JP2002030173A - Rubber composition and conductive roll using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rubber composition capable of manufacturing conductive rolls which excel in all of low resistance, non-staining properties, low hardness, and low cost. SOLUTION: A foam can be obtained by foaming a rubber composition comprising an epichlorohydrin based polymer having an EO ratio of 50 mol% to 80 mol% and/or an NBR and, at the same time, a chemical foaming agent and a foaming auxiliary in a compounding amount of 3<a/b<10 and, simultaneously, 4<a+b<20, provided that the chemical foaming agent and the foaming auxiliary are a wt.% and b wt.%, respectively, based on 100 wt.% polymer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition formed into a foam using a chemical foaming agent and a foaming aid, and a conductive roll using the same.

[0002]

2. Description of the Related Art In a conductive mechanism of an electrophotographic apparatus such as a laser beam printer, an electrophotographic copying machine, and a facsimile machine, a charging roll for uniformly charging a photosensitive drum and a toner supply roll for conveying toner. Various rolls such as a developing roll for attaching toner to a photoreceptor and a transfer roll for transferring a toner image from a photoreceptor to a sheet are used, and these rolls are required to have conductive performance. It is a conductive roll.

In this type of conductive roll, conventionally,
The electrical resistance of the roll is controlled by kneading and dispersing a conductivity-imparting agent such as carbon black or metal oxide in rubber.

Japanese Patent Application Laid-Open No. 58-87572 discloses a transfer roll coated with epichlorohydrin rubber in which the polymer itself has conductivity without using a conductivity-imparting agent, and Japanese Patent Application Laid-Open No. 1-142569 discloses an epichlorohydrin rubber. There is disclosed a charging roll using as a surface elastic layer. Further, in Japanese Patent Application Laid-Open No.
A conductive roll using epichlorohydrin rubber or NBR as a material is disclosed.

In order for the conductive roll to exhibit sufficient electric characteristics, it is necessary to increase the nip width to some extent. In order to increase the nip width,
Softening agents such as DBP and DOP are used in the rubber composition for the conductive roll, or the hardness is reduced as a foam using a foaming agent.

[0006]

However, in the case of a conductive roll in which a conductivity-imparting agent is mixed and dispersed in rubber, it is difficult to control the dispersion of the conductivity-imparting agent, and a variation in local resistance occurs due to uneven dispersion of the conductivity. was there.

On the other hand, even in a conductive roll using epichlorohydrin rubber, there is a limit in the range of adjustment of electric resistance, and it is necessary to use a conductivity-imparting agent in order to further lower the resistance. There is a problem that variation in the electrical resistance occurs. Furthermore, in a conventional conductive roll using epichlorohydrin rubber, there is a problem that epichlorohydrin rubber is expensive and thus disadvantageous in cost.

When a softening agent such as DBP or DOP is used, there is a problem that the softening agent deposits on the roll surface and contaminates the photoreceptor. Also, in the case of forming a foam, it was difficult to obtain a roll having a Shore E hardness of 40 or less due to the variation of the foaming agent.

Further, epichlorohydrin rubber and NBR
Japanese Patent Application Laid-Open No. H11-90928, which discloses a conductive roll using as a material, does not disclose or suggest any suggestion that the compounding amounts of the chemical blowing agent and the foaming auxiliary satisfy a certain relationship. It has not been.

As described above, it is difficult for conventional conductive rolls to satisfy both low resistance, non-staining properties and low hardness to the extent that they can be satisfied. Therefore, conductive rolls having better performance are demanded. In addition to the above-described performance, there is a need for a conductive roll that is advantageous at the time of cost.

The present invention has been made in view of the above problems, and uses a rubber composition and a rubber composition capable of producing a conductive roll excellent in all of low resistance, non-staining property, low hardness and low cost. It is an object of the present invention to provide a conductive roll that has been used.

