JP2006105374A - Conductive roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductive roll capable of reducing environment dependence of electric resistance while keeping a sufficiently low resistance value, hardly contaminating other members by bleeding and bloom of constituents, having superior ozone resistance and stability in dimension, and inhibiting the increase of resistance in continuous power distribution. <P>SOLUTION: In this conductive roll comprising a core and a conductive elastic layer formed on a surface of the core, the conductive elastic layer 11 is composed of a continuous phase and one or more non-continuous phases, and an ion conductive agent of 1-20 wt% is mixed and included in advance only in the non-continuous layers composed of ethylene oxide-propylene oxide-allyl glycidyl ether copolymer. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a conductive roll, and more particularly to a conductive roll that can suppress an increase in resistance during energization, reduce a change in resistance value, and reduce environmental fluctuations.

In an electrophotographic apparatus such as a copying machine, a printer or a facsimile, a conductive rubber roll is used as a charging roll, a developing roll, a toner supply roll or a transfer roll.
These conductive rubber rolls need to have a moderately stable electric resistance value. In particular, the transfer roll is a member used to transfer the electrostatic latent image formed on the photoconductor to paper, and the electrical resistance value is an important parameter in terms of function.

Conventionally, as a method for imparting conductivity to this type of rubber roll, there are a method using an electronic conductive rubber and a method using an ionic conductive rubber.
The electronic conductive rubber is obtained by blending a polymer with a conductive filler such as metal oxide powder or carbon black. The conductive rubber roll using the electronic conductive rubber has a problem that it is difficult to control the electric resistance value. In particular, when carbon black is used as a conductive filler, there is no stable correlation between the amount of carbon black added and the volume resistivity of the polymer, and there is a slight change in the amount of carbon black added. Since there is a region where the electric resistance value changes rapidly, it is very difficult to control the electric resistance value. Furthermore, there is a problem that the electric resistance value itself tends to depend on the applied voltage.

  In addition, since the conductive filler is difficult to uniformly disperse in the polymer, specifically the elastomer, the electric resistance value tends to vary in the circumferential direction and the width direction of the rubber roll. Furthermore, even if the large variation in the electric resistance value is reduced, the variation in the electric resistance value in a minute range on the order of μm still exists. For this reason, in recent years when technology for improving image quality such as digitization and colorization is remarkable, ion conductive rubber tends to be used more favorably than electronic conductive rubber.

In order to obtain ionic conductivity, a technique of using ionic conductive rubber such as acrylonitrile butadiene rubber, urethane rubber or epichlorohydrin rubber alone or in combination and further blending with other materials is employed.
When acrylonitrile butadiene rubber or urethane rubber is used, the volume resistivity value of the rubber material is only 10 ^9.6 Ωcm or more, and the electrical resistance value of the roll is only ^108.2 Ω or more. It cannot be used for applications requiring a relatively low electrical resistance value such as a transfer roll in an electrophotographic apparatus.
Further, there is a problem that ozone resistance is not good only with acrylonitrile butadiene rubber.
Therefore, blending of acrylonitrile butadiene rubber having high electric resistance with epichlorohydrin rubber having low electric resistance has been performed. In this way, the electrical resistance can be adjusted simply by changing the blend ratio, and the electrical resistance can be easily controlled.

However, when epichlorohydrin rubber is used, there is a problem that toxic hydrogen chloride gas or dioxin may be generated during incineration. Particularly, in recent years, environmental issues have become very important, and it is demanded to use a material having a low possibility of environmental pollution even in the conductive roll, and it is also required to enable recycling.
Furthermore, since epichlorohydrin rubber has a large electrostatic capacity, there is also a problem that the time difference from when a voltage is applied to when a current flows is large. In particular, as the electrophotographic mechanism increases in speed, it is required to obtain a stable current from voltage application.

Therefore, development of a conductive rubber composition having a low electrical resistance value and not using epichlorohydrin rubber has been underway.
For example, in Japanese Patent Application Laid-Open No. 2002-212413 (Patent Document 1), the applicant of the present application is 100% by weight of a conductive polymer obtained by mixing an ethylene oxide-propylene oxide-allyl glycidyl ether terpolymer and acrylonitrile butadiene rubber. On the other hand, a conductive rubber composition is provided in which a non-halogen quaternary ammonium salt is blended at a ratio of 0.1 wt% or more and 7.0 wt% or less.
However, the conductive rubber composition described in Patent Document 1 does not consider the environmental dependency of the electrical resistance value, and there is room for improvement from this viewpoint.

On the other hand, in order to obtain ionic conductivity, there is also a technique of blending a conductive oligomer containing a polyether structure such as polyethylene oxide or a conductive plasticizer (both Mn is 10,000 or less).
The conductive oligomer or conductive plasticizer must be added in a certain amount for adjusting the electric resistance, and since it is not fixed in the polymer composition, there is a problem that it causes bleed and bloom. is there. In particular, when used as a conductive roll for a copying machine or a printer, if a conductive oligomer or conductive plasticizer migrates, the photosensitive member is contaminated, the image is stained, and in the worst case, the photosensitive member is altered or destroyed. In some cases.

