Crosslinked rubber composition and power transmission belt using the same

Abstract

This is a crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition. The uncrosslinked rubber composition contains a first rubber component of ethylene-α-olefin elastomer in which the α-olefin is propylene, a second rubber component of ethylene-1-butenediene polymer, and an α,β-unsaturated carboxylic acid metal salt.

Description

Technical Field

[0001] The present invention relates to a crosslinked rubber composition and a transmission belt using the same.

Background Art

[0002] Ethylene-α-olefin elastomers are widely used as the rubber component of crosslinked rubber compositions for forming rubber products. For example, Patent Documents 1 and 2 disclose using a blend rubber of ethylene propylene diene terpolymer and ethylene-1-butene copolymer as the rubber component of the crosslinked rubber composition forming the belt body of a transmission belt.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

[0004] The present invention is a crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition, wherein the uncrosslinked rubber composition contains a first rubber component of an ethylene-α-olefin elastomer in which the α-olefin is propylene, a second rubber component of an ethylene-1-butene diene terpolymer, and a metal salt of an α,β-unsaturated carboxylic acid. The α,β-unsaturated carboxylate metal salt comprises zinc dimethacrylate. .

[0005] The present invention is a transmission belt at least partially formed of the crosslinked rubber composition of the present invention.

Brief Description of the Drawings

[0006] [Figure 1] It is a perspective view of a V-belt piece. [Figure 2] It is a perspective view of a toothed belt piece. [Modes for carrying out the invention]

[0007] The embodiments will be described in detail below.

[0008] The crosslinked rubber composition X according to this embodiment is obtained by crosslinking an uncrosslinked rubber composition X'. The uncrosslinked rubber composition X' contains a first rubber component of ethylene-α-olefin elastomer in which the α-olefin is propylene, a second rubber component of ethylene-1-butene dienterpolymer (EBDM), and an α,β-unsaturated carboxylic acid metal salt as a cocrosslinking agent.

[0009] Incidentally, crosslinked rubber compositions using ethylene propylene dienterpolymer or ethylene propylene copolymer as rubber components have low tackiness in the uncrosslinked rubber composition before crosslinking. Therefore, when forming an uncrosslinked molded product using the uncrosslinked rubber composition, for example, when laminating sheet-like uncrosslinked rubber compositions or when compounding the uncrosslinked rubber composition with fibrous members, there is a problem of poor moldability due to the poor adhesion of the uncrosslinked rubber composition.

[0010] To address this problem, according to the crosslinked rubber composition X of the embodiment, the uncrosslinked rubber composition X' before crosslinking contains a first rubber component of ethylene-α-olefin elastomer in which the α-olefin is propylene, a second rubber component of EBDM, and an α,β-unsaturated carboxylic acid metal salt as a co-crosslinking agent. This suppresses a decrease in the hardness of the crosslinked rubber composition X after crosslinking, while providing excellent moldability of the uncrosslinked rubber composition X' before crosslinking. This is thought to be because the second rubber component increases the tackiness of the uncrosslinked rubber composition X' before crosslinking, while the α,β-unsaturated carboxylic acid metal salt increases the crosslinking density of the first and second rubber components, thereby suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking.

[0011] Here, the first rubber component includes ethylene propylene dienterpolymer (EPDM) and / or ethylene propylene copolymer (EPR). Therefore, the first rubber component may consist only of EPDM, only of EPR, or as a blend of EPDM and EPR. The first rubber component preferably contains EPDM in order to suppress a decrease in the hardness of the crosslinked rubber composition X after crosslinking, while obtaining excellent moldability of the uncrosslinked rubber composition X' before crosslinking.

[0012] The ethylene content of the first rubber component is preferably 40% by mass or more and 70% by mass or less, more preferably 45% by mass or more and 55% by mass or less, and even more preferably 50% by mass or more and 53% by mass or less, from the viewpoint of obtaining excellent moldability of the uncrosslinked rubber composition X' before crosslinking while suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking.

