JP2006117870A - Method for producing semiconductive foamed rubber member and the semiconductive foamed rubber member - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a foamed rubber member environmentally friendly, stable from a viewpoint of quality, such as durability, capable of being used for office automation equipment, and capable of being given at a low cost. <P>SOLUTION: This foamed rubber member is produced by preparing a rubber composition which contains a water-absorbing rubber containing ethylene oxide units and does not contain a chemical foaming agent, then vulcanizing the rubber composition under normal pressure, without applying pressure to the composition, and vaporizing moisture contained in the rubber composition, so that foam is formed. The water-absorbing rubber has a water content of not less than 0.1 pt. by mass and not more than 1.0 pt. by mass, before vulcanization, and subjected to the vulcanization under the normal pressure with microwave vulcanization (UHF) and/or hot air vulcanization (VAF). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a method for producing a semiconductive foamed rubber member and a semiconductive foamed rubber member, and is suitably used as a rubber roll in, for example, an image forming apparatus such as an OA apparatus, such as a copying machine, a printer, or a facsimile.

  As rubber rollers for various office automation equipment such as printers, copiers, facsimile machines, and other image forming apparatuses, a charging roll for uniformly charging the photosensitive drum, a toner supply roll for conveying toner, and a toner photosensitive Various semiconductive rubber rolls such as a developing roll for adhering to a body and a transfer roll for transferring a toner image from a photoreceptor to a sheet are used.

Such a semiconductive rubber roll is generally composed of a cylindrical cored bar and a cylindrical semiconductive foamed rubber member fixed around the cored bar. The semiconductive foamed rubber member is designed with required characteristics such as electric resistance, durability, voltage dependency, non-contamination, hardness, dimensional stability, etc., depending on the application.

As a method for obtaining a foamed rubber member, Japanese Patent Application Laid-Open No. 2003-64224 (Patent Document 1), Japanese Patent Application Laid-Open No. 2004-9588 (Patent Document 2), Japanese Patent Application Laid-Open No. 2002-221859 (Patent Document 3), etc. A method is employed in which a chemical foaming agent is blended with rubber and the chemical foaming agent is gasified when the rubber is vulcanized.
However, with this method, the chemical foaming agent is a chemical substance that is likely to have an adverse effect on the human body, so it not only has environmental problems, but also vulcanizes the vaporized substance and the substance after reaction (reaction residue). Then you can't pull it out of the rubber. Therefore, a step of heating the vulcanized rubber at a high temperature (secondary vulcanization) is indispensable in order to remove the vaporized substance and the substance after the reaction. As a result, there is a problem that the manufacturing cost of the foamed rubber member increases.

  Therefore, a method of mixing an already foamed resin or a resin foamed by heating, called a microballoon, has been proposed. However, the microballoon is expensive, and the manufacturing cost of the foamed rubber member increases, and the uniformity of the foamed state of the rubber changes depending on the dispersion state of the microballoon in the rubber. Also, it is extremely difficult to uniformly mix the microballoon with the rubber.

  Also proposed is a method of mechanically mixing rubber latex and vulcanizing it after foaming. However, since the foaming state changes depending on the elapsed time after mixing, extremely high production management is required, and thus it is inevitable that the manufacturing cost increases. Further, since latex is originally made by dispersing rubber in water, the resulting rubber member has extremely low water resistance and is not particularly suitable for use in OA equipment.

On the other hand, foamed members that are environmentally friendly using materials other than rubber have also been studied.
For example, a method of foaming a thermoplastic resin by mixing carbon dioxide into a thermoplastic resin and extruding it (carbon dioxide gas foaming extrusion method). A method of curing (mechanical foaming method) has been proposed. However, vulcanized rubber has advantages such as excellent high-temperature stability and low persistence of low-molecular components, but high-temperature stability cannot be obtained with thermoplastic resins, and low-molecular components are not available with two-component mixed urethane resins. Is likely to occur. In particular, foamed members for use in OA equipment are required to have a small dimensional change even at high temperatures and not to contaminate a photoreceptor or paper. However, in order to obtain such performance, it is absolutely necessary to use rubber. .

  As described above, if an attempt is made to obtain a foamed rubber member using a widely used chemical foaming agent, there will be problems in environmental aspects and manufacturing costs. Moreover, the method of mixing microballoons with rubber causes a problem in manufacturing cost, and is not practical considering the dispersibility of microballoons in rubber. In addition, the method using rubber latex has problems in that the production cost is problematic and only a rubber member having low water resistance can be obtained. Furthermore, even if a material other than rubber is used, it is difficult to obtain a member that satisfies the required characteristics in various applications.

