Transmission v belt

Abstract

The present invention relates to a transmission V-belt, which is a transmission V-belt comprising a cured form of a first rubber composition, wherein the first rubber composition comprises a polymer component (A) containing an ethylene-α-olefin elastomer, a crosslinking agent (B) containing a sulfur-based crosslinking agent, and short fibers (C), wherein the short fibers (C) are oriented along the belt width direction, the rubber hardness (JIS-A) of the cured form is 91 degrees or more, and the elongation at break of the cured form in the belt length direction is 100% or more.

Description

Technical Field

[0001] This invention relates to V-belts for transmission comprising cured rubber compositions containing ethylene-α-olefin elastomers. Background Technology

[0002] Among V-belts that transmit power via friction, there are two types: raw-edge V-belts, where the friction drive surface (V-shaped side) is an exposed rubber layer, and wrapped V-belts, where the friction drive surface (V-shaped side) is covered by a cover fabric. These types are used according to their respective applications, depending on the surface properties of the friction drive surface (the coefficient of friction between the rubber layer and the cover fabric). Furthermore, among raw-edge belts, besides raw-edge V-belts without teeth, there are also raw-edge toothed V-belts with teeth only on the lower surface (inner circumference) to improve flexibility, and raw-edge toothed V-belts with teeth on both the lower (inner) and upper (outer) surfaces to improve flexibility (raw-edge double-sided toothed V-belts).

[0003] These V-belts are used in a wide range of fields, including automobiles and industrial machinery. Among them, the V-belts used in belt transmissions on self-propelled two-wheeled vehicles, snowmobiles, and large agricultural machinery are called transmission belts.

[0004] V-belts are used under high loads due to increased transmission capacity and the larger / higher horsepower of equipment. Therefore, to prevent buckling deformation (bending), it is necessary to improve the rigidity (resistance to lateral pressure) in the belt width direction of V-belts.

[0005] Especially for transmission belts, a high degree of lateral pressure resistance is required to withstand the harsh movements caused by pulley slippage. For example, for the large V-belts used in the power transmission mechanisms of the largest agricultural machinery (especially belt-driven transmissions), there are standard belts in the American Society of Agricultural Bioengineers (ASABE) equivalent to HL-HQ (as described in ISO 3410:1989), with a belt width (top width) of 44.5-76.2 mm and a belt thickness of 19.8-30.5 mm. There are also non-standard belts, for example, with a belt thickness of 36 mm. In such large agricultural machinery, to transmit enormous loads, very high tension needs to be applied to the V-belt, resulting in very high lateral pressure on the V-belt from the pulleys.

[0006] Furthermore, the transmission belt operates at a low temperature during startup, but becomes hot during operation due to engine heat. Therefore, a rubber composition capable of withstanding a wide temperature range from low to high is required. Additionally, transmission belts require high adhesion to prevent peeling of the rubber composition from the core or reinforcing fibers, and resistance to flexural fatigue to withstand stress concentration in the tooth valleys caused by repeated engagement and disengagement with the pulleys. Moreover, high abrasion resistance is also required to withstand wear caused by contact with the pulleys. Existing large V-belts struggle to meet these requirements.

[0007] As described above, in order to meet the various requirements for transmission V-belts, transmission V-belts using various rubber compositions containing chloroprene rubber and ethylene-α-olefin elastomer as polymer components have been proposed.

[0008] For example, Japanese Patent Application Publication No. 2012-241831 (Patent Document 1) discloses a transmission belt in which the compression rubber layer comprises fatty acid amide and short fibers. Examples of rubber components include chloroprene rubber and ethylene-α-olefin elastomers, and examples of vulcanizing agents or crosslinking agents include metal oxides, organic peroxides, and sulfur-based vulcanizing agents. Furthermore, in the examples, a toothed V-belt was made using a rubber composition comprising chloroprene rubber and sulfur. Moreover, examples (Example 7) show a rubber composition with a hardness of 94° and an elongation at break of 70% in the right-angle direction of the short fibers, and examples (Examples 1-6) show a rubber composition with a hardness of 86-88° and an elongation at break of 180-245% in the right-angle direction of the short fibers.

[0009] Furthermore, Japanese Patent Application Publication No. 2009-52740 (Patent Document 2) discloses a V-belt characterized in that the compression rubber layer is composed of an organic peroxide-based crosslinker of a rubber composition comprising 5 to 50 parts by mass of short fibers in 100 parts by mass of ethylene-α-olefin rubber with an ethylene content of 40 to 70% by mass, wherein the short fibers contain 5 to 40 parts by mass of poly(p-phenylenebenzodioxane). The belt contains PBO short fibers, and the elongation at break in the compression rubber layer is 70% or more. It is described that an elongation at break in the length direction of the belt is 70% or more, more preferably 200% or more. This property makes it difficult for the belt to crack, resulting in a belt with a longer service life. Furthermore, it is described that the hardness (JIS-A) of the substance formed by crosslinking the rubber composition can be in the range of 85 to 93. By setting the JIS-A hardness to 85 or more, the wear resistance of the belt can be significantly improved when combined with PBO short fibers. A hardness (JIS-A) exceeding 93 becomes too hard and easily cracks due to repeated bending, which is therefore undesirable. In this document, the crosslinking agent must be an organic peroxide; as a comparative example, an example of crosslinking with sulfur is described.

[0010] Furthermore, Japanese Patent Application Publication No. 2018-141554 (Patent Document 3) discloses a transmission belt comprising a cured rubber composition. This rubber composition includes a rubber component containing an ethylene-α-olefin elastomer, an α,β-unsaturated carboxylic acid metal salt, magnesium oxide, an organic peroxide, and an inorganic filler. The magnesium oxide is present in a proportion of 2 to 20 parts by mass relative to 100 parts by mass of the rubber component, and in a proportion of 5 parts by mass or more relative to 100 parts by mass of the α,β-unsaturated carboxylic acid metal salt. It is described that by forming such a configuration, the hardness and modulus of the cured rubber composition for the transmission belt can be improved without compromising cold resistance, heat resistance, adhesion, flexural fatigue resistance, or wear resistance. It is also stated that the rubber hardness (JIS-A) of the cured rubber composition can be 90 to 100 degrees. In this document, the crosslinking agent must also be an organic peroxide; the use of sulfur for crosslinking is not considered.

[0011] Existing technical documents

[0012] Patent documents

[0013] Patent Document 1: Japanese Patent Application Publication No. 2012-241831

[0014] Patent Document 2: Japanese Patent Application Publication No. 2009-52740

[0015] Patent Document 3: Japanese Patent Application Publication No. 2018-141554 Summary of the Invention

[0016] The problem that the invention aims to solve

[0017] As can be seen from Patent Documents 1-3, sulfur-based crosslinking has been widely used in chloroprene rubber, and organic peroxide-based crosslinking has been widely used in ethylene-α-olefin elastomers. The reasons are as follows: for chloroprene rubber, which has double bonds in its main chain, sulfur-based crosslinking is easy, and the cured product obtained by sulfur crosslinking exhibits excellent physical properties. In contrast, for ethylene-α-olefin elastomers, which do not have double bonds in their main chain, sulfur-based crosslinking is not effective, and the physical properties of the cured product cannot be sufficiently improved. Organic peroxides are effective in improving the physical properties of cured ethylene-α-olefin elastomers, but ethylene-α-olefin elastomers crosslinked with organic peroxides tend to become brittle, and when applied to V-belts for transmission, they are prone to cracking, requiring improvement. In particular, as disclosed in Patent Document 3, if α,β-unsaturated carboxylic acid metal salts and magnesium oxide are used to increase hardness and modulus, a contradictory relationship exists—promoting cracking—making it difficult to sufficiently improve the lifespan of transmission V-belts.

[0018] Therefore, the objective of this invention is to improve the resistance to bending fatigue and suppress cracking of a V-belt for transmission, which is a cured rubber composition containing ethylene-α-olefin elastomer as a polymer component, while ensuring resistance to lateral pressure, wear resistance, and adhesion to fibrous components such as short fibers, thereby increasing belt life.

[0019] Methods for solving problems

[0020] To achieve the aforementioned objectives, the inventors conducted in-depth research and discovered that by combining a polymer component (A) containing an ethylene-α-olefin elastomer, a crosslinking agent (B) containing a sulfur-based crosslinking agent, and short fibers (C), and by adjusting the hardness and elongation at break of the cured rubber composition in which the short fibers (C) are oriented along the belt width direction to a specific range, it is possible to provide a V-belt for transmission that ensures resistance to lateral pressure, abrasion resistance, and adhesion to fibrous components such as short fibers, while also improving resistance to flexural fatigue and suppressing cracking, thereby increasing belt life.

[0021] That is, the transmission V-belt of the present invention is a transmission V-belt comprising a cured form of a first rubber composition, wherein the first rubber composition comprises a polymer component (A) containing an ethylene-α-olefin elastomer, a crosslinking agent (B) containing a sulfur-based crosslinking agent, and short fibers (C), wherein the short fibers (C) are oriented along the belt width direction, the rubber hardness (JIS-A) of the cured form is 91 degrees or more, and the elongation at break of the cured form in the belt length direction is 100% or more. In the transmission V-belt, the matrix rubber hardness (JIS-A) of the cured rubber composition after removing the short fibers (C) from the rubber composition can be 83 degrees or more. The first rubber composition may further comprise a crosslinking accelerator (D). The crosslinking accelerator (D) may comprise a sulfur-containing crosslinking accelerator. The sulfur-containing crosslinking accelerator may comprise a sulfur-containing crosslinking accelerator having heterocycles containing oxygen and nitrogen. The first rubber composition may further comprise a co-crosslinking agent (E). The co-crosslinking agent (E) may comprise a bismaleimide compound. The first rubber composition may further include an adhesion improver (F). The proportion of the sulfur-based crosslinking agent may be 1.2 parts by mass or more relative to 100 parts by mass of the polymer component (A). The first rubber composition may further include a softener (G). The proportion of the softener (G) may be 0.1 to 10 parts by mass relative to 100 parts by mass of the polymer component (A). The transmission V-belt may have a compression rubber layer and / or an extension rubber layer formed from the cured product of the first rubber composition. The transmission V-belt may also have an adhesive rubber layer formed from the cured product of a second rubber composition, which may include a polymer component (a) containing an ethylene-α-olefin elastomer and a crosslinking agent (b) containing a sulfur-based crosslinking agent. The transmission V-belt may be a serrated V-belt with teeth at least on the inner circumferential side. The transmission V-belt may be a speed-changing belt. The average thickness of the transmission V-belt as a whole may be 19.8 to 36 mm. The transmission V-belt may be a serrated V-belt used in a layout including reverse bending.

