JP5904670B2 - Conductive rubber composition, transfer roller and method for producing the same, and image forming apparatus - Google Patents

Description

The present invention, the conductive rubber composition, the conductive rubber composition to foam and crosslink comprises a cylindrical roller body formed by a transfer roller used incorporated in an image forming apparatus using an electrophotographic method The present invention relates to a manufacturing method thereof and an image forming apparatus incorporating the transfer roller.

For example, in an image forming apparatus using electrophotography such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, or a complex machine of these, paper (plastic film such as an OHP film) is roughly processed through the following steps. An image is formed on the surface of the same.
First, the surface of the photoconductive photoconductor is exposed in a uniformly charged state, and an electrostatic latent image corresponding to the formed image is formed on the surface (charging step → exposure step).

Next, the toner, which is minute colored particles, is brought into contact with the surface of the photoreceptor in a state where the toner is charged to a predetermined potential in advance. Then, the toner is selectively attached to the surface of the photoconductor according to the potential pattern of the electrostatic latent image, and the electrostatic latent image is developed into a toner image (development process).
Next, the toner image is transferred to the surface of the paper (transfer process) and further fixed (fixing process), whereby an image is formed on the surface of the paper.

In the transfer step, the toner image formed on the surface of the photoconductor is not only directly transferred to the surface of the paper, but also transferred to the surface of the image carrier (primary transfer step) and then transferred to the surface of the paper. In some cases, retransfer is performed (secondary transfer process).
The toner image is transferred from the surface of the photoreceptor to the surface of the paper in the transfer step, transferred from the surface of the photoreceptor to the surface of the image carrier in the primary transfer step, or the image carrier in the secondary transfer step. For example, a transfer roller having a predetermined roller resistance value provided with a cylindrical roller body made of a conductive rubber composition is used.

For example, in the case of direct transfer, in a transfer process, when a predetermined transfer voltage is applied between a photoconductor and a transfer roller that are pressed against each other with a predetermined pressing force, paper is passed between the two, A toner image formed on the surface of the photoconductor is transferred to the surface of the paper.
Recently, as a transfer roller used for a general-purpose laser printer or the like especially for emerging countries, there is a tendency to use a general-purpose material as much as possible and to have a structure that is as simple as possible and can be manufactured at low cost.

Using general-purpose materials to make the structure simple and cost-effective, the spread of laser printers in emerging countries, and the promotion and promotion of office automation and factory automation, etc. It is important to improve the technological capabilities of emerging countries and ultimately alleviate the so-called North-South problem.
In order to meet the above requirements, as the transfer roller, a roller body having a porous structure is widely used. According to the roller body having such a porous structure, it is possible to reduce the material cost by reducing the forming material, and it is also possible to reduce the weight to reduce the transportation cost. Moreover, even if the blending of the plasticizer is omitted or the blending ratio is reduced, the roller body can impart an appropriate flexibility to the roller body.

Further, in order to manufacture such a roller body having a porous structure, for example, the following continuous manufacturing method is adopted in order to improve the productivity of the roller body and further reduce the production cost of the transfer roller. It is preferable (patent documents 1, 2, etc.).
That is, the conductive rubber composition is extruded into a long cylindrical shape using an extrusion molding machine, and the extruded cylindrical body is continuously cut as it is long without being cut. Continuously foaming and crosslinking by continuously passing through a continuous crosslinking device including a device and a hot-air crosslinking device, and then cutting to a predetermined length, the roller body is continuously and highly productive. Can be manufactured.

Further, as the rubber component constituting the conductive rubber composition, conventionally, only an ionic conductive rubber such as epichlorohydrin rubber is used, or acrylonitrile butadiene rubber (NBR) as a crosslinkable rubber is used as the ionic conductive rubber. It was common to use together.
A conductive rubber composition has been prepared by blending the rubber component with a crosslinking agent component for crosslinking the rubber component, a foaming agent component for foaming, and the like.

Of these, the latter combined system is necessary for forming a transfer roller having the same roller resistance value, and the blending ratio of expensive ion conductive rubber can be reduced, so that the material cost can be reduced to some extent. it can.
However, in order to further reduce the production cost of the transfer roller in response to the above requirement, it is desirable to use a material that is more versatile and less expensive than the NBR as the crosslinkable rubber. .

Therefore, it has been studied to use styrene butadiene rubber (SBR) and ethylene propylene diene rubber (EPDM) in combination as the crosslinkable rubber.
In the combined system, the material cost can be further suppressed while maintaining good ozone resistance of the roller body.
That is, it is necessary to form a transfer roller having the same roller resistance value, and the blending ratio of the expensive ion conductive rubber can be reduced as described above. Moreover, since SBR is more versatile and less expensive than NBR, the material cost can be further reduced.

However, since SBR has insufficient resistance to ozone generated inside a laser printer or the like, that is, ozone resistance, EPDM is used together as described above.
Since EPDM itself is not only excellent in ozone resistance, but also acts to suppress ozone degradation of SBR, it can improve the ozone resistance of the roller body.

Japanese Patent Laid-Open No. 2002-221859 JP 2006-117870 A

  However, since SBR is nonpolar and has a very low microwave absorption efficiency, the conductive rubber composition containing SBR is continuously extruded as described above, and then the microwave crosslinking apparatus and the hot air crosslinking apparatus are combined. Even if it is continuously passed through the continuous crosslinking apparatus, the conductive rubber composition may not be sufficiently heated by microwave irradiation in the microwave crosslinking apparatus.

For example, in a microwave crosslinking apparatus, the temperature of the conductive rubber composition does not reach the foaming temperature. As a result, the foamed roller body is insufficiently foamed, and the required flexibility cannot be satisfied. There may be a problem that it cannot be manufactured.
If heating time is extended by ignoring productivity, these problems can be solved, but by adopting a continuous manufacturing method, the productivity of the roller body is improved and the production cost of the transfer roller is reduced. The effect will not be obtained.

It is an object of the present invention to include SBR as a crosslinkable rubber, and after extrusion, the required flexibility is sufficiently foamed and crosslinked by a continuous crosslinking apparatus including a microwave crosslinking apparatus and a hot-air crosslinking apparatus. To provide a conductive rubber composition capable of producing a sufficiently satisfactory roller main body, a transfer roller including the roller main body made of the conductive rubber composition, a manufacturing method thereof, and an image forming apparatus incorporating the transfer roller. is there.

