Rubber composition for sheet conveying roller and sheet conveying roller

Abstract

To provide a rubber composition which enables manufacture of a sheet conveyance roller that is excellent in a coefficient of friction and abrasion resistance.SOLUTION: A rubber composition for a sheet conveyance roller contains an ethylene-αolefin-diene copolymer as a base material rubber, a sulfur-based crosslinking agent, and a coumarone-indene resin. The rubber composition for the sheet conveyance roller is preferably obtained by mixing the base material rubber and the coumarone-indene resin at a temperature equal to or higher than a softening point of the coumarone-indene resin and preparing a mixture, and mixing the mixture with the sulfur-based crosslinking agent.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to rubber compositions used to form sheet-conveying rollers. [Background technology]

[0002] Various types of sheet transport rollers are incorporated into the sheet transport mechanisms of devices such as electrostatic copiers, laser printers, plain paper facsimiles, and all-in-one machines thereof, as well as image forming devices such as inkjet printers, and automated teller machines (ATMs).The sheet transport rollers rotate while in contact with sheets such as paper and plastic film, transporting the sheets by friction.

[0003] Ethylene propylene diene monomer copolymer (EPDM) is often used as a material for sheet transport rollers due to its cost and ozone resistance. However, rollers made from EPDM tend to have a low coefficient of friction due to the influence of components such as fillers contained in paper (also known as paper dust). Therefore, efforts are being made to increase the initial coefficient of friction of sheet transport rollers.

[0004] For example, Patent Document 1 describes a rubber member for preventing double feeding in a paper feeder, which is composed mainly of EPDM, uses a white rubber reinforcing agent as a reinforcing agent, and is compounded with an abrasion-resistant white rubber (see Patent Document 1). Note that the rubber member in Patent Document 1 uses a peroxide as a cross-linking agent. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-302268 Summary of the Invention [Problem to be solved by the invention]

[0006] Patent Document 1 proposes the use of a tackifier to improve the gripping power of rubber members. However, in rubber compositions using peroxide as a crosslinking agent, the incorporation of a coumarone-indene resin tends to reduce abrasion resistance. The present disclosure has been made in view of the above circumstances, and an object of the present disclosure is to provide a rubber composition that can be used to produce a sheet conveying roller having an excellent coefficient of friction and wear resistance. [Means for solving the problem]

[0007] The rubber composition for a sheet conveying roller of the present disclosure, which has been able to solve the above-mentioned problems, is characterized by containing an ethylene-α-olefin-diene copolymer as a base rubber, a sulfur-based crosslinking agent, and a coumarone-indene resin. The rubber composition contains an ethylene-α-olefin-diene copolymer as a base rubber, a sulfur-based crosslinking agent, and a coumarone-indene resin, and the coefficient of friction and wear resistance of the cured product are improved. [Effects of the Invention]

[0008] According to the present disclosure, a sheet conveying roller having an excellent coefficient of friction and wear resistance can be manufactured. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a perspective view illustrating an example of a sheet conveying roller according to the present disclosure. [Figure 2] FIG. 2 is a schematic diagram illustrating a method for measuring a friction coefficient. DETAILED DESCRIPTION OF THE INVENTION

[0010] <Rubber composition for sheet conveying roller> The rubber composition for a sheet conveying roller (hereinafter sometimes simply referred to as "rubber composition") contains an ethylene-α-olefin-diene copolymer as a base rubber, a sulfur-based crosslinking agent, and a coumarone-indene resin.

[0011] (Base rubber) The rubber composition contains an ethylene-α-olefin-diene copolymer as a base rubber. The ethylene-α-olefin-diene copolymer is a copolymer in which a double bond is introduced into the main chain by adding a small amount of a diene component to ethylene and an α-olefin. One type of ethylene-α-olefin-diene copolymer may be used alone, or two or more types may be used in combination.

[0012] Examples of the α-olefin include propylene, 1-butene, 1-hexene, and 1-octene. Examples of the diene component include ethylidene norbornene (ENB), 1,4-hexadiene (1,4-HD), and dicyclopentadiene (DCP), with ethylidene norbornene being preferred.

