JP2025151845A - Cross-linked rubber and paper feed roll - Google Patents

Abstract

The present invention provides a cross-linked rubber product and a paper feed roll that can suppress the increase in cost, the increase in 100% modulus, and the bloom-bleed phenomenon that are caused by the incorporation of carbon nanotubes.
[Solution] A cross-linked rubber product containing a polymer component, the polymer component having ethylene propylene diene rubber and/or ethylene propylene rubber as a main component, and the cross-linked rubber product further containing a donor-acceptor molecular compound and carbon nanotubes, the donor-acceptor molecular compound being represented by formula (1).

[Selected Figure] Figure 1

Description

The present invention relates to a cross-linked rubber product and a paper feed roll.

Ethylene propylene diene rubber and/or ethylene propylene rubber have no double bonds in the molecular backbone, and are therefore characterized by excellent heat resistance, ozone resistance, and light resistance. For this reason, ethylene propylene diene rubber and/or ethylene propylene rubber are used in packing, hoses, electric wires, belts, etc., and are particularly widely used in office automation (OA) equipment such as electrostatic copiers, laser printers, and facsimiles, as well as paper feed rolls in automatic teller machines (Patent Documents 1 to 3).

Japanese Patent Application Laid-Open No. 2004-101958 Japanese Patent Application Laid-Open No. 2005-314019 Japanese Utility Model Application Laid-Open Publication No. 3-95345

As mentioned above, ethylene propylene diene rubber and/or ethylene propylene rubber have no double bonds in their molecular backbones, resulting in excellent heat resistance, ozone resistance, and light resistance. On the other hand, ethylene propylene diene rubber and/or ethylene propylene rubber have low polarity and higher electrical resistance than, for example, urethane. Therefore, "cross-linked rubber products containing polymer components primarily composed of ethylene propylene diene rubber and/or ethylene propylene rubber" have been prone to attracting atmospheric dust and foreign matter due to static electricity. In particular, when "cross-linked rubber products containing polymer components primarily composed of ethylene propylene diene rubber and/or ethylene propylene rubber" are used as materials for paper feed rolls, friction between the paper and the paper feed roll during paper feed can cause static electricity to build up on the paper feed roll surface, resulting in paper dust adhering to the paper feed roll's surface and a decrease in the paper feed roll's coefficient of friction. It is desirable for the friction coefficient of the paper feed roll to remain constant in order to facilitate paper feed. Therefore, it is desirable to make "cross-linked rubber products containing ethylene propylene diene rubber and/or a polymer component primarily composed of ethylene propylene rubber" less susceptible to static electricity. In other words, it is desirable to keep the volume electrical resistivity of "cross-linked rubber products containing ethylene propylene diene rubber and/or a polymer component primarily composed of ethylene propylene rubber" low.

As a method for lowering the volume electrical resistivity of a "cross-linked rubber product containing a polymer component primarily composed of ethylene propylene diene rubber and/or ethylene propylene rubber," for example, a method using conductive carbon black is known (Patent Document 3). In this disclosure, "conductive" refers to electrical conductivity. Conductive carbon black is easily mixed with ethylene propylene diene rubber and/or ethylene propylene rubber, which have low polarity, and can reduce the volume electrical resistivity of the cross-linked rubber product by using conductive carbon black. However, in order to reduce the volume electrical resistivity of the cross-linked rubber product by incorporating conductive carbon black (more specifically, for example, to reduce the volume electrical resistivity to ¹⁰ Ω·cm or less), it is necessary to increase the amount of conductive carbon black incorporated in the cross-linked rubber product (more specifically, for example, the amount must be 10 parts by mass or more per 100 parts by mass of rubber). If the amount of conductive carbon black incorporated is 10 parts by mass or more per 100 parts by mass of rubber, the cross-linked rubber product turns a deep black color, which can make it difficult to color rubber products made of the cross-linked rubber product. Furthermore, when the cross-linked rubber product is used for a paper feed roll, there has been a problem that, due to the deep black color of the cross-linked rubber product, when white paper sheets rub against the paper feed roll, the paper sheets are easily stained black.

As another method for lowering the volume electrical resistivity of a "cross-linked rubber product containing a polymer component primarily composed of ethylene propylene diene rubber and/or ethylene propylene rubber," blending an antistatic agent into the cross-linked rubber product is known. However, antistatic agents generally have low compatibility with ethylene propylene diene rubber and/or ethylene propylene rubber, which have low polarity. Therefore, blending an antistatic agent into the cross-linked rubber product in the amount required to exert an antistatic effect can easily cause the bloom-bleed phenomenon, which can easily contaminate items that come into contact with the rubber product made from the cross-linked rubber. In particular, when such cross-linked rubber products are used in paper feed rolls, the bloom-bleed phenomenon can cause problems, such as paper sheets being contaminated, leading to printing defects, and a decrease in the coefficient of friction of the paper feed roll. Therefore, there is a need to suppress the bloom-bleed phenomenon in cross-linked rubber products.

As yet another method for lowering the volume electrical resistivity of a "cross-linked rubber product containing a polymer component primarily composed of ethylene propylene diene rubber and/or ethylene propylene rubber," a method of compounding carbon nanotubes with the cross-linked rubber product is known (see Patent Documents 1 and 2). Carbon nanotubes are more effective at reducing the volume electrical resistivity of the cross-linked rubber product than conductive carbon black, and therefore the volume electrical resistivity of the cross-linked rubber product can be reduced with a smaller compounding amount compared to the amount of conductive carbon black required to achieve this effect. However, in order to reduce the volume electrical resistivity of the cross-linked rubber product by compounding carbon nanotubes (more specifically, for example, to reduce the volume electrical resistivity to ¹⁰ Ω·cm or less), the compounding amount of carbon nanotubes in the cross-linked rubber product must be increased (more specifically, for example, the compounding amount must be greater than 2.0 parts by mass per 100 parts by mass of rubber). Because carbon nanotubes are expensive, compounding an amount greater than 2.0 parts by mass per 100 parts by mass of rubber significantly increases the compounding cost. At the same time, the modulus of the cross-linked rubber at 100% elongation (hereinafter also referred to as "100% modulus") increases significantly, which can make it difficult to properly maintain the physical properties (in other words, the 100% modulus) of the "cross-linked rubber product containing a polymer component whose main component is ethylene propylene diene rubber and/or ethylene propylene rubber." In particular, when such a cross-linked rubber product is used for a paper feed roll, the significant increase in the 100% modulus leads to a decrease in the coefficient of friction between the paper feed roll and paper sheets. Therefore, when carbon nanotubes are used, it is required to keep the compounding amount of carbon nanotubes low and to effectively keep the volume electrical resistivity of the cross-linked rubber product low.

