JP2013256583A - Method for producing foamed rubber member and transfer roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a production method for producing a foamed rubber member of a roller body or the like having always stable physical properties by suppressing dispersion in each batch of physical properties, especially hardness, caused by external factors such as fluctuation of an outside air temperature; and to provide a transfer roller including a roller body having stable physical properties such as hardness, which is produced by the production method.SOLUTION: In a production method, a precursor of a foamed rubber member is foamed and crosslinked in a vulcanizing can through following stages, namely: the first stage for holding the precursor at a fixed temperature below a foaming start temperature of the precursor for a fixed time; the second stage for holding it at a fixed temperature near the foaming start temperature of the precursor for a fixed time; and the third stage for holding it at a fixed temperature higher than the temperature in the second stage for a fixed time. A transfer roller includes a cylindrical conductive foamed rubber member produced by the production method as a roller body.

Description

  The present invention relates to a production method for producing a foamed rubber member from an unfoamed, uncrosslinked rubber composition, and a transfer roller comprising a cylindrical and conductive foamed rubber member produced by the production method as a roller body. is there.

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

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

In the transfer step, the toner image formed on the surface of the photoconductor is not only directly transferred to the surface of the paper, but also transferred to the surface of the image carrier (primary transfer step) and then transferred to the surface of the paper. In some cases, retransfer is performed (secondary transfer process).
Further, a series of image formation is completed by removing the toner remaining on the surface of the photoreceptor after the transfer (cleaning process).

Among the above-described steps, a transfer roller having a foamed roller main body and imparting conductivity according to the application is used for the transfer step.
The roller body of the transfer roller is formed by extruding a crosslinkable rubber composition containing a conductivity imparting agent and a foaming agent into a cylindrical shape through a die of an extruder, and the unfoamed and uncrosslinked base material is formed. And a foaming / crosslinking step in which the precursor is foamed by being pressurized and heated with pressurized steam in a vulcanizing can and crosslinked.

Of these, the foaming / crosslinking step in the vulcanizing can is generally carried out by providing two cross-linking steps (Patent Document 1).
Specifically, pressurized steam is introduced into the vulcanization can containing the precursor, and the temperature in the vulcanization can is first raised to a certain temperature near the foaming start temperature of the precursor. The precursor is foamed and cross-linked by holding at the temperature for a certain time (first stage).

Next, after a predetermined time has elapsed, the temperature in the vulcanization can is further raised to a constant temperature higher than the first stage, and then held at the temperature for a certain period of time to further crosslink the precursor (second stage) ).
Thereafter, the roller body of the transfer roller is manufactured by cooling to room temperature, taking out the foamed and crosslinked precursor from the vulcanizing can, and polishing the outer peripheral surface thereof as necessary.

In the first and second stages, the temperature is controlled as described above by adjusting the amount of pressurized water vapor introduced into the vulcanizing can and controlling the pressure in the vulcanizing can.
That is, by changing the amount of pressurized water vapor introduced into the vulcanization can so that the pressure inside the vulcanization can reach the saturated water vapor pressure at the target temperature, the temperature inside the vulcanization can The temperature is adjusted to a predetermined temperature corresponding to the water vapor pressure.

  Further, after taking out the foamed and crosslinked precursor from the vulcanization can through the two-stage foaming / crosslinking process, it is further heated in a hot air oven prior to polishing to complete the secondary crosslinking, that is, crosslinking. In some cases (Patent Document 2).

Japanese Patent Laying-Open No. 2005-41108 JP 2002-113735 A

However, the roller body manufactured through the two-stage foaming / crosslinking process has a problem that physical properties, particularly hardness, easily varies from batch to batch due to external factors such as changes in outside air temperature due to seasonal changes.
That is, since the temperature at the start of the introduction of the pressurized steam in the first stage varies with the change in the outside air temperature, the pressure increase speed and time from the start of the introduction of the pressurized steam until the predetermined pressure is reached. , As well as the temperature rise rate and time associated therewith. Then, the amount of heat received by the precursor during the pressurization and temperature rise changes, and the crosslinking start temperature fluctuates. As a result, the physical properties, particularly hardness, of the roller body manufactured through the above steps vary from batch to batch. .

Such variation is hardly eliminated even if the foamed and crosslinked precursor as described above is taken out of the vulcanizing can and then subjected to secondary crosslinking. In addition, there is a possibility that the cross-linking proceeds excessively due to the secondary cross-linking, and the foamed rubber member becomes harder than necessary.
An object of the present invention is to produce a foamed rubber member such as the roller main body, which always has stable physical properties by suppressing physical variations due to external factors such as fluctuations in outside air temperature, particularly hardness, from batch to batch. It is in providing the manufacturing method of.

  Another object of the present invention is to provide a transfer roller having a roller body manufactured by the above manufacturing method and having stable physical properties such as hardness.

The present invention relates to a method for producing a foamed rubber member, comprising a molding step of molding the precursor of the foamed rubber member from an unfoamed and uncrosslinked rubber composition having foamability and crosslinkability, and the precursor , Including a foaming / crosslinking step in which foaming is performed while being foamed by pressurization and heating with pressurized steam in a vulcanization can,
A first stage in which the temperature in the vulcanization can is raised to a certain temperature below the foaming start temperature of the precursor and then held at the temperature for a certain period of time;
A second stage in which the temperature in the vulcanization can is raised to a constant temperature in the vicinity of the foaming start temperature of the precursor, and then held at the temperature for a certain period of time to foam and crosslink the precursor; and After foaming, the temperature in the vulcanization can is further raised to a constant temperature higher than that in the second stage, and then the third stage in which the precursor is further crosslinked by maintaining the temperature at the temperature for a certain period of time. It is characterized by being continuously carried out in a can.

