JP2009008725A - Rubber roll - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber roll which is separated to rubber and core metal when it is discarded, which is inexpensive and which can be coated without being ground. <P>SOLUTION: In a method for manufacturing a rubber roll, a rubber sponge tube composed of closed cells having an expansion ratio of 2.5 to 5 and a closed-cell foam rate of 70% or more is formed by being principally composed of an ethylene-propylen-diene copolymerization rubber having a Moonye viscosity (ML1+4, 100°C) of 5-40 in non-oil extension, and an ethylene content of 45-65 wt.%; kneading a rubber composition having blending composition with azodicarbonamide by addition (X pts.wt.) of 2-10 pts.wt. as a foaming agent and zinc stearate or zinc oxide of 0.7X -1.3X pts.wt. as an auxiliary agent, continuously extruding the rubber composition at a point of time when the Mooney viscosity is within 35-55, and then heating the rubber composition by concurrently using hot air (HAV) and high-frequency heating (UHF), and simultaneously performing foaming and vulcanization at 150-250°C; and the rubber roll is formed by inserting the core metal in a hollow part of the obtained tube. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a roll using a rubber sponge tube, and the roll is a paper feeding roll used for a printing machine, a copying machine, a fax machine, a printer, and a paper feeding roll for use in a paper discharge, and further, an electrophotographic copying machine, It is suitable for various rubber sponge roll applications such as a roll used around a photoconductor such as a fax, printer charging roll, developing roll, toner supply roll, transfer roll, and cleaning roll.

Conventionally, for example, paper feed rolls for use in printing machines, copiers, fax machines and printers, paper feeding rolls for paper discharge applications, or electrophotographic copiers, fax machines, printer charging rolls, developing rolls, toner supply rolls, and transfer. Various rolls used around the photoconductor such as a roll and a cleaning roll are formed by forming a rubber sponge layer around the core shaft body, and then polishing the outer surface so that it has a predetermined outer diameter. It is processed into a multi-layer roll having functionality by covering or coating the tube.
There is an increasing demand for cost reduction of the multi-layer roll having the above functionality, and there is a demand for a functional roll that can be processed by a simpler process.

  For example, Japanese Patent Application Laid-Open No. 2006-264339 reports a low-hardness roll excellent in releasability that does not require a base roll polishing step (polishing-free) and can be removed in a state with good dimensional accuracy. ing. However, in this method, since the unvulcanized rubber and the core metal are integrally formed with a mold, the rubber portion and the core metal are vulcanized and bonded. It is impossible to take out only gold and reuse it. Moreover, it cannot be said that the manufacture by a metal mold sufficiently satisfies the demand for cost reduction.

  In mold molding, it is possible to produce a roll that can be separated at the time of disposal by first molding a rubber sponge tube and then inserting a metal core, but this method is more costly than integral molding. Is not used.

  In order to solve such a problem, as disclosed in JP-A-2004-323701, the present invention and the like are manufactured by a continuous vulcanization method and used as a roll in a non-polished state, and a sponge tube Invented a rubber sponge roll using Since the manufacturing method of the present invention is a continuous vulcanization method, it is inexpensive to form a sponge tube, and a core bar is inserted into the sponge tube to form a roll. Become. Further, since the rubber sponge tube obtained by the present invention has sufficient hardness and dimensional stability, the tube having the functional material can be further coated or coated on the surface without polishing the rubber surface after inserting the metal core. The roll surface can be made functional while increasing the smoothness of the surface and used as a functional roll for OA applications.

However, as a result of manufacturing a roll by the method described in Japanese Patent Application Laid-Open No. 2004-323701, there is no problem when using a method of covering a surface of a rubber sponge tube with a coating tube. In case it turns out that there is a big problem.
That is, since the sponge tube has open cells, the sponge surface has innumerable holes in the rubber surface layer, and the coating agent penetrates into the rubber, resulting in innumerable pinholes on the coat surface. found.

  Therefore, in the method described in JP-A-2004-323701, it is substantially impossible to produce a roll by coating in an unpolished state. On the other hand, a method of covering the sponge tube with a resin tube and making it into a roll is possible, but in this method, the rubber sponge tube hangs up after a long period of use, or the rubber sponge outer layer and the resin tube layer are separated. There is a problem that a gap is formed between them and the functionality is impaired.