[0013] Examples of the ethylene-α-olefin-diene copolymer include ethylene-propylene-diene copolymer (EPDM), ethylene-butene-diene copolymer (EBDM), and ethylene-propylene-butene-diene copolymer (EPBDM).

[0014] The ethylene content of the ethylene-α-olefin-diene copolymer is preferably 40% by mass or more, more preferably 42% by mass or more, and even more preferably 43% by mass or more, and is preferably 79% by mass or less, more preferably 78% by mass or less, and even more preferably 77% by mass or less. If the ethylene unit content is within the above range, the rubber is easily available commercially and can be molded into a sheet conveying roller, thereby obtaining a rubber suitable for the sheet conveying roller.

[0015] The diene content of the ethylene-α-olefin-diene copolymer is preferably 0.5% by mass or more, more preferably 0.7% by mass or more, and even more preferably 1.0% by mass or more, and is preferably 15% by mass or less, more preferably 14% by mass or less, and even more preferably 13% by mass or less. If the diene unit content is within the above range, a rubber suitable for a sheet conveying roller can be obtained that is easily available as a commercial product and can be molded into a sheet conveying roller.

[0016] The ethylene-α-olefin-diene copolymer may be an oil-extended type in which flexibility is adjusted by adding an extender oil, or a non-oil-extended type in which no extender oil is added, and either type may be used. In the case of the oil-extended type, the mass of the added extender oil is treated as a processing aid.

[0017] The base rubber is preferably composed solely of an ethylene-α-olefin-diene copolymer. The base rubber may contain rubber components other than the ethylene-α-olefin-diene copolymer. In this case, the content of the ethylene-α-olefin-diene copolymer in the base rubber is preferably 50% by mass or more, more preferably 80% by mass or more, and even more preferably 90% by mass or more.

[0018] Examples of the other rubber components include epichlorohydrin rubber, ethylene-propylene copolymer (EPM), ethylene-butene copolymer (EBR), ethylene-octene copolymer (EOR), acrylonitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), natural rubber (NR), isoprene rubber (IR), chloroprene rubber (CR), acrylic rubber, butyl rubber, silicone rubber, etc. These other rubber components may be used alone or in combination of two or more.

[0019] (coumarone-indene resin) The rubber composition contains a coumarone-indene resin, which can increase the coefficient of friction of the resulting roller.

[0020] The coumarone-indene resin is a copolymer containing coumarones and indenes as monomer components, with the total content of coumarones and indenes in the total monomer components being 50% by mass or more. Examples of the coumarones include coumarone, methylcoumarone, etc. The content of coumarone in the total monomer components is preferably 1% by mass to 20% by mass. Examples of the indenes include indene, methylindene, etc. The content of indenes in the total monomer components is preferably 40% by mass to 95% by mass. The coumarone-indene resin may contain other monomer components in addition to coumarones and indenes, such as styrene, vinyltoluene, and dicyclopentadiene.

[0021] The softening point of the coumarone-indene resin is preferably 200°C or lower, more preferably 150°C or lower. If the softening point is 200°C or lower, the resin can be easily mixed uniformly with the rubber during kneading. The lower limit of the softening point of the coumarone-indene resin is not particularly limited, but is usually about -25°C. From the viewpoint of kneading workability, the softening point of the coumarone-indene resin is preferably 40°C or higher, more preferably 60°C or higher. The softening point of the coumarone-indene resin is measured in accordance with JIS K2207 (2006).

[0022] The content of the coumarone-indene resin in the rubber composition is preferably 1 part by mass or more, more preferably 3 parts by mass or more, and even more preferably 4 parts by mass or more, per 100 parts by mass of the base rubber, and is preferably 15 parts by mass or less, more preferably 13 parts by mass or less, and even more preferably 12 parts by mass or less. If the content of the coumarone-indene resin is 1 part by mass or more, the coefficient of friction of the obtained roll is further improved, and if it is 15 parts by mass or less, the processability, such as kneading processability, of the rubber composition is improved.

[0023] (Crosslinking agent) The rubber composition contains a sulfur-based crosslinking agent as a crosslinking agent. By crosslinking the rubber composition containing the ethylene-α-olefin-diene copolymer and the coumarone-indene resin with the sulfur-based crosslinking agent, the effect of improving the friction coefficient of the cured product can be further enhanced and a decrease in wear resistance can be suppressed.