  According to the present invention, prior to the first stage of the conventional two-stage foaming / crosslinking process, that is, the second stage in the present invention, the temperature in the vulcanizing can is caused to the foamed rubber member. After raising the temperature to a constant temperature below the foaming start temperature of the precursor, by carrying out the first stage that is held at the temperature for a certain time, the conditions at the start of temperature rise in the next second stage, that is, the temperature, Variation in pressure can be reduced.

  For this reason, the pressure increase rate and time from the start of temperature increase in the second stage to the predetermined temperature, and the temperature increase rate and time thereby are made substantially constant, and the amount of heat received by the precursor during the pressure increase and temperature increase is determined. A change can be made small and the fluctuation | variation of a crosslinking start temperature can be suppressed. As a result, the physical properties of the foamed rubber member such as a roller body manufactured through the molding process and the foaming / crosslinking process, particularly the hardness, are suppressed from varying from batch to batch, and the foamed rubber member is hardened. It becomes possible to always stabilize physical properties such as the above.

In the present invention, it is preferable to set the holding time in the first stage to be equal to or less than the holding time in the second stage.
When the holding time in the first stage exceeds the holding time in the second stage, the crosslinking reaction precedes in the first stage, and in the precursor, the bubble wall due to the gas generated by foaming of the foaming agent is present. Even if the precursor is not sufficiently formed and the precursor cannot be sufficiently foamed to a predetermined dimension or foamed to a predetermined dimension, the foamed rubber member may be harder than a predetermined hardness.

Moreover, in this invention, it is preferable to set the temperature rising time in said 1st step more than the temperature rising time in said 2nd step.
When the temperature rise time in the first stage is smaller than the temperature rise time in the second stage, due to the rapid temperature rise, the crosslinking reaction precedes in the first stage, and in the precursor, by foaming of the foaming agent Even if the bubble wall due to the generated gas is not sufficiently formed and the precursor cannot be sufficiently foamed to a predetermined dimension, or even if the precursor is foamed to a predetermined dimension, the foamed rubber member becomes harder than a predetermined hardness. There is a risk.

The present invention is a transfer roller comprising a cylindrical and conductive foamed rubber member manufactured by the manufacturing method of the present invention as a roller body.
According to the present invention, it is possible to provide a transfer roller that is manufactured by the manufacturing method of the present invention and includes a roller main body with stable physical properties that does not vary in physical properties such as hardness for each batch.

According to the present invention, in order to manufacture a foamed rubber member such as the roller main body, which has stable physical properties, while suppressing physical variations due to external factors such as fluctuations in outside air temperature, particularly hardness, from batch to batch. The manufacturing method of can be provided.
Moreover, according to this invention, the transfer roller provided with the roller main body manufactured with the said manufacturing method and having stable physical properties, such as hardness, can be provided.

It is a graph which shows the change of the pressure and temperature in a vulcanization can in a foaming / bridge | crosslinking process among the manufacturing methods of the foamed rubber member of this invention. It is a perspective view which shows an example of a transfer roller provided with the roller main body as a foaming rubber member manufactured by the manufacturing method of this invention. It is a graph which shows the change of the pressure and temperature in a vulcanization can at the time of the conventional two-stage heat pressurization implemented by the comparative example of this invention.

<< Method for producing foamed rubber member >>
The method for producing a foamed rubber member of the present invention comprises a molding step for molding a precursor of the foamed rubber member from an unfoamed and uncrosslinked rubber composition, and the precursor in pressurized water in a vulcanizing can. It is equipped with a foaming / crosslinking process in which foaming is performed by pressurizing and heating with steam to cause foaming.
<Molding process>
Of the above, in the molding step, the unfoamed and uncrosslinked rubber composition that is the basis of the foamed rubber member is molded by an arbitrary molding method such as an extrusion molding method to obtain a predetermined foamed rubber member. A precursor having a corresponding three-dimensional shape is produced.

<Foaming / crosslinking process>
FIG. 1 is a graph showing changes in pressure and temperature in a vulcanizing can in a foaming / crosslinking step in the method for producing a foamed rubber member of the present invention.
Referring to FIG. 1, in the foaming / crosslinking step, the following three steps are continuously performed in a vulcanization can to foam and crosslink the precursor to produce a foamed rubber member. .

(the first stage)
First, the foamed rubber member precursor molded in the molding step is accommodated in a conventional vulcanizing can, and in a sealed state, pressurized steam is introduced into the vulcanizing can, and the introduction of t ₀ is started. From the time point to the time point t ₁ , the internal pressure is increased from P ₀ to P ₁ . Then, the temperature in the vulcanization can rises from the temperature T ₀ to a temperature T ₁ that matches the pressure (saturated water vapor pressure) P ₁ .

Then, pressurized at time t ₁ the temperature reaches the T ₁ of the the vulcanizer, the maintaining the pressure P ₁ by adjusting the pressurized steam amount to be introduced into the vulcanizer, whereby the vulcanizer Is maintained at T ₁ for a certain period of time from the time point t _{1 to} the time point t ₂ .
The temperatures T ₁ is set to a constant value below the foaming starting temperature of the precursor. As a result, for example, the influence of external factors such as changes in outside air temperature due to seasonal changes can be eliminated as much as possible, and the conditions at the start of temperature rise in the next second stage, that is, variations in temperature and pressure can be reduced. .

The temperatures T ₁ may, depending on the foaming starting temperature of the precursor of the foamed rubber member is set to any value below the foaming starting temperature.
For example, when the foaming start temperature of the precursor is about 138 ° C. or more and 141 ° C. or less, the temperature T ₁ is not limited to this, but for example, it is preferably 80 ° C. or more, and preferably 110 ° C. or less.

If the temperature T ₁ is less than 80 ° C., the influence of external factors such as fluctuations in the outside air temperature due to the provision of the first stage is eliminated, and the conditions at the start of temperature rise in the second stage, that is, the temperature and pressure There is a possibility that the effect of reducing the variation cannot be sufficiently obtained.
On the other hand, if the temperature T ₁ is greater than 110 ° C. is the cause and the cross-linking reaction the first step progresses, in the precursor, and cell walls due to the gas generated by the foaming of the foaming agent is no longer sufficiently formed The foamed rubber member may become harder than a predetermined hardness even if the precursor cannot be sufficiently foamed to a predetermined dimension or even if the precursor is expanded to a predetermined dimension.

Further, the holding time _{t 1-2} of between _{t 1} to maintain the temperatures _{T 1} to _{t 2,} the holding time from _{t 3} when maintaining the temperature _{T 2} in the second stage to be described later to _{t 4} t _It is preferable to set to _3-4 or less, that is, t _1-2 ≦ t _3-4 .
Holding longer than the time _{t 1-2} is the retention time _{t 3-4,} in other words _{t 1-2> t 3-4,} will be cross-linking reaction in the first stage proceeds, in the precursor, blowing of the blowing agent The foamed rubber member becomes harder than the predetermined hardness even if the bubble wall due to the gas generated by the gas is not sufficiently formed, and the precursor cannot be sufficiently foamed to a predetermined size or foamed to a predetermined size. There is a risk of Further, the total time required for the foaming / crosslinking process becomes too long, and the productivity of the foamed rubber member may be lowered.

Incidentally holding time _{t 1-2,} even within the range, preferably set to more than 0.5 times the retention time _{t 3-4.}
If the holding time _t1-2 is less than 0.5 times the holding time _t3-4 , the effect of external factors such as fluctuations in outside air temperature due to the provision of the first stage is eliminated, and the rise in the second stage. There is a risk that the effect of reducing variations in conditions at the start of temperature, that is, temperature and pressure, cannot be sufficiently obtained.

Further, the temperature increase time t _0-1 between t ₀ and t ₁ during the temperature increase from the temperature T ₀ to the temperature T ₁ is a temperature T ₁ in the second stage described later. It is preferable to set the temperature rise time t _2-3 from t ₂ to t ₃ during the temperature rise from T ₂ to T ₂ , that is, t _0-1 ≧ t _2-3 .
When the temperature rise time t _0-1 is shorter than the temperature rise time t _2-3 , that is, when t _0-1 <t _2-3 , the temperature gradient of the temperature rise in the first stage becomes too large and abrupt. Due to the temperature rise, the crosslinking reaction precedes in the first stage, and in the precursor, the bubble wall due to the gas generated by the foaming of the foaming agent is not sufficiently formed, and the precursor is sufficiently brought to a predetermined size. Even if foaming cannot be performed or foaming can be performed to a predetermined size, the foamed rubber member may be harder than a predetermined hardness.

It should be noted that the temperature rise time t _0-1 is preferably set to not more than twice the temperature rise time t _2-3 , particularly about 5/3 times, even within the above range.
If the temperature rise time t _0-1 exceeds twice the temperature rise time t _2-3 , the total time required for the foaming / crosslinking process becomes too long, and the productivity of the foamed rubber member may be reduced. is there.
(Second stage)
Then, at the time of the t _2, by adjusting the pressurized steam amount to be introduced into the vulcanizing can to raise its internal pressure from P ₁ to P _2. Then the temperature of the vulcanizing rises from the T _1, to a temperature T ₂ commensurate with the pressure (saturated vapor pressure) P _2.

Then, pressurized at time t ₃ when temperature reaches the T ₂ of the in vulcanizer, wherein maintaining the pressure P ₂ by adjusting the pressurized steam amount to be introduced into the vulcanizer, whereby the vulcanizer Is maintained at T ₂ for a certain period of time between the time point t _{3 and} the time point t ₄ .
The temperature T ₂ is set to a constant value of the foam starting temperature near the precursor. Then, the precursor is foamed by the foaming agent and is crosslinked by the crosslinking agent.

The temperature T ₂ may be in response to the foaming starting temperature of the precursor, it is set to an arbitrary value of the foaming starting temperature near.
For example, when the foaming start temperature of the precursor is about 138 ° C. or higher and 141 ° C. or lower, the temperature T ₂ is not limited to this, but is preferably in the range of 138 ° C. or higher and 148 ° C. or lower, for example.

Temperature T ₂ in less than the above range, there may not be or is crosslinked or is sufficiently foamed precursor, when it exceeds the above range Conversely, crosslinking proceeds excessively, foamed rubber member having a predetermined hardness There is a risk of becoming harder.
Nao said temperature T ₂ is preferably as high in the above range, and particularly preferably between 143 ° C. or higher. When temperature T ₂ is within this range, the foam precursors, and more to match the balance of progress of cross-linking, to further reduce the physical properties of the foamed rubber member, especially hardness, variation of each batch, the It becomes possible to stabilize the physical properties such as hardness of the foamed rubber member even better.

Further, the holding time t _3-4 between t ₃ and t ₄ for maintaining the temperature T ₂ is not limited to this, but is preferably 7 minutes or more, particularly preferably 8 minutes or more, and 13 minutes or less. In particular, it is preferably 12 minutes or less.
When the holding time t _3-4 is less than the above range, the precursor may not be sufficiently foamed or crosslinked.

Moreover, when holding time _t3-4 exceeds the said range, bridge | crosslinking advances excessively and there exists a possibility that a foamed rubber member may become harder than predetermined | prescribed hardness. Further, the total time required for the foaming / crosslinking process becomes too long, and the productivity of the foamed rubber member may be reduced.
Further, the temperature increase time t _2-3 between t ₂ and t ₃ during the temperature increase from the temperature T ₁ to the temperature T ₂ is also due to the temperature difference between the two temperatures. Although different, when the temperatures T ₁ and T ₂ are within the above-mentioned preferred ranges, for example, it is preferably 1 minute or more, particularly preferably 2 minutes or more, and preferably 5 minutes or less, particularly 4 minutes or less.

When the temperature increase time _t2-3 is less than the above range, the crosslinking proceeds excessively due to a rapid temperature rise, and the foamed rubber member may become harder than a predetermined hardness.
Further, when the temperature rising time t _2-3 exceeds the above range, too long time of the total required for the foam-crosslinking process, the productivity of the foamed rubber member may be deteriorated.
(Third stage)
Then, at the time of the t ₄ when foaming by the blowing agent has ceased, by adjusting the pressurized steam amount to be introduced into the vulcanizing can to raise its internal pressure from P ₂ to P _3. Then, the temperature in the vulcanization can rises from T ₂ to a temperature T ₃ commensurate with the pressure (saturated water vapor pressure) P ₃ .

Then, pressurized at time t ₅ the temperature reaches the T ₃ in the vulcanizer, maintaining the pressure P ₃ by adjusting the pressurized steam amount to be introduced into the vulcanizer, whereby the vulcanizer the temperature is kept at the T ₃ over a certain period of time between the time of the t ₅ to the time of t _6.
Wherein the temperature _{T 3} is set to temperature _{T 2} or more predetermined values. Thereby, the crosslinking of the precursor can be almost completed.

Wherein the temperature T ₃ can be set to any value temperature T ₂ above.
For example, when the temperature T ₂ is in the range of 138 ° C. or higher and 148 ° C. or lower as described above, the temperature T ₃ is not limited to this, but is preferably 155 ° C. or higher, for example, 165 ° C. or lower. Is preferred.
The temperature T ₃ is lower than the above range, it takes a long time to complete the crosslinking of the precursor, too long the total time required for the foam-crosslinking step is a possibility that the productivity of the foamed rubber member is lowered is there.

Further, when the temperature T ₃ exceeds the above range, the foaming and cross-linked in step too large amount of energy the total required, the productivity of the foamed rubber member may be deteriorated.
The holding time t _5-6 between t ₅ and t ₆ for maintaining the temperature T ₃ is not limited to this, but is preferably 15 minutes or more, particularly preferably 18 minutes or more, particularly 25 minutes or less, particularly It is preferably 22 minutes or less.

If holding time _t5-6 is less than the said range, there exists a possibility that bridge | crosslinking of a precursor cannot fully be completed.
Moreover, when holding time _t5-6 exceeds the said range, the total time which a foaming and bridge | crosslinking process requires becomes too long, and there exists a possibility that productivity of a foamed rubber member may fall.
Furthermore, the temperature increase time t _4-5 from t ₄ to t ₅ during the temperature increase from the temperature T ₂ to the temperature T ₃ is also due to the temperature difference between the two temperatures. Although different, when the temperatures T ₂ and T ₃ are within the above-mentioned preferred ranges, for example, it is preferably 1 minute or more, particularly preferably 2 minutes or more, and preferably 5 minutes or less, particularly 4 minutes or less.

When the temperature increase time t _4-5 is less than the above range, the crosslinking proceeds excessively due to a rapid temperature increase, and the foamed rubber member may become harder than a predetermined hardness.
Moreover, when temperature rising time _t4-5 exceeds the said range, the total time which a foaming and bridge | crosslinking process requires becomes long too much, and there exists a possibility that productivity of a foamed rubber member may fall.
After the temperature inside the vulcanizing can is maintained at the temperature T ₃ and the time point t ₆ is reached, the amount of pressurized steam introduced into the vulcanizing can is adjusted, and the internal pressure gradually decreases from P _3. And lower the temperature in the vulcanization can.

The pressure stops the introduction of pressurized steam at time t _7, which has dropped to P _4, and cooled to room temperature by natural cooling, foaming takes the crosslinked said precursor from the vulcanizer, optionally The foamed rubber member is obtained by polishing the surface.
The temperature drop time t _6-7 between t6 and t7 at the time of cooling, the pressure P ₄ for stopping the introduction of pressurized steam, and the like can be arbitrarily set.

According to the production method of the present invention, by adding a heating step below the foaming start temperature of the precursor in the first stage to the foaming / crosslinking step, as described above, fluctuations in the outside air temperature, etc. It is possible to manufacture a foamed rubber member having always stable physical properties by suppressing variation in physical properties, particularly hardness, for each batch due to external factors.
According to the manufacturing method of the present invention, a roller body of a transfer roller of an image forming apparatus using the electrophotography, in which physical properties such as hardness are required to be strictly stable for each batch. , Can be preferably produced.

<Transfer roller>
FIG. 2 is a perspective view showing an example of a transfer roller provided with a roller body as a foamed rubber member manufactured by the manufacturing method of the present invention.
With reference to FIG. 2, the transfer roller 1 of this example includes the roller body 2 and a shaft 4 inserted through a through hole 3 at the center of the roller body 2.

The shaft 4 is integrally formed of a metal such as aluminum, an aluminum alloy, or stainless steel.
The roller body 2 and the shaft 4 are electrically joined together by, for example, a conductive adhesive, and are mechanically fixed and integrated to form the transfer roller 1.
The roller body 2 as a foamed rubber member is prepared by preparing an unfoamed, uncrosslinked conductive rubber composition having foamability and crosslinkability, and extruding the conductive rubber composition into a cylindrical shape. Next, the precursor is inserted into the vulcanizing can with a temporary shaft for crosslinking inserted through the precursor through hole 3, and the precursor is subjected to the three-stage heating in the vulcanizing can. After foaming and crosslinking, it is manufactured by cutting to a predetermined length and further finishing to a predetermined outer diameter and surface roughness by polishing the outer peripheral surface 5 as necessary.

As the conductive rubber composition used as the basis of the roller body 2, a composition having an arbitrary composition according to specifications required for the transfer roller 1 can be used.
In particular, a conductive rubber composition imparted with ionic conductivity using an ionic conductive rubber also serving as a rubber component is preferred as the conductivity imparting agent.
<< Conductive rubber composition >>
<Ion conductive rubber>
As the rubber component, it is preferable to use the ion conductive rubber and the crosslinkable rubber in combination.

  Among these, as ionic conductive rubber, epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide binary copolymer (ECO), epichlorohydrin-propylene oxide binary copolymer, epichlorohydrin-allyl glycidyl ether binary copolymer, epichlorohydrin- 1 type of ethylene oxide-allyl glycidyl ether terpolymer (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymer, and epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether quaternary copolymer Or 2 or more types are mentioned.

As the epichlorohydrin rubber, among the above examples, a copolymer containing ethylene oxide, particularly ECO and / or GECO is preferable.
In both copolymers, the ethylene oxide content is preferably 30 mol% or more, particularly preferably 50 mol% or more, and preferably 80 mol% or less.
Ethylene oxide serves to lower the roller resistance value of the transfer roller 1. However, when the ethylene oxide content is less than the above range, such a function cannot be obtained sufficiently, and the roller resistance value of the transfer roller 1 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 segmental movement of the molecular chain is hindered, so that the roller resistance value of the transfer roller 1 tends to increase. In addition, the hardness of the roller body 2 after crosslinking may increase, or the viscosity of the conductive rubber composition before crosslinking may increase when heated and melted.
The epichlorohydrin content in ECO is the remaining amount of the ethylene oxide content. That is, the epichlorohydrin content is preferably 20 mol% or more, preferably 70 mol% or less, and particularly preferably 50 mol% or less.

Further, the allylic glycidyl ether content in GECO is preferably 0.5 mol% or more, particularly preferably 2 mol% or more, more preferably 10 mol% or less, and particularly preferably 5 mol% or less.
The allyl glycidyl ether itself functions to secure a free volume as a side chain, thereby suppressing the crystallization of ethylene oxide and reducing the roller resistance value of the transfer roller 1. However, when the allyl glycidyl ether content is less than the above range, such a function cannot be obtained, so that the roller resistance value of the transfer roller 1 may not be sufficiently reduced.

  On the other hand, allyl glycidyl ether functions as a crosslinking point at the time of GECO crosslinking, so when the allyl glycidyl ether content exceeds the above range, the GECO crosslinking density becomes high, and segment movement of molecular chains is hindered. On the contrary, the roller resistance value of the transfer roller 1 tends to increase. Further, the tensile strength, fatigue characteristics, bending resistance, etc. of the roller body 2 may be reduced.

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

The blending ratio of epichlorohydrin rubber is preferably 5 parts by mass or more, particularly 10 parts by mass or more, and preferably 40 parts by mass or less, particularly 30 parts by mass or less, in 100 parts by mass of the total amount of rubber.
If the blending ratio is less than the above range, the roller body 2 may not be provided with good ionic conductivity.

On the other hand, when the above range is exceeded, the blending ratio of the crosslinkable rubber is relatively decreased, and there is a possibility that the effect obtained by blending various crosslinkable rubbers described later cannot be sufficiently obtained.
<Crosslinkable rubber>
Examples of the crosslinkable rubber include one or more of styrene butadiene rubber (SBR) and acrylonitrile butadiene rubber (NBR). These rubbers have a good crosslinkability, and also function to impart good rubber elasticity and flexibility to the roller body 2 after crosslinking.

Further, when ethylene propylene diene rubber (EPDM) is further blended as the crosslinkable rubber, the resistance of the roller body 2 to ozone generated in the image forming apparatus can be improved.
(SBR)
As the SBR, any of various SBRs synthesized by copolymerizing styrene and 1,3-butadiene by various polymerization methods such as an emulsion polymerization method and a solution polymerization method can be used. In addition, as SBR, there are an oil-extended type in which flexibility is adjusted by adding an extending oil, and a non-oil-extended type in which flexibility is not added, either of which can be used.

Furthermore, as the SBR, any of SBR of high styrene type, medium styrene type, and low styrene type classified by styrene content can be used. Various physical properties of the roller body can be adjusted by changing the styrene content and the degree of crosslinking.
One or more of these SBRs can be used.
(NBR)
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. One or more of these NBRs can be used.

Furthermore, SBR and NBR can be used in combination.
The blending ratio of SBR and / or NBR is preferably 40 parts by mass or more, particularly 60 parts by mass or more, and particularly 90 parts by mass or less, particularly 80 parts by mass or less, in 100 parts by mass of the total amount of rubber. preferable.
When the blending ratio is less than the above range, the effect of imparting good crosslinkability to the conductive rubber composition described above by using SBR and / or NBR, and good rubber for the roller body 2 after crosslinking are obtained. There is a possibility that the effect of imparting elasticity and flexibility cannot be obtained sufficiently.

On the other hand, when the above range is exceeded, there is a possibility that the blending ratio of EPDM becomes relatively small and the roller body 2 cannot be given good ozone resistance. Further, the blending ratio of epichlorohydrin rubber is relatively reduced, and there is a possibility that good ionic conductivity cannot be imparted to the roller body 2.
In addition, the said mixture ratio is a mixture ratio of SBR itself as solid content contained in the oil-extended type SBR when using an oil-extended type SBR. Moreover, when using SBR and NBR together, it is the total blending ratio.
(EPDM)
As EPDM, any of various EPDMs in which a double bond is introduced into the main chain by adding a small amount of a third component (diene component) to ethylene and propylene can be used. As the EPDM, various products are provided depending on the kind and amount of the third component. Representative examples of the third component include ethylidene norbornene (ENB), 1,4-hexadiene (1,4-HD), dicyclopentadiene (DCP), and the like. A Ziegler catalyst is generally used as the polymerization catalyst.

The blending ratio of EPDM is preferably 5 parts by mass or more, more preferably 40 parts by mass or less, and particularly preferably 20 parts by mass or less, in 100 parts by mass of the total rubber content.
When the blending ratio is less than the above range, there is a possibility that good ozone resistance cannot be imparted to the roller body 2.
On the other hand, when the above range is exceeded, the blending ratio of SBR and / or NBR becomes relatively small, and by mixing these rubbers, the roller body 2 made of the conductive rubber composition is used. There is a possibility that the effect of imparting good crosslinkability to the precursor to be obtained and the effect of imparting good rubber elasticity and flexibility to the roller body 2 after crosslinking may not be sufficiently obtained. Further, the blending ratio of epichlorohydrin rubber is relatively reduced, and there is a possibility that good ionic conductivity cannot be imparted to the roller body.

(Other rubber)
As a rubber component, polar rubber such as chloroprene rubber (CR), butadiene rubber (BR), and acrylic rubber (ACM) can be further blended to finely adjust the roller resistance value of the transfer roller 1.
<Foaming agent>
As the foaming agent, any of various foaming agents that can generate gas by heating to foam the precursor can be used.

Examples of the foaming agent include azodicarbonamide (H ₂ NOCN = NCONH ₂ , ADCA), 4,4′-oxybis (benzenesulfonylhydrazide) (OBSH), N, N-dinitrosopentamethylenetetramine (DPT), and the like. 1 type or 2 types or more are mentioned.
The blending ratio of the foaming agent is preferably 1 part by mass or more, particularly 2 parts by mass or more, preferably 8 parts by mass or less, particularly 6 parts by mass or less, per 100 parts by mass of the total amount of rubber.

If the blending ratio is less than the above range, the precursor may not be foamed well. On the other hand, if the above range is exceeded, excessive foaming will cause the cross-sectional shapes of the outer peripheral surface and inner peripheral surface of the precursor to become clean circles, the inner diameter dimension will be uneven, and the cell distribution will be uneven. There is a risk of unevenness in hardness and conductivity.
You may mix | blend the foaming adjuvant which reduces the decomposition temperature of the said foaming agent and assists the foaming. As the foaming aid, urea is preferably used.

The blending ratio of the foaming aid is preferably 1 part by mass or more, particularly 2 parts by mass or more, preferably 5 parts by mass or less, particularly 3 parts by mass or less, per 100 parts by mass of the total amount of rubber.
If the blending ratio is less than the above range, the effect of assisting foaming of the foaming agent by the foaming aid cannot be sufficiently obtained, and the precursor may not be foamed satisfactorily. On the other hand, when the above range is exceeded, the foaming temperature of the foaming agent becomes too low, and foaming proceeds in a very short time. Therefore, the foam is excessively foamed and the cross-sectional shapes of the outer peripheral surface and inner peripheral surface of the precursor are clean. There is a possibility that the shape may become circular, the inner diameter may be uneven, the cell distribution may be uneven, and the hardness and conductivity may be uneven.

