JP2000302921A - Conductive rubber composition and conductive belt using the same - Google Patents

Abstract

(57) [Problem] To provide a conductive belt having both excellent elasticity and high rigidity and capable of both preventing image disturbance and suppressing meandering. A conductive belt is formed from a conductive rubber composition comprising 40 parts by weight or more and 100 parts by weight or less of silica mixed with 100 parts by weight of a rubber mainly composed of epichlorohydrin rubber. The terminal hydroxyl group of silica is masked with a masking substance such as a silane coupling agent.
Tensile stress M ₁₀₀ when this conductive belt is stretched by 100%
Is a 80kgf / cm ² or more 120kgf / cm ^2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used in an image forming apparatus such as a copying machine, a printer, a facsimile, etc., in which an image is formed by an electrophotographic system or an electrostatic printing system.
The present invention relates to a conductive rubber composition suitable for a conductive belt, a conductive roller, and the like, and a conductive belt using the conductive rubber composition.

[0002]

2. Description of the Related Art Various belts such as an intermediate transfer belt, a transport belt, a transfer belt, a fixing belt, and a developing belt are used in an image forming apparatus. For example, when an image is formed by an electrophotographic image forming apparatus using an intermediate transfer belt, first, an electrostatic latent image is formed on a photosensitive drum. Next, toner is supplied onto the photosensitive drum to form a toner image. This toner image is temporarily transferred from the photosensitive drum to the intermediate transfer belt, and further transferred from the intermediate transfer belt to a printing medium such as paper and fixed. Thus, a desired image is printed. The electrical resistance of the intermediate transfer belt needs to be about 10 ⁴ Ω to 10 ¹² Ω (that is, conductive) due to the toner image transfer mechanism.

[0003] In order to make the belt conductive, a rubber composition in which conductive powder such as carbon black is blended with rubber is sometimes used. However, this conductive belt has a problem that the electric resistance depends on the applied voltage, and a constant resistance value cannot be obtained. Also, in this conductive belt, there is no linear relationship between the amount of the conductive powder and the electrical resistance, and there is a region where the electrical resistance changes extremely due to a slight difference in the amount of the conductive powder. There is also a problem that it is difficult to set a stable electric resistance.

Examples of conductive belts whose electric resistance hardly depends on applied voltage include epichlorohydrin-ethylene oxide copolymer, acrylonitrile-butadiene copolymer, hydrogenated acrylonitrile-butadiene copolymer, chloroprene rubber, acrylic rubber, urethane rubber and the like. In some cases, rubber that is ion-conductive and has a small electric resistance of the polymer itself is used. Such a rubber composition is disclosed in, for example, JP-A-9-59434.

However, when this rubber composition is used for, for example, an intermediate transfer belt, distortion such as elongation tends to occur because of the rubber. When the distortion occurs, the rotation speed of the intermediate transfer belt with respect to the rotation speed of the drive shaft decreases,
The toner image on the intermediate transfer belt is disturbed, and the electrostatic latent image cannot be accurately reproduced on the printing medium.
In particular, in color printing, four color toners of black, magenta, cyan, and yellow are used, so that the relative positions of the respective toners are shifted due to the extension of the intermediate transfer belt, and color unevenness, image unevenness, and the like are likely to occur. . In order to prevent the image from being disturbed, an intermediate transfer belt that has high rigidity and hardly causes distortion is required.

JP-A-63-31263 discloses a conductive belt in which a conductive powder is dispersed in a highly rigid resin such as polyimide. The use of the high rigidity resin increases the rigidity of the intermediate transfer belt. Thereby, distortion of the intermediate transfer belt is suppressed, and image disturbance such as color unevenness is suppressed.

However, since the conductive belt made of such a high-rigidity resin is inferior in elasticity, there is a problem that a tension jig such as a tensioner is required to maintain the tension of the belt while being stretched. is there. Further, when this conductive belt is used, there is also a problem that the conductive belt meanders due to poor elasticity.