[0022] Invention Effects

[0023] In the V-belt for transmission of the present invention, the hardness and elongation at break of the cured rubber composition, which combines a polymer component (A) containing an ethylene-α-olefin elastomer, a crosslinking agent (B) containing a sulfur-based crosslinking agent, and short fibers (C), and in which the short fibers (C) are oriented along the belt width direction, are adjusted to a specific range. Therefore, while ensuring resistance to lateral pressure, abrasion resistance, and adhesion to fibrous components such as short fibers, it is possible to improve resistance to flexural fatigue and suppress cracking, thereby increasing belt life. In particular, the V-belt for transmission of the present invention exhibits excellent resistance to flexural fatigue; therefore, even when used in a layout including so-called "reverse bending" where the back side of the V-belt is bent inwards, cracking can be effectively prevented. Furthermore, in the gearboxes of large agricultural machinery requiring high horsepower and significant thickness, high resistance to lateral pressure and flexural fatigue is required; the V-belt for transmission of the present invention demonstrates high durability and increases belt life. Therefore, the V-belt for transmission of the present invention is suitable for use as a gearbox, and is most suitable for use as a gearbox for large agricultural machinery. Attached Figure Description

[0024] Figure 1 This is a schematic partial cross-sectional perspective view showing an example of the transmission V-belt (cut-edge toothed V-belt) of the present invention.

[0025] Figure 2 It is Figure 1 A schematic cross-sectional view of a V-belt used for transmission cut along its length.

[0026] Figure 3 This is a schematic perspective view illustrating the method for determining the 8% flexural stress of the cross-linked rubber molded body obtained in the examples.

[0027] Figure 4 This is a schematic perspective view of the double-toothed V-belt fabricated in the embodiment.

[0028] Figure 5 This is a schematic diagram showing the layout of the biaxial durability running test of the transmission V-belt obtained in the embodiment.

[0029] Figure 6 This is a schematic diagram showing the layout of the reverse bending durability test of the transmission V-belt obtained in the embodiment.

[0030] Figure 7 This is a schematic diagram illustrating the method for determining the reverse bending crack test of the transmission V-belt obtained in the embodiments. Detailed Implementation

[0031] [Rubber Composition]

[0032] The transmission V-belt of the present invention comprises a cured rubber composition (first rubber composition) comprising a polymer component (A) containing an ethylene-α-olefin elastomer, a crosslinking agent (B) containing a sulfur-based crosslinking agent, and short fibers (C).

[0033] (A) Polymer composition

[0034] From the perspective of excellent cold resistance, heat resistance and weather resistance, polymer component (A) contains ethylene-α-olefin elastomer (first ethylene-α-olefin elastomer).

[0035] In ethylene-α-olefin elastomers, the structural units can include ethylene units, α-olefin units, and may also include diene units. Therefore, ethylene-α-olefin elastomers include ethylene-α-olefin copolymer rubbers, ethylene-α-olefin-diene terpolymer rubbers, etc.

[0036] Examples of α-olefins used to form α-olefin units include, for example, propylene, butene, pentene, methylpentene, hexene, octene, and other chain-like α-olefins. 3-12 Alkenes, etc. Among these α-olefins, α-C olefins such as propylene are preferred. 3-4 Olefins (especially propylene).

[0037] Non-conjugated diene monomers are typically used as diene monomers to form diene units. Examples of non-conjugated diene monomers include dicyclopentadiene, methylene norbornene, ethylidene norbornene, 1,4-hexadiene, and cyclooctadiene. Among these diene monomers, ethylidene norbornene and 1,4-hexadiene (especially ethylidene norbornene) are preferred.

[0038] Representative examples of ethylene-α-olefin elastomers include: ethylene-α-olefin rubbers [ethylene-propylene rubber (EPM), ethylene-butene rubber (EBM), ethylene-octene rubber (EOM), etc.], ethylene-α-olefin-diene rubbers [ethylene-propylene-diene terpolymer (EPDM)], etc.

[0039] These ethylene-α-olefin elastomers can be used alone or in combination of two or more. Among them, ethylene-α-C is preferred from the viewpoint of excellent cold resistance, heat resistance, and weather resistance. 3-4 Ethylene-α-olefin-diene terpolymer rubbers, such as olefin-diene terpolymer rubbers, are particularly preferred, especially EPDM. Therefore, the proportion of EPDM relative to the total ethylene-α-olefin elastomer can be 50% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more (especially 95% by mass or more), and can also be 100% by mass (EPDM only).

[0040] In ethylene-α-olefin elastomers, the ratio (mass ratio) of ethylene to α-olefin can be 40 / 60 to 90 / 10, preferably 45 / 55 to 85 / 15 (e.g., 50 / 50 to 80 / 20), and more preferably 52 / 48 to 70 / 30. Particularly in ethylene-propylene-diene terpolymers, the ratio (mass ratio) of ethylene to propylene can be 35 / 65 to 90 / 10, preferably 40 / 60 to 80 / 20, more preferably 45 / 55 to 70 / 30, and most preferably 50 / 50 to 60 / 40.

[0041] The diene content of ethylene-α-olefin elastomers (especially ethylene-α-olefin-diene terpolymer rubbers such as EPDM) can be 15% by mass or less (e.g., 0.1 to 15% by mass), preferably 10% by mass or less (e.g., 0.3 to 10% by mass), more preferably 5% by mass or less (e.g., 0.5 to 5% by mass), more preferably 4% by mass or less (e.g., 1 to 4% by mass), and most preferably 3% by mass or less (e.g., 1 to 3% by mass). Excessive diene content may compromise high heat resistance.

[0042] It should be noted that, in this application, diene content refers to the mass ratio of diene monomer units in all units constituting the ethylene-α-olefin elastomer, which can be determined by conventional methods or based on the monomer ratio.

[0043] The iodine value of the ethylene-α-olefin elastomer containing diene units is, for example, 3 to 40, preferably 5 to 30, and more preferably 10 to 20. If the iodine value is too low, the crosslinking of the rubber composition is insufficient, which can easily lead to wear and adhesion; conversely, if the iodine value is too high, the rubber composition tends to scorch and shorten, making it difficult to handle and reducing its heat resistance.

[0044] It should be noted that, in this application, the iodine value of the ethylene-α-olefin elastomer can be determined by conventional methods, such as infrared spectroscopy.

[0045] The Mooney viscosity [ML(1+4)125°C] of the uncrosslinked ethylene-α-olefin elastomer can be 80 or less, for example, 10 to 80, preferably 20 to 70, more preferably 30 to 50, and most preferably 35 to 45. If the Mooney viscosity is too high, the flowability of the rubber composition may decrease, and the processability during mixing may be reduced.

[0046] It should be noted that in this application, the Mooney viscosity can be determined according to the method of JIS K 6300-1 (2013), with the following test conditions: using an L-shaped rotor, the test temperature is 125°C, preheating for 1 minute, and rotor working time is 4 minutes.

[0047] The proportion of ethylene-α-olefin elastomer in polymer component (A) should be 50% by mass or more, preferably 80% by mass or more, further preferably 90% by mass or more, and most preferably 100% by mass (ethylene-α-olefin elastomer only). If the proportion of ethylene-α-olefin elastomer in the polymer component is too low, the heat resistance and cold resistance may decrease.

[0048] Within the scope of not impairing the effects of the present invention, polymer component (A) may contain other rubber components besides ethylene-α-olefin elastomer, such as diene rubbers [e.g., natural rubber, isoprene rubber, butadiene rubber, chloroprene rubber, styrene-butadiene rubber (SBR), vinylpyridine-styrene-butadiene copolymer rubber, acrylonitrile-butadiene rubber (nitrile rubber); hydrogenated nitrile rubber (including a mixed polymer of hydrogenated nitrile rubber and unsaturated carboxylic acid metal salts), etc., hydrides of the above diene rubbers], olefin rubbers (e.g., polyoctene rubber, ethylene-vinyl acetate copolymer rubber, chlorosulfonated polyethylene rubber, alkylated chlorosulfonated polyethylene rubber, etc.), epichlorohydrin rubber, acrylic rubber, silicone rubber, polyurethane rubber, fluororubber, etc.

[0049] The proportion of other rubber components in polymer component (A) can be 50% by mass or less, preferably 20% by mass or less, and more preferably 10% by mass or less.

[0050] (B) Crosslinking agent (vulcanizing agent)

[0051] The crosslinking agent (B) comprises a sulfur-based crosslinking agent (a first sulfur-based crosslinking agent). In the prior art, organic peroxides are used as crosslinking agents for ethylene-α-olefin elastomers. However, in this invention, by using a sulfur-based crosslinking agent to crosslink the ethylene-α-olefin elastomer, the flexural fatigue resistance (cracking resistance) of the cured product can be improved.

[0052] Examples of sulfur-based crosslinking agents include: powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, highly dispersed sulfur, and sulfur chlorides (sulfur monochloride, sulfur dichloride, etc.). These sulfur-based crosslinking agents can be used alone or in combination of two or more. Among these, powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersed sulfur are preferred, with powdered sulfur being particularly preferred.

[0053] The proportion of the sulfur-based crosslinking agent relative to 100 parts by mass of polymer component (A) can be selected from, for example, about 1 part by mass to about 10 parts by mass, preferably 1.2 parts by mass or more, for example 1.2 to 5 parts by mass, more preferably 1.3 to 3 parts by mass, further preferably 1.5 to 2.5 parts by mass, more preferably 1.6 to 2.3 parts by mass, and most preferably 1.8 to 2.2 parts by mass. If the proportion of the sulfur-based crosslinking agent is too low, the hardness, resistance to lateral pressure, and abrasion resistance of the rubber may decrease; if it is too high, not only may the resistance to flexural fatigue decrease, but blooming (precipitation on the surface) may also occur.

[0054] The crosslinking agent (B) may also contain organic peroxides as other crosslinking agents (or vulcanizing agents). Examples of organic peroxides commonly used in the crosslinking of rubber and resins include diacid peroxides, peroxide esters, and dialkyl peroxides (e.g., dicumyl peroxide, tert-butylcumyl peroxide, 1,1-dibutylperoxy-3,3,5-trimethylcyclohexane, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, 1,3-bis(tert-butylperoxyisopropyl)benzene, di-tert-butyl peroxide, etc.). These organic peroxides can be used alone or in combination of two or more. Furthermore, the organic peroxides are preferably those with a decomposition temperature of about 150 to about 250°C (e.g., about 175°C to about 225°C) due to thermal decomposition and a half-life of about 1 minute.

[0055] The proportion of organic peroxide relative to 100 parts by weight of sulfur-based crosslinking agent can be 100 parts by weight or less, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less. Excessive proportion of organic peroxide may reduce the flexural fatigue resistance of the cured product. Crosslinking agent (B) is particularly preferably substantially free of organic peroxide, and most preferably free of organic peroxide.

