JP3469170B2 - Rubber composition and conductive roll using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a rubber composition made 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 in an electrophotographic apparatus such as a laser beam printer, an electrophotographic copying machine and a facsimile apparatus, 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 adhering toner to a photoconductor and a transfer roll for transferring a toner image from a photoconductor 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.

Further, Japanese Unexamined Patent Publication (Kokai) No. 58-85772 discloses a transfer roll coated with an epichlorohydrin rubber having conductivity itself without using a conductivity-imparting agent, and in Japanese Unexamined Patent Publication No. 1-142569, epichlorohydrin rubber is disclosed. There is disclosed a charging roll using as a surface elastic layer. Further, in JP-A-11-190928,
A conductive roll using epichlorohydrin rubber or NBR as a material is disclosed.

Further, in order for the above conductive roll to exhibit sufficient electric characteristics, it is necessary to increase the nip width to some extent. Therefore, in order to increase the nip width,
A rubber composition for a conductive roll uses a softening agent such as DBP or DOP, or a foaming agent is used to reduce the hardness as a foam.

[0006]

However, in 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 the unevenness of the distribution of the conductivity imparts a local resistance variation. was there.

On the other hand, even in the case of a conductive roll using epichlorohydrin rubber, there is a limit to the adjustment range of the electric resistance, and it is necessary to use a conductivity-imparting agent in order to further reduce the resistance. There was a problem that the variation of the static resistance occurs. Further, the conductive roll using the conventional epichlorohydrin rubber has a problem that it is disadvantageous in cost because the epichlorohydrin rubber is expensive.

Further, 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 photosensitive member. Even 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 variable amount of the foaming agent.

Furthermore, epichlorohydrin rubber and NBR
Japanese Patent Application Laid-Open No. 11-190928, which discloses a conductive roll using as a material, does not disclose or suggest that the compounding amounts of the chemical foaming agent and the foaming auxiliary agent are amounts satisfying a certain relationship. It has not been.

As described above, it is difficult for the conventional conductive roll to satisfy all of low resistance, non-staining property, and low hardness, and a conductive roll having more excellent performance is demanded. In addition to the above performance, there is a need for a conductive roll which is advantageous in terms of cost.

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

[0012]

In order to solve the above problems, the present invention firstly provides an EO ratio of 50 mol% to 80%.
A rubber obtained by forming a foam using a chemical foaming agent and a foaming aid in a polymer composed of not more than mol% of epichlorohydrin-based polymer or a polymer composed of a mixture of the epichlorohydrin-based polymer and acrylonitrile-butadiene rubber (NBR). In the composition, the compounding amount of the chemical foaming agent and the foaming aid is 100% by weight of the polymer.
When the chemical foaming agent is a% by weight and the foaming aid is b% by weight, 3 <a / b <10 and 4 <a + b <20,
Provided is a rubber composition containing hydrotalcite as an acid acceptor. Further, the present invention provides an electrically conductive roll, characterized in that the rubber composition is formed into a roll. Furthermore, the EO ratio is 50 mol% or more 8
A rubber composition comprising a polymer comprising 0 mol% or less of an epichlorohydrin-based polymer and / or an acrylonitrile butadiene rubber (NBR) and a chemical foaming agent and a foaming aid to form a foam. And 3 when the compounding amount of the foaming aid is 100% by weight of the polymer and the chemical foaming agent is a% by weight and the foaming aid is b% by weight.
Provided is a conductive roll, which is obtained by forming a rubber composition of <a / b <10 and 4 <a + b <20 into a roll.

The epichlorohydrin-based polymer is a copolymer of epichlorohydrin, ethylene oxide and allyl glycidyl ether, and the polymer itself has conductivity. Since the rubber composition is provided with conductivity by using this polymer, it is not necessary to disperse the conductivity imparting agent. EO of the above epichlorohydrin-based polymer
The ratio (mol% of ethylene oxide to epichlorohydrin-based polymer) is set to 50 mol% or more and 80 mol% or less because the amount of the epichlorohydrin-based polymer used increases when the EO ratio is 50 mol% or less. This is because it is disadvantageous in terms of cost, and on the other hand, when it is 80 mol% or more, crystallization of ethylene oxide proceeds and becomes inactive, ionic conductivity is impaired, and resistance increases.

Further, there is an advantage that the resistance value can be adjusted by using the NBR.

The chemical blowing agent is azodicarbonamide, N, N'-dinitronpentamethylenetetramine,
4,4′-oxybis (benzenesulfonyl hydrazide) and the like can be mentioned. Examples of the foaming aid include urea and the like.

