JP2003130039A - Rubber sponge tube and rubber sponge roll using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber sponge tube having a high rotary torque resistance and a low specific gravity, and a high quality of rubber sponge roll having fine uniform foaming cells without huge foamed cells on a grinding face. SOLUTION: A rubber sponge tube for a roll is so constituted that it has a skin layer at the inside and outside faces and an average foaming cell diameter is enlarged gradually from the tube inside and outside faces to the center direction of the thick wall in the tube section and the maximum foaming cell exists within 20-60% of the tube wall thickness from the inside of the tube section to the outside. It is preferable that the chief component of the rubber sponge tube is ethylene-polypropylene rubber. Further, a core shaft body is inserted in the rubber sponge tube, and the average foaming cell diameter of polished surface the external face of which is ground is 200 μm or smaller and any huge foaming cell does not exist in the rubber sponge roll.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber sponge roll for rolls and a rubber sponge roll using the same, and more particularly to a paper feed roll for paper-sucking, paper-discharging, etc. used in printing machines, copying machines, fax machines, printers, Further, it is suitable for various rubber sponge rolls such as electrophotographic copying machines, faxes, printer charging rolls, developing rolls, toner supply rolls, transfer rolls, cleaning rolls, and other rolls used around photosensitive members.

[0002]

2. Description of the Related Art Conventionally, for example, paper feeding rolls used for printing machines, copying machines, fax machines, printers for paper absorption and paper discharge applications, and electrophotographic copying machines, fax machines, charging rolls for developing machines, developing rolls, Toner supply roll,
For various roll applications such as transfer rolls and cleaning rolls used around the photoconductor, a rubber sponge layer is formed around the core shaft, and then the outer surface is polished to a predetermined outer diameter.

Further, various rubber sponge rolls described above, for example, paper feed rolls for paper suction, paper discharge, etc. used in printing machines, copying machines, fax machines, printers, and electrification of electrophotographic copying machines, fax machines, printers. In all rubber sponge rolls such as rolls, developing rolls, toner supply rolls, transfer rolls, and rolls used around the photosensitive member such as a cleaning roll, the uniformity of the state of the polishing surface that is the outer surface of the rubber sponge roll, that is, the polishing surface There is an increasing demand for rubber sponge rolls that have a fine foam diameter but no abnormal foaming in the exposed foam cells.

In order to form a rubber sponge layer around the above-mentioned mandrel, various rubber polymers are mixed with carbon black,
In addition to oils, fillers, vulcanizing agents, vulcanization accelerators, and other functional agents, foaming agents and foaming aids can be used with devices such as closed kneaders (Banbury, intermix, kneader), open rolls, etc. After kneading to obtain a rubber composition, the above rubber composition is filled around the core metal and vulcanized and foamed by a high temperature press. Method The above rubber composition is charged into a crosshead type extruder, the periphery of the core metal is covered with the rubber composition, and then the rubber composition is charged into a steam oven or a hot air oven to be vulcanized and foamed. Alternatively, while hot rubber (HAV) is added while continuously charging the above rubber composition into an extruder and continuously extruding it into a tubular shape,
It is obtained by inserting a core metal into a tube which is continuously vulcanized and foamed in a furnace using a heat source such as high frequency heating (UHF) or a heat ray radiation heater.

[0005]

The rubber sponge roll obtained by the above method or method does not have a rubber sponge skin layer at the interface between the rubber sponge layer and the core metal, or has a foamed cell wall thickness of Since only a rubber sponge skin thin film of the same degree exists, the rotation torque becomes low when used as a rubber sponge roll. Therefore, although the cost increases, there is no choice but to add a step of applying an adhesive to the core shaft.

According to the method, since a skin layer thicker than the foam cell wall is formed on the inner surface of the rubber sponge tube, when used as a rubber sponge roll, the rubber sponge roll can have a high rotation torque regardless of the presence of an adhesive. .

However, the conventional rubber sponge roll prepared by the method has low foaming in order to obtain a fine foamed cell diameter, but there is a problem that the material used increases because of low foaming, that is, high specific gravity. Therefore, in order to improve this, the present inventor firstly determined that the tube cross-section average foam cell diameter was 18
Although it is 0-220 μm, the specific gravity is 0.29-0.3
No. 5 sponge tube (Japanese Patent Laid-Open No. 9-169864
No.) is found.