[0013] When the first rubber component contains EPDM, examples of its diene component include 5-ethylidene-2-nobornene (ENB), 5-vinyl-2-nobornene (VNB), dicyclopentadiene, and 1,4-hexadiene. From the viewpoint of obtaining excellent moldability of the uncrosslinked rubber composition X' before crosslinking while suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking, ENB is preferred among these. In this case, the ENB content (diene content) of the EPDM contained in the first rubber component is preferably 4% by mass or more and 12% by mass or less, more preferably 6% by mass or more and 10% by mass or less, and even more preferably 7.5% by mass or more and 8.5% by mass or less, from the same viewpoint as above.

[0014] The ethylene content of the second rubber component, EBDM, is preferably 40% to 60% by mass, more preferably 45% to 55% by mass, and even more preferably 48% to 52% by mass, from the viewpoint of obtaining excellent moldability of the uncrosslinked rubber composition X' before crosslinking, while suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking.

[0015] From the viewpoint of homogenizing the crosslinked rubber composition X after crosslinking, it is preferable that the ethylene content of the second rubber component differs from that of the first rubber component by a small amount. Specifically, from the same viewpoint as above, the difference between the ethylene content of the first rubber component and the ethylene content of the second rubber component is preferably 10% by mass or less, more preferably 7% by mass or less, even more preferably 5% by mass or less, and even more preferably 3% by mass or less. From the same viewpoint as above, it is preferable that the ethylene content of the second rubber component is less than that of the first rubber component. From the same viewpoint as above, the content ratio of the ethylene content of the second rubber component to the ethylene content of the first rubber component is preferably 0.9 or more and less than 1, more preferably 0.93 or more and 0.99 or less, and even more preferably 0.95 or more and 0.98 or less.

[0016] Examples of the diene component of the second rubber component include ENB, VNB, dicyclopentadiene, and 1,4-hexadiene. From the viewpoint of obtaining excellent moldability of the uncrosslinked rubber composition X' before crosslinking while suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking, ENB is preferred among these. In this case, the ENB content (diene content) of the EBDM second rubber component is preferably 4% by mass or more and 10% by mass or less, more preferably 6% by mass or more and 8% by mass or less, and even more preferably 6.5% by mass or more and 7.5% by mass or less, from the same viewpoint.

[0017] When the first rubber component contains EPDM with ENB as the diene component, the ENB content of the second rubber component EBDM is preferably small compared to the ENB content of the EPDM contained in the first rubber component, from the viewpoint of homogenizing the crosslinked rubber composition X after crosslinking. Specifically, the difference between the ENB content of the EPDM contained in the first rubber component and the ENB content of the EBDM contained in the second rubber component is preferably 3% by mass or less, more preferably 2% by mass or less, and even more preferably 1.5% by mass or less, from the same viewpoint as above. The ENB content of the EBDM contained in the second rubber component is preferably less than the ENB content of the EPDM contained in the first rubber component, from the same viewpoint as above. The content ratio of the ENB content of the EBDM contained in the second rubber component to the ENB content of the EPDM contained in the first rubber component is preferably 0.8 or more and less than 1, more preferably 0.83 or more and 0.95 or less, and even more preferably 0.85 or more and 0.9 or less, from the same viewpoint as above.

[0018] The content A1 of the first rubber component in the uncrosslinked rubber composition X' is preferably greater than the content A2 of the second rubber component, from the viewpoint of obtaining excellent moldability of the uncrosslinked rubber composition X' before crosslinking, while suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking. The mass ratio (A1 / A2) of the content A1 of the first rubber component to the content A2 of the second rubber component is preferably greater than 50 / 50 and 95 / 5 or less, more preferably 60 / 40 or more and 85 / 15 or less, and even more preferably 65 / 35 or more and 75 / 25 or less, from the same viewpoint as above.

[0019] The uncrosslinked rubber composition X' may contain rubber components other than the first and second rubber components in amounts less than the total content of the first and second rubber components. Examples of rubber components other than the first and second rubber components include ethylene-1-butene copolymer (EBR), chloroprene rubber (CR), and hydrogenated nitrile rubber (H-NBR).