[0056] The proportion of sulfur-based crosslinking agent in crosslinking agent (B) can be 50% by mass or more, preferably 70% by mass or more, further preferably 90% by mass or more, and more preferably 100% by mass. If the proportion of sulfur-based crosslinking agent is too low, the flexural fatigue resistance of the cured product may decrease.

[0057] The proportion of crosslinking agent (B) relative to 100 parts by mass of polymer component (A) can be selected from, for example, about 1 part by mass to about 10 parts by mass, for example, 1.2 to 10 parts by mass, preferably 1.3 to 8 parts by mass, further preferably 1.5 to 5 parts by mass, more preferably 1.6 to 3 parts by mass, and most preferably 1.8 to 2.5 parts by mass.

[0058] (C) Short fiber

[0059] As a short fiber (C), it is widely used for example: polyolefin fibers (polyethylene fibers, polypropylene fibers, etc.), polyamide fibers (e.g., aliphatic polyamide fibers such as polyamide 6 fibers, polyamide 66 fibers, polyamide 46 fibers, etc.; polyaramid fibers, etc.), and polyalkylene aryl fibers [e.g., polyethylene terephthalate (PET) fibers, polyethylene naphthalate (PEN) fibers, etc.]. 2-4 Alkylene C 6-14 [Aromatic ester fibers, etc.], vinylon fibers, polyvinyl alcohol fibers, poly(p-phenylene benzo[2]) Synthetic fibers such as PBO fiber; natural fibers such as cotton, linen, and wool; and inorganic fibers such as carbon fiber.

[0060] These short fibers can be used alone or in combination of two or more. Among these short fibers, synthetic fibers (e.g., polyamide fibers, polyalkylene aryl fibers, etc.) are widely used, with polyamide fibers being preferred. From the viewpoint of rigidity and high strength, modulus, and easy protrusion on the surface, short fibers containing at least polyaramid fibers are further preferred. From the viewpoint of an excellent balance of various properties, a combination of polyaramid fibers and aliphatic polyamide fibers is more preferred. Polyaramid fibers are commercially available, for example, under trade names such as "Conex," "Nomex," "Kevlar," "Technora," and "Twaron."

[0061] When the short fibers are a combination of polyaramid fibers and aliphatic polyamide fibers, the proportion of aliphatic polyamide fibers relative to 100 parts by weight of polyaramid fibers can be less than 100 parts by weight, for example, 1 to 100 parts by weight, preferably 5 to 80 parts by weight, more preferably 10 to 70 parts by weight, and more preferably 30 to 60 parts by weight. Excessive proportion of aliphatic polyamide fibers may reduce the rigidity of the cured product.

[0062] The average fineness of the short fibers (C) is, for example, 0.1 to 50 dtex, preferably 1 to 10 dtex, more preferably 1.5 to 5 dtex, and even more preferably 2 to 3 dtex. If the average fineness is too high, the mechanical properties in the cured rubber composition may be reduced; if it is too low, it may be difficult to disperse uniformly.

[0063] The average length of the short fibers (C) is, for example, 1 to 20 mm, preferably 1.2 to 15 mm (e.g., 1.5 to 10 mm), more preferably 2 to 5 mm, and even more preferably 2.5 to 4 mm. If the average length of the short fibers is too short, the mechanical properties (e.g., modulus) in the orientation direction (texture direction) of the short fibers may not be sufficiently improved; conversely, if it is too long, the dispersibility of the short fibers in the rubber composition may decrease, and the resistance to flexural fatigue may decrease.

[0064] From the viewpoint of the dispersibility and adhesiveness of short fibers in the rubber composition, it is preferable that at least the short fibers undergo adhesive treatment (or surface treatment). It should be noted that it is not necessary for all short fibers to undergo adhesive treatment; adhesive-treated short fibers and untreated short fibers (untreated short fibers) can be mixed or combined.

[0065] In the bonding treatment of short fibers (C), various bonding treatments can be performed, such as treatment solutions containing an initial condensate of phenols and formalin (prepolymers of phenolic or methyl phenolic resins, etc.), treatment solutions containing rubber components (or latex), treatment solutions containing the aforementioned initial condensate and rubber components (latex), and treatment solutions containing reactive compounds (adhesive compounds) such as silane coupling agents, epoxy compounds (epoxy resins, etc.), and isocyanate compounds. In a preferred bonding treatment, the short fibers are treated with the aforementioned treatment solution containing the initial condensate and rubber components (latex), particularly with at least a resorcinol-formaldehyde-latex (RFL) solution. Such treatment solutions can be used in combination; for example, the short fibers can be pretreated with conventional adhesive components, such as epoxy compounds (epoxy resins, etc.) and reactive compounds (adhesive compounds) such as isocyanate compounds, and then treated with an RFL solution.

[0066] The proportion of short fibers (C) relative to 100 parts by mass of polymer component (A) is, for example, 5 to 100 parts by mass, preferably 10 to 50 parts by mass, more preferably 20 to 40 parts by mass, and more preferably 25 to 35 parts by mass. If the proportion of short fibers is too low, the mechanical properties of the cured rubber composition may be reduced; conversely, if the proportion is too high, it may be difficult to disperse uniformly, and the flexural fatigue resistance may be reduced.

[0067] In this invention, by orienting the short fibers (C) along the width direction of the belt and making the texture direction of the short fibers (C) the width direction of the belt, the hardness and rigidity of the polymer component (A) can be improved, and the resistance to lateral pressure of the belt can be improved.

[0068] It should be noted that in this application, "texture direction" is not only the length direction of the short fiber, but can also be a direction within ±5° of the length direction. Therefore, "texture direction" can also refer to "a direction that is approximately parallel to the length direction of the short fiber", and "texture direction is the width direction" can also be called "texture direction is approximately parallel to the width direction".

[0069] (D) Crosslinking accelerator

[0070] The rubber composition may also contain a crosslinking accelerator (D). In addition, in combination with sulfur-based crosslinking agents, from the viewpoint of maximizing the crosslinking promotion effect, it is preferable that the crosslinking accelerator (D) includes a sulfur-containing crosslinking accelerator (a first sulfur-containing crosslinking accelerator).

[0071] Examples of sulfur-containing crosslinking accelerators include: thiuram accelerators [e.g., tetramethylthiuram monosulfide (TMTM), tetramethylthiuram disulfide (TMTD), tetraethylthiuram disulfide (TETD), tetrabutylthiuram disulfide (TBTD), bispentamethylenethiuram tetrasulfide (DPTT), etc.], sulfenamide accelerators [e.g., N-cyclohexyl-2-benzothiazole sulfenamide (CBS), N-tert-butyl-2-benzothiazole sulfenamide (TBBS), etc.], and thiomorpholine accelerators [e.g., 4,4'-dithiodimorpholine (DTD)]. M), 2-(4'-morpholinodithio)benzothiazole, etc.; thiazole accelerators [e.g., 2-mercaptobenzothiazole (MBT), zinc salt of MBT, 2-mercaptobenzothiazole dibenzothiazole disulfide (MBTS), etc.]; thiourea accelerators [e.g., ethylidene thiourea, trimethylthiourea (TMU), diethylthiourea (EDE), etc.]; dithiocarbamate accelerators [e.g., sodium dimethyl dithiocarbamate, zinc diethyl dithiocarbamate (EZ), zinc dibutyl dithiocarbamate (BZ), etc.]; xanthate accelerators (e.g., zinc isopropyl xanthate), etc.], etc.

[0072] These sulfur-containing crosslinking accelerators can be used alone or in combination of two or more. Among these sulfur-based crosslinking accelerators, from the viewpoint of suppressing scorching and improving the hardness of the cured product, it is preferable to include […]. Sulfur-containing crosslinking accelerators, such as azoles, furazolidone, and morpholine, which contain heterocycles containing oxygen and nitrogen (especially thiomorpholine accelerators), are sulfur-containing crosslinking accelerators.

[0073] The sulfur-containing crosslinking accelerator containing a sulfur-containing heterocycle containing oxygen and nitrogen can be a combination of a sulfur-containing crosslinking accelerator containing a sulfur-containing heterocycle containing oxygen and nitrogen (especially thiomorpholine accelerators) and other sulfur-containing crosslinking accelerators (especially thiuram accelerators and / or sulfenamide accelerators), with a mass ratio of the former / the latter of 99 / 1 to 10 / 90, preferably 95 / 5 to 20 / 80, more preferably 90 / 10 to 30 / 70, more preferably 80 / 20 to 50 / 50, and most preferably 70 / 30 to 60 / 40.

[0074] In addition to sulfur-containing crosslinking accelerators, crosslinking accelerators (D) may also include sulfur-free crosslinking accelerators.

[0075] Examples of sulfur-free crosslinking accelerators include: guanidine accelerators [e.g., diphenylguanidine (DPG), di-o-tolylguanidine (DOTG), etc.], aldehyde-amine or aldehyde-amine accelerators [e.g., hexamethylenetetramine, etc.].

[0076] The proportion of sulfur-free crosslinking accelerator relative to 100 parts by weight of sulfur-containing crosslinking accelerator can be 100 parts by weight or less, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less. If the proportion of sulfur-free crosslinking accelerator is too high, the scorch inhibition effect may be reduced.

[0077] The proportion of sulfur-containing crosslinking accelerator in the crosslinking accelerator (D) can be 50% by mass or more, preferably 70% by mass or more, further preferably 90% by mass or more, and more preferably 100% by mass. If the proportion of sulfur-containing crosslinking accelerator is too low, the scorch inhibition effect may be reduced.

[0078] The proportion of the crosslinking accelerator (D) relative to 100 parts by mass of the polymer component (A) can be selected from, for example, from about 0.1 parts by mass to about 10 parts by mass, for example, from 0.5 to 8 parts by mass, preferably from 1 to 7 parts by mass, further preferably from 1.5 to 5 parts by mass, more preferably from 2 to 4 parts by mass, and most preferably from 2.5 to 3.5 parts by mass.

[0079] The proportion of the sulfur-containing crosslinking accelerator having heterocycles containing oxygen and nitrogen relative to 100 parts by mass of polymer component (A) is, for example, 0.1 to 5 parts by mass, preferably 0.3 to 4 parts by mass, more preferably 0.5 to 3 parts by mass, more preferably 1 to 2.5 parts by mass, and most preferably 1.5 to 2 parts by mass.

[0080] (E) Co-crosslinking agent (crosslinking aid)

[0081] The rubber composition may also contain a co-crosslinking agent (E). In addition, from the viewpoint of improving lateral pressure resistance and abrasion resistance, it is preferable that the co-crosslinking agent (E) contains a bismaleimide compound.

[0082] Examples of bismaleimide compounds include: aliphatic bismaleimides (e.g., N,N'-1,2-ethylidene bismaleimide, 1,6'-bismaleimide-(2,2,4-trimethyl)cyclohexane, etc.), aromatic bismaleimides {e.g., N,N'-m-phenylene bismaleimide, 4-methyl-1,3-phenylene bismaleimide, 4,4'-diphenylmethane bismaleimide, 2,2-bis[4-(4-maleimidephenoxy)phenyl]propane, 4,4'-diphenyl ether bismaleimide, 4,4'-diphenyl sulfone bismaleimide, 1,3-bis(3-maleimidephenoxy)benzene, etc.}, etc.