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

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

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

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

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

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

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

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

Further, when the hydrotalcite or the like is used in combination with magnesium oxide or potassium oxide, a higher acid receiving effect can be obtained, and contamination of the photoreceptor can be prevented more reliably.
The blending ratio of the acid acceptor is preferably 0.2 parts by mass or more, particularly 0.5 parts by mass or more, preferably 5 parts by mass or less, particularly 3 parts by mass or less, per 100 parts by mass of the total amount of rubber. preferable.
If the blending ratio is less than the above range, the above-described effect due to the inclusion of the acid acceptor may not be sufficiently obtained. On the other hand, if the above range is exceeded, the hardness of the roller body after crosslinking may increase.

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

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

Examples of the filler include one or more of zinc oxide, silica, carbon, carbon black, clay, talc, calcium carbonate, magnesium carbonate, aluminum hydroxide, and the like.
By blending the filler, the mechanical strength of the roller body can be improved.
In addition, it is possible to impart electronic conductivity to the roller body by using conductive carbon black as a filler.

The blending ratio of the filler is preferably 5 parts by mass or more, preferably 50 parts by mass or less, particularly preferably 20 parts by mass or less, per 100 parts by mass of the total amount of rubber.
Examples of the scorch inhibitor include one or more of N-cyclohexylthiophthalimide, phthalic anhydride, N-nitrosodiphenylamine, 2,4-diphenyl-4-methyl-1-pentene, and the like. . N-cyclohexylthiophthalimide is particularly preferable.

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

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

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

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

Example 1
<Preparation of conductive rubber composition>
As rubber, NBR [JSR N250SL manufactured by JSR Corporation, low nitrile NBR, acrylonitrile content: 20%] 71 parts by mass, and ECO [HYDRIN (registered trademark) T3108 manufactured by Nippon Zeon Co., Ltd.] 23 parts by mass Blended.

  And each component shown in following Table 1 was mix | blended with the said rubber part, and it knead | mixed for 3 to 5 minutes at 80 degreeC using the closed kneading machine, and prepared the conductive rubber composition.

Each component in Table 1 is as follows.
Foaming agent masterbatch: Mixing and kneading 4 parts by mass of ADCA foaming agent (trade name Binhore AC # 3 manufactured by Eiwa Kasei Kogyo Co., Ltd.) as a foaming agent in 6 parts by mass of NBR as described above.
Foaming aid: Urea-based foaming aid [trade name cell paste 101 manufactured by Eiwa Kasei Kogyo Co., Ltd.]
Filler A: Carbon black HAF [SEAST (Seast, registered trademark) 3 manufactured by Tokai Carbon Co., Ltd.]
Filler B: Heavy calcium carbonate [Whiten (registered trademark) BF-300 manufactured by Shiraishi Calcium Co., Ltd.]
Acid acceptor: Hyrodtalcite [DHT-4A-2 manufactured by Kyowa Chemical Industry Co., Ltd.]
Cross-linking agent: 200-mesh 5% oil-filled sulfur accelerator TS: Tetramethylthiuram disulfide [Noxeller (registered trademark) TS manufactured by Ouchi Shinsei Chemical Co., Ltd.]
Accelerator DM: Di-2-benzothiazyl disulfide [Noxeller DM manufactured by Ouchi Shinsei Chemical Co., Ltd.]
Acceleration aid (1): Stearic acid Acceleration aid (2): Zinc oxide 2 types Anti-aging agent: Nickel dibutyldithiocarbamate [Antagage (ANTAGE, registered trademark) NBC manufactured by Kawaguchi Chemical Industry Co., Ltd.]
<Manufacture of roller body>
The conductive rubber composition is supplied to an extruder having a diameter of 90 mm and extruded into a cylindrical shape having an outer diameter of about 14.9 mm and an inner diameter of about 4.7 mm. And a temporary shaft for cross-linking having an outer diameter of 3 mm was inserted into the center through hole and accommodated in the vulcanizing can.

Next, pressurized steam was introduced into the vulcanizing can and subjected to heating and pressurization in three stages from the first stage to the third stage shown in FIG. 1 to foam and crosslink the precursor. The foaming temperature was 138 to 141 ° C. The heating and pressing conditions are as follows.
(the first stage)
Temperature rising time t _0-1 : 5 minutes Holding time t _1-2 : 10 minutes Holding temperature T ₁ : 100 ° C
(Second stage)
Temperature rising time t _2-3 : 3 minutes Holding time t _3-4 : 10 minutes Holding temperature T ₂ : 140 ° C
(Third stage)
Temperature rising time t _4-5 : 3 minutes Holding time t _5-6 : 20 minutes Holding temperature T ₃ : 160 ° C
Temperature drop time t _6-7 : 5 minutes <Preparation of transfer roller>
A shaft made of a metal (SUM-24L) having an outer diameter of φ8.0 mm, in which a conductive thermosetting adhesive is applied to the outer peripheral surface, is press-fitted into the center through hole of the foamed and cross-linked precursor, and in a hot air oven The thermosetting adhesive was cured (secondary cross-linking) by heating at 160 ° C. for 60 minutes, whereby the precursor and the shaft were electrically joined and mechanically fixed.

Next, the outer peripheral surface of the precursor is traverse-ground using a cylindrical grinder to finish the outer diameter to φ16.33 ± 0.15 mm and cut both ends to produce a roller body. Was made.
Example 2
A roller body was produced in the same manner as in Example 1 except that the three-stage heating and pressing conditions in the vulcanizing can were changed as follows, and a transfer roller was produced.