JP 2004-323701 A

  The present invention solves the problems of the invention described in Japanese Patent Application Laid-Open No. 2004-323701, and provides a rubber roll that can separate rubber and cored bar at the time of disposal, is inexpensive, and can be coated without being polished. With the goal.

The above object is achieved by a rubber roll in which a core metal is inserted into a rubber sponge tube substantially free of a hole having a diameter of 70 μm or more on the outer surface, and the rubber part and the core metal are not substantially bonded. In the present invention, it is preferable that the resistance value is 10 ⁴ Ω or less when a voltage of 10 V is applied between the metal core and the metal plate by applying a load of 300 gf to both ends of the metal core and applying a voltage of 10 V between the metal core and the metal plate. is there. Furthermore, this is a case where the surface of the rubber sponge tube of the present invention is coated. More preferably, the surface of the rubber roll is coated with a semiconductive coating agent. More preferably, the rubber constituting the rubber sponge tube is an ethylene-propylene-diene copolymer rubber having an ethylene content of 45 to 65% by weight, and the diene compound is ethylidene norbornene.

  Further, the present invention is mainly composed of an ethylene-propylene-diene copolymer rubber having an oil-free extension, Mooney viscosity (ML1 + 4, 100 ° C.) of 5 to 40 and an ethylene content of 45 to 65% by weight, and azodicarboxylic as a foaming agent. A rubber composition containing 2 to 10 parts by weight of amide (X parts by weight), 0.7X to 1.3X parts by weight of zinc stearate or zinc oxide as an auxiliary agent, and a Mooney viscosity of 35 to 55 After the rubber composition is continuously extruded at a time within the range, the rubber composition is heated using hot air (HAV) and high frequency (UHF) in combination, and foaming and vulcanization are simultaneously performed at 150 to 200 ° C. Forming a rubber sponge tube composed of closed cells with a foaming ratio of 2.5 to 5 times and a single bubble ratio of 70% or more, and inserting a cored bar into the hollow part of the obtained tube It is a method of manufacture.

  The rubber used for the rubber sponge used in the present invention is not particularly defined. However, ethylene-propylene-diene copolymer rubber (EPDM) is used because it has high polymer weather resistance and ozone resistance, does not contain halogen, and is relatively inexpensive even without the addition of an antioxidant. It is desirable. Furthermore, since it is desired that the roll of the present invention has a smooth surface skin at the time of extrusion and good physical properties such as compression set, the Mooney viscosity (ML1 + 4, 100 ° C.) is 5 to 40 without oil. It is preferable that an ethylene-propylene-diene copolymer rubber having an ethylene content of 45 to 65% by weight as a main component. If the Mooney viscosity is less than 5, the extruded shape cannot be maintained at the time of extrusion, and the compression set is poor, resulting in sag during long-term use. If the Mooney viscosity exceeds 40, the extruded skin will not be smooth, and the roll cannot be used in an unpolished state. The Mooney viscosity is a value measured based on JIS K 6395.

  The ethylene content of EPDM is preferably 45 to 65% by weight, and if the ethylene content is less than 45% by weight, the green strength is low and the processability is very poor. If the ethylene content is increased, the green strength increases, but if it exceeds 65% by weight, the crystallinity in the polymer increases and the compression set deteriorates. The preferred ethylene content is in the range of 50-60% by weight.

  Examples of the diene component constituting EPDM include dicyclopentadiene, ethylidene norbornene, and 1,4-hexadiene. Ethylidene norbornene is preferred for foam molding. About the content of a diene component, the range normally used, ie, the range of 4-12 weight%, is used suitably by this invention.

  Examples of such EPDM include EPT # 4021 and # 4010 manufactured by Mitsui Chemicals, EP11 and EP21 manufactured by JSR, and Esprene 524 and 5724 manufactured by Sumitomo Chemical. In addition, when a plurality of rubbers having different Mooney viscosities and ethylene contents are blended, the blended rubber has a Mooney viscosity (ML1 + 4, 100 ° C.) of 5 to 40 and an ethylene content of 45 to 65% by weight. A suitable example is one in which the diene component is ethylidene norbornene and the diene content is 4 to 12% by weight.

