JP2007276152A - Conductive rubber roller, its manufacturing method and electrophotographic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a suitable manufacturing method of a conductive rubber roller using a foamed rubber tube due to microwave vulcanization. <P>SOLUTION: A raw material rubber composition wherein a main agent rubber is constituted of a mixture of an acrylonitrile rubber and an epichlorohydrin rubber is extruded into a cylindrical shape, the extrudate is irradiated with a microwave in a microwave vulcanizing furnace to be vulcanized and foamed to be formed into a foamed rubber tube and a conductive shaft core body is inserted in the foamed rubber tube under pressure to form a vulcanized foamed rubber layer on the conductive shaft core body. In this manufacturing method of the conductive rubber roller, the irradiation intensity of microwave irradiation is 1.0-3.0 kW/m<SP>2</SP>, the internal temperature of the foamed rubber tube during microwave irradiation is 190-240°C, the thickness of the foamed rubber tube is 4-10 mm and JIS tensile strength is 1.5-7.0 MPa. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a conductive rubber roller, in particular, a conductive rubber roller used in an electrophotographic apparatus such as a copying machine, a printer, and an electrostatic recording apparatus, and further relates to a manufacturing method thereof. The present invention also relates to an electrophotographic apparatus using the conductive rubber roller as a transfer roller.

  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. Conventionally, in order to impart conductivity to the rubber layer of these rollers, a conductive filler such as carbon black is added to the rubber material, or an ion conductive rubber material such as acrylonitrile butadiene rubber or epichlorohydrin rubber is used. (For example, Patent Document 1). However, these rubber rollers are loaded with a high voltage for a long time when used in the image forming apparatus. As a result, in any rubber roller, there is a change in the rubber layer due to the durability of energization due to long-term use, which in turn causes a change in the electric resistance value.

  For this reason, the conductive rubber roller uses an ionic conductive acrylonitrile butadiene rubber or epichlorohydrin rubber as a main rubber, which has a relatively small change in durability of its electric resistance, or a rubber material provided with an ionic conductive agent as a material for imparting conductivity. (For example, patent document 2).

  However, at present, copying machines and printers are required to have higher speed and longer life, and conductive rubber rollers are required to have even stronger energization durability.

  In addition, after these raw rubber compositions added with a vulcanizing agent, a foaming agent, a filler and the like are kneaded into an unvulcanized cylindrical molded body with a mold, an extruder, etc., This unvulcanized cylindrical molded body is vulcanized and foamed by heating to form a foamed rubber tube. Thereafter, a shaft core body is press-fitted into the foam rubber tube, and if necessary, the outer diameter is cylindrically polished into a roller shape to obtain a conductive rubber roller. The conductive rubber roller may have a functional surface layer formed on the surface depending on the purpose of use.

  Examples of methods for producing foamed rubber tubes include vulcanization can vulcanization using high-pressure steam (Patent Document 3), in-mold vulcanization using a cylindrical mold (Patent Document 4), and vulcanization using microwave irradiation (UHF vulcanization). Sulfur) (Patent Document 5) and the like are known. However, in these vulcanization methods, although there are limitations on the raw rubber used, the material to be blended, the thickness, etc., UHF vulcanization is the preferred method because vulcanization foaming can be performed in a short time and with certainty.

By the way, in patent document 5, although the rubber material aiming at the improvement of electricity supply durability is examined, the vulcanization foaming apparatus reaches 45 m in total length. That is, the actual situation is that the detailed manufacturing method has not been sufficiently studied.
JP 2002-287456 A Japanese Patent Laid-Open No. 2003-064224 JP 11-114978 A JP-A-11-201140 Japanese Patent Laid-Open No. 2002-221859

  Accordingly, an object of the present invention is to provide a suitable manufacturing method of a conductive rubber roller using a foamed rubber tube by UHF vulcanization, and to provide various conductive rubber rollers of an electrophotographic apparatus having high durability. is there.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors use acrylonitrile butadiene rubber and epichlorohydrin rubber as the main rubber, and form an unvulcanized cylinder during foam vulcanization in a microwave vulcanization furnace. The inventors have found that the above-mentioned problems can be solved by controlling the core temperature of the body, have further studied, and have finally reached the present invention.

