JP2003055491A - Electroconductive ethylene/propylene rubber foam and image-forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive ethylene/propylene rubber foam improved in changes in electrical resistance when used, a member composed of the foam such as a transfer member and the like, and an image-forming device equipped with these members. SOLUTION: The electroconductive ethylene/propylene rubber foam comprises an ethylene/propylene rubber foam containing an electroconductive material, and has a specific volume resistivity ranging from 10<4> to 10<10> Ωcm and giving a change, before and after continuous dynamic energization at 100 V for 12 hr, which satisfies the equation: ρ2 /ρ1 <=5 (wherein ρ1 is the specific volume resistivity before energization; and ρ2 is the specific volume resistivity after energization). The image-forming device is equipped with a member composed of the electroconductive ethylene/propylene rubber foam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive ethylene propylene rubber foam having improved electric current durability and compression set, and more particularly, to an electrophotographic device such as a copying machine, a facsimile, a printer or an electrostatic device. The present invention relates to a conductive ethylene propylene rubber foam suitable as a material for forming a transfer member or the like mounted on a recording apparatus, a member such as a transfer member made of this foam, and an image forming apparatus equipped with these members.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic image forming apparatus such as a copying machine, a facsimile, a printer, etc., a transfer roller, a bias roller, a backup roller, a toner supply in addition to a charging roller for charging an image forming member. Various members such as a roller, a cleaning roller, and a paper feeding roller are used, and ethylene propylene rubber foam is often used as a material for forming these members.
The ethylene propylene rubber foam is often used mainly because it is stable against ozone, NO _x , heat and the like and has good durability. The various rollers are sometimes used in an insulated state, but are often used in a state in which a conductive material such as carbon is added to a rubber raw material to impart conductivity. When electrical conductivity is imparted by a conductive material in this way, the electrical resistance has the advantage that it is less dependent on the environment such as temperature and humidity, while the electrical resistance varies widely, and even when used. There was a problem that the electric resistance changed while I was there. This change in electrical resistance means that the chain of conductive materials such as carbon breaks or recombines when a voltage is applied under a dynamic load such as rolling (called dynamic energization). To happen
It is estimated to occur. Among the above problems, it has been found that the improvement in the variation of the electric resistance of the conductive ethylene propylene rubber foam can be improved depending on the processing conditions of the foam, and the present inventors have already proposed (special feature Japanese Patent Application No. 2000-295696, Japanese Patent Application No. 2000-29
5697). However, the actual situation is that no good solution has been found for the change in electric resistance when the conductive ethylene propylene rubber foam is used.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and is made of a conductive ethylene propylene rubber foam and a conductive ethylene propylene rubber foam having an improved change in electric resistance during use. It is an object of the present invention to provide various members for an image forming apparatus and an image forming apparatus equipped with this member.

[0004]

Means for Solving the Problems As a result of intensive studies to achieve the above-mentioned object, the present inventors have found that the volume resistivity value is within a specific range, and before and after continuous energization under specific conditions. When a conductive ethylene propylene rubber foam having a change in volume specific resistance value within a specific range is used, the change in electric resistance during use is improved, and the compression set is improved. Found that you can get. The present invention has been completed based on such findings. That is, the present invention is an ethylene propylene rubber foam containing a conductive material, having a volume specific resistance value of 10 ⁴ to 10 ¹⁰ Ωcm, and 100
The change in the volume resistivity before and after the dynamic energization for 12 hours continuously at V is the following equation ρ ₂ / ρ ₁ ≦ 5 (where ρ ₁ is the volume resistivity before energization, ρ ₂ is the volume after energization) Conductive ethylene propylene rubber foam, which is characterized by satisfying a specific resistance value. A transfer member, a primary transfer member, a secondary transfer member, and a cleaning member for an image forming body, which are made of this conductive ethylene propylene rubber foam. ，
Provided is a bias member, a backup member, a charging member, a developing member or a paper feeding member, and an image forming apparatus equipped with one or more of these members.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION The conductive ethylene propylene of the present invention
The rubber foam has a volume resistivity value of 10^Four-10^TenΩc
m, and was dynamically energized at 100 V for 12 hours continuously.
The change in volume resistivity before and after is given by ρ₂/ Ρ₁≤5 (Where ρ₁Is the volume resistivity before energization, ρ₂After energizing
Shows the volume resistivity value of. ) Is satisfied. body
The product resistivity value is preferably 10^Four-10⁸Ωcm, special
Preferably 10^Four-10⁷Ωcm. Volume specific resistance
In the change of the resistance value, ρ₂/ Ρ₁If> 5, image formation
Resistance value when used as a component of a shape device
Is increased, causing an image defect, which is preferable.
Absent. The change in the volume resistivity value is preferably ρ₂/ Ρ
₁≦ 3, more preferably ρ₂/ Ρ₁≦ 2. Book
The conductive ethylene propylene rubber foam of the invention has the above-mentioned requirements.
In addition to the above, it is preferable that the compression set is 20% or less.
And more preferably 15% or less. In addition, according to the present invention
Conductive ethylene propylene rubber foam has a density of 0.1-
0.5 g / cm ³Is preferred, and more preferably
0.2-0.4 g / cm³Is. Further, the conductivity of the present invention
The ethylene propylene rubber foam has an average foam cell diameter of 3
It is preferably 0 to 150 μm, and more preferably
It is 30 to 100 μm.