[0020] Examples of α,β-unsaturated carboxylate metal salts include metal diacrylate and metal dimethacrylate. Examples of metal diacrylate include zinc diacrylate and magnesium diacrylate. Examples of metal dimethacrylate include zinc dimethacrylate and magnesium dimethacrylate. It is preferable that the α,β-unsaturated carboxylate metal salts include one or more of these, and it is more preferable to include metal dimethacrylate, and even more preferable to include zinc dimethacrylate, from the viewpoint of obtaining excellent moldability of the uncrosslinked rubber composition X' before crosslinking while suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking. Examples of commercially available α,β-unsaturated carboxylate metal salts include Actor ZMA manufactured by Kawaguchi Chemical Industries Co., Ltd.

[0021] The content B of the α,β-unsaturated carboxylate metal salt in the uncrosslinked rubber composition X' is preferably 5 to 100 parts by mass, more preferably 10 to 30 parts by mass, and even more preferably 15 to 25 parts by mass, based on 100 parts by mass of the total content of the first and second rubber components, from the viewpoint of obtaining excellent moldability of the uncrosslinked rubber composition X' before crosslinking while suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking. The mass ratio (B / A2) of the content B of the α,β-unsaturated carboxylate metal salt in the uncrosslinked rubber composition X' to the content A2 of the second rubber component is preferably 0.4 to 2, more preferably 0.5 to less than 1, and even more preferably 0.6 to 0.7, from the same viewpoint as above. It is preferable that the content B of the α,β-unsaturated carboxylate metal salt in the uncrosslinked rubber composition X' is less than the content A2 of the second rubber component.

[0022] The unvulcanized rubber composition X' preferably further contains a tackifier from the viewpoint of obtaining excellent moldability of the unvulcanized rubber composition X' before vulcanization. Examples of the tackifier include phenolic resin-based tackifiers, petroleum resin-based tackifiers, rosin resin-based tackifiers, terpene resin-based tackifiers, coumarone-indene resin-based tackifiers, and the like. Examples of the phenolic resin-based tackifier include alkylphenol resins, alkylphenol formaldehyde resins, phenol formaldehyde resins, and the like. Examples of the petroleum resin-based tackifier include C5-C9 petroleum resins made from C5 fraction and C9 fraction as raw materials, C5 petroleum resins made from C5 fraction as raw material, C9 petroleum resins made from C9 fraction as raw material, dicyclopentadiene-based petroleum resins, and the like. Examples of the rosin resin-based tackifier include rosin ester resins, hydrogenated rosin ester resins, and the like. Examples of the terpene resin-based tackifier include polyterpene resins, styrene-modified terpene resins, and the like. Examples of the coumarone-indene resin-based tackifier include coumarone-indene resins, hydrogenated coumarone-indene resins, and the like. The tackifier preferably contains one or more of these, and preferably contains a phenolic resin-based tackifier and / or a petroleum resin-based tackifier from the viewpoint of suppressing the decrease in the hardness of the vulcanized rubber composition X after vulcanization, and more preferably contains an alkylphenol resin and / or a C5-C9 petroleum resin. Examples of commercially available alkylphenol resin tackifiers include Tamanol (registered trademark) 100S, 200N, 510, 521, 526, 586, 7509, etc. manufactured by Arakawa Chemical Industries Co., Ltd. Examples of commercially available C5-C9 petroleum resin tackifiers include Petrotac (registered trademark) 60, 70, 90, 90V, 90HS, 100V, etc. manufactured by Tosoh Corporation.

[0023] The content C of the tackifier in the unvulcanized rubber composition X' is preferably 1 part by mass or more and 10 parts by mass or less, more preferably 2 parts by mass or more and 7 parts by mass or less, still more preferably 3 parts by mass or more and 5 parts by mass or less, based on 100 parts by mass of the total content of the first and second rubber components, from the viewpoint of obtaining excellent moldability with the unvulcanized rubber composition X' before vulcanization while suppressing the decrease in the hardness of the vulcanized rubber composition X after vulcanization. The mass ratio (C / A2) of the content C of the tackifier in the unvulcanized rubber composition X' to the content A2 of the second rubber component is preferably 0.08 or more and 0.25 or less, 0.09 or more and 0.2 or less, 0.1 or more and 0.15 or less, from the same viewpoint as above.