That is, in the present invention, a raw rubber composition in which the base rubber is composed of a mixture of acrylonitrile rubber and epichlorohydrin rubber is extruded into a cylindrical shape, and then vulcanized and foamed by microwave irradiation in a microwave vulcanizing furnace. In the method of manufacturing a conductive rubber roller, a foam rubber tube is formed, and then a conductive shaft core is press-fitted into the foam rubber tube to form a vulcanized foam rubber layer on the conductive shaft core. The irradiation intensity is 1.0 kW / m ² or more and 3.0 kW / m ² or less, the inside of the foam rubber tube during microwave irradiation is 190 ° C. or more and 240 ° C. or less, and the thickness of the foam rubber tube is 4 mm or more. Conductive rubber characterized by being 10 mm or less and having a JIS tensile strength (JIS K6251-1993) of 1.5 MPa to 7.0 MPa. It is a manufacturing method of over La.

The present invention also relates to a conductive rubber roller having a vulcanized foam rubber layer on a conductive shaft core, wherein the vulcanized foam rubber layer is composed of acrylonitrile rubber and epichlorohydrin rubber as the main rubber, and the raw rubber composition is cylindrical. The raw rubber composition extruded from the vulcanized foam and then vulcanized and foamed is extruded into a cylindrical shape, and the raw rubber composition is 1.0 kW in a microwave vulcanizing furnace. / M ² or more and 3.0 kW / m ² or less of microwave irradiation, the inside of the foam rubber tube during the microwave irradiation is heated to 190 ° C. or more and 240 ° C. or less, and the thickness of the foam rubber tube is Conductivity characterized by being 4 mm or more and 10 mm or less and having a JIS tensile strength (JIS K6251-1993) of 1.5 MPa or more and 7.0 MPa or less. Is Murora.

  Furthermore, the present invention is the electrophotographic apparatus, wherein the transfer roller is the conductive rubber roller.

  According to the present invention, it is possible to provide a conductive rubber roller having high durability. The conductive rubber roller of the present invention is suitable as various conductive rubber rollers for electrophotographic apparatuses, particularly as transfer rollers.

  A perspective view of an example of the conductive rubber roller manufactured by the present invention is shown in FIG.

  In FIG. 1, 1 is a conductive shaft core body, and a conductive vulcanized foam rubber layer 2 is formed on the outer periphery of the conductive shaft core body 1.

  The conductive shaft core 1 is usually a solid bar or hollow bar made of iron, steel, brass, non-rust steel, etc., and the surface thereof is plated with nickel or the like. And in this invention, it is preferable that an outer diameter is 4 mm or more and 10 mm or less.

  In the present invention, the vulcanized foam rubber layer is used in which the main rubber is a mixture of acrylonitrile butadiene rubber and epichlorohydrin rubber, and the foaming agent, vulcanizing agent, vulcanization accelerator, stabilizer, conductive agent and the like are necessary. The auxiliary materials are compounded and kneaded to form a raw rubber composition, then extruded into a cylindrical shape from an extruder, vulcanized and foamed in a microwave vulcanization (UHF) furnace, and further vulcanized in a hot air heating (HAV) furnace. Then, the foamed rubber tube is cut to a predetermined length, and the conductive shaft core is press-fitted into the cut foamed rubber tube. Note that an adhesive may be applied to the shaft body in advance.

  What is important here is to control the intensity of the microwave irradiated during vulcanization foaming and the temperature of the raw rubber composition formed into a cylindrical shape during irradiation as described later. Furthermore, it is important that the JIS tensile strength (JIS K6251-1993) of the foamed rubber tube used as the vulcanized foamed rubber layer is 1.5 MPa or more and 7.0 MPa or less.

