air that has entered between the mandrel 9 and the rubber tube 10 causes unevenness on the inner surface of the belt after vulcanization, a so-called bear phenomenon occurs. Therefore, the film thickness is likely to be non-uniform, which is unlikely to occur in the injection method or the pressing method. Moreover, in order to adjust and smooth the belt thickness, a polishing step is required not only on the outer surface but also on the inner surface of the belt, which makes the polishing step after the vulcanization step complicated.

In view of the above, it is an object of the present invention to provide a method for manufacturing a conductive belt which can homogenize electric resistance and can obtain high strength physical properties. Another object of the present invention is to provide a method for manufacturing a conductive belt having excellent ozone resistance in addition to the above objects. Further, another object of the present invention is to provide a method of manufacturing a conductive belt, which can omit the polishing step of the inner surface of the rubber tube in the polishing step which is the final manufacturing step of the conductive belt.

[0009]

In order to achieve the above object, the inventors of the present invention believe that extrusion molding is optimal for making the electric resistance of the conductive belt uniform, and the rubber in the subsequent vulcanization step is considered. As a result of diligent research on means to prevent aging of the rubber, the rubber tube is fitted to the core such as a mandrel to shield the rubber tube from the air when the unvulcanized rubber tube is vulcanized, and the cover that wraps the outer surface I came up with the idea of vulcanizing with.

According to this method, however, the air can be blocked, but the air cannot be prevented from entering between the core and the rubber tube. Therefore, if an elastic body is used as the cover and a high pressure is applied to the elastic body from the outside to gradually bring the inner surface of the rubber tube into close contact with the core, the air entrapped when the rubber tube is inserted is removed and the air enters. We obtained the knowledge that this can be prevented.

Therefore, in the method for manufacturing a conductive belt according to the present invention, an extrusion molding step of extruding rubber mixed with a conductive material to form an unvulcanized rubber tube, and an unvulcanized rubber tube after the extrusion step. After being fitted to the core, it is vulcanized by a vulcanizing device.In the vulcanizing step, the outer surface of the rubber tube is covered with an elastic body to block contact with air, and this elastic body is Fluid pressure was applied to such a degree that the rubber tube was brought into close contact with the core, and the rubber tube was heated so as to be vulcanized.

The elastic body may be in any form as long as it can press the rubber tube to the core side and bring it into close contact, but a bag-shaped elastic body, that is, a rubber bladder is used, and fluid pressure is applied from the outside. , For example, if you apply air pressure,
It is optimal because the rubber bladder adheres to the outer surface of the rubber tube and blocks air. As for the air pressure to be applied, it is appropriate to apply a high pressure such that the rubber tube comes into close contact with the core mold and air does not enter between the two, for example, about 14 kg / cm ² .

Regarding the high temperature heating in the vulcanization process, various heating methods such as a heater heating method and a fluid heating method can be considered, and the arrangement of the heat source is not specified.
As the most efficient heating method, it is possible to adopt a method in which the core has a hollow double structure and high-temperature steam is circulated in the core. Further, the steam temperature and the heating time are appropriately selected and vulcanized according to the thickness of the rubber tube.

When the conductive belt is used as a transfer / conveying belt of an image forming apparatus such as a copying machine, ozone is generated by applying a voltage as described above, so that the conductive belt itself must have ozone resistance. . EPDM is used as the ozone resistant rubber, and it may be used. However, in a copying machine, a fixing device is disposed adjacent to the transfer portion, and thus flame retardancy is also required.

However, since EPDM has no flame retardancy, it is generally preferable to use chloroprene, which is generally flame-retardant, as a main material, and to add an antioxidant to it in order to impart ozone resistance. . Therefore, as a preferred embodiment of the present invention, a flame-retardant rubber is used, and an ozone anti-aging agent is mixed into the flame-retardant rubber and extrusion molding is performed to add flame retardancy and ozone resistance.

After the vulcanization is completed, the core is pulled out together with the rubber tube, the belt is pulled out from the core, the rubber tube is polished, and the conductive belt is completed through a polishing step of adjusting the belt thickness and smoothing. To do.