[0024] Examples of the sulfur-based crosslinking agent include sulfur and organic sulfur-containing compounds. Examples of the sulfur include powdered sulfur, oil-treated powdered sulfur, precipitated sulfur, colloidal sulfur, and dispersible sulfur. Examples of the organic sulfur-containing compound include tetramethylthiuram disulfide and N,N-dithiobismorpholine. The crosslinking agent is preferably sulfur. One of the sulfur-based crosslinking agents may be used alone, or two or more of them may be used in combination.

[0025] The content of the sulfur-based crosslinking agent in the rubber composition is preferably 0.1 part by mass or more, more preferably 0.2 part by mass or more, and preferably 10 parts by mass or less, more preferably 5 parts by mass or less, per 100 parts by mass of the base rubber. When the content of the sulfur-based crosslinking agent is 0.1 part by mass or more and 10 parts by mass or less, a crosslinked product suitable for a roller can be obtained.

[0026] (Vulcanization accelerator) The rubber composition may contain a vulcanization accelerator. Either an inorganic accelerator or an organic accelerator can be used as the vulcanization accelerator. Examples of the inorganic accelerator include slaked lime, magnesia (MgO), and litharge (PbO). Examples of the organic accelerator include a thiazole accelerator, a thiuram accelerator, a sulfenamide accelerator, and a dithiocarbamate accelerator. The vulcanization accelerators may be used alone or in combination of two or more. As the vulcanization accelerator to be combined with the sulfur-based crosslinking agent, it is preferable to use a thiazole accelerator and a thiuram accelerator in combination.

[0027] Examples of the thiazole accelerator include 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, 2-(N,N-diethylthiocarbamoylthio)benzothiazole, and 2-(4'-morpholinodithio)benzothiazole, and di-2-benzothiazolyl disulfide is preferred.

[0028] Examples of the thiuram accelerator include tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, tetrakis(2-ethylhexyl)thiuram disulfide, and dipentamethylenethiuram tetrasulfide, with tetramethylthiuram monosulfide being preferred.

[0029] The amount of the thiazole accelerator used is preferably 0.1 part by weight or more and 10 parts by weight or less per 100 parts by weight of the base rubber. The amount of the thiuram accelerator used is preferably at least 0.1 part by weight and no more than 10 parts by weight per 100 parts by weight of the base rubber.

[0030] (Vulcanization accelerator) The rubber composition may contain a vulcanization accelerator aid. Examples of the vulcanization accelerator aid include zinc oxide. The amount of the vulcanization accelerator aid used is preferably 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the base rubber.

[0031] (Other ingredients) The rubber composition may contain compounding agents that are commonly used as compounding agents for rubber, such as fillers, processing aids, antioxidants, hindering agents, and pigments, as long as they do not detract from the spirit of the present disclosure.

[0032] The filler may be any of those commonly used as compounding agents for rubber, such as carbon black, silica, calcium carbonate, talc, clay, magnesium carbonate, aluminum oxide, etc. By compounding a filler, the mechanical strength, etc. of the resulting roller can be improved.

[0033] The amount of the filler, per 100 parts by mass of the base rubber, is preferably at least 3 parts by mass, more preferably at least 5 parts by mass, and even more preferably at least 10 parts by mass; it is preferably at most 100 parts by mass, more preferably at most 70 parts by mass, even more preferably at most 50 parts by mass, and particularly preferably at most 28 parts by mass.

[0034] When carbon black is used as the filler, the amount of carbon black is preferably 3 parts by mass or less, and more preferably 1 part by mass or less, per 100 parts by mass of the base rubber. By reducing the amount of carbon black used, it is possible to prevent the sheet from becoming soiled during transport.

[0035] Examples of the processing aid include fatty acids having 12 to 30 carbon atoms (such as stearic acid), fatty acid esters, fatty acid metal salts, fatty acid amides, hydrocarbons (paraffin), and process oils.

[0036] Examples of the antioxidant include nickel diethyldithiocarbamate and nickel dibutyldithiocarbamate.

