JPH1165269A - Conductive rubber composition and conductive elastic roller using the rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a conductive rubber compsn. with uniform resistance, excellent ozone resistance, low hardness and excellent formability by mixing an acrylonitrile-butadiene rubber containing a specified amt. of acrylonitrile and an epichlorohydrin rubber containing a specified amt. of ethylene oxide in a specified mixing ratio. SOLUTION: The compsn. contains an acrylonitrile-butadiene rubber containing 18 to 40 wt.% acrylonitrile and having 30 to 60 Mooney viscosity at 100 deg.C, and an epichlorohydrin rubber containing 10 to 40 mol.% ethylene oxide in 80:20 to 20:80 weight ratio of mixing. NBR and ECO are compounded in the conductive rubber compsn. by generally 30 to 80 wt.% in total to the whole rubber compsn., and preferably by 50 to 70 wt.%. Moreover, a conductive filler is preferably compounded in the conductive rubber compsn. to decrease the resistance and to control the resistance.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive rubber composition and a conductive elastic roller using the rubber composition, and more particularly, to a transfer roller for an image forming apparatus such as an electrophotographic copying machine, a laser printer, and a facsimile. The present invention relates to a conductive rubber composition suitable for a rubber elastic layer of a conductive elastic roller such as a charging roller and a developing roller, and a conductive elastic roller using the rubber composition.

[0002]

2. Description of the Related Art Conventionally, copiers, laser printers,
Various studies have been made to optimize the conductivity of a conductive rubber composition used in a rubber elastic layer of a conductive elastic roller such as a transfer roller, a charging roller, and a developing roller in an image forming apparatus such as a facsimile machine. . For example, in Japanese Patent Application Laid-Open No. 9-134609, the use of a polar rubber such as acrylonitrile butadiene rubber (NBR) or epichlorohydrin rubber (ECO) as a rubber component reduces the resistance unevenness of the conductive rubber composition. I have.

[0003]

However, when the above-mentioned polar rubber is used, the resistance unevenness of the rubber composition can be reduced to a certain extent. However, since NBR has a double bond in the main chain, it can be used alone. If ECO is used, it has a drawback that it is susceptible to ozone deterioration, and ECO has poor workability at the time of kneading and extrusion molding, and when it is used alone, the rubber composition cannot be stably molded into a desired shape. There are drawbacks. Therefore, by using a mixture of NBR and ECO, it is conceivable to compensate for the disadvantage that NBR easily deteriorates by ozone and the defect that ECO has poor workability.
Although there is a description that BR and ECO are used in combination, optimal NBR and EC0 that can reduce uneven resistance and obtain a rubber composition excellent in moldability (workability) and ozone resistance can be obtained. No consideration has been given to the mixing ratio of. In order to obtain a high quality image, it is important for the conductive elastic roller used for the transfer roller and the developing roller of the image forming apparatus to reduce the resistance of the roller and reduce the resistance unevenness. There is a demand for lowering the resistance of the composition itself and reducing resistance unevenness.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described circumstances. By mixing NBR and ECO, the resistance non-uniformity is small in a low-resistance region showing a relatively low resistance as a whole, It is an object of the present invention to provide a conductive rubber composition having excellent hardness, excellent ozone resistance, and excellent moldability, and a conductive elastic roller using the rubber composition.

[0005]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and have found that acrylonitrile-butadiene rubber (NBR) having a specific acrylonitrile amount and epichlorohydrin rubber (ECO) having a specific ethylene oxide amount are obtained. By mixing at a specific mixing ratio, a conductive rubber composition that exhibits a relatively low resistance value as a whole, has no resistance unevenness, and is excellent in ozone resistance, and has low hardness and excellent moldability. It has been found that it can be obtained. That is, in the present invention, the acrylonitrile-butadiene rubber having an acrylonitrile amount of 18 to 40% by weight and a Mooney viscosity at 100 ° C of 30 to 60 according to claim 1;
Epichlorohydrin rubber having an ethylene oxide content of 10 to 40 mol% is in a weight ratio (acrylonitrile-butadiene rubber: epichlorohydrin rubber) of 80: 20-2.
The present invention provides a conductive rubber composition which is contained in a ratio of 0:80.

In the conductive rubber composition of the present invention, NBR and ECO are added such that the total amount of both of them is generally 30 to 80% by weight, preferably 50 to 70% by weight based on the whole rubber composition. It is good to mix.

[0007] In addition to NBR and ECO, various rubbers conventionally used as rubber components of this kind of conductive rubber composition may be blended, and such rubber may be ethylene-propylene-diene copolymer. Rubber (EPDM rubber), chloroprene rubber (CR), acrylic rubber and the like.

The rubber composition of the present invention is formed into a tube and used as an elastic layer of a conductive elastic roller such as a transfer roller, a charging roller, and a developing roller in an image forming apparatus such as a copying machine, a laser printer, and a facsimile. Although it is common (claim 2), it can be formed into a shape other than the tube shape and used, for example, formed into a belt shape and used for a transfer belt in an image forming apparatus.

The use of NBR having an acrylonitrile content of 18 to 40% by weight in the conductive rubber composition of the present invention depends on the ratio of NBR in the rubber component in the rubber composition and the mixing ratio of NBR and ECO. Acrylonitrile content is less than 18% by weight
When NBR is used, the number of double bonds in the rubber composition is relatively increased, and the ozone resistance of the rubber composition is reduced. When NBR having an acrylonitrile content of more than 40% by weight is used, the rubber hardness of the rubber composition is greatly increased. This is because Also,
The reason for using an NBR having a Mooney viscosity at 100 ° C. of 30 to 60 is that NBR in the rubber component in the rubber composition is used.
Although the degree varies depending on the ratio of BR and the mixing ratio of NBR and ECO, the Mooney viscosity of NBR is generally 30%.
If it is smaller than this, the processability of the rubber composition decreases because the NBR is easily torn, and if it is larger than 60, the processability of the rubber composition decreases because the NBR becomes hard.

The amount of ethylene oxide is 10 to 40.
% Of ECO depends on the mixing ratio of NBR and ECO, etc., but the amount of ethylene oxide is 10%.
When ECO is used in an amount less than mol%, the electrical resistance of the rubber composition becomes too large, and when ECO is used in which the amount of ethylene oxide is more than 40 mol%, the resistance unevenness of the rubber composition becomes remarkable. It is.

The mixing ratio (weight ratio) of NBR and ECO is set to be 80:20 to 20:80. When the ratio of NBR is more than 80, the rubber having a double bond in the rubber composition is used. This is because the ozone resistance of the rubber composition is reduced due to an increase in the number of components, and when the ratio of ECO is more than 80, the resistance unevenness of the rubber composition becomes severe.

In the conductive rubber composition of the present invention, it is preferable to mix a conductive filler to reduce the resistance and adjust the resistance value. Carbon black, metal powder, or the like can be used as the conductive filler. When using carbon black, generally 5 to 100 parts by weight of the rubber component of the composition
It is advisable to add 60 parts by weight, preferably 20 to 50 parts by weight. The reason for setting the compounding amount of the carbon black to the above range is that when the compounding amount of the carbon black is more than 60 parts by weight, the composition is molded into a tube as described later,
When a conductive shaft is fitted into the tube to form a conductive elastic roller, the electric resistance of the conductive elastic roller greatly depends on the applied voltage, which is not preferable. Is no longer obtained. Examples of the carbon black include channel black, furnace black, acetylene black and the like. In addition, it is appropriate that the particle size of the carbon black is generally 18 to 120 nm, preferably 22 to 90 nm for reasons such as conductivity.

The conductive rubber composition of the present invention is preferably used after vulcanization, and can also be used as a foam by blending a foaming agent with a vulcanizing agent. Also,
An anti-aging agent, a reinforcing agent, a filler, and the like can be added as necessary.

As the vulcanizing agent, for example, peroxides and the like can be used in addition to sulfur and organic sulfur-containing compounds. Examples of the organic sulfur-containing compound include tetramethylthiuram disulfide, N, N-dithiobismorpholine and the like. Examples of the peroxide include benzoyl peroxide. In addition, among these, when foaming is performed together with vulcanization, it is preferable to use sulfur because the balance between the vulcanization speed and the foaming speed is improved. It is preferable to mix a vulcanization accelerator together with a vulcanizing agent. As the vulcanization accelerator, for example, an inorganic accelerator such as slaked lime, magnesia (MgO), litharge (PbO), or an organic accelerator described below is used. be able to. As the organic accelerator, for example,
Thiazole vulcanization accelerators such as 2-mercaptobenzothiazole and N-cyclohexyl-2-benzothiazolesulfene; and aliphatic primary amines such as n-butylamine, tert-butylamine and propylamine, and 2-mercaptobenzothiazole. An oxidative condensate of an aliphatic secondary amine such as dicyclohexylamine, pyrrolidine and piperidine with 2-mercaptobenzothiazole;
Sulfenamide-based vulcanization accelerators such as an oxidative condensate of an alicyclic primary amine with 2-mercaptobenzothiazole, an oxidative condensate of a morpholine compound and 2-mercaptobenzothiazole, and tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (T
MTD), tetraethylthiuram dimonosulfide (T
ETD), tetrabutylthiuram dimonosulfide (T
Thiuram-based vulcanization accelerators such as BTD), dipentamethylenethiuram tetrasulfide (DPTT), zinc dimethyldithiocarbamate (@nMDC), zinc diethyldithiocarbamate (ZnEDC), zinc di-n-butylcarbamate (@nBDC), etc. Dithiocarbamate-based vulcanization accelerators and the like can be used. Further, a vulcanization accelerating aid can be blended, and for example, metal compounds such as zinc white and fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid can be used.

Examples of the foaming agent include azodicarbonamide, N.P. An organic blowing agent such as N-dinitrosopentamethylenetetramine is used. The amount of the foaming agent is about 5 to 11 parts by weight based on 100 parts by weight of the rubber component of the composition. If the amount is less than 5 parts by weight, the foaming becomes insufficient, and if the amount is more than 11 parts by weight, the foaming agent inhibits vulcanization and vulcanization becomes insufficient. When the composition is a foam, flexibility is improved. Therefore, as described later, the composition is formed into a tube, and a conductive shaft is fitted into the tube to form a conductive elastic roller.When this is used for a transfer roller, for example, the toner when pressing the transfer member is used. Disturbance of the image hardly occurs, and an image with good image quality can be obtained.

Examples of the filler include powders of silica, clay, talc, calcium carbonate, dibasic phosphite (DLP), basic magnesium carbonate, alumina and the like. The addition of a filler improves the strength of the rubber composition.

Examples of the antioxidants include imidazoles such as 2-mercaptobenzimidazole, phenyl-α-naphthylamine, N, N′-di-β-naphthyl-p-phenylenediamine, and N-phenyl-N ′. −
Examples include amines such as isopropyl-p-phenylenediamine, and phenols such as di-tert-butyl-p-cresol and styrenated phenol.

The kneading, vulcanization and molding of the constituent materials of the rubber composition can be carried out by conventional methods. For example, kneading is performed at 60 to 120 ° C. for 5 to 30 minutes using a known rubber kneading device such as an open roll or a Banbury mixer. Vulcanization of the kneaded product may be performed at 150 to 180 ° C. for 5 to 30 minutes by, for example, an electric press or can vulcanization.
Further, vulcanization may be performed by irradiation with an electron beam.

The molding can be performed before or simultaneously with the vulcanization. For example, after the kneaded material is compression-molded in a roller-shaped mold, the mold is heated and vulcanized. Alternatively, vulcanization may be performed by injection molding, transfer molding, or extrusion molding while molding into a desired shape such as a tube shape (roller shape), a sheet shape, or a belt shape.

FIG. 1 shows a conductive elastic roller 10 formed by molding a rubber composition of the present invention into a tube and fitting a conductive shaft 2 into the inner diameter of the tube 1. Examples of the conductive shaft 2 include copper, aluminum, carbon steel,
A shaft made of stainless steel or the like can be used. In addition,
As the conductive shaft 2, not only a rod-shaped body as shown in this figure but also a tubular (pipe-shaped) body can be used. Also,
Instead of the conductive shaft, as shown in FIGS. 3A and 3B, a short rod-shaped body 5 is provided at the center of both end faces of the metal drum 4.
Using the conductive drum 6 having the
1 having a relatively large inner diameter
Of the conductive elastic roller 20 shown in FIG.
It may be. In addition, such a type of the conductive elastic roller 20 may be referred to as a conductive elastic drum.

The above-mentioned conductive elastic roller 10 is preferably produced by the following method from the viewpoint of workability and roller performance. That is, the constituent materials of the rubber composition part are kneaded with a kneader at 60 to 120 ° C. for 5 to 30 minutes, formed into a tube with an extruder, and the shaft 2 is fitted into the inner diameter of the tube 1. And 5-3 at 120-180 ° C
Vulcanization is performed for 0 minute, secondary vulcanization is performed at 150 to 160 ° C. for 1 to 4 hours, and final finishing such as surface polishing is performed to obtain a conductive elastic roller.

When the conductive elastic roller 10 is formed using the conductive rubber composition of the present invention, the electric resistance of the conductive elastic roller 10 can be set to a low resistance region of 10 ³ -10 ¹⁰ Ω, and Since the resistance irregularity of the rubber composition is small, the resistance irregularity on the surface of the conductive elastic roller 10 (the surface of the tube 1) is extremely small.

The electric resistance of the conductive elastic roller 1 is a value measured by the measuring method shown in FIG. That is, the conductive elastic roller 10 is installed on the aluminum plate 3 such that the outer peripheral surface 1a of the rubber tube 1 is in contact with the surface of the aluminum plate 3, and a load W of 500 g is applied to both ends of the conductive shaft 2 in units of 500 g. 10 from one end of the conductive shaft 2.
The current value (A) when a voltage of 00 V was applied was measured, and the electrical resistance R (Ω) was obtained according to Ohm's law.

[0024]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on examples and comparative examples. (Example 1) NBR [Acrylonitrile content: 18% by weight, Mooney viscosity (100 ° C): 32] (Nipol D, manufactured by Zeon Corporation)
N401LL) 50 parts by weight ECO [Ethylene oxide amount: 34.5 mol%] (Daiso, Epichrom-CG104) 50 parts by weight Carbon black (Tokai Carbon, Seast 3) 2
3 parts by weight ・ Sulfur 1.5 parts by weight ・ Zinc flower 5 parts by weight ・ Stearic acid 1 part by weight ・ Blowing agent (manufactured by Eiwa Chemical Co., Vinhole AC # 3) 8 parts by weight 100
Kneaded at 10 ° C for 10 minutes. Then, it was formed into a tube by an extruder, and a stainless steel shaft was inserted into the inner diameter of the tube. After vulcanization at 160 ° C. for 30 minutes and secondary vulcanization at 160 ° C. for 2 hours, final finishing such as polishing was performed, and the diameter was 18.7 mm and the length was 35 cm.
A conductive elastic roller having a rubber layer thickness of 5.35 mm was obtained.

(Example 2) NBR manufactured by Zeon Corporation, Nip
ol DN115 [Acrylonitrile content: 40.5% by weight, Mooney viscosity (100 ° C.): 58] A conductive elastic roller was prepared in the same manner as in Example 1 except that the weight was changed to 50 parts by weight.

Example 3 As an ECO, Epichromer CG104 manufactured by Daiso [ethylene oxide content: 3
4.5 mol%] and 70 parts by weight of Epichromer H [amount of ethylene oxide: 0 mol%] manufactured by Daiso Co., Ltd., to make the ethylene oxide amount of the whole ECO to be blended 10 mol%. Except for the above, a conductive elastic roller was prepared in the same manner as in Example 1.

Example 4 As an ECO, Epichromer CG104 manufactured by Daiso [ethylene oxide content: 3
4.5 mol%], and 30 parts of Epichromer C [ethylene oxide content: 51 mol%] manufactured by Daiso Co., Ltd.
A conductive elastic roller was prepared in the same manner as in Example 1 except that the amount of ethylene oxide was 39 mol% with respect to the whole ECO to be mixed by using parts by weight.

Example 5 Example 1 except that the amounts of NBR and ECO were changed to 60 parts by weight and 40 parts by weight, respectively.
A conductive elastic roller was prepared in the same manner as described above.

Example 6 Example 1 except that the amounts of NBR and ECO were changed to 30 parts by weight and 70 parts by weight, respectively.
A conductive elastic roller was prepared in the same manner as described above.

(Comparative Example 1) NBR was manufactured by Nippon Synthetic Rubber, JS
RN260S [Acrylonitrile content: 15% by weight, Mooney viscosity (100 ° C.): 62] A conductive elastic roller was prepared in the same manner as in Example 1, except that the weight was changed to 50 parts by weight.

(Comparative Example 2) NBR manufactured by Nippon Synthetic Rubber, JS
R 215SL [Acrylonitrile content: 48% by weight, Mooney viscosity (100 ° C.): 45] A conductive elastic roller was prepared in the same manner as in Example 1, except that the weight was changed to 50 parts by weight.

(Comparative Example 3) NBR was Nipol DN21
9 [acrylonitrile amount 33.5% by weight, Mooney viscosity
(100 ° C.): 27] A conductive elastic roller was prepared in the same manner as in Example 1, except that the weight was changed to 50 parts by weight.

(Comparative Example 4) NBR was replaced with Nipol DN20
2H [acrylonitrile amount: 31% by weight, Mooney viscosity
(100 ° C.): 78] A conductive elastic roller was prepared in the same manner as in Example 1 except that the amount was changed to 50 parts by weight and ECO was not used.

Comparative Example 5 A conductive elastic roller was produced in the same manner as in Example 1 except that ECO was changed to 50 parts by weight of Epichrom-H [ethylene oxide content: 0 mol%] manufactured by Daiso.

Comparative Example 6 A conductive elastic roller was produced in the same manner as in Example 1 except that ECO was changed to 50 parts by weight of Epichrom-C [ethylene oxide content: 51 mol%] manufactured by Daiso.

Comparative Example 7 Example 1 was repeated except that the amounts of NBR and ECO were changed to 90 parts by weight and 10 parts by weight, respectively.
A conductive elastic roller was prepared in the same manner as described above.

Comparative Example 8 A conductive elastic roller was prepared in the same manner as in Example 1 except that the amounts of NBR and ECO were changed to 15 parts by weight and 85 parts by weight, respectively.

The Asker hardness C of each of the conductive elastic rollers of Examples and Comparative Examples prepared as described above was measured using a rubber hardness meter “DD2 type C” manufactured by Kobunshi Keiki and the following performance was measured. An evaluation test was performed.

<Electrical Resistance Measurement Test> The electric resistance value of the conductive elastic roller was measured by the method shown in FIG. 2 and the logarithm thereof was obtained.

<Resistance unevenness test> As shown in FIG. 5, a conductive elastic roller 10 is placed on a work table, and a voltage is applied between one end of the shaft 2 and the surface of the tube 1 so that the surface of the tube 1 is different. 3 points (10cm from the other end of shaft 2, 1
The resistance value at three points of 7.5 cm and 25 cm) is obtained,
The logarithmic difference between these maximum and minimum values was determined.

<Ozone resistance test> A rubber plate-shaped test piece (60 mm x 10 mm x 2) was prepared by removing the foaming agent from the formulations of the above Examples and Comparative Examples, and vulcanizing the same as in the Examples.
mm) and an ozone concentration of 25 pph
After standing for 96 hours in an atmosphere at 40 ° C. for 10 hours, the test piece was stretched 10%. And, the one in which a crack was generated during this elongation was regarded as pass (○), and the one in which no crack was generated was rejected (x).

<Workability> In each of the above Examples and Comparative Examples, the workability in each step such as kneading, extrusion molding, vulcanization, etc. of the rubber material was comprehensively judged, and those having good workability were passed. (○), those which were not suitable for practical use due to poor workability were rejected (×). The results of the above performance evaluation tests are shown in Table 1 below.

[0043]

[Table 1]

In Table 1, the evaluation values of volume resistance and resistance unevenness are logΩ.

As shown in Table 1, the conductive elastic rollers of Examples 1 to 6 had an electric resistance of 4.8 to 6.0, a resistance unevenness of 0.3 to 0.4, and a hardness of 37 to 42. Within the range, the resistance unevenness was small in a relatively low-resistance region, and the hardness was low. The rubber composition itself had good ozone resistance and good processability.

On the other hand, the rubber composition of Comparative Example 1 has poor ozone resistance, and the conductive elastic roller manufactured using this rubber composition has almost the same volume resistance, resistance unevenness and hardness as those of the rubber roller of Example. However, it was found that it was not suitable for use in an image forming apparatus in terms of ozone resistance. This is because NBR containing too little acrylonitrile
(7 acrylonitrile amount: 15% by weight), it is considered that the ratio of double bonds was relatively increased (butadiene amount was increased).

The rubber composition (conductive elastic roller) of Comparative Example 2 was unsuitable because it used NBR (acrylonitrile content: 48% by weight), which had too much acrylonitrile, because the hardness increased.

The rubber composition of Comparative Example 3 uses NBR (Mooney viscosity (100 ° C.): 78) whose Mooney viscosity is too low, so that the processability is poor and a ribbon-shaped continuous member to be inserted into an extruder is used. When forming or inserting the ribbon-shaped continuous member into the extruder, there was a problem that the ribbon-shaped continuous member was cut.

The rubber composition of Comparative Example 4 used NBR (Mooney viscosity (100 ° C.): 78) having an excessively high Mooney viscosity, so that the processability was poor and problems occurred during extrusion molding.

Since the rubber composition of Comparative Example 5 uses ECO (ethylene oxide content: 0 mol%) having too little ethylene oxide, the resistance value becomes large, and the conductivity of the rubber composition as a conductive elastic roller is increased. The resistance value of the elastic roller (l
ogΩ) increased to 6.5. Therefore, the conductive elastic roller was not suitable for practical use.

Since the rubber composition of Comparative Example 6 used ECO (ethylene oxide content: 50 mol%) having an excessively large amount of ethylene oxide, the resistance unevenness was large, and the conductivity of the rubber composition as a conductive elastic roller was large. Resistance unevenness of elastic roller
(logΩ) was large at 0.8. Therefore, the conductive elastic roller was not suitable for practical use.

The rubber composition of Comparative Example 7 had a compounding ratio of NBR and ECO (NBR: ECO) of 90:10, an excessive amount of NBR, and a rubber having a double bond in the main chain in the rubber composition. Ozone resistance was poor because the amount of components was too large, and was unsuitable for use in an image forming apparatus in terms of ozone resistance.

The rubber composition of Comparative Example 8 had a compounding ratio of NBR and ECO (NBR: ECO) of 15:85, and the compounding amount of ECO was too large. Resistance unevenness of conductive elastic roller (log
Ω) was 0.9, which was large. Therefore, the conductive elastic roller was not suitable for practical use.

[0054]

As is clear from the above description, according to the present invention, a relatively low resistance value as a whole is obtained, the resistance unevenness is small, the hardness is low, the moldability is excellent, and the ozone resistance is improved. Thus, a conductive rubber composition having excellent properties can be obtained. Therefore, the conductive rubber composition is formed into, for example, a tube to form a conductive roller, and the conductive roller is applied to a transfer roller or a developing roller used in an image forming apparatus in which ozone is present, so that the conductive roller is stable. Thus, there is an effect that a formed image can be formed.

[Brief description of the drawings]

FIG. 1 is an overall view of a specific example of a conductive elastic roller using a conductive rubber composition of the present invention as a rubber elastic layer.

FIG. 2 is a schematic view showing a method for measuring the electric resistance of a conductive elastic roller.

FIG. 3 is a perspective view (A) and a sectional view (B) of a conductive drum.
It is.

FIG. 4 is a perspective view of another specific example (conductive elastic drum) of a conductive elastic roller using the conductive rubber composition of the present invention as a rubber elastic layer.

FIG. 5 is a schematic view showing a method for measuring electric resistance unevenness of a conductive elastic roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Tube of conductive rubber composition 2 Conductive shaft 10 Conductive elastic roller

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 15/16 G03G 15/16

Claims (3)

[Claims] An acrylonitrile content of 18 to 40% by weight.
Acrylonitrile butadiene rubber having a Mooney viscosity of 30 to 60 at 100 ° C. and epichlorohydrin rubber having an ethylene oxide content of 10 to 40 mol% in a weight ratio (acrylonitrile butadiene rubber: epichlorohydrin rubber) of 80:20 to 20: An electrically conductive rubber composition containing the composition at a ratio of 80. 2. A conductive elastic roller formed by fitting a conductive core member into an inner diameter portion of a tubular molded body of the conductive rubber composition according to claim 1. 3. The conductive elastic roller according to claim 2, wherein the electric resistance is in the range of 10 ³ Ω to 10 ¹⁰ Ω.