Therefore, there is a method of blending a low molecular weight ionic conductive agent instead of the conductive oligomer or the conductive plasticizer. As this technique, the present applicant has proposed using an organometallic salt containing a fluoro group and / or a sulfonyl group as a conductive agent in Japanese Patent Application Laid-Open No. 2004-18788 (Patent Document 2).
However, there is a problem that the resistance is likely to increase when energized continuously even when a conductive oligomer or conductive plasticizer is used or when a low molecular weight ionic conductive agent is used. This is because the ionic conductive agent causes electricity to flow by polarization, and therefore, if polarization occurs continuously, the electric charge is biased with respect to the applied voltage.
JP 2002-212413 A JP 2004-18788 A

  The present invention has been made in view of the above-described problems. The resistance value hardly increases even during continuous energization, and the environmental dependency of the electrical resistance is reduced while maintaining a low resistance value. Another object of the present invention is to provide a conductive roll that is less contaminated by other members due to odor and bloom, and that is excellent in ozone resistance and dimensional stability.

In order to solve the above problems, the present invention is a conductive roll comprising a cored bar and a conductive elastic layer on the surface of the cored bar,
The conductive elastic layer is composed of a continuous phase and one or more discontinuous phases.
An ionic conductive agent is premixed in a proportion of 1 to 20% by weight only in the discontinuous layer composed of an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer, and
With respect to a total of 100 parts by mass of the polymer constituting the continuous phase and the polymer constituting the discontinuous phase, the content of the polymer constituting the continuous phase is 60 parts by mass or more and less than 80 parts by mass, and the conductive agent The content of the ethylene oxide-propylene oxide-allyl glycidyl ether copolymer containing 1 to 20% by weight is 1 to 25 parts by mass, and a conductive roll is provided.

The present inventor has repeatedly studied the mechanism of resistance increase during continuous energization, and when an ionic conductive agent is introduced into the continuous phase, ions tend to move, and thus ion bias tends to occur. It became difficult to flow, and as a result, it was found that the resistance value increased.
As a result of further investigation based on such knowledge, an ionic conductive agent is mixed in advance only with the EO-PO-AGE copolymer used as the resistance adjusting agent, and the EO-PO-AGE copolymer containing the ionic conductive agent is mixed. The present inventors have found that it is possible to suppress an increase in resistance during continuous energization by making the polymer a discontinuous phase independent of the continuous phase and making the ionic conductive agent difficult to move to the continuous phase.
In addition, when the ionic conductive agent is included in the discontinuous phase as described above, contamination of other members due to bleed or bloom of the ionic conductive agent can be reduced. Furthermore, since the ionic conductive agent is present in the discontinuous phase, it is not easily affected by the environment such as temperature and humidity, and the environmental dependency of the electrical resistance value can be reduced.

The content of the ionic conductive agent contained in the EO-PO-AGE copolymer is 1 to 20% by weight. The amount of the EO-PO-AGE copolymer is X (% by weight), and the content of the ionic conductive agent is When Y (% by weight) is indicated, the value of {Y / (X + Y)} × 100 is included in the range of 1-20.
The content of the ionic conductive agent is set to 1 to 20% by weight. When the content is less than 1% by weight, the electrical dependency of the electrical resistance increases. On the other hand, when the content is more than 20% by weight, the resistance during continuous energization By increasing the rise.

  In addition, with respect to a total of 100 parts by mass of the polymer constituting the continuous phase and the polymer constituting the discontinuous phase, the content of the polymer constituting the continuous phase is 60 parts by mass or more and less than 80 parts by mass. When the blending ratio of the polymer constituting the continuous phase is less than 60 parts by mass, it becomes difficult to exist as a continuous phase even if a technique such as dynamic crosslinking is used. On the other hand, if it is 80 parts by mass or more, the volume fraction of the discontinuous phase becomes too low, and the resistance value of the conductive roll of the present invention cannot be sufficiently lowered.

  Furthermore, the amount of the EO-PO-AGE copolymer containing the conductive agent is 1 part by mass or more and 25 parts by mass or less because if it exceeds 25 parts by mass, the compression set of the conductive roll of the present invention increases. On the other hand, when the amount is less than 1 part by mass, a sufficient amount of the conductive agent cannot be blended, and the resistance value of the conductive roll of the present invention cannot be sufficiently reduced.

  In the present invention, the electric resistance value can be controlled to some extent by changing the ratio of the continuous phase and the discontinuous phase while fixing the blending amount of the conductive agent. Further, if dynamic crosslinking is used, a relatively high fraction component can be brought into the discontinuous phase, and the ratio of the polymer constituting the discontinuous phase can be increased.