(the first stage)
Temperature rising time t _0-1 : 5 minutes Holding time t _1-2 : 10 minutes Holding temperature T ₁ : 80 ° C
(Second stage)
Temperature rising time t _2-3 : 3 minutes Holding time t _3-4 : 10 minutes Holding temperature T ₂ : 140 ° C
(Third stage)
Temperature rising time t _4-5 : 3 minutes Holding time t _5-6 : 20 minutes Holding temperature T ₃ : 160 ° C
Temperature drop time t _6-7 : 5 minutes << Example 3 >>
A roller body was produced in the same manner as in Example 1 except that the three-stage heating and pressing conditions in the vulcanizing can were changed as follows, and a transfer roller was produced.

(the first stage)
Temperature rising time t _0-1 : 5 minutes Holding time t _1-2 : 10 minutes Holding temperature T ₁ : 80 ° C
(Second stage)
Atsushi Nobori time _{t 2-3:} 3 minute hold time _t 3-4: 10 minutes holding temperature _T 2: 145 ° C.
(Third stage)
Temperature rising time t _4-5 : 3 minutes Holding time t _5-6 : 20 minutes Holding temperature T ₃ : 160 ° C
Temperature drop time t _6-7 : 5 minutes << Example 4 >>
A roller body was produced in the same manner as in Example 1 except that the three-stage heating and pressing conditions in the vulcanizing can were changed as follows, and a transfer roller was produced.

(the first stage)
Temperature rising time t _0-1 : 5 minutes Holding time t _1-2 : 5 minutes Holding temperature T ₁ : 100 ° C
(Second stage)
Temperature rising time t _2-3 : 3 minutes Holding time t _3-4 : 10 minutes Holding temperature T ₂ : 140 ° C
(Third stage)
Temperature rising time t _4-5 : 3 minutes Holding time t _5-6 : 20 minutes Holding temperature T ₃ : 160 ° C
Temperature drop time t _6-7 : 5 minutes << Comparative Example 1 >>
A roller body was produced in the same manner as in Example 1 except that the first stage was omitted and the conventional two-stage heating and pressurization shown in FIG. . The heating and pressing conditions were as follows.

(the first stage)
Temperature rising time t _0-11 : 5 minutes Holding time t _11-12 : 10 minutes Holding temperature T ₁₁ : 140 ° C
(Second stage)
Temperature rising time t _12-13 : 3 minutes Holding time t _13-14 : 20 minutes Holding temperature T ₁₂ : 160 ° C
Temperature drop time _t14-15 : 5 minutes _<< Hardness measurement >>
The Asker C-type hardness of the roller body of the transfer roller produced in the examples and comparative examples was measured at a temperature of 23 ° C. and a measurement load at three locations on the outer peripheral surface of the roller body in the center in the width direction and in the vicinity of both ends. An average value was obtained by measurement under the condition of 500 g.

A plurality of the above examples and comparative examples were produced by repeatedly performing a series of operations under various conditions of the initial temperature T ₀ in the vulcanizing can (the numbers are shown in Table 2). The variation (standard deviation) σ of the average value of the Asker C hardness of the roller body of the transfer roller was determined.
The results are shown in Table 2.

From the results of Examples 1 to 4 and Comparative Example 1 in Table 2, in the foaming / crosslinking process, instead of the conventional two-stage heating and pressurization, the three-stage heating and pressurization of the present invention was carried out. It was found that the variation in hardness due to the variation in the initial temperature T ₀ based on external factors such as temperature can be reduced.
In addition, from the results of Examples 1 to 4, in these examples where the foaming start temperature of the precursor is 138 ° C. or higher and 141 ° C. or lower, the second variation is considered in consideration of further reducing the variation in the hardness. stage temperature T ₂ of 138 ° C. or higher, is preferably in the range of 148 ° C. or less, it was found that more preferable to inter alia 143 ° C. or higher.

DESCRIPTION OF SYMBOLS 1 Transfer roller 2 Roller main body 3 Through-hole 4 Shaft 5 Outer peripheral surface

Claims (4)

A method for producing a foamed rubber member, comprising: a molding step of molding a precursor of the foamed rubber member from an unfoamed, uncrosslinked rubber composition; and the precursor is added by pressurized steam in a vulcanizing can. Including a foaming / crosslinking step of foaming with pressure and heating, and the foaming / crosslinking step,
A first stage in which the temperature in the vulcanization can is raised to a certain temperature below the foaming start temperature of the precursor and then held at the temperature for a certain period of time;
A second stage in which the temperature in the vulcanization can is raised to a constant temperature in the vicinity of the foaming start temperature of the precursor, and then held at the temperature for a certain period of time to foam and crosslink the precursor; and After foaming, the temperature in the vulcanization can is further raised to a constant temperature higher than that in the second stage, and then the third stage in which the precursor is further crosslinked by maintaining the temperature at the temperature for a certain period of time. A method for producing a foamed rubber member, which is carried out continuously in a can.   The method for producing a foamed rubber member according to claim 1, wherein the holding time in the first stage is set to be equal to or less than the holding time in the second stage.   The method for producing a foamed rubber member according to claim 1 or 2, wherein the temperature raising time in the first stage is set to be equal to or higher than the temperature raising time in the second stage.   A transfer roller comprising a cylindrical and conductive foamed rubber member manufactured by the manufacturing method according to any one of claims 1 to 3 as a roller body.

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