In this polishing step, the surface and the inner surface of the belt are also polished, but if the surface of the core used in the vulcanization step is mirror-finished, the inner surface of the belt will be smooth after the completion of vulcanization. Therefore, as an optimum embodiment of the present invention, by using a mirror-finished core in the vulcanization step, the inner surface polishing step of the rubber tube in the polishing step after the vulcanization step is omitted.

[0018]

As described above, the rubber flow becomes minute in the extrusion molding process and the vulcanization process, so that the conductive material is uniformly distributed. Therefore, it is possible to provide a conductive belt with extremely small unevenness in electrical resistance. Moreover, in the vulcanization process, the elastic body and the core vulcanize the rubber tube in a state where the contact with the air is blocked, so that the deterioration of the rubber can be suppressed as much as possible and a conductive belt having excellent strength and physical properties can be obtained. It can be provided. If the core is made hollow and steam is circulated inside the core to heat it, the rubber tube comes into contact with the mold core, so that the heat transfer efficiency is improved and the vulcanization time can be shortened. .

When an unvulcanized rubber tube is made of rubber having poor ozone resistance, and an ozone anti-aging agent is mixed and extruded and then vulcanized, air is blocked by an elastic body and a core. As compared with the case of the vulcanization can method shown in FIG. 5, the problem that the antioxidant sublimes into the gas phase or reacts with oxygen during the vulcanization and disappears is reduced. be able to. Also, if the surface of the mold core is mirror-finished, the inner surface of the rubber tube can be omitted in the polishing process for adjusting the belt thickness and smoothing after the vulcanization process, and only the outer surface can be polished. Therefore, the number of manufacturing steps can be reduced.

[0020]

Embodiments Embodiments shown in the accompanying drawings will be described below. FIG. 1 is a schematic configuration diagram of an extrusion molding machine used in a method for manufacturing a conductive belt according to the present invention, and FIG. 2 is a schematic sectional view of a vulcanizing apparatus.

In the extrusion molding machine 15, the rubber raw material in the hopper (not shown) is pushed into the screw and is kneaded into a fluid state in the cylinder 16 by heating from the outside to move forward, and is advanced from the forming die 17 at the tip into a tube shape. The unvulcanized rubber tube 18 is extruded and solidified by an external cooling device (not shown). Table 1 shows the mixing ratio (parts by weight) of the rubber raw material.

[0022]

[Table 1]

As shown in FIG. 2, the vulcanization device 20 includes a vulcanization can 2
A bladder 22, which is a rubber elastic body, is arranged in the interior of the vulcanization unit 1 over the entire circumference thereof, and a hollow core 23 is erected in the center of the vulcanization can 21 so as to be removable. The core 23 uses a double structure in which the inner cylinder 24 is connected and arranged in the center of the inside,
The method of circulating the heated steam A is adopted.
Further, the surface of the core 23 is mirror-finished so that the polishing of the inner surface of the rubber tube can be omitted in the polishing step. Further, a high air pressure B is supplied from the outside of the bladder 22, and the air pressure B is set to a high pressure of 14 kg / cm ² with respect to the unvulcanized rubber tube 18 having a thickness of 0.8 mm. In addition, the lid 2 is provided at the upper opening of the vulcanization can 21.
5 is provided so that the vulcanization can 21 can be closed during vulcanization.

In order to manufacture a conductive belt using the extrusion molding machine 15 and the vulcanization apparatus 20 having the above-mentioned structure, rubber having a compounding ratio shown in Table 1 is extruded to form an unvulcanized rubber tube 18. Then, this unvulcanized rubber tube is fitted into the core 23, and is inserted and fixed inside the vulcanizing can 21 of the vulcanizing device 20. Next, from the outer surface of this rubber tube, bladder 2
2 is inflated by air pressure so as to be in close contact, and heated from inside the core 23 with steam to vulcanize the rubber tube.
During this vulcanization, high-temperature steam A from the lower part of the core 23 rises inside the inner cylinder 24, then flows from the upper end of the inner cylinder 24 to the inner wall side of the core, and heats the inner wall surface of the core. After that, since the steam circulation path that flows out to the outside is formed, the rubber tube that is in close contact with the core 23 is quickly heated and vulcanized, so that the heating time can be shortened.

