JP2002187157A - Manufacturing method for expanded rubber roller and imaging device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an expanded rubber roller which shows the compatibility of low hardness with low compression permanent set and a little variability of hardness or electric resistance, with fine expanded cells. SOLUTION: The manufacturing method for the expanded rubber roller with a rubber foam layer formed on the outer periphery of a shaft comprises (1) the steps of forming an adhesive layer by applying an adhesive to the outer periphery of the shaft, (2) the step of obtaining an unexpanded rubber roller by extruding and molding an expanded rubber composition, in a cylindrical shape, onto the outer periphery of the shaft with the formed adhesive layer, using a rubber extruder, (3) the step of setting the unexpanded rubber roller inside a previously temperature-controlled split mold and vulcanize/expand the roller while pressurizing it under a specified pressure for a specified time, (4) the step of opening the split mold and unload the roller from the split mold and (5) the step of adjusting the obtained roller to a specified outside diameter.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a foamed rubber roller and an image forming apparatus.
Low hardness and low compression set are compatible, having fine foam cells, and small variation in hardness and electric resistance.
Laser printers, a method of manufacturing a foamed rubber roller suitably used as a member for an image forming apparatus such as an electrophotographic apparatus such as a facsimile or an electrostatic recording apparatus, and the image forming apparatus equipped with the foamed rubber roller obtained by the method It is about.

[0002]

2. Description of the Related Art In recent years, with the progress of electrophotographic technology, image forming apparatuses such as electrophotographic apparatuses and electrostatic recording apparatuses are used for charging, developing, transferring, supplying toner, and cleaning. Roller-shaped members, such as a charging roller, a developing roller, a transfer roller, a toner supply roller, a cleaning roller, a bias roller, and a paper feed roller, are often used as components of such components. These rollers need to have low hardness in order to obtain high-quality images, and usually rollers made of foamed rubber are often used. However, it is difficult for the foamed rubber roller to have both low hardness and low compression set, and it is effective to increase the foaming ratio in order to make the foamed rubber roller having a low hardness. There was a problem that distortion became high.
Further, in recent image forming apparatuses, foamed rubber having fine foamed cells is required in order to obtain a high-quality image. In particular, a roller formed of foamed rubber having an average foamed cell of 30 to 100 μm is required. Have been. Further, there is a demand for imparting conductivity to the foamed rubber roller, and a roller having a predetermined electric resistance level and a small variation in electric resistance has been demanded.

[0003] By the way, conventionally, a foamed rubber roller is manufactured as follows. First, the foamed rubber composition,
After being formed into a cylindrical shape using a rubber extruder, it is cut into predetermined dimensions. Next, the dummy shaft is inserted into the inside diameter of the cylindrical object. This is set in a vulcanizer, vulcanized by a steam vulcanization method, and foamed. Then, it is taken out of the vulcanization can and further heated in a hot air furnace to remove distortion and the like, and the dummy shaft is removed to obtain a foamed rubber cylindrical material. Next, after applying an adhesive to the outer periphery of the shaft and drying the shaft, the shaft is press-fitted into the above-mentioned foamed rubber cylinder, and the shaft is heated in an oven to perform a bonding treatment. After being taken out of the oven and cooled, the surface of the foamed rubber cylinder is polished and shaped to obtain a foamed rubber roller. There are various other methods for producing the foamed rubber roller, but with the conventional production method, it is difficult to obtain a foamed rubber roller that satisfies the above requirements, and the production process is complicated. There was a problem of getting high.

[0004]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above circumstances, and has both low hardness and low compression set, has fine foam cells, and has uneven hardness and electric resistance. An object of the present invention is to provide a method for stably manufacturing a small foamed rubber roller at a low cost by a simple process.