The conductive agent used in the present invention is preferably an ionic conductive agent containing a fluoro group or a sulfonyl group. Specifically, an organometallic salt containing a fluoro group or / and a sulfonyl group is more preferable, and a salt having an anion having a fluoro group or / and a sulfonyl group is more preferable.
Such a salt exhibits a higher degree of dissociation because a functional group such as a fluoro group or a sulfonyl group has an electron-withdrawing property and an anion is further stabilized. Thereby, a very low electrical resistance value can be obtained with a small amount of addition. Furthermore, when such a highly conductive salt is used, the constitution of including a conductive agent in the discontinuous phase employed in the present invention and keeping it independent is particularly remarkable in preventing resistance increase during continuous use. Exerts a positive effect. That is, the salt with high conductivity as described above is particularly easy to move in the system. Therefore, if the salt with high conductivity is introduced into the continuous phase, the ion bias becomes very large, and resistance during continuous use is increased. The rise is likely to be significantly greater than salts with low conductivity.

In the conductive roll of the present invention, the conductive elastic layer is
When it consists of two phases of a continuous phase and a discontinuous phase composed of an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer containing 1 to 20% by weight of a conductive agent;
A continuous phase, a first discontinuous phase composed of an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer containing 1 to 20% by weight of a conductive agent, an ethylene propylene diene copolymer rubber (hereinafter referred to as "EPDM") May be composed of three phases of the second discontinuous phase.

In the case of the above-described three phases, the presence of a discontinuous phase composed of EPDM as a discontinuous phase not containing a conductive agent can provide ozone resistance to the conductive roll of the present invention. There are advantages.
In addition, the first discontinuous phase, the second discontinuous phase, and the continuous phase may each be composed of two or more polymers, and even if each of them is finely divided into a plurality of phases, the gist and effect of the present invention are achieved. It doesn't matter if it is satisfied.

Furthermore, when there is a first discontinuous phase composed of an EO-PO-AGE copolymer containing a conductive agent) and a second discontinuous phase composed of EPDM, It is preferable to exist so as to surround the second discontinuous phase.
The phase structure of the continuous phase and the discontinuous phase in the present invention can be observed, for example, with a phase mode of an atomic force microscope (AFM) type scanning probe microscope (SPM).

  Moreover, when it is set as the three phases of the said continuous phase and a 1st, 2nd discontinuous phase, the 1st discontinuous layer which contained the said ion conductive agent with respect to a total of 100 mass parts of these three-phase polymers. It is preferable that the polymer of 1-25 mass parts and the polymer of the 2nd discontinuous layer which consists of ethylene propylene diene copolymer rubber shall be 5-30 mass parts.

By setting it as the said structure, the ratio of the 1st discontinuous phase containing a electrically conductive agent can be suppressed, without impairing electroconductivity very much. As a result, even if the blending amount of the conductive agent is reduced, a low electrical resistance value can be maintained in the conductive roll of the present invention.
In addition, the affinity between the polymer of each phase and the conductive agent is evaluated from the volume resistivity of the polymer of each phase described later and the volume resistivity of the polymer of each phase in a state including the conductive agent. It can be said that the lower the rate, the higher the affinity between the polymer and the conductive agent.

When the volume resistivity of the EO-PO-AGE copolymer is R1, and the volume resistivity of the polymer constituting the continuous phase is R2, it is preferable that 0.2 ≦ log ₁₀ R2−log ₁₀ R1 ≦ 5. More preferably, 0.5 ≦ log ₁₀ R2-log ₁₀ R1 ≦ 4, and further preferably 1 ≦ log ₁₀ R2-log ₁₀ R1 ≦ 3.
This is because when the value of the above formula is smaller than 0.2, the conductive agent easily shifts to the continuous phase. On the other hand, if the value of the above equation is larger than 5, it is difficult to realize low resistance as a whole.

  As the polymer constituting the continuous phase, acrylonitrile butadiene rubber (hereinafter referred to as NBR) is preferable among polymers satisfying the above conditions, and among them, low nitrile NBR and / or medium-high nitrile NBR is more preferable. By using NBR in the continuous phase, it is possible to make the resistance value as low as possible as a whole, and to prevent the transfer of the conductive agent and the increase in resistance during continuous energization. Note that low nitrile NBR is particularly preferable as the material for the continuous phase. This is because the low nitrile NBR has a low electric resistance value to some extent and a low Tg, so that the temperature dependency of viscoelasticity near room temperature is small, thereby reducing the environmental dependency of the electric resistance value. Moreover, as polymer Tg which comprises a continuous phase, -40 degrees C or less is preferable, and -50 degrees C or less is more preferable.

  Furthermore, in the conductive elastic layer of the present invention, 0.5 to 5 parts by mass of a vulcanizing agent, 1 to 10 parts by mass of carbon, and a foaming agent with respect to 100 parts by mass of the polymer of the continuous phase and the discontinuous phase. 3 to 12 parts by mass, and 10 to 60 parts by mass of an inorganic filler such as calcium carbonate is preferable.