  In addition, the measurement of JIS tensile strength was performed by vulcanizing the raw rubber composition with a pressure press at a temperature reached by the cylindrical raw rubber composition being vulcanized and foamed by microwave irradiation. A standard test piece specified by JIS is prepared. In addition, the arrival temperature at the time of vulcanization foaming of the cylindrical raw material rubber composition is a fluorescent optical fiber thermometer so that the measurement point is at least 1 mm from the surface of the raw rubber composition extruded from the extruder in a cylindrical shape. The fiber sensor “FS400-20M” (trade name, manufactured by Anritsu Keiki Co., Ltd.) of “Amos FL-2000” (trade name, manufactured by Anritsu Keiki Co., Ltd.) is mounted, and the cylindrical raw rubber composition is placed in a microwave vulcanizing furnace. It is conveyed and vulcanized and foamed, the ultimate temperature is measured, and it is set as the temperature at the time of producing the JIS test piece with a pressure press.

  The raw rubber used for the vulcanized foam rubber layer of the present invention is acrylonitrile butadiene rubber and epichlorohydrin rubber whose main rubber has ion conductivity, and these are predetermined amounts, usually 90/10 or less and 20/80 or more in mass ratio. , Preferably 85/15 or less, 50/50 or more, and used as a mixture. In addition, polystyrene polymer material, polyolefin polymer material, polyester polymer material, polyurethane polymer material, thermoplastic elastomer such as RVC, acrylic resin, styrene vinyl acetate copolymer, butadiene acrylonitrile copolymer, etc. It is also possible to use a mixture of an appropriate amount of other polymer materials, other rubbers, elastomers, and resins.

In the present invention, ionic conductive acrylonitrile butadiene rubber and epichlorohydrin rubber are used as the main rubber, and this is not always necessary. However, in order to stably exhibit conductivity, for example, acetylene black, ketjen black (trademark) ) Conductive carbon black, metal oxides such as TiO ₂ , SnO ₂ , ZnO, SnO ₂ / SbO ₃ solid solution, electronic conductive conductive agents such as metal powders such as Cu and Ag, ions such as LiCIO ₄ and NaSCN It is also possible to appropriately select and add a conductive agent or the like. When conductive carbon black is used as the conductive agent, it is suitably 5 to 100 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the raw rubber. In place of the addition of a conductive agent, the raw rubber has a polar structure exhibiting ionic conductivity in the main chain or in the side chain, for example, an amide bond, an ester bond, a carboxyl group, or an ammonium group (bond). May be used.

In the present invention, fillers such as carbon black, calcium carbonate, and SiO ₂ can be used to adjust the flexibility, mechanical strength, etc. of the vulcanized foam rubber layer. The filler is used in an amount of 100 parts by mass or less, preferably 5 parts by mass or more and 50 parts by mass or less, based on 100 parts by mass of the raw rubber.

  In the present invention, a foaming agent is usually used to form a vulcanized foam rubber layer. As the blowing agent, for example, an organic blowing agent such as azodicarbonamide (ADCA), dinitrosopentamethylenetetraamine (DPT), p-toluenesulfonyl hydrazide (TSH), oxybisbenzenesulfenyl hydrazide (OBSH) alone or It can be used by mixing. The amount used varies depending on the flexibility of the vulcanized foam rubber layer, the mechanical strength, the vulcanizing agent used, etc., but is usually 1 to 50 parts by mass, preferably 2 to 100 parts by mass of the raw rubber. It is suitable that it is not less than 40 parts by mass. The decomposition temperature of the foaming agent is determined by adding a foaming aid such as urea, urea-based compounds such as urea resin, metal oxides such as zinc oxide and lead oxide, and compounds mainly composed of salicylic acid and stearic acid. It can also be reduced.

  Examples of the vulcanizing agent used in the present invention include sulfur, peroxides, metal oxides, etc., preferably sulfur. These vulcanizing agents are usually used together with a vulcanization accelerator. When sulfur is used as the vulcanizing agent, it varies depending on the strength of the raw rubber, foaming agent, vulcanized foamed rubber layer, etc., but is usually 1 part by mass or more and 50 parts by mass or less with respect to 100 parts by mass of the raw rubber. The amount is preferably 2 parts by mass or more and 10 parts by mass or less.

