JPH07242779A - Rubber composition and paper feeding rubber roller produced using the same - Google Patents

Abstract

PURPOSE:To obtain a rubber compsn. which is weather-and abrasion-resistant and has a low hardness, rubber elasticity, and a high coefficient of friction by adjusting the mol.wt. of an ethylene-propylene rubber and the amt. of a softener compounded and keeping the content of simple sulfur low. CONSTITUTION:A rubber compsn. is obtd. by compounding 100 pts.wt. rubber component mainly comprising an ethylene-propylene rubber (pref. an ethylene- propylene-diene terpolymer) having an average mol.wt. of 300,000 or higher and an ethylene content of 60-80wt.% with 90-190 pts.wt. softener (pref. a combination of a mineral oil with an ester plasticizer) and keeping the content of simple sulfur to 0.2wt.% or lower. The content of sulfur derived from a vulcanization accelerator is pref. kept to 0.5-1.0wt.%. When the compsn. is used as a rubber layer 2 of a paper feed (transport) roller 3 of an OA machine, the roller is excellent in durability and easy in maintenance without causing problems such as blocking with or stain on paper.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rubber roller for paper feeding, which is preferably used for paper feeding in copying machines, facsimiles and the like, and more particularly to a composition of a rubber layer coated on the surface of the rubber roller.

[0002]

2. Description of the Related Art Conventionally, as a characteristic required for a rubber roller for paper feeding of this type, rubber hardness is JIS-A scale 2
It has a low hardness of about 0 to 40 °, it maintains a friction coefficient of 1.2 or more against general paper such as neutral paper, and wear resistance with little surface abrasion against repeated paper feeding. And the like.

A polynorbornene-based vulcanized rubber has been optimally used as a material satisfying this demand. This rubber has an appropriate hardness of JIS-A hardness of 40 or less, and is generally said to have excellent properties such as rubber elasticity, mechanical strength and abrasion resistance. There is. However, this polynorbornene-based rubber material,
For example, there is a lack of weather resistance.
As shown in Japanese Patent Publication No. 346, etc., there is also one in which ethylene propylene diene copolymerization (EPDM) rubber is blended to improve weather resistance.

[0004]

However, in the case where EPDM rubber is blended with this polynorbornene rubber, a large amount of a softening agent is blended in order to prevent the rubber hardness from becoming high. The agent bleeds to the roller surface, the surface of the roller becomes slippery, the coefficient of friction is lowered, and the paper cannot be fed well. In addition, the softening agent interferes with the interaction between polymer molecules, so that sufficient abrasion resistance cannot be obtained, and there is a problem that the life of the roller is shortened due to abrasion damage on the roller surface. Further, there is a problem that the recording paper is soiled by the softening agent or the like bleeding on the roller surface, or the recording paper sticks to the roller surface due to stickiness and cannot be fed well.

To prevent the softening agent from bleeding on the roller surface, a mixture of this polynorbornene rubber and EPDM rubber with a porous filler has also been proposed (Japanese Patent Laid-Open No. 188043/1988). However, according to this, there is a problem that the rubber hardness increases due to the blending of the filler and the blending amount of the softening agent increases, which repeats a vicious circle.

On the other hand, there is a sheet feeding roller made of a rubber material other than the polynorbornene vulcanized rubber. For example, natural rubber,
General-purpose vulcanized rubbers such as chloroprene rubber (CR), styrene butadiene rubber (SBR), ethylene propylene rubber (EPR), and ethylene propylene diene terpolymer (EPDM) rubber are used as the paper feed roller material. However, with these general-purpose rubber materials, JIS-A
In order to obtain a rubber hardness of 40 or less, a large amount of a softening agent must be blended, which causes a problem that properties such as rubber elasticity, mechanical strength, and abrasion resistance are significantly reduced. It was

Under such circumstances, if an attempt is made to provide a paper feed roller mainly composed of an EPR or EPDM rubber type rubber material among these materials, in that case, an example of EPDM rubber is used. As will be described, with a conventionally known low molecular weight compound, when trying to obtain the required properties of JIS-A hardness of 40 or less, a high friction coefficient like polynorbornene rubber and natural rubber cannot be obtained. . Also,
It does not have the abrasion resistance characteristics of polynorbornene rubber and natural rubber. The fact that a large amount of softening agent interferes with the interaction between polymer molecules is the same as described above.

