JP2019158917A - Rubber composition, rubber roller, and image forming apparatus - Google Patents

Abstract

To provide a rubber composition with which a foam, such as a roller body can be formed, which has high dimensional accuracy of an outer diameter compared with a current one because of its high open cell ratio and is excellent in dimensional stability of the outer diameter, a rubber roller that includes a cylindrical roller body formed of a foam obtained by foaming and crosslinking the rubber composition, and an image forming apparatus that includes the rubber roller.SOLUTION: A rubber composition contains three types of rubber: diene rubber; ethylene-propylene rubber; ion conductive rubber, ADCA as a foaming agent, and 4,4'-Dithiodimorpholine as a crosslinking agent. A rubber roller includes a cylindrical roller body formed of a foam obtained by foaming and crosslinking the rubber composition. An image forming apparatus includes the rubber roller.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a rubber composition, a rubber roller including a roller body made of a foam obtained by crosslinking and foaming the rubber composition, and an image forming apparatus including the rubber roller.

For example, in an image forming apparatus using an electrophotographic method such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, or a complex machine of these, as the market has matured in recent years, There is a tendency for higher image quality and higher image formation speed.
As a transfer roller that is one of the parts of an image forming apparatus, for example, a rubber composition containing rubber, a foaming agent, a cross-linking agent, etc. is formed into a cylindrical shape and then foamed and cross-linked. A rubber roller including a conductive roller body made of foam is used (Patent Document 1).

In Patent Document 1, two types of rubbers, epichlorohydrin rubber and acrylonitrile butadiene rubber, are used in combination as the rubber that is the basis of the foam.
In addition, azodicarbonamide or 4,4′-oxybis (benzenesulfonylhydrazide) is used as the foaming agent, and sulfur is used as the crosslinking agent.

JP 2008-216462 A

In order to satisfy the above-mentioned requirements and to form a delicate transfer image when the rubber roller is used as, for example, a transfer roller, the outer diameter has high dimensional accuracy and the outer diameter is in the environment. Therefore, it is required to be difficult to change, that is, to have excellent dimensional stability.
For this purpose, the foam that is the basis of the roller main body is a foam structure in which a plurality of bubbles constituting the foam communicate with each other and open to the outside of the foam, that is, a foam structure with a high continuous cell rate. It can be considered.

Foams with many closed closed cells that do not communicate with other bubbles and with a low open cell ratio are expanded and contracted depending on the environment of the gas in the closed cells. This is because stability decreases and the outer diameter is likely to change depending on the environment.
However, in the conventional rubber composition such as Patent Document 1 in which the rubber, the foaming agent, and the crosslinking agent described above are combined, a rubber roller having a roller body having a high open cell ratio that satisfies the above-described requirements is manufactured. There is a problem that it is difficult.

An object of the present invention is to provide a rubber composition capable of forming a foamed body such as a roller body having high dimensional accuracy of an outer diameter as compared with the current state and having excellent dimensional stability of the outer diameter because the open cell ratio is high. It is to provide.
Another object of the present invention is to provide a rubber roller including a cylindrical roller body made of a foam obtained by foaming and crosslinking the rubber composition, and an image forming apparatus including the rubber roller.

The present invention relates to a rubber composition for forming a foam for use in an image forming apparatus utilizing electrophotography, which includes a diene rubber, an ethylene propylene rubber, and an ion conductive rubber, and a foaming agent. A rubber composition comprising an azodicarbonamide, and 4,4'-dithiodimorpholine as a crosslinking agent.
Moreover, this invention is a rubber roller containing the cylindrical roller main body which consists of a foam which foamed and bridge | crosslinked the said rubber composition.

  Furthermore, the present invention is an image forming apparatus including the rubber roller.

According to the present invention, since the open cell ratio is high, a rubber composition capable of forming a foamed body such as a roller main body having a higher dimensional accuracy of the outer diameter than the current state and excellent in dimensional stability of the outer diameter. Can be provided.
In addition, according to the present invention, it is possible to provide a rubber roller including a cylindrical roller body made of a foam obtained by foaming and crosslinking the rubber composition, and an image forming apparatus including the rubber roller.