[0037] The hardness (Durometer type A hardness) of the cured product of the rubber composition is preferably 10 or more, more preferably 15 or more, and even more preferably 20 or more, and is preferably 90 or less, more preferably 85 or less, and even more preferably 80 or less. If the hardness of the cured product is 10 or more, the hardness becomes suitable for sheet conveyance, and the conveying force is further improved, and if the hardness is 90 or less, it is easier to press-fit the roller shaft.

[0038] <Production of Rubber Composition for Sheet Conveying Roller> The rubber composition for a sheet conveying roller can be prepared by blending a base rubber and, if necessary, other raw materials, and kneading them using a kneader, a Banbury mixer, an open roll, etc. The kneading method and conditions are appropriately selected depending on the production scale.

[0039] The method for producing the rubber composition preferably comprises a first step of mixing a base rubber and a coumarone-indene resin to prepare a mixture, and a second step of mixing the mixture with a sulfur-based crosslinking agent to prepare a rubber composition. In other words, the rubber composition is preferably obtained by mixing a base rubber and a coumarone-indene resin to prepare a mixture, and then mixing the mixture with a sulfur-based crosslinking agent.

[0040] In the first step, a mixture is prepared by mixing the base rubber and the coumarone-indene resin. The mixing temperature (material temperature) when mixing the base rubber and the coumarone-indene resin is preferably equal to or higher than the softening point of the coumarone-indene resin. Mixing at a temperature equal to or higher than the softening point of the coumarone-indene resin allows the resin to be uniformly mixed into the rubber. When the softening point of the coumarone-indene resin is T°C, the mixing temperature in the first step is more preferably T+3°C or higher, and even more preferably T+5°C or higher. There are no particular limitations on the upper limit of the mixing temperature in the first step, but it is usually less than 200°C.

[0041] The mixing in the first step can be carried out using a kneader, a Banbury mixer, an open roll or the like, and is preferably carried out using a kneader.

[0042] In the first step, the base rubber and the coumarone-indene resin may be mixed alone, or other components (vulcanization accelerator, vulcanization accelerator aid, filler, processing aid, antioxidant) other than the sulfur-based crosslinking agent may also be mixed.

[0043] In the second step, the mixture is mixed with a sulfur-based crosslinking agent to prepare a rubber composition. The mixing temperature (material temperature) when mixing the mixture with the sulfur-based crosslinking agent is preferably 30°C or higher, more preferably 40°C or higher, and even more preferably 50°C or higher, and is preferably 150°C or lower, more preferably 120°C or lower, and even more preferably 100°C or lower.

[0044] The mixing in the second step can be carried out using a kneader, a Banbury mixer, an open roll, or the like, and is preferably carried out using an open roll.

[0045] In the first step, the base rubber and the coumarone-indene resin may be mixed alone, or other components (vulcanization accelerator, vulcanization accelerator aid, filler, processing aid, antioxidant) other than the sulfur-based crosslinking agent may also be mixed.

[0046] <Sheet transport roller> The sheet conveying roller of the present disclosure is obtained by curing the rubber composition for a sheet conveying roller. The shape of the sheet transport roller may be cylindrical, columnar, polygonal tubular, or polygonal pillar. When the sheet transport roller is cylindrical or polygonal tubular, the paper feed roller preferably has a shaft. The material of the shaft is not particularly limited, and examples include metal, ceramic, and resin.

[0047] An example of a sheet conveying roller is shown in Figure 1. The sheet conveying roller 1 shown in Figure 1 includes a roller body 2 formed by molding the rubber composition of the present disclosure into a cylindrical shape and cross-linking it. A through-hole 3 with a circular cross section is provided in the center of the roller body 2, and a cylindrical shaft 4 that is connected to a drive system (not shown) is inserted into and fixed to the through-hole 3. The outer circumferential surface of the roller body 2 is formed into a cylindrical shape concentric with the through-hole 3 and the shaft 4.

[0048] The roller body 2 and the shaft 4 are fixed to each other so as not to cause idling, for example, by press-fitting the shaft 4, whose outer diameter is larger than the inner diameter of the through-hole 3, into the through-hole 3 of the roller body 2. In other words, a certain idling torque (the limit torque at which idling does not occur) is ensured between the two by the interference based on the diameter difference between the two.

