JP2017203970A - Transfer roller and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transfer roller with smaller rubber hardness and being flexible, and moreover, with a diameter of a foam cell smaller than conventional ones, and to provide a manufacturing method of the transfer roller.SOLUTION: A transfer roller 1 includes a foam body of a conductive rubber composition including: rubber; a crosslinking component; an OBSH as a foaming agent; and a sodium hydrogen carbonate 0.25-2.5 pts.mass with regard to the OBSH 1 pt.mass, and has Asker C type hardness of 25-35°, and an average cell diameter of foam cells of 120 μm or less. A manufacturing method includes a step of forming the conductive rubber composition into a cylinder shape and foaming by a single step while maintaining a temperature at 120-140°C.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a transfer roller and a manufacturing method thereof.

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, the paper of a paper or a plastic film is roughly processed through the following steps. An image is formed on the surface.
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, toner, which is fine colored particles, is brought into contact with the surface of the photoreceptor in a state of being 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).
Then, when the developed toner image is transferred to the surface of the paper (transfer process) and further fixed (fixing process), an image is formed on the surface of the paper.

Further, the photoconductor after transferring the toner image is prepared for use in the next image formation by removing the toner remaining on the surface (cleaning step).
In the transfer process, the toner image formed on the surface of the photoconductor may be transferred directly to the surface of the paper, or may be transferred primarily to the surface of the image carrier and then transferred to the surface of the paper. .

In the transfer step, in order to transfer the toner image onto the surface of the paper or the surface of the image carrier, a transfer roller made of a rubber foam and having conductivity is widely used.
In order to impart conductivity to the transfer roller, the rubber is blended with a crosslinking component for crosslinking the rubber, and a foaming agent for decomposing by heating to generate gas and foam the rubber. In general, an ion conductive rubber is used as the rubber, or the conductive rubber composition is prepared by blending a conductive agent.

That is, the transfer roller is manufactured by forming the conductive rubber composition into a cylindrical shape and heating to foam and crosslink.
In order to cope with higher image quality of image forming apparatuses in recent years, the transfer roller has a rubber hardness as small and flexible as possible, and the cell diameter of the foam cell constituting the foam is as small as possible and the outer periphery. The surface is required to be smooth.

As the foaming agent, for example, azodicarbonamide (ADCA), 4,4′-oxybisbenzenesulfonyl hydrazide (OBSH), or the like is used (Patent Document 1, etc.).
When both foaming agents are compared, OBSH has a tendency to obtain a foam cell having a smaller diameter than ADCA. Therefore, when producing a foam having a small diameter foam cell, OBSH is selected as the foaming agent. It is common.

  However, since OBSH also functions as a rubber cross-linking accelerator, for example, during heating after molding, the rubber cross-linking reaction precedes foaming due to decomposition of the OBSH. As a result, it becomes difficult to escape from the foam through the gas, and more gas is taken into the individual foamed cells. As a result, the cell diameter of the foamed cells tends to increase.

  Therefore, when OBSH is used alone as a foaming agent, it is possible to produce a transfer roller that can sufficiently meet recent demands, has a small rubber hardness, is flexible, and has a foamed cell smaller in diameter than the present state. Can not.

JP 2001-227532 A JP 2002-113734 A

  An object of the present invention is to provide a transfer roller having a small rubber hardness and being flexible and having a foamed cell having a smaller diameter than the current state, and a method for manufacturing such a transfer roller.

  The present invention relates to rubber, a crosslinking component for crosslinking the rubber, OBSH as a foaming agent for foaming the rubber, and 0.25 to 2.5 parts by mass of carbonic acid per 1 part by mass of the OBSH. A transfer roller comprising a foam of a conductive rubber composition containing sodium hydrogen, having an Asker C-type hardness of 25 ° to 35 °, and an average cell diameter of foamed cells of 120 μm or less.

The present invention is also a method for producing the transfer roller, wherein the conductive rubber composition is extruded into a cylindrical shape and then held at a temperature of 120 ° C. or higher and 140 ° C. or lower with pressurized steam in a vulcanizing can. And a step of foaming in one stage.
Further, the present invention is a method for producing the transfer roller, wherein the conductive rubber composition is extruded through a cylinder and continuously passed through a continuous crosslinking apparatus including a microwave crosslinking apparatus and a hot-air crosslinking apparatus. However, it is characterized by including a step of foaming in one step while maintaining the temperature at 120 ° C. or more and 140 ° C. or less.

  According to the present invention, it is possible to provide a transfer roller in which the rubber hardness is small and flexible, and the foamed cell has a smaller diameter than the current state, and a method for manufacturing the transfer roller.

It is a perspective view which shows an example of embodiment of the transfer roller of this invention. It is a block diagram which shows the outline of the continuous bridge | crosslinking apparatus used for manufacture of the transfer roller of this invention.

<Transfer roller>
As described above, the conductive rubber composition used as the basis of the transfer roller of the present invention includes rubber, a crosslinking component for crosslinking the rubber, OBSH as a foaming agent for foaming the rubber, and 1 part by mass of OBSH. 0.25 parts by mass or more and 2.5 parts by mass or less of sodium hydrogen carbonate are contained.

According to the conductive rubber composition, it is possible to form a transfer roller having a small rubber hardness and being flexible and having a foamed cell having a smaller diameter than the current state.
Specifically, using such a conductive rubber composition, the rubber hardness is exhibited by going through the same manufacturing process as in the case of using a conventional conductive rubber composition using OBSH alone as a foaming agent. The transfer roller of the present invention having an Asker C-type hardness of 25 ° or more and 35 ° or less and an average cell diameter of foamed cells of 120 μm or less can be produced.