It is a perspective view which shows an example of embodiment of the rubber roller of this invention.

<Rubber composition>
As described above, the present invention relates to rubbers including diene rubbers, ethylene propylene rubbers, and ion conductive rubbers, azodicarbonamide (ADCA) as a foaming agent, and 4,4′-dithiodidies as a crosslinking agent. It is a rubber composition containing morpholine.

According to the present invention, by combining the above three kinds of rubber, ADCA as a foaming agent, and 4,4′-dithiodimorpholine as a crosslinking agent, the open cell ratio of the foam is made higher than the present state. Can do.
Then, it is possible to form a foamed body such as a roller body of a rubber roller, which has a higher dimensional accuracy of the outer diameter than the current state and is excellent in dimensional stability of the outer diameter.

<Rubber>
As the rubber, at least three kinds of diene rubber, ethylene propylene rubber, and ion conductive rubber are used in combination as described above.
Among these, diene rubber and ethylene propylene rubber function to give, for example, good properties as rubber, that is, flexible, low compression set, and resistance to settling to foams such as roller bodies. To do.
In addition, the ion conductive rubber imparts appropriate ionic conductivity to the rubber composition. For example, the roller resistance value of a rubber roller having a roller body made of a foam of the rubber composition is suitable as a transfer roller or the like. Function to adjust to the desired range.

In addition, ethylene propylene rubber and ion conductive rubber have less elongation at the time of foaming than diene rubber, and promote bubble breakage by interaction with ADCA and 4,4'-dithiodimorpholine. Also works.
As a result, the open cell ratio of the foam can be increased.
(Diene rubber)
As the diene rubber, various diene rubbers that can be cross-linked with 4,4′-dithiodimorpholine can be used because the main chain contains a double bond in the main chain and has sulfur crosslinkability.

Examples of the diene rubber include natural rubber, isoprene rubber (IR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), and the like.
In particular, as the diene rubber, at least one of NBR, SBR, and BR is preferable.
・ NBR
NBR includes low nitrile NBR having an acrylonitrile content of 24% or less, 25 to 30% medium nitrile NBR, 31 to 35% medium nitrile NBR, 36 to 42% high nitrile NBR, 43% or more Any very high nitrile NBR can be used.

In addition, NBR includes 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. In the present invention, in order to prevent contamination of the photoconductor, etc. It is preferable to use a non-oil-extended NBR that does not contain an extending oil that can be a bleed substance.
One or more of these NBRs can be used.
・ 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 high styrene type, medium styrene type, and low styrene type classified by styrene content, any of which can be used.
Further, SBR includes 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. In the present invention, in order to prevent contamination of the photoconductor, etc. In addition, it is preferable to use a non-oil-extended type SBR that does not contain an extending oil that can be a bleed substance.

One or more of these SBRs can be used.
・ BR
As the BR, any of various BRs having a polybutadiene structure in the molecule and having crosslinkability can be used.
In particular, a high cis BR having a cis-1,4 bond content of 95% or more, which can exhibit good properties as a rubber in a wide temperature range from a low temperature to a high temperature, is preferable.

In addition, as BR, there are an oil-extended type in which flexibility is adjusted by adding an extending oil, and a non-oil-extended type in which the flexibility is not added. In addition, it is preferable to use a non-oil-extended BR that does not contain an extending oil that can become a bleed substance.
One or more of these BRs can be used.
(Ethylene propylene rubber)
The ethylene-propylene rubber has a function as the rubber described above and also has excellent ozone resistance, so that it also functions to improve the ozone resistance of a foamed body such as a roller body.

Examples of the ethylene propylene rubber include ethylene propylene rubber (EPM) which is a copolymer of ethylene and propylene, and ethylene propylene diene rubber (EPDM) which is a copolymer of ethylene, propylene and diene.
In particular, EPDM having sulfur crosslinkability and capable of crosslinking with 4,4′-dithiodimorpholine is preferable.