  The vulcanization accelerator can be appropriately selected from conventionally known ones. Since it is generally known that the combined use of a thiazole vulcanization accelerator and a thiuram vulcanization accelerator has an effect on the C setting property, a thiazole vulcanization accelerator and a thiuram vulcanization accelerator are used. It is preferable to use together. Specific examples of thiazole accelerators include 2-mercaptobenzothiazole (BMT), dibenzothiazyl disulfide (BMTS), etc., which have low scorch properties and are used in combination with thiuram vulcanization accelerators. Dibenzothiazyl disulfide (BMTS) is preferred. Examples of thiuram vulcanization accelerators include tetramethylthiuram monosulfide (TMTM), tetraethylthiuram disulfide (TETD), tetrakis (2-ethylhexyl) thiuram disulfide (TOTD), and dipentamethylenethiuram tetrasulfide (TPTT). Tetrakis (2-ethylhexyl) thiuram disulfide (TOTD) having excellent scorch properties is preferred. Other thiazole vulcanization accelerators and thiuram vulcanization accelerators can also be used by adjusting the use conditions.

  The vulcanization accelerator is used in an amount of 1 to 10 parts by weight, preferably 2 to 5 parts by weight, per 100 parts by weight of the raw rubber.

  Hereinafter, the production of the foam rubber tube for the vulcanized foam rubber layer will be described.

  FIG. 2 shows an apparatus for producing a foamed rubber tube by continuous vulcanization using microwaves.

  In the figure, 11 is an extruder, 12 is a microwave vulcanization (UHF) furnace, 13 is a hot air vulcanization (HAV) furnace, 14 is a take-up machine, and 15 is a regular cutting machine.

  The raw rubber composition for the vulcanized foam rubber layer described above is kneaded using a closed kneader such as a Banbury mixer or a kneader, and then molded into a ribbon shape using an open roll and a ribbon molding dispenser. It is thrown into. Next, the raw rubber composition is usually extruded in a cylindrical shape from an extruder with an inner diameter of 2 mm to 10 mm and an outer diameter of 4 mm to 16 mm. The cylindrical molded body is placed on a Teflon-coated mesh belt or a roller coated with Teflon resin in the UHF furnace 12 and conveyed into the UHF furnace 12.

The cylindrical molded body carried into the UFH furnace 12 is irradiated with microwaves having an irradiation intensity of 1.0 kW / m ² or more and 3.0 kW / m ² or less, and the cylindrical molded body is 190 in the UFH furnace 12. C. to 240.degree. C. and vulcanized and foamed. This vulcanized and foamed cylindrical molded body is further transported to the HAV furnace 13 by a roller coated with Teflon resin, and vulcanization and foaming is completed. In addition, it is important to complete vulcanization foaming so that the foamed rubber tube obtained may be 4 mm or more and 10 mm or less.

In the present invention, the microwave irradiation intensity in the UHF furnace 12 is set to 1.0 kW / m ² or more and 3.0 kW / m ² or less. By setting the irradiation intensity within this range, the JIS tensile strength is 1.5 MPa or more and 7.0 MPa or less, and a rubber tube having higher durability can be provided.

That is, when the microwave irradiation intensity is less than 1.0 kW / m ² , the temperature of the raw rubber composition molded into a cylindrical shape is less than 190 ° C. regardless of the thickness of the molded body of the raw rubber composition. As a result, vulcanization and foaming are insufficient, and the resulting foamed rubber tube has a JIS tensile strength of less than 1.5 MPa. This is considered to reduce the crosslinking rate by vulcanization inside the rubber tube, and the durability as a conductive rubber roller is reduced. On the other hand, when it is larger than 2.5 kW / m ² , the inside of the raw rubber composition is heated to over 240 ° C., and the JIS tensile strength of the resulting foamed rubber tube becomes larger than 7.0 MPa. That is, the rubber as the base material is overvulcanized, and the desired hardness cannot be obtained. In addition, when the molded body is thin, microwaves may concentrate on the irradiated surface and ignite. In addition, when the UHF furnace is small, the electric field strength increases, and discharge may occur. It is not preferable.