The present invention is a conductive rubber composition that can be foamed and crosslinked by a continuous crosslinking apparatus including a microwave crosslinking apparatus and a hot-air crosslinking apparatus, and includes at least styrene butadiene rubber, ethylene propylene diene rubber, and epichlorohydrin rubber. rubber component, a crosslinker component for crosslinking the rubber component, and as blowing agent component, the rubber component per 100 parts by per 0.1 part by weight or more, of the following 4 parts by mass, azodicarboxylate as blowing agent It contains only amide (H ₂ NOCN = NCONH ₂ , ADCA) and carbon black HAF in a proportion of 5 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the total rubber content. is there.

The present invention also provides a transfer roller comprising a cylindrical roller body made of the conductive rubber composition of the present invention.
The present invention also includes a step of continuously foaming and cross-linking the roller body by a continuous cross-linking device including a microwave cross-linking device and a hot-air cross-linking device while the conductive rubber composition is extruded into a cylindrical shape. A transfer roller manufacturing method characterized in that the transfer roller is formed.
Furthermore, the present invention is an image forming apparatus in which the transfer roller of the present invention is incorporated.
According to the present invention, as a crosslinkable rubber combined with epichlorohydrin rubber, by using SBR and EPDM in combination instead of the conventional NBR as described above, while maintaining good ozone resistance of the roller body, Material costs can be reduced.

That is, as described above, SBR is more versatile and less expensive than NBR, and can further reduce the blending ratio of epichlorohydrin rubber necessary for forming a transfer roller having the same roller resistance value. Material costs can be reduced.
However, since SBR has insufficient resistance to ozone generated inside a laser printer or the like, that is, ozone resistance, EPDM is used in the present invention.

The EPDM itself not only has excellent ozone resistance, but also functions to suppress the ozone degradation of SBR, so that the ozone resistance of the roller body can be greatly improved.
In addition, as described above, SBR is nonpolar and has a very low microwave absorption efficiency. However, according to the present invention, carbon black HAF having a high microwave absorption efficiency is blended at the predetermined ratio. Thereby, the absorption efficiency of the microwave as the whole conductive rubber composition can be improved.

  Therefore, at the initial stage of passing through the inside of the microwave cross-linking device among the continuous cross-linking devices, the extruded cylindrical body can be heated to a temperature higher than the foaming temperature at an early stage to start foaming. Without extending, it is possible to produce a roller body that is efficiently and sufficiently foamed and sufficiently crosslinked and sufficiently satisfies the required flexibility with high productivity.

In the present invention, the reason why carbon black is limited to HAF (particle diameter of about 26 to 30 nm) is as follows.
That is, most of carbon black functions as an electronic conductive agent that imparts electronic conductivity to the roller body due to the so-called “electroconductive” property in which electrons hop between adjacent carbon blacks in the conductive rubber composition. To do.

Carbon black having a smaller particle diameter than HAF is superior to the HAF in terms of microwave absorption efficiency.
However, such a carbon black having a small particle size is difficult to disperse uniformly in the conductive rubber composition and tends to be biased in distribution, and thus tends to be biased in the electronic conductivity. There is a problem that the roller resistance value is likely to be uneven. Unevenness of the roller resistance value causes unevenness of the image density of the formed image.

On the other hand, carbon black having a particle diameter larger than that of HAF has insufficient microwave absorption efficiency as compared with HAF. Therefore, even if the carbon black is blended, the microwave as a whole of the conductive rubber composition is mixed. The effect of improving the absorption efficiency is not obtained.
In contrast, carbon black HAF has excellent microwave absorption efficiency and can be uniformly dispersed in the conductive rubber composition.

  Therefore, by selectively using HAF as carbon black, the microwave absorption efficiency of the entire conductive rubber composition is improved, and the extruded cylindrical body is converted into a continuous cross-linking apparatus as described above. A roller body that can be efficiently and sufficiently foamed and cross-linked without extending the heating time, sufficiently satisfies the required flexibility, and does not cause unevenness in the roller resistance value of the transfer roller. It becomes possible to manufacture with high productivity.

In the present invention, the blending ratio of the carbon black HAF is limited to 5 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the total amount of rubber for the following reason.
That is, when the blending ratio is less than the above range, the effect of improving the microwave absorption efficiency as a whole of the conductive rubber composition by blending the carbon black HAF cannot be obtained.
On the other hand, when the above range is exceeded, the electronic conductivity due to the carbon black HAF becomes too strong, so that the roller resistance value of the transfer roller tends to be excessively reduced, and the roller resistance value exceeds the required predetermined range. It cannot be maintained.

In addition, it is difficult to uniformly disperse excess carbon black HAF in the conductive rubber composition, and the distribution tends to be biased, so that the electronic conductivity is also biased, resulting in the roller resistance value of the transfer roller. There is also a problem that unevenness is likely to occur.
On the other hand, by setting the blending ratio of carbon black HAF within the above range,
-Suppressing an excessive decrease in the roller resistance value, maintaining the roller resistance value within a required predetermined range,
-While eliminating the uneven distribution of the carbon black HAF and maintaining the unevenness of the roller resistance value in the smallest possible range,
-As described above, the microwave absorption efficiency of the entire conductive rubber composition is improved, and the extruded cylindrical body is efficiently processed by a continuous crosslinking apparatus without extending the heating time, and It becomes possible to sufficiently foam and crosslink.

Further, in the rubber composition of the present invention, the foaming agent component is limited to only ADCA as a foaming agent of 0.1 parts by weight or more and 4 parts by weight or less per 100 parts by weight of the total amount of the rubber. Depending on the reason.
That is, when ADCA is used as a foaming agent , it is common to use a urea-based foaming aid in combination. The urea foaming aid functions to promote foaming by lowering the decomposition temperature of ADCA .

However, in the manufacturing method using the continuous crosslinking apparatus, the substantially entire cylindrical body extruded into a cylindrical shape is heated almost uniformly. Therefore, the decomposition temperature of the ADCA by blending a urea foaming aid is low, the ADCA is a short time from the start of heating, decomposing almost simultaneously and uniformly across substantially of the tubular body, As a result of the expansion of adjacent foaming cells that are expanding due to foaming and restraining expansion by mutual expansion force, the cell diameter of the foamed cells constituting the porous structure becomes fine.

In contrast, ADCA is when high decomposition temperature of the ADCA not at all blended urea foaming aid, be substantially uniformly heated substantially the entire tubular body, contained in the tubular body during The timing of disassembly and foaming will vary. Specifically, each ADCA tends to decompose and foam due to various factors such as the contact area with the rubber component that varies depending on the particle size or shape of the ADCA particles, the position in the cylindrical body, etc. The timing will be different.