As EPDM, various copolymers obtained by copolymerizing ethylene, propylene, and diene can be used.
Examples of the diene include ethylidene norbornene (ENB) and dicyclopentadiene (DCPD).
EPDM is classified into 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. In addition, it is preferable to use a non-oil-extended EPDM that does not contain an extending oil that can become a bleed substance.
One or more of these EPDMs can be used.

(Ion conductive rubber)
Examples of the ion conductive rubber include epichlorohydrin rubber and polyether rubber.
Among these, as epichlorohydrin rubber, for example, epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer, epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allyl glycidyl ether binary copolymer, epichlorohydrin-ethylene oxide- Examples include allylic glycidyl ether terpolymer, epichlorohydrin-propylene oxide-allyl glycidyl ether ternary copolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer, and the like.

Examples of the polyether rubber include an ethylene oxide-allyl glycidyl ether binary copolymer and an ethylene oxide-propylene oxide-allyl glycidyl ether terpolymer.
Among them, a copolymer containing ethylene oxide, particularly an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer (GECO) having sulfur crosslinkability and capable of crosslinking with 4,4′-dithiodimorpholine is preferable.

The ethylene oxide content in GECO is preferably 30 mol% or more, particularly preferably 50 mol% or more, and more preferably 80 mol% or less.
As described above, ethylene oxide imparts ionic conductivity to the rubber composition, and functions to lower the roller resistance value of a rubber roller including a roller body made of a foam of the rubber composition, for example.

However, when the ethylene oxide content is less than this range, such a function cannot be obtained sufficiently, and 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 segment movement of the molecular chain is hindered, so that the roller resistance value tends to increase.

Moreover, the roller main body after bridge | crosslinking may become hard too much, or the viscosity at the time of heat-melting of the rubber composition before bridge | crosslinking may raise, and the workability and foamability of the said rubber composition may fall.
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 as a side chain to secure a free volume, thereby suppressing the crystallization of ethylene oxide and reducing the roller resistance value.

However, if the allyl glycidyl ether content is less than this range, such a function cannot be obtained sufficiently, and the roller resistance value may not be sufficiently reduced.
On the other hand, allyl glycidyl ether functions as a crosslinking point when GECO is crosslinked.
For this reason, when the allyl glycidyl ether content exceeds the above range, the GECO crosslinking density becomes too high, which prevents the molecular chain segmental motion and tends to increase the roller resistance.

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, particularly preferably 19.5 mol% or more, more preferably 69.5 mol% or less, particularly preferably 60 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.

In the present invention, any of these GECOs can be used.
One or more of these ion conductive rubbers can be used.
(Mixing ratio)
The blending ratio of the ion conductive rubber is preferably 20 parts by mass or more, particularly 25 parts by mass or more, preferably 40 parts by mass or less, particularly 35 parts by mass or less, in 100 parts by mass of the total amount of rubber.

If the blending ratio of the ion conductive rubber is less than this range or exceeds the range, in either case, for example, the roller resistance value of the rubber roller may not be adjusted to a range suitable as a transfer roller or the like.
In addition, when the blending ratio of the ion conductive rubber is less than the above range, the ratio of the diene rubber which is less likely to cause bubble breakage due to the large elongation at the time of foaming is relatively large, and the open cell ratio of the foam In some cases, sufficient effects cannot be obtained.

Furthermore, when the blending ratio of the ion conductive rubber exceeds the above range, the ratio of the diene rubber and the ethylene propylene rubber is relatively decreased. In some cases, it is not possible to impart good characteristics as a rubber.
In addition, the proportion of ethylene propylene rubber may be relatively reduced, and it may not be possible to impart good ozone resistance to foams such as roller bodies.

On the other hand, by setting the blending ratio of the ion conductive rubber within the above range, for example, the roller resistance value of the rubber roller can be adjusted to a range suitable as a transfer roller or the like.
In addition, by increasing the open cell ratio of the foam, it is possible to form a roller body or the like that has high dimensional accuracy of the outer diameter and is excellent in dimensional stability of the outer diameter.
Furthermore, it is possible to impart good characteristics as rubber or good ozone resistance to a foamed body such as a roller body.