However, in the rubber sponge roll in which the core shaft is inserted into the sponge tube and the outer diameter is polished, since the foam cells of the tube cross section are fine, the foam cells exposed on the polishing surface are fine and uniform at first glance. Although it is a foam cell, in fact, there is a problem that there is a huge foam cell to some extent. Further, in any of the method to form a rubber sponge layer around the core shaft described above, the manufacturing process of the rubber composition is the same, and the compounding of the rubber, particularly the dispersion of the foaming agent is performed by kneading the rubber composition. Even with sufficient caution, there are huge bubbles on the polished surface to some extent, and it is unavoidable to discard them by visual inspection. This problem can be found only after the polishing step, which is the final step of the rubber sponge roll production, and further exacerbates the problem. The presence of such giant foam cells on the polishing surface significantly reduces the functionality of the rubber sponge roll.

The present invention solves these drawbacks of the prior art and has a high rotational torque resistance, a low specific gravity while having fine and uniform foam cells on the polishing surface, and a huge foam on the polishing surface. It is an object of the present invention to provide a rubber sponge tube which is most suitable for use as a roll having no cells and a rubber sponge roll using the same.

[0010]

The first invention of the present invention is as follows:
In a rubber sponge tube having a skin layer on the inner and outer surfaces of the tube, the average foam cell diameter gradually increases from the inner and outer surfaces of the tube toward the center of the thickness of the tube cross section,
The maximum foam cell diameter is 20 to 60% of the tube wall thickness from the inner surface to the outer surface of the tube cross section, and more preferably 20 to 5
It is a rubber sponge tube for rolls present in the range of 0%. Here, the average foam cell diameter refers to an image analysis device (Toyobo Co., Ltd.) that cuts a surface that is equidistant from the inner surface of the tube cross section toward the center of the wall thickness, and the average foam cell diameter of the surface is described later. It is a value measured by an image analyzer V10) manufactured by.

That is, since the rubber sponge tube has the skin layer thicker than the foam cell wall on the inner surface, the rotation torque resistance can be increased for the rubber sponge roll application. The rotation resistance value is preferably 5 kgf-cm or more, and for that purpose, substantially about 0.1 mm to 1.0 mm.
It is preferable to have a tube inner surface skin layer having a thickness of 0.2 mm to 0.5 mm. The outer surface of the tube also has a skin layer, and the thickness of the skin layer is about 0.1.
It is preferable that the thickness is from mm to 1.0 mm, and further from 0.2 mm to 0.5 mm. Here, the skin layer refers to a uniform fine pore layer or a non-pore layer having an average foam cell diameter of 100 μm or less, preferably 50 μm or less. Further, the foam cell diameter gradually increases from the inner and outer surfaces of the rubber sponge tube toward the center of the wall thickness of the tube cross section, and the maximum foam cell diameter becomes 20 to 60% of the tube wall thickness from the inner surface to the outer surface of the tube cross section, Since the composition is preferably present in the range of 20 to 50%, low specific gravity and few materials used,
By inserting the core shaft into this rubber sponge tube and polishing the outer surface, the foam cells in the part that becomes the surface of the rubber sponge roll are only fine foam cells, and the roll has a uniform outer surface state with no giant foam cells. A rubber sponge tube for use is obtained.

The above rubber sponge tube includes natural rubber (NR), isoprene rubber (IR), styrene rubber (SBR), butadiene rubber (BR), chloroprene rubber (CR), ethylene propylene rubber (EPDM, E).
PM), butyl rubber (IIR), halogenated butyl rubber, polyisobutylene rubber, nitrile rubber (NBR),
Various rubber materials such as chlorosulfonated polyethylene rubber (CSM), acrylic rubber (ACM, ANM), urethane rubber (U), silicone rubber (Q), and epichlorohydrin rubber can be used.

Next, a second invention of the present invention is a rubber sponge tube containing ethylene propylene rubber as a main component among the above rubber components.