[0012]

Means for Solving the Problems To solve the above problems, the present invention firstly requires that the EO ratio be 50 mol% or more and 80 mol% or more.
Mol% or less of epichlorohydrin polymer and / or N
A rubber composition in which a foam is formed by using a chemical foaming agent and a foaming assistant in a polymer containing BR as a main component, and the compounding amount of the chemical foaming agent and the foaming assistant is set to the polymer 100
Assuming that the chemical foaming agent is a wt% and the foaming assistant is b wt%, 3 <a / b <10 and 4 <a + b
<20 is provided.

The epichlorohydrin polymer is a copolymer of epichlorohydrin, ethylene oxide and allyl glycidyl ether, and the polymer itself has conductivity. By using this polymer, conductivity is imparted to the rubber composition, so that there is no need to disperse the conductivity imparting agent. EO of the above epichlorohydrin polymer
The ratio (mol% of ethylene oxide with respect to the epichlorohydrin polymer) is set to 50 mol% or more and 80 mol% or less because the use amount of the epichlorohydrin polymer becomes large when the EO ratio is 50 mol% or less. On the other hand, if the content is 80 mol% or more, the crystallization of ethylene oxide proceeds to make it inactive, ionic conductivity is impaired, and the resistance is increased.

There is also an advantage that the resistance value can be adjusted by using NBR.

The above-mentioned chemical blowing agents include azodicarbonamide, N, N'-dinitronpentamethylenetetramine,
4,4'-oxybis (benzenesulfonylhydrazide) and the like. The foaming aid includes urea and the like.

When the compounding amount of the chemical foaming agent and the foaming assistant is 100% by weight of the polymer and 100% by weight of the polymer and the foaming assistant is b% by weight, 3 <a / b <10. , And 4 <a + b <20. The relationship between a and b is as shown in FIG. 1. In FIG. 1, the hatched portion is a range that satisfies the above condition. Within this range, the hardness of the rubber composition can be reduced, and a suitable nip width can be obtained when a roll is formed.

As described above, in the present invention, the EO ratio is 50
By using an epichlorohydrin-based polymer and / or a polymer having NBR as a main component in an amount of not less than 80% by mole and not more than 80% by mole, there is no need to disperse the conductivity imparting agent,
The resistance of the rubber composition can be reduced and the cost can be reduced without variation in local resistance. Furthermore, by setting the usage of the foaming agent and the foaming aid within a certain range,
The rubber composition can have an appropriate low hardness without using a softening agent that contaminates the photoreceptor.

When an epichlorohydrin polymer is used, hydrogen chloride is generated during the vulcanization reaction, which causes inhibition of vulcanization and contamination of the photoreceptor. Therefore, an acid acceptor such as magnesium oxide or trilead tetroxide must be used. Use to remove hydrogen chloride, but magnesium oxide has the problem of poor dispersion,
Trilead tetroxide has the problem that its use is limited by heavy metals. On the other hand, when hydrotalcite is used as an acid acceptor, it reacts with chlorine ions of hydrogen chloride to become insoluble in water and has excellent dispersibility. Better because less.

The hydrotalcite has a structural formula of Mg1-xAlx (OH) ² (CO3) x / 2.mH2.
It is a hydrous layered compound of basic magnesium aluminum hydroxide carbonate hydrate represented by O (0 <x ≦ 0.5, m is a real number). In addition, sulfur is used as a vulcanizing agent. In addition, 1 to 50% by weight of calcium carbonate is used as a filler.

The rubber composition of the present invention is excellent in all of low resistance, non-staining property, low hardness and low cost, and can be widely used. Above all, it can be suitably used as a conductive rubber roll for laser beam printers, electrostatic copying machines, facsimile machines, ATMs, etc., taking advantage of the above excellent properties.

The conductive roll of the present invention can be prepared by a conventional method. That is, the mixture is charged into a rubber kneading device such as an open roll, a Banbury mixer, a kneader or the like at a required composition, kneaded at 100 ° C. for about 1 to 20 minutes, and then preformed into a tube by a single screw extruder. The preform 160 ° C., After 30 minutes vulcanization, after polishing the surface by inserting a metal core, and a roll and cut to the required dimensions.

The hardness of the conductive roll is Shore E
Is preferably from 20 to 40, and more preferably from 25 to 35. With this range, a sufficient nip width can be obtained.