[0008]

As described above, the conductive belt made of rubber has excellent elasticity but insufficient rigidity.
A conductive belt made of a high-rigidity resin is excellent in rigidity but inferior in elasticity. To achieve both image distortion prevention and meandering suppression, a conductive belt that has both excellent elasticity and high rigidity is required.
In fact, such conductive belts have not been provided yet. The present invention has been made in view of such a problem, and provides a conductive belt having both excellent elasticity and high rigidity, and a conductive rubber composition suitable for the conductive belt and the like. That is the purpose.

[0009]

Means for Solving the Problems The invention made to achieve the above-mentioned object is to provide a conductive material comprising 100 parts by weight of a rubber mainly composed of epichlorohydrin rubber and 40 parts by weight or more and 100 parts by weight or less of silica. Rubber composition.

[0010] The molded article molded from the conductive rubber composition of the present invention has the inherent elasticity of rubber. Further, since silica is compounded in the rubber composition, the silica acts as a reinforcing agent, and the rigidity of the molded article is increased. That is, by using the conductive rubber composition of the present invention, a molded article having both excellent elasticity and high rigidity can be obtained. Such a conductive rubber composition is suitable for a conductive belt requiring particularly excellent elasticity and high rigidity.

In the present invention, the silica is preferably one in which the terminal hydroxyl groups are masked. Usually, silica has a hydroxyl group (silanol group) or a siloxane group on its surface. When this silica is blended into epichlorohydrin rubber, hydroxyl groups and siloxane groups have a correlation with each other by hydrogen bonds, or have a correlation with rubber molecules by hydrogen bonds,
At the time of kneading due to an increase in the viscosity (Mooney viscosity) of the rubber composition,
Workability at the time of extrusion etc. will be reduced. When the terminal hydroxyl group of silica is masked, hydrogen bonding between silica particles or between silica and rubber molecules is suppressed, and an increase in viscosity is suppressed. Specifically, the terminal hydroxyl group of the silica reacts with another compound (hereinafter, referred to as a “masking substance”), whereby the silica surface is covered with the masking substance and hydrogen bonding is suppressed.

Preferred masking substances include silane coupling agents. Since the silane coupling agent causes a chemical reaction (e.g., a vulcanization reaction) with epichlorohydrin rubber or the like, the effect of reinforcing the molded product is enhanced.

In the conductive belt of the present invention, in order to achieve both excellent elasticity and high rigidity, the tensile stress at 100% elongation is 80 kgf / cm ² or more and 120 kgf / cm ^2.
It is preferably 2.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive rubber composition of the present invention is mainly composed of epichlorohydrin rubber. Epichlorohydrin rubber is a copolymer of epichlorohydrin and ethylene oxide, and may contain a third component. Examples of the third component include allyl glycidyl ether and the like. Since allyl glycidyl ether has an unsaturated bond, its inclusion as a third component enables cross-linking of epichlorohydrin rubber with sulfur or the like. Epichlorohydrin rubber is an ionic conductive rubber, and is a rubber having a small electric resistance of the polymer itself.
Therefore, by using this epichlorohydrin rubber, conductivity is imparted to the rubber composition. of course,
A conductive powder such as carbon black and metal powder may be blended with the epichlorohydrin rubber to further improve the conductivity.

In the conductive rubber composition of the present invention, another rubber may be blended with the epichlorohydrin rubber. As the rubber to be blended, for example, acrylonitrile-
In addition to ion conductive rubbers such as butadiene copolymer, hydrogenated acrylonitrile-butadiene copolymer, chloroprene rubber, acrylic rubber, and urethane rubber, natural rubber, butadiene rubber, EPDM, styrene-butadiene rubber, isoprene rubber and the like are included. . When epichlorohydrin rubber is blended with another rubber, the proportion of epichlorohydrin rubber in the total rubber is preferably at least 50% by weight, more preferably at least 80% by weight in order not to impair the properties of the epichlorohydrin rubber. .