That is, as described above, various rubbers can be used as the material of the rubber sponge tube, but the general characteristics required for various rubber sponge rolls such as heat resistance, ozone resistance, and compression strain resistance, and the rubber rolls. Considering the ease of disposal after use, ethylene propylene rubber (EPD
It is preferable that the main component is M, EPM). Furthermore, to 100 parts by weight of the rubber polymer in the rubber sponge composition,
It is preferable that the ethylene propylene rubber is 70 parts by weight or more. In addition, as ethylene propylene rubber, in order to form fine foam cells at the rubber sponge tube outer layer portion at the time of vulcanization and foaming, the Mooney viscosity (ML1
+4, 100 ° C.) 5 to 40 is preferable, and 15 to 35 is more preferable. Furthermore, the vulcanization rate is fast
It is preferable to use ethylidene norbornene (ENB) type as the three components from the viewpoint of balance with foaming and molding processability. Examples of such ethylene propylene rubber include EP21 and EP51 manufactured by JSR, Esplen 514 and Esplen 524 manufactured by Sumitomo Chemical Co., Ltd., EPT3012P, EPT3045 and EPT401 manufactured by Mitsui Chemicals.
0, EPT4021.

In addition to the conductive agent, oil, filler, vulcanizing agent, vulcanization accelerator, and other functional chemicals, a foaming agent is added to the above rubber material as a rubber compounding agent in a general kneading method, that is, sealing. Type kneader (Banbury, Intermix,
Kneading is performed using an apparatus such as a kneader) or an open roll to obtain a rubber composition.

As the foaming agent, organic foaming agents such as N, N'-dinitrosopentamethylenetetramine (DPT), azodicarbonamide (ADCA), 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH) and urea ( C
N ₄ N ₂ O) and other foaming aids, sodium hydrogen carbonate (Na
It is possible to use an inorganic foaming agent such as HCO ₃ ) or a mixture thereof in combination, and to use ADCA and OBSH.
Is preferred. The blending amount of the foaming agent is preferably 2 to 20 parts by weight, and more preferably 5 to 15 parts by weight based on 100 parts by weight of the rubber polymer.

When the conductive agent is used, the compounding amount of the conductive agent is 5-100 with respect to 100 parts by weight of the rubber polymer.
Part by weight is preferable, and more preferably 30 to 80 parts by weight. Here, examples of the conductive agent include carbon black, graphite, and conductive zinc white.

Next, as a method for producing a rubber sponge tube using this rubber composition, the following method is suitable. First, the above rubber composition is put into an extruder and continuously extruded into a tube shape, and the tube immediately after extrusion is introduced into the heating furnace preferably within 5 seconds, more preferably within 3 seconds, and the heating furnace is heated. Inside, hot air (HAV) and high frequency heating (UHF) are used together, and hot air (HAV) is 130
The high frequency heating (UHF) output is set to 1 kW to 10 kW, preferably 3 kW to 7 kW while setting the temperature to 250 to 250 ° C., preferably 150 to 230 ° C. When the heating furnace is divided into several zones, the heating zone that uses hot air and high frequency heating together is installed first, and the heating zone that follows it is
It is preferable to heat only by hot air. The time for passing through the heating furnace is preferably 1 to 10 minutes, more preferably 1.5 to 7 minutes. In this way, by adopting the method of vulcanizing and foaming the tube immediately after extrusion by using hot air and high frequency heating, there is a skin layer on the inner and outer surfaces of the tube, and foaming from the inner and outer surfaces of the tube toward the center of the wall thickness of the tube cross section. The rubber sponge tube of the present invention in which the cell diameter gradually increases and the maximum foam cell diameter exists in the range of 20 to 60%, more preferably 20 to 50% of the tube wall thickness from the inner surface to the outer surface of the tube cross section. Can be easily obtained continuously. Further, as the aging of this rubber sponge tube, it is possible to perform heat treatment at a temperature of 70 to 180 ° C. for 1 hour to 7 days.

Next, a third invention of the present invention is a roll having an outer surface polished by inserting a core shaft into the rubber sponge tube of the first or second invention.