The present disclosure makes it possible to provide a cross-linked rubber product that suppresses the increase in cost and 100% modulus due to the incorporation of carbon nanotubes, suppresses the occurrence of the bloom-bleed phenomenon, keeps the volume electrical resistivity low, and, when used in a paper feed roll, suppresses the occurrence of paper sheet staining due to the cross-linked rubber product, as well as a paper feed roll having a rubber layer made of the cross-linked rubber product.

The cross-linked rubber product according to one embodiment of the present disclosure is
A cross-linked rubber product containing a polymer component,
the polymer component contains ethylene propylene diene rubber and/or ethylene propylene rubber as a main component,
The cross-linked rubber further contains a donor-acceptor molecular compound and carbon nanotubes,
The donor-acceptor molecular compound is represented by the following formula (1):
the content of the donor-acceptor molecular compound is 0.5 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component,
The content of the carbon nanotubes is 0.3 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the polymer component.

(In formula (1), R1 and R2 each independently represent _CH3 ( _CH2 ) ₁₆ -CO- _OCH2 , _CH3 ( _CH2 ) ₉ , _CH3 ( _{CH2 ) 13} , or _HOCH2 ; R3 and R4 each independently represent _CH3 , _C2H5 , _HOCH2 , _HOC2H4 , or _HOCH2CH ( _CH3 ); R5 represents _C2H4 , _C3H6 , or ( _CH2 ) _{9 ;} and R6 represents _{CH3 ( CH2 ) 9} or _CH3 ( _CH2 ) ₁₆ .)

The present invention makes it possible to provide a cross-linked rubber product and a paper feed roll having a rubber layer made of the cross-linked rubber product, which suppresses the increase in cost and 100% modulus due to the incorporation of carbon nanotubes, suppresses the occurrence of the bloom-bleed phenomenon, keeps the volume electrical resistivity low, and, when used in a paper feed roll, suppresses the occurrence of paper sheet staining due to the cross-linked rubber product.

FIG. 1 is a schematic diagram showing the shape of a paper feed roll according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram for explaining a part of a method for measuring the coefficient of friction μ of the paper feed roll and a part of a method for measuring the size of the black stained area on the paper sheet caused by the paper feed roll. FIG. 3 is a schematic cross-sectional view of a paper feed mechanism involved in the paper feed test.

Description of the embodiments of the present disclosure
First, embodiments of the present disclosure will be listed and described.
[1] The cross-linked rubber product of the present disclosure is
A cross-linked rubber product containing a polymer component,
the polymer component contains ethylene propylene diene rubber and/or ethylene propylene rubber as a main component,
The cross-linked rubber further contains a donor-acceptor molecular compound and carbon nanotubes,
The donor-acceptor molecular compound is represented by the following formula (1):
the content of the donor-acceptor molecular compound is 0.5 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the polymer component,
The content of the carbon nanotubes is 0.3 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the polymer component.

(In formula (1), R1 and R2 each independently represent _CH3 ( _CH2 ) ₁₆ -CO- _OCH2 , _CH3 ( _CH2 ) ₉ , _CH3 ( _{CH2 ) 13} , or _HOCH2 ; R3 and R4 each independently represent _CH3 , _C2H5 , _HOCH2 , _HOC2H4 , or _HOCH2CH ( _CH3 ); R5 represents _C2H4 , _C3H6 , or ( _CH2 ) _{9 ;} and R6 represents _{CH3 ( CH2 ) 9} or _CH3 ( _CH2 ) ₁₆ .)

This makes it possible to provide a cross-linked rubber product and a paper feed roll having a rubber layer made of the cross-linked rubber product, which suppresses the increase in cost and 100% modulus that would otherwise result from the incorporation of carbon nanotubes, suppresses the occurrence of the bloom-bleed phenomenon, keeps the volume electrical resistivity low, and, when used in a paper feed roll, suppresses the occurrence of paper sheet staining due to the cross-linked rubber product.

[2] In the above [1], the content of the carbon nanotubes may be 0.8 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component. This makes it possible to provide a cross-linked rubber product that suppresses an increase in 100% modulus due to the incorporation of carbon nanotubes, suppresses the occurrence of the bloom-bleed phenomenon, keeps the volume electrical resistivity lower, and, when used in a paper feed roll, suppresses the occurrence of staining of paper sheets due to the cross-linked rubber product, and a paper feed roll having a rubber layer made of the cross-linked rubber product.

[3] In the above [1] or [2], the carbon nanotubes may be single-walled carbon nanotubes. This makes it possible to provide a cross-linked rubber product and a paper feed roll having a rubber layer made of the cross-linked rubber product, which suppresses the increase in cost and 100% modulus due to the incorporation of carbon nanotubes, suppresses the occurrence of the bloom-bleed phenomenon, keeps the volume electrical resistivity low, and, when used in a paper feed roll, suppresses the occurrence of staining of paper sheets due to the cross-linked rubber product.

[4] In any of [1] to [3] above, the carbon black content is preferably less than 10 parts by mass per 100 parts by mass of the polymer component. This makes it possible to provide a cross-linked rubber product that, when used in a paper feed roll, can further suppress the occurrence of staining of paper sheets caused by the cross-linked rubber product, and a paper feed roll having a rubber layer made of the cross-linked rubber product.

[5] The paper feed roll of the present disclosure has a rubber layer made of the cross-linked rubber described above in [1] to [4].

This makes it possible to provide a paper feed roll with a rubber layer made of a cross-linked rubber product, which suppresses the increase in cost and 100% modulus that would otherwise result from the incorporation of carbon nanotubes, suppresses the occurrence of bloom and bleed, keeps the volume electrical resistivity low, and, when used in a paper feed roll, suppresses the occurrence of paper sheet staining due to the cross-linked rubber product.

[Details of the embodiment of the present disclosure]
An embodiment of the present disclosure (hereinafter also referred to as "the present embodiment") will be described. However, the present embodiment is not limited thereto. In this specification, notation in the form of "A to Z" means the upper and lower limits of a range (i.e., A or more and Z or less). When no unit is specified for A and a unit is specified only for Z, the unit of A and the unit of Z are the same.

[Embodiment 1: Cross-linked rubber]
A cross-linked rubber product according to one embodiment of the present disclosure will be described.
The cross-linked rubber product of the present embodiment is
A cross-linked rubber product containing a polymer component,
the polymer component contains ethylene propylene diene rubber and/or ethylene propylene rubber as a main component,
The cross-linked rubber further contains a donor-acceptor molecular compound and carbon nanotubes,
The donor-acceptor molecular compound is represented by the following formula (1):
the content of the donor-acceptor molecular compound is 0.5 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component,
The content of the carbon nanotubes is 0.3 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the polymer component.