JP 2003-64224 A Japanese Patent Laid-Open No. 2004-9588 Japanese Patent Laid-Open No. 2002-221859

  The present invention has been made in view of such various problems, and in particular, without using a chemical foaming agent, without using a press or a vulcanizing can, a semiconductor foam rubber member is produced by an environmentally preferable method at the time of manufacture. The issue is to manufacture.

In order to solve the above problems, the present invention firstly prepares a rubber composition containing water selected from the following (1) to (4) without containing a chemical foaming agent:
A semiconductive foamed rubber member characterized in that the rubber composition is vulcanized under normal pressure without being pressurized, and the water contained in the rubber composition is vaporized to cause foaming. Manufacturing method.
(1) A rubber composition containing a rubber component having ionic conductivity and water absorption;
(2) a rubber composition comprising a hydrophobic rubber component having ionic conductivity and a water-absorbing polymer;
(3) a rubber composition comprising a water-absorbing rubber component having no ionic conductivity and an ionic conductive agent;
(4) A rubber composition comprising a hydrophobic rubber component having no ionic conductive material, an ionic conductive agent, and a water-absorbing polymer is provided.

As said (1), the rubber composition containing the water absorption rubber containing an ethylene oxide unit is mentioned.
As said (2), the rubber composition which made the NBR rubber contain the ionic conductive agent is mentioned.
As said (3), the rubber composition which made the natural rubber contain polyvinyl alcohol (water absorbing polymer) is mentioned.
Examples of (4) include a rubber composition in which an ionic conductive agent and polyvinyl alcohol are contained in EPDM rubber.

  As described above, in the present invention, a rubber composition containing moisture and having ionic conductivity is prepared, and the rubber composition is vulcanized under pressure conditions such as press, can vulcanization, and injection. Instead, it is vulcanized under normal pressure to evaporate the water contained in the rubber composition and cause foaming.

  As the water-containing rubber composition, a rubber composition containing a water-absorbing rubber containing an ethylene oxide unit is most preferably used, and if necessary, chloroprene rubber and / or chlorosulfonated polyethylene is blended with low gas permeability. And preparing a kneaded product in which a filler composed of carbon or calcium carbonate is blended with the rubber composition, vulcanizing the kneaded product under normal pressure, and forming by vaporizing foaming during the vulcanization. preferable.

  The reason why the copolymer rubber having the ethylene oxide unit is used is that the ethylene oxide unit is hydrophilic, so that the copolymer rubber of the ethylene oxide unit can contain moisture at a required water absorption rate. Moreover, since the rubber | gum containing an ethylene oxide unit has ionic conductivity, it can be set as the semiconductive foamed rubber member which has a required electrical resistance value. Since the degree of semiconductivity depends on the content of the ethylene oxide unit, the content is set according to the application.

Moisture contained in the rubber is trapped mainly in ethylene oxide units at a molecular level, and the dispersibility of water is very high. When the water contained in the rubber in such a highly dispersed state is exposed to a high temperature environment without being pressurized, it evaporates and foams in the rubber while maintaining dispersibility, depending on the viscosity of the rubber. . It is recognized that vaporization foaming occurs symmetrically in the left-right and up-down directions in the three-dimensional network formed by the rubber component. In the foamed material formed by vaporization foaming, the bubbles are uniformly dispersed, the cell diameter is relatively large, and the bubbles are not continuous cells but are closed cells.
By using such a foaming mechanism, it is possible to easily form a foam member in a very uniform foam state without using a chemical foaming agent. Moreover, the obtained rubber member can be provided with the required semiconductivity by means of an ethylene oxide unit having ionic conductivity.

  As described above, in the present invention, since the rubber composition containing no chemical foaming agent is vulcanized and molded, it is excellent in terms of the environment and the stability of quality. Moreover, since the secondary vulcanization for removing the vaporized substance and reaction residue of the chemical foaming agent is not required, a foamed rubber member can be obtained at low cost. Furthermore, since the rubber composition is vulcanized at normal pressure without adopting a press method using a press, a vulcanizing can, etc., the water contained in the rubber is vaporized and a large number of independent in the rubber member. Bubbles can be formed, and the manufacturing process is simple.

  Even when a moderately water-absorbing filler or a slightly water-absorbing rubber is used, a foaming phenomenon occurs, but such a foaming phenomenon is extremely random, and only a member in a non-uniform foamed state can be obtained. On the other hand, when a rubber containing an ethylene oxide unit is used, a foamed member having a uniform foamed state can be obtained even though the composition of the rubber composition is simple and the mechanism is extremely easy.