Since the conductive roll of the present invention is configured as described above, it is possible to prevent an increase in resistance during continuous energization. As an index thereof, a roll resistance value R [Ω] in an environment of 23 ° C. and a relative humidity of 55%, and a roll resistance value R100 [Ω] in the same environment when a constant voltage of 1000 V is continuously applied for 100 hours, Preferably have a relationship of log ₁₀ R100−log ₁₀ R ≦ 0.5. This is because if the value of the above formula exceeds 0.5, the increase in resistance during continuous energization increases, which may impede practical use.

Since the conductive roll of the present invention has a low electrical resistance value, it can be used for applications requiring a relatively low electrical resistance value, such as a transfer belt or a transfer roll of a color electrophotographic apparatus.
Specifically, the roll resistance value R [Ω] in an environment of 23 ° C. and relative humidity 55% is log _10.
R <0.9 is preferred. When the roll resistance value is larger than the above range, good conductivity cannot be obtained when the conductive member is used, and the roll resistance value is not suitable for practical use.

The conductive roll of the present invention has a low electrical resistance environment dependency. As an index, a roll resistance value RLL [Ω] under an environment of 10% relative humidity 20% and a roll resistance value RHH [Ω] under a condition of 32% relative humidity 80% are expressed as Δlog ₁₀ R = log It is preferable to have a relationship of ₁₀ RLL-log ₁₀ RHH ≦ 1.5.
This is because if the index value of the environmental dependency of the roll resistance value is larger than 1.5, the resistance value changes greatly due to the environmental change, so that a larger power source is required, and the electrophotographic apparatus using such a conductive roll This is because power consumption and product cost increase.

Furthermore, the conductive roll of the present invention was measured in accordance with a vulcanized rubber and thermoplastic rubber permanent strain test method described in JIS K 6262 under the conditions of a measurement temperature of 70 ° C., a measurement time of 22 hours, and a compression rate of 25%. The permanent set is preferably 30% or less.
This is because if the compression set is larger than 30%, the dimensional change becomes too large to be suitable for practical use. In addition, More preferably, it is 25% or less, and it is so good that it is small.

  The use of the conductive roll of the present invention is not particularly limited, but it is suitably used as an intermediate transfer roll in an image forming apparatus such as a copying machine, a printer, or a facsimile. The conductive roll of the present invention includes a charging roll for uniformly charging the photosensitive drum, a developing roll for attaching the toner to the photosensitive member, a toner supply roll for transporting the toner, and a transfer belt from the inside. It can also be used as a drive roll for driving.

  The conductive elastic layer of the conductive roll according to the present invention includes a continuous phase and one or more discontinuous phases. In this way, while controlling the morphology, the ionic conductive agent is unevenly distributed in the discontinuous phase composed of the EO-PO-AGE copolymer, and is independent of the continuous phase. A low electrical resistance value necessary for practical use can be obtained while preventing an increase in resistance during energization. In addition, a small increase in resistance during continuous energization has the effect of improving durability and extending product life.

In the conductive roll according to the present invention, the environmental dependency of electrical resistance is also kept low, and the quality is improved, for example, stable operability is obtained.
In the conductive roll according to the present invention, the migration of the conductive agent to the outside of the product can be suppressed, and contamination, alteration, and destruction of the member in contact with the conductive roll according to the present invention can be prevented.
By using the conductive roll of the present invention having the effects as described above for a developing roll, a charging roll, a transfer roll or the like of an electrophotographic apparatus, a good image can be stably formed. Therefore, the conductive roll of the present invention is particularly suitable as a conductive roll for a color copying machine or a color printer that requires high image quality.

  In particular, in the conductive elastic layer, a second discontinuous phase not containing an ionic conductive agent is provided, and the first discontinuous phase in which the ionic conductive agent is unevenly distributed is surrounded by the second discontinuous phase. Thus, the volume fraction of the first discontinuous phase in which the conductive agent is unevenly distributed can be suppressed without significantly impairing the conductivity. That is, even when the amount of the first discontinuous phase polymer containing the ionic conductive agent is reduced, a low electrical resistance value as a whole can be obtained. Since a salt having an anion having a fluoro group and a sulfonyl group, which is a conductive agent suitably used in the present invention, is expensive, an increase in cost can be suppressed by reducing the amount of the salt added.

Hereinafter, the conductive roll of the present invention will be described in detail.
As shown in FIG. 1, the conductive roll 10 is attached by press-fitting a core metal 12 into a hollow portion of a cylindrical conductive elastic layer 11. Examples of the core metal 12 include a metal core made of metal such as aluminum, aluminum alloy, SUS or iron, or ceramic.

The schematic structure of the conductive elastic layer 11 of the first embodiment of the conductive roll 10 is shown in FIG.
The conductive elastic layer 11 includes a continuous phase 1, a first discontinuous phase 2, and a second discontinuous phase 3. The three phases have a sea-island structure. The first discontinuous phase 2 and the second discontinuous phase 3 exist substantially uniformly in the continuous phase 1, and the first discontinuous layer 2 exists so as to surround the second discontinuous phase 3. The volume fraction is continuous phase 1> second discontinuous phase 3> first discontinuous phase 2.