(In formula (1), R1 and R2 each independently represent _CH3 ( _CH2 ) ₁₆ -CO- _OCH2 , _CH3 ( _CH2 ) ₉ , _CH3 ( _{CH2 ) 13} , or _HOCH2 ; R3 and R4 each independently represent _CH3 , _C2H5 , _HOCH2 , _HOC2H4 , or _HOCH2CH ( _CH3 ); R5 represents _C2H4 , _C3H6 , or ( _CH2 ) _{9 ;} and R6 represents _{CH3 ( CH2 ) 9} or _CH3 ( _CH2 ) ₁₆ .)

The present disclosure makes it possible to provide a cross-linked rubber product and a paper feed roll having a rubber layer made of the cross-linked rubber product that suppresses the increase in cost and 100% modulus due to the incorporation of carbon nanotubes, suppresses the occurrence of the bloom-bleed phenomenon, keeps the volume electrical resistivity low, and, when used in a paper feed roll, suppresses the occurrence of paper sheet staining due to the cross-linked rubber product. The reasons for this are presumed to be as follows.

(a) The cross-linked rubber product according to this embodiment further contains carbon nanotubes, and the content of the carbon nanotubes is 0.3 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component. This keeps the amount of carbon nanotubes appropriately low, thereby minimizing the increase in cost and 100% modulus due to the incorporation of carbon nanotubes. Furthermore, carbon nanotubes can reduce the volume electrical resistivity without inducing the bloom-bleed phenomenon, thereby suppressing the occurrence of the bloom-bleed phenomenon in the cross-linked rubber product. Furthermore, because the parts by mass of carbon nanotubes are sufficiently low relative to the parts by mass of the polymer component, it is possible to suppress the occurrence of staining of paper sheets due to the cross-linked rubber product when used in a paper feed roll.

(b) The cross-linked rubber product according to this embodiment further contains a donor-acceptor molecular compound, which is represented by the above formula (1), and the content of the donor-acceptor molecular compound is 0.5 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component. As a result, even if the blending amount of carbon nanotubes, which have the effect of reducing volume electrical resistivity, is kept low, the effect of reducing volume electrical resistivity is enhanced by the donor-acceptor molecular compound.

As a result, it is possible to suppress the increase in cost and 100% modulus caused by the incorporation of carbon nanotubes, suppress the occurrence of bloom and bleed phenomena, keep the volume electrical resistivity low, and, when used in paper feed rolls, suppress the occurrence of staining of paper sheets caused by the cross-linked rubber.

<Polymer component>
The polymer component is primarily composed of ethylene propylene diene rubber and/or ethylene propylene rubber. This allows the cross-linked rubber to have excellent weather resistance. The phrase "the polymer component is primarily composed of ethylene propylene diene rubber and/or ethylene propylene rubber" means that the total content of the ethylene propylene diene rubber and/or ethylene propylene rubber is 70 parts by mass or more per 100 parts by mass of the polymer component. The upper limit of the total content may be 100 parts by mass or less. The polymer component may be composed of ethylene propylene diene rubber and/or ethylene propylene rubber. The ethylene propylene diene rubber and/or ethylene propylene rubber may be non-oil-extended, oil-extended, or a mixture of non-oil-extended and oil-extended grades. The diene unit contained in the ethylene propylene diene rubber is not particularly limited, and may be, for example, ethylidene norbornene, 1,4-hexadiene, dicyclopentadiene, or the like. From the viewpoint of a fast vulcanization rate, the diene unit may be ethylidene norbornene. The polymer component may contain only one type of ethylene propylene diene rubber and/or one type of ethylene propylene rubber, or may contain two or more types of ethylene propylene diene rubber and/or two or more types of ethylene propylene rubber. The polymer component may contain other polymer components as long as the main component is ethylene propylene diene rubber and/or ethylene propylene rubber. Examples of materials for the other polymer components include natural rubber, isoprene rubber, butadiene rubber, butyl rubber, styrene butadiene rubber, polynorbornene rubber, butadiene-nitrile rubber, chloroprene rubber, halogenated butyl rubber, acrylic rubber, and epichlorohydrin rubber.

The total content of the ethylene propylene diene rubber and/or ethylene propylene rubber is preferably 80 parts by mass or more per 100 parts by mass of the polymer component. This makes it easier to maintain the high weather resistance of the ethylene propylene diene rubber and/or ethylene propylene rubber. The lower limit of the total content of the ethylene propylene diene rubber and/or ethylene propylene rubber is more preferably 90 parts by mass or more. The upper limit of the total content of the ethylene propylene diene rubber and/or ethylene propylene rubber may be 100 parts by mass or less, 99 parts by mass or less, or 98 parts by mass or less. The total content of the ethylene propylene diene rubber and/or ethylene propylene rubber may be 80 parts by mass or more and 100 parts by mass or 90 parts by mass or more and 100 parts by mass or less per 100 parts by mass of the polymer component.

<Crosslinking agent>
The crosslinking agent is not particularly limited, but examples thereof include sulfur, sulfur-based organic compounds such as tetraalkylthiuranium disulfide, metal compounds such as magnesium oxide, organic peroxides, and resin crosslinking agents. The crosslinking agent may be sulfur, which is inexpensive, easily available, and has excellent abrasion resistance. Examples of organic peroxides (in other words, peroxide crosslinking agents) include dicumyl peroxide.

<Donor-acceptor molecular compounds>
The cross-linked rubber further contains a donor-acceptor molecular compound. The donor-acceptor molecular compound is represented by the following formula (1). The content of the donor-acceptor molecular compound is 0.5 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component. This makes it possible to suppress an increase in cost and an increase in 100% modulus resulting from the blending of carbon nanotubes in the cross-linked rubber, and also to keep the volume electrical resistivity low.

(In formula (1), R1 and R2 each independently represent _CH3 ( _CH2 ) ₁₆ -CO- _OCH2 , _CH3 ( _CH2 ) ₉ , _CH3 ( _{CH2 ) 13} , or _HOCH2 ; R3 and R4 each independently represent _CH3 , _C2H5 , _HOCH2 , _HOC2H4 , or _HOCH2CH ( _CH3 ); R5 represents _C2H4 , _C3H6 , or ( _CH2 ) _{9 ;} and R6 represents _{CH3 ( CH2 ) 9} or _CH3 ( _CH2 ) ₁₆ .)