The vulcanization under normal pressure is preferably performed by microwave vulcanization (UHF) and / or hot air vulcanization (VAF).
Microwave vulcanization in which microwaves are applied to a rubber composition for vulcanization can heat not only the exterior of the rubber composition but also the interior to substantially the same state. Therefore, microwave vulcanization provides a foamed rubber member that is extremely productive and has an excellent foam balance between the inside and the outside of the rubber composition. Simultaneously with the microwave vulcanization, the rubber composition may be kept at a high temperature and heat treatment may be used in combination.
In hot-air vulcanization in which a rubber composition is heated with hot air, the outside of the rubber composition first reaches a high temperature, so that moisture evaporated inside does not easily leak to the outside, and an extremely high-magnification foamed rubber member is obtained. However, when hot air vulcanization is used alone, it takes a long time to vulcanize, and it is preferable to use microwave vulcanization together.

In the water-absorbing rubber containing the ethylene oxide unit, the water absorption before vulcanization is preferably 0.1 or more and 1.5% by weight.
If the water absorption is less than 0.1% by weight, sufficient foaming may not be obtained. If the water absorption rate exceeds 1.5% by weight, abnormal foaming may occur partially. More preferably, it is 0.2 to 1.0% by weight.

In order to adjust the water absorption to the above range, it is preferable to add a water absorption adjusting agent. Calcium oxide is preferably used as the water absorption adjusting agent. Since calcium oxide traps moisture in the rubber, the water absorption rate of the rubber can be reduced by mixing calcium oxide, and as a result, the expansion ratio of the rubber member can be controlled.
In addition, an ionic conductive material may be used as the water absorption rate adjusting agent, and by mixing the ionic conductive material, water absorption by the rubber can be promoted or water can be easily retained.

  In addition, by blending chloroprene rubber or / and chlorosulfonated polyethylene (for example, Hypalon (trade name)) or butadiene rubber with a low gas permeability as a rubber component, it is difficult to permeate the vaporized gas through the rubber, resulting in bubbles. Thus, the foamed portion can be reliably generated and the number of independent foamed portions can be increased. By increasing the number of independent foamed portions in the foamed member, shape maintainability can be improved, and foreign matters such as toner can be prevented from entering the bubbles. In addition, even if it does not mix | blend rubber | gum with small gas permeability, when it foams by the vaporization of the water | moisture content of this invention, it can be set as independent foaming, but when rubber | gum with small gas permeability is mix | blended, each independent bubble ( The size of the cell) is smaller than when not blended. Therefore, it is preferable not to mix the rubber having low gas permeability when it is desired to increase the elastic force, and to mix rubber having low gas permeability when it is desired to maintain the hardness.

  Furthermore, when a rubber or calcium carbonate filler is included in the rubber composition, the temperature increase of the rubber composition can be promoted during vulcanization, and the time for the vulcanization process can be shortened. In particular, when performing the microwave vulcanization, blending the carbon powder with the rubber composition is extremely effective for shortening the vulcanization process. Moreover, the carbon powder enables control of the electronic conductivity of the foamed rubber member.

The compounding amount of the carbon or calcium carbonate is 10 to 50 parts by mass, more preferably 30 to 40 parts by mass with respect to 100 parts by mass of the rubber component.
The carbon powder is preferably carbon powder having an average particle size of 80 nm or more. Carbon powder having an average particle size of 80 nm or more can impart semiconductivity having a required electric resistance value because of its extremely low conductivity.

  Furthermore, it is preferable to include 1 to 10 parts by mass of hydrotalcite with respect to 100 parts by mass of the rubber component.

Secondly, the present invention provides a semiconductive foamed rubber member produced by the above method.
Furthermore, it is not limited to the foamed rubber member manufactured by the said method, The filler which consists of 10-50 mass parts carbon or calcium carbonate with respect to 100 mass parts of said rubber components, and the rubber component containing ethylene oxide containing water absorbing rubber And a foam molded into a roll from a composition not containing a chemical foaming agent. More than half of the foamed part tends to be an independent foamed part, and the resistance value of the roll (logΩ) 6) to 8 are provided. A semiconductive foamed rubber member is provided.

  Since the semiconductive foamed rubber member of the present invention is ionic conductive and has a required electric resistance value stably and has a required elastic force and hardness, it is particularly suitable for a transfer roll, a developing roll, and a charging roll for OA equipment. It is suitably used for cleaning rolls, toner supply rolls, and the like.

As described above, according to the method for producing a semiconductive foamed rubber member of the present invention, since no chemical foaming agent is used, environmental deterioration in the production process can be prevented, and the foamed rubber member produced with the chemical foaming agent is produced. Therefore, the environment in use can be improved.
Furthermore, since it can be performed under normal pressure without using a press or a vulcanizing can, the manufacturing process can be simplified, and a foamed rubber member can be provided at low cost.