[0083] These bismaleimide compounds can be used alone or in combination of two or more. Among them, aromatic bismaleimides (aromatic bismaleimides) such as N,N'-m-phenylene bismaleimide are preferred from the viewpoint of excellent heat resistance.

[0084] In addition to bismaleimide compounds, co-crosslinking agents (E) may also include other co-crosslinking agents.

[0085] Other co-crosslinking agents include, for example, polyfunctional (iso)cyanurates [e.g., triallyl isocyanurate (TAIC), triallyl cyanurate (TAC), etc.], polydienes (e.g., 1,2-polybutadiene), metal salts of α,β-unsaturated carboxylic acids [e.g., zinc (meth)acrylate, magnesium (meth)acrylate, etc.], oximes (e.g., quinone dioxime), guanidines (e.g., diphenylguanidine), polyfunctional (meth)acrylates [e.g., ethylene glycol di(meth)acrylate, butanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, etc.], etc.

[0086] The proportion of other co-crosslinking agents relative to 100 parts by weight of the bismaleimide compound can be 100 parts by weight or less, preferably 50 parts by weight or less, more preferably 30 parts by weight or less, and even more preferably 10 parts by weight or less. Excessive proportion of other co-crosslinking agents may reduce the improvement effect on lateral pressure resistance and wear resistance. From the viewpoint of improving flexural fatigue resistance, the co-crosslinking agent (E) is particularly preferably free of metal salts of α,β-unsaturated carboxylic acids such as zinc (meth)acrylate, and most preferably free of metal salts of α,β-unsaturated carboxylic acids.

[0087] The proportion of bismaleimide compound in the co-crosslinking agent (E) can be 50% by mass or more, preferably 70% by mass or more, further preferably 90% by mass or more, and more preferably 100% by mass. If the proportion of bismaleimide compound is too low, the effect of improving lateral pressure resistance and wear resistance may be reduced.

[0088] The proportion of the co-crosslinking agent (E) relative to 100 parts by mass of the polymer component (A) can be selected from, for example, about 0.1 parts by mass to about 10 parts by mass, such as 0.3 to 8 parts by mass, preferably 0.5 to 5 parts by mass, more preferably 0.8 to 4 parts by mass, more preferably 1 to 3 parts by mass, and most preferably 1.5 to 2.5 parts by mass. If the proportion of the co-crosslinking agent (E) is too low, the wear resistance may be reduced; if it is too high, the flexural fatigue resistance may be reduced.

[0089] (F) Adhesion improver

[0090] From the viewpoint of improving the adhesion between the polymer component (A) and the fiber components (the short fibers (C), the core, the reinforcing fabric, etc., described later), the rubber composition may also contain an adhesion improver (F).

[0091] Examples of adhesive modifiers (F) include: resorcinol-formaldehyde resins (condensates of resorcinol and formaldehyde), amino resins [condensates of nitrogen-containing cyclic compounds and formaldehyde, such as melamine resins like hexamethylol melamine, hexaalkoxymethyl melamine (hexamethoxymethyl melamine, hexabutoxymethyl melamine, etc.), urea resins like hydroxymethyl urea, benzoguanamine resins like hydroxymethyl benzoguanamine resin], and their co-condensates (resorcinol-melamine-formaldehyde co-condensates, etc.). Resorcinol-formaldehyde resins, amino resins, and the aforementioned co-condensates can be initial condensates (prepolymers) of nitrogen-containing cyclic compounds such as resorcinol and / or melamine with formaldehyde.

[0092] These adhesion improvers (F) can be used alone or in combination of two or more. Among them, resorcinol-formaldehyde resin and melamine resin are preferred, with resorcinol-formaldehyde resin being particularly preferred.

[0093] The proportion of the adhesiveness improver (F) relative to 100 parts by mass of the polymer component (A) can be selected from, for example, about 0.1 parts by mass to about 10 parts by mass, for example, 0.3 to 8 parts by mass, preferably 0.5 to 5 parts by mass, further preferably 0.8 to 4 parts by mass, more preferably 1 to 3 parts by mass, and most preferably 1.5 to 2.5 parts by mass.

[0094] (G) Softeners (oils)

[0095] From the viewpoint of improving resistance to flexural fatigue, rubber compositions may also contain a softener (G) as an oil (oil component). The softener (G) can be a so-called plasticizer.

[0096] Examples of softeners (G) include: mineral oil softeners {e.g., petroleum softeners [paraffin oils, alicyclic oils (cycloalkanes), aromatic oils, etc.], coal tar softeners [coal tar, coumarone-indene resin, etc.], etc.}, vegetable oil softeners {e.g., fatty oil softeners [stearic acid, stearic acid metal salts, and other fatty acids or their metal salts; stearates and other fatty acid esters; stearamides and other fatty acid amides; fatty oils, etc.]; to Softeners derived from pine trees [pine tar, rosin, oil gum (oil paste), etc.], synthetic softeners {e.g., synthetic resin softeners [hydrocarbon synthetic oils (low molecular weight paraffin, low molecular weight wax, phenolic resin, liquid ethylene-α-olefin copolymer, etc.), liquid rubber (liquid polybutene, liquid polybutadiene, liquid isoprene rubber, etc.)], synthetic plasticizers (dioctyl phthalate and other phthalates, polyester plasticizers, dioctyl sebacate, etc. C 6-18 Alkane dicarboxylic acid esters, etc.

[0097] These softeners (G) can be used alone or in combination of two or more. Among them, petroleum-based softeners such as paraffin oils and C-type softeners such as stearic acid are preferred. 8-24 Fatty acids (including their metal salts, esters, and amides), with petroleum-based softeners and C being particularly preferred. 8-24 Combinations of fatty acids.

[0098] In the case of softener (G) being a petroleum-based softener and C 8-24 In the case of a combination of fatty acids, C 8-24 The proportion of fatty acids relative to 100 parts by weight of petroleum softener is, for example, 1 to 100 parts by weight, preferably 3 to 80 parts by weight, more preferably 5 to 50 parts by weight, and even more preferably 10 to 30 parts by weight.

[0099] From the viewpoint of improving resistance to lateral pressure and wear, the proportion of the softener (G) relative to 100 parts by mass of the polymer component (A) can be 10 parts by mass or less (e.g., 0.1 to 10 parts by mass, particularly 5 parts by mass or less), for example 0 to 8 parts by mass, preferably 0.1 to 6 parts by mass, further preferably 0.3 to 5 parts by mass, more preferably 0.5 to 4 parts by mass, and most preferably 1 to 3 parts by mass.

[0100] (H) Inorganic fillers (fillers)

[0101] The rubber composition may also contain inorganic fillers (H). Examples of inorganic fillers (H) include: carbonaceous materials (carbon black, graphite, etc.), metal compounds or synthetic ceramics (metal oxides such as magnesium oxide, calcium oxide, barium oxide, iron oxide, copper oxide, zinc oxide, titanium oxide, and aluminum oxide; metal silicates such as calcium silicate and aluminum silicate; metal carbides such as silicon carbide and tungsten carbide; metal nitrides such as titanium nitride, aluminum nitride, and boron nitride; metal carbonates such as magnesium carbonate and calcium carbonate; metal sulfates such as calcium sulfate and barium sulfate), and mineral materials (zeolite, diatomaceous earth, calcined diatomaceous earth, activated clay, alumina, silica, talc, mica, kaolin, sericite, bentonite, montmorillonite, saponite, clay, etc.). These inorganic fillers may be used alone or in combination of two or more.

[0102] Among these inorganic fillers, carbonaceous materials such as carbon black (first carbon black), metal oxides such as magnesium oxide and zinc oxide (first metal oxide), and mineral materials such as silicon dioxide (first silicon dioxide) are preferred. From the viewpoint of improving hardness, modulus and wear resistance, it is particularly preferred that the rubber composition contains at least carbon black.

[0103] Examples of carbon blacks include SAF, ISAF, HAF, FEF, GPF, and HMF. These carbon blacks can be used alone or in combination of two or more. Among them, HAF is preferred from the viewpoint of achieving a good balance between reinforcing effect and dispersibility, and improving wear resistance.

[0104] The average particle size of carbon black can be selected from, for example, the range of about 5 nm to about 200 nm, such as about 10 nm to about 150 nm, preferably about 15 nm to about 100 nm, and more preferably about 20 nm to about 80 nm (especially about 30 nm to about 50 nm). If the average particle size of carbon black is too small, it may be difficult to disperse it uniformly; if it is too large, the hardness, modulus and wear resistance may be reduced.

[0105] Silica includes dry silica, wet silica, and surface-treated silica. Furthermore, silica can be classified according to its manufacturing method, such as dry-process silica, wet-process silica, colloidal silica, precipitated silica, and gel-process silica (silica gel). These silicas can be used alone or in combination of two or more. From the viewpoint of having a high number of surface silanol groups and strong chemical bonding with rubber, wet-process silica, with hydrated silicic acid as its main component, is preferred.

[0106] The average particle size of silica is, for example, 1–1000 nm, preferably 3–300 nm, more preferably 5–100 nm, and even more preferably 10–50 nm. If the particle size of silica is too large, the mechanical properties of the rubber may be reduced; if it is too small, it may be difficult to disperse uniformly.

[0107] In addition, silica can be either non-porous or porous, and the nitrogen adsorption specific surface area based on the BET method is, for example, 50–400 m². 2 / g, preferably 70-350m 2 / g, further preferably 100-300m 2 / g, more preferably 150-250m 2 / g. When the specific surface area is too large, it may be difficult to disperse evenly; when the specific surface area is too small, the mechanical properties of the rubber may be reduced.

[0108] The total proportion of inorganic filler (H) relative to 100 parts by weight of the polymer component (A) can be selected from about 10 parts by weight to about 150 parts by weight, for example, 40 to 100 parts by weight, preferably 50 to 90 parts by weight, and more preferably 70 to 80 parts by weight. If the proportion of inorganic filler (H) is too low, the hardness, modulus, and abrasion resistance of the cured rubber composition may decrease; conversely, if the proportion is too high, the flexural fatigue resistance may decrease.

[0109] When the inorganic filler (H) contains carbon black and metal oxides, the proportion of metal oxides relative to 100 parts by mass of carbon black is, for example, 1 to 100 parts by mass, preferably 3 to 50 parts by mass, more preferably 5 to 30 parts by mass, and most preferably 10 to 20 parts by mass.