  Moreover, in this invention, the thickness of the foamed rubber tube after foaming shall be 4 mm or more and 10 mm or less. This is the range in which uniform vulcanization foaming is possible in the UHF furnace of the present invention. When the thickness is less than 4 mm, the microwaves are concentrated on the surface of the rubber layer, and there is a possibility of ignition during vulcanization foaming, which is not preferable. On the other hand, when the thickness is larger than 10 mm, it is not preferable because the temperature inside the rubber layer and the surface temperature are likely to be uneven, and foaming unevenness and hardness unevenness of the obtained foamed rubber tube are generated.

  When both the microwave irradiation intensity and the rubber layer thickness are within the range defined in the present invention, the internal temperature of the rubber tube is 190 ° C. or higher and 240 ° C. or lower. This temperature can be obtained by measuring with a temperature measuring means such as a thermocouple in advance when heat treatment is performed at a predetermined winner strength, and keeping correspondence with the setting conditions of the heat treatment temperature range of the present invention. .

  The cylindrical molded body vulcanized and foamed in the UHF furnace 12 sent to the HAV furnace 13 is normally further vulcanized with hot air in the range of 180 ° C. to 230 ° C. to form a foam rubber tube. The foamed rubber tube, which has been vulcanized, is taken up by the take-up machine 14 and then sent to the regular cutting machine 15 where it is cut into a predetermined length.

  The lengths of the UHF furnace 12, the HAV furnace 13 and the take-up machine 14 of the above apparatus are not particularly limited, but in the present invention, they can be 4 m, 6 m and 1 m, respectively. In addition, the distance between each device is 0.1 m or more and 1.0 m or less. If it carries out like this, the full length of the vulcanization | foaming apparatus except an extruder will be about 13 m, and it is a very short thing.

  The foamed rubber tube fed from the take-up machine 14 is cut into a predetermined size by a regular cutting machine 15 to obtain a foamed rubber tube for a vulcanized foamed rubber layer. Thereafter, a conductive shaft core is press-fitted into the foamed rubber tube to obtain the conductive rubber roller of the present invention. Note that when the shaft core has an outer diameter sufficiently larger than the inner diameter of the foam rubber tube, an adhesive is not necessarily required, but it is preferable to apply the adhesive depending on the material and outer diameter of the shaft core. Various adhesives can be used as the adhesive, but a hot melt adhesive is suitable.

  Further, after the shaft core body is press-fitted, both ends of the vulcanized foam rubber layer can be cut through to the length of the product and adjusted. Furthermore, the surface of the vulcanized foam rubber layer can be cylindrically polished to obtain a product thickness. For this cylindrical polishing, a rubber roller press-fitted with a shaft core body is set in a polishing machine equipped with a polishing grindstone GC80, and the outer diameter is a predetermined size at a rotational speed of 2000 rpm and a feed speed of 500 m / min. Polishing to 14 mm.

  The conductive rubber roller manufactured as described above has a surface layer if necessary, and is useful as various conductive rubber rollers, particularly a transfer roller, of an electrophotographic apparatus.

  FIG. 3 is an explanatory diagram of 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 FIG. 3 is a laser printer using an electrophotographic process cartridge, and its schematic configuration is shown.

  The image forming apparatus includes a drum-type electrophotographic photosensitive member (hereinafter referred to as “photosensitive drum”) 21 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. This photosensitive drum 21 is rotationally driven by a driving means (not shown) at a predetermined process speed (circumferential speed), for example, 50 mm / sec, in the direction of arrow R1.

  The surface of the photosensitive drum 21 is uniformly charged by the charging roller 22. The charging roller 22 is disposed in contact with the surface of the photosensitive drum 21, and is driven to rotate in the direction of arrow R2 as the photosensitive drum 21 rotates in the direction of arrow R1. An oscillating voltage (AC voltage VAC + DC voltage VDC) is applied to the charging roller 22 by a charging bias application power source (high voltage power source), whereby the surface of the photosensitive drum 21 is uniformly charged to −600 V (dark portion potential Vd). Is done. The surface of the charged photosensitive drum 21 is scanned and exposed by a laser beam 23 output from a laser scanner and reflected by a mirror, that is, a laser beam 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 21.