The present invention has been made to solve such problems, and an object thereof is to provide ethylene propylene rubber (EPR) and ethylene propylene diene copolymerization (EPDM) excellent in weather resistance. It is an object of the present invention to provide a rubber feed roller which contains rubber as a main component and has various characteristics such as low hardness, high friction coefficient and abrasion resistance. The present invention also provides a rubber composition having the above-mentioned properties as a rubber material for such a rubber roller for feeding.

[0009]

In order to achieve this object, the rubber composition of the present invention contains an ethylene propylene rubber having an average molecular weight of 300,000 or more and an ethylene content of 60 to 80% by weight as a main component. A softening agent was added in an amount of 90 to 190 parts by weight to 100 parts by weight of this ethylene-propylene rubber component, and a vulcanization accelerator was added while suppressing the amount of elemental sulfur to 0.2% by weight or less. The point is to become. In this case, it is preferable to add an ester plasticizer as a softening agent in addition to the mineral oil.

The paper feeding rubber roller of the present invention is mainly composed of an ethylene propylene rubber having an average molecular weight of 300,000 or more and an ethylene content of 60 to 80% by weight as a composition of the rubber layer on the roller surface. A rubber composition in which the softening agent is blended in the range of 90 to 190 parts by weight with respect to 100 parts by weight of the ethylene-propylene rubber component, and the amount of elemental sulfur contained is suppressed to 0.2% by weight or less. The gist is to have the following. Also in this case, it is preferable to add an ester plasticizer as a softening agent in addition to the mineral oil.

The EPR or EPDM rubber has an average molecular weight of 300,000 or more. This allows, for example, EPDM
Taking rubber as an example, Mooney viscosity (121 ° C ML1 +
4) is in the range of 150 to 200. In this case, when the Mooney viscosity is 150 or less, the roller surface is greatly worn by the paper, and the replacement life of the roller is short, so that it cannot be used. If the Mooney viscosity exceeds 200, rubber kneading becomes difficult in production. The optimum Mooney viscosity range is
170 to 190.

And above all, these EPRs and EPs
The reason why the rubber material is limited to the DM rubber material is that these rubber materials have excellent environmental resistance characteristics against ozone, light rays and the like. This property eliminates the need for compounding an anti-aging agent for rubber materials. The antiaging agent and the like contaminate the paper, the photosensitive drum, and the like, but these problems are eliminated, and the effect of improving the copy quality and facilitating maintenance is produced.

On the other hand, the ethylene compounding ratio of the EPR or EPDM rubber polymer is 60 to 80.
It is preferably in the range of% by weight. If the blending ratio of ethylene is 60% by weight or less, the roller surface is largely worn by the paper, and the roller cannot be used until the required replacement life. If the ethylene ratio exceeds 80% by weight, the required rubber elasticity cannot be obtained.

On the other hand, as the kind of the softening agent, paraffin type and naphthene type mineral oils containing no aromatic component are most preferable. This is because the aromatic component seriously contaminates the photosensitive drum. As the amount of the softening agent to be blended, rubber material 1
It is preferably in the range of 90 to 190 parts by weight (phr) with respect to 00 parts by weight. 90 phr softener
Below, a rubber with a predetermined low rubber hardness (rubber A hardness of 40 or less) cannot be obtained, and if it exceeds 190 phr, mineral oil bleeds from the rubber surface, which stains the paper, sticks to the paper, and the friction coefficient. This lowers the paper feed rate and causes a paper feed failure.

However, when an ester plasticizer is added as a softening agent in addition to the mineral oil, the ester plasticizer has a poor compatibility with the ethylene propylene rubber as compared with the mineral oil, so that the ester bleeder bleeds earlier than the mineral oil. Thus, a layer rich in ester plasticizer can be formed on the roll surface. Unlike mineral oils, ester plasticizers do not stick to paper and, on the other hand, make it difficult for paper dust to stick and maintain the initial coefficient of friction.

Examples of the ester-based plasticizer include adipate such as dioctyl adipate, dioctyl sebacate, sebacate such as dibutyl sebacate, phthalate such as dioctyl phthalate and dibutyl phthalate, trioctyl trimellitate, Examples thereof include trimellitic acid esters such as tributyl trimellitate, tricresyl phosphate, tributyl phosphate, trioctyl phosphate, and other phosphate esters. Fatty acid esters such as adipate and sebacate are preferred, and sebacate such as dioctyl sebacate and dibutyl sebacate are particularly preferred.

The amount of the ester plasticizer compounded is preferably in the range of 5 to 50% by weight based on the ethylene propylene rubber component. If it is less than 5% by weight, the effect of abrasion resistance cannot be exerted for a long period of time.
If it is more than 10% by weight, the bleeding on the roller surface is too much and the friction coefficient is too small. The range of 10% to 30% is particularly preferable.

Rubber vulcanizing (accelerating) agents are generally known such as mercaptobenzothiazole (MBT), cyclohexylbenzosulfonamide (CBS), tetramethylthiuram disulfide, zinc butyldithiocarbamate (Zn BDC), and sulfur (S) alone. There are various types. The content of the sulfur component is preferably in the range of 0.5 to 1.0% by weight with respect to the rubber composition, and when sulfur alone is added to the rubber composition, the amount of sulfur alone is kept to 0.2% by weight or less. Is good. Even if the amount of sulfur alone is reduced, by setting the average molecular weight of the EPDM rubber polymer to 300,000 or more, it is possible to reduce the amount of abrasion of the rubber after it is worn due to abrasion with the paper.

[0019]

EXAMPLES The present invention will be described in detail below based on examples. In the following description, "%" means "% by weight"
And “part” means “part by weight”. Example 1 200 parts of EPDM rubber (trade name "Esprene 670F" manufactured by Sumitomo Chemical Co., Ltd.) consisting of 100 parts of ethylene propylene diene copolymer (EPDM) polymer and 100 parts of paraffinic mineral oil (softening agent) was added. Total sulfur content of sulfur accelerator is 0.6%, of which sulfur content is 0.1
% To form a rubber composition. In this case EPD
Mooney viscosity (ML121 ° C) of M polymer is 180,
This is about 32 as the average molecular weight of the EPDM polymer.
Although it corresponds to 10,000, the ethylene / propylene content ratio is adjusted to 70% as the ethylene content in this EPDM rubber composition.

As the vulcanization accelerator, thiazole, thiuram, or the like is used in combination, and the sulfur alone is 0.1%.
In addition. Others actually use EPDM as a vulcanization aid.
To 100 parts of rubber, 1 phr of stearic acid and 5 phr of zinc oxide were added, 1 phr of carbon black was added as a colorant, and 10 phr of calcium carbonate (C _a CO ₃ ) was added as a filler. Then, as shown in FIG. 1, the rubber composition was coated around a roller shaft 1 to form a rubber layer 2, and then heated and vulcanized at a predetermined temperature to produce a paper feeding rubber roller 3.

Example 2 To 200 parts of EPDM rubber consisting of 100 parts of ethylene propylene diene copolymer (EPDM) polymer and 100 parts of paraffinic mineral oil (softening agent), dioctyl sebacate (as an ester plasticizer) was added. DOS) 5
It is a mixture of parts. In addition, the compounding of the vulcanization accelerator and the like are the same as in Example 1. In the case of this Example 2, EP
The Mooney viscosity (ML121 ° C) of DM polymer is 20.
0, which corresponds to an average molecular weight of EPDM polymer of approximately 350,000.

Example 3 To 200 parts of EPDM rubber consisting of 100 parts of ethylene-propylene-diene copolymer (EPDM) polymer and 100 parts of paraffinic mineral oil (softening agent), dioctyl sebacate (as an ester plasticizer) was added. 20 parts, which is larger than that in Example 2, was blended. In addition, the compounding of the vulcanization accelerator and the like are the same as in Examples 1 and 2.
In the case of this Example 3, the Mooney viscosity (ML121 ° C.) of the EPDM polymer is 200 as in Example 2, which is E.
This corresponds to an average molecular weight of the PDM polymer of about 350,000 (same as in Example 2). Example 4 To 200 parts of EPDM rubber consisting of 100 parts of ethylene propylene diene copolymer (EPDM) polymer and 100 parts of paraffinic mineral oil (softening agent), dioctyl sebacate (DOS) was further added as an ester plasticizer. Instead, 20 parts of a trimellitic acid ester material was blended. In addition, the compounding of the vulcanization accelerator and the like are similar to those in Examples 1 to 3. In the case of this Example 4, the Mooney viscosity (ML121 ° C.) of the EPDM polymer is 200 and EPD.
The M polymer average molecular weight of approximately 350,000 is the same as in Examples 2 and 3.