[0005]

Means for Solving the Problems The present inventors have made intensive studies to achieve the above object, and as a result, have extruded a foamed rubber composition into a cylindrical shape on the outer periphery of a shaft having an adhesive layer formed thereon. It has been found that a foamed rubber roller having the above characteristics can be obtained by subjecting the unfoamed rubber roller obtained as described above to pressure vulcanization, foaming and post-vulcanization. The present invention has been completed based on such findings. That is, the present invention relates to a method for manufacturing a foamed rubber roller in which a rubber foam layer is formed on the outer periphery of a shaft,
(1) a step of applying an adhesive to the outer periphery of the shaft to form an adhesive layer; Extrusion molding to obtain an unfoamed rubber roller, (3)
Setting the unfoamed rubber roller in a split mold whose temperature has been adjusted in advance, vulcanizing and foaming while applying a predetermined pressure for a predetermined time, and (4) opening the split mold to obtain the above obtained mold. And (5) a step of adjusting the obtained roller to a predetermined outside diameter. Further, the present invention also provides an image forming apparatus equipped with the conductive foam roller obtained by the above manufacturing method.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the method for producing a foamed rubber roller of the present invention, a foamed rubber composition containing a rubber additive such as a raw rubber, a foaming agent and a vulcanizing agent is used. Raw rubber includes natural rubber, nitrile rubber, ethylene propylene rubber, styrene butadiene rubber, butadiene rubber,
Examples include isoprene rubber, silicone rubber, urethane rubber, acrylic rubber, chloroprene rubber, and epichlorohydrin rubber, and ethylene propylene rubber is preferred. As the ethylene propylene rubber, an ethylene propylene rubber having an iodine value of 35 to 45 and a Mooney viscosity ML _{1 + 4} (100 ° C.) of 20 to 50 is particularly preferably used. The iodine value is particularly preferably 35 to 40, and the Mooney viscosity ML _{1 + 4} (100 ° C.) is particularly preferably 30 to 45.
When the iodine value is less than 35, the compression set of the foam is 20 to
When the iodine value exceeds 40% and the iodine value exceeds 45, the durability of the ethylene propylene rubber foam to ozone and the like decreases. If the Mooney viscosity is less than 20, the viscosity of the unvulcanized rubber composition using the same becomes too small and foaming occurs excessively, so that the cell becomes coarse. Since the viscosity of the rubber composition increases and foaming becomes insufficient, the foam density increases.

The ethylene propylene rubber foam may be appropriately selected from other components as long as the ethylene propylene rubber is made of the above-mentioned ethylene propylene rubber. (A) 0.5 to 5 parts by weight of a vulcanizing agent, (B) 1 to 15 parts by weight of a foaming agent, and (C) 10 to 80 parts by weight of rubber per 100 parts by weight of rubber.
Parts by weight, 10 to 60 parts by weight of (D) filler and 1 to 80 parts by weight of (E) conductive material, and vulcanization and foaming. When a material other than ethylene propylene rubber is used as the raw material rubber, it is also preferable to add the components (A) to (E) to 100 parts by weight of the raw material rubber in the same manner. Ingredients can be added. Various vulcanizing agents can be used as the component (A), but a sulfur-based vulcanizing agent is preferred because foaming and vulcanization of the ethylene propylene rubber composition can be easily controlled. Here, the sulfur-based vulcanizing agent refers to a combination of sulfur and a vulcanization accelerator or a sulfur-containing organic compound. Examples of the vulcanization accelerator include thiazoles, sulfenamides, thioureas, thiurams,
Examples thereof include dithiocarbamates, guanidines, aldehyde amines, and aldehyde ammonias. One of these can be used alone, or two or more can be used in combination. Examples of the sulfur-containing organic compound include morpholine disulfide, tetraalkylthiuram disulfide, dipentamethylenethiuram tetrasulfide, and the like. The amount of the vulcanizing agent added is ethylene propylene rubber rubber 1
The amount is preferably 0.5 to 5 parts by weight based on 00 parts by weight.