The resistance value of the conductive roll is 1 × 10 ^5.0
It is preferably at least Ω and below 1 × 10 ^9.0 Ω.

In a state where the conductive roll is formed into a cylindrical shape,
Its thickness is 2 mm to 10 mm, preferably 3 mm to 6 m
m. This is because if the thickness is less than 2 mm, an appropriate nip is indispensable. If the thickness is more than 10 mm, the member is too large to be suitable for reduction in size and weight.

[0025]

Embodiments of the present invention will be described below. The conductive roll of the present invention is formed into a cylindrical roll from a rubber composition comprising the following composition, and a conductive shaft (axial core) is pressed into a hollow portion thereof, or both are joined with an adhesive. It is fixed.

The rubber composition has an EO ratio of 50 mol%.
A rubber composition obtained by forming a foam using a chemical foaming agent and a foaming aid on a polymer containing at least 80 mol% of an epichlorohydrin polymer and / or NBR as a main component, wherein the chemical foaming agent and When the compounding amount of the foaming aid is 100 wt% of the polymer and the chemical foaming agent is a wt% and the foaming assistant is b wt%, 3 <a / b <10 and 4
<A + b <20.

When the above polymer uses an epichlorohydrin polymer having an EO ratio of 50 mol% or more and 80 mol% or less, hydrotalcite is used as an acid acceptor.

Azodicarboside and urea are used as a chemical foaming agent and a foaming assistant, respectively.

[0029]

EXAMPLES As shown in Table 1 below, for Examples 1 to 3 and Comparative Examples 1 to 4, compositions having the formulations shown in Table 1 were prepared, and the compositions were rolled (tubular). After injection molding, it was cut and fitted on a conductive shaft (axial core) to produce a conductive roll.

More specifically, NBR (acrylonitrile butadiene rubber), epichlorohydrin-based polymer and chemical foaming agent (Vinihole AC # manufactured by Eiwa Chemical Co., Ltd.) described in Table 1 are used.
R), a foaming aid (Cell Paste 101 manufactured by Eiwa Kasei),
Hydrotalcite (Kyowa Chemical's DHT-4A-2) was charged into a kneader as the composition shown in Table 1, and at 100 ° C.,
After kneading for about 20 minutes, the mixture was extruded from a rubber kneading apparatus. Next, after vulcanizing the preform at 160 ° C. for 30 minutes, a metal shaft diameter (Φ6) is inserted, polished and cut, and a conductive rubber roll (outer diameter φ12, length 220 m) is cut.
m) was prepared.

[0031]

[Table 1]

The numerical unit at the top of the table is% by weight.

[Embodiments 1 to 3] In each of Embodiments 1 to 3, the EO ratio is 50 mol% or more and 80 mol%.
A rubber composition obtained by forming a foam using the following epichlorohydrin-based polymer and / or NBR-based polymer with a chemical foaming agent, wherein the polymer is 100% by weight.
When the compounding amounts of the chemical foaming agent and the foaming assistant with respect to are respectively a weight% and b weight%, 3 <a / b <10 and 4 <
A rubber roll is formed from a rubber composition satisfying a + b <20. When an epichlorohydrin polymer is blended (Examples 2 and 3), hydrotalcite is used as an acid acceptor.

On the other hand, in Comparative Examples 1 to 4, rubber rolls were formed from rubber compositions outside the scope of the present invention. That is, the ratio of the compounding amounts of the chemical foaming agent and the foaming auxiliary is 3 <a.
/ B <10 not satisfied (Comparative Examples 1 and 3), EO
Examples in which the ratio does not satisfy the condition of 50 mol% or more (Comparative Examples 2 and 4) are shown.

The rubber rolls of Examples 1 to 3 and Comparative Examples 1 to 4 were tested and / or evaluated in terms of hardness, electric resistance, presence or absence of photoconductor contamination, and cost as follows.

(Measurement of Hardness) In an environment of 23 ° C. and 55%,
A load of 500 g was applied, and the hardness was measured with a Shore E hardness meter.