Therefore, while passing through the continuous bridge device, and eventually almost all of the ADCA to decompose in the tubular body, although the foam, decomposing almost simultaneously, the number of ADCA starting the foaming decreases The opportunity for the adjacent foam cells, which are expanding due to foaming, to suppress expansion by mutual expansion force is reduced, and the foam cell diameter of the roller body is increased.
Therefore, the diameter of the foam cell is larger, and therefore, the roller body that can reduce the material cost by further reducing the forming material, and further reduce the weight and reduce the transportation cost can be obtained by using the extrusion molding machine and the continuous crosslinking device. It becomes possible to manufacture continuously and stably.

In the conductive rubber composition of the present invention, the rubber content is at least one selected from the group consisting of acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butadiene rubber (BR), and acrylic rubber (ACM). It preferably contains some kind of polar rubber. Thereby, the roller resistance value of the transfer roller can be finely adjusted.
In the transfer roller of the present invention, the roller main body is a step of continuously foaming and cross-linking by a continuous cross-linking device including a microwave cross-linking device and a hot air cross-linking device while extruding the conductive rubber composition into a cylindrical shape. It is preferable that it is formed through. As a result, as described above, the productivity of the roller body can be improved and the production cost of the transfer roller can be further compressed.

According to the present invention, SBR is included as a crosslinkable rubber, and after extrusion, the required flexibility is obtained by foaming and crosslinking efficiently and sufficiently by a continuous crosslinking apparatus including a microwave crosslinking apparatus and a hot-air crosslinking apparatus. To provide a conductive rubber composition capable of producing a sufficiently satisfactory roller body, a transfer roller provided with a roller body composed of the conductive rubber composition, a method for producing the same , and an image forming apparatus incorporating the transfer roller. it can.

It is a perspective view which shows the external appearance of an example of embodiment of the transfer roller of this invention. It is a block diagram explaining the outline of the continuous bridge | crosslinking apparatus used for manufacture of the said transfer roller. It is a figure explaining the method to measure the roller resistance value of the said transfer roller.

<< Conductive rubber composition >>
The conductive rubber composition of the present invention comprises a rubber component containing at least SBR, EPDM, and epichlorohydrin rubber, a crosslinking agent component for crosslinking the rubber component, and a total amount of 100 parts by mass of the rubber component as a foaming agent component. Including only 0.1 part by weight or more and 4 parts by weight or less of ADCA , carbon black HAF is contained in a ratio of 5 parts by weight or more and 25 parts by weight or less per 100 parts by weight of the total amount of the rubber. To do.

<SBR>
As the SBR, any of various SBRs synthesized by copolymerizing styrene and 1,3-butadiene by various polymerization methods such as an emulsion polymerization method and a solution polymerization method can be used. In addition, as SBR, there are an oil-extended type in which flexibility is adjusted by adding an extending oil, and a non-oil-extended type in which flexibility is not added, either of which can be used.

Furthermore, as the SBR, any of SBR of high styrene type, medium styrene type, and low styrene type classified by styrene content can be used. Various physical properties of the roller body can be adjusted by changing the styrene content and the degree of crosslinking.
One or more of these SBRs can be used.
The blending ratio of SBR is 40 parts by mass or more, particularly 60 parts by mass or more in 100 parts by mass of the total rubber content when the rubber content is only 3 types of SBR, EPDM and epichlorohydrin rubber and does not contain polar rubber. Is preferably 90 parts by mass or less, and particularly preferably 80 parts by mass or less. Moreover, when polar rubber is included, although it depends on the blending ratio of the polar rubber, it is preferably 30 parts by mass or more and preferably 50 parts by mass or less in 100 parts by mass of the total rubber content.

When the blending ratio is less than the above range, there is a possibility that the effect of using SBR, as described above, that is high in versatility and low in cost and has a low electric resistance value, may not be obtained.
On the other hand, when the above range is exceeded, the blending ratio of EPDM is relatively reduced, and there is a possibility that good ozone resistance cannot be imparted to the roller body. Further, the blending ratio of epichlorohydrin rubber is relatively reduced, and there is a possibility that good ionic conductivity cannot be imparted to the roller body.

In addition, the said mixture ratio is a mixture ratio of SBR itself as solid content contained in the oil-extended type SBR when using an oil-extended type SBR.
<EPDM>
As EPDM, any of various EPDMs in which a double bond is introduced into the main chain by adding a small amount of a third component (diene component) to ethylene and propylene can be used. As the EPDM, various products are provided depending on the kind and amount of the third component. Representative examples of the third component include ethylidene norbornene (ENB), 1,4-hexadiene (1,4-HD), dicyclopentadiene (DCP), and the like. A Ziegler catalyst is generally used as the polymerization catalyst.

The blending ratio of EPDM is preferably 5 parts by mass or more, more preferably 40 parts by mass or less, and particularly preferably 20 parts by mass or less, in 100 parts by mass of the total rubber content.
If the blending ratio is less than the above range, there is a possibility that good ozone resistance cannot be imparted to the roller body.
On the other hand, when the above range is exceeded, the effect of using SBR is sufficiently obtained that the blending ratio of SBR is relatively reduced, the versatility is high and the cost is low, and the electrical resistance value is low. There is a risk of not. Further, the blending ratio of epichlorohydrin rubber is relatively reduced, and there is a possibility that good ionic conductivity cannot be imparted to the roller body.

<Epichlorohydrin rubber>
As epichlorohydrin rubber, epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allyl glycidyl ether binary copolymer, epichlorohydrin-ethylene oxide-allyl One or more of glycidyl ether terpolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymer, and epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer Is mentioned.

As the epichlorohydrin rubber, among the above examples, a copolymer containing ethylene oxide, particularly ECO and / or GECO is preferable.
In both copolymers, the ethylene oxide content is preferably 30 mol% or more, particularly preferably 50 mol% or more, and preferably 80 mol% or less.
Ethylene oxide serves to lower the roller resistance value of the transfer roller. However, when the ethylene oxide content is less than the above range, such a function cannot be sufficiently obtained, and thus there is a possibility that the roller resistance value of the transfer roller cannot be sufficiently reduced.

On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs and the segmental movement of the molecular chain is hindered, so that the roller resistance value of the transfer roller tends to increase. In addition, the hardness of the roller body after crosslinking may increase, or the viscosity of the conductive rubber composition before crosslinking may increase when heated and melted.
The epichlorohydrin content in ECO is the remaining amount of the ethylene oxide content. That is, the epichlorohydrin content is preferably 20 mol% or more, preferably 70 mol% or less, and particularly preferably 50 mol% or less.