  In order to produce a smooth and tubeless sponge tube required by the present invention, the balance between the rubber tension of the cell wall and the foaming force, that is, the balance between the vulcanization speed and the foaming speed must be appropriate. Is mentioned. If the vulcanization speed is too higher than the foaming speed, the surface does not become smooth because it swells while the viscosity is high. Conversely, if the foaming speed is too fast than the vulcanization speed, the cracked gas vulcanizes with the cell walls broken. When this phenomenon occurs in the skin layer, it becomes a pinhole.

As a foaming agent to be blended when producing a sponge tube, azodicarbonamide (ADCA) is preferably used. As a general foaming agent, N, N′-dinitrosopentamethylenetetramine (DPT) can be mentioned, but this is not preferable in the present invention because it has a problem of contaminating the photoreceptor. In addition, 4,4'-oxybisbenzenesulfonyl hydrazide (OBSH) is also used as a general foaming agent, but although this does not have a problem of contamination, the decomposition temperature is reduced due to the auxiliary effect of other rubber compounding chemicals. Since the temperature drops to 120-140 ° C, the foaming speed becomes faster than the vulcanization speed, and when used in the sponge tube of the present invention, a large number of pinholes with a size of 80 µm to 2 mm are opened on the outer surface, and a uniform coating process can be performed. Disappear. Therefore, foaming agents other than ADCA, that is, inorganic foaming agents such as DPT, OBSH, or sodium bicarbonate (NaHCO ₃ ) are not preferable, and in the present invention, these can be used in combination with ADCA. It is preferable to use a much smaller amount than ADCA for the purpose of balancing vulcanization and foaming. Preferably, a foaming agent other than ADCA is not substantially used together. The addition amount of ADCA is preferably 2 to 10 parts by weight, more preferably 4 to 8 parts by weight with respect to 100 parts by weight of EPDM.

  The decomposition temperature of ADCA alone is 210 ° C. However, it is known that the decomposition temperature of ADCA is lowered by a compound of lead, zinc, cadmium, urea, borax, ethanolamine, an alkaline compound, a vulcanization accelerator, or the like during rubber compounding. In particular, zinc oxide and zinc stearate used as a vulcanization accelerating aid in a general rubber compound have a great effect of lowering the decomposition temperature, and when they are added in an amount equal to the amount of foaming agent added, the decomposition temperature is lowered to about 160 ° C. In order to produce a sponge tube having a smooth surface and no pinholes, foaming is preferably performed at 150 to 200 ° C., particularly around 160 ° C., due to the balance with vulcanization, and zinc stearate or zinc oxide is used as an auxiliary agent. It is preferable to add 0.7 to 1.3 times the ADCA added weight. Of course, zinc stearate and zinc oxide may be used in combination, and in that case, the total added weight is preferably within the above range.

The foaming ratio of the rubber for the functional rubber sponge roll used in OA equipment is preferably 2.5 to 5 times, and the surface (outer layer) of the rubber sponge roll is coated, and the coating liquid is placed inside the rubber sponge roll. In order not to permeate, it is important that the bubbles present in the surface layer of the rubber spons roll are composed of closed cells. More preferably, the expansion ratio is 2.5 to 4 times.
The above expansion ratio is a value calculated from the formula of the specific gravity of the rubber before foaming and the specific gravity of the foam based on JIS K7112, and the expansion ratio = the specific gravity of the rubber before foaming / the specific gravity of the rubber of the foam. In the present invention, the expansion ratio of rubber can be controlled by the amount of foaming agent added. That is, in order to increase the expansion ratio, the addition amount of the foaming agent may be increased. Conversely, in order to decrease the expansion ratio, the addition amount of the foaming agent may be decreased.

In the present invention, it is a preferred embodiment to mix a conductive agent with rubber to form a conductive sponge tube. When the conductive agent is used, the blending amount of the conductive agent is preferably 5 to 100 parts by weight, and more preferably 30 to 80 parts by weight with respect to 100 parts by weight of the rubber polymer. Examples of the conductive agent used in the present invention include carbon black, graphite, and conductive zinc white. In addition to the foaming agent, auxiliary agent and conductive agent, oil, filler, vulcanizing agent, vulcanization accelerator and other various functional agents can be added as rubber compounding chemicals. The degree of electrical conductivity is such that the resistance value becomes 10 ⁴ Ω or less when a voltage of 10 V is applied between the metal core and the metal plate with a load of 300 gf applied to both ends of the metal core and a voltage of 10 V is applied between the metal core and the metal plate. Conductivity is particularly preferred. In order to improve the conductive performance, the amount of the conductive agent to be added may be increased.