(Measurement of Electric Resistance Value) In an environment of 23 ° C. and 55%, a load of 500 g was applied to both ends of the shaft of the conductive roll on the metal cylinder, and 1 mm was applied between the shaft and the metal cylinder.
The conductive roll was indirectly rotated by rotating the metal cylinder while applying a voltage of KV. At this time, 3
The resistance was measured six times, and the average value was determined.

(Measurement of contamination of photoreceptor) A conductive roll was pressed against the photoreceptor with a load of 500 g at a temperature of 40 ° C. and a humidity of 9
After leaving for 2 weeks in a room within 0%, contamination on the surface of the photoreceptor was visually confirmed and evaluated as follows. The photoreceptor is a photoreceptor built in a copying machine, and is mainly made of polycarbonate. In the table, ：: indicates contamination, ×: indicates no contamination.

In the table, when the cost was lower than in the conventional case, it was indicated by ○, and when the cost was the same or higher, it was indicated by x. Furthermore, the overall evaluation was shown as a judgment, and when it was superior in various aspects as compared with the conventional one, it was evaluated as ○, and when it was equivalent or inferior to the conventional, it was evaluated as x.

The ratio of the amount of the chemical foaming agent to the amount of the foaming aid a / b
The conductive roll of Comparative Example 1 having a value of less than 3 had a problem in hardness and was not practical. Comparative Example 2 using an equal mixture of an epichlorohydrin polymer having an EO ratio of less than 50 mol% and NBR had a problem that the cost was high. In Comparative Example 3 in which the ratio a / b of the compounding amount of the chemical foaming agent to the foaming aid was larger than 10, there was a problem with the hardness and it was not practical. In Comparative Example 4 in which only the epichlorohydrin polymer having an EO ratio of less than 50 mol% was used as a polymer, it was necessary to mix LiClO4 as a conductivity-imparting agent in order to obtain appropriate electric resistance, and the cost was high. Photoreceptor contamination was observed, making it impractical.

On the other hand, using only NBR as a polymer,
The compounding amounts of the chemical foaming agent and the foaming auxiliary are respectively a weight% and b
3 <a / b <10 and 4 <a + b <
The roll of Example 1, which is No. 20, is a high-performance conductive roll excellent in all of low resistance, non-staining property, low hardness and low cost. Further, the conductive rolls of the other Examples 2 and 3 also include:
It was also confirmed that the roll was excellent.

[0042]

As is apparent from the above description, according to the present invention, a chemical foaming agent is added to an epichlorohydrin polymer having an EO ratio of 50 mol% to 80 mol% and / or a polymer mainly containing NBR. Is used to form a foam, and the compounding amount of the chemical foaming agent and the foaming auxiliary used is set to an amount that satisfies a certain relationship, so that all characteristics of low resistance, non-staining and low hardness are excellent. In addition, it is possible to obtain a low-cost rubber composition and reduce the cost. As an example of a molded product of the rubber composition of the present invention, a conductive roll is used for a conductive roll used in a conductive mechanism of an electrophotographic apparatus in OA equipment such as a laser beam printer, a copying machine, a facsimile, and an ATM. Extremely useful.

[Brief description of the drawings]

FIG. 1 is a drawing showing the blending amounts of a chemical foaming agent a and a foaming assistant b.

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Claims (4)

[Claims] 1. A foam obtained by adding a chemical foaming agent and a foaming aid to an epichlorohydrin-based polymer and / or a polymer mainly containing acrylonitrile butadiene rubber (NBR) having an EO ratio of 50 mol% or more and 80 mol% or less. Wherein the compounding amount of the chemical foaming agent and the foaming aid is 100 wt% of the polymer, and the chemical foaming agent is a wt% and the foaming assistant is b wt%. 3 <a /
A rubber composition, wherein b <10 and 4 <a + b <20. 2. The polymer according to claim 1, wherein the polymer has an EO ratio of 50 mol% or more.
The rubber composition according to claim 1, which contains 0 mol% or less of the epichlorohydrin-based polymer and contains hydrotalcite as an acid acceptor. 3. A conductive roll obtained by molding the rubber composition according to claim 1 into a roll. 4. The conductive roll according to claim 3, wherein the hardness is 20 to 40 in Shore E.