Further, the allylic glycidyl ether content in GECO is preferably 0.5 mol% or more, particularly preferably 2 mol% or more, more preferably 10 mol% or less, and particularly preferably 5 mol% or less.
The allyl glycidyl ether itself functions to secure a free volume as a side chain, thereby suppressing the crystallization of ethylene oxide and reducing the roller resistance value of the transfer roller. However, when the allyl glycidyl ether content is less than the above range, such a function cannot be obtained, so that the roller resistance value of the transfer roller may not be sufficiently reduced.

  On the other hand, allyl glycidyl ether functions as a crosslinking point at the time of GECO crosslinking, so when the allyl glycidyl ether content exceeds the above range, the GECO crosslinking density becomes high, and segment movement of molecular chains is hindered. On the contrary, the roller resistance value of the transfer roller tends to increase. Further, the tensile strength, fatigue characteristics, bending resistance, etc. of the roller body may be reduced.

The epichlorohydrin content in GECO is the remaining amount of the ethylene oxide content and the allyl glycidyl ether content. That is, the epichlorohydrin content is preferably 10 mol% or more, particularly 19.5 mol% or more, preferably 69.5 mol% or less, particularly preferably 60 mol% or less.
As GECO, in addition to a copolymer in the narrow sense obtained by copolymerizing the above three types of monomers, a modified product obtained by modifying epichlorohydrin-ethylene oxide copolymer (ECO) with allyl glycidyl ether is also known. Any GECO can be used in the present invention.

The blending ratio of epichlorohydrin rubber is preferably 5 parts by mass or more, particularly 10 parts by mass or more, and preferably 40 parts by mass or less, particularly 30 parts by mass or less, in 100 parts by mass of the total amount of rubber.
If the blending ratio is less than the above range, there is a possibility that good ionic conductivity cannot be imparted to the roller body.

On the other hand, when the above range is exceeded, the effect of using SBR is sufficiently obtained that the blending ratio of SBR is relatively reduced, the versatility is high and the cost is low, and the electrical resistance value is low. There is a risk of not. Further, the blending ratio of EPDM is relatively reduced, and there is a possibility that good ozone resistance cannot be imparted to the roller body.
<Polar rubber>
When polar rubber is blended, the roller resistance value of the transfer roller can be finely adjusted as described above. In addition, it is possible to form a porous structure that is as uniform as possible without causing uneven foaming.

Examples of the polar rubber include one or more of NBR, CR, BR, and ACM. NBR and / or CR are particularly preferable.
Among these, as NBR, any of low nitrile NBR, medium nitrile NBR, medium high nitrile NBR, high nitrile NBR, and extremely high nitrile NBR classified by acrylonitrile content can be used.

Further, as CR, for example, the crystals synthesized by emulsion polymerization of chloroprene and classified based on the sulfur-modified type and non-sulfur-modified type classified according to the type of molecular weight modifier used at that time, and the crystallization rate. Any of a slow conversion type, a moderate conversion type, and a fast conversion type CR can be used.
The blending ratio of the polar rubber can be arbitrarily set according to the roller resistance value of the target transfer roller, but is particularly preferably 5 parts by mass or more, particularly 20 parts by mass or more in 100 parts by mass of the total rubber content. 40 parts by mass or less is preferable.

If the blending ratio is less than the above range, the effect of finely adjusting the roller resistance value of the transfer roller or eliminating foaming unevenness may not be obtained sufficiently.
In addition, when the above range is exceeded, the effect of using SBR that the blending ratio of SBR is relatively small, versatility is high and cost is low, and electric resistance is low cannot be obtained sufficiently. There is a fear. Further, the blending ratio of EPDM is relatively reduced, and there is a possibility that good ozone resistance cannot be imparted to the roller body. Furthermore, the blending ratio of epichlorohydrin rubber is relatively reduced, and there is a possibility that good ionic conductivity cannot be imparted to the roller body.

<Carbon black HAF>
As carbon black HAF, in addition to HAF in a narrow sense, for example, HAF-LS-SC, HAF-LS, HAF-HS, HAF-VHS, etc., particle diameter is 26-30 nm, iodine adsorption amount is 82-90 mg / g, DBP oil absorption amount 71~160cm ³ / 100g, and the bulk density is in the range of 290~465kgm ^-3, include one or more of a variety of HAF class.

The blending ratio of the carbon black HAF needs to be 5 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the total amount of rubber. The reason for this is as described above.
In consideration of further improving the effects described above, the blending ratio of carbon black HAF is preferably 20 parts by mass or less per 100 parts by mass of the total amount of rubber, even within the above range.

<Foaming agent component>
As the foaming agent component, as explained above, only ADCA of 0.1 parts by mass or more and 4 parts by mass or less per 100 parts by mass of the total amount of rubber is used alone.
If the blending ratio of ADCA is less than the above range, the amount of the ADCA is basically insufficient, the rubber component cannot be sufficiently foamed by the decomposition, and the roller body cannot have a porous structure.

On the other hand, when exceeding the above range, despite the fact that no urea-based foaming aid is blended at all as described above, the number of ADCA that decomposes almost simultaneously in the cylindrical body and starts foaming increases. Adjacent foaming cells that are expanding due to foaming have more opportunities to suppress expansion by mutual expansion force, and the foamed cell diameter of the roller body cannot be made sufficiently large.
On the other hand, by setting the blending ratio of ADCA within the range of 0.1 parts by weight or more and 4 parts by weight or less per 100 parts by weight of the total amount of rubber, the foamed cell diameter was as large as possible and the foam was sufficiently foamed. A roller body having a porous structure can be obtained.

In consideration of further improving these effects, the blending ratio of ADCA is preferably 1 part by mass or more even within the above range .

<Crosslinking agent component>
Examples of the crosslinking agent component for crosslinking the rubber component include a crosslinking agent and an accelerator.
Among these, examples of the crosslinking agent include one or more of sulfur-based crosslinking agents, thiourea-based crosslinking agents, triazine derivative-based crosslinking agents, peroxide-based crosslinking agents, various monomers, and the like. Of these, sulfur-based crosslinking agents are preferred.