Moreover, in the conductive foamed rubber member of the present invention, the bubbles are uniformly dispersed, and more than half of the foamed state often becomes closed cells. Therefore, when applied to a single-layer rubber roll, for example, a toner supply roll, the toner can be prevented from entering the inside of the foamed rubber member, the change in hardness of the rubber roll accompanying use can be suppressed, and extremely good durability performance can be obtained. .
On the other hand, when applied to a rubber roll having a multi-layer structure in which a solid rubber is disposed in the outer layer, more than half of the bubbles are likely to become closed cells, so that a very good restoring property can be obtained. In addition, the foamed rubber member, which is composed mainly of open cells, tends to return to its original shape after compression, but in the case of a multi-layer structure, it is constrained by the outer layer, so it is in its original shape. It becomes difficult to restore.
In addition, the cell diameter of the bubbles can be adjusted by the presence or absence of a rubber having a low gas permeability in the water-absorbing rubber, whereby the elasticity, hardness, strength, etc. can be appropriately set.

Embodiments of the present invention will be described below.
The semiconductive foamed rubber member of the present invention is formed by foaming a rubber composition that does not contain a chemical foaming agent. Foaming is a copolymer rubber (hereinafter referred to as the water-absorbing copolymer rubber) containing an ethylene oxide unit. This is achieved by evaporating the moisture adsorbed on the ethylene oxide-containing water-absorbing rubber by exposing it to a high temperature environment under normal pressure. Therefore, no chemical foaming agent reactants or reaction residues remain, and more than half of the foamed portion is easily formed as closed cells, so that contaminants from outside enter the rubber member. It is a rubber member that is difficult to recover, has excellent recoverability, and has excellent durability.

In the ethylene oxide-containing water-absorbing rubber, the content of the ethylene oxide unit is desirably 30 mol% to 98 mol%. By setting the content of the ethylene oxide unit within the above range, it is possible to obtain a rubber that contains appropriate moisture and has a good balance of physical properties. Preferably it is 50-95 mol%, and if it is this range, management of a water absorption rate will become easy. More preferably, it is 60 to 95%.
Examples of the ethylene oxide-containing water-absorbing rubber include epichlorohydrin rubber, nitrile rubber, and ethylene oxide-propylene oxide-allyl glycidyl ether copolymer.

You may mix | blend other rubber | gum as a rubber component. Examples of the rubber include chloroprene rubber, chlorosulfonated polyethylene, butadiene rubber, styrene butadiene rubber, natural rubber, NBR rubber, and urethane rubber.
Of these, chloroprene rubber and chlorosulfonated polyethylene have low gas permeability, so that the water vaporized during heating is less likely to permeate the rubber, ensuring that the foamed state is independently foamed and air bubbles. The size of the cell (cell size) can be made smaller than that before blending. Therefore, when it is desired to enlarge the bubbles, it is preferable not to blend these rubbers having low gas permeability.
The other rubber other than the ethylene oxide-containing water-absorbing rubber is desirably 95 parts by mass or less of the entire rubber component. When there is too much other rubber or dispersion is poor, a rubber member in a good foamed state may not be obtained.

  The water absorption before vulcanization of the ethylene oxide-containing water-absorbing rubber is preferably 0.1 to 1% by weight, more preferably 0.2 to 1.0% by weight. If the water absorption is less than 0.1% by weight, sufficient foaming may not be obtained. If the water absorption rate exceeds 1% by weight, abnormal foaming may occur partially. It is preferable that the water absorption rate of the rubber containing the ethylene oxide unit as a raw material satisfies the above range, but even when it is outside the above range, a suitable foaming state can be achieved by adding a water absorption rate adjusting agent to the rubber composition. It is possible to do.

There are two types of water absorption adjusters: one that traps moisture in rubber, and the other that promotes water absorption by rubber and facilitates water retention. The former includes calcium oxide and the like, and the latter includes ionic conductive material, water-absorbing polymer (polyvinyl alcohol, etc.) and the like. Examples of the ion conductive material include quaternary ammonium perchlorate, quaternary imonium salt, and imide lithium salt.
The blending amount of the water absorption rate adjusting agent may be selected according to the desired foaming state, and for example, 0.1 to 2.0 parts by mass is preferable per 100 parts by mass of the entire rubber component.