As the foaming agent of the component (B), for example,
azo compounds such as p, p'-oxybis (benzenesulfonyl hydrazide) (OBSH), benzenesulfonyl hydrazide, toluenesulfonyl hydrazide, etc .; azo compounds such as azodicarbonamide (ADCA) and azobisisobutyronitrile; Dinitrosopentamethylenetetramine, N, N'-dimethyl-N,
Organic blowing agents such as nitroso compounds such as N'-dinitrosoterephthalamide; and inorganic blowing agents such as sodium bicarbonate and ammonium bicarbonate. Among them, OB
SH, ADCA or a foaming agent using them in combination is preferable. The amount of the foaming agent added is ethylene propylene rubber 10
1 to 10 parts by weight, preferably 3 to 8 parts by weight, based on 0 parts by weight. It is preferable that the particle diameter of the foaming agent be as small as possible in order to reduce the size of the foam cells. The particle diameter of the blowing agent is preferably 10 μm or less, and 5 μm
The following are particularly preferred. As the process oil of the component (C), paraffin-based process oil, naphthene-based process oil and aromatic-based process oil can be used. Among these, a paraffin-based process oil is preferable because it does not contaminate other members such as a photoconductor. The addition amount of the process oil is preferably 20 to 70 parts by weight based on 100 parts by weight of ethylene propylene rubber,
Particularly preferred is 40 to 70 parts by weight. If the amount of the process oil is less than 20 parts by weight, the viscosity of the unfoamed rubber composition becomes large and the processability becomes poor, and the foaming becomes insufficient, so that the density of the foam becomes large. Also,
If the amount of the process oil exceeds 70 parts by weight, the viscosity of the unvulcanized rubber composition becomes too low, and excessive foaming occurs, resulting in a disadvantage that cells become coarse.
Examples of the filler for the component (D) include calcium carbonate, magnesium carbonate, silica, magnesium silicate, and clay. Of these, calcium carbonate is preferred from the viewpoint of stabilizing the foam cells. The amount of filler
10-6 per 100 parts by weight of ethylene propylene rubber
0 parts by weight is preferable, and 20 to 50 parts by weight is particularly preferable. If the amount of the filler is less than 10 parts by weight, the foam cells are not stable and become non-uniform.
When the amount exceeds the weight part, the compression set of the ethylene propylene rubber foam becomes large.

As the conductive material of the component (E), conductive carbon black such as Ketjen black and acetylene black; SAF, ISAF, HAF, FEF, GPF, S
Carbon black for rubber such as RF, FT, MT; carbon black for ink such as carbon oxide black, pyrolytic carbon black, graphite; conductive metal oxide such as tin oxide, titanium oxide, zinc oxide; nickel, copper, etc. Metals: conductive whiskers such as carbon whiskers, graphite whiskers, titanium carbide whiskers, conductive potassium titanate whiskers, conductive barium titanate whiskers, conductive titanium oxide whiskers, and conductive zinc oxide whiskers. The amount of the conductive material to be added is preferably from 1 to 80 parts by weight, particularly preferably from 5 to 60 parts by weight, per 100 parts by weight of the ethylene propylene rubber. By adding the conductive material, the foamed rubber roller of the present invention can be adjusted to a volume resistivity of 10 ⁴ to 10 ¹⁰ Ω · cm. In the foamed rubber roller of the present invention, the volume resistivity is 10 ⁵ to
It is particularly preferable that the thickness be in the range of 10 ⁸ Ω · cm from the viewpoint of obtaining good images. In the ethylene propylene rubber foam, in addition to the above additives, vulcanization accelerators such as zinc white and stearic acid, anti-scorch agents, tackifiers, and other rubber additives do not impair the effects of the present invention. It can be appropriately added within the range.