Examples of sulfur-based crosslinking agents include powdered sulfur and organic sulfur-containing compounds. Among these, examples of the organic sulfur-containing compound include tetramethylthiuram disulfide and N, N-dithiobismorpholine. In particular, sulfur such as powdered sulfur is preferred.
The blending ratio of sulfur is preferably 0.2 parts by mass or more, particularly 1 part by mass or more, preferably 5 parts by mass or less, particularly 3 parts by mass or less, per 100 parts by mass of the total amount of rubber.

If the blending ratio is less than the above range, the cross-linking speed of the entire conductive rubber composition becomes slow, and the time required for cross-linking becomes long, and the productivity of the roller body may be lowered. When the above range is exceeded, there is a possibility that the compression set of the roller body after crosslinking becomes large or excessive sulfur blooms on the outer peripheral surface of the roller body.
Examples of the accelerator include inorganic accelerators such as slaked lime, magnesia (MgO), and resurge (PbO), and one or more organic accelerators.

  Examples of the organic accelerator include guanidine accelerators such as di-o-tolylguanidine, 1,3-diphenylguanidine, 1-o-tolylbiguanide, dicatechol borate di-o-tolylguanidine salt; 2-mercapto Thiazole accelerators such as benzothiazole and di-2-benzothiazyl disulfide; sulfenamide accelerators such as N-cyclohexyl-2-benzothiazylsulfenamide; tetrametherthiuram monosulfide, tetramethylthiuram One type or two or more types of thiuram accelerators such as disulfide, tetraethylthiuram disulfide, and dipentamethylene thiuram tetrasulfide;

As the accelerator, one or more kinds of optimum accelerators may be selected from the various accelerators according to the type of the crosslinking agent to be combined. For example, when sulfur is used as a crosslinking agent, it is preferable to select and use a thiuram accelerator and / or a thiazole accelerator as an accelerator.
Moreover, since the acceleration | stimulation mechanism of a crosslinking agent changes with kinds, it is preferable to use 2 or more types together. The blending ratio of the individual accelerators used in combination can be arbitrarily set, but is preferably 0.1 parts by mass or more, particularly preferably 0.5 parts by mass or more, per 100 parts by mass of the total amount of rubber. Hereinafter, it is particularly preferably 2 parts by mass or less.

As the cross-linking agent component, an accelerator aid may be further blended.
Examples of the acceleration aid include one or more metal compounds such as zinc oxide; fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid; and other conventionally known acceleration aids.
The blending ratio of the accelerator aid can be appropriately set according to the kind and combination of the rubber component, the kind and combination of the crosslinking agent and accelerator, and the like.

<Others>
You may mix | blend various additives with a conductive rubber composition as needed. Examples of the additive include acid acceptors, plastic components (plasticizers, processing aids, etc.), deterioration inhibitors, fillers, scorch inhibitors, ultraviolet absorbers, lubricants, pigments, antistatic agents, flame retardants, Examples thereof include a compatibilizer, a nucleating agent, and a co-crosslinking agent.

Of these, the acid-accepting agent functions to prevent the chlorine-based gas generated from the epichlorohydrin rubber during the crosslinking of the rubber from remaining in the roller body, thereby inhibiting the crosslinking and contamination of the photoreceptor.
As the acid acceptor, various substances that act as an acid acceptor can be used, but hydrotalcites or magsarat are preferable because of excellent dispersibility, and hydrotalcites are particularly preferable.

Further, when the hydrotalcite or the like is used in combination with magnesium oxide or potassium oxide, a higher acid receiving effect can be obtained, and contamination of the photoreceptor can be prevented more reliably.
The blending ratio of the acid acceptor is preferably 0.2 parts by mass or more, particularly 0.5 parts by mass or more, preferably 5 parts by mass or less, particularly 2 parts by mass or less, per 100 parts by mass of the total amount of rubber. preferable.
If the blending ratio is less than the above range, the above-described effect due to the inclusion of the acid acceptor may not be sufficiently obtained. On the other hand, if the above range is exceeded, the hardness of the roller body after crosslinking may increase.

Examples of the plasticizer include various plasticizers such as dibutyl phthalate (DBP), dioctyl phthalate (DOP), and tricresyl phosphate, and various waxes such as polar wax. Examples of the processing aid include fatty acids such as stearic acid.
The blending ratio of these plastic components is preferably 5 parts by mass or less per 100 parts by mass of the total amount of rubber. For example, this is to prevent the photosensitive member from being contaminated when it is attached to the image forming apparatus or during operation. In view of this object, it is particularly preferable to use a polar wax as the plastic component.

Examples of the deterioration preventing agent include various antiaging agents and antioxidants.
Of these, the antioxidant functions to reduce the environmental dependency of the roller resistance value of the transfer roller and to suppress an increase in the roller resistance value during continuous energization. Examples of the antioxidant include nickel diethyldithiocarbamate [NOCRACK (registered trademark) NEC-P manufactured by Ouchi Shinsei Chemical Co., Ltd.], nickel dibutyldithiocarbamate [NOCRACK NBC manufactured by Ouchi Shinsei Chemical Industrial Co., Ltd. ] Etc. are mentioned.

Examples of fillers include carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, etc. other than zinc oxide, silica, carbon, HAF, and that do not aggregate or function as an electronic conductive agent. Or 2 or more types are mentioned.
By blending the filler, the mechanical strength of the roller body can be improved.
Examples of the scorch inhibitor include one or more of N-cyclohexylthiophthalimide, phthalic anhydride, N-nitrosodiphenylamine, 2,4-diphenyl-4-methyl-1-pentene, and the like. . N-cyclohexylthiophthalimide is particularly preferable.

The blending ratio of the scorch inhibitor is preferably 0.1 parts by mass or more per 100 parts by mass of the total amount of rubber, and is preferably 5 parts by mass or less, particularly preferably 1 part by mass or less.
The co-crosslinking agent refers to a component that itself has a function of crosslinking and also having a function of crosslinking the rubber component to polymerize the whole.
Examples of the co-crosslinking agent include methacrylic acid esters, ethylenically unsaturated monomers represented by metal salts of methacrylic acid or acrylic acid, and polyfunctional polymers using functional groups of 1,2-polybutadiene. 1 type, or 2 or more types, such as dioxime.