[0110] (I) Other ingredients

[0111] The rubber composition may also contain other components (I). Examples of other components (I) include commonly used additives compounded in rubber, such as crosslinking delay agents, anti-aging agents (antioxidants, heat aging agents, flexural cracking agents, ozone deterioration agents, etc.), colorants, tackifiers, lubricants, coupling agents (silane coupling agents, etc.), stabilizers (UV absorbers, heat stabilizers, etc.), flame retardants, and antistatic agents. These additives may be used alone or in combination of two or more. Among them, general-purpose anti-aging agents (primary anti-aging agents), etc.

[0112] The total proportion of other components (I) relative to 100 parts by mass of the polymer component (A) is, for example, 0.1 to 15 parts by mass, preferably 0.3 to 10 parts by mass, and more preferably 0.5 to 7 parts by mass. The proportion of the anti-aging agent relative to 100 parts by mass of the polymer component (A) is, for example, 0.1 to 5 parts by mass, preferably 0.2 to 3 parts by mass, and more preferably 0.3 to 1 part by mass.

[0113] (J) Properties of cured rubber compositions

[0114] Although the cured rubber composition described above has high rubber hardness and modulus, it also possesses the elongation at break required for transmission V-belts. In other words, the cured composition achieves a balance between improved rubber hardness and modulus and resistance to flexural fatigue. For example, in Patent Document 1, examples with high hardness have low elongation at break, while examples with high elongation at break have low hardness, failing to achieve a balance of these properties. In contrast, in this invention, by balancing these properties, resistance to lateral pressure, wear resistance, and resistance to flexural fatigue can be simultaneously improved, thereby enhancing the durability of the transmission V-belt.

[0115] Specifically, the hardness (JIS-A) of the cured product of the above-mentioned rubber composition [the hardness of the rubber containing short fibers (C) in the cured product] is 91 degrees or more, for example, 91 to 98 degrees, preferably 91.5 to 97 degrees, more preferably 92 to 96 degrees, more preferably 92.5 to 95 degrees, and most preferably 93 to 94 degrees. When the hardness of the rubber containing short fibers is too low, the resistance to lateral pressure and abrasion is reduced.

[0116] The cured rubber composition of the above-mentioned rubber composition, including the short fiber (C) removed rubber composition [the short fiber (C) excluding rubber composition], also has a high rubber hardness (base rubber hardness). The base rubber hardness (JIS-A) can be 83 degrees or higher, for example, 83 to 95 degrees, preferably 83.5 to 93 degrees, more preferably 84 to 90 degrees, more preferably 85 to 89 degrees, and most preferably 86 to 88 degrees. If the base rubber hardness is too low, the resistance to lateral pressure and abrasion may decrease.

[0117] The difference in hardness between the short-fiber rubber and the matrix rubber can be less than 10 degrees, preferably less than 9.5 degrees, more preferably less than 9 degrees, more preferably less than 8 degrees, and most preferably less than 7 degrees. If the difference is too large, the wear resistance of the rubber may be reduced.

[0118] It should be noted that in this application, the rubber hardness (JIS-A) is measured according to JIS K 6253 (2012) for the cured product that has been pressed and crosslinked for 20 minutes at a temperature of 170°C and a pressure of 2 MPa. Specifically, the measurement is performed by the method described in the examples below.

[0119] The cured product of the above-mentioned rubber composition [cured product containing short fibers (C)] has an elongation at break of 100% or more in the strip length direction, for example, 100-200%, preferably 101-180%, more preferably 102-160%, more preferably 103-150%, and most preferably 104-130%. If the elongation at break is too low, the resistance to flexural fatigue decreases.

[0120] It should be noted that in this application, the elongation at break is measured according to JIS K 6251 (2017), and more specifically, it is measured by the method described in the examples described later.

[0121] The cured product of the above-mentioned rubber composition [cured product containing short fibers (C)] also exhibits excellent resistance to lateral pressure and high 8% flexural stress. The 8% flexural stress can be 5 MPa or more, for example, 5 to 30 MPa, preferably 5.5 to 20 MPa, more preferably 6 to 15 MPa, more preferably 6.5 to 10 MPa, and most preferably 7 to 9 MPa.

[0122] It should be noted that, in this application, the 8% bending stress is determined by the method described in the embodiments described later.

[0123] V-belts for transmission

[0124] The transmission V-belt of the present invention can be either a cloth-covered V-belt or a cut-edge V-belt, but from the viewpoint of ensuring resistance to lateral pressure and improving resistance to bending fatigue, a cut-edge V-belt is preferred.

[0125] Cut-edge V-belts include cut-edge V-belts and cut-edge toothed V-belts. Furthermore, cut-edge toothed V-belts can be broadly classified into cut-edge toothed V-belts with teeth formed only on the inner circumference and cut-edge double-sided toothed V-belts with teeth formed on both the inner and outer circumferences. From the viewpoint of requiring a high level of resistance to lateral pressure and bending fatigue, cut-edge toothed V-belts and cut-edge double-sided toothed V-belts are preferred. From the viewpoint of using in more demanding conditions and requiring a high level of performance, cut-edge double-sided toothed V-belts are particularly preferred. Toothed V-belts are V-belts where the side of the compressed rubber layer contacts the pulley, and are particularly preferred for transmission belts in gearboxes with continuously variable gear ratios during belt travel. Additionally, cut-edge V-belts used in configurations including reverse bending are also preferred.

[0126] Figure 1 This is a schematic partial cross-sectional perspective view showing an example of the serrated V-belt of the present invention. Figure 2 It is Figure 1 A schematic cross-sectional view of a toothed V-belt cut along its length.

[0127] In this example, the serrated V-belt 1 has toothed portions on its inner circumferential surface, which are alternately arranged with toothed peaks 1a and toothed valleys 1b along the length direction of the belt (direction A in the figure). The cross-sectional shape of the toothed peaks 1a in the length direction is approximately semi-circular (curved or wavy), and the cross-sectional shape in the direction orthogonal to the length direction (width direction or direction B in the figure) is trapezoidal. That is, each toothed peak 1a protrudes approximately semi-circularly from the cross-section of the toothed valley 1b in direction A in the belt thickness direction. The serrated V-belt 1 has a layered structure, with a first reinforcing fabric 2, an extended rubber layer 3, an adhesive rubber layer 4, a compression rubber layer 5, and a second reinforcing fabric 6 sequentially layered from the outer circumferential side of the belt towards the inner circumferential side (the side where the toothed portions are formed). The cross-sectional shape in the belt width direction is a trapezoid with the belt width decreasing from the outer circumferential side to the inner circumferential side. In addition, a core 4a is embedded in the adhesive rubber layer 4, and the aforementioned toothed portion is formed in the compression rubber layer 5 by a molding die with toothed parts.

[0128] The height and spacing of the toothed portions are the same as those of conventional toothed V-belts. In the compressed rubber layer, the height of the toothed portions (the height of the toothed peak based on the toothed valley) is approximately 50% to approximately 95% (particularly approximately 60% to approximately 80%) of the overall thickness of the compressed rubber layer, and the spacing of the toothed portions (the distance between the central portions of adjacent toothed portions) is approximately 50% to approximately 250% (particularly approximately 80% to approximately 200%) of the toothed portion height. The same applies when the toothed portions are formed by extending the rubber layer.

[0129] The overall thickness (average thickness) of the cut-edge V-belt of the present invention can be 8 mm or more, for example, 8 to 50 mm, preferably 9 to 45 mm (especially 10 to 40 mm), and more preferably 10 to 36 mm (especially 11 to 32 mm). These thickness ranges can be selected according to the application. For cut-edge V-belts used in electric two-wheelers, snowmobiles, etc., the overall thickness of the belt is, for example, 8 to 18 mm, preferably 10 to 14 mm, and more preferably 11 to 13 mm. In addition, for cut-edge V-belts used in large agricultural machinery (especially gear belts), the overall thickness of the belt can be 18 mm or more, for example, 18 to 40 mm, preferably 19 to 38 mm, more preferably 19.8 to 36 mm, and more preferably 19.8 to 30.5 mm. The cut-edge V-belt of the present invention can balance lateral pressure resistance and bending fatigue resistance, and is therefore particularly suitable for cut-edge V-belts with a thickness of 18 mm or more. If the thickness is too thin, the resistance to lateral pressure may be reduced; if it is too thick, the flexibility may be reduced, resulting in lower transmission efficiency and reduced resistance to bending fatigue.

[0130] It should be noted that, in this application, when the compression rubber layer and / or extension rubber layer have toothed portions, the overall thickness of the strip refers to the thickness at the top of the toothed portion (the maximum thickness of the strip).

[0131] In the cut-edge V-belt of the present invention, it is preferable that the compression rubber layer and / or the extension rubber layer are formed from the cured product of the above-mentioned rubber composition, more preferably that at least the compression rubber layer is formed from the cured product of the above-mentioned rubber composition, and even more preferably that both the compression rubber layer and the extension rubber layer are formed from the cured product of the above-mentioned rubber composition.

[0132] (Adhesive rubber layer)

[0133] The cut-edge V-belt of the present invention may not include an adhesive rubber layer, but from the viewpoint of improving the adhesion between the core and the compression rubber layer, and between the core and the extension rubber layer (or the main body of the extension rubber layer) to suppress peeling of the core from the aforementioned layers, it is preferable to include an adhesive rubber layer. The adhesive rubber layer may be formed from a rubber composition (second rubber composition) comprising a polymer component (a) containing an ethylene-α-olefin elastomer and a crosslinking agent (b) containing a sulfur-based crosslinking agent.

[0134] (a) Polymer composition

[0135] Including preferred methods (methods other than diene content), the ethylene-α-olefin elastomer (second ethylene-α-olefin elastomer) can be selected from the ethylene-α-olefin elastomers exemplified in the above-described polymer component (A).

[0136] The diene content of the second ethylene-α-olefin elastomer (especially ethylene-α-olefin-diene terpolymer rubbers such as EPDM) can be 15% by mass or less (e.g., 0.5 to 15% by mass), preferably 10% by mass or less (e.g., 1 to 10% by mass), more preferably 8% by mass or less (e.g., 3 to 8% by mass), more preferably 7% by mass or less (e.g., 3.5 to 7% by mass), and most preferably 5% by mass or less (e.g., 4 to 5% by mass). Excessive diene content may compromise high heat resistance.

[0137] Polymer component (a) may also contain other rubber components besides the second ethylene-α-olefin elastomer. The other rubber components and their proportions [the proportions in polymer component (a)] can be selected from the other rubber components and their proportions exemplified in the above-mentioned section on polymer component (A).

[0138] (b) Crosslinking agent

[0139] Including the preferred method, the sulfur-based crosslinking agent (second sulfur-based crosslinking agent) can be selected from the sulfur-based crosslinking agents exemplified in the above-mentioned crosslinking agent (B) item.