[0010] The foamed rubber composition used in the present invention is prepared by adding additives other than a vulcanizing agent and a foaming agent to the above-mentioned raw rubber in a range of 110 to 18;
Kneading is performed at a temperature of about 0 ° C. using a kneader, a Banbury mixer or the like. After cooling the kneaded product, a vulcanizing agent and a foaming agent are added, and the mixture is kneaded at a temperature of about 50 to 90 ° C. to obtain a foamed rubber composition. In the method for manufacturing a foamed rubber roller of the present invention, first, an adhesive is applied to the outer periphery of the shaft to form an adhesive layer [Step (1)]. Examples of the shaft include a metal member obtained by plating a steel material such as sulfur free-cutting steel with zinc or the like, and a metal member such as aluminum, stainless steel, and magnesium alloy. The adhesive includes a hot melt type, a solvent drying type, a heat crosslinking type and the like. In the present invention, any type can be used. Among them, when the heat cross-linking type is used, the heat cross-linking of the adhesive proceeds simultaneously with the vulcanization and foaming in the step (3), so that the adhesion between the foamed rubber and the shaft becomes strong. When the split mold is opened, the foamed rubber is preferable because the shaft does not peel off.

Next, the above foamed rubber composition is extruded into a cylindrical shape using a rubber extruder on the outer periphery of the shaft on which the adhesive layer is formed to obtain an unfoamed rubber roller [step (2)]. As the rubber extruder, a crosshead type extruder is suitably used. That is, it is preferable to extrude the foamed rubber composition from a direction perpendicular to the traveling direction of the shaft with a die provided with a shaft feed mechanism, and cover the outer periphery of the shaft with the foamed rubber composition. Rather than the method of coating with an extruder as described above, for example, when the outer periphery of the shaft is coated by winding a foamed rubber composition in a sheet shape around the shaft, the vulcanization and foaming in step (3) Further, a gap is easily formed between the foamed rubber and the shaft, which is not preferable. The extrusion speed by the rubber extruder is
0.4 to 4 m / min is preferred. Further, the extrusion temperature is important, and it is necessary to set the extrusion temperature to a temperature lower than the temperature at which the foamed rubber composition vulcanizes and foams. The extrusion temperature is preferably lower than the temperature in the vulcanization and foaming steps by 30 ° C. or more. The extrusion temperature can be, for example, 40 to 130 ° C.

The unfoamed rubber roller obtained by the extrusion molding is set in a split mold whose temperature has been adjusted in advance, and is vulcanized by foaming while applying a predetermined pressure for a predetermined time [step (3)]. In order for the foamed rubber roller to have fine foam cells, the unfoamed rubber roller is vulcanized under pressure,
It is important to foam. The pressure applied to the split mold is 9.8 × 10 ^{5 to} 9.8 × 10 ⁶ Pa (about 10 to 100 Pa).
kg / cm ² ), preferably 1.9 × 10 ^{6 to} 7.9 × 10
⁶ Pa (about 20 to 80 kg / cm ² ). The temperature for vulcanization and foaming is appropriately determined depending on the composition of the foamed rubber composition, but is usually 140 to 180 ° C. The time for vulcanization and foaming in the split mold is usually about 5 to 30 minutes. The proportion of the unfoamed rubber roller occupying the mold cavity is preferably 95 to 105% by volume in order to reduce the hardness variation and the electrical resistance variation of the foamed rubber roller.

After vulcanizing and foaming the unfoamed rubber roller in the split mold, the split mold is opened and the roller is taken out of the split mold (step (4)). When the split mold is opened, the roller expands due to the foaming pressure. It is important that the expansion is uniform in order to obtain uniformity of the size of the foamed cells, and also uniformity of hardness and electric resistance. Therefore, it is preferable to design the apparatus such that the split mold is opened uniformly.

Next, the foamed rubber roller is adjusted to a predetermined outer diameter [Step (5)]. The method for adjusting the foam rubber roller to a predetermined outer diameter is not particularly limited,
Methods such as polishing with a rotary grindstone, peeling with a blade, and the like can be given. As polishing with a rotating grindstone, traverse polishing using a grindstone narrower than the length of the roller,
Although there is plunge polishing using a grindstone having a width substantially equal to the length of the roller, plunge polishing is preferable because productivity is good. Step (4) and / or step (5) above
It is preferable to perform post-vulcanization of the foamed rubber roller after [Step (6)]. Post-vulcanization stabilizes the form of the foam cells of the foamed rubber roller, stabilizes the hardness, dimensions and electrical resistance of the foamed rubber roller, reduces compression set, and reduces processing strain. Further, by post-vulcanizing the foamed rubber roller, it is possible to disperse the low molecular compound present in the foamed rubber composition. Therefore, it is possible to prevent contamination when the foamed rubber roller is used in contact with the image forming body. Can be. The post-vulcanization temperature and time are 70-200 ° C,
It is about 15 to 300 minutes.