[0049] The shaft 4 is made of, for example, metal, ceramic, hard resin, etc. A plurality of roller bodies 2 may be fixed to a single shaft 4 at a plurality of locations, as required. Methods for manufacturing the roller body 2 include a method in which a rubber composition is molded into a cylindrical shape by extrusion molding or the like, and then crosslinked by press crosslinking or the like; a method in which a rubber composition is molded into a cylindrical shape by transfer molding or the like, and simultaneously crosslinked;

[0050] At any point during the manufacturing process, the outer circumferential surface of the roller body 2 may be polished to a predetermined surface roughness, knurled, textured, or the like, as needed. Also, both ends of the roller body 2 may be cut so that the outer circumferential surface has a predetermined width. The outer circumferential surface of the roller body 2 may be covered with an optional coating layer.

[0051] The roller body 2 may also be formed in a two-layer structure, with an outer layer on the outer peripheral surface side and an inner layer on the through-hole 3 side. In this case, it is preferable that at least the outer layer is formed from the rubber composition of the present disclosure. However, in consideration of simplifying the structure, improving productivity, and reducing manufacturing costs, it is preferable that the roller body 2 have a single-layer structure as shown in FIG. 1.

[0052] The roller body 2 may also have a porous structure. However, in order to improve abrasion resistance and reduce compression set, making it less likely to develop dents due to deformation even if contact at one point continues for a relatively long period of time, it is preferable that the roller body 2 has a substantially non-porous structure.

[0053] Depending on the application of the sheet conveying roller 1, the through hole 3 may be provided at a position eccentric to the center of the roller body 2. Furthermore, the outer circumferential surface of the roller body 2 may not be cylindrical but may have an irregular shape, for example, a cylindrical outer circumferential surface with a partially cut-out shape. To manufacture a sheet conveying roller 1 having a roller body 2 with such an irregular shape, the roller body 2 may be directly molded into an irregular shape by the manufacturing method described above and then crosslinked, or the roller body 2 molded into a cylindrical shape may be post-processed to have the irregular shape.

[0054] Alternatively, the roller body 2 may be deformed into an irregular shape by press-fitting the shaft 4, which has a deformed shape corresponding to the irregular shape of the roller body 2, into the through-hole 3 of the roller body 2 formed into a cylindrical shape. In this case, polishing, knurling, or embossing of the outer peripheral surface 5 is performed on the cylindrical outer peripheral surface before deformation. 5, improving workability.

[0055] <Image forming device> The sheet conveying roller of the present disclosure can be incorporated into various image forming apparatuses that use electrophotography, such as laser printers, electrostatic copiers, plain paper facsimile machines, or combination machines of these. The sheet conveying roller of the present disclosure can also be incorporated into inkjet printers, ATMs, etc.

[0056] The sheet conveying roller of the present disclosure rotates while in contact with a sheet, conveying the sheet by friction. The sheet may be a single sheet such as a sheet of paper or a continuous sheet such as continuous paper. The sheet conveying roller can be used as, for example, a paper feed roller, a conveying roller, a platen roller, a paper discharge roller, etc. [Example]

[0057] The present disclosure will be described in detail below using examples, but the present disclosure is not limited to the following examples, and all modifications and embodiments that do not deviate from the spirit of the present disclosure are included within the scope of the present disclosure.

[0058] [Evaluation method] (1)Hardness The hardness of the cured rubber composition was measured in accordance with JIS K6253-3 (2012). Specifically, the rubber composition was pressed at 160°C for 30 minutes to produce a 2 mm thick sheet. Three of these sheets were stacked together to avoid the influence of the measurement substrate, and the pressure plate of a Type A durometer was brought into contact with the sheet. The value was read 3 seconds after the contact.