[0140] The proportion of the second sulfur-based crosslinking agent relative to 100 parts by weight of polymer component (a) is, for example, 0.1 to 5 parts by weight, preferably 0.3 to 3 parts by weight, more preferably 0.5 to 1.5 parts by weight, more preferably 0.6 to 1.3 parts by weight, and most preferably 0.8 to 1.2 parts by weight. If the proportion of the sulfur-based crosslinking agent is too low, the rubber hardness and lateral pressure resistance may decrease; if it is too high, the sulfur-based crosslinking agent may easily bloom on the surface of the uncrosslinked rubber sheet, thus raising concerns about contamination and reduced adhesion.

[0141] Crosslinking agent (b) may also include organic peroxides in addition to second-sulfur crosslinking agents. The organic peroxides and their proportions can be selected from the organic peroxides and their proportions exemplified in the section on crosslinking agents (B) above.

[0142] The proportion of the second sulfur-based crosslinking agent in the crosslinking agent (b) can be 50% by mass or more, preferably 70% by mass or more, further preferably 90% by mass or more, and more preferably 100% by mass.

[0143] The proportion of crosslinking agent (b) relative to 100 parts by mass of polymer component (a) is, for example, 0.1 to 5 parts by mass, preferably 0.3 to 3 parts by mass, more preferably 0.5 to 1.5 parts by mass, more preferably 0.6 to 1.3 parts by mass, and most preferably 0.8 to 1.2 parts by mass.

[0144] (c) Short fiber

[0145] The second rubber composition may also contain short fibers (c). Including preferred methods (other than proportions), the short fibers (c) may be selected from the short fibers exemplified in the above-described item of short fibers (C).

[0146] The proportion of short fibers (c) relative to 100 parts by mass of polymer component (a) is, for example, 100 parts by mass or less, preferably 50 parts by mass or less, and more preferably 10 parts by mass or less. The second rubber composition preferably contains substantially no short fibers (c), and more preferably no short fibers (c).

[0147] (d) Crosslinking accelerator

[0148] The second rubber composition may also contain a crosslinking accelerator (d). Including preferred methods (other than proportions), the crosslinking accelerator (d) may be selected from the crosslinking accelerators exemplified in the section on crosslinking accelerators (D) above.

[0149] When the crosslinking accelerator (d) is a combination of a sulfur-containing crosslinking accelerator (especially a thiomorpholine accelerator) having heterocycles containing oxygen and nitrogen and other sulfur-containing crosslinking accelerators (especially thiuram accelerators and / or sulfenamide accelerators), the mass ratio of the two is 1 / 99 to 90 / 10, preferably 5 / 95 to 70 / 30, more preferably 10 / 90 to 50 / 50, and more preferably 20 / 80 to 30 / 70.

[0150] Including preferred embodiments, the proportion of sulfur-containing accelerator (second sulfur-containing accelerator) contained in crosslinking accelerator (d) [the proportion in crosslinking accelerator (d)] can be selected from the proportion of the first sulfur-containing accelerator.

[0151] The proportion of the crosslinking accelerator (d) relative to 100 parts by mass of polymer component (a) is, for example, 0.1 to 10 parts by mass, preferably 0.3 to 7 parts by mass, more preferably 0.5 to 5 parts by mass, more preferably 1 to 3 parts by mass, and most preferably 1.5 to 2.5 parts by mass.

[0152] (e) Co-crosslinking agent

[0153] The second rubber composition may also contain a co-crosslinking agent (e). Including preferred methods (other than proportions), the co-crosslinking agent (e) may be selected from the co-crosslinking agents exemplified in the above-described co-crosslinking agent (E) section.

[0154] The proportion of the co-crosslinking agent (e) relative to 100 parts by mass of the polymer component (a) is, for example, 100 parts by mass or less, preferably 50 parts by mass or less, and more preferably 10 parts by mass or less. The second rubber composition preferably contains substantially no co-crosslinking agent (e), more preferably no co-crosslinking agent (e).

[0155] (f) Adhesion improver

[0156] The second rubber composition may also contain an adhesion improver (f). The adhesion improver (f) may be selected from the adhesion improvers exemplified in the above section on adhesion improvers (F).

[0157] Among the above-mentioned adhesion improvers, resorcinol-formaldehyde resin and melamine resin are preferred as adhesion improvers (f), and a combination of resorcinol-formaldehyde resin and melamine resin is particularly preferred.

[0158] When the adhesion improver (f) is a combination of resorcinol-formaldehyde resin and melamine resin, the proportion of resorcinol-formaldehyde resin relative to 100 parts by weight of melamine resin can be selected from about 10 parts by weight to about 1000 parts by weight, for example, 20 to 300 parts by weight, preferably 30 to 100 parts by weight, and more preferably 50 to 80 parts by weight.

[0159] The proportion of the adhesion improver (f) relative to 100 parts by mass of polymer component (a) can be selected from, for example, about 0.1 parts by mass to about 30 parts by mass, for example, 0.5 to 20 parts by mass, preferably 1 to 15 parts by mass, more preferably 2 to 10 parts by mass, and more preferably 3 to 8 parts by mass.

[0160] (g) softener

[0161] The second rubber composition may further include a softener (g). The softener (g) may be selected from the softeners exemplified in the section on softeners (G) above. Among the softeners mentioned above, petroleum-based softeners such as paraffin oils are preferred as softeners (g).

[0162] From the viewpoint of improving adhesion, the proportion of the softener (g) relative to 100 parts by mass of the polymer component (a) can be 1 part by mass or more, for example, 1 to 50 parts by mass, preferably 2 to 30 parts by mass, more preferably 3 to 20 parts by mass, more preferably 5 to 15 parts by mass, and most preferably 8 to 12 parts by mass.

[0163] (h) Inorganic fillers

[0164] The second rubber composition may also contain an inorganic filler (h). The inorganic filler (h) may be selected from the inorganic fillers exemplified in the section on inorganic fillers (H) above.

[0165] Among the aforementioned inorganic fillers, carbonaceous materials such as carbon black, mineral materials such as silica, and metal oxides such as zinc oxide are preferred as inorganic fillers (h). From the viewpoint of being able to take into account both the mechanical properties and adhesiveness of the cured rubber composition, a combination of carbon black (second carbon black), silica (second silica), and metal oxide (second metal oxide) is particularly preferred.

[0166] As the second carbon black, it can be selected from the first carbon black exemplified in the section on inorganic fillers (H). Among the above carbon blacks, FEF is preferred as the second carbon black from the viewpoint of adhesion, etc. Including preferred methods, the average particle size of the second carbon black can be selected from the average particle size of the first carbon black.

[0167] As the second silica, including in a preferred manner, it may be selected from the first silica exemplified in the section on inorganic fillers (H).

[0168] The proportion of the second silica relative to 100 parts by weight of the second carbon black is, for example, 5 to 200 parts by weight, preferably 10 to 100 parts by weight, more preferably 30 to 80 parts by weight, and even more preferably 40 to 60 parts by weight. If the proportion of silica is too low, the effect of improving adhesion may not be apparent.

[0169] The proportion of the second metal oxide relative to 100 parts by mass of the second carbon black is, for example, 1 to 100 parts by mass, preferably 3 to 50 parts by mass, more preferably 5 to 30 parts by mass, and most preferably 10 to 20 parts by mass.

[0170] The total proportion of inorganic filler (h) relative to 100 parts by mass of the polymer component (a) can be selected from about 10 parts by mass to about 100 parts by mass, for example, 20 to 80 parts by mass, preferably 30 to 70 parts by mass, and more preferably 40 to 60 parts by mass. If the proportion of inorganic filler is too small, the elastic modulus may be insufficient and the resistance to lateral compression may be reduced; if the proportion is too large, the elastic modulus may be too high and the resistance to flexural fatigue may be reduced.

[0171] (i) Other components

[0172] The second rubber composition may also contain other components (i). Other components (i) may be selected from the other components exemplified in the section on other components (i) above.

[0173] The total proportion of other components (i) relative to 100 parts by mass of the polymer component (a) is, for example, 0.1 to 15 parts by mass, preferably 0.3 to 10 parts by mass, and more preferably 0.5 to 7 parts by mass. The proportion of the anti-aging agent (second anti-aging agent) relative to 100 parts by mass of the polymer component (a) is, for example, 0.1 to 10 parts by mass, preferably 0.5 to 5 parts by mass, and more preferably 1 to 3 parts by mass.

[0174] [Core]

[0175] As the core, there are no particular limitations, and core wires (twisted ropes) arranged at predetermined intervals in the width direction of the belt can generally be used. The core wires extend along the length direction of the belt, typically extending parallel to the length direction of the belt at predetermined intervals. For the core wire, at least a portion of it needs to be in contact with the adhesive rubber layer; any of the following configurations can be used: embedding the core wire in the adhesive rubber layer, embedding the core wire between the adhesive rubber layer and the extension rubber layer, or embedding the core wire between the adhesive rubber layer and the compression rubber layer. From the viewpoint of improving durability, embedding the core wire in the adhesive rubber layer is preferred. It should be noted that in the case of a V-belt without an adhesive rubber layer, the configuration of embedding the core wire between the extension rubber layer and the compression rubber layer is acceptable.

[0176] As the material for the fiber constituting the core wire, materials such as those exemplified in the section on short fibers (C) can be used. Among fibers with the above-mentioned materials, from the viewpoint of high modulus, polyethylene terephthalate, polyethylene 2,6-naphthalate, etc., are commonly used. 2-4 Synthetic fibers such as polyester fibers (polyalkylene arylate fibers) and polyarylamide fibers, and inorganic fibers such as carbon fibers, with alkylene arylates as the main structural unit, are preferred. Polyester fibers (polyethylene terephthalate fibers, polyethylene naphthalate fibers, etc.) and polyamide fibers are preferred.

[0177] As the core yarn, a twisted rope using multifilament yarn (e.g., ply twisted, unidirectional twisted, straight twisted, etc.) can typically be used. The total fineness of the twisted rope can be, for example, 2200–13500 dtex (especially 6600–11000 dtex). The twisted rope can contain, for example, 1000–10000 monofilament yarns, preferably 2000–8000, and more preferably 4000–6000 monofilament yarns. The average diameter of the core yarn (the diameter of the twisted rope) can be, for example, 0.5–3 mm, preferably about 0.6 mm to about 2 mm, and more preferably about 0.7 mm to about 1.5 mm.

[0178] To improve adhesion to the rubber component, the core wire can be bonded (or surface-treated) using the same method as the short fibers. Preferably, the core wire is bonded using at least RFL liquid.