  FIG. 3 shows a conductive elastic layer 11 according to the second embodiment. The conductive elastic layer 11 is composed of one continuous phase 1 ′ and one first discontinuous phase 2 ′. One discontinuous phase 2 ′ has a sea-island structure. The volume fraction is continuous phase 1 '> first discontinuous phase 2'.

In any of the embodiments shown in FIGS. 2 and 3, the first discontinuous phase 2, 2 ′ is composed of an EO-PO-AGE copolymer containing 1 to 20% by weight of an ionic conductive agent. As the EO-PO-AGE copolymer, a copolymer having EO: PO: AGE = 90: 4: 6 is preferably used.
On the other hand, the ionic conductive agent is not added to the continuous phase 1, 1 ′ and the second discontinuous phase 3, low nitrile NBR is used as the polymer constituting the continuous phase 1, 1 ′, and the second discontinuous phase 3 EPDM, which is a low-polarity ozone-resistant rubber, is used as a polymer constituting the above.

In the first embodiment shown in FIG. 2, the continuous phase 1 comprising low nitrile NBR is 60-80 parts by mass (preferably 70 parts by mass), and EO-PO-AGE co-polymer containing 1-20% by weight of a conductive agent. The first discontinuous phase 2 made of coalescence is 1 to 25 parts by mass (preferably 10 parts by mass), and the second discontinuous phase 3 made of EPDM is 5 to 30 parts by mass (preferably 20 parts by mass).
In 2nd Embodiment shown in FIG. 3, the 1st discontinuous phase 2 is 20-40 mass parts, and the continuous phase 1 is 60-80 mass parts.

  Examples of the ionic conductive agent blended in the first discontinuous phase 2 by 1 to 20% by weight include lithium-bis (trifluoromethanesulfonyl) imide and lithium-trifluoromethane, which are salts having an anion having a fluoro group and a sulfonyl group. Sulfonate or lithium-tris (trifluoromethanesulfonyl) methane is used. By using these anion-containing salts, it is possible to improve the environmental dependency of the electrical resistance value, and further, the dissociation degree is very large and the EO-PO-AGE copolymer constituting the discontinuous phase This is also preferable from the viewpoint of high compatibility.

  The EO-PO-AGE copolymer used in the first discontinuous phase 2 has a copolymerization ratio set so that the electrical resistance can be reduced while maintaining the physical properties (compression permanent strain and hardness) of the conductive roll. In the copolymer, the ethylene oxide ratio is 55 mol% or more and 95 mol% or less. Ionic conductivity is exhibited because oxonium ions and metal cations in the polymer (for example, lithium ions in the conductive agent) are stabilized by ethylene oxide units and propylene oxide units, By being transported by segment motion. In general, the ethylene oxide unit has higher ion stabilizing power than the propylene oxide unit. Therefore, when the ratio of the ethylene oxide unit is as high as 55 mol% or more and 95 mol% or less, more ions can be stabilized and the resistance can be further reduced.

  The conductive agent is preliminarily mixed with the EO-PO-AGE copolymer, and a known method can be used as the mixing method. For example, after dry blending with a Henschel mixer or tumbler, a blend containing a conductive agent and an EO-PO-AGE copolymer is melt-mixed with a single or twin screw extruder, a Banbury mixer or a kneader. Etc. can be used. You may mix in inert gas atmosphere, such as nitrogen, as needed for the purpose of preventing deterioration of a polymer.

  In the present invention, when a salt is used as a conductive agent, a part of the ions generated from the added salt is converted into a single ion by using an anion adsorbent, etc., so that the conductivity is stabilized and the conductivity is improved when a small amount is added. it can. Examples of the anion adsorbent include synthetic hydrotalcite mainly composed of Mg and Al, Mg-Al-based, Sb-based, or Ca-based inorganic ion exchangers and ion sites that fix anions in the chain ( Known compounds such as co) polymers are useful.

Further, the conductive elastic layer of the present invention contains a vulcanizing agent, a foaming agent, an inorganic filler, carbon and the like.
As the vulcanizing agent to be added, sulfur is particularly preferable because low electrical resistance can be realized. Moreover, when foaming is performed together with vulcanization, it is preferable to use sulfur from the viewpoint of improving the balance between the vulcanization speed and the foaming speed.
In addition, organic sulfur-containing compounds and peroxides can be used as the vulcanizing agent, and these can be used together or sulfur and these can be used together. In particular, when EPDM is used as a polymer constituting the second discontinuous phase, the peroxide phase can effectively vulcanize these rubber phases. Examples of the organic sulfur-containing compound include tetraethylthiuram disulfide or N, N-dithiobismorpholine. Examples of the peroxide include dicumyl peroxide and benzoyl peroxide.
The addition amount of the vulcanizing agent is 0.5 parts by mass or more and 5 parts by mass or less, preferably 1 part by mass or more and 3 parts by mass or less with respect to 100 parts by mass of the polymer component.