When the chemical foaming agent and the foaming aid are blended in amounts of a chemical foaming agent a weight% and a foaming aid b weight% with respect to 100% by weight of the polymer, 3 <a / b <10. , And 4 <a + b <20. The relationship between a and b is as shown in FIG. 1, and in FIG. 1, the shaded area is the range that satisfies the above condition. Within this range, the hardness of the rubber composition can be reduced, and an appropriate nip width can be obtained when the rubber composition is used as a roll.

As described above, in the conductive roll of the present invention,
By using a polymer composed of an epichlorohydrin-based polymer having an EO ratio of 50 mol% or more and 80 mol% or less and / or NBR, it is not necessary to disperse the conductivity-imparting agent, so that there is no variation in local resistance. It is possible to reduce the resistance and cost. Furthermore, by setting the amounts of the foaming agent and the foaming auxiliary agent to be within a certain range, it is possible to obtain an appropriate low hardness without using a softening agent that contaminates the photoreceptor.

When an epichlorohydrin-based polymer is used, hydrogen chloride is generated during the vulcanization reaction, which causes vulcanization inhibition and contamination of the photoconductor. Therefore, an acid acceptor such as magnesium oxide or trilead tetraoxide is used. Although hydrogen chloride is removed by using it, magnesium oxide has a problem of poor dispersion,
Trilead tetroxide has a problem that its use is limited due to heavy metals. On the other hand, when hydrotalcite is used as the acid acceptor, it reacts with the chlorine ions of hydrogen chloride to become an insoluble matter in water, and since it has excellent dispersibility, it has an effect on the physical properties due to the kneading state and processing. Better because it is less.

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

Since the rubber composition of the present invention is excellent in low resistance, non-staining property, low hardness and low cost, it can be widely used. In particular, by utilizing the above excellent characteristics, it can be suitably used as a conductive rubber roll for laser beam printers, electrostatic copying machines, facsimile machines, ATMs and the like.

The conductive roll of the present invention can be prepared by a conventional method. That is, the mixture is put into a rubber kneading device such as an open roll, a Banbury mixer, a kneader, etc. in a required composition, kneaded at 100 ° C. for about 1 to 20 minutes, and then preformed into a tube shape 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.
It is preferably 20 or more and 40 or less, and more preferably 25 or more and 35 or less. Within this range, a sufficient nip width can be secured.

The resistance value of the conductive roll is 1 × 10 ^5.0.
It is preferably Ω or more and 1 × 10 ^9.0 Ω or less.

The conductive roll is formed into a cylindrical shape,
The wall thickness is 2 mm to 10 mm, preferably 3 mm to 6 m
m. This is because if the wall thickness is 2 mm or less, an appropriate nip cannot be obtained, and if the wall thickness is 10 mm or more, the member is too large and it is not suitable for reduction in size and weight.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION 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 composed of the following composition, and the conductive shaft (axial core) is press-fitted into the hollow part of the roll, or both are bonded 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 in a polymer containing epichlorohydrin-based polymer and / or NBR as a main component in an amount of 80 mol% or more and not more than 80 mol%. When the compounding amount of the foaming aid is 100% by weight of the polymer and a chemical foaming agent is a% by weight and the foaming aid is b% by weight, 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 the chemical foaming agent and the foaming auxiliary agent, 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 (cylindrical). After injection molding, it was cut and fitted into a conductive shaft (axial core) to manufacture a conductive roll.

More specifically, NBR (acrylonitrile-butadiene rubber), epichlorohydrin-based polymer, and chemical foaming agent (Vinehole AC # manufactured by Eiwa Chemical Co., Ltd.) shown in Table 1 are used.
R), a foaming aid (Cell paste 101 manufactured by Eiwa Kasei),
Hydrotalcite (Kyowa Chemical's DHT-4A-2) having the composition shown in Table 1 was put into a kneader, and at 100 ° C, 1 to
After kneading for about 20 minutes, it was extruded from a rubber kneading device. Then, after vulcanizing the preform for 30 minutes at 160 ° C., a metal shaft diameter (Φ6) is inserted, and the conductive rubber roll (outer diameter Φ12, length 220 m) is inserted by polishing and cutting.
A conductive roll of m) was prepared.

[0031]

[Table 1]

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

[Examples 1 to 3] Example 1 is a conductive roll formed by using NBR, and Example 2 is an epichlorohydrin-based polymer having an EO ratio of 50 mol% to 80 mol% and NBR. A conductive roll formed using the mixture, Example 3 has an EO ratio of 50 mol%
A conductive roll formed by forming a foam by using a chemical foaming agent in a polymer composed of not less than 80 mol% of epichlorohydrin-based polymer. The rubber compositions for forming the conductive rolls of Examples 1 and 2 have the following chemical blending ratios of 100% by weight of the polymer and a foaming aid of 100% by weight, respectively.
3 <a / b <10 and 4 <a + b <20. When an epichlorohydrin-based polymer is blended (Example 2,
In 3), hydrotalcite is used as an acid acceptor.