[0179] [Reinforced Fabric]

[0180] In cases where the slit-edge V-belt of the present invention includes reinforcing fabric, examples include: a configuration in which the reinforcing fabric is laminated on both the compression rubber layer and the extension rubber layer (or, if the insert is integrally formed with the compression rubber layer, it is a tooth) (the inner peripheral surface of the compression rubber layer and the outer peripheral surface of the extension rubber layer); a configuration in which the reinforcing fabric is laminated on the surface of either the compression rubber layer or the extension rubber layer; and a configuration in which the reinforcing layer is embedded in the compression rubber layer and / or the extension rubber layer (e.g., the configuration described in Japanese Patent Application Publication No. 2010-230146). In most cases, the reinforcing fabric is laminated on the surface (inner peripheral surface of the compression rubber layer and outer peripheral surface of the extension rubber layer) of at least one of the compression rubber layer and the extension rubber layer, for example, in a configuration where the reinforcing fabric is laminated on both the inner peripheral surface (lower surface) of the compression rubber layer and the outer peripheral surface (upper surface) of the extension rubber layer.

[0181] The reinforcing fabric can be formed from materials such as woven fabric, wide-angle canvas, knitted fabric, non-woven fabric, etc. (especially woven fabric). It can be bonded as needed, for example, treated with RFL liquid (impregnation treatment, etc.), or the adhesive rubber can be rubbed into the above-mentioned fabric through friction treatment. After the above-mentioned adhesive rubber and the above-mentioned fabric are laminated (coated), they are laminated or embedded in the compression rubber layer and / or extension rubber layer in the above-mentioned form.

[0182] [Manufacturing method of V-belt for transmission]

[0183] The manufacturing method of the transmission V-belt of the present invention is not particularly limited, and conventional methods can be used. In the case of a toothed V-belt, for example, a laminate consisting of a reinforcing fabric (lower fabric) and a compression rubber layer sheet (uncrosslinked rubber sheet) can be placed with the reinforcing fabric facing down in a flat toothed mold with alternating teeth and grooves, and pressed at a temperature of about 60°C to about 100°C (especially about 70°C to about 80°C) to produce a toothed gasket (a gasket that is not fully crosslinked and is in a semi-crosslinked state) with toothed portions formed therein, and then the two ends of the toothed gasket are cut vertically from the top of the toothed portion. Furthermore, an inner mold (made of cross-linked rubber) with alternating teeth and grooves can be applied to a cylindrical mold. After the teeth engage with the grooves, a toothed gasket is wound and joined at the top of the toothed section. A first adhesive rubber layer sheet (lower adhesive rubber: uncross-linked rubber sheet) is layered on the wound toothed gasket. Then, the core thread (twisted rope) forming the core is wound in a spiral shape, and a second adhesive rubber layer sheet (upper adhesive rubber: the same as the above adhesive rubber layer sheet), an extension rubber layer sheet (uncross-linked rubber sheet), and a reinforcing fabric (upper fabric) are wound sequentially on it to form a molded body. Then, after being covered with a sheath (a sheath made of cross-linked rubber), the mold is placed in a vulcanizing tank. After a cross-linking process to prepare a sleeve by cross-linking at a temperature of 120-200°C (especially 150-180°C), a cutting process to form and compress the rubber layer is performed by cutting it in a V-shaped cross-section using a cutter or the like.

[0184] For a toothed V-belt without reinforcing fabric, a laminate can be prepared by pre-pressing and compressing a sheet of compression rubber and a sheet of first adhesive rubber.

[0185] It should be noted that, as a method for orienting the orientation direction of short fibers along the width direction in stretch rubber sheets and compression rubber sheets, conventional methods can be cited, such as rolling rubber into a sheet by passing it between a pair of calendering rolls with a predetermined gap, cutting both sides of the rolled sheet with the short fibers oriented in the rolling direction along a direction parallel to the rolling direction, and cutting the rolled sheet at a right angle to the rolling direction in a way that forms the strip forming width (length in the strip width direction), and joining the sides cut along the direction parallel to the rolling direction together, etc. For example, the method described in Japanese Patent Application Publication No. 2003-14054 can be used. By such a method, the uncrosslinked sheet with the short fibers oriented is crosslinked in such a way that the orientation direction of the short fibers is the width direction of the strip.

[0186] Example

[0187] The present invention will now be described in more detail based on embodiments, but the present invention is not limited to these embodiments. It should be noted that the following details the raw materials used in the embodiments.

[0188] [raw material]

[0189] (Polymer composition)

[0190] EPDM1: "EP93" manufactured by JSR Corporation, with an ethylene content of 55% by mass and a diene content of 2.7% by mass.

[0191] EPDM2: "EP24" manufactured by JSR Corporation, with an ethylene content of 54% by mass and a diene content of 4.5% by mass.

[0192] (Cross-linking agents, cross-linking accelerators, and cross-linking aids)

[0193] Sulfur: "Powdered sulfur" manufactured by Amway Chemical Company.

[0194] Organic peroxide: "P-40MB(K)" manufactured by Nippon Yuko Co., Ltd.

[0195] Crosslinking accelerator A: "Nocuser TT" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0196] Crosslinking accelerator B: "Nocuser CZ" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0197] Crosslinking accelerator C: "Barnock R" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0198] Co-crosslinking agent A (bismaleimide): "Barnock PM" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0199] Co-crosslinking agent B (zinc methacrylate): Sanshin Chemical Industry Co., Ltd., "Sanestel SK-30".

[0200] (Fiber component)

[0201] Para-polymer polyaramid staple fiber: manufactured by Teijin Corporation, Twaron cut yarn, average fiber length 3mm

[0202] Nylon staple fiber: Manufactured by Asahi Kasei Corporation, Leona cut yarn, average fiber length 3mm

[0203] Core yarn: Two bundles of polyaramid fiber multifilaments with a fineness of 1680 dtex are combined and initially twisted to create a tufted yarn. Three of these tufted yarns are then combined and finally twisted in the opposite direction to the initial twist to create a twisted rope with a total fineness of 10080 dtex.

[0204] Reinforcing fabric: 2 / 2 twill nylon canvas (0.50mm thick).

[0205] (Other ingredients)

[0206] Carbon Black A (HAF): "N330" manufactured by CABOT Japan Co., Ltd.

[0207] Carbon Black B (FEF): "N550" manufactured by CABOT Japan Co., Ltd.

[0208] Silica: "Ultrasil VN3" manufactured by Evonik Degussa Japan Co., Ltd., with a BET specific surface area of ​​175 m². 2 / g

[0209] Paraffin oil: "ダイアナプロセスオイルPW90" manufactured by Idemitsu Kosan Co., Ltd.

[0210] Anti-aging agent A: "Noclac" manufactured by Ouchi Shinsei Chemical Industry Co., Ltd.

[0211] CD

[0212] Anti-aging agent B: "NonFruit OD3" manufactured by Seiko Chemical Co., Ltd.

[0213] Zinc oxide: Two types of zinc oxide manufactured by Sakai Chemical Industry Co., Ltd.

[0214] Stearic acid: Stearic acid (tsubaki) manufactured by Nippon Oil Co., Ltd.

[0215] Magnesium oxide: Kyowa Chemical Industry Co., Ltd.'s "Kyowa Mag 150"

[0216] Adhesion improver A (resorcinol-formaldehyde resin): "POWERPLAST PP-1860" manufactured by Singh Plasticisers & Resins Pvt. Ltd.

[0217] Adhesion improver B (hexamethoxymethyl melamine): "POWERPLAST PP-1890S" manufactured by Singh Plasticisers & Resins Pvt. Ltd.

[0218] Examples 1-9 and Comparative Examples 1-4

[0219] [Rubber Hardness]

[0220] Uncrosslinked rubber sheets with the composition shown in Table 1 were crosslinked by compression at a temperature of 170°C, a pressure of 2 MPa, and a time of 20 minutes to produce crosslinked rubber sheets (100 mm × 100 mm × 2 mm thick). Regarding rubber hardness, according to JIS K 6253 (2012), a laminate formed by overlapping three crosslinked rubber sheets was used as a sample, and the hardness was measured using a type A hardness tester. Regarding the hardness of the matrix rubber, a crosslinked rubber sheet without short fibers was prepared by removing short fibers from the above compound, and all other measurements were performed in the same manner. The results are shown in Table 3.

[0221] [Elongation at break]

[0222] Uncrosslinked rubber sheets with the composition shown in Table 1 were crosslinked by compression at a temperature of 170°C, a pressure of 2 MPa, and a time of 20 minutes to produce crosslinked rubber sheets (100 mm × 100 mm × 2 mm thick). These crosslinked rubber sheets were punched using a SUPPER DUMBBELL cutter (manufactured by DUMBBELL Corporation) to produce dumbbell-shaped No. 3 test pieces. The elongation at break was measured using the prepared test pieces according to JIS K 6251 (2017). The tensile speed was set to 500 mm / min, and the test temperature was set to 23°C. It should be noted that the measurement was performed with the length direction of the test piece perpendicular to the grain (the length direction of the short fibers). The results are shown in Table 3.

[0223] [8% Bending Stress]

[0224] Uncrosslinked rubber compositions with the compositions shown in Table 1 were subjected to compression crosslinking at a temperature of 170°C, a pressure of 2 MPa, and a time of 20 minutes to produce crosslinked rubber molded bodies (60 mm × 25 mm × 6.5 mm thick). The short fibers were oriented parallel to the length direction of the crosslinked rubber molded body. Figure 3As shown, the cross-linked rubber molded body 21 is supported on a pair of rotatable rollers (6mm in diameter) 22a and 22b with a 20mm gap. A metal pressing member 23 is placed on the center of the upper surface of the cross-linked rubber molded body 21 in the width direction (orthogonal to the orientation direction of the short fibers). The front end of the pressing member 23 has a semi-circular shape with a diameter of 10mm, which allows for smooth pressing of the cross-linked rubber molded body 21. In addition, during pressing, frictional force exists between the lower surface of the cross-linked rubber molded body 21 and the rollers 22a and 22b due to the compression deformation of the cross-linked rubber molded body 21. However, by allowing the rollers 22a and 22b to rotate, the effect of friction is reduced. The front end of the pressing member 23 contacts the upper surface of the cross-linked rubber molded body 21, and the unpressed state is set as the initial position. The pressing member 23 is pressed downwards from this state onto the upper surface of the cross-linked rubber molded body 21 at a speed of 100 mm / min, and the stress when the bending deformation is 8% is measured as the bending stress. By measuring the bending stress in a direction orthogonal to the orientation direction of the short fibers, if the bending stress is high, it can be determined that the resistance to the buckling deformation, known as concave bending, during belt movement is high, which can be used as an indicator of high load transmission and high durability. It should be noted that the measurement temperature is assumed to be the belt temperature during movement, set to 120°C.

[0225] [The presence or absence of a spray of cream on the film]

[0226] Uncrosslinked rubber composition rolled into a sheet with a thickness of 2 mm is left to stand at 25°C for 14 days. The rubber surface is then visually inspected to check for blooming (the precipitation of crosslinking agents and other additives on the sheet surface). Generally, even if blooming occurs, the physical properties of the rubber do not change significantly, but the workability during strip forming may be reduced due to decreased tackiness. Therefore, it is preferable to avoid blooming.