  By kneading such a composition using a general kneading method, for example, a closed kneader (Banbury, intermix, kneader), an open roll, or the like, an EPDM composition can be obtained first. .

  The Mooney viscosity of the EPDM composition after kneading is preferably from 35 to 55, and particularly preferably from 40 to 50. If the Mooney viscosity is lower than 35, the tube may be cut or stretched and thinned during the continuous vulcanization process after extrusion. If the Mooney viscosity exceeds 55, the extruded skin may be deteriorated and may not be used without polishing. The Mooney viscosity after kneading can be controlled by the addition amount of a filler such as carbon black and the addition amount of a plasticizer. That is, in order to increase Mooney viscosity, the amount of filler added should be increased or the amount of plasticizer should be reduced. Conversely, in order to decrease the Mooney viscosity, the amount of filler should be decreased or the amount of plasticizer should be increased.

As a method for producing a rubber sponge tube satisfying the above-mentioned requirements of the present invention using such a rubber composition, the present invention can separate and discard the rubber sponge and the core metal, and obtain an inexpensive roll. A continuous vulcanization system is used.
In the continuous vulcanization method, the rubber composition is continuously extruded by an extruder, and the rubber composition is heated by hot air (HAV), high-frequency heating (UHF), far-infrared heater, etc. under atmospheric pressure, and foamed and vulcanized. It is a method to perform simultaneously.

  In the present invention, as a preferable continuous vulcanization system, the rubber composition is put into an extruder, continuously extruded into a tube shape, and the tube immediately after extrusion is preferably within 5 seconds, more preferably 3 It is introduced into the heating furnace within a second, and in the heating furnace, hot air (HAV) and high-frequency heating (UHF) are preferably used in combination, and the hot air (HAV) is 130 ° C. to 250 ° C., preferably 150 ° C. to There is a method in which the high frequency heating (UHF) output is set to 1 kW to 10 kW, preferably 0.2 kW to 3.0 kW while being set to 230 ° C.

  A rubber sponge having a skin layer with a smooth surface and substantially free of pinholes can be obtained by adjusting HAV and UHF in combination so as to obtain a rubber sponge having a single foam ratio of 70% or more. The time for passing through the heating furnace is preferably 1 to 10 minutes, and more preferably 1.5 to 7 minutes. In this way, by using HAV and UHF together with the tube immediately after extrusion, a rubber sponge tube having substantially no hole on the surface can be obtained easily and continuously at the target expansion ratio.

The structure of the foam cell of the rubber sponge tube formed by continuous vulcanization cannot be a complete closed cell (single bubble) or a complete open cell, and the single bubble and the open cell are present in an arbitrary ratio. The single foam ratio represents the ratio of closed cells in the foam cell, and the specific gravity (material specific gravity) of the EPDM mixed composition before foaming and vulcanization, the specific gravity of rubber after foaming and vulcanization, and the water absorption Calculated from the rate.
Single bubble ratio = 100− (rubber sponge specific gravity × water absorption / 100) / (1−rubber sponge specific gravity / rubber fabric specific gravity before foaming) × 100
The water absorption is a value obtained by leaving the sample completely submerged in tap water under a reduced pressure of 535 mmHg for 3 minutes and then obtaining the water absorption (%) = water absorption weight / weight of rubber sponge sample before water absorption × 100. A certain single bubble is a case where the single bubble ratio is 70% or more in the above formula, and a continuous bubble is a case where it is 50% or less.

In addition, the sponge tube produced by continuous vulcanization has almost no variation in the longitudinal direction of the tube of the skin layer and the foaming ratio compared to the rubber part of the sponge roll produced in a batch by a cylindrical mold, that is, non-polished A rubber sponge tube with little hardness unevenness in the longitudinal direction can be obtained even when used in the above. Of course, in the case of the sponge roll produced by the cylindrical mold, the core metal and the rubber part are bonded, which is also a big difference from the rubber roll of the present invention.
Further, as the aging of the rubber sponge tube of the present invention, it is possible to perform a heat treatment for 1 hour to 7 days at a temperature of 70 to 180 ° C.