The foamed rubber roller thus obtained is characterized by having both low hardness and low compression set, having fine foam cells, and having small variations in hardness and electric resistance. Therefore, the foamed rubber roller of the present invention is mounted on an image forming apparatus such as an electrophotographic apparatus such as a copying machine, a laser printer, and a facsimile, and an electrostatic recording apparatus, and includes a charging roller, a developing roller, a transfer roller, a toner supply roller, It is suitably used as a cleaning roller, a bias roller, a paper feed roller, or the like.

[0016]

Next, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. The physical properties of the conductive roller obtained in the examples were measured according to the following methods. (1) Physical Properties of Rubber Foam (a) Cell Diameter and Number of Cells Using a CCD video camera manufactured by Hilox, about 70
Photographs were taken at double magnification, and the cell diameter and cell number of the image were measured. (B) Asker C hardness Measured according to JIS K6301. (C) Density The weight of the rubber foam in the air was divided by the volume. (D) Compression set Measured in accordance with JIS K 6382 (Home Rubber for Cushion). (E) Volume resistivity The volume resistivity ρ was calculated from the following resistance of the conductive roller by the following equation. R = (ρr ₂ / Ld) ln (r ₂ / r ₁ ) where R: resistance of conductive roller ρ: volume resistivity of rubber foam L: contact length in axial direction d: nip width r ₁ : shaft Radius of conductive roller r ₂ : outer radius of conductive roller ln: natural logarithm (2) Resistance of conductive roller A load of 500 g is applied to both ends of the roller to be tested and pressed on a copper plate to obtain a resistivity meter R8340A (manufactured by Advantest Co.) ), A voltage of 100 V was applied to measure the resistance value. (3) Variation in resistance of conductive roller A cylindrical gold electrode is pressed against the roller under test with a load of 1000 g, and 72 points on the outer periphery of the roller are measured with a resistivity meter R8340A.
(Manufactured by Advantest Corporation), and the difference between the maximum value and the minimum value was regarded as resistance variation. In Table 1, the digit means the difference between the maximum value and the minimum value of the common logarithm of the 72 measured resistance values.

EXAMPLE 1 An adhesive (Chemrock 250X, manufactured by Lord Far East, Inc.) is applied to the outer periphery of a metal shaft (outer diameter 6 mm, length 260 mm) and air-dried to obtain a shaft with an adhesive. Was. Adhesive layer thickness after air drying is 1
0 to 30 μm [Step (1)]. Iodine value is 3
6. EPD with Mooney viscosity ML _{1 + 4} (100 ° C) of 39
55 L of the ingredients shown in Table 1 with respect to 100 parts by weight of M
Kneading using a kneader to prepare a foamed rubber composition,
Using a crosshead extruder (manufactured by Mitsuba Seisakusho), this foamed rubber composition is extruded into a cylindrical shape around the outer periphery of the shaft with the adhesive, and a non-foamed rubber roller (in which the foamed rubber and the shaft are integrated) An outer diameter of 22 mm and a length of 240 mm) were obtained [Step (2)]. This unfoamed rubber roller was set in a cylindrical mold, and a pressure of 3.2 × 10 ⁵ Pa was applied thereto, followed by vulcanization and foaming at 175 ° C. for 20 minutes [step (3)]. Next, the pressure of the split mold was released to obtain a foamed rubber roller with a skin layer in which the shaft and the foamed rubber were firmly adhered with an adhesive [step (4)]. The foamed rubber roller was placed in an oven adjusted to 180 ° C. for 4 hours.
Post vulcanization was performed [Step (6)]. The obtained foamed rubber roller was polished with a rotary grindstone by plunge polishing to obtain a foamed rubber roller having an outer diameter of 20 mm and a length of 230 mm [Step (5)]. Table 1 shows the physical properties of the foam rubber roller.