  The electrostatic latent image is reversely developed as a toner image by attaching negatively charged toner by a developing bias applied to the developing roller 24a of the developing device 24.

  On the other hand, a transfer material 27 such as paper fed from a paper feed unit is guided by a transfer guide, and is transferred to a transfer unit (transfer nip unit) T between the photosensitive drum 21 and the transfer roller 26 on the photosensitive drum 21. The toner image is supplied so as to match the timing of the toner image. The toner image on the photosensitive drum 21 is transferred onto the surface of the transfer material 27 supplied to the transfer portion T by the transfer bias applied to the transfer roller 26 by the transfer bias application power source. At this time, the toner (residual toner) that is not transferred to the transfer material 27 and remains on the surface of the photosensitive drum 21 is removed by the cleaning blade 28 and accommodated in the waste toner container 29.

  On the other hand, the transfer material 27 that has passed through the transfer portion T is separated from the photosensitive drum 21 and conveyed to the fixing device 30 where the toner image is fixed and processed as an image formed product (print) outside the image forming apparatus main body. To be discharged.

  In the image forming apparatus, the conductive rubber roller of the present invention can be used as a charging roller, a developing sleeve, and a transfer roller, and is particularly preferable as a transfer roller.

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

(Energization durability)
A conductive rubber roller is pressed against an aluminum drum with an outer diameter of 30 mm rotating at 30 rpm so that a load of 4.9 N is applied to each of the exposed ends of the shaft core. The resistance value R ₁ is measured under an environment of RH. Next, a constant current of 8 μA was continuously applied between the shaft core and the aluminum drum for 200 hours in an environment of 50 ° C. and 50% RH as it was, and then 23 ° C. and 50% RH (N / N ) Place in the environment for more than 24 hours. Thereafter, the surface of the roller is visually observed, and it is confirmed whether or not “tearing” occurs in the vulcanized foamed rubber layer. Next, the resistance value R ₂ is measured again for the surface where no tear is observed. The absolute value of log (R ₂ / R ₁ ) is obtained from R ₁ and R ₂ obtained here, and is defined as “fluctuation” in the current-carrying durability. In addition, it shows that the electricity supply durability of a conductive rubber roller is so good that this value is small, and it is preferable that it is 2.2 or less.

(Temperature inside foamed rubber tube during microwave irradiation)
A fiber sensor “FS400-20M” (trade name, manufactured by Anritsu Keiki Co., Ltd.) of a fluorescent fiber optic thermometer “Amos FL-2000” (trade name, manufactured by Anritsu Keiki Co., Ltd.) is extruded from an extruder. The tube is inserted into an unfoamed rubber tube, conveyed with the rubber tube into UHF, and the temperature in the tube in the UHF furnace is measured. The fixing of the sensor is not particularly limited as long as it can be installed at least 1 mm from the surface of the rubber tube after vulcanization and foaming, and may be fixed with heat-resistant tape or the like.

(JIS tensile strength of vulcanized foam rubber layer)
The JIS tensile strength of the vulcanized foam rubber layer was measured by the method described in JIS K6251-1993. The test piece was heated at the temperature inside the foamed rubber tube at the time of microwave irradiation as described above as the test piece preparation temperature, and heated for 15 minutes each using a commonly used heating press machine. A rubber sheet of No. 3 is obtained. A 20 mm mark is attached to the test piece, and a tensile test is performed with a commonly used tensile tester. The number of tests was N = 3. In addition, the value which remove | divided the maximum tensile force obtained by each test by the cross-sectional area of a test piece is averaged, and let the value be JIS tensile strength (MPa).