The above conductive ethylene propylene rubber foam can be obtained by using, as a raw material rubber, an ethylene propylene rubber having an iodine value of 26 to 45 and a Mooney viscosity ML _{1 + 4} (100 ° C.) of 20 to 50. it can.
Iodine value is preferably 35-40, Mooney viscosity ML
_{1 + 4} (100 ° C.) is preferably 30 to 45. When the iodine value is less than 26, the effect of improving the change in electric resistance during use is insufficient, and the compression set of the foam increases. Further, if the iodine value exceeds 45, the durability of the conductive ethylene propylene rubber foam against ozone or the like becomes small, which is not preferable. When the Mooney viscosity is less than 20, the viscosity of the unvulcanized rubber composition using the same becomes too small and foaming occurs excessively, which causes the disadvantage of coarse cells, and when the Mooney viscosity exceeds 50. However, the viscosity of the unvulcanized rubber composition increases and the foaming becomes insufficient, so that the foam density increases, which is not preferable. In the conductive ethylene propylene rubber foam of the present invention, other components may be appropriately selected as long as the above-mentioned ethylene propylene rubber is used, but (A) is preferably added to 100 parts by weight of the raw material rubber. Vulcanizing agent 0.5 to 5 parts by weight, (B) foaming agent 1 to 15 parts by weight, (C) process oil 10 to 80
It can be obtained by adding parts by weight, (D) 10 to 60 parts by weight of the filler, and (E) 1 to 80 parts by weight of the conductive material, and vulcanizing and foaming. As the vulcanizing agent as the component (A), various vulcanizing agents can be used, but a sulfur-based vulcanizing agent is preferable because the 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, dithiocarbamates, guanidines, aldehyde amines, and aldehyde ammonias, and one of these may be used alone or two or more may be used. It can be mixed and used. Examples of the sulfur-containing organic compound include morpholine disulfide, tetraalkyl thiuram disulfide, dipentamethylene thiuram tetrasulfide and the like. The addition amount of the vulcanizing agent is preferably 0.5 to 5 parts by weight with respect to 100 parts by weight of ethylene propylene rubber.

Examples of the foaming agent as the component (B) include, for example,
Sulfonyl hydrazides such as p, p′-oxybis (benzenesulfonyl hydrazide) (OBSH), benzenesulfonyl hydrazide and toluenesulfonyl hydrazide, azo compounds such as azodicarbonamide (ADCA) and azobisisobutyronitrile, N, N′- Dinitrosopentamethylene tetramine, N, N'-dimethyl-N,
Organic foaming agents such as nitroso compounds such as N'-dinitrosoterephthalamide; inorganic foaming agents such as sodium bicarbonate and ammonium bicarbonate. OB among these
SH, ADCA, or a foaming agent using these in combination is preferable. The amount of foaming agent added is 10% ethylene propylene rubber.
1 to 10 parts by weight is preferable with respect to 0 parts by weight, and 3 to 8 parts by weight is particularly preferable. The foaming agent preferably has a particle size as small as possible in order to make the foaming cell small. The particle size of the foaming agent is preferably 10 μm or less, and 5 μm
The following are particularly preferred. As the process oil as the component (C), paraffin-based process oil, naphthene-based process oil and aromatic process oil can be used. Of these, paraffin-based process oil is preferable because it does not contaminate other members such as the photoconductor. The amount of the process oil added is preferably 20 to 70 parts by weight with respect to 100 parts by weight of ethylene propylene rubber,
Particularly preferred is 40 to 70 parts by weight. If the amount of the process oil added is less than 20 parts by weight, the viscosity of the rubber composition will be high and the processability will be poor, and the foaming will be insufficient, resulting in an increase in the density of the foam. On the other hand, if the amount of the process oil added exceeds 70 parts by weight, the viscosity of the unvulcanized rubber composition becomes too small and foaming occurs excessively, so that the cells become coarse. Examples of the filler as the component (D) include calcium carbonate, magnesium carbonate, silica, magnesium silicate, clay and the like. Of these, calcium carbonate is preferable from the viewpoint of stabilizing the foam cells. The amount of the filler added is preferably 10 to 60 parts by weight, more preferably 20 to 50 parts by weight, based on 100 parts by weight of ethylene propylene rubber. If the amount of the filler added is less than 10 parts by weight, the foam cells are not stable and become non-uniform, and if the amount of the filler added exceeds 60 parts by weight, the compression set of the ethylene propylene rubber foam is large. turn into.