[0018]

[Table 1]

(Note) (1) Iodine value is 36, Mooney viscosity ML _{1 + 4} (100
(C) 39 (2) Tokai Carbon Co., Ltd., TB # 5500 (3) Nitto Powder Chemical Co., Ltd., Novelite A (4) Idemitsu Kosan Co., Ltd., Diana Process Oil PW90 (5) 2-mercaptobenzothiazole ( 6) Neocelbon N # 1000M, manufactured by Eiwa Chemical Co., Ltd.
[P, p'-oxybis (benzenesulfonylhydrazide)]

[0020]

The foamed rubber roller of the present invention has both low hardness and low compression set, has fine foam cells, and has a small variation in hardness and electric resistance, and can be used in copiers, laser printers, facsimile machines and the like. It is suitably used as a member for an image forming apparatus such as an electrophotographic apparatus and an electrostatic recording apparatus.

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Claims (13)

[Claims] 1. A method for manufacturing a foamed rubber roller in which a rubber foam layer is formed on the outer periphery of a shaft, wherein (1) a step of applying an adhesive to the outer periphery of the shaft to form an adhesive layer;
(2) a step of extruding the foamed rubber composition into a cylindrical shape using a rubber extruder on the outer periphery of the shaft on which the adhesive layer is formed to obtain an unfoamed rubber roller; Set in a split mold whose temperature has been adjusted in advance,
Vulcanizing and foaming while applying pressure at a predetermined pressure for a predetermined time, (4) opening the split mold, removing the roller obtained above from the split mold, and (5) obtaining the roller obtained above. A method for manufacturing a foamed rubber roller, comprising a step of adjusting the roller to a predetermined outer diameter. 2. The method according to claim 1, further comprising, after the step (4) and / or the step (5), (6) a step of performing post-curing for a predetermined time in a heating furnace adjusted to a predetermined temperature. The manufacturing method as described. 3. The method according to claim 1, wherein the adhesive is a heat-crosslinkable adhesive. 4. The method according to claim 1, wherein the foamed rubber composition contains ethylene propylene rubber as a rubber component. 5. An ethylene propylene rubber having an iodine value of 3
Mooney viscosity at 5 to 45 and 100 ° C is ML
_The method according to claim 4, wherein _{1 + 4} is 20 to 50. 6. The method according to claim 1, wherein the foamed rubber composition contains a conductive material. 7. The method according to claim 1, wherein the temperature of the extrusion molding in the step (2) for obtaining the unfoamed roller is lower than the temperature of the vulcanization and foaming in the step (3) by 30 ° C. or more. The manufacturing method as described. 8. The method according to claim 1, wherein in the step (3) of vulcanizing and foaming the unfoamed rubber roller, the ratio of the unfoamed rubber roller to the cavity of the mold is 95 to 105% by volume.
8. The method according to any one of items 1 to 7. 9. The method according to claim 1, wherein in the step (5) of adjusting the roller to a predetermined outer diameter, the adjustment is performed using a plunge type polishing machine. 10. The method according to claim 1, wherein the foamed rubber roller has a foamed rubber density of 0.1 to 0.5 g / cm ³ and a compression set of 15% or less. . 11. The foamed rubber roller has an average foamed cell diameter of the foamed rubber of 30 to 100 μm.
11. The method according to any one of items 10 to 10. 12. The production method according to claim 1, wherein the foamed rubber roller has a volume resistivity of 10 ⁴ to 10 ¹⁰ Ω · cm. 13. An image forming apparatus equipped with a foamed rubber roller obtained by the method according to claim 1. Description: