JP2001227532A - Rubber composition for conductive roller and conductive roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a conductive rubber roller having an electric resistance value uniform over the whole surface of an outer peripheral surface. SOLUTION: In this rubber composition for a conductive roller installed on the outer periphery of core metal, a chemical foaming agent composed of azodicarvone amide or 4.4 oxybisbenzene sulfonyl hydrazide is blended with a rubber base material as a chemical foaming agent. The particle size distribution of the chemical foaming agent is 5 to 70 μm. The particle size is set not more than 10 μm. The content is set not more than 10% in the chemical foaming agent. This conductive roller is molded by vulcanizing this rubber composition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber composition for a conductive roll and a conductive roll, and more particularly, to a conductive roll for a developing device in a laser beam printer, a copying machine, a facsimile, an ATM or the like. It is used for the mechanism.

[0002]

2. Description of the Related Art In order to improve the quality of an image formed by an image forming apparatus using an electrophotographic process, a developer transported to a developing area for visualizing an electrostatic latent image is required. It is necessary to charge to the amount of charge and to supply the developer uniformly to the developing area. In such an image forming apparatus, conductive rolls having various required characteristics are used. Such rolls include a charging roll (which uniformly charges the photoreceptor), a toner supply roll (which moves toner from the toner box to the developing roll), a developing roll (which moves toner to the exposed photoreceptor), and There is a transfer roll (to move the toner transferred to the photoconductor to paper or the like).

Normally, image formation by an image forming apparatus is performed in the following steps. First, a charging roll uniformly charges an electrostatic latent image holder such as a photosensitive drum (charging), and then irradiates a light image to form an electrostatic latent image on the electrostatic latent image carrier by image exposure (exposure) ). Next, the developer (toner) charged by the developing device is supplied from the toner supply roll to the developing roll, and further supplied from the developing roll onto the latent image carrier on which the electrostatic latent image is formed, to be visualized. A toner image is formed (development). The developed image thus obtained is transferred to a printing medium such as paper via a transfer roll and fixed (transfer and fixing).

The above-mentioned conductive roll is generally composed of a cylindrical cored bar and a vulcanized rubber roll which is concentrically attached to the outer peripheral surface of the cored bar. Resistance, variation thereof, environmental dependence, voltage dependence), non-staining properties, low hardness, dimensional stability, etc. are required. Among the performances required for the above-described conductive roll, control of low hardness and electric resistance are particularly important issues.

[0005] As an attempt to lower the hardness, a softener may be used. However, the softener has problems such as contamination of the photoreceptor. Therefore, the entire rubber roll is generally formed of a foamable elastic body. For foaming rubber, chemical foaming, dissolution foaming, micro-balloon method and the like can be mentioned. Among them, chemical foaming is mainly used from the viewpoint of cost.

The above-mentioned chemical foaming is obtained by blending a conductive agent and a chemical foaming agent with a rubber component as a main component, and forming the mixture by heating and foaming. The most common chemical blowing agents are organic blowing agents, ie, substances that undergo a chemical decomposition reaction under the influence of heat and release gas. In this method, gas is rapidly released in a certain temperature range, so that relatively large bubbles are formed, and a conductive roll having low hardness and excellent elasticity can be obtained.

[0007]

However, when a rubber roll made of an elastic foam is formed by using a chemical foaming agent, the chemical foaming agent explosively releases gas due to a chemical reaction. Is significantly affected by the temperature conditions, and tends to generate a portion that causes abnormal foaming. For example, when the foamed elastic body is foamed into a roll shape, the distribution of the received heat differs in the axial direction and the radial direction, so that the foamed state and the foam shape have positional variations.
As a result, the electric resistance increases in the part where abnormal foaming occurs,
The electric resistance locally varies. As described above, when the electric resistance locally varies, there is a problem that a formed image is disturbed.

The present invention has been made in view of the above problems, and has as its object to provide a conductive roll free from abnormal foaming when the conductive roll is formed into an elastic foam using a chemical foaming agent. .

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relates to a rubber composition for a conductive roll attached to the outer periphery of a metal core, wherein the rubber base material comprises azodicarbon as a chemical foaming agent. A chemical blowing agent composed of amide or 4.4 oxybis-benzenesulfonyl hydrazide is blended, and the particle size distribution of the chemical blowing agent is 5 to 70 μm and the content of the particle size of 10 μm or less is 10% or less in the chemical blowing agent. There is provided a rubber composition for a conductive roll.

According to the above invention, the inventor of the present invention carried out experiments by selecting various types, particle sizes and particle size distribution ratios of chemical blowing agents. As a result, the present invention comprises the above-mentioned azodicarbonamide or 4.4 oxybis-benzenesulfonyl hydrazide, In addition, when the particle size distribution is 5 to 70 μm and the content of particles having a particle size of 10 μm or less is 10% or less, it has been found that occurrence of abnormal foaming can be prevented. It has also been found that it is particularly preferable to use azodicarbonamide as the chemical blowing agent.

In particular, in the present invention, it is important that the particle diameter of the chemical foaming agent is 10 μm or less in the chemical foaming agent. The reason is that at the same temperature, the foaming agent with a small particle size has a shorter time to gasification, so when the vulcanization temperature is increased, the gasification of the foaming agent with a small particle size progresses too much, resulting in a large cell diameter. There is a problem that abnormal foaming occurs. In addition, if the vulcanization temperature is lowered, the gasification of the foaming agent is delayed and the variation in the diameter of the foaming cell can be suppressed, but it is not preferable to lower the vulcanization temperature from the viewpoint of productivity.

The particle size distribution range of the chemical blowing agent is 5 to 70 μm.
If it is out of this range, the foamed cell diameter is too small or too large in a vulcanized state, and the foamed cell diameter varies, and the entire outer peripheral surface of the obtained rubber roll is generated. This is because uniform electric resistance cannot be obtained.

As the rubber substrate, a material made of semiconductive NBR or a mixture of NBR and pyrind rubber is preferably used.

It is preferable that the chemical foaming agent is blended in an amount of 1% by weight to 15% by weight with respect to 100% by weight of the rubber base material. If the compounding amount of the chemical foaming agent is out of the above range, the rubber roll obtained by vulcanization molding cannot obtain the required low hardness (Shore E hardness 30 to 40, preferably Shore E hardness 30 to 35). by.

According to the present invention, the rubber composition described above is vulcanized and molded, and the chemical foaming agent has a foam cell diameter distribution of 30%.
２００200 μm, providing a conductive roll wherein the foam cells occupy 30-70% by volume, preferably 50-60% by volume.

The occupation ratio of the foam cells in the rubber roll is set to 30 to 70% by volume because, when this volume% is used, the rubber roll can have a suitable low hardness of 30 to 40 Shore E hardness. . If the Shore E hardness is less than 30, it is too soft and the compression strain becomes too large, and if it is more than 40, it is too hard and abrasion when it comes in contact with a rigid photoreceptor is large, and image defects are liable to occur. It depends.

As the rubber substrate, any one of the above-mentioned acrylonitrile-butadiene rubber (NBR) and epichlorohydrin rubber, or a mixture of these,
It is preferred as a raw material for the conductive rubber roll of the present invention because of its high polarity, but one or more of ethylene-propylene-diene copolymer rubber (EPDM), acrylic rubber, urethane rubber, SBR, CR and the like are blended. You may use it.

Examples of the conductivity-imparting agent include carbon black such as channel black, fast black and acetylene black, an electronic conductive agent such as carbon fiber, and an ionic conductive agent such as lithium salt and zinc white. . These are used alone or in combination of two or more. Carbon black is preferred because its conductivity is hardly affected by temperature and humidity, and it also exhibits an excellent reinforcing effect. The compounding amount of the conductivity-imparting agent may be in the range known in the art, but in the case of carbon black, it is in the range of 3 to 50 parts by weight, preferably 5 to 40 parts by weight based on 100 parts by weight of the rubber component.

Further, a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, a vulcanization retarder, a filler and the like are appropriately compounded in the rubber composition.
As the vulcanizing agent, for example, sulfur, organic sulfur-containing compounds such as N, N-dithiobismorpholine, and organic peroxides such as benzoyl peroxide can be used. Examples of the vulcanization accelerator include slaked lime, magnesia (Mg
O), litharge (PbO) and the like, and organic promoters described below can be used. Examples of the organic accelerator include 2-mercaptobenzothiazole and N-
A thiazole vulcanization accelerator such as cyclohexyl-2-benzothiazolesulfene, N-butylamine, ter
an oxidative condensate of an aliphatic primary amine such as t-butylamine and propylamine with 2-mercaptobenzothiazole;
Oxidative condensates of aliphatic secondary amines such as dicyclohexylamine, pyrrolidine and piperidine with 2-mercaptobenzothiazole, oxidative condensates of alicyclic primary amines with 2-mercaptobenzothiazole, morpholine compounds and 2-mercapto Sulfenamide vulcanization accelerators such as oxidized condensates with benzothiazole, tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram dimonosulfide (TETD), tetrabutylthiuram dimono Thiuram-based vulcanization accelerators such as sulfide (TBTD) and dipentamethylenethiuram tetrasulfide (DPTT); zinc dimethyldithiocarbamate (ZnMDC);
Zinc diethyldithiocarbamate (ZnEDC), di-
A dithiocarbamate-based vulcanization accelerator such as zinc N-butylcarbamate (ZnBDC) can be used. These vulcanization accelerators can be used alone or in admixture of two or more. Examples of the vulcanization accelerator include, for example, metal oxides such as zinc oxide and magnesium oxide, and stearic acid, oleic acid, palmitic acid, and fatty acid-based vulcanization accelerators such as behenic acid.
One or more of these can be used.

A reinforcing agent is usually used as another additive, but when carbon black is blended as a conductivity-imparting agent, it also functions as a reinforcing agent. Furthermore, an antioxidant, a wax, and the like can be added as necessary.
Examples of the antioxidant include imidazoles such as 2-mercaptobenzimidazole, phenyl-α-naphthylamine, N, N′-di-6-naphthyl-p-phenylenediamine, and N-phenyl-N′-isopropyl-p.
-Amines such as phenylenediamine, di-tert-
Examples include phenols such as butyl-p-cresol and styrenated phenol.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail. FIG. 1 shows a cylindrical conductive roll 1 according to an embodiment of the present invention, and a cylindrical cored bar (shaft) 2 is press-fitted into a hollow portion thereof.

The conductive roller 1 is formed on a rubber substrate by using azodicarbonamide (ADCA) or 4.4 oxybis-benzenesulfonyl hydrazide (OCD) as a chemical foaming agent.
A rubber composition containing a chemical foaming agent comprising BSH), wherein the chemical foaming agent has a particle size distribution of 5 to 70 μm and a content of particle size of 10 μm or less in the chemical foaming agent of 10% or less. It is molded.

As the rubber substrate, acrylonitrile-
Butadiene rubber (NBR) or a mixture of NBR and pyrind rubber is preferably used, but is not limited thereto. The chemical foaming agent is blended in an amount of 1% by weight to 15% by weight with respect to 100% by weight of the rubber base material.

The above rubber composition is prepared by kneading a rubber component, a chemical foaming agent and other necessary components, extruding it into a cylindrical shape by an extruder, preforming it, cutting it into predetermined dimensions, and forming a preformed product. I am getting it. The preform is put into a vulcanizer, and the chemical foaming agent is gasified and foamed, and vulcanized at a temperature at which the rubber component is crosslinked. The conditions of the vulcanization treatment vary depending on the types and mixing ratios of additives such as a rubber component, a chemical foaming agent and a crosslinking agent, and are appropriately adjusted. A core metal (φ6) made of a metal shaft is inserted into the hollow of the vulcanized cylindrical conductive roller 1 and is polished and cut to finish.

The conductive roller 1 has voids (foam cells) in which the chemical foaming agent foams, and the diameter of the foam cells is 30.
２００200 μm, and the foam cells are uniformly distributed in the roller 1 and occupy 30% by volume to 70% by volume in the roller 1.

(Examples) Using the materials shown in Table 1 below, Examples 1 to 3 and Comparative Example 1 shown in Table 2
2 was produced.

In each of the examples and comparative examples, as a chemical foaming agent, trade name VINYLALL AC # manufactured by Eiwa Chemical Industry Co., Ltd.
An azodicarbonamide (ADCA) consisting of R, vinyl hole AC # 3, and vinyl hole AC # 3C was used. The minimum, maximum and particle size of these three ADCAs are
The content of m is as shown in Table 1.

[0028]

[Table 1]

[0029]

[Table 2]

That is, when the content is 10 μm or less, the vinyl acetate AC # R is 2.3% and the vinyl halide AC # 3 is 10.6%.
% And the ratio of the vinyl holes AC # 3C is 90.8%. Therefore, when the vinyl holes AC # 3 and the vinyl holes AC # 3C are used, the particle diameter of 10 μm or less exceeds 10%. In Examples 1 to 3, the vinyl holes AC # R having 10% or less of 10 μm or less were used, while Comparative Example 1
2 is a vinyl hole AC # having 10% or less of 10% or more.
3, was used VINYFOR AC # 3 C. In each of the examples and comparative examples, a urea auxiliary having a product name of “Cell Paste 101” manufactured by Eiwa Chemical Industry Co., Ltd. was used as a foaming auxiliary.

In Example 1, only NBR of the trade name "DN223" of Zeon Corporation was used as the rubber base material. In Example 2, as the rubber base material, the product name “CG1
02 "only epichlorohydrin was used. In Example 3, a mixture of the above NBR and epichlorohydrin in an amount of 50% by weight was used. In Comparative Examples 1 and 2, only the NBR was used as a rubber substrate.

In Examples 1 to 3 and Comparative Examples 1 and 2, A
The compounding amount of DCA was 8% by weight based on 100% by weight of the rubber base material, and the compounding amount of the foaming aid composed of "cell paste 101" was also 8% by weight based on 100% by weight of the rubber base material. . In each of the Examples and Comparative Examples, 2% by weight of the product name "powder sulfur" manufactured by Tsurumi Chemical Co., Ltd. as a vulcanizing agent, and "Noxeller CZ" manufactured by Ouchi Shinko Chemical Co., Ltd. as a vulcanization accelerator. % By weight.

The conductive rolls of Examples 1 to 3 and Comparative Examples 1 and 2 were prepared by kneading a rubber base material, ADCA, cell paste, powdered sulfur and Noxeller CZ with a 10 L kneader.
After being extruded into a cylindrical shape by a φ60 extruder and preformed, it was cut into a predetermined size to obtain a preformed body. The preform was put into a vulcanizer and heated at 160 ° C. for 30 minutes. A metal shaft (φ6) was inserted into a vulcanized cylindrical conductive roll, and was polished and cut to have an outer diameter of 15 mm and an axial length of 220 mm.

The Shore E hardness, the abnormal foaming rate, the roll resistance (Ω), and the circumferential variation (resistance unevenness) of the resistance of the above Examples 1 to 3 and Comparative Examples 1 and 2 were measured.

The hardness was measured with a Shore E hardness meter while applying a load of 500 g to a conductive rubber roller passing through a cored bar.

The abnormal foaming rate (%) is determined by cutting a conductive roll with a length of 10 mm in the axial direction, and when there is a gap of about 1 mm square or more that can be visually confirmed on the cut surface, it is regarded as “abnormal foaming”. The value obtained by dividing the number of cut surfaces having abnormal foaming by the total number of cut surfaces was defined as an abnormal foaming ratio.

As shown in FIG. 2, a roll resistance R is set to an internal resistance r (10 k) connected to a positive side of a power supply 4 by mounting a conductive rubber roller 1 passing through a metal core 2 on an aluminum drum 3.
Ω) was connected to one end of the aluminum drum 3 and to the other end of the conductive rubber roller 1 connected to the negative side of the power supply 4. The voltage applied to the internal resistance r of the electric wire was detected and set as a detected voltage V. In this device, when the applied voltage is E, the roll resistance R becomes R
= R × E / (V−r), but the term −r is considered to be minute this time, and R = r × E / V. 500 on both ends of core 2
While applying a load F of each g and rotating at 30 rpm, 100 detection voltages V when the applied voltage E was 2 KV were measured for 4 seconds, and R was calculated by the above equation. The average value of the calculated 100 R values was defined as the roll resistance R. Also,
Ratio between maximum and minimum resistance value (maximum resistance value / minimum resistance value)
Was determined to be uneven circumference.

The measured Shore E hardness, abnormal foaming rate, roll resistance value, and peripheral unevenness were as shown in Table 2. First, the abnormal foaming rate was 0% in Example 1, 2% in Example 2, and 1% in Example 3, indicating that the occurrence of abnormal foaming was almost eliminated. On the other hand, as the chemical foaming agent of Comparative Example 1, 10
In the case of using vinyl hole AC # 3 having a content of 10.6% or less, the abnormal foaming rate becomes 25%, and the vinyl hole AC # 3C having a content of 90.8% of 10 μm or less in Comparative Example 2 is used.
In the case of using, the abnormal foaming ratio reached 86%.

From the above relationship of the abnormal foaming ratio, the peripheral unevenness of the electric resistance was 1.2 or less in Examples 1 to 3, whereas Comparative Example 1 was not.
It was 1.31 in Comparative Example 2 and 1.59 in Comparative Example 2, and it was confirmed that unevenness occurred in electric resistance.

In Examples 1 to 3 and Comparative Example 1, the Shore E hardness was in the preferred range of 30 to 33. However, as a chemical foaming agent, vinyl alcohol AC # 3C having 90.8% of ADCA of 10 μm or less was used. Comparative Example 2 used had a Shore E hardness of 2
At 7, it was a bit too soft.

[0041]

As is apparent from the above description, according to the present invention, azodicarbonamide or 4.4 oxybis-benzenesulfonyl hydrazide is used as the chemical blowing agent, and the particle size distribution of the chemical blowing agent is 5%. When the content of the chemical foaming agent having a particle size of 70 μm or less and a particle size of 10 μm or less is 10% or less, occurrence of abnormal foaming of the foaming agent during vulcanization can be prevented. As a result, the electric resistance of the entire outer peripheral surface of the conductive roll can be made substantially uniform without unevenness, and when the conductive roll is used for the conductive mechanism of the developing device, an image excellent in quality can be provided. it can.

[Brief description of the drawings]

FIG. 1 is a perspective view of a conductive rubber roll.

FIG. 2 is a schematic diagram showing a device for measuring an electric resistance value of a rubber roller.

[Explanation of symbols]

 1 conductive rubber roll 2 core metal

Claims (4)

[Claims] 1. A rubber composition for a conductive roll attached to the outer periphery of a metal core, comprising: a chemical foaming agent comprising azodicarbonamide or 4.4 oxybis-benzenesulfonylhydrazide as a chemical foaming agent on a rubber base material. The chemical foaming agent has a particle size distribution of 5 to 70 μm and a particle size of 1
A rubber composition for a conductive roll having a content of 0 μm or less in a chemical foaming agent of 10% or less. 2. The rubber composition for a conductive roll according to claim 1, wherein the rubber substrate comprises acrylonitrile-butadiene rubber (NBR) or NBR and pyrind rubber. 3. The rubber composition for a conductive roll according to claim 1, wherein the chemical foaming agent is blended in an amount of 1% by weight to 15% by weight with respect to 100% by weight of the rubber base material. object. 4. The rubber composition according to claim 1, which is vulcanized and molded, wherein the chemical foaming agent has a foam cell diameter distribution of 30 to 200 μm, and A conductive roll occupying 30 to 70% by volume.