Comparative Example 1 200 parts of EPDM rubber consisting of 100 parts of ethylene propylene diene copolymer (EPDM) polymer and 100 parts of paraffinic mineral oil (softening agent) was added to a vulcanization accelerator as a total sulfur content of 0 parts. 0.6%, of which 0.1% of the sulfur alone was added to produce a rubber composition, which is the same as in Example 1 in this respect. However, the difference from Example 1 is that the EPDM polymer of Comparative Example 1 has a low Mooney viscosity (ML121 ° C.) of 120 and an average molecular weight of about 40,000. The effect of the low molecular weight of EPDM rubber is investigated.

Comparative Example 2 200 parts of EPDM rubber consisting of 100 parts of ethylene-propylene-diene copolymer (EPDM) polymer and 100 parts of paraffinic mineral oil (softening agent) was added to the vulcanization accelerator in a total sulfur content of 0. A rubber composition was produced by adding 0.1% of sulfur alone, of which the polyethylene content in the EPDM polymer was 50%.
And the average molecular weight is as low as about 120,000.

COMPARATIVE EXAMPLE 3 The average molecular weight (Moonie viscosity) and polyethylene content of the EPDM polymer were the same as in Example 1 of the present invention.
The effect was investigated by lowering the compounding amount of paraffinic mineral oil as a softening agent to 80 parts.

Comparative Example 4 The average molecular weight (Moonie viscosity) and the polyethylene content of the EPDM polymer were the same as in Example 1 of the present invention, and the blending amount of the paraffinic mineral oil as a softening agent was the same as that in Comparative Example 3. On the contrary, the effect was investigated by increasing the copy to 180 copies.

Comparative Example 5 A vulcanization accelerator was added to 100 parts of EPDM polymer and 100 parts of paraffinic mineral oil (softening agent) in a total sulfur content of 0.6.
%, Mooney viscosity is 200 (average molecular weight 350,000)
However, this Comparative Example 5 is particularly characterized in that a large amount of a single sulfur component as a vulcanization accelerator is blended to 0.3%. Then, the wear resistance and the like of the roller are investigated by adding a large amount of this elemental sulfur content.

Comparative Example 6 A vulcanization accelerator was added to 100 parts of EPDM polymer and 100 parts of paraffinic mineral oil (softening agent) in a total sulfur amount of 0.6.
%, Mooney viscosity is 200 (average molecular weight 320,000)
In Comparative Example 6, 60 parts by weight of dioctyl sebacate (DOS) as an ester plasticizer was blended in addition to the paraffinic mineral oil.
Then, the effect of adding a large amount of this ester-based plasticizer on the degree of decrease in the friction coefficient of the roller and the wear resistance is investigated. Next, Example 1 which is a product of the present invention
4 and various rubber rollers shown in Comparative Examples 1 to 6 were subjected to various tests. The results are shown in Table 1 below.

[0029]

[Table 1]

The "friction coefficient after endurance (μ)" in the test items shown in Table 1 was obtained by rotating the paper feed roller at a high speed and A4.
Feeding speed of 150 mm for copy paper of neutral size (neutral paper)
This is a value obtained by measuring the coefficient of friction on the roller surface when the paper is fed at a speed of / sec and the paper feed count reaches 100,000. The "diameter fluctuation amount (mm)" indicates the difference between the initial roller outer diameter and the roller outer diameter measured when 100,000 sheets are fed as described above.

As is clear from this table, the EPDM polymer having a small average molecular weight of about 40,000 (having a low Mooney viscosity) as in Comparative Example 1 has an extremely low friction coefficient after endurance, and The amount of fluctuation in the roller diameter was also large, resulting in severe wear of the roller surface.

Even if the EPDM polymer has an average molecular weight of 300,000 or more (high Mooney viscosity), if the polyethylene content in the EPDM polymer is low as in Comparative Example 2, the durable friction coefficient is still obtained. And the wear of the roller surface was severe, resulting in unusable use.