On the other hand, in Comparative Examples 1 to 4, rubber rolls are molded from a rubber composition 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 is not satisfied (Comparative Examples 1 and 3), EO
Examples (Comparative Examples 2 and 4) in which the ratio does not satisfy the condition of 50 mol% or more are shown.

The rubber rolls of Examples 1 to 3 and Comparative Examples 1 to 4 were tested and / or evaluated for hardness, electric resistance value, presence / absence of contamination of photoreceptor and cost.

(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 electrical resistance value) In an environment of 23 ° C. and 55%, a load of 500 g is applied to both ends of the shaft of the conductive roll on a metal cylinder, and 1 is 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 in the circumferential direction
The resistance was measured 6 times, and the average value was calculated.

(Measurement of Contamination of Photoreceptor) A conductive roll was pressed against the photoreceptor with a load of 500 g, and the temperature was 40 ° C. and the humidity was 9
It was left for 2 weeks in a room of 0%, and the contamination on the surface of the photoreceptor was visually confirmed and evaluated as follows. The photoconductor is a photoconductor incorporated in a copying machine, and contains polycarbonate as a main raw material. In the table, ◯: indicates contamination, x: indicates no contamination.

In the table, when the cost was lower than the conventional one, it was marked with ◯, and when it was the same as the conventional one or higher, it was marked with x. Furthermore, the comprehensive evaluation was shown as a judgment, and when it was excellent in various aspects than the conventional one, it was marked with ◯, and when it was equivalent or inferior to the conventional, it was marked with x.

Ratio a / b of compounding amount of chemical foaming agent and foaming auxiliary agent
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 epichlorohydrin-based polymer and NBR having an EO ratio of less than 50 mol% had a problem of high cost. Further, in Comparative Example 3 in which the ratio a / b of the blending amounts of the chemical foaming agent and the foaming auxiliary agent is larger than 10, there was a problem in hardness and it was not practical. In Comparative Example 4 in which only an epichlorohydrin-based 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. The photoreceptor was found to be contaminated and was not practical.

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

[0042]

As is apparent from the above description, according to the present invention, a polymer comprising an epichlorohydrin-based polymer having an EO ratio of 50 mol% to 80 mol%, or the epichlorohydrin-based polymer and an acrylonitrile-butadiene rubber. A chemical foaming agent is used in a polymer composed of a mixture with (NBR) to form a foam, and the compounding amounts of the chemical foaming agent and the foaming aid to be used are set to an amount satisfying a certain relationship, so that the resistance is low. In addition, it is possible to obtain a rubber composition excellent in all properties of non-staining property and low hardness, and at a low cost. As an example of the molded product of the rubber composition of the present invention, a conductive roll is used as a conductive roll used in a conductive mechanism of an electrophotographic apparatus in an OA device such as a laser beam printer, a copying machine, a facsimile, and an ATM. Extremely useful. The same applies to the conductive roll of the present invention in which a polymer made of acrylonitrile butadiene rubber (NBR) is formed with a chemical foaming agent and a foaming auxiliary agent to form a foam, and the compounding amounts of the chemical foaming agent and the foaming auxiliary agent are specified. In addition, it is extremely useful as a conductive mechanism of an electrophotographic apparatus.

[Brief description of drawings]

FIG. 1 is a drawing showing the compounding amounts of a chemical foaming agent a and a foaming auxiliary agent b.

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Claims (4)

(57) [Claims] 1. A polymer comprising an epichlorohydrin-based polymer having an EO ratio of 50 mol% or more and 80 mol% or less ,
Or the epichlorohydrin-based polymer and acrylonitol
A rubber composition in which a foam is formed by using a chemical foaming agent and a foaming auxiliary agent in a polymer composed of a mixture with a butadiene rubber (NBR), the chemical foaming agent and the foaming auxiliary agent. The blending amount of the polymer 10
When 0% by weight of the chemical foaming agent is a% by weight and the bubbling aid is b% by weight, 3 <a / b <10 and 4 <a
+ B <20 and contains hydrotalcite as an acid acceptor
The rubber composition according to to have. 2. A roll comprising the rubber composition according to claim 1.
A conductive roll characterized by being molded . 3. The EO ratio is 50 mol% or more and 80 mol% or less.
Below epichlorohydrin-based polymer and / or acryloni
A polymer made of tolyl butadiene rubber (NBR),
A foam formed using a chemical foaming agent and a foaming aid.
A composition comprising the chemical foaming agent and foaming auxiliary agent
The amount of the chemical blowing agent is 100% by weight of the polymer.
% By weight, and b% by weight as a foaming aid, 3 <a / b <
10 and a rubber composition satisfying 4 <a + b <20
Conductive roll characterized by being molded into a roll. 4. The conductive roll according to claim 2 , wherein the hardness is 20 or more and 40 or less in Shore E.