  Since the rubber sponge tube thus obtained is smooth and free from pinholes, the roll of the present invention can be obtained by inserting a core shaft body (core metal). The rubber sponge roll by the vulcanization foaming method with a cylindrical mold is an integral molding, so it is impossible to separate and discard the rubber and the core metal. However, the rubber roll of the present invention forms a sponge tube by continuous vulcanization. Since the core bar is inserted after molding, the roll can be easily disposed of by separating rubber and metal. By setting the inner diameter of the sponge tube to a diameter 5 to 20% smaller than the outer diameter of the core metal, the rubber is tightly fixed to the core metal with sufficient force.

  In the present invention, the diameter (outer diameter) of the rubber roll is suitably 4 to 30 mm, and the diameter of the core metal is suitably 5 to 16 mm. Further, the thickness of the rubber layer of the rubber roll is suitably 2 to 10 mm. The length of the rubber roll is generally 210 to 340 mm, although it depends on the application. Examples of the core bar include iron, stainless steel, aluminum, copper, and the like, and of course the surface may be plated. Further, it may be made of plastics other than metal or wood. When producing a roll, it is desirable to insert the cored bar in a state where the inner diameter is increased by flowing air to the inner diameter portion of the rubber sponge tube, since the residual strain of the rubber can be reduced.

The functional roll of the present invention can be obtained by coating the surface (outer layer) of the rubber sponge tube obtained as described above with a functional coating agent such as semiconductive.
The coating agent varies depending on the function to be imparted, but when imparting semiconducting performance, a nylon-based polymer such as N-methoxymethylated nylon is the main component, and highly conductive carbon such as ketjen black is beaded. Liquids dispersed by a mold disperser are known. Examples of the coating method include a method of directly applying to the tube surface, a method of applying a coating liquid to the surface by spraying, a method of dipping, and the like, and the dipping method is most preferable. The thickness of the surface layer (coating layer) applied by coating is generally 50 to 300 μm. The amount of the conductive carbon contained in the coating layer is preferably 2 to 10% by weight although it depends on the conductivity of the carbon.

  The roll thus obtained is excellent in smoothness and excellent in uniformity of resistance value in a local region of one roll in the semiconductive region, and is therefore suitably used for applications such as a charging roll and a developing roll. The

  Another method for producing an inexpensive functional roll using a non-abrasive sponge tube is to cover the outer layer of the sponge with a functional resin tube smoother than rubber, and then insert the core shaft body into the sponge tube. Are known. However, in the case of this method, as described above, the rubber sponge sag after long-term use, and a gap is formed between the sponge outer layer and the functional resin tube layer, and the functionality such as semiconductivity is impaired. There's a problem. On the other hand, in the case of the rubber roll of the present invention, since the outer side is not covered with a tube, there is no problem that a gap is formed by sag.

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.
According to the present invention, “substantially no hole having a diameter of 70 μm or more exists on the outer surface” means that 100 points of 1 cm × 1 cm are arbitrarily selected from the surface of the rubber sponge tube and magnified by a microscope. Mean that the total number of holes having a diameter of 70 μm or more is 1 or less on average (if 100 places cannot be taken from one rubber sponge roll, Select 100 locations from multiple rubber rolls). And the diameter of 70 μm or more means that the diameter when the exposed area of the hole exposed on the surface is converted to a circle is 70 μm or more.

In the present invention, “the rubber part and the core metal are not substantially bonded” means that the core metal is scratched by injecting 1 to ⁴ kgf / cm ² of air between the core metal and the rubber. This means that the mandrel can be easily removed from the rubber sponge tube without any problems.

Example 1
Table 1 shows the contents of the rubber composition used in Example 1. The rubber material used was EPT # 4021 manufactured by Mitsui Chemicals. This is EPDM having a Mooney viscosity (ML1 + 4, 100 ° C.) of 24, an ethylene content of 53% by weight, and ethylidene norbornene as a diene compound. As the carbon black, Toka Black # 5500 manufactured by Tokai Carbon Co., Ltd. was used. As a foaming agent, 5 parts by weight were added to 100 parts by weight of EPDM using VINYHALL AC # 3 manufactured by Eiwa Kasei Kogyo Co., Ltd. as ADCA. As auxiliary agents, 5 parts of zinc oxide and 1 part of zinc stearate were added in a total of 6 parts by weight. As the vulcanization accelerator, 2-mercaptobenzothiazole, zinc dimethyldithiocarbamate, and zinc dibutyldithiocarbamate manufactured by Ouchi Shinsei Chemical Co., Ltd. were used.