As the conductive material of the component (E), conductive carbon black such as Ketjen black or acetylene black; SAF, ISAF, HAF, FEF, GPF, S
Carbon black for rubber such as RF, FT, MT; carbon black for ink such as oxidized carbon 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, conductive zinc oxide whiskers, etc. are mentioned in the present invention. Is preferably carbon black. The amount of the conductive material added is preferably 1 to 80 parts by weight with respect to 100 parts by weight of ethylene propylene rubber,
5 to 60 parts by weight is particularly preferred. In addition to the above additives, the ethylene-propylene rubber foam of the present invention contains zinc white,
Vulcanization accelerating aids such as stearic acid, scorch inhibitors, tackifiers, and other rubber additives can be appropriately added within a range that does not impair the effects of the present invention.

The conductive ethylene propylene rubber of the present invention
Regarding the method of manufacturing foam, manufacture roller-shaped members
The case will be described as an example. First, ethylene propylene
Add 110 to 180 additives other than vulcanizing agent and foaming agent to rubber
Use a kneader, Banbury mixer, etc. at a temperature of about ℃
And knead. After cooling this kneaded product, a vulcanizing agent and
Add a foaming agent, knead at a temperature of about 50 to 90 ° C, and
To obtain a composition. Then, using an extruder, this rubber composition
The product is extruded into a cylindrical shape and cut into a predetermined length. Dummy
Insert the shaft into the cylindrical object and set it in the preheated mold.
At a given temperature for a given time (usually at 140-180 ° C)
Heat for about 5 to 30 minutes. Uniform and fine foam cells
In order to obtain a foam that has
It is important to mold so that it is filled without any material. Uniform
And to obtain the foam with fine foam cells, the mold
The pressure applied to is also important, 9.8 × 10^Five~ 9.8 x 1
0⁶Pa (about 10 to 100 kg / cm²) Degree is preferred
1.9 × 10⁶~ 7.9 x 10⁶Pa (about 20-80k
g / cm²) Is particularly preferable. Heating to obtain foam
As the method, in addition to the above-mentioned mold method, high frequency method, hot air method, flow method
There are moving bed method, vulcanization can method, etc. Among these heating methods
Even if the mold method has uniform and fine foam cells,
Points to obtain ethylene propylene rubber foam with low strain
Therefore, it is particularly preferable. Heated at the above specified temperature for a specified time
Then, by opening the mold, ethylene propylene
To obtain a foam. After removing the dummy shaft, the dummy
This shaft is pre-coated with an adhesive instead of the shaft
Insert and heat with hot air etc., ethylene propylene rubber
Adhesive treatment between foam and shaft and post-vulcanization of foam
Do at the same time. The temperature and time in this case are 140 to 20.
It is about 0 ° C. and about 15 to 60 minutes. Foam with shaft
Grinding the outer periphery of the body with a grindstone, peeling with a blade
The desired outer diameter is obtained by adjusting the outer diameter to a desired value.
After this, the internal stress remaining in the roller was further removed.
Annealing to reduce the compression set
Is preferred. The temperature and time of the annealing treatment are 70 to
It is about 200 ° C. and about 15 to 300 minutes. Conductive ethylene
The roller-shaped member made of propylene rubber foam is
In addition to the manufacturing method, use an injection molding machine instead of the extruder.
Pour the rubber composition into the mold with the dummy shaft set.
It can also be manufactured by putting in and heating and foaming.
It Thus, the raw material rubber has an iodine value of 26-4.
5, and Mooney viscosity ML_{1+ Four}(100 ° C) is 20-5
Foaming by using ethylene propylene rubber of 0
The compression set of the body can be reduced to 20% or less, and the foam
Density is 0.1-0.5g / cm³And the average foam cell diameter is 30
Conductive ethylene with uniform fine cells of ~ 150 μm
A propylene rubber foam can be obtained. like this
Inventive conductive ethylene propylene rubber with characteristics
Foam is a transfer member, primary transfer member, secondary transfer member, toner
-Supply member, cleaning member for image forming body, bias
Member or backup member, charging member,
Suitable as a material for forming image members or paper feed members
It is something. Its shape is roll or blade.
You can In the image forming apparatus, these parts
One kind or two or more kinds of materials can be attached.