The blending ratio of the ethylene propylene rubber is preferably 1 part by mass or more, particularly 5 parts by mass or more, preferably 20 parts by mass or less, particularly 15 parts by mass or less, in 100 parts by mass of the total amount of rubber.
When the blending ratio of the ethylene propylene rubber is less than this range, good ozone resistance may not be imparted to the foamed body such as the roller body.

In addition, since the elongation at foaming is relatively large, the proportion of the diene rubber that hardly causes bubble breakage increases, and the effect of increasing the open cell ratio of the foam may not be sufficiently obtained.
On the other hand, when the blending ratio of the ethylene propylene rubber exceeds the above range, the ratio of the diene rubber is relatively decreased, and good properties as a rubber cannot be imparted to the foamed body such as the roller body. In some cases.

Furthermore, the ratio of the ion conductive rubber is reduced, and for example, the roller resistance value of the rubber roller may not be adjusted to a range suitable for a transfer roller or the like.
On the other hand, favorable ozone resistance can be provided to foams, such as a roller main body, by making the mixture ratio of ethylene propylene-type rubber into said range.
In addition, by increasing the open cell ratio of the foam, it is possible to form a roller body or the like that has high dimensional accuracy of the outer diameter and is excellent in dimensional stability of the outer diameter.

Furthermore, it is possible to impart good characteristics as rubber to a foam such as a roller body, or to adjust the roller resistance value of the rubber roller to a range suitable for a transfer roller or the like.
The blending ratio of the diene rubber is the remaining amount of the ion conductive rubber and the ethylene propylene rubber.
That is, the blending ratio of the diene rubber may be set so that the total amount of the rubber becomes 100 parts by mass when the blending ratio of the ion conductive rubber and the ethylene propylene rubber is set to a predetermined value within the above range.

<Crosslinking component>
As the crosslinking component, it is preferable to use a crosslinking agent for crosslinking the rubber and a crosslinking accelerator for promoting the crosslinking of the rubber by the crosslinking agent.
(Crosslinking agent)
Among the above, as described above, at least 4,4′-dithiodimorpholine is used as the crosslinking agent.
4,4′-dithiodimorpholine is a known crosslinking agent as exemplified in Patent Document 1, for example.

However, sulfur is the only cross-linking agent that has actually been verified in the examples of Patent Document 1, and 4,4′-dithiodimorpholine is merely exemplified as an example of the cross-linking agent. .
Moreover, in the example of Patent Document 1, as described above, only two types of epichlorohydrin rubber and NBR are used as the rubber.

Patent Document 1 discloses that, in addition to the above two types, three types of rubber added with ethylene propylene-based rubber, 4,4'-dithiodimorpholine as a crosslinking agent and ADCA as a foaming agent are used in combination. It is not described.
Further, the patent literature also discloses that the open cell ratio of the foam can be increased by the above-described configuration, and that a foam such as a roller body having high dimensional accuracy of the outer diameter and excellent dimensional stability can be formed thereby. 1 is not described at all.

These configurations and effects are new facts that the inventor has made clear for the first time in the present invention.
In consideration of further improving the above effects, it is preferable to use 4,4′-dithiodimorpholine alone as the crosslinking agent.
However, other crosslinking agents may be used in combination as long as the effects are not impaired.

Examples of other crosslinking agents include sulfur-based crosslinking agents other than 4,4′-dithiodimorpholine, thiourea-based crosslinking agents, triazine derivative-based crosslinking agents, peroxide-based crosslinking agents, and various monomers. .
Examples of other sulfur-based crosslinking agents include sulfur such as powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur, and organic sulfur-containing compounds such as tetramethylthiuram disulfide. .

The crosslinking agent can be appropriately selected depending on the type of rubber to be combined.
For example, when the rubber is a diene rubber, EPDM, and GECO, all having sulfur crosslinkability, a sulfur crosslinker containing at least 4,4′-dithiodimorpholine may be used as the crosslinker.
In particular, it is preferable to use 4,4'-dithiodimorpholine alone as described above.