Thereafter, the rubber tube is taken out together with the core 23, and the cylindrical vulcanized rubber tube is taken out from the core 23. In the polishing step, only the surface of the removed rubber tube is polished to adjust the belt thickness and smooth it.

Table 2 shows the average value of the partial electric resistance and the maximum electric resistance of the ten belts of Examples 1 and 2 in which the vulcanizing conditions were changed by using the extrusion molding machine 15 and the vulcanizing apparatus 20 having the above-mentioned structures. The results of measurement of the ratio between the value and the minimum value, and the breaking strength and breaking elongation of the belt are shown. In Table 2, for comparison with these Examples 1 and 2, the conventional injection method (Comparative Example 1) shown in FIG. 3 and, as shown in FIG. 5, extrusion molding followed by vulcanization in a vulcanization can The measurement results of the molded vulcanization can method (Comparative Example 2) are also shown.

[0027]

[Table 2]

In the injection method, since the conductive material is in an inhomogeneous dispersed state due to turbulent flow and is fixed by vulcanization termination, as shown in Table 2, the maximum value / minimum value of electric resistance is extruded. It is significantly larger than the method and shows that the electrical resistance is uneven. Further, the fact that the belt breaking strength and the belt breaking elongation are higher than in Comparative Example 2 is considered to be a result of preventing the rubber from being deteriorated by oxygen during vulcanization.

[0029]

As is clear from the above description,
According to the present invention, an unvulcanized rubber tube mixed with a conductive material and formed by extrusion molding is insulated from air by using a core and an elastic body in a vulcanization process, and a high pressure is applied to prevent generation of a bear. Since the rubber tube is vulcanized while being in close contact with the core, the conductive material is homogenized and uneven electrical resistance can be prevented, and at the same time, rubber deterioration due to oxygen can be prevented.

Even when a rubber containing a flame-retardant rubber such as chloroprene and an ozone anti-aging agent is used, the anti-aging agent sublimes into the gas phase or reacts with oxygen during vulcanization. However, the ozone resistance can be sufficiently maintained without disappearing.

Further, in the vulcanizing step, if a core having a mirror-finished surface is used, in the belt polishing step for adjusting the belt thickness and smoothing, only one outer surface needs to be polished.
It also has an advantage that complexity of the polishing process can be eliminated.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an outline of an extrusion molding machine used in a method for producing a conductive belt according to the present invention.

FIG. 2 is a schematic cross-sectional view of the vulcanizing apparatus.

FIG. 3 is a diagram showing a belt manufacturing method by an injection method.

FIG. 4 is a diagram showing a belt manufacturing method by a press system.

FIG. 5 is a diagram showing a belt manufacturing method using a vulcanizing can.

[Explanation of symbols]

 15 Extrusion Molding Machine 17 Forming Die 18 Unvulcanized Rubber Tube 20 Vulcanizing Device 21 Vulcanizing Can 22 Bladder 23 Core 24 Inner Cylinder A Steam B Air Pressure

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Claims (3)

[Claims] 1. An extrusion molding step of extruding a rubber mixed with a conductive material to form an unvulcanized rubber tube, and a non-vulcanized rubber tube after the extruding step is fitted to a core by a vulcanizing device. It consists of a vulcanization process to vulcanize, and in the vulcanization process,
The outer surface of the rubber tube is covered with an elastic body so as to block contact with air, and a fluid pressure is applied to the elastic body to such an extent that the rubber tube adheres to the core, and the rubber tube is heated and vulcanized. A method for manufacturing a conductive belt. 2. The method for producing a conductive belt according to claim 1, wherein the conductive belt is extruded by mixing an ozone anti-aging agent for preventing aging due to ozone when the conductive belt is used. 3. The inner surface polishing step of the rubber tube in the polishing step after the vulcanization step is omitted by using a mirror-finished core in the vulcanization step.
A method for producing the conductive belt described.