[0010]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. The physical properties of the foams obtained in each example were measured according to the following methods. (1) Cell diameter and number of cells Using a CCD video camera manufactured by Hi-Rox, about 70
Photographs were taken at double magnification, and the cell diameter and the number of cells of the image were measured. (2) Asker C hardness It was measured according to JIS K6301. (3) The weight of the density rubber foam in air was divided by the volume. (4) Compression set Measured according to JIS K6382 (foam rubber for cushion). (5) Dynamic energization test It was performed using a tester having the mechanism shown in FIG. While continuously applying a voltage of 100 V by the voltage applying means 3, the roller to be tested 1 is pressed against the metal drum 2 by applying a load of 500 g to each end, and rolling is performed as indicated by an arrow. Hold for 12 hours. The resistance R of the roller before and after the dynamic energization test was measured using a resistivity meter R8340A (manufactured by Advantest), and the volume resistivity ρ ₁ before energization and the volume resistivity ρ after energization were performed as follows.
₂ was calculated. (6) Volume resistivity value The volume resistivity ρ (ρ ₁ and ρ ₂ ) was calculated from the following resistance of the conductive roller by the following formula. R = (ρr ₂ / Ld) ln (r ₂ / r ₁ ) where R: resistance of the conductive roller ρ: volume specific resistance of the rubber foam L: axial contact length d: nip width r ₁ : shaft Radius r ₂ : outer radius of conductive roller ln: natural logarithm

Example 1 100 parts by weight of EPDM having an iodine value of 36 and a Mooney viscosity ML _{1 + 4} (100 ° C.) of 39 were kneaded with the compounding ingredients shown in Table 1 using a kneader to obtain an unvulcanized product. A rubber foam composition was prepared. This rubber foam composition was extruded into a tubular shape (inner diameter 4 mm, outer diameter 20 mm, length 24
0 mm). A dummy shaft made of stainless steel (diameter 4 mm, length 300 mm) was passed through this tubular material, and vulcanized in a cylindrical mold at 170 ° C. for 15 minutes,
Foaming was performed to obtain a tubular foam. This tubular foam was placed in an air oven and post-vulcanized at 180 ° C. for 1 hour. Remove the dummy shaft from the tubular foam and press fit the metal shaft (outer diameter 6 mm) with the hot melt adhesive wrapped around the tubular foam to
After heat-bonding treatment at 20 ° C for 70 minutes, after cooling, the surface is polished and a conductive roller (outer diameter 12 mm, length 220 m) is used.
m) was obtained. The physical properties of this conductive roller are shown in Table 1.

Example 2 EPDM having an iodine value of 26 and a Mooney viscosity ML _{1 + 4}
A conductive roller (outer diameter 12 mm, length 220 m) was used in the same manner as in Example 1 except that (100 ° C.) having a temperature of 45 was used.
m) was obtained. The physical properties of this conductive roller are shown in Table 1.

Example 3 EPDM having an iodine value of 26 and a Mooney viscosity ML _{1 + 4}
Example 1 except that (100 ° C.) having a temperature of 100 was used.
Conductive roller (outer diameter 12 mm, length 220
mm) was obtained. The physical properties of this conductive roller are shown in Table 1.

Example 4 A conductive roller (outer diameter 12 mm, length 220 mm) was obtained in the same manner as in Example 1 except that the foaming agent having an average particle diameter of 2 μm was used. The physical properties of this conductive roller are shown in Table 1.