The rubber composition contains a filler made of carbon such as carbon black or calcium carbonate. The filler is blended in a proportion of 5 to 65 parts by mass, more preferably 10 to 50 parts by mass, with respect to 100 parts by mass of the rubber component. In addition, it is desirable to control the water absorption rate of a filler to 1.0 mass part or less from a viewpoint of stabilizing the foaming state of a rubber composition.
When carbon powder is blended, the average particle size of the carbon powder is preferably 80 nm or more, and more preferably 100 to 500 nm. If it is within this range, uniform dispersion can be obtained and the carbon conductivity is difficult to speak. , And can be used so as to exhibit ionic conductivity in a region of about 10 to 5 KV.
Furthermore, when using chlorine containing rubbers, such as epichlorohydrin and a chloroprene rubber, hydrosartite is mix | blended in the ratio of 1-10 mass parts with respect to 100 mass parts of rubber components.

The rubber composition is vulcanized at normal pressure by microwave vulcanization (UHF) or hot air vulcanization (VAF), and it is particularly preferable to perform vulcanization with VAF following vulcanization with UHF.
For example, by extruding a rubber composition into a predetermined shape such as a tube shape and then immediately performing UHF, a certain degree of vulcanization can be performed at an early stage of vulcanization. The foaming state can be adjusted. UHF is originally suitable for vulcanization of rubber having a high dielectric constant and ionic conductivity. On the other hand, since VAF heats rubber by applying hot air, it is more suitable to perform vulcanization to some extent than to perform VAF from the beginning.

The foamed rubber member of the present invention is suitable for a semiconductive foamed rubber roll for OA equipment. The semiconductive foam rubber roll can be manufactured by the following method, for example.
FIG. 1 shows a production apparatus by continuous vulcanization of a semiconductive foam rubber roll. The apparatus includes an extruder 10, a UHF layer 11, VAF layers 12 to 16, a take-up machine 17, a cooling water tank 18, a winding device 19, and an automatic cutter 20. The winding device 19 from the extruder 10 is continuously conveyed by the conveyor 30 and continuously conveys the rubber tube G extruded from the extruder 10. The total length of the manufacturing process line is 45 m in the case of the apparatus shown in FIG.

  After the rubber composition is kneaded by an airtight kneader, an open roll or the like, the extruder 10 is supplied with a continuous ribbon shape by a transport vehicle A. Of the VAF layers 12 to 16, only the first VAF layer 12 conveys the rubber tube by a roller conveyor, and the other VAF layers are belt conveyors. A roller conveyor is used between S1 between the UHF layer 11 and the VAF layer 12 and between S2 between adjacent VAF layers, and these conveyors are continuous.

  In detail, as shown in FIG. 2, the axis L1 of the roller 50 of the roller conveyor between the layers is arranged at a required angle θ from the orthogonal direction L3 of the axis L2 in the conveying direction of the rubber tube G, and is rotated. The tube G is twisted at the required angle. The advancing direction of the rubber tube G is advanced at a predetermined speed by driving the conveyor and rotating guide rollers 51 and 52 arranged on both sides in the width direction of the conveyor. In addition, each roller of the roller conveyor of the UHF layer 11 may be arranged as described above, and the rubber tube may be twisted. The conveyor in the VAF layers 13 to 16 is also a roller conveyor, and these rollers are used to form rubber tubes. Twist may be added.

  In the apparatus of FIG. 1, the lengths of the respective VAF layers 12 to 16 are sequentially set to 6 m, 4 m, 4 m, 8 m, and 8 m as illustrated. The length S1 between the UHF layer 11 and the VAF layer 12 and the length S2 between adjacent VAF layers are about 0.1 m to 5 m, respectively. The cooling water tank 18 is conveyed while immersing the vulcanized rubber tube in the water tank using a mesh conveyor continuous with the belt conveyor.

  In the above apparatus, the rubber composition kneaded by the extruder 10 is extruded as a tube having a required shape, and immediately after being extruded, the rubber composition is vulcanized to a certain extent in the UHF layer 11 and then sequentially into the VAF layers 12 to 16. The vulcanization is completed with the final VAF layer 16.

  At the time of continuous vulcanization in which vulcanization proceeds by passing through the UHF layer 11 and the VAF layers 12 to 16 as described above, S1 between the UHF layer 11 and the VAF layer 12, S2 between adjacent VAF layers, UHF11 layer, In the VAF layers 12 to 16, the rubber tube to be conveyed is twisted little by little by the guide roll of the roller conveyor, and finally is rotated more than 1/2 rotation.

  The tube after vulcanization is taken up by a take-up device 19 and then cut into a required dimension by an automatic cutter 20 to obtain a rubber roll having a required shape. If this is processed, and a core metal coated with a hot melt adhesive is inserted and heated, a conductive foam rubber roll can be obtained. The surface of the rubber roll is polished as necessary.

  Examples of the present invention and comparative examples will be described in detail below.