[0024] The softening point of the tackifier is preferably 70°C or higher and 100°C or lower, from the viewpoint of obtaining excellent moldability with the unvulcanized rubber composition X' before vulcanization while suppressing the decrease in the hardness of the vulcanized rubber composition X after vulcanization. This softening point is measured by the ring and ball method.

[0025] The unvulcanized rubber composition X' preferably contains a vulcanizing agent for thermally vulcanizing the first and second rubber components. Examples of the vulcanizing agent include sulfur and organic peroxides. Examples of the organic peroxide include α,α'-di(t-butylperoxy)diisopropylbenzene, dicumyl peroxide, 1,3-bis(t-butylperoxyisopropyl)benzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, and the like. The organic peroxide preferably contains one or more of these, and more preferably contains α,α'-di(t-butylperoxy)diisopropylbenzene. Either sulfur or an organic peroxide may be blended as the vulcanizing agent, or both sulfur and an organic peroxide may be blended. The blending amount D1 of sulfur in the unvulcanized rubber composition X' is, for example, 0.3 parts by mass or more and 0.7 parts by mass or less based on 100 parts by mass of the total content of the first and second rubber components. The blending amount D2 of the organic peroxide in the unvulcanized rubber composition X' is, for example, 2.5 parts by mass or more and 3.5 parts by mass or less based on 100 parts by mass of the total content of the first and second rubber components.

[0026] The uncrosslinked rubber composition X' preferably further contains carbon black from the viewpoint of suppressing a decrease in the hardness of the crosslinked rubber composition X after crosslinking. Examples of carbon black include channel black, furnace black, thermal black, and acetylene black. Examples of furnace black include SAF, ISAF, N-339, HAF, N-351, MAF, FEF, SRF, GPF, ECF, and N-234. Examples of thermal black include FT and MT. The carbon black preferably contains one or more of these, and from the same viewpoint as above, it is more preferable to include furnace black and even more preferable to include ISAF.

[0027] The carbon black content E in the uncrosslinked rubber composition X' is preferably 30 to 80 parts by mass, more preferably 40 to 60 parts by mass, and even more preferably 45 to 55 parts by mass, based on 100 parts by mass of the total content of the first and second rubber components, in order to suppress a decrease in the hardness of the crosslinked rubber composition X after crosslinking and to suppress excessive hardness.

[0028] The uncrosslinked rubber composition X' preferably contains short fibers to suppress a decrease in the hardness of the crosslinked rubber composition X after crosslinking. Examples of short fibers include para-aramid short fibers, meta-aramid short fibers, poly-paraphenylenebenzobisoxazole short fibers, nylon 6 short fibers, nylon 6,6 short fibers, nylon 4,6 short fibers, polyethylene terephthalate short fibers, polyethylene naphthalate short fibers, etc. Examples of para-aramid short fibers include poly-paraphenylene terephthalamide (PPTA) short fibers and co-poly-paraphenylene-3,4'-oxydiphenylene terephthalamide short fibers. The short fibers preferably contain one or more of these, and from the same viewpoint as above, it is more preferable to include para-aramid short fibers, and even more preferable to include poly-paraphenylene terephthalamide short fibers.

[0029] The content F of short fibers in the uncrosslinked rubber composition X' is preferably 10 to 40 parts by mass, more preferably 15 to 30 parts by mass, and even more preferably 20 to 25 parts by mass, based on 100 parts by mass of the total content of the first and second rubber components, in order to suppress a decrease in the hardness of the crosslinked rubber composition X after crosslinking and to suppress excessive hardness.

[0030] The uncrosslinked rubber composition X' may also contain, as needed, process oils, vulcanization accelerators, vulcanization accelerators, processing aids, antioxidants, etc.

[0031] The uncrosslinked rubber composition X' can be prepared by mixing the first and second rubber components in a rubber mixer such as a kneader, Banbury mixer, or open roll mixer, and then adding a rubber compounding agent containing an α,β-unsaturated carboxylic acid metal salt and a crosslinking agent and mixing them together. Then, an uncrosslinked molded body is formed using this uncrosslinked rubber composition X', and the uncrosslinked molded body is heated and pressurized to crosslink the uncrosslinked rubber composition X', thereby obtaining the crosslinked rubber composition X according to the embodiment.