In formula (1), it is preferable that R1 is _CH3 ( _CH2 ) ₉ , R2 is _CH3 ( _CH2 ) ₁₃ , R3 is _CH3 , R4 is _CH3 , R5 is ( _CH2 ) ₉ , and R6 is _CH3 ( _CH2 ) ₉ . This makes it possible to further suppress the increase in cost and the increase in 100% modulus resulting from the incorporation of carbon nanotubes in the cross-linked rubber, and also to further reduce the volume electrical resistivity.

The content of the donor-acceptor molecular compound may be 0.7 parts by mass or more and 2.0 parts by mass or less, 0.9 parts by mass or more and 2.0 parts by mass or less, or 1.0 parts by mass or more and 2.0 parts by mass or less, per 100 parts by mass of the polymer component.

<Carbon nanotubes>
The cross-linked rubber further contains carbon nanotubes. The carbon nanotubes may be single-walled carbon nanotubes or multi-walled carbon nanotubes. Since the electrical conductivity of single-walled carbon nanotubes is higher than that of multi-walled carbon nanotubes, the carbon nanotubes are preferably single-walled carbon nanotubes, from the viewpoint of making it easier to keep the volume electrical resistivity of the cross-linked rubber low.

There is no particular lower limit to the average length of the carbon nanotubes, but it is preferably 5 μm or more, for example. There is no particular upper limit to the average length of the carbon nanotubes.

The carbon nanotube content is 0.3 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component. This makes it possible to suppress increases in cost and an increase in 100% modulus due to the incorporation of carbon nanotubes in the cross-linked rubber product, suppress the occurrence of bloom and bleed phenomena, keep the volume electrical resistivity low, and, when used in a paper feed roll, suppress the occurrence of paper staining due to the cross-linked rubber product. From the perspective of keeping the volume electrical resistivity even lower, the carbon nanotube content may be 0.5 parts by mass or more and 2.0 parts by mass or less, 0.8 parts by mass or more and 2.0 parts by mass or less, or 1.0 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component.

Carbon black
The carbon black content is preferably less than 10 parts by mass relative to 100 parts by mass of the polymer component. This makes it possible to prevent the cross-linked rubber product from turning dark black, making it impossible to color products made from the cross-linked rubber product. Furthermore, when used as a paper feed roll, it is possible to make it difficult for white paper sheets to become black and stained when the paper feed roll having a dark black rubber layer rubs against the white paper sheets. The carbon black content is preferably 0 parts by mass or more and less than 10 parts by mass relative to 100 parts by mass of the polymer component, more preferably 0 parts by mass or more and 5 parts by mass or less, even more preferably 0 parts by mass or more and 1 part by mass or less, and most preferably 0 part by mass.

Other ingredients
Other components include, for example, softeners, vulcanization accelerators, vulcanization accelerator aids, scorch inhibitors, fillers, and antioxidants. Examples of softeners include paraffinic petroleum-based blended oils with low naphthenic and aromatic component contents, poly-α-olefins, and long-chain alkyl carbonates. The amount of softener blended is not particularly limited and can be set appropriately. The vulcanization accelerator is not particularly limited and may be a thiazole such as dibenzothiazyl disulfide, a sulfenamide such as N-cyclohexyl-2-benzothiazole sulfenamide, a thiuram such as tetramethylthiuram disulfide, or a dithiocarbamate such as zinc dimethyldithiocarbamate. These vulcanization accelerators may be used alone or in combination of two or more. The amount of vulcanization accelerator blended is not particularly limited and can be set appropriately. Examples of vulcanization accelerators include metal oxides such as zinc oxide, fatty acids such as stearic acid and oleic acid, and zinc stearate. The content of the vulcanization accelerator is not particularly limited and can be set as appropriate. Examples of scorch inhibitors include maleic anhydride, thioimine compounds, sulfenamide compounds, and sulfonamide compounds. The amount of the scorch inhibitor is not particularly limited and can be set as appropriate. Examples of fillers include silica, calcium carbonate, magnesium carbonate, aluminum hydroxide, clay, talc, diatomaceous earth, mica, wood chips, and cork, as well as straw, bamboo, metal, glass, or polymer fibers. These fillers may be used alone or in combination. The amount of the filler is not particularly limited and can be set as appropriate. Examples of antioxidants include amine-based antioxidants, phenol-based antioxidants, and sulfur-based antioxidants. The amount of the antioxidant is not particularly limited and can be set as appropriate.

<Method for producing cross-linked rubber>
The cross-linked rubber product according to the present embodiment can be produced, for example, by the following method. First, a compound consisting of predetermined amounts of polymer components, carbon nanotubes, a donor-acceptor molecular compound, a cross-linking agent, and, if necessary, predetermined amounts of fillers, softeners, and other additives such as vulcanization accelerators, vulcanization accelerator aids, scorch inhibitors, and antioxidants is kneaded using a known kneading machine such as a kneader or open roll to obtain an unvulcanized rubber composition. When the rubber composition contains sulfur as a cross-linking agent, the rubber composition preferably contains a vulcanization accelerator. Next, the cross-linked rubber product according to the present embodiment can be obtained by vulcanizing and molding the rubber composition under predetermined heating conditions. Examples of methods for vulcanizing and molding the rubber composition include extrusion molding and transfer molding. For example, the rubber composition is introduced into a predetermined transfer molding mold and vulcanized (primary vulcanization) at a temperature of 140°C to 180°C for approximately 5 to 30 minutes, thereby simultaneously cross-linking the rubber composition and molding it into a tubular shape. If necessary, the tubular molded product (cross-linked rubber product) may be subjected to vulcanization (secondary vulcanization) at a temperature of 140°C to 190°C for approximately 30 to 180 minutes. By performing secondary vulcanization in this manner, it is possible to volatilize low-molecular-weight components that are likely to cause the bloom-bleed phenomenon. Thereafter, the tubular molded product (cross-linked rubber product) is polished, for example, with a cylindrical polishing machine until it has the desired outer diameter, and then cut to the desired length, thereby obtaining a cross-linked rubber product in a shape suitable for a paper feed roll.

[Embodiment 2: Paper Feed Roll]
A paper feed roll according to an embodiment of the present disclosure will be described with reference to Fig. 1. Fig. 1 is a schematic diagram showing the shape of a paper feed roll according to an embodiment of the present disclosure.

The paper feed roll 10 of this embodiment has a rubber layer 11 made of the cross-linked rubber described in embodiment 1.