The conductive rubber composition of the present invention contains silica. Usually, precipitated silica is used.
The precipitated silica has a particle diameter of 10 nm to 30 nm.
These particles are of the order of magnitude, and these particles form a structure in a row like grapes. Since silica acts as a reinforcing agent, the rigidity of a molded article (for example, a conductive belt) formed from the conductive rubber composition is increased.

The compounding amount of silica must be 40 parts by weight or more and 100 parts by weight or less with respect to 100 parts by weight of rubber.
In particular, it is preferably from 45 parts by weight to 70 parts by weight. If the amount is less than the above range, the rigidity of the molded product may be insufficient. Conversely, if the amount exceeds the above range, not only may the electrical resistance of the conductive rubber composition increase, but also the processability may decrease.

The silica used in the conductive rubber composition of the present invention preferably has a terminal hydroxyl group masked with a masking substance. A mask is a reaction in which terminal hydroxyl groups react with a masking substance, whereby the silica surface is covered with the masking substance. Since the masked silica has low reactivity with the rubber molecules, the increase in the viscosity of the conductive rubber composition due to the bonding between the silica and the rubber molecules is suppressed.

Examples of the masking substance include silane coupling agents, silylating agents, ethylene glycol, polyethylene glycol, propylene glycol and the like. Among these masking substances, a silane coupling agent is preferable because it can cause a chemical reaction (for example, a vulcanization reaction) with a base rubber such as epichlorohydrin rubber. Examples of the silane coupling agent to be used include bis (3-triethoxysilylpropyl) tetrasulfane, 3-mercaptopropyltrimethoxysilane and the like. Specific examples of silica masked with a silane coupling agent include, for example, trade names “Capsil 8113”, “Capsil 8108”, and “Capsil 7108” of Degussa Corporation.

The conductive rubber composition of the present invention is usually used after being crosslinked. The cross-linking form is not particularly limited, but it is generally cross-linked with a cross-linking agent such as, for example, triazine, sulfur or peroxide. In particular, triazine is preferable because the tensile stress of the molded article can be set relatively large. When the conductive rubber composition is crosslinked with a triazine, it is preferable that a metal oxide as an acid acceptor is blended. Suitable metal oxides include zinc oxide and magnesium oxide.

The conductive rubber composition of the present invention can be obtained by kneading epichlorohydrin rubber, silica, a cross-linking agent, other additives and the like, for example, with an internal mixer. The conductive rubber composition is molded by a known molding method such as an extrusion molding method, and is crosslinked to obtain a desired molded article. Of course, molding and crosslinking may be performed in the same step.

A preferred use of the conductive rubber composition of the present invention is a conductive belt. Specifically, the conductive rubber composition is used for an intermediate transfer belt, a transport belt, a transfer belt, a fixing belt, a developing belt, and the like of an image forming apparatus. Since the conductive belt formed from the conductive rubber composition of the present invention is mainly composed of epichlorohydrin rubber, it has a high elasticity inherent in rubber. For this reason, tension is maintained for a long period of time, for example, in a state of being stretched and stretched between pulleys. Therefore, a tension jig such as a tensioner is not required. Further, since the conductive belt is rich in elasticity and easily deformed, meandering during use is suppressed.

The rigidity of the conductive belt is increased by the addition of silica, and the distortion during rotation is small. Therefore, the reduction in the rotation speed of the conductive belt with respect to the rotation speed of the drive shaft can be suppressed. Therefore, for example, when this conductive belt is used for the intermediate transfer belt, the disturbance of the image due to the disturbance of the toner image is suppressed, and the electrostatic latent image can be accurately reproduced on the printing medium. In particular, even in the case of color printing, since the relative positional relationship between the four color toners of black, magenta, cyan and yellow does not shift, color unevenness and the like are prevented.