[Examples 1-7 and Comparative Examples 1-2]
The components and blending amounts of the rubber compositions of the examples and comparative examples are shown in Table 1 below. In Table 1, the unit of the numerical value indicating the component amount is part by mass.

Manufacturers, trade names, etc., of the respective components described in Table 1 are as follows.
(Water absorption rubber)
Epichlorohydrin rubber A: Rubber containing ethylene oxide unit manufactured by Daiso Corporation
“CG102”
Water absorption 0.33% by weight when compounded with rubber composition
Epichlorohydrin rubber B: Rubber containing ethylene oxide unit manufactured by Daiso Corporation
"Epichromer D"
Water absorption 0.42% by weight when blended with rubber composition
Polyether rubber: An ethylene oxide unit-containing rubber manufactured by Nippon Zeon Co., Ltd.
"ZSN8030"
Water absorption at blending with rubber composition 0.70% by weight
The water absorption rates of the rubbers A, B and C were measured with a Karl Fischer moisture meter.
(Other rubber)
Chloroprene rubber: “Shoprene WRT” manufactured by Showa Denko
Chlorosulfonated polyethylene: manufactured by DuPont Dow Elastomer Japan Co., Ltd.
"Hypalon (registered trademark)"
NBR (nitrile rubber): “DN401LL” manufactured by Nippon Zeon Co., Ltd.
(Filler)
Calcium carbonate: light calcium carbonate treated with fatty acid (Shiraishi calcium)
(Product Name) "Average particle size of about 20nm
Carbon black: Weakly conductive carbon black manufactured by Asahi Carbon Co., Ltd.
“Asahi # 15”, average particle size 122 nm
Hydrosartite: “DHT-4A-2” manufactured by Kyowa Chemical Industry Co., Ltd.
(Water absorption rate adjusting agent)
Calcium oxide: “CML31” manufactured by Omi Chemical Co., Ltd.
Perchloric acid quaternary ammonium salt: Nippon Carlid Co., Ltd. ion conductive material "A-902"
(Chemical foaming agent)
Azodicarbonamide: “Vinihole AC # R” manufactured by Eiwa Kasei Kogyo Co., Ltd.
Urea compound: “Cell Paste 101” manufactured by Eiwa Chemical Industry Co., Ltd.

(Production method of Examples 1-7)
In each 10 liter kneader, each composition shown in Table 1 was kneaded so that rubber, filler, zinc white, and a water absorption adjusting agent were added as required, and the discharge temperature was 110 ° C. Next, the following accelerator and vulcanizing agent were added to the obtained kneaded material and dispersed in the kneaded material with a roll to obtain a rubber composition. Thereafter, the rubber composition was taken out in the form of a ribbon.

5 parts by mass of zinc white was blended per 100 parts by mass of rubber.
As a vulcanizing agent, 1.0 parts by mass of ions per 100 parts by mass of rubber and 0.3 parts by mass of ethylenethiourea per 100 parts by mass of rubber were blended.

Manufacturing method (1)
The rubber composition was extruded into a tube shape having an inner diameter of 6 mm and an outer diameter of 12 mm at a die temperature of 50 ° C. using a vacuum rubber extruder having a diameter of 60 mm. At that time, moisture other than moisture adsorbed on the bubbles and rubber can be removed. Thereafter, the tubular composition was inserted into a φ5 mm metal shaft and heated at 160 ° C. for 30 minutes under normal pressure to vulcanize and foam the tubular rubber composition.

Manufacturing method (2)
The above rubber composition was extruded into a tube shape having an inner diameter of φ6 mm and an outer diameter of φ12 mm at a die temperature of 50 ° C. with a vacuum rubber extruder of φ60 mm, and subsequently, a microwave vulcanization (UHF) layer under normal pressure, The tubular rubber composition was vulcanized and foamed through a hot air vulcanization (VAF) layer. Thereafter, the foamed rubber member was cooled through a cooling water tank.

(Production method of Comparative Examples 1 and 2)
Each compound shown in Table 1 was put into a 10 liter kneader, and rubber, filler, zinc white and chemical foaming agent were added and kneaded so that the discharge temperature was 110 ° C. Next, the following accelerator and vulcanizing agent were added to the obtained kneaded material and dispersed in the kneaded material with a roll to obtain a rubber composition. Thereafter, the rubber composition was taken out in the form of a ribbon.

5 parts by mass of zinc white was blended per 100 parts by mass of rubber.
As a vulcanizing agent, 1.0 parts by mass of ions per 100 parts by mass of rubber and 0.3 parts by mass of ethylenethiourea per 100 parts by mass of rubber were blended.