Further, for example, in the case where the ion conductive rubber is ECO having no sulfur crosslinkability, for example, a sulfur-based crosslinker containing at least 4,4′-dithiodimorpholine as a crosslinker and ECO for crosslinking For example, a thiourea crosslinking agent or the like may be used in combination.
When 4,4'-dithiodimorpholine is used alone as a crosslinking agent, the blending ratio is preferably 0.1 parts by mass or more, particularly 0.3 parts by mass or more per 100 parts by mass of the total amount of rubber. It is preferable that the amount is not more than 5 parts by mass, particularly not more than 5 parts by mass.

If the blending ratio of 4,4'-dithiodimorpholine is less than this range, the effect of increasing the open cell ratio of the foam may not be sufficiently obtained.
In addition, the rubber cannot be sufficiently crosslinked, and the above-described good characteristics as rubber may not be imparted to a foamed body such as a roller body.
On the other hand, even if the blending ratio exceeds the above range, not only the effect is not obtained, but also excess 4,4'-dithiodimorpholine bleeds on the outer peripheral surface of the roller body to contaminate the photoreceptor. There is a case to do.

On the other hand, by setting the blending ratio of 4,4′-dithiodimorpholine within the above range, the open cell ratio of the foamed body such as the roller main body is increased while suppressing the contamination of the photoreceptor. Or good properties as rubber can be imparted to the foam.
In addition, when using together with other crosslinking agents, such as sulfur, with 4,4'-dithiodimorpholine, what is necessary is just to set so that the total mixture ratio of both may become the said range.

  In addition, the blending ratio of 4,4′-dithiodimorpholine in the combined use system with other cross-linking agent is 100% by mass considering the maintenance of the effect of increasing the open cell ratio of the above-mentioned foam. It is preferably 0.1 parts by mass or more, particularly 0.3 parts by mass or more per part.

(Crosslinking accelerator)
Examples of the crosslinking accelerator for promoting the crosslinking of rubber with 4,4'-dithiodimorpholine include thiazole accelerators, thiuram accelerators, sulfenamide accelerators, dithiocarbamate accelerators, and the like. 1 type or 2 types or more are mentioned.

Among these, it is preferable to use a thiuram accelerator.
Examples of the thiuram accelerator include one or more of tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide and the like.
Considering that the effect of promoting the crosslinking of rubber by 4,4′-dithiodimorpholine is sufficiently expressed, the mixing ratio of the thiuram accelerator is 0.3 parts by mass or more per 100 parts by mass of the total amount of rubber. It is preferably less than or equal to parts by mass.

<Foaming component>
(Foaming agent)
As the foaming component, at least ADCA is used as described above, among the foaming agents that decompose by heating to generate gas.

By using ADCA together with the above-mentioned three types of rubber and 4,4′-dithiodimorpholine as a cross-linking agent, the open cell ratio of the foam is increased and the dimensional accuracy of the outer diameter is high. A roller body having excellent stability can be formed.
In consideration of further improving this effect, it is preferable to use ADCA alone as the foaming agent.

However, other foaming agents may be used in combination as long as the effects are not impaired.
Examples of other foaming agents include 4,4′-oxybis (benzenesulfonylhydrazide) (OBSH), N, N-dinitrosopentamethylenetetramine (DPT), and the like.
In particular, OBSH is preferable.

The blending ratio of the foaming agent can be appropriately set according to the foaming ratio of the target foam.
For example, when ADCA is used alone as a foaming agent to produce a roller body of a transfer roller, the blending ratio of ADCA is preferably 0.3 parts by mass or more per 100 parts by mass of rubber, and 8 parts by mass. It is preferable that:

If the blending ratio of ADCA is less than this range, the effect of increasing the open cell ratio of the foam may not be sufficiently obtained.
In addition, when the blending ratio of ADCA is less than the above range or exceeds the range, in any case, a foam having a foaming ratio suitable as a roller body of the transfer roller may not be obtained.

On the other hand, by setting the blend ratio of ADCA in the above range, it is possible to form a foam having a foaming ratio suitable for the roller body of the transfer roller while increasing the open cell ratio of the foam.
In consideration of further improving this effect, the blending ratio of ADCA is preferably 0.5 parts by mass or more, and preferably 6 parts by mass or less, even in the above range.