[0032] The hardness of the crosslinked rubber composition X according to this embodiment, as measured by a Type A durometer, is preferably A86 or higher, more preferably A88 or higher, and even more preferably A90 or higher. This hardness is measured using a Type A durometer in accordance with JIS K6253-3:2012.

[0033] The crosslinked rubber composition X according to this embodiment can be suitably used, for example, to form at least a portion of a power transmission belt.

[0034] Specifically, for example, in the V-belt B of the friction transmission belt shown in Figure 1, the rubber belt body 10 is composed of an adhesive rubber layer 101 in which the core wire 11 is embedded, an inner compression rubber layer 102 whose inner surface is covered with reinforcing fabric 12, and an outer stretch rubber layer 103 whose outer surface is covered with reinforcing fabric 13. Any one, two, or all three of these adhesive rubber layers 101, compression rubber layer 102, and stretch rubber layer 103 can be formed from the crosslinked rubber composition X according to the embodiment. In the toothed belt C of the interlocking transmission belt shown in Figure 2, the rubber belt body 20 is composed of a back rubber portion 201 in which the core wire 21 is embedded and a toothed rubber portion 202 covered with reinforcing fabric 22. Either or both of these back rubber portion 201 and toothed rubber portion 202 can be formed from the crosslinked rubber composition X. Furthermore, the core wires 11 and 21 are provided with an adhesive layer for bonding to the belt bodies 10 and 20, and this adhesive layer can be formed from the cross-linked rubber composition X. In addition, the reinforcing fabrics 12, 13, and 22 are provided with internally impregnated adhesive portions and / or inner adhesive layers for bonding to the belt bodies 10 and 20, and these internally impregnated adhesive portions and / or inner adhesive layers can be formed from the cross-linked rubber composition X.

[0035] The manufacturing methods for these V-belts B and toothed belts C may include a step of forming a cylindrical uncrosslinked slab (uncrosslinked molded body) having the steps of laminating sheet-like uncrosslinked rubber compositions X' and / or compounding the uncrosslinked rubber composition X' with the core wires 11, 21 of fiber members and reinforcing fabrics 12, 13, 22, and a step of producing a cylindrical belt slab by heating and pressurizing the uncrosslinked slab to crosslink the uncrosslinked rubber composition X' and form a crosslinked rubber composition X. In this process, the step of forming a cylindrical uncrosslinked slab includes the steps of laminating sheet-like uncrosslinked rubber compositions X' and / or compounding the uncrosslinked rubber compositions X' with the core wires 11, 21 of the fiber members and the reinforcing fabrics 12, 13, 22. However, since the tackiness of the uncrosslinked rubber compositions X' is enhanced, high adhesion between the sheets of the sheet-like uncrosslinked rubber compositions X' and / or high adhesion of the uncrosslinked rubber compositions X' to the core wires 11, 21 and the reinforcing fabrics 12, 13, 22 can be obtained, and excellent moldability can be obtained with the uncrosslinked rubber compositions X' in the formation of the uncrosslinked slab.

[0036] The manufacturing method for V-belt B and toothed belt C may include a step of applying an adhesive treatment to the core wires 11 and 21 by immersing them in a rubber adhesive obtained by dissolving an uncrosslinked rubber composition X' in an organic solvent, followed by heating, thereby coating the outer circumference of the core wires 11 and 21 with an overcoat layer of the uncrosslinked rubber composition X'. The overcoat layer is formed as an adhesive layer at the interface between the core wires 11 and 21 and the belt body 10 and 20 when the uncrosslinked slab is heated and pressurized. At this time, the core wires 11 and 21 obtain high tackiness due to the overcoat layer of the uncrosslinked rubber composition X', and thus excellent moldability can be obtained in the molding of the uncrosslinked slab due to the overcoat layer of the uncrosslinked rubber composition X'.