Manufacturing method << 1 >>
The rubber composition was extruded into a tube shape having an inner diameter of 6 mm and an outer diameter of 12 mm at a die temperature of 50 ° C. using a vacuum rubber extruder having a diameter of 60 mm. At that time, moisture other than moisture adsorbed on the bubbles and rubber can be removed. Thereafter, the tubular composition is inserted into a φ5 mm metal shaft and heated in a pressurized environment at 160 ° C. for 30 minutes using a vulcanizing can to vulcanize and foam the tubular rubber composition. I let you.

Manufacturing method << 2 >>
The above rubber composition was extruded into a tube shape having an inner diameter of φ6 mm and an outer diameter of φ12 mm at a die temperature of 50 ° C. with a vacuum rubber extruder of φ60 mm, and subsequently, a microwave vulcanization (UHF) layer under normal pressure, The tubular rubber composition was vulcanized and foamed through a hot air vulcanization (VAF) layer. Thereafter, the foamed rubber member was cooled through a cooling water tank.

In the production methods (1) and (2) of the above examples and the production methods << 1 >> and << 2 >> of the comparative examples, the UHF layer has two lengths of about 2 m and an output of 3 kW, and a tubular rubber composition there. Was passed at a speed of about 6.0 m / min so that the surface temperature of the tube at the outlet of the UHF layer was 130 ° C to 160 ° C.
Also, the VAF layer has a length of 4 m and three hot air temperatures of 200 ° C. are arranged, and the tubular rubber composition after passing through the UHF layer is allowed to pass therethrough, and the surface temperature of the tube at the VAF layer outlet is 180 ° C. to 210 ° C. It was made to become ° C.

  The tubular foamed rubber members obtained in the above examples and comparative examples were cut to a predetermined length. A cored bar coated with a hot melt adhesive was inserted into the hollow inner surface of the cut tube, heated, and then the surface was polished as necessary. Thus, a semiconductive foam rubber roll having an outer diameter of 16 mm and a core metal diameter of 10 mm was obtained.

[Evaluation]
The following measurements and evaluations were performed on the foamed rubber members of Examples and Comparative Examples prepared as described above. The results are shown in Table 1.

(Roll resistance value)
A semiconductive foam rubber roll 1 with a core 2 as shown in FIG. 3 is mounted on an aluminum drum (hereinafter referred to as an aluminum drum) 3 as shown in FIG. The end of the lead wire having an internal resistance r (10 kΩ) connected to the one end surface of the aluminum drum 3 was connected to the other end surface of the rubber roll 1 and the end of the lead wire connected to the negative side of the power source 4 was energized. And the voltage concerning internal resistance r was detected and it was set as detection voltage V. In this apparatus, when the applied voltage is E, the resistance value R of the roll is
R = r × E / (V−r)
However, r is considered to be minute and R = r × E / V.
With a load F of 500 g applied to both ends of the core metal 2 and rotating the aluminum drum 3 at 30 rpm, the detection voltage V when the applied voltage E is 1 kV is measured 100 times in 4 seconds, and the above R was calculated by the formula. The average of 100 calculated R values was defined as a roll resistance value. The above measurement was performed under constant temperature and humidity conditions of a temperature of 23 ° C. and a relative humidity of 55%.
The roll resistance values in Table 1 were expressed in log Ω (common logarithm).

(Cell diameter)
The cross section of the rubber roll was observed at a magnification of x100, and the cell diameter of the bubbles was examined. In Table 1, “Large”, “Medium”, and “Low” indicate the following states, respectively. Each showed the most frequent particle size.
Large: Range cell with an average major axis of 300-800 μm Medium: Range cell with an average major axis of 100-300 μm Small: Range cell with an average major axis of 10-100 μm

(Bubble state)
The cross section of the rubber roll was observed at a magnification of × 100, and the case where most of the bubbles were closed cells was displayed as “independent”, and the case where most of the bubbles were open cells was displayed as “continuous” in Table 1.

(Residual foaming agent)
Residues were detected from a chart obtained by a gas chromatograph mass spectrometer.

(Comprehensive evaluation)
Conductivity, roll resistance value, cell diameter, bubble state, presence / absence of residual foaming agent are comprehensively evaluated when used as a roll for image forming apparatus, and listed as ◎, ○, × in order of good evaluation. did.

[Consideration of results]
As shown in Table 1, the common logarithmic values of the roll resistance values of Examples 1 to 7 were stable at 6.1 to 6.9. This range is sufficiently practical for use in, for example, OA equipment applications. Further, in the rubber rolls of Comparative Examples 1 and 2, all of the bubbles were open cells, whereas in Examples 1 to 7, all of the closed cells were occupied. Therefore, the durability of the rubber roll was extremely high.