Moreover, when using other foaming agents, such as OBSH, together with ADCA, what is necessary is just to set so that the total mixture ratio of both may become the said range.
However, the mixing ratio of ADCA in the combined system is 1.0 parts by mass or more per 100 parts by mass of the total amount of rubber, taking into consideration that the effect of increasing the open cell ratio of the foam described above is maintained. It is preferably 5 parts by mass or more.

(Foaming aid)
As the foaming component, together with ADCA, a foaming aid that lowers the decomposition temperature of the ADCA and promotes the decomposition may be used in combination.
Examples of foaming aids that can be combined with ADCA include urea (H ₂ NCONH ₂ ) -based foaming aids.
The blending ratio of the foaming aid is preferably 0.1 parts by mass or more and preferably 5 parts by mass or less per 100 parts by mass of the total amount of rubber.

<Carbon black>
In the rubber composition, for example, various carbon blacks that can function as a rubber reinforcing agent, filler, electronic conductive agent, and the like may be blended.
The blending ratio of the carbon black is preferably 1 part by mass or more, particularly 3 parts by mass or more, preferably 10 parts by mass or less, particularly preferably 7 parts by mass or less, per 100 parts by mass of the total amount of rubber.

<Others>
You may mix | blend various additives with a rubber composition in arbitrary ratios as needed.
Examples of additives include acid acceptors, fillers other than carbon black, cross-linking aids, deterioration inhibitors, scorch inhibitors, plasticizers, lubricants, pigments, antistatic agents, flame retardants, neutralizing agents, Examples thereof include a nucleating agent and a co-crosslinking agent.
The rubber composition of the present invention is a foam of a rubber composition incorporated in an image forming apparatus using electrophotography such as a laser printer, an electrostatic copying machine, a plain paper facsimile machine, and a complex machine thereof. It is suitably used as a material for forming various members made of a body.
Examples of the member include a rubber roller such as a transfer roller as described above.

《Rubber roller》
FIG. 1 is a perspective view showing an example of an embodiment of a rubber roller of the present invention.
Referring to FIG. 1, a rubber roller 1 of this example includes a roller main body 2 made of a foam of a rubber composition containing each of the above components and formed in a porous and single-layered cylindrical shape, and a roller main body. The shaft 4 is inserted into and fixed to the central through hole 3.

The shaft 4 is integrally formed of a metal such as aluminum, an aluminum alloy, or stainless steel.
The shaft 4 is, for example, electrically joined to the roller body 2 via a conductive adhesive and mechanically fixed, or a through-hole having an outer diameter larger than the inner diameter of the through-hole 3. By being press-fitted into the roller 3, the roller body 2 is electrically joined and mechanically fixed.
Further, both of them may be used together, and the shaft 4 may be electrically joined to the roller body and mechanically fixed.

<Manufacture of rubber rollers>
In order to produce the rubber roller 1 of the present invention, first, the rubber composition comprising the above-described components is extruded into a cylindrical shape using an extruder, then cut into a predetermined length, and a vulcanized can In the inside, it is pressurized and heated with pressurized steam to foam and crosslink.

Next, the foamed and cross-linked cylindrical body is heated using an oven or the like, secondarily cross-linked, cooled, and then polished to have a predetermined outer diameter to form the roller body 2.
The shaft 4 can be inserted through the through-hole 3 and fixed at an arbitrary time from after the tubular body is cut to after polishing.
However, after the cutting, it is preferable to first perform secondary crosslinking and polishing with the shaft 4 inserted through the through hole 3.

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 4, the workability of the polishing can be improved, and the deflection of the outer peripheral surface 5 can also be suppressed.
As described above, the shaft 4 is inserted into the through-hole 3 of the tubular body before the secondary cross-linking through a conductive adhesive, particularly a conductive thermosetting adhesive, and then secondary cross-linked. Or what is necessary is just to press-fit the thing with an outer diameter larger than the internal diameter of the through-hole 3 in the through-hole 3. FIG.

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 4 is electrically joined to the roller body 2 and mechanically. Fixed to.
In the latter case, electrical joining and mechanical fixing are completed simultaneously with press-fitting.
Moreover, as described above, both of these may be used in combination.