Further, as in Comparative Example 3, when the blending amount of the softening agent was small, the rubber hardness was too high, and the durable friction coefficient was too low to be used. On the contrary, it was softened as in Comparative Example 4. When the compounding amount of the agent was too large, the material was too soft to be molded into a rubber roller.

On the other hand, in the case of the product of the present invention, in each of Examples 1 and 2, the rubber A has an appropriate rubber hardness of 40 or less, and the rubber roller has an initial hardness before use. A high coefficient of friction was shown both at the stage and after using 100,000 sheets of paper, and the result was that the variation in roller diameter due to the durability test was small and the abrasion resistance was excellent.

Further, it was confirmed that, in Examples 3 and 4 in which the ester plasticizer was mixed in a relatively large amount, a high friction coefficient was maintained even after the roller was used for a long time. This is because ester-based plasticizers are less compatible with ethylene / propylene-based rubbers than mineral oils, and therefore bleed onto the roller surface before mineral oils. It is considered that unlike the above, the paper did not stick to the paper, and conversely, the initial friction coefficient could be maintained in order to prevent the paper dust from contacting the roller surface.

However, as in Comparative Example 6, when the amount of the ester plasticizer is too large, the friction coefficient of the roller surface after use for a certain period of time is extremely lowered, and the roller surface is worn and damaged. However, it was found that the fluctuation of the roller diameter was large. This is because if the amount of the ester plasticizer blended is too large, the bleeding of this material on the roller surface becomes too large. The amount of the plasticizer blended is appropriately in the range of 5 to 50% by weight, and the range of 10 to 30% is particularly preferable.

On the other hand, as in Comparative Example 5, even when the amount of elemental sulfur as the vulcanization accelerator is too large, the roller surface is greatly worn and damaged after a certain period of use, and the variation of the roller diameter is large. Cannot be used. Therefore, it can be said that when the vulcanization accelerator is blended, it is desirable to keep the blending amount of elemental sulfur to be as low as 0.2% or less.

The present invention is not limited to the above embodiments, and various materials can be mixed without departing from the gist of the present invention. For example, as the softener, only paraffinic mineral oils are shown in the above examples, but it is needless to say that naphthene mineral oils and the like can be applied. Further, it is of course possible to appropriately mix an antiaging agent and other inorganic fillers.

[0039]

As is apparent from the above description, according to the rubber roller for paper feeding of the present invention, the molecular weight of ethylene propylene rubber (EPR, EPDM rubber) having excellent weather resistance and the blending amount of the softening agent are set. By adjusting and controlling the amount of elemental sulfur contained in the vulcanization accelerator even when blended, it not only has weather resistance but also has low hardness, rubber elasticity, high friction coefficient, and wear resistance. A product having various characteristics such as characteristics can be obtained. Therefore, applying this to a roller for feeding (conveying) of various office automation equipment such as a copying machine and a facsimile has excellent durability as a roller, does not cause problems such as paper jam and paper stain, and is easy to maintain. It is extremely beneficial to the industry.

[Brief description of drawings]

FIG. 1 is a perspective view of a sheet feeding roller according to an embodiment of the present invention.

[Explanation of symbols]

 1 roller shaft 2 rubber layer 3 paper feed roller

Claims (4)

[Claims] 1. An ethylene propylene rubber component having an average molecular weight of 300,000 or more and an ethylene content of 60 to 80% by weight as a main component.
A paper feed characterized by containing a softening agent in an amount of 90 to 190 parts by weight with respect to 0 parts by weight, and an amount in which the amount of elemental sulfur contained is suppressed to 0.2% by weight or less. Rubber composition for rollers. 2. The rubber composition for a sheet feeding roller according to claim 1, wherein an ester plasticizer is added as the softening agent in addition to mineral oil. 3. A paper feeding rubber roller having a rubber layer on the surface thereof, wherein the rubber layer is mainly composed of ethylene propylene rubber having an average molecular weight of 300,000 or more and an ethylene content of 60 to 80% by weight. A softener is blended in an amount of 90 to 190 parts by weight with respect to 100 parts by weight of the ethylene-propylene rubber component, and the amount of elemental sulfur contained is 0.2.
A rubber roller for sheet feeding, which is composed of a rubber composition blended in a range of not more than 10% by weight. 4. The rubber roller for sheet feeding according to claim 3, wherein an ester plasticizer is added as the softening agent in addition to mineral oil.