Tension at the time of 100% extension of this conductive belt
Stress M₁₀₀Is 80 kgf / cm ²More than 120kgf
/ Cm²The following is preferable, and 90 kgf / cm²Above 11
5kgf / cm²The following are particularly preferred. Tensile stress M
₁₀₀Is less than the above range, the rigidity of the conductive belt is
In some cases, the temperature may be reduced to easily cause distortion.
Conversely, the tensile stress M₁₀₀Exceeds the above range, conductive
Belt elasticity decreases and meandering is likely to occur
Sometimes.

[0025]

EXAMPLES Hereinafter, the effects of the present invention will be clarified based on examples, but it is needless to say that the present invention should not be construed as being limited based on the description of the examples.

Example: 100 parts by weight of epichlorohydrin rubber (trade name "Epichromer CG102" of Daiso), 60 parts by weight of silica masked with a silane coupling agent (trade name "Capsil 8113" of Degussa) Triazine (trade name “OF-10” of Daiso Corporation)
0 ") 5 parts by weight and 5 parts by weight of zinc oxide as an acid acceptor were charged into a 10 liter kneader and kneaded at 140 ° C. for 20 minutes to obtain a conductive rubber composition of Example.

Comparative Examples 1 and 2 The conductive rubber compositions of Comparative Examples 1 and 2 were the same as in the Examples except that the amount of silica was varied as shown in Table 1 below. I got something.

[Comparative Example 3] 20 parts by weight of chloroprene rubber (neoprene WRT, trade name of Showa Denko DuPont) and EPDM rubber (trade name, Esplen 5 of Sumitomo Chemical Co., Ltd.)
05A ") and 80 parts by weight of acetylene black (carbon black by Denka Kagaku, trade name" DENKA BLACK ")
25 parts by weight and 3 parts by weight of sulfur were charged into a 10 liter kneader and kneaded at 120 ° C. for 10 minutes to obtain a conductive rubber composition of Comparative Example 3.

Comparative Example 4 A conductive belt formed by a centrifugal molding method was obtained from a resin composition in which 15 parts by weight of carbon black was blended with 100 parts by weight of a polyimide, and Comparative Example 4 was obtained.

[Measurement of Tensile Stress] A conductive rubber composition of each of Examples and Comparative Examples 1 to 3 was filled in a mold and vulcanized at a vulcanization temperature of 180 ° C. for 20 minutes to obtain a slab having a thickness of 2 mm. It was created. This slab is JIS dumbbell 1 with a cutting machine
I punched it into a letter. Further, the conductive belt of Comparative Example 4 was
Similarly, it was punched into a JIS dumbbell No. 1. Using these test pieces, in accordance with JIS-K6301, 50 mm
/ Subjected to a tensile test at a tensile speed of min, to determine the tensile stress _{M 100} at 100% elongation. The results are shown in Table 1 below.

[Sandering test] The conductive rubber compositions of Examples and Comparative Examples 1 to 3 were extruded in a belt shape by an extruder, crosslinked in a vulcanizer at 180 ° C. for 30 minutes, and further polished on the surface Thus, a conductive belt was obtained. These conductive belts and the conductive belt of Comparative Example 4 were subjected to a meandering test. In the meandering test, the conductive belt was stretched on a pulley in a stretched state of 5% and rotated at a rotation speed of 75 rpm for 100 hours. Then, the amount of displacement of the conductive belt after rotation was measured. The results are shown in Table 1 below. The greater the meandering of the conductive belt, the greater the amount of this deviation.

[Measurement of Volume Specific Resistance] The volume specific resistance (Ω · Ω) of the conductive belts of Examples and Comparative Examples 1 to 4 was measured.
cm). Measurements were taken along the circumference of the belt.
The test was performed at four locations along the longitudinal direction. The logarithmic value (log) of the obtained volume resistivity was obtained, and an average and unevenness (a value obtained by subtracting the minimum value from the maximum value) were derived. These results are shown in Table 1 below.