As described above, the rubber roller 1 of the present invention can be suitably used as a transfer roller in, for example, an image forming apparatus using electrophotography.
However, the rubber roller 1 of the present invention can be used as, for example, a charging roller, a developing roller, or a cleaning roller.

<Image forming apparatus>
The image forming apparatus of the present invention is characterized by incorporating the rubber roller 1 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 as described above. It is done.

Hereinafter, the present invention will be further described based on examples and comparative examples. However, the configuration of the present invention is not necessarily limited to these examples and comparative examples.
<Example 1>
(Rubber composition)
As the rubber, 30 parts by mass of GECO, 60 parts by mass of NBR, both non-oil-extended, and 10 parts by mass of EPDM were blended.

  Then, while kneading 100 parts by mass of the total amount of the three types of rubber using a Banbury mixer, first, among the components shown in Table 1 below, a foaming agent and carbon black are added and kneaded, and then a crosslinking agent and a crosslinking aid. And kneaded to prepare a rubber composition.

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: ADCA
Crosslinking agent: 4,4'-dithiodimorpholine Crosslinking accelerator: Tetramethylthiuram monosulfide (Rubber roller)
The prepared rubber composition was supplied to an extruder and extruded into a cylindrical shape, and then cut into a predetermined length and mounted on a temporary bridging shaft having an outer diameter of φ2.2 mm.

Next, in a vulcanizing can, pressurized steam is applied at 120 ° C. for 10 minutes, then at 160 ° C. for 20 minutes, and the cylindrical body is foamed by the gas generated by the decomposition of the foaming agent and rubber. Were crosslinked.
Next, this cylindrical body is reattached to a shaft having an outer diameter of φ5 mm coated with a conductive thermosetting adhesive on the outer peripheral surface, and heated in an oven at 160 ° C. for 60 minutes for secondary crosslinking, The thermosetting adhesive was cured, electrically joined to the shaft, and mechanically fixed.
Then, after shaping both ends of the cylindrical body, the outer peripheral surface thereof is traverse ground using a cylindrical grinder to finish the outer diameter to φ15.0 mm (tolerance ± 0.1 mm) to form a roller body, A rubber roller was produced.

<Example 2>
A rubber composition was prepared in the same manner as in Example 1 except that the blending ratio of ADCA as a foaming agent was 4.0 parts by mass per 100 parts by mass of the total amount of rubber, and a rubber roller was produced.
<Example 3>
A rubber composition was prepared in the same manner as in Example 1 except that the blending ratio of ADCA as a foaming agent was 6.0 parts by mass per 100 parts by mass of the total amount of rubber, and a rubber roller was produced.
<Example 4>
A rubber composition was prepared in the same manner as in Example 1 except that 2.0 parts by mass of ADCA and 2.0 parts by mass of OBSH were used in combination as a foaming agent per 100 parts by mass of the total amount of rubber. Manufactured.

<Example 5>
The same amount of SBR was used in place of NBR, and 0.3 parts by mass of 4,4'-dithiodimorpholine and 2.0 parts by mass of sulfur were combined as a crosslinking agent per 100 parts by mass of rubber. A rubber composition was prepared in the same manner as in Example 2 except that a rubber roller was manufactured.
<Example 6>
The rubber was used in the same manner as in Example 2 except that the same amount of BR was used instead of NBR, and the blending ratio of 4,4'-dithiodimorpholine was 5.0 parts by mass per 100 parts by mass of the total amount of rubber. A composition was prepared to produce a rubber roller.

<Comparative example 1>
A rubber composition was prepared in the same manner as in Example 2 except that 5.0 parts by mass of sulfur was blended per 100 parts by mass of the rubber instead of 4,4'-dithiodimorpholine as a crosslinking agent, A rubber roller was produced.
<Comparative example 2>
A rubber composition was prepared in the same manner as in Example 1 except that only 4.0 parts by mass of OBSH was blended per 100 parts by mass of rubber instead of ADCA as a foaming agent, and a rubber roller was produced.
<Comparative Example 3>
A rubber composition was prepared in the same manner as in Example 2 except that EPDM was omitted and the NBR blending ratio was 70 parts by mass in 100 parts by mass of rubber.