[0227] [Belt Manufacturing]

[0228] On the surface of a cross-linked rubber inner mold with a toothed shape, a sheet-shaped toothed gasket with a toothed portion is wound and bonded to a laminate formed by pre-laminating a compression rubber layer sheet and reinforcing fabric of a specified thickness with the composition shown in Table 1. Then, a lower adhesive rubber sheet with the composition shown in Table 2, a core wire, an upper adhesive rubber sheet with the composition shown in Table 2, and a flat extended rubber layer sheet with the composition shown in Table 1 are wound sequentially to form a molded body. Next, a cross-linked rubber outer mold with a toothed shape and a sheath are covered on the surface of the molded body. The mold is placed in a vulcanizing tank, and cross-linking is performed at a temperature of 170°C, a time of 40 minutes, and a pressure of 0.9 MPa to obtain a sleeve. It should be noted that the cross-linking conditions are selected similarly to those for the uncross-linked adhesive rubber layer sheet, compression rubber layer sheet, and extended rubber layer sheet. The sleeve is cut into a V-shape using a cutter and then precision-machined into a speed belt. That is, a speed belt is manufactured. Figure 4 The structure shown is a double-sided toothed V-belt with serrated edges (reinforcing fabric not shown). Specifically, a double-sided toothed V-belt with serrated edges was fabricated where a compression rubber layer 13 and an extension rubber layer 14 are formed on both sides of an adhesive rubber layer 11 with embedded core wire 12. Each of the compression rubber layer 13 and the extension rubber layer 14 has embedded teeth 16 and 17 (dimensions: upper width 20 mm, thickness 10 mm, outer circumference 817 mm). The results of the following evaluation tests on the obtained double-sided toothed V-belt with serrated edges are shown in Table 3.

[0229] [Dual-axis endurance running test]

[0230] Dual-axis durability running test, such as Figure 5 The test was conducted using a biaxial running test machine comprising a 50mm diameter drive (Dr.) pulley and a 125mm diameter driven (Dn.) pulley. A serrated V-belt was mounted on each pulley. The drive pulley speed was set to 5600 rpm, and the driven pulley load was set to 22.8 N·m. The belt was run for 72 hours at an ambient temperature of 80°C. The sides of the serrated double-sided toothed V-belt (the surfaces in contact with the pulleys) were visually inspected after the test to check for peeling between the core wire and the adhesive rubber layer. Additionally, the change in the upper width of the serrated double-sided toothed V-belt before and after the running test was calculated (upper width before the running test - upper width after the running test). A smaller change in upper width indicates better wear resistance.

[0231] [Reverse Bending Durability Running Test (Dynamic Reverse Bending Test)]

[0232] Reverse bending durability running test, such as Figure 6 The test was conducted using a triaxial running test machine comprising a 97.6 mm diameter drive (Dr.) pulley, a 77.9 mm diameter driven (Dn.) pulley, and a 79.4 mm diameter idler pulley. A double-sided toothed V-belt with serrated edges was mounted on each pulley. Tension was applied to the belt by dropping a 40 kgf hammer onto the drive pulley. The contact angle of the idler pulley (relative to the center angle of the arc of contact between the belt and pulley) was adjusted to 15°. The drive pulley speed was set to 3600 rpm, and the driven and idler pulleys were left unloaded. The belt was run at an ambient temperature of 120°C until its service life was reached. It should be noted that the service life was determined when the depth of the cracks (length in the belt thickness direction) in the toothed valleys of the double-sided toothed V-belt reached 2 mm or more. A longer running time before reaching service life indicates better resistance to bending fatigue.

[0233] [Reverse Bending Crack Test (Static Reverse Bending Test)]

[0234] Reverse bending crack test, such as Figure 7As shown, a serrated V-belt 30 with its inner and outer circumferential surfaces reversed is clamped between two parallel flat plates. The distance between the two plates is gradually narrowed at a rate of 50 mm / min. The distance between the plates at which cracks occur in the tooth valley of the serrated V-belt is measured. The shorter the distance between the plates at which cracks occur, the better the bending fatigue resistance (cracking resistance) is considered.

[0235]

[0236] [Table 2]

[0237] Table 2 (For bonding rubber layers)

[0238] composition Quality EPDM2 100 Carbon Black B 30 silicon dioxide 15 Paraffin oil 10 Anti-aging agent B 2 Zinc oxide 5 Adhesion Improver A 2 Adhesion improver B 3 Crosslinking accelerator A 1 Crosslinking accelerator B 0.5 Crosslinking accelerator C 0.5 Sulfur 1 total 170

[0239]

[0240] As can be clearly seen from the results in Table 3, Comparative Examples 1 and 2, which were crosslinked with organic peroxides, had high rubber hardness but low elongation at break, particularly poor resistance to flexural fatigue. Comparative Example 3, which reduced the amount of sulfur, did not sufficiently improve rubber hardness, resulting in reduced lateral pressure resistance and peeling, and also had low abrasion resistance. Comparative Example 4, which increased the amount of bismaleimide, had low elongation at break and low resistance to flexural fatigue.

[0241] In Examples 1-9, the rubber exhibits high hardness and elongation at break, achieving a good balance between wear resistance and flexural fatigue resistance, resulting in excellent durability. In Example 1, which contains a high amount of paraffin oil, the wear resistance is slightly reduced. In Examples 4-9, which contain bismaleimide as a co-crosslinking agent, the rubber exhibits exceptionally high hardness and excellent wear resistance.

[0242] Comparing Examples 5-7, a decrease in abrasion resistance was observed when the amount of sulfur was low, while a decrease in flexural fatigue resistance was observed when the amount of sulfur was high. Furthermore, in Example 7, where the amount of sulfur was high, blooming occurred in the uncrosslinked rubber sheet. Comparing Examples 5, 8, and 9, a decrease in flexural stress and abrasion resistance was observed when the amount of bismaleimide (the co-crosslinking agent) was low, while a decrease in elongation at break and flexural fatigue resistance was observed when the amount of bismaleimide was high. It should be noted that in Comparative Example 4, where the amount of bismaleimide was further increased, the decrease in elongation at break and flexural fatigue resistance reached an unacceptable level.

[0243] Industrial availability

[0244] The transmission V-belt of the present invention can be applied to transmission V-belts used in various fields of automobiles and industrial machinery, such as cloth-wrapped V-belts and cut-edge V-belts. From the viewpoint of improving resistance to lateral pressure while improving resistance to bending fatigue, it is preferably applied to cut-edge V-belts. As the cut-edge V-belt mentioned above, it can be applied to cut-edge V-belts, cut-edge toothed V-belts with toothed portions (cut-edge toothed V-belts, cut-edge double-sided toothed V-belts, etc.).

[0245] Furthermore, from the viewpoint of being able to balance resistance to lateral pressure and resistance to bending fatigue, the transmission V-belt of the present invention is preferably used in V-belts (transmission belts) used in transmissions (belt-type continuously variable transmissions) in automatic two-wheeled vehicles, ATVs (four-wheel off-road vehicles), snowmobiles, large agricultural machinery, etc., where the gear ratio changes continuously during belt movement, and in cut-edge V-belts used in layouts including reverse bending. From the viewpoint of being able to achieve high resistance to lateral pressure, wear resistance, and resistance to bending fatigue, it is particularly preferred to use transmission belts (e.g., large belts equivalent to HL to HQ in the ASABE standard) used in large agricultural machinery (comb harvesters, lawn mowers, etc.) requiring high horsepower of 75kW / piece or more.

[0246] The present invention has been described in detail with reference to specific embodiments; however, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the invention.

[0247] This application is based on Japanese Patent Application No. 2021-022748 filed on February 16, 2021 and Japanese Patent Application No. 2022-005960 filed on January 18, 2022, the contents of which are incorporated herein by reference.

[0248] Symbol Explanation

[0249] 1…V-belt for transmission

[0250] 2, 6…reinforced fabric

[0251] 3…Extended rubber layer

[0252] 4… Adhesive rubber layer

[0253] 4a…core

[0254] 5…Compression rubber layer

Claims

1. A transmission V-belt, comprising a cured material of a first rubber composition, wherein, The first rubber composition comprises a polymer component (A) containing an ethylene-α-olefin elastomer, a crosslinking agent (B) containing a sulfur-based crosslinking agent, and short fibers (C). The short fibers (C) are oriented along the width direction of the belt. The cured material has a rubber hardness (JIS-A) of 91 degrees or higher, and The elongation at break of the cured material along its length is 101-180%. The proportion of the sulfur-based crosslinking agent is between 1.2 and 10 parts by mass relative to 100 parts by mass of the polymer component (A). The proportion of the short fiber (C) is 25 to 35 parts by mass relative to 100 parts by mass of the polymer component (A).

2. The power transmission V-belt according to claim 1, wherein The matrix rubber hardness (JIS-A) of the cured rubber composition after removing the short fibers (C) from the first rubber composition is 83 degrees or higher.

3. The power transmission V-belt according to claim 1 or 2, wherein The first rubber composition further comprises a crosslinking accelerator (D), and the crosslinking accelerator (D) comprises a sulfur-containing crosslinking accelerator.

4. The power transmission V-belt according to claim 3, wherein The sulfur-containing crosslinking accelerator comprises a sulfur-containing crosslinking accelerator having heterocycles containing oxygen and nitrogen.

5. The power transmission V-belt according to claim 1 or 2, wherein The first rubber composition further comprises a co-crosslinking agent (E), and the co-crosslinking agent (E) comprises a bismaleimide compound.

6. The power transmission V-belt according to claim 1 or 2, wherein The first rubber composition further comprises an adhesion improver (F).

7. The power transmission V-belt according to claim 1 or 2, wherein The first rubber composition further comprises a softener (G), and the softener (G) is in the proportion of 0.1 to 10 parts by mass relative to 100 parts by mass of the polymer component (A).

8. The power transmission V-belt according to claim 1 or 2, wherein It has a compression rubber layer and / or an extension rubber layer formed from the cured product of the first rubber composition.

9. The V-belt for transmission according to claim 1 or 2, wherein, It also includes an adhesive rubber layer formed from the cured product of the second rubber composition. The second rubber composition comprises a polymer component (a) containing an ethylene-α-olefin elastomer and a crosslinking agent (b) containing a sulfur-based crosslinking agent.

10. The transmission V-belt according to claim 1 or 2, wherein it is a tangential toothed V-belt having teeth on at least the inner circumferential side.

11. The V-belt for transmission according to claim 1 or 2, wherein it is a variable speed belt.

12. The power transmission V-belt of claim 1 or 2, wherein The overall average thickness of the belt is 19.8–36 mm.

13. The transmission V-belt according to claim 1 or 2, wherein it is a cut-edge V-belt used in a layout including reverse bending.

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