Furthermore, a vulcanization accelerator may be blended, and as the vulcanization accelerator, inorganic accelerators such as slaked lime, magnesia (MgO) or risurge (PbO) and organic accelerators described below can be used. Organic accelerators include thiazoles such as 2-mercapto-benzothiazole or dibenzothiazyl disulfide; sulfenamides such as N-cyclohexyl-2-benzothiazylsulfenamide; tetramethylthiuram monosulfide, tetramethylthiuram Examples thereof include thiurams such as disulfide, tetraethylthiuram disulfide or dipentamethylenethiuram tetrasulfide; thioureas and the like, and these can be used alone or in appropriate combination.
The addition amount of the vulcanization accelerator is 0.5 part by mass or more and 5 parts by mass or less, preferably 1 part by mass or more and 4 parts by mass or less with respect to 100 parts by mass of the polymer component.

  Further, a vulcanization acceleration aid may be blended. Examples of the vulcanization acceleration aid include metal oxides such as zinc white; fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid; and other conventionally known vulcanization accelerations. Auxiliaries are mentioned.

Furthermore, as described above, a chemical foaming agent is blended for imparting flexibility and the like, and the addition amount of the foaming agent is 3 parts by mass or more and 12 parts by mass or less with respect to 100 parts by mass of the polymer component.
In addition, for the purpose of improving the mechanical strength, an inorganic filler is blended as necessary within a range that does not impair electrical characteristics and other physical properties. Examples of the filler include powders such as silica, carbon black, clay, talc, calcium carbonate, magnesium carbonate, and aluminum hydroxide. The addition amount of the filler is 60 parts by mass or less with respect to 100 parts by mass of the polymer.
In addition, a softener such as oil, an anti-aging agent, and the like can be blended.

  In the present embodiment, 5 parts by mass of carbon black, 20 parts by mass of light calcium carbonate, 1.5 parts by mass of powdered sulfur as a vulcanizing agent, 1.5 parts by mass of each of the two vulcanization accelerators, 0. 5 parts by mass, 6 parts by mass of a foaming agent, and 6 parts by mass of a foaming aid are blended.

The electroconductive elastic layer of the electroconductive roll of the present invention is more preferably non-chlorine and non-bromine without using a component having chlorine or bromine. Specifically, a composition that does not contain chlorine or bromine as a polymer, and does not use a salt containing chlorine or bromine such as lithium perchlorate, sodium perchlorate or quaternary ammonium perchlorate, By using a non-chlorine and non-bromine composition as a whole, there is no risk of corroding, rusting, or contaminating the metal surface such as the core of the conductive roll. In addition, incineration after use is very easy and can be made environmentally friendly products.
However, a polymer containing a halogen such as chlorine may be used. In this case, it is preferable to add an acid acceptor such as hydrotalcite in order to suppress the addition amount as much as possible and prevent deterioration of the polymer due to dehydrochlorination reaction and rusting of the kneader.

Below, the conductive roll 10 demonstrates a manufacturing method.
First, an ionic conductive agent and an EO-PO-AGE copolymer are kneaded for 3 minutes at a temperature of 60 ° C. using a kneader. Low nitrile NBR, EPDM, and other various compounding agents are blended into the kneaded material obtained and kneaded again at a temperature of 60 ° C. for 4 minutes with an open roll or a closed kneader to produce a conductive polymer composition.

This conductive polymer composition is put into a single screw extruder having a diameter of 60 mm, extruded into a hollow tube at 60 ° C. and preformed, and the raw rubber tube is cut into a predetermined size to obtain a preform. When this preform is put into a pressurized steam vulcanizing can and foamed, the chemical foaming agent gasifies and foams, and the rubber component is crosslinked at a temperature (160 ° C.) for 15 to 70 minutes to vulcanize. Get a rubber tube. Vulcanization conditions are measured with a curast meter or the like, and are appropriately adjusted with a 95% torque rise time t95 [minute] as a guide.
In order to prevent contamination of other members such as a photoconductor and reduce compression set, it is desirable to set conditions so that a sufficient vulcanization amount can be obtained.

The foaming ratio is 100% or more and 500% or less, preferably 150% or more and 300% or less, and has a hardness measured by a type E durometer described in JIS K 6253 of 60 degrees or less, preferably 40 degrees or less. It is preferable to make it a foam roll.
After preparing the cored bar 12 and applying a hot melt adhesive to the outer peripheral surface thereof, the cored bar is inserted into the vulcanized rubber tube obtained above, heated and bonded, then the surface is polished and the conductive elastic layer 11 is finished to the target dimension.