  In particular, when the rubber rolls of Examples 3 to 7 were subjected to surface polishing and used as a toner supply roll with a single layer, the initial characteristics could be maintained for a very long time. Furthermore, even when a heat-shrinkable tube made of PFA or nylon (registered trademark) is attached to the outer layer of the surface-polished roll and used as a charging roll or the like, the initial characteristics can be maintained for a very long time. did it.

  Moreover, the comparison of Examples 5-7 shows that the foaming ratio can be changed and the roll resistance value can be controlled without changing the cell diameter by using the water absorption rate adjusting agent. It was.

  Also, in the case of the comparative example using a chemical foaming agent, the foaming agent remained, so it was not possible to make it as it is, and it was reconfirmed that a process such as secondary vulcanization was required in consideration of the environment. It was done. At the same time, it was confirmed that the present invention is extremely advantageous in terms of manufacturing cost and environment.

  In addition, although an Example performs continuous vulcanization under a normal pressure, even when it keeps at 200 degreeC in the oven which does not pressurize, for example, even if it inserts a metal core to a roll and vulcanizes, According to the blending ratio, a sample close to the above example can be formed. That is, it is not limited to continuous vulcanization as long as vulcanization is performed under normal pressure without pressure.

  According to the present invention, a foamed rubber member having semiconductivity can be obtained simply and at low cost, and the foamed rubber member is excellent in durability and environmentally. It is useful as a semiconductive foam rubber roll for a roller mechanism built in OA equipment such as image forming apparatuses such as a printer, a printer and a facsimile machine. In particular, the foamed rubber member of the present invention is suitable as a toner supply roll, a transfer roll, a developing roll, a charging roll, a cleaning roll, and the like.

It is explanatory drawing which shows the manufacturing process of the semiconductive foamed rubber roll of this invention. (A), (B) is a partially expanded perspective view of FIG. It is the schematic of the semiconductive foamed rubber roll of this invention. It is explanatory drawing which shows the measuring method of the roll resistance value of a rubber roll.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Foam rubber roll 2 Core metal 3 Aluminum drum 4 Power supply 10 Extruder 11 UHF layer 12-16 VAF layer 17 Take-out machine 18 Cooling water tank 19 Winding device 20 Automatic cutter 30 Conveyor 50 Roller 51, 52 Guide roller

Claims (9)

A rubber composition containing water selected from the following (1) to (4) without containing a chemical foaming agent is prepared,
A semiconductive foamed rubber member characterized in that the rubber composition is vulcanized under normal pressure without being pressurized, and the water contained in the rubber composition is vaporized to cause foaming. Manufacturing method.
(1) A rubber composition containing a rubber component having ionic conductivity and water absorption;
(2) a rubber composition comprising a hydrophobic rubber component having ionic conductivity and a water-absorbing polymer;
(3) a rubber composition comprising a water-absorbing rubber component having no ionic conductivity and an ionic conductive agent;
(4) A rubber composition comprising a hydrophobic rubber component having no ionic conductive material, an ionic conductive agent, and a water-absorbing polymer.   The method for producing a semiconductive foamed rubber member according to claim 1, wherein the rubber composition contains a water-absorbing rubber containing an ethylene oxide unit.   The method for producing a semiconductive foam rubber member according to claim 1 or 2, wherein the vulcanization under normal pressure is performed by microwave vulcanization (UHF) or / and hot air vulcanization (VAF).   The method for producing a semiconductive foamed rubber member according to any one of claims 1 to 3, wherein the water absorption rate of the water absorbent rubber before vulcanization is 0.1 or more and 1.5% by weight.   The semiconductive foamed rubber member manufactured with the manufacturing method of any one of Claims 1 thru | or 4.   The semiconductive foamed rubber member according to claim 5, wherein a filler made of carbon or calcium carbonate is blended at a ratio of 5 to 65 parts by mass with respect to 100 parts by mass of the rubber component.   The semiconductive foamed rubber member according to claim 5 or 6, wherein chloroprene rubber or / and chlorosulfonated polyethylene having low gas permeability are blended with ethylene oxide-containing water-absorbing rubber as a rubber component.   A roll comprising a rubber component containing an ethylene oxide-containing water-absorbing rubber and a composition containing 10 to 50 parts by mass of carbon or calcium carbonate with respect to 100 parts by mass of the rubber component and no chemical foaming agent. Semi-conductive, characterized in that the foam is formed of a foamed body, more than half of the foamed part is an independent foamed part, and has a roll resistance value (log Ω) of 6-8. Foam rubber member.   A rubber roll for an image forming apparatus, comprising the semiconductive foamed rubber member according to any one of claims 5 to 8.

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