(Production of rubber composition)
EPDM, Talker Black # 5500 (carbon black), zinc oxide, and zinc stearate in the compounding chemicals of Example 1 shown in Table 1 were put into a kneader of a closed kneader, kneaded for 8 minutes, and taken out from the kneader. Then, it was cooled while being continuously formed into a sheet with an open roll, and A kneaded dough was produced. Next, the kneaded dough A is again put into the kneader of the closed kneader, and the remaining compounding chemicals, foaming agent, sulfur, and vulcanization accelerator, are added and kneaded for 5 minutes, and then taken out from the kneader of the closed kneader. Then, it was cooled while being continuously formed into a ribbon shape with an open roll, and a ribbon-shaped B-kneaded dough was produced. The Mooney viscosity of the B-kneaded dough is as shown in Table 1.

(Production of rubber sponge tube)
Next, the ribbon-like B-kneaded dough is put into an extruder and continuously extruded in a tube shape, and after 2 seconds, it is put into a heating furnace using 200 ° C. hot air (HAV) and 1 kW high-frequency heating (UHF) for 3 minutes. It was introduced, and the temperature of the tube after passing for 1 minute was increased to 160 ° C. to perform vulcanization. By measuring the inner and outer diameters immediately after molding using a taper gauge and vernier caliper, and adjusting them to the target dimensions, a rubber sponge with an inner diameter of 5 mm × outer diameter of 11.5 mm, a foaming ratio of 3 times, and a single foam ratio of 88% The tube body was continuously formed. This was cut into a length of 340 mm, subjected to secondary vulcanization at 120 ° C. for 5 hours in an oven for the purpose of dimensional stabilization, etc., and cooled to 25 ° C. to produce a rubber sponge tube of Example 1.
The resistance value of the rubber sponge roll was confirmed by applying a voltage of 10 V between the metal core and the metal plate with a load of 300 gf applied to both ends of the metal core, and confirming that the resistance value was 2.5 × 10 ³ Ω. there were.

(Production of rubber sponge roll)
Next, a metal core shaft of φ6 mm × length 310 mm is inserted into the rubber sponge tube using air, and both ends of the rubber sponge tube are cut so that the surface length of the rubber sponge portion is 305 mm, and the rubber sponge layer A rubber sponge roll having a size of 6 mm (core shaft body diameter) × φ12 mm × length 305 mm was prepared.
In order to observe the presence or absence of holes on the surface of the rubber sponge tube, 10 places were observed with a microscope by the method described above, and no holes with a diameter of 70 μm or more were observed at any of the places.

(Rubber sponge roll surface coating)
Resistance adjustment layer forming material: Epichlorohydrin rubber (“Epichromer C” manufactured by Daiso Corporation) 100 parts by weight, hard clay 40 parts by weight, lead tan 5 parts by weight, processing aid 1 part by weight, ethylenethiourea 1.5 parts by weight After kneading with two rolls, it was dissolved in a mixed solution of methyl ethyl ketone and toluene.

Protective layer forming material: N-methoxymethylated nylon: 100 parts by weight was dissolved in a mixed solution of methanol and water, ketjen black: 5 parts by weight was added, and the mixture was dispersed with a bead type disperser.
The resistance adjustment layer forming material was coated to a thickness of 80 μm after drying and heat treatment, and the protective layer molding material was coated to a thickness of 5 μm after drying, followed by drying and heat treatment.
When the state of adhesion between the rubber part and the cored bar of the obtained rubber sponge roll was observed by the method described above, it was confirmed that the rubber part and the cored bar were naturally peeled off, and that both were not substantially bonded. .

(Rubber sponge roll evaluation)
About the roll produced in Example 1, the external appearance of the coating surface was test | inspected.

Comparative Example 1
In Comparative Example 1, EPT # 4021 manufactured by Mitsui Chemicals, Inc. was added as a foaming agent, and a total of 10 parts by weight was added to each of five parts of vinylol AC # 3 and neoselbon N # 1000S. In the molding process, a UHF output was 0.6 kW in order to obtain the same specific gravity as in Example 1, and a foam having the same size and specific gravity was obtained in the same manner as in Example 1 except that. The single bubble rate was 45%. As a result of measuring arbitrary 100 places having a width of 1 cm ^{2 on} the sponge surface, a total of 282 holes of 80 μm or more were observed. The foam was subjected to the same roll processing and coating treatment as in Example 1 to obtain a functional roll.
This foam was subjected to the same roll processing as in Example 1, and the resistance value was confirmed by the same method as in Example 1. As a result, it was 2.7 × 10 ³ Ω. Subsequently, the coating process was performed and the functional roll was obtained.