Comparative Example 1 EPDM having an iodine value of 19 and Mooney viscosity ML _{1 + 4}
A conductive roller (outer diameter 12 mm, length 220 m) was used in the same manner as in Example 1 except that the roller (100 ° C.) was 38.
m) was obtained. The physical properties of this conductive roller are shown in Table 1.

[0016]

[Table 1]

(Note) (1) Iodine number 36, Mooney viscosity ML _{1 + 4} (100
EPDM with a temperature of 39) (2) Iodine number of 26, Mooney viscosity ML _{1 + 4} (100
EPDM of 45) (3) Iodine number of 26, Mooney viscosity ML _{1 + 4} (100
EPDM (4) with an iodine value of 19, Mooney viscosity ML _{1 + 4} (100)
(5) Tokai Carbon Co., Ltd., TB # 5500 (6) Nitto Koka Kogyo Co., Ltd., Nobelite A (7) Idemitsu Kosan Co., Ltd., Dianaprosena Oil PW90 (8) 2-mercaptobenzothiazole (9) Neocerbon N # 5000 manufactured by Eiwa Chemical Industry Co., Ltd.
[P, p'-oxybis (benzenesulfonyl hydrazide), average particle diameter 11 μm] (10) Eiwa Chemical Co., Ltd., Neocerbon N # 1000
M [p, p'-oxybis (benzenesulfonyl hydrazide), average particle diameter 2 μm]

[0018]

The conductive ethylene propylene rubber foam of the present invention has an improved change in electric resistance during use and an improved compression set and the like. It is suitable as a material for forming a primary transfer member, a secondary transfer member, a toner supply member, an image forming member cleaning member, a bias member, a backup member, a charging member, a developing member or a paper feeding member.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing an outline of a testing machine used for a dynamic energization test.

[Explanation of symbols]

1: Roll under test 2: Metal drum 3: Voltage applying means

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) G03G 15/02 101 G03G 15/02 101 15/08 501 501/08 501A 501D 15/16 103 15/16 103 21/10 H01B 1/20 Z H01B 1/20 C08L 91:00 // (C08L 23/16 G03G 21/00 312 91:00)

Claims (9)

[Claims] 1. An ethylene propylene rubber foam comprising a conductive material, having a volume resistivity value of 10 ⁴ to 10 ^4.
The change in volume specific resistance value before and after dynamic energization at ¹⁰ Ωcm and 100 V for 12 hours continuously is expressed by the following equation ρ ₂ / ρ ₁ ≦ 5 (where ρ ₁ is the volume specific resistance value before energization, ρ ₂ shows a volume specific resistance value after energization.) Is a conductive ethylene propylene rubber foam. 2. The conductive ethylene propylene rubber foam has a compression set of 20% or less.
Conductive ethylene propylene rubber foam described in 1. 3. The conductive ethylene propylene rubber foam according to claim 1, wherein the conductive ethylene propylene rubber foam has a density of 0.1 to 0.5 g / cm ³ . 4. The conductive ethylene propylene rubber foam according to claim 1, wherein the conductive ethylene propylene rubber foam has an average foam cell diameter of 30 to 150 μm. 5. A conductive ethylene propylene rubber foam is obtained by using, as a raw material rubber thereof, ethylene propylene rubber having an iodine value of 26 to 45 and a Mooney viscosity ML _{1 + 4} of 20 to 50 at 100 ° C. Claim 1
4. The conductive ethylene propylene rubber foam according to any one of 4 above. 6. The conductive ethylene-propylene rubber foam comprises 0.5 to 5 parts by weight of (A) a vulcanizing agent and 1 to (B) a foaming agent based on 100 parts by weight of the ethylene-propylene rubber according to claim 5. 6. A rubber composition comprising 15 parts by weight, (C) 10 to 80 parts by weight of process oil, (D) 10 to 60 parts by weight of filler, and (E) 1 to 80 parts by weight of conductive material. The electrically conductive ethylene propylene rubber foam according to. 7. The conductive ethylene propylene rubber foam according to claim 6, wherein the foaming agent has a particle size of 10 μm or less. 8. A transfer member, a primary transfer member, a secondary transfer member, a toner supply member, a cleaning member for an image forming body, and a bias, which are made of the conductive ethylene propylene rubber foam according to any one of claims 1 to 7. Member, backup member, charging member, developing member or paper feeding member. 9. An image forming apparatus equipped with one or more members according to claim 8.