That is, when the conductive rubber composition is formed into a cylindrical shape to produce a transfer roller, and then heated for foaming and crosslinking, it functions as an endothermic foaming agent and has a lower decomposition temperature than OBSH. As a result of the endothermic reaction, the temperature rise of the rubber immediately before the OBSH is decomposed is suppressed, and the crosslinking of the rubber is delayed.
Therefore, excessive gas generated by the subsequent decomposition of OBSH easily escapes from the foam through the rubber partition walls, and the amount of gas taken into the individual foam cells is reduced, so that the average cell diameter of the foam cells is increased. It is adjusted to the range of 120 μm or less, which is 20 μm or more smaller than the case where OBSH is used alone without using sodium bicarbonate.

In addition, in the said conductive rubber composition, it is based on the following reason that the mixture ratio of sodium hydrogencarbonate is limited to 0.25 mass part or more and 2.5 mass parts or less per 1 mass part of OBSH.
That is, if the blending ratio of sodium bicarbonate is less than this range, the effect of reducing the cell diameter of the foamed cells by delaying the crosslinking of the rubber by using sodium bicarbonate together with OBSH cannot be obtained. The average cell diameter of the foam cell exceeds the range of 120 μm or less.

On the other hand, when the blending ratio of sodium hydrogen carbonate exceeds the above range, the effect of delaying the rubber cross-linking by the sodium hydrogen carbonate is too strong, and the cross-linking of the rubber is hindered. The rubber hardness is less than 25 ° in terms of Asker C-type hardness, so that the strength of the transfer roller is insufficient, and settling or the like tends to occur.
On the other hand, by setting the blending ratio of sodium hydrogen carbonate within the above range, the Asker C-type hardness is 25 ° or more and 35 ° or less as described above, and it is moderately flexible and hardly causes settling or the like. In addition, the transfer cell of the present invention can be obtained in which the average cell diameter of the foamed cells is 120 μm or less, which is smaller than the current state and the outer peripheral surface is smooth.

In consideration of further improving this effect, the blending ratio of sodium hydrogen carbonate is preferably 0.3 parts by mass or more per 1 part by mass of OBSH even in the above range, and is 1.8 parts by mass or less. Is preferred.
The reason why the Asker C-type hardness of the transfer roller of the present invention is limited to a range of 25 ° to 35 ° and the average cell diameter of the foamed cells is limited to a range of 120 μm or less is as described above.

In other words, if the Asker C-type hardness is less than 25 °, the transfer roller is insufficient in strength and tends to cause settling or the like. If the Asker C-type hardness exceeds 35 °, the transfer roller cannot be provided with good flexibility.
In addition, when the average cell diameter of the foamed cells exceeds 120 μm, the smoothness of the outer peripheral surface of the transfer roller is lowered, and it becomes impossible to sufficiently meet the recent demand for higher image quality of the image forming apparatus.

On the other hand, the Asker C-type hardness and the average cell diameter of the foamed cells are within the above ranges, respectively, which can sufficiently meet the demand for higher image quality and are moderately flexible and less likely to cause settling. It is possible to provide a transfer roller in which the foam cell has a smaller diameter than the current state.
In consideration of further improving this effect, the average cell diameter of the foamed cells is preferably less than 100 μm even in the above range.

The lower limit of the average cell diameter of the foamed cells is not particularly limited, but is preferably 82 μm or more, particularly 84 μm or more. When the average cell diameter is less than this range, the Asker C-type hardness of the transfer roller exceeds the above-described range, and there is a possibility that good flexibility cannot be imparted to the transfer roller.
In Patent Document 2, two types of foaming agents having different decomposition temperatures of 10 ° C. or more are used in combination. First, the temperature at which only the foaming agent on the low temperature side decomposes, that is, the decomposition temperature of the foaming agent on the low temperature side, After forming the closed cell structure by performing the first stage foaming process that is held at a temperature lower than the decomposition temperature of the foaming agent, the temperature at which the foaming agent on the high temperature side decomposes, that is, the temperature above the decomposition temperature of the foaming agent on the high temperature side It is possible to break the closed cell structure formed earlier by carrying out the second stage foaming process to keep the foamed cells in communication with each other, that is, to reduce the hardness of the foam by the above two stage foaming process. Have been described.

Patent Document 2 also describes sodium bicarbonate as well as OBSH as an example of the foaming agent.
However, as is clear from the above mechanism, in the two-stage foaming process described in Patent Document 2, a large number of foamed cells generated in the first stage foaming process are communicated with each other in the second stage foaming process. Therefore, even if OBSH and sodium bicarbonate are used in combination as foaming agents, the Asker C-type hardness is 25 ° or more and 35 ° or less, and the average cell diameter of the foamed cells is 120 μm or less. The same transfer roller as in the present invention cannot be formed.

  Incidentally, although the average cell diameter of Example 1 of Patent Document 2 is as small as 80 μm, this is because foaming is mechanically suppressed using a mold during the first stage foaming treatment. For example, as is clear from the results of Conventional Example 2 described later, when foaming and cross-linking treatment using a vulcanizing can or a continuous cross-linking apparatus is performed, the average cell diameter is 120 μm or less by the mechanism described above in the configuration of Patent Document 2. It will be out of range. For this reason, the Asker C-type hardness may fall below a range of 25 ° or more.

<Rubber>
Examples of the rubber that forms the conductive rubber composition include various rubbers that can be foamed by the action of a foaming agent and that can be crosslinked by the action of a crosslinking component.
In particular, epichlorohydrin rubber having ionic conductivity is preferable in consideration of imparting appropriate conductivity to the conductive rubber composition.

(Epichlorohydrin rubber)
As the epichlorohydrin rubber, various polymers having epichlorohydrin as a repeating unit and having ionic conductivity can be used.
Examples of such epichlorohydrin rubber include epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allyl glycidyl ether binary copolymer, epichlorohydrin-ethylene oxide. 1 type or 2 types of allyl glycidyl ether terpolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer, etc. The above is mentioned.

Among them, a copolymer containing ethylene oxide, particularly ECO and / or GECO is preferable.
The ethylene oxide content in both copolymers 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 this range, such a function cannot be obtained sufficiently, so that the roller resistance value may not be sufficiently reduced.

On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs and the segment motion of the molecular chain is hindered, so that the roller resistance value tends to increase. In addition, the transfer roller after crosslinking may become too hard, or the viscosity of the conductive rubber composition before crosslinking may increase when heated and melted, resulting in a decrease in workability.
The epichlorohydrin content in ECO is the remaining amount of 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.
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 this range, such a function cannot be obtained, so that the roller resistance value may not be sufficiently reduced.

On the other hand, since allyl glycidyl ether functions as a crosslinking point during GECO crosslinking, when the allyl glycidyl ether content exceeds the above range, the GECO crosslinking density becomes too high, preventing the molecular chain segment movement. On the other hand, the roller resistance value tends to increase.
The epichlorohydrin content in GECO is the remaining amount of ethylene oxide content and allyl glycidyl ether content. That is, the epichlorohydrin content is preferably 10 mol% or more, more preferably 15 mol% or more, and preferably 69.5 mol% or less, particularly 48 mol% or less.

As GECO, in addition to the above-described copolymer in the narrow sense obtained by copolymerization of the three types of monomers, a modification obtained by modifying epichlorohydrin-ethylene oxide copolymer (ECO) with allyl glycidyl ether. Things are also known, and such modified products can also be used as GECO.
The blending ratio of the epichlorohydrin rubber is preferably 20 parts by mass or more and preferably 40 parts by mass or less per 100 parts by mass of the total amount of rubber in the combined use system with other rubber described in the following paragraph.

If the blending ratio of epichlorohydrin rubber is less than this range, there is a possibility that good ionic conductivity cannot be imparted to the transfer roller.
On the other hand, when the blending ratio of epichlorohydrin rubber exceeds the above range, the ratio of other rubbers becomes relatively small, and there is a risk that the effects of using each rubber described below may not be sufficiently obtained. There is.

(Other rubber)
As rubber, other rubber may be used in combination with epichlorohydrin rubber.
Examples of such other rubbers include styrene butadiene rubber (SBR), ethylene propylene diene rubber (EPDM), acrylonitrile butadiene rubber (NBR), chloroprene rubber (CR), butadiene rubber (BR), and acrylic rubber (ACM). There may be mentioned at least one selected from the group.

In particular, EPDM and NBR are preferably used in combination.
EPDM functions to improve the ozone resistance, aging resistance, weather resistance, etc. of the transfer roller.
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 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.

In addition, as EPDM, 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.
One or more of these EPDMs can be used.
NBR also improves the mechanical strength and durability of the transfer roller, and gives the transfer roller properties such as rubber, that is, a property that is flexible and has a low compression set and is less likely to cause settling. To work.

As NBR, any of low nitrile NBR, medium nitrile NBR, medium high nitrile NBR, high nitrile NBR, and extremely high nitrile NBR classified according to acrylonitrile content can be used.
NBR includes an oil-extended type in which flexibility is adjusted by adding extension oil and a non-oil-extended type in which flexibility is not added, either of which can be used.

One or more of these NBRs can be used.
The blending ratio of EPDM is preferably 5 parts by mass or more and preferably 20 parts by mass or less per 100 parts by mass of the total amount of rubber.
When the blending ratio of EPDM is less than this range, there is a possibility that good ozone resistance or the like cannot be imparted to the transfer roller.

On the other hand, when the blending ratio of EPDM exceeds the above range, the ratio of epichlorohydrin rubber is relatively decreased, and there is a possibility that good ionic conductivity cannot be imparted to the transfer roller. Moreover, there is a possibility that the ratio of NBR is reduced, so that the mechanical strength and the like of the transfer roller cannot be improved, and good characteristics as rubber cannot be imparted.
The blending ratio of NBR is the remaining amount of epichlorohydrin rubber and EPDM. That is, the NBR blending ratio may be set so that the total amount of rubber becomes 100 parts by mass when the blending ratio of epichlorohydrin rubber and EPDM is set to a predetermined value.

When using an oil-extended type as EPDM and / or NBR, the blending ratio of the oil-extended type rubber is the ratio of the rubber itself as a solid content excluding the extending oil.
<Crosslinking component>
Examples of the crosslinking component for crosslinking the rubber include a crosslinking agent and a crosslinking accelerator.
Among these, as the crosslinking agent, a sulfur-based crosslinking agent is particularly preferable.

Examples of the sulfur-based crosslinking agent include sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, or organic sulfur-containing compounds such as tetramethylthiuram disulfide and N, N-dithiobismorpholine. In particular, sulfur is preferable.
The blending ratio of sulfur is preferably 0.5 parts by mass or more and preferably 3 parts by mass or less per 100 parts by mass of the total amount of rubber.

For example, when oil-treated powder sulfur, dispersible sulfur, or the like is used as sulfur, the blending ratio is the ratio of sulfur itself as an active ingredient contained therein.
Examples of the crosslinking accelerator include thiuram accelerators and thiazole accelerators. It is preferable to use two or more types of crosslinking accelerators in combination because the crosslinking promotion mechanism varies depending on the type.

  Among these, as thiuram accelerators, for example, tetramethylthiuram monosulfide (TS), tetramethylthiuram disulfide (TT, TMT), tetraethylthiuram disulfide (TET), tetrabutylthiuram disulfide (TBT), tetrakis (2-ethylhexyl) One type or two or more types such as thiuram disulfide (TOT-N) and dipentamethylene thiuram tetrasulfide (TRA) can be used.

The blending ratio of the thiuram accelerator is preferably 0.5 parts by mass or more and preferably 3 parts by mass or less per 100 parts by mass of the total amount of rubber.
Examples of thiazole accelerators include 2-mercaptobenzothiazole (M), di-2-benzothiazolyl disulfide (DM), zinc salt of 2-mercaptobenzothiazole (MZ), and cyclohexyl 2-mercaptobenzothiazole. One or two of amine salts (HM, M60-OT), 2- (N, N-diethylthiocarbamoylthio) benzothiazole (64), 2- (4′-morpholinodithio) benzothiazole (DS, MDB) and the like More than species.

The blending ratio of the thiazole accelerator is preferably 0.5 parts by mass or more and preferably 3 parts by mass or less per 100 parts by mass of the total amount of rubber.
<Foaming agent>
As the foaming agent, OBSH is used as described above. Although it is not limited to this as OBSH, for example, such as Neo-Selbon (registered trademark) N # 1000SW, N # 1000S, N # 5000, N # 1000M, N # 5000 #, SB # 51 manufactured by Eiwa Chemical Industry Co., Ltd. 1 type or 2 types or more are mentioned.

The blending ratio of OBSH is preferably 2 parts by mass or more, particularly 3 parts by mass or more, preferably 6 parts by mass or less, particularly 5 parts by mass or less, per 100 parts by mass of the total amount of rubber.
If the blending ratio of OBSH is less than this range, the rubber cannot be sufficiently foamed. Therefore, the Asker C-type hardness of the transfer roller exceeds the aforementioned range, and there is a possibility that good flexibility cannot be imparted to the transfer roller.

In addition, when the blending ratio of OBSH exceeds the above range, adjacent foamed cells that have fired simultaneously suppress expansion due to mutual expansion force, so that the average cell diameter of the foamed cells becomes excessively small, and transfer is performed instead. There is a possibility that the Asker C-type hardness of the roller exceeds the above-described range, and good flexibility cannot be imparted to the transfer roller.
On the other hand, by setting the blending ratio of OBSH within the above range, the Asker C-type hardness is in the above-described range, and an appropriately flexible transfer roller can be formed.

Moreover, as sodium hydrogencarbonate used together with OBSH, it is not limited to this, For example, the brand name SELVON FE-507, FE-507R, SC-P, SC-K, FE-512, etc. made by Eiwa Chemical Industry Co., Ltd. 1 type or 2 types or more are mentioned.
Of these, FE-507 and SC-K are preferred. Any one of these may be used alone, or two may be used in any ratio.

The blending ratio of sodium bicarbonate needs to be 0.25 parts by mass or more and 2.5 parts by mass or less per 1 part by mass of OBSH. The reason for this is as described above.
<Other ingredients>
You may mix | blend various additives with a rubber composition further as needed. Examples of the additive include a crosslinking accelerator, an acid acceptor, and a filler.

Among these, examples of the crosslinking accelerating aid include metal compounds such as zinc oxide (zinc white); fatty acids such as stearic acid, oleic acid, and cottonseed fatty acid, and one or more conventionally known crosslinking accelerating aids. Can be mentioned.
The blending ratio of the crosslinking accelerating aid is preferably individually 0.1 parts by mass or more and preferably 7 parts by mass or less per 100 parts by mass of the total amount of rubber.

The acid acceptor functions to prevent the chlorine-based gas generated from the epichlorohydrin rubber or the like during crosslinking from remaining in the transfer roller, thereby inhibiting crosslinking or contamination of the photoreceptor.
As the acid acceptor, various substances acting as an acid acceptor can be used. Among them, hydrotalcite or magsarat having excellent dispersibility is preferable, and hydrotalcite is particularly preferable.

Further, when 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 more reliably prevented.
The mixing 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. .
If the blending ratio of the acid acceptor is less than this range, the effect of blending the acid acceptor may not be sufficiently obtained. Further, when the blending ratio of the acid acceptor exceeds the above range, the hardness of the transfer roller after crosslinking may increase.

Examples of the filler include one or more of zinc oxide, silica, carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, and the like.
By blending a filler, the mechanical strength of the transfer roller can be improved.
In addition, by using conductive carbon black as a filler, transfer is performed through a process of imparting electronic conductivity to the transfer roller or continuously passing through a continuous crosslinking apparatus including a microwave crosslinking apparatus and a hot-air crosslinking apparatus described later. When manufacturing a roller, the absorption efficiency of the microwave as the whole of a conductive rubber composition can be improved.

HAF is preferable as the conductive carbon black. HAF is particularly excellent in microwave absorption efficiency and can be uniformly dispersed in the conductive rubber composition, so that the transfer roller can be given as uniform electronic conductivity as possible.
The blending ratio of the conductive carbon black is preferably 5 parts by mass or more and preferably 20 parts by mass or less per 100 parts by mass of the total amount of rubber.

In addition, as additives, various additives such as deterioration inhibitors, scorch inhibitors, plasticizers, lubricants, pigments, antistatic agents, flame retardants, neutralizers, nucleating agents, co-crosslinking agents, etc., in any proportion You may mix with.
<Transfer roller>
FIG. 1 is a perspective view showing an example of an embodiment of a transfer roller of the present invention.

Referring to FIG. 1, a transfer roller 1 of this example is formed in a single-layered cylindrical shape by a rubber foam made of a conductive rubber composition containing the above-described components, and is formed in a central through hole 2. The shaft 3 is inserted and fixed.
The shaft 3 is integrally formed of a metal such as aluminum, an aluminum alloy, or stainless steel.

The shaft 3 is electrically joined to the transfer roller 1 via, for example, a conductive adhesive and is mechanically fixed, or the through-hole 2 having an outer diameter larger than the inner diameter of the through-hole 2. By being press-fitted into the transfer roller 1, it is electrically joined to the transfer roller 1 and is mechanically fixed and rotated integrally.
The transfer roller 1 needs to have an Asker C-type hardness of 25 ° or more and 35 ° or less and an average cell diameter of foamed cells of 120 μm or less. The average cell diameter is preferably 82 μm or more, particularly 84 μm or more even in the above range. These reasons are as described above.

Note Asker-C hardness of the transfer roller 1, the Japanese Industrial Standard JIS _{K7312 -1996} incorporated in Annex 2 of "Physical testing method for thermosetting polyurethane elastomer molded product" by the Japan Rubber Association Standard SRIS0101 "expansion Using a type C hardness tester (for example, Asker rubber hardness tester C type manufactured by Kobunshi Keiki Co., Ltd.) conforming to “Physical Test Method for Rubber”, it is expressed by a value measured by the following method.

That is, with the both ends of the shaft 3 integrated with the transfer roller 1 fixed to the support base as described above, the push needle of the type C hardness tester is pressed against the center of the transfer roller 1. Furthermore, a load of 10 N (≈1 kgf) is added to measure Asker C-type hardness.
The average cell diameter of the foamed cells is the longest diameter (μm) and the shortest diameter of the 30 largest foamed cells included in the field of view of the outer peripheral surface 4 of the transfer roller 1 observed at a magnification of 200 times using a microscope. From (μm), formula (1):
Cell diameter (μm) = (major axis + minor axis) / 2 (1)
This is expressed by the average value of the cell diameters of the individual foamed cells obtained by the above.

All tests are performed in an environment of a temperature of 23 ° C. and a relative humidity of 55%.
The transfer roller 1 of the present invention is incorporated in 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, and is used as a photosensitive member. The toner image formed on the surface can be used to transfer to the surface of the paper or the surface of the image carrier.

<< Production Method I of Transfer Roller >>
In the manufacturing method of the present invention for manufacturing the transfer roller 1, first, the conductive rubber composition composed of the above-described components is extruded into a cylindrical shape using an extruder, and then to a predetermined length. Cut and hold in a vulcanizing can at a temperature of 120 ° C. or higher and 140 ° C. or lower and foam in one step.

The foaming temperature is in the above range for the following reason.
That is, if the foaming temperature is less than this range, foaming is insufficient, the average cell diameter of the transfer roller 1 falls below the above-mentioned range of 82 μm or less, and the Asker C-type hardness exceeds the range of 35 ° or less. There is a possibility that good flexibility cannot be imparted to the roller 1.
On the other hand, when the foaming temperature exceeds the above range, foaming becomes excessive, the average cell diameter of the transfer roller 1 exceeds the above-mentioned range of 120 μm or less, and the smoothness of the outer peripheral surface is lowered. There is a risk that it will not be possible to sufficiently meet the demand for higher image quality of the device.

After foaming, the temperature inside the vulcanizing can is raised to the above foaming temperature, in particular 150 ° C or more, and kept for a short time of about 25 minutes or less, so that the crosslinking of rubber that has progressed even during foaming is completed. It may be.
However, it must not be kept at a high temperature for a longer time than this. If heating at a high temperature is continued for a long time, it becomes the second stage foaming treatment described in Patent Document 2 described above, and the average cell diameter of the foamed cells exceeds the range of 120 μm or less. is there.

In the present invention, the heating at a high temperature for completing the crosslinking is preferably as short as possible within the above range, and in some cases, such heating may be omitted.
Next, the foamed and cross-linked cylindrical body is heated using an oven or the like, subjected to secondary cross-linking, then cooled, and further polished to have a predetermined outer diameter.
The shaft 3 can be fixed by being inserted into the through-hole 2 at an arbitrary time after the cylindrical body is cut and after polishing.

However, after the cutting, it is preferable to perform secondary crosslinking and polishing with the shaft 3 inserted through the through hole 2 first. Thereby, the curvature, deformation | transformation, etc. of a cylindrical body by the expansion-contraction at the time of secondary bridge | crosslinking can be suppressed. Further, by polishing while rotating around the shaft 3, the workability of the polishing can be improved, and the deflection of the outer peripheral surface 4 can be suppressed.
As described above, the shaft 3 is inserted into the through-hole 2 of the tubular body before the secondary cross-linking through a conductive adhesive, particularly a thermosetting adhesive, and then secondary cross-linked. What is necessary is just to press-fit into the through-hole 2 what is larger in outer diameter than the inner diameter of the hole 2.

In the former case, the thermosetting adhesive is cured simultaneously with the secondary cross-linking of the cylindrical body by heating in the oven, and the shaft 3 is electrically joined to the transfer roller 1 and mechanically. Fixed to. In the latter case, electrical joining and mechanical fixing are completed simultaneously with press-fitting.
According to the production method of the present invention, the extruded cylindrical body is held at a temperature of 120 ° C. or higher and 140 ° C. or lower in a vulcanizing can and foamed in one step, whereby Asker C-type hardness is obtained. The transfer roller of the present invention having an angle of 25 ° to 35 ° and an average cell diameter of foamed cells of 120 μm or less can be produced.

<Transfer roller manufacturing method II>
In another production method of the present invention for producing the transfer roller 1, a continuous crosslinking apparatus including a microwave crosslinking apparatus and a hot air crosslinking apparatus is used.
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 5 of this example is based on a transfer roller 1 obtained by continuously extruding a conductive rubber composition using an extruder 6. The microwave bridge device 8, the hot-air bridge device 9, and the cylinder body 7 are sequentially formed in the course of continuous conveyance by a conveyor or the like (not shown) without cutting the long tubular body 7 to be long. Is disposed at a constant speed.

In the production method using the continuous crosslinking device 5, first, the above-described extruder 6 is mixed while the components described above are kneaded and the conductive rubber composition formed into a ribbon shape or the like is continuously supplied to the extruder 6. By operating, the long cylindrical body 7 is continuously extruded.
Next, while the extruded cylindrical body 7 is continuously conveyed at a constant speed by the conveyor and the take-up machine 10, the microwave is first irradiated while passing through the microwave crosslinking apparatus 8 in the continuous crosslinking apparatus 5. The rubber forming the cylindrical body 7 is crosslinked to a certain degree of crosslinking density.

Next, the rubber is further foamed by passing through the hot air cross-linking device 9 while continuing the conveyance and blown with hot air of 120 ° C. or higher and 140 ° C. or lower, and is crosslinked to a predetermined cross-linking density.
Thereafter, when the cylindrical body 7 is cooled, foaming and crosslinking in one stage in the temperature range of the cylindrical body 7 are completed.

In addition, the inside of the microwave bridge | crosslinking apparatus 8 can be heated to the temperature of 120 to 140 degreeC, and rubber | gum can also be foamed with bridge | crosslinking.
Also in that case, since the cylindrical body 7 continuously foams through both devices 8 and 9, it can be regarded as foaming in one stage.
The conveyance speed of the cylindrical body 7, the microwave dose irradiated by the microwave bridge device 8, the set temperature and length of the hot air bridge device 9 (each of which is divided into a plurality of regions, the temperatures of 120 ° C. or higher and 140 ° C. or lower) Etc. can be changed stepwise within a range, etc., so that the cylindrical body 7 in which the foamed state of rubber, the crosslinking density, etc. are set to predetermined values can be continuously produced, and the productivity can be improved.

In addition, in order to make the irradiation dose of microwaves and the degree of heating uniform throughout the cylindrical body 7 and to make the foaming state and the crosslinking density as constant as possible, the cylindrical body 7 in the middle of conveyance should be twisted. It may be.
Thereafter, the foamed and cross-linked cylindrical body 7 is cut to a predetermined length, and the same process as in the previous manufacturing method I is performed, whereby the transfer roller 1 of the present invention is manufactured.

That is, the cylindrical body 7 cut to a predetermined length is heated using an oven or the like to be secondarily crosslinked, cooled, and then polished to have a predetermined outer diameter.
The shaft 3 can be fixed by being inserted into the through-hole 2 at an arbitrary time after the cylindrical body is cut and after polishing.
However, after the cutting, it is preferable to perform secondary crosslinking and polishing with the shaft 3 inserted through the through hole 2 first. Thereby, the curvature, deformation | transformation, etc. of a cylindrical body by the expansion-contraction at the time of secondary bridge | crosslinking can be suppressed. Further, by polishing while rotating around the shaft 3, the workability of the polishing can be improved, and the deflection of the outer peripheral surface 4 can be suppressed.

As described above, the shaft 3 is inserted into the through-hole 2 of the tubular body before the secondary cross-linking through a conductive adhesive, particularly a thermosetting adhesive, and then secondary cross-linked. What is necessary is just to press-fit into the through-hole 2 what is larger in outer diameter than the inner diameter of the hole 2.
In the former case, the thermosetting adhesive is cured simultaneously with the secondary cross-linking of the cylindrical body by heating in the oven, and the shaft 3 is electrically joined to the transfer roller 1 and mechanically. Fixed to. In the latter case, electrical joining and mechanical fixing are completed simultaneously with press-fitting.

  According to the production method of the present invention, the extruded cylindrical body is continuously passed through the continuous cross-linking device 5 including the microwave cross-linking device 8 and the hot-air cross-linking device 9 at 120 ° C. or higher and 140 ° C. or lower. By maintaining the temperature and foaming in one step, the transfer roller of the present invention having an Asker C-type hardness of 25 ° or more and 35 ° or less and an average cell diameter of the foamed cells of 120 μm or less can be produced.

<Example 1>
(Preparation of rubber composition)
As rubber, GECO [HYDRIN (registered trademark) T3108 manufactured by Nippon Zeon Co., Ltd.] 30 parts by mass, EPDM (Esprene (registered trademark) 505A manufactured by Sumitomo Chemical Co., Ltd., non-oil-extended) 10 parts by mass, and NBR [ 60 parts by mass of Nipol (registered trademark) DN401LL manufactured by Nippon Zeon Co., Ltd., non-oil-extended, bound acrylonitrile amount: 18.0% (center value)].

  Then, while kneading 100 parts by mass of these rubbers using a Banbury mixer, first, carbon black and hydrotalcite are added and kneaded among the components shown in Table 1 below, and the remaining components are added and kneaded. Thus, a conductive rubber composition was prepared.

Each component in Table 1 is as follows. In addition, the mass part in Table 1 is a mass part per 100 mass parts of the total amount of rubber.
Foaming agent OBSH: Neoselbon (registered trademark) N # 1000SW manufactured by Eiwa Kasei Kogyo Co., Ltd.
Sodium hydrogen carbonate: Mixture of trade name SELVON FE-507 and SELVON SC-K manufactured by Eiwa Kasei Kogyo Co., Ltd. Mass ratio (FE-507): (SC-K) = 1: 2 Carbon black: HAF, Tokai Product name SEAST 3 made by Carbon Co., Ltd.
Hydrotalcite: acid acceptor, DHT-4A-2 manufactured by Kyowa Chemical Industry Co., Ltd.
Powder sulfur: Crosslinker, manufactured by Tsurumi Chemical Co., Ltd. Crosslink accelerator DM: Di-2-benzothiazyl disulfide, Shandong Shanxian Chemical Co. Ltd .. Product name SUNSINE MBTS
Cross-linking accelerator TS: Tetramethylthiuram disulfide, Sunseller (registered trademark) TS manufactured by Sanshin Chemical Industry Co., Ltd.
The blending ratio of sodium bicarbonate was 0.375 parts by mass per 1 part by mass of OBSH.

(Manufacture of transfer rollers)
The prepared conductive rubber composition is supplied to an extruder and extruded into a cylindrical shape having an outer diameter of φ10 mm and an inner diameter of φ3.0 mm, and then cut into a predetermined length to provide a temporary bridge for outer diameter of φ2.2 mm. Attached to the shaft.
Then, in the vulcanization can, pressurized steam is used to pressurize and heat at 135 ° C. for 10 minutes, then 160 ° C. for 20 minutes to foam the cylindrical body with the gas generated by the decomposition of the foaming agent, and the rubber. Cross-linked.

Next, this cylindrical body is reattached to the shaft 3 having an outer diameter of φ5 mm coated with a conductive thermosetting adhesive on the outer peripheral surface, and is subjected to secondary crosslinking by heating in an oven at 160 ° C. for 60 minutes, The thermosetting adhesive was cured, electrically joined to the shaft 3, and mechanically fixed.
Then, after cutting both ends of the cylindrical body, the outer peripheral surface 4 is traverse-grinded using a cylindrical grinding machine to finish the outer diameter to φ12.5 mm (tolerance ± 0.1 mm), and the transfer roller 1 is manufactured. .

<Example 2>
A conductive rubber composition was prepared in the same manner as in Example 1 except that the amount of sodium hydrogen carbonate was 4 parts by mass per 100 parts by mass of the total amount of rubber, and a transfer roller 1 was produced. The blending ratio of sodium hydrogen carbonate was 1 part by mass per 1 part by mass of OBSH.
<Example 3>
A conductive rubber composition was prepared in the same manner as in Example 1 except that the amount of sodium hydrogen carbonate was 9.5 parts by mass per 100 parts by mass of the total amount of rubber, and a transfer roller 1 was produced. The blending ratio of sodium hydrogen carbonate was 2.375 parts by mass per 1 part by mass of OBSH.

<Comparative example 1>
A conductive rubber composition was prepared in the same manner as in Example 1 except that the amount of sodium hydrogen carbonate was 0.5 parts by mass per 100 parts by mass of the total amount of rubber, and a transfer roller 1 was produced. The mixing ratio of sodium bicarbonate was 0.125 parts by mass per 1 part by mass of OBSH.
<Comparative example 2>
A conductive rubber composition was prepared in the same manner as in Example 1 except that the amount of sodium hydrogen carbonate was 10.5 parts by mass per 100 parts by mass of the total amount of rubber, and a transfer roller 1 was produced. The blending ratio of sodium hydrogen carbonate was 2.625 parts by mass per 1 part by mass of OBSH.

<Conventional example 1>
A conductive rubber composition was prepared in the same manner as in Example 1 except that sodium hydrogen carbonate was not blended, and a transfer roller 1 was produced.
<Conventional example 2>
The cylindrical body formed in Example 1 was pressurized and heated at 135 ° C. for 10 minutes with pressurized steam in a vulcanizing can and subjected to the first stage foaming treatment, and then pressurized at 165 ° C. for 3 hours. A transfer roller 1 was produced in the same manner as in Example 1 except that the second foaming treatment was performed by heating.

This conventional example 2 corresponds to the structure of Patent Document 2 in which OBSH and sodium hydrogen carbonate are combined as a foaming agent and foamed and crosslinked in a vulcanizing can without using a mold at the first stage of crosslinking. .
<Measurement and evaluation of Asker C-type hardness>
The Asker C-type hardness of the transfer roller 1 manufactured in Examples, Comparative Examples, and Conventional Examples was measured according to the measurement method described above. Then, those having an Asker C hardness of 25 ° or more and 35 ° or less were evaluated as good (◯), and those less than 25 ° and those exceeding 35 ° were evaluated as defective (x).

<Measurement and evaluation of average cell diameter>
The average cell diameter of the foamed cells of the transfer roller 1 manufactured in Examples, Comparative Examples, and Conventional Examples was measured according to the measurement method described above. And the thing with an average cell diameter of 120 micrometers or less was evaluated as favorable ((circle)), and the thing exceeding 120 micrometers was evaluated as bad (x).
The above results are shown in Tables 2 and 3.

From the results of Conventional Example 2 in Table 3, in the configuration of Patent Document 2, even if OBSH and sodium bicarbonate are combined as the foaming agent, the Asker C-type hardness is 25 ° or more and 35 ° or less, and the average of the foamed cells It was found that a transfer roller having a cell diameter of 120 μm or less could not be produced.
On the other hand, from the results of Examples 1 to 3 in Table 2 and Table 3 and Conventional Example 1, sodium bicarbonate is used in combination with OBSH as the foaming agent, and the heating temperature of the cylindrical body is 120 ° C. or higher and 140 ° C. or lower. It was found that a transfer roller with a small rubber hardness and a soft outer periphery, and a smooth outer peripheral surface can be manufactured by setting to 1 and foaming in one step. It was.

However, from the results of Examples 1 to 3 and Comparative Examples 1 and 2, in order to obtain the above effect, the blending ratio of sodium hydrogencarbonate is 0.25 parts by mass or more and 2.5 parts by mass or less per 1 part by mass of OBSH. It was found that it was necessary.
<Example 4>
The same conductive rubber composition as prepared in Example 1 is formed into a long ribbon shape, and continuously supplied to the extruder 6 to be extruded into a long cylindrical shape having an outer diameter of φ10 mm and an inner diameter of φ3.0 mm. And continuously passing through the continuous cross-linking device 5 including the microwave cross-linking device 8 and the hot-air cross-linking device 9 while continuously feeding out the extruded cylindrical body 7 without being cut. And then continuously cooled by passing through cooling water.

The output of the microwave crosslinking apparatus 8 was 6 to 12 kW, the control temperature in the tank was 135 ° C., the control temperature in the tank of the hot air crosslinking apparatus 9 was 135 ° C., and the effective length of the heating tank was 8 m.
Next, after cutting this cylindrical body into a predetermined length, it is attached to a shaft 3 having an outer diameter of φ5 mm and coated with a conductive thermosetting adhesive on the outer peripheral surface, and heated in an oven at 160 ° C. for 60 minutes. In addition to the secondary crosslinking, the thermosetting adhesive was cured to be electrically joined to the shaft 3 and mechanically fixed.

After both ends of the cylindrical body 7 are cut, the outer peripheral surface 4 is traverse-ground using a cylindrical grinder to finish the outer diameter to φ12.5 mm (tolerance ± 0.1 mm) to produce the transfer roller 1. did.
<Example 5>
A transfer roller 1 was produced in the same manner as in Example 4 except that the same conductive rubber composition as that prepared in Example 2 was used.

<Example 6>
A transfer roller 1 was produced in the same manner as in Example 4 except that the same conductive rubber composition as that prepared in Example 3 was used.
<Comparative Example 3>
A transfer roller 1 was produced in the same manner as in Example 4 except that the same conductive rubber composition prepared in Comparative Example 1 was used.

<Comparative example 4>
A transfer roller 1 was produced in the same manner as in Example 4 except that the same conductive rubber composition as that prepared in Comparative Example 2 was used.
<Conventional example 3>
A transfer roller 1 was produced in the same manner as in Example 4 except that the same conductive rubber composition as that prepared in Conventional Example 1 was used.

  The above-mentioned Examples, Comparative Examples, and Conventional Examples were measured and evaluated for the Asker C-type hardness and the average cell diameter was measured and evaluated. The results are shown in Table 4.

From the results of Examples 4 to 6 in Table 4, Comparative Examples 3 and 4, and Conventional Example 3, it was found that the same effects as the vulcanized can crosslinking can be obtained even by continuous crosslinking.
That is, from the results of Examples 4 to 6 and Conventional Example 3, foaming is performed in one stage by using sodium bicarbonate together with OBSH as a foaming agent and setting the heating temperature of the cylindrical body to 120 ° C. or more and 140 ° C. or less. As a result, it was found that a transfer roller having a Asker C-type hardness and an average cell diameter in the above ranges, a small rubber hardness and a softness, and a smooth outer peripheral surface can be produced.

  However, from the results of Examples 4 to 6 and Comparative Examples 3 and 4, in order to obtain the above effect, the blending ratio of sodium hydrogen carbonate is 0.25 parts by mass or more and 2.5 parts by mass or less per 1 part by mass of OBSH. It was found that it was necessary.

DESCRIPTION OF SYMBOLS 1 Transfer roller 2 Through-hole 3 Shaft 4 Outer peripheral surface 5 Continuous bridge | crosslinking apparatus 6 Extruder 7 Cylindrical body 8 Microwave bridge | crosslinking apparatus 9 Hot-air bridge | crosslinking apparatus 10 Take-out machine

Claims (4)

  Rubber, a crosslinking component for crosslinking the rubber, 4,4′-oxybisbenzenesulfonylhydrazide (OBSH) as a foaming agent for foaming the rubber, and 0.25 parts by mass or more per 1 part by mass of the OBSH; A transfer roller comprising a foam of a conductive rubber composition containing sodium hydrogen carbonate of 2.5 parts by mass or less, having an Asker C-type hardness of 25 ° or more and 35 ° or less, and an average cell diameter of foamed cells of 120 μm or less. .   The transfer roller according to claim 1, wherein the average cell diameter is 82 μm or more.   The method for producing a transfer roller according to claim 1 or 2, wherein the conductive rubber composition is extruded into a cylindrical shape, and then heated at 120 ° C or higher and 140 ° C or lower with pressurized steam in a vulcanizing can. A method for producing a transfer roller, comprising a step of foaming in one step while maintaining the temperature.   3. The method for producing a transfer roller according to claim 1, wherein a continuous crosslinking apparatus including a microwave crosslinking apparatus and a hot-air crosslinking apparatus is continuously formed while the conductive rubber composition is extruded into a cylindrical shape. A method for producing a transfer roller, comprising a step of foaming in a single stage while maintaining a temperature of 120 ° C. or higher and 140 ° C. or lower while passing through.

Images