[0059] (2) Friction coefficient measurement As shown in Figure 2, plain paper 11 (P paper, manufactured by Fujifilm Business Innovation) was placed on a horizontally placed polytetrafluoroethylene (PTFE) plate 10. The roller body 2 of the sheet transport roller 1 was placed on this paper 11, and a vertical load W1 (= 300 gf) was applied to the shaft 4 to press it against the plate 10. Next, in an environment of 23°C temperature and 55% relative humidity, the roller body 2 was rotated at 200 rpm in the direction indicated by the dashed arrow R1, and the conveying force F (gf) applied to the load cell 12 connected to one end of the paper 11 was measured. The initial coefficient of friction μ was calculated from the measured conveying force F and the vertical load W1 (=300 gf) using formula (1). μ=F(gf) / W1(gf) (1)

[0060] (3) Forced wear test As shown in Figure 2, plain paper 11 (P paper, manufactured by Fujifilm Business Innovation) was placed on a horizontally placed polytetrafluoroethylene (PTFE) plate 10. The roller body 2 of the sheet transport roller 1 was placed on this paper 11, and a vertical load W1 (= 500 gf) was applied to the shaft 4 to press it against the plate 10. Next, the roller body 2 was rotated continuously at 200 rpm for 10 minutes in the direction indicated by the dashed arrow R1 at a temperature of 23°C and a relative humidity of 55%. After that, the abrasion weight loss rate (%) was calculated using the mass W0 (g) of the roller body 2 before rotation and the mass W1 (g) of the roller body 2 after rotation using the following formula (2). Abrasion weight loss rate (%) = 100 × (W0 - W1) / W0 (Equation 2)

[0061] [Preparation of Rubber Composition] The raw materials were mixed to obtain the formulation shown in Table 1, and a rubber composition was prepared. Specifically, first, the raw materials except for the crosslinking agent were mixed using a kneader to prepare a mixture. At this time, mixing was continued for 1 minute after the temperature inside the kneader tank (material temperature) reached 105°C. Next, the obtained mixture and the crosslinking agent were mixed using an open roll to prepare a rubber composition. At this time, the set temperature of the open roll (material temperature) was 50°C. The measurement results of the cured product of the obtained rubber composition are shown in Table 1.

[0062] The coefficients of friction are also shown as indexed values. Rubber compositions Nos. 1 to 6 were indexed based on the coefficient of friction of rubber composition No. 4, which was set to 100. Rubber compositions Nos. 7 to 9 were indexed based on the coefficient of friction of rubber composition No. 8, which was set to 100. Rubber compositions Nos. 10 to 12 were indexed based on the coefficient of friction of rubber composition No. 11, which was set to 100.

[0063] [Table 1]

[0064] The raw materials used in Table 1 are as follows: EPDM1: "ESPRENE (registered trademark) 505A" manufactured by Sumitomo Chemical (ethylene-propylene-ethylidene norbornene copolymer, ethylene content 50% by mass, diene content 9.5% by mass) EPDM2: Sumitomo Chemical's "Esprene 670F" (oil-extended EPDM) (ethylene content 66% by mass, diene content 4.0% by mass, oil content 100 parts by mass per 100 parts by mass of EPDM) Coumarone-indene resin: Nitto Chemical Co., Ltd., "Knit Resin (registered trademark) Coumarone G-90" (coumarone-indene-styrene copolymer resin, softening point 90°C) Sulfur: Tsurumi Chemical, 5% sulfur with oil Organic peroxide: NOF Corp., "Percumyl (registered trademark) D" (dicumyl peroxide) Vulcanization accelerator 1: "Noccela (registered trademark) TOT-N" (tetrakis(2-ethylhexyl)thiuram disulfide) manufactured by Ouchi Shinko Chemical Industry Co., Ltd. Vulcanization accelerator 2: Ouchi Shinko Chemical Industry's "Noccela DM" (di-2-benzothiazyl disulfide) Zinc oxide: Mitsui Mining & Smelting Co., Ltd., zinc oxide type 2 Stearic acid: NOF Corp., Tsubaki stearate Carbon black: Tokai Carbon Co., Ltd., Seast (registered trademark) 3 Calcium carbonate: BF-300, manufactured by Bihoku Funka Kogyo Co., Ltd.