The core shaft is inserted into the rubber sponge tube according to the first or second aspect of the present invention. At this time, the core shaft may be made of metal or resin. It is also possible to apply an adhesive to the core shaft. Then, a rubber sponge roll having a desired outer diameter can be obtained by polishing the outer surface of the tube with a polishing machine as in the conventional polishing of a rubber sponge tube.

Next, in the fourth aspect of the present invention, the average foamed cell diameter of the polishing surface is 200 μm or less, preferably 100 μm.
Below is a rubber sponge roll with no giant foam cells on the polishing surface.

The average foam cell diameter gradually increases from the inner and outer surfaces of the tube toward the center of the wall thickness of the tube cross section,
The maximum foam cell diameter is 20 to 60% of the tube wall thickness from the inner surface to the outer surface of the tube cross section, and more preferably 20 to 5
Due to the structure existing in the range of 0%, the outer surface of the rubber sponge layer is polished by a polishing machine, preferably with a wall thickness of 0.8 mm or less,
More preferably, a rubber sponge roll having an average foam cell diameter of 200 μm or less, preferably 100 μm or less on the polished surface of the present invention can be easily obtained by polishing an amount having a wall thickness of 0.5 mm or less. The amount of polishing is preferably the same as the amount of polishing the skin layer of the rubber sponge tube or less, but it may be slightly larger than that of the skin layer.

Further, the giant foam cell is a foam cell having a cell diameter of 3 times or more, and unsuitably more than 2 times the average foam cell diameter of the polished outer peripheral surface. When the average foam cell diameter is 150 μm, it means a foam cell diameter of 450 μm or more, and a foam cell diameter of only 0.45 mm is also a huge foam cell. This huge foam cell is one on the polishing surface of one roll
The presence of even individual pieces cannot be said to be a uniform polished surface. If a rubber sponge roll is produced using the above-mentioned rubber sponge tube of the present invention, it is possible to easily obtain a uniform rubber sponge roll having a polished surface with no large foam cells on the polished surface.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the rubber sponge tube of the present invention and the rubber sponge roll using the same will be described with reference to Examples and Comparative Examples.

[0025]

EXAMPLES Examples 1 to 2 Table 1 shows the compounding contents of the rubber compositions used in the examples. As the rubber material, EPT # 4021 manufactured by Mitsui Chemicals, Inc. was used. This is a fast vulcanizing type Mooney viscosity 24 (ML1 + 4, 100 ° C.) whose third component is ENB. The carbon black is a combination of Denka Black manufactured by Denki Kagaku Co., Ltd., which is acetylene black as the carbon of the conductive material in Example 1, and Asahi # 35 manufactured by Asahi Carbon Co., Ltd. as the general carbon, and Tokai is used as the carbon of the conductive material in Example 2. Carbon Talker Black # 7270S
B and MT-N manufactured by Degussa as general carbon
990 combinations were selected. The foaming agent used in both Example 1 and Example 2 was ADCI in combination with Vinyl Hall AC # 3 manufactured by Eiwa Chemical Industry Co., Ltd. and OBSH as Neocellbon N # 1000S manufactured by Eiwa Chemical Industry Co., Ltd. The vulcanization accelerators used were all manufactured by Ouchi Shinko Kagaku.

[0026]

[Table 1]

(Preparation of rubber composition) EPDM, carbon black, zinc white # in the compounded chemicals of the examples shown in Table 1
1. Stearic acid was put into a kneader of a closed kneader, kneaded for 8 minutes, taken out from the kneader, and then continuously formed into a sheet by an open roll and cooled to prepare an A kneading dough. Then, the kneaded dough A was again charged into the kneader of the closed kneader, and the remaining compounding chemicals such as a foaming agent, sulfur and a vulcanization accelerator were added thereto, and the mixture was kneaded for 5 minutes and taken out from the kneader of the closed kneader. While continuously forming into a ribbon shape with an open roll and cooling, a ribbon-like B kneading material was produced.