Among these, as the ethylenically unsaturated monomer, for example
(a) monocarboxylic acids such as acrylic acid, methacrylic acid, crotonic acid,
(b) dicarboxylic acids such as maleic acid, fumaric acid, itaconic acid,
(c) an ester or anhydride of the unsaturated carboxylic acid of (a) (b),
(d) the metal salt of (a) to (c),
(e) aliphatic conjugated dienes such as 1,3-butadiene, isoprene, 2-chloro-1,3-butadiene,
(f) aromatic vinyl compounds such as styrene, α-methylstyrene, vinyltoluene, ethylvinylbenzene, divinylbenzene,
(g) vinyl compounds having a heterocyclic ring such as triallyl isocyanurate, triallyl cyanurate, vinylpyridine,
(h) In addition, one or more kinds of vinyl cyanide compounds such as (meth) acrylonitrile or α-chloroacrylonitrile, acrolein, formylsterol, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone and the like can be mentioned.

Further, the ester of the unsaturated carboxylic acid (c) is preferably an ester of a monocarboxylic acid.
Examples of the esters of the monocarboxylic acids include methyl (meth) acrylate, ethyl (meth) acrylate, n-propyl (meth) acrylate, i-propyl (meth) acrylate, n-butyl (meth) acrylate, i-butyl ( (Meth) acrylate, n-pentyl (meth) acrylate, i-pentyl (meth) acrylate, n-hexyl (meth) acrylate, cyclohexyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, octyl (Meth) acrylate, i-nonyl (meth) acrylate, tert-butylcyclohexyl (meth) acrylate, decyl (meth) acrylate, dodecyl (meth) acrylate, hydroxymethyl (meth) acrylate, hydroxyethyl (meth) acrylate ( Alkyl esters of (meth) acrylic acid;
Aminoalkyl esters of (meth) acrylic acid such as aminoethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate, butylaminoethyl (meth) acrylate;
(Meth) acrylates having an aromatic ring such as benzyl (meth) acrylate, benzoyl (meth) acrylate, allyl (meth) acrylate;
(Meth) acrylates having an epoxy group such as glycidyl (meth) acrylate, metaglycidyl (meth) acrylate, and epoxycyclohexyl (meth) acrylate;
(Meth) acrylates having various functional groups such as N-methylol (meth) acrylamide, γ- (meth) acryloxypropyltrimethoxysilane, tetrahydrofurfuryl methacrylate;
One or more polyfunctional (meth) acrylates such as ethylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, ethylene dimethacrylate (EDMA), polyethylene glycol dimethacrylate, and isobutylene ethylene dimethacrylate; Is mentioned.

  The conductive rubber composition of the present invention containing each of the above components can be prepared in the same manner as before. First, the rubber component is blended at a predetermined ratio and kneaded, and then the additives other than the foaming agent component and the crosslinking agent component are added and kneaded, and finally the foaming agent component and the crosslinking agent component are added and kneaded. A conductive rubber composition can be obtained. For the kneading, for example, a kneader, a Banbury mixer, an extruder or the like can be used.

<Transfer roller and method for manufacturing the same >
FIG. 1 is a perspective view showing an appearance of an example of an embodiment of a transfer roller of the present invention.
Referring to FIG. 1, the transfer roller 1 of this example includes a cylindrical roller body 2 having a single layer structure, and a shaft 4 inserted through a through hole 3 at the center of the roller body 2.
The shaft 4 is integrally formed of a metal such as aluminum, an aluminum alloy, or stainless steel. The roller body 2 and the shaft 4 are electrically joined together with, for example, a conductive adhesive, and are mechanically fixed and rotated integrally.

  The roller body 2 extrudes the conductive rubber composition of the present invention into a long cylindrical shape using an extrusion molding machine as described above, and does not cut the extruded cylindrical body. The foam is continuously foamed and cross-linked by continuously passing through a continuous cross-linking apparatus including a microwave cross-linking apparatus and a hot-air cross-linking apparatus while being continuously sent out to a predetermined length. It is preferable to manufacture by cutting and polishing the outer peripheral surface 5 as necessary.

FIG. 2 is a block diagram for explaining an outline of an example of the continuous crosslinking apparatus.
Referring to FIGS. 1 and 2, a continuous crosslinking apparatus 6 of this example is obtained by continuously extruding the conductive rubber composition using an extruder 7. The microwave bridging device 9 and hot air bridging are sequentially arranged on the way of continuous conveyance by a conveyor or the like (not shown) without cutting the long cylindrical body 8 that is the basis of the roller body 2. The apparatus 10 and the take-up machine 11 for taking up the cylindrical body 8 at a constant speed are provided.

First, for example, each of the above components is kneaded into the extruder 7 and the extruder 7 is operated while continuously supplying the conductive rubber composition formed into a ribbon shape or the like, thereby forming a long cylindrical shape. The body 8 is continuously extruded.
Next, while the extruded cylindrical body 8 is continuously conveyed at a constant speed by the conveyor and the take-up machine 11, the microwave crosslinking apparatus 9 is first passed through the continuous crosslinking apparatus 6. The conductive rubber composition forming the cylindrical body 8 is crosslinked to a certain degree of crosslinking by irradiation with microwaves. Moreover, the inside of the microwave bridge | crosslinking apparatus 9 can be heated to fixed temperature, ADCA can be decomposed | disassembled with the said bridge | crosslinking, and a conductive rubber composition can also be made to foam.

Subsequently, the hot air is passed through the hot air cross-linking device 10 while continuing the conveyance, and ADCA is decomposed to further foam the conductive rubber composition, and the conductive rubber composition is cross-linked to a predetermined degree of cross-linking. Let
Next, the cylindrical body 8 is cooled by passing cooling water or the like (not shown), whereby the foaming and cross-linking steps of the cylindrical body 8 are completed.

The details of the continuous crosslinking device 6 are as described in, for example, Patent Documents 1 and 2 described above.
The conveyance speed of the cylindrical body 8, the microwave dose irradiated by the microwave bridging device 9, the set temperature and length of the hot air bridging device 10 (each of which can be changed in stages separately) By setting, the cylindrical body 8 in which the degree of cross-linking, the degree of foaming, etc. of the conductive rubber composition is set to an arbitrary constant value can be continuously obtained.

Further, in order to make the microwave irradiation dose and the degree of heating as uniform as possible in the entire cylindrical body 8 and to make the degree of crosslinking and foaming constant as much as possible, the cylindrical body 8 being transported is twisted. May be.
Thereafter, the cylindrical body 8 is cut into a predetermined length, and the outer peripheral surface 5 is polished as necessary, whereby the roller body 2 having a porous structure is manufactured. Further, the cylindrical body 8 is temporarily stored, for example, by winding it on a winder (not shown), and the roller body 2 is manufactured by sequentially sending it to the processes after the cutting according to demand. Good.