"Example"
Hereinafter, the conductive roll of the present invention will be described with reference to examples and comparative examples.
(Examples 1-5, Comparative Examples 1-6)
The EO-PO-AGE copolymer of EO: PO: AGE = 90: 4: 6 and the ionic conductive agent were kneaded for 3 minutes at a temperature of 60 ° C. using a kneader. At this time, five types of kneaded materials having a conductive agent content of 0.5 wt%, 1.0 wt%, 10 wt%, 20 wt%, and 25 wt% were prepared.
Low nitrile NBR, EPDM, and other various compounding agents are blended in the obtained kneaded materials in the amounts shown in Table 1, and kneaded again at a temperature of 60 ° C. for 4 minutes using an open roll or a closed kneader. A polymer composition was prepared. However, in Comparative Example 5, a kneaded product of a conductive agent and an EO-PO-AGE copolymer was not blended.

This conductive polymer composition was put into a single screw extruder of φ60 mm, extruded into a hollow tube shape at 60 ° C. and preformed, and this raw rubber tube was cut into a predetermined size to obtain a preform. This preform was put into a pressurized steam vulcanizing can, and the foaming agent was gasified and foamed. At the same time, the rubber component was vulcanized at a temperature (160 ° C.) for 30 minutes to obtain a vulcanized rubber tube.
After preparing the cored bar and applying hot melt adhesive to the outer peripheral surface, insert the cored bar into the vulcanized rubber tube obtained above, heat and bond it, then polish the surface and polish the conductive elastic layer Finished to target dimensions. The dimensions of the conductive elastic layer of the conductive roll were an inner diameter of 6 mm, an outer diameter of 14 mm, and a length of 230 mm.
In the obtained conductive roll, low nitrile NBR formed a continuous phase, EO-PO-AGE copolymer containing a conductive agent formed a first discontinuous phase, and EPDM formed a second discontinuous phase. It was.

The following products were used for each component in the table.
-NBR: "Nippol 401LL" manufactured by Nippon Zeon Co., Ltd. (glass transition temperature -52 ° C)
・ EPDM: “EPT4045” manufactured by Mitsui Chemicals, Inc.
-EO-PO-AGE copolymer; "ZSN8030" (glass transition temperature -63 ° C) manufactured by Nippon Zeon Co., Ltd.
Conductive agent: lithium-bis (trifluoromethanesulfonyl) imide or lithium-trifluoromethanesulfonateFiller 1; HAF carbon ("Seast 3" manufactured by Tokai Carbon Co., Ltd.)
・ Filler 2: Light calcium carbonate (Maruo Calcium Co., Ltd.)
・ Foaming agent: “Vinihole AC # 3” manufactured by Eiwa Chemical Industry Co., Ltd.
・ Foaming aid: “Cell Paste 101” manufactured by Eiwa Chemical Industry Co., Ltd.
・ Vulcanizing agent: Powdered sulfur (manufactured by Tsurumi Chemical Co., Ltd.)
・ Vulcanization aid 1; “Noxera-DM” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ Vulcanization aid 2; “Noxera-TS” manufactured by Ouchi Shinsei Chemical Co., Ltd.

(Roll resistance value)
In an atmosphere at a temperature of 23 ° C. and a relative humidity of 55%, the conductive elastic layer 41 through the cored bar 42 is mounted on the φ30 aluminum drum 43 as shown in FIG. The tip of the conducting wire having resistance r (100Ω to 10 kΩ) was connected to one end surface of the aluminum drum 43 and the tip of the conducting wire connected to the negative side of the power source 44 was connected to the other end surface of the conductive elastic layer 41 to conduct electricity. The conductive roll 40 was indirectly rotated by applying a load F of 500 g to both ends of the core metal 42 and rotating the aluminum drum 43 while applying a voltage of 1000 V between the core metal 42 and the aluminum drum 43. At this time, resistance measurement was performed 36 times in the circumferential direction, and the average value was obtained. The value of the internal resistance was adjusted so as to increase the effective number of the measured value as much as possible according to the level of the resistance value of the roll. In the apparatus of FIG. 4, when the applied voltage is E, the roll resistance value R is R = r × E / V−r, but this time the term −r is regarded as minute and R = r × E / V The roll resistance value R was calculated from the detection voltage V applied to the resistance r. In the table, the logarithmic value of the average value of the roll resistance value is used. In the present invention, the common logarithm log ₁₀ R of the average value of roll resistance values is preferably less than 9.0.

(Roll resistance value environment dependency)
About the conductive roll produced by the Example and the comparative example, roll resistance value was measured like the above in the environment of 10 degreeC relative humidity 20% (LL environment) and 32 degreeC relative humidity 80% (HH environment). Then, from the roll resistance value RLL [Ω] under the environment of 10% relative humidity 20% and the roll resistance value RHH [Ω] under the condition of 32 ° C. relative humidity 80%, Δlog ₁₀ R = log ₁₀ RLL− The environmental dependence value was calculated according to the log ₁₀ RHH equation. This value is preferably 1.5 or less.

(Resistance increase during continuous energization)
A constant voltage of 1000 V was continuously applied to the roll for 100 hours in the same state as when measuring the roll resistance value in an environment of 23 ° C. and 55% relative humidity. The initial roll resistance value R and the roll resistance value R100 after 100 hours of application are measured in the same manner as described above, and using these values, the amount of increase in resistance during continuous energization: log ₁₀ R100−log ₁₀ R is calculated. did. This value is preferably 0.5 or less. Since the rotation speed of the aluminum drum is 30 rpm and the diameter is 30 mmφ, the linear velocity during rotation is 94 mm / min.