[0028]

[Table 2]

(Production of Rubber Sponge Tube) Next,
2.5 seconds after the above ribbon-shaped B kneading dough was put into an extruder and continuously extruded in a tube shape, it was introduced into a heating furnace using hot air (HAV) at 200 ° C. and high frequency heating (UHF) at 4 kW for 3 minutes. Then, a continuous rubber sponge tube body having an inner diameter of 6.5 mm and an outer diameter of 22.5 mm (thickness of 8 mm) was molded. This was cut into a length of 330 mm to prepare a rubber sponge tube of the example.

[0030]

[Table 3]

(Observation of rubber sponge tube) At this time,
The tube cross section of Example 2 was enlarged and photographed to observe the state of the foam cells. FIG. 3 is a cross-sectional photograph of the rubber sponge tube of Example 2 (FIG. 1 is a schematic cross-sectional view of the rubber sponge tube of Example 2), showing that a skin layer is present on the inner and outer surfaces of the rubber sponge tube, and the tube from the inner and outer surfaces of the tube. The average foam cell diameter gradually increases toward the center of the wall thickness of the cross section, and the maximum foam cell (diameter 380 μm) is 40% of the tube wall thickness from the inner surface to the outer surface of the tube cross section.
I confirmed that it was in the position. Similarly, as a result of observing the cross section of the rubber sponge tube of Example 1, it was confirmed that it had the same foam cell structure. Further, as a result of measuring the specific gravity of the rubber sponge tubes of Examples, it was confirmed that the specific gravity was 0.34 and 0.32 in Example 1 and Example 2, respectively, and it was confirmed that the sponge had a sufficiently small specific gravity.

(Preparation of rubber sponge roll) Next, a metal core shaft having a diameter of 8 mm and a length of 310 mm is inserted into the above rubber sponge tube by using air, and the rubber sponge is made to have a surface length of 305 mm. Both ends of the tube were cut. Then, the outer diameter is polished using a cylindrical polishing machine, and the size of the rubber sponge layer portion is φ8 mm (core metal diameter) × φ22 mm (outer diameter after polishing) × length 305 mm
A rubber sponge roll was prepared. The polishing amount at this time was 0.3 to 0.4 mm in wall thickness.

(Evaluation of Rubber Sponge Roll) The rubber sponge rolls of Example 1 and Example 2 were produced, and the average foam cell diameter on the outer peripheral surface was measured using an image analyzer (Image Analyzer V10 manufactured by Toyobo Co., Ltd.). The average foam cell diameter is
It is the result of converting the average cell area obtained by the average foam cell area = total foam cell area / total number of foam cells into a circle-equivalent diameter after deleting the foam cells of 1/2 or less of the maximum cell diameter as noise. . The average foamed cell diameters on the polished outer peripheral surfaces of Example 1 and Example 2 were 170 μm and 140 μm, respectively,
It was confirmed that the cells were in a finely foamed state. Further, 100 rubber sponge rolls of each of Example 1 and Example 2 were produced, and the presence of giant foam cells on the outer peripheral surface of the polishing was visually observed. Giant foam cells have a cell diameter of 3 times or more of the average foam cell diameter of the polished outer peripheral surface, and therefore can be easily visually judged, but in each of Example 1 and Example 1, one out of 100 cells was also found. It was confirmed that there was no giant foam cell (510 μm or more in Example 1 and 420 μm or more in Example 2), and it was a fine and uniform foam cell state. Next, the anti-rotation torque between the rubber sponge tube and the metal core was measured. It was confirmed that both Example 1 and Example 2 have a weight of 9 kgf-cm or more, and the skin layer is present on the inner surface of the rubber sponge tube, so that it can be used as a roll of various types even in consideration of durability.

(Evaluation as Copier Roll) The rubber sponge rolls of Example 1 and Example 2 were used as the transfer roll of the electrophotographic copying machine. As a result, it was confirmed that a fine pattern could be clearly transferred, and that no white spots occurred during solid black transfer, and the results in Table 4 are marked with a circle. Next, the rubber sponge rolls of Example 1 and Example 2 were used as a photoconductor cleaning roll of an electrophotographic copying machine. As a result, the toner adhering to the photoconductor due to the transfer residue could be uniformly cleaned over the entire width. Furthermore, A
It was confirmed that this performance was maintained even after 100,000 sheets of 4 sheets were passed, and the results in Table 4 were marked with ◯.