By carrying out continuous crosslinking using the continuous crosslinking device 6, the productivity of the roller body 2 can be improved and the production cost of the transfer roller 1 can be further compressed.
<Roller resistance value and its unevenness evaluation>
The transfer roller 1 provided with the roller body 2 has a roller resistance value of 10 ¹⁰ Ω or less, particularly 10 ⁹ Ω or less, measured at a normal temperature and humidity environment of a temperature of 23 ° C. and a relative humidity of 55% at an applied voltage of 1000 V. Is preferred.

FIG. 3 is a diagram for explaining a method of measuring the roller resistance value of the transfer roller 1.
With reference to FIGS. 1 and 3, in the present invention, the roller resistance value is represented by a value measured by the following method.
That is, an aluminum drum 12 that can be rotated at a constant rotational speed is prepared, and the outer peripheral surface 5 of the roller body 2 of the transfer roller 1 that measures the roller resistance value from above the outer peripheral surface 13 of the aluminum drum 12. Abut.

A DC power source 14 and a resistor 15 are connected in series between the shaft 4 of the transfer roller 1 and the aluminum drum 12 to constitute a measuring circuit 16. The DC power supply 14 is connected to the shaft 4 on the (−) side and to the resistor 15 on the (+) side. The resistance value r of the resistor 15 is 100Ω.
Next, with both ends of the shaft 4 being subjected to a load F of 500 g and the roller body 2 being in pressure contact with the aluminum drum 12, the aluminum drum 12 is rotated (rotation speed: 30 rpm) while the direct current is passed between the two. When the applied voltage E of 1000 V DC is applied from the power supply 14, the detection voltage V applied to the resistor 15 is measured. Measurement is performed 100 times in 4 seconds.

From the detection voltage V and the applied voltage E (= 1000 V), the roller resistance value R of the transfer roller 1 is basically the formula (i ′):
R = r × E / (V−r) (i ′)
Sought by. However, since the term (−r) in the denominator in the formula (i ′) can be regarded as minute, in the present invention, the formula (i):
R = r × E / V (i)
The roller resistance value of the transfer roller 1 is determined by the value obtained by the above.

  Then, a roller resistance value R is obtained from the detected voltage V for 100 times by the above equation (i), and the average value is used as the roller resistance value R of the roller. Further, the ratio (maximum resistance value / minimum resistance value) between the maximum resistance value and the minimum resistance value among the roller resistance values for 100 times is obtained, and when the ratio is 1.2 or less, there is no unevenness (◎) A value exceeding 1.2 and 1.3 or less is slightly uneven, but a practical level (◯), and exceeding 1.3 is evaluated as defective (x).

<Hardness and other>
The roller body 2 is 500 gf (≈4) in a normal temperature / humidity environment at a temperature of 23 ° C. and a relative humidity of 55% according to the measurement method defined in Japan Rubber Association Standard SRIS 0101 “Physical Test Method for Expanded Rubber”. It is preferable that the Asker C-type hardness measured by applying a load of .9 N) is 40 ° or less.

This is because the roller body whose Asker C hardness exceeds the above range is insufficient in flexibility, and has an effect of ensuring a wide nip width to improve toner transfer efficiency and an effect of reducing damage to the photoreceptor. It is because it is not possible.
The roller body 2 can be adjusted to have a predetermined compression set, dielectric loss tangent, or the like. In order to adjust the compression set, Asker C-type hardness, roller resistance value, dielectric loss tangent, etc., for example, the type and amount of each component constituting the rubber composition may be adjusted.

<Image forming apparatus>
The image forming apparatus of the present invention is characterized by incorporating the transfer roller of the present invention. Examples of the image forming apparatus of the present invention include various image forming apparatuses using electrophotography such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, or a complex machine of these.

<Example 1>
(Preparation of conductive rubber composition)
As rubber, 70 parts by mass of SBR [Sumitomo SBR 1502 manufactured by Sumitomo Chemical Co., Ltd.], 10 parts by mass of EPDM [Esprene (registered trademark) EPDM505A manufactured by Sumitomo Chemical Co., Ltd.], and ECO [manufactured by Nippon Zeon Co., Ltd.] HYDRIN (registered trademark) T3108] 20 parts by mass were blended.

As the carbon black HAF, manufactured by Tokai Carbon Co. of Co. trade name Seast 3 [arithmetic average particle diameter: 28nm, iodine adsorption: 80mg / g, DBP oil absorption: 101 cm ^3/100 g, bulk density: 380kgm ^-3] Was blended at a rate of 5 parts by mass per 100 parts by mass of the total rubber content.
Furthermore, as the foaming agent component, only an ADCA foaming agent (trade name Binihol AC # 3 manufactured by Eiwa Kasei Kogyo Co., Ltd.) is blended in a proportion of 2 parts by mass per 100 parts by mass of the total rubber content, and urea-based No foaming aid was blended.

  Each component shown in Table 1 below was further blended with the rubber component, carbon black HAF, and foaming agent component, and kneaded using a Banbury mixer to prepare a conductive rubber composition.

Each component in Table 1 is as follows.
Acid acceptor: Hydrotalcite [DHT-4A-2 manufactured by Kyowa Chemical Industry Co., Ltd.]
Crosslinking agent: powdered sulfur accelerator DM: di-2-benzothiazyl disulfide [Shandong Shanxian Chemical Co. Ltd .. Product name SUNSINE MBTS
Accelerator TS: Tetrametherthiuram monosulfide [Sunseller (registered trademark) TS manufactured by Sanshin Chemical Industry Co., Ltd.]
(Manufacture of transfer rollers)
The conductive rubber composition is supplied to an extruder and extruded into a long cylindrical shape having an outer diameter of φ10 mm and an inner diameter of φ3.0 mm, and the extruded cylindrical body 8 remains long without being cut. While continuously sending out, it is continuously foamed and cross-linked by continuously passing through the continuous cross-linking device 6 including the microwave cross-linking device 9 and the hot-air cross-linking device 10 shown in FIG. It was made to cool continuously.

The output of the microwave crosslinking apparatus 9 was 6 to 12 kW, the control temperature in the tank was 150 to 250 ° C., the control temperature in the tank of the hot-air crosslinking apparatus 10 was 150 to 250 ° C., and the effective length of the heating tank was 8 m.
The outer diameter of the cylindrical body 8 after foaming was approximately φ15 mm.
Next, the cylindrical body 8 is cut to a predetermined length to form a roller main body 2, and the roller main body 2 is mounted on a shaft having an outer diameter of φ5 mm with a conductive thermosetting adhesive applied to the outer peripheral surface. Then, the roller body 2 and the shaft 4 were electrically bonded and mechanically fixed by heating in an oven at 160 ° C. for 60 minutes to cure the thermosetting adhesive.