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

The rubber materials used in each example and comparative example are as follows.
・ NBR: Acrylonitrile butadiene rubber “NIPOL DN401LL” (trade name, manufactured by Nippon Zeon Co., Ltd.)
GECO: Epichlorohydrin rubber “Hydrin G3106” (trade name, manufactured by Nippon Zeon Co., Ltd.)
DM: Dibenzothiazyl disulfide “Noxeller DM-P” (trade name, thiazole vulcanization accelerator, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
-TOT: Tetrakis (2-ethylhexyl) thiuram disulfide "Noxeller TOT-N" (trade name, thiuram disulfide vulcanization accelerator, manufactured by Ouchi Shinsei Chemical Co., Ltd.)
・ Sulfur "Salfax PMC" (trade name, manufactured by Tsurumi Chemical Co., Ltd.)
・ ADCA: Azodicarbonamide “Vinihol AC” (trade name, manufactured by Eiwa Kasei Kogyo Co., Ltd.)

Examples 1-6
After knead | mixing 80 mass parts of NBR and 20 mass parts of GECO with a Banbury mixer 2 mass parts of sulfur as a vulcanizing agent, 1 mass part of DM as a vulcanization accelerator and 2 mass parts of TOT, and 3 mass parts of ADCA as a foaming agent, Further kneading with an open roll. Next, the raw rubber composition was molded into a ribbon shape by a ribbon molding dispenser, and charged into an extruder. The raw rubber composition was extruded from an extruder, formed into a cylindrical shape, and introduced into a UHF furnace. The cylindrical molded product was vulcanized and foamed by irradiation with microwaves in the UHF furnace. The microwave irradiation intensity was in the range of 1.0 kW / m ² to 3.0 kW / m ² as shown in Table 1.

  Next, the cylindrical molded product vulcanized and foamed in the UHF furnace was conveyed to a HAV furnace set at 200 ° C. by feeding hot air to complete the vulcanization.

  The vulcanization and foaming conditions for all processes are set so that the cylindrical molded body (foam rubber tube) after vulcanization has an inner diameter of 5 mm and the thickness of the foamed layer is in the range of 4 mm to 10 mm as shown in Table 1. did.

  Thereafter, the foamed rubber tube having been completely vulcanized was taken up at 2.5 m / min with a take-up machine, conveyed to a fixed length cutting machine, and cut into a length of 24 cm. Next, the cut cylindrical rubber tube is press-fitted with an iron shaft core body having an outer diameter of 6 mm and a length of 26 cm nickel-plated, and further coated with an adhesive. The length of the vulcanized foam rubber layer is Both ends were cut off to 23 cm to obtain a roller having a vulcanized foam rubber layer formed on the shaft core.

  The roller having this vulcanized foam rubber layer is set in a polishing machine equipped with a grinding wheel GC80, and polished so that the outer diameter is 14 mm at a rotation speed of 2000 rpm and a feed speed of 500 m / min, thereby producing a conductive rubber roller. did.

  On the other hand, at the temperature reached by the cylindrical molded body by vulcanization foaming in the UHF furnace, the raw rubber composition is vulcanized and foamed with a pressure press to produce a test piece for measuring JIS tensile strength, The JIS tensile strength was measured and shown in Table 1. Further, the energization durability of the obtained conductive rubber roller was examined and shown in Table 1.

Comparative Examples 1-4
In order to obtain a cylindrical molded body of the raw rubber composition so that the thickness of the foamed rubber tube after vulcanization foaming is 11 mm (Comparative Examples 1 and 2) or 3.2 mm (Comparative Examples 3 and 4). A foamed rubber tube was obtained in the same manner as in Example 1 or 2 except that a die was set. Thereafter, the foam rubber tube was cut, and the shaft core body was press-fitted in the same manner as in Example 1. Both ends of the vulcanized foam rubber layer were cut off to obtain a roller having a vulcanized foam rubber layer.

  In Comparative Examples 1 and 2, the surface of the vulcanized foam rubber layer was polished in the same manner as in Example 1 to obtain a conductive rubber roller having an outer diameter of 14 mm, and in Comparative Examples 3 and 4, the energization durability was examined as it was. . The results are shown in Table 1.

  On the other hand, test pieces were prepared in the same manner as described above at the temperature reached by the cylindrical molded product of the raw rubber composition in the UHF furnace, and the JIS tensile strength was measured and shown in Table 1.