[Measurement of Speed Reduction Ratio] The conductive belts 1 of Examples and Comparative Examples 1 to 4 were subjected to speed reduction ratio evaluation. First, as shown in FIG.
The conductive belt 1 was stretched between the drive shaft 3 and the driven shaft 5 of the m. Then, a weight 7 having a weight of 10 kg was hung on the driven shaft 5 to apply tension to the conductive belt 1. Next, drive shaft 3
Was rotated in the direction indicated by arrow A. The rotation speed is 7
It was set to 5 rpm. In this state, the rotation speed of the driven shaft 5 was measured. Further, the number of rotations when a load of 2.0 kgf / cm ² was applied to the driven shaft 5 by the powder brake motor was also measured. The rotation speed when no load is applied is R1
And when the rotation speed when a load is applied is R2,
The value represented by the following formula ((R1−R2) / R1) × 100 (%) was taken as the speed reduction rate. The measurement is
The test was performed under the conditions of a room temperature of 23 ° C. and a humidity of 55%. The measurement results are shown in Table 1 below.

[0034]

[Table 1]

The permissible range for each evaluation item in Table 1 is as follows:
The meandering test deviation is 8 mm or less, and the volume resistivity is 7
It is 11 or less, especially 8 or more, 10 or less, the volume resistivity logarithm unevenness is 0.5 or less, especially 0.3 or less, and the speed reduction rate is 1.0 or less. In Table 1, the conductive belt of Comparative Example 1 is small tensile stress M ₁₀₀ is, the speed reduction ratio is has become larger. Further, since the conductive belt of Comparative Example 2 is greater tensile stress M ₁₀₀ is, the amount of meander test deviation is has become larger. The conductive rubber composition of Comparative Example 2 was poor in workability during kneading and extrusion. Further, since the conductive belt of Comparative Example 3 is smaller tensile stress M ₁₀₀ has the speed reduction ratio has become large and larger volume resistivity logarithm unevenness. The conductive belt of Comparative Example 4 had a tensile stress M ₁₀₀
Therefore, the deviation amount of the meandering test has increased. On the other hand, the conductive belts of the examples show good values in all evaluation items. These evaluation results confirmed the superiority of the present invention.

The present invention has been described above by taking an intermediate transfer belt as an example. However, the conductive rubber composition of the present invention can be used for various conductive materials such as a conductive belt other than the intermediate transfer belt and a conductive roller. It can be used for applications.

[0037]

As described above, according to the conductive rubber composition of the present invention, a molded product having both excellent elasticity and high rigidity can be obtained. Further, according to the conductive belt of the present invention, both prevention of image disturbance and suppression of meandering are achieved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a state of a speed reduction rate test.

[Explanation of symbols]

 Reference Signs List 1 conductive belt 3 drive shaft 5 driven shaft 7 weight

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G03G 15/20 102 G03G 15/20 102 F term (Reference) 2H032 BA09 BA18 DA13 2H033 BA08 BA10 BA11 BA12 BA17 BA19 2H077 AD07 FA22 FA25 3F049 BA13 LA02 LA05 LA07 LB03 4J002 AC012 AC032 AC062 AC072 AC092 AC112 BB152 BC052 BG042 BP022 CH041 CK022 DJ016 FB086 FB096 FB266 FD110 FD140 GM01 GQ02

Claims (5)

[Claims] 1. A conductive rubber composition comprising 100 parts by weight of a rubber mainly composed of epichlorohydrin rubber and 40 parts by weight or more and 100 parts by weight or less of silica. 2. The conductive rubber composition according to claim 1, wherein the silica has a terminal hydroxyl group masked. 3. The conductive rubber composition according to claim 2, wherein the terminal hydroxyl group of the silica is masked by a reaction with a silane coupling agent. 4. A conductive belt using the conductive rubber composition according to any one of claims 1 to 3. 5. A tensile stress at 100% elongation is 80 kgf.
Conductive belt according to claim 4, which is / cm ² or more 120 kgf / cm ^2.