Next, both ends of the roller body 2 are cut, and then the outer peripheral surface 5 is traverse-ground using a cylindrical grinder so that the outer diameter of the roller body is finished to φ12.5 mm (tolerance ± 0.1 mm). Manufactured.
<Examples 2 to 5, Comparative Examples 1 and 2>
Carbon black HAF is blended in an amount of 3 parts by mass (Comparative Example 1), 10 parts by mass (Example 2), 15 parts by mass (Example 3), and 20 parts by mass (Example 4). ), 25 parts by mass (Example 5), and 30 parts by mass (Comparative Example 2), a conductive rubber composition was prepared in the same manner as in Example 1 to produce a transfer roller.

<Example 6>
A conductive rubber composition was prepared in the same manner as in Example 3 except that the blending ratio of SBR as a rubber component was 80 parts by mass and the blending ratio of ECO was 10 parts by mass, and a transfer roller was manufactured.
<Example 7>
As rubber, NBR [JSR N250SL manufactured by JSR Corporation, low nitrile NBR, acrylonitrile content 20%] 30 parts by mass is added, and the blending ratio of SBR is 40 parts by mass. A conductive rubber composition was prepared in the same manner as in Example 3 to produce a transfer roller.

<Example 8>
In addition to adding 30 parts by mass of CR (Showaden (registered trademark) WRT manufactured by Showa Denko Elastomer Co., Ltd.), which is a polar rubber, as the rubber component, and Example 3 except that the blending ratio of SBR was 40 parts by mass Similarly, a conductive rubber composition was prepared and a transfer roller was produced.

<Measurement of roller resistance and unevenness evaluation>
The roller resistance value of the transfer roller manufactured in each Example and Comparative Example at an applied voltage of 1000 V was measured by the measurement method shown in FIG. 3 described above in a normal temperature and normal humidity environment at a temperature of 23 ° C. and a relative humidity of 55%. It was measured. The roller resistance value R was evaluated as good (◯) when it was 10 ^6.5 Ω or more and 10 ¹⁰ Ω or less, and was evaluated as poor (x) when it was not. In Tables 2 and 3, the roller resistance value R is shown as a logR value.

Further, the ratio of the maximum resistance value to the minimum resistance value (maximum resistance value / minimum resistance value) of the roller resistance value was obtained by the method described above, and the unevenness of the roller resistance value was evaluated according to the following criteria.
A: The ratio is 1.2 or less. No unevenness. Good.
○: The ratio exceeds 1.2 and is 1.3 or less. Although it is slightly uneven, it is a practical level.

X: The ratio exceeded 1.3. There is unevenness. Bad.
<Roller body hardness measurement>
The Asker C-type hardness of the roller body 2 of the transfer roller manufactured in each example and comparative example was measured by the measurement method described above in a normal temperature and normal humidity environment with a temperature of 23 ° C. and a relative humidity of 55%. The Asker C-type hardness was evaluated as good (◯) when it was 40 ° or less and poor (×) when it exceeded 40 °.

  The above results are shown in Tables 2 and 3.

From the results of Examples 1 to 8 in Table 2 and Table 3, by blending carbon black HAF with a conductive rubber composition containing SBR as a crosslinkable rubber, extrusion and continuous using a continuous crosslinking apparatus. It has been found that it is possible to produce a roller body that is sufficiently foamed and cross-linked by sufficient cross-linking and sufficiently satisfies the required flexibility.
However, from the results of Examples 1 to 8 and Comparative Example 1, in order to obtain the above effect, the blending ratio of the carbon black HAF needs to be 5 parts by mass or more per 100 parts by mass of the total amount of rubber. understood.

Further, from the results of Examples 1 to 8 and Comparative Example 2, when the blending ratio of carbon black HAF is too large, the roller resistance value of the transfer roller is excessively lowered and unevenness occurs in the roller resistance value. It turned out that the said mixture ratio needs to be 25 mass parts or less per 100 mass parts of total amounts of a rubber part.
Further, from the results of Examples 1 to 5, in order to further improve the above-described effect and to manufacture a roller main body having particularly small unevenness of the roller resistance value, the blending ratio of the carbon black is within the above range. It turned out that it is preferable to set it as 20 mass parts or less per 100 mass parts of total amount of a minute.

  Further, from the results of Example 3 and Examples 7 and 8, it was found that the roller resistance value of the transfer roller can be finely adjusted by blending polar rubber as a rubber component.

DESCRIPTION OF SYMBOLS 1 Transfer roller 2 Roller main body 3 Through-hole 4 Shaft 5 Outer peripheral surface 6 Continuous bridge | crosslinking apparatus 7 Extruder 8 Cylindrical body 9 Microwave bridge | crosslinking apparatus 10 Hot-air bridge | crosslinking apparatus 11 Take-out machine 12 Aluminum drum 13 Outer peripheral surface 14 DC power supply 15 Resistance 16 Measuring circuit F Load V Detection voltage

Claims (5)

  A conductive rubber composition that can be foamed and cross-linked by a continuous cross-linking device including a microwave cross-linking device and a hot-air cross-linking device, the rubber content including at least styrene butadiene rubber, ethylene propylene diene rubber, and epichlorohydrin rubber, Contains only 0.1 parts by mass or more and 4 parts by mass or less of azodicarbonamide as a foaming agent per 100 parts by mass of the total amount of the rubber as a crosslinking agent component for crosslinking a rubber component and a foaming agent component. In addition, a conductive rubber composition comprising carbon black HAF at a ratio of 5 parts by mass or more and 25 parts by mass or less per 100 parts by mass of the total amount of the rubber.   The conductive rubber composition according to claim 1, wherein the rubber component further contains at least one polar rubber selected from the group consisting of acrylonitrile butadiene rubber, chloroprene rubber, butadiene rubber, and acrylic rubber.   A transfer roller comprising a cylindrical roller body made of the conductive rubber composition according to claim 1. A method of manufacturing a transfer roller according to claim 3, wherein the roller body, while extruding the conductive rubber composition into a tubular shape, the microwave bridge device and the hot-air crosslinking device a continuous bridge device including A transfer roller manufacturing method, wherein the transfer roller is formed through a process of continuously foaming and cross-linking. An image forming apparatus incorporating the transfer roller according to claim 3 .

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