[0035]

[Table 4]

Comparative Examples 1 to 3 Table 1 shows the compounding contents of the rubber composition used in Comparative Examples. In Comparative Example 1, EPT # 4021 manufactured by Mitsui Chemicals, Inc. was used, and in Comparative Examples 2 to 3, Esplen 505A manufactured by Sumitomo Chemical Co., Ltd. was used. Esplen 505A is a high-speed vulcanizing type material that is oil-free, has a Mooney viscosity of 45 (ML1 + 4, 100 ° C.), and has a third component of ENB. Also,
In the case of Comparative Example 2 and Comparative Example 3 in which Esplen 505A was used, PW-380 manufactured by Idemitsu Kosan Co., Ltd., which is a paraffin-based process oil, was blended as the oil, and the carbon amount was adjusted, and Example 1 was used. It is the same.

(Preparation of Rubber Composition) In Comparative Example 1, a rubber composition was prepared in exactly the same procedure as in Examples 1 and 2. In Comparative Examples 2 to 3, oil is used as a compounding chemical, which is the same as the kneader of the closed type kneader containing EPDM, carbon black, zinc white # 1 and stearic acid of Examples 1 to 2. Oil is also added at the same time as it is added.
Further, in Comparative Example 3, since the foaming agent is sufficiently dispersed,
Before adding sulfur and a vulcanization accelerator, only a foaming agent is added, and the mixture is kneaded for 5 minutes in a kneader of a closed kneading machine, taken out of the kneader, and continuously molded into a sheet by an open roll while cooling, A kneaded dough containing a foaming agent was prepared. Then, again, the kneading machine of the closed type kneader was charged with the kneaded dough containing the foaming agent, the remaining compounding chemicals of sulfur and the vulcanization accelerator were added thereto, kneaded for 5 minutes, and taken out from the kneader of the closed type kneading machine. While continuously forming into a ribbon shape with an open roll and cooling, a ribbon-like B kneading material was produced. The kneading step was performed three times in total to sufficiently disperse the foaming agent.

(Production of Rubber Sponge Tube) Comparative Example 1
For continuous extrusion foam vulcanization, a rubber sponge tube was prepared by foam vulcanizing only with hot air of 220 degrees without using high frequency heating in a heating furnace. Comparative Example 2 to Comparative Example 3 were introduced into a heating furnace 7 seconds after continuous extrusion, and hot air (HA
V) and 3 kW of high frequency heating (UHF) were combined and passed through a heating furnace for 3 minutes to prepare a rubber sponge tube of the same size as in Example 1. The other conditions are the same as those in the first embodiment.

(Observation of Rubber Sponge Tube) Example 1
Similarly, the tube cross sections of Comparative Examples 1 to 3 were enlarged and the state of the foam cells was observed. Comparative Examples 1 to 3
In common, there was a skin layer on the inner and outer surfaces of the tube. However, FIG. 4 is a cross-sectional photograph of the rubber sponge tube of Comparative Example 2 (FIG. 2 is a schematic cross-sectional view of the rubber sponge tube of Comparative Example 2). In Comparative Example 2, the foamed state is uniform throughout, but the foamed cell diameter is It was large, and the state was such that the maximum cells corresponding to the tube cross section of Example 2 were present in the entire tube cross section. Also, in Comparative Examples 1 and 3, the foaming state was uniform throughout. In addition, as a result of measuring the specific gravity of the rubber sponge tube of each comparative example, it was 0.31, 0.32 and 0.34 for Comparative example 1, Comparative example 2 and Comparative example 3, respectively.

(Production of Rubber Sponge Roll) Next, a rubber sponge roll of a comparative example was produced in the same procedure as in Example 1.