The present disclosure makes it possible to provide a paper feed roll 10 having a rubber layer 11 made of a cross-linked rubber product, which suppresses the increase in cost and 100% modulus due to the incorporation of carbon nanotubes, suppresses the occurrence of the bloom-bleed phenomenon, keeps the volume electrical resistivity low, and, when used in a paper feed roll, suppresses the occurrence of paper sheet staining due to the cross-linked rubber product. The reasons for this are presumably as described above in (a) and (b).

<Paper feed roll>
The paper feed roll 10 of this embodiment includes a rubber layer 11 made of the cross-linked rubber product according to embodiment 1. Specifically, for example, the paper feed roll 10 of this embodiment is configured by inserting a core 12 into the rubber layer 11 made of the cross-linked rubber product according to embodiment 1 ( FIG. 1 ). The rubber layer 11 and the core 12 may be bonded together with an adhesive. The configuration of the paper feed roll 10 other than the material of the rubber layer 11, such as the shape of the paper feed roll 10 (e.g., cylindrical or D-shaped), the surface processing method (e.g., polishing, knurling, embossing, or a concave-convex pattern), the thickness of the rubber layer 11, the material of the core 12, and the diameter of the core 12, may be the same as those typically used for paper feed rolls. The rubber layer 11 preferably constitutes the outermost layer of the roll that contacts the sheet material. Such a paper feed roll 10 can be used as a pickup roll, feed roll, or retard roll in office automation equipment, automatic teller machines, or the like.

<Rubber layer>
The rubber layer 11 is made of the cross-linked rubber product according to embodiment 1. This makes it possible to provide a paper feed roll 10 including the rubber layer 11 made of the cross-linked rubber product, which can suppress an increase in cost and an increase in 100% modulus due to the incorporation of carbon nanotubes, suppress the occurrence of the bloom-bleed phenomenon, keep the volume electrical resistivity low, and, when used in a paper feed roll, suppress the occurrence of staining of paper sheets due to the cross-linked rubber product.

≪Applications≫
The paper feed roll according to this embodiment can transport not only paper but also various other sheet materials such as overhead projector sheets and plastic sheets.

<Manufacturing method of paper feed roll>
The paper feed roll 10 according to this embodiment can be manufactured by a conventionally known method, except that the cross-linked rubber according to the first embodiment is used as the material for the rubber layer 11 .

The present invention will be explained in detail below using examples, but the present invention is not limited to these examples.

<<Preparation of cross-linked rubber and paper feed roll>>
The cross-linked rubber products according to Samples 1 to 13 and Samples 101 to 139, and paper feed rolls having a rubber layer made of the cross-linked rubber products were produced as follows.

First, the following materials were prepared.
<Materials>
First ethylene propylene diene rubber (EPDM): "EP22" (trademark) manufactured by ENEOS
Second EPDM: ENEOS "EP107F" (trademark)
Carbon black: Ketjenblack EC300J (trademark) manufactured by Lion Specialty Chemicals Co., Ltd.
Donor-acceptor molecular compound: "BN-105" (trademark) manufactured by Boron Laboratory Co., Ltd.
Carbon nanotubes: OCSiAl single-walled carbon nanotubes "TUBALL SWCNT 93%" (trademark)
Graphene: Graphene powder "GNH-XZ (unmodified)" (trademark) manufactured by KISCO Corporation
Carbon fiber: Teijin Limited's milled fiber "HT M100 40MU" (trademark)
Antistatic agent: "TBX-8310" (trademark) manufactured by Sanko Kogyo Co., Ltd.
Stearic acid: Kao Corporation's "Lunac S-30" (trademark)
Polyethylene glycol: "PEG #4000" (trademark) manufactured by Sanyo Chemical Industries, Ltd.
Zinc oxide: Zinc oxide No. 1 (trademark) manufactured by Seido Chemical Co., Ltd.
Long-chain dialkyl carbonate: "LIALCARB SR-1000/R" (trademark) manufactured by Mitsui Fine Chemicals, Inc.
Paraffin-based petroleum-based blended oil (process oil): "PW90" (trademark) manufactured by Idemitsu Kosan Co., Ltd.
Sulfur (crosslinking agent): "Sulfax A" (trademark), powdered sulfur manufactured by Tsurumi Chemical Industry Co., Ltd.
First vulcanization accelerator: "Noccela DM" (trademark) manufactured by Ouchi Shinko Chemical Co., Ltd.
Second vulcanization accelerator: "Noccela TRA" (trademark) manufactured by Ouchi Shinko Chemical Co., Ltd.
Third vulcanization accelerator: "Noccela BZ" (trademark) manufactured by Ouchi Shinko Chemical Co., Ltd.
Fourth vulcanization accelerator: "Noccela EZ" (trademark) manufactured by Ouchi Shinko Chemical Co., Ltd.
Fifth vulcanization accelerator: "Noccela TTTE" (trademark) manufactured by Ouchi Shinko Chemical Co., Ltd.
Peroxide crosslinking agent: NOF Corporation's "Perkmyl D" (trademark)

<Preparation of cross-linked rubber>
Rubber compositions were obtained by mixing the ingredients shown in Tables 1 to 11 using a kneader. Next, the rubber compositions were subjected to vulcanization molding (primary vulcanization) using a sheet-shaped mold at 170°C for 15 minutes, to obtain sheet-shaped cross-linked rubber products measuring 140 mm x 180 mm x 2 mm. Note that for samples using sulfur as the cross-linking agent, secondary vulcanization was carried out for 30 minutes at a temperature of 170°C.

As described above, cross-linked rubber products according to Samples 1 to 13 and Samples 101 to 139 were prepared. Note that in Tables 1 to 11, the carbon nanotube content of 2.0 parts by mass or less means that the increase in cost due to the inclusion of carbon nanotubes is suppressed.

<Preparation of a paper feed roll having a rubber layer made of a cross-linked rubber product>
Rubber compositions were obtained by mixing the ingredients shown in Tables 1 to 11 using a kneader. Next, the rubber compositions were subjected to vulcanization molding (primary vulcanization) in a predetermined mold at 170°C for 15 minutes to obtain cylindrical cross-linked rubber products with an outer diameter of 21 mm, an inner diameter of 9 mm, and a length of 50 mm. For samples using sulfur as the cross-linking agent, secondary vulcanization was performed for 30 minutes at a temperature of 170°C. Next, this cross-linked rubber product was fitted into a core with a diameter of 10 mm and cut to a width of 10 mm. This was then inserted into a polyacetal resin shaft core as shown in FIG. 1 as a rubber layer. The surface of the rubber layer was then polished to an outer diameter of 20 mm to produce paper feed rolls equipped with a rubber layer made of the cross-linked rubber product of each sample.

In this way, paper feed rolls were produced that had rubber layers made from the cross-linked rubber products of Samples 1 to 13 and Samples 101 to 139.

<Evaluation of cross-linked rubber properties>
<Tensile strength>
The tensile strength of the cross-linked rubber product for each sample was determined by carrying out a tensile test in accordance with JIS K6251. The measuring machine used was an autograph "AGS-X" (trademark) manufactured by Shimadzu Corporation. The shape of the sample was a No. 3 dumbbell. The results obtained are shown in the "Tensile strength [MPa]" column of Tables 1 to 11.

<Tear strength>
The tear strength of the cross-linked rubber product for each sample was determined by carrying out a tear test in accordance with JIS K6252. The measuring machine used was an autograph "AGS-X" (trademark) manufactured by Shimadzu Corporation. The sample shape was an angle shape (no notch). The results obtained are shown in the "Tear strength [N/mm]" column of Tables 1 to 11.

<Young's modulus>
The Young's modulus of the cross-linked rubber product for each sample was measured by the following method. The Young's modulus of the cross-linked rubber product was determined by carrying out a tensile test in accordance with JIS K6251. The measuring machine used was an autograph "AGS-X" (trademark) manufactured by Shimadzu Corporation. The shape of the sample was a No. 3 dumbbell. The tensile stress at an elongation strain of 1% and the tensile stress at an elongation strain of 10% were measured, and the slope of the line connecting these two points was calculated, which was taken as the Young's modulus. The results obtained are shown in the "Young's modulus [MPa]" column of Tables 1 to 10.

<100% modulus>
The 100% modulus of the cross-linked rubber product of each sample was measured by the following method. The 100% modulus of the cross-linked rubber product was determined by carrying out a tensile test in accordance with JIS K6251. The measuring machine used was an autograph "AGS-X" (trademark) manufactured by Shimadzu Corporation. The sample shape was a No. 3 dumbbell. The tensile stress at an elongation strain of 100% was measured, and this was taken as the 100% modulus. The results obtained are shown in the "100% Mod [MPa]" column of Tables 1 to 11. Furthermore, for the cross-linked rubber product of each sample, the difference [MPa] from the 100% modulus of Sample 101 was calculated by subtracting the 100% modulus value of the cross-linked rubber product of Sample 101 (that is, a cross-linked rubber product constituted by a base component such as ethylene propylene diene rubber and containing no carbon nanotubes) from the 100% modulus value of the cross-linked rubber product of that sample. The results obtained are shown in the column "Difference [MPa] from 100% Mod of Sample 101" in Tables 1 to 11. The difference [MPa] from the 100% modulus of Sample 101 being 7.0 MPa or less means that the increase in 100% modulus due to the addition of carbon nanotubes was suppressed.

<Whether or not the bloom and bleed phenomenon occurs>
The paper feed roll for each sample was left to stand for 168 hours under conditions of a temperature of 70°C and a humidity of 90%, and then the paper feed roll was visually observed to determine whether or not the bloom-bleed phenomenon had occurred. The results obtained are shown in the "Presence or Absence of Bloom-Bleed" column of Tables 1 to 11. When "absence" is entered in the "presence or absence of bloom-bleed" column, it means that the occurrence of the bloom-bleed phenomenon has been suppressed.

<Black stains on paper sheets caused by paper feed rolls>
For each sample paper feed roll, the degree of black staining of paper sheets by the paper feed roll was determined using the following method. First, the paper feed roll 10, test paper, and friction coefficient measurement jig were left for one hour at a temperature of 22°C and a humidity of 55% (Figure 2). Next, an 80 mm x 210 mm sheet of paper P ("Xerox 4200" manufactured by Fuji Xerox Co., Ltd.) connected to a load cell 30 was sandwiched between the paper feed roll 10, which was composed of a rubber layer 11 and a shaft core 12, and a Teflon (registered trademark) base plate 20. As shown by the vertical arrow in Figure 2, the paper feed roll 10 was pressed against the base plate 20 with a vertical load W (W = 250 gf). Next, the paper feed roll 10 was rotated in the direction indicated by arrow a in the figure at a peripheral speed of 300 mm/s for three seconds. After that, the degree of staining of the paper P on the contact surface with the paper feed roll 10 was visually confirmed. The evaluation criteria were as follows. The results obtained are shown in the column "Black stains on paper sheets" in Tables 1 to 11. An evaluation result of A means that the occurrence of stains on paper sheets caused by the cross-linked rubber was suppressed.
(Evaluation criteria)
A: The size of the black stained area on the paper P confirmed by visual inspection was 0.5 mm or less in width and 4 mm or less in length.
B: The size of the black stained area on the paper P confirmed by visual inspection is more than 0.5 mm in width and/or more than 4 mm in length.

<Paper feed test>
The paper feed rolls for Samples 8 and 101 were mounted on a color multifunction printer (DocuCentre C6550I, manufactured by Fuji Xerox Co., Ltd.) and a paper feed test was conducted by running a Fuji Xerox "Xerox 4200" printer through the paper feed rolls. A cross-sectional schematic diagram of the paper feed mechanism of the multifunction printer used in the paper feed test is shown in Figure 3. The paper feed mechanism includes a paper cassette loaded with paper (paper P) as a sheet material, a pickup roll 10P that contacts the leading edge of the upper surface of the paper P to feed the paper P from the paper cassette, and a separation mechanism 10S located downstream of the pickup roll 10P in the paper transport direction, which separates and transports the paper P fed from the pickup roll 10P one sheet at a time. The separation mechanism 10S includes a feed roll 10F (an example of a paper feed roller) and a retard roll 10R that includes a rubber layer 11 and a torque limiter and is positioned below the feed roll 10F and pressed against and facing the feed roll 10F. The feed roll 10F is a drive roller that is driven by a drive source (not shown) to rotate about its axis, with the axis being perpendicular to the conveyance direction of the paper P. The feed roll 10F contacts the top surface (front surface) of the paper P fed from the paper cassette and is driven to rotate, thereby conveying the paper P downstream (see the dotted arrow in FIG. 3). A nip that holds the paper P fed from the paper cassette is formed between the feed roll 10F and the retard roll 10R. When multiple sheets of paper P are conveyed overlapping each other through this nip, a torque limiter provided on the retard roll 10R applies conveyance resistance to the paper P from the bottom (back surface) side, preventing double feeding of the paper P conveyed by the feed roll 10F. The retard roll 10R is disposed in the separation mechanism 10S. To facilitate evaluation, the paper feed test and measurements were performed under a temperature of 10°C and humidity of 15%, which is a temperature that is more likely to cause paper dust to adhere to the paper feed roll due to paper feed, as opposed to a normal indoor environment (e.g., a temperature of 22°C and humidity of 55%). The paper feed roll, test paper, and paper feed tester were left in this environment for at least 24 hours before the paper feed test began. The paper feed rolls for each sample were used as the pickup roll 10P, feed roll 10F, and retard roll 10R. The same sample was used for the pickup roll 10P, feed roll 10F, and retard roll 10R.

<Measurement of friction coefficient μ>
The friction coefficient μ of the rubber layer of the paper feed rolls of Samples 8 and 101 was measured using the following method. First, the paper feed roll 10, the measurement paper, and the measurement jig were left for 24 hours at a temperature of 10°C and a humidity of 15% ( FIG. 2 ). Next, a sheet of paper P (Xerox 4200 manufactured by Fuji Xerox Co., Ltd.) measuring 80 mm x 210 mm and connected to a load cell 30 was sandwiched between the paper feed roll 10, which was composed of the rubber layer 11 and the shaft core 12, and a Teflon (registered trademark) base plate 20. As shown by the vertical arrow in FIG. 2 , the paper feed roll 10 was pressed against the base plate 20 with a vertical load W (W = 250 gf). Next, the paper feed roll 10 was rotated in the direction indicated by arrow a in the figure at a peripheral speed of 300 mm/s, and the force pulling the paper P, i.e., the generated friction force (force F indicated by the white arrow in FIG. 2 ), was measured with the load cell 30. The coefficient of friction μ was calculated from F [gf] and the load W [gf] using the following formula (2): The coefficient of friction μ was measured before the paper feed test and after 50 sheets of paper P had been fed in the paper feed test.
Friction coefficient μ=F [gf]/W [gf] Equation (2)
Next, based on the measured coefficient of friction μ, the decrease in the coefficient of friction μ between before the paper feed test and after 50 sheets of paper P had been fed in the paper feed test was calculated. The decrease in the coefficient of friction μ for sample 8 was 0.247 for the pickup roll, 0.180 for the feed roll, and 0.233 for the retard roll. The decrease in the coefficient of friction μ for sample 101 was 0.793 for the pickup roll, 0.667 for the feed roll, and 0.627 for the retard roll. From the above, it was found that the paper feed roll for sample 8 has an exceptionally excellent effect of suppressing the decrease in the coefficient of friction between the paper feed roll 10 and the paper P compared to the paper feed roll for sample 101.

<Volume Electrical Resistivity>
The volume electrical resistivity of the cross-linked rubber products of each sample was measured under the following conditions using a resistivity chamber "R12702A" (trademark) (main electrode diameter: 50 mm) manufactured by Nippon Denkei Co., Ltd. and an ultra-high resistance meter "8340A" manufactured by Advantest Corporation. The results obtained are shown in the "Volume electrical resistivity [Ω·cm]" column of Tables 1 to 11. A volume electrical resistivity of 1.0×10 ¹³ Ω·cm or less means that the volume electrical resistivity is kept low.
(conditions)
・Charge time: 5 seconds ・Applied voltage: 50V

The cross-linked rubber products of Samples 1 to 13 correspond to Examples. The cross-linked rubber products of Samples 101 to 139 correspond to Comparative Examples. It was found that, compared to the cross-linked rubber products of Samples 101 to 139, the cross-linked rubber products of Samples 1 to 13 suppress the increase in cost and 100% modulus resulting from the incorporation of carbon nanotubes, suppress the occurrence of the bloom-bleed phenomenon, and maintain a low volume electrical resistivity.

The differences between the Examples and the Comparative Examples are shown below in more detail.
Sample 101: Since the compound contains only EPDM, zinc oxide, and a peroxide crosslinking agent, the volume resistivity is greater than 1.0×10 ¹³ Ω·cm.
Sample 102: Carbon black (conductive carbon black) was included in the formulation, but the content was only 5.0 parts by mass per 100 parts by mass of the polymer component, and a donor-acceptor molecular compound and carbon nanotubes were not included, so the volume resistivity was greater than 1.0 × 10 ¹³ Ω·cm.
Samples 103 and 104: Since the blend contains 10.0 parts by mass or more of carbon black (conductive carbon black) per 100 parts by mass of the polymer component, the volume electrical resistivity is 1.0× ¹⁰ Ω cm or less. However, compared to the paper feed rolls having a rubber layer made of the cross-linked rubber products of Samples 1 to 13, the paper feed rolls having a rubber layer made of the cross-linked rubber products of Samples 103 and 104 cause a greater degree of black staining of paper sheets caused by the paper feed roll.
Samples 105 to 111: Carbon fiber was contained in the blend in an amount of 20.0 parts by mass or less per 100 parts by mass of the polymer component, but the conductivity of the carbon fiber was low and a donor-acceptor molecular compound and carbon nanotubes were not contained, so the volume resistivity was greater than 1.0 x 10 ¹³ Ω·cm.
Samples 112 to 114: Carbon nanotubes are included in the formulation, but the content is small, at 2.0 parts by mass or less per 100 parts by mass of the polymer component, and no donor-acceptor molecular compound is included, so the volume electrical resistivity is greater than 1.0 x 10 ¹³ Ω·cm.
Sample 115: Because the blend contains 3.0 parts by mass of carbon nanotubes per 100 parts by mass of the polymer component, the volume resistivity is 1.0 x 10 ¹³ Ω·cm or less. However, because the carbon nanotube content exceeds 2.0 parts by mass per 100 parts by mass of the polymer, there is a significant increase in cost.
Sample 116: Because the blend contains 5.0 parts by mass of carbon nanotubes per 100 parts by mass of the polymer component, the volume resistivity is 1.0 x ¹⁰ Ω cm or less, but because the carbon nanotube content exceeds 2.0 parts by mass per 100 parts by mass of the polymer component, there is a significant increase in cost and a large increase in 100% modulus.
Samples 117 to 121: The formulation contains 10.0 parts by mass or less of graphene, a nanocarbon material like carbon nanotubes, per 100 parts by mass of the polymer component. However, the conductivity of graphene is low, and no donor-acceptor molecular compound or carbon nanotubes is contained, so the volume resistivity is greater than 1.0 x 10 ¹³ Ω cm.
Samples 122 and 123: Although the donor-acceptor molecular compound was contained in the formulation in an amount of 2.0 parts by mass or less per 100 parts by mass of the polymer component, the conductivity of the donor-acceptor molecular compound was low and no carbon nanotubes were contained, so the volume resistivity was greater than 1.0 x 10 ¹³ Ω·cm.
Samples 124 and 125: Although the donor-acceptor molecular compound was contained in an amount of 4.0 parts by mass or less per 100 parts by mass of the polymer component, the conductivity of the donor-acceptor molecular compound was low and no carbon nanotubes were contained, so the volume resistivity was greater than 1.0 x ¹⁰ Ω cm. Furthermore, the content of the donor-acceptor molecular compound exceeded 2.0 parts by mass per 100 parts by mass of the polymer component, so bloom and bleed were likely to occur.
- Sample 126: The blend contains 2.0 parts by mass of a donor-acceptor molecular compound per 100 parts by mass of the polymer component, and also contains 2.0 parts by mass of graphene, a nanocarbon material like carbon nanotubes, per 100 parts by mass of the polymer component. However, since no carbon nanotubes are contained, the volume electrical resistivity is greater than 1.0 x 10 ¹³ Ω·cm.
Samples 127 to 135: The donor-acceptor molecular compound was contained in the blend in an amount of 2.0 parts by mass or less per 100 parts by mass of the polymer component, and the carbon fiber content was 15.0 parts by mass or less per 100 parts by mass of the polymer component, but carbon nanotubes were not contained, so the volume electrical resistivity was greater than 1.0 x 10 ¹³ Ω·cm.
Sample 136: The donor-acceptor molecular compound was contained in an amount of 2.0 parts by mass per 100 parts by mass of the polymer component, and the conductive carbon black was contained in an amount of 5.0 parts by mass per 100 parts by mass of the polymer component, but since no carbon nanotubes were contained, the volume resistivity was greater than 1.0 x 10 ¹³ Ω·cm.
Samples 137 to 138: Although an antistatic agent was included in the formulation, the content was small, at 10 parts by mass or less per 100 parts by mass of the polymer component, and since a donor-acceptor molecular compound and carbon nanotubes were not included, the volume resistivity was greater than 1.0 x 10 ¹³ Ω·cm.
Sample 139: Since the antistatic agent was contained in an amount of 15 parts by mass per 100 parts by mass of the polymer component in the formulation, the volume electrical resistivity was 1.0 × ¹⁰ Ω·cm or less. However, since the content of the antistatic agent exceeded 10 parts by mass per 100 parts by mass of the polymer component, blooming and bleeding were likely to occur.