[0065] [Manufacturing of sheet transport rollers] The rubber composition obtained above was transferred to a cylindrical shape at 165°C for 30 minutes. A shaft (outer diameter 12 mm) was pressed into the cylindrical molded body, and the rubber roller was ground using a cylindrical grinder to an outer diameter of 21 mm. The rubber roller portion was then cut to a width of 25 mm to produce a sheet conveying roller. The evaluation results of the obtained sheet conveying roller are shown in Table 1.

[0066] Rubber compositions Nos. 1 to 3, 7, and 10 contain an ethylene-α-olefin-diene copolymer as a base rubber, a sulfur-based crosslinking agent, and a coumarone-indene resin. Rubber compositions Nos. 4, 8, and 11 contain an ethylene-α-olefin-diene copolymer as a base rubber and a sulfur-based crosslinking agent, but do not contain a coumarone-indene resin.

[0067] The sheet conveying rollers formed from rubber compositions Nos. 1 to 3, 7, and 10 all had low abrasion weight loss rates and excellent abrasion resistance. Furthermore, the sheet conveying rollers formed from rubber compositions Nos. 1 to 3 had improved friction coefficients compared to the sheet conveying roller formed from rubber composition No. 4, which did not contain a coumarone-indene resin. Similarly, the sheet conveying rollers formed from rubber compositions Nos. 7 and 10 had improved friction coefficients compared to the sheet conveying rollers formed from rubber compositions Nos. 8 and 11, which did not contain a coumarone-indene resin.

[0068] Rubber compositions Nos. 5, 6, 9, and 12 contain an ethylene-α-olefin-diene copolymer as a base rubber, an organic peroxide-based crosslinking agent, and a coumarone-indene resin. The sheet conveying rollers formed from these rubber compositions Nos. 5, 6, 9, and 12 had excellent coefficients of friction but very poor wear resistance.

[0069] The present disclosure (1) is a rubber composition for a sheet conveying roller, characterized by containing an ethylene-α-olefin-diene copolymer as a base rubber, a sulfur-based crosslinking agent, and a coumarone-indene resin.

[0070] The present disclosure (2) is the rubber composition for a sheet-conveying roller according to the present disclosure (1), wherein the content of the coumarone-indene resin is 1 to 15 parts by mass per 100 parts by mass of the base rubber.

[0071] The present disclosure (3) is a rubber composition for a sheet conveying roller according to the present disclosure (1) or (2), which is obtained by mixing a base rubber and a coumarone-indene resin at a temperature equal to or higher than the softening point of the coumarone-indene resin to prepare a mixture, and then mixing this mixture with a sulfur-based crosslinking agent.

[0072] The present disclosure (4) is a sheet conveying roller obtained by curing the rubber composition for a sheet conveying roller according to any one of the present disclosures (1) to (3). [Explanation of symbols]

[0073] 1: Sheet conveying roller, 2: Roller body, 3: Through hole, 4: Shaft, 10: Plate, 11: Paper, 12: Load cell

Claims

1. The rubber composition contains an ethylene-α-olefin-diene copolymer as a base rubber, a sulfur-based crosslinking agent, a filler, and a coumarone-indene resin, the content of the filler is 3 parts by weight to 28 parts by weight per 100 parts by weight of the base rubber, A rubber composition for a sheet conveying roller, characterized in that the content of the coumarone-indene resin is 3 to 15 parts by mass per 100 parts by mass of the base rubber.

2. The rubber composition contains a thiazole-based accelerator and a thiuram-based accelerator as vulcanization accelerators, the amount of the thiazole accelerator used is 0.1 parts by weight or more and 10 parts by weight or less per 100 parts by weight of the base rubber, 2. The rubber composition for a sheet-conveying roller according to claim 1, wherein the amount of the thiuram accelerator used is 0.1 parts by weight or more and 10 parts by weight or less per 100 parts by weight of the base rubber.

3. 3. The rubber composition for a sheet conveying roller according to claim 1, which is obtained by mixing a base rubber and a coumarone-indene resin at a temperature equal to or higher than the softening point of the coumarone-indene resin to prepare a mixture, and then mixing this mixture with a sulfur-based crosslinking agent.

4. A sheet conveying roller obtained by curing the rubber composition for a sheet conveying roller according to any one of claims 1 to 3.

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