<Dimensional stability evaluation>
The outer diameters of the roller bodies of the rubber rollers manufactured in Examples and Comparative Examples were respectively set in a low temperature and low humidity environment at a temperature of 10 ° C. and a relative humidity of 15%, and in a high temperature and high humidity environment at a temperature of 30 ° C. and a relative humidity of 80%. It was measured.

Specifically, the rubber roller was first allowed to stand for 120 hours in a high temperature and high humidity environment, and then the outer diameter of the roller body was measured. Next, after measuring the outer diameter, the rubber roller was immediately transferred to a low temperature and low humidity environment and allowed to stand for 30 minutes, and then the outer diameter of the roller body was measured again.
Then, the difference between the outer diameter measured in a high-temperature and high-humidity environment and the outer diameter measured in a low-temperature and low-humidity environment was determined, and the difference was 0.05 mm or less. A case where the difference exceeded 0.05 mm was evaluated as poor dimensional stability (x). The results are shown in Tables 2 and 3.

From the results of Examples 1 to 6 and Comparative Examples 1 to 3, a rubber roller was obtained by using three types of diene rubber, ethylene propylene rubber, ion conductive rubber, ADCA, and 4,4'-dithiodimorpholine in combination. It was found that the dimensional stability of the outer diameter of the roller body can be improved.
From the results of Examples 1 to 3, the blending ratio when ADCA is used alone as a foaming agent is preferably 0.3 parts by mass or more, particularly 0.5 parts by mass or more per 100 parts by mass of the total amount of rubber, It has been found that the content is preferably 8 parts by mass or less, particularly 6 parts by mass or less.

From the results of Example 4, in the combined system of ADCA and OBSH, the total blending ratio may be set within the above range, but in order to maintain the effect of increasing the open cell ratio of the foam, It has been found that the blending ratio is preferably 1.0 part by mass or more, particularly 1.5 parts by mass or more, per 100 parts by mass of the total amount of rubber.
From the results of Examples 1 to 6, it was found that EPDM is preferable as the ethylene propylene rubber, and epichlorohydrin rubber, particularly GECO, is preferable as the ion conductive rubber.

From the results of Examples 1, 5, and 6, it was found that the diene rubber is preferably at least one selected from the group consisting of NBR, SBR, and BR.
The blending ratio when 4,4'-dithiodimorpholine alone is used as the crosslinking agent is preferably 0.1 parts by weight or more, particularly 0.3 parts by weight or more, per 100 parts by weight of the total amount of rubber. It has been found that it is preferably 6 parts by mass or less, particularly 5 parts by mass or less.

  Furthermore, from the results of Example 5, in the combined system of 4,4′-dithiodimorpholine and sulfur, the total blending ratio may be set within the above range, but the effect of increasing the open cell ratio of the foam is maintained. In order to achieve this, it has been found that the blending ratio of 4,4'-dithiodimorpholine is preferably 0.1 parts by mass or more, particularly 0.3 parts by mass or more per 100 parts by mass of the total amount of rubber.

1 Rubber roller 2 Roller body 3 Through hole 4 Shaft 5 Outer peripheral surface

Claims (6)

  A rubber composition for forming a foam for use in an image forming apparatus utilizing electrophotography, comprising a diene rubber, an ethylene propylene rubber, and an ion conductive rubber, and azodicarbonamide as a foaming agent , And 4,4'-dithiodimorpholine as a crosslinking agent.   The rubber composition according to claim 1, wherein the diene rubber is at least one selected from the group consisting of acrylonitrile butadiene rubber, styrene butadiene rubber, and butadiene rubber.   The rubber composition according to claim 1, wherein the ethylene propylene rubber is ethylene propylene diene rubber.   The rubber composition according to any one of claims 1 to 3, wherein the ion conductive rubber is epichlorohydrin rubber.   A rubber roller comprising a cylindrical roller body made of a foam obtained by foaming and crosslinking the rubber composition according to any one of claims 1 to 4.   An image forming apparatus comprising the rubber roller according to claim 5.

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