On the other hand, in a cross-linked rubber product whose main polymer component is ethylene propylene diene rubber and/or ethylene propylene rubber, the cross-linked rubber product contains a donor-acceptor molecular compound and carbon nanotubes, and the donor-acceptor molecular compound is represented by the above formula (1), the content of the donor-acceptor molecular compound is 0.5 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component, and the content of the carbon nanotubes is 0.3 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component (i.e., Samples 1 to 13), it is possible to keep low the increase in cost and 100% modulus due to the incorporation of carbon nanotubes, suppress the occurrence of bloom-bleed, reduce volume electrical resistivity, and, when used in a paper feed roll, suppress the occurrence of staining of paper sheets due to the cross-linked rubber product.

It was also found that the paper feed roll having a rubber layer made of the cross-linked rubber product of Sample 8 suppressed the decrease in the coefficient of friction between the paper feed roll and the paper caused by paper passing, compared to the paper feed roll having a rubber layer made of the cross-linked rubber product of Sample 101. The reason for the suppression of the decrease in the coefficient of friction is thought to be that the paper feed roll of Sample 8 suppressed the buildup of electricity caused by paper passing and the adhesion of paper powder resulting from this electricity.

From the above, it was confirmed that the cross-linked rubber products of Samples 1 to 13 suppress the increase in cost and increase in 100% modulus resulting from the incorporation of carbon nanotubes, suppress the occurrence of the bloom-bleed phenomenon, keep the volume electrical resistivity low, and, when used in paper feed rolls, suppress the occurrence of staining of paper sheets due to the cross-linked rubber product. Note that, although only ethylene propylene diene rubber is listed as the polymer component in the examples, because ethylene propylene diene rubber and ethylene propylene rubber are the same except for the presence or absence of a diene component, it is expected that similar effects will be achieved whether the polymer component is ethylene propylene rubber or whether the polymer component is both ethylene propylene diene rubber and ethylene propylene rubber.

Although the embodiments and examples of the present invention have been described above, it is also planned from the outset that the configurations of the above-mentioned embodiments and examples may be combined as appropriate.

The embodiments and examples disclosed herein are illustrative in all respects and should not be considered limiting. The scope of the present invention is indicated by the claims, not by the above-described embodiments and examples, and is intended to include all modifications equivalent to and within the scope of the claims.

10 Paper feed roll 10F Feed roll 10S Separation mechanism 10R Retard roll 10P Pick-up roll 11 Rubber layer 12 Shaft core 20 Base plate 30 Load cell P Paper F Friction force W Load

Claims (5)

A cross-linked rubber product containing a polymer component,
the polymer component contains ethylene propylene diene rubber and/or ethylene propylene rubber as a main component,
The cross-linked rubber further contains a donor-acceptor molecular compound and carbon nanotubes,
The donor-acceptor molecular compound is represented by the following formula (1):
the content of the donor-acceptor molecular compound is 0.5 parts by mass or more and 2.0 parts by mass or less with respect to 100 parts by mass of the polymer component,
The cross-linked rubber product, wherein the content of the carbon nanotubes is 0.3 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component.

(In formula (1), R1 and R2 each independently represent _CH3 ( _CH2 ) ₁₆ -CO- _OCH2 , _CH3 ( _CH2 ) ₉ , _CH3 ( _{CH2 ) 13} , or _HOCH2 ; R3 and R4 each independently represent _CH3 , _C2H5 , _HOCH2 , _HOC2H4 , or _HOCH2CH ( _CH3 ); R5 represents _C2H4 , _C3H6 , or ( _CH2 ) _{9 ;} and R6 represents _{CH3 ( CH2 ) 9} or _CH3 ( _CH2 ) ₁₆ .) The cross-linked rubber product according to claim 1, wherein the content of the carbon nanotubes is 0.8 parts by mass or more and 2.0 parts by mass or less per 100 parts by mass of the polymer component. The cross-linked rubber product according to claim 1 or claim 2, wherein the carbon nanotubes are single-walled carbon nanotubes. The cross-linked rubber product according to claim 1 or claim 2, wherein the carbon black content is less than 10 parts by mass per 100 parts by mass of the polymer component. A paper feed roll having a rubber layer made of the cross-linked rubber product according to claim 1 or 2.