Comparative Examples 5 and 6
Addition to the microwave irradiation intensity 0.5 kW / m ² (Comparative Example 5) or 3.5 kW / m ² (Comparative Example 5) in the same manner as in Example 3 was produced foamed rubber tube, Comparative Example 5 However, vulcanization foaming could not be performed due to insufficient temperature, and in Comparative Example 6, the microwave irradiation intensity was too strong, so that a part of the foamed rubber tube was burned, and the ultimate temperature could not be measured. Therefore, in these comparative examples, no conductive rubber roller was manufactured.

  Table 1 also shows the result of measuring the JIS tensile strength with the test piece prepared at the temperature reached by the cylindrical molded product of the raw rubber composition in Comparative Example 5.

  The conductive rubber rollers produced in Examples 1 to 6 have a JIS tensile strength within the range specified in the present invention, and the energized endurance does not cause tearing in the vulcanized foamed rubber layer. Is small enough.

On the other hand, in Comparative Examples 1 to 4 in which the thickness of the foamed rubber tube was more than 10 mm or less than 4 mm, the JIS tensile strength of the vulcanized foamed rubber layer was less than 1.5 MPa or more than 7.0 MPa, and tearing occurred due to current durability. . Moreover, the microwave irradiation intensity is pressurized硫不foot in less than 1.0 kW / m ² (Comparative Example 5), also 3.0 kW / m ² exceeds becomes (Comparative Example 6) In vulcanization excess, either unsuitable Met.

It is a perspective view of an example of a conductive rubber roller concerning the present invention. It is a block diagram explaining the vulcanization molding apparatus which concerns on this invention. 1 is a schematic explanatory diagram of an image forming apparatus according to the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shaft body 2 Vulcanized rubber layer 11 Extruder 12 Microwave vulcanization (UHF) furnace 13 Hot-air vulcanization (HAV) furnace 14 Take-out machine 15 Regular cutting machine 21 Photosensitive drum 22 Charging roller 23 Exposure means 24 Developing device 24a Developing roller 25 Toner 26 Transfer roller 27 Transfer material 28 Cleaning blade 29 Waste toner container 30 Fixing device

Claims (3)

A raw rubber composition in which the main rubber is composed of a mixture of acrylonitrile rubber and epichlorohydrin rubber is extruded into a cylindrical shape, and then vulcanized and foamed by microwave irradiation in a microwave vulcanizing furnace to obtain a foamed rubber tube. Then, in the method for producing a conductive rubber roller, a conductive shaft core body is press-fitted into the foamed rubber tube, and a vulcanized foam rubber layer is formed on the conductive shaft core body.
The microwave irradiation has an irradiation intensity of 1.0 kW / m ² or more and 3.0 kW / m ² or less, and the inside of the foam rubber tube during the microwave irradiation is 190 ° C. or more and 240 ° C. or less, and the thickness of the foam rubber tube Is 4 mm or more and 10 mm or less, and JIS tensile strength (JIS K6251-1993) is 1.5 MPa or more and 7.0 MPa or less, The manufacturing method of the conductive rubber roller characterized by the above-mentioned. In a conductive rubber roller having a vulcanized foam rubber layer on a conductive shaft core,
The vulcanized foam rubber layer is composed of a foam rubber tube in which the main rubber is made of acrylonitrile rubber and epichlorohydrin rubber, the raw rubber composition is extruded into a cylindrical shape, and then vulcanized and foamed.
The raw rubber composition in which the vulcanized foam has been extruded into a cylindrical shape is irradiated with microwaves at an irradiation intensity of 1.0 kW / m ² or more and 3.0 kW / m ² or less in a microwave vulcanization furnace. The inside of the foamed rubber tube being irradiated is heated to 190 ° C or higher and 240 ° C or lower,
A conductive rubber roller, wherein the foamed rubber tube has a thickness of 4 mm or more and 10 mm or less, and a JIS tensile strength (JIS K6251-1993) of 1.5 MPa or more and 7.0 MPa or less.   An electrophotographic apparatus, wherein the transfer roller is the conductive rubber roller according to claim 2.