[0037] The manufacturing method for V-belt B and toothed belt C may include the steps of: soaking the reinforcing fabric 12, 13, 22 in a low-viscosity rubber glue made by dissolving uncrosslinked rubber composition X' in an organic solvent, and then heating it, thereby covering the surface of the yarn constituting the reinforcing fabric 12, 13, 22 with a soaking layer of uncrosslinked rubber composition X'; and / or coating the surface of the reinforcing fabric 12, 13, 22 facing the belt body 10, 20 with a high-viscosity rubber glue made by dissolving uncrosslinked rubber composition X' in an organic solvent, and then heating it, thereby covering the surface of the reinforcing fabric 12, 13, 22 facing the belt body 10, 20 with a coating layer of uncrosslinked rubber composition X'. The soaking layer is formed in the internal impregnation adhesive portion that covers the surface of the yarn inside the reinforcing fabric 12, 13, 22 when the uncrosslinked slab is heated and pressurized. The coating layer is formed on the inner adhesive layer at the interface between the reinforcing fabrics 12, 13, 22 and the belt bodies 10, 20 when the uncrosslinked slab is heated and pressurized. At this time, high adhesion to the reinforcing fabrics 12, 13, 22 is obtained by the soaking layer and / or coating layer of the uncrosslinked rubber composition X', so that excellent moldability can be obtained in the molding of the uncrosslinked slab due to the soaking layer and / or coating layer of the uncrosslinked rubber composition X'. [Examples]

[0038] (Uncrosslinked rubber composition) Uncrosslinked rubber compositions were prepared for the following Examples 1-5 and Comparative Examples 1-2. Their respective compositions are also shown in Table 1.

[0039] <Example 1> In a kneader, the first rubber component, EPDM (EP33, manufactured by ENEOS Material Co., Ltd., ethylene content: 52% by mass, ENB content: 8.1% by mass), and the second rubber component, EBDM (K-9330M, manufactured by Mitsui Chemicals, Ltd., ethylene content: 50% by mass, ENB content: 7.1% by mass), were added in a mass ratio of first rubber component / second rubber component = 83.7 / 16.3 and kneaded. Then, for every 100 parts by mass of the total content of the first and second rubber components, 20 parts by mass of the co-crosslinking agent zinc dimethacrylate (Actor ZMA, manufactured by Kawaguchi Chemical Industry Co., Ltd.), 50 parts by mass of carbon black ISAF, 10 parts by mass of process oil, 5 parts by mass of the vulcanization accelerator zinc oxide, and 0.5 parts by mass of the processing aid stearic acid were added and kneaded. Finally, for every 100 parts by mass of the total content of the first and second rubber components, the crosslinking agent sulfur (Seimi OT) was added. 0.5 parts by mass of (manufactured by Tsurumi Chemical Industries, Ltd.) and 7 parts by mass of the organic peroxide α,α'-di(t-butylperoxy)diisopropylbenzene (peroximon F-40, manufactured by NOF Corporation, purity: 40%) (2.8 parts by mass of active ingredient) were added and kneaded further. The kneaded material was discharged from the kneader and cooled, then the material was put back into the kneader and kneaded again. To this, 22 parts by mass of PPTA short fibers (Kevlar 119, manufactured by DuPont, fiber length: 3 mm) were added for a total content of 100 parts by mass of the first and second rubber components and kneaded to produce an uncrosslinked rubber composition, which was designated as Example 1. The kneading temperature was set to a temperature higher than the softening point of the tackifier used in Example 4 described later.

[0040] Here, the difference between the ethylene content of the first rubber component and the ethylene content of the second rubber component is 2% by mass. The content ratio of the ethylene content of the second rubber component to the ethylene content of the first rubber component is 0.96. The difference between the ENB content of the EPDM rubber component and the ENB content of the EBDM rubber component is 1% by mass. The content ratio of the ENB content of the EBDM rubber component to the ENB content of the EPDM rubber component is 0.88.

[0041] <Example 2> An uncrosslinked rubber composition was prepared in the same manner as in Example 1, except that the mass ratio of the first rubber component to the second rubber component was set to first rubber component / second rubber component = 67.5 / 32.5, and this was designated as Example 2.

[0042] <Example 3> An uncrosslinked rubber composition was prepared in the same manner as in Example 1, except that the mass ratio of the first rubber component to the second rubber component was set to first rubber component / second rubber component = 51.2 / 48.8, and this was designated as Example 3.