(Compression set)
Using a cylindrical test piece obtained by cutting the conductive rolls produced in Examples and Comparative Examples with a width of 10 mm parallel to the end face, in accordance with the permanent strain test method for vulcanized rubber and thermoplastic rubber described in JIS K 6262, The compression set was measured under the conditions of a measurement temperature of 70 ° C., a measurement time of 22 hours, and a compression rate of 25%. When the value of this compression set exceeds 30%, the dimensional change when it becomes a roll becomes so large that it is likely not suitable for practical use.

(Ozone degradation)
A cylindrical test piece obtained by cutting the conductive rolls produced in Examples and Comparative Examples with a width of 10 mm parallel to the end face was compressed by 25% and left in an ozone atmosphere at a concentration of 5 ppm at 40 ° C. for 96 hours. The presence or absence was confirmed visually. The case where no crack was observed was evaluated as “◯”, and the case where a crack was observed was evaluated as “×”.

As is apparent from Table 1, the conductive roll of the present invention has a low roll resistance value, reduced environmental dependency of the roll resistance value, low compression set, excellent ozone resistance, and continuous energization. It can be seen that there is little increase in resistance at the time.
However, the conductive roll of Comparative Example 1 has a large environmental dependency of the roll resistance value, the conductive roll of Comparative Example 2 has a large resistance increase during continuous energization, and the conductive rolls of Comparative Examples 3 and 6 have compression set. However, the conductive roll of Comparative Example 4 is inferior in ozone resistance, and the conductive roll of Comparative Example 5 does not have a sufficiently low roll resistance value, and the roll resistance value is also highly dependent on the environment. Thus, the electroconductive roll created by the comparative example has a certain problem practically.

It is the schematic of the electroconductive roll of this invention. It is a schematic diagram which shows 1st Embodiment of the electroconductive elastic layer of the electroconductive roll of this invention. It is a schematic diagram which shows 2nd Embodiment of the electroconductive elastic layer of the electroconductive roll of this invention. It is the schematic of the measuring apparatus of roll resistance value.

Explanation of symbols

1, 1 ′ continuous phase 2, 2 ′ first discontinuous phase 3 second discontinuous layer 10 conductive roll 11 conductive elastic layer 12 cored bar

Claims (8)

A conductive roll comprising a cored bar and a conductive elastic layer on the surface of the cored bar,
The conductive elastic layer is composed of a continuous phase and one or more discontinuous phases.
An ionic conductive agent is premixed in a proportion of 1 to 20% by weight only in the discontinuous layer composed of an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer, and
With respect to a total of 100 parts by mass of the polymer constituting the continuous phase and the polymer constituting the discontinuous phase, the content of the polymer constituting the continuous phase is 60 parts by mass or more and less than 80 parts by mass, and the conductive agent The content of the ethylene oxide-propylene oxide-allyl glycidyl ether copolymer containing 1 to 20% by weight is 1 to 25 parts by mass.   The conductive roll according to claim 1, wherein the conductive agent contained in the ethylene oxide-propylene oxide-allyl glycidyl ether copolymer is an ionic conductive agent containing a fluoro group or a sulfonyl group.   The conductive elastic layer is composed of two phases of the continuous phase and a discontinuous phase composed of an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer containing 1 to 20% by weight of the conductive agent. Or the electroconductive roll of Claim 2. The conductive elastic layer comprises the continuous phase, a first discontinuous phase composed of an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer containing 1 to 20% by weight of the conductive agent, and an ethylene propylene diene copolymer. Consists of three phases of second discontinuous phase composed of polymer rubber,
The polymer of the first discontinuous layer is 1 to 25 parts by mass with respect to a total of 100 parts by mass of the polymer constituting the continuous phase and the polymer constituting the first and second discontinuous phases, and ethylene propylene diene The conductive roll according to claim 1 or 2, wherein the polymer of the second discontinuous layer made of copolymer rubber is 5 to 30 parts by mass.   The conductive roll according to any one of claims 1 to 4, wherein the polymer constituting the continuous phase is acrylonitrile butadiene rubber. A roll resistance value R [Ω] in an environment of 23 ° C. and a relative humidity of 55% and a roll resistance value R100 [Ω] in the same environment when a constant voltage of 1000 V is continuously applied for 100 hours are expressed as log ₁₀ R100-log ₁₀
The electroconductive roll of any one of Claim 1 thru | or 5 which has the relationship of R <= 0.5.   The conductive roll according to any one of claims 1 to 6, wherein the compression set at 70 ° C and 25% compression is 30% or less.   The conductive roll according to claim 1, which is used as a charging roll, a developing roll, a toner supply roll, or a transfer roll in an image forming apparatus.

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