(Evaluation of Rubber Sponge Roll) The average foam cell diameter on the polished outer peripheral surface of the rubber sponge roll was measured in the same manner as in Example 1. As a result, Comparative Example 1 was 260 μm and was not a fine foam cell. Also on the polished surface, the sponge foam cell wall was in a fluffy state. Subsequently, Comparative Example 2 and Comparative Example 3
The average foamed cell diameter of each polished outer peripheral surface is 250 μm.
m and 220 μm. In Comparative Example 3, since the kneading for producing the rubber composition was performed once, the dispersed state of the foaming agent was improved, and the average foam cell diameter was slightly smaller than that of Comparative Example 2. Subsequently, 100 rubber sponge rolls of the comparative example were produced in the same manner as in Example 1, and the presence of giant foam cells on the peripheral surface was visually observed. As a result, Comparative Example 1,
Comparative Example 2 and Comparative Example 3 each 8 (780 μm or more),
There were 10 (750 μm or more) and 7 (660 μm or more) giant cells. It was revealed that huge foam cells still exist even if the dispersion of the foaming agent is improved. In addition, the anti-rotation torque between the rubber sponge tube and the metal core was measured. 9 kgf-cm in Comparative Example 1, Comparative Example 2 and Comparative Example 3
That was all.

(Evaluation as Copier Roll) The rubber sponge rolls of Comparative Example 1, Comparative Example 2 and Comparative Example 3 shown in Table 4 were used as a transfer roll of an electrophotographic copying machine. As a result, it was confirmed that there was a roll in which a fine pattern could not be partially and vividly transferred, and that there was a roll in which white spots were generated during solid black transfer. When the cause of this was investigated in detail, it was confirmed that the transfer failure occurred in the huge foam cell portion, and the result in Table 4 was marked with x. Next, the rubber sponge rolls of Comparative Example 1, Comparative Example 2 and Comparative Example 3 were used as a photoconductor cleaning roll of an electrophotographic copying machine. As a result, at the beginning of use, the toner adhering to the photoconductor could be cleaned and there was no problem in practice, but there was a roll in which the toner remained partially. Following this, when 100,000 sheets of A4 paper were passed, streaky scratches became conspicuous on the photoconductor,
In that portion, there was a state in which toner remained.
Then, by observing the cleaning roll in the area where the photoconductor had a streak-like scratch, it was confirmed that a giant foam cell was present at the same position, and the result in Table 4 was marked with x.

[0043]

EFFECT OF THE INVENTION A rubber sponge tube having a high rotation torque and a low specific gravity can be obtained, and a rubber sponge roll having fine and uniform foam cells on the polishing surface and having no huge foam cells can be obtained. .

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a rubber sponge tube of Example 2.

FIG. 2 is a schematic sectional view of a rubber sponge tube of Comparative Example 2.

FIG. 3 is a cross-sectional photograph of the rubber sponge tube of Example 2.

FIG. 4 is a cross-sectional photograph of a rubber sponge tube of Comparative Example 2.

[Explanation of symbols]

1 Inner surface of tube 2 Outer surface of tube 3 Maximum foamed cell A Tube thickness B 20% position from inner surface of tube thickness to outer surface C 60% position from inner surface of tube thickness to outer surface

Claims (7)

[Claims] 1. In a rubber sponge tube having a skin layer on the inner and outer surfaces of the tube, the average foam cell diameter gradually increases from the inner and outer surfaces of the tube toward the center of the wall thickness of the tube cross section, and the maximum foam cell extends from the inner surface of the tube cross section. A rubber sponge tube for rolls present in the range of 20 to 60% of the tube wall thickness toward the outer surface. 2. The rubber sponge tube for rolls according to claim 1, wherein the maximum foam cells of the rubber sponge tube for rolls are present in the range of 20 to 50% of the tube wall thickness from the inner surface to the outer surface of the tube cross section. 3. The rubber sponge tube according to claim 1, which comprises ethylene propylene rubber as a main component. 4. A rubber sponge roll having an outer surface polished by inserting a core shaft into the rubber sponge tube according to claim 1. 5. The average foam cell diameter of the polishing surface is 200 μm.
The rubber sponge roll according to claim 4, which is the following and has no large foam cells on the polishing surface. 6. The rubber sponge tube according to claim 1, wherein the rubber sponge tube contains a conductive agent. 7. The rubber sponge roll according to claim 4, wherein the rubber sponge tube contains a conductive agent.