[0043] <Example 4> An uncrosslinked rubber composition was prepared in the same manner as in Example 2, except that 4 parts by mass of an alkylphenol resin tackifier (Tamanol 510, manufactured by Arakawa Chemical Industries, Ltd., softening point: 75°C to 95°C) was added per 100 parts by mass of the total content of the first and second rubber components. This was designated as Example 4.

[0044] <Example 5> An uncrosslinked rubber composition was prepared in the same manner as in Example 4, except that the amount of zinc dimethacrylate added was 40 parts by mass per 100 parts by mass of the total content of the first and second rubber components. This was designated as Example 5.

[0045] <Comparative Example 1> An uncrosslinked rubber composition was prepared in the same manner as in Example 1, except that only EPDM, the first rubber component, was used as the rubber component, and this was designated as Comparative Example 1.

[0046] <Comparative Example 2> An uncrosslinked rubber composition was prepared in the same manner as in Example 2, except that it did not contain zinc dimethacrylate, and this was designated as Comparative Example 2.

[0047] [Table 1]

[0048] (Test methods and results) The following tests were conducted on the uncrosslinked rubber compositions and the crosslinked rubber compositions obtained from Examples 1-5 and Comparative Examples 1-2. The test results are shown in Table 1.

[0049] <Adhesive strength> Tack tests were performed on each of the uncrosslinked rubber compositions of Examples 1-5 and Comparative Examples 1-2 using a pickup-type tack meter (Tack Tester IMC-1567, manufactured by Imoto Seisakusho Co., Ltd.). The tack meter has a cylindrical aluminum adhesive disc with a diameter of 50 mm and a thickness of 14 mm, with an axis extending horizontally in the front-to-back direction, and a fixing plate below it for setting the test piece. The upper end of the adhesive disc is connected to a load cell and is provided to move up and down together with the load cell. The specific test method is as follows.

[0050] Each uncrosslinked rubber composition was formed into a sheet, and strip-shaped test pieces for tackiness testing were cut from it. The test pieces were horizontally attached to the fixing plate of the tack meter with double-sided tape. The adhesive disc was lowered at a speed of 30 mm / min so that it was close to the fixing plate, and the outer surface of the adhesive disc was pressed against the test piece with a load of 4.9 N. After 10 seconds, the adhesive disc was raised at a speed of 30 mm / min so that it was separated from the fixing plate. The peel force (tack force) when the adhesive disc peeled off the test piece was measured with a load cell. The adhesive strength was evaluated as a relative value with the peel force of Comparative Example 1 set to 1.

[0051] <Hardness> The uncrosslinked rubber compositions of Examples 1-5 and Comparative Examples 1-2 were heated and pressurized to produce sheet-like crosslinked rubber compositions, and their hardness was measured using a Type A durometer in accordance with JIS K6253-3:2012 as test specimens. [Industrial applicability]

[0052] The present invention is useful in the field of crosslinked rubber compositions and power transmission belts using the same. [Explanation of Symbols]

[0053] BV belt C Toothed belt 10,20 Belt body 101 Adhesive rubber layer 102 Compressed rubber layer 103 Stretchable rubber layer 11,21 Core wire 12,13,22 Reinforcement fabric 201 Back elastic section 202 Tooth rubber part

Claims

1. A crosslinked rubber composition obtained by crosslinking an uncrosslinked rubber composition, The aforementioned uncrosslinked rubber composition is a crosslinked rubber composition containing a first rubber component of ethylene-α-olefin elastomer in which the α-olefin is propylene, a second rubber component of ethylene-1-butenediene polymer, and an α,β-unsaturated carboxylic acid metal salt, The aforementioned α,β-unsaturated carboxylate metal salt is a crosslinked rubber composition containing zinc dimethacrylate.

2. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition wherein the ethylene content of the first rubber component is 40% by mass or more and 70% by mass or less.

3. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition in which the first rubber component comprises ethylene propylene dienterpolymer.

4. In the crosslinked rubber composition described in claim 3, A crosslinked rubber composition in which the diene component of the ethylene propylene dienterpolymer contained in the first rubber component is 5-ethylidene-2-nobornene, and the ENB content of the ethylene propylene dienterpolymer contained in the first rubber component is 4% by mass or more and 12% by mass or less.

5. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition wherein the ethylene content of the second rubber component is 40% by mass or more and 60% by mass or less.

6. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition in which the difference between the ethylene content of the first rubber component and the ethylene content of the second rubber component is 10% by mass or less.

7. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition in which the ethylene content of the second rubber component is less than the ethylene content of the first rubber component.

8. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition in which the diene component of the ethylene-1-butenediene polymer of the second rubber component is 5-ethylidene-2-nobornene, and the ENB content of the ethylene-1-butenediene polymer of the second rubber component is 4% by mass or more and 10% by mass or less.

9. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition in which the content of the first rubber component in the uncrosslinked rubber composition is greater than the content of the second rubber component.

10. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition in which the content of the α,β-unsaturated carboxylic acid metal salt in the uncrosslinked rubber composition is less than the content of the second rubber component.

11. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition wherein the uncrosslinked rubber composition further contains a tackifier.

12. In the crosslinked rubber composition described in claim 11, The crosslinked rubber composition includes a phenolic resin-based tackifier.

13. In the crosslinked rubber composition described in claim 11, A crosslinked rubber composition in which the mass ratio of the content of the tackifier in the uncrosslinked rubber composition to the content of the second rubber component is 0.08 or more and 0.25 or less.

14. In the crosslinked rubber composition described in claim 7, A crosslinked rubber composition in which the ethylene content ratio of the second rubber component to the ethylene content of the first rubber component is 0.9 or more and less than 1.

15. In the crosslinked rubber composition described in claim 3, A crosslinked rubber composition in which both the ethylene propylene dienterpolymer contained in the first rubber component and the ethylene-1-butene dienterpolymer of the second rubber component are 5-ethylidene-2-nobornene, and the difference between the ENB content of the ethylene propylene dienterpolymer contained in the first rubber component and the ENB content of the ethylene-1-butene dienterpolymer of the second rubber component is 2% by mass or less.

16. In the crosslinked rubber composition described in claim 3, A crosslinked rubber composition in which both the ethylene propylene dienterpolymer contained in the first rubber component and the ethylene-1-butene dienterpolymer of the second rubber component are 5-ethylidene-2-nobornene, and the ENB content of the ethylene-1-butene dienterpolymer of the second rubber component is less than the ENB content of the ethylene propylene dienterpolymer contained in the first rubber component.

17. In the crosslinked rubber composition described in claim 16, A crosslinked rubber composition in which the ENB content ratio of the ethylene-1-butene dienter polymer of the second rubber component to the ENB content of the ethylene propylene dienter polymer contained in the first rubber component is 0.8 or more and less than 1.

18. In the crosslinked rubber composition described in claim 9, A crosslinked rubber composition in which the mass ratio of the content of the first rubber component to the content of the second rubber component is greater than 50 / 50 and less than or equal to 95 / 5.

19. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition wherein the content of the α,β-unsaturated carboxylic acid metal salt in the uncrosslinked rubber composition is 5 parts by mass or more and 100 parts by mass or less based on the total content of the first and second rubber components (100 parts by mass).

20. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition wherein the mass ratio of the content of the α,β-unsaturated carboxylic acid metal salt in the uncrosslinked rubber composition to the content of the second rubber component is 0.4 or more and 2 or less.

21. In the crosslinked rubber composition described in claim 12, The crosslinked rubber composition contains an alkylphenol resin as the tackifier.

22. In the crosslinked rubber composition described in claim 11, A crosslinked rubber composition wherein the content of the tackifier in the uncrosslinked rubber composition is 1 part by mass or more and 10 parts by mass or less per 100 parts by mass of the total content of the first and second rubber components.

23. In the crosslinked rubber composition described in claim 11, A crosslinked rubber composition in which the tackifier has a softening point of 70°C or higher and 100°C or lower.

24. In the crosslinked rubber composition described in claim 1, A crosslinked rubber composition having a hardness of A86 or higher, as measured using a Type A durometer in accordance with JIS K6253-3:2012.

25. A power transmission belt, at least a portion of which is formed of the crosslinked rubber composition described in any one of claims 1 to 24.

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