Comparative Example 2
In Comparative Example 2, 2.5 parts by weight of vinylol AC # 3 and neoselbon N # 1000S were added as foaming agents. In the molding process, a UHF output was 0.6 kW in order to obtain the same specific gravity as in Example 1, and a foam having the same size and specific gravity was obtained in the same manner as in Example 1 except that. The single bubble rate was 65%. A total of 125 holes of 80 μm or more were observed on the surface of the sponge, measuring 100 arbitrary points of 1 cm ² . The foam was subjected to the same roll processing and coating treatment as in Example 1 to obtain a functional roll. This foam was subjected to the same roll processing as in Example 1, and the resistance value was confirmed by the same method as in Example 1. As a result, it was 2.7 × 10 ³ Ω. Subsequently, the coating process was performed and the functional roll was obtained.

Comparative Example 3
In Comparative Example 3, 2 parts by weight of zinc oxide was added as an auxiliary agent. In the molding process, a UHF output was 0.6 kW in order to obtain the same specific gravity as in Example 1, and a foam having the same size and specific gravity was obtained in the same manner as in Example 1 except that. The single bubble rate was 35%. A total of 323 holes of 80 μm or more were observed on the sponge surface when 100 arbitrary 1 cm ² sites were measured. The foam was subjected to the same roll processing and coating treatment as in Example 1 to obtain a functional roll. This foam was subjected to the same roll processing as in Example 1, and the resistance value was confirmed by the same method as in Example 1. As a result, it was 2.8 × 10 ³ Ω. Subsequently, the coating process was performed and the functional roll was obtained.

(Rubber sponge roll evaluation)
In Comparative Examples 1 to 3, the same evaluation as in Example 1 was performed. Comparative Example 1 was a continuous foam sponge tube, and the coating agent soaked in the coating process, and 102 pinholes per roll were generated on the coating surface. Comparative Example 2 was a continuous foam sponge tube as in Comparative Example 1, and the coating agent soaked in the coating process, generating 38 pinholes per roll on the coating surface. In Comparative Example 3, since the vulcanization was faster than the foaming, many fine holes were opened on the surface of the rubber sponge, and innumerable pinholes were generated on the surface in the coating process.

  When images were produced using the rubber sponge rolls of Example 1 and Comparative Examples 1 to 3 as a transfer roll of a laser printer, good images were obtained in the Examples. The hole portion was blank and a good image could not be obtained.

Claims (5)

  A rubber roll in which a cored bar is inserted into a rubber sponge tube substantially free of holes having a diameter of 70 μm or more on the outer surface, and the rubber part and the cored bar are not substantially bonded. 2. The rubber roll according to claim 1, wherein a resistance value of 10 ⁴ Ω or less is obtained when a load of 300 gf is applied to both ends of the core metal and placed on the metal plate and a voltage of 10 V is applied between the core metal and the metal plate.   The rubber roll according to claim 1 or 2, which is coated with a semiconductive coating agent.   The rubber roll according to any one of claims 1 to 3, wherein the rubber constituting the rubber sponge tube is an ethylene-propylene-diene copolymer rubber having an ethylene content of 45 to 65% by weight, and the diene compound is ethylidene norbornene. .   An oil-free, Mooney viscosity (ML1 + 4, 100 ° C.) of 5 to 40, ethylene content of 45 to 65% by weight of ethylene-propylene-diene copolymer rubber as a main component, and azodicarbonamide added as a blowing agent ( X part by weight) A rubber composition containing 2 to 10 parts by weight, zinc stearate or zinc oxide 0.7 to 1.3X parts by weight as an auxiliary agent, and a Mooney viscosity within a range of 35 to 55 After the rubber composition is continuously extruded, the rubber composition is heated using hot air and high frequency in combination, and foaming and vulcanization are simultaneously performed at 150 to 200 ° C., with a foaming ratio of 2.5 to 5 times. A method for producing a rubber roll, in which a rubber sponge tube composed of closed cells having a single bubble ratio of 70% or more is formed, and a cored bar is inserted into a hollow portion of the obtained tube.